JP2019028159A - Phase difference film, polarizing plate with optical compensation layer, image display device, and method for manufacturing phase difference film - Google Patents

Abstract

To provide a phase difference film that can achieve an image display device in which a hue in an oblique direction is neutral.SOLUTION: A phase difference film can be used for a polarizing plate 100 with an optical compensation layer 30, where Re(550) is 10 nm to 400 nm, Re(450)/Re(550) is 0.8 to 0.9, and the Nz coefficient is 0.3 to 0.7. The phase difference film is formed of a resin film containing a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a retardation film, a polarizing plate with an optical compensation layer, an image display device, and a method for producing a retardation film.

  In recent years, with the widespread use of thin displays, image display devices (organic EL display devices) equipped with organic EL panels have been proposed. The organic EL panel has a highly reflective metal layer, and is likely to cause problems such as external light reflection and background reflection. Therefore, it is known to prevent these problems by providing a polarizing plate with an optical compensation layer (circular polarizing plate) on the viewing side. It is also known to improve the viewing angle by providing a polarizing plate with an optical compensation layer on the viewing side of the liquid crystal display panel. As a general polarizing plate with an optical compensation layer, a retardation film and a polarizer are laminated so that a slow axis and an absorption axis form a predetermined angle (for example, 45 °) according to the application. Are known. However, when the conventional retardation film is used for a polarizing plate with an optical compensation layer, there is a problem that an undesired color shift occurs in an oblique hue.

Japanese Patent No. 3325560

  The present invention has been made in order to solve the above-described conventional problems, and a main object thereof is a retardation film capable of realizing an image display device in which a hue in a diagonal direction is neutral, and such a retardation film. It is to provide a manufacturing method.

The retardation film of the present invention has Re (550) of 10 nm to 400 nm, Re (450) / Re (550) of 0.8 to 0.9, and Nz coefficient of 0.3 to 0.7. is there.
In one embodiment, the retardation film is composed of a resin film including a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence.
In an aspect in which a polarizing plate with an optical compensation layer (circular polarizing plate) is provided, the polarizing plate with an optical compensation layer includes an optical compensation layer made of the retardation film and a polarizer, and the retardation of the optical compensation layer is slow. The angle formed between the phase axis and the absorption axis of the polarizer is 35 ° to 55 °.
In another embodiment, the polarizing plate with an optical compensation layer includes an optical compensation layer made of a retardation film and a polarizer, and an angle formed by the slow axis of the optical compensation layer and the absorption axis of the polarizer is It is 80 ° to 100 ° or −10 ° to 10 °.
According to another aspect of the present invention, an image display device is provided. The image display device includes the polarizing plate with an optical compensation layer.
According to another aspect of the present invention, a method for producing a retardation film is provided. In this production method, a laminate of the shrinkable film and the coating film is formed by applying a birefringent material containing a cellulose resin and a cinnamate ester copolymer on the shrinkable film and drying it. And stretching the laminate, and shrinking the laminate in a direction orthogonal to the stretching direction, thereby setting the refractive index characteristics of the coating film to nx>nz> ny. Including.
In one embodiment, the shrinkage ratio of the shrinkable film in the direction orthogonal to the stretching direction is 0.50 times to 0.99 times.

  According to the present invention, Re (550) is 10 nm to 400 nm, Nz coefficient is 0.3 to 0.7, and Re (450) / Re (550) is 0.8 to 0.9. Thus, a retardation film capable of realizing a polarizing plate with an optical compensation layer whose hue in an oblique direction is neutral can be obtained.

It is a schematic sectional drawing of the polarizing plate with an optical compensation layer by one Embodiment of this invention.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment.

(Definition of terms and symbols)
The definitions of terms and symbols in this specification 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 maximum (ie, the slow axis direction), and “ny” is the direction orthogonal to the slow axis in the plane (ie, the fast axis direction). “Nz” is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re (λ)” is an in-plane retardation measured with light having a wavelength of λ nm at 23 ° C. For example, “Re (550)” is an in-plane retardation measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Thickness direction retardation (Rth)
“Rth (λ)” is a retardation in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, “Rth (550)” is a retardation in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is determined by the formula: Rth = (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.

