JP2021076759A - Polarization plate with retardation layer and image display device - Google Patents

Abstract

To provide a polarization plate with a retardation layer capable of realising an image display device having lower luminance in an oblique direction at a black display and a smaller color shift in the oblique direction.SOLUTION: A polarization plate with a retardation layer includes: a polarization plate including a polarizer; a first retardation layer arranged adjacent to the polarization plate, in which a refractive index characteristic exhibits a relation of nz>nx>ny; and a second retardation layer arranged adjacent to the first retardation layer, in which a refractive index characteristic exhibits a relation of nx>ny=nz. An absorption axis of the polarizer and a slow axis of the first retardation layer are substantially orthogonal, and the absorption axis of the polarizer and a slow axis of the second retardation layer are substantially parallel.SELECTED DRAWING: Figure 1

Description

The present invention relates to a polarizing plate with a retardation layer and an image display device.

In an image display device (for example, a liquid crystal display device), various optical films in which a polarizer and a retardation film are combined are generally used in order to perform optical compensation. A circularly polarizing plate, which is a kind of the above optical film, can usually be manufactured by combining a polarizing element and a λ / 4 plate. However, the λ / 4 plate generally exhibits a characteristic that the phase difference value increases as the wavelength becomes shorter, that is, a so-called “positive wavelength dispersion characteristic”, and the wavelength dispersion characteristic is large. Therefore, there is a problem that desired optical characteristics (for example, function as a λ / 4 plate) cannot be exhibited over a wide wavelength range. In order to avoid such a problem, in recent years, a retardation film exhibiting a wavelength dispersion characteristic in which the retardation value increases as the wavelength becomes longer on the long wavelength side, that is, a so-called "reverse dispersion characteristic" has been proposed. However, the retardation film exhibiting the inverse dispersion characteristic has a problem in terms of cost.

In order to deal with the above problems, a technique has been proposed for correcting the wavelength dispersion characteristics of the λ / 4 plate by combining various retardation films with the λ / 4 plate having positive wavelength dispersion characteristics. (See, for example, Patent Document 1). However, these techniques have a problem that the brightness in the diagonal direction at the time of black display is not sufficiently reduced and the color shift in the diagonal direction is large.
Patent No. 3174367

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide an image display device having a small oblique brightness at the time of black display and a small oblique color shift. It is to provide a polarizing plate with a retardation layer which can be realized.

The polarizing plate with a retardation layer according to the embodiment of the present invention is a polarizing plate containing a polarizing element; and is arranged adjacent to the polarizing plate and has a refractive index characteristic of nz>nx> ny. It has a retardation layer; and a second retardation layer arranged adjacent to the first retardation layer and having a refractive index characteristic of nx> ny = nz. The absorption axis of the polarizer and the slow axis of the first retardation layer are substantially orthogonal to each other, and the absorption axis of the polarizer and the slow axis of the second retardation layer are substantially orthogonal to each other. Is parallel to.
In one embodiment, the laminate of the first retardation layer and the second retardation layer satisfies the following relationship:
Re (450) / Re (550)> 0.82
Re (650) / Re (550) <1.18.
According to another aspect of the present invention, an image display device is provided. This image display device includes an image display cell and the above-mentioned polarizing plate with a retardation layer arranged on the visual side of the image display cell.
In one embodiment, the image display device is an IPS mode liquid crystal display device.

According to the embodiment of the present invention, in the polarizing plate with a retardation layer, the first retardation layer showing the relationship of the refractive index characteristic of nz> nx> ny and the refractive index characteristic are nx> ny = in order from the polarizing plate side. By arranging the second retardation layer showing the relationship of nz, the brightness in the diagonal direction at the time of black display is small and the color shift in the diagonal direction is small without using the retardation film showing the inverse dispersion characteristic. A polarizing plate with a retardation layer that can realize an image display device can be obtained.

It is schematic cross-sectional view of the polarizing plate with a retardation layer by one Embodiment of this invention. It is a color shift diagram of the liquid crystal display device of Example 1. It is a color shift diagram of the liquid crystal display device of Comparative Example 1. It is a color shift diagram of the liquid crystal display device of Comparative Example 2. It is a color shift diagram of the liquid crystal display device of Comparative Example 3.

Hereinafter, typical embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols herein are as follows.
(1) Refractive index (nx, ny, nz)
"Nx" is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and "ny" is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advance axis direction). Is the refractive index of, and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
“Re (λ)” is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is obtained by the formula: Rth (λ) = (nx−nz) × d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.
(5) Substantially parallel or orthogonal The term "substantially parallel" includes the case of 0 ° ± 5.0 °, preferably 0 ° ± 3.0 °, and more preferably 0 ° ± 1. It is 0 °. The term "substantially orthogonal" includes the case of 90 ° ± 5.0 °, preferably 90 ° ± 3.0 °, and more preferably 90 ° ± 1.0 °. In addition, the term "parallel" or "orthogonal" in the present specification also includes the case where the term is substantially parallel or orthogonal.
(6) Angle When referring to an angle herein, the angle includes both clockwise and counterclockwise with respect to the reference direction. Therefore, for example, "45 °" means ± 45 °.

