KR20170091082A - Polyvinyl alcohol polymer film and method for producing same - Google Patents

Abstract

(I) and (II): ???????? Δn (MD) _Ave ? 1.3 占^10-3 (I)? N (TD) _Ave ? 1.3 占^10-3 (II) MD) _Ave represents a value obtained by averaging the birefringence of the PVA polymer film in the film thickness direction, and? N (TD) _Ave represents the birefringence of the PVA polymer film in the film flow direction Of the PVA polymer film. Such a PVA polymer film can be stretched at a high magnification without causing breakage even when a method of stretching at a relatively high stretching magnification at the time of dyeing or at a relatively high stretching temperature is employed, Can be produced with good workability, high yield, low cost, and good productivity.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a polyvinyl alcohol polymer film,

The present invention relates to an optical film such as a polarizing film produced from a polyvinyl alcohol polymer film (hereinafter sometimes referred to as " PVA "), a production method thereof, and a polarizing film produced from the PVA polymer film .

A polarizing plate having light transmission and shielding functions is an important component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The field of application of this liquid crystal display device is also broadly ranging from small electronic devices such as electronic calculators and wrist watches at the beginning of development to notebook PCs, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, vehicle navigation systems, portable telephones, And the like. Especially, in a liquid crystal monitor, a liquid crystal television, etc., a large-sized screen is being developed.

The polarizing plate is generally prepared by a method in which a PVA polymer film is uniaxially stretched, followed by dyeing using iodine or a dichroic dye, a method in which a PVA polymer film is dyed, uniaxially stretched and then fixed with a boron compound , A polarizing film is produced by a method of performing dyeing and fixing treatment at the same time as the above method, and a protective film such as cellulose triacetate film or acetic acid-butyric acid cellulose film is applied to one or both sides of the polarizing film obtained thereby do.

In recent years, along with the expansion of use of liquid crystal display devices, in addition to the enhancement of display quality, further cost reduction and further improvement in handling properties are required. From the viewpoint of cost reduction, it is possible to improve the production speed at the time of producing the polarizing film, to prevent the stretching break (break) at the time of stretching the PVA polymer film so as to reduce the breaking loss and improve the yield, It is necessary to prevent stretching work accompanying breakage and interruption of stretching and dyeing work.

In addition, as one of the improvements in productivity in the production of a polarizing film, there is a demand for shortening the drying time in the production of the polarizing film. From this point of view, as a raw film for producing polarizing films, A PVA polymer film having a thickness of about 75 占 퐉 has been generally used, but recently, a thinner PVA polymer film having a thickness of less than 70 占 퐉 has been demanded.

However, as the PVA polymer film becomes thinner, there is a problem that the film tends to be broken when stretched at a high magnification. From this viewpoint, even if it is thin, the film can be stretched at a high magnification without causing breakage, A PVA polymer film capable of producing a polarizing film having the same or higher polarizing performance with good workability, high yield, low cost, and good productivity has been demanded.

Conventionally, for the purpose of improving the stretchability of a PVA polymer film, improving uniformity at the time of stretching, and improving polarizing performance and durability in a polarizing film obtained by stretching a PVA polymer film, an undiluted solution containing a PVA polymer (The ratio of the transporting speed of the PVA polymer film between the rolls used for film formation) and the moisture content of the PVA polymer film at the time of film formation, etc. have been carried out .

In such a conventional technique, for example, when a PVA polymer film is produced using a drum-form film, the ratio of [the winding speed of the obtained PVA polymer film] / [the speed of the drum located in the uppermost stream to which the film- Is set to 0.8 to 1.3 (Patent Document 1).

It is also possible to provide a PVA polymer film which can be produced with good workability, in a high yield, at a low cost, and with good productivity, without stretching a stretched film, such as a polarizing film, (Δn (MD) _Ave ) obtained by averaging the birefringence of the PVA polymer film in the thickness direction of the film in the machine direction and the birefringence of the PVA polymer film in the thickness direction of the film PVA polymer films whose values (DELTA n (TD) _Ave ) satisfy a specific relationship are known (see Patent Documents 2 and 3).

Japanese Patent Application Laid-Open No. 2001-315141 International Publication No. 2012/132984 International Publication No. 2013/137056

Recently, in order to improve the optical performance such as the polarization performance of the obtained polarizing film, a method of stretching the polarizing film to a relatively high drawing magnification at the time of dyeing at the time of producing the polarizing film may be adopted, A relatively high temperature may be employed even in the main stretching referred to as stretching. However, in the PVA polymer films described in Patent Documents 1 to 3, even in such a case, there is room for further improvement in that a high limit stretching magnification is exhibited. In the PVA polymer films described in Patent Documents 1 to 3, there is a problem that the film width is narrowed by stretching to a high magnification, and the area of the finally obtained polarizing film becomes small.

It is an object of the present invention to provide a method of stretching at a high magnification without causing breakage because the stretching ratio at a relatively high stretching ratio at the time of dyeing or the stretching ratio at a relatively high stretching temperature is adopted is high, It is intended to provide a PVA polymer film capable of producing a stretched film such as a polarizing film with good workability, high yield, low cost, and good productivity by suppressing reduction of the film width at the time of stretching. It is also an object of the present invention to provide a method for continuously and continuously producing a PVA polymer film having excellent properties as described above with high productivity. It is also an object of the present invention to provide an optical film such as a polarizing film produced from the PVA polymer film.

As a result of intensive studies conducted by the present inventors in order to achieve the above object, it has been found that the value obtained by averaging the birefringence index in the machine direction (longitudinal direction) of the PVA polymer film in the thickness direction of the film, When the values obtained by averaging the birefringence index in the thickness direction of the film in the respective specific ranges are used in a case where a method of stretching to a relatively high stretching ratio at the time of dyeing is employed or a case where a relatively high stretching temperature is adopted, The stretching film such as a polarizing film excellent in optical performance such as polarization performance can be prevented from stopping the stretching operation while preventing the film from being easily broken even when stretched at a high magnification, And can be produced at a high yield, at a low cost, and with good productivity.

In particular, the value obtained by averaging the birefringence index in the machine direction (longitudinal direction) of the PVA polymer film in the thickness direction of the film and the value obtained by averaging the birefringence index in the thickness direction of the PVA polymer film in the thickness direction of the film are The above-mentioned PVA polymer film in a specific range can be obtained even when the thickness of the film is thinner than the thickness of the PVA polymer film conventionally used for the production of polarizing films, a thickness of about 10 to 65 탆, It is possible to uniaxially stretch smoothly at a high magnification without causing breakage, thereby making it possible to further thin the polarizing film at the time of production thereof, thereby further shortening the drying time at the time of producing the polarizing film I found out I could.

The inventors of the present invention have found out that the above PVA polymer film having a high limiting draw ratio can be obtained by discharging a film forming stock solution containing a PVA polymer onto a first drying roll of a film forming apparatus having a plurality of drying rolls, The ratio of the main stream of the final drying roll to the main stream of the first drying roll is set to a specific range and the film width of the PVA polymer film when the volatile fraction becomes a specific value The shrinkage ratio calculated from the specific range can be continuously and smoothly produced with high productivity.

The present inventors have also found that, in the production of a PVA polymer film having a high critical stretch ratio by the above-described method, the surface temperature of each dry roll when the volatile fraction of the PVA polymer film is in a specific range, It has been found that it is preferable to set the average value in a specific range, that the volatilization fraction of the stock film-forming liquid should be within a specific range, and that the peripheral velocity of the first drying roll should be within a specific range.

