JP6444732B2 - Laminated film - Google Patents

Description

  The present invention relates to a laminated film useful as a raw film for producing a polarizing film, a film roll formed by winding the film, and a method for producing a polarizing film using the laminated film.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. As a polarizing film constituting the polarizing plate, a polyvinyl alcohol film (hereinafter referred to as “polyvinyl”). alcohol "and" PVA "and is sometimes abbreviated) iodine dye stretched film was oriented uniaxially stretched (I ₃ ^- and I ₅ ^-, etc.), such as a dichroic organic dye dichroic dye is adsorbed What you are doing is the mainstream. Such a polarizing film can be obtained by uniaxially stretching a PVA film preliminarily containing a dichroic dye, adsorbing a dichroic dye simultaneously with uniaxial stretching of the PVA film, or dichroic after uniaxially stretching the PVA film. Manufactured by adsorbing dyes.

  LCDs are used in a wide range of devices such as small devices such as calculators and wrist watches, 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. However, in recent years, it is often used for mobile applications such as small notebook personal computers and mobile phones, and there is an increasing demand for thinner polarizing plates.

  One way to reduce the thickness of the polarizing plate is to reduce the thickness of the polarizing film. To this end, it is conceivable to reduce the thickness of the PVA film that is the raw material of the polarizing film. However, a thin PVA film is likely to be stretched at the time of stretching, and the productivity and yield of the polarizing film are lowered, which leads to high costs.

  As a technique for producing a thin polarizing film without causing breakage during stretching, a method is known in which a thin PVA layer is formed on a thermoplastic resin film by a coating method and the laminate is stretched (for example, patents). See references 1 and 2).

Japanese Patent No. 4804588 Japanese Patent No. 4815544

However, the method using a laminate formed by forming a PVA layer on a thermoplastic resin film by a coating method has the following problems.
(I) The coating operation and the subsequent drying operation are complicated.
(Ii) Since the heat treatment for insolubilizing the PVA layer needs to be performed in the state of a laminate, the thermoplastic resin film used is limited to a film that can be stretched even after the heat treatment, resulting in an increase in cost.
(Iii) A laminate in which a PVA layer is formed on a thermoplastic resin film by a coating method has a relatively high adhesive strength between the thermoplastic resin film and the PVA layer, and such a laminate having a high adhesive strength. When the film is stretched, an appropriate neck-in of the PVA layer is hindered, and it is difficult to obtain a polarizing film having excellent polarization performance.

  The present invention provides a laminated film for producing a polarizing film, a thin PVA, which is capable of easily producing a polarizing film which is less likely to be stretched during stretching even when a thin PVA film is used and which has excellent polarizing performance. Even when a film is used, it is difficult to cause stretching breakage at the time of stretching, and a laminated film capable of extremely easily producing a polarizing film excellent in polarizing performance, a film roll in which they are wound, and It aims at providing the manufacturing method of the polarizing film using the said laminated | multilayer film.

  As a result of intensive studies to achieve the above object, the inventors of the present invention, when producing a polarizing film using a thin single-layer PVA film, have a water process such as a swelling process and a dyeing process performed before stretching. After passing through the step of bringing into contact with the film, curling is likely to occur at both ends in the width direction of the film. In the above, the thermoplastic resin film is laminated on the PVA film with an adhesive strength of a specific value or less, curling is suppressed, the occurrence of stretch breakage can be reduced, and the adhesive strength is below the specific value. In this case, when the thermoplastic resin film is finally removed, it is found that the removal becomes extremely easy, and further studies are made based on these findings. Invention was allowed to complete.

That is, the present invention
[1] PVA film and the thermoplastic resin film is adjacent to a laminate film for a polarizing film producing state, and are adhesive strength 10 mN / 15 mm or less between both films, the thickness of the polyvinyl alcohol film Laminated film of 45 μm or less ;
[2] The laminated film according to [1] , which is a long laminated film;
[3] The laminated film of [ 2 ] above, wherein the width of the thermoplastic resin film is 1.1 times or more of the width of the PVA film;
[4] A film roll formed by winding the laminated film of [ 2 ] or [ 3 ] above;
[5] A method for producing a polarizing film, comprising a water contact step in which any one of the above laminated films [1] to [ 3 ] is brought into contact with water, and then a stretching step in which the PVA film is stretched;
[6] The method according to the above [ 5 ], wherein in the stretching step, the thermoplastic resin film and the PVA film are adjacent to each other;
[7] The production method of the above [ 5 ], comprising a step of removing the thermoplastic resin film before the stretching step;
About.

  According to the present invention, even when a thin PVA film is used, a laminated film for producing a polarizing film that is less likely to be stretched at the time of stretching and can easily produce a polarizing film having excellent polarizing performance, Even when thin PVA film is used, it is difficult to cause stretching breakage during stretching, and a laminated film that can extremely easily produce a polarizing film having excellent polarization performance, and a film roll formed by winding them up And the manufacturing method of the polarizing film using the said laminated | multilayer film is provided.

