CN118671872A - Polarizing film, polarizing plate, and method for producing polarizing film - Google Patents
Polarizing film, polarizing plate, and method for producing polarizing film Download PDFInfo
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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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00634—Production of filters
- B29D11/00644—Production of filters polarizing
-
- 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
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
-
- 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
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Ophthalmology & Optometry (AREA)
- Mechanical Engineering (AREA)
- Polarising Elements (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
Provided is a polarizing film wherein breakage in the absorption axis direction is suppressed. The polarizing film of the present invention is composed of a polyvinyl alcohol resin film containing a dichroic material, and has an orientation function of 0.30 or less. In 1 embodiment, the polarizing film has a thickness of 8 μm or less. The polarizing plate of the present invention comprises: the polarizing film, and a protective layer disposed on at least one side of the polarizing film.
Description
The present application is a divisional application of application number 202080012812.1, which is the title of polarizing film and polarizing plate, and the method for manufacturing the polarizing film, and the application of which is the application number 2020, 2 and 6.
Technical Field
The present invention relates to a polarizing film, a polarizing plate, and a method for producing the polarizing film.
Background
In a liquid crystal display device, which is a typical image display device, polarizing films are disposed on both sides of a liquid crystal cell due to an image forming method. As a method for producing a polarizing film, for example, the following method has been proposed: a laminate including a resin substrate and a polyvinyl alcohol (PVA) -based resin layer is stretched and then dyed to obtain a polarizing film on the resin substrate (for example, patent document 1). With such a method, a polarizing film having a small thickness can be obtained, and thus, attention has been paid as a method for contributing to the reduction in thickness of image display devices in recent years. However, the thin polarizing film described above has a problem in that it is easily broken (easily broken) along the absorption axis direction.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 2001-343521
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a polarizing film in which breakage in the absorption axis direction is suppressed.
Solution for solving the problem
The polarizing film according to the embodiment of the present invention is composed of a polyvinyl alcohol resin film containing a dichroic material, and has an orientation function of 0.30 or less.
In 1 embodiment, the thickness of the polarizing film is 8 μm or less.
In 1 embodiment, the polarizing film has a single transmittance of 40.0% or more and a polarization degree of 99.0% or more.
In 1 embodiment, the puncture strength of the polarizing film is 30gf/μm or more.
The polarizing film according to another embodiment of the present invention is composed of a polyvinyl alcohol resin film containing a dichroic material, and has a puncture strength of 30gf/μm or more.
According to another aspect of the present invention, there is provided a polarizing plate. The polarizing plate comprises: the polarizing film, and a protective layer disposed on at least one side of the polarizing film.
According to another aspect of the present invention, there is provided a method for producing the polarizing film described above. The manufacturing method comprises the following steps: forming a polyvinyl alcohol resin layer containing iodide or sodium chloride and containing a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate to form a laminate; and sequentially performing an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment for shrinking the laminate by 2% or more in the width direction by heating while conveying the laminate in the longitudinal direction. The total stretching multiplying power of the air auxiliary stretching treatment and the water stretching treatment is 3.0-4.5 times relative to the original length of the laminated body; the stretching magnification of the air auxiliary stretching treatment is larger than that of the stretching treatment in water.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, by setting the orientation function to 0.30 or less, or by setting the puncture strength to 30gf/μm or more, a polarizing film in which breakage in the absorption axis direction is suppressed can be realized. In the past, it has been difficult to obtain acceptable optical characteristics (typically, the monomer transmittance and the polarization degree) for a polarizing film having a small orientation function, but according to the present invention, it is possible to achieve both of such a small orientation function and acceptable optical characteristics. Further, according to the present invention, such a large puncture strength and acceptable optical characteristics can be combined.
Drawings
Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention.
Fig. 2 is a schematic diagram showing an example of a drying shrinkage process using a heating roller.
Detailed Description
Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.
A. Polarizing film
The polarizing film according to the embodiment of the present invention is composed of a polyvinyl alcohol (PVA) resin film containing a dichroic material (typically iodine or a dichroic dye), and has an orientation function of 0.30 or less. With such a configuration, the polarizing film can be significantly prevented from being split (broken) in the absorption axis direction. As a result, a polarizing film (as a result, a polarizing plate) having very excellent bending properties can be obtained. Such a polarizing film (as a result, a polarizing plate) can be applied to an image display device that is preferably curved, more preferably a bendable image display device, and further preferably a foldable image display device. The orientation function is, for example, 0.25 or less, preferably 0.22 or less, more preferably 0.20 or less, still more preferably 0.18 or less, and particularly preferably 0.15 or less. The lower limit of the orientation function may be, for example, 0.05. If the orientation function is too small, acceptable monomer transmittance and/or polarization degree may not be obtained.
The orientation function (f) is determined by measuring, for example, the polarized light as measurement light by using a Fourier transform infrared spectrometer (FT-IR) and attenuated total reflection spectroscopy (ATR: attenuated total reflection). Specifically, the measurement was performed in a state where the stretching direction of the polarizing film was parallel and perpendicular to the polarizing direction of the measurement light, and the intensity of 2941cm -1 of the absorbance spectrum obtained was used, and was calculated by the following formula. Here, the intensity I is a value of 2941cm -1/3330cm-1 with 3330cm -1 as a reference peak. The alignment was complete when f=1, and random when f=0. Further, the peak of 2941cm -1 is considered to be the absorption of vibration due to the main chain (-CH 2 -) of PVA in the polarizing film.
f＝(3<cos2θ>-1)/2
＝(1-D)/[c(2D+1)]
＝-2×(1-D)/(2D+1)
Wherein,
C= (in the case of vibration of 3cos 2β-1)/2,2941cm-1, β=90°.
