TWI843007B - Polarizing plate, polarizing plate with phase difference layer, and organic electroluminescent display device - Google Patents

Abstract

The present invention provides a polarizing plate and a polarizing plate with a phase difference layer that significantly suppress discoloration when used in an organic EL display device. The polarizing plate of the embodiment of the present invention includes: a polyvinyl alcohol resin layer, a protective layer disposed on the visual side of the polyvinyl alcohol resin layer, and an adhesive layer disposed on the side of the polyvinyl alcohol resin layer opposite to the visual side. The polyvinyl alcohol resin layer includes a first polyvinyl alcohol resin layer that functions as a polarizer and a second polyvinyl alcohol resin layer disposed on the visual side of the first polyvinyl alcohol resin layer. The thickness of the second polyvinyl alcohol-based resin layer is 0.03µm to 2µm; the boric acid concentration of the surface of the polyvinyl alcohol-based resin layer on the side opposite to the visual side is greater than the boric acid concentration of the surface of the visual side, and the difference is 0.3 weight % or more; the moisture permeability of the protective layer on the visual side is 200g/ ^m2 ·24h or more.

Description

Polarizing plate, polarizing plate with phase difference layer, and organic electroluminescent display device

The present invention relates to a polarizing plate, a polarizing plate with a phase difference layer, and an organic electroluminescent (EL) display device.

In recent years, with the popularity of thin displays, displays equipped with organic EL panels (organic EL display devices) have been proposed. Organic EL panels have a highly reflective metal layer, so they are prone to problems such as external light reflection or background reflection. It is known that such problems can be prevented by placing a circular polarizing plate on the viewing side (for example, patent documents 1~3). However, the circular polarizing plate (actually a polarizing plate contained in the circular polarizing plate) provided in the organic EL display device has the problem of easy discoloration. Prior art documents Patent documents

Patent document 1: Japanese Patent Publication No. 2003-311239 Patent document 2: Japanese Patent Publication No. 2002-372622 Patent document 3: Japanese Patent Publication No. 3325560

Problem to be solved by the invention This invention is made to solve the above-mentioned previous problems. Its main purpose is to provide a polarizing plate and a polarizing plate with a phase difference layer that can significantly suppress discoloration when used in an organic EL display device.

Means for Solving the Problem The polarizing plate of the embodiment of the present invention comprises: a polyvinyl alcohol resin layer, a protective layer disposed on the visual side of the polyvinyl alcohol resin layer, and an adhesive layer disposed on the side of the polyvinyl alcohol resin layer opposite to the visual side. The polyvinyl alcohol resin layer comprises a first polyvinyl alcohol resin layer functioning as a polarizer and a second polyvinyl alcohol resin layer disposed on the visual side of the first polyvinyl alcohol resin layer. The thickness of the second polyvinyl alcohol resin layer is 0.03µm to 2µm; the boric acid concentration of the surface of the polyvinyl alcohol resin layer on the side opposite to the visual side is greater than the boric acid concentration of the surface of the visual side, and the difference is 0.3% by weight or more; the moisture permeability of the protective layer on the visual side is 200g/ ^m2 ·24h or more. In one embodiment, the boric acid concentration of the first polyvinyl alcohol resin layer is 14% by weight or more. In one embodiment, the monomer transmittance of the first polyvinyl alcohol-based resin layer is 42.5% or more, the ratio of the cross absorbance A ₅₅₀ at a wavelength of 550nm to the cross absorbance A ₂₁₀ at a wavelength of 210nm (A ₅₅₀ /A ₂₁₀ ) is 1.4 or more, the ratio of the cross absorbance A ₄₇₀ at a wavelength of 470nm to the cross absorbance A ₆₀₀ at a wavelength of 600nm (A ₄₇₀ /A ₆₀₀ ) is 0.7 or more, and the cross b value is greater than -10. In one embodiment, the iodine concentration of the polarizer is 2 wt% to 10 wt%. In one embodiment, the absolute value of the polarization change of the polarizer after being exposed to ammonia vapor at 60°C for 2 hours |ΔP| is 50% or less. According to another aspect of the present invention, a polarizing plate with a phase difference layer is provided. The polarizing plate with a phase difference layer has the above-mentioned polarizing plate and the phase difference layer. According to yet another aspect of the present invention, an organic electroluminescent display device is provided. The organic electroluminescent display device has the above-mentioned polarizing plate or the above-mentioned polarizing plate with a phase difference layer.

Effect of the invention According to the embodiment of the present invention, for the polyvinyl alcohol resin layer of the polarizing plate, a second polyvinyl alcohol resin layer is provided adjacent to the first polyvinyl alcohol resin layer that functions as a polarizer, and the following concentration gradient is provided, wherein the concentration gradient makes the boric acid concentration of the surface of the second polyvinyl alcohol resin layer on the viewing side smaller than the boric acid concentration of the surface of the first polyvinyl alcohol resin layer on the side opposite to the viewing side by a predetermined value or more, thereby realizing a polarizing plate and a polarizing plate with a phase difference layer that significantly suppress discoloration when used in an organic EL display device.

The following describes the embodiments of the present invention, but the present invention is not limited to these embodiments.

A. Polarizing plate A-1. Overall structure of polarizing plate FIG. 1 is a schematic cross-sectional view of a polarizing plate of an embodiment of the present invention. The polarizing plate 100 of the illustrated example includes: a polyvinyl alcohol (PVA) resin layer 10, a protective layer (visual side protective layer) 30 provided on the visual side of the PVA resin layer 10, and an adhesive layer 40 disposed on the side of the PVA resin layer 10 opposite to the visual side. The PVA resin layer 10 includes a first PVA resin layer 11 that functions as a polarizer and a second PVA resin layer 12 provided on the visual side of the first PVA resin layer 11. The second PVA-based resin layer 12 can also function as a bonding layer for bonding the first PVA-based resin layer 11 and the visual side protective layer 30. Representatively, the optical functional layer can be bonded through the adhesive layer 40. Representative examples of the optical functional layer include another protective layer (inner protective layer) and a phase difference layer. The inner protective layer can be omitted as appropriate. When the optical functional layer is a phase difference layer, a polarizing plate with a phase difference layer is formed. The polarizing plate with a phase difference layer will be described in item B below. The polarizing plate 100 can also be bonded to the organic EL panel through the adhesive layer 40.

