Polarizer

Abstract

To provide a polarizing plate which is excellent in scratch resistance, and suppresses occurrence of cracking in a retardation film even when stored for a long period of time under normal temperature and normal humidity environment after a heat durability test.SOLUTION: A polarizing plate includes: a polarizing film in which a dichroic dye is adsorbed and oriented to a polyvinyl alcohol-based resin film; protective films having a hard coat layer provided on a base material film; and a retardation film having a tensile elastic modulus at a temperature of 23°C of 3,000 MPa or less. The two or more protective films are laminated on a first surface side of the polarizing film. The retardation film is laminated on a second surface side opposite to the first surface side of the polarizing film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polarizing plate, and more particularly to a display device including the polarizing plate.

Background Art

[0002] Liquid crystal display devices (LCDs) are widely used not only in liquid crystal televisions but also in mobile applications such as personal computers and mobile phones, and in-vehicle applications such as car navigation systems. Usually, a liquid crystal display device has a liquid crystal panel member in which polarizing plates are bonded to both sides of a liquid crystal cell with an adhesive, and display is performed by controlling light from a backlight member with the liquid crystal panel member. In addition, organic EL display devices have also recently begun to be widely used in mobile applications such as televisions and mobile phones, and in-vehicle applications such as car navigation systems, similar to liquid crystal display devices. In liquid crystal display devices and organic EL display devices, a retardation film may be used to impart functions such as an enlarged viewing angle or prevention of external light reflection.

[0003] As an optical element constituting a liquid crystal display device and an organic EL display device, the opportunity for a polarizing plate to be mounted on a vehicle is increasing. A polarizing plate used in an in-vehicle display device is often exposed to a high-temperature environment as compared with a polarizing plate used in mobile applications such as televisions and mobile phones, and it is required to have small characteristic changes at higher temperatures (high-temperature durability).

[0004] When an in-vehicle display device is used in a car navigation system or the like, a touch panel function is required. In recent years, on-cell type and in-cell type display devices are increasingly used as display devices having a touch panel function. In these types of display devices, since a polarizing plate is disposed on the outermost surface on the viewing side, in addition to high-temperature durability, a function of preventing damage (scratch resistance) is also required.

[0005] Patent Document 1 describes a polarizing plate including a retardation film made of a cyclic olefin resin film in order to enlarge the viewing angle. Patent Document 2 also describes that a film using a cyclic olefin resin may be used for a retardation film that functions as a λ / 4 plate constituting the polarizing plate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In a retardation film incorporated in a polarizing plate, such as the above-mentioned retardation film composed of a cyclic olefin-based resin film, even if no cracks are confirmed after a heat endurance test, cracks may be confirmed when it is stored for a long time in a normal temperature and normal humidity environment thereafter.

[0008] An object of the present invention is to provide a polarizing plate that is excellent in scratch resistance and suppresses the occurrence of cracks in the retardation film even when stored for a long time in a normal temperature and normal humidity environment after a heat endurance test.

Means for Solving the Problems

[0009] 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 provided with a hard coat layer on a base film, A retardation film having a tensile elastic modulus of 3000 MPa or less at a temperature of 23°C, and comprising: On the first surface side of the polarizing film, two or more of the protective films are laminated, A polarizing plate in which the retardation film is laminated on the second surface side opposite to the first surface side of the polarizing film. 〔2〕 Among the two or more protective films laminated on the first surface side, the water vapor permeability of at least one protective film at a temperature of 40°C and a relative humidity of 90% is 200 g / m2 ·more than one day, the polarizing plate according to [1]. [3] Among the two or more protective films laminated on the first surface side, the moisture permeability of the protective film laminated closest to the polarizing film at a temperature of 40 ° C and a relative humidity of 90% is 200 g / m 2 ·more than one day, the polarizing plate according to [1] or [2]. [4] Among the two or more protective films laminated on the first surface side, the base film of at least one protective film is a cellulose-based resin film, the polarizing plate according to any one of [1] to [3]. [5] The retardation film is a cyclic olefin-based resin film, the polarizing plate according to any one of [1] to [4]. [6] 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 [1] to [5]. [7] Further, the polarizing plate according to any one of [1] to [6], which has an adhesive layer on the side opposite to the polarizing film side of the retardation film. [8] A display device having the polarizing plate according to [7] and a display element, The polarizing plate is laminated on the display element via the adhesive layer, the display device. [Advantages of the Invention]

[0010] According to the present invention, it is possible to provide a polarizing plate having excellent scratch resistance and suppressing the occurrence of cracks in the retardation film even when stored for a long period in a normal temperature and normal humidity environment after a heat durability test. [Brief Description of the Drawings]

[0011]

Figure 1

[0012] 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 dichroic dyes are 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 provided with a hard coat layer (hereinafter sometimes referred to as an "HC layer") on a base film, and a retardation film 21 having a tensile elastic modulus 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.

[0013] As described above, in the polarizing plate 1, two or more protective films 12 and 13 including an HC layer are laminated on the first surface 11a side of the polarizing film 11. Thereby, the pencil hardness of the surface on the protective film 12 and 13 side of the polarizing plate 1 can be improved, and excellent scratch resistance can be imparted to the polarizing plate 1.

[0014] After the polarizing plate 1 has undergone a heat endurance test of being held at a temperature of 105°C for 500 hours, even if it is held for about one month in a normal temperature and humidity environment of 23°C and 55% relative humidity, it is possible to suppress the occurrence of cracks (fractures) in the retardation film 21. The reason is presumed as follows. When the polarizing plate 1 is cooled after the heat endurance test and held in a normal temperature and humidity environment, moisture (water vapor) in the atmosphere is likely to be taken into the polarizing plate. The moisture taken into the polarizing plate causes dimensional changes in the polarizing film including the PVA-based resin film. When the force generated along with the dimensional change of the polarizing film acts on the retardation film, it is considered that cracks (fractures) may occur in the retardation film. On the other hand, since two or more protective films 12 and 13 are laminated on the first surface 11a side of the polarizing film 11 in the polarizing plate 1, the amount of moisture taken into the polarizing plate 1 can be suppressed, and furthermore, the dimensional change of the polarizing film 11 can be suppressed. Therefore, it is presumed 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.

