Method for restoring optical properties of polarizer deteriorated in high temperature environment

Abstract

The present invention provides a method for restoring the optical properties of a polarizer that has been degraded in a high temperature environment. The method for restoring the optical properties of a polarizer according to an embodiment of the present invention comprises: treating the polarizer that has been degraded in a high temperature environment in an environment of 40°C to 65°C and 85% RH to 95% RH for more than 40 minutes.

Description

Technical Field

[0001] The present invention relates to a method for restoring the optical properties of a polarizing plate that has deteriorated in a high-temperature environment. Background Art

[0002] In image display devices such as liquid crystal display devices and organic electroluminescent (EL) display devices, polarizers have been widely used for the purpose of realizing image display and / or improving the performance of the image display. For polarizers, when heat treatment is to be performed for a specific purpose, they are sometimes exposed to a high temperature environment in actual use and / or molded into a given shape in a high temperature environment. In the vast majority of the above-mentioned cases, the optical properties of the polarizer (representatively polarization degree, monomer transmittance, hue) will be significantly degraded. Therefore, it is required to restore the optical properties of the polarizer that has been degraded in a high temperature environment.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 8-136731 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The present invention has been made to solve the above-mentioned conventional problems, and a main object of the present invention is to provide a method for satisfactorily restoring the optical properties of a polarizing plate that has deteriorated in a high-temperature environment.

[0008] Solutions to the problem

[0009] The method for restoring the optical properties of a polarizer according to an embodiment of the present invention includes:

[0010] The polarizing plate whose optical properties have deteriorated in a high temperature environment is treated in an environment of 40° C. to 65° C. and 85% RH to 95% RH for 40 minutes or more.

[0011] In one embodiment, the polarizer satisfies the following relationship:

[0012] P H -P0=ΔP1≤-0.005(%)

[0013] P R -P H =ΔP2≥+0.005(%)

[0014] b H -b0=Δb1≥+0.3

[0015] b R -bH =Δb2≤-0.3

[0016] in,

[0017] P0 is the polarization degree before degradation, P H is the polarization degree after degradation and before the above treatment, P R is the degree of polarization after the treatment; b0 is the hue b value before degradation, b H is the hue b value after degradation and before the treatment, b R is the hue b value after the processing.

[0018] In one embodiment, the polarizer further satisfies the following relationship:

[0019] Ts H -Ts0=ΔTs1≥+0.3(%)

[0020] Ts R -Ts H =ΔTs2≤-0.3(%)

[0021] in,

[0022] Ts0 is the single body transmittance before degradation, Ts H is the single body transmittance after degradation and before the above treatment, Ts R is the single body transmittance after the treatment.

[0023] In one embodiment, the polarizer is a polarizer that has been placed in an environment at 100° C. or higher.

[0024] In one embodiment, the polarizing plate is a polarizing plate formed into a given shape.

[0025] Effects of the Invention

[0026] According to the embodiment of the present invention, by treating a polarizing plate whose optical properties have deteriorated in a high-temperature environment in a heating / humidifying environment under given conditions for a given time or longer, the deteriorated optical properties can be well restored. DETAILED DESCRIPTION

[0027] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0028] The method for recovering the optical properties of the polarizer of the embodiment of the present invention includes: heating / humidifying the polarizer whose optical properties have deteriorated in a high temperature environment. The heating / humidification treatment is usually carried out in the form of a durability test of the polarizer. The conventional polarizer is subjected to heating / humidification treatment on the premise that the optical properties of the polarizer are deteriorated (the degree of degradation is used as an indicator of durability). In other words, it is common knowledge in the art that the optical properties of the polarizer are deteriorated due to heating / humidification treatment. On the other hand, the inventors found that by subjecting the polarizer whose optical properties have deteriorated in a high temperature environment to heating / humidification treatment, the deteriorated optical properties can be restored, thereby completing the present invention. That is, the present invention is completed based on a technical idea that is contrary to the common sense of the art, and the effect is an unexpected excellent effect. The heating temperature in the heating / humidification treatment is 40°C to 65°C, for example, 55°C to 65°C, preferably 57°C to 63°C, more preferably 58°C to 62°C, and further preferably about 60°C. Too high or too low a heating temperature may result in the inability to fully restore the optical properties. The humidity in the heating / humidification treatment is 85% RH to 95% RH, preferably 87% RH to 93% RH, more preferably 88% RH to 92% RH, and further preferably about 90% RH. Too high or too low humidity may result in the inability to fully restore the optical properties. The treatment time is more than 40 minutes, preferably more than 50 minutes, more preferably more than 1 hour, and further preferably more than 2 hours. The upper limit of the treatment time can be, for example, 5 hours. When the treatment time is too short, the optical properties may not be fully restored. On the other hand, since even if the treatment time is excessively extended, the obtained effect will not be substantially changed, an excessively long treatment time is sometimes inefficient.

