KR20100049604A

KR20100049604A - Polyvinyl alcohol film and method for producing the same

Info

Publication number: KR20100049604A
Application number: KR1020107003672A
Authority: KR
Inventors: 다카시 네리오; 데츠시 하야시; 사토루 후지타
Original assignee: 가부시키가이샤 구라레
Priority date: 2007-08-24
Filing date: 2008-08-08
Publication date: 2010-05-12
Also published as: KR101544626B1; JP5943974B2; WO2009028141A1; JP5649820B2; CN101784590B; CN102789022A; JPWO2009028141A1; TW200914469A; CN101784590A; JP2015003524A; TWI445718B; CN102789022B

Abstract

Disclosed is a polyvinyl alcohol film which is useful for producing a polarizing film having only a few wrinkles. The polyvinyl alcohol film is an optical film which uses a polyvinyl alcohol resin as a main raw material. The inclination of the optical axis in the film width direction is 45-1350 with respect to the film length direction over the entire width of the film. The polyvinyl alcohol film may have a limiting drawing ratio of more than 6.0 but not more than 8.0, and a swelling elongation ratio of about 100-124%.

Description

Polyvinyl alcohol film and its manufacturing method {POLYVINYL ALCOHOL FILM AND METHOD FOR PRODUCING THE SAME}

Related application

This application claims the priority of Japanese Patent Application No. 2007-218544 for which it applied in Japan on August 24, 2007, and is referred to as a part of this application with reference to the whole.

The present invention relates to a polyvinyl alcohol film that can be preferably used for the production of a high performance polarizing film and a method for producing the same.

A polarizing plate having a light transmitting and shielding function, together with a liquid crystal having a light switching function, is a basic component of a liquid crystal display (LCD). This LCD is also widely used in small devices such as electronic calculators and wristwatches in the early days, and has been widely used in laptop PCs, word processors, liquid crystal color projectors, in-vehicle navigation systems, and liquid crystal televisions. Therefore, the polarizing plate which is excellent in polarization performance is calculated | required more than the conventional product.

A polarizing plate generally swells a polyvinyl alcohol film (hereinafter abbreviated as "PVA film"), and then, on both sides of the polarizing film produced by uniaxial stretching and dyeing, a protective film such as a cellulose triacetate (TAC) film. It is prepared by attaching.

In recent years, with the improvement of the function, the refinement, and the image quality of an image display apparatus, the polarizing plate used for it is also required more optical characteristics, such as a higher degree of polarization, and in-plane uniformity. When the PVA film is stretched and dyed to produce a polarizing film, dyeing unevenness occurs, which causes a decrease in optical properties and in-plane uniformity, and the polarizing plate obtained by using such a polarizing film is used for an image display device. When applied, it appears as a display unevenness of the screen, various studies have been attempted to eliminate it.

The display unevenness resulting from the above-mentioned dyeing unevenness is a thing of the stripe form continuous in the longitudinal direction of a polarizing film, or the thing of the shape of an archeous form continuous in the film width direction of a film (henceforth a "boeing stain"). ) Is a problem. Regarding the former, the influence of the wrinkles caused by the expansion in the film width direction of the film at the time of the swelling treatment of the PVA film is considered to be one factor. In order to reduce this, in patent document 1, when manufacturing a polarizing film from a PVA film through each process of uniaxial stretching and dyeing, it is proposed to use a sponge rubber width expansion roll in the swelling process of a PVA film prior to these processes. Moreover, in patent document 2, after extending | stretching to TD direction (film width direction of a film) using the crown roll of curvature 3% or more at the time of swelling process of a PVA film, it is proposed to uniaxially stretch and dye, and to manufacture a polarizing film. It is. However, this method also does not completely eliminate wrinkles generated during the production of the polarizing film, and further improvement is required.

On the other hand, recently, it is known that the latter boeing stain originates from the dyeing stain which arises by the fine unevenness | corrugation (thickness stain) which a PVA film has in the longitudinal direction. Then, in patent document 3, when manufacturing a PVA film using the drum film forming machine which has two or more dry rolls, in order to reduce a thick stain, the volatilization fraction of the PVA film of the dry roll located in a most upstream side peeling the film from the drying roll at the time when reached from 10 to 50% by weight, and also less than that of the main (周) speed (V ₁₎ and, for the first time to 10% by weight of volatile matter in the PVA film of the drying roll positioned on the most upstream side The main speed ratio (V ₂ / V ₁ ) of the main speed (V ₂ ) of the drying roll located at the time point of setting is 1.0 to 1.3. Thereby, the thick uneven stain of a PVA film can be reduced and the reduction of the bowing unevenness of a polarizing film can be achieved.

Moreover, in order to improve the polarization performance of a polarizing plate, although processing conditions, such as a chemical | medical agent prescription in the processing process of a polarizing film, an extending method, are important, the high stretchability of the PVA film used as a raw material of a polarizing film also matters. Therefore, in Patent Document 4, the peripheral speed ratio (V ₄ / V ₃₎ of the peripheral velocity (V ₄₎ of the take-up roll of the PVA film velocity (V ₃₎ and the film of the drying roll positioned at the most upstream side at the time of manufacture It has been proposed to 0.8 to 1.3, in Patent Document 5, the, state of the peripheral velocity (V ₅₎ and the peripheral velocity (V ₆₎ of the take-up rolls of the drying roll positioned at the time-volatile content rate of the film is 10% or less A method of setting the speed ratio (V ₆ / V ₅ ) to 0.9 to 1.1 is proposed, and in Patent Document 6, the shrinkage of the discharge width W1 of the film forming undiluted solution and the film width W2 after the film forming (W1-W2) It is proposed to suppress the width shrinkage so that / W1 is 0 to 0.15, and production of a film excellent in stretchability has been achieved by these methods. However, with the method described in this document, it was still insufficient to produce an optical film which gave better high stretchability.

