Polarizing plate and display device using same

Abstract

Provided are: a polarizing plate that has excellent durability in high temperatures and high humidity, that can improve resistance to ultraviolet rays of a display device, and that has high crack resistance; and a display device using the same. The polarizing plate is characterized in that: transmittance of a protective film A is 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, 50.0% or more at a wavelength of 500 nm, and 4.0% or less at a wavelength of 380 nm; the protective film A is not cracked by a mandrel having a diameter of 3 mm in a bending resistance test conforming to JIS K 5600-5-1 standards; and the moisture permeability TA and TB of protective films A and B at 40°C and 90% RH simultaneously satisfy conditions (1) and (2).　(1): 300g / m2 / day > TA > 100g / m2 / day (2): 70g / m2 / day ≥ TB

Description

Polarizing plate and display device using the same

[0001] The present invention relates to a polarizing plate and a display device using the same.

[0002] A polarizing plate used in a liquid crystal display device includes a polarizer formed by adsorbing an iodine compound or an organic dye onto a polyvinyl alcohol (PVA) film and stretching the PVA film to orient the iodine compound or the organic dye. Because polarizers formed using PVA films are poor in strength and water resistance, protective films are attached to both sides of the polarizer to protect the polarizer.

[0003] Conventionally, a hard-coated film in which a hard-coating layer is provided on one side of a triacetyl cellulose (TAC) film has been generally used as a protective film for a polarizing plate (see, for example, Patent Document 1). However, the moisture permeability of a hard-coated film using a TAC film as a substrate is 300 to 1000 g / m ２ / day, and there was a problem that moisture absorption of the polarizer could not be sufficiently suppressed under high temperature and high humidity conditions, causing deterioration of the polarizer. Therefore, in order to improve the moisture resistance compared to protective films using TAC film as a base material, various protective films using cycloolefin polymer (COP) or polyethylene terephthalate (PET) as a base material have been developed (see, for example, Patent Document 2). The moisture permeability of the protective film is 5 to 100 g / m ２ / day.

[0004] JP 2016-175991 A JP 2006-30807 A

[0005] In recent years, there are display devices that are used under extremely high temperatures and humidity, such as display devices for in-vehicle applications, and polarizing plates used in such display devices are also required to have durability under high temperature and high humidity environments.

[0006] By using a protective film made of a low-moisture-permeable substrate such as the above-mentioned COP or PET, it is possible to sufficiently reduce the penetration of moisture from the outside of the polarizing plate into the polarizer. However, it has been found that when a polarizing plate is exposed to a high-temperature environment, moisture contained in the substrate of the protective film or moisture contained in the adhesive used to attach the protective film to the polarizer penetrates and remains inside the polarizing plate, causing deterioration of the polarizer due to this moisture.

[0007] Furthermore, some display devices are subject to deterioration due to ultraviolet rays (UV light), with the brightness and color development being significantly impaired over time, and therefore the protective film for the polarizing plate is also required to be able to be resistant to ultraviolet rays.

[0008] In addition, there is a growing demand for display devices with complex designs, such as curved surfaces. However, when punching polarizing plates with such shapes, cracks can occur in the hard coat layer of the polarizing plate, resulting in a decrease in yield.

[0009] Therefore, an object of the present invention is to provide a polarizing plate that has excellent durability under high temperature and high humidity conditions, can improve the resistance of a display device to ultraviolet rays, and has high crack resistance, and a display device using the same.

[0010] The polarizing plate according to the present invention is a polarizing plate having a protective film A bonded to one surface of a polarizer and a protective film B bonded to the other surface, wherein the transmittance of the protective film A is 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, 50.0% or more at a wavelength of 400 nm, and 4% or less at a wavelength of 380 nm, and the protective film A does not crack when used with a mandrel having a diameter of 3 mm in a bending resistance test in accordance with JIS K 5600-5-1, and the moisture permeabilities TA and TB of the protective films A and B at 40°C and 90% RH simultaneously satisfy the following conditions (1) and (2): ２ / day>TA>100g / m ２ / day...(1) 70g / m ２ / day≧TB (2)

[0011] A display device according to the present invention includes the above polarizing plate.

[0012] According to the present invention, it is possible to provide a polarizing plate that has excellent durability under high temperature and high humidity conditions, can improve the resistance of a display device to ultraviolet light, and has high crack resistance, and a display device using the same.

[0013] FIG. 1 is a cross-sectional view showing a schematic configuration of a display device including a polarizing plate according to an embodiment.

