JP2017182020A - Method for manufacturing polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing film capable of suitably suppressing fracture of a polarizer during manufacturing and easily stretching a film at a high magnification.SOLUTION: A method for manufacturing a polarizing film comprises: a stretching step of obtaining a stretched film by stretching a belt-like resin film which uses a polyvinyl alcohol resin as a forming material; a sticking step of obtaining a laminate film laminated with the stretched film and a belt-like base material film by sticking the base material film to at least one surface of the stretched film; and a polarizer forming step of forming the stretched film as a polarizer by dyeing the stretched film by a dichroism pigment and stretching the whole laminate film in a longitudinal direction. A stretch ratio in the longitudinal direction of the base material film in the sticking step is less than a stretch ratio in the longitudinal direction of the stretched film in the stretching step.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a polarizing film.

  Conventionally, a liquid crystal display device is known as an image display device. The liquid crystal display device has a liquid crystal panel and a polarizer provided on both surfaces of the liquid crystal panel. As a polarizer, a polarizing film is known in which a dichroic dye such as iodine is adsorbed and oriented on a stretched film obtained by stretching a polyvinyl alcohol (PVA) resin film.

  As a manufacturing method of a polarizing film, for example, a method described in Patent Document 1 is known. In the production method described in Patent Document 1, first, a polyvinyl alcohol-based resin coating film is formed on the surface of a base film to provide a resin layer, and then a laminated film of the resin layer and the base film is stretched. Next, the resin layer is dyed with iodine, which is a dichroic dye, and then further stretched in one direction. Thus, the polarizing film is manufactured using the resin layer as a polarizer.

  As another method for producing a polarizing film, a method is known in which a polyvinyl alcohol-based resin film and a substrate film are laminated and then stretched, and further, iodine staining and stretching are performed.

JP 2000-338329 A

  In recent years, liquid crystal display devices are required to be smaller and thinner in order to reduce weight. For this reason, it has been studied to reduce the thickness of the polarizer and polarizing film constituting the liquid crystal display device.

  In addition, it is known that when the stretching ratio of the polarizer is increased when the resin layer dyed with a dichroic dye is stretched during production, the polarization characteristics of the polarizer are easily improved. Therefore, in recent years, a polarizing film used for a liquid crystal display device has been required to have a thin polarizer stretched at a high stretching ratio.

  However, if the thickness of the polarizer is reduced during the production of the polarizing film, the resin layer (polarizer) tends to break when the film is stretched. Moreover, when it is going to manufacture the polarizing film which raised the draw ratio from the conventional thing, since the load of a processing apparatus will increase at the time of an extending | stretching process, production efficiency will fall easily.

  Therefore, there has been a demand for a manufacturing method that can reduce the load on the apparatus during stretching while suppressing breakage of the polarizer in stretching.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the manufacturing method of the polarizing film which suppresses the fracture | rupture of a polarizer suitably at the time of manufacture, and is easy to extend | stretch at high magnification. .

  In order to solve the above-described problems, an embodiment of the present invention includes a stretching step of stretching a strip-shaped resin film using a polyvinyl alcohol-based resin as a forming material to obtain a stretched film, and a strip-shaped film on at least one surface of the stretched film. Pasting the base film, a pasting step to obtain a laminated film in which the stretched film and the base film are laminated, dyeing of the stretched film with a dichroic dye, and the longitudinal direction of the whole laminated film A polarizer forming step using the stretched film as a polarizer, and the base film in the laminating step has a longitudinal draw ratio of the stretched film in the stretching step. Provided is a method for producing a polarizing film that is less than the draw ratio in the longitudinal direction.

  In one aspect of the present invention, in the bonding step, the base film may be a manufacturing method that is unstretched in the longitudinal direction.

  In 1 aspect of this invention, it is good also as a manufacturing method which the said polarizer formation process immerses the said laminated | multilayer film dye | stained the said stretched film in the aqueous solution containing a boric acid, and extends | stretches in the said aqueous solution.

  In 1 aspect of this invention, it is good also as a manufacturing method which extends | stretches the said resin film using the fixed end extending | stretching method in the said extending process.

  In one embodiment of the present invention, the resin film may have a thickness of 15 μm or more and 75 μm or less.

  In 1 aspect of this invention, it is good also as a manufacturing method which bonds the said stretched film and the said base film through a water-system adhesive agent in the said bonding process.

  In 1 aspect of this invention, it is good also as a manufacturing method which has the polarizing film formation process which cuts the said polarizer into plurality and obtains the said polarizing film after the said polarizer formation process.

  According to the present invention, it is possible to provide a method for producing a polarizing film that suitably suppresses breakage of the polarizer during production and that can be easily stretched at a high magnification.

It is a schematic sectional drawing which shows the polarizing film manufactured using the manufacturing method of the polarizing film which concerns on this embodiment. It is a schematic diagram which shows an example of an extending process. It is a schematic diagram which shows an example of a bonding process. It is a schematic diagram which shows an example of the dyeing | staining process in a polarizer formation process. It is a schematic diagram which shows an example of the extending | stretching process in a polarizer formation process. It is a schematic diagram which shows a mode that a test piece is extended in an Example.

  Hereinafter, the manufacturing method of the polarizing film which concerns on this embodiment is demonstrated, referring FIGS. In all the drawings below, the dimensions and ratios of the respective constituent elements are appropriately changed in order to make the drawings easy to see.

[Polarized film]
FIG. 1: is a schematic sectional drawing which shows the polarizing film manufactured using the manufacturing method of the polarizing film which concerns on this embodiment. As shown in the figure, a polarizing film 10 produced by the method for producing a polarizing film of this embodiment has a polarizer 1. Further, the polarizing film 10 may have a protective film 2 formed on one surface of the polarizer 1.

  As the polarizer 1, a uniaxially stretched polyvinyl alcohol resin film having a dichroic dye adsorbed and oriented can be used. The material for forming the polarizer 1 will be described later in detail.

  The protective film 2 protects the surface of the polarizer 1. The protective film 2 is bonded to the surface of the polarizer 1 via, for example, an adhesive layer or a pressure-sensitive adhesive layer. The forming material of the protective film 2 will be described in detail later.

  The polarizing film 10 may have a film having an optical function such as a retardation film or a brightness enhancement film on the surface of the polarizer 1 as necessary.