On the other hand, Patent Document 7, Non (V ₈ / V ₇₎ to 1.000 in the film-forming raw liquid and the discharged first peripheral velocity of the drying rolls (V _7), then the second velocity (V ₈₎ of the drying roll The ratio (V ₁₀ / V ₈ ) of the circumferential speed (V ₈ ) of the second drying roll and the circumferential speed (V ₁₀ ) of the drying roll positioned until the volatilization fraction of the film becomes 8 mass% is set to 1.100. It carries out in the range of 0.995-1.050, and ratio of the main speed (V ₁₁ ) of the drying roll located at the time when the volatile fraction of a film turns into 13 mass%, and the main speed (V ₁₂ ) of the drying roll located next. by the (V ₁₂ / V ₁₁₎ in the range of 0.950 ~ 0.999, not a fine cracks and voids occur on the polarizing film obtained in the case goyeon Shinhan, there has been proposed a PVA film which can be produced a polarizing film with high yield.

Moreover, in patent document 8, with respect to the optical film comprised from a thermoplastic resin film, the angle which the extrusion direction from a melt extruder and the slow axis in each point make

When the magnitude of the retardation value at each point is set to Re, [sin ² 2

] × [sin ² (π · Re / 550)]

4.0 × 10 ^- been proposed for reducing the optically modified by an optical film that satisfies ^5, and also in Patent Document 9, the non-crystalline (非晶性) with respect to the optical film with a thermoplastic resin, the film width direction of the film It is proposed to reduce the phase difference deviation by setting the orientation angle of the central portion in 80 to 90 °. However, the method of patent document 8, 9 is a method of reducing the phase difference variation of a film by controlling the orientation angle of the protective film which is one of the constituent materials of a polarizing plate, and is not a method of controlling the characteristic as a polarizing element. In addition, with the manufacturing methods of patent documents 8 and 9, manufacture of the film using polyvinyl alcohol (henceforth "PVA") type resin used as a polarizing element is impossible.

Japanese Laid-Open Patent Publication 2005-227649 Japanese Laid-Open Patent Publication 2005-284047 Japanese Unexamined Patent Publication No. 2002-79531 Japanese Unexamined Patent Publication No. 2001-315141 JP 2001-315146 A Japanese Unexamined Patent Publication No. 2002-28942 Japanese Laid-Open Patent Publication 2005-324355 International Publication 03/081299 Japanese Laid-Open Patent Publication 2005-134768

In view of these findings, the present invention aims to provide a PVA film having high stretchability as well as suppressing diffusion in the film width direction even when swelling treatment or the like is performed.

Moreover, in this invention, it is hard to generate | occur | produce the stripe-shaped display unevenness which originates in the wrinkles etc. at the time of a swelling process of a PVA film, and it aims at providing the polarizing film which is excellent in an optical characteristic and is uniform in a film width direction.

As a result of various studies conducted by the present inventors in order to achieve the above object, it has been found that the properties of the PVA film suddenly change around 45 ° and 135 ° of the orientation angle with respect to the longitudinal direction of the film. And by carrying out the orientation angle of a film in the 45-135 degree range, it was understood that residual stress in the longitudinal direction of a film can be reduced, and as a result, extending | stretching property can be improved more when uniaxial stretching is performed. . Moreover, by making the orientation angle of a film into the said range, the residual stress in a film width direction can be increased, As a result, the spread in the film width direction at the time of a swelling process in a user machining process can also be suppressed. It became clear.

That is, this invention is an optical film which uses PVA system resin as a main raw material, The inclination (orientation angle) of the optical axis over the whole film width direction of a film is 45-135 degrees with respect to a film longitudinal direction, It is a PVA film characterized by the above-mentioned. .

By using the PVA film of this invention, especially the spreading | diffusion to the film width direction of a PVA film at the time of swelling can be suppressed, and it can reduce that wrinkles generate | occur | produce in a PVA film at the time of swelling process in a user processing process. Can be. Thereby, the stripe-shaped dyeing unevenness (optical unevenness) which exists in the longitudinal direction can be reduced, and it is excellent in an optical characteristic and can provide a uniform polarizing film in a film width direction.

The invention will be more clearly understood from the following description of the preferred embodiments with reference to the accompanying drawings. However, embodiments and figures are for illustration and description only, and should not be used to define the scope of the invention. The scope of this invention is defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the measurement range of the orientation angle of the PVA film of this invention.
It is a schematic block diagram of the drum type film forming machine used for manufacture of the PVA film of this invention.

To practice the invention Best form for

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The PVA film of this invention is an optical film which uses PVA system resin as a main raw material, and the inclination (orientation angle) of the optical axis over the whole film width direction of a film is 45-135 degrees with respect to the longitudinal direction of a film.

The orientation angle of the PVA film of this invention is measured based on the parallel Nicole rotation method, and shall be an orientation angle represented by 0-180 degrees in this specification. In this invention, it is necessary that the orientation angle is 45-135 degrees with respect to the longitudinal direction of a film over the whole film width direction of a PVA film, It is preferable that it is 55-125 degrees, More preferably, it is 60-120 degrees Do. When the orientation angle is less than 45 ° or exceeds 135 °, the diffusion in the film width direction cannot be suppressed at the time of the swelling treatment of the polarizing film, and the stretchability is lowered.