[0014] FIG. 1 is a cross-sectional view showing a schematic configuration of a display device including a polarizing plate according to an embodiment.

[0015] The polarizing plate 10 includes a polarizer 1, a protective film A laminated on one side of the polarizer 1, and a protective film B laminated on the other side of the polarizer 1. The polarizer 1 is formed by adsorbing iodine or a dye onto a polyvinyl alcohol (PVA) film and orienting the film. Because the PVA constituting the polarizer 1 has poor strength and water resistance, protective films A and B are laminated to both sides of the polarizer 1.

[0016] The protective film A is a hard-coated film in which a hard-coat layer 3 (HC layer) is laminated on one side of a TAC film 2. The hard-coat layer 3 is a functional layer that coats the flexible TAC film 2 and imparts hardness to the protective film A. It can be formed by applying and curing a coating liquid containing a UV-curable material. The pencil hardness of the protective film A (hard-coated film) is preferably 3H or higher. Furthermore, since the TAC film 2 has low water vapor barrier properties (high moisture permeability), the moisture permeability of the protective film A is adjusted by the hard-coat layer 3. Specifically, by incorporating a hydrophobic material into the hard-coat layer 3, the moisture permeability of the protective film A can be adjusted within the range described below. The content of the hydrophobic material in the hard-coat layer 3 is preferably 0.1% by mass or more and 4.0% by mass or less. The content of the hydrophobic material in the hard-coat layer 3 is more preferably 0.2% by mass or more. The content of the hydrophobic material in the hard-coat layer 3 is more preferably 1.5% by mass or less. Examples of hydrophobic materials that can be contained in the hard coat layer 3 include cycloolefin polymers. Furthermore, the protective film A preferably has UV-blocking properties. Specifically, by incorporating an ultraviolet absorber into the hard coat layer 3, the transmittance of the protective film A for light of a predetermined wavelength can be adjusted to the range described below. Examples of ultraviolet absorbers that can be incorporated into the hard coat layer 3 include benzophenone-based compounds. The content of the ultraviolet absorber in the hard coat layer 3 can be, for example, 1% by mass or more and 10% by mass or less. The TAC film 2 of the protective film A is bonded to the polarizer 1 using a water-based glue (aqueous PVA solution). Furthermore, inorganic fine particles (silica fine particles) may be incorporated into the hard coat layer 3 to improve the mechanical strength of the hard coat layer 3. However, this is not preferred because it reduces the flexibility of the hard coat layer 3 and may cause cracks in the hard coat layer of the polarizer when the polarizer is punched, for example.

[0017] Display devices, particularly those for in-vehicle use, are required to have complex designs, such as curved surfaces, and there is a risk of cracks occurring in the hard coat layer 3 of the protective film A when punching a polarizing plate. Therefore, the protective film A preferably has high flex resistance, and specifically, it preferably does not crack when punched with a mandrel having a diameter of 3 mm in a flex resistance test in accordance with JIS K 5600-5-1. By satisfying this condition, cracks are less likely to occur in the hard coat layer, even when punching a polarizing plate into a complex shape, and a decrease in yield can be suppressed.

[0018] The thickness of the TAC film 2 used in the protective film A is not particularly limited, but is preferably 25 μm or more and 100 μm or less. The film thickness of the hard coat layer 3 is not particularly limited, but is preferably 2 μm or more and 15 μm or less. The film thickness of the hard coat layer 3 is more preferably 3 μm or more, and even more preferably 5 μm or more. The film thickness of the hard coat layer 3 is more preferably 9 μm or less, and even more preferably 8 μm or less. If the film thickness of the hard coat layer 3 is too thin, the moisture permeability of the protective film A may become too high, and the moisture permeability TA of the protective film A described below may not satisfy the range of condition (1). If the film thickness of the hard coat layer 3 is too thick, the moisture permeability of the protective film A may become too low, and the moisture permeability TA of the protective film A described below may not satisfy the range of condition (1), and this may hinder the thinning of the polarizing plate 10. However, the thickness of the TAC film 2 and the film thickness of the hard coat layer 3 can be changed as appropriate as long as the moisture permeability and transmittance of the protective film A are within the ranges described below and no cracks occur when using a mandrel with a diameter of 3 mm in the bending resistance test.

[0019] The protective film B is a low-moisture permeable film and can be made of any one of cycloolefin polymer, polyethylene terephthalate, and polymethyl methacrylate, with cycloolefin polymer being particularly preferred. The protective film B is attached to the polarizer 1 via an ultraviolet-curable adhesive. The thickness of the protective film B is not particularly limited, but is preferably 10 to 100 μm.

