TWI689745B - Method for manufacturing polarizing film - Google Patents

Abstract

The present invention provides a method for manufacturing a polarizing film. Even when a thin polyvinyl alcohol film is used, the film is less likely to be broken during stretching or drying, and a polarizing film with excellent polarizing performance can be easily manufactured.

The present invention is a manufacturing method which is a manufacturing method of a polarizing film having an extending step of extending a polyvinyl alcohol film, which has gas and/or gas sprayed at both ends of the polyvinyl alcohol film with water adhering to the surface in the width direction Steps to contact the thin body. The polyvinyl alcohol film having a water immersion step of immersing the polyvinyl alcohol film in water, and the water adhering to the surface is ideal for removing the polyvinyl alcohol film immersed in water by the water immersion step from the water.

Description

Method for manufacturing polarizing film

The present invention relates to a method of manufacturing a polarizing film. Even when a thin polyvinyl alcohol film is used, it can suppress the folding of the end of the polyvinyl alcohol film, and it is difficult to cause the film to break during stretching or drying, and A polarizing film excellent in polarizing performance can be easily manufactured.

A polarizing plate having a function of transmitting and shielding light is a basic constituent element of a liquid crystal display (LCD) together with liquid crystal that changes the polarization state of light. Most polarizing plates have a structure in which a protective film such as cellulose triacetate (TAC) film is bonded to the surface of the polarizing film. As the polarizing film constituting the polarizing plate, a polyvinyl alcohol film (hereinafter sometimes referred to as "poly "Vinyl alcohol" (abbreviated as "PVA") uniaxially stretched and oriented stretched film adsorbs iodine-based dyes (I ₃ ^- or I ₅ ^- etc.) or dichroic dyes of dichroic organic dyes has become mainstream. As described above for the polarizing film, it is common to uniaxially stretch the PVA film containing the dichroic dye in advance, to adsorb the dichroic dye simultaneously with the uniaxial stretching of the PVA film, to adsorb the dichroic dye after uniaxially stretching the PVA film, etc. And continuously manufactured.

The LCD is used in a wide range of small devices such as computers and watches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal TVs, car navigation systems, mobile phones, and measurement equipment used inside and outside the house. But in recent years it has become especially popular for small Mobile applications such as notebook computers or mobile phones, and the demand for thinner polarizers has become stronger.

As one method of thinning the polarizing plate, the thinning of the polarizing film can be mentioned. Therefore, the thinning of the PVA film which is the raw material of the polarizing film can be considered. However, a thin PVA film is prone to breakage of the film during stretching or drying, and the productivity or yield of the polarizing film will be reduced, and it will easily lead to high cost.

As a technique for producing a thin polarizing film without breaking the film, a method of forming a thin PVA layer on a plastic film by a coating method and extending the laminate (for example, see Patent Documents 1 and 2 etc.) ).

Prior technical literature Patent Literature

Patent Literature 1 Japanese Patent No. 4804588

Patent Literature 2 Japanese Patent No. 4815544

However, the method of using a laminate formed by forming a PVA layer on a plastic film by a coating method has the following problems.

(i) The coating operation or the subsequent drying operation is complicated.

(ii) Since the heat treatment for the insolubilization of the PVA layer needs to be performed in the state of a laminate, the plastic film used is limited to those that can be stretched after the heat treatment, and the cost becomes high.

(iii) In a laminate formed by forming a PVA layer by a coating method on a plastic film, the adhesion strength between the plastic film and the PVA layer is high, and extending the laminate with a high adhesion strength as described above will hinder PVA The layer is moderately neck-in, and it is difficult to obtain a polarizing film with excellent polarizing performance.

An object of the present invention is to provide a method for manufacturing a polarizing film. Even when a thin PVA film is used, the film is less likely to be broken during stretching or drying, and a polarizing film with excellent polarizing performance can be easily manufactured.

The inventors of the present case have repeatedly studied carefully to achieve the aforementioned object and found that when a polarized film is manufactured using a thin PVA film, water is attached to the water contact step of contacting the water with the PVA film through the swelling step or the dyeing step before stretching In the PVA film on the rear surface, it is easy to buckle at the end in the width direction, and the reason mentioned above is that it is easy to cause discontinuity of stretching in the subsequent stretching step, and there is water attached to the surface after stretching. It is still easy to buckle at the end in the width direction, and the above causes, after the drying step, it will easily cause the film to break due to shrinkage, and spray air at the both ends in the width direction of the PVA film with water attached to the surface The thin body such as gas, contact with plastic film, etc., can suppress the occurrence of buckling of the width end of the PVA film, and can reduce the film breakage (discontinuity, etc.) during stretching or drying. Produced, and based on such knowledge, further repeated discussion to complete the present invention.

That is, the present invention relates to the following.

[1] A manufacturing method, which is a manufacturing method of a polarizing film having an extending step of extending a PVA film, which has a method of spraying gas and/or contacting a thin body at both widthwise ends of a PVA film with water adhering to the surface A step of.

[2] The manufacturing method as described in [1] above, which has a water immersion step of immersing the PVA film in water, and the PVA film with water adhered to the surface is the PVA film immersed in water by the water immersion step, the latter is taken out from the water .

[3] The manufacturing method according to [2] above, wherein the water immersion step is at least one selected from the group consisting of a swelling step, a dyeing step, a cross-linking step, an extension step, and a fixing treatment step.

[4] The manufacturing method according to the above [2] or [3], which is a manufacturing method having a step of bringing the thin body into contact with both ends of the PVA film on the surface in the width direction, and having The dipping step is to immerse the PVA film immersed in water from the water after the PVA film is in contact with one or more rollers, and from the PVA film after leaving the water surface to the first contact roller, the thin body and the PVA film Both ends in the width direction are in contact.

[5] The manufacturing method as described in [4] above, wherein the thin body is located at both ends in the width direction with respect to the length of the longitudinal direction of the PVA film from the time the PVA film leaves the water surface to the roller that first contacts the PVA film The ratio of the length of the PVA film in the longitudinal direction of the contact portion is 10% or more.

[6] The manufacturing method according to any one of the aforementioned [2] to [5], which is a manufacturing method having a step of bringing the thin body into contact with both ends in the width direction of the PVA film on which water adheres to the surface, At the part of the PVA film away from the water surface, both ends of the PVA film in the width direction are in contact with the thin body.

[7] The manufacturing method according to any one of the above [1] to [6], which is a manufacturing method having a step of bringing the thin body into contact with both ends in the width direction of the PVA film on which water is attached, having Two or more rollers in which the PVA film with water adhered to the surface are in sequence contact, and between at least one set of two consecutive rollers, the thin body is brought into contact with both ends of the PVA film in the width direction.

[8] The manufacturing method according to the aforementioned [7], wherein the lengthwise direction of the part of the PVA film at the portion where the thin body is in contact with the widthwise ends of the lengthwise direction of the PVA film between the two consecutive rollers The proportion of the length is more than 10%.

[9] The manufacturing method according to any one of the aforementioned [1] to [8], which is a manufacturing method having a step of bringing a thin body into contact with both ends in the width direction of a PVA film with water attached to the surface, wherein the The width of the thin body is more than 1cm.

[10] The manufacturing method according to any one of the aforementioned [1] to [9], which is a manufacturing method having a step of bringing a thin body into contact with both ends in the width direction of a PVA film on which water adheres to the surface, wherein The water contact angle of the thin body of the part where the PVA film contacts is 90° or less.

[11] The manufacturing method according to any one of the above [1] to [10], which has a step of spraying a gas with a blowing speed of 0.1 m/sec or more on both ends of the PVA film in which water adheres to the surface in the width direction.

[12] The manufacturing method according to any one of the aforementioned [1] to [11], which has a step of bringing the plastic film into contact with both ends in the width direction of the PVA film to which water adheres to the surface.

[13] The manufacturing method according to any one of the above [1] to [12], which has, before the extending step, spraying gas and/or contacting thin bodies at both ends of the PVA film with water adhering to the surface in the width direction Steps.

[14] The manufacturing method according to any one of the aforementioned [1] to [13], wherein the thickness of the PVA film is 50 μm or less.

According to the present invention, a method for manufacturing a polarizing film is provided. Even when a thin PVA film is used, the film is less likely to break during stretching or drying, and a polarizing film with excellent polarizing performance can be easily manufactured.