Hereinafter, the present invention will be described in detail.
In the laminated film of the present invention, the PVA film and the thermoplastic resin film are adjacent to each other.

[PVA film]
As PVA constituting the PVA film, vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate, etc. Those obtained by saponifying a polyvinyl ester obtained by polymerizing one or more of the above can be used. Among the above-mentioned vinyl esters, a compound having a vinyloxycarbonyl group (H ₂ C═CH—O—CO—) in the molecule is preferable from the viewpoint of ease of production of PVA, availability, cost, etc. More preferred is vinyl acetate.

  The polyvinyl ester is preferably obtained using only one or two or more vinyl esters as monomers, and more preferably obtained using only one vinyl ester as a monomer. However, as long as the effect of the present invention is not significantly impaired, a copolymer of one or more vinyl esters and other monomers copolymerizable therewith may be used.

  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 and 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, etc. Vinyl ether; vinyl cyanide such as (meth) acrylonitrile; halogenated vinyl such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; vinegar Allyl compounds such as allyl acid and allyl chloride; maleic acid or salts thereof, esters or acid anhydrides; itaconic acid or salts thereof, esters or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; unsaturated sulfonic acids or salts thereof And so on. Said polyvinyl ester 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 is preferably 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester, and is preferably 10 mol% or less. More preferably, it is more preferably 5 mol% or less.

  As the above-mentioned PVA, those not graft-copolymerized can be preferably used, but PVA can be used for one or more kinds of graft copolymer as long as the effects of the present invention are not significantly impaired. It may be modified with a monomer. The said graft copolymerization can be performed with respect to at least one of polyvinyl ester and PVA obtained by saponifying it. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; α-olefins having 2 to 30 carbon atoms, and the like. The proportion of structural units derived from the graft copolymerizable monomer in the polyvinyl ester or PVA is preferably 5 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester or PVA.

  In the PVA, a part of the hydroxyl group may be cross-linked or may not be cross-linked. The PVA may have a hydroxyl group partially reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or may not react with these compounds to form an acetal structure. Also good.

  The degree of polymerization of the above PVA is not particularly limited, but is preferably 1000 or more. When the polymerization degree of PVA is 1000 or more, there is an advantage that the polarizing performance of the obtained polarizing film can be further improved. If the degree of polymerization of PVA is too high, it tends to lead to an increase in the production cost of PVA and poor processability during film formation, so the degree of polymerization of PVA is more preferably in the range of 1000 to 10,000, More preferably, it is in the range of 1500-8000, and particularly preferably in the range of 2000-5000. In addition, the polymerization degree of PVA as used in this specification means the average degree of polymerization measured according to description of JISK6726-1994.

  The saponification degree of PVA is preferably 99.0 mol% or more, more preferably 99.8 mol% or more, and 99.9 mol% from the viewpoint of good wet heat resistance of the obtained polarizing film or the like. It is still more preferable that it is above. In this specification, the saponification degree of PVA refers to the vinyl alcohol unit relative 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. Refers to the proportion (mol%) occupied by the number of moles. The degree of saponification can be measured according to the description of JIS K6726-1994.

  The PVA film may contain a plasticizer together with the above PVA. When the PVA film contains a plasticizer, it is possible to improve the handleability and stretchability of the PVA film. As the plasticizer, polyhydric alcohol is preferably used, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. PVA film Can contain one or more of these plasticizers. Among these, glycerin is preferable because the stretchability of the PVA film becomes better.

  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 still more preferably 7 to 14 parts by mass with respect to 100 parts by mass of PVA. . When the content of the plasticizer in the PVA film is 3 parts by mass or more with respect to 100 parts by mass of PVA, the stretchability of the PVA film is improved. On the other hand, when the content of the plasticizer in the PVA film 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 handling property of the PVA film is reduced. be able to.

  In addition, when a PVA film is produced using a film-forming stock solution for producing a PVA film, which will be described later, the film-forming property is improved and the occurrence of film thickness unevenness is suppressed, and a metal roll is used for film formation. Since a PVA film can be easily peeled off from these metal rolls and belts when a belt or a belt is used, it is preferable to add a surfactant to the film-forming stock solution. When a PVA film is produced from a film-forming stock solution containing a surfactant, the PVA film may contain a surfactant. There are no particular limitations on the type of surfactant that is blended in the film-forming stock solution for producing the PVA film, and thus the surfactant contained in the PVA film, but from the viewpoint of releasability from a metal roll or belt, an anion is used. Surfactants or nonionic surfactants are preferred, and nonionic surfactants are particularly preferred.

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

Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide and oleic acid diethanolamide; polyoxy An allyl phenyl ether type such as alkylene allyl phenyl ether is preferred.
These surfactants can be used alone or in combination of two or more.