[0015] 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 a 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.

[0016] The polarizing plate 1 may further have functional layers such as an antistatic layer, another retardation layer different from the retardation film 21, and another protective layer for protecting the surface of the polarizing film 11 different from the protective films 12 and 13.

[0017] 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 or the like of the display device. 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.

[0018] (Display device) The display device can include the 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 can be arranged such that the second surface 11b side of the polarizing film 11 faces the display element side. The polarizing plate 1 may be laminated on the display element via the adhesive layer 35 shown in FIG. 1. When the polarizing plate 1 does not have the adhesive layer 35, it may be laminated on the display element via an adhesive or an adhesive agent. Examples of the display device include a liquid crystal display device and an organic EL device.

[0019] Hereinafter, the film and layer constituting the polarizing plate 1 will be described in detail. (Polarizing film) The polarizing film 11 is an absorption-type 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 orthogonal to the absorption axis (parallel to the transmission axis). As the polarizing film 11, a film in which dichroic dyes are adsorbed and oriented on a uniaxially stretched PVA-based resin film can be preferably used.

[0020] 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 still 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 production of the polarizing film 11, and to achieve high optical characteristics. By setting the thickness of the polarizing film to 20 μm or less, it is possible to further suppress a decrease in visibility when placed in a high-temperature environment.

[0021] The polarizing film 11 can be manufactured, for example, by a method including a step of stretching a PVA-based resin film; a step of adsorbing a dichroic dye by dyeing the PVA-based resin film with the dichroic dye; a step of treating the PVA-based resin film adsorbed with the dichroic dye with a crosslinking solution such as an aqueous boric acid solution; and a step of washing with water after the step of treating with the crosslinking solution.

[0022] As the PVA-based resin film, one obtained by forming a film of a polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") can be used. Examples of the PVA-based resin include those obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. In this specification, "(meth)acryl" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl", "(meth)acrylate", and the like.

[0023] 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. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The average degree of polymerization of the PVA-based resin is usually 1000 or more and 10000 or less, and preferably 1500 or more and 5000 or less. The average degree of polymerization of the PVA-based resin can be determined in accordance with JIS K 6726.

[0024] The method for forming a film of PVA-based resin is not particularly limited, and a known method is adopted. The thickness of the PVA-based resin film used for the raw film when manufacturing a polarizing film is not particularly limited. 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 raw film is preferably 40 μm or more and 75 μm or less, and more preferably 45 μm or less.

[0025] The stretching of the PVA-based resin film is preferably uniaxial stretching. The uniaxial stretching can be performed before the dyeing of the dichroic dye, simultaneously with the dyeing, or after the dyeing. When the uniaxial stretching is performed after the dyeing, this uniaxial stretching may be performed before or during the crosslinking treatment. Also, the uniaxial stretching may be performed in a plurality of these steps. In the case of uniaxial stretching, it may be stretched uniaxially between rolls with different peripheral speeds, or it may be stretched uniaxially using a hot roll. The uniaxial stretching may be dry stretching performed in the air, or wet stretching performed in a state where the PVA-based resin film is swollen using a solvent or water. The stretching ratio is usually 3 to 8 times.

[0026] As a method for dyeing the PVA-based resin film with a dichroic dye, for example, a method of immersing the PVA-based resin film in an aqueous solution containing the dichroic dye is adopted. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the PVA-based resin film is subjected to an immersion treatment in water before the dyeing treatment.

[0027] As the crosslinking treatment after the dyeing with the dichroic dye, usually, a method of immersing the dyed PVA-based resin film in an aqueous solution containing boric acid is adopted. When iodine is used as the dichroic dye, this aqueous solution containing boric acid preferably contains potassium iodide.

[0028] (Protective film) The protective films 12 and 13 have a base film and an HC layer. It is preferable that the HC layer of the protective films 12 and 13 is 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.

[0029] The 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 a "protective film group") are preferably 5 or less, more preferably 3 or less, and most preferably 2. When the protective film group includes 6 or more protective films, it becomes difficult to adjust the curl (warp) of the polarizing plate 1. The protective films 12 and 13 constituting the protective film group are preferably laminated via the bonding layer 31 as shown in FIG. 1, and it is more preferable that both surfaces of the bonding layer 31 are in direct contact with the protective films 12 and 13 constituting the protective film group. In the polarizing plate 1, the base film of each of the protective films 12 and 13 constituting the protective film group is preferably disposed on the side of the polarizing film 11, and the HC layer is preferably disposed on the surface side of the polarizing plate 1 (the side opposite to the side of the polarizing film 11).

[0030] The thickness of the protective film is not particularly limited, but is usually 1 μm or more and 100 μm or less, preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 55 μm or less, and still more preferably 15 μm or more and 50 μm or less, from the viewpoints of strength and handleability.

[0031] Of the protective films 12 and 13 constituting the protective film group, one or both of the materials and thicknesses of the base film and the HC layer may be the same, or both of the materials and thicknesses of the base film and the HC layer may be different from each other.

[0032] At least one of the protective films in the protective film group preferably 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 300 g / m 2·It is more preferably above ·day, and the upper limit value is usually 5000 g / m 2 ·day or less, and 2000 g / m 2 ·day or less is preferable, and 1000 g / m 2 ·day or less is more preferable. In the polarizing plate 1, it is sufficient that one or more protective films among the protective film group have a moisture permeability within the above range. By setting the moisture permeability of the protective film within the above range, it is possible to suppress the polyene formation and coloring of the polarizing film 11 by the heat endurance test described later.