The inventors of the present invention have conducted further studies based on the above findings and completed the present invention.

That is,

[1] A PVA polymer film characterized by satisfying the following formulas (I) and (II)

? N (MD) _Ave ? 1.3 占^10-3 (I)

? N (TD) _Ave ? 1.3 占^10-3 (II)

(MD) _Ave represents a value obtained by averaging the birefringence of the PVA polymer film in the machine direction of the film in the thickness direction thereof, and? N (TD) _Ave represents a value obtained by averaging the birefringence of the PVA polymer film in the thickness direction of the PVA polymer film Represents a value obtained by averaging the birefringence index of the film in the thickness direction of the film.

[2] The PVA polymer film according to [1], wherein the thickness is in the range of 10 to 65 μm,

[3] The PVA polymer film according to the above [1] or [2], which is a original film for producing an optical film,

[4] The PVA polymer film of [3], wherein the optical film is a polarizing film,

[5] A method for producing a PVA polymer film,

(a) a film-forming stock solution containing a PVA polymer is discharged onto a first drying roll of the film-forming apparatus using a film-forming apparatus having a plurality of drying rolls whose rotation axes are parallel to each other, Further dried with a dry roll to form a film;

At that time,

(b) the ratio (S _L / S ₁ ) of the peripheral speed (S _L ) of the final drying roll to the peripheral speed (S ₁ ) of the _first drying roll is set to 0.955 to 0.980;

(c) shrinkage percentage is calculated from the PVA-based polymer film has a width (H ₉₎ at which the PVA based polymer film width (H ₂₀₎ and the volatile fraction at which the volatile fraction is 20% by mass was 9% by mass (( 1 - H ₉ / H ₂₀ ) × 100) (%) is 1% or more.

[6] From the drying rolls when the volatile fraction of the PVA polymer film is 20 mass%, the surface temperature of each drying roll up to the drying roll when the volatile fraction of the PVA polymer film becomes 9 mass% The production method of the above-mentioned [5], wherein the average value is 85 [deg.] C or higher,

[7] The production method of the above [5] or [6], wherein the volatile fraction of the undiluted solution is 60 to 75% by mass,

[8] The first peripheral velocity of the drying rolls (S ₁₎ to 8 ~ 25 m / minute according to the above [5] to [7] The method of any one of,

[9] An optical film produced from the PVA polymer film of [3] above,

[10] the optical film of [9], which is a polarizing film.

Since the PVA polymer film of the present invention has a high limiting stretching magnification even when a method of stretching to a relatively high stretching ratio at the time of dyeing is employed or when a relatively high stretching temperature is adopted, Even if the film is uniaxially stretched at a high magnification, the film is not easily broken, whereby a stretched film such as a polarizing film can be produced at a high yield and at a low cost with good productivity without interrupting the stretching operation.

In particular, the PVA polymer film of the present invention is characterized in that the thickness of the film is thinner than the thickness of the PVA polymer film conventionally used for producing a polarizing film or the like, a thickness of about 10 to 65 탆, It is possible to uniaxially stretch smoothly at a high magnification without causing breakage, and accordingly, it is possible to further thin the film when the stretched film is produced, It is possible to further shorten the manufacturing process and improve the productivity.

In recent years, PVA polymer films having a length of more than 5000 m are also used as original films for polarizing film production. Since the PVA polymer films of the present invention have a high critical stretching magnification, The polarizing film can be stretched at a high magnification, whereby the amount of the polarizing film to be obtained from the PVA polymer film can be made larger than in the prior art.

Further, by employing the production method of the present invention, the PVA polymer film of the present invention having the above-described excellent characteristics can be smoothly and continuously produced with high productivity.

Brief Description of the Drawings Fig. 1 is a schematic view showing a sampling method for measuring Δn (MD) _Ave of a PVA polymer film.
Fig. 2 is a schematic view showing a sampling method for measuring Δn (TD) _Ave of a PVA polymer film.

Hereinafter, the present invention will be described in detail.

Generally, in a transparent film produced by using a transparent polymer such as a PVA polymer, the polymer chain is oriented in the flow direction (machine direction: longitudinal direction) due to plastic deformation or distortion due to shear stress, Are macroscopically aligned, thereby generating birefringence peculiar to the polymer.

The birefringence [? N (MD)] in the machine flow direction in the PVA polymer film is expressed by the following equation

[i], and the birefringence [? n (TD)] in the width direction is obtained from the following expression [ii].

? N (MD) = nMD - nz [i]

? N (TD) = nTD - nz [ii]

NMD is the refractive index of the film in the machine direction (longitudinal direction) of the film, nTD is the refractive index in the width direction of the film, and nz is the refractive index in the thickness direction of the film.

The PVA polymer film of the present invention is different from the conventional PVA polymer film in that it satisfies the following formulas (I) and (II).

? N (MD) _Ave ? 1.3 占^10-3 (I)

? N (TD) _Ave ? 1.3 占^10-3 (II)

(MD) _Ave represents a value obtained by averaging the birefringence of the PVA polymer film in the machine direction of the film in the thickness direction thereof, and? N (TD) _Ave represents a value obtained by averaging the birefringence of the PVA polymer film in the thickness direction of the PVA polymer film Represents a value obtained by averaging the birefringence index of the film in the thickness direction of the film.

That is, as shown in the above formulas (I) and (II), in the PVA polymer film of the present invention, the mechanical flow direction of the PVA polymer film (the line direction when the PVA polymer film is continuously formed) (MD) _Ave " obtained by averaging the birefringence index of the film in the thickness direction of the film " may be referred to as MD in the longitudinal direction ", and the width direction (direction perpendicular to the longitudinal direction) of the PVA polymer film, DELTA (TD) _Ave " obtained by averaging the birefringence index of the film in the thickness direction of the film (hereinafter sometimes referred to as the " width direction (TD) "

By satisfying the above-mentioned formulas (I) and (II), the PVA polymer film of the present invention can be used in a case where a method of stretching to a relatively high stretching magnification at the time of dyeing is adopted, Whereby the film is unlikely to be broken even if it is uniaxially stretched at a high magnification in the production of a stretched film such as a polarizing film and the stretching operation accompanying the breakage of the film is not caused, It is possible to produce a stretched film having a thin film excellent in optical performance such as performance at a high yield with good productivity.

PVA-based polymer film of the present invention, this would be exhibited to a more remarkable effect of the invention, in view of their ease of manufacture, it is preferable that _{Δn (MD) Ave 1.3 × 10} -3 less, 1.0 × 10 ^- More preferably no greater than ³ , even more preferably no greater than 0.9 x 10 ^-3 , particularly preferably no greater than 0.8 x 10 ^-3 , more preferably no greater than 0.7 x 10 ^-3 , more preferably no greater than 0.75 x 10 ^-3 Do.

The PVA polymer film of the present invention preferably has a Δn (TD) _Ave of 1.2 × 10 ^-3 or less and a film thickness of 1.15 × 10 ^-3 μm, in view of the effects of the present invention being more remarkably exhibited, more preferably not more than 10 ^-3, more preferably not more than 1.1 × ^10-3, and further, 1.0 × 10 ^-3, it is preferable and more preferably at least, not less than 1.05 × 10 ^-3.