A. Retardation Film Re (550) of the retardation film of the present invention is 10 nm to 400 nm. Furthermore, the retardation film has Re (450) / Re (550) of 0.8 to 0.9 and an Nz coefficient of 0.3 to 0.7. That is, the retardation film exhibits a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and the refractive index characteristic has a relationship of nx>nz> ny. In one embodiment, the retardation film is composed of a resin film including a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence. The retardation film of the present invention can be laminated on a polarizer (or polarizing plate) and used as a polarizing plate with an optical compensation layer. The retardation film of the present invention has a Re (450) / Re (550) of 0.8 to 0.9 and an Nz coefficient of 0.3 to 0.7. When used as a plate, it is possible to achieve a neutral (ie, no undesired color) hue in an oblique direction.

  In one embodiment, the in-plane retardation Re (550) of the retardation film is 100 nm to 180 nm, more preferably 110 nm to 170 nm, still more preferably 120 nm to 160 nm, and particularly preferably 130 nm to 150 nm. In another embodiment, the in-plane retardation Re (550) of the retardation film is 190 nm to 360 nm, more preferably 200 nm to 340 nm, still more preferably 210 nm to 320 nm, and particularly preferably 220 nm to 300 nm. If the in-plane retardation of the retardation film is within the above range, the angle between the retardation film and the polarizer between the slow axis direction of the retardation film and the absorption axis direction of the polarizer is about 45 ° or about The polarizing plate with an optical compensation layer obtained by laminating at 135 ° can be used as a circularly polarizing plate capable of realizing excellent antireflection characteristics. The polarizing plate with an optical compensation layer obtained by laminating so that the angle formed between the slow axis direction of the retardation film and the absorption axis direction of the polarizer is about 0 ° or about 90 ° is an excellent viewing angle. It can be used as a polarizing plate with an optical compensation layer capable of realizing the characteristics.

  As described above, the in-plane retardation of the retardation film has a value of Re (450) / Re (550) of 0.8 to 0.9. Re (450) / Re (550) is preferably 0.82 to 0.88, more preferably 0.84 to 0.86, and particularly preferably about 0.85. That is, the retardation film satisfies the relationship of Re (450) <Re (550) and exhibits reverse dispersion wavelength characteristics. Furthermore, the in-plane retardation of the retardation film preferably satisfies the relationship of Re (550) <Re (650). By satisfying such a relationship, a more excellent reflection hue can be achieved.

  As described above, the Nz coefficient of the retardation film is 0.3 to 0.7, more preferably 0.4 to 0.6, still more preferably 0.45 to 0.55, and particularly preferably. About 0.5. If the Nz coefficient is in such a range, a better reflection hue can be achieved.

The absolute value of the photoelastic coefficient of the retardation film is preferably 40 × 10 ⁻¹² (m ² / N) or less, more preferably 1 × 10 ⁻¹² (m ² / N) to 30 × 10 ^{−. 12} (m ² / N), more preferably 1 × 10 ⁻¹² (m ² / N) to 20 × 10 ⁻¹² (m ² / N). If the absolute value of the photoelastic coefficient is in such a range, the flexibility of the image display device (particularly, the organic EL panel) can be maintained while ensuring a sufficient phase difference even with a small thickness. The change in the phase difference due to the stress (resulting in the color change of the organic EL panel) can be further suppressed.

  The retardation film preferably has a glass transition temperature (Tg) of 100 ° C. or higher. The lower limit of the glass transition temperature is more preferably 110 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 130 ° C. or higher. On the other hand, the upper limit of the glass transition temperature is preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. If the glass transition temperature is excessively low, the heat resistance tends to deteriorate, there is a possibility of causing a dimensional change after film formation, and the image quality of the resulting organic EL panel may be lowered. If the glass transition temperature is excessively high, the molding stability at the time of film molding may deteriorate, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

  The thickness of the retardation film is preferably 10 μm to 150 μm, more preferably 30 μm to 120 μm, and still more preferably 50 μm to 100 μm. With such a thickness, the desired in-plane retardation and Nz coefficient can be obtained.