  That is, the polarizing film manufactured in the manufacturing method of the polarizing film of this embodiment is only the polarizer 1 in the case of the minimum layer configuration, and has various functions having desired optical characteristics and mechanical characteristics as necessary. It can be set as the multilayered structure which laminated | stacked the layer which has.

[Production method of polarizing film]
2-5 is explanatory drawing which shows the manufacturing method of the polarizing film which concerns on this embodiment. The manufacturing method of the polarizing film of this embodiment is as follows:
(1) Stretching a strip-shaped resin film using a polyvinyl alcohol-based resin as a forming material to obtain a stretched film (2) Bonding a strip-shaped base film on at least one surface of the stretched film, Bonding step for obtaining a laminated film in which a base film is laminated (3) Polarization using a stretched film as a polarizer by dyeing a stretched film with a dichroic dye and stretching in the longitudinal direction of the entire laminated film Child forming step (4) A protective film laminating step for laminating a protective film on the surface of the polarizer (5) A polarizing film forming step for forming a polarizing film by dividing the polarizer and the protective film into plural pieces.
Hereinafter, it demonstrates in order.

<Extension process>
FIG. 2 is a schematic diagram illustrating an example of a stretching process. In the stretching step, a belt-shaped resin film using a polyvinyl alcohol-based resin as a forming material is stretched to obtain a stretched film. FIG. 2A shows a state in which the resin film 11 is stretched by a fixed-end lateral stretching method to obtain a stretched film 12, and FIG. 2B shows a state in which the resin film 11 is stretched by hot roll stretching to obtain a stretched film 12. Indicates.

  In the method shown in FIG. 2A, the resin film 11 unwound from the unwinding roll 101 is introduced into a heating furnace (not shown). In the heating furnace, the resin film 11 is sequentially conveyed in the longitudinal direction of the resin film 11 while both ends of the resin film 11 in the width direction are held by the plurality of holding portions 109. The holding part 109 stretches the resin film 11 in the width direction (TD direction indicated by reference sign D1 in the figure) by applying a force that spreads in the width direction to the resin film 11 to form a stretched film 12A.

  Here, with respect to the longitudinal direction of the stretched film 12A (MD direction indicated by reference sign D2 in the figure), the rotational speed of the unwinding roll 101 and the rolls such as the transport roll and the winding roll disposed on the downstream side Depending on the difference, it may be stretched or shrunk, or may not be stretched.

  In the method shown in FIG. 2B, the resin film 11 unwound from the unwinding roll 101 is wound around a heating roll 102 and a pair of nip rolls 103 and 104 that rotate at a higher speed than the heating roll, and thus in the longitudinal direction. It is conveyed to. The resin film 11 is heated by the heating roll 102. Further, the resin film 11 is stretched in the longitudinal direction (MD direction indicated by reference sign D3 in the figure) between the heating roll 102 and the nip rolls 103 and 104 due to a difference in peripheral speed between the heating roll 102 and the nip rolls 103 and 104. Thus, the stretched film 12B is obtained.

(Resin film)
As a polyvinyl alcohol-type resin which forms the resin film 11, what saponified the polyvinyl acetate-type resin can be used. As the polyvinyl acetate resin, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate can be used. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The polyvinyl alcohol resin preferably has a saponification degree of 80.0 mol% or more. When the saponification degree of the polyvinyl alcohol-based resin is 80.0 mol% or more, the water resistance after forming the polarizer is likely to be high, and the property to withstand a wet environment and a high temperature environment is likely to be high. The saponification degree is more preferably 90.0 mol% or more, further preferably 94.0 mol% or more, and most preferably 100 mol% (completely saponified product).

Here, “degree of saponification” is the unit ratio (mol%) of the rate at which the acetate residue contained in the polyvinyl acetate resin, which is the raw material of the polyvinyl alcohol resin, has been changed to a hydroxyl group by the saponification step. It is a numerical value defined by the following formula. Further, the saponification degree can be obtained by a method defined in JIS K 6726 (1994).
Degree of saponification (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100

  The polyvinyl alcohol-based resin may be modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol resins modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, alkyl esters of unsaturated carboxylic acids, acrylamide, and the like can be used. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When the modification ratio is less than 30 mol%, the adsorption of the dichroic dye is hardly inhibited, and the polarization performance is not easily lowered by the modification.

  As described above, the material for forming the resin film 11 used in the present embodiment may not be a pure polyvinyl alcohol resin. Various chemicals may be used depending on the degree of saponification, the type of monomer to be copolymerized, and the type of residue that modifies PVA. It has a structure. As described above, polyvinyl alcohol resin is used as a basic skeleton, and derivatives that can be employed are collectively referred to as “polyvinyl alcohol resin” in the present embodiment.

  The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, more preferably 1500 to 8000, and still more preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined by a method defined by JIS K 6726 (1994).

  The resin film 11 is obtained by forming the polyvinyl alcohol resin as described above. The method for forming the resin film 11 is not particularly limited. For example, a solvent casting method in which a polyvinyl alcohol resin solution is applied on a support and dried, a melt extrusion method in which a polyvinyl alcohol resin containing water is melt-kneaded and extruded onto a support by an extruder, a polyvinyl alcohol resin Examples include a gel film forming method in which an aqueous solution is discharged into a poor solvent. Among these, since a more transparent film is obtained, the solvent casting method or the melt extrusion method is preferable.

Hereinafter, the solvent casting method will be described in more detail.
When the resin film 11 is formed using the solvent casting method, water or polar organic solvents such as alcohols, ketones, and esters can be used as the solvent for dissolving the polyvinyl alcohol-based resin. It is preferable to use it. A polar organic solvent may be appropriately added to the aqueous solution of the polyvinyl alcohol resin.

  Moreover, a plasticizer can be added to the polyvinyl alcohol resin solution used. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. Only one type of plasticizer may be used, or two or more types may be used in combination. In particular, ethylene glycol and glycerin are preferably used. Moreover, antiblocking agents, such as surfactant, can also be used together as needed.

  The polyvinyl alcohol resin solution used in these methods can be obtained, for example, by dissolving the polyvinyl alcohol resin in water heated to 80 to 90 ° C. The solid content concentration of the polyvinyl alcohol-based resin is preferably in the range of 6 wt% to 50 wt%. When the concentration of the solid content is less than 6% by weight, the viscosity becomes too low, the fluidity at the time of forming the resin layer becomes too high, and it becomes difficult to obtain a uniform film. On the other hand, when the concentration of the solid content exceeds 50% by weight, the viscosity becomes too high and the fluidity at the time of forming the resin layer becomes low, so that film formation becomes difficult.