1‧‧‧PVA film

2‧‧‧plastic film

3‧‧‧End of plastic film upstream side (fixed end)

4‧‧‧End of plastic film on the downstream side (free end)

5‧‧‧Position of the plastic film at the two ends of the PVA film in the width direction

6‧‧‧PVA film end in the width direction

7‧‧‧PVA film and plastic film contact part

8‧‧‧Water

9‧‧‧The position where the PVA film leaves from the water

10‧‧‧PVA film is the roller that first contacts after leaving the water

11‧‧‧ One of two consecutive rolls

13‧‧‧Guide roller

14‧‧‧Roll

15‧‧‧PVA film roll

Figs. 1 (a) and (b) are schematic diagrams (method A) showing an example of a method of contacting both ends in the width direction of a PVA film on which a thin plastic film and water adhere to the surface.

FIGS. 2 (a) and (b) are schematic diagrams (method B) showing an example of a method of contacting the wide ends of a PVA film on which a thin plastic film and water adhere to the surface.

FIG. 3 is a schematic diagram showing the positions of L1 and L2 in a specific embodiment.

FIG. 4 is a schematic diagram showing the positions of L3 and L4 in a specific embodiment.

Fig. 5 is a schematic diagram showing a method for manufacturing a polarizing film of Example 7.

[Forms for carrying out the invention]

The present invention will be described in detail below.

The manufacturing method of the present invention for manufacturing a polarizing film has an extending step of extending a PVA film. Then, in the manufacturing method of the present invention, there is a method for adhering the water generated by performing the water contact step of contacting the PVA film with water through the swelling step, the dyeing step, the cross-linking step, the stretching step, the fixing treatment step, etc. to the surface The step of blowing gas and/or the step of bringing the thin body into contact at both ends of the PVA film in the width direction. Generally, when a polarizing film is manufactured using a PVA film, it is likely to buckle at the end in the width direction of the PVA film after passing through the water contact step, and the foregoing causes the film to be easily caused by a discontinuous stretching of the stretching step or shrinkage of the drying step Fracture, etc., but as mentioned above, by blowing gas at both ends of the PVA film in the state where water is attached to the surface to contact the thin body, the folds of the PVA film at the end of the width direction can be suppressed It can reduce the occurrence of film breakage during stretching or drying, and can be stretched at a higher stretch ratio, and can easily produce a polarizing film with excellent polarizing performance.

In the manufacturing method of the present invention, the step of injecting gas and the step of contacting the thin body may be used at the same time, or only one of them may be used. In addition, when two steps are used at the same time, two steps can be performed on the same part of the PVA film on which water adheres to the surface (for example, one side and the other side of the part of the PVA film respectively), or on the PVA The other part of the film is implemented in two steps.

[PVA film]

As the PVA constituting the PVA film, by polymerizing vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, trimethyl vinyl acetate, vinyl versatate, vinyl laurate Polyvinyl esters obtained from one or more vinyl esters such as esters, vinyl stearate, vinyl benzoate, and isopropenyl acetate are obtained by dip saponification. Among the above vinyl esters, compounds having a vinyloxycarbonyl group (H ₂ C=CH-O-CO-) in the molecule are preferred from the viewpoints of ease of production, ease of acquisition, cost, etc. of PVA, and vinyl acetate Esters are better.

The aforementioned polyvinyl ester is preferably obtained by using only one kind or two or more kinds of vinyl esters as monomers, and preferably obtained by using only one kind of vinyl esters as monomers, as long as the effects of the present invention are not made Within the scope of substantial damage, it can also be a copolymer of one or more vinyl esters and other monomers copolymerizable with these.

Examples of other monomers that can be copolymerized with the vinyl ester include, for example, ethylene, propylene, 1-butene, isobutene and the like having 2 to 30 carbon atoms; (meth)acrylic acid or its salts; Methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate (Meth)acrylates such as esters, third butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate; (Meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N,N-dimethyl (meth) acrylamide, diacetone ( Meth) acrylamide, (meth) acrylamide propanesulfonic acid or its salt, (meth) acrylamide (Meth)acrylamide derivatives such as aminopropyl dimethylamine or its salts, N-hydroxymethyl(meth)acrylamide or its derivatives; N-vinylmethylamide, N-ethyleneacetylamide N-vinylamide such as amine, N-vinylpyrrolidone, etc.; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, Vinyl ethers such as third butyl vinyl ether, dodecyl vinyl ether, and octadecyl vinyl ether; vinyl cyanide such as (meth)acrylonitrile; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, etc. Vinyl halide; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or anhydrides; itaconic acid or its salts, esters or anhydrides; vinyl silanes such as vinyl trimethoxysilane Base compound; unsaturated sulfonic acid or its salt, etc. The aforementioned polyvinyl ester may have one or more structural units derived from the aforementioned other monomers.

The proportion of the structural units derived from the other monomers occupied by the aforementioned polyvinyl ester is preferably 15 mol% or less, and more preferably 10 mol% or less based on all the structural units constituting the polyvinyl ester. 5 mol% is particularly good.

As the aforementioned PVA, those without graft copolymerization can be suitably used, but as long as the effect of the present invention is not significantly impaired, the PVA may be a single monomer that can be graft copolymerized by one or more than two kinds. Body and modified. This graft copolymerization can be performed on at least one of polyvinyl ester and PVA obtained by saponifying it. Examples of the graft copolymerizable monomer include unsaturated carboxylic acid or its derivative; unsaturated sulfonic acid or its derivative; and α-olefin having 2 to 30 carbon atoms. The proportion of the structural units derived from the monomers that can be graft copolymerized in the polyvinyl ester or PVA is preferably 5 mol% or less based on the molar number of all the structural units constituting the polyvinyl ester or PVA.

In the aforementioned PVA, a part of its hydroxyl group may or may not be cross-linked. In addition, in the aforementioned PVA, a part of the hydroxyl group may react with aldehyde compounds such as acetaldehyde and butyraldehyde to form an acetal structure, or may not react with such compounds to form an acetal structure.

The degree of polymerization of the aforementioned PVA is not particularly limited, but it is preferably 1,000 or more. With a polymerization degree of PVA of 1,000 or more, the polarization performance of the obtained polarizing film can be further improved. When the degree of polymerization of PVA is too high, there is a tendency to increase the manufacturing cost of PVA or the poor passability of the process during film formation, so the degree of polymerization of PVA is preferably in the range of 1,000 to 10,000, and the degree of polymerization of 1,500 to 8,000 Very good in the range, best in the range of 2,000~5,000. In addition, the degree of polymerization of PVA in this specification means the average degree of polymerization measured based on the description of JIS K6726-1994.

From the point of view that the obtained polarizing film has good moisture and heat resistance, the saponification degree of PVA is preferably 99.0 mol% or more, more preferably 99.8 mol% or more, and most preferably 99.9 mol% or more. Furthermore, the saponification degree of PVA in this specification means the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units obtained by saponification conversion to vinyl alcohol units with respect to PVA. Proportion of mole units occupied by alcohol units (mol%). The degree of saponification can be measured according to the description of JIS K6726-1994.

The PVA film may also contain both the aforementioned PVA and plasticizer. For PVA film, try to improve the handleability and extensibility of PVA film by including plasticizer. As the plasticizer, a polyhydric alcohol is preferably used. Specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylol. Propane, etc., and The PVA film may contain one or more of these plasticizers. Among these, glycerin is preferable from the viewpoint that the stretchability of the PVA film is better.

Relative to 100 parts by mass of PVA, the content of the plasticizer in the PVA film is preferably 3 to 20 parts by mass, more preferably 5 to 17 parts by mass, and particularly preferably 7 to 14 parts by mass. When the content of the plasticizer in the PVA film is 3 parts by mass or more relative to 100 parts by mass of PVA, the extensibility of the PVA film can be improved. On the other hand, when the content of the plasticizer in the PVA film is 20 parts by mass or less relative to 100 parts by mass of PVA, the plasticizer can be suppressed from being bleed-out on the surface of the PVA film to treat the PVA film Sexual decline.

