TW201915063A - Polarizing plate, polarizing plate roll, and method for producing polarizing film - Google Patents

Abstract

Provided is a polarizing plate that exhibits excellent optical properties and for which variability in the optical properties is suppressed. The polarizing plate according to the present invention is a polarizing plate that has a polarizing film wherein the polarizing film is constituted of an iodine-containing polyvinyl alcohol resin film and has a thickness of not more than 8 [mu]m, a single transmittance of at least 45%, and a degree of polarization of at least 97%.

Description

Polarizing film, polarizing plate, polarizing plate roll and manufacturing method of polarizing film

The invention relates to a method for manufacturing polarizing film, polarizing plate, polarizing plate roll material and polarizing film.

Background of the Invention With the popularity of thin displays, displays (OLEDs) equipped with organic EL panels and displays (QLEDs) using display panels using inorganic materials such as quantum dots have also been proposed. Such panels have a highly reflective metal layer, so it is prone to problems such as external light reflection or background reflection. However, it is known that the circular polarizing plate with the polarizing film and the λ / 4 plate is provided on the viewing side at this time to prevent such problems. For the manufacturing method of the polarizing film, for example, there has been proposed a method of extending a laminate having a resin substrate and a polyvinyl alcohol (PVA) resin layer, and then applying a dyeing treatment to obtain a polarizing film on the resin substrate (for example Patent Literature 1). By this method, a thin polarizing film can be obtained, so it can contribute to the thinning of the image display device in recent years and attracts attention. However, as the above-mentioned conventional thin polarizing film has insufficient optical characteristics, it is required to further improve the optical characteristics of the thin polarizing film.

Prior Art Literature Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. 2001-343521

SUMMARY OF THE INVENTION Problems to be Solved by the Invention The present invention was made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing film, a polarizing plate, a polarizing plate roll material having excellent optical characteristics, and a method for manufacturing the polarizing film.

Means for Solving the Problem The polarizing film of the present invention has a thickness of 8 μm or less, a single transmittance of 45% or more, and a degree of polarization of 97% or more. In one embodiment, the single transmittance is 46% or less, and the degree of polarization is 99% or less. According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate has a polarizing film and a protective layer, which is disposed on at least one side of the polarizing film. In one embodiment, the width of the polarizing plate is 1000 mm or more, and the difference between the maximum value and the minimum value of the unit transmittance at the position in the width direction is 0.5% or less. In one embodiment, the difference between the maximum value and the minimum value of the unit transmittance in the 50 cm ² area of the polarizing plate is 0.2% or less. According to another aspect of the present invention, a polarizing plate roll is provided. The polarizing plate roll is formed by winding the polarizing plate in a roll shape. According to another aspect of the present invention, a method for manufacturing a polarizing film is provided. This manufacturing method is the manufacturing method of the polarizing film described above, and it includes the following steps: forming a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of the elongated thermoplastic resin base material to produce The laminated body; and, the above-mentioned laminated body is sequentially subjected to aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment. It shrinks by more than 2% in the width direction. In one embodiment, the content of the halide in the polyvinyl alcohol-based resin layer is 5 to 20 parts by weight relative to 100 parts by weight of the polyvinyl alcohol-based resin. In one embodiment, the extension magnification in the above-mentioned air assist extension processing is 2.0 times or more. In one embodiment, the drying shrinkage treatment step is a step of heating using a heating roller. In one embodiment, the temperature of the heating roller is 60 ° C. to 120 ° C., and the shrinkage rate in the width direction of the laminate obtained by performing the drying shrinkage treatment is 2% or more.

Effect of the Invention According to the present invention, it is possible to provide an optical characteristic having an excellent polarizing film thickness of 8 μm or less, a single transmittance of 45% or more, and a degree of polarization of 97% or more.

Forms for Carrying Out the Invention Embodiments of the present invention will be described below, but the present invention is not limited by these embodiments.

A. Polarizing film The polarizing film of one embodiment of the present invention has a thickness of 8 μm or less, a single transmittance of 45% or more, and a degree of polarization of 97% or more. Generally speaking, the transmittance of the monomer has a trade-off relationship with the degree of polarization, so if the transmittance of the monomer is increased, the degree of polarization will decrease, and if the polarized degree is increased, the transmittance of the monomer will decrease. Therefore, conventionally, a thin polarizing film that satisfies the optical characteristics of the single body transmittance of 45% or more and the polarization degree of 97% or more is difficult to apply. The polarizing film according to one embodiment of the present invention has excellent optical characteristics such as a single transmittance of 45% or more and a degree of polarization of 97% or more as described above. In addition, by using the polarizing film of this embodiment, a polarizing plate with suppressed variations in optical characteristics can be realized. One of the achievements of the present invention is to realize the thin polarizing film (polarizing plate). The polarizing film (polarizing plate) can be used for image display devices, and is particularly suitable for circular polarizing plates for organic EL display devices.

The thickness of the polarizing film is preferably 1 μm to 8 μm, preferably 1 μm to 7 μm, and more preferably 2 μm to 5 μm.

The polarizing film should show absorption dichroism at any wavelength from 380nm to 780nm. The single transmittance of the polarizing film is preferably 46% or less. The polarization degree of the polarizing film is preferably 97.5% or more, and more preferably 98% or more. On the other hand, the upper limit of polarization is preferably 99%. The above-mentioned monomer transmittance is representatively a Y value obtained by using an ultraviolet visible light spectrophotometer to measure and correct the optical performance. The above-mentioned polarizing degree is representatively obtained by transmitting the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and corrected for the visual performance. Polarization (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100

