JP7610433B2 - Polarizing plate - Google Patents

Description

The present invention relates to a polarizing plate and further to a display device equipped with a polarizing plate.

Liquid crystal display devices (LCDs) are widely used not only in LCD televisions, but also in mobile applications such as personal computers and mobile phones, and in-vehicle applications such as car navigation systems. Typically, LCDs have a liquid crystal panel member in which polarizing plates are attached to both sides of a liquid crystal cell with an adhesive, and display is achieved by controlling the light from a backlight member with the liquid crystal panel member. In recent years, organic electroluminescence (EL) display devices have also begun to be widely used in mobile applications such as televisions and mobile phones, and in-vehicle applications such as car navigation systems, just like LCDs. In LCDs and organic EL display devices, retardation films are sometimes used to provide functions such as expanding the viewing angle or preventing reflection of external light.

Polarizing plates are increasingly being installed in vehicles as optical elements that make up liquid crystal display devices and organic EL display devices. Polarizing plates used in in-vehicle displays are more often exposed to high-temperature environments than polarizing plates used in mobile applications such as televisions and mobile phones, and are therefore required to exhibit less change in properties at high temperatures (high-temperature durability).

When used in car navigation systems and the like, in-vehicle display devices need to have a touch panel function. In recent years, on-cell and in-cell display devices have been increasingly used as display devices with touch panel functions. In these types of display devices, a polarizing plate is placed on the outermost surface on the viewing side, so they are required to have high temperature durability as well as scratch prevention functionality (scratch resistance).

Patent Document 1 describes a polarizing plate including a retardation film made of a cyclic olefin resin film in order to expand the viewing angle. In addition, Patent Document 2 describes that a film made of a cyclic olefin resin may be used for the retardation film that functions as a λ/4 plate constituting the polarizing plate.

Patent No. 5383594 JP 2014-194483 A

In retardation films that are incorporated into polarizing plates, such as the above-mentioned retardation films made of cyclic olefin resin films, even if no cracks are found after a heat durability test, cracks may be found if the film is subsequently stored for a long period of time under normal temperature and humidity conditions.

The present invention aims to provide a polarizing plate that has excellent scratch resistance and suppresses the occurrence of cracks in the retardation film even when stored for a long period of time under normal temperature and humidity conditions after a heat durability test.

The present invention provides the following polarizing plate.
[1] A polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film;
a protective film having a hard coat layer provided on a substrate film;
A retardation film having a tensile modulus of elasticity of 3000 MPa or less at a temperature of 23° C.;
Two or more of the protective films are laminated on the first surface side of the polarizing film,
the retardation film is laminated on a second surface side of the polarizing film opposite to the first surface side.
[2] The polarizing plate according to [1], wherein at least one of the two or more protective films laminated on the first surface side has a moisture permeability of 200 g/ ^m2 ·day or more at a temperature of 40° C. and a relative humidity of 90%.
[3] The polarizing plate according to [1] or [2], wherein, among the two or more protective films laminated on the first surface side, the protective film laminated closest to the polarizing film has a moisture permeability of 200 g/ ^m2 ·day or more at a temperature of 40° C. and a relative humidity of 90%.
[4] The polarizing plate according to any one of [1] to [3], wherein the base film of at least one of the two or more protective films laminated on the first surface side is a cellulose-based resin film.
[5] The polarizing plate according to any one of [1] to [4], wherein the retardation film is a cyclic olefin resin film.
[6] The polarizing plate according to any one of [1] to [5], wherein the retardation film has an in-plane retardation value of 80 nm or more at a wavelength of 550 nm.
[7] The polarizing plate according to any one of [1] to [6], further comprising a pressure-sensitive adhesive layer on the side of the retardation film opposite to the polarizing film.
[8] A display device comprising the polarizing plate according to [7] and a display element,
The display device, wherein the polarizing plate is laminated on a display element via the pressure-sensitive adhesive layer.

The present invention provides a polarizing plate that has excellent scratch resistance and suppresses the occurrence of cracks in the retardation film even when stored for a long period of time under normal temperature and humidity conditions after a heat durability test.

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

Hereinafter, preferred embodiments of the polarizing plate and the display device will be described with reference to the drawings.
(Polarizing plate)
Fig. 1 is a schematic cross-sectional view showing a polarizing plate according to the present embodiment. The polarizing plate 1 includes a polarizing film 11 in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin film (hereinafter, sometimes referred to as a "PVA-based resin film"), protective films 12 and 13 in which a hard coat layer (hereinafter, sometimes referred to as an "HC layer") is provided on a substrate film, and a retardation film 21 having a tensile modulus of elasticity of 3000 MPa or less at a temperature of 23 ° C. As shown in Fig. 1, in the polarizing plate 1, two or more protective films 12 and 13 are laminated on the first surface 11a side of the polarizing film 11, and a retardation film 21 is laminated on the second surface 11b side opposite to the first surface 11a side of the polarizing film 11.

As described above, the polarizing plate 1 has two or more protective films 12, 13, each including an HC layer, laminated on the first surface 11a side of the polarizing film 11. This improves the pencil hardness of the surface of the polarizing plate 1 facing the protective films 12, 13, thereby imparting excellent scratch resistance to the polarizing plate 1.

After a heat endurance test in which the polarizing plate 1 is held at a temperature of 105°C for 500 hours, the polarizing plate 1 can be prevented from cracking in the retardation film 21 even if it is held at a normal temperature and humidity environment of 23°C and 55% relative humidity for about one month. The reason for this is presumed to be as follows. If the polarizing plate 1 is cooled after the heat endurance test and held at a normal temperature and humidity environment, moisture (water vapor) in the air is easily taken into the polarizing plate. The moisture taken into the polarizing plate causes dimensional changes in the polarizing film containing the PVA-based resin film. It is thought that cracks may occur in the retardation film when a force generated by the dimensional change of the polarizing film acts on the retardation film. On the other hand, since the polarizing plate 1 has two or more protective films 12 and 13 laminated on the first surface 11a side of the polarizing film 11, the amount of moisture taken into the polarizing plate 1 can be suppressed, and the dimensional change of the polarizing film 11 can be further suppressed. Therefore, it is believed that the force acting on the retardation film 21 provided on the second surface 11b side of the polarizing film 11 can be reduced, and the occurrence of cracks in the retardation film 21 can be suppressed.