In addition, when a PVA film is produced using a film-forming stock solution for manufacturing a PVA film described later, the film-forming property can be improved and the occurrence of unevenness in the thickness of the film can be suppressed. It is easy to see the peeling of the PVA film of the metal roller or the conveyor belt, and it is desirable to blend the surfactant in the film-forming raw solution. When manufacturing a PVA film from a film-forming stock solution blended with a surfactant, a surfactant may be included in the PVA film. The type of surfactant blended in the film-forming stock solution used to make the PVA film, or even the surfactant contained in the PVA film, is not particularly limited, but from the standpoint of releasability from metal rollers or conveyor belts, anions Non-ionic surfactants are preferred, and non-ionic surfactants are particularly preferred.

As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate; a sulfate type such as octyl sulfate; a sulfonic acid type such as dodecylbenzenesulfonate and the like are suitable.

As nonionic surfactants, for example, alkyl ether type such as polyoxyethylene oil ether; alkyl phenyl ether type such as polyoxyethylene octyl phenyl ether; alkyl ester type such as polyoxyethylene lauryl ester; polyoxyethylene Alkylamine type such as laurylamine ether; Alkylamine type such as polyoxyethylene laurylamide; Polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; Diethanolamide laurate, diethanolamide oleate Alkanol amine type such as amine; allyl phenyl ether type such as polyoxyallyl allyl phenyl ether, etc.

These surfactants can be used alone or in combination of two or more.

When blending the surfactant in the film-forming stock solution used to manufacture the PVA film, the content of the surfactant in the film-forming stock solution, or even the content of the surfactant in the PVA film, relative to the film-forming stock solution or PVA film contains The PVA 100 parts by mass is preferably in the range of 0.01 to 0.5 parts by mass, and more preferably in the range of 0.02 to 0.3 parts by mass. When the content of the surfactant is 0.01 parts by mass or more relative to 100 parts by mass of PVA, the film formability and 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 can be prevented from overflowing on the surface of the PVA film and causing agglomeration, thereby deteriorating the handleability.

The PVA film may be composed of only PVA, or may be composed of only PVA and the aforementioned plasticizer and/or surfactant, but may contain antioxidants, anti-freezing agents, pH adjusters, masking agents, anti-coloring, if necessary Agents, oils and other components other than the aforementioned PVA, plasticizers and surfactants.

The PVA content in the PVA film is preferably in the range of 50 to 100% by mass, more preferably in the range of 80 to 100% by mass, and particularly preferably in the range of 85 to 100% by mass.

The thickness of the PVA film is not particularly limited, but especially when a thin PVA film is used, the aforementioned folds are easily generated at the ends in the width direction, and when the thin PVA film is used, the effects of the present invention are more significantly exerted In view of this, the thickness is preferably 50 μm or less, more preferably 45 μm or less, particularly preferably 35 μm or less, very preferably 25 μm or less, and most preferably 20 μm or less. The lower limit of the thickness of the PVA film is not particularly limited, but from the viewpoint that the polarizing film can be manufactured more smoothly, the thickness is preferably 3 μm or more. In addition, the PVA film may be a single layer, or may be a laminate of a PVA layer and other layered layers, but a single layer is preferable from the viewpoint that the effect of the present invention can be more significantly exerted. In the case of a laminate, the thickness of the PVA layer is preferably in the aforementioned range.

The shape of the PVA film is not particularly limited, but from the viewpoint that the polarizing film can be continuously manufactured with good productivity, a long film is preferable. The length of the elongated film is not particularly limited, and can be appropriately set according to the application of the polarizing film to be manufactured, and can be set in the range of, for example, 5 to 20,000 m. The width of the elongated film is not particularly limited, and can be set to, for example, 50 cm or more. However, in recent years, a wide polarizing film is required, preferably 1 m or more, more preferably 2 m or more, and particularly preferably 4 m or more. The upper limit of the width of the elongated film is not particularly limited, but when the width is too wide, in the case of manufacturing a polarizing film with a practical device, it tends to become difficult to uniformly extend, so the width of the PVA film It is preferably 7m or less.

The manufacturing method of the PVA film is not particularly limited, and a manufacturing method in which the thickness and width of the film after film formation becomes more uniform can be appropriately adopted. For example, the PVA film can be used in which the aforementioned PVA is dissolved in a liquid medium, and if necessary A film-forming stock solution in which a plasticizer, a surfactant, and other components are further dissolved, or contains PVA, and if necessary, further contains a plasticizer, a surfactant, other components, and a liquid medium, and a PVA-melting film-forming stock solution is manufactured. When the film-forming stock solution contains at least one plasticizer, surfactant, and other components, these components are preferably uniformly mixed.

Examples of the liquid medium used for the preparation of the film-forming stock solution include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and ethylene glycol. , Glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., and one or two of these can be used the above. Among them, water is ideal from the viewpoint of low load on the environment or recyclability.

The volatile fraction of the film-forming stock solution (the content of the film-forming stock solution of the volatile components such as liquid media that are volatilized or removed by evaporation during film-making) varies depending on the film-forming method and film-forming conditions, but 50~ The range of 95% by mass is better, the range of 55 to 90% by mass is better, and the range of 60 to 85% by mass is particularly good. By the volatile fraction of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution will not become too high, it will be filtered or defoamed smoothly during the preparation of the film-forming stock solution, and it will be easy to produce foreign matter or have fewer defects PVA film. On the other hand, when the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution will not become too low, making it easier to manufacture industrial PVA thin films.

Examples of the film forming method when forming the PVA thin film using the above film forming raw solution include, for example, a cast film forming method, an extrusion film forming method, a wet film forming method, a colloidal film method, etc., and a cast film forming method Method, extrusion film making method is more ideal. Only one type of these methods may be used, or two or more types may be used in combination. Among these film forming methods, the extrusion film forming method is more preferable from the viewpoint of obtaining a PVA film having a uniform thickness and width and good physical properties. The PVA film can be dried or heat-treated as required.

[PVA film with water attached to the surface]

In the manufacturing method of the present invention, there is a method of spraying gas and/or bringing a thin body into contact with the both ends of the PVA film in the width direction where water generated by the step of contacting the PVA film with water is adhered to the surface step. The polarizing film can usually be manufactured through various steps such as swelling step, dyeing step, cross-linking step, stretching step, fixing treatment step, etc. The manufacturing method of the present invention may have one or more of these steps as water Contact steps.

The water contacting step may be a water spraying step for spraying water to the PVA film, or a water immersion step of immersing the PVA film in water, any one is acceptable, but the ease and productivity of manufacturing from the polarizing film, etc. In view of this, the water immersion step is more ideal. In particular, from the viewpoint that a polarizing film with better polarizing performance can be easily manufactured, the manufacturing method of the present invention has at least one selected from the group consisting of a swelling step, a dyeing step, a cross-linking step, an extension step, and a fixing treatment step The step is preferably a water immersion step, and it is more preferable to have at least one step selected from the group including a swelling step, a dyeing step, and a cross-linking step as a water immersion step. The PVA film immersed in water by the water immersion step after being taken out from the water is usually a PVA film in which the aforementioned water adheres to the surface.

The water used in the water contacting step is not limited to pure water. For the purpose of each step, an aqueous solution as described later or an aqueous dispersion liquid may be further used.

Including the steps that can be adopted as the water contact step, the steps that can be adopted in the manufacturing method of the present invention are explained in more detail below.

. Swelling step

The swelling treatment in the swelling step can be performed by immersing the PVA film in water. The temperature of the water when immersed in water is preferably in the range of 20 to 40°C, more preferably in the range of 22 to 38°C, and particularly preferably in the range of 25 to 35°C. In addition, as the time of immersion in water, for example, it is preferably in the range of 0.5 to 5 minutes, and more preferably in the range of 1 to 3 minutes. Furthermore, the water immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or may be a mixture of water and an aqueous medium.

. Dyeing steps

The dyeing treatment in the dyeing step can be performed by immersing the PVA film in an aqueous solution containing a dichroic dye. The concentration of the dichroic pigment in the aqueous solution containing the dichroic pigment can be appropriately set according to the type of dichroic pigment to be used, etc. For example, it can be set in the range of 0.001 to 1% by mass, but using iodine-potassium iodide When the aqueous solution is an aqueous solution containing a dichroic dye, the concentration of iodine (I ₂ ) used is preferably in the range of 0.01 to 1.0% by mass from the viewpoint of allowing the PVA film to efficiently adsorb the iodine-based dye, and is used as The concentration of potassium iodide (KI) is preferably in the range of 0.01 to 10% by mass. The temperature of the aqueous solution containing the dichroic pigment is preferably in the range of 20 to 50°C, and more preferably in the range of 25 to 40°C, from the viewpoint of allowing the PVA film to efficiently adsorb the dichroic dye. Furthermore, when a PVA film containing a dichroic dye in advance is used, the dyeing step can be omitted.