Θ: angle of molecular chain with respect to stretching direction
Beta: angle of transition dipole moment relative to molecular chain axis
D= (I ⊥)/(I//) (in this case, the more oriented the PVA molecules, the larger D becomes)
I ⊥: measuring the absorption intensity when the polarization direction of light is perpendicular to the stretching direction of the polarizing film
I //: measuring the absorption intensity when the polarization direction of light is parallel to the stretching direction of the polarizing film
The thickness of the polarizing film is preferably 8 μm or less, more preferably 7 μm or less, further preferably 5 μm or less, particularly preferably 3 μm or less, and particularly preferably 2 μm or less. The lower limit of the thickness of the polarizing film may be, for example, 1 μm. The thickness of the polarizing film may be 2 μm to 6 μm in 1 embodiment, 2 μm to 4 μm in another embodiment, 2 μm to 3 μm in yet another embodiment, 5.5 μm to 7.5 μm in yet another embodiment, and 6 μm to 7.2 μm in yet another embodiment. By making the thickness of the polarizing film extremely thin in this way, the heat shrinkage can be made extremely small. It is presumed that such a constitution also contributes to suppression of breakage in the absorption axis direction.
The polarizing film preferably exhibits absorption dichroism at any of wavelengths 380nm to 780 nm. The monomer transmittance of the polarizing film is preferably 40.0% or more, more preferably 41.0% or more. The upper limit of the transmittance of the monomer may be 49.0%, for example. The monomer transmittance of the polarizing film is 40.0% to 45.0% in 1 embodiment. The polarization degree of the polarizing film is preferably 99.0% or more, more preferably 99.4% or more. The upper limit of the degree of polarization may be, for example, 99.999%. The polarization degree of the polarizing film is 99.0% to 99.99% in 1 embodiment. According to the present invention, although the orientation function is very small as described above, such practically acceptable monomer transmittance and polarization degree can be achieved. This is presumably due to a manufacturing method described later. The monomer transmittance is typically a Y value obtained by measurement with an ultraviolet-visible spectrophotometer and by sensitivity correction. The polarization degree is typically obtained by the following equation based on the parallel transmittance Tp and the orthogonal transmittance Tc obtained by measurement using an ultraviolet-visible spectrophotometer and performing sensitivity correction.
The polarization degree (%) = { (Tp-Tc)/(tp+tc) } 1/2 ×100
The puncture strength of the polarizing film is 30gf/μm or more, preferably 35gf/μm or more, more preferably 40gf/μm or more, still more preferably 45gf/μm or more, and particularly preferably 50gf/μm or more. The upper limit of the puncture strength may be 80gf/μm, for example. By setting the puncture strength of the polarizing film to such a range, the polarizing film can be significantly suppressed from being split in the absorption axis direction. As a result, a polarizing film (as a result, a polarizing plate) having very excellent bending properties can be obtained. The puncture strength indicates the rupture resistance of the polarizing film when the polarizing film is punctured with a predetermined strength. The puncture strength can be expressed, for example, as: a predetermined needle was attached to a compression tester, and the polarizing film was broken at a predetermined speed (breaking strength) when the needle penetrated the polarizing film. The puncture strength means the puncture strength per unit thickness (1 μm) of the polarizing film, as can be seen from the unit.
The polarizing film is constituted of the PVA-based resin film containing iodine as described above. Preferably, the PVA-based resin constituting the PVA-based resin film (substantially polarizing film) contains an acetoacetyl-modified PVA-based resin. With such a constitution, a polarizing film having a desired puncture strength can be obtained. When the total amount of the PVA-based resin is 100 wt%, the blending amount of the acetoacetyl-modified PVA-based resin is preferably 5wt% to 20 wt%, more preferably 8 wt% to 12 wt%. When the blending amount is in such a range, the puncture strength can be set to a more appropriate range.
The polarizing film can be typically produced using a laminate of two or more layers. Specific examples of the polarizing film obtained by using the laminate include a polarizing film obtained by using a laminate of a resin base material and a PVA-based resin layer formed on the resin base material. A polarizing film obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, as follows: a step of applying a PVA-based resin solution to a resin substrate and drying the same to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate was stretched and dyed to prepare a polarizing film from the PVA-based resin layer. In the present embodiment, it is preferable that a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin is formed on one side of a resin base material. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching. Further, stretching preferably further includes subjecting the laminate to air stretching at a high temperature (for example, 95 ℃ or higher) before stretching in the aqueous boric acid solution. In the embodiment of the present invention, the total draw ratio is, for example, 3.0 to 4.5 times, which is significantly smaller than usual. Even with such a total magnification of stretching, a polarizing film having acceptable optical characteristics can be obtained by a combination of addition of a halide and a drying shrinkage treatment. Further, in the embodiment of the present invention, the stretching ratio of the air-assisted stretching is larger than that of the stretching in boric acid water. By adopting such a constitution, a polarizing film having acceptable optical characteristics can be obtained even if the total magnification of stretching is small. Further, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. In 1 embodiment, a method for manufacturing a polarizing film includes: the laminate was subjected to an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is coated on the thermoplastic resin, crystallinity of PVA can be improved, and high optical characteristics can be achieved. Further, by simultaneously improving the orientation of PVA in advance, problems such as degradation and dissolution of the orientation of PVA can be prevented when immersed in water in a subsequent dyeing step and stretching step, and high optical characteristics can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, disorder of orientation of polyvinyl alcohol molecules and decrease of orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This improves the optical properties of the polarizing film obtained by the treatment step of immersing the laminate in a liquid, such as dyeing treatment and stretching in water. Further, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical characteristics can be improved. The obtained laminate of the resin substrate and the polarizing film may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizing film), or may be used by peeling the resin substrate from the laminate of the resin substrate and the polarizing film and laminating any appropriate protective layer suitable for the purpose on the peeled surface. Details of the method for producing the polarizing film are described in item C below.