A. Overall Configuration of Polarizing Plate with Difference Layer FIG. 1 is a schematic cross-sectional view of the polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 100 with a retardation layer in the illustrated example has a polarizing plate 10, a first retardation layer 20, and a second retardation layer 30. The polarizing plate 10 includes a polarizer 11, a first protective layer 12 arranged on one side of the polarizer 11, and a second protective layer 13 arranged on the other side of the polarizer 11. .. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, if the first retardation layer 20 can also function as a protective layer for the polarizer 11, the second protective layer 13 may be omitted.

The first retardation layer 20 is typically arranged adjacent to the polarizing plate 10 as shown in the illustrated example. The first retardation layer 20 shows a relationship in which the refractive index characteristics are nz> nx> ny. The second retardation layer 30 is typically arranged adjacent to the first retardation layer 20 as shown in the illustrated example. The second retardation layer 30 shows a relationship in which the refractive index characteristic is nx> ny = nz. As used herein, the term "adjacent" means that they are laminated directly or via only an adhesive layer (eg, an adhesive layer or an adhesive layer). That is, an optical functional layer (for example, another retardation layer) between the polarizing plate 10 and the first retardation layer 20 and between the first retardation layer 20 and the second retardation layer 30. Means that there is no intervention. On the other hand, the illustrated configuration is merely an example, and is between the polarizing plate 10 and the first retardation layer 20 and / or between the first retardation layer 20 and the second retardation layer 30. Needless to say, any suitable optical functional layer can be arranged according to the purpose.

The first retardation layer 20 is arranged so that its slow phase axis is orthogonal to the absorption axis of the polarizer 11. The second retardation layer 30 is arranged so that its slow-phase axis is parallel to the absorption axis of the polarizer 11. The first retardation layer 20 and the second retardation layer 30 having the specific refractive index characteristics as described above are laminated in the order as described above, and the first retardation layer 20 and the second retardation layer 20 and the second By setting the slow axis direction of the retardation layer 30 with respect to the absorption axis direction of the polarizer in this way, the image display device has a small luminance in the diagonal direction at the time of black display and a small color shift in the diagonal direction. It is possible to obtain a polarizing plate with a retardation layer that can realize the above.

The polarizing plate with a retardation layer may further have a conductive layer or an isotropic base material with a conductive layer (not shown). The conductive layer or the isotropic base material with the conductive layer is typically provided on the outside (opposite side of the polarizing plate 10) of the second retardation layer 30. When a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate with a retardation layer has a so-called touch sensor incorporated between an image display cell (for example, a liquid crystal cell or an organic EL cell) and the polarizing plate. It can be applied to an inner touch panel type input display device.

The polarizing plate with a retardation layer may further include other retardation layers. The optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of other retardation layers can be appropriately set according to the purpose.

The polarizing plate with a retardation layer may be single-wafered or elongated. As used herein, the term "long" means an elongated shape having a length sufficiently long with respect to the width, and for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width. Including. The long-shaped polarizing plate with a retardation layer can be wound in a roll shape.

Practically, an adhesive layer (not shown) is provided on the opposite side of the second retardation layer from the polarizing plate, and the polarizing plate with the retardation layer can be attached to the image display cell. Further, it is preferable that a release film is temporarily adhered to the surface of the pressure-sensitive adhesive layer until a polarizing plate with a retardation layer is used. By temporarily attaching the release film, the pressure-sensitive adhesive layer can be protected and rolls can be formed.

The overall thickness of the polarizing plate with a retardation layer is preferably 20 μm to 200 μm, more preferably 40 μm to 170 μm, and particularly preferably 50 μm to 120 μm. Hereinafter, details of each layer constituting the polarizing plate with a retardation layer will be described.

B. Polarizing plate B-1. Polarizer As the polarizer 11, any suitable polarizer can be adopted. For example, the resin film forming the polarizer may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer system partially saponified film. Examples thereof include those which have been dyed and stretched with a bicolor substance such as iodine or a bicolor dye, and polyene-based oriented films such as a dehydrated product of PVA and a dehydrogenated product of polyvinyl chloride. Preferably, since the PVA-based film is excellent in optical properties, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment or while dyeing. Alternatively, it may be stretched and then dyed. If necessary, the PVA-based film is subjected to a swelling treatment, a cross-linking treatment, a washing treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible not only to clean the dirt on the surface of the PVA-based film and the blocking inhibitor, but also to swell the PVA-based film to prevent uneven dyeing. Can be prevented.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizer obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The polarizer obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying the resin base material. It is produced by forming a PVA-based resin layer on the resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further include, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. The obtained resin base material / polarizer laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizer), and the resin base material is peeled off from the resin base material / polarizer laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of the method for producing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire description of these publications is incorporated herein by reference.

The thickness of the polarizer is preferably 15 μm or less, more preferably 1 μm to 12 μm, further preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is in such a range, curling during heating can be satisfactorily suppressed, and good appearance durability during heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

B-2. Protective Layer The protective layer 12 and the protective layer 13 (if any) are each formed of any suitable film that can be used as a protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

As will be described later, the polarizing plate with a retardation layer is typically arranged on the viewing side of the image display device, and the protective layer 12 is arranged on the viewing side. Therefore, the protective layer 12 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment, if necessary. Further / or, if necessary, the protective layer 12 is provided with a process for improving visibility when visually recognizing through polarized sunglasses (typically, a (elliptical) circularly polarized light function is provided, and an ultra-high phase difference is provided. May be given). By performing such a process, excellent visibility can be realized even when the display screen is visually recognized through a polarized lens such as polarized sunglasses. Therefore, the polarizing plate with a retardation layer can be suitably applied to an image display device that can be used outdoors.