Examples of the dichroic dye include iodine-based dyes (I ₃ ^- or I ₅ ^-, etc.) and dichroic organic dyes. The iodine pigment can be obtained, for example, by contacting iodine (I ₂ ) with potassium iodide. Examples of dichroic organic dyes include 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; Direct Orange 26, 39, 106, 107, etc. Among these dichroic dyes, iodine-based dyes are particularly preferred from the viewpoints of handleability, availability, and polarizing performance. Furthermore, the dichroic pigment may be one kind alone, or two or more kinds, any one may be, for example, I ₃ ^- and I ₅ ^-may be a balanced mixture.

. Crosslinking steps

If the cross-linking step is performed, when the PVA film is cross-linked and the stretching step is performed at a relatively high temperature and in a wet manner, the PVA can be effectively prevented from dissolving out of water. According to the aforementioned viewpoints and the like, the crosslinking step is preferably performed after the dyeing step. The cross-linking treatment can be performed by immersing the PVA film in an aqueous solution containing a cross-linking agent. As the crosslinking agent, one or more types of boron compounds such as boric acid such as boric acid and borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, and more preferably in the range of 2 to 7% by mass. The aqueous solution containing the cross-linking agent may also contain additives such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50°C, and more preferably in the range of 25 to 40°C.

Unlike the stretching step described later, in the water contact step and/or when the water contact step passes through a plurality of steps, the PVA film can be stretched between the water contact steps. By performing the aforementioned extension (front extension), it is possible to prevent the PVA film from wrinkling. From the viewpoint of the polarizing performance of the obtained polarizing film, based on the original length of the PVA film before stretching, the stretching ratio of the front stretching is preferably 4 times or less, and more preferably in the range of 1.5 to 3.5 times. Also, regarding the extension magnification in each water contact step, for example, as the extension magnification in the swelling step, it is preferably in the range of 1.1 to 3 times, more preferably in the range of 1.2 to 2.5 times, and particularly preferably in the range of 1.4 to 2.3 times ; As the stretching magnification of the dyeing step, 2 times or less is better, more preferably 1.8 times or less, especially in the range of 1.1 to 1.5 times; as the stretch magnification of the cross-linking step, 2 times or less is better, 1.5 times or less is better, Very good within the range of 1.05~1.3 times.

. Extended steps

In the stretching step of stretching the PVA film, the stretching method is not particularly limited, and it can be performed by any of a wet stretching method and a dry stretching method. In the case of the wet stretching method, it can be carried out in one or more aqueous solutions containing boron compounds such as boric acid such as boric acid, borax, etc., or it can be fixed in the aforementioned aqueous solution containing dichroic dyes or described later In the treatment bath. In addition, in the case of the dry stretching method, the stretching can be carried out while maintaining the room temperature, the stretching can be carried out while applying heat with a whip, or the stretching can be performed after absorbing water. Among these, from the viewpoint of the uniformity of the thickness of the obtained polarizing film in the width direction, the wet stretching method is preferable, and the stretching in a boric acid aqueous solution is more preferable. The concentration of boric acid in the aqueous solution of boric acid is preferably in the range of 0.5 to 6.0% by mass, more preferably in the range of 1.0 to 5.0% by mass, and particularly preferably in the range of 1.5 to 4.0% by mass. The aforementioned aqueous solution containing a boron compound may also contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass.

In the stretching step, the temperature when stretching the PVA film is preferably in the range of 30 to 90°C, more preferably in the range of 40 to 80°C, and particularly preferably in the range of 50 to 70°C.

The stretching ratio of the stretching step is preferably 1.2 times or more, 1.5 times or more, and 2 times or more, from the viewpoint of obtaining a polarizing film with more excellent polarizing performance. Moreover, based on the original length of the PVA film used, the full stretch magnification (the magnification that multiplies the stretch magnification of each stretch) including the preceding stretch magnification is preferably 5.5 times or more, more preferably 5.7 times or more, and 5.8 times The above is better, 5.9 times more excellent. By setting each stretching magnification within the aforementioned range, a polarizing film with more excellent polarizing performance can be obtained. The upper limit of the aforementioned full extension magnification is not particularly limited, but it is preferably 8 times or less.

The stretching of the PVA film in the stretching step is preferably uniaxial stretching from the viewpoint of the performance of the polarizing film obtained. The direction of uniaxial extension is not particularly limited, and uniaxial extension or lateral uniaxial extension of the long film can be used. However, from the viewpoint of easily obtaining a polarizing film with more excellent polarizing performance, The shaft extension is better. The uniaxial extension in the longitudinal direction can be performed by using an extension device having a plurality of rollers parallel to each other, and changing the peripheral speed between the rollers. On the other hand, horizontal uniaxial stretching can be performed using a tenter type stretching machine.

.Fixed processing steps

The fixing process in the fixing process step is mainly performed to strongly adsorb the dichroic dye of the extended PVA film. The fixing treatment can be performed by immersing the extended PVA film in a fixing treatment bath. As a fixed treatment bath, borate containing boric acid, borax, etc. can be used An aqueous solution of one or more boron compounds. Furthermore, if necessary, an iodine compound or a metal compound may be added to the fixed treatment bath. The concentration of the boron compound in the aqueous solution containing the boron compound used as the fixed treatment bath is generally preferably in the range of 2 to 15% by mass, and more preferably in the range of 3 to 10% by mass. The temperature of the fixed treatment bath is preferably in the range of 15 to 60°C, and more preferably in the range of 25 to 40°C.

[Procedure of gas injection]

The gas blowing in the step of spraying gas at both ends in the width direction of the PVA film with water adhered to the surface by the water contact step or the like can reduce the shrinkage caused by the drying step even after the stretching step The breakage of the thin film occurs, but the breakage of the thin film when manufacturing the polarizing film is particularly likely to occur during stretching, so it is desirable to have this gas blowing step before the stretching step. In this case, as long as at least one step selected from the group including the swelling step, the dyeing step, and the cross-linking step is used as the water contact step, and the water after passing the water contact step adheres to the PVA on the surface The film can be sprayed with gas at both ends in the width direction. Furthermore, when there are a plurality of steps for blowing the gas, at least one of the steps is preferably before the extending step.

When the manufacturing method of the present invention has a plurality of water contacting steps, for all of these water contacting steps, gas is blown at both ends in the width direction of the PVA film on which the water adheres to the surface after passing through the water contacting step, or In some of these water contacting steps, gas may be sprayed at both ends of the PVA film on the surface in the width direction after the water contacting step passes through the water contacting step. As a preferred aspect of the present invention, all can have a dyeing step, a cross-linking step, an extension step, and a fixing process in this order The step is a water contacting step, and among them, a state in which a gas is sprayed at both ends in the width direction of the PVA film on which the water adheres to the surface at least after the swelling step, the dyeing step, and the cross-linking step can be cited, as a further aspect of the present invention A good aspect may have a swelling step, a dyeing step, a cross-linking step, an extension step, and a fixing treatment step in this order as the water contact step, and at least the swelling step, the dyeing step, the cross-linking step and After the fixing process, water adheres to the surface of the PVA film, and the gas is sprayed at both ends in the width direction.

The type of gas to be sprayed is not particularly limited, and examples thereof include nitrogen, argon, and air. From the viewpoint of low cost, air is preferable.

The wind speed of the blown gas is not particularly limited. From the viewpoint of more effectively suppressing the occurrence of buckling in the widthwise end of the PVA film, it is preferably 0.1 m/sec or more, more preferably 0.5 m/sec or more, 1.0 m It is particularly good for more than /second, and the best is more than 1.5m/second. The upper limit of the wind speed is not particularly limited, but when the wind speed is too high, there is a tendency for wrinkles to easily occur in the PVA film, and the wind speed is preferably 20 m/sec or less.

The direction of the injected gas is not particularly limited, but from the viewpoint of effectively suppressing the occurrence of buckling in the widthwise end of the PVA film, the widthwise central portion of the PVA film faces the widthwise outer side and slightly along the PVA The film surface is ideal for blowing.