B. Polarizing plate
Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention. The polarizing plate 100 includes: a polarizing film 10, a1 st protective layer 20 disposed on one side of the polarizing film 10, and a2 nd protective layer 30 disposed on the other side of the polarizing film 10. The polarizing film 10 is the polarizing film of the present invention described in item a above. One of the 1 st protective layer 20 and the 2 nd protective layer 30 may be omitted. As described above, one of the 1 st protective layer and the 2 nd protective layer may be a resin base material used for the production of the polarizing film.
The 1 st and 2 nd protective layers are formed of any appropriate thin film that can be used as a protective layer for a polarizing film. Specific examples of the material as the main component of the film include cellulose resins such as Triacetylcellulose (TAC), transparent resins such as polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, and acetate resins. Further, a thermosetting resin such as a (meth) acrylic resin, a urethane resin, a (meth) acrylic urethane resin, an epoxy resin, or a silicone resin, an ultraviolet curable resin, or the like can be mentioned. Further, for example, a vitreous polymer such as a siloxane polymer can be used. In addition, a polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007) can also be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain, and for example, a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be used. The polymer film may be, for example, an extrusion molded product of the above resin composition.
When the polarizing plate 100 is applied to an image display device, the thickness of the protective layer (outer protective layer) disposed on the side opposite to the display panel is typically 300 μm or less, preferably 100 μm or less, more preferably 5 μm to 80 μm, and still more preferably 10 μm to 60 μm. In the case of performing the surface treatment, the thickness of the outer protective layer is a thickness including the thickness of the surface treatment layer.
When the polarizing plate 100 is applied to an image display device, the thickness of the protective layer (inner protective layer) disposed on the display panel side is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and still more preferably 10 μm to 60 μm. In 1 embodiment, the inner protective layer is a phase difference layer having any suitable phase difference value. In this case, the in-plane retardation Re (550) of the retardation layer is, for example, 110nm to 150nm. "Re (550)" is the in-plane retardation measured at 23℃with light having a wavelength of 550nm by the formula: re= (nx-ny) x d. Here, "nx" is a refractive index in a direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis (i.e., the fast axis direction) in the plane, "nz" is a refractive index in the thickness direction, and "d" is a thickness (nm) of the layer (thin film).
C. Method for producing polarizing film
The method for producing a polarizing film according to embodiment 1 of the present invention comprises: forming a polyvinyl alcohol resin layer (PVA resin layer) containing a halide and a polyvinyl alcohol resin (PVA resin) on one side of a long thermoplastic resin substrate to form a laminate; and sequentially performing an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment for shrinking the laminate by 2% or more in the width direction by heating while conveying the laminate in the longitudinal direction. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heated roller, and the temperature of the heated roller is preferably 60 to 120 ℃. The shrinkage in the width direction of the laminate due to the drying shrinkage treatment is preferably 2% or more. According to the above manufacturing method, the polarizing film described in item a above can be obtained. In particular, by producing a laminate having a PVA-based resin layer containing a halide, stretching the laminate into a multi-stage stretching including air-assisted stretching and in-water stretching, and heating the stretched laminate with a heating roller, a polarizing film having excellent optical characteristics (typically, monomer transmittance and unit absorbance) can be obtained.
C-1. Production of laminate
As a method for producing the laminate of the thermoplastic resin base material and the PVA-based resin layer, any suitable method can be used. The PVA-based resin layer is preferably formed on the thermoplastic resin substrate by coating a coating liquid containing a halide and a PVA-based resin on the surface of the thermoplastic resin substrate and drying. As described above, the content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.
As a coating method of the coating liquid, any suitable method can be employed. For example, a roll coating method, a spin coating method, a bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (comma coating method, etc.), and the like can be cited. The coating and drying temperature of the coating liquid is preferably 50 ℃ or higher.
The thickness of the PVA based resin layer is preferably 2 μm to 30 μm, more preferably 2 μm to 20 μm. By making the thickness of the PVA-based resin layer before stretching extremely thin and reducing the total stretching ratio as described later, a polarizing film having acceptable monomer transmittance and polarization degree even if the orientation function is extremely small can be obtained.
Before forming the PVA-based resin layer, the thermoplastic resin substrate may be subjected to a surface treatment (for example, corona treatment or the like), or an easy-to-adhere layer may be formed on the thermoplastic resin substrate. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.
C-1-1. Thermoplastic resin substrate
As the thermoplastic resin base material, any suitable thermoplastic resin film can be used. Details of the thermoplastic resin base material are described in, for example, japanese patent application laid-open No. 2012-73580. The entire disclosure of this publication is incorporated by reference into this specification.
C-1-2. Coating liquid
The coating liquid contains a halide and a PVA-based resin as described above. The coating liquid is typically a solution obtained by dissolving the halide and the PVA-based resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various diols, polyols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used singly or in combination of two or more. Among these, water is preferable. The PVA-based resin concentration of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. When the resin concentration is such, a uniform coating film can be formed to adhere to the thermoplastic resin substrate. The halide content in the coating liquid is preferably 5 parts by weight to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.
The coating liquid may be mixed with an additive. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. They can be used for the purpose of further improving the uniformity, dyeing property, and stretchability of the resulting PVA-based resin layer.
As the PVA-based resin, any suitable resin may be used. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer can be cited. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be determined according to JIS K6726-1994. By using the PVA-based resin having such a saponification degree, a polarizing film excellent in durability can be obtained. If the saponification degree is too high, gelation may occur. As described above, the PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin.