[0029] Typically, the polarizing plate includes a polarizer and a protective layer disposed on one or both sides of the polarizer.

[0030] Typically, the polarizer is formed of a resin film containing a dichroic substance (e.g., iodine, a dichroic dye). As the resin film, any appropriate resin film that can be used as a polarizer can be used. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.

[0031] As a specific example of a polarizer composed of a single-layer resin film, there can be cited a polarizer obtained by subjecting a PVA-type resin film to a dyeing treatment using iodine and a stretching treatment (representatively uniaxial stretching). The above-mentioned dyeing using iodine can be performed, for example, by immersing the PVA-type film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after the dyeing treatment, or it can be performed while dyeing. In addition, dyeing can also be performed after stretching. The PVA-type resin film can be subjected to swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, etc. as needed. For example, by immersing the PVA-type resin film in water for washing before dyeing, not only can the dirt and anti-blocking agent on the surface of the PVA-type film be washed away, but the PVA-type resin film can also be swelled to prevent uneven dyeing.

[0032] As specific examples of polarizers obtained using a laminate, there can be listed: a laminate using a resin substrate and a PVA-type resin layer (PVA-type resin film) laminated on the resin substrate, or a laminate using a resin substrate and a PVA-type resin layer formed by coating the resin substrate. The polarizer obtained using a laminate using a resin substrate and a PVA-type resin layer formed by coating the resin substrate can be made by the following method: for example, a PVA-type resin solution is applied to a resin substrate, and the PVA-type resin layer is formed on the resin substrate by drying, thereby obtaining a laminate of the resin substrate and the PVA-type resin layer; the laminate is stretched and dyed to make the PVA-type resin layer into a polarizer. In the present embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution for stretching. In addition, stretching may further include stretching the laminate in a gas atmosphere at a high temperature (for example, above 95°C) before stretching in a boric acid aqueous solution as required. The obtained laminate of resin substrate / polarizer can be used directly (that is, the resin substrate can be made into a protective layer of polarizer), or the resin substrate can be peeled off from the laminate of resin substrate / polarizer, and any appropriate protective layer consistent with the purpose can be laminated on the peeled surface for use. The details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The records of these patent documents are cited in this specification as a reference.

[0033] As the thickness of the polarizer, any appropriate thickness can be adopted according to the purpose. The thickness of the polarizer is, for example, 35 μm or less, preferably 20 μm or less, more preferably 15 μm or less, further preferably 12 μm or less, particularly preferably 10 μm or less, further particularly preferably 8 μm or less, especially preferably 6 μm or less, and most preferably 5 μm or less. The lower limit of the thickness of the polarizer is preferably 2 μm, more preferably 1 μm.

[0034] The protective layer can be formed by any appropriate film that can be used as a protective layer of a polarizer. Specific examples of the material that becomes the main component of the film include: cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyether sulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth) acrylic acid, acetates and other transparent resins. In addition, thermosetting resins or ultraviolet curing resins such as (meth) acrylic acid, carbamates, (meth) acrylic acid carbamates, epoxies, silicones, etc. can also be listed. In addition, glassy polymers such as siloxane polymers can also be listed. 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 imide 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, and for example, a resin composition containing an alternating copolymer formed by isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film can be, for example, an extrusion molding of the above resin composition.

[0035] When the polarizer is applied to an image display device, the protective layer (inner protective layer) disposed on the display unit side is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re (550) is 0nm to 10nm, and the phase difference Rth (550) in the thickness direction is -10nm to +10nm. Here, "Rth (λ)" is the phase difference in the thickness direction measured at 23°C with light of a wavelength of λnm. For example, "Rth (550)" is the phase difference in the thickness direction measured at 23°C with light of a wavelength of 550nm. When the thickness of the layer (film) is set to d (nm), Rth (λ) can be calculated by the formula: Rth (λ) = (nx-nz) × d. nz is the refractive index in the thickness direction.

[0036] When the polarizer is disposed on the visible side of the image display device, the protective layer (outer protective layer) disposed on the opposite side of the inner protective layer may be subjected to surface treatments such as hard coating, anti-reflection, anti-adhesion, and anti-glare as required. And / or, the outer protective layer may be subjected to treatments to improve visual recognition when visually recognized through polarized sunglasses (representatively, treatments to impart (elliptical) polarization function and treatments to impart ultra-high phase difference) as required.

