KR20220140735A - A method of recovering the optical properties of a polarizing plate deteriorated under a high-temperature environment - Google Patents

Abstract

Provided is a method capable of well recovering the optical properties of a polarizing plate deteriorated under a high-temperature environment. The method for recovering optical properties of a polarizing plate according to an embodiment of the present invention includes treating a polarizing plate whose optical properties deteriorated under a high-temperature environment for 40 minutes or more in an environment of 40°C to 65°C and 85%RH to 95%RH.

Description

A method of recovering the optical properties of a polarizing plate deteriorated under a high-temperature environment

The present invention relates to a method of recovering optical properties of a polarizing plate deteriorated under a high temperature environment.

A polarizing plate is widely used in image display apparatuses, such as a liquid crystal display device and an organic electroluminescent (EL) display apparatus, in order to implement|achieve an image display and/or to improve the performance of the said image display. The polarizing plate may be heat-treated for a specific purpose, exposed to a high-temperature environment in actual use, and/or may be molded into a predetermined shape under a high-temperature environment. In most of these cases, the optical properties (typically polarization degree, single transmittance, color) of the polarizing plate may be significantly deteriorated. Accordingly, there is a demand for a technique for recovering the optical properties of a polarizing plate deteriorated under a high-temperature environment.

Japanese Patent Laid-Open No. 8-136731

The present invention has been made in order to solve the above conventional problems, and its main object is to provide a method capable of recovering favorably the optical properties of a polarizing plate deteriorated under a high-temperature environment.

The method for recovering optical properties of a polarizing plate according to an embodiment of the present invention includes treating a polarizing plate whose optical properties deteriorated under a high-temperature environment for 40 minutes or more in an environment of 40°C to 65°C and 85%RH to 95%RH.

In one embodiment, the polarizing plate satisfies the following relationship:

P _H -P ₀ =ΔP ₁ ≤-0.005(%)

P _R -P _H =ΔP ₂ ≥+0.005 (%)

b _H -b ₀ =Δb ₁ ≥+0.3

b _R -b _H =Δb ₂ ≤-0.3

where P ₀ is the polarization degree before degradation, P _H is the polarization degree after degradation and before the treatment, and P _R is the polarization degree after the treatment; b ₀ is the color b value before deterioration, b _H is the color b value after deterioration and before the treatment, and b _R is the color b value after the treatment.

In one embodiment, the polarizing plate also satisfies the following relationship:

Ts _H -Ts ₀ =ΔTs ₁ ≥+0.3(%)

Ts _R -Ts _H =ΔTs ₂ ≤-0.3(%)

Here, Ts ₀ is the single transmittance before deterioration, Ts _H is the single transmittance after deterioration and before the said process, Ts _R is the single transmittance after the said process.

In one embodiment, the said polarizing plate is a polarizing plate set in the environment of 100 degreeC or more.

In one embodiment, the said polarizing plate is a polarizing plate shape|molded by the predetermined shape.

According to the embodiment of the present invention, by treating a polarizing plate whose optical properties deteriorated under a high-temperature environment for a predetermined time or longer under a heating/humidifying environment under predetermined conditions, the deteriorated optical properties can be restored favorably.

EMBODIMENT OF THE INVENTION Hereinafter, although typical embodiment of this invention is described, this invention is not limited to these embodiment.

A method of recovering optical properties of a polarizing plate according to an embodiment of the present invention includes heating and humidifying a polarizing plate whose optical properties have deteriorated under a high-temperature environment. Heating and a humidification process are normally performed as a durability test of a polarizing plate. The provision of a normal polarizing plate for heating and humidification is premised on that the optical properties of the polarizing plate are deteriorated (the degree of deterioration is used as an index of durability). In other words, it is common knowledge in the art that the optical properties of the polarizing plate are deteriorated by heating and humidification treatment. On the other hand, the present inventors have completed the present invention by finding that the deteriorated optical properties can be recovered by heating and humidifying a polarizing plate having deteriorated optical properties under a high-temperature environment. That is, the present invention has been made based on the technical common knowledge in the art and the technical idea in the reverse direction, and the effect is an unexpectedly excellent effect. The heating temperature in the heating and 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, still more preferably It is usually about 60°C. Even if the heating temperature is too high or too low, the optical properties may not be sufficiently recovered. Humidity in the heating and humidification treatment is 85%RH to 95%RH, preferably 87%RH to 93%RH, more preferably 88%RH to 92%RH, still more preferably about 90% is RH. Even if the humidity is too high or too low, the optical properties may not be sufficiently recovered. The treatment time is 40 minutes or longer, preferably 50 minutes or longer, more preferably 1 hour or longer, and still more preferably 2 hours or longer. The upper limit of the treatment time may be, for example, 5 hours. If the processing time is too short, the optical properties may not be sufficiently recovered. On the other hand, since the effect obtained does not change substantially even if the processing time is lengthened excessively, an excessively long processing time may not be efficient.