In the embodiment of the present invention, the difference between the boric acid concentration of the surface of the PVA resin layer 10 (substantially the first PVA resin layer 11) on the side opposite to the visual side and the boric acid concentration of the surface of the PVA resin layer 10 (substantially the second PVA resin layer 12) on the visual side (hereinafter sometimes referred to as the boric acid concentration gradient) is 0.3 wt% or more. More specifically, the boric acid concentration of the first PVA resin layer is greater than the boric acid concentration of the second PVA resin layer, so that a boric acid concentration gradient is formed in which the boric acid concentration of the surface of the PVA resin layer on the side opposite to the visual side is greater than the boric acid concentration of the surface on the visual side. The boric acid concentration gradient is preferably 0.4 wt% or more, more preferably 0.5 wt% or more. The boric acid concentration gradient can be, for example, 27 wt% or less. When the inventors applied the polarizing plate and the polarizing plate with a phase difference layer to the organic EL display device, they encountered a new issue that the polarizing plate and the polarizing plate with a phase difference layer would discolor. They actively examined the issue and found that the cause of the discoloration was ammonia (essentially ammonium ions) generated from the organic EL panel. It was also found that the higher the boric acid concentration in the polarizer, the more it could inhibit the above-mentioned discoloration, so the higher the boric acid concentration, the easier it is to block ammonium ions. Based on the above-mentioned knowledge and understanding, it was found that a second PVA-based resin layer is arranged adjacent to the polarizer (the first PVA-based resin layer) to form a two-layer structure of a PVA-based resin layer, and the following concentration gradient is set. The concentration gradient is such that the boric acid concentration on the surface of the viewing side of the PVA-based resin layer is lower than the boric acid concentration on the surface on the side opposite to the viewing side by a predetermined value or more. In this way, ammonium ions invading the polarizer from the organic EL panel side can be blocked as much as possible, and the PVA-based resin layer on the viewing side (the side farther from the organic EL panel) can easily discharge ammonium ions, thereby solving the new problem. This is presumably because the cross-linking density of PVA resin decreases as it moves away from the organic EL panel, so ammonium ions are less likely to penetrate the polarizer (first PVA resin layer), and even if they do penetrate, they are easily detached from the visual side. In addition, by making the second PVA resin layer function as an adhesive for bonding the polarizer and the protective layer, there is no need to set up a second PVA resin layer with a different adhesive, which is also beneficial from the perspective of thinness, manufacturing efficiency, and cost.

The boric acid concentration of the second PVA-based resin layer (when applied) is less than 1 wt%, preferably less than 0.8 wt%, more preferably less than 0.5 wt%, more preferably less than 0.2 wt%, and even more preferably substantially zero. If the concentration of the second PVA-based resin layer is within the above range, the above-mentioned desired boric acid concentration gradient can be achieved between the polarizer (first PVA-based resin layer) having practical optical properties. Here, the boric acid concentration of the polarizer (first PVA-based resin layer) is preferably greater than 15 wt%, more preferably greater than 16 wt%, and more preferably 16 wt% to 26 wt%. If the boric acid concentration of the polarizer is within the above range, practical optical properties can be obtained, and the above-mentioned desired boric acid concentration gradient can be achieved between the second PVA-based resin layer. In addition, the ease of adjusting the curling during bonding can be well maintained and the curling during heating can be well suppressed, while the appearance durability during humidification can be improved. The boric acid concentration can be determined, for example, by Fourier transform infrared spectroscopy (FT-IR). The details are as follows. For the second PVA-based resin layer, a Fourier transform infrared spectrophotometer (e.g., manufactured by Perkin Elmer, trade name "SPECTRUM2000") is used to measure the intensity of the boric acid peak (665 cm ^-1 ) and the intensity of the reference peak (2941 cm ^-1 ) by attenuated total reflection spectroscopy (ATR) measurement using polarized light as the measurement light. The boric acid amount index is calculated from the obtained boric acid peak intensity and the reference peak intensity using the following formula, and the boric acid concentration is calculated from the calculated boric acid amount index using the following formula. (Boric acid amount index) = (Intensity of the boric acid peak at 665 cm ^-1 ) / (Intensity of the reference peak at 2941 cm ^-1 ) (Boric acid concentration) = (Boric acid amount index) × 6.61 + 0.47

The thickness of the second PVA-based resin layer is 0.03µm to 2µm, preferably 0.03µm to 1µm, more preferably 0.04µm to 0.5µm, more preferably 0.04µm to 0.1µm, and particularly preferably 0.05µm to 0.1µm. If the thickness of the second PVA-based resin layer is within the above range, ammonium ions can be more easily discharged. As a result, when the polarizing plate and the polarizing plate with a phase difference layer are applied to an organic EL display device, discoloration can be more effectively suppressed.

The polarization change ΔP of the polarizing plate after being exposed to ammonia vapor at 60°C for 2 hours is preferably less than 50%, more preferably less than 25%, and more preferably less than 10%. The smaller the polarization change ΔP, the better, and ideally it is zero. According to the implementation form of the present invention, by adopting the structure as described above, the intrusion of ammonium ions into the polarizer (the first PVA-based resin layer) can be well suppressed, and the ammonium ions can be well discharged from the polarizer. As a result, even if the polarizing plate is exposed to ammonia, the change in polarization (essentially the reduction in polarization) can be significantly suppressed. The polarizing plate (as a result, a polarizing plate with a phase difference layer) can well suppress discoloration when used in an organic EL display device.

The first PVA-based resin layer (polarizer), the second PVA-based resin layer, the protective layer, and the adhesive layer are described in detail below.

A-2. The first PVA resin layer As mentioned above, the first PVA resin layer functions as a polarizer. Therefore, in this manual, the first PVA resin layer is sometimes referred to as a polarizer. The polarizer is typically composed of a PVA resin film containing a dichroic substance (typically iodine).