[0037] The thickness of the protective layer can be any appropriate thickness. The thickness of the protective layer is, for example, 10 μm to 90 μm, preferably 20 μm to 80 μm, more preferably 20 μm to 60 μm, and further preferably 20 μm to 40 μm. It should be noted that, when surface treatment is performed, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

[0038] The polarizer can be used as a visible side polarizer or as a back side polarizer. In addition, the polarizer can also have any appropriate optical functional layer according to the purpose. As the optical functional layer, for example, a phase difference layer, a conductive layer for a touch panel, and a reflective polarizer can be cited. In practice, an adhesive layer is provided on the polarizer as the outermost layer on the display unit side, and the polarizer is provided to be able to be bonded to the display unit.

[0039] In an embodiment of the present invention, the polarizer is a polarizer in which optical properties have deteriorated in a high temperature environment. As such a polarizer, for example, a polarizer that has been heat-treated for a specific purpose and a polarizer that has been actually used in a high temperature environment can be cited. The specific temperature of the high temperature environment is 100°C or more in one embodiment, 120°C or more in another embodiment, 140°C or more in another embodiment, and 160°C or more in another embodiment. The upper limit of the temperature can be, for example, 200°C.

[0040] In one embodiment, the polarizer is a polarizer formed into a given shape. Such a polarizer is placed in a high temperature environment as described above during forming. As a polarizer formed into a given shape, for example, a polarizer applied to a curved image display device can be cited. As a curved image display device, for example, virtual reality (VR) glasses, and digital signs set on a curved wall or column can be cited.

[0041] Hereinafter, the degradation and recovery of the optical characteristics of a polarizing plate (substantially, a polarizer) will be described with respect to the polarization degree, single-body transmittance, and hue a value and b value as representative examples.

[0042] According to an embodiment of the present invention, the polarization degree of the polarizer preferably satisfies the following relationship:

[0043] P H -P0=ΔP1≤-0.005(%)

[0044] P R -P H =ΔP2≥+0.005(%)

[0045] Where P0 is the polarization degree before degradation (the polarization degree before being placed in a high temperature environment: initial polarization degree), P His the polarization degree after degradation and before heating / humidification treatment, P R It is the degree of polarization after heating / humidification treatment (polarization degree after recovery). That is, according to an embodiment of the present invention, for a polarizer whose degree of polarization is reduced by less than -0.005% (that is, more than 0.005% in absolute value on the negative side) in a high temperature environment, its degree of polarization can be restored to a value substantially the same as the initial degree of polarization or a value close to the initial degree of polarization. In more detail, the absolute value of ΔP2 is the same as the absolute value of ΔP1 or slightly smaller than the absolute value of ΔP1. In one embodiment, when the degree of polarization of a polarizer having a single body transmittance of about 41% to 41.5% is reduced by, for example, up to about 0.05% in an environment of 100°C to 130°C, the degree of polarization can be restored to a value substantially the same as the initial degree of polarization by performing a heating / humidification treatment. In another embodiment, when the polarization degree of a polarizing plate having a monomer transmittance of about 41% to 41.5% is reduced by, for example, about 55% at most in an environment of about 150°C, the polarization degree can be restored to a difference of about 0.01% to 0.02% from the initial polarization degree by heating / humidification treatment. In another embodiment, when the polarization degree of a polarizing plate having a monomer transmittance of about 42.5% to 43% is reduced by, for example, about 10% at most in an environment of 100°C to 130°C, the polarization degree can be restored to a value substantially the same as the initial polarization degree or a value exceeding the initial polarization degree by heating / humidification treatment. In another embodiment, when the polarization degree of a polarizing plate having a monomer transmittance of about 42.5% to 43% is reduced by, for example, about 94% at most in an environment of about 150°C (i.e., reduced to the extent that the polarization performance substantially disappears), the polarization degree can be restored to a difference of less than 0.1% from the initial polarization degree by heating / humidification treatment even in such a case.

