JP2011111526A - Polyvinyl alcohol-based polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based polymer film having a small dimensional change when swelled, and to provide a method for producing the polyvinyl alcohol-based polymer film and a method for producing a polarizing film by using the polyvinyl alcohol-based polymer film. <P>SOLUTION: The polyvinyl alcohol-based polymer film includes air bubbles each having 0.5-0.9 μm diameter by ≥1.0×10<SP>4</SP>pieces per 1 cm<SP>2</SP>film area. The method for producing the polyvinyl alcohol-based polymer film includes the steps of: dissolving a polyvinyl alcohol-based polymer in water including air bubbles each having 0.5-0.9 μm diameter; preparing a film-forming stock solution including air bubbles each having 0.5-0.9 μm diameter by ≥1.0×10<SP>5</SP>pieces per 1 cm<SP>3</SP>; and forming the polyvinyl alcohol-based polymer film by using the film-forming stock solution. The method for producing the polarizing film includes the steps of dyeing and uniaxially-stretching the polyvinyl alcohol-based polymer film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyvinyl alcohol polymer film containing fine bubbles, a method for producing the same, and a method for producing a polarizing film. The polyvinyl alcohol polymer film of the present invention can be preferably used for the purpose of producing a polarizing film.

  A polarizing plate that selectively transmits specific polarized light is an important member that constitutes a liquid crystal display (LCD) together with a liquid crystal that changes the polarization state of light. LCDs are used in a wide range of applications such as small devices such as calculators and wristwatches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors.

  Conventionally used polarizing plates are produced by bonding a protective film such as a cellulose triacetate film or an acetic acid / butyric acid cellulose film on one or both sides of a polarizing film. In many cases, the polarizing film is a polyvinyl alcohol polymer (hereinafter, “polyvinyl alcohol polymer” may be abbreviated as “PVA”). After the film is swollen with water, iodine or a dichroic dye is used. It is manufactured by performing a dyeing treatment by uniaxial stretching, a uniaxial stretching, a fixing treatment with a boron compound, and the like.

  In general, a PVA film having high water absorption can be easily dyed with iodine or a dichroic dye, so that the line speed in the polarizing film manufacturing process can be increased and the productivity is excellent. However, the PVA film tends to absorb water excessively in the swelling process, the dimensional change rate in the direction perpendicular to the flow direction of the PVA film (so-called width direction) increases, wrinkles are generated in the entire PVA film, or the width direction of the PVA film The problem that the end is bent is likely to occur. Therefore, a PVA film having a small dimensional change in the swelling process has been demanded.

By the way, the PVA film containing a bubble is known. For example, an embroidery base film having a water-soluble polyvinyl alcohol resin as a main component, having open cells or closed cells, and a density of 0.05 to 1.0 g / cm ³ is known (Patent Document 1). reference). Patent Document 1 describes a method in which a polyvinyl alcohol-based resin is dissolved in water or an organic solvent to prepare a polyvinyl alcohol-based resin solution, the solution is foamed, and this is formed into a film. However, the size of the bubbles specifically described in Patent Document 1 is relatively large, and is easily defoamed in the process of forming the PVA film, and it is difficult to obtain a PVA film having stable quality. there were.

  Further, it is known that a recording medium having an ink receiving layer has a porous structure containing polyvinyl alcohol (see Patent Document 2). Patent Document 2 describes that after a coating liquid prepared by dissolving polyvinyl alcohol in water is stirred so that fine bubbles are formed, this is applied to a substrate and then dried. In addition, it is described that the average particle diameter of fine bubbles is 1.5 μm or less. However, it is difficult to obtain a PVA film having a small dimensional change in the swelling process when manufacturing a polarizing film or the like simply by including fine bubbles in the PVA polymer.

JP 11-217457 A JP 2001-39024 A

  An object of this invention is to provide the PVA film with a small dimensional change at the time of swelling, and its manufacturing method. Moreover, an object of this invention is to provide the manufacturing method of the polarizing film using the said PVA film.

As a result of intensive studies to achieve the above object, the present inventors swelled by including 1.0 × 10 ⁴ or more bubbles having a diameter of 0.5 to 0.9 μm per 1 cm ² of PVA film area. The present inventors have found that the dimensional change at the time can be reduced, and further studied based on the knowledge to complete the present invention.