As shown in FIG. 1, each film constituting the polarizing plate 1 can be laminated via bonding layers 31 to 33. The bonding layers 31 to 33 are layers using an adhesive or pressure-sensitive adhesive. The bonding layer 31 for bonding the protective film 12 and the protective film 13 is preferably a layer using a pressure-sensitive adhesive. The bonding layer 32 for bonding the protective film 13 and the polarizing film 11, and the bonding layer 33 for bonding the polarizing film 11 and the retardation film 21 are both preferably layers using an adhesive.

The polarizing plate 1 may further have functional layers such as an antistatic layer, a retardation layer other than the retardation film 21, and a protective layer other than the protective films 12 and 13 for protecting the surface of the polarizing film 11.

The polarizing plate 1 can be used as an optical element constituting a display device. Therefore, the polarizing plate 1 may have an adhesive layer 35 (FIG. 1) for bonding the polarizing plate 1 to a display element of the display device or the like. The polarizing plate 1 may further have a release film that covers and protects the adhesive layer 35 and is peelable from the adhesive layer 35.

(Display Device)
The display device may include a polarizing plate 1 and a display element such as a liquid crystal cell or an organic electroluminescence (EL) element. In the display device, the polarizing plate 1 may be disposed so that the second surface 11b side of the polarizing film 11 faces the display element. The polarizing plate 1 may be laminated to the display element via an adhesive layer 35 shown in FIG. 1, and when the polarizing plate 1 does not have an adhesive layer 35, it may be laminated to the display element via an adhesive or bonding agent. Examples of the display device include a liquid crystal display device and an organic EL device.

The films and layers that constitute the polarizing plate 1 will now be described in detail.
(Polarizing film)
The polarizing film 11 is an absorptive polarizing film that has the property of absorbing linearly polarized light having a vibration plane parallel to its absorption axis and transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to the transmission axis). A suitable example of the polarizing film 11 is a uniaxially stretched PVA-based resin film having a dichroic dye adsorbed and oriented thereon.

The thickness of the polarizing film 11 is usually 50 μm or less, preferably 5 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less, and even more preferably 5 μm or more and 20 μm or less. By setting the thickness of the polarizing film 11 within these ranges, it is possible to maintain handleability while preventing breakage, cracking, etc. during the manufacture of the polarizing film 11, and to simultaneously achieve high optical properties. By setting the thickness of the polarizing film to 20 μm or less, it is possible to further suppress the decrease in visibility when placed in a high-temperature environment.

The polarizing film 11 can be produced by a method including, for example, a step of stretching a PVA-based resin film; a step of dyeing the PVA-based resin film with a dichroic dye to adsorb the dichroic dye; a step of treating the PVA-based resin film with the adsorbed dichroic dye with a crosslinking liquid such as an aqueous boric acid solution; and a step of washing with water after the step of treating with the crosslinking liquid.

The PVA-based resin film may be a film made of polyvinyl alcohol-based resin (hereinafter, sometimes referred to as "PVA-based resin"). Examples of PVA-based resins include polyvinyl acetate-based resins obtained by saponification. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers that can be copolymerized with vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. In this specification, "(meth)acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl" and "(meth)acrylate".

The saponification degree of the PVA-based resin is usually 85 mol% or more and 100 mol% or less, and preferably 98 mol% or more. The PVA-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The average polymerization degree of the PVA-based resin is usually 1,000 or more and 10,000 or less, and preferably 1,500 or more and 5,000 or less. The average polymerization degree of the PVA-based resin can be determined in accordance with JIS K 6726.

The method for forming a film from the PVA-based resin is not particularly limited, and known methods can be used. There are no particular limitations on the thickness of the PVA-based resin film used as the original film when producing a polarizing film. For example, in order to make the thickness of the polarizing film 25 μm or less, the thickness of the PVA-based resin film as the original film is preferably 40 μm or more and 75 μm or less, and more preferably 45 μm or less.

The stretching of the PVA-based resin film is preferably uniaxial stretching. The uniaxial stretching can be performed before, simultaneously with, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the crosslinking treatment. The uniaxial stretching may also be performed at a plurality of these stages. In the uniaxial stretching, the film may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a heated roll. The uniaxial stretching may be dry stretching in which the film is stretched in the air, or wet stretching in which the film is stretched in a state where it is swollen with a solvent or water. The stretching ratio is usually 3 to 8 times.

One method for dyeing a PVA-based resin film with a dichroic dye is, for example, to immerse the PVA-based resin film in an aqueous solution containing the dichroic dye. Iodine or a dichroic organic dye is used as the dichroic dye. It is preferable to immerse the PVA-based resin film in water before the dyeing process.

The crosslinking treatment after dyeing with a dichroic dye usually involves immersing the dyed PVA-based resin film in an aqueous solution containing boric acid. When iodine is used as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

(Protective film)
The protective films 12 and 13 each have a base film and an HC layer. The protective films 12 and 13 preferably have the HC layer formed so as to be in direct contact with the base film. The HC layer is preferably provided on one side of the base film, but may be provided on both sides.

The number of protective films 12 and 13 laminated on the first surface 11a side of the polarizing film 11 (hereinafter, two or more protective films laminated on the first surface 11a side may be collectively referred to as the "protective film group") is preferably 5 or less, more preferably 3 or less, and most preferably 2. If the protective film group includes six or more protective films, it becomes difficult to adjust the curl (warping) of the polarizing plate 1. As shown in FIG. 1, the protective films 12 and 13 constituting the protective film group are preferably laminated via an attachment layer 31, and both sides of the attachment layer 31 are more preferably in direct contact with the protective films 12 and 13 constituting the protective film group. In both of the protective films 12 and 13 constituting the protective film group, it is preferable that the base film is disposed on the polarizing film 11 side of the polarizing plate 1, and the HC layer is disposed on the surface side of the polarizing plate 1 (opposite the polarizing film 11 side).

The thickness of the protective film is not particularly limited, but is usually 1 μm or more and 100 μm or less, and from the viewpoint of strength and ease of handling, it is preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 55 μm or less, and even more preferably 15 μm or more and 50 μm or less.