In one embodiment, the transmittance of a thin polarizing film with a thickness of 8 μm or less is represented by a laminate of a polarizing film (refractive index on the surface: 1.53) and a protective film (refractive index: 1.50) as the measurement object, and ultraviolet-visible light spectroscopy is used Photometer to determine. Depending on the refractive index of the surface of the polarizing film and / or the refractive index of the surface of the protective film in contact with the air interface, the reflectance of each layer at the interface will change, and as a result, the measured value of the transmittance may change. Therefore, for example, when a protective film with a refractive index other than 1.50 is used, the measured value of the transmittance can be corrected according to the refractive index of the surface of the protective film in contact with the air interface. Specifically, the correction value C of the transmittance is represented by the following formula using polarized light reflectance R ₁ (transmission axis reflectance) parallel to the transmission axis of the interface between the protective film and the air layer. _{C = R 1 -R 0 R 0} = ((1.50-1) 2 /(1.50+1) 2) × (T 1/100) R 1 = ((n 1 -1) 2 / (n 1 +1) _{^{2) × (T 1/100}} ) here, R ₀ is a refractive index of transmission axis reflectance of the protective film is 1.50, n ₁ is the refractive index of the protective film to be used, and T ₁ is transmittance of the polarizing film rate. For example, when using a substrate with a surface refractive index of 1.53 (cycloolefin-based film, hard-coated film, etc.) as the protective film, the correction amount C is about 0.2%. At this time, adding 0.2% to the measured transmittance can be converted to transmittance when using a protective film with a surface refractive index of 1.50. In addition, after calculation according to the above formula, the amount of change in the correction value C when the transmittance T _{1 of the} polarizing film is changed by 2% is 0.03% or less, so the influence of the transmittance of the polarizing film on the value of the correction value C is limited. In addition, when the protective film has absorption other than surface reflection, appropriate correction can be performed according to the absorption amount.

Any and appropriate polarizing films can be used for the polarizing film. Representatively, the polarizing film can be produced by 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 substrate and a PVA-based resin layer formed on the resin substrate by coating. 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 can be produced, for example, by applying a PVA-based resin solution to the resin base material, and It is dried to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; and the laminate is stretched and dyed to make the PVA-based resin layer into a polarizing film. In the present embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution and stretching. Furthermore, if necessary, the stretching may further include aerial stretching the laminate at a high temperature (for example, 95 ° C. or higher) before stretching in the boric acid aqueous solution. The resulting resin substrate / polarizing film laminate can be used directly (that is, the resin substrate can be used as the protective layer of the polarizing film), or the resin substrate can be peeled from the resin substrate / polarizing film laminate and the peeling surface Depending on the purpose, an arbitrary and appropriate protective layer may be used later. The details of the manufacturing method of the polarizing film are described in, for example, Japanese Patent Laid-Open No. 2012-73580. In this specification, the entire contents of this gazette are used as a reference.

The method for manufacturing a polarizing film of the present invention includes the following steps: forming a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate to form a laminate; and, The above-mentioned layered body is sequentially subjected to an air assisted stretching process, a dyeing process, an underwater stretching process, and a drying shrinkage process which heats the above-mentioned layered body while being transported in the longitudinal direction, thereby shrinking it in the width direction 2% or more. Thereby, it is possible to provide a polarizing film having excellent optical characteristics and suppressed optical characteristics. The thickness of the polarizing film is 8 μm or less, the monomer transmittance is 45% or more, and the degree of polarization is 97% or more. That is, by introducing auxiliary extension, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical characteristics can be achieved. At the same time, increasing the orientation of PVA in advance can prevent problems such as lowering of orientation and dissolution of PVA when immersed in water in the subsequent dyeing step and extension step, and high optical characteristics can be achieved. In addition, when the PVA-based resin layer is immersed in a liquid, it is possible to suppress the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the alignment as compared to the case where the PVA-based resin layer does not contain a halide. Therefore, it is possible to improve the optical characteristics of the polarizing film produced by the treatment step performed by immersing the laminate in a liquid such as dyeing treatment and water extension treatment. In addition, the transmission drying shrinkage process shrinks the laminate in the width direction, which can improve the optical characteristics.

B. Polarizing plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The polarizing plate 100 includes: a polarizing film 10; a first protective layer 20 disposed on one side of the polarizing film 10; and a second 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 the above item A. One of the first protective layer 20 and the second protective layer 30 may be omitted. In addition, as described above, one of the first protective layer and the second protective layer may also be a resin substrate used for the manufacture of the polarizing film.

The polarizing plate may be long or thin. When the polarizing plate is elongated, it should be wound into a roll to form a polarizing plate roll. Then the polarizing plate has excellent optical characteristics and the variation of the optical characteristics is also small. In one embodiment, the width of the polarizing plate is 1000 mm or more, and the difference (D1) between the maximum value and the minimum value of the unit transmittance at the position in the width direction is 0.5% or less. The upper limit of D1 is preferably 0.4%, and more preferably 0.3%. The smaller D1 is, the better, but the lower limit is, for example, 0.01%. As long as D1 is within the above range, a polarizing plate with excellent optical characteristics can be industrially produced. In another embodiment, the difference (D2) between the maximum value and the minimum value of the unit transmittance of the polarizing plate in a region of 50 cm ² is 0.2% or less. The upper limit of D2 is preferably 0.15%, and more preferably 0.1%. The smaller D2 is, the better, but the lower limit is, for example, 0.01%. As long as D2 is within the above range, the brightness unevenness of the display screen can be suppressed when the polarizing plate is used in the image display device.

The first and second protective films are formed of any suitable films that can be used as protective layers for polarizing films. Specific examples of the material of the main component of the film include cellulose resins such as triethyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, and polyacetyl Transparent resins such as imine-based, polyether-based, poly-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth) acrylic, and acetate-based. In addition, thermosetting resins such as (meth) acrylic system, urethane system, (meth) acrylate urethane system, epoxy system, and polysiloxane system, ultraviolet curing resin, etc. may also be mentioned. Other examples include glassy polymers such as siloxane-based polymers. Moreover, the polymer film described in Japanese Patent Laid-Open No. 2001-343529 (WO01 / 37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted amide imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used And, for example, a resin composition having an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded 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 more It should be 10μm ~ 60μm. In addition, when surface treatment is performed, the thickness of the outer protective layer includes 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 (inside 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 one embodiment, the inner protective layer is a phase difference layer having any appropriate phase difference value. At this time, the in-plane retardation Re (550) of the retardation layer is, for example, 110 nm to 150 nm. "Re (550)" is the in-plane phase difference measured at 23 ° C with light having a wavelength of 550 nm, and is obtained by the transmission formula: Re = (nx-ny) × d. Here, "nx" is the refractive index in the direction in which the in-plane refractive index becomes maximum (that is, the direction of the slow axis), and "ny" is the refractive index in the direction orthogonal to the slow axis (that is, the direction of the fast axis) in the plane , "Nz" is the refractive index in the thickness direction, and "d" is the thickness (nm) of the layer (thin film).