In addition, PVA-based in polymer films, in many cases there is a change in value in the transverse direction (TD) Δn (MD) _Ave and / or Δn (TD) at _Ave of the film, particularly in the transverse direction both end portions Δn (MD) _Ave (I) and (II) at the central portion in the width direction (TD) of the PVA polymer film, and it is sufficient that the PVA polymer film is in the width direction centered on the central portion of the PVA polymer film in the width direction (I) and (II) are preferably satisfied over the entirety of 80% or more of the segment (TD). Both ends in the width direction (TD) of the PVA polymer film that do not satisfy the formulas (I) and (II) can be cut and removed (ear picking) before stretching the PVA polymer film in the longitudinal direction (MD) .

PVA-based polymer film "Δn (MD) _Ave" [PVA-based polymer a value averaged in the direction of the thickness of the film of birefringence in a longitudinal direction (MD) of the film; and "Δn (TD) _Ave" [PVA-based polymer film (A value obtained by averaging the birefringence index in the width direction (TD) of the film in the thickness direction of the film) can be measured by the following method.

"1" Measurement method of Δn (MD) _Ave : (Here, measurement method of Δn (MD) _Ave at the center of the width direction (TD) of the PVA polymer film is exemplified here.)

(i) From the central portion in the width direction (TD) of the film, as shown in Fig. 1 (a), MD × TD = 2 mm × 10 Mm is cut and the three pieces are sandwiched with a PET film having a thickness of 100 占 퐉 on both sides and further inserted into a wooden frame and mounted on a microtome device.

(ii) Next, the pieces thus obtained are sliced at intervals of 10 占 퐉 in parallel with the lengthwise direction MD of the pieces as shown in Fig. 1 (b) (PET film and wooden frame are not shown) , 10 slice pieces for observation (MD x TD = 2 mm x 10 m) shown in Fig. 1 (c) are prepared. Of the slice pieces, five slice pieces having smooth slice surfaces and no slice thickness unevenness are selected, and the slice pieces are each placed on a slide glass and the slice thickness is measured with a microscope (manufactured by KYENS). In addition, the observation is performed at a field of view of 10 times the berth and 20 times the object (200 times the total).

(iii) Subsequently, the slice pieces were tilted as shown in (d) of Fig. 1 so as to observe the sliced surfaces, and the sliced surfaces were placed on the slide glass with the sliced surfaces facing upward, and sealed with cover glass and silicone oil (refractive index: 1.04) Five retardations of the slice pieces are measured using a photoelasticity evaluation system "PA-micro" (manufactured by Photonic Lattice Co., Ltd.).

(iv) In a state in which the retardation distribution of each slice convenience is displayed on the measurement screen of " PA-micro ", a line? perpendicular to the surface of the original film is traced across the slice piece, and line analysis is performed on the line? To obtain retardation distribution data in the thickness direction of the film. In addition, the observation is performed at a field of view of 10 times the berth and 20 times the object (200 times the total). Further, in order to suppress the error caused by the change of the position where the line segment? Passes on the slice piece, the average value of the retardation is adopted with the line width of 300 pixels.

(v) The value of the retardation distribution in the thickness direction of the film obtained above is divided by the thickness measured by the microscope to obtain the birefringence index Δn (MD) in the thickness direction of the film, and the birefringence Δn MD) distribution. The average value of the birefringence index? N (MD) distribution in the thickness direction of each of the five slice pieces is further averaged to be? N (MD) _Ave.

&Quot; 2 " Measurement of Δn (TD) _Ave :

(Here, the measurement method of? N (TD) _Ave at the center of the width direction (TD) of the PVA polymer film is exemplified.)

(i) From the central portion in the width direction (TD) of the film, as shown in Fig. 2 (a), at an arbitrary position in the longitudinal direction (MD) of the PVA polymer film, MD x TD = 10 mm x 2 Mm is cut and the three pieces are sandwiched with a PET film having a thickness of 100 占 퐉 on both sides and further inserted into a wooden frame and mounted on a microtome device.

(ii) Next, the pieces thus obtained are sliced at an interval of 10 占 퐉 in parallel with the width direction TD of the pieces as shown in Fig. 2 (b) (PET film and wooden frame are not shown) 10 pieces of observation slices (MD 占 TD = 10 占 퐉 占 2 mm) shown in Fig. 2 (c) are prepared. Of the slice pieces, five slice pieces having smooth slice surfaces and no slice thickness unevenness are selected, and the slice pieces are each placed on a slide glass and the slice thickness is measured with a microscope (manufactured by KYENS). In addition, the observation is performed at a field of view of 10 times the berth and 20 times the object (200 times the total).

(iii) Then, the slice pieces were tilted as shown in (d) of Fig. 2 so as to observe the slice surface, and the slice surfaces were placed on the slide glass with the slice surface facing upward, and sealed with a cover glass and silicone oil (refractive index: 1.04) Five retardations of the slice pieces are measured using a photoelasticity evaluation system "PA-micro" (manufactured by Photonic Lattice Co., Ltd.).

(iv) In a state in which the retardation distribution of each slice convenience is displayed on the measurement screen of " PA-micro ", a line? perpendicular to the surface of the original film is traversed across the slice piece, and line analysis is performed on the segment? To obtain retardation distribution data in the thickness direction of the film. In addition, the observation is performed at a field of view of 10 times the berth and 20 times the object (200 times the total). Further, in order to suppress the error caused by the change of the position where the line segment? Passes on the slice piece, the average value of the retardation is adopted with the line width being 300 pixels.

(v) The value of the retardation distribution in the thickness direction of the film obtained above is divided by the thickness measured by the microscope to obtain the birefringence index DELTA n (TD) distribution in the thickness direction of the film, and the birefringence DELTA n TD) distribution. The average value of the birefringence index DELTA n (TD) distribution in the thickness direction of each of the five slice pieces is further averaged to be " DELTA n (TD) _{Ave &} quot ;.

The thickness of the PVA polymer film of the present invention can be in the range of 5 to 150 占 퐉, but it is preferably 10 to 65 占 퐉 when used as the original film for polarizing film production. Since the PVA polymer film of the present invention has a high critical stretching magnification even when a method of stretching to a relatively high stretching magnification at the time of dyeing or a case of employing a relatively high stretching temperature is employed, It is possible to stretch at a high magnification without causing breakage of the film when the thickness is in the range of 10 to 65 占 퐉 which is thinner than the PVA polymer film having a thickness of about 75 占 퐉 which was often used as the original film, A PVA polymer film having a thickness of 10 to 65 占 퐉 can be stretched at a high magnification so that a stretched film having optical properties such as the same or higher polarizing performance can be produced with good yield and smoothly with good productivity, Can be made thinner than in the prior art, and the drying time in the production of the polarizing film can be shortened, It is possible to improve the manufacturing speed of the flow. In view of the above, the thickness of the PVA polymer film is more preferably 60 占 퐉 or less, more preferably 50 占 퐉 or less, and even more preferably 40 占 퐉 or less, furthermore 30 占 퐉 or less.

On the other hand, when the thickness of the PVA polymer film is too thin, the PVA polymer film has a thickness of 15 mu m or more because the film tends to be easily broken during the uniaxial stretching for producing the polarizing film More preferably 18 탆 or more, and particularly preferably 20 탆 or more.

The width of the PVA polymer film of the present invention is not particularly limited. However, since the liquid crystal television and monitor have become large in recent years, the width is preferably 2 m or more, more preferably 3 m or more More preferably 4 m or more. Further, in the case of producing a polarizing plate using a realistic production machine, if the width of the film is too large, uniform uniaxial stretching may become difficult. Therefore, the width of the PVA polymer film is preferably 8 m or less.