That is, the present invention
[1] A polyvinyl alcohol polymer film containing at least 1.0 × 10 ⁴ bubbles having a diameter of 0.5 to 0.9 μm per 1 cm ² of film area,
[2] The polyvinyl alcohol polymer film of [1], having a thickness of 5 to 200 μm,
[3] The polyvinyl alcohol polymer film of [1] or [2], wherein the bubbles are formed from air,
[4] The polyvinyl alcohol polymer film according to any one of the above [1] to [3], which is a single layer film,
[5] The polyvinyl alcohol polymer film according to any one of the above [1] to [4], which is a polyvinyl alcohol polymer film for producing a polarizing film,
[6] Manufactured by dissolving a polyvinyl alcohol polymer in water containing bubbles having a diameter of 0.5 to 0.9 μm and containing 1.0 × 10 ⁵ or more bubbles having a diameter of 0.5 to 0.9 μm per cm ³ A method for producing a polyvinyl alcohol polymer film, comprising preparing a film stock solution and obtaining a polyvinyl alcohol polymer film using the film forming stock solution,
[7] A method for producing a polarizing film for dyeing and uniaxially stretching the polyvinyl alcohol-based polymer film of [5] above,
About.

  ADVANTAGE OF THE INVENTION According to this invention, the PVA film suitable for polarizing film manufacture with a small dimensional change at the time of swelling is provided. Moreover, according to this invention, the manufacturing method of the PVA film which can manufacture the said PVA film easily is provided. Furthermore, according to this invention, the manufacturing method of the polarizing film which can manufacture easily the polarizing film which has a small dimensional change at the time of swelling and has the outstanding quality is provided.

The present invention is described in further detail below.
As PVA which comprises the PVA film of this invention, what is manufactured by saponifying the polyvinyl-ester type polymer obtained by superposing | polymerizing 1 type (s) or 2 or more types of vinyl ester can be used. Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate and the like. Among these vinyl esters, vinyl acetate is preferred from the viewpoints of availability, ease of production of PVA, cost, and the like.

  The above-mentioned polyvinyl ester polymer is preferably obtained using only one or two or more kinds of vinyl esters as a monomer, and obtained using only one kind of vinyl ester as a monomer. Is more preferable, but may be a copolymer of one or more vinyl esters and other monomers copolymerizable therewith, as long as the effects of the present invention are not impaired. .

  Examples of other monomers copolymerizable with the vinyl ester include, for example, α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; (meth) acrylic acid or a salt thereof; (Meth) methyl acrylate, (meth) ethyl acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, ( (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate; (meth) acrylamide, N-methyl ( (Meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acryl (Meth) acrylamide derivatives such as amide, (meth) acrylamide propanesulfonic acid or salts thereof, (meth) acrylamidepropyldimethylamine or salts thereof, N-methylol (meth) acrylamide or derivatives thereof; N-vinylformamide, N-vinyl N-vinylamides such as acetamide and N-vinylpyrrolidone; 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, poly Vinyl ethers such as oxyethylene vinyl ether; Vinyl cyanides such as (meth) acrylonitrile; Vinyl chloride, vinylidene chloride, vinyl fluoride, fluoride Vinyl halides such as vinylidene; vinyl carbonates such as vinyl ethyl carbonate; dihydroxybutene derivatives such as 3,4-diacetoxy-1-butene and 3,4-diethoxy-1-butene; allyl compounds such as allyl acetate and allyl chloride; Mention may be made of maleic acid or a salt or ester thereof; itaconic acid or a salt or ester thereof; a vinylsilyl compound such as vinyltrimethoxysilane; an unsaturated sulfonic acid. Said polyvinyl ester-type polymer can have a structural unit derived from 1 type, or 2 or more types of an above described other monomer.

  The proportion of structural units derived from the other monomers in the polyvinyl ester polymer is 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester polymer. Preferably, it is 10 mol% or less, more preferably 5 mol% or less.

  In the PVA used in the present invention, a part of the hydroxyl group may be cross-linked or may not be cross-linked. The PVA used in the present invention may have a hydroxyl group partially reacted with aldehydes such as formalin, acetaldehyde, butyraldehyde and benzaldehyde to form an acetal structure, or without reacting with aldehydes and the like. The structure may not be formed.