The polarizing plate typically includes a polarizer and a protective layer disposed on one side or both sides of the polarizer.

The polarizer is typically composed of a resin film containing a dichroic substance (eg, iodine, dichroic dye). Any suitable resin film which can be used as a polarizer is employable as a resin film. The resin film is typically a polyvinyl alcohol-based resin (hereinafter, referred to as “PVA-based resin”) film. A single-layered resin film may be sufficient as a resin film, and the laminated body of two or more layers may be sufficient as it.

As a specific example of the polarizer comprised from a single-layered resin film, the thing by which the dyeing process by iodine and the extending|stretching process (typically uniaxial stretching) were given to the PVA-type resin film is mentioned. The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. Preferably the draw ratio of the said uniaxial stretching is 3 to 7 times. Extending|stretching may be performed after a dyeing process, and may be performed, dyeing|staining. Moreover, you may dye|dye after extending|stretching. A swelling process, a crosslinking process, a washing process, a drying process, etc. are given to a PVA-type resin film as needed. For example, by immersing the PVA-based resin film in water and washing with water before dyeing, it is possible to not only wash the surface of the PVA-based film from stains and anti-blocking agents, but also to swell the PVA-based resin film to prevent staining of dyeing.

As a specific example of a polarizer obtained using a laminate, a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate The polarizer obtained using is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate is applied, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate. obtaining a laminate of a base material and a PVA-based resin layer; It can be produced by; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer. In this embodiment, extending|stretching includes extending|stretching by immersing a laminated body in boric-acid aqueous solution typically. In addition, the stretching may further include air stretching the laminate at a high temperature (for example, 95° C. or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained laminate of the resin substrate/polarizer may be used as it is (that is, the resin substrate may be used as a protective layer of the polarizer), and the resin substrate is peeled from the laminate of the resin substrate/polarizer, may be used by laminating an appropriate protective layer of The detail of the manufacturing method of such a polarizer is described in Unexamined-Japanese-Patent No. 2012-73580, and Unexamined-Japanese-Patent No. 6470455, for example. The description of these patent documents is incorporated herein by reference.

As the thickness of the polarizer, any appropriate thickness may be employed depending on 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, still more preferably 12 µm or less, particularly preferably 10 µm or less, and still more particularly preferably Preferably, it is 8 µm or less, particularly preferably 6 µm or less, and most preferably 5 µm or less. The minimum of the thickness of a polarizer becomes like this. Preferably it is 2 micrometers, More preferably, it is 1 micrometer.

The protective layer is formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of the material used as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyethersulfone, and poly and transparent resins such as sulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based and acetate-based resins. Moreover, thermosetting resins, such as (meth)acrylic type, a urethane type, a (meth)acrylic urethane type, an epoxy type, a silicone type, or ultraviolet curable resin, etc. are mentioned. In addition to this, for example, glassy polymers, such as a siloxane type polymer, are also mentioned. Moreover, the polymer film described in Unexamined-Japanese-Patent No. 2001-343529 (WO01/37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, isobutyl and a resin composition comprising an alternating copolymer comprising ren and N-methylmaleimide and an acrylonitrile/styrene copolymer. The polymer film may be, for example, an extrusion molding of the resin composition.