The average polymerization degree of the PVA-based resin may be appropriately selected according to purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. The average polymerization degree can be determined according to JIS K6726-1994.
As the above-mentioned halide, any suitable halide may be used. For example, iodide and sodium chloride may be mentioned. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.
The amount of the halide in the coating liquid is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin, and more preferably 10 to 15 parts by weight relative to 100 parts by weight of the PVA-based resin. If the amount of the halide exceeds 20 parts by weight relative to 100 parts by weight of the PVA-based resin, the halide may ooze out and the finally obtained polarizing film may be clouded.
In general, the orientation of the polyvinyl alcohol molecules in the PVA-based resin is increased by stretching the PVA-based resin layer, but when the PVA-based resin layer after stretching is immersed in a liquid containing water, the orientation of the polyvinyl alcohol molecules may be disordered and the orientation may be decreased. In particular, when a laminate of a thermoplastic resin and a PVA-based resin layer is stretched in boric acid water, the degree of orientation tends to be significantly reduced when the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin. For example, stretching of a PVA film itself in boric acid water is usually performed at 60 ℃, whereas stretching of a laminate of a-PET (thermoplastic resin base) and a PVA-based resin layer is performed at a temperature as high as about 70 ℃, and in this case, the orientation of PVA at the initial stage of stretching is reduced at a stage before the stretching in water is increased. In contrast, by producing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and stretching the laminate at a high temperature in air (auxiliary stretching) before stretching the laminate in boric acid water, crystallization of the PVA-based resin in the PVA-based resin layer of the laminate after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, disorder of orientation and decrease of orientation of polyvinyl alcohol molecules can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This improves the optical properties of the polarizing film obtained by the treatment step of immersing the laminate in a liquid, such as dyeing treatment and stretching in water.
C-2, air assisted stretching treatment
In particular, in order to obtain high optical characteristics, a method of 2-stage stretching in which dry stretching (auxiliary stretching) and stretching in boric acid water are combined is preferable. By introducing the auxiliary stretching as in the 2-stage stretching, the stretching can be performed while suppressing crystallization of the thermoplastic resin base material. Further, in the case of coating a PVA-based resin on a thermoplastic resin substrate, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate, it is necessary to lower the coating temperature as compared with the case of coating a PVA-based resin on a metal cylinder in general, and as a result, there is a problem that crystallization of the PVA-based resin is relatively low and sufficient optical characteristics are not obtained. In contrast, by introducing the auxiliary stretching, even when the PVA-based resin is coated on the thermoplastic resin, crystallinity of the PVA-based resin can be improved, and high optical characteristics can be achieved. In addition, by simultaneously improving the orientation of the PVA-based resin in advance, it is possible to prevent problems such as a decrease in orientation and dissolution of the PVA-based resin when immersed in water in the subsequent dyeing step and stretching step, and to achieve high optical characteristics.
The stretching method of the air-assisted stretching may be fixed-end stretching (for example, stretching using a tenter), or free-end stretching (for example, stretching the laminate unidirectionally by passing it between rolls having different circumferential speeds), and free-end stretching may be positively employed in order to obtain high optical characteristics. In one embodiment, the air stretching process includes a heated roll stretching step of stretching the laminate by using a peripheral speed difference between heated rolls while conveying the laminate in the longitudinal direction thereof. The air stretching treatment typically includes a zone stretching process and a heated roll stretching process. The order of the region stretching step and the heat roller stretching step is not limited, and the region stretching step may be performed first, or the heat roller stretching step may be performed first. The region stretching step may be omitted. In 1 embodiment, the zone stretching step and the heat roller stretching step are sequentially performed. In another embodiment, the stretching is performed by grasping the film end portion and expanding the distance between the tenters in the flow direction in the tenter stretching machine (the expansion of the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (the direction perpendicular to the flow direction) is set to be arbitrarily close. The stretching ratio in the flow direction can be preferably set so as to be closer to the free end stretching. In the case of the free end stretching, it is calculated by a shrinkage ratio= (1/stretch ratio) 1/2 in the width direction.
The air-assisted stretching may be performed in one stage or may be performed in multiple stages. When the stretching is performed in multiple stages, the stretching ratio is the product of the stretching ratios in the respective stages. The stretching direction in the air-assisted stretching is preferably substantially the same as the stretching direction in the underwater stretching.
The stretching ratio in the air-assisted stretching is preferably 1.0 to 4.0 times, more preferably 1.5 to 3.5 times, and still more preferably 2.0 to 3.0 times. When the stretching magnification of the air-assist stretching is in such a range, the total stretching magnification can be set to a desired range when combined with the underwater stretching, and a desired orientation function can be achieved. As a result, a polarizing film in which breakage in the absorption axis direction is suppressed can be obtained. Further, as described above, the stretching ratio of the air-assisted stretching is larger than that of the stretching in boric acid water. By adopting such a constitution, a polarizing film having acceptable optical characteristics can be obtained even if the total magnification of stretching is small.
The stretching temperature of the air-assisted stretching may be set to any appropriate value depending on the material forming the thermoplastic resin base material, the stretching method, and the like. The stretching temperature is preferably not less than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably not less than the glass transition temperature (Tg) +10 ℃ of the thermoplastic resin substrate, particularly preferably not less than tg+15 ℃. On the other hand, the upper limit of the stretching temperature is preferably 170 ℃. By stretching at such a temperature, crystallization of the PVA-based resin can be suppressed from proceeding rapidly, and defects caused by the crystallization (e.g., impeding orientation of the PVA-based resin layer caused by stretching) can be suppressed.