The protective films 12 and 13 constituting the protective film group may have the same material and/or thickness of the base film and HC layer, or may have different materials and/or thicknesses of the base film and HC layer.

At least one of the protective films in the protective film group has a moisture permeability of 200 g/m ² ·day or more at a temperature of 40° C. and a relative humidity of 90%, and more preferably 300 g/m ² ·day or more. The upper limit is usually 5000 g/m ² ·day or less, preferably 2000 g/m ² ·day or less, and more preferably 1000 g/m ² ·day or less. In the polarizing plate 1, it is sufficient that one or more of the protective films in the protective film group have a moisture permeability in the above range. By setting the moisture permeability of the protective film in the above range, it is possible to suppress the polarizing film 11 from being polyenized and colored in the heating durability test described later.

It is preferable that the protective film 12, which is laminated closest to the polarizing film side of the protective film group, has a moisture permeability in the above range. When manufacturing the polarizing plate 1, as described below, the protective film 12 may be laminated to the polarizing film 11 using a bonding agent (adhesive or pressure-sensitive adhesive) such as a water-based adhesive, and then the bonding layer 32 may be formed by a drying process, and then the protective film 13 may be laminated. In this case, by setting the moisture permeability of the protective film 12, which is laminated closest to the polarizing film 11 side of the protective film group, in the above range, it is easy to remove moisture contained in the bonding agent by the drying process.

As long as the protective film 12 laminated closest to the polarizing film 11 side of the protective film group has a moisture permeability in the above range, the moisture permeability of the other protective film 13 other than the protective film 12 included in the protective film group is not particularly limited. The moisture permeability of the other protective film 13 may be smaller than that of the protective film 12. The moisture permeability of the other protective film 13 at a temperature of 40° C. and a relative humidity of 90% is not particularly limited, but is preferably 1000 g/m ² ·day or less, more preferably 500 g/m ² ·day or less. The moisture permeability of the protective film 13 is preferably more than 20 g/m ² ·day, more preferably 30 g/m ² ·day or more. By setting the upper limit of the moisture permeability of the other protective film 13 to the above range, the rate of moisture uptake into the polarizing plate 1 after the heat durability test can be suppressed. As a result, it is easier to ensure time for stress relaxation of the polarizing film 11, and it is considered that the occurrence of cracks in the retardation film 21 can be suppressed. By setting the lower limit of the moisture permeability of the other protective film 13 within the above range, it is possible to prevent the polarizing film 11 from being polyenized and colored during a heat durability test. The moisture permeability of the protective films 12 and 13 can be measured by the method described in the examples described later.

In the above, a case has been described in which the moisture permeability of protective film 12 is 200 g/ ^m2 ·day or more and the moisture permeability of other protective film 13 is 1000 g/ ^m2 ·day or less. However, even if this moisture permeability relationship is reversed, it is possible to prevent the polarizing film 11 from becoming polyenated and becoming discolored during a heat durability test.

The base film constituting the protective film 12, 13 is preferably made of a resin material having excellent transparency, mechanical strength, thermal stability, moisture shielding properties, etc., but is not particularly limited thereto. Examples of such resin materials include one or more of methyl (meth)acrylate resins, polyolefin resins, cyclic olefin resins, polyvinyl chloride resins, cellulose resins, styrene resins, acrylonitrile-butadiene-styrene resins, acrylonitrile-styrene resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene terephthalate resins, polyethylene terephthalate resins, polysulfone resins, polyethersulfone resins, polyarylate resins, polyamideimide resins, and polyimide resins. These resins may be used after any suitable polymer modification. Examples of polymer modifications include copolymerization, crosslinking, molecular end modification, stereoregularity control, and mixing, including cases involving reactions between different polymers.

It is preferable that the base film of at least one of the protective films in the protective film group is a cellulose-based resin film formed using a cellulose-based resin as the resin material. It is more preferable that the base films of all of the protective films constituting the protective film group are cellulose-based resin films.

The cellulose-based resin may be an organic acid ester or mixed organic acid ester of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose are replaced with acetyl groups, propionyl groups, and/or butyryl groups. Examples include cellulose acetate, propionate, butyrate, and mixed esters thereof. Among these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, and the like are preferred.

The resin material constituting the substrate film may contain appropriate additives as long as the transparency is not impaired. Examples of additives include antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, retardation reducing agents, stabilizers, processing aids, plasticizers, impact resistance aids, matting agents, antibacterial agents, and fungicides. One or more of these additives may be used, or multiple types may be used in combination.

The thickness of the base film is not particularly limited, but can be, for example, 1 μm or more, 3 μm or more, 10 μm or more, or 30 μm or more, and is usually 90 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. The base film usually has a single-layer structure, but may have a multi-layer structure of two or more layers.

The HC layer constituting the protective films 12 and 13 is preferably, but not limited to, a cured layer of an ultraviolet-curable resin formed on a substrate film. Examples of ultraviolet-curable resins include (meth)acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The HC layer may contain additives to improve the surface hardness. Examples of additives include, but are not limited to, inorganic fine particles, organic fine particles, or mixtures thereof.

The thickness of the HC layer is preferably 10 μm or less, more preferably 8 μm or less, and is usually 0.1 μm or more, may be 1 μm or more, or may be 4 μm or more. If the thickness of the HC layer exceeds 10 μm, the curl (warping) of the protective films 12 and 13 becomes large, making it difficult to adjust the curl of the polarizing plate 1.

The protective films 12 and 13 preferably have a hardness of H or more, more preferably 2H or more, and may be 3H or more, or may be 4H or more, according to the pencil hardness test specified in JIS K 5600-5-4:1999 "General test methods for coating materials - Part 5: Mechanical properties of coating films - Section 4: Scratch hardness (pencil method)" (when the substrate film on which the HC layer is formed is placed on a glass plate and the measurement is performed on the HC layer side).

The HC layer can be formed, for example, by applying a composition for forming an HC layer (hereinafter sometimes referred to as "composition for forming an HC layer") containing an ultraviolet-curable resin and, if necessary, additives, etc., onto a substrate film, and curing the composition by irradiating it with ultraviolet light.

