TW201842386A - Polarizer, image display device and method for producing said image display device - Google Patents

Abstract

Provided is a polarizer which can maintain excellent optical characteristics, even in humid environments. This polarizer is equipped with a polarizing film comprising an iodine-containing polyvinyl alcohol resin film, and a protective film positioned on at least one side of the polarizing film. The protective film covers the peripheral end faces of the polarizing film, and the permeability of this protective film does not exceed 300 g/m2/24 hr. In one embodiment, this polarizer has color loss that does not exceed 100 [mu]m after being maintained at a temperature of 85 DEG C and a relative humidity of 85% for 120 hours.

Description

Polarizing plate, image display device, and manufacturing method of the image display device

The invention relates to a polarizing plate, an image display device and a method for manufacturing the image display device.

BACKGROUND OF THE INVENTION In an image display device (such as a liquid crystal display device, an organic EL display device, and a quantum dot display device), because of its image formation method, a polarizing plate is often arranged on at least one side of a display unit. However, the polarizing plate has a durability problem in which the optical characteristics of the polarizing film that substantially controls the optical characteristics of the polarizing plate are reduced in a humidified environment. More specifically, in a humidified environment, the polarization performance at the end of the polarizing film sometimes disappears, and as a result, a so-called fading phenomenon occurs in the image display device.

Prior Art Literature Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. 2000-338329

SUMMARY OF THE INVENTION Problems to be Solved by the Invention The present invention has been made to solve the above problems, and its main object is to provide a polarizing plate capable of maintaining excellent optical characteristics even in a humidified environment, an image display device including the polarizing plate, and the polarizing plate. Simple manufacturing method of image display device.

Means for Solving the Problems The polarizing plate of the present invention includes a polarizing film composed of an iodine-containing polyvinyl alcohol resin film, and a protective film disposed on at least one side of the polarizing film; and the protective film The peripheral end surface of the polarizing film is covered, and the moisture permeability of the protective film is 300 g / m ² / 24hr or less. In one embodiment, the protective film covering the peripheral end surface of the polarizing film also covers one entire surface of the polarizing film. In one embodiment, the moisture permeability of the protective film is 150 g / m ² / 24hr or less. In one embodiment, the protective film is made of a cycloolefin-based resin or a (meth) acrylic resin having a glutaridine imine structure. In one embodiment, the amount of discoloration of the polarizing plate after being held in an environment of 85 ° C. and 85% RH for 120 hours is 100 μm or less. According to another aspect of the present invention, an image display device can be provided. The image display device includes a display unit and the above-mentioned polarizing plate arranged on at least one side of the display unit; and a protective film arranged on the polarizing film of the polarizing plate on the side opposite to the display unit covers the peripheral end face of the polarizing film. According to another aspect of the present invention, a method for manufacturing an image display device can be provided. The manufacturing method includes the following steps: arranging a polarizing film on one side of a display unit; arranging a protective film having a size larger than the polarizing film on the side of the polarizing film so as to extend from all four sides constituting the outer periphery of the polarizing film. The surface on the opposite side of the display unit; and the extended end portion covering the peripheral end face of the polarizing film; and the polarizing film is composed of an iodine-containing polyvinyl alcohol resin film, and the moisture permeability of the protective film is 300 g / m ² / 24hr or less. In one embodiment, a length of a portion where the protective film extends is 1 mm or more. In one embodiment, the protective film is adhered to the polarizing film on the side opposite to the display unit by an adhesive.

Advantageous Effects of Invention According to the present invention, a polarizing plate capable of maintaining excellent optical characteristics even in a humidified environment can be realized by covering (sealing) an outer peripheral end face of a polarizing film with a protective film having a predetermined moisture permeability. Accordingly, an image display device capable of maintaining excellent optical characteristics and preventing discoloration even in a humidified environment can be realized. In addition, according to the present invention, a simple manufacturing method of the image display device can be realized. In one embodiment, the manufacturing method includes the following steps: using a protective film having a size larger than the polarizing film, covering the entire surface of the polarizing film on the side opposite to the display unit and the entire peripheral end surface. According to the embodiment, an image display device capable of maintaining excellent optical characteristics even in a humidified environment can be manufactured extremely simply.

Embodiments for Implementing the Invention Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Polarizing Plate A-1. Overall Configuration of Polarizing Plate A polarizing plate according to an embodiment of the present invention includes a polarizing film and a protective film disposed on at least one side of the polarizing film. FIG. 1A is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention, and FIG. 1B is a schematic plan view of the polarizing plate of FIG. 1A. The polarizing plate 100 illustrated in the figure includes a polarizing film 10, a protective film 21 disposed on one side of the polarizing film 10, and a protective film 22 disposed on the other side. The protective films 21 and 22 are laminated on the polarizing film by an adhesive layer (specifically, an adhesive layer and an adhesive layer: not shown). The adhesive layer represents that the upper system is formed of a PVA-based adhesive or an activated energy ray-curable adhesive. The adhesive layer represents that the upper layer is formed of an acrylic adhesive. One of the protective films 21 and 22 may be omitted depending on the purpose, the configuration of the polarizing plate and / or the image display device, the method of manufacturing the polarizing plate and / or the image display device, and the like. In the embodiment of the present invention, at least one of the protective films 21 and 22 (the protective film 22 in the illustrated example) covers the peripheral end surface of the polarizing film 10. In the embodiment of the present invention, the polarizing film is made of a film of a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") containing iodine. When the polarizing film contains iodine, the effect of covering (sealing) the polarizing film with a protective film is remarkable. The thickness of the polarizing film is typically 8 μm or less. When the polarizing film contains iodine and its thickness is very thin like this, the density of iodine in the polarizing film becomes high, and the stability of iodine is easily reduced with humidification, so the effect of sealing the polarizing film is more significant. Practically, an adhesive layer 40 is provided as the outermost layer on the display unit side of the polarizing plate, so that the polarizing plate is bonded to the display unit (for example, a liquid crystal cell) 300 through the adhesive layer. The protective film 22 only needs to cover the peripheral end faces of the polarizing film 10, and the protective film 21 and the peripheral end faces of the adhesive layer 40 may be entirely covered, partially covered, or uncovered. In the example shown in FIG. 1A, the protective film 22 covers the peripheral end faces of the polarizing film 10, the protective film 21, and the adhesive layer 40. In one embodiment, as shown in FIG. 1A, the protective film 22 covers the entire end surface of the polarizing film 10 and one surface of the polarizing film (the surface opposite to the display unit in the illustrated example). In addition, the protective film 22 only needs to cover the peripheral end surface of the polarizing film 10 so that the peripheral end surface is sealed, and it is not necessary to adhere to the peripheral end surface. In the embodiment of the present invention, the moisture permeability of the protective film (the protective film 22 in the example in the figure) covering the end surface around the polarizing film is 300 g / m ² / 24hr or less, and preferably 150 g / m ² / 24hr or less.