[0033] It is preferable that the protective film 12 laminated closest to the polarizing film side among the protective film group has a moisture permeability within the above range. When manufacturing the polarizing plate 1, as described later, after laminating the protective film 12 on the polarizing film 11 using an adhesive (adhesive or pressure-sensitive adhesive) such as an aqueous adhesive, a bonding layer 32 is 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 laminated closest to the polarizing film 11 side among the protective film group within the above range, it is easy to remove the moisture contained in the adhesive by the drying process.

[0034] If the protective film 12 laminated closest to the polarizing film 11 side among the protective film group has a moisture permeability within the above range, the moisture permeability of the other protective films 13 other than the protective film 12 contained in the protective film group is not particularly limited. The moisture permeability of the other protective films 13 may be smaller than the moisture permeability of the protective film 12. The moisture permeability of the other protective films 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, and 500 g / m 2 ·day or less is more preferable. The above moisture permeability of the protective film 13 is preferably more than 20 g / m 2 ·day, and preferably 30 g / m 2It is more preferable that it is ·day or more. By setting the upper limit value of the moisture permeability of the other protective film 13 within the above range, the rate of moisture uptake into the polarizing plate 1 after the heat endurance test can be suppressed. As a result, it becomes easier to secure the 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 value of the moisture permeability of the other protective film 13 within the above range, it is possible to suppress the polyene formation and coloring of the polarizing film 11 due to the heat endurance test. The moisture permeability of the protective films 12 and 13 can be measured by the method described in the examples below.

[0035] In the above, the moisture permeability of the protective film 12 is 200 g / m 2 ·day or more, and the moisture permeability of the other protective film 13 is 1000 g / m 2 ·day or less has been described. However, even when the relationship of this moisture permeability is reversed, it is possible to suppress the polyene formation and coloring of the polarizing film 11 due to the heat endurance test.

[0036] The base films constituting the protective films 12 and 13 are not particularly limited, but are preferably made of a resin material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, etc. Examples of such resin materials include (meth)acrylic acid methyl-based resins, polyolefin-based resins, cyclic olefin-based resins, polyvinyl chloride-based resins, cellulose-based resins, styrene-based resins, acrylonitrile-butadiene-styrene-based resins, acrylonitrile-styrene-based resins, polyvinyl acetate-based resins, polyvinylidene chloride-based resins, polyamide-based resins, polyacetal-based resins, polycarbonate-based resins, modified polyphenylene ether-based resins, polybutylene terephthalate-based resins, polyethylene terephthalate-based resins, polysulfone-based resins, polyethersulfone-based resins, polyarylate-based resins, polyamideimide-based resins, and polyimide-based resins, etc. One or more selected from these resins may be used. These resins may be used after performing any appropriate polymer modification. Examples of polymer modification include copolymerization, crosslinking, molecular end modification, stereoregularity control, and mixing including cases involving reactions between different polymers.

[0037] It is preferable that the base film of at least one protective film among the group of protective films 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 the protective films constituting the group of protective films are cellulose-based resin films.

[0038] The cellulose-based resin may be an organic acid ester or a mixed organic acid ester of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups, and / or butyryl groups. For example, those composed of cellulose acetate, cellulose propionate, cellulose butyrate, and their mixed esters, etc. are mentioned. Among them, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, etc. are preferable.

[0039] The resin material constituting the base film may be appropriately blended with suitable additives as long as the transparency is not impaired. Examples of additives include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, retardation reducing agents, stabilizers, processing aids, plasticizers, impact resistance aids, matting agents, antibacterial agents, fungicides, etc. One or more of these additives can be used, and a plurality of types may be used in combination.

[0040] The thickness of the base film is not particularly limited. For example, it can be 1 μm or more, may be 3 μm or more, may be 10 μm or more, may be 30 μm or more. Also, it is usually 90 μm or less, may be 70 μm or less, may be 60 μm or less, may be 50 μm or less. The base film usually has a single-layer structure, but may have a multilayer structure of two or more layers.

[0041] The HC layer constituting the protective films 12, 13 is not particularly limited, but is preferably a cured product layer of an ultraviolet curable resin formed on the base film. Examples of the ultraviolet curable resin include (meth)acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, epoxy resins, etc. The HC layer may contain additives in order to improve the surface hardness. The additives are not particularly limited, but examples include inorganic fine particles, organic fine particles, or a mixture thereof.

[0042] The thickness of the HC layer is preferably 10 μm or less, more preferably 8 μm or less, and usually 0.1 μm or more, may be 1 μm or more, may be 4 μm or more. When the thickness of the HC layer exceeds 10 μm, the curl (warp) of the protective films 12, 13 becomes large, making it difficult to adjust the curl of the polarizing plate 1.

[0043] The protective films 12 and 13 preferably have a pencil hardness of H or higher, more preferably 2H or higher, and may be 3H or higher, or 4H or higher, as measured by the pencil hardness test specified in JIS K 5600-5-4:1999 "General Test Methods for Paints - Part 5: Mechanical Properties of Paint Films - Section 4: Scratch Hardness (Pencil Method)" (when the substrate film with the HC layer formed is placed on a glass plate and measured on the HC layer side).

[0044] 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 additives as necessary on the substrate film, and curing this by ultraviolet irradiation.

[0045] (Retardation film) The retardation film 21 is a film having retardation, 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 elasticity of the retardation film 21 at 23°C is 3000 MPa or less, and may be 2800 MPa or less. Usually, it is 1000 MPa or more, and may be 2000 MPa or more. The tensile modulus of elasticity can be measured by the method described in the examples below.