Moreover, since the PVA film of this invention has such a specific orientation angle | corner over the whole film width direction, it is especially excellent in stretchability. For example, in the PVA film of this invention, the limit draw ratio measured by the measuring method mentioned later becomes like this. Preferably it is more than 6.0 and 8.0 or less, More preferably, it is 6.1-7.0. When the limit draw ratio is 6.0 or less, there is a tendency that good polarization performance is not expressed. On the other hand, when the limit draw ratio exceeds 8.0, since the neck-in of a film becomes large, there exists a possibility that a width yield may worsen.

As a method of manufacturing the PVA film of this invention, the drum film forming method, the belt film forming method, the wet film forming method (discharge into a poor solvent) using the film forming undiluted | stock solution containing PVA, for example, the gel film forming method (cold-gelled After which the solvent is extracted and removed). Among these, the drum film forming method is preferable. Hereinafter, the method of manufacturing the PVA film of this invention by the drum film forming method is demonstrated.

The PVA film of this invention uses the drum film forming machine provided with the some drying roll of which the rotating shafts were parallel to each other, and formed the film forming undiluted | stock solution containing 50-90 mass% of volatile matter PVA by a hopper plate, T-die, and I-. It discharges from known discharge apparatuses, such as a die and a lip coater die, and discharges in a film form on the 1st dry roll of a drum film making machine, and a 2nd vaporization of water, an organic solvent, etc. is carried out on this drum. It can be manufactured by peeling with a drying roll, drying one by one, passing through the peripheral surface of the downstream drying roll, and finally winding up. The speed can also be adjusted by using a motor, a transmission, etc. suitably for driving each roll.

It is preferable that the number of the dry rolls in a drum film forming machine is three or more, It is more preferable that it is four or more, It is further more preferable that it is 5-30. It is preferable that the some dry roll is formed with metals, such as nickel, chromium, copper, iron, stainless steel, for example, and it is especially hard to corrode the roll surface, and is also formed with the metal material which has a mirror gloss. It is more preferable. Moreover, in order to improve durability of a drying roll, it is more preferable to use the drying roll which plated the nickel layer, the chromium layer, the nickel / chromium alloy layer, etc. combining single layer or two or more layers.

The drum film forming machine may be provided with a floating drying device and / or a humidity control device together with the plurality of drying rolls. When a floating drying apparatus and / or a humidity control apparatus are installed, these apparatuses are often applied with respect to the film after passing a drying roll. A floating drying apparatus means the apparatus which dries in the state which floated the film by blowing hot air from the lower part of a film, upper part, or both. At this time, even if it separates into several dry sections, it does not interfere. Moreover, although a floating state can mention the method of fixing both ends of a film, or making it free with a clip tenter, a pin tenter, etc., but there is no restriction | limiting in particular. Moreover, a humidity control apparatus will not be restrict | limited in particular if it is a device which can continuously humidify a film through the room humidified by the temperature of 20-80 degreeC, and humidity of 50-95% RH.

In the PVA film of the present invention, in order to control the alignment angle over the entire film width direction to 45 to 135 °, the film-forming film-forming stock solution discharged from the discharge device is transferred to a drum film forming machine provided with a plurality of drying rolls. And the dimensional change rate in the longitudinal direction of the film in this section is R _MD (%) and the dimensional change rate in the film width direction of the film in a section in which the volatile fraction of the PVA film falls from 16 mass% to 8 mass%. When using R _TD (%), R _MD and R _TD Going to expression

R _MD / R _TD <1.000

It is preferable to dry to satisfy.

In addition, in a long disc film, MD (Machinery Direction) shall represent a longitudinal direction, and TD (Transverse Direction) shall represent a film width direction.

The value of R _MD / R _{TD in} the present invention is not particularly limited as long as it is less than 1.000, but from the viewpoint of productivity, 0.800 to 0.999 is preferable, 0.900 to 0.995 is more preferable, and 0.950 to 0.990 is still more preferable. If the R _MD / R _TD value is less than 0.800, it is not practical in terms of productivity.

As a method for adjusting the dimensional change rate, S 'is the main speed of the drying roll located immediately after the volatile fraction is 16% by mass, and S' is the main speed of the drying roll located immediately after the volatile fraction is 8% by mass. What is necessary is just to control so that the circumferential speed ratio S '/ S may be 0.950-0.90, 0.960-0.987 are more preferable, and 0.965-0.985 are more preferable. In addition, when a volatile matter reaches 8 mass% in a floating drying apparatus, the conveyance speed of the PVA film in the floating drying apparatus exit shall be S '.

When the circumferential speed ratio S '/ S exceeds 0.990, the tension of the film applied in the longitudinal direction at the time of film forming becomes stronger, so that the PVA film of the present invention may not be obtained. On the other hand, when circumferential speed ratio S '/ S is less than 0.950, a film will loosen when it passes each dry roll, and there exists a possibility that wrinkles may arise or it may wind up only on a dry roll.

Since the PVA film of this invention can suppress the spread | diffusion to a TD direction at the time of swelling process, generation | occurrence | production of the wrinkles resulting from this diffusion can be suppressed, and also dyeing | staining stain (optical stain) can be reduced. Diffusion in the TD direction (hereinafter referred to as swelling elongation) refers to the film width before swelling (the film width of the raw film) L, and the film width after immersing and swelling the film for 5 minutes in water at 30 ° C. ',

Swelling Elongation = L '/ L × 100 (%)

It shall be represented by.