For example, after the polarizing plate is kept under the environment of 85 ° C and 85% RH for 120 hours, the discoloration amount is preferably 100 μm or less, more preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. The lower limit of the amount of fading is preferably zero, and is 5 μm in one embodiment. The amount of fading can be calculated in the following manner: a test piece of a predetermined size is cut out from a polarizing plate (or a polarizing film), and the test piece is formed with two sides opposite to the direction perpendicular to the extending direction and the extending direction, respectively. The direction of extension represents the direction of the absorption axis that can correspond to the polarizing film. For example, the extending direction may correspond to the long-side direction (conveying direction (MD direction)) of the polarizing plate. Next, the test piece was adhered to the glass plate with an adhesive, and then placed in an oven at 85 ° C. and 85% RH for 120 hours to humidify. The discolored state of the end portion of the test piece after humidification when the humidified test piece was placed in a state of orthogonal polarization with the standard polarizing plate was observed with a microscope. Specifically, the amount of discoloration (amount of discoloration: μm) from the end of the test piece (polarizing plate or polarizing film) was measured. As shown in FIG. 2, the larger the value of the discoloration amount a from the end portion in the extension direction and the discoloration amount b from the end portion which is orthogonal to the extension direction, the larger the value. In addition, the polarization characteristics in the faded region are significantly low, and the function as a polarizing plate cannot be practically implemented. Therefore, the smaller the amount of fading, the better.

The polarizing plate of the embodiment of the present invention may be disposed on the viewing side of the display panel, or may be disposed on the opposite side from the viewing side, or may be a pair of polarizing plates of the embodiment of the present invention disposed on both sides.

A-2. Polarizing film The polarizing film 10 is made of a PVA-based resin film containing iodine as described above.

As the PVA-based resin forming the PVA-based resin film, any appropriate resin can be used. Examples 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 an ethylene-vinyl acetate copolymer. The saponification degree of PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.9 mol%, and more preferably 99.0 mol% to 99.5 mol%. The degree of saponification is determined in accordance with JIS K 6726-1994. By using the PVA-based resin having the saponification degree, a polarizing film having excellent durability can be obtained. When the saponification degree 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 degree of polymerization is usually 1000 to 10,000, preferably 1200 to 5000, and more preferably 1500 to 4500. The average degree of polymerization can be obtained in accordance with JIS K 6726-1994.

As described above, the polarizing film contains iodine. The polarizing film is substantially a PVA-based resin film in which iodine is aligned by adsorption. The iodine concentration in the PVA-based resin film is, for example, 5.0% by weight to 12.0% by weight. The boric acid concentration in the PVA-based resin film is, for example, 12 to 25% by weight.

As described above, the thickness of the PVA-based resin film (polarizing film) is 8 μm or less, preferably 7 μm or less, and more preferably 6 μm or less. On the other hand, the thickness of the PVA-based resin film is preferably 1.0 μm or more, and more preferably 2.0 μm or more.

The above-mentioned polarizing film preferably exhibits absorption dichroism at any wavelength from 380nm to 780nm. The single transmittance of the polarizing film is preferably 40.0% to 46.0%, and more preferably 41.0% to 45.0%. The polarization degree of the polarizing film should be more than 99.9%, more preferably more than 99.95%, and more preferably more than 99.98%. When a polarizing plate is applied to a reflective liquid crystal display device or an organic EL display device, the polarization degree of the polarizing film should be 90% or more, more preferably 93% or more, and more preferably 95% or more. As mentioned above, covering (sealing) the surrounding end face of the polarizing film with the protective film can have both the excellent optical characteristics (good balance of the single transmittance and polarization) and excellent durability (even in a humidified environment) Maintaining said excellent optical characteristics).

A-3. Protective film The protective films 21 and 22 are formed of an arbitrary and appropriate film that can be used as a protective film of a polarizing film. Examples of the material for forming the film include (meth) acrylic resins, cellulose resins such as cellulose diacetate and cellulose triacetate, cycloolefin resins such as norbornene resin, olefin resins such as polypropylene, and Ester resins such as ethylene phthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. The "(meth) acrylic resin" means an acrylic resin and / or a methacrylic resin.

In one embodiment, the (meth) acrylic resin is a (meth) acrylic resin having a glutaridine imine structure. The (meth) acrylic resin having a glutariminium structure (hereinafter also referred to as a glutarimide resin) is described in, for example, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Application Publication No. 2006-328329, Japanese Patent Application Publication No. 2006-328334, Japanese Patent Application Publication No. 2006-337491, Japanese Patent Application Publication No. 2006-337492, Japanese Patent Application Publication No. 2006-337493, Japanese Patent Application Publication No. 2006- Japanese Patent Publication No. 337569, Japanese Patent Application Publication No. 2007-009182, Japanese Patent Application Publication No. 2009-161744, and Japanese Patent Application Publication No. 2010-284840. These references are cited in this specification.

In the embodiment of the present invention, the resin substrate used in manufacturing the polarizing plate (to be described later in Section C) may be directly used as a protective film.

In the embodiment of the present invention, the protective film (the protective film 22 in the example in the figure) covering the peripheral end surface of the polarizing film can maintain the optical characteristics of the polarizing plate even in a humidified environment, and can improve the durability of the polarizing plate. . Therefore, the protective film should have a barrier function. In this specification, "having a barrier function" means that the amount of penetration of oxygen and / or water vapor into the polarizing film can be suppressed, and the polarizing film can be substantially isolated from these.