When the polarizing plate is applied to an image display device, it is preferable that the protective layer (inner protective layer) disposed on the display cell side is optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm, and the retardation Rt(550) in the thickness direction is -10 nm to +10 nm. Here, "Rth(λ)" is the phase difference in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with the light of wavelength 550nm in 23 degreeC. Rth(λ) is obtained by the formula: Rth(λ)=(nx-nz)×d when the thickness of the layer (film) is d(nm). nz is the refractive index in the thickness direction.

When the polarizing plate is disposed on the viewer side of the image display device, the protective layer (outer protective layer) disposed on the opposite side to the inner protective layer may be subjected to hard coat treatment, anti-reflection treatment, anti-stick treatment, anti-glare treatment, etc. may be subjected to surface treatment. In addition, even if the outer protective layer is subjected to a treatment for improving visibility when visually viewed through polarized sunglasses (typically, imparting a (other) circularly polarized light function, imparting an ultra-high phase difference), if necessary. good night.

Any suitable thickness of the protective layer may be employed. 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, still more preferably 20 µm to 40 µm. In addition, when surface treatment is performed, the thickness of a protective layer is the thickness including the thickness of a surface treatment layer.

A polarizing plate may be used as a viewing side polarizing plate, and may be used as a back side polarizing plate. In addition, the polarizing plate may further have arbitrary appropriate optical function layers according to the objective. As an optical function layer, a retardation layer, the conductive layer for touch panels, and a reflection type polarizer are mentioned, for example. Practically, the polarizing plate is provided with an adhesive layer as the outermost layer on the side of the display cell, and the polarizing plate can be bonded to the display cell.

In the embodiment of the present invention, the polarizing plate is a polarizing plate whose optical properties are deteriorated under a high-temperature environment. Examples of such a polarizing plate include a polarizing plate heat-treated for a specific purpose, and a polarizing plate actually used in a high-temperature environment. The specific temperature of the high-temperature environment is 100°C or higher in one embodiment, 120°C or higher in another embodiment, 140°C or higher in another embodiment, and 160°C or higher in another embodiment. The upper limit of the temperature may be, for example, 200 °C.

In one embodiment, the polarizing plate is a polarizing plate shape|molded by the predetermined shape. When such a polarizing plate is molded, it is placed under a high-temperature environment as described above. As a polarizing plate shape|molded into the predetermined shape, the polarizing plate applied to the curved image display apparatus is mentioned, for example. Examples of the curved image display device include virtual reality (VR) goggles and digital signage formed on curved wall surfaces and pillars.

Hereinafter, polarization degree, single transmittance, and hue a value and b value are demonstrated about deterioration and recovery|restoration of the optical characteristic of a polarizing plate (substantially a polarizer) as a representative example.

According to an embodiment of the present invention, the polarizing plate preferably satisfies the following relationship with respect to the degree of polarization:

P _H -P ₀ =ΔP ₁ ≤-0.005(%)

P _R -P _H =ΔP ₂ ≥+0.005 (%)

Here, P ₀ is the polarization degree before deterioration (polarization degree before being placed in a high-temperature environment: initial polarization degree), P _H is the polarization degree after deterioration and before heating and humidification treatment, and P _R is the polarization degree after heating and humidification treatment (polarization degree after recovery). That is, according to the embodiment of the present invention, for a polarizing plate whose polarization degree is lowered by -0.005% or less (that is, 0.005% or more in absolute value on the negative side) under a high-temperature environment, the polarization degree is set to substantially the same value as the initial polarization degree or it It can be restored to a near value. More specifically, the absolute value of ΔP ₂ is equal to or slightly smaller than the absolute value of ΔP ₁ . In one embodiment, in a polarizing plate having a single transmittance of about 41% to 41.5%, the degree of polarization can be reduced by, for example, about 0.05% at most in an environment of 100°C to 130°C, by heating and humidifying treatment, The polarization degree may be restored to a value substantially equal to the initial polarization degree. In another embodiment, in the case of a polarizing plate having a single transmittance of about 41% to 41.5%, the polarization degree can be reduced at most by, for example, about 55% in an environment near 150°C. The difference with the degree of polarization can be recovered to about 0.01% to 0.02%. In another embodiment, in a polarizing plate having a single transmittance of about 42.5% to 43%, the polarization degree can be reduced by, for example, at most about 10% in an environment of 100°C to 130°C, by heating and humidifying treatment, The polarization degree may be restored to a value substantially equal to the initial polarization degree or to a value exceeding the initial polarization degree. In another embodiment, a polarizing plate having a single transmittance of about 42.5% to 43% may have a polarization degree of, for example, a maximum of about 94% (that is, to the extent that polarization performance is substantially lost) under an environment near 150°C. Therefore, even in such a case, the difference between the polarization degree and the initial polarization degree can be recovered to 0.1% or less by heating and humidifying treatment.