B. Production method of retardation film The above retardation film can be obtained by the production method of the present invention. The method for producing a retardation film of the present invention comprises applying a birefringent material containing a cellulose resin and a cinnamate ester copolymer on a shrinkable film and drying it, thereby coating the shrinkable film and the film. A step of producing a laminate with a film, and a step of stretching the laminate and causing the laminate to contract in a direction orthogonal to the stretching direction so that the refractive index characteristic of the coating film is nx>nz> ny. Including.

  In the conventional manufacturing method, the in-plane retardation Re (550) is 10 nm to 400 nm, Re (450) / Re (550) is 0.8 to 0.9, and the Nz coefficient is 0.3 to 0.00. It was difficult to obtain a retardation film of 7. Specifically, the in-plane retardation Re (550), Re (450) / Re (550), and the Nz coefficient are in a trade-off relationship with each other, and all these values are within the desired range. It was difficult to obtain a retardation film. On the other hand, according to the manufacturing method, an ideal retardation film in which all the values are within the desired range can be obtained.

B-1. Production process of laminate The production process of the retardation film is a process of producing a laminate of the shrinkable film and the coating film by applying a birefringent material on the shrinkable film and drying as described above. Including.

  The shrinkable film preferably has a shrinkage ratio in the direction orthogonal to the stretching direction in the range of 0.50 to 0.99 times in the stretching step described below. The shrinkage ratio is preferably 0.60 times to 0.98 times, and more preferably 0.75 times to 0.95 times.

  The material for forming the shrinkable film is not particularly limited, but is preferably a thermoplastic resin because it is suitable for the stretching treatment described later. Specifically, for example, acrylic resins, polyolefin resins such as polyethylene and polypropylene (PP), polyester resins such as polyethylene terephthalate (PET), polyamides, polycarbonate resins, norbornene resins, polystyrene, polyvinyl chloride, polyvinylidene chloride, tri Examples thereof include cellulose resins such as acetylcellulose, polyethersulfone, polysulfone, polyimide, polyacryl, acetate resin, polyarylate, polyvinyl alcohol, and mixtures thereof. A liquid crystal polymer or the like can also be used. The shrinkable film is preferably a uniaxial or biaxial stretched film formed from one or more of the above forming materials. As the shrinkable film, for example, a commercially available product may be used. Commercially available products include, for example, “Space Clean” manufactured by Toyobo Co., Ltd., “Fancy Wrap” manufactured by Gunze Co., Ltd., “Trephan” manufactured by Toray Industries, Inc., and “Lumirror” manufactured by Toray Industries, Inc. "Arton" manufactured by JSR Corporation, "Zeonor" manufactured by Nippon Zeon Co., Ltd., "Suntech" manufactured by Asahi Kasei Corporation, and the like.

  The thickness of the shrinkable film is not particularly limited, but is, for example, in the range of 10 μm to 300 μm, preferably in the range of 20 μm to 200 μm, and more preferably in the range of 40 μm to 150 μm. The surface of the shrinkable film may be subjected to a surface treatment for the purpose of improving the adhesion with the birefringent layer. Examples of the surface treatment include chemical or physical treatment such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric impact exposure, and ionizing radiation treatment. Moreover, the primer layer by application | coating of undercoat (for example, adhesive substance) may be formed in the shrinkable film surface.