[0046] Examples of the retardation film 21 having the above tensile modulus of elasticity include olefin-based resin films formed using olefin-based resins. Examples of olefin-based resins include chain aliphatic olefins such as ethylene and propylene, or resins mainly containing structural units derived from alicyclic olefins such as norbornene and its substituents (hereinafter sometimes collectively referred to as "norbornene-based monomers"). Mainly containing structural units means that the proportion of the structural units contained in the resin is 50% or more based on the amount of substance. The olefin-based resin may be a copolymer using two or more monomers.

[0047] The retardation film 21 is preferably a cyclic olefin resin film formed using a cyclic olefin resin which is a resin mainly containing a structural unit derived from an alicyclic olefin. Typical examples of the alicyclic olefin constituting the cyclic olefin resin include norbornene-based monomers and the like. Norbornene is a compound in which one carbon-carbon bond of norbornane is a double bond, and according to the IUPAC nomenclature, it is named bicyclo[2,2,1]hept-2-ene. Examples of substituents of norbornene include 3-substituted products, 4-substituted products, and 4,5-disubstituted products with the double bond position of norbornene being the 1,2-position, and further examples include dicyclopentadiene, dimethanooctahydronaphthalene, and the like.

[0048] The cyclic olefin resin may or may not have a norbornane ring in its structural unit. Examples of norbornene-based monomers that form a cyclic olefin resin having no norbornane ring in its structural unit include those that form a 5-membered ring by ring opening, typically norbornene, dicyclopentadiene, 1- or 4-methylnorbornene, and 4-phenylnorbornene. When the cyclic olefin resin is a copolymer, the molecular arrangement state is not particularly limited, and it may be a random copolymer, a block copolymer, or a graft copolymer.

[0049] More specific examples of the cyclic olefin-based resin include, for example, ring-opening polymers of norbornene-based monomers, ring-opening copolymers of norbornene-based monomers and other monomers, polymer modified products obtained by adding maleic acid, cyclopentadiene, etc. thereto, and polymers or copolymers obtained by hydrogenating these; addition polymers of norbornene-based monomers, and addition copolymers of norbornene-based monomers and other monomers, etc. Examples of other monomers in the case of forming a copolymer include α-olefins, cycloalkenes, and non-conjugated dienes, etc. Further, the cyclic olefin-based resin may be a copolymer using one or more of norbornene-based monomers and other alicyclic olefins. Among these, as the cyclic olefin-based resin, a resin obtained by hydrogenating a ring-opening polymer or ring-opening copolymer using a norbornene-based monomer is preferable.

[0050] Commercially available products of the cyclic olefin-based resin using the above norbornene-based monomer include, all by their trade names, "Zeonex" and "Zeonor" sold by Nippon Zeon Co., Ltd., "Arton" sold by JSR Corporation, etc. Films of these cyclic olefin-based resins and their stretched films can also be obtained as commercially available products. For example, all by their trade names, "Zeonor Film" from Optes Co., Ltd., "Arton Film" from JSR Corporation, and "ESINA" from Sekisui Chemical Co., Ltd., etc.

[0051] As the phase difference film 21, 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 can also be used. For example, as the mixed resin containing two or more types of olefin resins, a mixture of the above-described cyclic olefin resin and a linear aliphatic olefin resin can be mentioned. When using a mixed resin of an olefin resin and another thermoplastic resin, an appropriate one is selected as the other thermoplastic resin according to the purpose. Specific examples of the other thermoplastic resin 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, polyether sulfone resins, polyether ether ketone resins, polyarylate resins, liquid crystalline resins, polyamideimide resins, polyimide resins, and polytetrafluoroethylene resins, etc. These thermoplastic resins can be used alone or in combination of two or more. Further, the above thermoplastic resin can also be used after performing any appropriate polymer modification. Examples of polymer modification include copolymerization, crosslinking, molecular end modification, and imparting stereoregularity, etc.

[0052] 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, preferably about 40% by weight or less, based on the total resin. By setting the content of the other thermoplastic resin within this range, a phase difference film 21 with a small absolute value of the photoelastic coefficient, showing good wavelength dispersion characteristics, and excellent in durability, mechanical strength, and transparency can be obtained.

[0053] The retardation film 21 may contain other components such as residual solvents, stabilizers, plasticizers, antioxidants, antistatic agents, and ultraviolet absorbers as necessary. Further, a leveling agent may be contained to reduce the surface roughness.

[0054] 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, and may also be 300 nm or less, or may be 200 nm or less. The retardation film 21 is preferably a stretched film.

[0055] Generally, the higher the in-plane retardation value of the retardation film 21, the more uniform the molecular orientation of the retardation film 21, so there is a tendency for cracks to occur when an external force is applied. As described above, the polarizing plate 1 has a structure in which two or more protective films 12 and 13 are laminated on the first surface 11a of the polarizing film 11. Therefore, even when the polarizing plate 1 including the retardation film 21 having the above high in-plane retardation value is held for a long time in a normal temperature and normal humidity environment after a heat durability test, the dimensional change of the polarizing film 11 can be suppressed, and accordingly, 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.

[0056] 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 obtained 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 direction perpendicular to the slow axis in the plane, d is the thickness [nm] of the retardation film 21.]

[0057] The retardation film 21 may have a retardation value of 0 (zero) in the thickness direction, or may have a retardation value in the thickness direction. The retardation value in the thickness direction 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, and may also be 100 nm or less, 80 nm or less, 60 nm or less. The retardation value in the thickness direction of the retardation film 21 can be measured by the method described in the examples below. The retardation value Rth(λ) in the thickness direction of the retardation film 21 at a wavelength λ [nm] refers to the retardation value in the thickness direction of the retardation film 21 at a temperature of 23°C, and is obtained by the following formula (ii). Rth(λ) = [((nx + ny) / 2) - nz] × d (ii) [In 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 direction orthogonal to the slow axis in the plane, nz is the refractive index in the thickness direction, d is the thickness [nm] of the retardation film 21.]