  As a method of coating a polyvinyl alcohol resin solution on a support, roll coating methods such as wire bar coating method, reverse coating method and gravure coating, die coating method, comma coater method, lip coating method, spin coating method, screen Known methods such as a coating method, a fountain coating method, a dipping method, and a spray method can be appropriately selected and employed.

  In the solvent cast method, after a polyvinyl alcohol-based resin solution is applied on a support to form a resin layer, the resin layer formed on the support is dried at a low temperature to such an extent that it can be peeled off from the support, It is preferable to change the conditions and dry the resin layer peeled from the support. Hereinafter, the step of drying to such an extent that it can be peeled off from the support is referred to as “first drying step”, and the step of drying the resin layer peeled off from the support base is referred to as “second drying step”.

  As a support body here, a release film, a stainless steel belt, a chill roll etc. are mentioned, for example.

  In the first drying step, “a degree that can be peeled off from the support” means that the solvent is removed from the applied resin solution to form a film-like coating film (hereinafter simply referred to as a film), and the film can be peeled off. is there. Empirically, it has been found that the film can be stably peeled if the moisture content of the film is dried to 30% by weight or less. Further, it is preferable that the moisture content of the film is dried to 20% by weight or less because it can be more easily peeled off.

  In addition, the moisture content said here is the ratio of the moisture contained in a film, and points out the value calculated | required by the dry weight method. The moisture content can be determined by the following method.

First, after leaving the peeled film at room temperature (approximately 25 ° C., 55% RH) for 30 minutes or more, the mass of the film is measured. The film is then dried in a 105 ° C. oven for 60 minutes. After removing from the oven, leave it for a few minutes until the temperature of the film returns to room temperature. The film mass is then remeasured.
Using the mass of the obtained film before drying (mass before drying) and the mass of the film after drying (mass after drying), the water content is obtained from the following formula.
Water content (%) = {(mass before drying) − (mass after drying)} / (mass before drying) × 100

  In the manufacturing process, it is preferable to set a drying condition in which the film can be peeled by performing a preliminary experiment and perform drying under the condition. For example, as a film drying condition, it is preferably dried for 1 to 30 minutes in a temperature range of 40 ° C. to 60 ° C., and more preferably 3 to 20 minutes at 50 ° C.

  In the first drying step, by drying at a low temperature, drying shrinkage is unlikely to occur in the film, and curling of the end portion can be prevented. Also, in the first drying step, the film is not completely dried, but is dried to such an extent that it can be peeled off from the support. it can.

  After the first drying step, the film is peeled from the support. Next, in the second drying step, the film is dried. In a 2nd drying process, conditions are changed from a 1st drying process and a film is fully dried. Specifically, in the second drying step, the film is dried at a higher drying temperature than in the first drying step.

  The drying temperature in the second drying step is preferably higher than the set temperature in the first drying step and 150 ° C. or lower. The drying temperature in the second drying step is more preferably 120 ° C. or less, and further preferably 100 ° C. or less. The drying temperature in the second drying step is more preferably 60 ° C. or higher, and further preferably 70 ° C. or higher.

  As a drying method that can be adopted in the second drying step, there are various methods such as a method of spraying hot air, a method of contacting with a hot roll, and a method of heating with an IR heater, all of which can be suitably used. The drying temperature in the first drying step and the second drying step is a drying facility in which a drying furnace is provided and drying is performed in a drying furnace, such as a method of blowing hot air or a method of heating with an IR heater. Means the ambient temperature in the drying equipment. In the case of contact-type drying equipment such as a hot roll, it means the surface temperature of the hot roll.

  As described above, a resin film can be produced by a melt casting method. The resin film produced by such a solvent casting method is difficult to peel off from the end when the resin film is stretched in the dyeing process or the crosslinking process after the resin film is bonded to the base material, and the cutting of the film is suppressed. Will be good.

The resin film 11 is preferably a single layer.
The thickness of the resin film 11 is preferably 15 μm or more. Moreover, the thickness of the resin film 11 is preferably 75 μm or less, and more preferably 60 μm or less. Industrially, the width of the resin film 11 is practically 1500 mm or more and 6000 mm or less.

(Stretching method)
In the stretching step, the resin film 11 as described above is stretched to obtain a stretched film 12. The stretching method may be free end stretching or fixed end stretching.

  Here, “free end stretching” refers to stretching the film in one direction without suppressing shrinkage of the film in the direction orthogonal to the stretching direction. Examples of the free end stretching method include a method of stretching an unstretched resin film due to a difference in rotational speed between two or more rolls, and a method called a long span stretching method. The long span stretching method uses a longitudinal stretching machine having two pairs of nip rolls and an oven arranged therebetween, and stretches the unstretched resin film in the oven by a difference in rotational speed between the two pairs of nip rolls. It is.

  “Fixed end stretching” refers to stretching while suppressing shrinkage of the film in a direction perpendicular to the stretching direction when the film is stretched in one direction. As a method of stretching at the fixed end, for example, in roll stretching performed using a transport roll while heating in a heating furnace, a method of shortening the distance between the rolls and stretching in the transport direction, hot roll stretching, stretching by a tenter method. Can be mentioned.

  The stretching process may be performed in one stage or in multiple stages. The stretching step may be uniaxial stretching or biaxial stretching. Furthermore, oblique stretching may be used.

  In this embodiment, it is preferable to stretch the resin film 11 by fixed end stretching in the stretching step to obtain a stretched film 12. In general, in the fixed end stretching, since it is easier to make the stretched film 12 thinner than the free end stretching, the stretched film 12 can be suitably thin.

  The stretching ratio of the stretched film 12 obtained by the stretching process can be, for example, 1.5 times or more, and is preferably 4 times or more. Although there is no restriction | limiting in particular in the upper limit of a draw ratio, Usually, it is 8 times or less, and it is preferable to set it as 6 times or less.

  For example, the thickness of the stretched film 12 obtained by stretching is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 7 μm or less.

<Bonding process>
Drawing 3 is a mimetic diagram showing an example of a pasting process. In the bonding step, a belt-like substrate film is bonded to at least one surface of the stretched film 12, and a laminated film 30 in which the stretched film 12 and the substrate film 21 are laminated with their longitudinal directions aligned is obtained.