C. Method for manufacturing polarizing film The method for manufacturing polarizing film according to an embodiment of the present invention includes the following steps: forming a halide and polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate The polyvinyl alcohol-based resin layer (PVA-based resin layer) is formed to form a laminate; and, the laminate is sequentially subjected to aerial assisted extension treatment, dyeing treatment, underwater extension treatment and drying shrinkage treatment. The drying shrinkage treatment system The laminate is heated while being transported in the longitudinal direction, thereby contracting it by 2% or more in the width direction. The halide content in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. Drying shrinkage treatment should be processed by heating roller, and the temperature of heating roller should be 60 ℃ ~ 120 ℃. The shrinkage rate in the width direction of the laminate obtained by performing the drying shrinkage treatment is preferably 2% or more. The polarizing film described in the above item A can be produced according to the above manufacturing method. In particular, a polarizing film having excellent optical characteristics (typically, monomer transmittance and polarization degree) and suppressed variations in optical characteristics can be produced by producing a laminate including a PVA-based resin layer containing a halide Then, the extension of the above-mentioned layered body is set to a multi-stage extension including air-assisted extension and underwater extension, and then the extended layered body is heated by a heating roller. Specifically, by using a heating roller in the drying shrinkage treatment step, it is possible to uniformly shrink the entire laminate while transporting the laminate. This can not only improve the optical characteristics of the polarizing film produced, but also stably produce a polarizing film with excellent optical characteristics, and can suppress variations in the optical characteristics of the polarizing film (especially the single transmittance).

C-1. Production of laminated body The method of producing a laminated body of a thermoplastic resin base material and a PVA-based resin layer can adopt any appropriate method. It is preferable to apply a coating solution containing a halide and a PVA-based resin to the surface of the thermoplastic resin substrate and dry it, thereby forming a PVA-based resin layer on the thermoplastic resin substrate. As described above, the halide content in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.

The method for applying the coating liquid can be any appropriate method. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a doctor blade coating method (comma coating method, etc.), etc. are mentioned. The coating and drying temperature of the coating liquid is preferably 50 ° C or higher.

The thickness of the PVA-based resin layer is preferably 3 μm to 40 μm, and more preferably 3 μm to 20 μm.

Before forming the PVA-based resin layer, the thermoplastic resin substrate may be subjected to surface treatment (eg, corona treatment, etc.), or an easy adhesion layer may be formed on the thermoplastic resin substrate. By performing the above treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.

C-1-1. Thermoplastic resin base material The thickness of the thermoplastic resin base material is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. If it is greater than 300 μm, for example, the thermoplastic resin substrate may take a long time to absorb water during the water stretching process described below, and may cause excessive load on the stretching.

The water absorption rate of the thermoplastic resin substrate is preferably 0.2% or more, and more preferably 0.3% or more. Thermoplastic resin substrate absorbs water, and water can play the role of plasticizer for plasticization. As a result, the extension stress can be greatly reduced and the extension can be performed at a high rate. On the other hand, the water absorption rate of the thermoplastic resin substrate is preferably 3.0% or less, and more preferably 1.0% or less. By using such a thermoplastic resin base material, it is possible to prevent the dimensional stability of the thermoplastic resin base material from being significantly reduced during manufacturing, which may cause defects such as deterioration of the appearance of the polarizing film produced. It can prevent the base material from breaking when extending in water, or the PVA-based resin layer peeling off from the thermoplastic resin base material. In addition, the water absorption rate of the thermoplastic resin base material can be adjusted by, for example, introducing a modified group into the constituent material. The water absorption rate is a value determined in accordance with JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 120 ° C or lower. By using such a thermoplastic resin base material, the crystallization of the PVA-based resin layer can be suppressed, and the extensibility of the laminate can be sufficiently ensured. In addition, considering the use of water to plasticize the thermoplastic resin base material and good water extension, it is preferably 100 ° C or lower, more preferably 90 ° C or lower. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably 60 ° C or higher. By using such a thermoplastic resin base material, it is possible to prevent defects such as deformation of the thermoplastic resin base material (such as unevenness, sag, wrinkle, etc.) when coating and drying the coating solution containing the PVA-based resin In this case, the laminate can be produced satisfactorily. In addition, the PVA-based resin layer can be stretched well at an appropriate temperature (for example, about 60 ° C). In addition, the glass transition temperature of the thermoplastic resin substrate can be adjusted by, for example, heating by using a crystallization material that can introduce a modified group into the constituent material. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

As the constituent material of the thermoplastic resin base material, any suitable thermoplastic resin can be used. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, and polycarbonate resins. , And other copolymer resins. Among these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are more desirable.

In one embodiment, an amorphous (uncrystallized) polyethylene terephthalate resin is preferably used. Among them, the use of amorphous (difficult to crystallize) polyethylene terephthalate resins is particularly preferred. Specific examples of the amorphous polyethylene terephthalate-based resin include copolymers further containing isophthalic acid and / or cyclohexane dicarboxylic acid as the dicarboxylic acid, or cyclohexane dicarboxylic acid. Methanol or diethylene glycol is a copolymer of glycol.