C-3 insolubilization treatment, dyeing treatment and crosslinking treatment
If necessary, insolubilization treatment is performed after the air-assisted stretching treatment and between the underwater stretching treatment and the dyeing treatment. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, the crosslinking treatment is performed after the dyeing treatment and before the stretching treatment in water. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. Details of the insolubilization treatment, dyeing treatment, and crosslinking treatment are described in, for example, japanese patent application laid-open No. 2012-73580 (mentioned above).
C-4 in-water stretching treatment
The stretching treatment in water is performed by immersing the laminate in a stretching bath. The stretching treatment in water can be performed at a temperature lower than the glass transition temperature (typically about 80 ℃) of the thermoplastic resin base material and the PVA-based resin layer, and can be performed while suppressing crystallization of the PVA-based resin layer. As a result, a polarizing film having excellent optical characteristics can be produced.
Any suitable method may be used for stretching the laminate. Specifically, the stretching may be performed at a fixed end or at a free end (for example, a method of stretching a laminate unidirectionally by passing the laminate between rolls having different peripheral speeds). The free end stretch is preferably selected. Stretching of the laminate may be performed in one stage or may be performed in multiple stages. When the stretching is performed in multiple stages, the total stretching ratio is the product of the stretching ratios in the respective stages.
The stretching in water is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water). By using an aqueous boric acid solution as the stretching bath, rigidity against tensile force applied at the time of stretching and water resistance against dissolution in water can be imparted to the PVA-based resin layer. Specifically, boric acid generates a tetrahydroxyboric acid anion in an aqueous solution and crosslinks with the PVA-based resin through hydrogen bonds. As a result, the PVA-based resin layer can be stretched well by imparting rigidity and water resistance, and a polarizing film having excellent optical characteristics can be produced.
The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, particularly preferably 3 to 5 parts by weight, relative to 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be obtained. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent may be used.
Preferably, the iodide is mixed in the stretching bath (boric acid aqueous solution). By adding iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. Specific examples of iodides are described above. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, relative to 100 parts by weight of water.
The stretching temperature (liquid temperature of the stretching bath) is preferably 40 to 85 ℃, more preferably 60 to 75 ℃. At such a temperature, the PVA-based resin layer can be stretched at a high rate while suppressing dissolution. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60 ℃ or higher from the viewpoint of the relationship with the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ℃, there is a concern that the stretching cannot be performed satisfactorily even if plasticization of the thermoplastic resin substrate by water is considered. On the other hand, the higher the temperature of the stretching bath is, the higher the solubility of the PVA-based resin layer becomes, and there is a concern that excellent optical characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.
The stretching ratio based on stretching in water is preferably 1.0 to 3.0 times, more preferably 1.0 to 2.0 times, still more preferably 1.0 to 1.5 times. When the stretching magnification in the underwater stretching is in such a range, the total magnification of stretching can be set to a desired range, and a desired orientation function can be achieved. As a result, a polarizing film in which breakage in the absorption axis direction is suppressed can be obtained. The total stretching ratio (total of stretching ratios in combination of the air-assisted stretching and the underwater stretching) is, for example, 3.0 to 4.5 times, preferably 3.0 to 4.0 times, more preferably 3.0 to 3.5 times, the original length of the laminate. By adding a halide to the coating liquid, adjusting the stretching ratio of the air-assisted stretching and the stretching in water, and appropriately combining the drying shrinkage treatment, a polarizing film having acceptable optical characteristics can be obtained even at the total ratio of such stretching.
C-5 drying shrinkage treatment
The drying shrinkage treatment may be performed by zone heating in which the entire zone is heated, or may be performed by heating a conveying roller (using a so-called heating roller) (heating roller drying method). Both are preferably used. By drying with the heating roller, the laminate can be effectively prevented from curling by heating, and a polarizing film excellent in appearance can be produced. Specifically, by drying the laminate while the laminate is in a state of being brought along the heated roller, crystallization of the thermoplastic resin base material can be effectively promoted to increase the crystallinity, and even at a low drying temperature, the crystallinity of the thermoplastic resin base material can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material increases, and the PVA-based resin layer is allowed to shrink due to drying, so that curling can be suppressed. Further, by using the heating roller, the laminate can be dried while maintaining a flat state, and therefore, not only curling but also the generation of wrinkles can be suppressed. At this time, the laminate is shrunk in the width direction by the drying shrinkage treatment, whereby the optical characteristics can be improved. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage in the width direction of the laminate due to the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%.
Fig. 2 is a schematic diagram showing an example of the drying shrinkage treatment. In the drying shrinkage process, the laminate 200 is dried while being conveyed by the conveying rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the example shown in the figure, the conveying rollers R1 to R6 are arranged so as to heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate alternately and continuously, but for example, the conveying rollers R1 to R6 may be arranged so as to heat only one surface (for example, the surface of the thermoplastic resin substrate) of the laminate 200 continuously.
The drying condition can be controlled by adjusting the heating temperature of the conveying roller (temperature of the heating roller), the number of heating rollers, the contact time with the heating roller, and the like. The temperature of the heating roller is preferably 60 to 120 ℃, more preferably 65 to 100 ℃, particularly preferably 70 to 80 ℃. An optical laminate which can satisfactorily increase the crystallinity of a thermoplastic resin, satisfactorily suppress curling, and has extremely excellent durability can be produced. The temperature of the heating roller may be measured by a contact thermometer. In the example of the figure, 6 conveying rollers are provided, but there is no particular limitation as long as the conveying rollers are plural. The number of the conveying rollers is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) of the laminate with the heating roller is preferably 1 to 300 seconds, more preferably 1 to 20 seconds, and still more preferably 1 to 10 seconds.