  The birefringent material preferably comprises a resin composition comprising a polymer having a positive intrinsic birefringence and a polymer having a negative intrinsic birefringence. The resin composition typically includes a cellulose resin and a cinnamate copolymer. The resin composition can be obtained by blending a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence. As a method for blending the polymer, methods such as melt blending and solution blending can be used. The melt blending method in the case where an additive having an aromatic hydrocarbon ring or an aromatic heterocycle is contained in the resin composition is an addition having a resin and an aromatic hydrocarbon ring or an aromatic heterocycle by heating. In this method, the agent is melted and kneaded. The solution blending method is a method in which a resin and an additive having an aromatic hydrocarbon ring or aromatic heterocycle are dissolved in a solvent and blended. Solvents used for solution blending include, for example, chlorinated solvents such as methylene chloride and chloroform; aromatic solvents such as toluene and xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, and propanol. Alcohol solvents; ether solvents such as dioxane and tetrahydrofuran; dimethylformamide, N-methylpyrrolidone and the like can be used. It is also possible to blend after dissolving each resin and an additive having an aromatic hydrocarbon ring or aromatic heterocycle in a solvent, and it is also possible to dissolve each resin powder, pellets, etc. in a solvent after kneading. Is possible. The obtained blended resin solution can be added to a poor solvent to precipitate the resin composition, or it can be used as it is. Details of the cinnamic acid ester copolymer that can be used in the present embodiment are described in, for example, Japanese Patent No. 6048556. This publication is incorporated herein by reference in its entirety.

  The birefringent material may include a solvent that dissolves the resin composition. The solvent can be appropriately determined according to the type of the resin composition, and examples thereof include chloroform, dichloromethane, toluene, methylene chloride, xylene, cyclohexanone, and cyclopentanone. A solvent may be used individually by 1 type and may use 2 or more types together.

  The birefringent material may contain an additive as necessary. Examples of the additive include a deterioration inhibitor, an ultraviolet inhibitor, an optical anisotropy modifier, a plasticizer, an infrared absorber, and a filler. The additive may be solid or liquid.

  Any appropriate application method can be adopted as a method of applying the birefringent material on the shrinkable film. Examples of the coating method include spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, and gravure printing. Moreover, a multilayer coating can also be employ | adopted as needed in the case of application | coating. Thereby, the laminated body of a shrinkable film and a birefringent material can be obtained. The application thickness of the birefringent material can be appropriately set so that the obtained retardation film has a desired thickness.

  As a method for drying the birefringent material after application, any appropriate drying method may be employed depending on the birefringent material. Examples of the drying method include natural drying, air drying by blowing air, low temperature drying, and heat drying, and a combination of these methods may be used. The drying method is preferably low-temperature drying from the viewpoint of suppressing shrinkage of the shrinkable film before the stretching step described later. The drying temperature of the low temperature drying is preferably 20 ° C to 100 ° C.

B-2. Stretching process of laminated body In the stretching process of the laminated body, the refractive index characteristic of the coating film is set to nx>nz> ny by stretching the laminated body and contracting the laminated body in a direction orthogonal to the stretching direction. Typically, the shrinkable film is shrunk by stretching the laminate while heating, and the coating film is shrunk by shrinkage of such a shrinkable film. In one embodiment, the laminate is stretched in the width direction (TD direction) and contracted in the longitudinal direction (MD direction).

  The draw ratio of the laminate is preferably 1.01 to 3.5 times, more preferably 1.5 to 3 times, and still more preferably 2 to 2.5 times. Any suitable stretching machine such as a roll stretching machine, a tenter stretching machine, and a biaxial stretching machine can be adopted as the stretching machine used for stretching the laminate.

  The stretching temperature (heating temperature) of the laminate is preferably 25 ° C to 300 ° C, more preferably 50 ° C to 200 ° C, still more preferably 60 ° C to 180 ° C, and particularly preferably 130 ° C to 160 ° C. ° C. Further, preferably, the laminate is preheated before stretching. The preheating time is preferably 10 seconds to 10 minutes, more preferably 15 seconds to 5 minutes.