[0046] According to an embodiment of the present invention, the single transmittance of the polarizer preferably satisfies the following relationship:

[0047] Ts H -Ts0=ΔTs1≥+0.3(%)

[0048] Ts R -Ts H =ΔTs2≤-0.3(%)

[0049] Wherein, Ts0 is the monomer transmittance before degradation (the monomer transmittance before being placed in a high temperature environment: the initial monomer transmittance), Ts H is the single body transmittance after degradation and before heating / humidification treatment, Ts Ris the single transmittance after heating / humidification treatment (single transmittance after recovery). According to an embodiment of the present invention, similarly to the case of polarization degree, for a polarizer whose single transmittance increases by more than 0.3% in a high temperature environment, its single transmittance can be restored to a value substantially the same as the initial single transmittance or a value below the initial single transmittance. More specifically, the absolute value of ΔTs2 is the same as the absolute value of ΔTs1 or is greater than the absolute value of ΔTs1.

[0050] The initial polarization degree of the polarizing plate (substantially a polarizer) is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more. The single transmittance of the polarizing plate (substantially a polarizer) is preferably 40.0% to 46.0%, and more preferably 41.0% to 43.5%.

[0051] According to an embodiment of the present invention, the hue b value of the polarizer preferably satisfies the following relationship:

[0052] b H -b0=Δb1≥+0.3

[0053] b R -b H =Δb2≤-0.3

[0054] b0 is the hue b value before degradation (the hue b value before being placed in a high temperature environment: the initial b value), b H is the hue b value after degradation and before heating / humidification treatment, b R It is the hue b value after heating / humidification treatment (the hue b value after recovery). According to an embodiment of the present invention, for a polarizer whose hue b value increases by more than 0.3 in a high temperature environment, its hue b value can be restored to a value substantially the same as the initial b value or a value below the initial b value. In other words, the hue of a polarizer that has deteriorated from neutral to colored can be restored to a neutral hue equivalent to the initial hue or a hue that is more neutral than the initial hue. In more detail, the absolute value of Δb2 is the same as the absolute value of Δb1 or is greater than the absolute value of Δb1. Similarly, with respect to the hue a value of the polarizer, it is preferred to satisfy the following relationship:

[0055] a H -a0=Δa1<0

[0056] a R -a H =Δa2≥+0.3

[0057] a0 is the hue a value before degradation (the hue a value before being placed in a high temperature environment: the initial a value), a H is the hue a value after degradation and before heating / humidification treatment, a Ris the hue a value after heating / humidification treatment (the hue a value after recovery). According to an embodiment of the present invention, for a polarizer whose hue a value has decreased in a high temperature environment, its hue a value can be restored to a value greater than the initial a value. In other words, a polarizer whose hue has deteriorated from neutral to colored can be restored to a hue that is more neutral than the initial hue. In more detail, the absolute value of Δa2 is the same as the absolute value of Δa1 or is greater than the absolute value of Δa1.

[0058] Example

[0059] The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. In addition, unless otherwise specifically stated, the "parts" and "%" in the examples are by weight.

[0060] <Example 1>

[0061] A polyvinyl alcohol film with a thickness of 75 μm (manufactured by Kuraray Co., Ltd.: VF-PS7500) was used, and it was stretched to a stretch ratio of 2.5 times while being immersed in pure water at 30°C for 60 seconds, dyed in an iodine aqueous solution at 30°C (weight ratio: pure water / iodine (I) / potassium iodide (KI) = 100 / 0.01 / 1) for 45 seconds, stretched in a 4 wt% boric acid aqueous solution to a total stretch ratio of 5.8 times, immersed in pure water for 10 seconds, and dried at 60°C for 3 minutes while maintaining the tension of the film to obtain a polarizer (thickness 28 μm).

[0062] A triacetylcellulose (TAC) film (thickness 80 μm) was laminated on one side of the obtained polarizer as an inner protective layer, and an HC-TAC film was laminated on the other side as an outer protective layer to obtain a polarizing plate. It should be noted that the HC-TAC film is a film having a hard coating (HC) layer (thickness 7 μm) formed on the above-mentioned TAC film, and the TAC film was laminated in such a way that it became the polarizer side.

[0063] The obtained polarizer was punched into a size of 40 mm × 40 mm, and its TAC film side was bonded to an alkali glass plate via an acrylic adhesive to obtain a measurement sample. Two measurement samples were prepared, one was placed in an oven set at 100°C for 5 minutes, and the other was placed with its HC surface in contact with a heating plate set at 100°C (manufactured by AS ONE, product name "Shamal Hot Plate HHP-401") and placed for 5 minutes. In this way, the optical properties of each measurement sample (polarizer) were degraded. The measurement sample whose optical properties had deteriorated was placed in a chamber set at 65°C and 95% RH for 2 hours and subjected to heating / humidification treatment. The polarization degree, monomer transmittance, hue a value and hue b value of the measurement sample at the initial stage (before heating), after degradation (after heating) and before heating / humidification treatment (hereinafter referred to as after degradation), and after heating / humidification treatment (after recovery) were measured using "V7100" manufactured by JASCO Corporation. The results are shown in Table 1.

