KR20140130363A - Polyvinyl alcohol-type polymer film and method for producing same - Google Patents

Abstract

(assignment)
A PVA polymer film capable of producing a polarizing film having a high absorbance of a long wavelength region and a high degree of polarization, and a process for producing the same.
(Solution)
A PVA polymer film having a crystal length cycle in water of 14.5 to 16.0 nm. When a PVA polymer film is produced by using a film production apparatus having a plurality of drying rolls and heat treatment rolls whose rotation axes are parallel to each other, the film is dried so that T _{1 → 2} represented by the formula (I) is 60 to 75 By weight based on the total weight of the PVA polymer film.
_{T 1 → 2 = {T 1} × (40-V 1) + T 2 × (V 1 -V 2)} / (40-V 2) (I)
(T ₁ is the first surface temperature (℃) of the drying roll, V ₁ is the first-volatile content ratio (% by weight of the film at the time of separation from the drying rolls; a is only 10 ~ 30), T ₂ is the second drying (° C) of the surface temperature of each drying roll from the roll to the final drying roll, and V ₂ represents the volatile content (% by mass) of the film at the time of peeling from the final drying roll.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyvinyl alcohol polymer film,

The present invention relates to a polyvinyl alcohol polymer film (hereinafter sometimes referred to as " PVA "), a process for producing the same, and a polarizing film produced from the PVA polymer film. More specifically, the present invention relates to a PVA polymer film capable of producing a polarizing film having a high absorbance of a long wavelength region and a high degree of polarization, a method of producing the same, and a method of producing the PVA polymer film having an absorbance in a long wavelength region And a polarizing film having a high degree of polarization.

A polarizing plate having light transmission and shielding functions is a fundamental component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The application fields of this LCD are also widely used in small-sized devices such as electronic calculators and wrist watches in the early development stage and recently in the fields of laptop PCs, word processors, liquid crystal projectors, vehicle navigation systems, liquid crystal televisions, personal telephones, And so on. With the expansion of the application field of such an LCD, a polarizing plate of a neutral gray color excellent in color has been demanded in order to improve the polarizing performance and to improve the color display quality.

The polarizing plate is generally produced by uniaxially stretching a monoaxial stretched or dyed monoaxially stretched polymer film and then fixing the monoaxially stretched film with a boron compound (in some cases, two or more (TAC) film or acetic acid-butyric acid cellulose (CAB) film is stuck to the obtained polarizing film.

For the purpose of improving the color of the polarizing film, studies have been conducted mainly from the viewpoints of the structure of the PVA-based polymer or the PVA-based polymer film as a raw material for producing the polarizing film and the manufacturing conditions for producing the polarizing film . For example, a modified PVA film having a polymerization degree of 1,500 to 5,000, an ethylene unit content of 1 to 4% by mole and a 1,2-glycol bond content of 1.4% by mole or less, and a YI value of 20 or less, A polarizing film produced by axial stretching and having a b value of 3 or less is known (see Patent Document 1).

Japanese Patent Application Laid-Open No. 2003-342322 Japanese Laid-Open Patent Publication No. 2006-188655

 Polymer, 46, 7436-7442 (2005)  Macromolecules, 39 (8), 2921-2929 (2006)  &Quot; Physics of Polymers " by Scheringer Pearek Tokyo, p. 143-154  Journal of Polymer Science: Polymer Physics Edition, Vol. 18, 1343-1359 (1980)

However, in the conventional polarizing film described in Patent Document 1, there is a case where an optical transition occurs in a liquid crystal display device. It is believed that this variation is caused by the fact that the polarizing film is visually reddish, that is, the absorbance of a long wavelength region (for example, a visible light region of 680 nm or more) of the polarizing film is low. Patent Document 1 does not disclose a means for eliminating the above-mentioned deviation or increasing the absorbance of a long wavelength region while maintaining a high degree of polarization.

It is therefore an object of the present invention to provide a PVA polymer film capable of producing a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization. It is another object of the present invention to provide a process for producing a PVA polymer film in which the PVA polymer film can be smoothly and continuously produced. It is another object of the present invention to provide a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization.

It is considered that the absorbance of the long wavelength region of the polarizing film changes as the crystal structure of the polarizing film changes. The polarizing film is generally produced by immersing the PVA polymer film in water in which various drugs are dissolved in one or two or more of each step such as dyeing, uniaxial stretching, fixing treatment, etc. The PVA polymer film When the PVA polymer film is immersed in water, a part of the crystalline portion of the PVA polymer film is dissolved to increase the size of the noncrystalline portion. That is, the crystal structure of the PVA polymer film in water is different from the crystal structure before immersion in water. The present inventors have focused on the crystal structure of the PVA polymer film in water in order to increase the absorbance of the polarizing film in the long wavelength region. It has been found that a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization can be easily obtained by setting the crystal length period in water as a scale representing the crystal structure within a specific range.

Further, the inventors of the present invention have studied the drying process when the PVA polymer film is produced by drying the film-forming stock solution containing the PVA polymer by means of wide angle X-ray diffraction or DSC, and as a result, It is found that the crystallization of the PVA polymer starts at the time when the volatile fraction of the film becomes about 40 mass%. From this, the film production condition when the volatile fraction of the film in the film production is 40 mass% or less is adjusted , It was thought that the crystal length period in the water of the obtained PVA polymer film could be adjusted. A film production apparatus comprising a plurality of drying rolls and heat treatment rolls whose rotation axes are parallel to each other is used and a film-forming stock solution containing a PVA polymer is placed on a first drying roll located on the most upstream side of the film production apparatus And the PVA polymer film is further dried by a drying roll after the second drying roll succeeding to the first drying roll to the downstream side of the first drying roll so that the volatile fraction of the film during the production of the film is 40 mass% It has been found that the aforementioned PVA polymer film having a crystal length cycle in a specific range in water can be smoothly and continuously produced by setting the average value of the temperature of the drying roll in a specific drying section within a specific range.

Based on the above findings, the present inventors have repeatedly studied to complete the present invention. That is,

(1) A PVA polymer film characterized by having a crystal length cycle in water of 14.5 to 16.0 nm.

Further, according to the present invention,

(2) A film-making apparatus comprising a plurality of drying rolls and heat-treating rolls whose rotation axes are parallel to each other is used, and a film-forming stock solution containing a PVA-based polymer is discharged onto the first drying roll of the film- Dried, and further dried with a subsequent drying roll to form a PVA polymer film, the PVA polymer film is dried so that T _{1? 2} represented by the following formula (I) satisfies the following formula (II) .

