Polarizing plate with retardation layers and organic el display device

Abstract

To provide a polarizing plate with retardation layers, which offers superior heat resistance.SOLUTION: A polarizing plate with retardation layers provided herein comprises a polarizing plate, a first retardation layer, a first adhesive layer, a second retardation layer, and a second adhesive layer arranged in the described order, the first and second retardation layers containing a liquid crystal compound. The first adhesive layer has a thickness in a range of 5 to 30 μm and an elasticity modulus in a range of 105 to 106 Pa at 25°C. The second adhesive layer is made of an adhesive containing 70 wt.% or more of an alkyl(meth)acrylate in a base polymer, and has an elastic modulus of 9.0×104 Pa or less at 25°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polarizing plate with a retardation layer and an organic EL display device. [Background technology]

[0002] In recent years, with the spread of flat panel displays, image display devices (organic EL display devices) equipped with organic EL panels have been proposed. Organic EL panels have a highly reflective metal layer, which can easily cause problems such as reflection of external light and glare of the background. It is known that these problems can be prevented by providing a polarizing plate with a retardation layer (circular polarizing plate) on the viewing side. However, when the retardation layer of such a polarizing plate with a retardation layer is a laminate in which two retardation layers containing a liquid crystal compound are bonded together with an adhesive, and this polarizing plate with a retardation layer is bonded to an organic EL panel via the adhesive, problems such as low heat resistance and cracks or unevenness in the retardation layer may occur. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3325560 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate with a retardation layer that has excellent heat resistance, and an organic EL display device that uses such a polarizing plate with a retardation layer. [Means for solving the problem]

[0005] The polarizing plate with a retardation layer of the present invention has a polarizing plate, a first retardation layer, a first pressure-sensitive adhesive layer, a second retardation layer, and a second pressure-sensitive adhesive layer in this order, and the first retardation layer and the second retardation layer contain a liquid crystal compound, and the first pressure-sensitive adhesive layer has a thickness of 5 μm to 30 μm and an elastic modulus at 25° C. of 10 5 Pa~10 6 Pa, the second pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive containing 70% by weight or more of alkyl (meth)acrylate in a base polymer, and has an elastic modulus of 9.0 × 10 at 25°C. 4 Pa or less. According to another aspect of the present invention, there is provided an organic EL display device, which includes the above-described polarizing plate with a retardation layer. [Effects of the Invention]

[0006] According to the present invention, the thickness of the first pressure-sensitive adhesive layer is 5 μm to 30 μm, and the modulus of elasticity at 25° C. is 10 5 Pa~10 6 Pa, and the second pressure-sensitive adhesive layer contains 70% by weight or more of alkyl (meth)acrylate in the base polymer, and has an elastic modulus of 9.0 × 10 at 25°C. 4 Pa or less, a polarizing plate with a retardation layer having excellent heat resistance can be realized. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0009] A. Polarizing plate with retardation layer Fig. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. As shown in Fig. 1, a polarizing plate with a retardation layer 100 includes a polarizing plate 10, a first retardation layer 20, a first pressure-sensitive adhesive layer 30, a second retardation layer 40, and a second pressure-sensitive adhesive layer 50, in this order. That is, the first retardation layer 20 and the second retardation layer 40 are laminated with the first pressure-sensitive adhesive layer 30 interposed therebetween. The first retardation layer 20 and the second retardation layer 40 contain a liquid crystal compound. The first pressure-sensitive adhesive layer 30 has a thickness of 5 µm to 30 µm and an elastic modulus at 25°C of 10 5 Pa~10 6 The second adhesive layer 50 is made of an adhesive containing 70% by weight or more of alkyl (meth)acrylate in a base polymer, and has an elastic modulus of 9.0×10 Pa at 25° C. 4 The retardation layer-attached polarizing plate 100 has excellent heat resistance, and the occurrence of cracks in the first retardation layer 20 and / or the second retardation layer 40, as well as the occurrence of unevenness, can be suppressed.