The thickness of the protective layer 12 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm. When the surface treatment is applied, the thickness of the protective layer 12 is a thickness including the thickness of the surface treatment layer.

The protective layer 13 is preferably optically isotropic in one embodiment. As used herein, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. Say. In another embodiment, the protective layer 13 can be a retardation layer having any suitable retardation value. In this case, the in-plane retardation Re (550) of the retardation layer is, for example, 110 nm to 150 nm. The thickness of the protective layer 13 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm. From the viewpoint of thinning, the protective layer 13 may be omitted in one embodiment.

C. First Phase Difference Layer The first retardation layer 20 shows a relationship in which the refractive index characteristics are nz>nx> ny as described above. A layer (film) exhibiting such a refractive index characteristic may be referred to as a "positive biaxial plate", a "positive B plate", or the like.

The in-plane retardation Re (550) of the first retardation layer is preferably more than 0 nm and 70 nm or less, more preferably more than 0 nm and 60 nm or less, and further preferably more than 0 nm and 50 nm or less. Yes, especially preferably 10 nm to 50 nm. The retardation Rth (550) in the thickness direction of the first retardation layer is preferably −200 nm to −50 nm, more preferably −120 nm to −50 nm, and further preferably −100 nm to −60 nm. The Nz coefficient of the first retardation layer is preferably −1.0 or less, more preferably −10 to −1.0, and even more preferably −8.0 to −1.6. By providing the first retardation layer having such optical characteristics, the absorption axis of the polarizer can be suitably compensated, and the luminance in the oblique direction at the time of black display of the image display device can be reduced. In addition, the color shift in the diagonal direction can be reduced.

The thickness of the first retardation layer is preferably 1 μm to 170 μm, more preferably 2 μm to 150 μm, further preferably 3 μm to 120 μm, and particularly preferably 4 μm to 50 μm. When the thickness of the first retardation layer is within such a range, the handleability at the time of manufacturing is excellent, and the optical uniformity of the obtained image display device can be improved.

The first retardation layer can have any suitable configuration. Specifically, the retardation film may be used alone, or may be a laminate of two or more retardation films of the same or different sheets. In the case of a laminated body, the first retardation layer may include an adhesive layer or an adhesive layer for adhering two or more retardation films. Preferably, the first retardation layer is a single retardation film. By adopting such a configuration, it is possible to reduce the deviation and unevenness of the phase difference value due to the contraction stress of the polarizer and / or the heat of the light source, and it is possible to contribute to the thinning of the obtained image display device.

The optical properties of the retardation film can be set to any suitable value depending on the configuration of the first retardation layer. For example, when the first retardation layer is a retardation film alone, it is preferable that the optical characteristics of the retardation film are equal to the optical characteristics of the first retardation film. Therefore, it is preferable that the retardation value of the pressure-sensitive adhesive layer, the adhesive layer, etc. used when laminating the retardation film on the polarizer and / or the second retardation layer is as small as possible.

As the retardation film, a film having excellent transparency, mechanical strength, thermal stability, moisture shielding property, etc., and which is less likely to cause optical unevenness due to distortion is preferably used. As the retardation film, a stretched film of a polymer film containing a thermoplastic resin as a main component is preferably used. As the thermoplastic resin, a polymer exhibiting negative birefringence is preferably used. By using a polymer showing negative birefringence, a retardation film having a refractive index ellipsoid of nz> nx> ny can be easily obtained. Here, "showing negative birefringence" means that when the polymer is oriented by stretching or the like, the refractive index in the stretching direction becomes relatively small. In other words, it means that the refractive index in the direction orthogonal to the stretching direction increases. Examples of the polymer showing negative birefringence include a polymer in which a chemical bond or a functional group having a large polarization anisotropy such as an aromatic ring or a carbonyl group is introduced into a side chain. Specific examples thereof include acrylic resins, styrene resins, and maleimide resins.

The acrylic resin can be obtained, for example, by addition polymerization of an acrylate-based monomer. Examples of the acrylic resin include polymethylmethacrylate (PMMA), polybutylmethacrylate, polycyclohexylmethacrylate and the like.

The styrene-based resin can be obtained, for example, by addition-polymerizing a styrene-based monomer. Examples of the styrene-based monomer include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene, and the like. Examples thereof include 2,5-dichlorostyrene and pt-butylstyrene.

The maleimide-based resin can be obtained, for example, by addition polymerization of a maleimide-based monomer. Examples of the maleimide-based monomer include N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, and N- (2-propylphenyl). ) Maleimide, N- (2-isopropylphenyl) maleimide, N- (2,6-dimethylphenyl) maleimide, N- (2,6-dipropylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2-methyl-6-ethylphenyl) maleimide, N- (2-chlorophenyl) maleimide, N- (2,6-dichlorophenyl) maleimide, N- (2-bromophenyl) maleimide, N- (2,6) Examples thereof include −dibromophenyl) maleimide, N- (2-biphenyl) maleimide, and N- (2-cyanophenyl) maleimide. The maleimide-based monomer can be obtained from, for example, Tokyo Chemical Industry Co., Ltd.

In the above addition polymerization, the birefringence characteristics of the obtained resin can also be controlled by substituting the side chain, maleimide-forming, or grafting reaction after the polymerization.