The heating roller may be provided in a heating furnace (for example, an oven) or may be provided in a usual production line (in a room temperature environment). Preferably, the air supply device is arranged in a heating furnace provided with an air supply means. By using the drying by the heating roller and the hot air drying in combination, abrupt temperature changes between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of the hot air drying is preferably 30 to 100 ℃. The hot air drying time is preferably 1 to 300 seconds. The wind speed of the hot air is preferably about 10m/s to 30 m/s. The wind speed is the wind speed in the heating furnace, and can be measured by a mini-blade type digital anemometer.
C-6. Other treatments
The washing treatment is preferably performed after the stretching treatment in water and before the drying shrinkage treatment. The washing treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.
Examples
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in examples and comparative examples are weight basis.
(1) Thickness of (L)
The measurement was performed using an interference film thickness meter (product name "MCPD-3000" manufactured by tsukamu electronics corporation). The calculated wavelength range used in the thickness calculation was 400nm to 500nm, and the refractive index was 1.53.
(2) Orientation function
The polarizing films obtained in examples and comparative examples were subjected to attenuated total reflection spectroscopy (ATR: attenuated total reflection) on the surfaces of the polarizing films using a Fourier transform infrared spectrometer (FT-IR) (trade name: front, manufactured by PERKIN ELMER Co.) and polarized infrared light as measuring light. The crystallites, which made the polarizing film closely adhered, were made of germanium, and the incidence angle of the measured light was set to 45 °. The orientation function is calculated according to the following procedure. The absorbance spectra were measured with the polarized light (measurement light) as polarized light (s-polarized light) vibrating parallel to the surface of the germanium crystal sample, and the stretching directions of the polarized film were arranged perpendicular (∈) and parallel (/ /) with respect to the polarization direction of the measurement light. From the absorbance spectrum obtained, I (2941 cm -1 intensity) was calculated with reference to (3330 cm -1 intensity). I ⊥ is (2941 cm -1 intensity)/(3330 cm -1 intensity) obtained from the absorbance spectrum obtained when the stretching direction of the polarizing film is arranged perpendicular (∈) to the polarizing direction of the measurement light. I // is the absorbance spectrum obtained when the stretching direction of the polarizing film is arranged parallel (///) to the polarizing direction of the measurement light (2941 cm -1 intensity)/(3330 cm -1 intensity). Here, (2941 cm -1 intensity) is the absorbance of 2941cm -1 when 2770cm -1 and 2990cm -1, which are the bottoms of the absorbance spectra, are set as the base lines, (3330 cm -1 intensity) is the absorbance of 3330cm -1 when 2990cm -1 and 3650cm -1 are set as baseline. Using the obtained I ⊥ and I //, an orientation function f was calculated according to equation 1. The alignment was complete when f=1, and random when f=0. Further, the peak of 2941cm -1 is considered to be the absorption of vibration due to the main chain (-CH 2 -) of PVA in the polarizing film. Further, the peak of 3330cm -1 is considered to be the absorption of vibration due to the hydroxyl group of PVA.
(1) F= (3 < cos2θ > -1)/2
＝(1-D)/[c(2D+1)]
Wherein,
c＝(3cos2β-1)/2
In the case of 2941cm -1 used as described above,
Θ: angle of molecular chain with respect to stretching direction
Beta: angle of transition dipole moment relative to molecular chain axis
D＝(I⊥)/(I//)
I ⊥: measuring the absorption intensity when the polarization direction of light is perpendicular to the stretching direction of the polarizing film
I //: measuring the absorption intensity when the polarization direction of light is parallel to the stretching direction of the polarizing film
(3) Monomer transmittance and polarization degree
The polarizing film was peeled from the laminate of polarizing film/thermoplastic resin substrate used in examples and comparative examples, and the single transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc measured by an ultraviolet-visible spectrophotometer (manufactured by japan spectroscopy corporation) were respectively used as Ts, tp, and Tc of the polarizing film. These Ts, tp, and Tc are Y values obtained by measuring and correcting the visibility through a 2-degree field of view (C light source) of JIS Z8701.
From Tp and Tc obtained, the polarization degree P is obtained by the following formula.
The polarization degree P (%) = { (Tp-Tc)/(tp+tc) } 1/2 ×100
It was confirmed that equivalent measurement results were obtained by using any spectrophotometer, as the spectrophotometer was also possible to perform equivalent measurement by using "LPF-200" manufactured by tsukamu electronics corporation.
(4) Breaking strength
The polarizing film was peeled off from the laminate of polarizing film/thermoplastic resin substrate used in examples and comparative examples, and the laminate was placed on a compression tester (manufactured by Kato-tech Co., ltd., product name "NDG5" type for measuring needle penetration force) equipped with a needle, and the laminate was then subjected to puncture at a puncture speed of 0.33 cm/sec under room temperature (23 ℃ C.+ -. 3 ℃ C.) to determine the strength at which the polarizing film was broken as breaking strength (puncture strength). For the evaluation value, the breaking strength of 10 test pieces was measured and the average value thereof was used. The diameter of the needle at the front end of the needle0.5R needle. The measured polarizing film was held and fixed by a jig having a circular opening with a diameter of about 11mm from both sides of the polarizing film, and the center of the opening was pierced with a needle for testing. The breaking strength per unit thickness was used as an index of the breaking difficulty, and evaluated according to the following criteria.
O: breaking strength exceeding 30gf/μm
X: breaking strength of 30gf/μm or less
Example 1
As the thermoplastic resin base material, an amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape and a water absorption of 0.75% and a Tg of about 75℃was used. One side of the resin substrate was subjected to corona treatment (treatment conditions: 55 W.min/m 2).
At 9:1 an aqueous PVA solution (coating liquid) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (trade name "GOHSEFIMER Z410", manufactured by Nippon chemical Co., ltd.).
The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was subjected to free-end unidirectional stretching to 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ℃.
Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insolubilization treatment).