[0010] Each layer constituting the retardation layer-attached polarizing plate 100 will be described in detail below.

[0011] B. Polarizing plate The polarizing plate 10 typically includes a polarizer, a first protective layer disposed on one side of the polarizer, and a second protective layer disposed on the other side of the polarizer. The polarizer is typically an absorptive polarizer. Either the first protective layer or the second protective layer may be omitted.

[0012] B-1.Polarizer Any appropriate polarizer can be used as the polarizer. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0013] Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, as well as polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. Polarizers obtained by dyeing a PVA film with iodine and uniaxially stretching it are preferred because of their excellent optical properties.

[0014] The dyeing with iodine is carried out, for example, by immersing the PVA film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the PVA film may be stretched and then dyed. If necessary, the PVA film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA film in water and washing it before dyeing, it is possible to wash away dirt and antiblocking agents on the surface of the PVA film, and also to swell the PVA film, thereby preventing uneven dyeing.

[0015] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching can optionally further include in-air stretching the laminate at an elevated temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. The obtained resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate and any appropriate protective layer depending on the purpose may be laminated on the peeled surface. Details of such a method for producing a polarizer are described, for example, in JP 2012-73580 A. The entire disclosure of this publication is incorporated herein by reference.

[0016] The thickness of the polarizer is, for example, 1 μm to 35 μm. In one embodiment, the thickness of the polarizer is preferably 1 μm to 15 μm, more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is within this range, curling during heating can be effectively suppressed, and good appearance durability during heating can be obtained.

[0017] B-2.Protective layer The first and second protective layers are formed of any suitable protective film that can be used to protect a polarizer. Specific examples of materials that can be used as the main component of the protective film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxy resins, and silicones. Other examples include glassy polymers such as siloxane polymers. Polymer films described in JP 2001-343529 A (WO 01 / 37007) can also be used. Examples of materials that can be used for this film include a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in its side chains and a thermoplastic resin having substituted or unsubstituted phenyl and nitrile groups in its side chains, such as a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer.The polymer film can be, for example, an extrusion molded product of the above resin composition.

[0018] The thickness of the protective film is preferably 10 μm to 100 μm. The protective film may be laminated on the polarizer via an adhesive layer (specifically, an adhesive layer or a pressure-sensitive adhesive layer), or may be laminated in close contact with the polarizer (without an adhesive layer). The adhesive layer is formed of any appropriate adhesive. Examples of adhesives include water-soluble adhesives containing polyvinyl alcohol-based resins as their main component. The water-soluble adhesives containing polyvinyl alcohol-based resins as their main component may preferably further contain a metal compound colloid. The metal compound colloid may be one in which metal compound fine particles are dispersed in a dispersion medium, and may be electrostatically stabilized due to mutual repulsion of like-charged particles of the fine particles, thereby maintaining permanent stability. The average particle diameter of the fine particles forming the metal compound colloid may be any appropriate value as long as it does not adversely affect optical properties such as polarization properties. The average particle diameter is preferably 1 nm to 100 nm, more preferably 1 nm to 50 nm. This is because the fine particles can be uniformly dispersed in the adhesive layer, ensuring adhesion and suppressing knicks. The term "knicks" refers to local irregular defects that occur at the interface between the polarizer and the protective film. The pressure-sensitive adhesive layer is made of any appropriate pressure-sensitive adhesive.

[0019] C. Retardation layer As described above, the first and second retardation layers contain a liquid crystal compound. Typically, the first and second retardation layers are composed of alignment-fixed layers of a liquid crystal composition containing a liquid crystal compound. In this specification, the term "alignment-fixed layer" refers to a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The alignment-fixed layer of the liquid crystal compound can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing the liquid crystal compound to the surface, orienting the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. In one embodiment, the substrate is any appropriate resin film, and the alignment-fixed layer formed on the substrate can be transferred to the surface of another layer constituting a polarizing plate with a retardation layer. Specific examples of liquid crystal compounds and details of a method for forming the alignment-fixed layer are described in JP 2006-163343 A, the disclosure of which is incorporated herein by reference.