The PVA polymer film of the present invention preferably has a mass swelling degree of 180 to 250%, more preferably 185 to 240%, and further preferably 190 to 230%. If the mass swelling degree of the PVA polymer film is too low, the film is not stretched well, and it tends to be difficult to produce a stretched film having excellent optical performance. On the other hand, if the mass swelling degree is too high, Or a high-durability polarizing film may not be obtained in some cases.

Means the percentage of the value obtained by dividing the mass when the PVA polymer film is immersed in distilled water at 30 DEG C for 30 minutes divided by the mass after drying at 105 DEG C for 16 hours after the immersion, Can be measured by the method described in the following examples.

Examples of the PVA polymer forming the PVA polymer film of the present invention include PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, a modified PVA polymer obtained by graft copolymerizing a comonomer with the main chain of the PVA , A modified PVA polymer produced by saponifying a modified polyvinyl ester obtained by copolymerizing a vinyl ester and a comonomer, a modified PVA polymer obtained by crosslinking a part of the hydroxyl groups of the unmodified PVA or the modified PVA polymer with aldehydes such as formalin, butylaldehyde and benzaldehyde Called polyvinyl acetal resin.

When the PVA polymer forming the PVA polymer film of the present invention is a modified PVA polymer, the modification amount in the PVA polymer is preferably 15 mol% or less, more preferably 5 mol% or less.

Examples of the vinyl ester used in the production of the PVA polymer include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, vinyl laurate, vinyl stearate, vinyl benzoate , Vinyl versatate, and the like. These vinyl esters can be used singly or in combination. Among these vinyl esters, vinyl acetate is preferable from the viewpoint of productivity.

Examples of the comonomer include olefins having 2 to 30 carbon atoms (e.g.,? -Olefin, etc.) such as ethylene, propylene, 1-butene and isobutene; Acrylic acid or a salt thereof; Acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl acrylate For example, 1 to 18 carbon alkyl esters of acrylic acid); Methacrylic acid or a salt thereof; Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2- Methacrylic acid esters such as ethylhexyl, octadecyl methacrylate and the like (for example, alkyl esters having 1 to 18 carbon atoms in methacrylic acid); Acrylamide, N-methylacrylamide, N-ethyl acrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamidepropanesulfonic acid or salts thereof, acrylamidopropyldimethylamine or salts thereof, An acrylamide derivative such as an amide or a derivative thereof; Methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid or a salt thereof, methacrylamide propyldimethylamine or a salt thereof, N-methylol methacrylamide or a derivative thereof Acrylamide derivatives; N-vinyl amides such as N-vinyl formamide, N-vinyl acetamide and N-vinyl pyrrolidone; Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether Ethers; Nitriles such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; Allyl compounds such as allyl acetate and allyl chloride; Unsaturated dicarboxylic acids such as maleic acid and itaconic acid, and salts and esters thereof; Vinylsilyl compounds such as vinyltrimethoxysilane; Isopropenyl acetate; Unsaturated sulfonic acid or a derivative thereof. Of these,? -Olefins are preferable, and ethylene is particularly preferable.

The average degree of polymerization of the PVA polymer forming the PVA polymer film of the present invention is preferably 1,000 or more, more preferably 1,500 or more, and still more preferably 2,000 or more, from the viewpoint of the polarizing performance and durability of the resulting polarizing film . On the other hand, the upper limit of the average degree of polymerization of the PVA polymer is preferably 8000 or less, more preferably 6000 or less, from the viewpoints of ease of production of the homogeneous PVA polymer film and elongation property.

Here, the "average degree of polymerization" of the PVA polymer in the present specification means the average degree of polymerization measured in accordance with JIS K 6726-1994, and the PVA polymer is subjected to re-saponification and purification, Is obtained from the viscosity.

The degree of saponification of the PVA polymer forming the PVA polymer film of the present invention is preferably 95.0 mol% or more, more preferably 98.0 mol% or more, and more preferably 99.0 mol% or more in view of the polarizing performance and durability of the resulting polarizing film. Or more, and most preferably 99.3 mol% or more.

Here, the " degree of saponification " of the PVA polymer in the present specification refers to the degree of saponification of the PVA polymer with respect to the total mole number of a structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit by saponification and a vinyl alcohol unit Quot; refers to the ratio (mole%) of the unit of moles. The saponification degree of the PVA polymer can be measured in accordance with the description of JIS K 6726-1994.

The production method of the PVA polymer film of the present invention is not particularly limited and any method can be used as long as it can produce a PVA polymer film satisfying the above-mentioned formulas (I) and (II). However, In the polymer film,

(a) a film-forming apparatus having a plurality of drying rolls whose rotating shafts are parallel to each other is used, and a film-forming stock solution containing a PVA polymer is discharged onto a first drying roll of the film-forming apparatus to partially dry it, Further dried with a dry roll to form a film; At that time,

(b) the ratio (S _L / S ₁ ) of the peripheral speed (S _L ) of the final drying roll to the peripheral speed (S ₁ ) of the _first drying roll is set to 0.955 to 0.980;

(c) shrinkage percentage is calculated from the PVA-based polymer film has a width (H ₉₎ at which the PVA based polymer film width (H ₂₀₎ and the volatile fraction at which the volatile fraction is 20% by mass was 9% by mass (( 1 - H ₉ / H ₂₀ ) x 100) (%) is 1% or more;

According to the production method of the present invention, continuous production can be smoothly performed with high productivity.

The method of producing the PVA polymer film of the present invention will be described in detail below.

The film forming stock solution containing a PVA polymer film can be prepared by mixing a PVA polymer with a liquid medium to prepare a solution, or by dissolving a PVA polymer pellet or the like containing a liquid medium into a melt.

The melting of the PVA polymer in the liquid medium, the melting of the PVA polymer pellet including the liquid medium, and the like can be carried out using a stirring mixer, a melt extruder, or the like.

Examples of the liquid medium to be used at this time include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, diethylenetriamine and the like. Can be used singly or in combination of two or more kinds. Of these, water, dimethylsulfoxide, or a mixture of both is preferably used, and water is more preferably used.

It is preferable to add a plasticizer to the stock solution for the purpose of promoting dissolution or melting of the PVA polymer in a liquid medium, improving processability at the time of film production, and improving the stretchability of the obtained PVA polymer film.

As the plasticizer, a polyhydric alcohol is preferably used, and examples thereof include ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, , One species may be used singly or two or more species may be used in combination. Among them, one or two or more of glycerin, diglycerin and ethylene glycol are preferably used because they are excellent in the effect of improving the stretchability.

The amount of the plasticizer to be added is preferably 0 to 30 parts by mass, more preferably 3 to 25 parts by mass, and particularly preferably 5 to 20 parts by mass, based on 100 parts by mass of the PVA polymer. If the added amount of the plasticizer exceeds 30 parts by mass based on 100 parts by mass of the PVA polymer, the obtained PVA polymer film becomes too soft and handling properties may be deteriorated.

It is preferable to add a surfactant to the stock solution for the purpose of improving the peelability from the dry roll in producing the PVA polymer film and handling property of the resulting PVA polymer film. The kind of the surfactant is not particularly limited, but an anionic surfactant or a nonionic surfactant is preferably used.

As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfuric acid ester type such as octyl sulfate and a sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate are preferable.

Examples of the nonionic surfactant include alkyl ether types such as polyoxyethylene oleyl ether and the like, alkylphenyl ether types such as polyoxyethylene octylphenyl ether and the like, alkyl ester types such as polyoxyethylene laurate, Alkyl amines such as polyoxyethylene lauryl amino ether, alkyl amides such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, diethanol amide laurate, diethanol oleate Amide and the like, and allylphenyl ether type nonionic surfactants such as polyoxyalkylene allylphenyl ether are preferable. These surfactants may be used singly or in combination of two or more kinds.