The polarizer preferably has a ratio of the cross absorbance A ₅₅₀ at a wavelength of 550 nm to the cross absorbance A ₂₁₀ at a wavelength of 210 nm (A ₅₅₀ /A ₂₁₀ ) of 1.4 or more, a ratio of the cross absorbance A ₄₇₀ at a wavelength of 470 nm to the cross absorbance A ₆₀₀ at a wavelength of 600 nm (A ₄₇₀ /A ₆₀₀ ) of 0.7 or more, and a cross b value greater than -10. The polarizer used in the embodiment of the present invention has a much larger ratio (A ₅₅₀ /A ₂₁₀ ) and (A ₄₇₀ /A ₆₀₀ ) than a conventional thin polarizer. This means that the content of iodine ions that do not form a complex with PVA (absorption in the ultraviolet region near 210nm) in the polarizer is very small, while the content of PVA-iodine complex (absorption in the visible light region) is very large. In more detail, in the polarizer, the content of PVA-I ₅ ^-complex that absorbs near 600nm is very large, and the content of PVA-I ₃ ^-complex that absorbs near 480nm is maintained without a significant decrease. Here, the thickness of the polarizer means the length of the optical path, so when the thickness of the polarizer is simply reduced, the optical path will also become shorter, and the polarization performance will also decrease. The amount of iodine that can be contained in the polarizer is also limited, so in order to take into account both high polarization performance and thin polarizer, the iodine contained in the polarizer must be used efficiently. That is, by reducing the iodine ions that absorb light in the ultraviolet but do not contribute to polarization performance, and increasing the ratio of PVA-iodine complexes that absorb light in the visible light region, both high polarization performance and thinning of the polarizer can be taken into account. In other words, by increasing the ratio (A ₅₅₀ /A ₂₁₀ ), thinness and high optical properties can be achieved. In addition, by maintaining the ratio (A ₄₇₀ /A ₆₀₀ ) above a predetermined value, good polarization performance can be achieved in the entire visible light region. When the amount of iodine in a thin polarizer is limited, it is difficult to increase both the ratio (A ₅₅₀ /A ₂₁₀ ) and the ratio (A ₄₇₀ /A ₆₀₀ ) using conventional technology, but the polarizer used in the embodiment of the present invention can increase both of these. The ratio (A ₅₅₀ /A ₂₁₀ ) is preferably 1.8 or more, more preferably 2.0 or more, and more preferably 2.2 or more. The upper limit of the ratio (A ₅₅₀ /A ₂₁₀ ) may be, for example, 3.5. The ratio (A ₄₇₀ /A ₆₀₀ ) is preferably 0.75 or more, more preferably 0.80 or more, and more preferably 0.85 or more. The upper limit of the ratio (A ₄₇₀ /A ₆₀₀ ) is, for example, 2.00, and preferably 1.33. In addition, the orthogonal absorbance can be calculated using the following formula based on the orthogonal transmittance Tc measured when obtaining the polarization degree described later. Orthogonal absorbance=log10(100/Tc)

Furthermore, as mentioned above, the orthogonal b value of the polarizer is greater than -10, and is preferably greater than -7, and more preferably greater than -5. The upper limit of the orthogonal b value is preferably less than +10, and more preferably less than +5. According to the present invention, an orthogonal b value within the above range can be achieved. The orthogonal b value represents the hue when the polarizer (polarizing plate) is configured in an orthogonal state. The larger the absolute value of the number, the more the orthogonal hue (black display of the image display device) looks to be colored. For example, when the orthogonal b value is less than -10, that is, lower, the black display will look bluish, and the display performance will be reduced. That is, according to the implementation form of the present invention, a polarizer that can achieve excellent hue in black display can be obtained. In addition, the orthogonal b value can be measured by a spectrophotometer represented by LPF200.

The polarizer preferably shows absorption dichroism at any wavelength between 380nm and 780nm. The single transmittance of the polarizer is preferably below 46.0%, and more preferably below 45.0%. On the other hand, the single transmittance is preferably above 41.5%, more preferably above 42.0%, and more preferably above 42.5%. The polarization degree of the polarizer is preferably above 99.990%, and preferably below 99.998%. The polarizer used in the embodiment of the present invention can take into account both high single transmittance and high polarization degree. The above single transmittance is representative of the Y value measured by using an ultraviolet-visible spectrophotometer and corrected for visual sensitivity. In addition, the single transmittance is the value when the refractive index of one surface of the polarizing plate is converted to 1.50 and the refractive index of the other surface is converted to 1.53. The above polarization degree is calculated based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by a UV-visible spectrophotometer and corrected for visual sensitivity using the following formula. Polarization degree (%) = {(Tp-Tc)/(Tp+Tc)} ^{1 /2} ×100

The thickness of the polarizer is preferably 15µm or less, preferably 12µm or less, more preferably 10µm or less, and particularly preferably 8µm or less. On the other hand, the thickness of the polarizer is, for example, 1µm or more, and for example, 2µm or more, and for example, 3µm or more. If the thickness of the polarizer is within the above range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

The resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers made of a single layer of resin film include: polyvinyl alcohol (PVA) films, partially formalized PVA films, ethylene-vinyl acetate copolymer partially saponified films, and other hydrophilic polymer films dyed and stretched using dichroic substances such as iodine or dichroic dyes; polyene oriented films such as dehydrated PVA films or dehydrogenated polyvinyl chloride films, etc. It is preferable to use a polarizer obtained by dyeing a PVA film with iodine and then uniaxially stretching it because of its excellent optical properties.

The dyeing by iodine mentioned above can be performed, for example, by immersing the PVA film in an iodine aqueous solution. The stretching ratio of the above uniaxial stretching is preferably 3 to 7 times. The stretching can be performed after the dyeing treatment, or it can be performed while dyeing. In addition, it can also be dyed after stretching. The PVA film can be subjected to swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc. as needed. For example, by immersing the PVA film in water and washing it before dyeing, not only can the dirt or anti-adhesive on the surface of the PVA film be washed, but the PVA film can also be swollen, thereby preventing uneven dyeing.