As described above, the moisture permeability of the protective film (the protective film 22 in the example in the figure) covering the end face around the polarizing film is 300 g / m ² / 24hr or less, and preferably 150 g / m ² / 24hr or less, and more preferably 120 g / m ² / 24hr or less, more preferably 70 g / m ² / 24hr or less, and particularly preferably 20 g / m ² / 24hr or less. The lower limit of moisture permeability is, for example, 0.01g / m ² / 24hr, and should be lower than the detection limit. If the moisture permeability of the protective film is within this range, the polarizing film can be well protected from moisture and oxygen in the air. As a result, as long as the moisture permeability of the protective film covering the end surface around the polarizing film is within this range, the good optical characteristics of the polarizing film can be maintained even in a humidified environment. The moisture permeability can be measured in accordance with JIS Z0208. From the viewpoint of moisture permeability, the protective film is preferably composed of a cycloolefin-based resin or a (meth) acrylic resin having a glutaridine imine structure.

The thickness of the protective film can be increased before the effect of the present invention can be obtained, and an arbitrary and appropriate thickness can be adopted. The thickness of the protective film is, for example, 20 μm to 40 μm, and preferably 25 μm to 35 μm. In addition, when a surface treatment is performed, the thickness of the protective film is a thickness including the thickness of the surface treatment layer.

In one embodiment, the protective film (inner protective film) 21 between the polarizing film 10 and the adhesive layer 40 is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm, and the retardation Rth (550) in the thickness direction is -10 nm to +10 nm. The Re (550) of the inner protective film is preferably 0 nm to 8 nm, and more preferably 0 nm to 6 nm, and more preferably 0 nm to 3 nm. The Rth (550) of the inner protective film should be -8nm ~ + 8nm, more preferably -6nm ~ + 6nm, and even more preferably -3nm ~ + 3nm. In addition, "Re (550)" is an in-plane phase difference measured at 23 ° C with light having a wavelength of 550 nm. Re (550) is obtained by using the formula: Re (550) = (nx-ny) × d when the thickness of the layer (thin film) is d (nm). The "Rth (550)" is a phase difference in the thickness direction measured at 23 ° C with light having a wavelength of 550 nm. Rth (550) is obtained by using the formula: Rth (550) = (nx-nz) × d when the thickness of the layer (thin film) is d (nm).

In another embodiment, the inner protective film may have Re (550) capable of functioning as a so-called λ / 4 plate. This embodiment can be applied to, for example, a case where a polarizing plate functions as a circular polarizing plate and is used as an anti-reflection film of a reflective liquid crystal display device or an organic EL display device. At this time, Re (550) is preferably 120 nm to 160 nm, and more preferably about 140 nm. At this time, the inner protective film may be configured such that its slow axis is preferably formed at an angle of about 40 ° to 50 ° with respect to the absorption axis of the polarizing film, and more preferably at an angle of about 45 °.

A-4. Adhesive layer The adhesive layer 40 is formed of an arbitrary and appropriate adhesive. A typical example of the adhesive is an acrylic adhesive. The thickness of the adhesive layer is, for example, 5 μm to 100 μm, and preferably 10 μm to 30 μm.

B. Image display device The polarizing plate according to the embodiment of the present invention can be applied to an image display device. Therefore, the present invention also includes an image display device. Specific examples of the image display device include a liquid crystal display device, an organic electric field emission (EL) display device, and a quantum dot display device.

The image display device typically includes a display unit and a polarizing plate according to an embodiment of the present invention which is arranged on at least one side of the display unit. In one embodiment, as shown in FIG. 1A, the polarizing plate 100 is applied on the viewing side. In this embodiment, the protective film 22 disposed on the opposite side of the polarizing film 10 from the display unit 300 covers the peripheral end surface of the polarizing film 10, and also covers the side opposite to the display unit (viewing side in the example of the figure). The whole surface. In the example of the figure, the case where the polarizing plate of the embodiment of the present invention is applied to the viewing side portion of the image display device will be described, but the polarizing plate can also be applied to the back side portion of the image display device, and can also be applied. In both the viewing side portion and the back side portion of the image display device. In addition, since the image display device can adopt a well-known structure in the industry, detailed description is omitted.

C. Manufacturing method of the image display device The manufacturing method of the image display device of the present invention includes the following steps: arranging a polarizing film on one side of the display unit; and extending the size from all four sides constituting the outer periphery of the polarizing film. A protective film larger than the polarizing film is disposed on a surface of the polarizing film on the side opposite to the display unit; and the extended end portion covers a peripheral end surface of the polarizing film. In the following, as a representative example of the method for manufacturing an image display device of the present invention, an embodiment including the following steps will be described: a polarizing film is arranged on a viewing side portion of the image display device and a protective film covers the peripheral end surface of the polarizing film. This embodiment corresponds to the method for manufacturing an image display device described in the above item B.

C-1. Manufacturing a polarizing film A method for manufacturing a polarizing plate according to an embodiment of the present invention includes the following steps: forming a PVA-based resin layer on one side of a resin substrate; and laminating the resin substrate and the PVA-based resin layer The body is stretched and dyed, and this PVA-based resin layer is made into a polarizing film. In another embodiment, a laminated body of a resin substrate and a PVA-based resin film may be prepared, and then the laminated body may be dyed to make the PVA-based resin film into a polarizing film. Further, in another embodiment, a single PVA-based resin film may be stretched and dyed, and the PVA-based resin film may be made into a polarizing film. Hereinafter, a representative example will be described, including a method for producing a PVA-based resin layer on one side of a resin substrate.

C-1-1. Forming the PVA-based resin layer The formation method of the PVA-based resin layer may be any appropriate method. It is suitable to apply a coating liquid containing a PVA-based resin on a resin substrate and dry it to form a PVA-based resin layer.

The resin substrate may be formed of any appropriate thermoplastic resin. 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. Of these, norbornene-based resins and amorphous polyethylene terephthalate-based resins are preferred.