  As shown in FIG. 3, the stretched film 12 unwound from the unwinding roll 111 overlaps the base film 21 unwound from the unwinding roll 112 in a pair of rolls 113 and 114. A pressure sensitive adhesive or an adhesive (not shown) is disposed on one or both of the facing surfaces of the stretched film 12 and the base film 21. The stretched film 12 and the base film 21 are laminated through a pressure-sensitive adhesive or adhesive (not shown), and pasted by passing between a pair of rolls 113 and 114. Thereby, the laminated film 30 is obtained.

(Base film)
As the resin used for the base film 21, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like is used. The base film 21 is stretched together with the stretched film 12 in the polarizer forming step described later. Therefore, it is preferable to use the base film 21 that can be similarly stretched in a temperature range suitable for stretching the stretched film 12. In that case, an appropriate film may be selected based on the glass transition temperature Tg or the melting point Tm of the thermoplastic resin forming the base film 21.

  In this embodiment, the base film 21 has a stretching ratio in the longitudinal direction (MD direction indicated by reference sign D4 in the drawing) that is less than the stretching ratio in the longitudinal direction of the stretched film 12 in the stretching step. The base film 21 is preferably unstretched in the longitudinal direction. The degree of orientation in the longitudinal direction of the base film is preferably 0.5 or less. Moreover, the base film 21 may be extended | stretched in the transversal direction and may not be extended | stretched in a transversal direction.

  Here, the “stretch ratio” is “ratio of the length after stretching to the length before stretching” in the stretching direction, and is a value obtained by dividing the length after stretching by the length before stretching.

  In addition, about the draw ratio of the transversal direction of the base film 21 (TD direction indicated by reference sign D5 in the drawing), whichever is higher than the stretch ratio of the stretched film 12 in the transversal direction may be used.

  Specific examples of the thermoplastic resin that is a material for forming the base film 21 include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth) acrylic resins, cellulose ester resins, and polycarbonate resins. Resins, polyvinyl alcohol resins, vinyl acetate resins, polyarylate resins, polystyrene resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, and mixtures and copolymers thereof. It is done.

  The base film 21 may be a film formed using only one kind of the above-described resin, or may be a film formed using a mixture of two or more kinds of resins. Moreover, the base film 21 may be a single layer film or a multilayer film.

  Examples of the polyolefin resin include polyethylene and polypropylene. Polyethylene, polypropylene, and the like are preferable because they can be stably stretched at a high magnification. Moreover, an ethylene-polypropylene copolymer obtained by copolymerizing propylene with ethylene can also be used. Copolymerization can be performed with other types of monomers, and examples of other types of monomers copolymerizable with propylene include ethylene and α-olefins.

  The stereoregularity of the propylene resin constituting the propylene resin film is preferably substantially isotactic or syndiotactic. A propylene-based resin film made of a propylene-based resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength in a high-temperature environment.

  Arbitrary appropriate additives may be added to the base film 21 in addition to the thermoplastic resin. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. .

  The content of the thermoplastic resin exemplified above in the base film 21 is preferably 50% by mass to 100% by mass, more preferably 50% by mass to 99% by mass, and further preferably 60% by mass to 98% by mass. Especially preferably, it is 70 mass%-97 mass%. This is because when the content of the thermoplastic resin in the base film 21 is less than 50% by mass, the high transparency and the like inherent in the thermoplastic resin may not be sufficiently exhibited.

  Although the thickness of the base film 21 before stretching can be appropriately determined, it is generally preferably 1 μm to 500 μm, more preferably 1 μm to 300 μm, and more preferably 5 μm to 200 μm from the viewpoint of workability such as strength and handleability. More preferably, 5 μm to 150 μm is even more preferable.

  In order to improve the adhesion with the stretched film 12, the base film 21 may be subjected to corona treatment, plasma treatment, flame treatment, or the like on at least the surface on which the stretched film 12 is bonded. Moreover, in order to improve adhesiveness, the primer layer is formed on the surface of the base film 21 facing the stretched film 12 by using a material that exhibits a certain degree of strong adhesion to both the base film 21 and the stretched film 12. May be formed.

  The material for forming the primer layer is not particularly limited as long as it is a material that exhibits a certain degree of strong adhesion to both the base film 21 and the stretched film 12. For example, a thermoplastic resin excellent in transparency, thermal stability, stretchability, etc. is used. Specific examples include acrylic resins and polyvinyl alcohol resins, but are not limited thereto.

(Adhesive / Adhesive)
In the bonding step, the stretched film 12 and the base film 21 described above are bonded via an adhesive or a pressure-sensitive adhesive (pressure-sensitive adhesive).

In this specification, an “adhesive” is a liquid when it is applied to a base material and wets the base material and solidifies to develop adhesiveness (that is, until it solidifies, it exhibits adhesiveness). Not).
Further, in this specification, the “pressure-sensitive adhesive” is a flexible rubber-like material, and immediately exhibits adhesiveness by attaching itself. When using an adhesive, a solidification process is not required.

  At the time of stretching in the next step, it is preferable to use an adhesive because peeling hardly occurs even at a high stretching temperature.

  The pressure-sensitive adhesive is composed of a composition in which, for example, an acrylic resin, a styrene resin, a silicone resin, or the like is used as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto.

  The method for forming the pressure-sensitive adhesive layer on the base film 21 and the stretched film 12 is not particularly limited. For example, the base film 21 or the stretched film 12 can be formed by applying a solution containing each component including the above-described base polymer and drying it. Or it can also form by sticking the adhesive layer previously formed on the separator to the base material film 21 or the stretched film 12, and removing and transferring the separator.

  Examples of the adhesive include aqueous adhesives using polyvinyl alcohol resin aqueous solutions, aqueous urethane adhesives, aqueous polyester adhesives, aqueous vinyl acetate emulsion adhesives, aqueous acrylic adhesives, and the like. Among these, a polyvinyl alcohol resin aqueous solution is preferably used. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive.

  The method of laminating the film using the water-based adhesive is not particularly limited, and the adhesive is uniformly applied or poured onto the surface of the base film 21 or the stretched film 12, and the other film is applied to the application surface. Examples of the method include stacking and pasting with rolls and drying. For example, an adhesive agent is apply | coated under the temperature of 15 to 40 degreeC after the preparation, and the bonding temperature is the range of 15 to 30 degreeC, for example.