[0020] In one embodiment, the in-plane retardation Re(550) of the first retardation layer is preferably 200 nm to 300 nm, and the in-plane retardation Re(550) of the second retardation layer is preferably 100 nm to 150 nm. Therefore, in this case, the first retardation layer can function as a λ / 2 plate, and the second retardation layer can function as a λ / 4 plate. The angle between the absorption axis of the polarizer and the slow axis of the first retardation layer is preferably 5° to 25°, and particularly preferably about 15°. The angle between the absorption axis of the polarizer and the slow axis of the second retardation layer is preferably 65° to 85°, and particularly preferably about 75°. In another embodiment, the in-plane retardation Re(550) of the first retardation layer is preferably 120 nm to 160 nm, and the index ellipsoid of the second retardation layer satisfies the relationship nz>nx=ny. Therefore, in this case, the first retardation layer can function as a λ / 4 plate, and the second retardation layer can function as a so-called positive C plate. The angle between the absorption axis of the polarizer and the slow axis of the first retardation layer is preferably 39° to 51°, and particularly preferably about 45°.

[0021] C-1. First retardation layer In one embodiment, the first retardation layer may be composed of an aligned, solidified layer of a liquid crystal composition containing a discotic liquid crystal compound aligned substantially vertically. In this specification, the term "discotic liquid crystal compound" refers to a compound having a disk-shaped mesogenic group in its molecular structure, to which two to eight side chains are radially bonded via ether or ester bonds. The thickness of the first retardation layer may be set to obtain a desired in-plane retardation, and is preferably 1 μm to 20 μm, more preferably 1 μm to 12 μm. The liquid crystal composition containing the discotic liquid crystal compound is not particularly limited as long as it contains a discotic liquid crystal compound and exhibits liquid crystallinity. The content of the discotic liquid crystal compound in the liquid crystal composition is preferably 40 parts by weight or more but less than 100 parts by weight, based on 100 parts by weight of the total solid content of the liquid crystal composition. A retardation film composed of an aligned, solidified layer of a liquid crystal composition containing a discotic liquid crystal compound aligned substantially vertically can be obtained by the method described in JP-A-2001-56411.

[0022] In another embodiment, the first retardation layer may be composed of a fixed alignment layer in which rod-shaped liquid crystal compounds are aligned in the slow axis direction of the retardation layer (homogeneous alignment). Examples of liquid crystal compounds include liquid crystal compounds whose liquid crystal phase is a nematic phase (nematic liquid crystals). Examples of such liquid crystal compounds that can be used include liquid crystal polymers and liquid crystal monomers. The mechanism by which the liquid crystal compound exhibits liquid crystallinity may be either lyotropic or thermotropic. When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking the liquid crystal monomer. Any appropriate liquid crystal monomer may be used as the liquid crystal monomer. For example, polymerizable mesogen compounds described in JP-A-2002-533742 (WO 00 / 37585), EP 358208 (US 5,211,877), EP 66137 (US 4,388,453), WO 93 / 22397, EP 0261712, DE 19504224, DE 4408171, and GB 2280445 can be used. Specific examples of such polymerizable mesogen compounds include BASF's product name LC242, Merck's product name E7, and Wacker-Chem's product name LC-Sillicon-CC3767. The thickness of the first retardation layer can be set so as to obtain a desired in-plane retardation, and is preferably 1 μm to 10 μm, and more preferably 1 μm to 6 μm.

[0023] C-2. Second retardation layer The second retardation layer that can function as a λ / 4 plate can be formed using the materials and methods described above in section C-1 for the first retardation layer.