[0058] The thickness of the retardation film 21 is not particularly limited, but is preferably 15 μm or more and 80 μm or less, more preferably 18 μm or more and 45 μm or less, and most preferably 20 μm or more and 30 μm or less. When the thickness of the retardation film is less than 15 μm, it is difficult to handle the film, and it tends to be difficult to exhibit a predetermined retardation value. On the other hand, when the thickness of the retardation film exceeds 80 μm, the processability deteriorates, and the transparency tends to decrease or the weight of the obtained polarizing plate 1 tends to increase.

[0059] The retardation film 21 can be obtained by using a resin film formed using the above-described resin and stretching the resin film. The resin film can be obtained, for example, by film formation by a casting method or a melt extrusion method from a solution containing the above-described olefin resin. When forming a film using a mixture of two or more resins, the film formation method is not particularly limited. For example, a method of producing a film by a casting method using a uniform solution obtained by stirring and mixing resin components with a solvent at a predetermined ratio, and a method of producing a film by a melt extrusion method by melt-mixing resin components at a predetermined ratio can be mentioned.

[0060] Examples of the stretching treatment of the resin film include known uniaxial stretching in the longitudinal direction, tenter uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, and the like. In addition to appropriately adjusting the stretching ratio and the stretching speed so that a desired retardation value is obtained, various temperatures such as the preheating temperature, stretching temperature, heat set temperature, and cooling temperature during stretching, and the pattern thereof may be appropriately selected.

[0061] When the retardation film 21 is the above-described cyclic olefin resin film, for example, it can be obtained by using a film-like material obtained by previously performing a stretching treatment using the above-described cyclic olefin resin, laminating a shrinkable film having a predetermined shrinkage rate thereto, and heating and shrinking the laminate. Thereby, a retardation film 21 having high uniformity and a large retardation value can be obtained.

[0062] (Functional layer) The polarizing plate 1 may have one or more functional layers such as an antistatic layer, another retardation layer different from the retardation film 21, and another protective layer for covering and protecting the surface of the polarizing film 11 different from the protective films 12 and 13.

[0063] The antistatic layer is a layer for suppressing the charging of the polarizing plate 1. 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. The antistatic layer can be provided, for example, between the polarizing film 11 and the retardation film 21, or between the polarizing film 11 and the protective film 12 in the polarizing plate 1, or on the side opposite to the polarizing film 11 of the retardation film 21. The antistatic layer is preferably laminated on these films via an adhesive layer.

[0064] Another retardation layer is a layer having an in-plane retardation value or a retardation value in the thickness direction. Another 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 or the like. The positive C-plate is used, for example, when the polarizing plate 1 is used in an IPS-mode liquid crystal display device or the like. Another retardation layer can be provided, for example, between the polarizing film 11 and the retardation film 21, or on the side opposite to the polarizing film 11 side of the retardation film 21. Another retardation layer may be a stretched film obtained by stretching a resin film, or may be a cured product layer of a polymerizable liquid crystal compound. Another retardation layer can be laminated on the polarizing film 11 and the retardation film 21 via an adhesive layer. When another retardation layer is a cured product 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.

[0065] 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 provided via a bonding layer between the polarizing film 11 and the retardation film 21. In this case, the bonding layer provided between the polarizing film 11 and the other protective layer is provided so as to be in contact with the polarizing film 11 and the other protective layer respectively, and the bonding 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. Examples of the other protective layer include a film formed using the resin material described for the base films constituting the protective films 12 and 13. The other protective layer preferably has no retardation, and examples thereof include a cellulose-based resin film having no retardation or a cyclic olefin-based resin film having no retardation.

[0066] (Bonding layer) Examples of the bonding layers 31 to 33 for bonding the films and layers constituting the polarizing plate 1 include a layer formed using a known adhesive or a layer formed using a known pressure-sensitive adhesive.

[0067] Examples of the adhesive include adhesives other than pressure-sensitive adhesives (pressure-sensitive adhesives), such as aqueous adhesives, active energy ray-curable adhesives, or thermosetting adhesives, and preferably aqueous adhesives or active energy ray-curable adhesives. The thickness of the bonding layer formed using the adhesive may be, for example, 0.01 μm or more, 0.1 μm or more, 0.5 μm or more, 1 μm or more, and may also be, for example, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less.

[0068] Examples of the aqueous adhesive include an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin, an aqueous two-component urethane-based emulsion adhesive, etc. Among them, an aqueous adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is preferably used. As the polyvinyl alcohol-based resin, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate, a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, or a modified polyvinyl alcohol-based polymer obtained by partially modifying their hydroxyl groups can be used. The aqueous adhesive can contain a crosslinking agent such as an aldehyde compound (glyoxal, etc.), an epoxy compound, a melamine-based compound, a methylol compound, an isocyanate compound, an amine compound, a polyvalent metal salt, etc.

[0069] When using an aqueous adhesive as the adhesive, after laminating with the film to be bonded, it is preferable to carry out a drying process for removing the water contained in the aqueous adhesive. After the drying process, a curing process for curing at a temperature of, for example, 20 to 45°C may be provided.

[0070] An active energy ray curable adhesive is an adhesive containing a curable compound that cures upon irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, and is preferably an ultraviolet curable adhesive. The curable compound can be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include epoxy compounds (compounds having one or more epoxy groups in the molecule), oxetane compounds (compounds having one or more oxetane rings in the molecule), or combinations thereof. Examples of the radically polymerizable curable compound include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having a radically polymerizable double bond, or combinations thereof. A cationically polymerizable curable compound and a radically 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 above curable compound.