Specific examples of polarizers using a laminate include a laminate using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate using a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by the following steps: coating a PVA-based resin solution on the resin substrate and drying it, forming a PVA-based resin layer on the resin substrate, and obtaining a laminate of the resin substrate and the PVA-based resin layer; and extending and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer including a halogenated compound and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. The extension typically includes extending the laminate by immersing it in an aqueous boric acid solution. And if necessary, the stretching may further include stretching the laminate in the air at a high temperature (for example, above 95°C) before stretching in an aqueous boric acid solution. And, in this embodiment, the laminate is preferably subjected to a dry shrinking treatment in which the laminate is transported along the long side while being heated so as to shrink by more than 2% in the width direction. Typically, the manufacturing method of this embodiment includes sequentially performing an air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a dry shrinking treatment on the laminate. By introducing auxiliary stretching, the crystallinity of PVA can be improved even when PVA is coated on a thermoplastic resin, thereby achieving high optical properties. In addition, by improving the orientation of PVA in advance, it is possible to prevent the orientation of PVA from being reduced or dissolved when immersed in water in the subsequent dyeing step or stretching step, and to achieve high optical properties. Moreover, when the PVA-based resin layer is immersed in a liquid, the orientation disorder and the reduction of orientation of the polyvinyl alcohol molecules can be suppressed more than when the PVA-based resin layer does not contain halides. In this way, the optical properties of the polarizer obtained by the treatment steps of immersing the laminate in a liquid such as dyeing treatment and underwater stretching treatment can be improved. Furthermore, by shrinking the laminate in the width direction through a drying and shrinking treatment, the optical properties can be improved. The obtained resin substrate/polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer of the polarizer), or the resin substrate can be peeled off from the resin substrate/polarizer laminate and any appropriate protective layer can be applied to the peeled off area layer before use. The details of the manufacturing method of the polarizer are described in, for example, Japanese Patent Publication No. 2012-73580 and Japanese Patent License No. 6470455. The entire contents of these publications are cited in this specification for reference.

A-3. Second PVA resin layer The second PVA resin layer can be formed by applying a PVA resin aqueous solution and drying it. The average degree of polymerization of the PVA resin contained in the aqueous solution is preferably about 100 to 5000, more preferably 1000 to 4000. The average degree of saponification is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%. If the average degree of polymerization and the average degree of saponification are within the above range, the adhesion with the first PVA resin layer is good, and as a result, the discharge of ammonium ions at the interface with the first PVA resin layer can be prevented from having an adverse effect. As a result, when the polarizing plate and the polarizing plate with a phase difference layer are applied to an organic EL display device, discoloration can be better suppressed.

PVA resins preferably contain acetylacetyl groups. This is because the adhesion between the polarizer and the protective layer can be excellent, and the durability can be excellent. PVA resins containing acetylacetyl groups can be obtained, for example, by reacting PVA resins with benzophenone by any method. The acetylacetyl modification degree of the acetylacetyl-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol%, more preferably 1 mol% to 20 mol%, and particularly preferably 2 mol% to 7 mol%. In addition, the acetylacetyl modification degree is a value measured by NMR.

The resin concentration of the PVA-based resin aqueous solution is preferably 0.1% to 15% by weight, more preferably 0.5% to 10% by weight. The viscosity of the aqueous solution is preferably 1 to 50 mPa·s. The pH of the aqueous solution is preferably 2 to 6, more preferably 2.5 to 5, more preferably 3 to 5, and particularly preferably 3.5 to 4.5.

In one embodiment, the PVA resin aqueous solution (the second PVA resin layer in the end) may contain a metal compound colloid. The metal compound colloid is a metal compound fine particle dispersed in a dispersion medium, and the fine particles have the same charges repelling each other, thereby achieving electrostatic stabilization and thus having permanent stability.

The average particle size of the fine particles forming the metal compound colloid can be set to any appropriate value as long as it does not adversely affect the optical properties such as transparency and polarization characteristics. It is preferably 1nm~100nm, and more preferably 1nm~50nm. This is because the fine particles can be evenly dispersed in the second PVA-based resin layer.

Any appropriate metal compound can be used. Examples include metal oxides such as aluminum oxide, silicon dioxide, zirconium oxide, and titanium oxide; metal salts such as aluminum silicate, calcium carbonate, magnesium silicate, zinc carbonate, barium carbonate, and calcium phosphate; and minerals such as diatomaceous earth, talc, clay, and kaolin. It is preferable to use a metal compound colloid having a positive charge. Examples of the metal compound include aluminum oxide, titanium oxide, and aluminum oxide is particularly preferable.

A-4. Protective layer The visual side protective layer 30 and the inner protective layer (when the inner protective layer exists) are each formed of any appropriate film that can be used as a protective layer of the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetate cellulose (TAC) or polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyether sulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based transparent resins. In addition, thermosetting resins or ultraviolet curing resins such as (meth) acrylic acid, urethane, (meth) acrylic urethane, epoxy, and silicone can also be cited. Other examples include glassy polymers such as silicone polymers. In addition, the polymer film described in Japanese Patent Publication 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 group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl and nitrile group in the side chain can be used, such as an alternating copolymer composed of isobutylene and N-methylmaleimide, and a resin composition of an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above-mentioned resin composition.

The moisture permeability of the visual side protective layer is preferably 200 g/m ² ·24h or more, more preferably 300 g/m ² ·24h or more, more preferably 330 g/m ² ·24h or more, particularly preferably 360 g/m ² ·24h or more, and particularly preferably 400 g/m ² ·24h or more. The upper limit of the moisture permeability of the visual side protective layer may be, for example, 1000 g/m ² ·24h. If the moisture permeability of the visual side protective layer is within the above range, the discharge of ammonium ions can be further promoted, and as a result, the discoloration of the polarizing plate and the polarizing plate with a phase difference layer can be better suppressed. In this case, the visual side protective layer is preferably composed of a TAC film. In addition, the moisture permeability can be measured in accordance with JIS Z 0208.