T _{1 ? 2} = {T ₁ × (40 - V ₁ ) + T ₂ × (V ₁ - V ₂ )} / (40 - V ₂ ) (I)

60? T _{1 ? 2} ? 75 (II)

(Wherein, T ₁ represents a surface temperature (℃) of the first drying roll, V ₁ is from the second drying roll first represents the volatile matter ratio (% by weight) of the film at the time of separation from the drying roll, T ₂ is V ₂ represents the volatile content (% by mass) of the film at the time of peeling from the final drying roll just before the heat treatment roll, ), Where V ₁ is 10 to 30 (mass%).

Further, according to the present invention,

(3) a polarizing film produced from the PVA polymer film of (1).

According to the present invention, there is provided a PVA polymer film capable of producing a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization. Further, according to the present invention, there is provided a process for producing a PVA polymer film capable of continuously and continuously producing the PVA polymer film. Further, according to the present invention, there is provided a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization.

The PVA polymer film of the present invention has a crystal length cycle in water of 14.5 to 16.0 nm. In general, the crystal length period refers to an average length of one cycle of a repetition period of a crystal portion and randomly distributed random portions in a film, and a size of a crystal portion and a non- (See Patent Document 2). In the present invention, a PVA polymer film capable of producing a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization can be obtained by having a non-conventional constitution in which the crystal length cycle in water is in the above range. From the viewpoint of obtaining a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization, the crystal length period is preferably 14.7 nm or more, more preferably 15.0 nm or more, still more preferably 15.1 nm or more, desirable.

As a method of obtaining the crystal length period and the thickness of the crystal portion, an incineration (small angle) X-ray scattering method is known and described in Non-Patent Documents 1 to 4 and the like. The crystal length period of the PVA polymer film in the present invention in water is determined by the incineration X-ray scattering method. Specifically, as described later in the Examples, By analyzing the PVA polymer film. Here, the PVA polymer film used for measurement is immersed in water (distilled water) at 22 占 폚 for 24 hours. When the PVA polymer film is immersed in water as described above, a part of the crystalline portion of the PVA polymer film is dissolved to increase the size of the noncrystalline portion. Since the equilibrium structure reaches within 24 hours at 22 ° C in water, a PVA polymer film immersed in water at 22 ° C for 24 hours is used for measurement.

Examples of the PVA polymer forming the PVA polymer film include a PVA (unmodified PVA) obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, a modified PVA system 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 polymer, a vinyl ester and a comonomer, a modified PVA polymer obtained by crosslinking a part of the hydroxyl groups of the unmodified PVA or modified PVA polymer with an aldehyde such as formalin, butylaldehyde or benzaldehyde Called polyvinyl acetal resin.

When the PVA polymer forming the PVA polymer film 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 for producing the PVA polymer include vinyl acetate, vinyl formate, vinyl laurate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl stearate and vinyl benzoate. . 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 (e.g.,? -Olefins) having 2 to 30 carbon atoms 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, C1-18 alkyl esters of acrylic acid, etc.); 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 and the like); 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 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, with respect to the upper limit of the average degree of polymerization of the PVA polymer, the average degree of polymerization is preferably 8,000 or less, more preferably 6,000 or less, from the standpoints of ease of production of a homogeneous PVA polymer film and elongation properties.

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 is preferably 95.0 mol% or more, more preferably 98.0 mol% or more, and more preferably 99.0 mol% or more in terms of the polarizing performance and durability of the resulting polarizing film , 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 in terms of the total mole number of the structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit by saponification and the 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 PVA polymer film may contain, in addition to the above PVA polymer, plasticizers, surfactants, various additives other than those described below as an explanation of the production method of the present invention, for example, in an amount described later.

The thickness of the PVA polymer film is not particularly limited, but it is preferably 5 to 80 탆 when used as a disk for polarizing film production. A more preferable thickness is 20 to 80 占 퐉. When the thickness of the PVA polymer film is not more than the upper limit, drying at the time of producing the polarizing film tends to be performed quickly. On the other hand, when the thickness of the PVA polymer film is at least the lower limit, It is possible to more effectively suppress the occurrence of breakage of the film during axial stretching.

The width of the PVA polymer film is not particularly limited. However, since the liquid crystal television and the monitor have become large in recent years, the width of the PVA polymer film is preferably 2 m or more, more preferably 3 m or more And more preferably 4 m or more. 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 length of the PVA polymer film is not particularly limited and may be, for example, 50 to 30000 m.

The retardation value of the PVA polymer film is not particularly limited, but it is preferable that the retardation value is 100 nm or less since the retardation value tends to be improved as the retardation unevenness in the width direction of the polarizing film obtained becomes smaller. The retardation value can be measured by the method described later in Examples.

The PVA polymer film preferably has a mass swelling degree of 180 to 250%, more preferably 185 to 240%, further preferably 190 to 230%. If the mass swelling degree of the PVA polymer film is higher than the lower limit described above, the stretching becomes easy and the polarizing film having excellent polarization performance tends to be easily produced. On the other hand, when the mass swelling degree is lower than the upper limit, And the production of a highly durable polarizing film tends to be easier.

The mass swelling degree as used herein means the percentage of a value obtained by dividing the mass of PVA polymer film immersed in distilled water at 30 캜 for 30 minutes divided by mass after drying at 105 캜 for 16 hours after immersion, And can be measured by the method described later in the examples.

The method for producing the PVA polymer film of the present invention is not particularly limited, but the PVA polymer film of the present invention can be smoothly and continuously produced by the production method of the present invention described below.

Namely, the production method of the present invention for producing the PVA polymer film is characterized in that a plurality of drying rolls (the downstream side from the upstream side, sequentially referred to as the first drying roll, the second drying roll ...) And a heat treatment roll, and the film-forming stock solution containing the PVA polymer is discharged onto the first drying roll of the film production apparatus in the form of a film, dried, and further dried by a subsequent drying roll to obtain a PVA When a polymer film is produced, T _{1 ? 2} represented by the following formula (I) is dried so as to satisfy the following formula (II).

T _{1 ? 2} = {T ₁ × (40 - V ₁ ) + T ₂ × (V ₁ - V ₂ )} / (40 - V ₂ ) (I)

60? T _{1? 2} ? 75 (II)

In the formulas (I) and (II), T ₁ represents the surface temperature (캜) of the first drying roll, V ₁ represents the volatile content (mass%) of the film at the time of peeling from the first drying roll , T ₂ represents an average value (° C) of the surface temperatures of the respective drying rolls from the second drying roll to the final drying roll just before the heat-treating roll, and V ₂ represents the average value (Mass%) of the film at the time of film formation. V ₁ is 10 to 30 (mass%).