  From the viewpoint of increasing the strength of the film, the average degree of polymerization of PVA used in the present invention is preferably 800 or more, more preferably 1000 or more, further preferably 1500 or more, and 2000 or more. It is particularly preferred that Although there is no restriction | limiting in particular in the upper limit of the average degree of polymerization of PVA, since manufacture of PVA is industrially easy, it is preferable that it is 10,000 or less, It is more preferable that it is 8000 or less, It is that it is 6000 or less. Further preferred. In addition, the average degree of polymerization of PVA as used in this specification means the average degree of polymerization measured according to description of JIS K 6726-1994.

  Moreover, there is no limitation in particular in the saponification degree of PVA used in this invention, According to the use of a PVA film, it can adjust suitably. For example, if it is a use of a water-soluble film, it is preferable that the saponification degree of PVA exists in the range of 80-100 mol%, It is more preferable that it exists in the range of 82-95 mol%, 85-90 mol% More preferably, it is within the range. For fiber packaging use, optical use (for example, for polarizing film production, etc.), release use, etc., the saponification degree of PVA is preferably in the range of 88 to 100 mol%, and in the range of 95 to 100 mol%. It is more preferable that it is within the range of 98 to 100 mol%. In this specification, the degree of saponification of PVA refers to the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification of PVA. The ratio (mol%) occupied by the number of moles of alcohol units. The degree of saponification of PVA can be measured according to the description of JIS K 6726-1994.

  A plasticizer can be mix | blended with said PVA film. As the plasticizer, polyhydric alcohol is preferably used, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. These plasticizers may be used alone or in combination of two or more. Among these, glycerin is preferable from the viewpoints of volatility and plasticity.

  The content of the plasticizer in the PVA film is preferably in the range of 3 to 20 parts by mass, more preferably in the range of 4 to 18 parts by mass, with respect to 100 parts by mass of PVA, and 5 to 15 parts by mass. More preferably, it is within the range of parts. When the content of the plasticizer is 3 parts by mass or more with respect to 100 parts by mass of PVA, the flexibility of the PVA film is improved and the handleability is improved. On the other hand, when the content of the plasticizer is 20 parts by mass or less with respect to 100 parts by mass of PVA, the plasticizer bleeds out on the surface of the PVA film, and the handleability of the PVA film is reduced or the stretchability is reduced. Can be suppressed.

  Moreover, it is preferable to make a PVA film contain surfactant in order to improve the handleability of the film. Among the surfactants, anionic or nonionic surfactants are preferable. The anionic surfactant is preferably a sodium alkyl ether sulfonate such as sodium triethoxydodecane sulfonate, and the nonionic surfactant is preferably a polyoxyethylene alkyl ether (polyoxyethylene lauryl ether or the like). These surfactants may be used alone or in combination of two or more.

  The content of the surfactant in the PVA film is preferably within a range of 0.01 to 0.5 parts by mass, and within a range of 0.02 to 0.3 parts by mass with respect to 100 parts by mass of PVA. It is more preferable that it is in the range of 0.05 to 0.1 parts by mass. When the content of the surfactant is 0.01 parts by mass or more with respect to 100 parts by mass of PVA, the film forming property and the peelability can be improved. On the other hand, when the content of the surfactant is 0.5 parts by mass or less with respect to 100 parts by mass of PVA, the surfactant bleeds out on the surface of the PVA film, resulting in blocking, and handling properties are reduced. Can be suppressed.

The PVA film of the present invention may be composed only of PVA or only of PVA and the above-mentioned plasticizer and / or surfactant, except for the bubble part. It may contain other components other than the above-described PVA, plasticizer and surfactant, such as an inhibitor, an antifreezing agent, a pH adjuster, a concealing agent, an anti-coloring agent, an oil agent, and an inorganic filler.
The proportion of the total of PVA, plasticizer and surfactant in the portion other than the bubble portion of the PVA film of the present invention is preferably in the range of 50 to 100% by mass, and in the range of 80 to 100% by mass. It is more preferable that it is within the range of 95 to 100% by mass.

The PVA film of the present invention contains at least 1.0 × 10 ⁴ bubbles having a diameter of 0.5 to 0.9 μm per 1 cm ² of film area. If the diameter of the bubbles contained in the PVA film is too small, the dimensional stability of the PVA film cannot be improved. This is presumably because air bubbles that are too small cannot buffer the volume change during swelling of the PVA film. On the other hand, if the bubble diameter is too large, the color of the PVA film will appear whitish and the transparency will be lowered, which is not preferable.