[Procedure to contact thin body]

The contact of the thin body in the step of contacting the thin body at the both ends in the width direction of the PVA film with water adhered to the surface by the aforementioned water contact step or the like can be reduced even if it is performed after the stretching step The film breakage caused by shrinkage, but the manufacturing of polarized film The breakage of the thin film at the time is particularly likely to occur during stretching, so it is desirable to have the step of contacting the thin body before the stretching step. In this case, as long as at least one step selected from the group including the swelling step, the dyeing step, and the cross-linking step is used as the water contact step, and the water after passing through the water contact step adheres to the PVA on the surface Both ends of the film in the width direction may be in contact with the thin body. Furthermore, when there are a plurality of steps for contacting the thin body, at least one of the steps is preferably before the extending step.

When the manufacturing method of the present invention has a plurality of water contacting steps, for all of these water contacting steps, the thin body is brought into contact at both ends in the width direction of the PVA film on which the water adheres to the surface after passing through the water contacting step, Or for some of these water contacting steps, the thin body may be contacted at both ends in the width direction of the PVA film on which the water adheres to the surface after passing through the water contacting step. As a preferred aspect of the present invention, all may have a swelling step, a dyeing step, a cross-linking step, and an extension step in this order as a water contact step, and at least the swelling step, the dyeing step, and the cross-linking step may be mentioned. After the water adheres to the surface of the PVA film, both ends in the width direction contact the thin body.

The material constituting the aforementioned thin body is not particularly limited. For example, plastics; fabrics such as fabrics, knitted fabrics, and non-woven fabrics; composites obtained by impregnating plastics, etc. on these fabrics; metals; glass, etc., However, from the viewpoint that the effect of the present invention can be more significantly exhibited, the thin body is preferably a plastic film.

As the plastic constituting the aforementioned plastic film, for example, polyolefin (polyethylene, polypropylene, polymethylpentene, etc.), polystyrene, Various thermoplastic resins of polycarbonate, polyvinyl chloride, methacrylic resin, nylon, polyester (polyethylene terephthalate, etc.), and a plurality of monomer units constituting such thermoplastic resins Of copolymers, etc. In the plastic film, the plastic may contain only one kind, or two or more kinds, whichever is more. Among these, from the viewpoint of more effectively suppressing the generation of wrinkles at the end in the width direction of the PVA film, polyester and polyolefin are preferred, and polyester is more preferred. In addition, the method of manufacturing the plastic film is not particularly limited, and it can be manufactured by a well-known method such as melt forming or roll forming.

It is preferable that the water contact angle of the thin body in the portion in contact with the PVA film is 90° or less. When the water contact angle is 90° or less, the occurrence of buckling at the end in the width direction of the PVA film can be more effectively suppressed. From this viewpoint, the water contact angle is preferably 80° or less, and more preferably 60° or less. In addition, the above-mentioned water contact angle can be measured by the contact angle test described in the aforementioned JIS R3257: 1999, and specifically, in the examples, it can be measured by the method described later. The adjustment of the water contact angle can be carried out, for example, by corona treating the surface of the thin body using a corona surface treatment device (made by Kasuga Electric Co., Ltd.).

The thickness of the thin body is not particularly limited, but from the viewpoint of more effectively suppressing the generation of wrinkles at the end in the width direction of the PVA film, the thickness is preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 20 μm or more. In addition, the upper limit of the thickness of the thin body is not particularly limited. For example, the thickness can be set to 1 cm or less, but from the viewpoint of making the polarizing film more smoothly, the thickness is preferably 5 mm or less, more preferably 1 mm or less, Especially good is below 500μm, and best is below 100μm.

The shape of the thin body is not particularly limited, but the width of the thin body (the width of the PVA film when it is in contact with the PVA film) The length in the same direction is preferably 1 cm or more, more preferably 2 cm or more, particularly preferably 3 cm or more, and most preferably 5 cm or more. In addition, from the viewpoint of reducing interference such as damage to the PVA film or even the polarizing film, the width is preferably 20 cm or less. By exposing the thin body having the width as described above, at each end of the PVA film in the width direction, it is possible to ensure that the width of the portion where the PVA film contacts the thin body is preferably 0.5 cm or more, more preferably It is 1 cm or more, particularly preferably 1.5 cm or more, and most preferably 2 cm or more, and preferably 20 cm or less, more preferably 10 cm or less.

When the manufacturing method of the present invention has a water immersion step as a water contact step, as long as the PVA film immersed in water by the water immersion step is taken out from the water, the widthwise ends of the PVA film adhering to the surface of the water contact thin The shape may be sufficient. For example, the position where the thin body is contacted at both ends in the width direction of the PVA film is set to the time before the PVA film immersed in water by the water immersion step is taken out from the water, or The time point when the water is taken out, or the position may be set at a time point after the PVA film immersed in water by the water immersion step is taken out of the water. In addition, the contact of the thin bodies at both ends in the width direction of the PVA film may be performed only once, or may be performed twice or more. When the manufacturing method of the present invention includes the water immersion step as the water contact step, from the viewpoint of more effectively suppressing the occurrence of wrinkles at the ends of the PVA film in the width direction, at least one contact The position where both ends of the direction contact the thin body is set to take out the PVA film immersed in water through the water immersion step from the water The time point before, or the time point when the water is taken out is ideal. In this case, in the portion where the PVA film is separated from the water surface, both ends in the width direction of the PVA film become in contact with the thin body.

As a method of contacting the thin bodies at the both ends in the width direction of the PVA film on which water adheres to the surface, for example, method A: by using the upstream end of the PVA film as the moving direction The fixed end, and the end on the downstream side as one of the free ends is provided to the thin body near the two ends of the PVA film, according to the tension or water pressure caused by water, applied to the upper body of the thin body The position between any one of the side end and the downstream end is further down the end, and the method of contacting with the PVA film, method B: a pair of thin circular-shaped belt-shaped bodies are provided on the PVA Near the two ends of the film, and if necessary, move the part contacting the two ends of the PVA film in the width direction along the direction of movement of the PVA film, and the method of contacting the PVA film while moving from the viewpoint of easy operation, etc. , Method A is ideal. Furthermore, there is no particular limitation on the contact when the thin body is contacted at both ends of the PVA film in the width direction, and it can be contacted from the upper side in the vertical direction of the PVA film, or from the lower side in the vertical direction of the PVA film. can.

FIG. 1 is a schematic view showing a method of contact using Method A, (a) is a view seen from above in the vertical direction, and (b) is a view seen from the side. Fig. 1 shows that when the PVA film 1 moves in its longitudinal direction, the plastic film 2 as a pair of thin bodies provided near the both ends of the PVA film, from the vertically lower side of the PVA film 1 and the PVA film 1 State of contact. Plastic film 2, for the moving direction of PVA film, The end 3 on the upstream side is regarded as the fixed end, and the end 4 on the downstream side is regarded as the free end. Then, from the position 5 between the fixed end 3 and the free end 4 on the plastic film 2 to the free end 4, the end 6 in the width direction of the PVA film is brought into contact with the plastic film.

FIG. 2 is a schematic view showing a method of contact by method B, (a) is a view seen from above in the vertical direction, and (b) is a view seen from the side. FIG. 2 shows that when the PVA film 1 moves in its longitudinal direction, the plastic film 2 as a pair of circulating conveying belt-shaped thin bodies provided near the both ends of the PVA film, from the vertical direction of the PVA film 1 The lower side is in contact with the PVA film 1. The plastic film 2 in the form of a circulating conveyor belt is moved at a speed that is slightly the same as the moving speed of the PVA film along the moving direction of the PVA film at the portions where the two ends of the PVA film in the width direction contact.

In general, when manufacturing a polarizing film from a PVA film, after passing through the water contact step, it is preferable to remove the PVA film immersed in water through the water immersion step from the water (in one example, before the next water contact step), most One or two or more rolls (guide rolls, rolls, etc.) are used to hold and transport the PVA film. In the production method of the present invention, it is also preferable to use the roller as described above. For example, when there is one or more rollers that are in contact with the PVA film after the PVA film immersed in water by the water immersion step is taken out from the water, it is possible From the viewpoint of effectively suppressing the buckling of the end of the PVA film in the width direction, the contact between the thin body and the both ends of the PVA film in the width direction is relatively good from the time the PVA film leaves the water surface to the roller that first contacts it. ideal.