[0020] In the display device, the protective film B is disposed on the display panel 4 side, and the hard coat layer 3 of the protective film A is disposed on the viewing side (opposite the display panel 4). For example, an OLED (organic EL) device can be used as the display panel 4, and the protective film B and the display panel 4 are bonded together with, for example, an optically transparent adhesive (OCA) or an optically transparent resin (OCR).

[0021] As described above, the polarizer 1 and the TAC film 2 of the protective film A are bonded together using a water-based adhesive, and therefore moisture may remain in the adhesive layer and the TAC film 2 even after the drying process. If both protective films A and B were constructed using films with low moisture permeability, the intrusion of moisture from the outside would be suppressed, but in an extremely high-temperature environment such as the inside of a car in summer, moisture would be generated from the adhesive layer and / or the TAC film 2 and remain inside the polarizing plate 10, leading to deterioration of the polarizer 1. Therefore, in the polarizing plate 10 according to this embodiment, a difference is provided between the moisture permeability of the protective film A and the moisture permeability of the protective film B, and the moisture permeability of the protective film A and the moisture permeability of the protective film B are each set within a specific range, thereby suppressing moisture-induced deterioration of the polarizer 1.

[0022] Specifically, when the moisture permeabilities of protective films A and B at 40°C and 90% RH are TA and TB, respectively, TA and TB simultaneously satisfy the following conditions (1) and (2). Note that both the moisture permeabilities TA and TB are values ​​measured in accordance with JIS Z 0208-1976. ２ / day>TA>100g / m ２ / day...(1) 70g / m ２ / day≧TB (2)

[0023] By simultaneously satisfying the above conditions (1) and (2), it is possible to suppress the intrusion of moisture from the outside into the polarizing plate, while at the same time, when exposed to a high-temperature environment of, for example, 85°C, it is possible to discharge to the outside moisture generated from the adhesive layer for bonding the protective film A and the polarizer 1 and / or the TAC film 2 of the protective film A.

[0024] The moisture permeability TA of the protective film A is 145 g / m ２ / day or more, and 165 g / m ２ / day or more is more preferable. ２ / day or more, the amount of hydrophobic material contained in the hard coat layer 3 for adjusting the moisture permeability of the protective film A can be reduced, thereby improving the surface hardness of the hard coat layer 3. In addition, the moisture permeability TA of the protective film A is 290 g / m or more. ２ / day or less, and more preferably 240 g / m ２ / day or less is more preferable. ２ / day or less, moisture generated inside the polarizing plate 10 can be released while moisture intrusion from the outside into the polarizing plate 10 can be moderately suppressed, and deterioration of the polarizer can be suppressed for a longer period of time. Furthermore, since the protective film B is intended to completely block the ingress and egress of moisture, it is preferable that the moisture permeability TB of the protective film B is small, and in particular, it is preferable that the moisture permeability TB is 50 g / m or less. ２ It is more preferable that the number of days is equal to or less than 1 / day.

[0025] OLEDs are inherently susceptible to degradation by ultraviolet light. Therefore, it is preferable that the protective film A has a low ultraviolet transmittance, and specifically, the transmittance of light with a wavelength of 380 nm is preferably 4.0% or less. This makes it possible to prevent the display panel 4 from being deteriorated by ultraviolet light contained in external light, which would otherwise impair the brightness and color development of the display device, even when an OLED is used as the display panel 4.

[0026] On the other hand, the protective film A preferably has a transmittance of at least a predetermined value for wavelengths near blue that are longer than 380 nm. Specifically, it is preferably 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, and 50.0% or more at a wavelength of 400 nm. If the hard coat layer 3 absorbs too much light in the blue region, the hard coat layer 3 takes on a yellowish tint, which changes the emitted color of the display panel 4. In the present invention, by suitably suppressing the absorption of light in the blue region by the hard coat layer 3, it is possible to prevent the hard coat layer 3 from taking on a yellowish tint. Therefore, it is possible to prevent the emitted color (white) of the display panel 4 from becoming yellowish, and to prevent the color development of the display device from being impaired.