  The diameter of the bubbles in the PVA film can be measured by observing the PVA film with a microscope. Specifically, after the PVA film is pre-stained as necessary, the diameter of each bubble can be measured by observing the bubbles with a microscope (for example, 400 times magnification). Bubbles are usually spherical, so you can measure the diameter of any part of the round image observed with a microscope, but the bubble is not round and the image observed with a microscope is not round. For bubbles, the maximum length of the image can be considered as the diameter of the bubble.

Further, in the PVA film of the present invention, the number of bubbles having a diameter 0.5~0.9μm mentioned above is too small and since the effect of the present invention is not exhibited sufficiently, an area 1 cm ² per PVA film 1. It is 0 × 10 ⁴ or more, and preferably 1.5 × 10 ⁴ or more. When the number of bubbles in the PVA film is in the above range, the dimensional change when the PVA film is swollen can be reduced. The reason why the dimensional change when the PVA film is swollen is not clear, but it is considered that bubbles in the PVA film buffer the volume change when the PVA film is swollen. The upper limit of the number of bubbles is not particularly limited, but if the amount is too large, the strength of the film tends to decrease. Therefore, the number of bubbles is 1.0 × 10 ⁶ or less per cm ² area of the PVA film. It is preferable that the number is 1.0 × 10 ⁵ or less.

The number of bubbles can be measured using a microscope. Specifically, after pre-staining the PVA film as necessary, the number of bubbles having the above-mentioned diameter included per 1 mm ² area of the PVA film is measured with a microscope (for example, 400 times magnification). It can obtain | require by converting per 1 cm < ² > area.

  As the gas forming the bubbles contained in the PVA film of the present invention, for example, air, inert gas (nitrogen, argon, etc.), ozone, a volatile organic compound having a molecular weight of 100 or less can be used. When a gas that is difficult to dissolve in water is used as the gas to be formed, it is preferable because it is easy to include bubbles having the above diameter in the PVA film. As the gas, air is most easily used.

  The thickness of the PVA film of the present invention is preferably 5 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more. When the thickness is 5 μm or more, the PVA film is hardly broken. The upper limit of the thickness varies depending on the use of the PVA film, but is preferably 200 μm or less, and more preferably 100 μm or less from the viewpoint of cost. In addition, the thickness of a PVA film can measure the thickness of arbitrary 5 places, and can obtain | require as those average values.

  The PVA film of the present invention can be used in the form of a single layer film, depending on the application. Moreover, the PVA film of the present invention can be stored or transported as a roll obtained by winding a single layer film.

  The PVA film of the present invention can be produced by preparing a film-forming stock solution by dissolving PVA in water containing bubbles having a diameter of 0.5 to 0.9 μm, and using the film-forming stock solution. As a method for producing a PVA film from a film-forming stock solution, a cast film-forming method is preferred in which the film-forming stock solution is poured onto a metal roll or the like and dried to form a film.

  The film-forming stock solution is heated and stirred after supplying water containing bubbles, PVA, and, if necessary, a plasticizer, a surfactant, and other components into a container such as a tank. Can be prepared.

The number of bubbles having a diameter of 0.5 to 0.9 μm in the water containing bubbles is preferably 1.0 × 10 ⁵ or more per 1 cm ^{3 of} water containing bubbles, and 1.5 × 10 ⁵ or more. It is more preferable that When the number of bubbles is 1.0 × 10 ⁵ or more, the PVA film of the present invention can be easily produced. The upper limit of the number of bubbles in the water containing bubbles depends on the number of bubbles in the PVA film to be produced, but considering the use of a commercially available bubble generator, the number of bubbles is It is preferably 5.0 × 10 ⁷ or less per 1 cm ^{3 of} water containing bubbles.
Distilled water is preferably used as the water used when preparing the water containing bubbles.

  The water containing bubbles can be prepared using a commercially available microbubble generator or nanobubble generator, and by using the device, bubbles with a diameter of 0.5 to 0.9 μm can be stabilized. Can be generated. When the diameter of the generated bubbles is 0.9 μm or less, the bubbles are not easily affected by buoyancy and can be stably present in water.