It is preferable that it is 100 to 124%, as for the swelling elongation rate of the PVA film of this invention, it is more preferable that it is 102 to 123%, and it is still more preferable that it is 104 to 122%. When swelling elongation exceeds 124%, wrinkles may arise in the film after swelling, and there exists a possibility of generating a dyeing unevenness. On the other hand, when it is less than 100%, it is not realistic from a viewpoint of the characteristic of a film to be swollen, and a manufacturing method.

The PVA-based resin used in the present invention may be, for example, PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, fluorinated carboxylic acid or its derivative, unsaturated sulfonic acid or its derivative, carbon number 2-30

Modified PVA polymers obtained by graft copolymerization of olefins, vinyl esters, unsaturated carboxylic acids or derivatives thereof, unsaturated sulfonic acids or derivatives thereof, carbon atoms of 2 to 30

Part of the hydroxyl groups of the modified PVA-based polymer, unmodified PVA or modified PVA-based polymer prepared by saponifying a modified polyvinyl ester copolymerized with -olefin or the like is crosslinked with aldehydes such as formalin, butylaldehyde, benzaldehyde, and so-called polyvinyl acetal. Resin and the like.

As said vinyl ester used for manufacture of PVA system resin, For example, vinyl acetate, a vinyl formate, a vinyl laurate, a vinyl propionate, a vinyl butyrate, a vinyl pivalate, a vinyl versatate, a vinyl stearate, a vinyl benzoate, etc. Can be mentioned. These vinyl esters can be used individually or in combination. Among these vinyl esters, vinyl acetate is preferable from the viewpoint of productivity.

Moreover, as a comonomer copolymerizable with such a vinyl ester monomer, For example, C2-C30 olefins, such as ethylene, propylene, 1-butene, isobutene; Acrylic acid and salts 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, acrylic acid-C _1-18 alkyl ester); Methacrylic acid and its salts; Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-methacrylate ethylhexyl methacrylate pH decyl methacrylate, octadecyl such as methacrylic acid esters (e.g., methacrylic acid, -C ₁ _- ₁₈ alkyl ester); Acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and its salt, acrylamide propyl dimethylamine and its salt, N-methylol acryl Acrylamide derivatives such as amides and derivatives thereof; Meta, such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts thereof, N-methylolmethacrylamide and derivatives thereof Krylamide derivatives; N-vinylamides, such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; Vinyl 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, 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 carboxylic acids such as maleic acid and itaconic acid, and derivatives such as salts or esters thereof; Vinyl silyl compounds such as vinyl trimethoxysilane; Isopropenyl acetate is mentioned. Among these

-Olefins are preferred, and ethylene is particularly preferred.

Moreover, it is preferable that it is less than 15 mol%, and, as for the modification amount in a modified PVA system polymer, it is more preferable that it is 5 mol% or less.

As for the average degree of polymerization of the PVA system resin which forms the PVA film of this invention, 1000 or more are preferable, 1500 or more are more preferable, and 2000 or more are more preferable in terms of polarization performance, durability, etc. of the polarizing film obtained. On the other hand, the upper limit of the average degree of polymerization of the PVA-based resin is preferably 8000 or less, particularly preferably 6000 or less, in view of ease of production of a homogeneous PVA film, stretchability and the like.

"Average degree of polymerization" in this specification means the degree of polymerization measured according to JIS K 6726, and is calculated | required from the intrinsic viscosity measured in water of 30 degreeC after saponifying and refine | purifying PVA system resin again.

As for the saponification degree of PVA system resin which forms the PVA film of this invention, 95.0 mol% or more is preferable from a viewpoint of polarization performance, durability, etc. of the polarizing film obtained, 98.0 mol% or more is more preferable, 99.0 mol% or more More preferably, 99.3 mol% or more is the most preferable.

The "saponification degree" in this specification shows the ratio of the unit actually saponified to a vinyl alcohol unit among the units which can be converted into a vinyl alcohol unit by saponification, and saponification measured by the method of JISK6726. Means degrees.

When manufacturing the PVA film of this invention, a plasticizer is added to a film forming undiluted | stock solution from the surface of the melt | dissolution and melt | dissolution of the solvent of PVA system resin, the improvement of the processability at the time of film manufacture, the improvement of the elongation of the obtained PVA film, etc. It is preferable. As a plasticizer, polyhydric alcohol is preferable, For example, ethylene glycol, glycerin, diglycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylol propane, etc. are mentioned, These plasticizers are single Or combinations of two or more thereof. Among these, glycerin, diglycerol, or ethylene glycol is more preferably used because of the excellent effect of improving the stretchability.

As addition amount of a plasticizer, 1-30 mass parts is preferable with respect to 100 mass parts of PVA system resin, 3-25 mass parts is more preferable, 5-20 mass parts is especially preferable. When it is less than 1 mass part, dyeing property and stretchability may fall, and when more than 30 mass parts, a film may become too flexible and handleability may fall.