The visual side protection layer may also be subjected to surface treatments such as hard coating, anti-reflection treatment, anti-adhesion treatment, and anti-glare treatment as required. In addition, or alternatively, the visual side protection layer may be subjected to treatments useful for improving visibility when viewed through polarized sunglasses (typically, imparting (elliptical) circular polarization function and imparting ultra-high phase difference) as required. By performing the above treatments, even when viewing the display screen through polarized lenses such as polarized sunglasses, excellent visibility can still be achieved. Therefore, the polarizing plate and the polarizing plate with phase difference layer can also be suitably used in image display devices that can be used outdoors.

The thickness of the visual side protection layer 30 is preferably 10µm to 60µm, more preferably 15µm to 50µm. In addition, when surface treatment is applied, the thickness of the visual side protection layer 30 includes the thickness of the surface treatment layer.

The inner protective layer (when present) is preferably optically isotropic in one embodiment. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0nm~10nm, and the phase difference Rth(550) in the thickness direction is -10nm~+10nm. The thickness of another protective layer is preferably 5µm~80µm, preferably 10µm~40µm, and more preferably 10µm~30µm. The inner protective layer can be appropriately omitted in the embodiment of the present invention.

A-5. Adhesive layer The adhesives constituting the adhesive layer are typically acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the monomer type, amount, combination, and blending ratio of the base resin forming the adhesive, as well as the blending amount of the crosslinking agent, the reaction temperature, the reaction time, etc., an adhesive having the desired properties that meet the purpose can be prepared. The base resin of the adhesive can be used alone or in combination of two or more. From the perspective of transparency, processability, and durability, an acrylic adhesive (acrylic adhesive composition) is preferred. The acrylic adhesive composition typically includes a (meth)acrylic polymer as a main component. The (meth)acrylic polymer can be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more in the solid components of the adhesive composition. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a main component in terms of monomer units. In addition, (meth)acrylate refers to acrylate and/or methacrylate. The alkyl (meth)acrylate is preferably contained in a ratio of 80% by weight or more, preferably 90% by weight or more in the monomer components forming the (meth)acrylic polymer. The alkyl group of the alkyl (meth)acrylate can be, for example, a straight chain or branched chain alkyl group having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, and more preferably 3 to 6. A preferred alkyl (meth)acrylate is butyl acrylate. The monomers (comonomers) constituting the (meth)acrylic polymer include, in addition to (meth)acrylic acid alkyl esters, carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth)acrylates, heterocyclic vinyl monomers, etc. The acrylic adhesive composition preferably contains a silane coupling agent and/or a crosslinking agent. The silane coupling agent may be, for example, an epoxy-containing silane coupling agent. The crosslinking agent may be, for example, an isocyanate crosslinking agent and a peroxide crosslinking agent. In addition, the acrylic adhesive composition may also contain an antioxidant and/or a conductive agent. The details of the adhesive are described in, for example, Japanese Patent Publication No. 2006-183022, Japanese Patent Publication No. 2015-199942, Japanese Patent Publication No. 2018-053114, Japanese Patent Publication No. 2016-190996, and International Publication No. 2018/008712, and this specification refers to the descriptions of these publications as references.

The storage elastic modulus of the adhesive at 25°C is preferably 1.0×10 ⁴ Pa~1.0×10 ⁶ Pa, more preferably 1.0×10 ⁴ Pa~1.0×10 ⁵ Pa. If the storage elastic modulus of the adhesive is within the above range, interlayer peeling or convexity can be suppressed, thereby preventing adverse effects on the discharge of ammonium ions.

The latent deformation ΔCr of the adhesive at 70°C is, for example, less than 65µm, and may also be less than 50µm, less than 45µm, less than 40µm, less than 35µm, less than 30µm, less than 25µm, less than 20µm, or further less than 15µm. The lower limit of the latent deformation ΔCr is, for example, 0.5µm. If the latent deformation is within the range, interlayer peeling or embossing can be suppressed in the same way as in the case of storing the elastic modulus, thereby preventing adverse effects on the discharge of ammonium ions. In addition, the latent deformation value can be measured, for example, according to the following procedure: for an adhesive attached to a stainless steel test plate with a joint surface of 20mm long and 20mm wide, a load of 500gf is applied directly below the lead when the test plate is fixed. After the load is applied, the latent variable (offset) of the adhesive on the test plate is measured at each time point after 100 seconds and 3600 seconds, which are set as Cr ₁₀₀ and Cr ₃₆₀₀ respectively _. The latent variable ΔCr can be calculated from the measured Cr ₁₀₀ and Cr ₃₆₀₀ using ΔCr=Cr ₃₆₀₀ -Cr ₁₀₀ .

The thickness of the adhesive layer is preferably 2µm~40µm, more preferably 3µm~20µm, and even more preferably 4µm~15µm.

B. Polarizing plate with phase difference layer As described in the above-mentioned item A-1, the polarizing plate of the embodiment of the present invention can also be bonded with a phase difference layer through an adhesive layer 40 to form a polarizing plate with a phase difference layer. Therefore, the polarizing plate with a phase difference layer can also be included in the embodiment of the present invention. The polarizing plate with a phase difference layer of the embodiment of the present invention can significantly suppress discoloration when applied to an organic EL display device. The phase difference layer typically has a circular polarization function or an elliptical polarization function. The phase difference layer can typically exhibit reverse dispersion wavelength characteristics and can function as a λ/4 plate. The phase difference layer can be a stretched film of a resin film, or can be a directional solidification layer of a liquid crystal compound (a liquid crystal directional solidification layer). The phase difference layer is preferably a stretched film of a resin film. With the above-mentioned structure, the intrusion of ammonium ions into the polarizer can be effectively suppressed. Representative examples of the resin constituting the resin film include polycarbonate resins and polyester carbonate resins.