In a preferred embodiment, the thermoplastic resin base material is composed of a polyethylene terephthalate resin having isophthalic acid units. This is because the thermoplastic resin base material has extremely excellent extensibility and can suppress crystallization during elongation. We speculate that it is caused by the introduction of isophthalic acid units through transmission, giving the main chain a great buckling. The polyethylene terephthalate-based resin has terephthalic acid units and ethylene glycol units. The content ratio of the isophthalic acid unit is preferably 0.1 mol% or more relative to the total of all the repeating units, and more preferably 1.0 mol% or more. This is because a thermoplastic resin substrate with extremely excellent elongation can be produced. On the other hand, the content ratio of the isophthalic acid unit is preferably 20 mol% or less relative to the total of all repeating units, and more preferably 10 mol% or less. By setting the content ratio, the degree of crystallization can be favorably increased in the drying shrinkage treatment described later.

The thermoplastic resin base material may have been previously stretched (before the PVA-based resin layer is formed). In one embodiment, it is extended along the width direction of the long thermoplastic resin base material. The width direction is preferably a direction orthogonal to the extending direction of the laminate to be described later. In addition, the term "orthogonal" in this specification also includes the case where it is substantially orthogonal. In addition, "substantially orthogonal" includes 90 ° ± 5.0 °, preferably 90 ° ± 3.0 °, and more preferably 90 ° ± 1.0 °.

The extension temperature of the thermoplastic resin substrate should be Tg-10 ° C ~ Tg + 50 ° C relative to the glass transition temperature (Tg). The extension ratio of the thermoplastic resin base material is preferably 1.5 times to 3.0 times.

The method for stretching the thermoplastic resin substrate can adopt any suitable method. Specifically, it may be a fixed end or a free end. The extension method can be dry or wet. The extension of the thermoplastic resin substrate can be performed in one stage or in multiple stages. When performing in multiple stages, the above-mentioned stretching magnification is the product of the stretching magnifications in each stage.

C-1-2. Coating liquid As mentioned above, the coating liquid contains halide and PVA resin. The coating liquid represents a solution obtained by dissolving the halide and the PVA resin in a solvent. Examples of the solvent include polyhydric alcohols such as water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, and trimethylolpropane. Diamines, diethylenetriamine and other amines. These can be used alone or in combination of two or more. Among these, water is better. The concentration of the PVA resin in the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. As long as it is the resin concentration, a uniform coating film adhered to the thermoplastic resin substrate can be formed. The halide content in the coating liquid is preferably 5-20 parts by weight relative to 100 parts by weight of the PVA-based resin.

Additives can also be incorporated in the coating solution. Examples of additives include plasticizers and surfactants. Examples of plasticizers include polyhydric alcohols such as ethylene glycol and glycerin. The surfactant may, for example, be a nonionic surfactant. These can be used to further improve the uniformity, dyeability, and extensibility of the resulting PVA-based resin layer.

Any appropriate resin can be used for the PVA-based resin. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of the PVA 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 degree of saponification is determined in accordance with JIS K 6726-1994. By using the saponification degree PVA-based resin, a polarizing film excellent in durability can be obtained. When the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. In addition, the average degree of polymerization can be obtained in accordance with JIS K 6726-1994.

Any suitable halide can be used as the above-mentioned halide. Examples include iodide and sodium chloride. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred.

The amount of 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 is more than 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may overflow and the polarizing film finally made may become cloudy.

Generally speaking, when the PVA resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA resin layer becomes higher, but if the stretched PVA resin layer is immersed in a liquid containing water, there will be polyethylene The orientation of alcohol molecules is disordered and the alignment is reduced. Especially when the laminate of the thermoplastic resin and the PVA-based resin layer is stretched in boric acid water, in order to stabilize the stretching of the thermoplastic resin, when the laminate is stretched in boric acid water at a relatively high temperature, the degree of orientation decreases The tendency is remarkable. For example, the extension of the PVA film monomer in boric acid water is generally carried out at 60 ° C. In contrast, the extension of the laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is 70 The temperature before and after ℃ is carried out at a relatively high temperature. At this time, the orientation of the PVA at the initial stage of stretching will decrease before the stage of rise due to stretching in water. In this regard, after preparing a laminate of a halide-containing PVA-based resin layer and a thermoplastic resin base material, the laminate is subjected to high-temperature elongation (auxiliary extension) in air before being extended in boric acid water, thereby promoting auxiliary extension Crystallization of the PVA-based resin in the PVA-based resin layer of the later laminate. As a result, when the PVA-based resin layer is immersed in the liquid, the orientation disorder and the decrease in the orientation of the polyvinyl alcohol molecule can be suppressed more than when the PVA-based resin layer contains no halide. Therefore, it is possible to improve the optical characteristics of the polarizing film produced by the treatment step performed by immersing the laminate in a liquid such as dyeing treatment and water extension treatment.

C-2. Air-assisted extension processing Especially in order to obtain high optical characteristics, the two-stage extension method combining dry extension (auxiliary extension) and boric acid underwater extension will be selected. Such as the two-stage extension method, by introducing auxiliary extension, the extension of the thermoplastic resin substrate can be suppressed while suppressing the crystallization of the thermoplastic resin substrate, and the extension caused by the excessive crystallization of the thermoplastic resin substrate in the subsequent boric acid water extension The problem of lowered performance makes it possible to extend the laminate at a higher magnification. In addition, when coating the PVA resin on the thermoplastic resin substrate, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate, it is necessary to apply the PVA resin on a general metal drum The situation is even lower, and as a result, there is a problem that the crystallization of the PVA-based resin becomes relatively low and sufficient optical characteristics cannot be obtained. In this regard, by introducing auxiliary stretching, the crystallinity of the PVA-based resin can be improved even when the PVA-based resin is coated on the thermoplastic resin, and high optical characteristics can be achieved. At the same time, the orientation of the PVA-based resin is improved in advance to prevent problems such as reduced orientation and dissolution of the PVA-based resin when immersed in water in the subsequent dyeing step and extension step, and high optical characteristics can be achieved.