[0027] As described above, the polarizing plate 10 according to this embodiment includes, as protective films for the polarizer 1, protective film A having moisture permeability that satisfies the above-mentioned condition (1) and protective film B having moisture permeability that satisfies the above-mentioned condition (2). In this configuration, protective film B, which is disposed on the display panel 4 side, almost completely blocks the ingress and egress of moisture. On the other hand, protective film A, which is disposed on the viewing side, prevents moisture from entering the polarizing plate 10 from the outside but allows moisture generated inside the polarizing plate 10 to escape. Therefore, when the polarizing plate 10 according to this embodiment is used in a high-temperature environment, moisture generated inside the polarizing plate 10 does not remain, thereby suppressing deterioration of the polarizer 1 and enabling the optical performance of the polarizing plate 10 to be maintained for a longer period of time.

[0028] Furthermore, the transmittance of the protective film A is 4.0% or less at a wavelength of 380 nm. Therefore, even if an OLED, which is vulnerable to ultraviolet light, is used as the display panel 4, it is possible to prevent the display panel 4 from being deteriorated by ultraviolet light and the resulting loss of brightness and color development.

[0029] The transmittance of the protective film A is 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, and 50.0% or more at a wavelength of 400 nm, which prevents the hard coat layer 3 from being colored yellow and suppresses deterioration of the color development of the display device.

[0030] Furthermore, it is preferable that the protective film A does not crack when used with a mandrel having a diameter of 3 mm in a bending resistance test in accordance with JIS K 5600-5-1, so that cracks are unlikely to occur in the hard coat layer even when the polarizing plate is punched into a complex shape.

[0031] Examples of specific implementations of the present invention will be described below.

[0032] (Example 1) Composition 8 shown in Table 1 was applied as a coating liquid for forming a hard coat layer to a 40 μm-thick TAC film (product name: Fujitack TJ40UL, manufactured by Fujifilm Corporation) using a wire bar coater, and the film was dried by heating in an oven at 60° C. for 7 minutes. Then, ultraviolet light was applied to the coating film at an integrated light dose of 100 mJ / cm using a UV curing device with a high-pressure mercury lamp in a nitrogen atmosphere (oxygen concentration 500 ppm or less). ２ The resulting hard coat layer had a thickness of 3 μm after curing, forming a protective film A (hard coat film) according to Example 1. A COP film having a thickness of 26 μm was used as a protective film B.

[0033] A polarizer was attached to the TAC film surface of protective film A using water-based glue and dried, and then the protective film was attached to the polarizer using a UV-curable adhesive, and the UV-curable adhesive was cured by irradiating it with UV light, thereby obtaining a polarizing plate according to Example 1.

[0034]

[0035] (Examples 2 to 7, Comparative Examples 1 to 6) Polarizing plates according to Examples 2 to 7 and Comparative Examples 1 to 6 were produced in the same manner as in Example 1, except that compositions 1 to 7 and 9 shown in Table 1 were used as the coating liquid for forming the hard coat layer. The inorganic fine particles (silica fine particles) used in composition 7 are generally added to improve the mechanical strength of the hard coat layer.

[0036] Example 8 A polarizing plate according to Example 8 was produced in the same manner as in Example 1, except that a PET film having a thickness of 38 μm was used as the protective film B.

[0037] Example 9 A polarizing plate according to Example 9 was produced in the same manner as in Example 1, except that a PMMA film having a thickness of 40 μm was used as the protective film B.

[0038] (Moisture Permeability) Before being attached to a polarizer, the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B were measured under conditions of 40° C. and 90% humidity in accordance with JIS Z 0208-1976.

[0039] (Transmittance) The transmittance of the protective film A before being attached to the polarizer at wavelengths of 440 nm, 420 nm, 400 nm, and 380 nm was measured using a spectrophotometer (Hitachi High-Technologies Corporation's "U-4100") under conditions of a C light source and a 2-degree visual field.

[0040] (Yellowness Index) The transmission YI value of the protective film A before being attached to the polarizer was measured using a spectrophotometer (Hitachi High-Technologies Corporation's "U-4100") in accordance with JIS K 7373. When the transmission YI was 2.2 or less, the yellowness index was evaluated as good (less yellowish).

[0041] (Polarization Degree Evaluation) The polarization degrees of the polarizing plates according to Examples 1 to 9 and Comparative Examples 1 to 6 were measured. Thereafter, the polarizing plates were placed in a thermostatic chamber at 85°C and 85% RH, and the polarization degrees were measured 240 hours and 500 hours after placement. The polarization degrees were calculated by correcting the luminosity of the values ​​measured using an absorptiometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) using a 2-degree visual field (C light source) according to JIS Z 8701. A polarization degree of 99.3 or higher was considered good.