(Retardation film)
The retardation film 21 is a film having a phase difference, and is usually a stretched film obtained by stretching a resin film. The retardation film 21 preferably has a single-layer structure. The tensile modulus of the retardation film 21 at a temperature of 23° C. is 3000 MPa or less, and may be 2800 MPa or less, and is usually 1000 MPa or more, and may be 2000 MPa or more. The tensile modulus can be measured by the method described in the examples below.

An example of a retardation film 21 having the above tensile modulus is an olefin-based resin film formed using an olefin-based resin. Examples of olefin-based resins include resins that mainly contain structural units derived from chain aliphatic olefins such as ethylene and propylene, or alicyclic olefins such as norbornene and its substitutes (hereinafter, these may be collectively referred to as "norbornene-based monomers"). "Mainly containing structural units" means that the proportion of structural units contained in the resin based on the substance amount is 50% or more. The olefin-based resin may be a copolymer using two or more types of monomers.

The retardation film 21 is preferably a cyclic olefin resin film formed using a cyclic olefin resin, which is a resin mainly containing structural units derived from an alicyclic olefin. A typical example of an alicyclic olefin constituting a cyclic olefin resin is a norbornene monomer. Norbornene is a compound in which one carbon-carbon bond of norbornane becomes a double bond, and is named bicyclo[2,2,1]hept-2-ene according to the IUPAC nomenclature system. Examples of norbornene substitutions include 3-substitutions, 4-substitutions, and 4,5-disubstitutions, with the double bond positions of norbornene at the 1,2-positions, and further include dicyclopentadiene and dimethanooctahydronaphthalene.

The cyclic olefin resin may or may not have a norbornane ring in its constituent units. Examples of norbornene monomers forming a cyclic olefin resin that does not have a norbornane ring in its constituent units include those that become five-membered rings by ring opening, typically norbornene, dicyclopentadiene, 1- or 4-methylnorbornene, and 4-phenylnorbornene. When the cyclic olefin resin is a copolymer, the molecular arrangement is not particularly limited, and it may be a random copolymer, a block copolymer, or a graft copolymer.

More specific examples of cyclic olefin resins include ring-opening polymers of norbornene monomers, ring-opening copolymers of norbornene monomers and other monomers, polymer modifications to which maleic acid or cyclopentadiene has been added, and polymers or copolymers obtained by hydrogenating these; addition polymers of norbornene monomers, and addition copolymers of norbornene monomers and other monomers. Examples of other monomers that may be used in the copolymerization include α-olefins, cycloalkenes, and non-conjugated dienes. The cyclic olefin resin may also be a copolymer using one or more of a norbornene monomer and other alicyclic olefins. Among these, the cyclic olefin resin is preferably a resin obtained by hydrogenating a ring-opening polymer or ring-opening copolymer using a norbornene monomer.

Commercially available cyclic olefin resins using the above norbornene monomers include "ZEONEX" and "ZEONOR" sold by Zeon Corporation, and "ARTON" sold by JSR Corporation. Films and stretched films of these cyclic olefin resins are also available commercially, for example, "ZEONOR Film" sold by Optes Corporation, "ARTON Film" sold by JSR Corporation, and "ESCINA" sold by Sekisui Chemical Co., Ltd.

The retardation film 21 may be a film made of a mixed resin containing two or more types of olefin resins, or a film made of a mixed resin of an olefin resin and another thermoplastic resin. For example, a mixed resin containing two or more types of olefin resins may be a mixture of a cyclic olefin resin and a chain aliphatic olefin resin as described above. When using a mixed resin of an olefin resin and another thermoplastic resin, the other thermoplastic resin is appropriately selected depending on the purpose. Specific examples of other thermoplastic resins include polyvinyl chloride resins, cellulose resins, polystyrene resins, acrylonitrile/butadiene/styrene copolymer resins, acrylonitrile/styrene copolymer resins, (meth)acrylic resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene terephthalate resins, polyethylene terephthalate resins, polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyarylate resins, liquid crystal resins, polyamideimide resins, polyimide resins, and polytetrafluoroethylene resins. These thermoplastic resins can be used alone or in combination of two or more. The thermoplastic resins can also be used after any suitable polymer modification. Examples of polymer modification include copolymerization, crosslinking, molecular end modification, and stereoregularity impartation.

When using a mixed resin of an olefin resin and another thermoplastic resin, the content of the other thermoplastic resin is usually about 50% by weight or less, and preferably about 40% by weight or less, based on the total resin. By keeping the content of the other thermoplastic resin within this range, it is possible to obtain a retardation film 21 that has a small absolute value of the photoelastic coefficient, exhibits good wavelength dispersion characteristics, and is excellent in durability, mechanical strength, and transparency.

The retardation film 21 may contain other components as necessary, such as residual solvents, stabilizers, plasticizers, antiaging agents, antistatic agents, and UV absorbers. It may also contain a leveling agent to reduce surface roughness.

The retardation film 21 preferably has an in-plane retardation value, and the in-plane retardation value at a wavelength of 550 nm is preferably 80 nm or more, may be 90 nm or more, may be 100 nm or more, may be 300 nm or less, or may be 200 nm or less. The retardation film 21 is preferably a stretched film.

In general, the higher the in-plane retardation value of the retardation film 21, the more aligned the molecular orientation of the retardation film 21 is, so that it is more likely to crack when subjected to external force. As described above, the polarizing plate 1 has a structure in which two or more protective films 12, 13 are laminated on the first surface 11a of the polarizing film 11. Therefore, even if the polarizing plate 1 including the retardation film 21 having such a high in-plane retardation value is kept in a normal temperature and humidity environment for a long period of time after the heating durability test, the dimensional change of the polarizing film 11 can be suppressed, and the force acting on the retardation film 21 can be reduced, so that the occurrence of cracks in the retardation film 21 can be suppressed.

The in-plane retardation value of the retardation film 21 can be measured by the method described in the Examples below. The in-plane retardation value Re(λ) of the retardation film 21 at a wavelength λ [nm] refers to the in-plane retardation value of the retardation film 21 at a temperature of 23° C., and is calculated by the following formula (i).
Re(λ)=(nx-ny)×d(i)
[In formula (i),
nx is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction),
ny is the refractive index in the in-plane direction perpendicular to the slow axis,
d is the thickness [nm] of the retardation film 21.