  As the above-described microbubble generator or nanobubble generator, for example, “Bavitas” manufactured by Kyowa Kikai Co., Ltd. or “AS-MA1” manufactured by Asp Co., Ltd. can be preferably used. As operating conditions, from the viewpoint of efficiency in generating bubbles having the above diameter, when using “Bavitus” manufactured by Kyowa Kikai Co., Ltd., the air suction memory attached to the device is set to zero. It is preferable to operate under conditions that are in the range of 0.6 to 1.0, and it is more preferable to operate under conditions that are in the range of 0.7 to 0.9.

The number of bubbles having a diameter of 0.5 to 0.9 μm in the film-forming stock solution is preferably 1.0 × 10 ⁵ or more per 1 cm ^{3 of the} film-forming stock solution, and 1.5 × 10 ⁵ or more. It is more preferable that The upper limit of the number of bubbles depends on the number of bubbles in the PVA film to be manufactured, but is preferably 5.0 × 10 ⁷ or less per 1 cm ^{3 of} water containing bubbles. In addition, since the film-forming stock solution contains bubbles having a diameter of 0.5 to 0.9 μm, the stability of the bubbles in the film-forming stock solution is improved and remains inside the PVA film after film formation without being degassed. It becomes possible.

  The diameter and number of bubbles in the water containing the bubbles and the film-forming stock solution can be measured by a light scattering method, and specifically, can be measured by the method described later in the item of the examples.

  In producing a PVA film by a cast film forming method, a T-type slit die, a hopper plate, an I-die, a lip coater die, etc. are used, and a heated first roll that rotates the film forming stock solution located on the most upstream side ( Alternatively, the volatile matter is evaporated and dried from one side of the film discharged or cast onto the first roll (or belt), and then discharged or cast. The circumference of one or a plurality of rotating heated rolls disposed on the downstream side of the second heated roll (or drying roll) that passes through the other surface of the film is dried by passing it over the peripheral surface. It is possible to employ industrially preferably a method of further drying on the surface or passing through a hot-air drying apparatus and further winding the film on a winding apparatus. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

  There is no restriction | limiting in particular in the use of the PVA film of this invention, For example, although it can be used for a water-soluble film use, a fiber packaging use, an optical use, a mold release use etc., the PVA film of this invention is a dimensional change at the time of swelling. Therefore, it is preferably used for optical applications, and more preferably used for producing a polarizing film.

  The polarizing film can be produced by dyeing and uniaxially stretching the above PVA film, and further performing a fixing treatment, a drying treatment, a heat treatment or the like as necessary. There is no restriction | limiting in particular in the order of each process, You may perform two or more processes (for example, dyeing | staining and uniaxial stretching) simultaneously. Further, each step may be repeated a plurality of times.

  Dyeing can be performed before uniaxial stretching, at the same time as uniaxial stretching, or after uniaxial stretching, but PVA tends to increase the degree of crystallinity due to uniaxial stretching, and the dyeability may be lowered, so prior to uniaxial stretching. It is preferred to dye at any time or during the uniaxial stretching step.

  As dyes used for dyeing, iodine-potassium iodide or 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; Dichroic dyes such as yellow 8, 12, 44, 86, 87; Direct orange 26, 39, 106, 107 can be used. Dyeing can usually be performed by immersing the PVA film in a solution containing the dye, but the treatment conditions and treatment method are not particularly limited.

  The uniaxial stretching performed in the length direction of the PVA film may employ a wet stretching method or a dry heat stretching method, and may be performed in warm water (in a solution containing the dye or a fixed treatment bath described later), or water absorption. The latter PVA film may be used in the air. The stretching ratio is preferably 4 times or more, particularly preferably 5 times or more, as the length in the stretching direction. If the draw ratio is less than 4, it is difficult to obtain practically sufficient polarization performance and durability performance. The stretching temperature is not particularly limited, but when the PVA film is stretched in warm water (wet stretching), it is preferably in the range of 30 to 90 ° C, and in the case of dry heat stretching, it is in the range of 50 to 180 ° C. It is preferable to be within. The thickness of the PVA film after stretching depends on the thickness of the PVA film to be used, but is preferably in the range of 3 to 75 μm, and more preferably in the range of 10 to 50 μm.

  For the purpose of strengthening the adsorption of the dye to the PVA film, a fixing treatment is preferably performed. Boric acid or a boron compound can be added to the treatment bath used for the fixing treatment.

