CN113655556A - Polarizing film and method for producing polarizing laminate film - Google Patents
Polarizing film and method for producing polarizing laminate film Download PDFInfo
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- CN113655556A CN113655556A CN202110971393.0A CN202110971393A CN113655556A CN 113655556 A CN113655556 A CN 113655556A CN 202110971393 A CN202110971393 A CN 202110971393A CN 113655556 A CN113655556 A CN 113655556A
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- film
- polarizing
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- crosslinking
- stretching
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- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 125000001424 substituent group Chemical group 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- KKEYFWRCBNTPAC-UHFFFAOYSA-L terephthalate(2-) Chemical compound [O-]C(=O)C1=CC=C(C([O-])=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-L 0.000 description 1
- QPBYLOWPSRZOFX-UHFFFAOYSA-J tin(iv) iodide Chemical compound I[Sn](I)(I)I QPBYLOWPSRZOFX-UHFFFAOYSA-J 0.000 description 1
- NLLZTRMHNHVXJJ-UHFFFAOYSA-J titanium tetraiodide Chemical compound I[Ti](I)(I)I NLLZTRMHNHVXJJ-UHFFFAOYSA-J 0.000 description 1
- LDHQCZJRKDOVOX-UHFFFAOYSA-N trans-crotonic acid Natural products CC=CC(O)=O LDHQCZJRKDOVOX-UHFFFAOYSA-N 0.000 description 1
- 229920006352 transparent thermoplastic Polymers 0.000 description 1
- 239000006097 ultraviolet radiation absorber Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
- G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
- G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
- G02B5/305—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks including organic materials, e.g. polymeric layers
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
- G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/0012—Mechanical treatment, e.g. roughening, deforming, stretching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/14—Printing or colouring
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
- G02B1/14—Protective coatings, e.g. hard coatings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B38/0012—Mechanical treatment, e.g. roughening, deforming, stretching
- B32B2038/0028—Stretching, elongating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B38/00—Ancillary operations in connection with laminating processes
- B32B2038/0052—Other operations not otherwise provided for
- B32B2038/0076—Curing, vulcanising, cross-linking
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Polarising Elements (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
Abstract
The invention provides a polarizing film having high optical characteristics and suppressed shrinkage and a method for producing a polarizing laminate film. The polarizing film is a polarizing film in which iodine is oriented in the polyvinyl alcohol resin layer. The polarizing film has a boron content of 2.5 to 4.1 wt%, a visual sensitivity correction monomer transmittance (Ty) of more than 40.5%, and a ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm of less than 0.022.
Description
The present application is a divisional application having an application date of 2017, 11/30/2017, an application number of 201711247709.1, and an invention name of "method for producing a polarizing film and a polarizing laminate film".
Technical Field
The present invention relates to a polarizing film and a method for producing a polarizing laminate film.
Background
Polarizing plates are widely used in display devices such as liquid crystal display devices. The polarizing plate is generally configured by laminating a protective film on one or both surfaces of a polarizer layer containing a polyvinyl alcohol resin. With the development of mobile devices such as image display devices and thin televisions, there is an increasing demand for thinner polarizing plates.
As a method for manufacturing a polarizing plate having a polarizer layer of a thin film, the following methods are known: a polarizing laminate film in which a polarizer layer is formed on a base film is produced by stretching a laminate film in which a polyvinyl alcohol resin layer is formed by applying a coating liquid containing a polyvinyl alcohol resin to the base film, and then performing a dyeing treatment in which a dichroic dye is adsorbed to the polyvinyl alcohol resin layer (for example, patent document 1).
According to the above method, since the polyvinyl alcohol resin layer is formed by coating, the polyvinyl alcohol resin layer can be more easily formed into a film than a single layer (monomer) film containing a polyvinyl alcohol resin, and thus the polarizer layer can be more easily formed into a film.
Patent document 1 describes that stretching is performed at a high magnification to obtain excellent optical characteristics.
On the other hand, patent document 2 describes a polarizing plate in which the degree of boric acid crosslinking is increased in order to suppress the occurrence of blue leakage (blue leak), instead of being produced by a method in which a coating liquid containing a polyvinyl alcohol resin is applied to a base film as described above.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 5667016
Patent document 2: japanese patent No. 5985813
Disclosure of Invention
Problems to be solved by the invention
In order to increase the degree of polarization of the polarizer layer or the polarizing plate, it is considered to increase the draw ratio and the degree of boric acid crosslinking as described above, and to increase the shrinkage ratio. However, in these methods, the shrinkage force tends to increase when the polarizer layer or the polarizer is heated, and the polarizer layer or the polarizer is likely to be broken.
The present invention aims to provide a polarizing film having high optical properties and a small shrinkage force, and a method for producing a polarizing laminate film.
Means for solving the problems
The present invention provides a polarizing film, a polarizing plate, and methods for producing a polarizing laminated film and a polarizing plate described below.
[ 1] A polarizing film in which iodine is oriented in a polyvinyl alcohol resin layer,
a boron content of 2.5 to 4.1 wt%,
the visual sensitivity correction (Japanese: visual sensitivity correction) monomer transmittance (Ty) exceeds 40.5%,
the ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm was less than 0.022.
[ 2 ] A polarizing film according to [ 1], which has a width in the absorption axis direction of 2mm and a shrinkage force corresponding to a thickness of 5 μm of less than 1.77N/5 μm when kept at 80 ℃ for 4 hours.
[ 3 ] the polarizing film according to [ 1] or [ 2 ], which has a thickness of 10 μm or less.
[ 4 ] A polarizing plate comprising a protective film on at least one surface of the polarizing film according to any one of [ 1] to [ 3 ].
[ 5 ] A method for producing a polarizing laminate film, which comprises the following steps in this order:
a resin layer forming step of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film;
a stretching step of stretching the laminated film to obtain a stretched film;
a dyeing step of dyeing the polyvinyl alcohol resin layer of the stretched film with iodine to form a dyed layer, thereby obtaining a dyed laminate film;
a crosslinking step of crosslinking the dyed layer of the dyed laminated film with a crosslinking liquid containing boric acid to form a crosslinked layer, thereby obtaining a crosslinked laminated film; and
a deboronation step of forming a polarizer layer by reducing the boron content in the crosslinked layer of the crosslinked laminated film to obtain a polarizing laminated film,
the deboronation step includes a deboronation solution contact step of contacting the crosslinked layer with a deboronation solution having a boric acid concentration lower than a boric acid concentration of the crosslinked solution,
in the above-mentioned dehydration liquid contact step, the magnitude of the tension applied to the crosslinked laminated film is controlled so as to be smaller than the magnitude of the tension applied to the laminated film with a dyed layer in the above-mentioned crosslinking step.
[ 6 ] A method for manufacturing a polarizing plate, comprising:
a step of producing a polarizing laminate film by the production method described in [ 5 ];
a step of bonding a protective film to a surface of the polarizer layer opposite to the base film; and
and peeling off and removing the base material film.
Effects of the invention
According to the present invention, a polarizing film and a polarizing plate having high optical characteristics and suppressed shrinkage force can be provided. Further, according to the present invention, a method for producing a polarizing laminated film having a polarizer layer excellent in optical characteristics and small in shrinkage force and a method for producing a polarizing plate can be provided.
Drawings
Fig. 1 is a flowchart showing a method for producing a polarizing laminated film and a method for producing a polarizing plate according to the present invention.
Fig. 2 is a schematic cross-sectional view showing an example of the layer structure of the laminated film obtained in the resin layer forming step.
Fig. 3 is a schematic cross-sectional view showing an example of the layer structure of the stretched film obtained in the stretching step.
Fig. 4 is a schematic cross-sectional view showing an example of the layer structure of the polarizing laminated film obtained in the deboronation step.
Fig. 5 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate with a protective film obtained in the first protective film bonding step 1.
Fig. 6 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate with a single-sided protective film obtained in the peeling step.
Fig. 7 is a schematic cross-sectional view showing an example of the layer structure of the polarizing plate with a double-sided protective film obtained in the 2 nd protective film bonding step.
Detailed Description
< polarizing film >
The polarizing film is a polarizing film in which iodine is oriented in the polyvinyl alcohol resin layer, and can be obtained, for example, as a polarizer layer of a polarizing laminate film described later. The polarizing film has a boron content of 2.5 to 4.1 wt%, a visual sensitivity correction monomer transmittance (Ty) of more than 40.5%, and a ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm of less than 0.022. The polarizing film is a stretched film obtained by stretching a polyvinyl alcohol resin layer, and the stretching is preferably uniaxial stretching.