When manufacturing the PVA film in this invention, it is preferable to add surfactant to a film forming undiluted | stock solution from the viewpoint of the peelability improvement from the dry roll at the time of manufacture, the handleability of the obtained PVA film, etc. Although it does not specifically limit as a kind of surfactant, Anionic or nonionic surfactant is used preferably. As the anionic surfactant, for example, carboxylic acid type such as potassium laurate, sulfate ester type such as octyl sulfate, and sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate are preferable. As nonionic surfactant, For example, Alkyl ether type, such as polyoxyethylene oleyl ether, Alkylphenyl ether type, such as polyoxyethylene octylphenyl ether, Alkyl ester type, such as polyoxyethylene laurate, Polyoxyethylene Alkylamine type, such as lauryl amino ether, Alkylamide type, such as polyoxyethylene lauric acid amide, Polypropylene glycol ether type, such as polyoxyethylene polyoxypropylene ether, Alkanolamide type, such as oleic acid diethanamide, Poly Nonionic surfactants, such as allyl phenyl ether type, such as oxyalkylene allyl phenyl ether, are preferable. These surfactant can be used individually or in combination of 2 or more types.

As addition amount of surfactant, 0.01-1 mass part is preferable with respect to 100 mass parts of PVA system resin, 0.02-0.5 mass part is more preferable, 0.05-0.3 mass part is especially preferable. When less than 0.01 mass part, the effect of film forming property and peelability improvement may become difficult to show, On the other hand, when more than 1 mass part, it elutes on a film surface, it may cause blocking, and handling property may fall. .

A film forming raw material is a various additive, for example, stabilizer (for example, antioxidant, ultraviolet absorber, heat stabilizer, etc.), compatibilizer, antiblocking agent, flame retardant, in the range which does not impair the characteristic of the PVA film of this invention. It may contain an antistatic agent, a lubricant, a dispersing agent, a fluidizing agent, an antibacterial agent and the like. These additives can be used individually or in combination of 2 or more types.

50-90 mass% is preferable, and, as for the volatile matter fraction of the film forming undiluted | stock solution used when manufacturing the PVA film of this invention, 55-80 mass% is more preferable. If the volatilization fraction is less than 50 mass%, the viscosity increases, and in addition to filtration and defoaming, the film forming itself may be difficult. If the volatilization fraction is larger than 90 mass%, the viscosity may be too low, resulting in a loss of uniformity of the PVA film thickness.

In addition, the "volatile fraction of a film forming undiluted | stock solution" as used in this specification means the volatile fraction calculated | required by the following formula.

Volatilization fraction (mass%) of film forming undiluted | stock solution = {(Wa-Wb) / Wa} x 100

Wa: Mass of the uncoated undiluted solution (g)

Wb: mass (g) after drying film forming undiluted | stock solution of Wa (g) for 16 hours in 105 degreeC heat transfer dryer

The thickness of the PVA film of the present invention is preferably 20 to 150 µm, more preferably 25 to 120 µm, further preferably 30 to 100 µm in terms of practicality, ease of film production, ease of stretching treatment, and the like. . If the thickness of a PVA film is less than 20 micrometers, it will become easy to break | rupture at the time of uniaxial stretching for manufacturing a polarizing film. On the other hand, when the thickness of a PVA film becomes 150 micrometers or more, extending | stretching unevenness will arise easily at the time of uniaxial stretching for manufacturing a polarizing film.

The film forming undiluted solution for manufacturing the PVA film of this invention can be prepared by mixing PVA system resin with a solvent to make a solution, or melt | dissolving PVA system pellet etc. containing a solvent etc. as a melt liquid. Melting | dissolving PVA system pellet containing the solvent, solvent, etc. to a solvent of PVA system resin can be performed using a stirring mixing apparatus, a melt extruder, etc. Examples of the solvent used in that case include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, diethylenetriamine, and the like. Or combinations of two or more thereof. Among these, water, dimethyl sulfoxide, or a mixture of both is preferably used, and water is particularly preferably used.

In order to manufacture a polarizing film from the PVA film of this invention, what is necessary is just to dye | dye a PVA film, uniaxial stretching, a fixed process, a drying process, and heat processing as needed. The order of each step is not particularly limited, and two steps such as dye uniaxial stretching may be performed simultaneously. Moreover, you may repeat each process a plurality of times.

As a dye used for dyeing, iodine or a dichroic organic dye (for example, Direct Black 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, 23, 28, 31, 37) , 39, 79, 81, 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; dichroic dyes such as Direct Orange 26, 39, 106, 107), and the like. These dyes can be used individually or in combination of 2 or more types. Although dyeing can be normally performed by immersing a PVA film in the solution containing the said dye, the processing conditions and a processing method are not specifically limited.

The uniaxial stretching performed with respect to the longitudinal direction of the said PVA film may be, for example, a wet stretching method, and the wet stretching may be performed in a warm water (the solution containing the dye or in a fixed treatment bath described later). You may implement or you may implement in air using the PVA film after absorption. It is preferable to extend | stretch as much as possible until just before a PVA film is cut | disconnected, specifically, 4.0 times or more are preferable, 5.0 times or more are more preferable, 6.0 times or more is more preferable. If the draw ratio is smaller than 4.0 times, practical and sufficient polarization performance and durability are hardly obtained. Moreover, there is no upper limit in particular of draw ratio, but in order to perform uniform extending | stretching, it is preferable that it is 8.0 times or less. Moreover, although extending | stretching temperature is not specifically limited, 30-90 degreeC is preferable, 40-70 degreeC is more preferable, 45-65 degreeC is still more preferable. And 3-75 micrometers is preferable and, as for the thickness of the PVA film after extending | stretching, 10-50 micrometers is more preferable.

In manufacture of a polarizing film, in order to solidify adsorption | suction of the dye with respect to the uniaxially-stretched PVA film, it fixes in many cases. Boric acid and a boron compound are normally added to the processing bath used for the fixed treatment. Moreover, you may add an iodine compound in a process bath as needed.