The amount of the surfactant to be added is preferably 0.01 to 1 part by mass, more preferably 0.02 to 0.5 part by mass, and particularly preferably 0.05 to 0.3 part by mass, relative to 100 parts by mass of the PVA polymer. When the amount is less than 0.01 part by mass, the effect of improving the film formability and peelability may not be exhibited well. On the other hand, if the amount is more than 1 part by mass, the surfactant may elute on the surface of the film to cause blocking, .

The film-forming raw material may contain various additives such as a stabilizer (for example, an antioxidant, an ultraviolet absorber, a heat stabilizer, etc.), a compatibilizing agent, an antiblocking agent , A flame retardant, an antistatic agent, a lubricant, a dispersant, a fluidizing agent, an antibacterial agent, and the like. These additives may be used singly or in combination of two or more.

The volatile fraction of the film forming stock solution used in the production of the PVA polymer film is preferably 60 to 75 mass%, more preferably 65 to 70 mass%. If the volatilization rate of the stock solution is less than 60% by mass, the viscosity of the stock solution tends to be high, which makes filtration and defoaming difficult, and in some cases, the film formation itself becomes difficult. On the other hand, if the volatile fraction of the stock solution is larger than 75 mass%, the viscosity becomes too low, and the uniformity of the thickness of the PVA polymer film may be impaired.

Here, the " volatile fraction of the stock solution for film formation " in this specification means the volatile fraction obtained by the following formula [iii].

(% By mass) = {(W _a - W _b ) / W _a } × 100 [iii]

(G), W _a represents the mass (g) of the film-forming stock solution, and W _b represents the mass (g) after drying the film-forming stock solution of W _a (g) in a heat transfer dryer at 105 ° C for 16 hours.

In the film-forming apparatus having a plurality of drying rolls whose rotation axes are parallel to each other and used in the production of the PVA polymer film, the number of the drying rolls is preferably 3 or more, more preferably 4 or more, Is more preferable. The plurality of drying rolls are preferably formed of a metal such as, for example, nickel, chrome, copper, iron, stainless steel, and the like. In particular, the roll surface is not corroded well and is formed of a metallic material having mirror- Is more preferable. Further, in order to enhance the durability of the drying roll, it is more preferable to use a single layer or a combination of two or more layers of a dry roll plated with a nickel layer, a chromium layer, a nickel / chromium alloy layer or the like.

The roll surface temperature of each drying roll in a plurality of drying rolls is preferably 65 ° C or higher, more preferably 75 ° C or higher, and still more preferably 85 ° C or higher. The roll surface temperature of each drying roll is preferably 90 to 130 DEG C, more preferably 100 to 120 DEG C, relative to the roll surface temperature of the drying roll which can be used as a heat treatment roll in the final step or a process close thereto However, the roll surface temperature of the other drying rolls is preferably 100 ° C or lower.

The film forming apparatus used in the above manufacturing method may have a hot air drying type hot air drying apparatus, a heat treatment apparatus, a humidity control apparatus, and the like, in succession to a plurality of drying rolls, if necessary.

In the film-forming step of discharging the film-forming stock solution containing the PVA polymer onto the first drying roll of the film-forming apparatus, for example, a known film phase such as a T-shaped slit die, a hopper plate, an I- Using the discharge device (film-like flexible device), the film-forming raw material liquid containing the PVA polymer is discharged (smoothed) onto the first drying roll in a film form.

The stock film stock solution containing the PVA polymer discharged in the form of a film on the first drying roll is dried on the first drying roll so that the volatile fraction of the PVA polymer film is preferably 16 to 30 mass% 29% by mass, more preferably 18% by mass to 28% by mass, from the first drying roll.

It is possible to suppress the value of? N (MD) _Ave from becoming excessively large because the volatilization fraction of the PVA polymer film at the time of peeling from the first drying roll is equal to or more than the above lower limit. On the other hand, if the volatile fraction of the PVA polymer film at the time of peeling from the first drying roll is excessively high, the peeling from the first drying roll tends to become difficult, and in some cases, the peeling or unevenness tends to occur .

Here, the " volatile fraction of the PVA polymer film or PVA polymer film " in this specification means the volatile fraction obtained by the following formula [iv].

A (mass%) = {(W _c - W _d ) / W _c } × 100 [iv]

(In mass%) of the PVA polymer film or the PVA polymer film, W _c is the mass (g) of the sample collected from the PVA polymer film or the PVA polymer film, W _d is the mass (G) when the sample W _c (g) is dried in a vacuum dryer at a temperature of 50 캜 and a pressure of 0.1 ㎪ or less for 4 hours.

In a PVA polymer film or a PVA polymer film formed from a PVA polymer, a polyalcohol such as glycerin (plasticizer), a surfactant, and water, the above-mentioned " Time ", only water is mainly volatilized, and most of the components other than water are not volatilized and remain in the PVA polymer film or the PVA polymer film. Therefore, the volatilization of the PVA polymer film or the PVA polymer film The fraction can be obtained by measuring the moisture content (water content) contained in the PVA polymer film or the PVA polymer film.

In drying in the first drying roll, the roll surface temperature of the first drying roll is preferably 80 to 120 ° C, more preferably 85 ° C or more in terms of uniform drying and drying speed More preferably 90 占 폚 or higher, further preferably 105 占 폚 or lower, and even more preferably 99 占 폚 or lower. If the surface temperature of the first drying roll exceeds 120 ° C, the film tends to foam easily. On the other hand, when the surface temperature is lower than 80 ° C, drying on the first drying roll tends to become insufficient, .

The peripheral velocity (S ₁ ) of the first drying roll is preferably 8 to 25 m / min, because the PVA polymer film of the present invention is more easily produced, in addition to the uniform drying, the drying rate and the productivity of the PVA polymer film, minutes is preferred, and art peripheral speed (S ₁₎ is 10 more preferably at least m / min, more preferably not less than 12 m / min, and, 23 m / min is preferable, and 22 m / min or less than or less Is more preferable. If the peripheral velocity S ₁ of the first drying roll is less than 8 m / min, productivity tends to decrease and birefringence tends to increase. On the other hand, if the peripheral speed exceeds the first (S ₁₎ is 25 m / min in the drying roll tends to dry on the first drying roll insufficient.

The partial drying of the film-forming stock solution containing the PVA polymer discharged in the film form on the first drying roll may be performed only by the heat from the first drying roll, but it is heated by the first drying roll and is contacted with the first drying roll It is preferable that hot air is sprayed onto the surface of the PVA polymer film (hereinafter referred to as the "first dry roll noncontact surface") and heat is applied from both sides of the PVA polymer film to perform drying, .

In spraying the hot air onto the non-contact surface of the first dry roll of the PVA polymer film on the first dry roll, it is preferable to spray hot air at an air velocity of 1 to 10 m / sec to the entire area of the first dry roll non- More preferably 2 to 8 m / second, and more preferably 3 to 8 m / second.

If the air velocity of the hot air blown onto the non-contact surface of the first dry roll is too small, the PVA polymer film having a high critical limiting magnification factor, which is the object of the present invention, can not be obtained well. Condensation such as water vapor occurs, and the water droplets are dropped on the PVA polymer film, and defects in the finally obtained PVA polymer film are liable to occur. On the other hand, if the air velocity of the hot air blown onto the non-contact surface of the first drying roll is excessively large, a PVA polymer film having a high critical stretch ratio, which is the object of the present invention, can not be obtained well and the PVA polymer film Thickness irregularity occurs, and troubles such as occurrence of uneven dyeing are likely to occur.