Also, as described above, when the thin body is brought into contact with both ends of the PVA film in the width direction from the time the PVA film is separated from the water surface to the roller that first contacts, after the PVA film (both sides) is separated from the water surface The ratio of the length L2 of the PVA film in the lengthwise direction of the portion of the PVA film contacting the thin body at the both ends in the width direction with respect to the length L1 of the PVA film in the longitudinal direction up to the first contact roller (100×L2/L1( %)), from the viewpoint of effectively suppressing the generation of wrinkles at the end of the PVA film in the width direction, 10% or more is preferable, 30% or more is more preferable, and 80% or more is more preferable. The upper limit of the ratio is not particularly limited, for example, the ratio can be set to 95% or less.

FIG. 3 is a schematic diagram showing a case where the plastic film 2 as a thin body is contacted at both ends in the width direction of the PVA film 1 after the PVA film 1 is separated from the water surface to the roller 10 first contacted. Using method A, the positions of L1 and L2 when the plastic film 2 is brought into contact. In FIG. 3, the plastic film 2 is brought into contact with the starting position 5 at both ends in the width direction of the PVA film 1 at a time point before the PVA film 1 immersed in water by the water immersion step is taken out from the water. That is, at the portion where the PVA film 1 leaves from the water surface 8, the two ends of the PVA film 1 in the width direction are in contact with the plastic film 2. Therefore, in Figure 3, the starting point of L1 and the starting point of L2 are the same.

In addition, a PVA film having water adhered to the surface by the water contacting step or the like is preferably adhered to the surface of the PVA film immersed in the water by the water immersion step after the water is taken out from the water in order. In the case of two or more rollers, between at least one group of two consecutive rollers (between the PVA film leaving the upstream roller and contacting the downstream roller), the PVA film can be more effectively suppressed Wide end From the viewpoint of the generation of folds, it is also preferable to contact the thin bodies at both ends in the width direction of the PVA film. As a preferred aspect of the manufacturing method of the present invention, the widthwise ends of the PVA film that adheres the thin body and water to the surface between the PVA film leaving the water surface and the roller that first contacts the surface can be cited Contact, and then, after releasing the contact with the thin body, the PVA film with water adhered to the surface is sequentially contacted between at least one group of two consecutive rollers of at least one of the two or more rollers, and the thin body and the PVA are again brought into contact The method of contacting the two ends of the film in the width direction.

In addition, as described above, two or more rollers having a PVA film with water adhering to the surface sequentially contacted, and between at least one set of these two rollers in a row, the thin body and the width direction of the PVA film When the two ends are in contact, the ratio of the length L4 of the PVA film in the lengthwise direction of the portion of the PVA film that contacts the thin body at the two ends of the width direction with respect to the length L3 of the PVA film in the longitudinal direction (100× L4/L3 (%)), from the viewpoint of more effectively suppressing the generation of wrinkles at the end in the width direction of the PVA film, 10% or more is preferable, 30% or more is better, and 80% or more is more preferable. The upper limit of the ratio is not particularly limited, for example, the ratio can be set to 95% or less.

Fig. 4 shows a case where the plastic film 2 as a thin body is contacted at both ends in the width direction of the PVA film 1 between two consecutive rollers 11 in a group, and schematically shows that the plastic film 2 is contacted by the method A Time L3 and L4 position.

[Drying step]

The polarizing film can be manufactured by stretching, after further fixing treatment if necessary, and by drying. The drying conditions are not particularly limited, However, the drying temperature is preferably in the range of 30 to 150°C, and more preferably in the range of 50 to 130°C. By drying at a temperature within the aforementioned range, a polarizing film with good size stability can be easily obtained.

[Polarizer]

The polarizing film obtained as described above is generally used as a polarizing plate by bonding a protective film that is optically transparent and has mechanical strength on both sides or one side. As a protective film, cellulose triacetate (TAC) film, acetic acid can be used. Cellulose butyrate (CAB) film, acrylic film, polyester film, etc. In addition, examples of the adhesive for bonding include PVA-based adhesives and urethane-based adhesives. Among them, PVA-based adhesives are particularly suitable.

[Example]

The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In addition, the following shows each measurement or evaluation method of the wind speed of the gas, the water contact angle of the plastic film, the continuously-operable stretch magnification, and the polarizing performance of the polarizing film used in the following examples and comparative examples.

[Wind speed of gas]

Using an anemometer, it was obtained in accordance with the description of JIS A1431:1994 (Measurement Method of Air Volume of Air Conditioning/Ventilation Equipment). Specifically, the wind speed of the gas blown by the gas (air) blowing nozzle used in the following examples or comparative examples is obtained. The measurement was carried out under the conditions of temperature: 25°C and humidity: 50% RH.

[Water contact angle of plastic film]

From the same plastic film used in the following examples or comparative examples, an elongated rectangular film sheet of 200 mm × 15 mm was cut out, and the water contact angle of the surface contacting the PVA film of the film sheet was in accordance with JIS R3257 : 1999 (Test method for wettability of substrate glass surface). That is, let a water droplet of 4 μl or less rest on a horizontal film sheet, and according to the shape of the water droplet, measure the radius r (mm) of the surface where the water droplet contacts the film sheet and the height h from the surface of the film sheet to the apex of the water droplet (mm), and the water contact angle θ (°) is determined by the following formula (1).

θ=2tan ^-1 (h/r) (1)

Furthermore, the measurement was carried out five times, and the average value was used as the water contact angle of the plastic film. In addition, the measurement was performed under the conditions of temperature: 25°C and humidity: 50% RH.

[Extended magnification for continuous operation]

In the following examples or comparative examples, by adjusting the stretch ratio of the stretching step, the full stretch ratio can be increased in steps of 0.1 times, and the full stretch ratio set immediately before the full stretch ratio when the film breaks is generated The extension magnification is used as a continuous operation extension magnification.

[Polarizing properties of polarizing film]

(a) Determination of transmittance Ts

From the central part of the polarizing film in the width direction obtained in the following examples or comparative examples, two samples of a square with a length of 2 cm × a width of 2 cm were taken from the polarizing film, and a spectrophotometer with an integrating sphere (Japanese Spectrophotometer) was used. "V7100" manufactured by a company limited by shares), based on JIS Z8722:2009 (method of measuring object color), C light source and 2° field of view The visual sensitivity of the light area is corrected. For one sample, the transmittance of light at an inclination of 45° with respect to the longitudinal direction and the transmittance of light at an inclination of -45° are measured, and the average Ts1 (%) of these is obtained. The other samples were also subjected to the same measurement. The transmittance of light at an inclination of 45° and the transmittance of light at an inclination of -45° were measured, and the average Ts2 (%) of these was obtained. Ts1 and Ts2 are averaged by the following formula (2), and used as the transmittance Ts (%) of the polarizing film.

Ts=(Ts1+Ts2)/2 (2)

(b) Determination of polarization degree V

Transmittance T ∥ (%) when the two samples taken by the measurement of the transmittance Ts are parallel to the longitudinal direction and overlap, and transmittance T ⊥ of the light when overlapped perpendicular to the longitudinal direction (%) is measured in the same manner as in the above "(a) measurement of transmittance Ts", and the polarization degree V (%) is obtained by the following formula (3).

V={(T ∥ -T⊥)/(T ∥ +T⊥)} ^1/2 ×100 (3)

(c) Measurement of variation range (Ts) and variation range (V)

On the line of the central part of the polarizing film in the width direction obtained by the following examples or comparative examples, 5 places were set at intervals in the longitudinal direction, and for each of the various parts, the polarizing film was taken in the longitudinal direction of 2 cm × width direction Two samples of 2 cm square were carried out in the same manner as above, and the transmittance Ts (%) and the degree of polarization V (%) were obtained. Then, the difference between the maximum and minimum values of the five transmittances Ts obtained in each example or each comparative example is defined as the variation width (Ts), and the difference between the maximum and minimum values of the obtained polarization degree V is defined as variation Amplitude (V).