In one embodiment, an amorphous (uncrystallized) polyethylene terephthalate resin is preferably used. Among these, an amorphous (hardly crystallizable) polyethylene terephthalate-based resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate-based resin include a copolymer further containing isophthalic acid as a dicarboxylic acid or a copolymer further containing cyclohexanedimethanol as a glycol.

When the underwater stretching method is used in the stretching described later, the resin substrate absorbs water, and water can function as a plasticizer to plasticize. As a result, the stretching stress can be greatly reduced, and it can be stretched at a high magnification, and the stretchability is more excellent than that when stretched in the air. As a result, a polarizing film having excellent optical characteristics can be produced. In one embodiment, the water absorption of the resin substrate is preferably 0.2% or more, and more preferably 0.3% or more. On the other hand, the water absorption of the resin substrate is preferably 3.0% or less, and more preferably 1.0% or less. By using the resin substrate, it is possible to prevent defects such as a significant decrease in dimensional stability during production and deterioration in appearance of the obtained polarizing film. In addition, it is possible to prevent the substrate from being broken or the PVA-based resin layer from being peeled from the resin substrate when it is stretched in water. The water absorption of the resin substrate can be adjusted by, for example, introducing a modified base into the forming material. The water absorption is a value obtained in accordance with JIS K 7209.

The glass transition temperature (Tg) of the resin substrate is preferably 170 ° C or lower. By using the resin substrate, the crystallization of the PVA-based resin layer can be suppressed, and at the same time, the extensibility of the laminated body can be sufficiently ensured. In addition, considering the viewpoints of plasticizing a resin substrate with water and smoothly performing water elongation, the temperature is preferably 120 ° C or lower. In one embodiment, the glass transition temperature of the resin substrate is preferably 60 ° C or higher. By using the resin base material, it is possible to prevent the resin base material from being deformed (for example, unevenness, sagging, wrinkles, etc.) during coating and drying of the coating solution containing the PVA-based resin, and it can be performed well. Make a laminate. The PVA-based resin layer can be stretched well at an appropriate temperature (for example, about 60 ° C). In another embodiment, when the coating liquid containing a PVA-based resin is applied and dried, the glass transition temperature may be lower than 60 ° C. as long as the resin substrate is not deformed. The glass transition temperature of the resin substrate can be adjusted, for example, by heating a crystallizing material that introduces a modified material into a forming material. The glass transition temperature (Tg) is a value obtained in accordance with JIS K 7121.

The thickness of the resin substrate before stretching is preferably 20 μm to 300 μm, and 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 exceeds 300 μm, for example, it may take a long time for the resin substrate to absorb water during stretching in water, which may cause an excessive load on stretching.

The coating liquid represents a solution obtained by dissolving the PVA-based resin in a solvent. Examples of the solvent include water, dimethylmethylene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, and polyhydric alcohols such as trimethylolpropane. Amines such as ethylenediamine and diethylene glycol. These may be used alone or in combination of two or more kinds. Among them, water is preferred. 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. As long as the resin concentration is the same, a uniform coating film adhered to the resin substrate can be formed.

Additives can also be blended in the coating solution. Examples of the additives include plasticizers and surfactants. The plasticizer may be a polyhydric alcohol such as ethylene glycol or glycerin. The surfactant may be, for example, a nonionic surfactant. These can be used in order to further improve the uniformity, dyeability, and elongation of the obtained PVA-based resin layer. In addition, the additives may be easily accessible ingredients. By using the easy-contact component, the adhesion between the resin substrate and the PVA-based resin layer can be improved. As a result, problems such as peeling of the PVA-based resin layer from the substrate can be suppressed, and dyeing and water elongation described later can be performed favorably. For example, modified PVA such as acetoacetate-based modified PVA can be easily added.

The coating liquid may be applied by any appropriate method. Examples include 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 doctor blade coating method (comma coating method, etc.), and the like.

The coating and drying temperature of the coating liquid is preferably 50 ° C or higher.

Before forming the PVA-based resin layer, the resin substrate may be subjected to a surface treatment (for example, a corona treatment), or an easy-adhesion layer may be formed on the resin substrate. By performing the treatment, the adhesion between the resin substrate and the PVA-based resin layer can be improved.

The thickness of the PVA-based resin layer (before stretching) is preferably 3 μm to 20 μm.

C-1-2. Extension The extension method of the laminated body can adopt any appropriate extension method. Specifically, it may be a fixed-end extension or a free-end extension (for example, a method of uniaxially extending a laminated body through rollers having different peripheral speeds). Should be extended for the free end.

The extension direction of the laminated body can be appropriately set. In one embodiment, it extends along the longitudinal direction of the strip-shaped laminated body. At this time, the representative upper system adopts a method in which the laminated body is stretched between rollers having different rotation speeds. In another embodiment, it extends along the width direction of the long laminated body. At this time, the representative system uses the tenter stretcher for stretching.

The extension method is not particularly limited, and may be an aerial extension method or an underwater extension method. Should be extended in water. It can be stretched at a temperature lower than the glass transition temperature (typically about 80 ° C) of the resin substrate or the PVA-based resin layer by the water-stretching method, while suppressing the crystallization of the PVA-based resin layer and simultaneously High magnification extension. As a result, a polarizing film having excellent optical characteristics can be produced.

The extension of the laminate can be performed in one stage or in multiple stages. When carried out in multiple stages, for example, the free-end extension and the fixed-end extension may be combined, or the above-mentioned underwater extension method and the aerial extension method may be combined. In addition, when it is performed in multiple stages, the stretching magnification (maximum stretching magnification) of the laminated body described later is the product of the stretching magnifications at each stage.

The extension temperature of the laminated body can be set to an arbitrary and appropriate value in accordance with the forming material and extension method of the resin base material. When using the aerial stretching method, the stretching temperature should be above the glass transition temperature (Tg) of the resin substrate, more preferably the glass transition temperature (Tg) of the resin substrate + 10 ° C or more, and more preferably Tg + 15 ° C or more. On the other hand, the extension temperature of the laminated body is preferably 170 ° C or lower. Extending at the above-mentioned temperature can suppress rapid progress of crystallization of the PVA-based resin, and can further suppress an undesirable condition caused by the crystallization (for example, the orientation of the PVA-based resin layer is hindered by extension).