Next, the concentration was adjusted so that the monomer transmittance (Ts) of the finally obtained polarizing film became 41.6% in a dyeing bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ and immersed for 60 seconds (dyeing treatment).
Then, the resultant was immersed in a crosslinking bath (aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide with 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40℃for 30 seconds (crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4.0 wt% and potassium iodide: 5.0 wt%) at a liquid temperature of 62 ℃ and uniaxially stretched between rolls having different peripheral speeds (lengthwise direction) so that the total stretching ratio became 3.0 times (in-water stretching treatment: stretching ratio in-water stretching treatment: 1.25 times).
Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20 ℃ (washing treatment).
Thereafter, the resultant was dried in an oven maintained at 90℃and brought into contact with a SUS-made heating roller maintained at 75℃in surface temperature for about 2 seconds (drying shrinkage treatment). The shrinkage in the width direction of the laminate due to the drying shrinkage treatment was 2%.
In this way, a polarizing film having a thickness of 7.1 μm was formed on the resin substrate.
The orientation function, the monomer transmittance, the polarization degree and the breaking strength of the obtained polarizing film are shown in table 1.
Example 2
A polarizing film having a thickness of 6.6 μm was produced in the same manner as in example 1, except that the stretching ratio in the underwater stretching treatment was 1.45 times and the total stretching ratio was 3.5 times. The obtained polarizing film was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Example 3
A polarizing film having a thickness of 6.1 μm was produced in the same manner as in example 1, except that the stretching ratio in the underwater stretching treatment was 1.67 times and the total stretching ratio was 4.0 times. The obtained polarizing film was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Example 4
A polarizing film having a thickness of 5.6 μm was produced in the same manner as in example 1, except that the stretching ratio in the underwater stretching treatment was 1.87 times and the total stretching ratio was 4.5 times. The obtained polarizing film was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 1
A polarizing film having a thickness of 5.0 μm was produced in the same manner as in example 1, except that the stretching ratio in the stretching treatment in water was set to 2.4 times, the total stretching ratio was set to 5.5 times, and the liquid temperature of the stretching bath was set to 70 ℃. The width residual ratio of the obtained polarizing film was 48% (the shrinkage ratio in the width direction was 52%). The obtained polarizing film was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 2
A polarizing film having a thickness of 5.5 μm was produced in the same manner as in comparative example 1 except that the residual width was 43% (the shrinkage in the width direction was 57%). The obtained polarizing film was subjected to the same evaluation as in example 1. The results are shown in Table 1.
Comparative example 3
A polarizing plate having a thickness of 12 μm was produced by uniaxially stretching a long roll of a PVA based resin film (KURARAY CO., LTD, product name "PE 3000") having a thickness of 30 μm in the longitudinal direction by a roll stretcher so that the total stretching ratio became 6.0 times, simultaneously swelling, dyeing, crosslinking and washing the film, and finally drying the film. The obtained polarizing plate was subjected to the same evaluation as in example 1. The results are shown in Table 1.
TABLE 1
As is clear from table 1, the polarizing film of the example of the present invention has practically acceptable monomer transmittance and polarization degree, and the breaking strength along the absorption axis direction is very large. Such breaking strength means that the polarizing film is less likely to crack along the absorption axis direction.
Industrial applicability
The polarizing film and the polarizing plate of the present invention are suitable for use in a liquid crystal display device.
Description of the reference numerals
10 Polarizing film
201 St protective layer
30 Nd protective layer 2
100 Polarizing plate
Claims (6)
1. A polarizing film comprising a polyvinyl alcohol resin film containing a dichroic material,
The monomer transmittance of the polarizing film is 40.0% or more, and the polarization degree is 99.97% or more,
The orientation function of the polarizing film is 0.05 to 0.25,
The orientation function was measured by attenuated total reflection spectrometry using a fourier transform infrared spectrometer with polarized light as measurement light and with the stretching direction of the polarizing film parallel and perpendicular to the polarization direction of the measurement light, and the intensity of 2941cm -1 of the absorbance spectrum obtained was calculated by the following formula (1):
(1) f= (3 < cos 2 θ > -1)/2
＝(1-D)/[c(2D+1)]
＝-2×(1-D)/(2D+1)
In formula 1, θ represents an angle of a molecular chain with respect to the stretching direction; c represents (3 cos 2 β -1)/2; beta represents an angle of transition dipole moment with respect to a molecular chain axis, and is 90 ° in the case of vibration of 2941cm -1; d represents (I ⊥)/(I//); i represents the value of the absorption intensity of 2941cm -1 relative to the absorption intensity of 3330cm -1 as a reference peak, i.e., (intensity of 2941cm -1)/(intensity of 3330cm -1) in the obtained absorbance spectrum; i ⊥ denotes the I when the stretching direction of the polarizing film is arranged perpendicularly to the polarizing direction of the measurement light; i // denotes the I when the stretching direction of the polarizing film is arranged in parallel with respect to the polarizing direction of the measurement light.