  When a surfactant is blended in a film-forming stock solution for producing a PVA film, the content of the surfactant in the film-forming stock solution, and thus the content of the surfactant in the PVA film is determined as the film-forming stock solution or the PVA film. It is preferable that it exists in the range of 0.01-0.5 mass part with respect to 100 mass parts of PVA contained in, and it is more preferable that it exists in the range of 0.02-0.3 mass part. 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 may be composed only of PVA, or may be composed only of PVA and the above-described plasticizer and / or surfactant. If necessary, an antioxidant, an antifreeze agent, a pH adjuster, You may contain other components other than above-mentioned PVA, a plasticizer, and surfactant, such as a masking agent, a coloring inhibitor, and an oil agent.

  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 in the range of 85 to 100% by mass. Further preferred.

  Although there is no restriction | limiting in particular in the thickness of a PVA film, Since said curl is easy to generate | occur | produce with a thin PVA film and the effect of this invention is show | played more significantly in a thin PVA film, the said thickness may be 45 micrometers or less. Preferably, it is 35 μm or less, more preferably 25 μm or less. Although there is no restriction | limiting in particular in the minimum of the thickness of a PVA film, Since the polarizing film etc. can be manufactured more smoothly, it is preferable that the said thickness is 3 micrometers or more.

  Although there is no restriction | limiting in particular in the shape of a PVA film, Since a polarizing film etc. can be manufactured continuously with sufficient productivity, it is preferable that it is a long film. The length of the long film is not particularly limited, and can be set as appropriate according to the application of the polarizing film to be produced. For example, the length can be in the range of 5 to 20000 m. There is no restriction | limiting in particular in the width | variety of the said elongate film, For example, although it can be set to 50 cm or more, it is preferable that it is 1 m or more because a wide polarizing film is calculated | required in recent years, and it is 2 m or more. More preferably, it is 4 m or more. There is no particular limitation on the upper limit of the width of the long film, but if the width is too wide, it tends to be difficult to stretch uniformly when a polarizing film is produced with an apparatus in practical use. For some reasons, the width of the PVA film is preferably 7 m or less.

  The manufacturing method of a PVA film is not specifically limited, The manufacturing method from which the thickness and width | variety of the film after film forming become more uniform can be employ | adopted preferably, For example, above-mentioned PVA which comprises a PVA film, and as needed In addition, a film forming stock solution in which a plasticizer, a surfactant, and other components are dissolved in a liquid medium, and PVA, and if necessary, further include a plasticizer, a surfactant, other components, and a liquid medium, It can manufacture using the melt | dissolution film forming stock solution. When the film-forming stock solution contains at least one of a plasticizer, a surfactant, and other components, it is preferable that these components are uniformly mixed.

  Examples of the liquid medium used for the preparation of the membrane forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. , Trimethylolpropane, ethylenediamine, diethylenetriamine and the like, and one or more of them can be used. Among these, water is preferable from the viewpoint of a small environmental load and recoverability.

  The volatile fraction of the film-forming stock solution (the content ratio of volatile components such as a liquid medium removed by volatilization or evaporation during film formation in the film-forming stock solution) varies depending on the film-forming method, the film-forming conditions, etc. It is preferably in the range of mass%, more preferably in the range of 55 to 90 mass%, and still more preferably in the range of 60 to 85 mass%. When the volatile fraction of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during preparation of the film-forming stock solution, and there are few foreign matters and defects. Film production is facilitated. 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 does not become too low, and the production of an industrial PVA film becomes easy.

  Examples of the film forming method for forming a PVA film using the above-described film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method, and the like. A membrane method and an extrusion film forming method are preferred. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the extrusion film forming method is more preferable because a PVA film having a uniform thickness and width and good physical properties can be obtained. The PVA film can be dried or heat-treated as necessary.

[Thermoplastic resin film]
Examples of the thermoplastic resin constituting the thermoplastic resin film include various thermoplastic resins such as polyolefin (polyethylene, polypropylene, polymethylpentene, etc.), polystyrene, polycarbonate, polyvinyl chloride, methacrylic resin, nylon, polyethylene terephthalate, and the like. Examples thereof include a copolymer having a plurality of types of monomer units constituting these thermoplastic resins. In the thermoplastic resin film, only one kind of thermoplastic resin may be contained, or two or more kinds of thermoplastic resins may be contained. Among these, polyolefin is preferable because it has high stretchability. In addition, there is no restriction | limiting in particular in the method of manufacturing a thermoplastic resin film, It can manufacture by well-known methods, such as melt molding and calendar molding.