When using the water extension method, the liquid temperature of the extension bath is above 60 ° C, preferably 65 ° C to 85 ° C, and more preferably 65 ° C to 75 ° C. As long as the temperature is the same, the PVA-based resin layer can be suppressed from dissolving and can be stretched at a high rate. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. At this time, if the stretching temperature is lower than 60 ° C, even if the resin substrate is considered to be plasticized with water, it may not be stretched well. On the other hand, the higher the temperature of the extension bath, the higher the solubility of the PVA-based resin layer, and it is feared that excellent optical characteristics cannot be obtained. The immersion time of the laminated body in the extension bath is preferably 15 seconds to 5 minutes.

In the case of an underwater extension method, it is preferable to immerse the laminated body in an aqueous boric acid solution for extension (extension in boric acid). By using an aqueous boric acid solution as the stretching bath, the PVA-based resin layer can be provided with rigidity capable of withstanding the tension applied during stretching and water resistance insoluble in water. Specifically, boric acid generates a tetrahydroxyborate anion in an aqueous solution, and can be crosslinked with a PVA-based resin through hydrogen bonding. As a result, it is possible to impart rigidity and water resistance to the PVA-based resin layer, to extend well, and to produce a polarizing film having excellent optical characteristics.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and / or a borate in water of a solvent. In the present invention, the boric acid concentration is 4.5% by weight or less, preferably 2.0% to 4.5% by weight, and more preferably 2.5% to 4.0% by weight. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, etc. in a solvent may be used.

When the dichroic substance (typically iodine) is adsorbed on the PVA-based resin layer in advance by dyeing described later, it is preferable to mix iodide in the above-mentioned extension bath (aqueous boric acid solution). By blending iodide, the elution of iodine which has been adsorbed on the PVA-based resin layer can be suppressed. 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. Of these, potassium iodide is preferred. Relative to 100 parts by weight of water, the concentration of iodide is preferably 0.05 to 15 parts by weight, and more preferably 0.5 to 8 parts by weight.

Relative to the original length of the laminated body, the extension ratio (maximum extension ratio) of the laminated body should be 5.0 times or more. The high elongation ratio can be achieved by, for example, an elongation method in water (extension in boric acid). In addition, the "maximum extension ratio" in this specification means the extension ratio before the multilayer body is broken, and it is a value which is 0.2 lower than the value after confirming the extension ratio of the multilayer body after breaking.

In one embodiment, the laminated body is subjected to air stretching at a high temperature (for example, 95 ° C. or higher), and then the boric acid is extended in water and dyed later. The aerial extension can be defined as a preparatory or auxiliary extension relative to the extension in boric acid water, so it is hereinafter referred to as "air-assisted extension".

Sometimes, by combining aerial auxiliary extension, the laminated body can be extended at a higher magnification. As a result, a polarizing film having excellent optical characteristics (for example, polarization degree) can be produced. For example, when using a polyethylene terephthalate resin as the resin base material, it is possible to suppress the orientation of the resin base material and to simultaneously suppress the orientation of the resin base material by combining the air-assisted extension and the boric acid water extension, rather than only extending with boric acid water. Extending. The stretching tension of the resin substrate increases as its alignment improves, and it becomes difficult to stably stretch or crack. Therefore, by suppressing the orientation of the resin substrate and simultaneously stretching, the laminated body can be stretched at a higher rate.

In addition, by combining air-assisted extension, the orientation of the PVA-based resin can be improved, thereby improving the orientation of the PVA-based resin even after being extended in boric acid water. It is speculated that the specificity of the PVA-based resin is improved by using air-assisted extension in advance, so that the PVA-based resin becomes easily cross-linked with boric acid when it is stretched in boric acid water, and is stretched in a state where boric acid becomes the bonding point, and After being stretched in boric acid water, the orientation of the PVA-based resin can be improved. As a result, a polarizing film having excellent optical characteristics (for example, polarization degree) can be produced.

The extension magnification in aerial auxiliary extension should be 3.5 times or less. The extension temperature of air-assisted extension should be above the glass transition temperature of PVA resin. The elongation temperature should be 95 ℃ ~ 150 ℃. In addition, the maximum extension ratio when combining aerial assisted extension and the above-mentioned boric acid underwater extension is preferably 5.0 times or more, preferably 5.5 times or more, and more preferably 6.0 times or more relative to the original length of the laminate.

C-1-3. Dyeing The dyeing of the PVA-based resin layer is performed by causing the PVA-based resin layer to adsorb iodine. Examples of the adsorption method include a method of immersing a PVA-based resin layer (layered body) in a dye solution containing iodine, a method of applying the dye solution to a PVA-based resin layer, and spraying the dye solution to PVA. Method on the resin layer. Ideally, a method of immersing a PVA-based resin layer (layered body) in a dyeing solution. This is because iodine can be adsorbed well.

The above-mentioned dyeing solution is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.1 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 suitable to mix iodide with iodine solution. Specific examples of the iodide are as described above. Relative to 100 parts by weight of water, the blending amount of iodide is preferably 0.02 to 20 parts by weight, and more preferably 0.1 to 10 parts by weight. In order to suppress the dissolution of the PVA-based resin, the temperature of the dyeing liquid during dyeing should be 20 ° C to 50 ° C. When the PVA-based resin layer is immersed in the dyeing liquid, in order to ensure the transmittance of the PVA-based resin layer, the immersion time should be 5 seconds to 5 minutes. In addition, the dyeing conditions (concentration, liquid temperature, and immersion time) can be set so that the degree of polarization or monomer transmittance of the finally obtained polarizing film may fall within a predetermined range. In one embodiment, the immersion time is set so that the polarization degree of the obtained polarizing film is 99.98% or more. In another embodiment, the immersion time is set such that the unit transmittance of the obtained polarizing film is 40.0% to 42.5%.

The dyeing treatment can be performed at any appropriate time point. When performing the above-mentioned water stretching, it is preferable to perform it before the water stretching.