The temperature of the hot air blown onto the non-contact surface of the first dry roll of the PVA polymer film is preferably from 50 to 150 ° C, more preferably from 70 to 120 ° C, from the viewpoint of drying efficiency and uniformity of drying, To 95 < 0 > C. It is also preferable that the dew point temperature of the hot air jetted onto the non-contact surface of the first dry roll of the PVA polymer film is 10 to 15 占 폚. If the temperature of the hot air blown onto the non-contact surface of the first dry roll of the PVA polymer film is too low, the drying efficiency and uniform drying tend to deteriorate. On the other hand, if the temperature is too high, foaming tends to occur.

The method for spraying the hot air onto the non-contact surface of the first dry roll of the PVA polymer film is not particularly limited, and hot air having uniform air velocity and uniform temperature is applied to the first dry roll non-contact surface of the PVA polymer film, And a nozzle system, a rectification plate system, or a combination thereof is preferably employed among them. The direction of hot air blowing to the non-contact face of the first dry roll of the PVA polymer film may be opposite to the direction of the contact face of the first dry roll, 1) a direction substantially following the circumference of the roll surface of the dry roll), or may be other direction.

In drying the PVA polymer film on the first drying roll, it is preferable to discharge the volatile matter generated from the PVA polymer film by drying and hot air after spraying. The exhausting method is not particularly limited, but it is preferable to adopt an exhausting method in which the unevenness of the speed of the hot air blown onto the non-contact surface of the first dry roll of the PVA polymer film and the temperature unevenness do not occur.

The PVA polymer film dried on the first drying roll, preferably to a volatile fraction of 16 to 30 mass%, is peeled from the first drying roll, and this time, the first drying roll non-contact surface of the PVA polymer film is opposed to the second drying roll And dried on the second drying roll.

The ratio (S ₂ / S ₁ ) of the peripheral speed (S ₂ ) of the second drying roll to the peripheral speed (S ₁ ) of the first drying roll is preferably 1.005 to 1.090, more preferably 1.010 to 1.080. If the ratio (S ₂ / S ₁ ) is less than 1.005, the peeling point of the PVA polymer film from the first drying roll tends to become uneven, and the non-uniformity of the birefringence in the width direction tends to become large. When the ratio (S ₂ / S ₁ ) exceeds 1.090, it tends to be difficult to satisfy the ratio (S _L / S ₁ ) described later.

In the second drying roll, the roll surface temperature of the second drying roll is preferably 65 to 100 DEG C, more preferably 75 to 98 DEG C, and most preferably 85 to 98 DEG C in terms of uniform drying, Deg.] C to 96 [deg.] C.

The PVA polymer film dried in the second drying roll is peeled off from the second drying roll, and the third drying roll, the fourth drying roll, the fifth drying roll, etc., depending on the number of the drying rolls formed in the film forming apparatus, , And the like.

In the above manufacturing method, the ratio (S _L / S ₁ ) of the peripheral speed (S _L ) of the final drying roll to the peripheral speed (S ₁ ) of the _first drying roll is set to 0.955 to 0.980, Drying is performed while adjusting the applied tension. By setting the ratio (S _L / S ₁ ) within the above-mentioned range, the birefringent index of the film in the longitudinal direction (MD) the values averaged in the thickness direction [Δn (MD) _Ave] and a value [Δn (TD) _Ave] is, the above formula (I) and (II) averaging the birefringence in the transverse direction (TD) in the thickness direction of the film Of the PVA polymer film of the present invention can be smoothly produced.

The ratio (S _L / S ₁ ) in the production of the PVA polymer film is preferably 0.975 or less, more preferably 0.970 or less, and even more preferably 0.960 or less.

In the above-mentioned production method, when the film forming liquid discharged in the form of a film on the first drying roll is successively dried in a plurality of drying rolls, when the volatile fraction of the PVA polymer film becomes 20 mass% (1 - H ₉ / H ₂₀ ) × 100) calculated from the film width (H ₉ ) of the PVA polymer film when the film thickness (H ₂₀ ) and the volatile fraction of the PVA polymer film become 9 mass% %) Is set to 1% or more. (MD) _Ave ] obtained by averaging the birefringent index in the longitudinal direction (MD) in the film thickness direction and a value [Delta] n (TD) obtained by averaging the birefringent index in the width direction (TD) _Ave ], the PVA polymer film of the present invention satisfying the above-mentioned formulas (I) and (II) can be smoothly produced. From the standpoint of more smoothly producing the PVA polymer film of the present invention, the shrinkage ratio is preferably 1.5% or more, more preferably 2% or more. On the other hand, if the shrinkage percentage is too high, sagging and winding of the film tend to occur, and the processability tends to be poor. Therefore, the shrinkage percentage is preferably 4% or less, more preferably 3.5% More preferable. There is no particular limitation on the shrinkage percentage in the above-mentioned range. For example, there is a method of gradually narrowing the film width while maintaining the end portion of the PVA film between neighboring drying rolls, , A method of making the distance between neighboring drying rolls relatively long, and the like.

From the viewpoint that the PVA polymer film of the present invention can be produced more smoothly, it was confirmed that the volatile fraction of the PVA polymer film was 9 mass% from the dry roll when the volatile fraction of the PVA polymer film became 20 mass% , It is preferable that the average value of the surface temperatures of the respective drying rolls (all the drying rolls present in the section) up to the drying roll at the time of drying is 85 ° C or higher, more preferably 87 ° C or higher, Or more, more preferably 93 ° C or higher, further preferably 100 ° C or lower, and more preferably 95 ° C or lower. Here, "the drying roll when the volatile fraction of the PVA polymer film becomes 20 mass%" and "the drying roll when the volatile fraction of the PVA polymer film becomes 20 mass%" means that the volatile fraction of the PVA polymer film is 20% by mass and 9% by mass, respectively, of the PVA polymer film. When the PVA polymer film is formed using a film forming apparatus having a plurality of drying rolls, the PVA polymer film generally has a volatile fraction of less than 20% by mass in the dry roll, 9% by mass, the dry roll on the upstream side is referred to as " a dry roll when the volatile fraction of the PVA polymer film becomes 20% by mass " or " when the volatile fraction of the PVA polymer film becomes 9% Dry roll " of the present invention.

In the above production process, the final drying roll or the final drying roll and the final drying roll may be used as a heat treatment roll at a higher surface temperature. When the dry roll is used as a heat treatment roll, the roll surface temperature is preferably 90 to 130 캜, and more preferably 100 to 120 캜.

The PVA polymer film subjected to the above-mentioned drying treatment may be subjected to heat treatment, humidity treatment or the like, if necessary, and finally rolled in a roll to a predetermined length to obtain the PVA polymer film of the present invention.

The volatile fraction of the PVA polymer film finally obtained by the above series of treatments is preferably in the range of 1 to 5 mass%, more preferably in the range of 2 to 4 mass%.

The use of the PVA polymer film of the present invention is not particularly limited, but the PVA polymer film of the present invention has a high critical stretching magnification, whereby even when the stretched film is uniaxially stretched at the high magnification, A polarizing film, a retardation film, or the like is used in view of the fact that a stretched thin film having excellent optical performance can be produced at a high yield and with good productivity without causing a break in the stretching operation due to breakage of the film As a raw film for producing an optical film of the present invention. Such an optical film can be produced, for example, by performing a treatment such as uniaxial stretching using the PVA polymer film of the present invention.