  When using a water-based adhesive, after bonding the film, it is dried to remove water contained in the water-based adhesive. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. If it is less than 30 ° C., the adhesive surface tends to be peeled off. When it exceeds 90 ° C., the stretched film 12 is deformed by heat, and the optical performance of the polarizer may be deteriorated. The drying time can be 10 seconds to 1000 seconds.

  Moreover, a photocurable adhesive can also be used as a non-aqueous adhesive. As a photocurable adhesive agent, the mixture of an epoxy resin and a photocationic polymerization initiator etc. can be mentioned, for example. Moreover, the mixture of the component containing a (meth) acryloyl group and radical photopolymerization initiator etc. can be mentioned.

  A conventionally well-known method can be used as a method of bonding films with a photocurable adhesive. For example, an adhesive is applied to the adhesive surface of a film by casting method, Mayer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method, spraying method, etc. The method of irradiating light is mentioned. The casting method is a method in which two films as an object to be coated are moved in a substantially vertical direction, generally in a horizontal direction, or in an oblique direction between the two, and an adhesive is allowed to flow down and spread on the surface. is there.

  After the adhesive is applied to the surface of the film, the film is bonded by sandwiching it with a nip roll or the like, drying, or light irradiation. Moreover, the method of pressing this laminated body with a roll etc. and spreading it uniformly can also be used suitably.

  In order to improve adhesiveness, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment may be appropriately performed on the adhesion surface of the film. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  When a photocurable resin is used as an adhesive, the photocurable adhesive is cured by irradiating active energy rays after laminating the films. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.

  When the photocurable adhesive on the base film 21 and the stretched film 12 is cured by irradiation with active energy rays, various functions of the polarizing plate after undergoing all the steps, such as transmittance, hue, and transparency of these films. It is preferable to perform the curing under active energy ray irradiation conditions that do not decrease.

<Polarizer formation process>
4 and 5 are schematic views showing an example of a polarizer forming step. In the polarizer forming step, the stretched film 12 is dyed with a dichroic dye (hereinafter referred to as a dyeing process) and the entire laminated film 30 is stretched in the longitudinal direction (hereinafter referred to as a stretching process). And FIG. 4 is a schematic diagram illustrating an example of a dyeing process in the polarizer forming process, and FIG. 5 is a schematic diagram illustrating an example of a stretching process in the polarizer forming process.

(Dyeing process)
As shown in FIG. 4, the laminated film 30 is transported in the longitudinal direction by transport rollers 141 to 144. The laminated film 30 is immersed in a dye solution 151 in which a dichroic dye is dissolved in a dye bath 150 provided in the transfer path, and is conveyed while being dyed. Thereby, the stretched film 12 which the laminated film 30 has is dye | stained, and the laminated film 31 which has the dyed stretched film 13 is obtained.

  In the present embodiment, the stretched film 12 constituting the laminated film 30 is dyed with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes.

  The dyeing process is performed, for example, by immersing the entire laminated film 30 in a solution (dye solution) in which a dichroic dye is dissolved in a solvent. As a solvent for the dyeing solution, water is generally used, but an organic solvent compatible with water may be further added.

  The concentration of the dichroic dye is preferably 0.01% by mass to 10% by mass, more preferably 0.02% by mass to 7% by mass, and 0.025% by mass to 5% by mass. It is particularly preferred.

  When iodine is used as the dichroic dye, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01% by mass to 20% by mass in the dyeing solution.

  Of the iodides, it is preferable to add potassium iodide. When adding potassium iodide, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80, by mass ratio. , Particularly preferably in the range of 1: 7 to 1:70.

  The immersion time of the stretched film 12 in the dyeing solution is not particularly limited, but is preferably in the range of 15 seconds to 15 minutes, and more preferably 1 minute to 3 minutes. Moreover, it is preferable that the temperature of a dyeing | staining solution exists in the range of 10 to 60 degreeC, and it is more preferable that it exists in the range of 20 to 40 degreeC.

(Crosslinking treatment)
Following the dyeing process, a crosslinking process can be performed. The crosslinking treatment is performed, for example, by immersing the laminated film 31 having the dyed stretched film 13 in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One type of cross-linking agent may be used, or two or more types may be used in combination.

  As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density | concentration of the crosslinking agent in a crosslinking solution is not limited to this, It is preferable to exist in the range of 1 mass%-20 mass%, and it is more preferable that it is 6 mass%-15 mass%.

  Iodide may be added to the crosslinking solution. By adding iodide, the in-plane polarization characteristics of the resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The content of iodide is 0.05% by mass to 15% by mass, more preferably 0.5% by mass to 8% by mass.

  The immersion time of the laminated film 30 in the crosslinking solution is preferably 15 seconds to 20 minutes, and more preferably 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a crosslinking solution exists in the range of 10 to 80 degreeC.

(Extension process)
Next, as illustrated in FIG. 5, the laminated film 31 is transported in the longitudinal direction by transport rollers 161 to 164. The laminated film 31 is conveyed while being immersed in, for example, an aqueous boric acid solution 171 in a stretching bath 170 provided in the conveyance path. Furthermore, in the stretching bath 170, the entire laminated film 31 is stretched between the transport roll 162 and the transport roll 163. Thereby, the stretched film 13 is stretched to become a long polarizer 14. Thereby, a laminated film 31 having the polarizer 14 and the stretched base film 22 is obtained.

  In the stretching process, the laminated film 30 is uniaxially stretched. As the stretching method, either fixed end stretching or free end stretching can be employed. In addition, the stretching process may be performed in one stage or in multiple stages.

  In the stretching treatment, the laminated film can be stretched in water. Examples of the water used for underwater stretching include pure water, ion exchange water, distilled water, and tap water. In addition, when the stretching treatment is performed after the dyeing treatment described above, the dichroic dye adsorbed on the stretched film by the dyeing treatment is obtained by making the aqueous solution in which the dichroic dye is dissolved in the water used for the underwater stretching. Elution can be suppressed. Furthermore, it is good also as performing the above-mentioned bridge | crosslinking process simultaneously with extending | stretching process by making it the aqueous solution which melt | dissolved the boride compound in the water used by extending | stretching in water.

  The stretching treatment is performed, for example, by immersing the laminated film in a boric acid-containing aqueous solution at 50 ° C. or higher and stretching in the aqueous solution.