C-1-4. Other treatments In addition to elongation and dyeing, the above-mentioned PVA-based resin layer (layered body) can be appropriately subjected to the treatment required to form a polarizing film. Examples of the treatment required to make the polarizing film include insoluble treatment, crosslinking treatment, washing treatment, and drying treatment. The number and order of these processes are not particularly limited.

The said insolubilization process can be performed by immersing a PVA-type resin layer (layered body) in the boric-acid aqueous solution. By applying the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight relative to 100 parts by weight of water. The liquid temperature of the insoluble bath (aqueous boric acid solution) is preferably 20 ° C to 50 ° C. The insolubilization treatment is preferably performed before the above-mentioned water extension or the above-mentioned dyeing treatment.

The above-mentioned crosslinking treatment is typically performed by immersing a PVA-based resin layer (layered body) in an aqueous boric acid solution. By performing a crosslinking treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight relative to 100 parts by weight of water. When the crosslinking treatment is performed after the dyeing treatment, it is preferable to further mix iodide. By blending iodide, the elution of iodine which has been adsorbed on the PVA-based resin layer can be suppressed. With respect to 100 parts by weight of water, the blending amount of iodide is preferably 1 to 5 parts by weight. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) should preferably be 20 ° C to 60 ° C. The crosslinking treatment is preferably performed before the above-mentioned water stretching. In terms of a suitable embodiment, it is carried out in order by aerial stretching, dyeing treatment, and crosslinking treatment.

The said washing | cleaning process is representatively performed by immersing a PVA-type resin layer (layered body) in the potassium iodide aqueous solution. The drying temperature of the above drying treatment is preferably 30 ° C to 100 ° C.

In the above manner, a polarizing film can be formed on a resin substrate.

C-2. Arrangement of Polarizing Film In one embodiment, the laminated body of the resin substrate and the polarizing film obtained in the above item C-1 is directly disposed on the viewing side of the display unit 300. In this embodiment, the resin substrate is the protective film 21 of FIG. 1A. In another embodiment, a protective film is attached to the surface of the polarizing film of the laminated body of the resin substrate and the polarizing film, and then the resin substrate is peeled and removed. The obtained polarizing film / protective film multilayer system is disposed on the viewing side of the display unit 300. In this embodiment, the attached protective film is the protective film 21 of FIG. 1A. In any embodiment, as shown in FIG. 3 (a), the protective film 21 of the laminated body of the polarizing film 10 / the protective film 21 is adhered to the display unit 300 through the adhesive layer 40. In addition, as shown in FIG. 3 (a), the size of the laminated body is representatively smaller than that of the display unit 300.

C-3. Sealing the peripheral end face of the polarizing film Next, the protective end face 22 is used to cover the peripheral end face of the multilayer body (substantially the polarizing film 10) disposed on the display unit 300. In one embodiment, as shown in FIG. 3 (b), the protective film 22 having a size larger than that of the polarizing film 10 is configured to extend from the outer periphery of the polarizing film. The ideal system is configured to extend from all four sides constituting the outer periphery of the polarizing film. The length of the extending portion of the protective film 22 should be set to cover the entire surface of the end surface around the polarizing film. The length of the extending portion is, for example, 1 mm or more and 10 mm or less. The extending portion of the protective film can cover the peripheral end surface of the polarizing film by adjusting the softness (such as the elastic modulus) of the protective film by its own weight. Alternatively, the peripheral end face of the polarizing film may be covered by bending the extending portion of the protective film by an arbitrary and appropriate operation. With this configuration, as shown in FIG. 3 (c), the entire surface of the opposite surface of the display unit 300 of the polarizing film 10 and the entire surface of the peripheral end surface can be covered with the protective film 22. In addition, an adhesive layer (not shown) is formed substantially on the side surface of the polarizing film 10 of the protective film 22, and the protective film is bonded to the polarizing film on the side opposite to the display unit by the adhesive layer.

When the image display device is, for example, a transmissive liquid crystal display device, a backside polarizer, a backside optical member, and a backlight portion can be laminated on the backside of the display unit 300 by a procedure known in the industry.

The above embodiment is only an example. The same procedure can also be adopted on the back side portion of the image display device; or the visual recognition side portion of the image display device can adopt a well-known procedure in the industry, and only the back side portion of the image display device can adopt the same procedure. Examples

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measurement method of each characteristic is as follows.

(1) Thickness was measured with a digital micrometer (KC-351C manufactured by Anritsu Corporation). (2) Moisture permeability The protective film used in the examples and comparative examples was cut into a circular shape of 10 cmΦ to prepare a measurement sample. With respect to this measurement sample, the water vapor transmission rate (water vapor transmission rate) was measured by a water vapor transmission test method (cup method, in accordance with JIS Z 0208). The measurement conditions are as follows. A constant temperature and humidity tank was used for the measurement. Measurement temperature: 40 ° C Relative humidity: 92% Measurement time: 24 hours (3) Amount of discoloration The test piece (50mm × 50mm) was cut out from the polarizing plate used in the examples and comparative examples, and the test piece was bonded with an adhesive To the alkali-free glass plate, and the test piece is formed on two sides opposite to the direction perpendicular to the extending direction and the extending direction, respectively. Here, in the same manner as the procedure for manufacturing the liquid crystal display device of each of the examples and comparative examples, a peripheral film of the polarizing film was covered (sealed) with a protective film to produce a liquid crystal display device substitute. It was placed in an oven at 85 ° C. and 85% RH for 120 hours and humidified, and then the state of discoloration of the polarizing film end after humidification when it was placed in a state of orthogonal polarization with a standard polarizing plate was observed with a microscope. Specifically, the amount of discoloration (amount of discoloration: μm) from the end of the polarizing film was measured. MX61L manufactured by Olympus was used for the microscope, and the amount of fading was measured from the captured image at a magnification of 10 times. As shown in FIG. 2, the larger the value of the discoloration amount a from the end portion in the extension direction and the discoloration amount b from the end portion which is orthogonal to the extension direction, the larger the value.