In producing the polarizing film from the PVA polymer film of the present invention, the PVA polymer film of the present invention can be used for dyeing and uniaxially stretching. For example, the PVA polymer film of the present invention can be used for dyeing, Uniaxial stretching, fixing treatment, drying treatment, and heat treatment if necessary. The order of dyeing and uniaxial stretching is not particularly limited and may be a dyeing treatment before uniaxial stretching treatment, a dyeing treatment simultaneously with uniaxial stretching treatment, or a dyeing treatment after uniaxial stretching treatment . The uniaxial stretching, dyeing, and the like may be repeated a plurality of times. In particular, it is preferable to divide the uniaxial stretching into two or more stages, since uniform stretching can be easily performed.

Dyes used in the dyeing of PVA polymer films include iodine or dichroic organic dyes (e.g. DirectBlack 17, 19, 154; DirectBrown 44, 106, 195, 210, 223; DirectRed 2, 23, 28, 31 , Direct Blue 9, 12, 51, 98, Direct Green 9, 12, 51, 98, 37, 39, 79, 81, 240, 242, 247, DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, Dichromatic dyes such as Direct Yellow 8, 12, 44, 86, 87, Direct Color 26, 39, 106, 107, etc.). These dyes may be used singly or in combination of two or more. The dyeing can be usually carried out by immersing the PVA polymer film in a solution containing the dye, but the treatment conditions and the treatment method are not particularly limited.

The PVA polymer film of the present invention is particularly preferable in such a case because the PVA polymer film of the present invention has a high critical stretching magnification even when a stretching method at a relatively high stretching ratio is employed at the time of dyeing. The stretching magnification at the completion of dyeing is preferably at least 3 times, more preferably at least 3.4 times, and more preferably at least 3.5 times, from the viewpoint of improving the polarizing performance of the obtained polarizing film and the like based on the length of the original PVA polymer film And more preferably 5 times or less.

The uniaxial stretching can be carried out by either a wet stretching method or a dry heat stretching method, but from the viewpoint of the stability of the performance and quality of the obtained polarizing film, the wet stretching method is preferable. Examples of the wet stretching method include a method of stretching a PVA polymer film in an aqueous solution containing various components such as pure water, an additive and an aqueous medium, or an aqueous dispersion in which various components are dispersed, Specific examples of the axial stretching method include a method of uniaxial stretching in hot water containing boric acid, a method of uniaxial stretching in a solution containing the dye or in a fixed treatment bath to be described later, and the like. The uniaxial stretching is preferably carried out in the longitudinal direction (MD) of the PVA polymer film.

The stretching temperature in the uniaxial stretching treatment is not particularly limited. In the case of the wet stretching method, the stretching temperature is preferably in the range of 30 to 90 占 폚, more preferably in the range of 40 to 70 占 폚, And more preferably in the range of 50 to 180 DEG C in the dry heat stretching method.

It is preferable that the stretching magnification (uniaxial stretching ratio in the case of uniaxial stretching in multiple stages) of the uniaxial stretching process is as long as possible until the film is cut off from the viewpoint of the polarization performance, and specifically, More preferably 5 times or more, and still more preferably 5.5 times or more. The upper limit of the draw ratio is not particularly limited as long as the film does not break, but it is preferable that the upper limit of the draw ratio is 8.0 times or less for uniform drawing.

The thickness of the stretched film (polarizing film) is preferably 1 to 35 탆, more preferably 5 to 25 탆.

In the production of the polarizing film, in order to strengthen the adsorption of the dye to the uniaxially stretched film, fixing processing is often performed. As the fixing treatment, a method of immersing a film in a treatment bath to which boric acid and / or a boron compound is added is generally widely used. At that time, if necessary, an iodine compound may be added to the treatment bath.

It is preferable that the film subjected to the uniaxial stretching treatment or the uniaxial stretching treatment and the fixing treatment is continuously subjected to a drying treatment (heat treatment). The temperature of the drying treatment (heat treatment) is preferably 30 to 150 ° C, particularly preferably 50 to 140 ° C. If the temperature of the drying treatment (heat treatment) is too low, the dimensional stability of the obtained polarizing film tends to be deteriorated. On the other hand, if the temperature is too high, the polarizing performance tends to be deteriorated due to decomposition of the dye.

A polarizing plate can be formed by adhering a protective film having optically transparent and mechanical strength to both sides or one side of the polarizing film obtained as described above. As the protective film in this case, a cellulose triacetate (TAC) film, an acetic acid-butyric acid cellulose (CAB) film, an acrylic film, a polyester film or the like is used. As the adhesive for bonding the protective film, a PVA adhesive, a urethane adhesive, or the like is generally used, and among them, a PVA adhesive is preferably used.

The polarizing plate obtained as described above can be used as a component of a liquid crystal display device after being coated with a pressure-sensitive adhesive such as acrylic or the like and then bonded to a glass substrate. The retardation film, the viewing angle improving film, the luminance improving film, and the like may be simultaneously applied at the time of bonding the polarizing plate to the glass substrate.

Example

Hereinafter, the present invention will be described concretely with reference to Examples, but the present invention is not limited at all by the following Examples.

In the following Examples and Comparative Examples, the volatile fraction of the stock solution, the volatile fraction (moisture content) of the PVA polymer film or the PVA polymer film, and the physical properties of the PVA polymer film were measured by the following methods.

(1) Volatilization fraction of the film-forming solution:

Was obtained by the above-mentioned formula [iii].

(2) Volatile fraction of PVA polymer film or PVA polymer film (moisture content):

Was obtained according to the above-mentioned formula [iv]. The volatile fraction (moisture content) of the PVA polymer film or the PVA polymer film is measured using a sample collected from the central portion in the width direction (TD) of the PVA polymer film or the PVA polymer film taken out from the drying roll Respectively.

(3)? N (MD) of the PVA polymer film _Ave :

In a PVA Δn (MD) _Ave at the central portion in the width direction (TD) of the polymer film in the item of "" 1 "Δn (MD) method of measuring the _Ave" obtained by the above method, of this PVA-based polymer film Δn (MD) _Ave.

(4)? N (TD) of the PVA polymer film _Ave :

In a PVA Δn (TD) _Ave at the central portion in the width direction (TD) of the polymer film in the item of "" 2 "Δn (TD) measurement of _Ave" obtained by the above method, of this PVA-based polymer film Δn (TD) _Ave.

(5) Mass swelling degree of PVA polymer film:

The PVA polymer film was cut to 1.5 g and immersed in 1000 g of distilled water at 30 캜 for 30 minutes. After immersing for 30 minutes, the PVA polymer film was taken out. The surface of the PVA polymer film was washed with water, _e ) were measured. Subsequently, the PVA polymer film was dried in a dryer at 105 캜 for 16 hours, and its mass (W _f ) was measured. From the obtained masses (W _e and W _f ), the degree of mass swelling of the PVA polymer film was determined by the following formula (vi).