The boron in the polarizing film is boron derived from boric acid in a crosslinking liquid used for crosslinking a polyvinyl alcohol resin layer described later. When the boron content of the polarizing film is large, that is, the degree of crosslinking of the polyvinyl alcohol resin layer is high, the optical properties such as the degree of polarization can be improved, but the shrinkage force when heating the polarizing film tends to be large.
On the other hand, if the boron content of the polarizing film is small, that is, the degree of crosslinking is low, the shrinkage force of the polarizing film during heating can be reduced, but it tends to be difficult to obtain sufficient water resistance and excellent optical properties.
The boron content of the polarizing film may be 2.5 wt% or more and 4.1 wt% or less. This can suppress the shrinkage force generated when the polarizing film is heated. The boron content of the polarizing film is preferably 2.6 wt% or more and 4.0 wt% or less, and more preferably 2.7 wt% or more and 3.5 wt% or less. The boron content of the polarizing film was measured as described in examples below.
When the polarizing film is held at 80 ℃ for 4 hours, the width in the absorption axis direction (stretching direction) of the polarizing film is preferably 2mm, and the shrinkage force corresponding to the thickness of the polarizing film of 5 μm is less than 1.77N/5 μm, more preferably 1.70N/5 μm or less, further preferably 1.60N/5 μm or less, and may be 1.40N/5 μm or less. The lower limit of the contractile force is not particularly limited, but is preferably 0N/5 μm, usually 0.1N/5 μm or more, and may be 0.2N/5 μm or more. On the other hand, the polarizing film is preferably not expanded, and therefore, is preferably-0.01N/5 μm or more. The shrinkage force of the polarizing film is a value obtained by measuring the shrinkage force of the polarizing film (actually measured shrinkage force) and the thickness of the polarizing film according to the description of examples described later, and is calculated by converting the values into values corresponding to a thickness of 5 μm according to the following equation.
Shrinkage force [ N/5 μm ] (measured shrinkage force of polarizing film [ N ])/(thickness of polarizing film (measured value) [ μm ]) × 5
As described above, when the boron content of the polarizing film is increased by increasing the degree of crosslinking of the polyvinyl alcohol resin layer, the optical properties such as the degree of polarization can be improved, but the shrinkage force of the polarizing film becomes large. On the other hand, when the boron content in the polarizing film is decreased by decreasing the degree of crosslinking of the polyvinyl alcohol resin layer, it is difficult to obtain excellent optical characteristics.
Therefore, the polarizing film has a ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm of less than 0.022. Thus, the boron content is reduced to such an extent that the shrinkage force of the polarizing film can be suppressed, and when the visual sensitivity correction cell transmittance (Ty) exceeds 40.5% and the visual sensitivity correction cell transmittance (Ty) is 41.5%, excellent optical characteristics in which the visual sensitivity correction polarization degree (Py) exceeds 99.994 can be realized. The lower limit of the visual sensitivity correction monomer transmittance (Ty) is preferably 41.0% or more, more preferably 41.5% or more, and the upper limit is 50% or less, preferably 47% or less. The lower limit of the visual sensitivity correction polarization degree (Py) when the visual sensitivity correction single transmittance (Ty) is 41.5% is preferably 99.995 or more, and more preferably 99.996 or more.
The reason why the optical properties of the polarizing film can be improved by defining the ratio of the parallel absorbance/orthogonal absorbance at a wavelength of 475nm of the polarizing film will be described below. In the polyvinyl alcohol resin layer dyed with iodine, iodine is adsorbed and oriented in the polyvinyl alcohol resin layer. The adsorption-oriented iodine formation I3 -、I5 -And polyiodide complexes. Among these complexes, a polyiodide complex (I) having an absorption band at 475nm3 -Complex), orientation is easily disordered compared with other polyiodide complexes, and thus orientation is easily disorderedThis causes the polarization degree of the polarizing film to decrease.
In addition, there are a complex having relatively high orientation and a complex having relatively low orientation in a polyiodide complex having an absorption band at a wavelength of 475 nm. In order to increase the degree of polarization of the polarizing film, it is preferable to increase the content of a complex having relatively high orientation among polyiodide complexes having an absorption band at a wavelength of 475nm in the polyvinyl alcohol-based resin layer.
Among the polyiodide complexes having an absorption band at a wavelength of 475nm, the content of the complex having relatively high alignment properties can be evaluated by a ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475 nm. Here, the parallel absorbance at a wavelength of 475nm is a value obtained by converting the transmittance of polarized light emitted from the glan thompson prism when the direction thereof is parallel to the transmission axis of the sample (polarizing film) into absorbance. The orthogonal absorbance at 475nm is a value obtained by converting the transmittance, when the direction of polarized light emitted from the glan thompson prism is orthogonal to the transmission axis of the sample (polarizing film), into absorbance.
The smaller the ratio of the parallel absorbance/orthogonal absorbance at a wavelength of 475nm, the smaller the parallel absorbance, and the larger the orthogonal absorbance. This means that: as the above ratio is smaller, the content of a complex having relatively high orientation, which is oriented in a direction perpendicular to the transmission axis of the polarizing film (absorption axis direction of the polarizing film), among the complex of polyiodide having an absorption band at a wavelength of 475nm becomes larger. Therefore, by reducing the above ratio, the degree of polarization of the polarizing film can be improved.
By setting the ratio of the parallel absorbance/orthogonal absorbance at a wavelength of 475nm of the polarizing film to less than 0.022, the amount of the complex having low orientation is reduced, and the degree of polarization of the polarizing film can be improved. The upper limit of the above ratio is more preferably less than 0.0218, still more preferably less than 0.0217, and the lower limit is preferably 0.010 or more, still more preferably 0.015 or more.
The thickness of the polarizing film is preferably 10 μm or less, and more preferably 7 μm or less. The thickness of the polarizing film is 10 μm or less, whereby the polarizing plate described later can be made thin. The lower limit of the thickness of the polarizing film is preferably 1 μm or more, and more preferably 2 μm or more. Such a polarizing film is a polarizing film which can be made thin, has improved optical properties, and has a reduced shrinkage force.
As the polyvinyl alcohol resin and the polyvinyl alcohol resin layer constituting the polyvinyl alcohol resin layer of the polarizing film, a polyvinyl alcohol resin and a polyvinyl alcohol resin layer described later can be used. The polarizing film can be produced, for example, by a method for producing a polarizing laminate film described later.
< polarizing plate >
The polarizing film may be provided with a protective film on at least one surface thereof to form a polarizing plate. The polarizing plate may be a polarizing plate with a single-sided protective film in which a protective film is provided on one side of the polarizing film, or a polarizing plate with a double-sided protective film in which protective films are provided on both sides of the polarizing film. The 2 protective films of the polarizing plate with a double-sided protective film may be the same type of protective film or different types of protective films.
The material constituting the protective film may be the material described later, and may be produced, for example, by the method for producing the polarizing plate described later.
(use of polarizing plate)
The polarizing plate with a single-sided protective film or the polarizing plate with a double-sided protective film may be used as a composite polarizing plate by bonding peripheral members to each other, or as such a composite polarizing plate. As the peripheral members, there can be mentioned: a protective film for preventing damage, which is attached to the protective film; an adhesive layer laminated on a protective film (for example, in the case of a polarizing plate with a double-sided protective film) or a polarizer layer (for example, in the case of a polarizing plate with a single-sided protective film) for bonding the polarizing plate to a display unit or other optical member; a separator laminated on an outer surface of the adhesive layer; an optical compensation film such as a retardation film or other optical functional film laminated on a protective film (for example, in the case of a polarizing plate with a double-sided protective film) or a polarizer layer (for example, in the case of a polarizing plate with a single-sided protective film).
The pressure-sensitive adhesive layer as an example of the peripheral member may be laminated on the outer surface of any one of the protective films in the case of a polarizing plate with a double-sided protective film, or may be laminated on the release surface in the case of a polarizing plate with a single-sided protective film. The adhesive forming the adhesive layer comprises the following adhesive composition: in general, a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added to a base polymer such as a (meth) acrylic resin, a styrene resin, or a silicone resin. Further, a pressure-sensitive adhesive layer containing fine particles and exhibiting light scattering properties can be formed. The thickness of the adhesive layer is usually 1 to 40 μm, preferably 3 to 25 μm.
As another example of the peripheral member, an optical functional film includes: a reflective polarizing film that transmits a certain polarized light and reflects a polarized light showing a property opposite thereto; a film having an antiglare function and having a concavo-convex shape on the surface; a film having a surface antireflection function; a reflective film having a reflective function on a surface thereof; a semi-transmissive reflective film having both a reflective function and a transmissive function; viewing angle compensation films, and the like.