  Although there is no restriction | limiting in particular in the thickness of a thermoplastic resin film, Since the curl which generate | occur | produces in the both ends of the width direction of a PVA film can be suppressed more effectively, the said thickness is preferably 10 micrometers or more, 15 micrometers or more It is more preferable that it is 20 μm or more. Moreover, although there is no restriction | limiting in particular in the upper limit of the thickness of a thermoplastic resin film, Since the polarizing film etc. can be manufactured more smoothly, it is preferable that the said thickness is 100 micrometers or less.

  There is no restriction | limiting in particular in the shape of a thermoplastic resin film, What is necessary is just to select suitably according to the shape of said PVA film. When the PVA film is a long film, the thermoplastic resin film is also preferably a long film, and the length thereof can be within a range of 5 to 20000 m, for example.

  In the case where the thermoplastic resin film is a long film, the width is preferably 1.1 times or more the width of the PVA film. This is because, in the water contact step, the width of the PVA film tends to expand due to swelling, while the width of the thermoplastic resin film hardly changes. Therefore, when the width of the thermoplastic resin film satisfies the above relationship, This is because curling occurring at both end portions in the width direction can be more effectively suppressed even when swollen. From this viewpoint, the width of the thermoplastic resin film is more preferably 1.15 times or more, and further preferably 1.2 times or more the width of the PVA film. The upper limit of the width of the thermoplastic resin film is not particularly limited. However, even if it is made wider than necessary, no further curling suppression effect can be expected. Therefore, the width of the thermoplastic resin film is 1. of the width of the PVA film. It is preferably 8 times or less, and more preferably 1.6 times or less.

[Laminated film]
When the laminated film of the present invention is used as a raw film for producing a polarizing film, the adhesive strength between the PVA film and the thermoplastic resin film needs to be 200 mN / 15 mm or less. If the adhesive strength exceeds 200 mN / 15 mm, the removal of the thermoplastic resin film becomes considerably difficult, and the stretching process is performed in a state where the thermoplastic resin film and the PVA film are adjacent to each other as will be described later. In some cases, an appropriate neck-in of the PVA film is hindered, and it becomes difficult to obtain a polarizing film having excellent polarization performance. From this viewpoint, the adhesive strength is preferably 100 mN / 15 mm or less, more preferably 10 mN / 15 mm or less, and further preferably 5 mN / 15 mm or less. Moreover, not only when using the laminated | multilayer film of this invention as a raw film for polarizing film manufacture, but the said adhesive strength is less than 1.5 mN / 15mm, removal of a thermoplastic resin film becomes easier. From this viewpoint, the adhesive strength is more preferably less than 1.3 mN / 15 mm, and the two films are merely adjacent to each other and are not substantially bonded (adhesive strength is less than 1.0 mN / 15 mm). More preferably, In addition, the said adhesive strength can be measured by the T-shaped peeling test as described in JIS K6854-3: 1999, and can be specifically measured by the method mentioned later in an Example.

  There is no restriction | limiting in particular in the preparation method of the laminated | multilayer film of this invention, For example, after preparing said PVA film and a thermoplastic resin film, these are overlap | superposed or adhere | attached, and both are adjoined; A method of forming a PVA film on a thermoplastic resin film by applying and drying the above-mentioned film forming stock solution; in the latter case, the adhesive strength between the two films is defined in the present invention. Since it is usually difficult to adjust to a range within a range, a method in which a PVA film and a thermoplastic resin film are prepared and then superposed or bonded to each other is preferable. It is more preferable to prepare a resin film and then adjoin them without overlapping and substantially adhering them. . In addition, when using a long film as both a PVA film and a thermoplastic resin film, it is preferable to overlap or adhere | attach so that the center line of the width direction of both films may correspond substantially. It is preferable that the long laminated film formed by using a long film for both the PVA film and the thermoplastic resin film is wound into a roll to form a film roll from the viewpoint of handleability.

[Production method of polarizing film]
The laminated film of the present invention having an adhesive strength of 200 mN / 15 mm or less is used as a raw film for producing a polarizing film. On the other hand, the laminated film of the present invention having an adhesive strength of less than 1.5 mN / 15 mm suppresses the occurrence of curling even after passing through the step of contacting with water. Since it can be reduced and the removal of the thermoplastic resin film is extremely easy, it is conventionally known as a general PVA film application such as a raw film for producing a retardation film. Although it can use suitably for various uses, also in the said laminated | multilayer film, making use of the effect of this invention and using as a raw film for polarizing film manufacture are preferable.
Although there is no restriction | limiting in particular in the manufacturing method at the time of manufacturing a polarizing film using the laminated | multilayer film of this invention, Since the effect of this invention is show | played more notably, the process (water contact) which makes a laminated | multilayer film contact with water The manufacturing method which has a process (drawing process) and a process (drawing process) of extending a PVA film after that is preferable. When a thin PVA film is used as a single layer and a polarizing film is produced through a water contact step and a subsequent stretching step, curling occurs at both ends in the width direction of the film after the water contact step. Although the stretching break of the PVA film is likely to occur in the stretching step, the curling is suppressed by performing the water contact step on the laminated film of the present invention, and the stretching break of the PVA film in the stretching step can be prevented. .