[0071] An adhesive exhibits adhesiveness by attaching itself to an adherend and is so-called a pressure-sensitive adhesive. The adhesive can be composed of a pressure-sensitive adhesive composition mainly composed of a resin such as (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether. Among them, a pressure-sensitive adhesive composition based on a (meth)acrylic resin having excellent transparency, weather resistance, heat resistance, etc. is preferable. The adhesive may be of the active energy ray curable type or the thermosetting type. The thickness of the bonding 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.

[0072] Examples of the (meth)acrylic resin (base polymer) contained in the pressure-sensitive adhesive composition include polymers or copolymers having as a monomer one or more (meth)acrylic esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer with the base polymer. Examples of the polar monomer 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.

[0073] The pressure-sensitive adhesive composition may contain only the above base polymer, but usually further contains a crosslinking agent. Examples of the crosslinking agent include divalent or higher metal ions that form a metal carboxylate with a carboxyl group; polyamine compounds that form an amide bond with a carboxyl group; polyepoxy compounds and polyols that form an ester bond with a carboxyl group; and polyisocyanate compounds that form an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.

[0074] (Pressure-sensitive adhesive layer) The polarizing plate 1 may have a pressure-sensitive adhesive layer 35 for attaching the polarizing plate 1 to a display element or the like of a display device. The pressure-sensitive adhesive layer 35 is preferably provided on the side opposite to the polarizing film 11 side of the retardation film 21 of the polarizing plate 1. The pressure-sensitive adhesive layer 35 can be formed using a pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include the pressure-sensitive adhesive used to form the above bonding layer. The thickness of the pressure-sensitive 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.

[0075] (Release film) The polarizing plate 1 may have a release film that is separable 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. Examples of the release film include a film obtained by subjecting the surface of a base resin film on the adhesive layer 35 side to a release treatment such as silicone treatment. Examples of the resin material constituting the base resin film include a film formed using the resin materials described for the above-mentioned base film. The base resin film may have a single-layer structure or a multi-layer structure of two or more layers.

[0076] (Method for manufacturing a polarizing plate) The method for manufacturing the polarizing plate 1 is not particularly limited, and known methods can be used. For example, a protective film 12 is laminated on the first surface 11a of the polarizing film 11 using an aqueous adhesive, and a retardation film 21 is laminated on the second surface 11b of the polarizing film 11 using an aqueous adhesive. Through a drying process of removing water in the aqueous adhesive, a laminate of the protective film 12 / bonding layer 32 / polarizing film 11 / bonding layer 33 / retardation film 21 is produced. At this time, when using a laminate in which the difference in thickness between the protective film 12 and the retardation film 21 is 30 μm or less, it is easy to suppress the curl generated in the laminate, and a flat laminate is easily obtained. Then, a polarizing plate 1 can be obtained by laminating a protective film 13 via a bonding layer 31 on the protective film 12 side of the above laminate. 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 further laminating a protective film may be provided. When using a laminate in which the difference in thickness between the protective film 12 and the retardation film 21 is 30 μm or less as described above, the curl generated in the polarizing plate 1 is also easy to suppress, and a flat polarizing plate 1 is easily obtained.

[0077] In order to enhance the adhesiveness between the films and layers (protective films 12 and 13, polarizing film 11, retardation film 21, functional layers, etc.) that constitute the polarizing plate 1 and the bonding layer, a surface activation treatment may be performed on the bonding surfaces of these films and layers. Examples of the surface activation treatment include dry treatments such as corona treatment, plasma treatment, discharge treatment (such as glow discharge treatment), flame treatment, ozone treatment, UV ozone treatment, and ionization active ray treatment (such as ultraviolet treatment and electron beam treatment); and wet treatments such as ultrasonic treatment, saponification treatment, and anchor coat treatment using solvents such as water and acetone. These surface activation treatments may be performed alone or in combination of two or more.

Example

[0078] Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited by these examples.

[0079] [Measurement of Thickness] The thicknesses of the films and layers that constitute the polarizing plate were measured using an MH-15M digital micrometer manufactured by Nikon Corporation.

[0080] [Measurement of Moisture Permeability] The moisture permeability of the protective film was measured in an atmosphere of 40°C and 90% relative humidity in accordance with Appendix B of JIS K 7129:2008.

[0081] [Measurement of Retardation Value] The retardation values of the retardation film and other retardation layers were measured using a KOBRA-WPR retardation measuring device (manufactured by Oji Scientific Instruments Co., Ltd.).

[0082] [Measurement of Tensile Elastic Modulus] Test pieces with a width of 15 mm and a length of 150 mm were cut out from the retardation film parallel to the slow axis and the fast axis, respectively. Next, using the upper and lower grips of a tensile testing machine (AUTOGRAPH (registered trademark) AG-1S testing machine manufactured by Shimadzu Corporation), the two ends of the test piece in the long side direction were clamped so that the distance between the grips was 100 mm, and the test piece was pulled at a tensile speed of 50 mm / min in an environment of 23°C to create a stress-strain curve, and the tensile elastic modulus in the direction parallel to the slow axis and the fast axis at 23°C was calculated. Among the tensile elastic moduli in the directions parallel to the slow axis and the fast axis thus calculated, the one with the larger value was taken as the value of the tensile elastic modulus of the retardation film at 23°C.

[0083] [Measurement of storage elastic modulus] The storage elastic modulus G' of the adhesive layer A and the adhesive layer B was measured according to the following procedures [I] to [III]. [I] Two samples were taken out from each adhesive layer so that the weight of each was 25 ± 1 mg, and each sample was formed into a roughly spherical shape. [II] The two formed roughly spherical samples were respectively attached to the upper and lower surfaces of an I-shaped jig, and both the upper and lower surfaces were clamped with an L-shaped jig to form a measurement sample. The configuration of the measurement sample is L-shaped jig / adhesive layer A or adhesive layer B / I-shaped jig / adhesive layer / L-shaped jig. [III] The storage elastic modulus G' of the measurement sample was measured using a dynamic viscoelasticity measuring device "DVA-220" manufactured by IT Measurement Control Co., Ltd. under the conditions of a temperature of 23°C, a frequency of 1 Hz, and an initial strain of 1 N.