< method for producing polarizing laminate film >
Referring to fig. 1, a polarizing laminate film, which is an intermediate for producing a polarizing plate, is produced by a method including the following steps in this order:
a resin layer forming step S10 of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film;
a stretching step S20 of stretching the laminated film to obtain a stretched film;
a dyeing step S30 of dyeing the polyvinyl alcohol resin layer of the stretched film with iodine to form a dyed layer, thereby obtaining a dyed laminate film;
a crosslinking step S40 of crosslinking the dyed layer of the dyed laminated film with a crosslinking liquid containing boric acid to form a crosslinked layer, thereby obtaining a crosslinked laminated film;
and a deboronation step S50 of forming a polarizer layer by reducing the boron content in the crosslinked layer of the crosslinked laminated film, thereby obtaining a polarizing laminated film.
The polarizing laminate film of the present invention is characterized in that: a laminated film comprising a base film and a polarizer layer laminated on at least one surface of the base film, wherein a protective film is not laminated. The polarizing laminate film obtained by laminating the 1 st protective film on the polarizer layer in the 1 st protective film laminating step S60 described later is also referred to as a "polarizing laminate film with a protective film" for distinction from a polarizing laminate film.
(1) Resin layer forming step S10
Referring to fig. 2, this step is a step of forming a polyvinyl alcohol resin layer 6 on at least one surface of a base film 30 to obtain a laminated film 100. The polyvinyl alcohol resin layer 6 is a layer that becomes the polarizer layer 5 after passing through the stretching step S20, the dyeing step S30, the crosslinking step S40, and the deboronating step S50. The polyvinyl alcohol resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol resin to one surface or both surfaces of the base film 30 and drying the coating layer. The method of forming a polyvinyl alcohol resin layer by such coating is advantageous in that the polarizer layer 5 of a film can be easily obtained. Typically, the resin layer forming step S10 may be performed continuously while continuously feeding the base material film 30 continuously from a film roll, which is a long wound product of the base material film 30. The film conveyance may be performed using a guide roller or the like.
(substrate film)
The base film 30 may be made of a thermoplastic resin, and among them, it is preferably made of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such thermoplastic resins include, for example: polyolefin-based resins such as chain polyolefin-based resins and cyclic polyolefin-based resins (norbornene-based resins and the like); a polyester resin; (meth) acrylic resins; cellulose ester resins such as cellulose triacetate and cellulose diacetate; a polycarbonate-based resin; a polyvinyl alcohol resin; polyvinyl acetate resin; a polyarylate-based resin; a polystyrene-based resin; a polyether sulfone-based resin; a polysulfone-based resin; a polyamide resin; a polyimide-based resin; and mixtures, copolymers, and the like thereof.
The base film 30 may be a single layer composed of 1 resin layer containing 1 or 2 or more kinds of thermoplastic resins, or may be a multilayer structure in which a plurality of resin layers containing 1 or 2 or more kinds of thermoplastic resins are laminated. The base film 30 is preferably composed of: when the laminate film 100 is stretched in the stretching step S20 described later, such a resin may be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol resin layer 6.
Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers containing 2 or more kinds of chain olefins. The substrate film 30 containing a chain polyolefin resin is preferable from the viewpoint of ease of stable stretching at a high magnification. Among them, the substrate film 30 more preferably contains: polypropylene resins (polypropylene resins that are homopolymers of propylene, copolymers mainly of propylene), polyethylene resins (polyethylene resins that are homopolymers of ethylene, copolymers mainly of ethylene), and the like.
One example of a thermoplastic resin suitably used as the base film 30 is a copolymer mainly composed of propylene and a copolymer of propylene and another monomer copolymerizable therewith.
Examples of other monomers copolymerizable with propylene include: ethylene, alpha-olefins. The alpha-olefin is preferably an alpha-olefin having 4 or more carbon atoms, more preferably an alpha-olefin having 4 to 10 carbon atoms. Specific examples of the C4-10 alpha-olefin include: linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; vinylcyclohexane, and the like. The copolymer of propylene with other monomers copolymerizable therewith may be a random copolymer or a block copolymer.
The content of the other monomer is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight, in the copolymer. The content of other monomers in the copolymer can be determined by Infrared (IR) spectroscopic measurement according to the method described on page 616 of the handbook of polymer analysis (1995, published by the book store in hei house).
Among the above, as the polypropylene-based resin, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random copolymer is preferably used.
The stereoregularity of the polypropylene resin is preferably substantially isotactic or syndiotactic. The base film 30 containing a polypropylene resin having substantially isotactic or syndiotactic stereoregularity is excellent in handling properties and mechanical strength in a high-temperature environment.
The cyclic polyolefin resin is a general term for resins polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include: resins described in, for example, Japanese patent laid-open Nos. H1-240517, 3-14882 and 3-122137. Specific examples of the cyclic polyolefin resin include: ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (typically random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides of these. Among them, preferably used are: norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins.
The polyester resin is a resin having an ester bond, and generally a resin containing a polycondensate of a polycarboxylic acid or a derivative thereof and a polyol. As the polycarboxylic acid or a derivative thereof, a dicarboxylic acid having a valence of 2 or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a diol having a valence of 2 can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol.
As a typical example of the polyester resin, polyethylene terephthalate, which is a condensation product of terephthalic acid and ethylene glycol, can be cited. Although polyethylene terephthalate is a crystalline resin, polyethylene terephthalate in a state before crystallization treatment is easily subjected to treatment such as stretching. If necessary, the crystallization treatment may be performed by heat treatment during or after stretching. Further, a copolyester in which another kind of monomer is copolymerized with the polyethylene terephthalate skeleton to reduce crystallinity (or to make it amorphous) is also suitably used. Examples of such resins include: a resin obtained by copolymerizing cyclohexanedimethanol and isophthalic acid. These resins are also excellent in stretchability and thus can be suitably used.
Specific examples of the polyester-based resin other than polyethylene terephthalate and its copolymer include: polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polypropylene naphthalate, polycyclohexanedimethylene terephthalate, polycyclohexanedimethylene naphthalate.
The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example: poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymers; methyl methacrylate-acrylate- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymers (MS resins and the like); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylic acid norbornyl ester copolymer, etc.). Preference is given to using poly (meth) acrylic acid C such as polymethyl (meth) acrylate1-6The polymer containing an alkyl ester as a main component is preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).
The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include: cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate. Further, copolymers thereof, and modified hydroxyl groups partially with other substituents and the like are also included. Among them, cellulose triacetate (triacetyl cellulose) is particularly preferable. Cellulose triacetate is available in a large number of products, and is advantageous from the viewpoints of availability and cost.
Polycarbonate resins are engineering plastics containing a polymer in which monomer units are bonded via carbonate groups, and are resins having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin constituting the base film 30 may be: a resin called a modified polycarbonate in which a polymer skeleton is modified in order to reduce a photoelastic coefficient, or a copolymerized polycarbonate in which wavelength dependence is improved.
Among the above, polypropylene-based resins are preferably used from the viewpoint of stretchability, heat resistance, and the like.
The base film 30 may contain any suitable additive in addition to the thermoplastic resin. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like. The content of the thermoplastic resin in the base film 30 is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight.
The thickness of the base film 30 is usually 1 to 500. mu.m, preferably 1 to 300. mu.m, more preferably 5 to 200. mu.m, and still more preferably 5 to 150. mu.m, from the viewpoint of strength, handling properties, and the like.
(formation of polyvinyl alcohol resin layer)
The coating liquid applied to the base film 30 is preferably a polyvinyl alcohol resin solution obtained by dissolving a powder of a polyvinyl alcohol resin in a good solvent (e.g., water). As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl acetate resin can be used. The polyvinyl acetate-based resin may be, for example, a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate.
Examples of other monomers copolymerizable with vinyl acetate include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.
The saponification degree of the polyvinyl alcohol resin may be in the range of 80.0 to 100.0 mol%, but is preferably in the range of 90.0 to 99.5 mol%, and more preferably in the range of 94.0 to 99.0 mol%. If the saponification degree is less than 80.0 mol%, the water resistance and the moist heat resistance of the polarizing plate may be lowered. When a polyvinyl alcohol resin having a saponification degree of more than 99.5 mol% is used, the dyeing rate of iodine as a dichroic dye is lowered, the productivity is lowered, and a polarizing plate having sufficient polarizing performance may not be obtained.
The degree of saponification is: the acetoxy group (acetoxy group: -OCOCH) contained in a polyvinyl acetate resin as a raw material of a polyvinyl alcohol resin3) The change in proportion of hydroxyl groups in the saponification step is a parameter expressed as a unit ratio (mol%), and is defined by the following formula.