  By the polarizer forming step described above, the dichroic dye is adsorbed to the stretched film of the laminated film, and the dichroic dye is oriented in the film stretching direction (MD direction indicated by D6 in the drawing) in the stretching process. To do. Thereby, the stretched film which a laminated film has becomes the polarizer 14 which has an absorption axis in the extending direction of the film in a extending | stretching process.

  In addition, although it demonstrated as performing an extending | stretching process after a dyeing | staining process here, an extending | stretching process may be performed before a dyeing | staining process and a dyeing | staining process may be performed with respect to the extended laminated film. Further, a stretching process may be performed during the dyeing process.

  The stretching ratio in the stretching process can be, for example, more than 1 time, and is preferably 1.1 times or more. Although there is no restriction | limiting in particular in the upper limit of a draw ratio, Usually, it is 8 times or less, it is preferable to set it as 6 times or less, and it is more preferable to set it as 3 times or less.

  The total draw ratio of the polarizer that has undergone the stretching step and the polarizer forming step is preferably more than 5 times. According to the production method of the present invention, the draw ratio can be 6 times or more, and can be 7 times or more. Usually, the total draw ratio of the polarizer is 10 times or less.

(Other processing)
In addition, when using the plasticizer at the time of formation of the resin film 11 which is the raw material of the stretched film 12, the process which removes a plasticizer is performed prior to the dyeing | staining process and extending process mentioned above. The removal of the plasticizer is performed, for example, by immersing the laminated film 30 in water at room temperature to about 50 ° C., and causing the stretched film 12 to swell water, thereby eluting the plasticizer from the stretched film 12.

  In addition, after the cross-linking treatment or the underwater stretching treatment in the boric acid-containing aqueous solution, the laminated film is washed with water by immersing it in pure water, ion exchange water, distilled water, tap water, boric acid, etc. Wash away. Thereafter, the laminated film is dried. As the drying treatment, a known method such as natural drying, heat drying, air drying, or reduced pressure drying can be employed.

<Protective film bonding process>
In the protective film bonding step, a protective film is bonded to the surface of the polarizer obtained in the polarizer forming step. The method for bonding the polarizer and the protective film is not particularly limited. For example, a pressure-sensitive adhesive layer or an adhesive layer can be formed on either or both bonding surfaces of the polarizer and the protective film, and both can be bonded via the pressure-sensitive adhesive layer or the adhesive layer. As the adhesive and the pressure-sensitive adhesive, those similar to those used for bonding the base film and the resin film can be applied.

(Protective film)
The protective film may be a simple protective film having no optical function, or may be a protective film having both optical functions such as a retardation film and a brightness enhancement film.

  The material of the protective film is not particularly limited, but for example, a cyclic polyolefin resin film, a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, poly Examples of the film that have been widely used in the art include polyester-based resin films made of a resin such as butylene terephthalate, polycarbonate-based resin films, acrylic-based resin films, and polypropylene-based resin films.

  The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. An arbitrary retardation value can be imparted to the cyclic polyolefin-based resin film by stretching.

  Since the cyclic polyolefin resin film generally has poor surface activity, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment is performed on the surface to be bonded to the polarizer. preferable. Among these, plasma treatment and corona treatment that can be performed relatively easily are preferable.

  A liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film in order to improve viewing angle characteristics. Moreover, in order to provide a phase difference, what stretched the cellulose acetate type-resin film may be used. The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesiveness with the polarizing film. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  Optical layers such as a hard coat layer, an antiglare layer, and an antireflection layer can be formed on the surface of the protective film as described above. The method for forming these optical layers on the surface of the protective film is not particularly limited, and a known method can be used.

  The thickness of the protective film is preferably as thin as possible from the demand for thinning, is preferably 90 μm or less, and more preferably 50 μm or less. On the other hand, if it is too thin, the strength is lowered and the processability is poor, and therefore it is preferably 5 μm or more.

  In the manufacturing method of the polarizing film of this embodiment, after bonding a protective film to one surface of a polarizer, a base film is peeled from the other surface of a polarizer. The peeling method of a base film is not specifically limited, A normally known method is employable. The base film may be peeled off as it is after the protective film is pasted on the polarizer, or after the whole is wound into a roll after the protective film is pasted, it is peeled off by providing a separate peeling step. May be.

<Adhesive forming process>
Thus, the obtained laminated body may provide the layer of the adhesive for bonding to a glass cell.

  Examples of pressure-sensitive adhesives include base polymers such as acrylic resins, styrene resins, and silicone resins, cross-linking agents such as isocyanate compounds, epoxy compounds, and aziridine compounds, and silane coupling agents in consideration of adhesion between glass and the like. The composition which added these additives is mentioned. Furthermore, an ionic compound may be further contained as an antistatic agent for imparting antistatic properties to the pressure-sensitive adhesive layer. The ionic compound is a compound having an inorganic cation or an organic cation and an inorganic anion or an organic anion.

  The method for forming the pressure-sensitive adhesive layer on the laminate is not particularly limited. For example, the base film 21 or the stretched film 12 can be formed by applying a solution containing each component including the above-described base polymer and drying it. Alternatively, a pressure-sensitive adhesive previously formed on the separator can be bonded to the base film 21 or the stretched film 12. By using the separator, the surface of the pressure-sensitive adhesive can be protected until the polarizing plate is bonded to the liquid crystal cell.

<Polarizing film formation process>
The polarizing film shown in FIG. 1 is formed by appropriately dividing the laminate of the band-shaped polarizer and the band-shaped protective film thus obtained into a plurality of sheets. When cutting, the strip-shaped polarizer may be cut into sheets according to the size of the liquid crystal panel, and then the cut polarizer may be bonded to the liquid crystal panel.

  In the manufacturing method of the polarizing film of this embodiment, a polarizing film can be manufactured according to the above processes.

  In the manufacturing method of the polarizing film of this embodiment as described above, the following effects are obtained.

  First, in the manufacturing method of the polarizing film of this embodiment, prior to the bonding step, the resin film is stretched to obtain a stretched film, and the stretch ratio in the longitudinal direction of the stretched film is the length of the stretched film in the stretch step. It is supposed that the base film which is less than the draw ratio of a direction is bonded. In the following description, the laminated film having such a configuration used in the manufacturing method of the present embodiment is referred to as “laminated film A”.