[0084] [Measurement of pencil hardness] The protective film was placed on a glass plate such that the base film side of the protective film faced the glass plate. For the HC layer side of the protective film, a pencil hardness test specified in JIS K 5600-5-4:1999 "General test methods for paints - Part 5: Mechanical properties of paint films - Section 4: Scratch hardness (pencil method)" was performed to measure the pencil hardness of the protective film.

[0085] [Production of polarizing film]< A PVA-based resin film with a thickness of 40 μm made of a PVA-based resin having an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more was prepared. This PVA-based resin film was uniaxially stretched about 5 times by a dry method, and then immersed in pure water at 60 °C for 1 minute while maintaining the tension state. Thereafter, the PVA-based resin film was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5 / 100 at 28 °C for 60 seconds. Thereafter, the PVA-based resin film was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 °C for 300 seconds. Subsequently, it was washed with pure water at 26 °C for 20 seconds and then dried at 65 °C. In this way, a polarizing film with a thickness of 15 μm in which iodine as a dichroic dye was adsorbed and oriented was obtained on the PVA-based resin film.

[0086] <Production of Protective Film (1)> The following components were mixed to prepare a composition for forming an HC layer. 97.0 parts by mass of PET30 3.0 parts by mass of Irgacure 907 81.8 parts by mass of MEK Here, PET30 is a mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd.). Irgacure 907 is a photoinitiator (manufactured by BASF). MEK is methyl ethyl ketone.

[0087] A substrate film wound in a roll (cellulose acetate film TD40, manufactured by Fuji Film Co., Ltd., width 1,340 mm, film thickness 40 μm) was unwound, and the composition for forming an HC layer was applied by a die coating method using a slot die under the condition of a conveyance speed of 30 m / min, and dried at 60 °C for 150 seconds to form a coating layer. Thereafter, under a nitrogen purge and under the condition of an oxygen concentration of about 0.1%, an air-cooled metal halide lamp (manufactured by Eye Graphic Co., Ltd.) with an output of 160 W / cm was used to irradiate with an illuminance of 400 mW / cm 2 and an irradiation dose of 120 mJ / cm 2The coating layer was cured by irradiating ultraviolet rays to form an HC layer. The coating thickness of the coating layer was adjusted so that the film thickness of the HC layer became 7 μm. In this way, a protective film (1) having an HC layer on one side of the base film was obtained and 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.

[0088] <Production of Protective Film (2)> A protective film (2) was obtained in the same procedure as the production of the protective film (1), except that the thickness of the coating layer was adjusted so that the film thickness of the HC layer became 5 μm. The moisture permeability of the protective film (2) was 350 g / m 2 ·day. The pencil hardness of the protective film (2) was 3H.

[0089] <Production of Protective Film (3)> A protective film (3) was obtained in the same procedure as the production of the protective film (1), except that the thickness of the coating layer was adjusted so that the film thickness of the HC layer became 3 μm. The moisture permeability of the protective film (3) was 500 g / m 2 ·day. The pencil hardness of the protective film (3) was 3H.

[0090] <Production of a retardation laminate including a retardation film and another retardation layer> A retardation film and another retardation layer were produced according to the descriptions in paragraphs

[0106] to

[0109] of International Publication No. 2018 / 207798. Specifically, a uniaxially stretched retardation film with a thickness of 24 μm was obtained by performing uniaxial stretching on an unstretched cycloolefin polymer film (manufactured by JSR Corporation, trade name "ARTON Film"). When the tensile elastic modulus of the obtained retardation film at a temperature of 23°C was measured, it was 2742 MPa. Also, 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.

[0091] Next, a composition containing a rod-like liquid crystalline 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) at a wavelength of 550 nm of the other retardation layer was 0 nm, and the retardation value Rth(550) in the thickness direction at a wavelength of 550 nm was -100 nm.

[0092] <Preparation of Polyvinyl Alcohol-based Adhesive (PVA-based Adhesive)> 50 g of a modified PVA-based resin containing an acetoacetyl group (manufactured by Mitsubishi Chemical Corporation: Gosenex Z-410) 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, a PVA-based adhesive was prepared by blending the polyvinyl alcohol solution, maleic acid, glyoxal, and pure water so that each compound had the following concentrations. Polyvinyl alcohol concentration 3.0 wt% Maleic acid concentration 0.01 wt% Glyoxal concentration 0.15 wt%

[0093] <Preparation of Adhesive Layer A and Adhesive Layer B> As Adhesive Layer A, a commercially available sheet-like acrylic adhesive with a thickness of 5 μm (storage elastic modulus at 23 °C: 0.06 MPa) was prepared. As Adhesive Layer B, a commercially available sheet-like acrylic adhesive with a thickness of 25 μm (storage elastic modulus at 23 °C: 0.06 MPa) was prepared.

[0094] [Example 1] The protective film (1) obtained above was immersed in a 1.5 mol / L aqueous NaOH solution (saponification solution) maintained at a temperature of 55°C for 2 minutes, and then washed with water. After washing with water, the protective film (1) was immersed in a 0.05 mol / L aqueous sulfuric acid solution at a temperature of 25°C for 30 seconds, and then passed through running water for 30 seconds to make the protective film (1) in a neutral state. After repeating the water draining by an air knife on this protective film (1) three times, it was left to stand in a drying zone at a temperature of 70°C for 15 seconds to dry. Thus, a saponification-treated protective film (1) obtained by performing saponification treatment (surface activation treatment) on the HC layer and the base film was obtained.