Degree of saponification (mol%): 100 × (hydroxyl number) ÷ (hydroxyl number + acetic acid number)
The degree of saponification can be determined in accordance with JIS K6726-. The higher the degree of saponification, the higher the proportion of hydroxyl groups, and therefore the lower the proportion of acetate groups inhibiting crystallization.
The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified. Examples thereof include: the polyvinyl alcohol resin is modified with an olefin such as ethylene or propylene, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid, an alkyl ester of an unsaturated carboxylic acid, acrylamide or the like. The proportion of modification is preferably less than 30 mol%, more preferably less than 10 mol%. When the modification is performed at more than 30 mol%, it is difficult to adsorb iodine as a dichroic dye, and it tends to be difficult to obtain a polarizing plate having sufficient polarizing performance.
The polyvinyl alcohol resin preferably has an average polymerization degree of 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can be determined in accordance with JIS K6726-. When the average polymerization degree is less than 100, it is difficult to obtain a preferable polarizing performance, and when the average polymerization degree exceeds 10000, the solubility in a solvent is deteriorated, and it is difficult to form a polyvinyl alcohol resin layer in a method for producing a polarizing laminated film described later.
The coating liquid may contain additives such as a plasticizer and a surfactant as necessary. As the plasticizer, polyhydric alcohols, condensates thereof, and the like can be used, and examples thereof include: glycerin, diglycerin, triglycerol, ethylene glycol, propylene glycol, polyethylene glycol, and the like. The amount of the additive is preferably 20% by weight or less based on the polyvinyl alcohol resin.
The method of applying the coating liquid to the base film 30 may be appropriately selected from: wire bar coating method; roll coating methods such as reverse coating method, gravure coating; die coating; comma coating method; die lip coating; spin coating; screen coating; a spray coating method; an impregnation method; spraying, and the like.
The drying temperature and drying time of the coating layer (polyvinyl alcohol resin layer before drying) are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ℃ and preferably 60 to 150 ℃. In the case where the solvent contains water, the drying temperature is preferably 80 ℃ or higher.
The polyvinyl alcohol resin layer 6 may be formed only on one side of the base film 30, or may be formed on both sides. If the polarizing film is formed on both sides, the film can be prevented from being bent, which may occur when the polarizing laminated film is manufactured, and 2 polarizing plates can be obtained from 1 polarizing laminated film, which is also advantageous in terms of the production efficiency of the polarizing plate.
The thickness of the polyvinyl alcohol resin layer 6 in the laminated film 100 is preferably 3 to 30 μm, and more preferably 5 to 20 μm. In the case of the polyvinyl alcohol resin layer 6 having a thickness within this range, the polarizer layer 5 having a good dyeing property of iodine as a dichroic dye, an excellent polarizing property, and a sufficiently thin thickness (for example, a thickness of 10 μm or less) can be obtained through the stretching step S20 and the dyeing step S30 described later.
Before the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol resin layer 6, corona treatment, plasma treatment, flame (flame) treatment, or the like may be performed on at least the surface of the base film 30 on the side where the polyvinyl alcohol resin layer 6 is to be formed. For the same reason, the polyvinyl alcohol resin layer 6 may be formed on the base film 30 via an undercoat layer or the like.
The undercoat layer can be formed by applying a coating liquid for forming an undercoat layer to the surface of the base film 30 and then drying the applied liquid. The coating liquid contains a component that exerts a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol resin layer 6, and generally contains a resin component and a solvent that impart such adhesion. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability, and the like is preferably used, and examples thereof include a (meth) acrylic resin, a polyvinyl alcohol resin, and the like. Among them, a polyvinyl alcohol resin which imparts good adhesion is preferably used. More preferably a polyvinyl alcohol resin. As the solvent, a general organic solvent or aqueous solvent capable of dissolving the resin component is generally used, but it is preferable to form the undercoat layer from a coating liquid using water as a solvent.
In order to increase the strength of the undercoat layer, a crosslinking agent may be added to the coating liquid for forming the undercoat layer. Specific examples of the crosslinking agent include: epoxy-based, isocyanate-based, dialdehyde-based, metal-based (e.g., metal salt, metal oxide, metal hydroxide, organometallic compound), and polymer-based crosslinking agents. When a polyvinyl alcohol resin is used as the resin component for forming the undercoat layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, and the like are suitably used.
The thickness of the primer layer is preferably about 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm. When the thickness is less than 0.05 μm, the effect of improving the adhesion force between the base film 30 and the polyvinyl alcohol resin layer 6 may be small.
The method of applying the coating liquid for forming the undercoat layer to the base film 30 may be the same as the method of applying the coating liquid for forming the polyvinyl alcohol resin layer. The drying temperature of the coating layer comprising the coating liquid for forming the undercoat layer is, for example, 50 to 200 ℃, preferably 60 to 150 ℃. In the case where the solvent contains water, the drying temperature is preferably 80 ℃ or higher.
(2) Stretching step S20
Referring to fig. 3, this step is a step of stretching the laminated film 100 to obtain a stretched film 200 including a stretched base film 30 'and a polyvinyl alcohol resin layer 6'. The stretching is usually uniaxial. Typically, the stretching step S20 may be performed while the long laminated film 100 is being conveyed, or the stretching step S20 may be performed while the laminated film 100 is being conveyed while the laminated film 100 is continuously unwound from a film roll that is a wound product of the long laminated film 100. The film conveyance may be performed using a guide roller or the like.
The stretch ratio of the laminated film 100 may be appropriately selected depending on the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, and more preferably more than 5 times and 8 times or less, with respect to the original length of the laminated film 100. When the stretching ratio is 5 times or less, the polyvinyl alcohol resin layer 6' is not sufficiently oriented, and thus the polarization degree of the polarizer layer 5 may not be sufficiently increased. On the other hand, if the stretch ratio exceeds 17 times, the film is likely to break during stretching, and the thickness of the stretched film 200 becomes thinner than necessary, which may reduce the processability and workability in the subsequent steps. The stretching treatment is not limited to the one-stage stretching, and may be performed in a plurality of stages.
The stretching treatment may be longitudinal stretching in which the film is stretched in the longitudinal direction (film conveying direction), or may be transverse stretching or oblique stretching in which the film is stretched in the width direction. Examples of the longitudinal stretching method include inter-roll stretching in which stretching is performed using rolls, compression stretching, stretching using clips (clips), and the like, and examples of the transverse stretching method include a tenter method. The stretching treatment may be performed by either a wet stretching method or a dry stretching method, and the dry stretching method is preferably used in terms of being able to select a stretching temperature from a wide range.
The stretching temperature is set to a temperature at which fluidity is exhibited to such an extent that the entire polyvinyl alcohol resin layer 6 and the base film 30 can be stretched, and is preferably in the range of-30 ℃ to +30 ℃ of the phase transition temperature (melting point or glass transition temperature) of the base film 30, more preferably in the range of-30 ℃ to +5 ℃ of the phase transition temperature, and still more preferably in the range of-25 ℃ to +0 ℃. In the case where the substrate film 30 includes a plurality of resin layers, the phase transition temperature refers to the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.
When the stretching temperature is lower than the phase transition temperature of-30 ℃, it is difficult to achieve high stretching ratio of more than 5 times, or the fluidity of the base film 30 is too low, and the stretching treatment tends to be difficult. If the stretching temperature exceeds the phase transition temperature +30 ℃, the fluidity of the base film 30 tends to be too high, and stretching tends to be difficult. Since a high stretch ratio exceeding 5 times is more easily achieved, the stretching temperature is within the above range, and more preferably 120 ℃.
As a heating method of the laminated film 100 in the stretching process, there is provided: a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace adjusted to a predetermined temperature by blowing hot air); a method of heating the roll itself in the case of stretching using a roll; a heater heating method (a method in which an infrared heater, a halogen heater, a flat heater, or the like is provided above and below the laminated film 100 and heating is performed by radiant heat) or the like. In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of uniformity of stretching temperature.
Before the stretching step S20, a preheating step of preheating the laminated film 100 may be provided. As the preheating method, the same method as the heating method in the stretching treatment can be used. The preheating temperature is preferably in the range of-50 ℃ to. + -. 0 ℃ for stretching, more preferably in the range of-40 ℃ to-10 ℃ for stretching.
After the stretching process in the stretching step S20, a heat-setting treatment step may be provided. The heat-fixing treatment is as follows: the end of the stretched film 200 is held by a chuck, and heat treatment is performed at a temperature equal to or higher than the crystallization temperature of the polyvinyl alcohol resin while maintaining a stretched state. The crystallization of the polyvinyl alcohol resin layer 6' is promoted by the heat-setting treatment. The temperature of the heat-setting treatment is preferably in the range of-0 ℃ to-80 ℃ for stretching, and more preferably in the range of-0 ℃ to-50 ℃ for stretching.