  The drying treatment (heat treatment) of the PVA film is preferably performed within a range of 30 to 150 ° C, and more preferably within a range of 50 to 150 ° C.

  The polarizing film obtained as described above can be used as a polarizing plate by attaching a protective film optically transparent and having mechanical strength on both sides or one side. As the protective film, a cellulose acetate film, an acrylic film, a polyester film, or the like can be used.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, each measuring method of the number of bubbles in the water containing a bubble and film forming undiluted | stock solution, the number of bubbles in a PVA film, and the dimensional change rate at the time of swelling of a PVA film employ | adopted in the following Examples and Comparative Examples Is shown below.

Measurement of the number of bubbles in water and film-forming stock solution containing bubbles The number of bubbles in water and film-forming stock solution containing bubbles was measured by “LS-200” manufactured by Particle Measuring Systems. Specifically, the device is charged with 3 cm ^{3 of} water or film-forming stock solution containing bubbles, the particle diameter (assumed to be the diameter) and number of bubbles contained in 3 cm ³ are measured, and the numerical value is 1 / 3, the number of bubbles in water containing bubbles or 1 cm ^{3 of the} film forming stock solution was calculated.

Measurement of the number of bubbles in the PVA film After the PVA film containing bubbles was immersed in an aqueous solution of 0.02% by mass of iodine / 2% by mass of potassium iodide / 4% by mass of boric acid for 1 minute and dyed, a differential interference microscope Using “ECLIPSE E-600W” (manufactured by Nikon), the number of bubbles in a PVA film area of 1 mm ² was measured at a magnification of 400 times and converted to 1 cm ² .

Measurement of dimensional change rate during swelling of PVA film PVA film was cut into 15 cm length x 15 cm width, immersed in distilled water at 30 ° C. for 60 minutes, taken out from distilled water, and longitudinal direction (the film forming direction of PVA film) ) And the dimensional change rate of the central part in the lateral direction (direction perpendicular to the film forming direction of the PVA film on the PVA film) were obtained by the following formulas.
Dimensional change rate (%) = 100 × [length after swelling] / [length before swelling]

[Example 1]
Using "Bavitas" manufactured by Kyowa Kikai Co., Ltd., adjust the air suction amount to about 0.7 memory of the air gauge attached to the device so that air bubbles are contained in distilled water. Produced. In the water containing bubbles, the number of bubbles having a diameter of 0.5 to 0.9 μm was 2.2 × 10 ⁵ per 1 cm ^{3 of} water containing bubbles.
Next, 100 g of polyvinyl alcohol having an average degree of polymerization of 2400 and a saponification degree of 99 mol%, 12 g of glycerin, and 0.1 g of polyoxyethylene lauryl ether are added to 1000 g of water containing the above-mentioned bubbles and heated to 80 ° C. for 4 hours. The mixture was stirred to prepare a film-forming stock solution containing bubbles. In the film-forming stock solution containing bubbles, the number of bubbles having a diameter of 0.5 to 0.9 μm was 2.0 × 10 ⁵ per 1 cm ^{3 of the} film-forming stock solution.
The obtained film-forming stock solution containing bubbles was cooled to 60 ° C., cast and cast on a metal roll having a chrome plating surface at 60 ° C., and dried to obtain a 100 μm thick PVA film. In the PVA film, the number of bubbles having a diameter of 0.5 to 0.9 μm was 2.0 × 10 ⁴ per 1 cm ² of the PVA film.
When the dimensional change rate at the time of swelling of this PVA film was measured by the above method, it was 120% in length and 120% in width, and the dimensional change was good.