As described above, the present inventors have found that the crystallization of the PVA polymer is started when the volatile fraction of the film formed from the film-forming raw liquid reaches about 40% by mass. From this, the volatile fraction of the film in the film production is 40 mass% %, It is considered that the crystal length period in the water of the PVA polymer film obtained can be adjusted. In order to express the average value of the temperature of the dry roll, which is one of these film producing conditions, 1, the surface temperature of the drying roll (T _1), a first volatile content rate of the film at the time of separation from the drying rolls (V _1), a second average value of the surface temperature of each drying roll to final drying rolls from drying rolls (T ₂ ) And the volatile fraction (V ₂ ) of the film at the time of peeling from the final dried roll was used.

The above formula (I) was derived as follows. That is, a film-forming stock solution containing a PVA polymer is discharged in the form of a film on a first drying roll having a surface temperature T ₁ (캜) so that the volatile fraction of the film during film production on the first drying roll is V ₀ (mass%). a through drying until V ₁ (% by weight), the average value of the after peeling off the film from the first drying roll, and the second of the plurality of drying rolls (each drying roll after drying roll surface temperature is T ₂ ( when further dried ℃) a), and the peeling-volatile content rate of the film from the final drying rolls immediately before the heat treatment roll when the V ₂ (mass%), volatile content rate in the volatile content rate V ₀ (mass%) V ₂ ( The average value T _Ave (占 폚) of the surface temperature of the drying roll in the drying section up to the _heating temperature (Tg) (% by mass) can be represented by the following formula (I ').

T _Ave = T ₁ × (V ₀ - V ₁ ) / (V ₀ - V ₂ ) + T ₂ × (V ₁ - V ₂ ) / (V ₀ - V ₂ ) (I ')

Here, when the V ₀ of the formula (I ') is set to be V ₀ = 40 (mass%) in order to adjust the film production conditions when the volatile fraction of the film during the film production is 40 mass% or less, T _Ave Becomes equal to T _{1 ? 2} in the above formula (I).

In the production method of the present invention, it is necessary that the value of T _{1? 2} in the formula (I) satisfies the above formula (II) within the range of 60 to 75. By having T _{1? 2} within this range, it is possible to smoothly and continuously produce the above-mentioned PVA polymer film having a crystal length cycle in water in a specific range. T _{1 → 2} is preferably 61 or more, more preferably 63 or more, further preferably 64 or more, particularly preferably 64.5 or more, and more preferably 65 or more, in view of being able to more easily produce the PVA polymer film. And T _{1? 2} is preferably 72 or less, more preferably 69.5 or less.

In the production method of the present invention, a film production apparatus comprising a plurality of drying rolls and heat treatment rolls whose rotation axes are parallel to each other is used, and a film-forming stock solution containing a PVA polymer on a first drying roll of the film production apparatus Dried in a film form, dried, and further dried on a second roll of drying rolls subsequent to the first roll of the first roll, thereby producing a PVA polymer film. In the film production apparatus, the number of the drying rolls is preferably 3 or more, more preferably 4 or more, and further preferably 5 to 30.

The plurality of drying rolls are preferably formed of a metal such as nickel, chrome, copper, iron, stainless steel, and the like. Particularly, the surface of the drying roll is preferably formed of a metallic material hardly corroded and 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 film can be dried more uniformly with respect to the heating direction at the time of drying the film in the process of reaching the final drying roll immediately before the heat roll from the first drying roll, (Hereinafter sometimes referred to as a "first dry roll contact surface") contacting with a first dry roll and a film surface not contacting the first dry roll (hereinafter referred to as "first dry roll non-contact surface" ) Is preferably dried so as to alternately face each of the drying rolls from the first drying roll to the final drying roll.

If the surface temperature of a plurality of drying rolls is too high, a heat treatment effect is generated in a part of the PVA polymer film and the crystal structure tends to become uneven. When the surface temperature is too low, efficient drying tends to be difficult. Deg.] C, more preferably in the range of 40 to 85 [deg.] C, and still more preferably in the range of 60 to 75 [deg.] C. More specific surface temperatures for the individual dry rolls are preferably as described below.

In the film-forming step of discharging the film-forming stock solution containing the PVA polymer onto the first drying roll of the film-making apparatus, a known film-like film such as a T-shaped slit die, a hopper plate, an I- By using a discharging device (film-like flexible device), the film-forming raw liquid containing the PVA polymer can be discharged (softened) onto the first drying roll in the form of a film.

The film-forming stock solution containing the PVA polymer film can be prepared by mixing the PVA polymer with a liquid medium to prepare a solution, or by melting the PVA polymer pellet including a liquid medium to melt it .

Examples of the liquid medium to be used at this time include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine and diethylenetriamine, , One kind may be used alone, or two or more kinds may be used in combination. 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 raw material for film production from the viewpoints of promotion of dissolution or melting of the PVA polymer in a liquid medium, improvement in processability at the time of production of the PVA polymer film, and improvement in stretchability of the resulting PVA polymer film Do.

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 and trimethylolpropane. The species may be used singly or two or more species may be used in combination. Of these, glycerin, diglycerin, and ethylene glycol are preferable because they have an excellent effect of improving the stretchability.

The addition amount of the plasticizer is preferably 0 to 30 parts by mass relative to 100 parts by mass of the PVA polymer. When the added amount of the plasticizer is 30 parts by mass or less based on 100 parts by mass of the PVA polymer, the obtained PVA polymer film is not excessively soft and the handling property can be suppressed from being lowered. The amount of the plasticizer to be added is more preferably 3 parts by mass or more based on 100 parts by mass of the PVA polymer in view of handling properties of the obtained PVA polymer film and further from the viewpoint that the intended PVA polymer film can be produced more smoothly More preferably 5 parts by mass or more, further preferably 25 parts by mass or less, further preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

It is preferable to add a surfactant to the raw material for film production from the viewpoints 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.

The anionic surfactant is preferably an anionic surfactant such as a carboxylic acid type such as potassium laurate, a sulfuric acid ester type such as octylsulfate or a sulfonic acid type such as dodecylbenzenesulfonate.

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; alkyl ester types such as polyoxyethylene laurate; Alkylamines such as oxyethylene lauryl amino ether, alkyl amides such as polyoxyethylene lauric acid amide, polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether, lauric acid diethanolamide, oleic acid diethanolamide , And allyl phenyl ether type surfactants such as polyoxyalkylene allyl phenyl ether, and the like. These surfactants may be used singly or in combination of two or more.