[Example 1]

A long PVA film with a thickness of 20 μm and a width of 1 m (including PVA and glycerin and a surfactant, and the content of glycerin is 12 parts by mass relative to 100 parts by mass of PVA, and the content of the surfactant The content is 0.03 parts by mass of PVA film with respect to 100 parts by mass of PVA. PVA is a saponification product of a single polymer of vinyl acetate, the degree of polymerization of PVA is 2,400, and the degree of saponification of PVA is 99.9 mol%.), It is continuously wound out from its film roll, and is continuously supplied to the swelling step, the dyeing step, and the cross-linking step in this order.

Here, as a swelling step, the PVA film was immersed in distilled water (temperature: 30° C.) for 1 minute, during which it was uniaxially stretched at a stretch ratio of 2.0 times in the longitudinal direction. In addition, as a dyeing step, the PVA film was immersed in an aqueous solution containing an iodine pigment (concentration of iodine used: 0.05% by mass, concentration of potassium iodide used: 1.2% by mass, temperature: 30°C) for 2 minutes, during which It extends uniaxially in the longitudinal direction at an extension ratio of 1.2 times. In addition, as a crosslinking step, the PVA film was immersed in a boric acid aqueous solution (boric acid concentration: 2.6% by mass, temperature: 30° C.) for 2 minutes, during which it was uniaxially stretched at a stretch ratio of 1.1 times in the longitudinal direction.

In addition, regarding any one of the swelling step, the dyeing step, and the cross-linking step, the PVA film immersed in water through these steps is taken out from the water, and then the PVA film in the state where the water is attached to the surface in the width direction is two At the end, from the center of the PVA film in the width direction to the outside in the width direction, slightly along the surface of the PVA film, the air is blown at a wind speed of 2.0 m/sec. The blowing of air is performed using nozzles for air blowing.

Next, the aforementioned cross-linking step is a continuous stretching step, and a polarizing film is manufactured in this order through a fixing process step and a drying step. The stretching step is performed by uniaxially stretching the PVA film in a boric acid aqueous solution (boric acid concentration: 2.8% by mass, potassium iodide concentration: 5% by mass, temperature: 57°C) in the longitudinal direction at a stretching ratio of 1.9 times (including front stretching The full stretch magnification of the stretch magnification is 5.0 times). In addition, the fixing treatment step was performed by immersing the extended PVA film in a boric acid aqueous solution (boric acid concentration: 2.6% by mass, potassium iodide concentration: 5% by mass, temperature: 22°C) for 2 minutes. In addition, the drying step is performed by drying the stretched PVA film at 60°C for 1 minute. In addition, after the PVA film immersed in water by the fixing process step is taken out of the water, the two ends of the PVA film in the state where the water is attached to the surface in the width direction, from the center of the width direction of the PVA film toward the width direction On the outside, slightly along the surface of the PVA film, air was blown at a wind speed of 2.0 m/sec. The blowing of air is performed using nozzles for air blowing.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 1. In addition, in the manufacture of the aforementioned polarizing film, after passing through any water contact step, no wrinkle was seen at the end in the width direction of the PVA film.

[Examples 2 and 3]

The thickness of the PVA film was changed to 15 μm (Example 2) or 60 μm (Example 3), except that the polarizing film was continuously produced in the same manner as in Example 1.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 1. Furthermore, in any of Examples 2 and 3, in the manufacture of the polarizing film described above, after passing through any water contact step, no wrinkle was seen at the end of the PVA film in the width direction.

[Example 4]

In any of the swelling step, the dyeing step, the cross-linking step, and the fixing treatment step, the air velocity of the air blown at both ends in the width direction of the PVA film was 1.0 m/sec, except that it was the same as in Example 1. In this way, the polarizing film is continuously produced.

Then, the continuously-operable stretch magnification is determined by the above-mentioned method, and the polarizing film obtained when the continuously-operable stretch magnification is used is used to evaluate the polarizing performance of the polarizing film. The results of these are shown in Table 1. Furthermore, in the manufacture of the aforementioned polarizing film, after passing through the respective water contacting steps, slight folds of 0.5 mm in width are generated at both ends of the PVA film in the width direction.

[Example 5]

No air was blown to the fixing treatment step, except that it was carried out in the same manner as in Example 1, and a polarizing film was continuously produced.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 1. Furthermore, in the polarizing film During the manufacturing process, only after passing through the fixing process step, slight folds of 0.2 mm in width are generated at both ends of the PVA film in the width direction.

[Example 6]

With respect to the swelling step, the cross-linking step, and the fixing treatment step, air blowing was not performed, except that it was carried out in the same manner as in Example 1, and a polarizing film was continuously produced.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 1. In addition, in the manufacture of the aforementioned polarizing film, after passing through the cross-linking step and the fixing treatment step, a slight wrinkle of 0.7 mm in width is generated at both ends in the width direction of the PVA film.

[Comparative Example 1]

None of the swelling step, the dyeing step, the cross-linking step, and the fixing treatment step was carried out in the same manner as in Example 1 except that air was not blown, and a polarizing film was continuously produced.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 1. Furthermore, in the manufacture of the aforementioned polarizing film, after passing through the respective water contact steps, significant folds are generated at both ends of the PVA film in the width direction.

[Example 7]

A long PVA film with a thickness of 30 μm and a width of 1 m (including PVA, glycerin, and surfactant, the content of glycerin is 12 parts by mass relative to 100 parts by mass of PVA, and the content of surfactant 0.03 parts by mass of PVA film relative to 100 parts by mass of PVA. PVA is a saponification product of a single polymer of vinyl acetate, the degree of polymerization of PVA is 2,400, and the degree of saponification of PVA is 99.9 mol%.) The film roll is continuously wound out, and is continuously supplied to the swelling step, the dyeing step, and the cross-linking step in this order.

Here, as a swelling step, the PVA film was immersed in distilled water (temperature: 30° C.) for 1 minute, during which it was uniaxially stretched at a stretch ratio of 2.0 times in the longitudinal direction. Furthermore, as a dyeing step, the PVA film was immersed in an aqueous solution containing an iodine-based pigment (concentration of iodine used: 0.05% by mass, concentration of potassium iodide used: 1.2% by mass, temperature: 30°C) for 2 minutes, during which It extends uniaxially in the longitudinal direction at an extension magnification of 1.2 times. In addition, as a crosslinking step, the PVA film was immersed in a boric acid aqueous solution (boric acid concentration: 2.6% by mass, temperature: 30° C.) for 2 minutes, during which it was uniaxially stretched at a stretch ratio of 1.1 times in the longitudinal direction.

In addition, any one of the swelling step, the dyeing step, and the cross-linking step, as shown in FIG. 5, allows the PVA film immersed in water by these steps to adhere to the surface of the PVA after the water is taken out from the water The film is brought into contact with the guide roller, and thereafter, is further brought into contact with a pair of rollers. Then, after the PVA film leaves the water surface of each step and contacts the guide roller, the plastic film and the PVA film are brought into contact with each other in the width direction, and between the guide roller and the roller, Attach plastic film to water Both ends of the PVA film in the state of being in contact with the surface are in contact in the width direction. The plastic films used are all biaxially stretched polyethylene terephthalate (PET) films (“LUMIRROR” S10 manufactured by Toray Co., Ltd.) with a thickness of 75 μm and a width of 3 cm, and are treated by corona. The water contact angle between the PVA film and the surface on the contact side is adjusted to 57°. For the moving direction of the PVA film, the upstream end of the plastic film is used as the fixed end, and the downstream end is used as the free end, and By placing it under the vertical direction of the PVA film, the plastic film is brought into contact with both ends of the PVA film in the width direction (the width of the contact portion at each end is set to 2 cm).

In addition, in any one of the swelling step, the dyeing step, and the cross-linking step, by setting the position where the thin body is contacted at both ends in the width direction of the PVA film to be set to be immersed in water by each step At the time point before the PVA film is taken out from the water, at the part where the PVA film leaves from the water surface of the water in each step, both ends in the width direction of the PVA film are in contact with the plastic film. In any of the swelling step, the dyeing step, and the cross-linking step, 100×L2/L1 is set to 80%, and 100×L4/L3 is set to 80%.