[0042] (Brightness Evaluation) The polarizing plates according to Examples 1 to 9 and Comparative Examples 1 to 6 were each attached to a white OLED device using an adhesive, with the protective film A on the outermost surface. The LED device was energized and the brightness of the OLED device was visually confirmed, with a rating of ◯ indicating sufficient brightness and an × indicating insufficient brightness.

[0043] Thereafter, a light resistance test was performed by irradiating UV light from the viewing side (protective film A side) for 10 hours using a metal halide lamp type weather meter ("Eye Super UV Tester (registered trademark)" manufactured by Iwasaki Electric Co., Ltd.). Thereafter, a power was applied to the OLED device, and the luminance of the OLED device was visually confirmed. If the luminance was sufficient, it was evaluated as ◯, and if the luminance was insufficient, it was evaluated as ×.

[0044] (Bending Resistance Evaluation) Protective film A before being attached to a polarizer was bent with the hard coat layer facing inward, and a bending resistance test was performed in accordance with JIS K 5600-5-1. The mandrel diameter was reduced by 1 mm increments until it reached 3 mm, and the smallest diameter at which cracks did not occur in the hard coat layer was used as the evaluation result. An evaluation result of 3 mm or less was evaluated as pass (◯), and any other result was evaluated as fail (×).

[0045] (Evaluation of crack resistance) Using a press with a cutting blade, the polarizing plate was punched into a circle with a radius of 5 mm, and the presence or absence of cracks in the hard coat layer was visually confirmed. The case where no cracks occurred in the hard coat layer was evaluated as ◯, and the case where cracks occurred was evaluated as ×.

[0046] Table 2 shows the moisture permeability TA of protective film A, the moisture permeability TB of protective film B, the transmittance of protective film A at wavelengths of 440 nm, 420 nm, 400 nm, and 380 nm, the measured values ​​of the polarization degree of the polarizing plate (before and after the high-temperature, high-humidity durability test), and the results of the brightness evaluation used in Examples 1 to 9 and Comparative Examples 1 to 6. Table 3 also shows the results of the bending resistance evaluation and crack resistance evaluation.

[0047]

[0048]

[0049] The polarizing plates according to Examples 1 to 9 and Comparative Examples 2, 5, and 6 had moisture permeability TA of protective film A and moisture permeability TB of protective film B satisfying the above conditions (1) and (2), and exhibited high degrees of polarization even when placed in a thermostatic chamber at 85°C and 85% RH for 500 hours. The polarization degree test results after the high-temperature, high-humidity durability test according to Examples 1 to 9 and Comparative Examples 2, 5, and 6 mean that, even when exposed to high temperature and high humidity, there was no deterioration of the polarizer due to moisture entering the polarizing plate from the outside, nor due to moisture contained in protective film A and / or the adhesive used to bond protective film A.

[0050] On the other hand, the polarizing plates according to Comparative Examples 1 and 3 had a high moisture permeability TA of the protective film A exceeding the upper limit of the above-mentioned condition (1). The polarizing plates according to Comparative Examples 1 and 3 exhibited lower polarization degrees after 240 hours and 500 hours in a thermostatic chamber at 85°C and 85% RH than those of Examples 1 to 9 and Comparative Examples 2, 5 to 6. Comparing Comparative Examples 1 and 2 with Examples 1 to 9 and Comparative Examples 2, 5 to 6 suggests that the polarizer of Comparative Example 31 deteriorated as a result of moisture penetrating from the protective film A into the interior of the polarizing plate under high temperature and high humidity. In particular, comparing the polarizing plate according to Comparative Example 1 with Examples 3, 5 to 6 suggests that the thickness of the hard coat layer was too thin, causing the moisture permeability TA to exceed the upper limit of the condition (1). Furthermore, the thinner hard coat layer likely resulted in an insufficient amount of ultraviolet absorber, causing the transmittance of the protective film A to exceed 4.0% at a wavelength of 380 nm.

[0051] Furthermore, in the polarizing plate according to Comparative Example 4, the moisture permeability TA of protective film A is lower than the lower limit of the above-mentioned condition (1). The polarizing plate according to Comparative Example 4 also exhibited a lower polarization degree after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours than those of Examples 1 to 9 and Comparative Examples 2, 5 to 6. Comparing Comparative Example 4 with Examples 1 to 9 and Comparative Examples 2, 5 to 6, it is believed that in the polarizing plate according to Comparative Example 4, moisture penetration into the polarizing plate under high temperature and high humidity conditions was suppressed, but the polarizer deteriorated due to moisture contained in protective film A and / or the adhesive used to bond protective film A.