According to an embodiment of the present invention, the polarizing plate preferably satisfies the following relationship with respect to the single transmittance:

Ts _H -Ts ₀ =ΔTs ₁ ≥+0.3(%)

Ts _R -Ts _H =ΔTs ₂ ≤-0.3(%)

Here, Ts ₀ is the single transmittance before deterioration (single transmittance before being placed in a high-temperature environment: initial single transmittance), Ts _H is the single transmittance after deterioration and before heating and humidification treatment, Ts _R is the single unit after heating and humidification treatment Transmittance (single transmittance after recovery). According to the embodiment of the present invention, as in the case of polarization degree, for a polarizing plate whose single transmittance is increased by 0.3% or more under a high temperature environment, the single transmittance can be restored to a value substantially equal to or lower than the initial single transmittance. . More specifically, the absolute value of ΔTs ₂ is equal to or greater than the absolute value of ΔTs ₁ .

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

According to an embodiment of the present invention, the polarizing plate preferably satisfies the following relation with respect to the color b value:

b _H -b ₀ =Δb ₁ ≥+0.3

b _R -b _H =Δb ₂ ≤-0.3

b ₀ is the color b value before deterioration (the color b value before being placed in a high temperature environment: initial b value), b _H is the color b value after deterioration and before heating and humidification treatment, b _R is the color color after heating and humidification treatment b-value (color b-value after recovery). According to the embodiment of the present invention, with respect to a polarizing plate having a hue b value of 0.3 or more in a high-temperature environment, the hue b value can be restored to a value substantially equal to or less than the initial b value. In other words, it is possible to restore the deteriorated polarizing plate to a neutral color equivalent to the initial color or to a neutral color than the initial color by adding color from a neutral color. More specifically, the absolute value of Δb ₂ is equal to or greater than the absolute value of Δb ₁ . Likewise, the polarizing plate preferably satisfies the following relation with respect to the color a value:

a _H -a ₀ =Δa ₁ < 0

a _R -a _H =Δa2≥+0.3

a ₀ is the color a value before deterioration (color a value before being placed in a high-temperature environment: initial a value), a _H is the color a value after deterioration and before heating and humidification treatment, a _R is the color color after heating and humidification treatment a value (color a value after recovery). According to the embodiment of the present invention, with respect to a polarizing plate having a small hue a value under a high temperature environment, the hue a value can be restored to a value larger than the initial a value. In other words, it is possible to restore a polarizing plate that has been deteriorated by adding color from a neutral color to a more neutral color than the initial color. More specifically, the absolute value of Δa ₂ is equal to or greater than the absolute value of Δa ₁ .

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. The evaluation items in the Examples are as follows. In addition, unless otherwise indicated, "part" and "%" in Examples are based on weight.

<Example 1>

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

A triacetyl cellulose (TAC) film (80 µm in thickness) was bonded to one surface of the obtained polarizer as an inner protective layer, and an HC-TAC film was bonded to the other surface as an outer protective layer to obtain a polarizing plate. Moreover, the HC-TAC film was the film in which the hard-coat (HC) layer (thickness 7 micrometers) was formed in the said TAC film, it bonded together so that a TAC film might become a polarizer side.

The obtained polarizing plate was punched out to the size of 40 mm x 40 mm, the TAC film side was bonded to the alkali glass plate through the acrylic adhesive, and it was set as the measurement sample. Two measurement samples were prepared, one was put in an oven set at 100°C for 5 minutes, and the other was HC on a hot plate set at 100°C (manufactured by Azone Corporation, product name “Shamar Hot Plate HHP-401”). The sides were contacted and loaded for 5 minutes. In this way, the optical properties of each measurement sample (polarizing plate) were deteriorated. The measurement sample having deteriorated optical properties was put into a chamber set at 65°C and 95% RH for 2 hours, followed by heating and humidification. Polarization degree, single transmittance, and hue of the measurement sample in the initial stage (before heating), after deterioration (after heating), before heating/humidification treatment (hereinafter, only after deterioration), and after heating/humidification treatment (after recovery) The a-value and the color b-value were measured using "V7100" manufactured by Nippon Bunko Corporation. A result is shown in Table 1.