(3) Dyeing step S30
The process comprises the following steps: the polyvinyl alcohol resin layer 6 'of the stretched film 200 is dyed with iodine as a dichroic dye and is adsorbed and oriented to form a dyed layer, thereby obtaining a dyed laminate film including the base film 30' and the dyed layer. Typically, the dyeing step S30 may be continuously performed while the long stretched film 200 is conveyed, or the dyeing step S30 may be continuously performed while the stretched film 200 is conveyed, by continuously unwinding the stretched film 200 from a roll, which is a wound product of the long stretched film 200. The film conveyance may be performed using a guide roller or the like.
The dyeing step S30 can be performed by immersing the stretched film 200 in a solution containing iodine (dyeing bath). As the dyeing bath, a solution in which iodine is dissolved in a solvent may be used. Water is generally used as a solvent for the dyeing solution, but an organic solvent compatible with water may be further added. The concentration of iodine in the dyeing bath is preferably 0.01 to 10 parts by weight, more preferably 0.02 to 7 parts by weight, based on 100 parts by weight of the solvent. The immersion time in the dye bath is preferably adjusted according to the concentration of iodine in the dye bath so as to correct the monomer transmittance (Ty) to obtain a desired visual sensitivity.
In order to improve the dyeing efficiency, it is preferable to further add an iodide to the iodine-containing dyeing bath. 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, titanium iodide, and the like. The concentration of the iodide in the dyeing bath is preferably 0.01 to 20 parts by weight based on 100 parts by weight of the solvent. Among the iodides, potassium iodide is preferably added. When potassium iodide is added, the weight ratio of iodine to potassium iodide is preferably 1: 5 to 1: 100, and more preferably 1: 6 to 1: 80. The temperature of the dyeing bath is preferably 10-60 ℃, and more preferably 20-40 ℃.
In the dyeing step S30, an additional stretching process may be further performed on the stretched film 200. Examples of such embodiments include: 1) a mode in which after the stretching process is performed at a magnification lower than the target magnification in the stretching step S20, the stretching process is performed so that the total stretching magnification reaches the target magnification in the dyeing process in the dyeing step S30; as described later, in the case of performing the crosslinking treatment after the dyeing treatment, 2) a method in which after the stretching treatment is performed at a magnification lower than the target in the stretching step S20, the stretching treatment is performed until the total stretching magnification reaches the target magnification in the dyeing treatment in the dyeing step S30, and then the stretching treatment is performed in the crosslinking treatment so that the final total stretching magnification reaches the target magnification, and the like.
(4) Cross-linking step S40
This step is a step of crosslinking the dyed layer of the dyed laminated film to form a crosslinked layer, thereby obtaining a crosslinked laminated film including the base material film 30' and the crosslinked layer. The crosslinking step may be performed by immersing the dyed laminated film in a crosslinking solution containing a crosslinking agent containing at least boric acid. Typically, the crosslinking step S40 may be continuously performed while the long dyed laminated film is being conveyed, or the dyed laminated film may be continuously unwound from a roll of the long dyed laminated film and the crosslinking step S40 may be continuously performed while the dyed laminated film is being conveyed. The film conveyance may be performed using a guide roller or the like.
The crosslinking liquid may contain only boric acid as a crosslinking agent, or may contain a boron compound such as borax, or other crosslinking agents such as glyoxal and glutaraldehyde in addition to boric acid. The other crosslinking agents may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
As the crosslinking liquid, a solution in which boric acid is dissolved in a solvent can be used. As the solvent, water may be used, or an organic solvent having compatibility with water may be further contained. The content of boric acid in the crosslinking liquid is preferably 1 to 20 parts by weight, more preferably 5 to 15 parts by weight, per 100 parts by weight of the solvent, and the content of the crosslinking agent other than boric acid is preferably 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, per 100 parts by weight of the solvent.
The crosslinking liquid may further contain an iodide. By adding the iodide, the in-plane polarization characteristics of the dyed layer can be made more uniform. Specific examples of the iodide are the same as those described above. The content of the iodide in the crosslinking liquid is preferably less than 10 parts by weight, more preferably 8 parts by weight or less, and may be 0 part by weight (may not contain iodide) with respect to 100 parts by weight of the solvent. The lower limit of the temperature of the crosslinking liquid is preferably 40 ℃ or higher, and the upper limit thereof is preferably 82 ℃ or lower. When the temperature of the crosslinking solution exceeds 82 ℃, the polyvinyl alcohol resin in the dyed layer is partially eluted, and unevenness is likely to occur after dyeing.
By blending a crosslinking agent in the dyeing bath, the crosslinking treatment can be performed simultaneously with the dyeing treatment. Further, the treatment of immersing in the crosslinking agent-containing solution may be performed 2 or more times using 2 or more crosslinking agent-containing solutions having different compositions. By sufficiently performing the crosslinking treatment, the boron content in the dyed layer becomes large, and the orientation of the polyiodide complex can be improved. The stretching treatment may be performed in the crosslinking treatment. The specific mode of carrying out the stretching treatment in the crosslinking treatment is as described above.
In the crosslinking step S40, the unit length of the tension applied to the dye laminated film in the width direction is preferably 1N/cm or more, more preferably 2N/cm or more, and still more preferably 5N/cm or more. The upper limit of the tension is not particularly limited, but is preferably 30N/cm or less, and more preferably 20N/cm or less. In the crosslinking step S40, it is preferable to continuously apply tension in the stretching direction of the dyed laminate film so that the orientation of the polyvinyl alcohol resin to be the dyed layer does not relax.
For example, when the dyed laminate film is immersed in the crosslinking liquid in the crosslinking tank while being conveyed between 2 nip rollers and continuously subjected to the crosslinking treatment, the tension applied to the dyed laminate film can be adjusted by adjusting the rotation speed of the nip roller on the feed-in side and the rotation speed of the nip roller on the feed-out side.
(5) Boron removal step S50
Referring to fig. 4, the present process is as follows: the polarizing laminate film 300 including the base material film 30' and the polarizer layer 5 is obtained by forming the polarizer layer 5 by reducing the boron content in the crosslinked layer of the crosslinked laminate film. Typically, the deboning step S50 may be continuously performed while the long crosslinked laminated film is being conveyed, or the deboning step S50 may be continuously performed while the crosslinked laminated film is being conveyed while the crosslinked laminated film is being continuously unwound from a film roll that is a wound product of the long crosslinked laminated film. The film conveyance may be performed using a guide roller or the like.
The deboronation step S50 may include a deboronated liquid contact step of bringing a deboronated liquid having a boric acid concentration lower than that of the crosslinking liquid used in the crosslinking step S40 into contact with the crosslinked layer of the crosslinked laminated film. The deboronating solution contacting step may be performed by immersing the crosslinked laminated film in a deboronating solution, and washing the crosslinked layer of the crosslinked laminated film with a shower of the deboronating solution. The boron removal liquid may be a solution in which boric acid is dissolved in a solvent or a liquid containing no boric acid. As the solvent and the liquid containing no boric acid, water may be used, but an organic solvent having compatibility with water may be further contained. The content of boric acid in the boron removal liquid is preferably less than 10 parts by weight, more preferably 8 parts by weight or less, and may be 0.1 part by weight or more, based on the total weight of the solvent.
By performing a treatment of bringing the boron removal liquid into contact with the crosslinked layer, excess boric acid contained in the crosslinked layer and a polyiodide complex having low orientation can be removed. This reduces the boron content in the polarizer layer 5, and therefore reduces the shrinkage force when the polarizer layer 5 (polarizing film) is heated. In addition, the degree of polarization and the transmittance of the polarizer layer 5 of the polarizing laminate film 300 can be improved.
The boron removal liquid may comprise iodide. Specific examples of the iodide are the same as those described above. The content of the iodide in the boron removal liquid is preferably 15 parts by weight or less, more preferably 8 parts by weight or less, and preferably 5 parts by weight or more, relative to the total weight of the solvent. The color tone of the obtained polarizing laminate film can be adjusted by adjusting the iodide content in the boron removal liquid. The temperature of the boron removal liquid is preferably 70 ℃ or lower, more preferably 65 ℃ or lower. In addition, the temperature of the crosslinking liquid is preferably higher than that of the deboronating liquid.
By using 2 or more kinds of the boron removal liquid having different compositions, the boron removal liquid contact step can be performed 2 or more times. When the contact step of the boron removing solution is carried out a plurality of times, the treatment methods in the contact step of the boron removing solution may be the same or different.