The polarizing film obtained as mentioned above is normally used as a polarizing plate by attaching the protective film which is optically transparent and has mechanical strength to the both surfaces or single side | surface. As a protective film, a cellulose acetate type film, an acryl type film, a cycloolefin type film, a polyester type film, etc. are used normally. Moreover, as an adhesive agent for attaching a protective film, PVA-type adhesive agent is used preferably.

The polarizing plate obtained as mentioned above is apply | coated an acrylic adhesive etc., and is then attached to a glass substrate and used as a component of a liquid crystal display device. When attaching a polarizing plate to a glass substrate, you may attach retardation film, a viewing angle improvement film, a brightness improving film, etc. simultaneously.

Example

Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited at all by these. The scope of this invention is defined by the appended claims.

Examples of the values of R _MD / R _TD described in Examples and Comparative Examples, the angle of orientation of the PVA film, the volatile fraction in the film forming process, the thickness, the swelling elongation rate, the limit elongation ratio, wrinkles and dyeing stains, and the transmittance of the polarizing film The measurement was performed by the following method.

(Measurement method of R _MD / R _TD )

S is the main speed of the drying roll positioned immediately after the volatile fraction is 16% by mass, and the total film width of the PVA film passing through the circumferential surface of the drying roll is T, and immediately after the volatile fraction is 8% by mass. S 'and the total film width of the PVA film passing through the circumferential surface of the drying roll is T',

R _MD / R _TD = {(S '/ S) × 100} / {(T' / T) × 100}

Calculated by

(Measuring method of the orientation angle of a PVA film)

The orientation angle | corner collects the film sample of MD40mm x TD full width using the phase difference measuring instrument (KOBRA-WFD) by Oji Measurement Instruments Co., Ltd., and puts the surface which contacted the 1st dry roll at the time of film forming upward, Light (λ = 590 nm) was allowed to come in contact with each other, and was measured at a pitch of 50 mm in the film width direction in the range of 0 to 180 °.

In addition, measurement is carried out by superimposing measurement with a sample normally in the state which made the orientation (ground axis) of a wave plate into 0 degree, From the appearance retardation (R ') and orientation angle (φ') obtained as follows, The retardation (Rs) and orientation angle (phi) of the sample were computed according to the following formula.

Rs = {(R '-Ro) ² + Di ² × φ' ² } ^1/2

φs = 1/2 cos ^-1 {(R '-Ro) / Rs}

Ro: retardation of a wave plate

Di: coefficient determined by measurement wavelength and Ro

(Volatile fraction of PVA film)

The PVA film on the drying roll was divided into 10 equal parts in the film width direction, and the volatile fraction of the center point in the equal film width direction was used using a fiber-type infrared moisture meter ("IM-3SCV MODEL-1900 (L)" manufactured by Fuji Work Co., Ltd.). The average value of the 10 points | pieces was measured and it was set as the volatile fraction of a PVA film In addition, in the measurement, the analytical curve of an infrared moisture meter is measured using the PVA film which the volatile fraction in the area | region of 5-25 mass% is known previously. Was prepared and the volatile fraction was calculated from the obtained measured values.

(Measurement Method of Swelling Elongation of PVA Film)

The swelling elongation rate of the PVA film used the roll-shaped PVA film slit-cut to 650 mm width in the film width center part, it set the speed ratio of the exit / inlet of the swelling tank to swell to 1.2, and for 5 minutes in 30 degreeC pure water. The swelling process was performed and the film width of the swelling tank outlet was measured. The membrane width of the swelling tank inlet was L (= 650 mm) and the membrane width of the swelling tank outlet was L '(mm), and the numerical value represented by the following formula was defined as swelling elongation.

Swelling Elongation = L '/ L × 100 (%)

In addition, the "film width center part" prescribed | regulated in this invention is made into the range up to 50% in total spreading by the length of 25% similarly to the left and right from the center point with respect to the film full width, and makes the rest part in the full width It is called "end".

(Limit draw ratio of PVA film)

Two film samples of MD 130 mm x TD 40 mm were taken from the film width center part, the distance between chucks (inter-stretch) was set to 40 mm, and the sample was prepared in an aqueous solution of 0.05% iodine and 5% potassium iodide at 30 ° C. After immersion for 1 minute, two sheets were simultaneously drawn in the longitudinal direction at the same time in a 50% aqueous solution of boric acid at 50 ° C. at a rate of 2.2 m / sec, and the amount of elongation at the time when one of the two sheets was cut was the original dimension (40 mm). It divided into and made it the limit draw ratio of a PVA film.

(Evaluation method of wrinkles and stain stains)

Using the PVA film cut | disconnected to 650 mm width in the film width center part, each processing process of swelling, dyeing, extending | stretching, fixing, and drying was performed in this order, and the roll-shaped polarizing film was produced continuously. The conditions employ | adopted in performing each process are as follows.

<Swelling treatment process> It was immersed for 3 minutes in 30 degreeC pure water.

<Dyeing treatment process> It was immersed for 5 minutes in 33 degreeC aqueous solution of the concentration ratio 1/33 of iodine / potassium iodide.

<Drawing process process> In 50 degreeC potassium iodide 4 mass% + boric acid 4 mass% aqueous solution, it uniaxially stretched to total draw ratio 6.0 times.

<Fixing treatment process> It was immersed for 30 second in 4 mass% of potassium iodide + 2 mass% aqueous solution of 40 degreeC.

<Drying process> It dried for 2 minutes at 60 degreeC, maintaining tension.