[0064] <Example 2>

[0065] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, and except that the heating temperature was set to 130° C., the initial polarization degree, single transmittance, and hue a value and hue b value were measured in the same manner as in Example 1, after degradation, and after recovery. The results are shown in Table 1.

[0066] <Example 3>

[0067] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. The polarizing plate was used and the heating temperature was set to 150° C. The polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1. The results are shown in Table 1.

[0068] <Reference Example 1>

[0069] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, the polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1 except that the heating temperature was set to 40° C. and heating was performed only with a heating plate. The results are shown in Table 1.

[0070] <Reference Example 2>

[0071] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, and except that the heating temperature was set to 60° C., the initial polarization degree, single transmittance, and hue a value and hue b value were measured in the same manner as in Example 1. The results are shown in Table 1.

[0072] <Reference Example 3>

[0073] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, the polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1 except that the heating temperature was set to 80° C. The results are shown in Table 1.

[0074] <Example 4>

[0075] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was adjusted to the value shown in Table 1. Using this polarizing plate, the polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1. The results are shown in Table 1.

[0076] <Example 5>

[0077] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, and except that the heating temperature was set to 130° C., the initial polarization degree, single transmittance, and hue a value and hue b value were measured in the same manner as in Example 1, after degradation, and after recovery. The results are shown in Table 1.

[0078] <Example 6>

[0079] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. The polarizing plate was used and the heating temperature was set to 150° C. The polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1. The results are shown in Table 1.

[0080] <Reference Example 4>

[0081] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, the polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1 except that the heating temperature was set to 40° C. and heating was performed only with a heating plate. The results are shown in Table 1.

[0082] <Reference Example 5>

[0083] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, and except that the heating temperature was set to 60° C., the initial polarization degree, single transmittance, and hue a value and hue b value were measured in the same manner as in Example 1. The results are shown in Table 1.

[0084] <Example 7>

[0085] A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer was set to the value shown in Table 1. Using this polarizing plate, the polarization degree, single transmittance, hue a value, and hue b value at the initial stage, after degradation, and after recovery were measured in the same manner as in Example 1 except that the heating temperature was set to 80° C. The results are shown in Table 1.

[0086] [Table 1]

[0087]

[0088] It is clear from Table 1 that the embodiments of the present invention can restore the optical properties of the polarizer that has deteriorated in a high temperature environment. In addition, it is clear from the reference example that the optical properties will not deteriorate at all by heating at a low temperature. In addition, it is clear from reference example 3 and embodiment 7 that the heating temperature at which the optical properties deteriorate is different due to the different single transmittances of the polarizer (substantially a polarizer).

[0089] Industrial Applicability

[0090] The method according to the embodiment of the present invention can be suitably used to restore the optical properties of a polarizing plate after exposure to a high temperature environment.

Claims

1. A method for restoring the optical properties of a polarizer, the method comprising: The polarizer whose optical properties have deteriorated after being placed in an environment of 100°C or higher is treated in an environment of 58°C to 65°C and 88% RH to 95% RH for more than 2 hours. The polarizing plate comprises a polarizer and a protective layer disposed on one side or both sides of the polarizer, wherein the polarizer is composed of a polyvinyl alcohol resin film containing iodine. The single transmittance of the polarizer before degradation is 41.0% to 43.5%, and the polarization degree before degradation is above 99.9%. The polarizer satisfies the following relationship: P H -P0=ΔP1≤-0.005% P R -P H =ΔP2≥+0.005% b H -b0=Δb1≥+0.3 b R -b H =Δb2≤-0.3 Ts H -Ts0=ΔTs1≥+0.3% Ts R -Ts H =ΔTs2≤-0.3% in, P0 is the polarization degree before degradation, P H is the polarization degree after degradation and before the above treatment, P R is the degree of polarization after the processing; b0 is the hue b value before degradation, b H is the hue b value after degradation and before the treatment, b R is the hue b value after the processing; Ts0 is the single body transmittance before degradation, Ts H is the monomer transmittance after degradation and before the above treatment, Ts R is the single body transmittance after the treatment.

2. The method for restoring the optical properties of a polarizing plate according to claim 1, wherein: The polarizing plate with deteriorated optical properties is a polarizing plate formed into a curved shape.

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