The polymer showing negative birefringence may be copolymerized with other monomers. Brittleness, molding processability, and heat resistance can be improved by copolymerizing other monomers. Examples of the other monomer include olefins such as ethylene, propylene, 1-butene, 1,3-butadiene, 2-methyl-1-butene, 2-methyl-1-pentene and 1-hexene; acrylonitrile; acrylic acid. (Meta) acrylates such as methyl and methyl methacrylate; maleic anhydride; vinyl esters such as vinyl acetate and the like can be mentioned.

When the polymer showing negative birefringence is a copolymer of the styrene-based monomer and the other monomer, the blending ratio of the styrene-based monomer is preferably 50 mol% to 80 mol%. When the polymer showing negative birefringence is a copolymer of the maleimide-based monomer and the other monomer, the mixing ratio of the maleimide-based monomer is preferably 2 mol% to 50 mol%. By blending in such a range, a polymer film having excellent toughness and molding processability can be obtained.

The polymer exhibiting negative compound refraction is preferably a styrene-maleic anhydride copolymer, a styrene-acrylonitrile copolymer, a styrene- (meth) acrylate copolymer, a styrene-maleimide copolymer, or a vinyl ester-. Maleimide copolymers, olefin-maleimide copolymers and the like are used. These can be used alone or in combination of two or more. These polymers exhibit high negative birefringence and can be excellent in heat resistance. These polymers can be obtained from, for example, Nova Chemical Japan, Arakawa Chemical Industry Co., Ltd., and the like.

As the polymer exhibiting negative birefringence, a polymer having a repeating unit represented by the following general formula (I) is also preferably used. Such a polymer can exhibit even higher negative birefringence and can be excellent in heat resistance and mechanical strength. Such a polymer can be obtained, for example, by using an N-phenyl-substituted maleimide having a phenyl group having a substituent at least at the ortho position as the N-substituted maleimide-based monomer as a starting material.

In the above general formula (I), R _{1 to} R ₅ are independently of hydrogen, halogen atom, carboxylic acid, carboxylic acid ester, hydroxyl group, nitro group, or linear or branched group having 1 to 8 carbon atoms. Represents an alkyl group or an alkoxy group (where R ₁ and R ₅ are not hydrogen atoms at the same time), where R ₆ and R ₇ are hydrogen or a linear or branched alkyl or alkoxy group having 1 to 8 carbon atoms. Represents, and n represents an integer of 2 or more.

The polymer exhibiting negative birefringence is not limited to the above, and for example, a cyclic olefin copolymer as disclosed in Japanese Patent Application Laid-Open No. 2005-350544 can also be used. Further, a composition containing a polymer and inorganic fine particles as disclosed in Japanese Patent Application Laid-Open No. 2005-156862, Japanese Patent Application Laid-Open No. 2005-227427, etc. can also be preferably used. Further, as the polymer showing negative birefringence, one kind may be used alone, or two or more kinds may be used in combination. Further, these can be modified by copolymerization, branching, cross-linking, molecular terminal modification (or encapsulation), stereoregular modification and the like for use.

The polymeric film may further contain any suitable additive, if desired. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers, cross-linking agents, thickeners, etc. Can be mentioned. The type and content of the additive can be appropriately set according to the purpose. The content of the additive is typically about 3 to 10 parts by weight with respect to 100 parts by weight of the total solid content of the polymer film. If the content of the additive is excessively high, the transparency of the polymer film may be impaired, or the additive may seep out from the surface of the polymer film.

As the molding method of the polymer film, any suitable molding method can be adopted. For example, a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, a blow molding method, a powder molding method, an FRP molding method, a solve casting method and the like can be mentioned. Among these, the extrusion molding method and the solvent casting method are preferably used. This is because it is possible to obtain a retardation film having high smoothness and good optical uniformity. Specifically, in the extrusion molding method, a resin composition containing the above-mentioned thermoplastic resin, plasticizer, additive, etc. is heated and melted, and this is extruded into a thin film on the surface of a casting roll by a T-die or the like. This is a method of forming a film by cooling it. In the solve casting method, a concentrated solution (dope) in which the resin composition is dissolved in a solvent is defoamed and uniformly spread in a thin film on the surface of a metallic endless belt, a rotating drum, a plastic base material, or the like. , A method of forming a film by evaporating a solvent. The molding conditions can be appropriately set according to the composition and type of the resin to be used, the molding processing method, and the like.

The retardation film (stretched film) can be obtained by stretching the polymer film under arbitrary suitable stretching conditions. Specific examples of the stretching method include a vertical uniaxial stretching method, a horizontal uniaxial stretching method, a vertical and horizontal sequential biaxial stretching method, and a vertical and horizontal simultaneous biaxial stretching method. Preferably, a horizontal uniaxial stretching method, a vertical and horizontal sequential biaxial stretching method, and a vertical and horizontal simultaneous biaxial stretching method are used. This is because a biaxial retardation film can be preferably obtained. Since the refractive index in the stretching direction is relatively small in the polymer showing negative birefringence as described above, in the case of the lateral uniaxial stretching method, the polymer film has a slow axis in the transport direction ( The refractive index in the transport direction is nx). In the case of the longitudinal-horizontal sequential biaxial stretching method and the longitudinal-horizontal simultaneous biaxial stretching method, both the transport direction and the width direction can be set to the slow axis depending on the ratio of the longitudinal / horizontal stretching ratios. Specifically, when the stretching ratio in the vertical (conveying) direction is relatively large, the horizontal (width) direction becomes the slow-phase axis, and when the stretching ratio in the horizontal (width) direction is relatively large, the vertical (conveying) is performed. The direction is the slow axis.