Wrinkle measurement was visually observed whether or not wrinkles were generated at the outlet of the swelling tank in the swelling treatment step.

Evaluation of dyeing stain measures the amount of iodine-PVA complex at 5 mm intervals with respect to the film width direction of the obtained polarizing film, and dyes the difference of the maximum value and minimum value of the amount of iodine-PVA complex in the polarizing film whole width. It is shown as a stain. In addition, the measurement of the amount of complexes was performed as follows.

The iodine-PVA complex is known to generate a diffraction peak near the diffraction angle of 29 ° by X-ray diffraction. Using this, Rigaku Electric make X-ray diffractometer RU-300 (40 kV, 100 mA, slit system: 1/2, 0.15, 1/2, X-ray wavelength CuK

1 = 1.5404 kPa), the diffraction intensity curve (integrated for every 0.02 ° for 20 seconds) was obtained by the permeation method in the meridian direction for each of the samples cut in the film width direction at intervals of 5 mm in width. The peak area of the obtained diffraction intensity curve up to a diffraction angle of about 27 to 30 ° is used as the complex amount (counts), and the measured intensity is integrated time (20 seconds) and the X-ray irradiation area {sample width (5 mm) × slit width 1 mm}, the complex amount C (cps / mm ² ) per unit area was calculated. In the film width direction total width of the obtained polarizing film, when the maximum value of the complex amount C per unit area is C _MAX and the minimum value is C _MIN , the difference which subtracted C _MIN from C _MAX is made into following formula (I), The size was represented by the intensity of the staining stain.

(Measurement Method of Transmittance of Polarizing Film)

From the center part of the width direction of the polarizing film manufactured for evaluation of a wrinkle and a stain | dye unevenness, two square polarizing film samples of 40 mm x 40 mm which have one side parallel to the extending-axis direction of a polarizing film were taken. C light source, 2 degrees according to JIS Z 8722 (Measurement method of object color) using the spectrophotometer U-4100 (integrated sphere attached) manufactured by Hitachi High-Technologies Co., Ltd. for each polarizing film sample. After correcting the visibility of the visible light region of the field of view, the transmittance of the light when tilted at +45 degrees with respect to the stretching axis direction and the transmittance of light when tilted at −45 degrees with respect to one polarizing film sample were measured to obtain their average value Y1. It was.

Also about another polarizing film sample, the transmittance | permeability of the light at the time of inclination +45 degree with respect to a stretch-axis direction, and the transmittance of the light at the time of inclination of -45 degree were measured, and those average values (Y2) were calculated | required.

Y1 and Y2 calculated | required above were averaged, and it was set as the transmittance | permeability (Y) (%) of a polarizing film.

(Example 1)

The film forming undiluted | stock solution of the volatilization fraction 66 mass% which consists of 100 mass parts of PVA of 99.9 mol% of saponification degree, the average degree of polymerization 2400, 12 mass parts of glycerin, 0.1 mass part of diethanol laurate, and water using the drum film forming machine of FIG. (2) was discharged from the T die 1 to the first drying roll 3 (surface temperature 94 ° C., circumferential speed 14 m / min), and then peeled off by the second drying roll 4a, and then the second After the drying roll, drying was carried out at an average of 85 ° C. At that time, the dry roll immediately after the volatile fraction became 16 mass% was a 5th dry roll, and the dry roll immediately after the volatile fraction became 8 mass% was a 10th dry roll. R _MD / R _TD was 0.989 by setting the circumferential speed ratio S '/ S of the drying roll in this section (main speed of the 5th drying roll: S, main speed of the 10th drying roll: S') to 0.970. Then, it dried with the subsequent drying roll (-4b), and finally wound up by the winding-up apparatus 6, and obtained the PVA film 5 (75.3 micrometers in thickness, 3000 mm in film width). Table 1 shows the evaluation results of the obtained film.

(Example 2)

The film forming undiluted | stock solution of the volatilization fraction 66 mass% which consists of 100 mass parts of PVA of 99.9 mol% of saponification degree, the average degree of polymerization 2400, 12 mass parts of glycerin, 0.1 mass part of diethanol laurate, and water using the drum film forming machine of FIG. (2) was discharged from the T die 1 to the first drying roll 3 (surface temperature 93 ° C., circumferential speed 14 m / min), and then peeled off by the second drying roll 4a, and the second After drying roll, it dried at 80 degreeC on average. At that time, the drying roll immediately after the volatile fraction became 16 mass% was a 6th dry roll, and the drying roll immediately after the volatile fraction became 8 mass% was an 11th dry roll. R _MD / R _TD was 0.987 by setting the circumferential speed ratio S '/ S of the drying roll in this section (main speed of the 6th drying roll: S, main speed of the 11th drying roll: S') to 0.975. Subsequently, it dried with the subsequent drying rolls (-4b), and finally wound up by the winding-up apparatus 6, and obtained the PVA film 5 (thickness 75.7 micrometer film width 3000mm). Table 1 shows the evaluation results of the obtained film.