  As described above, a birefringent layer having a refractive index distribution of nx> nz> ny can be formed on the shrinkable film. The obtained birefringent layer may be peeled off from the shrinkable film and used as the retardation film of the present invention, or the birefringent layer (retardation film) and shrinkable without peeling off the birefringent layer from the shrinkable film. A laminate with a film may be used as it is.

C. FIG. 1 is a schematic cross-sectional view of a polarizing plate with an optical compensation layer according to one embodiment of the present invention. The polarizing plate 100 with an optical compensation layer of this embodiment includes a polarizer 10 and an optical compensation layer 30. The optical compensation layer 30 is made of the retardation film described in item A. In one embodiment, the angle formed by the slow axis of the optical compensation layer and the absorption axis of the polarizer is 35 ° to 55 °. In another embodiment, the angle formed by the slow axis of the optical compensation layer and the absorption axis of the polarizer is 80 ° to 100 ° or −10 ° to 10 °. Practically, a protective layer 20 can be provided on the opposite side of the polarizer 10 from the optical compensation layer 30 as in the illustrated example. Moreover, the polarizing plate with an optical compensation layer may include another protective layer (also referred to as an inner protective layer) between the polarizer 10 and the optical compensation layer 30. In the illustrated example, the inner protective layer is omitted. In this case, the optical compensation layer 30 can also function as an inner protective layer. With such a configuration, the polarizing plate with an optical compensation layer can be further reduced in thickness. Furthermore, if necessary, a conductive layer and a base material may be provided in this order on the side of the optical compensation layer 30 opposite to the polarizer 10 (that is, outside the optical compensation layer 30) (both not shown). The base material is closely adhered to the conductive layer. In the present specification, “adhesion lamination” means that two layers are directly and firmly laminated without an adhesive layer (for example, an adhesive layer or an adhesive layer). The conductive layer and the base material can be typically introduced into the polarizing plate 100 with an optical compensation layer as a laminate of the base material and the conductive layer. By further providing a conductive layer and a substrate, the polarizing plate 100 with an optical compensation layer can be suitably used for an inner touch panel type input display device.

C-1. Polarizer Any appropriate polarizer may be adopted as the polarizer 10. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

  Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene / vinyl acetate copolymer partially saponified films. In addition, there may be mentioned polyene-based oriented films such as those subjected to dyeing treatment and stretching treatment with dichroic substances such as iodine and dichroic dyes, PVA dehydrated products and polyvinyl chloride dehydrochlorinated products. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching is used because of excellent optical properties.

  The dyeing with iodine is performed, for example, by immersing a PVA film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed while dyeing. Moreover, you may dye | stain after extending | stretching. If necessary, the PVA film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment and the like. For example, by immersing the PVA film in water and washing it before dyeing, not only can the surface of the PVA film be cleaned of dirt and anti-blocking agents, but the PVA film can be swollen to cause uneven staining. Can be prevented.

  As a specific example of a polarizer obtained by using a laminate, a laminate of a resin substrate and a PVA resin layer (PVA resin film) laminated on the resin substrate, or a resin substrate and the resin Examples thereof include a polarizer obtained by using a laminate with a PVA resin layer applied and formed on a substrate. For example, a polarizer obtained by using a laminate of a resin base material and a PVA resin layer applied and formed on the resin base material may be obtained by, for example, applying a PVA resin solution to a resin base material and drying it. A PVA-based resin layer is formed thereon to obtain a laminate of a resin base material and a PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer a polarizer; obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, the stretching may further include, if necessary, stretching the laminate in the air at a high temperature (for example, 95 ° C. or higher) before stretching in the 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 of the polarizer), and the resin base material is peeled from the resin base material / polarizer laminate. Any appropriate protective layer according to the purpose may be laminated on the release surface. Details of a method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. This publication is incorporated herein by reference in its entirety.