[0052] Furthermore, in the polarizing plates according to Examples 1 to 9 and Comparative Examples 3 to 4 and 6, the transmittance of protective film A was 4.0% or less at a wavelength of 380 nm. Therefore, even after the light resistance test, there was no decrease in the brightness of the OLED device. Furthermore, the transmittance of protective film A was 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, and 50.0% or more at a wavelength of 400 nm, so the white light of the OLED device was not yellowish and had good color development.

[0053] On the other hand, the polarizing plates according to Comparative Examples 1 to 2 and 5 exceeded 4.0% at a wavelength of 380 nm, resulting in a decrease in the brightness of the OLED device after the light resistance test.

[0054] Furthermore, in the protective film A of the polarizing plate according to Comparative Example 6, cracks occurred in the hard coat layer when the mandrel diameter was less than 6 mm in the bending resistance test. Consequently, cracks also occurred in the hard coat layer during punching of the polarizing plate. This is because the flexibility of the hard coat layer was reduced due to the addition of inorganic fine particles to the hard coat layer of Comparative Example 6. In the protective film A of the polarizing plate according to Comparative Example 2, no cracks occurred in the hard coat layer during punching of the polarizing plate, but cracks occurred in the hard coat layer during the bending resistance test when the mandrel diameter was less than 4 mm. This is thought to be because the hard coat layer thickness of Comparative Example 2 was too thick, which deteriorated the results for the mandrel diameter.

[0055] From the above, it was confirmed that, according to the present invention, when the moisture permeability TA of protective film A and the moisture permeability TB of protective film B satisfy the above conditions (1) and (2), deterioration of the polarizer can be suppressed and the optical performance of the polarizing plate can be maintained even when exposed to an extremely harsh environment of high temperature and high humidity for a long period of time. Furthermore, when the transmittance of protective film A is 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, 50.0% or more at a wavelength of 400 nm, and 4.0% or less at a wavelength of 380 nm, impairment of the brightness and color development of the display device can be suppressed. Furthermore, when protective film A does not crack when used with a 3 mm diameter mandrel in a bending resistance test, it was confirmed that no cracks occur in the hard coat layer during punching of the polarizing plate.

[0056] In particular, the polarizing plates according to Examples 2 to 4 did not show a decrease in polarization degree after 240 hours in a thermostatic chamber at 85°C and 85% RH, and even after 500 hours, the polarization degree remained at a very high value of 99.4%. This is because, when comparing Examples 2 to 4 with the other Examples, the film thickness of the hard coat layer was in the range of 5 μm or more and 8 μm or less, and the moisture permeability TA of the protective film A was 165 g / m ２ / day or more 240g / m ２ / day or less, and furthermore, it is presumed that this is because the base material of protective film B was a cycloolefin polymer.

[0057] The present invention can be used as a polarizing plate for use in a display device, and is particularly suitable as a polarizing plate for a display device used in a high-temperature environment such as an in-vehicle application.

[0058] REFERENCE SIGNS LIST 1 Polarizer 2 TAC film 3 Hard coat layer 4 Display panel 10 Polarizing plate A, B Protective film

Claims

1. A polarizing plate having a protective film A bonded to one surface of a polarizer and a protective film B bonded to the other surface, wherein the transmittance of the protective film A is 90.0% or more at a wavelength of 440 nm, 86.0% or more at a wavelength of 420 nm, 50.0% or more at a wavelength of 400 nm, and 4.0% or less at a wavelength of 380 nm, wherein the protective film A does not crack when used with a mandrel having a diameter of 3 mm in a bending resistance test in accordance with JIS K 5600-5-1, and wherein the moisture permeabilities TA and TB of the protective films A and B at 40°C and 90% RH simultaneously satisfy the following conditions (1) and (2): ２ / day>TA>100g / m ２ / day...(1) 70g / m ２ / day≧TB (2) 2. The polarizing plate according to claim 1, wherein the protective film A is a hard-coated film in which a hard-coating layer containing an ultraviolet absorber is laminated on one surface of a triacetyl cellulose film.

3. The polarizing plate according to claim 1, wherein the protective film B is a film made of one of cycloolefin polymer, polyethylene terephthalate, and polymethyl methacrylate.

4. A display device comprising the polarizing plate according to any one of claims 1 to 3.

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