[Example 1] As a resin substrate, an amorphous polyethylene terephthalate film (IPA copolymerized PET) having a thickness of 100 μm and a Tg of 75 ° C. having 7 mol% isophthalic acid units was prepared. The surface of the film was corona treated (58 W / m2 / min). It is prepared to contain acetamidine modified PVA (manufactured by Japan Synthetic Chemical Industry Co., Ltd., trade name: GOHSEFIMER (registered trademark) Z-200, ratio of 1: 9, average degree of polymerization: 1200, degree of saponification: 98.5 mole% or more) at a ratio of 1: 9. , Acetylation degree of acetamidine: 5%) and PVA (average degree of polymerization: 4200, degree of saponification: 99.2 mole%) of PVA-based resin, and 13 parts by weight of potassium iodide is added to 100 parts by weight of the PVA-based resin A PVA-based resin aqueous solution (PVA-based resin concentration: 5.5% by weight) was prepared. The corona-treated surface of the resin substrate was coated with the aqueous solution so that the film thickness after drying was 13 μm, and dried by hot air drying in a gas environment at 60 ° C. for 10 minutes to form a 9 μm thick resin substrate. PVA-based resin layer. In this way, a laminated body is produced. The obtained laminated body was stretched to 2.4 times in air at 140 ° C (air-assisted extension). Next, the laminated body was immersed in a boric acid aqueous solution at a liquid temperature of 30 ° C. for 30 seconds to make the PVA-based resin layer insoluble. The boric acid aqueous solution in this step is 3 parts by weight with respect to 100 parts by weight of boric acid. Next, the laminated body is immersed and dyed in a dye solution containing iodine and potassium iodide at a liquid temperature of 30 ° C for any time, so that the monomer transmittance of the obtained polarizing film is about 42 to 45%. The dyeing solution uses water as a solvent, and the iodine concentration is within a range of 0.1 to 0.4% by weight, the potassium iodide concentration is within a range of 0.7 to 2.8% by weight, and the concentration ratio of iodine to potassium iodide is 1: 7. Next, the laminated body was immersed in a boric acid aqueous solution at 30 ° C. for 60 seconds to perform a crosslinking treatment on the PVA resin layer to which iodine was adsorbed. The boric acid aqueous solution in this step has a boric acid content of 3 parts by weight relative to 100 parts by weight of water, and a potassium iodide content of 3 parts by weight relative to 100 parts by weight of water. In addition, the laminated body was stretched in the boric acid aqueous solution at a stretching temperature of 70 ° C. to 2.3 times in the same direction as the previous air-assisted stretching (final stretching ratio: 5.50 times). The boric acid aqueous solution in this step has a boric acid content of 3.5 parts by weight relative to 100 parts by weight of water, and a potassium iodide content of 5 parts by weight relative to 100 parts by weight of water. Then, the laminated body was washed with an aqueous solution of 4 parts by weight with respect to 100 parts by weight of water with potassium iodide content, and then dried with warm air at 60 ° C. to obtain a 5 μm thick polarizing film on the resin substrate.

A cycloolefin-based film (manufactured by Zeon Corporation, ZF-12, thickness 13 μm) was bonded to the surface of the obtained polarizing film (the surface opposite to the resin substrate) with a hardening type adhesive. Specifically, a hardening type adhesive was coated on a polarizing film and a cycloolefin-based film to a thickness of 1.0 μm, and was bonded using a roll machine. Thereafter, visible light is irradiated from the cycloolefin-based film side to harden the hardening adhesive. Next, the resin substrate was peeled to obtain a polarizing plate having a structure of a polarizing film / cycloolefin-based film (protective film). The above-mentioned evaluation of the amount of discoloration was performed using the obtained polarizing plate. The results are shown in Table 1. The discolored state is shown in FIG. 4.

The liquid crystal panel was taken out from the IPS mode liquid crystal display device (manufactured by Apple, trade name "iPad (registered trademark) Air"), and after removing optical members such as a polarizing plate from the liquid crystal panel, the liquid crystal cell was taken out. The liquid crystal cell is used after being washed and cleaned on both surfaces (respectively outside the glass substrate) with alcohol. After forming an acrylic adhesive layer (thickness: 20 μm) on the surface of the polarizing film of the obtained polarizing plate, it was cut into the same size (approximately 150 mm × 200 mm) as the removed polarizing plate, and bonded to the liquid crystal by the adhesive layer. Visual side surface of the unit. Next, a cycloolefin-based film (Zeonor, manufactured by Japan Zeon Corporation, moisture permeability: 10 g / m ² / 24hr, thickness: 23 μm) with an acrylic adhesive layer (thickness: 20 μm) formed on the surface was disposed on the polarizer and the liquid crystal. The opposite side of the unit. Here, the cycloolefin-based film is arranged so as to extend from all four sides constituting the outer periphery of the polarizing plate. The length of the four sides extended is 5mm. The sheet hangs down due to its weight, and directly contacts the liquid crystal cell to cover and seal the outer peripheral end surface of the polarizing plate (polarizing film). In this way, the entire surface of the surface of the polarizing plate (polarizing film) opposite to the liquid crystal cell and the entire surface of the outer peripheral end face can be covered with a cycloolefin-based film (protective film). The same polarizing plate as described above was bonded to the back side of the liquid crystal cell via an acrylic adhesive layer (thickness: 20 μm). Thus, a liquid crystal panel is manufactured. The obtained liquid crystal panel was incorporated into the original liquid crystal display device, and the liquid crystal display device of this embodiment was manufactured.