C. Organic EL display device The polarizing plate described in the above item A and the polarizing plate with a phase difference layer described in the above item B can be applied to an organic EL display device. Therefore, an organic EL display device including a polarizing plate or a polarizing plate with a phase difference layer is also included in the embodiments of the present invention. The organic EL display device is typically provided with a polarizing plate or a polarizing plate with a phase difference layer on its viewing side. The polarizing plate with a phase difference layer is laminated in such a manner that the phase difference layer becomes the side of the organic EL unit (in such a manner that the polarizing plate becomes the viewing side). In one embodiment, the organic EL display device has a curved shape (substantially a curved display screen) and/or can be bent or folded. As mentioned above, when the inventors of the present invention applied the polarizing plate and the polarizing plate with a phase difference layer to the organic EL display device, they found a new problem that the polarizing plate and the polarizing plate with a phase difference layer would be discolored due to ammonia (essentially ammonium ions) generated from the organic EL panel, and solved the problem by the polarizing plate described in A and the polarizing plate with a phase difference layer described in B. That is, in the organic EL display device, the polarizing plate and the polarizing plate with a phase difference layer in the embodiment of the present invention have a significant effect.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to the examples, but the present invention is not limited to the examples. The methods for measuring the various properties are as described below. In addition, unless otherwise specified, the "parts" and "%" in the examples and comparative examples are based on weight. (1) Thickness The thickness of the first PVA-based resin layer is measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). In addition, the thickness of the second PVA-based resin layer is measured by cutting the polarizing plates of the examples and comparative examples, observing the cross section of the polarizing plates using a scanning electron microscope ("JSM7100F" manufactured by JEOL Ltd.), and measuring from the microscope image. (2) Single-body transmittance and polarization degree The polarizing plates used in the examples and comparative examples were measured using an ultraviolet-visible spectrophotometer ("LPF200" manufactured by Otsuka Electronics Co., Ltd.), and the measured single-body transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc were used as Ts, Tp, and Tc of the polarizer, respectively. These Ts, Tp, and Tc were measured using the 2-degree field of view (C light source) of JIS Z8701 and the Y values after the visual sensitivity correction. The polarization degree P was calculated from the obtained Tp and Tc using the following formula. Polarization degree P (%) = {(Tp-Tc)/(Tp+Tc)} ^{1 /2} × 100 The cross absorbance A ₂₁₀ was determined from the cross transmittance Tc ₂₁₀ at a measured wavelength of 210 nm, and the cross absorbance A ₅₅₀ was determined from the cross transmittance Tc ₅₅₀ at a measured wavelength of 550 nm using "U4100" manufactured by Hitachi High-Tech Corporation. The cross absorbance A ₄₇₀ was determined from the cross transmittance Tc ₄₇₀ at a measured wavelength of 470 nm, and the cross absorbance A 600 was determined from the cross transmittance Tc ₆₀₀ at a measured wavelength of 600 nm using "V- ₇₁₀₀ " manufactured by JASCO Corporation. (3) Moisture permeability was measured in accordance with JIS Z 0208. Specifically, the protective layer (film constituting the protective layer) used in the examples and comparative examples was cut into a 10 cm Φ circle to prepare a test sample. The moisture permeability of the test sample was measured at 40°C and 92% RH using "MOCON" manufactured by Hitachi Ltd. (4) Crossed b value The polarizing plate used in the examples and comparative examples was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100") to determine the hue in the crossed polarization state. The lower the cross b value (negative value and larger absolute value) of the polarizing plate, the more bluish the hue is rather than neutral. (5) Boric Acid Concentration The intensity of the boric acid peak (665 cm -1 ) and the intensity of the reference peak (2941 cm ^-1 ) were measured for the polarizing plates obtained in the Examples and Comparative Examples by attenuated total reflectance spectroscopy (ATR) using polarized light as the measurement light using a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name " ^SPECTRUM2000 "). The boric acid amount index was calculated from the obtained boric acid peak intensity and reference peak intensity using the following formula, and the boric acid concentration was determined from the calculated boric acid amount index using the following formula. (Boric acid index) = (Intensity of the boric acid peak at 665 cm ^-1 ) / (Intensity of the reference peak at 2941 cm ^-1 ) (Boric acid concentration) = (Boric acid index) × 6.61 + 0.47 (6) Ammonia decolorization test Pour 1.5 ml of a 10% ammonia solution into a glass bottle (cylindrical with a diameter of 30 mm and a depth of 50 mm). At this time, the distance from the liquid surface of the ammonia solution to the mouth of the glass bottle (upper end) is about 30 mm. Cut the polarizing plate obtained in the embodiment and the comparative example into a size of 30 mm × 30 mm as a test sample. Make the test sample cover the entire mouth of the glass bottle and in order to prevent steam from leaking from the gap, make the test sample stick to the edge of the glass bottle mouth through an adhesive layer. Heat the glass bottle covered with the test sample at 60°C for 2 hours. The polarization degree of the polarizing plate (actually a polarizer) before heating is P ₀ , and the polarization degree after heating is P ₂₀ . The absolute value of the change in polarization degree |ΔP| is calculated from the following formula. The smaller the |ΔP| is, the more the discoloration caused by ammonia is suppressed. |ΔP|=|P ₂₀ -P ₀ | Based on the obtained ΔP, the following criteria are used for evaluation. A: |ΔP| is less than 10%B: |ΔP| is greater than 10% and less than 25%C: |ΔP| is greater than 25% and less than 50%D: |ΔP| is greater than 50% and less than 75%E: |ΔP| is greater than 75%

[Example 1] 1. Preparation of polarizer As a thermoplastic resin substrate, a long amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100µm) with a Tg of about 75°C was used, and one side of the resin substrate was subjected to a corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetyl acetyl modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a ratio of 9:1, and the resulting mixture was dissolved in water to prepare a PVA aqueous solution (coating liquid). The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60°C to form a PVA resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (long side direction) in an oven at 130°C (air-assisted stretching treatment). Then, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilizing treatment). Next, the film was immersed in a dyeing bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 relative to 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the polarizer finally obtained became 43.0% (dyeing treatment). Next, the film was immersed in a crosslinking bath (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid relative to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Then, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4 weight%, potassium iodide concentration 5 weight%) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (long side direction) between rollers with different peripheral speeds to achieve a total stretching ratio of 5.5 times (underwater stretching treatment). Afterwards, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 3 weight parts of potassium iodide with 100 weight parts of water) at a liquid temperature of 20°C (cleaning treatment). Then, it was dried in an oven maintained at about 90°C while contacting a SUS heating roller maintained at a surface temperature of about 75°C (drying shrinkage treatment). According to the above method, a polarizer is formed on the resin substrate to obtain a laminate having a structure of resin substrate/polarizer (first PVA resin layer). The thickness of the polarizer (first PVA resin layer) is 5µm, and the single body transmittance is 43.0%.