As the stretching device used for the stretching, any suitable stretching device can be used. Specific examples include a roll stretching machine, a tenter stretching machine, a pantograph type or a linear motor type biaxial stretching machine, and the like. When stretching while heating, the temperature may be changed continuously or stepwise. Further, the stretching step may be divided into two or more times.

The stretching temperature (the temperature in the stretching oven when stretching the polymer film) is preferably around the glass transition temperature (Tg) of the polymer film. Specifically, it is preferably (Tg-10) ° C. to (Tg + 30) ° C., more preferably Tg to (Tg + 25) ° C., and particularly preferably (Tg + 5) ° C. to (Tg + 20) ° C. If the stretching temperature is too low, the retardation value and the direction of the slow phase axis may become non-uniform, or the polymer film may crystallize (white turbidity). On the other hand, if the stretching temperature is excessively high, the polymer film may melt or the phase difference may be insufficiently developed. The stretching temperature is typically 110 to 200 ° C. The glass transition temperature can be determined by the DSC method according to JISK7121-1987.

Any suitable method can be adopted as the method for controlling the temperature in the stretching oven. For example, a method using an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated for temperature control, a heat pipe roll, a metal belt, or the like can be mentioned.

The draw ratio when stretching the polymer film is set to an arbitrary appropriate value according to the composition of the polymer film, the type of volatile components, the residual amount of the volatile components, the desired retardation value, and the like. Can be done. It is preferably 1.05 times to 5.00 times. The feed rate during stretching is preferably 0.5 m / min to 20 m / min from the viewpoint of mechanical accuracy, stability, and the like of the stretching device.

The method of obtaining a retardation film using a polymer showing negative birefringence has been described above, but the retardation film can also be obtained by using a polymer showing positive birefringence. As a method for obtaining a retardation film using a polymer exhibiting positive birefringence, for example, JP-A-2000-23101, JP-A-2000-206328, JP-A-2002-207123 and the like are disclosed. Such a stretching method that increases the refractive index in the thickness direction can be used. Specifically, a method of adhering a heat-shrinkable film to one side or both sides of a film containing a polymer exhibiting positive birefringence and performing heat treatment can be mentioned. The refractive index in the thickness direction can be increased by shrinking the film under the action of the shrinking force of the heat-shrinkable film by heat treatment and shrinking the film in the length direction and the width direction, and nz> nx. A retardation film having a refractive index ellipsoid of> ny can be obtained.

As described above, the positive B plate used for the first retardation layer can be produced by using a polymer exhibiting either positive or negative birefringence. In general, when a polymer showing positive birefringence is used, it has an advantage in that there are many types of polymers to be selected, and when a polymer showing negative birefringence is used, a polymer showing positive birefringence is used. Compared with the case of using the above, there is an advantage in that a retardation film having excellent uniformity in the slow axis direction can be easily obtained due to the stretching method.

As the retardation film used for the first retardation layer, a commercially available optical film can be used as it is in addition to the above-mentioned film. Further, a commercially available optical film subjected to secondary processing such as stretching treatment and / or relaxation treatment can also be used.

The light transmittance of the retardation film at a wavelength of 590 nm is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The theoretical upper limit of the light transmittance is 100%, but since surface reflection occurs due to the difference in the refractive index between the air and the retardation film, the feasible upper limit of the light transmittance is approximately 94%. .. It is preferable that the first retardation layer as a whole has the same light transmittance.

The absolute value of the photoelastic coefficient of the retardation film is preferably 1.0 × 10 ^-10 (m ² / N) or less, more preferably 5.0 × 10 ^-11 (m ² / N) or less. Yes, more preferably 3.0 × ^10-11 (m ² / N) or less, and particularly preferably 1.5 × 10 ^-11 (m ² / N) or less. By setting the photoelastic coefficient in such a range, it is possible to obtain an image display device having excellent optical uniformity, small change in optical characteristics even in an environment such as high temperature and high humidity, and excellent durability. .. The lower limit of the photoelastic coefficient is not particularly limited, but is generally 5.0 × 10 ^-13 (m ² / N) or more, preferably 1.0 × 10 ^-12 (m ² / N) or more. .. If the photoelastic coefficient is excessively small, the expression of the phase difference may be reduced. The photoelastic coefficient is a value peculiar to the chemical structure of a polymer or the like, but the photoelastic coefficient can be reduced by copolymerizing or mixing a plurality of components having different signs (positive or negative) of the photoelastic coefficient.

The thickness of the retardation film can be set to an arbitrary appropriate value depending on the material for forming the retardation film and the configuration of the first retardation layer. When the first retardation layer is a retardation film alone, the thickness of the first retardation layer is preferably 1 μm to 170 μm, more preferably 2 μm to 150 μm, and further preferably 3 μm to 120 μm. , Particularly preferably 4 μm to 50 μm. By having such a thickness, a first retardation layer having excellent mechanical strength and display uniformity can be obtained.