[0095] The saponification-treated protective film (1) (hereinafter sometimes referred to as "the first protective film (1)"), a polarizing film, and a retardation laminate were laminated via the PVA-based adhesive prepared above to obtain a laminate (1). In the laminate (1), the absorption axis of the polarizing film and the slow axis of the retardation film were parallel. Also, 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 force between the retardation laminate and the polarizing film and the adhesive force between the polarizing film and the first protective film (1) were practically sufficient.

[0096] Next, a saponification-treated protective film (1) (hereinafter sometimes referred to as "the second protective film (1)") obtained by performing saponification treatment in the same procedure as above was laminated on the first protective film (1) side of the laminate (1) obtained above via an adhesive layer A. The second protective film (1) had the base film side as the bonding surface with the adhesive layer (A). Also, the retardation laminate side of the laminate (1) was subjected to corona treatment, and the surface of the adhesive layer B was subjected to corona treatment, and the corona-treated surface of the laminate (1) and the corona-treated surface of the adhesive layer (B) were laminated. Thus, a polarizing plate (1) was obtained. In the polarizing plate (1), both the first protective film (1) and the second protective film (1) were arranged on the same surface side of the polarizing film, the first protective film (1) was arranged at a position relatively close to the polarizing film, and the second protective film (1) was arranged at a position relatively far from the polarizing film.

[0097] [Example 2] A polarizing plate (2) was obtained in the same procedure as the production procedure of the polarizing plate (1) produced in Example 1, except that a saponified protective film (2) subjected to the same saponification treatment as the saponification treatment performed on the protective film (1) was used instead of the first protective film (1) and the second protective film (1).

[0098] [Example 3] A polarizing plate (3) was obtained in the same procedure as the production procedure of the polarizing plate (1) produced in Example 1, except that a saponified protective film (3) subjected to the same saponification treatment as the saponification treatment performed on the protective film (1) was used instead of the first protective film (1) and the second protective film (1).

[0099] [Comparative Example 1] A comparative polarizing plate (C1) was obtained in the same procedure as the production procedure of the polarizing plate (1) produced in Example 1, except that a saponified base film (cellulose acetate film TD40, manufactured by Fuji Film Co., Ltd., width 1,340 mm, film thickness 40 μm) subjected to the same saponification treatment as the saponification treatment performed on the protective film (1) was used instead of the second protective film (1).

[0100] [Comparative Example 2] A laminate (1) produced in the same procedure as in Example 1 was obtained and used as a comparative polarizing plate (C2).

[0101] [Comparative Example 3] A comparative polarizing plate (C3) was obtained in the same procedure as the production procedure of the polarizing plate (1) produced in Example 1, except that a saponified base film (cellulose acetate film TD40, manufactured by Fuji Film Co., Ltd., width 1,340 mm, film thickness 40 μm) subjected to the same saponification treatment as the saponification treatment performed on the protective film (1) was used instead of the first protective film (1).

[0102] [Evaluation of Crack Generation] For each of the polarizing plates obtained in the examples and the comparative polarizing plates obtained in the comparative examples, evaluation samples were prepared according to the following procedure, and the occurrence of cracks was evaluated. The polarizing plate or the comparative polarizing plate was cut into a size of 200 mm × 200 mm and bonded to a non-alkali glass with a thickness of 0.7 mm and a size of 300 mm × 300 mm via an adhesive layer B to prepare an evaluation sample.

[0103] The prepared evaluation sample was held in a heating environment at a temperature of 105°C for 500 hours and then cooled to a temperature of 23°C (room temperature). Then, after being held in a normal temperature and humidity environment at a temperature of 23°C and a relative humidity of 55% for 30 days, the retardation film of the polarizing plate or the comparative polarizing plate was observed to confirm the presence or absence of cracks. Furthermore, for the evaluation samples in which no cracks were observed at this point, the retardation film was also observed 7 days later (37 days after the start of holding in the normal temperature and humidity environment) to confirm the presence or absence of cracks. The results are shown in Table 1.

[0104]

Table 1

Explanation of symbols

[0105] 1 Polarizing plate, 11 Polarizing film, 11a First surface, 11b Second surface, 12, 13 Protective film, 21 Retardation film, 31 - 33 Bonding layer, 35 Adhesive layer.

Claims

1. A polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, A protective film provided with a hard coat layer on a base film, A retardation film having a tensile modulus of elasticity of 3000 MPa or less at a temperature of 23°C, and comprising: On the first surface side of the polarizing film, two or more of the protective films are laminated, On the second surface side of the polarizing film, which is opposite to the first surface side, the retardation film is laminated, Among the two or more of the protective films laminated on the first surface side, the moisture permeability of at least one protective film at a temperature of 40 ° C and a relative humidity of 90% is 200 g / m ２ ·day or more, a polarizing plate.

2. Among the two or more protective films laminated on the first surface side, the moisture permeability of the protective film laminated closest to the polarizing film at a temperature of 40 ° C and a relative humidity of 90% is 200 g / m ２ ・day or more, the polarizing plate according to claim 1.

3. The polarizing plate according to claim 1 or 2, 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.

4. The polarizing plate according to any one of claims 1 to 3, wherein the retardation film is a cyclic olefin-based resin film.

5. The polarizing plate according to any one of claims 1 to 4, wherein the in-plane retardation value of the retardation film at a wavelength of 550 nm is 80 nm or more.

6. Furthermore, the polarizing plate according to any one of claims 1 to 5, which has an adhesive layer on the side opposite to the retardation film side of the polarizing film.

7. A display device having the polarizing plate according to claim 6 and a display element, The display device, wherein the polarizing plate is laminated on the display element via the adhesive layer.

Images