2. Preparation of polarizing plate A second PVA resin layer is formed on the surface of the polarizing element (first PVA resin layer) of the laminate obtained above and a protective layer is laminated at the same time. The details are as follows. 6.02 parts of acetylacetyl-modified PVA (polymerization degree 1200, acetylacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, solid content concentration 4%, manufactured by Mitsubishi Chemical Corporation, trade name "GOHSENX Z-200"), 25 parts of an aqueous solution containing positively charged alumina colloid (average particle size 15 nm) at a solid content concentration of 3.2%, and 18.98 parts of pure water are mixed to obtain a water-based resin composition. The resin composition is applied to the surface of the first PVA resin layer in a manner such that the thickness after drying is 0.09µm, and the HC-TAC film is laminated using a roller machine, and then the resin composition is dried to form the second PVA resin layer and the polarizer and protective layer are laminated at the same time. In addition, the HC-TAC film is a film in which a hard coating (HC) layer (thickness 7µm) is formed on a triacetate cellulose (TAC) film (thickness 25µm), and the TAC film is laminated in a manner such that it becomes the side of the first PVA resin layer. The moisture permeability of the HC-TAC film is 427g/ ^m2・24h. Next, the resin substrate was peeled off, and an acrylic adhesive (thickness 20µm) was placed on the peeled surface to obtain a polarizing plate having a structure of a visual side protective layer (HC-TAC film)/a second PVA resin layer/a first PVA resin layer (polarizer)/an adhesive layer (acrylic adhesive). The boric acid concentration of the surface of the first PVA resin layer on the side opposite to the visual side was 17.5 wt%, and the boric acid concentration of the surface of the visual side of the second PVA resin layer was 17.0 wt%. In addition, the polarizer of the obtained polarizing plate has an A ₅₅₀ /A ₂₁₀ of 2.59, an A ₄₇₀ /A ₆₀₀ of 0.96, and an orthogonal b value of -1.6. The obtained polarizing plate was subjected to the evaluation of (6) above. The results are listed in Table 1. In addition, the acrylic adhesive was prepared in the following manner. A monomer mixture containing 91 parts of butyl acrylate, 6 parts of acrylamide, 2.7 parts of acrylic acid and 0.3 parts of 4-hydroxybutyl acrylate was fed into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler. 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were added to 100 parts of the monomer mixture, and nitrogen was introduced while slowly stirring to replace the nitrogen. The liquid temperature in the flask was maintained at about 55°C, and the polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer with a weight average molecular weight (Mw) of 2.7 million and Mw/Mn=3.8. To 100 parts of the solid content of the acrylic polymer solution, 0.1 parts of trihydroxymethylenepropane/toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 parts of a peroxide crosslinking agent (manufactured by NOF Corporation, trade name "NYPER BMT"), and 0.2 parts of an epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were mixed to obtain an acrylic adhesive.