-Water contact process As a water contact process, a swelling process process, a dyeing process process, a bridge | crosslinking process process, etc. are mentioned, for example, One or several processes of these can be employ | adopted. Since a polarizing film excellent in polarizing performance and the like can be easily produced, it is preferable to perform a swelling treatment step, a dyeing treatment step, and a crosslinking treatment step in this order as the water contact step. The contact between the laminated film and water in the water contact step may be either a method of spraying water on the laminated film or a method of immersing the laminated film in water. From the viewpoint, a method of immersing the laminated film in water is preferable. In addition, the water used is not limited to pure water, According to the objective of each process, the aqueous solution which is mentioned later, Furthermore, an aqueous dispersion liquid etc. can also be used.

  The swelling treatment in the swelling treatment step can be performed by immersing the laminated film in water. The temperature of 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 preferably in the range of 25 to 35 ° C. Further preferred. Moreover, as time to immerse in water, it is preferable to exist in the range of 0.5 to 5 minutes, for example, and it is more preferable to exist in the range of 1 to 3 minutes. In addition, the water at the time of immersing in water is not limited to a pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

The dyeing process in the dyeing process can be performed by immersing the laminated film in an aqueous solution containing a dichroic dye. The concentration of the dichroic dye in the aqueous solution containing the dichroic dye can be appropriately set according to the type of the dichroic dye used, for example, within a range of 0.001 to 1% by mass. However, when an iodine-potassium iodide aqueous solution is used as the aqueous solution containing the dichroic dye, the iodine-based dye can be efficiently adsorbed on the PVA film, so that the concentration of iodine (I ₂ ) used is Is preferably in the range of 0.01 to 1.0% by mass, and the concentration of potassium iodide (KI) used is preferably in the range of 0.01 to 10% by mass. The temperature of the aqueous solution containing the dichroic dye is preferably in the range of 20 to 50 ° C. because the dichroic dye can be efficiently adsorbed to the PVA film, and is in the range of 25 to 40 ° C. It is more preferable.

Examples of the dichroic dye, iodine based dye (I ₃ ^- and I ₅ ^-, etc.), and the like dichroic organic dyes. The iodine dye can be obtained, for example, by bringing iodine (I ₂ ) into contact with potassium iodide. Examples of the dichroic organic dye 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 and the like. Among these dichroic dyes, iodine-based dyes are preferable from the viewpoints of handleability, availability, and polarization performance. Incidentally, the dichroic dye may either be two or more even alone, for example, I ₃ ^- may be a balanced mixture as ^- and I _5.

  When the crosslinking treatment step is performed, crosslinking is introduced into the PVA film, and it is possible to effectively prevent the PVA from eluting into water when the stretching step is performed at a relatively high temperature and wet. From such a viewpoint, the crosslinking treatment step is preferably performed after the dyeing treatment step and before the stretching step. The crosslinking treatment can be performed by immersing the laminated film in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one or more of boron compounds such as boric acid and borate such as 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 a crosslinking agent may contain an auxiliary agent 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.

  Separately from the stretching step described below (the step of stretching the PVA film after the water contacting step), during the water contacting step and / or between the water contacting steps when the water contacting step spans multiple steps. The film can be stretched. By performing such stretching (pre-stretching), wrinkles can be prevented from entering the PVA film. The draw ratio of the pre-stretching is preferably 4 times or less based on the original length of the laminated film before stretching from the viewpoint of the polarizing performance of the polarizing film to be obtained, and the range of 1.5 to 3.5 times More preferably, it is within. Moreover, regarding the draw ratio in each water contact process, for example, the draw ratio in the swelling treatment process is preferably in the range of 1.1 to 3 times, and in the range of 1.2 to 2.5 times. More preferably, it is more preferably within the range of 1.4 to 2.3 times; the draw ratio in the dyeing treatment step is preferably 2 times or less, and preferably 1.8 times or less. More preferably, it is more preferably within a range of 1.1 to 1.5 times; the draw ratio in the crosslinking treatment step is preferably 2 times or less, more preferably 1.5 times or less. More preferably, it is within the range of 1.05 to 1.3 times.

  The laminated film subjected to the water contact step may be one unrolled from a film roll formed by winding a long laminated film as described above into a roll shape. A film roll and a film roll of a single layer thermoplastic resin film are prepared in advance, and each film is continuously unwound from these film rolls so that they are adjacent to each other. Also good.

-Stretching process A polarizing film can be manufactured by performing the extending | stretching process of extending | stretching a PVA film after passing through a water contact process, and also performing a fixing process and a drying process as needed. In the stretching step, the PVA film may be stretched in a state where the thermoplastic resin film and the PVA film are adjacent to each other, or after removing the thermoplastic resin film before the stretching step, the PVA The film may be stretched. In the former case, the thermoplastic resin film may be removed after the stretching step or the subsequent fixing treatment step and before the drying treatment step, or when the heat resistance of the thermoplastic resin film is high. The thermoplastic resin film may be removed after the drying process.