The retardation film 21 may have a thickness retardation value of 0 (zero), or may have a thickness retardation value. The thickness retardation value of the retardation film 21 at a wavelength of 550 nm may be, for example, 10 nm or more, 20 nm or more, 40 nm or more, 100 nm or less, 80 nm or less, or 60 nm or less. The thickness retardation value of the retardation film 21 can be measured by a method described in the examples below. The thickness retardation value Rth(λ) of the retardation film 21 at a wavelength λ [nm] refers to the thickness retardation value of the retardation film 21 at a temperature of 23° C., and is calculated by the following formula (ii).
Rth(λ)=[{(nx+ny)/2}-nz]×d (ii)
[In the formula (ii),
nx is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction),
ny is the refractive index in the in-plane direction perpendicular to the slow axis,
nz is the refractive index in the thickness direction,
d is the thickness [nm] of the retardation film 21.

The thickness of the retardation film 21 is not particularly limited, but is preferably 15 μm to 80 μm, more preferably 18 μm to 45 μm, and most preferably 20 μm to 30 μm. If the thickness of the retardation film is less than 15 μm, the film tends to be difficult to handle and to have difficulty in achieving the desired retardation value. On the other hand, if the thickness of the retardation film exceeds 80 μm, the film tends to have poor processability, reduced transparency, and a large weight for the obtained polarizing plate 1.

The retardation film 21 can be obtained by stretching a resin film formed using the above-mentioned resin. The resin film can be obtained, for example, by forming a film by a casting method or a melt extrusion method from a solution containing the above-mentioned olefin resin. When forming a film using a mixed resin of two or more kinds, the film formation method is not particularly limited, and examples include a method of forming a film by a casting method using a homogeneous solution obtained by stirring and mixing the resin components with a solvent in a predetermined ratio, and a method of melt mixing the resin components in a predetermined ratio and forming a film by a melt extrusion method.

Examples of stretching treatments for resin films include known longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching. In addition to appropriately adjusting the stretching ratio and stretching speed so as to obtain the desired retardation value, the various temperatures during stretching, such as the preheating temperature, stretching temperature, heat setting temperature, and cooling temperature, and their patterns may be appropriately selected.

When the retardation film 21 is the above-mentioned cyclic olefin resin film, it can be obtained, for example, by forming a film-like material using the above-mentioned cyclic olefin resin that has been subjected to a stretching process in advance, laminating a shrinkable film having a predetermined shrinkage rate to this, and then heat shrinking it. This makes it possible to obtain a retardation film 21 that is highly uniform and has a large retardation value.

(Functional layer)
The polarizing plate 1 may have one or more functional layers, such as an antistatic layer, a retardation layer other than the retardation film 21, or a protective layer other than the protective films 12 and 13 for covering and protecting the surface of the polarizing film 11.

The antistatic layer is a layer for preventing the polarizing plate 1 from being charged. The antistatic layer usually contains an antistatic agent such as an ionic compound, and can be, for example, a layer containing an antistatic agent and a resin. For example, the antistatic layer can be provided in the polarizing plate 1 between the polarizing film 11 and the retardation film 21, between the polarizing film 11 and the protective film 12, on the opposite side of the retardation film 21 from the polarizing film 11, etc. The antistatic layer is preferably laminated to these films via an attachment layer.

The other retardation layer is a layer having an in-plane retardation value or a retardation value in the thickness direction. The other retardation layer can be, for example, a retardation layer having a retardation value in the thickness direction at a wavelength of 550 nm, and can be, for example, a positive C plate. The positive C plate is used, for example, when the polarizing plate 1 is used in an IPS mode liquid crystal display device. The other retardation layer can be provided, for example, between the polarizing film 11 and the retardation film 21, or on the opposite side of the retardation film 21 from the polarizing film 11 side. The other retardation layer may be a stretched film obtained by stretching a resin film, or a cured layer of a polymerizable liquid crystal compound. The other retardation layer can be laminated to the polarizing film 11 and the retardation film 21 via an attachment layer. When the other retardation layer is a cured layer, it can also be provided so as to be in direct contact with these films by polymerizing and curing the polymerizable liquid crystal compound applied to the polarizing film 11 or the retardation film 21.

The other protective layer is a layer for covering and protecting the first surface 11a or the second surface 11b of the polarizing film 11. The other protective layer is preferably provided on the second surface 11b side of the polarizing film 11, and is preferably provided between the polarizing film 11 and the retardation film 21 via an adhesive layer. In this case, the adhesive layer provided between the polarizing film 11 and the other protective layer is preferably provided so as to be in contact with the polarizing film 11 and the other protective layer, respectively, and the adhesive layer provided between the other protective layer and the retardation film 21 is preferably provided so as to be in contact with the other protective layer and the retardation film 21, respectively. The other protective layer may be a film formed using the resin material described for the base film constituting the protective films 12 and 13. The other protective layer preferably does not have a retardation, and may be, for example, a cellulose-based resin film having no retardation, or a cyclic olefin-based resin film having no retardation.

(Laminating layer)
Examples of the bonding layers 31 to 33 for bonding the films and layers constituting the polarizing plate 1 include layers formed using a known adhesive, or layers formed using a known pressure-sensitive adhesive.

The adhesive is an adhesive other than a pressure-sensitive adhesive (adhesive), and examples of the adhesive include a water-based adhesive, an active energy ray-curable adhesive, and a heat-curable adhesive, and preferably a water-based adhesive or an active energy ray-curable adhesive. The thickness of the lamination layer formed using the adhesive may be, for example, 0.01 μm or more, 0.1 μm or more, 0.5 μm or more, or 1 μm or more, and may be, for example, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less.