D. Second Phase Difference Layer The second retardation layer 30 shows a relationship in which the refractive index characteristics are nx> ny = nz as described above. A layer (film) exhibiting such a refractive index characteristic may be referred to as a "positive uniaxial plate", a "positive A plate", or the like. Here, "ny = nz" includes not only the case where ny and nz are exactly equal, but also the case where ny and nz are substantially equal. Specifically, it means that the Nz coefficient exceeds 0.9 and is less than 1.1. The in-plane retardation Re (550) of the second retardation layer is preferably 80 nm to 200 nm, more preferably 100 nm to 160 nm, and even more preferably 110 nm to 150 nm. By providing the second retardation layer having such optical characteristics, the absorption axis of the polarizer can be suitably compensated, and the luminance in the oblique direction at the time of black display of the image display device can be reduced. In addition, the color shift in the diagonal direction can be reduced.

As the material for forming the second retardation layer, any suitable material can be adopted as long as the above-mentioned characteristics can be obtained. Specifically, the second retardation layer may be an alignment solidification layer of a liquid crystal compound (liquid crystal alignment solidification layer) or a retardation film (stretched film of a polymer film).

When the second retardation layer is a liquid crystal oriented solidified layer, the difference between nx and ny of the obtained retardation layer can be significantly increased as compared with the non-liquid crystal material by using the liquid crystal compound. The thickness of the retardation layer for obtaining a desired in-plane retardation can be remarkably reduced. As a result, it is possible to further reduce the thickness of the polarizing plate with a retardation layer (as a result, the image display device). As used herein, the term "aligned solidified layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within the layer and the oriented state is fixed. The "oriented solidified layer" is a concept including an oriented cured layer obtained by curing a liquid crystal monomer as described later. In the present embodiment, the rod-shaped liquid crystal compounds are typically oriented in a state of being aligned in the slow axis direction of the second retardation layer (homogeneous orientation).

Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, it is preferably a polymerizable monomer and / or a crosslinkable monomer, for example. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or cross-linking the liquid crystal monomer. After the liquid crystal monomers are oriented, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the oriented state can be fixed. Here, the polymer is formed by polymerization, and the three-dimensional network structure is formed by cross-linking, but these are non-liquid crystal. Therefore, the formed second retardation layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example. As a result, the formed second retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.

Specific examples of the liquid crystal compound and details of the method for forming the liquid crystal oriented solidified layer are described in, for example, JP-A-2006-163343 and JP-A-2006-178389. The descriptions in these publications are incorporated herein by reference.

The second retardation layer may be a stretched film of a polymer film as described above. Specifically, by appropriately selecting the type of polymer, stretching conditions (for example, stretching temperature, stretching ratio, stretching direction), stretching method, etc., the above desired optical characteristics (for example, refractive index characteristics, in-plane position) can be selected. A second retardation layer having (phase difference, phase difference in the thickness direction) can be obtained. More specifically, the stretching temperature is preferably 110 ° C. to 170 ° C., more preferably 130 ° C. to 150 ° C. The draw ratio is preferably 1.37 times to 1.67 times, more preferably 1.42 times to 1.62 times. Examples of the stretching method include lateral uniaxial stretching.

Any suitable resin can be adopted as the resin for forming the polymer film. Specific examples include resins constituting a positive compound refraction film such as norbornene-based resin, polycarbonate-based resin, cellulose-based resin, polyvinyl alcohol-based resin, and polysulfone-based resin. Of these, norbornene-based resins and polycarbonate-based resins are preferable.

The norbornene-based resin is a resin that is polymerized using a norbornene-based monomer as a polymerization unit. Examples of the norbornene-based monomer include norbornene and its alkyl and / or alkylidene substituents, for example, 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl. Polar group substituents such as these halogens such as -2-norbornene, 5-ethylidene-2-norbornene; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, alkyl and / or alkylidene thereof. Substitutes and polar group substituents such as halogen, such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6- Ethyl-1,4: 5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4 4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-Cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1, 4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1, 4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octa Hydronaphthalene, etc .; 3-4 weights of cyclopentadiene, eg, 4,9: 5,8-dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoinden, 4, Examples thereof include 11: 5, 10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentadianthracene and the like. The norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

As the polycarbonate-based resin, aromatic polycarbonate is preferably used. Aromatic polycarbonate can be typically obtained by reacting a carbonate precursor with an aromatic divalent phenolic compound. Specific examples of the carbonate precursor include phosgene, divalent phenols bischlorohomet, diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenyl carbonate, dinaphthyl carbonate and the like. Can be mentioned. Of these, phosgene and diphenyl carbonate are preferable. Specific examples of the aromatic dihydric phenol compound include 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, and bis (4-hydroxyphenyl). ) Methan, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) butane, 2, 2-Bis (4-hydroxy-3,5-dipropylphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethyl Cyclohexane and the like can be mentioned. These may be used alone or in combination of two or more. Preferably, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane are used. Used. In particular, it is preferable to use 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane together.

The thickness of the second retardation layer can be set to obtain the desired optical properties. When the second retardation layer is a liquid crystal oriented solidified layer, the thickness is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 to 5 μm. When the second retardation layer is a stretched film of a polymer film, the thickness is preferably 5 μm to 55 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 45 μm.

E. Laminated body of first retardation layer and second retardation layer The laminate of first retardation layer and second retardation layer preferably satisfies the following relationship:
Re (450) / Re (550)> 0.82
Re (650) / Re (550) <1.18.
The Re (450) / Re (550) of the laminate is more preferably 1.0 to 1.2, and even more preferably 1.0 to 1.1. The Re (650) / Re (550) of the laminated body is more preferably 0.8 to 1.0, still more preferably 0.9 to 1.0. According to the embodiment of the present invention, although the first retardation layer and the second retardation layer do not exhibit ideal inverse dispersion characteristics as a whole, the luminance in the diagonal direction at the time of black display is small. Moreover, it is possible to obtain a polarizing plate with a retardation layer that can realize an image display device having a small color shift in the oblique direction.