[Example 2] Instead of the cycloolefin-based film, a (meth) acrylic resin film (water permeability: 70 g / m ² / 24hr, thickness: 40 μm) having a glutaridine imine structure was used instead of the cycloolefin-based film. 1 In the same manner, a liquid crystal display device and a substitute are produced. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Example 3] Instead of the cycloolefin-based film, a (meth) acrylic resin film (water permeability: 120 g / m ² / 24hr, thickness: 20 μm) having a glutariminium structure was used instead of the cycloolefin-based film. 1 In the same manner, a liquid crystal display device and a substitute are produced. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Example 4] A liquid crystal display device and a substitute were produced in the same manner as in Example 1 except that the lengths of the four side extensions were set to 3 mm, respectively. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Example 5] A liquid crystal display device and a substitute were produced in the same manner as in Example 1 except that the lengths of the four-side extension portions were set to 1 mm, respectively. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Example 6] A PVA-based resin film (trade name "PE-6000" manufactured by Kuraray, thickness: 60 μm, average degree of polymerization: 2,400, degree of saponification 99.9 mole%) was immersed in a 30 ° C water bath for 1 minute, and After extending 1.2 times in the conveying direction, it was dipped in a 30 ° C aqueous solution with an iodine concentration of 0.04% by weight and a potassium concentration of 0.3% by weight, and then it was extended by 2 times based on the completely unstretched film (original length). Then, the stretched film was immersed in a 30 ° C aqueous solution having a boric acid concentration of 3% by weight and a potassium iodide concentration of 3% by weight, and was further extended to three times based on the original length, followed by immersion in a 4% by weight boric acid concentration and a potassium iodide concentration of 5 In a 60% by weight aqueous solution, it was further extended to 6 times based on the original length, and then dried at 70 ° C for 2 minutes, thereby obtaining a polarizing film having a thickness of 23 μm. Next, both sides of the polarizing film were coated with an aqueous PVA-based resin solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight), and cyclic olefin-based films (Japan Zeon Corporation, Zeonor ZF14, thickness: 13 μm) and cellulose triacetate film (Konica Minolta, Inc., KC4UY) were heated in an oven maintained at 60 ° C. for 5 minutes to obtain a polarizing plate. Subsequent procedures produced a liquid crystal display device and a substitute in the same manner as in Example 1. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1] A liquid crystal display device was produced in the same manner as in Example 1 except that a triacetyl cellulose (TAC) film (moisture permeability: 400 g / m ² / 24hr, thickness: 80 μm) was used instead of the cycloolefin-based film. Product. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1. The discolored state is shown in FIG. 5.

[Comparative Example 2] A cycloolefin-based film of the same size as the polarizing plate was used, and the film was disposed only on the side of the polarizing plate opposite to the liquid crystal cell (that is, the peripheral end surface of the polarizing plate was not covered). In the same manner as in Example 1, a liquid crystal display device and a substitute were produced. The replacement liquid crystal display device (3) was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3] On the surface of the polarizing film of the polarizing plate obtained in Example 1, a cycloolefin-based film (ZF-12, 13 μm, manufactured by Japan Zeon Corporation) was bonded with the same curing adhesive as in Example 1, and A polarizing plate having a configuration of a cycloolefin-based film (protective film) / polarizing film / cycloolefin-based film (protective film) was obtained. Only the thing that the polarizing plate is bonded to the alkali-free glass (that is, the one that does not cover the peripheral end surface of the polarizing plate) is used as a substitute for the liquid crystal display device. This liquid crystal display device substitute was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 4] Only the thing in which the polarizing plate obtained in Example 6 was bonded to an alkali-free glass (that is, the end face around the polarizing plate was not covered) was used as a substitute for the liquid crystal display device. This liquid crystal display device substitute was evaluated for the amount of discoloration in the same manner as in Example 1. The results are shown in Table 1.

[Table 1]

As is clear from Table 1, by covering the outer peripheral end surface of the polarizing plate (polarizing film) with a protective film having a predetermined moisture permeability, a polarizing plate that can maintain excellent optical characteristics even in a humidified environment (in terms of results Is an image display device).

Industrial Applicability The polarizing plate of the present invention can be applied to an image display device. The image display device is suitable for use in televisions, mobile phones, digital cameras, video cameras, portable game consoles, car navigation systems, photocopiers, printers, fax machines, clocks, microwave ovens, and the like.

10‧‧‧ polarizing film

21‧‧‧ protective film

22‧‧‧ protective film

40‧‧‧Adhesive layer

100‧‧‧ polarizing plate

300‧‧‧display unit

FIG. 1A is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. FIG. 1B is a schematic plan view of the polarizing plate of FIG. 1A. FIG. 2 is a schematic diagram for explaining calculation of the amount of fading. FIG. 3 is a schematic diagram for explaining an example of a method for manufacturing an image display device according to the present invention. FIG. 4 is an image showing a discoloration amount of a liquid crystal display device substitute corresponding to Example 1 after a humidification test. FIG. 5 is an image showing a discoloration amount of a liquid crystal display device substitute corresponding to Comparative Example 1 after a humidification test.

Claims (9)

A polarizing plate includes: a polarizing film composed of an iodine-containing polyvinyl alcohol resin film; and a protective film disposed on at least one side of the polarizing film; and the protective film covering a peripheral end surface of the polarizing film And the moisture permeability of the protective film is below 300g / m ² / 24hr. For example, the polarizing plate according to claim 1, wherein the protective film covering the peripheral end surface of the polarizing film also covers one side of the polarizing film. For example, the polarizing plate of claim 1 or 2, wherein the moisture permeability of the aforementioned protective film is 150 g / m ² / 24hr or less. The polarizing plate according to claim 3, wherein the protective film is made of a cycloolefin-based resin or a (meth) acrylic resin having a pentamidine imine structure. For example, the polarizing plate according to any one of claims 1 to 4, which has a discoloration amount of 100 μm or less after being held in an environment of 85 ° C. and 85% RH for 120 hours. An image display device comprising a display unit and a polarizing plate as in any one of claims 1 to 5 arranged on at least one side of the display unit; and an opposite side of the aforementioned polarizing film arranged on the polarizing plate from the display unit A protective film covers an end surface around the polarizing film. A method for manufacturing an image display device includes the following steps: arranging a polarizing film on one side of a display unit; arranging a protective film larger than the polarizing film in a manner extending from all four sides constituting the outer periphery of the polarizing film; A surface of the polarizing film on the opposite side to the display unit; and a peripheral end surface of the polarizing film is covered by the extended portion; and the polarizing film is made of an iodine-containing polyvinyl alcohol resin film, and the protective film The moisture permeability is below 300g / m ² / 24hr. The manufacturing method according to claim 7, wherein a length of a portion where the protective film is extended is 1 mm or more. The manufacturing method according to claim 7 or 8, wherein the protective film is adhered on the opposite side of the polarizing film from the display unit by an adhesive.