In the case where a plurality of steps of treating with a liquid containing boric acid are included in the crosslinking step and the deboronation step, all the steps of the subsequent stage are controlled so that the boric acid concentration of the liquid containing boric acid is lower and the tension applied to the film is reduced as compared with the step of the previous stage. For example: the boric acid concentration may be gradually decreased as the process proceeds to the subsequent step, may be temporarily decreased and then kept constant, or may be a combination of both. The tension applied to the film may be gradually reduced as the film proceeds to the subsequent step, or the tension may be temporarily reduced and then kept constant, or a combination of both. When a liquid having a boric acid concentration equal to or higher than that of the former step is used in the latter step, the latter step is a crosslinking step.
In the case where the crosslinking step includes a plurality of steps of treating with a liquid containing boric acid, all the steps after the crosslinking step are controlled to have a boric acid concentration lower than that in any of the plurality of steps and to reduce the tension applied to the film, and the boron removal step is preferably controlled to have a boric acid concentration lower than that in the last step of the crosslinking step and to reduce the tension applied to the film.
After the boron removal step S50, the polarizing laminate film is preferably dried. In the case of performing this drying treatment, it is preferable to prevent defects from occurring on the surface of the polarizer layer by using a deboronating solution containing no boric acid in the treatment of immersing in the deboronating solution immediately before the drying treatment. The drying treatment may be any suitable method such as natural drying, air-blowing drying, and heat drying. For example, in the case of heat drying, the drying temperature may be set to 20 to 95 ℃ and the drying time may be set to 1 to 15 minutes.
The magnitude of the tension applied to the crosslinked laminated film in the deboronating liquid contact step of the deboronating step S50 is preferably controlled so that: smaller than the magnitude of the tension applied to the dye laminated film in the crosslinking process S40. Thus, excess boric acid contained in the crosslinked layer and a complex of polyiodide having low orientation can be efficiently removed, and therefore, the shrinkage force when heating the polarizer layer is suppressed, and a polarizing laminate film having excellent optical properties can be efficiently produced. The unit length of the tension applied to the crosslinked laminated film in the deboronating step S50 in the width direction is preferably less than 16N/cm, and more preferably 14N/cm or less. The lower limit of the tension is preferably more than 0N/cm, more preferably 1N/cm. In the deboronation step S50, the crosslinked laminated film is preferably not substantially stretched. The term "not substantially stretched" means that the stretch ratio is 1.05 times or less.
In the case where the deboronation treatment is performed while the crosslinked laminated film is conveyed between 2 nip rolls as in the case of the dyed laminated film described above, the tension applied to the crosslinked laminated film can be adjusted by adjusting the rotation speed of the nip roll on the feed-in side and the rotation speed of the nip roll on the feed-out side.
The crosslinked layer of the crosslinked laminated film can be formed into a thin film by the above-described method. In the case where the deboronation treatment is performed at the above-described tension in the deboronation step S50, it is expected that the complex of polyiodide having low orientation and excessive boric acid contained in the crosslinked layer can be easily removed. Therefore, the polarizer layer formed by the above-described manufacturing method can be made thin, and the optical characteristics can be improved, and increase in shrinkage force can be suppressed.
< method for producing polarizing plate >
Referring to fig. 1, the method for manufacturing a polarizing plate of the present invention sequentially includes the steps of:
a1 st protective film bonding step S60 of bonding a1 st protective film to a surface of the polarizing layer of the polarizing laminated film produced by the above method, the surface being opposite to the base film; and
a peeling step S70 of peeling off and removing the base film.
The first protective film bonding step S60 and the peeling step S70 were performed to obtain the polarizing plate 1 with the single-sided protective film in which the 1 st protective film 10 was bonded to one surface of the polarizer layer 5 (fig. 6). As shown in fig. 1, after the peeling step S70, a 2 nd protective film bonding step S80 of bonding a 2 nd protective film 20 to the surface of the polarizing plate with single-sided protective film 500 exposed by the peeling and removal of the base film 30' (hereinafter, this surface is also referred to as "peeled surface") can be performed, and a polarizing plate with double-sided protective film 2 (fig. 7) can be obtained.
(6) 1 st protective film bonding step S60
Referring to fig. 5, in this step, the 1 st protective film 10 is laminated on the surface of the polarizing laminate film 300 opposite to the surface on the base film 30' (i.e., on the polarizer layer 5) to obtain a multilayer film 400. The 1 st protective film 10 corresponds to the protective film of the polarizing plate described above. Typically, the 1 st protective film bonding step S60 may be continuously performed while the long polarizing laminate film 300 is being conveyed, or the 1 st protective film bonding step S60 may be continuously performed while the polarizing laminate film 300 is being conveyed while the polarizing laminate film 300 is being continuously unwound from a film roll that is a wound product of the long polarizing laminate film 300. The film conveyance may be performed using a guide roller or the like.
In the case where the polarizing laminate film 300 has the polarizer layers 5 on both surfaces of the base film 30', the first protective films 10 are generally bonded to the respective polarizer layers 5 on both surfaces. In this case, the 1 st protective films 10 may be the same kind of protective film or different kinds of protective films.
The 1 st protective film 10 may be bonded to the polarizer layer 5 with the 1 st adhesive layer 15 interposed therebetween. The adhesive forming the 1 st adhesive layer 15 may be: an active energy ray-curable adhesive (preferably an ultraviolet ray-curable adhesive) containing a curable compound that is cured by irradiation with an active energy ray such as an ultraviolet ray, a visible light, an electron beam, or an X-ray, and an aqueous adhesive in which an adhesive component such as a polyvinyl alcohol resin is dissolved or dispersed in water.
In the case of bonding the 1 st protective film 10 using an active energy ray-curable adhesive, the 1 st protective film 10 is laminated on the polarizer layer 5 via the active energy ray-curable adhesive to be the 1 st adhesive layer 15, and then the adhesive layer is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron beam, or X-ray. Among them, ultraviolet rays are suitable, and as the light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used. In the case of using an aqueous adhesive, the 1 st protective film 10 may be laminated on the polarizer layer 5 via the aqueous adhesive, and then dried by heating.
In order to improve the adhesiveness to the polarizer layer 5 when the 1 st protective film 10 is bonded to the polarizer layer 5, the bonding surface of the 1 st protective film 10 and/or the polarizer layer 5 may be subjected to a surface treatment (easy adhesion treatment) such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, or saponification treatment, and among these, plasma treatment, corona treatment, or saponification treatment is preferably performed.
(the 1 st protective film)
The material constituting the 1 st protective film is preferably a light-transmitting (preferably optically transparent) thermoplastic resin, and examples of such a resin include: polyolefin resins such as chain polyolefin resins (polypropylene resins and the like) and cyclic polyolefin resins (norbornene resins and the like); cellulose ester resins such as cellulose triacetate and cellulose diacetate; a polyester resin; a polycarbonate-based resin; (meth) acrylic resins; a polystyrene-based resin; or mixtures, copolymers, etc. thereof. Specific examples of these thermoplastic resins include the thermoplastic resins described above for constituting the base film 30.
The 1 st protective film 10 may also be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film to which an arbitrary retardation value is given can be produced by stretching a film containing the above thermoplastic resin (uniaxial stretching, biaxial stretching, or the like), or forming a liquid crystal layer on the film.
A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer may be formed on the surface of the 1 st protective film 10 opposite to the polarizer layer 5. The surface treatment layer may be formed on the 1 st protective film 10 in advance before the 1 st protective film bonding step S60 is performed, or may be formed after the 1 st protective film bonding step S60 is performed or after the peeling step S70 described later is performed. The 1 st protective film 10 may contain 1 or 2 or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.
From the viewpoint of thinning of the polarizing plate, the thickness of the 1 st protective film 10 is preferably 90 μm or less, more preferably 50 μm or less, still more preferably 35 μm or less, and particularly preferably 30 μm or less. The thickness of the 1 st protective film 10 is usually 5 μm or more from the viewpoint of strength and workability.
(7) Peeling step S70
Referring to fig. 6, this step is a step of peeling off and removing the base film 30' from the multilayer film 400 to obtain a polarizing plate (polarizing plate 1 with a single-sided protective film). In the case where the polarizing laminate film 300 has the polarizer layers 5 on both surfaces of the base film 30' and the 1 st protective film 10 is bonded to the two polarizer layers 5, 2 polarizing plates 1 with one-side protective films are obtained from 1 polarizing laminate film 300 in the peeling step S70. Typically, the peeling step S70 may be continuously performed while the long multilayer film 400 is conveyed, or the peeling step S70 may be continuously performed while the multilayer film 400 is conveyed while the multilayer film 400 is continuously unwound from a roll of the long multilayer film 400. The film conveyance may be performed using a guide roller or the like.