F. Image display device The polarizing plate with a retardation layer according to the above items A to E can be applied to an image display device. Therefore, an embodiment of the present invention includes an image display device using such a polarizing plate with a retardation layer. Typical examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). The image display device typically has a phase difference between an image display cell (for example, a liquid crystal cell, an organic EL cell, an inorganic EL cell) and the above-mentioned items A to E arranged on the visual side of the image display cell. It has a layered polarizing plate. The polarizing plate with a retardation layer is laminated so that the second retardation layer 30 is on the image display cell side (the polarizing plate 10 is on the viewing side). In one embodiment, the image display device is a liquid crystal display device, preferably a liquid crystal display device in IPS mode. In such a liquid crystal display device, the effect of the polarizing plate with a retardation layer according to the embodiment of the present invention becomes remarkable.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows.

(1) Measurement of Phase Difference Value The in-plane phase difference between the first phase difference layer and the second phase difference layer used in Examples and Comparative Examples was automatically measured using KOBRA-WPR manufactured by Oji Measurement Co., Ltd. The measurement wavelength was 550 nm and the measurement temperature was 23 ° C.
(2) Luminance at the time of black display A black image was displayed on the liquid crystal display devices obtained in Examples and Comparative Examples, and the measurement was performed by the trade name "Conoscape" manufactured by AUTRONIC MELCHERS. Specifically, the brightness was measured by changing the azimuth angle from 0 ° to 360 ° in the polar angle 60 ° direction. The ratio of the maximum brightness to the brightness in the front direction of the measured brightness was defined as the brightness in this evaluation.
(3) Color shift For the liquid crystal display devices obtained in the examples and comparative examples, the azimuth angle was changed from 0 ° to 360 ° in the polar angle 60 ° direction using the product name "EZ Control160D" manufactured by ELDIM. The color tone was measured and plotted on the XY chromaticity diagram.

[Example 1]
1. 1. Preparation of polarizing plate 1-1. Preparation of Polarizer As the thermoplastic resin base material, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption of 0.75%, and a Tg of about 75 ° C. was used. One side of the resin base material was corona-treated.
100 weight of PVA-based resin in which polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z410") are mixed at a ratio of 9: 1. A PVA aqueous solution (coating solution) was prepared by dissolving 13 parts by weight of potassium iodide in water.
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13 μm to prepare a laminate.
The obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water), the polarizer finally obtained Immersion was carried out for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) became a predetermined value (dyeing treatment).
Then, it was immersed in a cross-linked bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight, potassium iodide concentration 5.0% by weight) at a liquid temperature of 70 ° C., the rolls having different peripheral speeds are vertically (longitudinal). In the direction), uniaxial stretching was performed so that the total stretching ratio was 5.5 times (underwater stretching treatment).
Then, the laminate was immersed in a washing bath at a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the drying shrinkage treatment was 5.2%.
In this way, a polarizer having a thickness of 5 μm was formed on the resin base material.

1-2. Fabrication of Polarizing Plate Acrylic film (surface refractive index 1.50, 40 μm) is applied as a protective layer on the surface of the polarizer obtained above (the surface opposite to the resin substrate), and an ultraviolet curable adhesive is applied. It was pasted together. Specifically, the curable adhesive was coated so as to have a total thickness of 1.0 μm, and bonded using a roll machine. Then, UV light was irradiated from the protective layer side to cure the adhesive. Next, after slitting both ends, the resin base material was peeled off to obtain a long polarizing plate having a protective layer / polarizer configuration. The obtained polarizing plate was punched into a size corresponding to a liquid crystal cell described later.

2. Preparation of First Phase Difference Layer A pellet resin of a styrene-maleic anhydride copolymer (manufactured by Nova Chemical Japan, trade name "Dylark D232") was prepared at 270 ° C. using a single-screw extruder and a T-die. The sheet-shaped molten resin was cooled with a cooling drum to obtain a film having a thickness of 100 μm. This film was uniaxially stretched at a free end in the transport direction at a temperature of 130 ° C. and a stretch ratio of 1.6 times using a roll stretcher to obtain a film having a phase-advancing axis in the transport direction (longitudinal stretching step). ..
The obtained film was uniaxially stretched at a fixed end in the width direction using a tenter stretching machine at a temperature of 135 ° C. so that the film width was 1.6 times the film width after the longitudinal stretching to a thickness of 50 μm. A biaxially stretched film was obtained (transverse stretching step).
The retardation film thus obtained has a phase-advancing axis (slow-phase axis in the width direction) in the transport direction, exhibits a relationship of refractive index characteristics of nz>nz> ny, and has an in-plane retardation Re (in-plane retardation Re). 550) was 37 nm, the phase difference Rth (550) in the thickness direction was −90 nm, and the Nz coefficient was -2.4. The obtained retardation film (positive B plate) was punched into a size corresponding to a liquid crystal cell described later to form a first retardation layer. Here, the punching was performed so that the absorption axis of the polarizer of the polarizing plate and the slow axis of the first retardation layer were orthogonal to each other.