[Example 2] A polarizing plate was obtained in the same manner as in Example 1 except that the conditions of the crosslinking treatment during the preparation of the polarizing element (the first PVA-based resin layer) were changed to change the boric acid concentration of the polarizing element. The boric acid concentration of the surface of the first PVA-based resin layer on the side opposite to the visual side was 21.8 wt%, and the boric acid concentration of the surface of the visual side of the second PVA-based resin layer was 19.7 wt%. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Example 3] A polarizing plate was obtained in the same manner as in Example 1 except that the thickness of the second PVA resin layer was set to 0.07µm and the conditions of the crosslinking treatment during the preparation of the polarizer (first PVA resin layer) were changed to change the boric acid concentration of the polarizer. The boric acid concentration of the surface of the first PVA resin layer on the side opposite to the visual side was 21.8 wt%, and the boric acid concentration of the surface of the visual side of the second PVA resin layer was 20.3 wt%. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Example 4] In addition to changing the conditions of the crosslinking treatment and the stretching treatment during the preparation of the polarizer (the first PVA-based resin layer) to change the optical properties of the polarizer, a laminate having a resin substrate/polarizer structure is obtained in the same manner as in Example 1. The thickness of the polarizer is 5µm, the single body transmittance is 43.0%, A ₅₅₀ /A ₂₁₀ is 1.37, A ₄₇₀ /A ₆₀₀ is 0.90, and the orthogonal b value is -2.62. The following procedure is to obtain a polarizing plate in the same manner as in Example 1. The boric acid concentration of the surface of the first PVA-based resin layer on the side opposite to the viewing side is 14.3% by weight, and the boric acid concentration of the surface of the viewing side of the second PVA-based resin layer is 13.9% by weight. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Example 5] A long roll of a 30μm thick polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000") was uniaxially stretched in the longitudinal direction to 5.9 times using a roll stretching machine, and simultaneously subjected to swelling, dyeing, crosslinking, and washing treatments, and finally dried to produce a polarizer (first PVA resin layer) with a thickness of 12μm. Specifically, the swelling treatment was performed in pure water at 20°C while being stretched to 2.2 times. Next, the dyeing treatment was performed in a 30°C aqueous solution in which the weight ratio of iodine to potassium iodide was 1:7 and the iodine concentration was adjusted to make the single unit transmittance of the obtained polarizer 43.0%, while being stretched to 1.4 times. Next, the crosslinking treatment adopts a two-stage crosslinking treatment. The first stage crosslinking treatment is to treat in an aqueous solution containing boric acid and potassium iodide at 40°C while extending to 1.2 times. The boric acid content of the aqueous solution in the first stage crosslinking treatment is set to 5.0% by weight, and the potassium iodide content is set to 3.0% by weight. The second stage crosslinking treatment is to treat in an aqueous solution containing boric acid and potassium iodide at 65°C while extending to 1.6 times. The boric acid content of the aqueous solution in the second stage crosslinking treatment is set to 4.3% by weight, and the potassium iodide content is set to 5.0% by weight. In addition, the washing treatment is carried out with a potassium iodide aqueous solution at 20°C. The potassium iodide content of the aqueous solution in the washing treatment is set to 2.6% by weight. Finally, the polarizer (first PVA resin layer) was dried at 70°C for 5 minutes to obtain a polarizer. A polarizing plate was obtained in the same manner as in Example 1 except that the polarizer (first PVA resin layer) was used. Here, the boric acid concentration of the surface of the first PVA resin layer on the side opposite to the visual side was 24 wt%, and the boric acid concentration of the surface of the visual side of the second PVA resin layer was 21.6 wt%. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Comparative Example 1] A laminate having a resin substrate/polarizer structure is obtained in the same manner as in Example 1. The same HC-TAC film as in Example 1 is bonded to the polarizer surface of the laminate through a UV-curable adhesive (thickness 1µm). That is, the second PVA-based resin layer is not formed. In the above manner, a polarizing plate having a visual side protective layer (HC-TAC film)/adhesive/polarizer/adhesive layer (acrylic adhesive) is obtained. The boric acid concentration of the surface of the PVA-based resin layer (polarizer only) on the side opposite to the visual side is 13.6% by weight, and the boric acid concentration of the visual side surface is 15.4% by weight. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Comparative Example 2] A polarizing plate was obtained in the same manner as in Comparative Example 1 except that the conditions of the crosslinking treatment during the preparation of the polarizer were changed to change the boric acid concentration of the polarizer. The boric acid concentration of the surface of the PVA resin layer (polarizer only) on the side opposite to the viewing side was 16.6 wt%, and the boric acid concentration of the surface on the viewing side was 18.6 wt%. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Comparative Example 3] A polarizing plate was obtained in the same manner as in Example 1 except that a HC-COP film was used as the visual side protective layer. The HC-COP film is a film having a hard coating (HC) layer (thickness 2µm) formed on a COP film (thickness 25µm), and its moisture permeability is 35g/ ^m2・24h. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

[Table 1]

[Evaluation] As is apparent from Table 1, according to the embodiment of the present invention, a polarizing plate having almost no change in polarization degree (i.e., no discoloration) even when exposed to ammonia can be obtained. That is, according to the embodiment of the present invention, a polarizing plate and a polarizing plate with a phase difference layer that suppress discoloration when used in an organic EL display device can be realized. On the other hand, the polarizing function of the polarizing plate of the comparative example is greatly reduced.

Industrial Applicability The polarizing plate of the present invention can be suitably used in organic EL display devices, and the polarizing plate with a phase difference layer can be suitably used as an anti-reflection circular polarizing plate for organic EL display devices.

10: PVA resin layer 11: 1st PVA resin layer (polarizer) 12: 2nd PVA resin layer 30: Protective layer 40: Adhesive layer 100: Polarizer

FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.

10: PVA resin layer

11: 1st PVA resin layer (polarizer)

12: Second PVA resin layer

30: Protective layer

40: Adhesive layer

100: Polarizing plate

Claims (7)

A polarizing plate comprises: a polyvinyl alcohol resin layer, a protective layer disposed on the visual side of the polyvinyl alcohol resin layer, and an adhesive layer, wherein the adhesive layer is disposed on the side of the polyvinyl alcohol resin layer opposite to the visual side and adjacent to the polyvinyl alcohol resin layer; the polyvinyl alcohol resin layer comprises a first polyvinyl alcohol resin layer functioning as a polarizer and a protective layer disposed on the first A second polyvinyl alcohol-based resin layer on the visual side of the polyvinyl alcohol-based resin layer; the thickness of the second polyvinyl alcohol-based resin layer is 0.03μm~2μm; the boric acid concentration of the surface of the polyvinyl alcohol-based resin layer on the side opposite to the visual side is greater than the boric acid concentration of the surface of the visual side, and the difference is 0.3 weight % or more; the moisture permeability of the protective layer on the visual side is 200g/ ^m2‧24h or more; the latent change of the adhesive constituting the adhesive layer at 70°C is less than 65μm; and the absolute value of the polarization change of the polarizing plate after being exposed to ammonia vapor in an environment of 60°C for 2 hours |ΔP| is less than 50%. As in claim 1, the polarizing plate, wherein the boric acid concentration of the first polyvinyl alcohol-based resin layer is greater than 14% by weight. A polarizing plate as claimed in claim 1 or 2, wherein the monomer transmittance of the first polyvinyl alcohol-based resin layer is greater than 42.5%, the ratio of its orthogonal absorbance _A550 at a wavelength of 550nm to its orthogonal absorbance _A210 at a wavelength of 210nm ( _A550 / _A210 ) is greater than 1.4, the ratio of its orthogonal absorbance _A470 at a wavelength of 470nm to its orthogonal absorbance _A600 at a wavelength of 600nm ( _A470 / _A600 ) is greater than 0.7, and the orthogonal b value is greater than -10. As in claim 1 or 2, the polarizing plate, wherein the iodine concentration of the first polyvinyl alcohol-based resin layer is 2% to 10% by weight. As in claim 1 or 2, the polarizing plate, wherein the adhesive constituting the aforementioned adhesive layer contains acrylic acid and acrylamide as monomer components. A polarizing plate with a phase difference layer, comprising a polarizing plate and a phase difference layer as described in any one of claims 1 to 5. An organic electroluminescent display device having a polarizing plate as in any one of claims 1 to 5 or a polarizing plate with a phase difference layer as in claim 6.

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