Next, the aforementioned cross-linking step is a continuous stretching step, and a polarizing film is manufactured in this order through a fixing process step and a drying step. The stretching step is performed by uniaxially stretching the PVA film in a boric acid aqueous solution (boric acid concentration: 2.8% by mass, potassium iodide concentration: 5% by mass, temperature: 57°C) in the longitudinal direction at a stretching ratio of 1.9 times (including front stretching The full stretch magnification of the stretch magnification is 5.0 times). In addition, the fixing treatment step was performed by immersing the extended PVA film in a boric acid aqueous solution (boric acid concentration: 2.6% by mass, potassium iodide concentration: 5% by mass, temperature: 22°C) for 2 minutes. In addition, the drying step is performed by drying the stretched PVA film at 60°C for 1 minute.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 2. In addition, in the manufacture of the aforementioned polarizing film, after passing through any water contact step, no wrinkle was seen at the end in the width direction of the PVA film.

[Examples 8 and 9]

The thickness of the PVA film was changed to 15 μm (Example 8) or 60 μm (Example 9), except that the polarizing film was continuously produced in the same manner as in Example 7.

Then, the continuously-operable stretch magnification is determined by the above-mentioned method, and the polarizing film obtained when the continuously-operable stretch magnification is used is used to evaluate the polarizing performance of the polarizing film. The results of these are shown in Table 2. In addition, in any of Examples 8 and 9, in the manufacture of the polarizing film described above, after passing through any water contact step, no wrinkles were seen at the end of the PVA film in the width direction.

[Example 10]

In any one of the swelling step, the dyeing step, and the cross-linking step, 100×L2/L1 was set to 5%, and 100×L4/L3 was set to 5%, except that the procedure was continued in the same manner as in Example 7. Polarized film.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 2. Furthermore, in the polarizing film During the manufacturing process, after passing through the water contact step, a slight wrinkle of 0.5 mm in width occurs at one end of the PVA film in the width direction.

[Example 11]

In the crosslinking step, there was no contact with the plastic film. Otherwise, it was carried out in the same manner as in Example 7, and a polarizing film was continuously produced.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 2. Furthermore, in the manufacture of the aforementioned polarizing film, after passing through the cross-linking step, slight folds of 0.5 mm in width are generated at both ends of the PVA film in the width direction.

[Example 12]

Regarding the contact of the plastic film, the width of the contact portion at each end was set to 1 cm, except that the polarizing film was continuously produced in the same manner as in Example 7.

Then, the continuously-operable stretch magnification is determined by the above-mentioned method, and the polarizing film obtained when the continuously-operable stretch magnification is used is used to evaluate the polarizing performance of the polarizing film. The results of these are shown in Table 2. In addition, in the manufacture of the aforementioned polarizing film, after passing through the water contact step, a slight wrinkle of 0.7 mm in width is generated at both ends of the PVA film in the width direction.

[Example 13]

For the plastic film used, polyethylene terephthalate (PET) film with a thickness of 75 μm and a width of 3 cm is used, and the water contact angle of the surface of the PVA film and the contact side is adjusted by corona treatment to Except for 100°, it carried out similarly to Example 7, and produced the polarizing film continuously.

Then, the continuously-operable stretch magnification is determined by the above-mentioned method, and the polarizing film obtained when the continuously-operable stretch magnification is used is used to evaluate the polarizing performance of the polarizing film. The results of these are shown in Table 2. Furthermore, in the manufacture of the aforementioned polarizing film, after passing through any water contact step, no folds were seen at the end of the PVA film in the width direction.

[Example 14]

For the plastic film used, a linear low-density polyethylene (LLDPE) film (made by SE620N TAMAPOLY Co., Ltd.) with a thickness of 50 μm and a width of 3 cm is used, and the PVA film and the contact side are made by corona treatment. The water contact angle of the surface was adjusted to 85°, except that the polarizing film was continuously produced in the same manner as in Example 7.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 2. In addition, in the manufacture of the aforementioned polarizing film, after passing through any water contact step, no wrinkle was seen at the end in the width direction of the PVA film.

[Comparative Example 2]

Any of the swelling step, the dyeing step, and the cross-linking step did not come into contact with the plastic film, except that the polarizing film was continuously produced in the same manner as in Example 7.

Then, using the above-mentioned method to obtain a continuously operable stretch magnification, and using the polarizing film obtained when the continuously-operable stretch magnification is used, the polarizing property of the polarizing film is evaluated by the above method can. The results of these are shown in Table 2. Furthermore, in the manufacture of the aforementioned polarizing film, after passing through the water contact step, significant folds are generated at both ends of the PVA film in the width direction.

[Comparative Example 3]

Any of the swelling step, the dyeing step, and the cross-linking step did not come into contact with the plastic film, except that the polarizing film was continuously produced in the same manner as in Example 8.

Then, using the above-mentioned method, a continuously operable stretch magnification is obtained, and using the polarizing film obtained when the continuously operable stretch magnification is used, the polarizing performance of the polarizing film is evaluated by the above-mentioned method. The results of these are shown in Table 2. Furthermore, in the manufacture of the aforementioned polarizing film, after passing through the respective water contact steps, significant folds are generated at both ends of the PVA film in the width direction.

Claims (12)

A manufacturing method comprising a polarizing film having a stretching step of uniaxially stretching a polyvinyl alcohol film having a thickness of 45 μm or less in a longitudinal direction using a stretching device including a plurality of rollers parallel to each other, The two ends of the polyvinyl alcohol film adhering to the surface in the width direction blow gas and/or contact the plastic so as to extend slightly along the surface of the polyvinyl alcohol film from the widthwise central portion side of the polyvinyl alcohol film toward the outside in the width direction The step of the film, in which the water contact angle of the plastic film in contact with the polyvinyl alcohol film is 60° or less. The manufacturing method according to claim 1, which has a water immersion step of immersing the polyvinyl alcohol film in water, and the polyvinyl alcohol film with water adhered to the surface is a polyvinyl alcohol film immersed in water by the water immersion step. Remove the latter with water. The manufacturing method according to claim 2, wherein the water immersion step is at least one selected from the group consisting of a swelling step, a dyeing step, a cross-linking step, an extension step, and a fixing treatment step. The manufacturing method according to claim 2 is a manufacturing method having a step of contacting the plastic film with water at both ends of the polyvinyl alcohol film attached to the surface in the width direction, which has a step of immersing in water by a water immersion step One or more rollers contacted by the polyvinyl alcohol film after the polyvinyl alcohol film is taken out of the water, and between the time when the polyvinyl alcohol film leaves the water surface and the roller that first contacts, the plastic film and the polyvinyl alcohol film Both ends in the width direction are in contact. The manufacturing method according to claim 4, wherein the plastic film is in contact at both ends in the width direction with respect to the length of the longitudinal direction of the polyvinyl alcohol film from the time the polyvinyl alcohol film leaves the water surface to the roller that is initially in contact The proportion of the length of the polyvinyl alcohol film in the longitudinal direction is 10% or more. The manufacturing method according to any one of claims 2 to 5, which is a manufacturing method having a step of contacting the plastic film with water at both ends of the polyvinyl alcohol film on the surface in the width direction, where the polyvinyl alcohol film leaves the water surface The part of the polyvinyl alcohol film in the width direction is in contact with the plastic film. The manufacturing method according to any one of claims 1 to 5, which is a manufacturing method having a step of contacting both ends of a polyvinyl alcohol film with water adhered to the surface in the width direction, having water adhered to the surface Two or more rollers that the polyvinyl alcohol film contacts in sequence, and between at least one group of two consecutive rollers, the plastic film is brought into contact with both ends of the polyvinyl alcohol film in the width direction. The manufacturing method according to claim 7, wherein between the two consecutive rollers, the lengthwise direction of the part of the polyvinyl alcohol film that the plastic film contacts at both ends in the width direction relative to the length of the lengthwise direction of the polyvinyl alcohol film The proportion of the length is more than 10%. The manufacturing method according to any one of claims 1 to 5, which is a manufacturing method having a step of contacting the widthwise ends of a polyvinyl alcohol film with water attached to the surface, the width of the plastic film is 1 Cm above. The manufacturing method according to any one of claims 1 to 5, which has a step of spraying a gas having a blowing speed of 0.1 m/sec or more on both ends in the width direction of the polyvinyl alcohol film to which water adheres to the surface. The manufacturing method according to any one of claims 1 to 5, which has a step of spraying gas and/or contacting the plastic film at both ends in the width direction of the polyvinyl alcohol film with water attached to the surface before the extending step. The manufacturing method according to any one of claims 1 to 5, wherein the thickness of the polyvinyl alcohol film is 35 μm or less.

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