  On the other hand, it was made of a stretched film material that the laminated film A has, and was obtained by laminating and laminating a non-stretched resin film and the same base film as the laminated film A has. The laminated body is drawn to the same draw ratio as that of the stretched film of the laminated film A, and the obtained laminated film is assumed. In the following description, the laminated film having such a configuration is referred to as “laminated film B”.

  That is, the laminated film A is formed by laminating a stretched film and a base film having a smaller draw ratio than the stretched film to form a laminated film, while the laminated film B is composed of a stretched film, a stretched film, A base film having the same draw ratio is laminated to form a laminated film.

  Generally, the stress (shear yield stress) required for stretching a film tends to increase as the strain increases, that is, as the draw ratio increases. Therefore, when the above two types of laminated films are assumed, the base film in the laminated film A can be stretched with a smaller stress than the base film in the laminated film B.

  On the other hand, the stretched film in laminated film A and the stretched film in laminated film B have the same draw ratio. Therefore, it can be considered that each stretched film has the same stress required for further stretching.

  Thus, the laminated film A can be stretched with a smaller stress than the laminated film B. Alternatively, when the laminated film is stretched with the same stress, the laminated film A can be stretched at a higher magnification than the laminated film B.

  In addition, the laminated film B is a laminated film in which a base film is bonded when the resin film is stretched. Therefore, hot roll stretching cannot be adopted for stretching the laminated film B, and the stretching method of the resin film is limited. On the other hand, in the laminated film A, prior to the bonding step, the resin film is stretched to form a stretched film. Therefore, it is easy to form a thin stretched film by stretching the resin film by a method advantageous for thinning the polarizer. Examples of “a method advantageous for thinning a polarizer” include hot roll stretching.

  Furthermore, in the manufacturing method of the polarizing film of this embodiment, since the stretched film is laminated with the base film during the stretching process in the polarizer forming step, compared with the case where the dyed stretched film is stretched alone, Hard to break. Therefore, the yield can be improved and the amount of waste can be reduced.

  By these, according to the manufacturing method of the polarizing film of this embodiment, the manufacturing method of the polarizing film which suppresses fracture | rupture of a polarizer suitably at the time of manufacture, and can be extended | stretched by high magnification easily can be provided.

  In addition, in this embodiment, although the base film 21 was bonded to the single side | surface of the stretched film 12 in the bonding process, it is also possible to bond the base film 21 on both surfaces of the stretched film 12 in the bonding process. Good. In that case, one base film is peeled off before the polarizer forming step.

  For example, in the bonding step, two types of substrate films having different thicknesses are used. First, a relatively thick substrate film is bonded to one surface of the stretched film 12, and then relative to the other surface of the stretched film. It is good also as sticking a thin base film on and then peeling off the thick base film initially pasted. In such a method, for example, even if both the base film and the stretched film are thin and handling at the time of pasting is difficult, first, the relatively thick base film and stretched film are pasted together. By making the laminate, the handling of the base film can be facilitated and the workability can be improved.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

  In this example, a test piece of a model sample was prepared by the method described later, and the stress required for stretching was measured and evaluated. In the production of the model sample, the resin film and the substrate film were bonded using the adhesive adjusted by the following method.

(Adhesive adjustment)
Polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Z-200, average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water to prepare a 3 mass% polyvinyl alcohol aqueous solution. .
In addition, a cross-linking agent (manufactured by Taoka Chemical Co., Ltd., Sumirez Resin (registered trademark) 650) was mixed with the obtained aqueous solution at a ratio of 1 part by mass with respect to 2 parts by mass of the polyvinyl alcohol powder to prepare an aqueous adhesive. .

  In the evaluation, physical property values were measured by the following methods.

(In-plane retardation measurement)
The in-plane retardation value (unit: nm) of the test piece was measured using KOBRA (registered trademark) -WPR manufactured by Oji Scientific Instruments. A value at a wavelength of 590 nm was adopted as the in-plane retardation value.

(Thickness measurement)
The thickness (unit: μm) of the test piece was measured with a contact-type thickness meter (manufactured by Nikon Corporation, DIGITAL READ OUT TC-101).

(Degree of orientation)
The degree of orientation of the test piece was calculated by in-plane retardation / thickness / 10.

[Example 1]
PVA raw film (trade name: VF-PE6000, manufactured by Kuraray Co., Ltd., thickness 60 μm, average polymerization degree 2400, saponification degree 99.9 mol% or more, containing plasticizer, orientation degree 0.01) is unwound from a roll. The film was continuously conveyed while being stretched in the width direction using a tenter stretching apparatus. Stretching conditions were a stretching temperature of 160 ° C., a horizontal uniaxial stretching ratio of 4.5 times, and a fixed end uniaxially stretched stretched PVA film roll was obtained. At this time, the orientation degree of the stretched PVA film was 2.76.

Next, the unstretched base film (polypropylene film, 90 μm, orientation degree 0.13) subjected to single-sided corona treatment is unwound from the roll, and the above-mentioned aqueous adhesive is applied to the corona-treated surface of the base film by gravure coating. did. The coating was performed so that the film thickness immediately after coating was 4 μm. The base film and the stretched PVA film were bonded together with a nip roll and dried at 60 ° C. for 4 minutes to obtain a single area layer film in which an unstretched base film was laminated on one surface of the stretched PVA film.
A rectangular test piece having an absorption axis direction of 150 mm and a transmission axis direction of 30 mm was produced from the obtained single-area layer film.

FIG. 6 is a schematic view showing how the obtained test piece is stretched.
First, the jig | tool 1100 for extending | stretching was attached to the both ends of the long side direction (MD direction) of the test piece 1000 so that it might become the distance between chuck | zippers 55mm, and the 30 degreeC dyeing bath which stored 0.11 mass% iodine aqueous solution was stored. For 60 seconds.
Next, the test piece 1000 pulled out from the dyeing bath is put in a crosslinking bath 1400 in which a crosslinking solution 1300 of potassium iodide: boric acid: water 5: 8: 100 (mass ratio) is stored, and a jig 1100 on one end side. And attached to a load cell 1500 provided in the crosslinking bath 1400. The crosslinking solution was maintained at 70 ° C.
Next, while immersing the test piece 1000 in the crosslinking solution 1300 for 90 seconds, the test piece 1000 is stretched 1.18 times by pulling the jig on the other end side, and the total draw ratio of PVA is 5.31 times in total ( 4.5 × 1.18 = 5.31 times).