The method of peeling and removing the base film 30' is not particularly limited, and peeling can be performed by the same method as the step S70 of peeling the separator (release film) performed on a general polarizing plate with an adhesive. The base film 30' may be peeled off immediately after the 1 st protective film bonding step S60, or may be once wound into a roll shape after the 1 st protective film bonding step S60, and peeled off while being unwound in the subsequent steps.
As described above, the multilayer film 400 obtained in the 1 st protective film laminating step S60 may be a film in which the polarizer layer 5 and the 1 st protective film 10 are laminated on both surfaces of the base film 30 ', respectively, that is, a film having a layer configuration of 1 st protective film 10/polarizer layer 5/base film 30'/polarizer layer 5/1 st protective film 10 (the 1 st adhesive layer 15 is omitted). At this time, 2 sheets of the polarizing plate 1 with the single-sided protective film were obtained from 1 sheet of the multilayer film 400 through 2 stages of peeling processes. In the peeling step in the 1 st stage, the film having the layer configuration of "1 st protective film 10/polarizer layer 5/base film 30'" is peeled from the multilayer film 400 having the above configuration, and the polarizing plate 1 with a single-sided protective film is obtained. In the peeling step in the 2 nd stage, the base film 30 'is peeled from the peeled film having the layer of "the 1 st protective film 10/the polarizer layer 5/the base film 30'", and the polarizing plate 1 with a single-sided protective film is further obtained.
(8) No. 2 protective film bonding step S80
Referring to fig. 7, this step is an arbitrary step of obtaining a polarizing plate 2 with a double-sided protective film by attaching a 2 nd protective film 20 to a polarizer layer 5 of the polarizing plate 1 with a single-sided protective film. Typically, the bonding step S80 may be continuously performed while the long polarizing plate with a single-sided protective film 1 is conveyed, or the polarizing plate with a single-sided protective film 1 may be continuously unwound from a film roll that is a wound product of the long polarizing plate with a single-sided protective film 1, and the 2 nd protective film bonding step S80 may be continuously performed while the polarizing plate with a single-sided protective film 1 is conveyed. The film conveyance may be performed using a guide roller or the like.
The 2 nd protective film 20 may be bonded to the polarizer layer 5 via the 2 nd adhesive layer 25. The composition and material of the 2 nd protective film 20 and the 2 nd adhesive layer 25, and the method of bonding the 2 nd protective film 20 are described in the 1 st protective film 10 and the 1 st adhesive layer 15, and the method of bonding the 1 st protective film 10, respectively. The 1 st protective film 10 and the 2 nd protective film 20 may be the same type of protective film or different types of protective films. The 1 st adhesive layer 15 and the 2 nd adhesive layer 25 may be formed of the same type of adhesive as each other, or may be formed of different types of adhesives.
[ examples ]
The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples.
[ transmittance of Vision sensitivity correction monomer (Ty) and degree of Vision sensitivity correction polarization (Py) ]
For each polarizing laminated film, the parallel transmittance and the orthogonal transmittance at a wavelength of 380 to 780nm were measured using an integrating sphere-equipped spectrophotometer ("V7100" manufactured by japan spectro corporation), and the monomer transmittance and the degree of polarization at each wavelength were calculated based on the following formulas.
Monomer transmittance (%) - (parallel transmittance + orthogonal transmittance)/2
Polarization degree (%) { (parallel transmittance → orthogonal transmittance)/(parallel transmittance + orthogonal transmittance) } × 100
In the measurement, light is incident from the side of the polarizing laminate film to be the polarizer layer, and the base film side of the polarizing laminate film is set as the detector side. Since the base film is sufficiently transparent, there is no difference between the optical properties measured with the polarizing laminate film and the optical properties measured only with the polarizer layer (polarizing film) of the polarizing laminate film, and the values of the optical properties measured with the polarizing laminate film can be said to be values in the case of measuring the optical properties only with respect to the polarizer layer (polarizing film).
Here, the "parallel transmittance" refers to a transmittance when the direction of polarized light emitted from the glan thompson prism is made parallel to the transmission axis of the polarizing film sample. The "orthogonal transmittance" refers to a transmittance when the direction of polarized light emitted from the glan thompson prism is orthogonal to the transmission axis of the polarizing film sample.
The transmittance and the degree of polarization of the resulting monomer were measured according to JIS Z8701: 1999 "color display method-XYZ color system and X10Y10Z10The 2 degree field of view (C light source) of the color system "was subjected to visual sensitivity correction, and the visual sensitivity correction single transmittance (Ty) and visual sensitivity correction polarization degree (Py) were obtained.
[ ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm ]
The parallel transmittance and the orthogonal transmittance at a wavelength of 475nm measured as described above were converted into a parallel absorbance and an orthogonal absorbance, respectively, based on the following formulae.
Absorbance ═ log10(T/T0)
In the above formula, T0T is a parallel transmittance or a perpendicular transmittance at a wavelength of 475nm, which is a light intensity of polarized light having a wavelength of 475nm emitted from the glan thompson prism and entering the polarizing laminate film.
[ measurement of boron content ]
After 0.2g of a polarizer layer (polarizing film) obtained by peeling and removing a base film from a polarizing laminate film was immersed in 100mL of hot water at a temperature of 95 ℃ for 60 minutes to completely dissolve the polarizer layer, 30g of a mannitol aqueous solution (12.5 wt%) was added to prepare a sample solution for measurement. An aqueous sodium hydroxide solution (1mol/L) was added dropwise until the sample solution for measurement reached a neutralization point, and the boron content (wt%) in the polyvinyl alcohol resin film was calculated from the amount added dropwise based on the following formula.
Boron content (% by weight) 1.08 × dropwise addition amount (mL) of sodium hydroxide solution/weight (g) of polarizing film
In the same manner, the boron content was calculated for the crosslinked layer obtained by peeling and removing the base film from the crosslinked laminated film before the deboronation step, and the change in the boron content before and after the deboronation step was confirmed.
[ measurement of contractile force ]
A sample having a width of 2mm and a length of 8mm, the length of which was longer in the absorption axis direction (stretching direction), was cut from the polarizing laminate film, the base film was peeled off and removed to obtain a sample for measuring a polarizer layer (polarizing film), and the thickness of the sample for measuring was measured by a contact film thickness meter (product name: DIGIMICRO MH-15M, Nikon Co., Ltd.). The measurement sample was mounted on a thermomechanical Analyzer (Thermo-Mechanical Analyzer: TMA) "EXSTAR-6000" (SII NanoTechnology, inc.) and the contraction force (actually measured contraction force) in the longitudinal direction (absorption axis direction, stretching direction) generated when the sample was held at 80 ℃ for 240 minutes was measured while keeping the dimension constant. The measured shrinkage force was divided by the thickness of the measured measurement sample, and multiplied by 5 μm to obtain a shrinkage force [ N/5 μm ] corresponding to a width of 2mm and a thickness of 5 μm (the following equation).
Shrinkage force [ N/5 μm ] (measured shrinkage force of polarizer layer (polarizing film) [ N ])/(thickness of polarizer layer (polarizing film) (measured value) [ μm ]) × 5
[ example 1]
(undercoat layer Forming step)
Polyvinyl alcohol powder ("Z-200", average degree of polymerization 1100, degree of saponification 99.5 mol%, manufactured by Nippon synthetic chemical industry Co., Ltd.) was dissolved in hot water at 95 ℃ to prepare a 3 wt% polyvinyl alcohol aqueous solution. To the obtained aqueous solution, a crosslinking agent ("Sumirez Resin 650" manufactured by takaki chemical corporation) was mixed in a proportion of 5 parts by weight relative to 6 parts by weight of the polyvinyl alcohol powder to obtain a coating liquid for forming a primer layer.
Subsequently, while continuously conveying a substrate film (unstretched polypropylene film, melting point: 163 ℃) having a thickness of 90 μm, one surface of the substrate film was subjected to corona treatment, and then the coating liquid for forming the undercoat layer was continuously applied to the corona-treated surface using a micro gravure coater and dried at 80 ℃ for 10 minutes, thereby forming an undercoat layer having a thickness of 0.2 μm.
(production of laminated film (resin layer Forming step))
Polyvinyl alcohol powder ("PVA 124" manufactured by kokumari corporation, average polymerization degree 2400, and saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ℃ to prepare a 7.5 wt% polyvinyl alcohol aqueous solution, which was used as a coating liquid for forming a polyvinyl alcohol resin layer.