The extension method of air-assisted extension can be fixed-end extension (such as the method of using a tenter stretching machine) or free-end extension (such as the method of uniaxially extending the laminate through rollers with different peripheral speeds) However, in order to obtain high optical characteristics, the free end extension can be actively used. In one embodiment, the aerial stretching process includes a heating roller stretching step, which is to transport the above-mentioned layered body along its longitudinal direction and at the same time extend using the circumferential speed difference between the heating rollers. The air stretching process typically includes a zone stretching step and a heating roller stretching step. In addition, the order of the region stretching step and the heating roller stretching step is not limited, and the region stretching step may be performed first, or the heating roller stretching step may be performed first. The region extension step can also be omitted. In one embodiment, the region extending step and the heating roller extending step are performed in sequence. Furthermore, in another embodiment, the film end is held in a tenter stretching machine, and the distance between the tenter machines is expanded in the flow direction to extend (the increase in the distance between the tenter machines 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. Preferably, it can be set to an extension magnification with respect to the flow direction to use free-end extension for approach. When the free end is extended, it is calculated as the shrinkage ratio in the width direction = (1 / extension ratio) ^1/2 .

The air-assisted extension can be performed in one stage or in multiple stages. When carried out in multiple stages, the stretching magnification is the product of the stretching magnifications in each stage. The extension direction in the air-assisted extension should be slightly the same as the extension direction in the water.

The extension magnification of air-assisted extension should be 2.0 to 3.5 times. The maximum extension magnification when combining air-assisted extension and underwater extension is preferably 5.0 times or more relative to the original length of the laminate, preferably 5.5 times or more, and more preferably 6.0 times or more. The "maximum elongation ratio" in this specification means the elongation ratio before the laminate is to be broken, and it is a value that is 0.2 lower than its value after confirming the elongation ratio of the laminate to break.

The extension temperature of the air-assisted extension can be set to an arbitrary and appropriate value according to the forming material of the thermoplastic resin base material, the extension method, and the like. The elongation temperature is preferably higher than the glass transition temperature (Tg) of the thermoplastic resin substrate, while the glass transition temperature (Tg) of the thermoplastic resin substrate is more than 10 ° C and more preferably Tg + 15 ° C. On the other hand, the upper limit of the extension temperature is preferably 170 ° C. Elongation at the above-mentioned temperature can suppress the rapid progress of crystallization of the PVA-based resin, thereby suppressing the disadvantages caused by the crystallization (for example, hindering the orientation of the PVA-based resin layer due to extension).

C-3. Insolubilization treatment If necessary, insolubilization treatment may be performed after the air-assisted extension treatment and before the water extension treatment or dyeing treatment. The above-mentioned insolubilization treatment represents that the PVA-based resin layer is immersed in an aqueous solution of boric acid. By performing the insolubilization treatment, the PVA-based resin layer can be provided with water resistance, and the orientation of the PVA can be prevented from decreasing when immersed in water. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight relative to 100 parts by weight of water. The liquid temperature of the insoluble bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C.

C-4. Dyeing treatment The above dyeing treatment is performed by dyeing the PVA-based resin layer with iodine. Specifically, it is performed by adsorbing iodine to the PVA-based resin layer. Examples of the adsorption method include a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and spraying the dyeing solution to the PVA Method on the resin layer. The method of immersing the laminate in the dyeing liquid (dyeing bath) is preferably used. This is because it can adsorb iodine well.

The above dyeing solution is preferably an aqueous iodine solution. The blending amount of iodine is preferably 0.05 parts by weight to 0.5 parts by weight relative to 100 parts by weight of water. In order to improve the solubility of iodine in water, it is appropriate to mix iodide in the iodine aqueous solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred. The blending amount of the iodide is preferably 0.1 to 10 parts by weight relative to 100 parts by weight of water, and more preferably 0.3 to 5 parts by weight. In order to suppress the dissolution of the PVA-based resin, the temperature of the dyeing liquid during dyeing is preferably 20 ° C to 50 ° C. When immersing the PVA-based resin layer in the dyeing solution, in order to ensure the transmittance of the PVA-based resin layer, the immersion time is preferably 5 seconds to 5 minutes, and more preferably 30 seconds to 90 seconds.

The dyeing conditions (concentration, liquid temperature, immersion time) can be set such that the monomer transmittance of the polarizing film finally obtained is 45% or more and the degree of polarization becomes 97% or more. The dyeing condition is preferably to use an iodine aqueous solution as the dyeing solution, and set the content ratio of iodine and potassium iodide in the iodine aqueous solution to be 1: 5 to 1:20. The content ratio of iodine and potassium iodide in the iodine aqueous solution is preferably 1: 5 ~ 1: 10. Through the above procedure, a polarizing film having the optical characteristics as described above can be produced.

When the layered body is immersed in a treatment bath containing boric acid (typically insoluble treatment) and then dyeing is carried out, the boric acid contained in the treatment bath will be mixed into the dyeing bath and the concentration of boric acid in the dyeing bath will vary As time changes, the dyeing may become unstable. In order to suppress the above-mentioned destabilization of the dyeing property, the upper limit of the boric acid concentration of the dyeing bath is adjusted to 4 parts by weight relative to 100 parts by weight of water, more preferably to 2 parts by weight. On the other hand, the lower limit of the boric acid concentration of the dyeing bath is preferably 0.1 part by weight, more preferably 0.2 part by weight, and still more preferably 0.5 part by weight with respect to 100 parts by weight of water. In one embodiment, a dyeing bath in which boric acid has been blended in advance is used for dyeing treatment. In this way, the ratio of the change in boric acid concentration when the boric acid in the treatment bath is mixed into the dyeing bath can be reduced. The amount of boric acid blended into the dyeing bath in advance (that is, the content of boric acid not derived from the above treatment bath) is preferably 0.1 to 2 parts by weight, more preferably 0.5 parts by weight relative to 100 parts by weight of water ~ 1.5 parts by weight.

C-5. Cross-linking treatment If necessary, cross-linking treatment may be performed after dyeing treatment and before extension treatment in water. The above-mentioned cross-linking treatment can be performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. By performing the cross-linking treatment, the PVA-based resin layer can be provided with water resistance, and the orientation of the PVA can be prevented from decreasing when immersed in high-temperature water during subsequent water stretching. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 5 parts by weight relative to 100 parts by weight of water. In addition, when the cross-linking treatment is performed after the above-mentioned dyeing treatment, it is preferable to further blend iodide. By blending iodide, the elution of iodine that has been adsorbed on the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight relative to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the cross-linking bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C.