  There is no restriction | limiting in particular in the extending | stretching process in an extending | stretching process, You may carry out by any of a wet extending | stretching method and a dry-type extending | stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing one or two or more of boron compounds such as boric acid such as boric acid and borax, or in an aqueous solution containing the dichroic dye described above. It can also be performed in a fixed treatment bath described later. In the case of the dry stretching method, stretching may be performed at room temperature, stretching may be performed while applying heat, or stretching may be performed after water absorption. Among these, the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, and it is more preferable to stretch in a boric acid aqueous solution. The concentration of boric acid in the boric acid aqueous solution 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, More preferably, it is in the range of -4.0% by mass. The aqueous solution containing the above boron compound may contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass.

  The temperature at which the PVA film is stretched in the stretching step is preferably in the range of 30 to 90 ° C, more preferably in the range of 40 to 80 ° C, and in the range of 50 to 70 ° C. Is more preferable.

  The stretching ratio in the stretching step is preferably 1.2 times or more, more preferably 1.5 times or more, and more preferably 2 times or more, because a polarizing film superior in polarization performance can be obtained. Is more preferable. In addition, the total draw ratio including the above-described draw ratio of the pre-stretch (the ratio obtained by multiplying the draw ratios of the respective stretches) is 5.5 times or more based on the original length of the laminated film used. Is preferably 5.7 times or more, more preferably 5.8 times or more, and particularly preferably 5.9 times or more. By setting each stretching ratio within the above range, a polarizing film having better polarizing performance can be obtained. The upper limit of the total draw ratio is not particularly limited, but 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 obtained polarizing film. There is no particular limitation on the direction of uniaxial stretching, and uniaxial stretching or lateral uniaxial stretching in the length direction of a long film can be adopted, but since it is easy to obtain a polarizing film superior in polarization performance, in the length direction Uniaxial stretching is preferred. Uniaxial stretching in the length direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

-Fixing process The fixing process in a fixing process is mainly performed in order to strengthen adsorption | suction of the dichroic dye to the stretched PVA film. The fixing treatment can be performed by immersing the stretched PVA film in a fixing treatment bath. As the fixing treatment bath, an aqueous solution containing one or more of boron compounds such as boric acid such as boric acid and borax can be used. Moreover, you may add an iodine compound and a metal compound in a fixed treatment bath as needed. In general, the concentration of the boron compound in the aqueous solution containing the boron compound used as the fixing treatment bath is 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 fixing treatment bath is preferably within a range of 15 to 60 ° C, and more preferably within a range of 25 to 40 ° C.

-Drying treatment process The conditions of the drying treatment in the drying treatment process are not particularly limited, but the drying temperature is preferably in the range of 30 to 150 ° C, and more preferably in the range of 50 to 130 ° C. A polarizing film excellent in dimensional stability is easily obtained by drying at a temperature within the above range.

  The polarizing film obtained as described above is usually used as a polarizing plate by attaching a protective film that is optically transparent and has mechanical strength to both sides or one side. As the protective film, a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like can be used. Examples of the adhesive for bonding include PVA adhesives and urethane adhesives, among which PVA adhesives are suitable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In addition, the measuring method of the adhesive strength between films employ | adopted in the following Examples and Comparative Examples and the polarizing performance of a polarizing film is shown below.

[Adhesive strength between films]
From the laminated film produced in the following examples or comparative examples, a strip-shaped film piece of 200 mm in the length direction and 15 mm in the width direction is cut out, and this film piece is used as described in JIS K6854-3: 1999. Then, the T-shaped peeling test was carried out 5 times, and the average value was defined as the adhesive strength. In this test, the measurement conditions were as follows: temperature: 28 ° C., humidity: 50% RH, tensile tester chuck interval: 50 mm, tensile speed: 250 mm / min (moving speed of the peeling point in the film piece was 125 mm / min). In addition, when both films are peeled off when the film is cut out because the adhesive strength is too low, such as when the two films are not substantially bonded, the adhesive strength between the films is evaluated as less than 1.0 mN / 15 mm. did.