[Example 2]
Using "Bavitas" manufactured by Kyowa Kikai Co., Ltd., adjust the air suction amount to about 0.7 memory of the air gauge attached to the device so that air bubbles are contained in distilled water. Produced. In the water containing bubbles, the number of bubbles having a diameter of 0.5 to 0.9 μm was 2.6 × 10 ⁵ per 1 cm ^{3 of} water containing bubbles.
Next, 100 g of polyvinyl alcohol having an average degree of polymerization of 2400 and a saponification degree of 99 mol%, 12 g of glycerin, and 0.1 g of polyoxyethylene lauryl ether are added to 1000 g of water containing the above-mentioned bubbles and heated to 80 ° C. for 4 hours. The mixture was stirred to prepare a film-forming stock solution containing bubbles. In the film-forming stock solution containing bubbles, the number of bubbles having a diameter of 0.5 to 0.9 μm was 2.3 × 10 ⁵ per 1 cm ^{3 of the} film-forming stock solution.
The obtained film-forming stock solution containing bubbles was cooled to 60 ° C., cast and cast on a metal roll having a chrome plating surface at 60 ° C., and dried to obtain a PVA film having a thickness of 100 μm. In the PVA film, the number of bubbles having a diameter of 0.5 to 0.9 μm was 2.3 × 10 ⁴ per 1 cm ² of the PVA film.
When the dimensional change rate at the time of swelling of this PVA film was measured by the above-mentioned method, it was 118% in length and 119% in width, and the dimensional change was good.

[Comparative Example 1]
Add 100g of polyvinyl alcohol with average polymerization degree of 2400, saponification degree of 99mol%, 12g of glycerin and 0.1g of polyoxyethylene lauryl ether to 1000g of distilled water, heat to 80 ° C and stir for 4 hours to contain bubbles A film-forming stock solution was prepared.
The obtained film-forming stock solution containing no bubbles was cooled to 60 ° C., cast and cast onto a metal roll having a chromium plating surface at 60 ° C., and dried to obtain a PVA film having a thickness of 100 μm.
When the dimensional change rate at the time of swelling of this PVA film was measured by the above-described method, it was 128% in length and 130% in width, and was a film having a large dimensional change.

[Comparative Example 2]
Using "Bavitas" manufactured by Kyowa Kikai Co., Ltd., adjust the air suction volume to about 0.5 memory with the air gauge memory attached to the device, so that distilled water contains air bubbles. Produced. In the water containing bubbles, the number of bubbles having a diameter of 0.5 to 0.9 μm was 9.5 × 10 ⁴ per 1 cm ^{3 of} water containing bubbles.
Next, 100 g of polyvinyl alcohol having an average degree of polymerization of 2400 and a saponification degree of 99 mol%, 12 g of glycerin, and 0.1 g of polyoxyethylene lauryl ether are added to 1000 g of water containing the above-mentioned bubbles and heated to 80 ° C. for 4 hours. The mixture was stirred to prepare a film-forming stock solution containing bubbles. In the film-forming stock solution containing bubbles, the number of bubbles having a diameter of 0.5 to 0.9 μm was 8.6 × 10 ⁴ per 1 cm ^{3 of the} film-forming stock solution.
The obtained film-forming stock solution containing bubbles was cooled to 60 ° C., cast and cast on a metal roll having a chrome plating surface at 60 ° C., and dried to obtain a PVA film having a thickness of 100 μm. In the PVA film, the number of bubbles having a diameter of 0.5 to 0.9 μm was 8.5 × 10 ³ per 1 cm ² of the PVA film.
When the dimensional change rate at the time of swelling of this PVA film was measured by the above-mentioned method, it was 125% in length and 128% in width, and was a film with large dimensional change.

  The PVA film of the present invention can be preferably used for optical applications such as for producing a polarizing film because the dimensional change during swelling is small.

Claims (7)

A polyvinyl alcohol polymer film containing at least 1.0 × 10 ⁴ bubbles having a diameter of 0.5 to 0.9 μm per 1 cm ² of film area.   The polyvinyl alcohol polymer film according to claim 1, which has a thickness of 5 to 200 µm.   The polyvinyl alcohol polymer film according to claim 1 or 2, wherein the bubbles are formed from air.   It is a single layer film, The polyvinyl alcohol-type polymer film of any one of Claims 1-3.   It is a polyvinyl alcohol-type polymer film for polarizing film manufacture, The polyvinyl alcohol-type polymer film of any one of Claims 1-4. A film-forming stock solution containing 1.0 × 10 ⁵ or more bubbles of 0.5 to 0.9 μm in diameter per cm ³ by dissolving a polyvinyl alcohol polymer in water containing bubbles of 0.5 to 0.9 μm in diameter A method for producing a polyvinyl alcohol polymer film, which is prepared and a polyvinyl alcohol polymer film is obtained using the stock solution.   The manufacturing method of the polarizing film which dye | stains and uniaxially stretches the polyvinyl alcohol-type polymer film of Claim 5.