(Example 3)

Using the drum film forming machine of FIG. 2, a film formation of 66 mass% of volatile matter consisting of 99.9 mol% of saponification degree, 100 mass parts of PVA having an average degree of polymerization of 2400, 12 mass parts of glycerin, 0.1 mass part of diethanol laurate, and water The stock solution 2 is discharged from the T die 1 to the first drying roll 3 (surface temperature 93 ° C., circumferential speed 14 m / min), and then peeled off by the second drying roll 4a, After 2 drying rolls, it dried at an average of 80 degreeC. At that time, the drying roll immediately after the volatile fraction became 16 mass% was a 6th dry roll, and the drying roll immediately after the volatile fraction became 8 mass% was an 11th dry roll. R _MD / R _TD was 0.998 by setting the peripheral speed ratio S '/ S of the drying roll in this section (main speed of the 6th drying roll: S, main speed of the 11th drying roll: S') to 0.985. Subsequently, it dried with the subsequent drying roll (-4b), and finally wound up by the winding-up apparatus 6, and obtained the PVA film 5 (thickness 75.4 micrometers, film width 3000mm). Table 1 shows the evaluation results of the obtained film.

(Example 4)

The film forming undiluted | stock solution of the volatilization fraction 66 mass% which consists of 100 mass parts of PVA of 99.9 mol% of saponification degree, 2400 mass parts of glycerol, 0.1 mass part of diethanol laurate, and water using the drum film forming machine of FIG. (2) was discharged from the T die 1 to the first drying roll 3 (surface temperature of 95 ° C., circumferential speed of 15 m / min), and then peeled off by the second drying roll 4a to obtain a second drying roll. After drying roll, it dried at 80 degreeC on average. At that time, the dry roll immediately after the volatile fraction became 16 mass% was a 7th dry roll, and the dry roll immediately after the volatile fraction became 8 mass% was a 12th dry roll. R _MD / R _TD was 0.985 by setting the peripheral speed ratio S '/ S of the drying roll in this section (main speed of the seventh drying roll: S, main speed of the twelfth drying roll: S') to 0.973. Subsequently, it dried with the subsequent drying roll (-4b), and finally wound up by the winding-up apparatus 6, and obtained the PVA film 5 (thickness 77.2 micrometers, film width 3000mm). Table 1 shows the evaluation results of the obtained film.

(Comparative Example 1)

According to the embodiment 1, by making the main sokbi S '/ S of the drying roll to 0.995 in the same manner except that the R _MD / R _TD to 1.007, PVA film (5) (75.7 ㎛, film width of 3000 ㎜ thickness) Got. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 2)

In the second embodiment, when the main sokbi S '/ S of the drying roll to 1.000 in the same manner except that the R _MD / R _TD to 1.007, PVA film (5) (76.4 ㎛, film width of 3000 ㎜ thickness) Got. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 3)

In the third embodiment, when the main sokbi S '/ S of the drying roll to 0.995 in the same manner except that the R _MD / R _TD to 1.007, PVA film (5) (75.0 ㎛, film width of 3000 ㎜ thickness) Got. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 4)

In the third embodiment, by a 0.991 a week sokbi S '/ S of the drying rolls in the same manner except that the R _MD / R _TD to 1.003, PVA film (5) (75.0 ㎛, film width of 3000 ㎜ thickness) Got. Table 1 shows the evaluation results of the obtained film.

As shown in Table 1, the PVA film of this invention enables high draw ratio by making orientation angle into the 45-135 degree range over the whole film width direction. Moreover, since the elongation rate with respect to the film film width direction at the time of swelling can be suppressed, wrinkle removal in a swelling process process is excellent, As a result, dyeing | staining stain strength is also reduced and high optical characteristics can be expressed.

Industrial availability

By this invention, in the swelling process of polarizing film manufacture, the PVA film with little diffusion into the film width direction in the water of a PVA film in water and excellent in high stretchability is provided. Moreover, the PVA film of this invention is useful also as a raw material film which can manufacture the polarizing film which has high optical characteristic and is uniform (no dyeing unevenness) in the film width direction by extending | stretching process.

As mentioned above, although the preferred embodiment was described referring drawings, those skilled in the art can easily assume various changes and correction within an obvious range by looking at this specification.

Accordingly, such changes and modifications are to be interpreted as being within the scope of the invention as defined by the claims.

Claims

As an optical film whose main raw material is polyvinyl alcohol-based resin,
The polyvinyl alcohol film whose inclination of the optical axis over the whole film width direction of a film is 45-135 degrees with respect to the longitudinal direction of a film.

The method of claim 1,
The polyvinyl alcohol film whose limit draw ratio of a polyvinyl alcohol film is more than 6.0 and 8.0 or less.

The method according to claim 1 or 2,
The polyvinyl alcohol film whose swelling elongation rate of a polyvinyl alcohol film is 100 to 124%.

As a method of manufacturing a polyvinyl alcohol film from a film forming undiluted | stock solution using the drum film forming machine provided with a some dry roll after a 1st dry roll and a 2nd dry roll,
Volatilization fraction of a film forming undiluted | stock solution is 50-90 mass%, and in the section in which the volatile fraction of the polyvinyl alcohol film sequentially dried by the said some drying roll falls from 16 mass% to 8 mass%, When the dimensional change rate in the longitudinal direction is R _MD and the dimensional change rate in the film film width direction is R _TD , R _MD and R _TD are represented by the following formulas.
R _MD / R _TD <1.000
The manufacturing method of the polyvinyl alcohol film in any one of Claims 1-3 which satisfy | fills.

The method of claim 4, wherein
Drying roll located immediately after the volatile fraction became 8 mass% as the main speed of the drying roll located immediately after the volatile fraction of the polyvinyl alcohol film dried sequentially by the several drying roll became 16 mass%. The manufacturing method of the polyvinyl alcohol film in which the circumferential speed ratio S '/ S satisfies 0.950-0.90 when the circumferential speed of is set to S'.

The polarizing film manufactured from the polyvinyl alcohol film in any one of Claims 1-3.