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 addition amount of the surfactant is 0.01 parts by mass or more based on 100 parts by mass of the PVA polymer, improvement in film composition, peelability and the like are likely to be improved. On the other hand, when the amount is 1 part by mass or less, It is possible to suppress the occurrence of blocking or the deterioration of handling properties.

In addition to the above components, various additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, etc.), compatibilizers, antiblocking agents, flame retardants, antistatic agents, lubricants, dispersants, fluidizers, . These additives may be used singly or in combination of two or more kinds.

The volatile fraction of the film-forming stock solution used in the production of the PVA polymer film is usually 40 mass% or more, preferably 50 to 90 mass%, and more preferably 60 to 80 mass%. If the volatile fraction of the membrane-forming raw solution is too low, the viscosity of the membrane-forming stock solution becomes excessively high, which makes filtration and defoaming difficult, or makes the membrane manufacturing itself difficult. On the other hand, if the volatile fraction of the film-forming stock solution is excessively high, the viscosity becomes too low and the uniformity of the thickness of the PVA polymer film may be impaired.

Here, the " volatile matter content of the film-forming stock solution " in this specification means the volatile matter content determined by the following formula (III).

(% By mass) = {(Wa - Wb) / Wa} x 100 (III)

(G) represents a mass (g) of the film-forming raw liquid, and Wb represents the mass (g) after drying the film-making raw liquid of Wa (g) in a heat transfer dryer at 105 DEG C for 16 hours.

Since the PVA polymer film of the present invention can be more easily produced in drying on the first drying roll of the film-forming stock solution discharged in the film form, the surface temperature (T ₁ ) of the first drying roll is preferably 60 to 90 ° C . From the viewpoint of securing a more stable productivity, the roll surface temperature (T ₁ ) of the first drying roll is more preferably 65 ° C or higher, more preferably 70 ° C or higher, still more preferably 85 ° C or lower, More preferably 80 占 폚 or lower, and particularly preferably 75 占 폚 or lower.

Drying of the film-forming stock solution discharged on the film in the first drying roll may be performed only by heating from the first drying roll. At the same time as heating with the first drying roll, hot air is blown to the non-contact face of the first drying roll, It is preferable to carry out drying by applying heat from both sides of the substrate in view of uniform drying and drying speed.

When blowing hot air onto the non-contact surface of the first drying roll of the film on the first drying roll, it is preferable to blow hot air of 1 to 10 m / sec in the wind speed over the entire area of the non-contact surface of the first drying roll, More preferably 8 m / sec of hot air, and more preferably 3 to 8 m / sec of hot air. If the air velocity of the hot air blown onto the non-contact surface of the first dry roll is excessively small, condensation such as water vapor is generated at the time of drying on the first drying roll, and the water droplets are dropped on the film to cause defects in the finally obtained PVA polymer film There is a possibility of occurrence. On the other hand, if the air velocity of the hot air blown onto the non-contact surface of the first dry roll is excessively large, the PVA polymer film finally obtained will have thickness irregularities, 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 film is preferably 50 to 150 ° C, more preferably 70 to 120 ° C, and more preferably 80 to 95 ° C Is more preferable. If the temperature of the hot air blown to the non-contact surface of the first dry roll of the film is too low, condensation such as water vapor may occur, and the droplet may fall on the film, which may cause defects in the finally obtained PVA polymer film. On the other hand, if the temperature is too high, drying unevenness may occur depending on the direction of the hot air, which may cause unevenness in the thickness of the finally obtained PVA polymer film.

The dew point temperature of hot air blown onto the non-contact surface of the first dry roll of the film is preferably 5 to 20 占 폚, and more preferably 10 to 15 占 폚. If the dew point temperature of the hot air blown to the non-contact surface of the first dry roll of the film is too low, the drying efficiency and uniform drying tend to decrease. On the other hand, if the dew point temperature is too high, foaming tends to occur.

The method for blowing hot air onto the non-contact surface of the first dry roll of the film is not particularly limited, and a hot air having uniform air velocity and uniform temperature can be uniformly sprayed on the non-contact surface of the first dry roll, Any of these methods can be employed, among which a nozzle method, a rectifying plate method, or a combination thereof is preferably employed. The direction of blowing hot air against the non-contact surface of the first dry roll of the film is a direction opposite to the direction of the non-contact surface of the first dry roll, Direction substantially along the circumference of the surface), or may be a direction other than the direction.

In drying the film on the first drying roll, it is preferable that the volatile matter generated from the film by drying and the hot air after blowing out are discharged. The exhausting method is not particularly limited, but it is preferable to employ an exhausting method in which the unevenness of the wind speed and the temperature unevenness of hot air blown onto the non-contact surface of the first dry roll of the film do not occur.

The peripheral speed (S ₁₎ of the drying roll 1 is, in view of drying speed and the PVA-based productivity of the polymer film, preferably 5 ~ 30 m / min. If the peripheral speed of the first (S ₁₎ of the drying roll 5 m / min under tends to be with the productivity is degraded, lowering the stretchability of the PVA-based polymer film is obtained. On the other hand, when the peripheral speed S ₁ of the first drying roll exceeds 30 m / min, the cut surface tends to have a high roughness when both end portions of the film are cut.

The film-forming raw liquid discharged in the form of a film on the first drying roll is dried on the first drying roll, and the volatile fraction of the film (volatile fraction of the film at the time of peeling from the first drying roll; V ₁ (mass%)) And is peeled from the first drying roll at 10 to 30 mass%. If the volatile fraction (V ₁ ) of the film at the time of peeling from the first drying roll is less than 10% by mass, the film passed through the first drying roll becomes hard and the processability is deteriorated. On the other hand, if the volatile fraction (V ₁ ) of the film at the time of peeling from the first drying roll exceeds 30% by mass, the drying on the first drying roll contact side becomes insufficient and the peeling failure tends to occur easily. In view of the above, the volatile fraction (V ₁ ) of the film at the time of peeling from the first drying roll is preferably at least 15 mass%, more preferably at least 18 mass%, even more preferably at least 20 mass% Further, it is preferably 29 mass% or less, more preferably 28 mass% or less, and further preferably 27 mass% or less.

Here, the "volatile matter content of the film" in the present specification means the volatile matter content determined by the following formula (IV).

V (mass%) = {(Wc - Wd) / Wc} x 100 (IV)

Wc is the mass (g) of the sample taken from the film, Wd is the amount of the sample Wc (g) in a vacuum dryer at a temperature of 50 占 폚 and a pressure of 0.1 占 ㎪ or less Mass (g) when dried with time.)