The tension required for stretching in the crosslinking bath was 6830 g, and the stress per unit cross-sectional area was 2183 g / mm ² . As the “tension necessary for stretching”, a stress measured at 1.18 times using a load cell 1500 in the stretching process was employed.

[Example 2]
Unwind PVA film (trade name: VF-PE2000, manufactured by Kuraray Co., Ltd., thickness 20 μm, average polymerization degree 2400, saponification degree 99.9 mol% or more, with plasticizer, orientation degree 0.04) from the roll. The film was continuously conveyed while being stretched in the width direction using a tenter stretching apparatus. Stretching conditions were a stretching temperature of 160 ° C., a horizontal uniaxial stretching ratio of 4.5 times, and a fixed end uniaxially stretched stretched PVA film roll was obtained. At this time, the orientation degree of the stretched PVA film was 2.90.

The test piece of Example 2 was dyed and stretched in the same manner as in Example 1 except that the stretched PVA film thus obtained was used and the crosslinking solution was maintained at 73 ° C. The stress of was measured. The tension required for stretching in the crosslinking bath was 3058 g, and the stress per unit cross-sectional area was 1062 g / mm ² .

[Comparative Example 1]
The base film used in Example 1 was sequentially bonded to both sides of the PVA original film used in Example 1 in the same manner as in Example 1, and dried at 60 ° C. for 4 minutes, whereby the PVA original film A double-sided laminated film in which an unstretched base film was laminated on both surfaces was obtained.

  Next, the obtained laminated film was stretched in the width direction using a tenter stretching apparatus. Stretching conditions were a stretching temperature of 160 ° C., a stretching ratio of 4.5 times in a horizontal uniaxial direction, and a stretched double-sided laminated film that was uniaxially stretched at a fixed end was obtained.

  Next, the base film on one side of the obtained stretched double-sided laminated film was peeled off to obtain a single area layer film. At this time, the total thickness was 34.8 μm.

The test piece of Comparative Example 1 was dyed and stretched in the same manner as in Example 1 except that the single-area layer film thus obtained was used, and the stress during stretching was measured. The tension required for stretching in the crosslinking bath was 6556 g, and the stress per unit cross-sectional area was 6280 g / mm ² .

[Comparative Example 2]
The base film used in Example 1 was sequentially bonded to both sides of the PVA original film used in Example 2 in the same manner as in Example 1, and both surfaces of the original film were processed in the same manner as in Comparative Example 1. A double-sided laminated film was obtained in which an unstretched base film was laminated.

  Next, the obtained laminated film was stretched in the width direction using a tenter stretching apparatus in the same manner as in Comparative Example 1 to obtain a stretched double-sided laminated film stretched uniaxially at a fixed end.

  Next, the base film on one side of the obtained stretched double-sided laminated film was peeled off to obtain a single area layer film. At this time, the total thickness was 33.4 μm.

The test piece of Comparative Example 2 was dyed and stretched in the same manner as in Example 2 except that the single-area layer film thus obtained was used, and the stress during stretching was measured. The tension required for stretching in the crosslinking bath was 4413 g, and the stress per unit cross-sectional area was 4404 g / mm ² .

  The results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

  As a result of the evaluation, although the thickness of the base film before stretching in the polarizer forming step is thicker in Example 1, and the total thickness is thicker in Example 1, the tension necessary for stretching is Comparative Example 1. It was equivalent. The stress per unit cross-sectional area was lower in Example 1 than in Comparative Example 1.

  Thus, it was found that Example 1 requires less stress for stretching and can be easily stretched, and it was confirmed that the present invention is useful.

  DESCRIPTION OF SYMBOLS 1,14 ... Polarizer, 30, 31 ... Laminated film, 10 ... Polarizing film, 11 ... Resin film, 12, 12A, 12B, 13 ... Stretched film, 21,22 ... Base film

FIG. 6 is a schematic view showing how the obtained test piece is stretched.
First, a stretching jig 1100 is attached to both ends of the long side direction ( TD direction) of the test piece 1000 so that the distance between chucks is 55 mm, and a 30 ° C. dyeing bath storing a 0.11 mass% iodine aqueous solution is stored. For 60 seconds.
Next, the test piece 1000 pulled out from the dyeing bath is put in a crosslinking bath 1400 in which a crosslinking solution 1300 of potassium iodide: boric acid: water 5: 8: 100 (mass ratio) is stored, and a jig 1100 on one end side. And attached to a load cell 1500 provided in the crosslinking bath 1400.
The crosslinking solution was maintained at 70 ° C.
Next, while immersing the test piece 1000 in the crosslinking solution 1300 for 90 seconds, the test piece 1000 is stretched 1.18 times by pulling the jig on the other end side, and the total draw ratio of PVA is 5.31 times in total ( 4.5 × 1.18 = 5.31 times).

Claims (7)

Stretching a strip-shaped resin film having a polyvinyl alcohol-based resin as a forming material to obtain a stretched film;
A laminating step of laminating a belt-like base film on at least one surface of the stretched film, and obtaining a laminated film in which the stretched film and the base film are laminated,
Dyeing the stretched film with a dichroic dye, stretching in the longitudinal direction of the entire laminated film, and a polarizer forming step using the stretched film as a polarizer,
The said base film in the said bonding process is a manufacturing method of the polarizing film whose draw ratio of a longitudinal direction is less than the draw ratio of the longitudinal direction of the said stretched film in the said extending process.   The method for producing a polarizing film according to claim 1, wherein in the bonding step, the base film is unstretched in the longitudinal direction.   The manufacturing method of the polarizing film of Claim 1 or 2 which the said polarizer formation process immerses the said laminated | multilayer film dye | stained the said stretched film in the aqueous solution containing a boric acid, and extends | stretches in the said aqueous solution.   The method for producing a polarizing film according to any one of claims 1 to 3, wherein in the stretching step, the resin film is stretched using a fixed end stretching method.   The method for producing a polarizing film according to claim 1, wherein the resin film has a thickness of 15 μm to 75 μm.   In the said bonding process, the manufacturing method of the polarizing film of any one of Claim 1 to 5 which bonds the said stretched film and the said base film through an aqueous adhesive.   The manufacturing method of the polarizing film of any one of Claim 1 to 6 which has a polarizing film formation process which cuts the said polarizer into plurality and obtains the said polarizing film after the said polarizer formation process.

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