While continuously conveying the base film having the undercoat layer produced in the undercoat layer forming step, the coating liquid for forming the polyvinyl alcohol resin layer is continuously applied to the surface of the undercoat layer using a die coater, and then dried at a temperature of 80 to 90 ℃, thereby forming a polyvinyl alcohol resin layer having a film thickness of 9 μm on the undercoat layer, and obtaining a laminated film including the base film/the undercoat layer/the polyvinyl alcohol resin layer.
(stretching Process)
The above laminated film was subjected to free-end uniaxial stretching (in-air stretching) 5.3 times at a maximum temperature of 150 ℃ during stretching using a floating longitudinal uniaxial stretching apparatus while being continuously conveyed, to obtain a stretched film. The thickness of the stretched polyvinyl alcohol resin layer was 5 μm.
(dyeing step)
While continuously transporting the stretched film, the film was continuously immersed in a dyeing bath containing iodine and potassium iodide at 30 ℃ (containing 0.35 parts by weight of iodine and 5.0 parts by weight of potassium iodide per 100 parts by weight of water) for a retention time of about 90 seconds, and a dyeing treatment of the polyvinyl alcohol resin layer was performed to obtain a dyed laminate film.
(crosslinking step)
While continuously transporting the dyed laminated film, the film was continuously immersed in a crosslinking solution containing boric acid at 78 ℃ (10.4 parts by weight of boric acid per 100 parts by weight of water) at a tension of 16N/cm and a residence time of 120 seconds, and then subjected to crosslinking treatment to obtain a crosslinked laminated film.
(boron removal Process)
Subsequently, while continuously transporting the crosslinked laminated film, the film was continuously immersed in a 65 ℃ solution containing boric acid and potassium iodide (2 parts by weight of boric acid per 100 parts by weight of water and 6.0 parts by weight of potassium iodide) at a tension of 1N/cm and a residence time of 60 seconds, thereby carrying out a deboration treatment. Thereafter, the substrate film was immersed in water at 7 ℃ for 5 seconds under a tension of 1N/cm, and further subjected to a deboronation treatment, and the liquid adhered to both surfaces was removed by an air blower and dried at a temperature of 60 ℃ to obtain a polarizing laminate film having a polarizer layer with a thickness of 5 μm on the substrate film.
From the obtained polarizing laminate film, an evaluation sample was obtained as described in [ preparation of sample for evaluation ] above, and the visual sensitivity correction monomer transmittance (Ty), the visual sensitivity correction polarization degree (Py), the shrinkage force, and the boron content of the sample for evaluation were calculated, and changes in the boron content before and after the deboronation step were examined. The results are shown in Table 1. In table 1, "decrease" in the column of the change in boron content indicates that the boron content after the deboronation step is smaller than the boron content before the deboronation step.
[ example 2 ]
A polarizing laminated film was obtained in the same manner as in example 1 except that the tension in the boron removal step was set to 5N/cm, and evaluated in the same manner as in example 1. The results are shown in Table 1.
[ example 3 ]
A polarizing laminated film was obtained in the same manner as in example 1 except that boric acid was used in an amount of 5 parts by weight in the deboronation step, and evaluated in the same manner as in example 1.
[ example 4 ]
A polarizing laminated film was obtained in the same manner as in example 1 except that boric acid was used in an amount of 5 parts by weight and the tension was used in an amount of 5N/cm in the deboronation step, and the evaluation was performed in the same manner as in example 1.
[ example 5 ]
A polarizing laminated film was obtained in the same manner as in example 1 except that boric acid was used in an amount of 5 parts by weight and the tension was used in an amount of 10N/cm in the deboronation step, and evaluated in the same manner as in example 1.
[ comparative example 1]
A polarizing laminated film was obtained in the same manner as in example 1 except that the tension in the boron removal step was set to 16N/cm, and evaluated in the same manner as in example 1.
[ comparative example 2 ]
A polarizing laminated film was obtained in the same manner as in example 1 except that boric acid was used in an amount of 3.5 parts by weight and the tension was set to 16N/cm in the deboronation step, and the evaluation was performed in the same manner as in example 1.
[ comparative example 3 ]
A polarizing laminated film was obtained in the same manner as in example 1 except that boric acid was used in an amount of 5 parts by weight and the tension was set to 16N/cm in the deboronation step, and the evaluation was performed in the same manner as in example 1.
[ Table 1]
As shown in table 1, the polarizing layers (polarizing films) of the polarizing laminated films obtained in examples 1 to 5 had a boron content of 2.5 wt% or more and 4.1 wt% or less, a visual sensitivity correction monomer transmittance (Ty) of more than 40.5%, and a ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm of less than 0.022. In addition, when the visual sensitivity correction monomer transmittance (Ty) of the polarizing layers (polarizing films) of examples 1 to 5 was 41.5, the visual sensitivity correction polarization degree (Py) exceeded 99.994. The contraction force in the longitudinal direction (absorption axis direction, stretching direction) of the polarizing layers (polarizing films) of examples 1 to 5 was suppressed to less than 1.77N/5 μm.
In comparative examples 1 to 3, the visual sensitivity correction polarization degree (Py) was low when the visual sensitivity correction monomer transmittance (Ty) was 41.5. This is presumably because: the magnitude of the tension applied to the crosslinked laminated film in the deboronation step is the same as the magnitude of the tension applied to the dyed laminated film in the crosslinking step. In comparative examples 1 to 3, the ratio of parallel absorbance/orthogonal absorbance at a wavelength of 475nm was relatively large. In examples 1 to 5 and comparative examples 1 to 3, the boron content decreased before and after the deboronation step, and excess boric acid contained in the crosslinked layer was removed in the deboronation step, and therefore it is estimated that in comparative examples 1 to 3, the removal of the polyiodide complex having low directionality in the deboronation step was insufficient.
Description of the symbols
1 polarizing plate with a single-sided protective film, 2 polarizing plates with double-sided protective films, 5 polarizer layers, 6 polyvinyl alcohol resin layers, 6 'stretched polyvinyl alcohol resin layers, 10 st protective films, 1 st adhesive layers, 15 st adhesive layers, 20 nd protective films, 2 nd adhesive layers, 25 nd adhesive layers, 30 base material films, 30' stretched base material films, 100 laminated films, 200 stretched films, 300 polarizing laminated films, and 400 multilayer films.
Claims (3)
1. A method for producing a polarizing laminate film, comprising the following steps in this order:
a resin layer forming step of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film;
a stretching step of stretching the laminated film to obtain a stretched film;
a dyeing step of dyeing the polyvinyl alcohol resin layer of the stretched film with iodine to form a dyed layer, thereby obtaining a dyed laminate film;
a crosslinking step of crosslinking the dyed layer of the dyed laminated film with a crosslinking solution containing boric acid to form a crosslinked layer, thereby obtaining a crosslinked laminated film; and
a deboronation step of forming a polarizer layer by reducing the boron content in the crosslinked layer of the crosslinked laminated film to obtain a polarizing laminated film,
the boric acid content in the crosslinking liquid is 5 to 15 parts by weight relative to 100 parts by weight of the solvent,
the deboronation step is a step of bringing the crosslinked layer into contact with a deboronation solution having a boric acid concentration lower than that of the crosslinked layer a plurality of times,
the deboronation step includes a step A of performing the deboronation solution contact step using a deboronation solution containing boric acid, the step A being a first step of the deboronation step, wherein a boric acid content in the deboronation solution containing boric acid used in the step A is 5.4 to 8.4 parts by weight lower than a boric acid content in the crosslinking solution with respect to 100 parts by weight of a solvent,
in the step A, the magnitude of the tension applied to the crosslinked laminated film is controlled so as to be 6N/cm to 15N/cm smaller than the magnitude of the tension applied to the laminated film with the dyed layer in the crosslinking step.
2. The method of producing a polarizing laminate film according to claim 1, wherein the boron removal step comprises performing the boron removal liquid contact step a plurality of times using 2 or more types of boron removal liquids having different compositions.
3. A method of manufacturing a polarizing plate, comprising in order:
a step of producing a polarizing laminate film by the production method according to claim 1 or 2;
a step of bonding a protective film to a surface of the polarizer layer opposite to the base film; and
and peeling and removing the base material film.
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| KR102444485B1 (en) | 2022-09-16 |
| TW201830063A (en) | 2018-08-16 |
| TWI795379B (en) | 2023-03-11 |
| JP2018091980A (en) | 2018-06-14 |
| CN108152876A (en) | 2018-06-12 |
| KR20180063828A (en) | 2018-06-12 |
| CN113655556B (en) | 2024-05-10 |
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