2. The polarizing film according to claim 1, which has a thickness of 8 μm or less.
3. The polarizing film according to claim 1 or 2, which has a puncture strength of 35gf/μm or more.
4. A polarizing film comprising a polyvinyl alcohol resin film containing a dichroic material,
The monomer transmittance of the polarizing film is 40.0% or more, and the polarization degree is 99.97% or more,
The polarizing film has an orientation function of 0.05 or more and a puncture strength of 35 gf/mu m or more,
The orientation function was measured by attenuated total reflection spectrometry using a fourier transform infrared spectrometer with polarized light as measurement light and with the stretching direction of the polarizing film parallel and perpendicular to the polarization direction of the measurement light, and the intensity of 2941cm -1 of the absorbance spectrum obtained was calculated by the following formula (1):
(1) f= (3 < cos 2 θ > -1)/2
＝(1-D)/[c(2D+1)]
＝-2×(1-D)/(2D+1)
In formula 1, θ represents an angle of a molecular chain with respect to the stretching direction; c represents (3 cos 2 β -1)/2; beta represents an angle of transition dipole moment with respect to a molecular chain axis, and is 90 ° in the case of vibration of 2941cm -1; d represents (I ⊥)/(I//); i represents the value of the absorption intensity of 2941cm -1 relative to the absorption intensity of 3330cm -1 as a reference peak, i.e., (intensity of 2941cm -1)/(intensity of 3330cm -1) in the obtained absorbance spectrum; i ⊥ denotes the I when the stretching direction of the polarizing film is arranged perpendicularly to the polarizing direction of the measurement light; i // denotes the I when the stretching direction of the polarizing film is arranged in parallel with respect to the polarizing direction of the measurement light.
5. A polarizing plate is provided with: the polarizing film according to any one of claims 1 to 4, and a protective layer disposed on at least one side of the polarizing film.
6. The method for producing a polarizing film according to any one of claims 1 to 4, comprising:
Forming a polyvinyl alcohol resin layer containing iodide or sodium chloride and containing a polyvinyl alcohol resin on one side of a long thermoplastic resin substrate to form a laminate; and
Sequentially performing an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment for shrinking the laminate by 2% or more in the width direction by heating while conveying the laminate in the longitudinal direction,
The total stretching magnification of the air-assisted stretching treatment and the underwater stretching treatment is 3.0 to 4.0 times relative to the original length of the laminated body,
The stretching magnification of the air auxiliary stretching treatment is larger than that of the stretching treatment in water.
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| JP2019-021236 | 2019-02-08 | ||
| JP2019021236 | 2019-02-08 | ||
| PCT/JP2020/004508 WO2020162531A1 (en) | 2019-02-08 | 2020-02-06 | Polarizing film, polarizing plate and method for manufacturing said polarizing film |
| CN202080012812.1A CN113412439A (en) | 2019-02-08 | 2020-02-06 | Polarizing film, polarizing plate, and method for producing polarizing film |
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| CN114730035A (en) * | 2019-11-11 | 2022-07-08 | 日东电工株式会社 | Polarizing film, polarizing plate and image display device |
| WO2024214690A1 (en) * | 2023-04-13 | 2024-10-17 | 日東電工株式会社 | Polarizing film, image display device, polarized sunglasses, and method for producing polarizing film |
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| JPS5783360A (en) * | 1980-11-11 | 1982-05-25 | Tipton Mfg Corp | Barrel polishing method |
| JP4279944B2 (en) | 1999-06-01 | 2009-06-17 | 株式会社サンリッツ | Manufacturing method of polarizing plate |
| JP2001343521A (en) | 2000-05-31 | 2001-12-14 | Sumitomo Chem Co Ltd | Polarizing plate and method for manufacturing the same |
| JP4691205B1 (en) * | 2010-09-03 | 2011-06-01 | 日東電工株式会社 | Method for producing optical film laminate including thin high-performance polarizing film |
| JP5361941B2 (en) * | 2010-09-03 | 2013-12-04 | 日東電工株式会社 | Method for producing laminate strip roll having polarizing film |
| KR101943664B1 (en) * | 2010-09-09 | 2019-01-29 | 닛토덴코 가부시키가이샤 | Method of producing thin polarizing film |
| JP4975186B1 (en) * | 2010-12-16 | 2012-07-11 | 日東電工株式会社 | Manufacturing method of polarizing film |
| TWI656011B (en) * | 2014-03-14 | 2019-04-11 | 日東電工股份有限公司 | Laminated body, extended laminated body, manufacturing method of extended laminated body, manufacturing method of optical film laminated body including polarizing film using these, and polarizing film |
| JP6075424B2 (en) * | 2014-09-30 | 2017-02-08 | 住友化学株式会社 | Polarizing plate, liquid crystal display device, and organic electroluminescence display device |
| JP6327222B2 (en) * | 2014-09-30 | 2018-05-23 | 住友化学株式会社 | Polarizing plate, polarizing plate with adhesive, and liquid crystal display device |
| CN107111035B (en) * | 2014-12-12 | 2020-05-29 | 住友化学株式会社 | Polarizing film manufacturing method and polarizing film |
| JPWO2016104741A1 (en) * | 2014-12-26 | 2017-09-28 | 富士フイルム株式会社 | Polarizer, polarizing plate and image display device |
| JP2016157081A (en) * | 2015-02-26 | 2016-09-01 | 日東電工株式会社 | Polarizing film with retardation layer, and image display device |
| JP2016191904A (en) * | 2015-03-30 | 2016-11-10 | 住友化学株式会社 | Polarizing plate |
| JP2017102476A (en) * | 2017-02-13 | 2017-06-08 | 日東電工株式会社 | Polarizing film, optical functional film laminate including polarizing film, method of manufacturing optical film laminate including polarizing film, and organic el display device having polarizing film |
| JP6409142B1 (en) * | 2018-02-13 | 2018-10-17 | 日東電工株式会社 | Polarizing film, polarizing plate, and manufacturing method of polarizing film |
| JP7041017B2 (en) * | 2018-07-25 | 2022-03-23 | 日東電工株式会社 | Method for manufacturing a polarizing film and a polarizing film |
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| JP2022111165A (en) | 2022-07-29 |
| KR20210126003A (en) | 2021-10-19 |
| WO2020162531A1 (en) | 2020-08-13 |
| JPWO2020162531A1 (en) | 2021-10-14 |
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| JP2024144775A (en) | 2024-10-11 |
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