The film dried to the volatile fraction V ₁ on the first drying roll is peeled from the first drying roll and this time preferably the first drying roll non-contact side of the film is opposed to the second drying roll, Dry the film with a dry 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 1.150, more preferably 1.010 to 1.100. If the ratio (S ₂ / S ₁ ) is less than 1.005, it is difficult to peel off from the first drying roll, and the film may be broken. On the other hand, when the ratio (S ₂ / S ₁ ) exceeds 1.150, it tends to be difficult to produce a target PVA polymer film.

The average value (T ₂ ) of the surface temperatures of the respective drying rolls from the second drying roll to the final drying roll immediately before the heat treatment roll (the average value of the surface temperatures of the individual drying rolls) It is preferably 50 to 75 占 폚 in that the film can be produced more smoothly. Particularly, from the viewpoint of ensuring more stable productivity, the average value (T ₂ ) is more preferably 55 ° C or higher, more preferably 60 ° C or higher, still more preferably 70 ° C or lower, and even more preferably 68 ° C or lower.

The volatile fraction (V ₂ ) of the film at the time of peeling from the final drying roll varies depending on the volatile fraction (V ₁ ) of the film at the time of peeling from the first drying roll and the like, but the PVA polymer film (V ₂ ) is preferably not less than 1% by mass, more preferably not less than 3% by mass, further preferably not more than 15% by mass, more preferably not more than 10% by mass And more preferably 9 mass% or less.

In order to more smoothly produce the PVA polymer film of the present invention, 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 0.975 to 1.150 And more preferably 0.980 to 1.100. When the ratio (S _L / S ₁ ) is less than 0.975, the film tends to be loosened between the drying rolls, and when the ratio (S _L / S ₁ ) exceeds 1.150, it is difficult to produce a desired PVA polymer film There is a tendency to lose.

The film thus dried is peeled off from the final drying roll, and heat treatment is carried out by the heat treatment roll on the downstream side thereof. The number of heat treatment rolls may be one, or a plurality of heat treatment rolls may be provided.

The surface temperature of the heat treatment roll is preferably 90 占 폚 or higher, more preferably 95 占 폚 or higher, and even more preferably 100 占 폚 or higher since a PVA polymer film excellent in heat resistance and water resistance can be obtained by appropriately proceeding crystallization. From the viewpoint of improving the stretchability of the obtained PVA polymer film, the surface temperature of the heat treatment roll is preferably 150 ° C or lower, more preferably 130 ° C or lower, and even more preferably 120 ° C or lower.

The heat treatment time is not particularly limited, but is preferably within a range of 3 to 60 seconds, and more preferably within a range of 5 to 30 seconds, in order to produce a desired PVA polymer film more smoothly.

The volatilization rate of the film before being provided to the heat treatment is generally equal to the value of V ₂ . During the heat treatment, the volatile fraction of the film may or may not be changed, either of which may be lower than the value of V ₂ , for example, during the heat treatment. In the production method of the present invention, the average value (T ₂ ) of the surface temperatures of the respective drying rolls from the second drying roll to the final drying roll is preferably 50 to 75 ° C as described above, and the average value (T ₂ ) It is preferable that the surface temperature of each drying roll from the second drying roll to the final drying roll is also within the range of 50 to 75 ° C. When the surface temperature of the heat-treating roll is set to 90 ° C. or higher as described above, Can be clearly distinguished.

The film production apparatus may have a hot air drying apparatus, a humidity control apparatus, or the like, if necessary, and may be subjected to, for example, a humidity treatment after the heat treatment. If necessary, both end portions (ear portions) of the film may be cut.

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 obtained PVA polymer film is preferably rolled into a roll with a predetermined length.

In order to produce a polarizing film from the PVA polymer film of the present invention, for example, the PVA polymer film may be dyed, uniaxially oriented, fixed, dried, and optionally subjected to heat treatment. 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 it is easy to perform uniform stretching.

Dyes used for dyeing PVA polymer films include iodine or dichromatic organic dyes (for example, Direct Black 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270, Direct Violet 9, 12, 28, 31, 37, 39, 79, 81, 240, 242, Direct Blue 1, 85, Direct Yellow 8, 12, 44, 86, 87, Direct Orange 26, 39, 106, 107, etc.). These dyes may be used singly or in combination of two or more. The dyeing can be carried out usually by immersing a PVA polymer film in a solution containing the dye. The treatment conditions and the treatment method are not particularly limited.

The uniaxial stretching in which the PVA polymer film is stretched in the flow direction (MD) or the like may be carried out by either a wet stretching method or a dry heat stretching method. In view of the stability of the obtained polarizing film and the stability of the quality thereof, Do. 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. Concrete 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 later fixed treatment bath, and the like. The film may be uniaxially stretched in air using a PVA polymer film after the absorption, or may be uniaxially stretched by other methods.

The stretching temperature at the time of uniaxial stretching is not particularly limited, but in the case of wet stretching, a temperature within a range of preferably 20 to 90 占 폚, more preferably 25 to 70 占 폚, and still more preferably 30 to 65 占 폚 is employed In the case of dry stretching, the temperature is preferably in the range of 50 to 180 ° C.

The stretching magnification (uniaxial stretching ratio in the case of uniaxial stretching in multiple stages) of the uniaxial stretching treatment is preferably stretched as far as possible until the film is cut off from the viewpoint of the polarization performance, and it is preferably four times or more 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 is not broken, but is preferably 8.0 times or less in order to perform uniform drawing.

In the production of the polarizing film, in order to strengthen the adsorption of the dye to the monoaxially stretched film, fixing treatment is often performed. As a 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 subsequently subjected to a drying treatment (heat treatment). The drying treatment (heat treatment) temperature is preferably 30 to 150 ° C, particularly preferably 50 to 140 ° C. If the drying treatment (heat treatment) temperature 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 accompanied with the decomposition of the dye tends to decrease.

According to the PVA polymer film of the present invention, it is possible to produce a polarizing film which is high in absorbance in a long wavelength region and which is difficult to generate rust. As an index showing the absorbance of the long wavelength region of the polarizing film, the absorbance at a measurement wavelength of 700 nm at a specific transmittance can be adopted. In the polarizing film produced from the PVA polymer film of the present invention, the absorbance (Abs) at a wavelength of 700 nm at a transmittance of 43.5% is preferably 3.0 or more, and particularly preferably 3.1 or more. The absorbance (Abs) can be obtained by the method described later in Examples.

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, a cellulose acetate (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. When the polarizing plate is attached to the glass substrate, the retardation film, the viewing angle improving film, the luminance improving film, and the like may be simultaneously applied.