  The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm to 12 μm, still more 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 between 380 nm and 780 nm. As described above, the single transmittance of the polarizer is 43.0% to 46.0%, preferably 44.5% to 46.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

C-2. Protective layer The protective layer 20 is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material as the main component of the film include cellulose resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based materials. And transparent resins such as polystyrene, polynorbornene, polyolefin, (meth) acryl, and acetate. Further, thermosetting resins such as (meth) acrylic, urethane-based, (meth) acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

  The protective layer 20 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, antisticking treatment, and antiglare treatment as necessary. Further / or, if necessary, the protective layer 20 may be treated to improve visibility when viewed through polarized sunglasses (typically, an (elliptical) circular polarization function is imparted, an ultrahigh phase difference is provided. May be applied). By performing such processing, excellent visibility can be achieved even when the display screen is viewed through a polarizing lens such as polarized sunglasses. Therefore, the polarizing plate with an optical compensation layer can be suitably applied to an image display device that can be used outdoors.

  The thickness of the protective layer 20 is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm. In addition, when the surface treatment is performed, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer.

  When an inner protective layer is provided between the polarizer 10 and the optical compensation layer 30, the inner protective layer is preferably optically isotropic. In this specification, “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. The inner protective layer can be composed of any suitable material as long as it is optically isotropic. The material may be appropriately selected from the materials described above for the protective layer 20, for example.

  The thickness of the inner protective layer is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and still more preferably 15 μm to 95 μm.

C-3. Conductive layer or conductive layer with substrate The conductive layer can be formed on any suitable substrate by any suitable film formation method (eg, vacuum deposition, sputtering, CVD, ion plating, spraying, etc.). Further, it can be formed by forming a metal oxide film. After film formation, heat treatment (for example, 100 ° C. to 200 ° C.) may be performed as necessary. By performing the heat treatment, the amorphous film can be crystallized. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. The indium oxide may be doped with divalent metal ions or tetravalent metal ions. Indium composite oxide is preferable, and indium-tin composite oxide (ITO) is more preferable. The indium-based composite oxide has characteristics that it has a high transmittance (for example, 80% or more) in the visible light region (380 nm to 780 nm) and a low surface resistance value per unit area.

  When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

  The surface resistance value of the conductive layer is preferably 300Ω / □ or less, more preferably 150Ω / □ or less, and further preferably 100Ω / □ or less.

  The conductive layer may be transferred from the base material to the optical compensation layer, and the conductive layer alone may be used as a constituent layer of the polarizing plate with the optical compensation layer, and optical compensation is performed as a laminate with the base material (conductive layer with base material). It may be laminated to a layer. Typically, as described above, the conductive layer and the base material can be introduced into the polarizing plate with an optical compensation layer as a conductive layer with a base material.

  Arbitrary appropriate resin is mentioned as a material which comprises a base material. Preferably, it is resin excellent in transparency. Specific examples include cyclic olefin resins, polycarbonate resins, cellulose resins, polyester resins, and acrylic resins.

  Preferably, the substrate is optically isotropic, and therefore the conductive layer can be used as a conductive layer with an isotropic substrate in a polarizing plate with an optical compensation layer. Examples of the material constituting the optically isotropic substrate (isotropic substrate) include, for example, a material having a main skeleton such as a norbornene-based resin or an olefin-based resin, a lactone ring, or glutar Examples thereof include materials having a cyclic structure such as an imide ring in the main chain of the acrylic resin. When such a material is used, when an isotropic substrate is formed, it is possible to suppress the expression of the phase difference accompanying the orientation of the molecular chain.

  The thickness of the substrate is preferably 10 μm to 200 μm, more preferably 20 μm to 60 μm.

C-4. Others Arbitrary appropriate pressure-sensitive adhesive layers or adhesive layers are used for laminating the layers constituting the polarizing plate with an optical compensation layer of the present invention. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive. The adhesive layer is typically formed of a polyvinyl alcohol-based adhesive.

  Although not shown, an adhesive layer may be provided on the optical compensation layer 30 side of the polarizing plate 100 with the optical compensation layer. By providing the pressure-sensitive adhesive layer in advance, it can be easily bonded to another optical member (for example, an organic EL cell). In addition, it is preferable that the peeling film is bonded together on the surface of this adhesive layer until it uses.