[Polarization performance of polarizing film]
(A) Measurement of transmittance Ts Two square samples of 2 cm in the length direction of the polarizing film and 2 cm in the width direction were collected from the central portion in the width direction of the polarizing film obtained in the following examples or comparative examples. Then, using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation), in accordance with JIS Z8722: 2009 (method for measuring object color), C light source, visibility in visible light region of 2 ° field of view Correction is performed, and the transmittance of light when tilted by 45 ° with respect to the length direction and the transmittance of light when tilted by −45 ° are measured for one sample, and the average value Ts1 (% ) Similarly, for the other sample, the light transmittance when tilted by 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following formula (1) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (1)

(B) Measurement of polarization degree V Light transmittance T‖ (%) and length direction when two samples collected by measurement of transmittance Ts are stacked so that their length directions are parallel to each other. Are measured in the same manner as in the case of “(a) Measurement of transmittance Ts”, and the degree of polarization V ( %).
V = {(T‖−T⊥) / (T‖ + T⊥)} ^1/2 × 100 (2)

[Example 1]
A long PVA film having a thickness of 30 μm and a width of 1 m (including PVA, glycerin and a surfactant, the glycerin content being 12 parts by mass with respect to 100 parts by mass of PVA, and the surfactant content being 100 parts by mass of PVA) PVA film is a saponified product of 0.03 parts by mass of PVA, which is a homopolymer of vinyl acetate, the degree of polymerization of PVA is 2400, and the degree of saponification of PVA is 99.9 mol%. Unwinding continuously from the film roll. On the other hand, a long linear low-density polyethylene film (LLDPE film, manufactured by Tamapoly Co., Ltd., SE620N) having a thickness of 50 μm and a width of 1.2 m was continuously unwound from the film roll. Then, the unwound films are overlapped so that the center lines in the width direction substantially coincide (the adhesive strength between the films is less than 1.0 mN / 15 mm), and the swelling process, the dyeing process, and the crosslinking process are continuously performed in this order. The long laminated film was brought into contact with water.
As the swelling treatment, the laminated film was immersed in distilled water (temperature: 30 ° C.) for 1 minute, and uniaxially stretched at a stretch ratio of 2 in the length direction during that time. In addition, as a dyeing treatment, the laminated film is in an aqueous solution containing iodine-based pigment (concentration of iodine used: 0.05 mass%, concentration of potassium iodide used: 1.2 mass%, temperature: 30 ° C.). And uniaxially stretched in the length direction at a stretch ratio of 1.2. Further, as a crosslinking treatment, the laminated film was immersed in an aqueous boric acid solution (boric acid concentration: 2.6 mass%, temperature: 30 ° C.) for 2 minutes, and uniaxially stretched at a draw ratio of 1.1 times in the length direction during that time. .

Following the water contact step, the stretching step was continuously performed. In the stretching step, the stretching process was performed in a state where the thermoplastic resin film and the PVA film are adjacent to each other. Thereafter, the thermoplastic resin film was removed, and the stretched PVA film was dried to continuously produce a polarizing film.
As the stretching treatment, the PVA film adjacent to the thermoplastic resin film is lengthened in an aqueous boric acid solution (boric acid concentration: 2.8% by mass, potassium iodide concentration: 5% by mass, temperature: 57 ° C.). The film was uniaxially stretched in the direction at a stretching ratio of 2.4 times (the total stretching ratio including the stretching ratio of the pre-stretching in the water contact step was 6.3 times). As a drying treatment, the stretched PVA film was dried at 60 ° C. for 1 minute.

  In the production of the polarizing film, no curling was observed at both ends in the width direction of the PVA film even after passing through any of the water contact steps, and no stretching breakage occurred in the stretching step. Moreover, the removal of the thermoplastic resin film was extremely easy. When the polarizing performance of the obtained polarizing film was measured according to the method described above, Ts = 43.5 (%) and V = 99.993 (%). The above results are summarized in Table 1.

[Example 2]
A polarizing film was continuously produced in the same manner as in Example 1 except that the thickness of the PVA film was changed to 15 μm. In the laminated film, the adhesive strength between the two films was less than 1.0 mN / 15 mm.

  In the production of the polarizing film, no curling was observed at both ends in the width direction of the PVA film even after passing through any of the water contact steps, and no stretching breakage occurred in the stretching step. Moreover, the removal of the thermoplastic resin film was extremely easy. When the polarizing performance of the obtained polarizing film was measured according to the method described above, Ts = 43.7 (%) and V = 999.93 (%). The above results are summarized in Table 1.

[Example 3]
Continuously in the same manner as in Example 1 except that a long low-density polyethylene film (LDPE film, manufactured by Tamapoly Co., Ltd., A-1) having a thickness of 50 μm and a width of 1.2 m was used as the thermoplastic resin film. A polarizing film was manufactured. In the laminated film, the adhesive strength between the two films was less than 1.0 mN / 15 mm.

  In the production of the polarizing film, no curling was observed at both ends in the width direction of the PVA film even after passing through any of the water contact steps, and no stretching breakage occurred in the stretching step. Moreover, the removal of the thermoplastic resin film was extremely easy. When the polarizing performance of the obtained polarizing film was measured according to the method described above, Ts = 43.4 (%) and V = 99.993 (%). The above results are summarized in Table 1.