Example

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

In the following Examples and Comparative Examples, the volatile fractions of the membrane-forming stock solution; The volatile fraction of the film; Surface temperature of drying roll and heat treatment roll; A crystal length cycle, a crystal thickness and an amorphous thickness of the PVA polymer film in water; The retardation value of the PVA polymer film; Mass swelling degree of PVA polymer film; The optical performance of the polarizing film was measured by the following method.

(1) The volatile matter content of the membrane raw material

Approximately 10 g of the film-forming stock solution was taken into a glass-made heat-resistant container, and the heat-resistant container was sealed, and the weight Wa (g) of the film-forming stock solution, excluding the weight of the outer package, was measured to four decimal places. Subsequently, the film-forming stock solution was placed in an electrothermal dryer at a temperature of 105 ° C as a heat-resistant container, and dried for 16 hours with the lid of the heat-resistant container opened. Then, the mass Wb (g) We measured up to four decimal places. From the obtained masses Wa and Wb, the volatile matter content (mass%) of the film-forming stock solution was determined by the above formula (III).

(2) Rate of volatilization of the film

(TD) between the adjacent rolls (between the first drying roll and the second drying roll, or between the final drying roll and the heat-treating roll), about 5 g The film sample of about 5 g cut from the central portion in the width direction (TD) of the obtained PVA film was sealed in a heat-resistant glass container and the mass Wc (g) of the film excluding the weight of the outer package was measured. Were measured up to 4 decimal places. Subsequently, the film was placed in a vacuum dryer at a temperature of 50 占 폚 and a pressure of 0.1 占 or less at the temperature of the heat-resistant container, and dried for 4 hours with the lid of the heat-resistant container being opened for 4 hours. Were measured up to 4 decimal places. From the obtained masses Wc and Wd, the volatile fraction V (mass%) of the film was obtained from the formula (IV).

(3) Surface temperature of the drying roll and the heat treatment roll

Five points of measurement were set in the width direction of the drying roll or heat treatment roll. Specifically, the center in the width direction was used as a center measurement point, and two points were respectively taken at intervals of 10 cm on both sides thereof, and five measurement points were lined up on a straight line. Then, the temperature (° C) of the roll surface of each point was measured up to one decimal place using a non-contact type surface thermometer. The average value of the roll surface temperatures of the respective points was defined as the surface temperature of each dry roll or heat treatment roll.

(4) Crystallization of PVA polymer film in water, length cycle, crystal thickness and non-thickness

In the present invention, with reference to the above-mentioned documents, the crystal length period, the crystal thickness and the non-crystalline thickness were determined while the sample was immersed in water. Here, the crystal length period, the crystal thickness (thickness of the crystal portion), and the non-constant thickness (thickness of the non-crystal portion) are derived from the correlation function K (z) as described in detail below. The correlation function K (z) is given by the Fourier transform of the scattering function obtained by the incineration X-ray scattering method, and is defined as Equation (V).

K (z) α∫ [0 → ∞] {q 2 · I (q) · cos (qz)} · dq (V)

The crystal length period, the crystal thickness and the irregular thickness in the water at the central portion of the PVA film in the width direction (TD) obtained in the following Examples or Comparative Examples were measured in the following " Measurement Method of " 2 " Analytical Method of Crystal Structure ". The crystal length period, the crystal thickness and the irregular thickness are obtained at five points in the middle of the width direction TD of the PVA film in the flow direction MD in consideration of the deviation of the measurement, The values obtained by averaging the five values obtained for each of the crystal thickness and the irregular thickness were taken as the crystal length period in the water of the PVA film, the crystal thickness in the water, and the irregular thickness in the water.

&Quot; 1 " Determination of crystal structure:

A plurality of film samples having a size of MD (flow direction) x TD = 2 cm x 1 cm were cut from the central portion in the width direction (TD) of the PVA film obtained in the following Examples or Comparative Examples. The film sample was laminated in the same direction until the thickness became about 1 mm so that no air bubbles would enter the film sample, and the film sample was immersed in distilled water having a mass ratio of 22 DEG C of about 1000 times for 24 hours. The sample was filled in an underwater measurement cell so that the MD was in the vertical direction, and transmission measurement was performed using a nanoscale X-ray structure evaluation apparatus (incinerating X-ray scattering measurement apparatus) "Nano Viewer" (manufactured by Rigaku Corporation).

The structure of the cell was such that a capton film having a thickness of 7.5 占 퐉 was used as a window material on the incident light side and the reflected light side, and the interval between the window materials was about 1.5 mm so that the sample to be measured could be sealed in water. If the cell is used, the sample can be placed underwater by the arrangement of the normal measurement in the apparatus.

[Measuring conditions]

X-ray: CuK? Ray

Wavelength: 0.15418 nm

Output: 40 kV-20 mA

First slit:? 0.4 mm

Second slit:? 0.2 mm

Third slit: 0.45 mm

Detector: Imaging plate size: 127 mm x 127 mm

Pixel size: 50 占 퐉 占 50 占 퐉

Camera length: 960 mm

X-ray exposure time: 2 hours

Environment temperature: 22 ℃

"2" Analysis of crystal structure:

At first, the dark noise generated by the dark current of the detector was subtracted from each measurement data. The measurement of the dark noise data was performed without X-ray irradiation in exactly the same arrangement as the measurement of the sample.

Incidentally, in the measurement by the incineration X-ray scattering method, since the scattering from the apparatus such as the slit, the air in the X-ray passage portion, and the water in the cell overlaps the scattering of the PVA film, Therefore, in the present invention, among the scattering intensities obtained by measuring samples, the scattering intensities resulting from the above are separately calculated and corrected by deducting from the scattering intensities obtained by measuring the samples.

From the scattering intensity image measured by the two-dimensional detector, the scattering intensity with respect to the scattering vector q was integrated in the azimuth direction, and the relationship between the scattering vector q and the one-dimensional profile of the scattering intensity I (q) was derived to obtain a scattering curve . The scattering intensity in the region where q is 2 nm ^-1 or more was fitted by the least squares method using the constant c, and the obtained constant c was subtracted from the scattering intensity using the obtained constant c as a base line. In addition, since the deviation of the data after correction by the constant c becomes a factor of error in obtaining the correlation function K (z), the least squares fitting using the Gaussian function is performed. The correlation function K (z) was derived by Fourier transform using the scattering curve thus obtained.