C-6. Stretching treatment in water Stretching treatment in water allows the laminate to be immersed in a stretch bath. By water stretching, it can be stretched at a temperature lower than the glass transition temperature of the thermoplastic resin substrate or the PVA-based resin layer (typically around 80 ° C), and can suppress the crystallization of the PVA-based resin layer. At the same time, high magnification extension. As a result, a polarizing film having excellent optical characteristics can be produced.

The method of extending the laminate can be any suitable method. Specifically, it may be a fixed-end extension or a free-end extension (for example, a method of uniaxially extending a laminate between rollers having different peripheral speeds). Preferably, the free end extension is selected. The extension of the laminate can be performed in one stage or in multiple stages. When performing in multiple stages, the stretching magnification (maximum stretching magnification) of the laminate to be described later is the product of the stretching magnification in each stage.

The extension in water is preferably carried out by immersing the laminate in an aqueous solution of boric acid (boric acid extension in water). By using an aqueous solution of boric acid as an extension bath, the PVA-based resin layer can be given rigidity to withstand tension during extension and water resistance insoluble in water. Specifically, boric acid generates tetrahydroxyboric acid anions in the aqueous solution and can be cross-linked with the PVA-based resin by hydrogen bonding. As a result, it is possible to impart rigidity and water resistance to the PVA-based resin layer and perform good stretching, thereby producing a polarizing film having excellent optical characteristics.

The aforementioned boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in a solvent, that is, water. On the other hand, the concentration of boric acid is preferably 1 part by weight to 10 parts by weight relative to 100 parts by weight of water, more preferably 3 parts by weight to 6.5 parts by weight, and particularly preferably 3.5 parts by weight to 5.5 parts by weight. By setting the concentration of boric acid to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film with higher characteristics can be manufactured. In addition to boric acid or borate, an aqueous solution obtained by dissolving boron compounds such as borax, glyoxal, glutaraldehyde and the like in a solvent can also be used.

It is suitable to blend iodide in the above extension bath (boric acid aqueous solution). By blending iodide, the elution of iodine that has been adsorbed on the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably 0.05 to 15 parts by weight relative to 100 parts by weight of water, and more preferably 0.5 to 8 parts by weight.

The extension temperature (the liquid temperature of the extension bath) is preferably 40 ° C to 85 ° C, and more preferably 60 ° C to 75 ° C. As long as the temperature is within the above range, the PVA-based resin layer can be suppressed from dissolving, and at the same time, it can be stretched at a high rate. Specifically, as described above, considering the relationship with the formation of the PVA-based resin layer, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60 ° C. or higher. At this time, if the elongation temperature is lower than 40 ° C, even if it is considered that the thermoplastic resin base material can be plasticized with water, it may not be able to elongate well. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and it may be impossible to obtain excellent optical characteristics. The immersion time of the laminate in the extension bath is preferably 15 seconds to 5 minutes.

The stretching magnification in the underwater stretching treatment is preferably 1.5 times or more, preferably 3.0 times or more. The total stretching ratio of the laminate is preferably 5.0 times or more relative to the original length of the laminate, and more preferably 5.5 times or more. By achieving the above-mentioned high extension magnification, a polarizing film with extremely excellent optical characteristics can be manufactured. The high extension ratio can be achieved by using an underwater extension method (boric acid underwater extension).

C-7. Drying shrinkage treatment The above-mentioned drying shrinkage treatment can be carried out through the area heating by heating the entire area, or through the heating of the conveying roller (so-called using a heating roller) (heating roller drying method). It is preferable to use both. By using a heating roller to dry, the heating curl of the laminate can be effectively suppressed, and a polarizing film excellent in appearance can be manufactured. Specifically, by drying the laminate along the heating roller, the crystallization of the thermoplastic resin substrate can be effectively promoted to increase the degree of crystallization, even at a relatively low drying temperature , Can still increase the crystallinity of thermoplastic resin substrates. As a result, the rigidity of the thermoplastic resin base material is increased to be able to withstand shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. In addition, by using a heating roller, the laminate can be dried while maintaining a smooth state. Therefore, not only the generation of curl but also the generation of wrinkles can be suppressed. At this time, the laminate can be shrunk in the width direction through the drying shrinkage treatment to improve the optical characteristics. It is because it can effectively improve the orientation of PVA and PVA / iodine complex. The shrinkage rate in the width direction of the laminate obtained by performing the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using a heating roller, the laminate can be transported while continuously shrinking in the width direction, and high productivity can be achieved.

Fig. 2 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage treatment, the transport rollers R1 to R6 and guide rollers G1 to G4 that have been heated to a predetermined temperature are used to transport the laminate 200 while drying. In the illustrated example, the conveying rollers R1 to R6 are arranged such that the surface of the PVA resin layer and the surface of the thermoplastic resin substrate can be alternately and continuously heated. One side of 200 (for example, thermoplastic resin substrate side).

The drying conditions can be controlled by adjusting the heating temperature of the conveyor roller (temperature of the heating roller), the number of heating rollers, and the contact time with the heating roller. The temperature of the heating roller is preferably 60 ° C to 120 ° C, more preferably 65 ° C to 100 ° C, and particularly preferably 70 ° C to 80 ° C. It is possible to increase the crystallinity of the thermoplastic resin well and suppress curl effectively, and to manufacture an optical laminate with extremely excellent durability. In addition, the temperature of the heating roller can be measured with a contact thermometer. There are six conveying rollers in the illustrated example, but there are no particular restrictions as long as there are a large number of conveying rollers. There are usually 2 to 40 conveying rollers, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roller is preferably 1 second to 300 seconds, preferably 1 to 20 seconds, and more preferably 1 to 10 seconds.