D. Image display apparatus The image display apparatus of this invention is equipped with a display cell and the polarizing plate with an optical compensation layer as described in said C term | claim on the visual recognition side of this display cell. The polarizing plate with an optical compensation layer is laminated so that the optical compensation layer is on the display cell side (so that the polarizer is on the viewing side).

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. The measuring method of each characteristic is as follows. Unless otherwise specified, “parts” and “%” in Examples and Comparative Examples are based on weight.
(1) Thickness It was measured using a dial gauge (manufactured by PEACOCK, product name “DG-205 type pds-2”).
(2) Retardation A 50 mm × 50 mm sample was cut out from each retardation film to obtain a measurement sample, and measurement was performed using Axoscan manufactured by Axometrics. The measurement wavelength was 450 nm, 550 nm, and the measurement temperature was 23 ° C.
Further, the average refractive index was measured using an Abbe refractometer manufactured by Atago Co., Ltd., and the refractive indexes nx, ny, nz, and Nz coefficients were calculated from the obtained retardation values.

[Synthesis Example 1]
In a glass ampule with a capacity of 75 mL, 28 g of diisopropyl fumarate, 5 g of monoethyl fumarate, 17 g of n-propyl 4-methoxycinnamate, and 2,5-dimethyl-2,5-di (2-ethylhexanoyl parper as a polymerization initiator) 1.40 g of oxy) hexane was added, and after nitrogen substitution and depressurization were repeated, the mixture was sealed under reduced pressure. This ampoule was placed in a constant temperature bath at 60 ° C. and held for 48 hours for radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 50 g of tetrahydrofuran. This polymer solution was dropped into 2 kg of methanol / water = 50/50 (wt% / wt%), precipitated, washed with 2 kg of methanol / water = 50/50 (wt% / wt%), and then washed at 80 ° C. with 10 kg. By vacuum drying for a time, 28 g of diisopropyl fumarate / monoethyl fumarate / 4-methoxycinnamate n-propyl copolymer was obtained. The number average molecular weight of the obtained polymer was 31,000, diisopropyl fumarate residue unit 56 mol%, monoethyl fumarate residue unit 13 mol%, 4-methoxycinnamic acid n-propyl residue unit 31 mol%. there were.

[Example 1]
1. Preparation of birefringent material Ethyl cellulose (ETHOCEL standard 300 manufactured by Dow Chemical Co., Ltd.), molecular weight Mn = 85,000, molecular weight Mw = 264,000, Mw / Mn = 3.1, total substitution degree as a cellulose resin DS = 2.5) 89 g, and 61 g of diisopropyl fumarate / monoethyl fumarate / 4-methoxycinnamate n-propyl copolymer obtained in Synthesis Example 1 were mixed with ethyl acetate: p-xylene: toluene = 1: 2: 7 (weight ratio) was dissolved into a 15% by weight resin solution, which was a birefringent material.
2. Production of Retardation Film On a shrinkable film (PP biaxially stretched film, 500 mm × 200 mm, thickness 60 μm), the above birefringent material was applied by a coater so that the thickness after drying was 76 μm. The laminated body of a shrinkable film and a coating film was produced by drying on the drying conditions for 15 degreeC / 15 minutes.
Next, after preheating the laminate at 153 ° C. for 60 seconds, a retardation film was formed on the shrinkable film by stretching 2.0 times in the TD direction at a stretching temperature of 153 ° C. using a simultaneous biaxial stretching machine. . Next, the retardation film was peeled from the shrinkable film.

[Example 2]
Implemented except that the birefringent material was coated so that the thickness after drying was 84 μm, the preheating temperature and the stretching temperature were 143 ° C., and the stretching ratio of the laminate was 2.5 times. A retardation film was produced in the same manner as in Example 1.