The z-coordinate value of the maximum point of the correlation function K (z) derived in the above-described manner is set as a decision length period. Further, a value calculated from an intersection of a straight line passing through a minimum point of the correlation function K (z) and a straight line approximating a slope 0 and a region having a small z is defined as a crystal thickness. Specifically, in the present invention, an intersection of a straight line approximating a correlation function K (z) by a least squares method is obtained for a straight line having an inclination of 0 passing through a minimum point of the correlation function K (z) and a range of z being 1.0 to 2.5 nm , And the z coordinate value of the intersection was defined as the crystal thickness. Further, a value obtained by subtracting the crystal thickness from the crystal length period was calculated as an irregular thickness.

(5) The retardation value of the PVA polymer film

The retardation value was measured over the entire width at a pitch of 50 mm in the width direction using the " KOBRA-WFD " (manufactured by Oji Instruments Co., Ltd., measurement wavelength: 590 nm) , And the average value thereof was defined as the retardation value of the PVA film.

(6) Mass swelling degree of PVA polymer film

The PVA film obtained in the following Examples or Comparative Examples was cut to about 1.5 g and immersed in 1000 g of distilled water at 30 DEG C for 30 minutes. After immersing for 30 minutes, the PVA film was taken out, , And its mass We (g) was measured up to 4 decimal places. Subsequently, the PVA film was dried in a dryer at 105 DEG C for 16 hours, and its mass Wf (g) was measured up to four decimal places. From the masses We and Wf obtained, the degree of mass swelling of the PVA film was determined by the following formula (VI).

Mass swelling (%) = (We / Wf) x 100 (VI)

(7) Optical performance of polarizing film

(i) the degree of polarization at a transmittance of 43.5%

As described in the following examples and comparative examples, in each of the examples and comparative examples, five kinds of polarizing films prepared by changing the iodine concentration in the iodine / potassium iodide / boric acid aqueous solution during the second stage stretching (Y) and the degree of polarization (P) were determined by the following method, and for each of the examples and the comparative examples, five points were measured with the horizontal axis and the polarization degree (P) Was plotted on a graph to prepare an approximate curve. The value of the degree of polarization (P) when the simple transmittance (Y) was 43.5% was determined from the approximate curve, and this value was used as "degree of polarization at transmittance 43.5%".

&Quot; 1 " Measuring method of mass transmittance (Y)

Two samples were taken from the central portion in the width direction of the polarizing film in a square of 4 cm (stretching direction of uniaxial stretching) × 4 cm (direction perpendicular to the stretching direction of uniaxial stretching). For these samples, the transmittance of the light was measured using a spectrophotometer " V-7100 " manufactured by Nippon Shokubai Co., In addition, according to JIS Z 8722 (measurement method of object color), the visibility of the visible region in the 2-degree field of view was corrected using the C light source. For one sheet of a sample, by measuring the light transmittance of the case inclined -45 degrees with respect to the stretching direction of the +45 degree of light transmittance, and a uniaxial stretching in the case inclined with respect to the stretching direction of the uniaxially oriented, their mean value (Y ₁₎ (%). For another sample, the transmittance of light when tilted by +45 degrees and the transmittance of light when tilted by -45 degrees were measured, and their average value (Y ₂ ) (%) was determined. Then, the obtained Y ₁ and Y ₂ were averaged by the following formula (VII) to give a single transmittance (Y) (%) of the polarizing film.

Bulk transmittance (Y) (%) = (Y ₁ + Y ₂ ) / 2 (VII)

&Quot; 2 " Measuring method of polarization degree (P):

(Y //) (%) in the case where the two samples collected in the " Measurement Method of Single Transmittance (Y) " are overlapped so that the stretching directions of their uniaxial stretching become parallel, and their transmittance The transmittance (Y⊥) (%) of light when the stretching directions of the axis elongation were orthogonalized was measured. Transmittance (Y //) and (Y⊥) are the same as in the above-mentioned " measurement method of single transmittance (Y) " And the transmittance and the transmittance of light when tilted at -45 degrees were obtained. The degree of polarization P (%) of the polarizing film was calculated from the transmittance (Y //) and (Y⊥) based on the following formula (VIII).

Degree of polarization (P) (%) = { (Y // - Y⊥) / (Y // + Y⊥)} 1/2 × 100 (VIII)

(ii) Absorbance (Abs) at a wavelength of 700 nm at a transmittance of 43.5%

Initially, as described in the following examples and comparative examples, in each of the examples and comparative examples, five kinds of polarizers prepared by changing the iodine concentration in the iodine / potassium iodide / boric acid aqueous solution during the second stage stretching Absorbance (Abs) at a measurement wavelength of 700 nm was determined for each of the films (all of which had a unit transmittance (Y) in the range of 42 to 44%) as follows. Namely, a Glan Taylor prism was attached to a spectrophotometer "V-7100" manufactured by Nippon Shokuhin Co., Ltd., and one sample of the polarizing film (the "(i) polarization degree at the transmittance of 43.5%" (Arbitrary one of two samples taken for each polarizing film in the " Measurement of Bulk Transmission Rate (Y) ") was used to measure a light beam having a measurement wavelength of 380 to 780 nm which passed through a prism and became linearly polarized The transmittance to light with a wavelength of 700 nm when the sample was transmitted was measured. At this time, the sample is rotated in a plane orthogonal to the optical axis to measure a change in transmittance, obtain the maximum value T ₀ of the transmittance and the minimum value T ₉₀ of the transmittance, and calculate the measured wavelength And the orthogonal transmittance Tc at 700 nm was calculated.

Tc = T ₀ × T ₉₀ / 100 (IX)

Then, the absorbance (Abs) at a measurement wavelength of 700 nm of the polarizing film was calculated from the following equation (X) using the orthogonal transmittance Tc.

Abs = 2 - logTc (X)

Then, from the results of the above "(i) the polarization degree at the transmittance of 43.5%" "the measurement method of the single transmittance (Y) of 1" and the absorbance at the measurement wavelength of 700 nm (Abs) Five points corresponding to the above five types of polarizing films were plotted on the abscissa with the abscissa and the absorbance (Abs) at a measurement wavelength of 700 nm as the ordinate, and an approximate straight line was created. From the approximate straight line, (Abs) at a measurement wavelength of 700 nm at a transmittance of 43.5% was determined as the absorbance (A) at a measurement wavelength of 700 nm when the transmittance was 43.5%.