The heating roller may be installed in a heating furnace (for example, an oven), or may be installed in a general manufacturing line (room temperature environment). It should be installed in the heating furnace with air supply mechanism. By using the heating roller for drying and hot air drying, the rapid temperature change between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying should be 30 ℃ ~ 100 ℃. Moreover, the hot air drying time should be 1 second to 300 seconds. The wind speed of hot air should be about 10m / s ~ 30m / s. In addition, the wind speed is the wind speed in the heating furnace, which can be measured with a mini fan-type digital anemometer.

C-8. Other treatments It is advisable to perform washing treatment after extension treatment in water and before drying shrinkage treatment. The above-mentioned cleaning treatment can be performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution. Examples

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measuring method of each characteristic is as follows. In addition, as long as there is no special note, "parts" and "%" in the examples and comparative examples are based on weight. (1) The thickness was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). (2) Transmittance and polarization of monomers The polarizing plates (protective film / polarizing film) of Examples and Comparative Examples were measured using an ultraviolet visible light spectrophotometer (V-7100 manufactured by Japan Spectroscopy Co., Ltd.) and measured The single transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc are respectively Ts, Tp, and Tc of the polarizing film. These Ts, Tp, and Tc are Y values obtained by measuring the 2 degree field of view (C light source) of JIS Z8701 and correcting the visual performance. In addition, the refractive index of the protective film is 1.50, and the refractive index of the surface of the polarizing film on the side opposite to the protective film is 1.53. From the obtained Tp and Tc, the polarization degree P was obtained by the following formula. Polarization P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100 In addition, the spectrophotometer can also use LPF-200 manufactured by Otsuka Electronics Co., Ltd. for equivalent measurement. As an example, for samples 1 to 3 having polarizing plates with the same configuration as the following examples, V-7100 and LPF-200 were used for measurement, and the measured single transmittance Ts and polarization degree P The measured values are listed in Table 1. As shown in Table 1, the difference between the measured value of the transmittance of the monomer of V-7100 and the measured value of the transmittance of the monomer of LPF-200 is 0.1% or less. It can be seen that the same measurement can be obtained regardless of the use of any spectrophotometer result. [Table 1] In addition, for example, when a polarizing plate with anti-glare (AG) surface treatment or an adhesive with diffusion properties is used as the measurement object, different measurement results will be obtained according to the spectrophotometer. At this time, by applying The measurement value obtained when each spectrophotometer measures the same polarizing plate is used as a reference to perform numerical conversion to compensate for the difference in the measurement value obtained by the spectrophotometer. (3) Variations in the optical characteristics of the long polarizing plate The long polarizing plates of the examples and the reference examples were cut out at five positions at equal intervals in the width direction, and then the measurement samples were cut out in accordance with the above (2) In the same manner, the individual transmittance of the central portion of each of the five measurement samples was measured. Next, the difference between the maximum value and the minimum value of the monomer transmittance measured at each measurement position is calculated, and this value is used as the variation of the optical characteristics of the long polarizing plate (the position of the long polarizing plate in the width direction) The difference between the maximum value and the minimum value of the single cell transmittance). (4) Variations in the optical characteristics of the sheet-shaped polarizing plate The measurement samples of 100 mm × 100 mm were cut out from the elongated polarizing plates of Examples and Reference Examples, and the optical characteristics of the sheet-shaped polarizing plate (50 cm ² ) were obtained Jagged. Specifically, in the same manner as in the above (2), the monomer transmittances at a total of 5 locations in the center and about 1.5 cm to 2.0 cm from the midpoint of each of the four sides of the measurement sample are measured. Next, calculate the difference between the maximum value and the minimum value of the monomer transmittance measured at each measurement position, and use this value as the variation of the optical characteristics of the sheet-shaped polarizer (the monomer transmittance in the area of 50 cm ² The difference between the maximum value and the minimum value).

[Example 1] 1. A polarized film thermoplastic resin substrate was produced by using a long-length amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 0.75% water absorption rate, Tg about 75 ° C) 100μm). Corona treatment is applied to one side of the resin substrate. In the PVA series made by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetylacetonyl modified PVA (manufactured by Japan Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") at 9: 1 To 100 parts by weight of the resin, 13 parts by weight of potassium iodide was added to prepare a PVA aqueous solution (coating solution). The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C., thereby forming a PVA-based resin layer with a thickness of 13 μm to produce a laminate. The obtained laminate was uniaxially stretched by 2.4 times in the longitudinal direction (longitudinal direction) between the rollers of different peripheral speeds in the oven at 130 ° C. in the longitudinal direction (longitudinal direction) (air-assisted extension). Next, the laminate was immersed in an insoluble bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40 ° C for 30 seconds (insoluble treatment). Next, adjust the concentration of the dyeing bath (the aqueous iodine solution obtained by mixing iodine and potassium iodide at a weight ratio of 1: 7 with respect to 100 parts by weight of water at a liquid temperature of 30 ° C) to adjust the concentration of the polarized film finally prepared The volume transmittance (Ts) becomes 45% or more and is simultaneously immersed in it for 60 seconds (dyeing treatment). Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40 ° C (crosslinking treatment ). Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.5% by weight) at a liquid temperature of 70 ° C, uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between the rollers having different peripheral speeds to increase the total stretching ratio Up to 5.5 times (extended treatment in water). Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20 ° C. (washing treatment). Thereafter, while being dried in an oven maintained at 90 ° C, the SUS-made heating roller whose contact surface temperature was maintained at 75 ° C was maintained for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate obtained by performing the drying shrinkage treatment was 5.2%. Through the above procedure, a polarizing film with a thickness of 5 μm was formed on the resin substrate. In addition, the same procedure was repeated to produce a total of five polarizing films. 2. Production of polarizing plates On the surface of each polarizing film prepared above (the surface opposite to the resin substrate), an acrylic film (surface refractive index 1.50, 40 μm) is bonded as a protective film through an ultraviolet curing adhesive. Specifically, the total thickness of the adhesive applied to the curing type is 1.0 μm, and the lamination is performed using a rolling machine. Thereafter, UV light is irradiated from the protective film side to harden the adhesive. Next, after cutting off both ends, the resin substrate was peeled off to obtain five long polarizing plates (width: 1300 mm) having a protective film / polarizing film configuration.