[Example 3]
A retardation film was produced in the same manner as in Example 2 except that the birefringent material was coated so that the thickness after drying was 83 μm, and the preheating temperature and the stretching temperature were 145 ° C.

[Example 4]
A retardation film was produced in the same manner as in Example 2 except that the birefringent material was coated so that the thickness after drying was 85 μm, and the preheating temperature and the stretching temperature were 147 ° C.

[Comparative Example 1]
A birefringent material was coated on a polyethylene terephthalate film (500 mm × 200 mm, thickness 60 μm) so that the thickness after drying was 72 μm, dried at 40 ° C./15 minutes, and further dried at 155 ° C./5 minutes. Except that the polyethylene terephthalate film was peeled from the laminate and the birefringent material film (film) was stretched, the preheating time was 40 seconds, and the preheating temperature and the stretching temperature were 143 ° C. A retardation film was produced in the same manner as in Example 1.

[Comparative Example 2]
A retardation film was produced in the same manner as in Comparative Example 1 except that the birefringent material was coated so that the thickness after drying was 75 μm, and the draw ratio was 2.5 times.

[Comparative Example 3]
A retardation film was produced in the same manner as in Comparative Example 1 except that the draw ratio was 3.0.

[Comparative Example 4]
A retardation film was produced in the same manner as in Comparative Example 1 except that the birefringent material was coated so that the thickness after drying was 83 μm.

[Comparative Example 5]
The birefringent material was coated so that the thickness after drying was 76 μm, the draw ratio was 2.5 times, and drying was not performed at 155 ° C./5 minutes (drying was one step) A retardation film was produced in the same manner as in Comparative Example 1 except that the preheating time was 60 seconds.

<Evaluation>
About the retardation film of an Example and a comparative example, the thickness at the time of coating, in-plane retardation Re (550), Nz coefficient, and Re (450) / Re (550) were measured or calculated. The results are shown in Table 1.

  The retardation film of the example has Re (550) of 10 nm to 400 nm, Re (450) / Re (550) of 0.8 to 0.9, and Nz coefficient of 0.3 to 0.00. 7. Such a retardation film can realize a polarizing plate with an optical compensation layer whose hue in an oblique direction is neutral.

  The polarizing plate with an optical compensation layer of the present invention is suitably used for an organic EL panel.

DESCRIPTION OF SYMBOLS 10 Polarizer 20 Protective layer 30 Optical compensation layer 100 Polarizing plate with optical compensation layer

Claims (7)

Re (550) is 10 nm to 400 nm,
Re (450) / Re (550) is 0.8 to 0.9,
Retardation film having an Nz coefficient of 0.3 to 0.7:
Here, Re (450) and Re (550) represent in-plane phase differences measured with light having wavelengths of 450 nm and 550 nm at 23 ° C., respectively.   The retardation film according to claim 1, comprising a resin film comprising a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence. An optical compensation layer comprising the retardation film according to claim 1 or 2 and a polarizer,
A polarizing plate with an optical compensation layer, wherein an angle formed between a slow axis of the optical compensation layer and an absorption axis of the polarizer is 35 ° to 55 °. An optical compensation layer comprising the retardation film according to claim 1 or 2 and a polarizer,
The polarizing plate with an optical compensation layer, wherein an angle formed between the slow axis of the optical compensation layer and the absorption axis of the polarizer is 80 ° to 100 ° or −10 ° to 10 °.   An image display device comprising the polarizing plate with an optical compensation layer according to claim 3. Applying a birefringent material containing a cellulose-based resin and a cinnamate copolymer on the shrinkable film and drying the laminate to produce a laminate of the shrinkable film and the coating film; and ,
Stretching the laminate, and shrinking the laminate in a direction perpendicular to the stretching direction, thereby setting the refractive index characteristic of the coating film to nx>nz> ny. Method. The method for producing a retardation film according to claim 6, wherein a shrinkage ratio of the shrinkable film in a direction orthogonal to the stretching direction is 0.50 times to 0.99 times.

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