Examples of water-based adhesives include adhesives made of an aqueous solution of polyvinyl alcohol-based resins, and aqueous two-liquid urethane-based emulsion adhesives. Among these, water-based adhesives made of an aqueous solution of polyvinyl alcohol-based resins are preferably used. Examples of polyvinyl alcohol-based resins that can be used include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, polyvinyl alcohol copolymers obtained by saponifying a copolymer of vinyl acetate and other monomers that can be copolymerized with it, and modified polyvinyl alcohol polymers in which the hydroxyl groups of these copolymers are partially modified. Water-based adhesives can contain crosslinking agents such as aldehyde compounds (such as glyoxal), epoxy compounds, melamine compounds, methylol compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

When using a water-based adhesive as the adhesive, it is preferable to carry out a drying process to remove the water contained in the water-based adhesive after laminating with the film to be bonded. After the drying process, a curing process may be carried out in which the product is cured at a temperature of, for example, 20 to 45°C.

The active energy ray curable adhesive is an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, and is preferably an ultraviolet ray curable adhesive. The curable compound can be a cationic polymerizable curable compound or a radical polymerizable curable compound. Examples of the cationic polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in the molecule), an oxetane compound (a compound having one or more oxetane rings in the molecule), or a combination thereof. Examples of the radical polymerizable curable compound include a (meth)acrylic compound (a compound having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having radical polymerizable double bonds, or a combination thereof. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination. The active energy ray curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating the curing reaction of the curable compound.

An adhesive exerts adhesive properties by attaching itself to an adherend, and is known as a pressure-sensitive adhesive. The adhesive can be composed of an adhesive composition whose main component is a resin such as a (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin. Among them, an adhesive composition whose base polymer is a (meth)acrylic resin, which has excellent transparency, weather resistance, heat resistance, etc., is preferable. The adhesive may be an active energy ray curable type or a heat curable type. The thickness of the attachment layer formed using the adhesive is usually 3 μm or more and 30 μm or less, and preferably 3 μm or more and 25 μm or less.

As the (meth)acrylic resin (base polymer) contained in the adhesive composition, for example, a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, is preferably used. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

The adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

(Adhesive Layer)
The polarizing plate 1 may have an adhesive layer 35 for attaching the polarizing plate 1 to a display element of a display device or the like. The adhesive layer 35 is preferably provided on the side of the retardation film 21 of the polarizing plate 1 opposite to the polarizing film 11 side. The adhesive layer 35 can be formed using an adhesive. Examples of the adhesive include the adhesive used to form the above-mentioned attachment layer. The thickness of the adhesive layer 35 is not particularly limited, but is usually 3 μm or more and 50 μm or less, preferably 5 μm or more and 40 μm or less, and may be 10 μm or more and 30 μm or less.

(Release film)
The polarizing plate 1 may have a release film that can be peeled off from the adhesive layer 35. The release film is used to cover and protect the surface of the adhesive layer 35 or to support the adhesive layer 35. An example of the release film is a film in which a release treatment such as silicone treatment has been applied to the surface of the base resin film on the side of the adhesive layer 35. An example of the resin material constituting the base resin film is a film formed using the resin material described above for the base film. The base resin film may have a single layer structure or a multilayer structure of two or more layers.

(Method of manufacturing polarizing plate)
The manufacturing method of the polarizing plate 1 is not particularly limited, and a known method can be used. For example, the protective film 12 is laminated on the first surface 11a of the polarizing film 11 using a water-based adhesive, and the retardation film 21 is laminated on the second surface 11b of the polarizing film 11 using a water-based adhesive, and a laminate of the protective film 12/attaching layer 32/polarizing film 11/attaching layer 33/retardation film 21 is produced through a drying process for removing water from the water-based adhesive. In this case, if the thickness difference between the protective film 12 and the retardation film 21 is 30 μm or less, curling occurring in the laminate is easily suppressed, and a flat laminate is easily obtained. Thereafter, the protective film 13 is laminated on the protective film 12 side of the laminate via the adhesive layer 31, whereby the polarizing plate 1 can be obtained. When the polarizing plate 1 has three or more protective films on the first surface 11a side of the polarizing film 11, a step of laminating a protective film may be further provided. When a laminate in which the difference in thickness between the protective film 12 and the retardation film 21 is 30 μm or less is used as described above, curling of the polarizing plate 1 is easily suppressed, and a flat polarizing plate 1 is easily obtained.

In order to increase the adhesion between the films and layers (protective films 12, 13, polarizing film 11, retardation film 21, functional layer, etc.) constituting the polarizing plate 1 and the lamination layer, a surface activation treatment may be applied to the lamination surface of these films and layers. Examples of surface activation treatments include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet light treatment, electron beam treatment, etc.); and wet treatments such as ultrasonic treatment using a solvent such as water or acetone, saponification treatment, and anchor coat treatment. These surface activation treatments may be performed alone or in combination of two or more.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Thickness Measurement]
The thickness of each film and layer constituting the polarizing plate was measured using a digital micrometer MH-15M manufactured by Nikon Corporation.

[Measurement of Moisture Permeability]
The moisture permeability of the protective film was measured in accordance with JIS K 7129:2008 Appendix B in an atmosphere at a temperature of 40°C and a relative humidity of 90%.

[Measurement of Phase Difference Value]
The retardation values of the retardation film and other retardation layers were measured using a retardation measuring device KOBRA-WPR (manufactured by Oji Scientific Instruments Co., Ltd.).

[Measurement of tensile modulus]
A test piece having a width of 15 mm and a length of 150 mm was cut out from the retardation film parallel to the slow axis and the fast axis. Next, the test piece was clamped at both ends in the long side direction with the upper and lower grips of a tensile tester (AUTOGRAPH (registered trademark) AG-1S tester manufactured by Shimadzu Corporation) so that the distance between the grips was 100 mm, and pulled at a tensile speed of 50 mm/min in an environment of 23 ° C. to create a stress-strain curve, and the tensile modulus in the direction parallel to the slow axis and the fast axis at 23 ° C. was calculated. The larger value of the tensile modulus in the direction parallel to the slow axis and the fast axis calculated in this way was taken as the tensile modulus of the retardation film at 23 ° C.