[Reference Example 1] A dyeing process was performed so that the polarized film finally prepared had a single transmittance (Ts) of 43% or more and less than 45%, except that six polarized lights were produced in the same manner as in Example 1. Film and polarizing plate.

[Example 2] Four drying polarizing films and polarizing plates were produced in the same manner as in Example 1 except that the oven temperature was 70 ° C and the heating roller temperature was 70 ° C during the drying shrinkage treatment. The shrinkage rate in the width direction of the laminate obtained by performing the drying shrinkage treatment was 2.5%.

[Reference Example 2] A dyeing process was carried out so that the polarized film finally produced had a single transmittance (Ts) of 43% or more and less than 45%, except that 6 polarized lights were produced in the same manner as in Example Film and polarizing plate.

[Comparative Example 1] Potassium iodide was not added to the PVA aqueous solution (coating liquid), and the stretching ratio in the air assisted stretching process was set to 1.8 times, and the heating roller was not used in the drying shrinkage process. In the same manner as in Example 1, an attempt was made to produce a polarizing film, but the PVA-based resin layer was dissolved during the dyeing process and the water extension process, and a polarizing film could not be produced.

[Comparative Example 2] Nine polarizing films and polarizing films were produced in the same manner as in Example 1 except that the stretching ratio in the air-assisted stretching process was set to 1.8 times, and that the heating roller was not used in the drying shrinkage process. board. However, a polarizing film with a single transmittance of more than 45% cannot be produced.

[Reference Example 3] The polarizing film prepared in the same manner as Comparative Example 2 was kept in a constant temperature and constant humidity area set at a temperature of 60 ° C. and a humidity of 90% RH for 30 minutes. Thereafter, a polarizing plate was produced in the same manner as in Example 1.

For each polarizing plate of Examples and Comparative Examples, the single transmittance and the degree of polarization were measured. The results are shown in Table 2 and Figure 3. FIG. 3 shows the approximate curves of the punctuation of Example 1 and the punctuation of Reference Example 1, the approximate curves of the punctuation of Example 2 and the punctuation of Reference Example 2, and the approximate curve of the punctuation of Comparative Example 2.

[Table 2]

The polarizing film produced by the manufacturing method of the comparative example does not simultaneously satisfy the monomer transmittance of 45% or more and the polarization degree of 97% or more. In addition, as shown by the approximate curve of the punctuation of Comparative Example 2, in the manufacturing method of Comparative Example 2, when the dyeing treatment is performed so that the single transmittance becomes 45% or more, the polarization degree is predicted to be less than 97%. In contrast, the polarizing film produced by the manufacturing method of the embodiment has excellent optical characteristics with a single transmittance of 45% or more and a polarization degree of 97% or more.

For each polarizing plate of Example 1 and Reference Example 3, the variations of the optical characteristics of the long and thin polarizing plates were measured. And the results are shown in Table 3.

[table 3]

The variation of the monomer transmittance of the long polarizing plate manufactured by the manufacturing method of the embodiment is 0.5% or less, and the variation of the monomer transmittance of the thin polarizing plate manufactured by the manufacturing method of the embodiment is Below 0.2%, the variation in optical characteristics is suppressed to a problem-free level. On the other hand, the polarizing plate of the reference example obtained through the step of humidifying the polarizing film has large variations in optical characteristics regardless of the strip shape and the sheet shape.

INDUSTRIAL APPLICABILITY The polarizing plate having the polarizing film of the present invention can be suitably used as a circular polarizing plate for organic EL display devices and inorganic EL display devices.

10‧‧‧ Polarizing film

20‧‧‧1st protective layer

30‧‧‧Second protective layer

100‧‧‧ Polarizer

200‧‧‧Layered body

R1 ~ R6‧‧‧Conveying roller

G1 ~ G4‧‧‧Guide roller

FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. Fig. 2 is a schematic diagram showing an example of drying shrinkage treatment using a heating roller. FIG. 3 is a graph showing the optical characteristics of polarizing plates produced in Examples and Comparative Examples.

Claims (11)

A polarizing film having a thickness of 8 μm or less, a single transmittance of 45% or more, and a polarization degree of 97% or more. The polarizing film of claim 1 has a single transmittance of 46% or less and a polarization degree of 99% or less. A polarizing plate, comprising: the polarizing film according to claim 1 or 2; the protective layer is arranged on at least one side of the polarizing film. The polarizing plate according to claim 3 has a width of 1000 mm or more, and the difference between the maximum value and the minimum value of the unit transmittance at the position in the width direction is 0.5% or less. For the polarizing plate of claim 3, the difference between the maximum value and the minimum value of the unit transmittance in the area of 50 cm ² is 0.2% or less. A polarizing plate roll material is formed by winding the polarizing plate according to claim 4 or 5 into a roll. A manufacturing method is a method of manufacturing a polarizing film as described in claim 1 or 2, and the method includes the following steps: forming a polyethylene containing a halide and a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate An alcohol-based resin layer to form a laminate; and, performing an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment on the laminate in this order, the drying shrinkage treatment conveys the laminate in the longitudinal direction At the same time, it is heated to shrink it by 2% or more in the width direction. The manufacturing method according to claim 7, wherein the content of the halide in the polyvinyl alcohol-based resin layer is 5 to 20 parts by weight relative to 100 parts by weight of the polyvinyl alcohol-based resin. The manufacturing method according to claim 7 or 8, wherein the extension magnification in the aforementioned air-assisted extension processing is 2.0 times or more. The manufacturing method according to any one of claims 7 to 9, wherein the aforementioned drying shrinkage treatment step is a step of heating using a heating roller. The manufacturing method according to claim 7, wherein the temperature of the heating roller is 60 ° C. to 120 ° C., and the shrinkage rate in the width direction of the laminate obtained by performing the drying shrinkage treatment is 2% or more.