Mass swelling degree (%) = (W _e / W _f ) × 100 [vi]

(6) Limit draw ratio and polarizing film width of PVA polymer film:

(MD) x width direction (TD) = 10 cm x 5 cm from the central portion of the PVA polymer film obtained in the following Examples or Comparative Examples in the width direction (TD) of the test piece Both ends in the longitudinal direction were fixed to the stretching jig so that the stretched portion had a size in the machine direction (MD) x width direction (TD) = 5 cm x 5 cm, and while immersed in water at 30 deg. C for 38 seconds, (First stage stretching) in the longitudinal direction (MD) at a stretching speed of 2.2 times the original length at a stretching speed of 30 m / min at a temperature of 30 DEG C containing 0.03 mass% of iodine and 3 mass% of potassium iodide, (Second-stage stretching) in the longitudinal direction (MD) to 3.5 times the original length at a stretching speed of 12 cm / min while immersing in an aqueous solution of potassium iodide for 90 seconds, followed by 3 mass% boric acid and potassium iodide A concentration of 3% by mass (3-stage stretching) in the longitudinal direction (MD) to 3.9 times the original length at a stretching speed of 12 cm / minute while immersing the substrate in a boric acid / potassium iodide aqueous solution at a temperature of 30 캜 containing about 30 seconds And then immersed in an aqueous solution of boric acid / potassium iodide at a temperature of about 63 캜 containing boric acid at 4% by mass and potassium iodide at a concentration of about 5% by mass, while being stretched at a draw rate of 12 cm / ), And the drawing magnification (ratio of the length at the time of breaking to the original length) when the test piece was broken and the width of the test piece at the time of breaking were read.

The same PVA polymer film was subjected to the aforementioned stretching test five times, and the average value thereof was taken as the limiting stretching magnification (times) of the PVA polymer film and the polarizing film width.

(7) Delivery of neck of PVA polymer film

The neck lead of the PVA polymer film was determined from the following formula [vii] from the limit stretching magnification, the polarizing film width and the film width before stretching (5 cm) obtained from the sample collected by the above method.

Neck Lead = polarizing film width ÷ (film width before stretching ÷ threshold stretching ratio) [vii]

Here, the higher the value of the neck lead, the wider the polarizing film width relative to the limiting draw ratio, and the larger the polarizing film area that can be collected.

[Example 1]

(1) Production of PVA polymer film:

(i) 100 parts by mass of PVA (saponification degree: 99.9 mol%, degree of polymerization: 2400) obtained by saponifying polyvinyl acetate, 12 parts by mass of glycerin, 0.1 part by mass of diethanolamide laurate and 66% by mass of water, T-die in the form of a film on a first drying roll (surface temperature: 93 캜, peripheral speed (S ₁ ) 16.0 m / min) of a film forming apparatus having a plurality of drying rolls whose axes of rotation were parallel to each other, On the roll, hot air of 90 占 폚 was blown onto the entire first dry roll non-contact surface at an air velocity of 5 m / sec while being dried until the volatile fraction became 21 mass%, then peeled off from the first dry roll, Thereafter, the resultant was further dried in a subsequent drying roll, and then subjected to heat treatment in a drying roll (heat treatment roll) having a surface temperature of 102 DEG C and then taken up to obtain a PVA polymer film (thickness: 60 m, width 3 m, %) Was obtained .

In this Example 1, the ratio (S _L / S ₁ ) of the peripheral speed (S _L ) of the final drying roll to the peripheral speed (S ₁ ) of the _first drying roll was set to 0.958. When the volatile fraction became 20 mass% (1 - H ₉ / H ₂₀ ) × 100) calculated from the film width (H ₂₀ ) of the PVA polymer film of the PVA polymer film and the film width (H ₉ ) of the PVA polymer film when the volatile fraction became 9 mass% 2.03%, the surface temperature of each dry roll up to the dry roll when the volatile fraction of the PVA polymer film was 9 mass% from the dry roll when the volatile fraction of the PVA polymer film became 20 mass% Was set at 90.0 ° C.

(MD) _Ave , Δn (TD) _Ave , mass swelling degree, limiting draw ratio and neck lead of the PVA polymer film obtained in the above (i) were measured by the above-mentioned method. It was like.

[Examples 2 and 3 and Comparative Examples 1 to 3]

(1) A PVA polymer film was produced in the same manner as in (1) of Example 1 except that the film forming conditions in the production of the PVA polymer film in Example 1 were changed as shown in the following Table 1 Respectively.

The Δn (MD) _Ave , Δn (TD) _Ave , the mass swelling degree, the limiting draw ratio and the neck lead of each of the PVA polymer films thus obtained were measured by the above-mentioned method, and the results are shown in Table 1 below.

As shown in Table 1 above, the PVA polymer films of Examples 1 to 3 have Δn (MD) _Ave [value obtained by averaging the birefringence of the PVA polymer film in the machine direction of the film in the thickness direction] and (I) and (II) satisfy the relation of DELTA n (TD) _Ave (the value obtained by averaging the birefringence in the width direction of the PVA polymer film in the thickness direction of the film) And the temperature at the time of stretching after the completion of the third stage of stretching was set to about 63 DEG C which is relatively high, all of them exhibited a high limit stretching magnification and exhibited a high neck drawability. Thus, the PVA polymer By using a film, it can be seen that a stretched film such as a polarizing film excellent in optical performance such as polarization performance can be produced with good productivity at a high yield, at a low cost, without stopping the stretching operation The.

On the contrary, since the PVA polymer films of Comparative Examples 1 to 3 do not satisfy the formulas (I) and (II), the PVA polymer films of Comparative Examples 1 to 3 all had the limiting draw ratio and the neck lead Respectively.

Claims (10)

A polyvinyl alcohol polymer film characterized by satisfying the following formulas (I) and (II).
? N (MD) _Ave ? 1.3 占^10-3 (I)
? N (TD) _Ave ? 1.3 占^10-3 (II)
(MD) _Ave represents a value obtained by averaging the birefringence of the polyvinyl alcohol polymer film in the machine direction of the film in the thickness direction of the film, and? N (TD) _Ave represents a value obtained by multiplying the polyvinyl alcohol polymer Represents a value obtained by averaging the birefringence index in the width direction of the film in the thickness direction of the film. The method according to claim 1,
Wherein the thickness is within a range of 10 to 65 占 퐉. 3. The method according to claim 1 or 2,
A polyvinyl alcohol-based polymer film which is an original film for optical film production. The method of claim 3,
Wherein the optical film is a polarizing film. A method for producing a polyvinyl alcohol-based polymer film,
(a) a film-forming apparatus having a plurality of drying rolls whose rotating shafts are parallel to each other is used, and a film-forming stock solution containing a polyvinyl alcohol polymer is discharged onto a first drying roll of the film-forming apparatus and partially dried Followed by further drying with a drying roll followed by film formation; At that time,
(b) the ratio (S _L / S ₁ ) of the peripheral speed (S _L ) of the final drying roll to the peripheral speed (S ₁ ) of the _first drying roll is set to 0.955 to 0.980;
(c) the film width (H ₂₀ ) of the polyvinyl alcohol polymer film when the volatile fraction became 20 mass% and the film width (H ₉ ) of the polyvinyl alcohol polymer film when the volatile fraction became 9 mass% (1 - H ₉ / H ₂₀ ) × 100) (%) of the polyvinyl alcohol-based polymer film is 1% or more. 6. The method of claim 5,
From the drying rolls when the volatile fraction of the polyvinyl alcohol polymer film becomes 20 mass%, the surface temperature of each drying roll up to the drying roll when the volatile fraction of the polyvinyl alcohol polymer film becomes 9 mass% Is 85 占 폚 or higher. A method for producing a polyvinyl alcohol-based polymer film, The method according to claim 5 or 6,
Wherein the volatile fraction of the stock solution is 60 to 75% by mass. 8. The method according to any one of claims 5 to 7,
A first peripheral speed (S ₁₎ to 8 ~ 25 m / min, method of producing a polyvinyl alcohol polymer film according to the drying rolls. An optical film produced from the polyvinyl alcohol-based polymer film according to claim 3. 10. The method of claim 9,
Polarizing film.

Images