[Measurement of storage modulus]
The storage modulus G' of the pressure-sensitive adhesive layer A and the pressure-sensitive adhesive layer B was measured according to the following procedures [I] to [III].
[I] Two samples, each weighing 25±1 mg, are taken from each pressure-sensitive adhesive layer, and each sample is molded into an approximately ball-like shape.
[II] Two molded samples in a roughly spherical shape are attached to the top and bottom surfaces of an I-shaped jig, and both the top and bottom surfaces are sandwiched between L-shaped jigs to prepare a measurement sample. The measurement sample has a configuration of L-shaped jig/adhesive layer A or adhesive layer B/I-shaped jig/adhesive layer/L-shaped jig.
[III] The storage modulus G' of the measurement sample is measured using a dynamic viscoelasticity measuring device "DVA-220" manufactured by IT Measurement and Control Co., Ltd. under the conditions of a temperature of 23°C, a frequency of 1 Hz, and an initial strain of 1 N.

[Measurement of Pencil Hardness]
The protective film was placed on a glass plate so that the base film side of the protective film faced the glass plate. The pencil hardness test specified in JIS K 5600-5-4:1999 "General test methods for coating materials - Part 5: Mechanical properties of coating films - Section 4: Scratch hardness (pencil method)" was carried out on the HC layer side of the protective film to measure the pencil hardness of the protective film.

<Preparation of Polarizing Film>
A 40 μm thick PVA-based resin film was prepared, which was made of a PVA-based resin having an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more. The PVA-based resin film was uniaxially stretched by about 5 times in a dry state, and was immersed in pure water at a temperature of 60° C. for 1 minute while maintaining a tension state. The PVA-based resin film was then immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.05/5/100 at a temperature of 28° C. for 60 seconds. The PVA-based resin film was then immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at a temperature of 72° C. for 300 seconds. The film was then washed with pure water at a temperature of 26° C. for 20 seconds, and then dried at a temperature of 65° C. In this way, a polarizing film having a thickness of 15 μm was obtained in which iodine as a dichroic dye was adsorbed and oriented on the PVA-based resin film.

<Preparation of Protective Film (1)>
The components shown below were mixed to prepare a composition for forming an HC layer.
PET30 97.0 parts by weight Irgacure 907 3.0 parts by weight MEK 81.8 parts by weight Here, PET30 is a mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd.).
Irgacure 907 is a photopolymerization initiator (manufactured by BASF).
MEK is methyl ethyl ketone.

The substrate film wound in a roll shape (cellulose acylate film TD40, manufactured by Fujifilm Corporation, width 1,340 mm, film thickness 40 μm) was unwound, and the composition for forming the HC layer was applied at a conveying speed of 30 m/min by a die coating method using a slot die, and dried at 60 ° C. for 150 seconds to form a coating layer. Thereafter, under conditions of nitrogen purge and oxygen concentration of about 0.1%, an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) with an output of 160 W/cm was used to irradiate ultraviolet rays with an illuminance of 400 mW/cm ² and an irradiation amount of 120 mJ/cm ² to harden the coating layer, thereby forming an HC layer. The coating thickness of the coating layer was adjusted so that the film thickness of the HC layer was 7 μm. In this way, a protective film (1) having an HC layer on one side of the substrate film was obtained, and this was wound up. The moisture permeability of the protective film (1) was 250 g/m ² ·day. The pencil hardness of the protective film (1) was 2H.

<Preparation of Protective Film (2)>
A protective film (2) was obtained in the same manner as in the preparation of the protective film (1), except that the thickness of the coating layer was adjusted so that the thickness of the HC layer was 5 μm. The moisture permeability of the protective film (2) was 350 g/ ^m2 ·day. The pencil hardness of the protective film (2) was 3H.

<Preparation of Protective Film (3)>
A protective film (3) was obtained in the same manner as in the preparation of the protective film (1), except that the thickness of the coating layer was adjusted so that the thickness of the HC layer was 3 μm. The moisture permeability of the protective film (3) was 500 g/m2· ^day . The pencil hardness of the protective film (3) was 3H.

<Preparation of Retardation Laminate Including Retardation Film and Other Retardation Layer>
A retardation film and other retardation layers were prepared according to the description in paragraphs [0106] to [0109] of International Publication No. 2018/207798. Specifically, an unstretched cycloolefin polymer film (manufactured by JSR Corporation, trade name "Arton Film") was uniaxially stretched to obtain a retardation film having a thickness of 24 μm. The tensile modulus of the obtained retardation film at a temperature of 23 ° C. was measured to be 2742 MPa. In addition, the in-plane retardation value Re (550) of the retardation film at a wavelength of 550 nm was 110 nm, and the retardation value Rth (550) in the thickness direction at a wavelength of 550 nm was 55 nm.

Next, a composition containing a rod-shaped liquid crystal compound was applied to one side of the retardation film obtained above to form another retardation layer, thereby obtaining a retardation laminate. The in-plane retardation value Re(550) of the other retardation layer at a wavelength of 550 nm was 0 nm, and the retardation value Rth(550) in the thickness direction at a wavelength of 550 nm was -100 nm.

<Preparation of polyvinyl alcohol adhesive (PVA adhesive)>
50 g of a modified PVA-based resin containing an acetoacetyl group (GOSENEX Z-410, manufactured by Mitsubishi Chemical Corporation) was dissolved in 950 g of pure water, heated at 90° C. for 2 hours, and then cooled to room temperature to obtain a polyvinyl alcohol solution. Next, the polyvinyl alcohol solution, maleic acid, glyoxal, and pure water were mixed so that each compound had the following concentration to prepare a PVA-based adhesive.
Polyvinyl alcohol concentration: 3.0% by weight
Maleic acid concentration: 0.01% by weight
Glyoxal concentration: 0.15% by weight

<Preparation of Pressure-Sensitive Adhesive Layer A and Pressure-Sensitive Adhesive Layer B>
As the pressure-sensitive adhesive layer A, a commercially available sheet-shaped acrylic pressure-sensitive adhesive (storage modulus at a temperature of 23° C.: 0.06 MPa) having a thickness of 5 μm was prepared.
As the pressure-sensitive adhesive layer B, a commercially available sheet-shaped acrylic pressure-sensitive adhesive (storage modulus at a temperature of 23° C.: 0.06 MPa) having a thickness of 25 μm was prepared.