3. 3. Preparation of second retardation layer A long norbornene-based resin film (manufactured by Zeon Corporation, trade name Zeonor, thickness 40 μm, photoelastic coefficient 3.10 × ^10-12 m ² / N) was 1.52 at 140 ° C. By uniaxially stretching the film, a long film having a thickness of 35 μm was produced. The retardation film thus obtained has a slow phase axis in the transport direction, has a refractive index characteristic of nz> nz = ny, has an in-plane retardation Re (550) of 135 nm, and is in the thickness direction. The phase difference Rth (550) was 135 nm. The obtained retardation film (positive A plate) was punched into a size corresponding to a liquid crystal cell described later to form a second retardation layer. Here, the punching was performed so that the absorption axis of the polarizer of the polarizing plate and the slow axis of the second retardation layer were parallel to each other.

4. Preparation of Polarizing Plate with Phase Difference Layer The polarizing plate obtained above, the first retardation layer and the second retardation layer are laminated in this order via an acrylic pressure-sensitive adhesive (thickness 12 μm), and the polarizing plate / A polarizing plate A with a retardation layer having a configuration of a first retardation layer (positive B plate) / a second retardation layer (positive A plate) was obtained. In a polarizing plate with a retardation layer, the absorption axis of the polarizer of the polarizing plate and the slow axis of the first retardation layer are orthogonal to each other, and the absorption axis of the polarizer and the slow axis of the second retardation layer Was parallel.

5. Manufacture of a liquid crystal display device The liquid crystal cell is removed from Apple's "iPad Pro" (equipped with an IPS mode liquid crystal cell), and the polarizing plate with a retardation layer is placed on the visible side of the liquid crystal cell via an acrylic adhesive (thickness 20 μm). A is pasted. Here, the polarizing plate A with a retardation layer was attached so that the second retardation layer was on the liquid crystal cell side. A commercially available polarizing plate (“NPF-SIG1423DU” manufactured by Nitto Denko KK) was attached to the back side of the liquid crystal cell via an acrylic adhesive (thickness 20 μm). Here, the polarizing plate was attached so that the absorption axis of the polarizer of the polarizing plate and the absorption axis of the polarizer of the polarizing plate A with a retardation layer were orthogonal to each other. A normal backlight unit or the like was incorporated into the liquid crystal panel thus obtained to produce a liquid crystal display device. The brightness of the obtained liquid crystal display device was 0.60. The results are shown in Table 1 together with the configuration of the polarizing plate with a retardation layer. Further, the color shift of the obtained liquid crystal display device is shown in FIG.

[Comparative Example 1]
The polarizing plate / first retardation layer (positive) is the same as in Example 1 except that the absorption axis of the polarizing element of the polarizing plate and the slow axis of the first retardation layer are laminated in parallel. A polarizing plate B with a retardation layer having a configuration of B plate) / second retardation layer (positive A plate) was obtained. A liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizing plate B with a retardation layer was used. The brightness of the obtained liquid crystal display device was 0.69. The results are shown in Table 1 together with the configuration of the polarizing plate with a retardation layer. Further, the color shift of the obtained liquid crystal display device is shown in FIG.

[Comparative Example 2]
A polarizing plate C with a retardation layer having a polarizing plate / positive B plate / positive A plate configuration was obtained in the same manner as in Example 1 except that the stacking order of the positive A plate and the positive B plate was reversed. A liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizing plate C with a retardation layer was used. The brightness of the obtained liquid crystal display device was 15.36. The results are shown in Table 1 together with the configuration of the polarizing plate with a retardation layer. Further, the color shift of the obtained liquid crystal display device is shown in FIG.

[Comparative Example 3]
It has a polarizing plate / positive B plate / positive A plate configuration in the same manner as in Comparative Example 2 except that the absorption axis of the polarizing element of the polarizing plate and the slow axis of the positive A plate are laminated so as to be orthogonal to each other. A polarizing plate D with a retardation layer was obtained. A liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizing plate D with a retardation layer was used. The brightness of the obtained liquid crystal display device was 0.76. The results are shown in Table 1 together with the configuration of the polarizing plate with a retardation layer. Further, the color shift of the obtained liquid crystal display device is shown in FIG.

As is clear from Table 1 and FIGS. 2 to 5, the liquid crystal display device of the embodiment of the present invention is superior in both brightness and color shift to the liquid crystal display device of the comparative example.

The polarizing plate with a retardation layer according to the embodiment of the present invention is suitably applied to an image display device, and can be particularly preferably applied to a liquid crystal display device.

10 Polarizing plate 11 Polarizer 12 Protective layer 13 Protective layer 20 First retardation layer 30 Second retardation layer 100 Polarizing plate with retardation layer

Claims (4)

A polarizing plate containing a polarizer and
A first retardation layer having a refractive index characteristic of nz>nx> ny, which is arranged adjacent to the polarizing plate,
It has a second retardation layer arranged adjacent to the first retardation layer and having a refractive index characteristic of nx> ny = nz.
The absorption axis of the polarizer and the slow axis of the first retardation layer are substantially orthogonal to each other.
The absorption axis of the polarizer and the slow axis of the second retardation layer are substantially parallel.
Polarizing plate with retardation layer. The polarizing plate with a retardation layer according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer satisfies the following relationship.
Re (450) / Re (550)> 0.82
Re (650) / Re (550) <1.18. An image display device comprising an image display cell and a polarizing plate with a retardation layer according to claim 1 or 2 arranged on the visual side of the image display cell. The image display device according to claim 3, which is an IPS mode liquid crystal display device.

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