&Quot; Example 1 &

(1) Production of PVA polymer film

(i) 100 parts by mass of PVA (saponification degree: 99.9 mol%, average degree of polymerization: 2400) obtained by saponifying polyvinyl acetate, 12 parts by mass of glycerin, 0.1 part by mass of diethanolamide laurate, and water at a volatile matter content of 66% by mass (The surface temperature (T ₁ ) of 70 ° C and the peripheral speed (S ₁ ) of 5.0 m / min) of a film-making apparatus equipped with a plurality of drying rolls and heat- , And dried on a first drying roll until a volatile fraction (V ₁ ) of 20% by mass was obtained by blowing hot air of 90 ° C at an air velocity of 5 m / sec to the entire first dry roll non-contact surface , And then peeled off from the first drying roll to further dry between the second drying roll to the final drying roll immediately before the heat treatment roll so that the front surface and back surface of any portion of the film alternately contact each drying roll After that, And peeled off from the seed drying roll. At this time, the average value (T ₂ ) of the surface temperatures of the respective drying rolls from the second drying roll to the final drying roll was set to 61 ° C. The volatile fraction (V ₂ ) of the film at the time of peeling from the final drying roll was 8 mass%. Finally, a heat treatment was performed with a heat treatment roll having a surface temperature of 105 占 폚, and then the sheet was wound in a roll form to obtain a PVA film (thickness 75 占 퐉, width 3.3 m, volatile matter content 3 mass%).

In this first embodiment, 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 set to 1.025, ₁ ), the ratio (S _L / S ₁ ) of the peripheral speed (S _L ) of the final drying roll was 0.982. Further, T _{1? 2} in the above formula (I) was calculated as 67. The film production conditions are summarized in Table 1 below.

(ii) a crystal length period, a crystal thickness and an irregular thickness in the water of the PVA film obtained in (i) above; The retardation value and the mass swell were measured by the above-mentioned method, and the results are shown in Table 2 below.

(2) Production of polarizing film

(i) A test piece having a flow direction (MD) x a width direction (TD) = 10 cm 占 12 cm was taken from the center of the width direction (TD) of the PVA film obtained in the above (1) Was fixed on the drawing jig so that the stretched portion had a size in the flow direction (MD) x the width direction (TD) = 6 cm x 12 cm, and a stretching speed of 12 cm / min (First stage stretching) in a flow direction (MD) at a rate of 1.5 times the original length, followed by a temperature of 30 占 폚 containing 0.028% by mass of iodine, 1% by mass of potassium iodide and 1% by mass of boric acid (Second-stage stretching) in a flow direction (MD) to a stretching speed of 12 cm / min to a stretching speed of 2.25 times the original length while being immersed in an aqueous iodine / potassium iodide / boric acid aqueous solution of boric acid, % And potassium iodide at a concentration of 4 mass% (Stretching at the third stage) in the flow direction (MD) to 5.8 times the original length at a stretching speed of 12 cm / minute while immersed in the aqueous solution of potassium iodide / potassium iodide for 4 minutes And dried to prepare a polarizing film.

(ii) In step (i), the same operation as in step (i) was performed except that the concentration of iodine in the iodine / potassium iodide / boric acid aqueous solution was changed from 0.028 mass% to 0.03 mass% at a temperature of 30 ° C during the second- (The stretching speed in each stretching step was the same as 12 cm / min in the above (i)) to prepare a polarizing film.

(iii) The same operation as in the above (i) was carried out except that the concentration of iodine in the iodine / potassium iodide / boric acid aqueous solution at a temperature of 30 ° C at the second stage of the step (i) was changed from 0.028 mass% to 0.032 mass% (The stretching speed in each stretching step was the same as 12 cm / min in the above (i)) to prepare a polarizing film.

(iv) The same operation as in the above (i) was carried out except that the concentration of iodine in the iodine / potassium iodide / boric acid aqueous solution at a temperature of 30 ° C at the second stage of the step (i) was changed from 0.028 mass% to 0.034 mass% (The stretching speed in each stretching step was the same as 12 cm / min in the above (i)) to prepare a polarizing film.

(v) The same operation as in the above (i) was carried out except that the concentration of iodine in the iodine / potassium iodide / boric acid aqueous solution at a temperature of 30 ° C during the second stage stretching was changed from 0.028 mass% to 0.036 mass% (The stretching speed in each stretching step was the same as 12 cm / min in the above (i)) to prepare a polarizing film.

(vi) Using the five types of polarizing films prepared in the above (i) to (v), the above-mentioned method (1) was used in the item of "(7) Polarization degree at 43.5% , The degree of polarization was measured and found to be 99.9%. Absorbance (Abs) was measured by the above-mentioned method in the item of "(7) Optical performance of polarizing film (ii) Absorbance at Absorbance at 700 nm at transmittance of 43.5% 3.2. The results are shown in Table 2 below.

&Quot; Examples 2 to 7 "

In the same manner as in (1) and (2) of Example 1, a PVA film and a polarizing film were produced in the same manner as in Example 1 except that the conditions for producing the PVA film were changed as shown in Table 1 below. .

(I) the degree of polarization at a transmittance of 43.5% and (7) the optical performance of a polarizing film (ii) the transmittance at a transmittance of 43.5% was measured using the polarizing film thus produced (Abs) at a wavelength of 550 nm (nm) ", the degree of polarization and the absorbance (Abs) thereof were measured by the method described above. The results are shown in Table 2 below.

&Quot; Comparative Examples 1 to 6 "

In the same manner as in (1) and (2) of Example 1, a PVA film and a polarizing film were produced in the same manner as in Example 1 except that the conditions for producing the PVA film were changed as shown in Table 1 below. .

(I) the degree of polarization at a transmittance of 43.5% and (7) the optical performance of a polarizing film (ii) the transmittance at a transmittance of 43.5% was measured using the polarizing film thus produced (Abs) at a wavelength of 550 nm (nm) ", the degree of polarization and the absorbance (Abs) thereof were measured by the method described above. The results are shown in Table 2 below.

&Quot; Comparative Example 7 &

As a result of changing the film production conditions in the production of the PVA film in Example 1 as shown in the following Table 1, it was found that the drying was poor on the first drying roll and the film could be peeled off from the first drying roll No, it came to a break. The volatile fraction of the broken film was measured and found to be 31% by mass.

Industrial availability

When the PVA polymer film of the present invention has a crystal length cycle in water of 14.5 to 16.0 nm and the PVA polymer film is used as a raw material, it is possible to produce a polarizing film having a high absorbance in a long wavelength region and a high degree of polarization , The PVA polymer film is very useful as a original film for producing a polarizing film and the production method of the present invention is useful as a method for smoothly and continuously producing the PVA polymer film of the present invention Do.

Claims (1)

A process for producing a polarizing film, which comprises dyeing, uniaxially stretching, fixing and drying a polyvinyl alcohol polymer film having a crystal length cycle of 14.5 to 16.0 nm in water.