Example 1
The protective film (1) obtained above was immersed in a 1.5 mol/L NaOH aqueous solution (saponification solution) kept at a temperature of 55° C. for 2 minutes, and then washed with water. The washed protective film (1) was immersed in a 0.05 mol/L sulfuric acid aqueous solution at a temperature of 25° C. for 30 seconds, and then passed under running water for another 30 seconds to neutralize the protective film (1). The protective film (1) was drained three times using an air knife, and then allowed to stay in a drying zone at a temperature of 70° C. for 15 seconds to dry. As a result, a saponified protective film (1) was obtained in which the HC layer and the substrate film were subjected to a saponification treatment (surface activation treatment).

A laminate (1) was obtained by laminating a saponified protective film (1) (hereinafter sometimes referred to as "first protective film (1)"), a polarizing film, and a retardation laminate via the PVA-based adhesive prepared above. In the laminate (1), the absorption axis of the polarizing film and the slow axis of the retardation film were parallel. In the laminate (1), the other retardation layer side of the retardation laminate was the polarizing film side, and the base film side of the first protective film (1) was the polarizing film side. The adhesive strength between the retardation laminate and the polarizing film, and the adhesive strength between the polarizing film and the first protective film (1) were sufficient for practical use.

Next, a saponified protective film (1) (hereinafter, sometimes referred to as "second protective film (1)"), which was saponified in the same manner as above, was laminated on the first protective film (1) side of the laminate (1) obtained above, via the adhesive layer A. The second protective film (1) had the base film side attached to the adhesive layer (A). In addition, the retardation laminate side of the laminate (1) was corona-treated, and the surface of the adhesive layer B was corona-treated, so that the corona-treated surface of the laminate (1) and the corona-treated surface of the adhesive layer (B) were laminated together. In this way, a polarizing plate (1) was obtained. In the polarizing plate (1), the first protective film (1) and the second protective film (1) were both arranged on the same surface side of the polarizing film, the first protective film (1) was arranged relatively close to the polarizing film, and the second protective film (1) was arranged relatively far from the polarizing film.

Example 2
A polarizing plate (2) was obtained in the same manner as the preparation procedure for the polarizing plate (1) prepared in Example 1, except that a saponified protective film (2) was used that had been subjected to the same saponification treatment as that performed on the protective film (1) instead of the first protective film (1) and the second protective film (1).

Example 3
A polarizing plate (3) was obtained in the same manner as the preparation procedure of the polarizing plate (1) prepared in Example 1, except that a saponified protective film (3) was used in place of the first protective film (1) and the second protective film (1), which had been subjected to a saponification treatment similar to that performed on the protective film (1).

Comparative Example 1
A comparative polarizing plate (C1) was obtained in the same manner as the preparation procedure for the polarizing plate (1) prepared in Example 1, except that a saponified substrate film (cellulose acylate film TD40, manufactured by Fujifilm Corporation, width 1,340 mm, film thickness 40 μm) was used instead of the second protective film (1) and subjected to the same saponification treatment as that performed on the protective film (1).

Comparative Example 2
A laminate (1) was prepared in the same manner as in Example 1, and this was used as a comparative polarizing plate (C2).

Comparative Example 3
A comparative polarizing plate (C3) was obtained in the same manner as the preparation procedure for the polarizing plate (1) prepared in Example 1, except that instead of the first protective film (1), a saponified substrate film (cellulose acylate film TD40, manufactured by Fujifilm Corporation, width 1,340 mm, film thickness 40 μm) was used that had been subjected to the same saponification treatment as that performed on the protective film (1).

[Evaluation of crack occurrence]
For each of the polarizing plates obtained in the examples and the comparative polarizing plates obtained in the comparative examples, evaluation samples were prepared by the following procedure, and the occurrence of cracks was evaluated. The polarizing plate or the comparative polarizing plate was cut to a size of 200 mm x 200 mm, and attached to an alkali-free glass sheet having a thickness of 0.7 mm and a size of 300 mm x 300 mm via the adhesive layer B to prepare an evaluation sample.

The evaluation samples thus prepared were held in a heated environment at 105°C for 500 hours, and then cooled to 23°C (room temperature). After that, they were held in a room temperature and humidity environment at 23°C and 55% relative humidity for 30 days, after which the retardation film of the polarizing plate or comparative polarizing plate was observed to check for the occurrence of cracks. Furthermore, for evaluation samples in which no cracks were observed at this point, the retardation film was observed again after another 7 days (37 days after the start of holding in the room temperature and humidity environment) to check for the occurrence of cracks. The results are shown in Table 1.

1 polarizing plate, 11 polarizing film, 11a first surface, 11b second surface, 12, 13 protective film, 21 retardation film, 31-33 bonding layers, 35 adhesive layer.

Claims (8)

a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film;
a protective film having a hard coat layer provided on a substrate film;
A retardation film having a tensile modulus of elasticity of 3000 MPa or less at a temperature of 23° C.;
a protective film group including two or more of the protective films laminated on a first surface side of the polarizing film;
The protective films constituting the protective film group are laminated to each other via an attachment layer,
Both sides of the attachment layer are in direct contact with the protective film,
A polarizing plate in which the retardation film is laminated on a second surface side opposite to the first surface side of the polarizing film (excluding the case where a polarizing film is laminated on the surface side of the protective film group opposite to the polarizing film side) . 2 . The polarizing plate according to claim 1 , wherein at least one of the two or more protective films laminated on the first surface side has a moisture permeability of 200 g/m ² ·day or more at a temperature of 40° C. and a relative humidity of 90%. 3. The polarizing plate according to claim 1, wherein the protective film laminated closest to the polarizing film among the two or more protective films laminated on the first surface side has a moisture permeability of 200 g/ ^m2 ·day or more at a temperature of 40°C and a relative humidity of 90%. The polarizing plate according to any one of claims 1 to 3, wherein the base film of at least one of the two or more protective films laminated on the first surface side is a cellulose-based resin film. The polarizing plate according to any one of claims 1 to 4, wherein the retardation film is a cyclic olefin resin film. The polarizing plate according to any one of claims 1 to 5, wherein the in-plane retardation value of the retardation film at a wavelength of 550 nm is 80 nm or more. The polarizing plate according to any one of claims 1 to 6, further comprising an adhesive layer on the side of the retardation film opposite to the polarizing film side. A display device comprising the polarizing plate according to claim 7 and a display element,
The display device, wherein the polarizing plate is laminated on a display element via the pressure-sensitive adhesive layer.

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