<Example 2>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was 130° C., polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Example 3>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was 150° C., polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Reference Example 1>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used, the heating temperature was set to 40° C., and heating only with a hot plate, the initial phase, the polarization degree after deterioration and after recovery, the single transmittance, and the hue a Values and color b-values were measured. A result is shown in Table 1.

<Reference Example 2>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was set to 60° C., polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Reference example 3>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was set to 80°C, polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Example 4>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. Except having used this polarizing plate, it carried out similarly to Example 1, and the polarization degree, single transmittance, and hue a value and hue b value after initial stage, after deterioration and recovery|restoration were measured. A result is shown in Table 1.

<Example 5>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was 130° C., polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Example 6>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was 150° C., polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Reference Example 4>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used, the heating temperature was set to 40° C., and heating only with a hot plate, the initial phase, the polarization degree after deterioration and after recovery, the single transmittance, and the hue a Values and color b-values were measured. A result is shown in Table 1.

<Reference Example 5>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was set to 60° C., polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

<Example 7>

A polarizing plate was produced in the same manner as in Example 1 except that the single transmittance of the polarizer became the value shown in Table 1. In the same manner as in Example 1 except that this polarizing plate was used and the heating temperature was set to 80°C, polarization degree, single transmittance, and hue a and hue b values were measured in the initial stage, after deterioration and after recovery. did. A result is shown in Table 1.

As is apparent from Table 1, according to the embodiment of the present invention, it is possible to recover the optical properties of the polarizing plate deteriorated under a high-temperature environment. Further, as is clear from the reference example, it is understood that the optical properties are not initially deteriorated by heating at a low temperature. Moreover, as is clear from Reference Example 3 and Embodiment 7, it turns out that the heating temperature at which deterioration of an optical characteristic occurs differs with the single transmittance of a polarizing plate (substantially a polarizer).

(Industrial Applicability)

The method according to the embodiment of the present invention can be suitably used for recovery of optical properties of a polarizing plate exposed to a high-temperature environment.

Claims (5)

A method of recovering optical properties of a polarizing plate, comprising treating a polarizing plate whose optical properties are deteriorated under a high temperature environment for 40 minutes or more under an environment of 40°C to 65°C and 85%RH to 95%RH. The method of claim 1,
A method of recovering optical properties of a polarizing plate in which the polarizing plate satisfies the following relationship.
P _H -P ₀ =ΔP ₁ ≤-0.005(%)
P _R -P _H =ΔP ₂ ≥+0.005 (%)
b _H -b ₀ =Δb ₁ ≥+0.3
b _R -b _H =Δb ₂ ≤-0.3
where P ₀ is the polarization degree before degradation, P _H is the polarization degree after degradation and before the treatment, and P _R is the polarization degree after the treatment; b ₀ is the color b value before deterioration, b _H is the color b value after deterioration and before the treatment, and b _R is the color b value after the treatment. 3. The method of claim 2,
A method of recovering optical properties of a polarizing plate in which the polarizing plate satisfies the following relationship.
Ts _H -Ts ₀ =ΔTs ₁ ≥+0.3(%)
Ts _R -Ts _H =ΔTs ₂ ≤-0.3(%)
Here, Ts ₀ is the single transmittance before deterioration, Ts _H is the single transmittance after deterioration and before the said process, Ts _R is the single transmittance after the said process. 4. The method according to any one of claims 1 to 3,
A method of recovering optical properties of a polarizing plate, wherein the polarizing plate is a polarizing plate placed under an environment of 100° C. or higher. 5. The method of claim 4,
A method of recovering optical properties of a polarizing plate, wherein the polarizing plate is a polarizing plate molded into a predetermined shape.