[ Reference Example 1 ]
A high-density polyethylene film (HDPE film, manufactured by Sanei Kaken Co., Ltd., PAC-4K-80) having a thickness of 50 μm and a width of 1.2 m as the thermoplastic resin film is used, and the PSA surface is PVA. A polarizing film was continuously produced in the same manner as in Example 1 except that they were superposed so as to be on the film side. In the laminated film, the adhesive strength between the two films was 150 mN / 15 mm.

  In the production of the polarizing film, no curling was observed at both ends in the width direction of the PVA film even after passing through any of the water contact steps, and no stretching breakage occurred in the stretching step. However, the removal of the thermoplastic resin film was not as easy as Example 1. When the polarizing performance of the obtained polarizing film was measured according to the method described above, Ts = 43.7 (%) and V = 99.948 (%). The above results are summarized in Table 1.

[Example 4 ]
Prior to the stretching step, a polarizing film was continuously produced in the same manner as in Example 1 except that the thermoplastic resin film was removed and the PVA film was stretched alone.

  In the production of the polarizing film, no curling was observed at both ends in the width direction of the PVA film even after passing through any of the water contact steps, and no stretching breakage occurred in the stretching step. Moreover, the removal of the thermoplastic resin film was extremely easy. When the polarizing performance of the obtained polarizing film was measured according to the method described above, Ts = 43.3 (%) and V = 99.994 (%) were obtained. The above results are summarized in Table 1.

[Comparative Example 1]
A polarizing film was continuously produced in the same manner as in Example 1 except that the PVA film was used as a single layer without using the thermoplastic resin film, and the water contact step and the subsequent stretching step were performed.

  In the production of the above polarizing film, after passing through the swelling treatment step, curling was observed at both ends in the width direction of the PVA film, the stretching break occurred in the stretching step, and a polarizing film could not be obtained. . Therefore, the polarizing performance of the polarizing film was not measured. The above results are summarized in Table 1.

[Comparative Example 2]
A long amorphous polyethylene terephthalate film (A-PET film, “Novaclear” manufactured by Mitsubishi Plastics, Inc.) having a thickness of 200 μm and a width of 1 m is added to an aqueous solution (PVA, glycerin and a surfactant) having a PVA concentration of 10% by mass. A PVA aqueous solution having a glycerin content of 12 parts by mass with respect to 100 parts by mass of PVA and a surfactant content of 0.03 parts by mass with respect to 100 parts by mass of PVA. A PVA film having a thickness of 30 μm is formed on the thermoplastic resin film by applying a saponified product, having a polymerization degree of PVA of 2400 and a PVA saponification degree of 99.9 mol%) and drying at 60 ° C. The formed laminated film was produced (adhesive strength between the thermoplastic resin film and the PVA film was 250 mN / 15 mm). The laminated film thus obtained was subjected to a swelling treatment, a dyeing treatment and a crosslinking treatment in this order in the same manner as in Example 1, and then a water contact step was carried out. The drying process was performed in this order and the polarizing film was continuously manufactured. In addition, since the adhesive strength between the PVA film and the thermoplastic resin film is high and it was extremely difficult to remove the thermoplastic resin film before the drying treatment after the stretching treatment, the thermoplastic resin film is removed after the drying treatment. Although the polarizing film was obtained, it was still difficult to remove the thermoplastic resin film.

  In the production of the polarizing film, no curling was observed at both ends in the width direction of the PVA film even after passing through any of the water contact steps, and no stretching breakage occurred in the stretching step. However, when the polarizing performance of the obtained polarizing film was measured according to the method described above, Ts = 43.5 (%) and V = 99.854 (%). The above results are summarized in Table 1.

  According to the present invention, even when a thin PVA film is used, it is difficult to cause stretching breakage during stretching, and a polarizing film having excellent polarization performance can be easily produced. A polarizing plate made of a polarizing film produced using a film can be suitably used for mobile applications such as small notebook computers and mobile phones.

Claims (7)

Polyvinyl alcohol film and a thermoplastic resin film is adjacent to a laminate film for a polarizing film producing state, and are adhesive strength 10 mN / 15 mm or less between both films, the thickness of the polyvinyl alcohol film is 45μm or less Is a laminated film. The laminated film according to claim 1 , which is a long laminated film. The laminated film according to claim 2 , wherein the width of the thermoplastic resin film is 1.1 times or more of the width of the polyvinyl alcohol film. Film roll comprising wound laminated film according to claim 2 or 3. The manufacturing method of the polarizing film which has the water contact process which makes the laminated | multilayer film of any one of Claims 1-3 contact with water, and the extending | stretching process of extending a polyvinyl alcohol film after that. The manufacturing method according to claim 5 , wherein the thermoplastic resin film and the polyvinyl alcohol film are adjacent to each other in the stretching step. The manufacturing method of Claim 5 which has the process of removing a thermoplastic resin film before a extending process.