[0024] The second retardation layer, which can function as a positive C plate, can be composed of any appropriate liquid crystal compound as long as the refractive index ellipsoid satisfies the relationship nz>nx=ny. Details of such liquid crystal compounds are described in Japanese Patent Publication Nos. 4,186,980 and 6,055,569, the disclosures of which are incorporated herein by reference. In one embodiment, the second retardation layer can be composed of a side-chain liquid crystal polymer represented by the following chemical formula (I) (where the numbers 65 and 35 represent the mole percent of the monomer unit, and are conveniently expressed as a block polymer with a weight-average molecular weight of 5,000) and a polymerizable liquid crystal exhibiting a nematic liquid crystal phase.

[0025] [ka]

[0026] D. First and Second Adhesive Layers As described above, the first pressure-sensitive adhesive layer has a thickness of 5 μm to 30 μm and a modulus of elasticity at 25° C. of 10 5 Pa~10 6 The thickness of the first pressure-sensitive adhesive is preferably 10 μm to 25 μm. The elastic modulus is preferably 1.1×10 5 Pa~1.9×10 5 Pa, and more preferably 1.2×10 5 Pa~1.8×10 5 It is Pa.

[0027] As described above, the second adhesive layer is made of an adhesive containing 70% by weight or more of alkyl (meth)acrylate in a base polymer, and has an elastic modulus of 9.0 × 10 at 25 °C. 4 The content of alkyl (meth)acrylate in the base polymer of the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer is preferably 75% by weight to 99% by weight, more preferably 80% by weight to 95% by weight. The elastic modulus is preferably 1.0×10 3 Pa ~ 9.0 × 10 4 Pa, more preferably 1.0×10 4 Pa~8.5×10 4 It is Pa.

[0028] The gel fraction of the first and second pressure-sensitive adhesive layers is preferably 40% to 95%, more preferably 50% to 95%, even more preferably 65% ​​to 93%, and particularly preferably 80% to 93%. If the gel fraction of the pressure-sensitive adhesive layer is low, the cohesive strength may be poor, which may cause problems with processability and handling. Furthermore, from the viewpoint of preventing appearance defects such as glue dents, the gel fraction immediately after the pressure-sensitive adhesive layer is preferably 60% or more, more preferably 63% or more, even more preferably 66% or more, and particularly preferably 70% or more.

[0029] The adhesive constituting the first adhesive layer and / or the second adhesive layer may contain a crosslinking agent, an ultraviolet absorber, a dye compound, etc. in the adhesive composition depending on the purpose and application.

[0030] D-1. Base polymer The adhesive constituting the first and second adhesive layers (hereinafter sometimes simply referred to as "adhesive layers") may be made of any appropriate material as long as it satisfies the above-mentioned properties. In one embodiment, the base polymer of the adhesive constituting the adhesive layer may be a (meth)acrylic polymer, a rubber-based polymer, or the like. Preferably, the base polymer is a (meth)acrylic polymer.

[0031] The (meth)acrylic polymer contains alkyl (meth)acrylate as a main component as a monomer unit. Examples of alkyl (meth)acrylate include those having a linear or branched alkyl group having 1 to 24 carbon atoms at the ester terminal. The alkyl (meth)acrylate can be used alone or in combination of two or more. Note that "alkyl (meth)acrylate" refers to alkyl acrylate and / or alkyl methacrylate.

[0032] In the adhesive constituting the first adhesive layer, the alkyl(meth)acrylate having an alkyl group having 1 to 24 carbon atoms at the ester terminal is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, based on the total amount of monofunctional monomer components forming the (meth)acrylic polymer. In the adhesive constituting the second adhesive layer, as described above, the alkyl(meth)acrylate is 70% by weight or more, based on the total amount of monofunctional monomer components forming the (meth)acrylic polymer.

[0033] The above-mentioned monomer components may contain a copolymerizable monomer other than alkyl (meth)acrylate as a monofunctional monomer component. The copolymerizable monomer can be used as the remainder of the alkyl (meth)acrylate in the monomer components. The copolymerizable monomer may include, for example, a cyclic nitrogen-containing monomer. As the cyclic nitrogen-containing monomer, any monomer having a polymerizable functional group with an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, and having a cyclic nitrogen structure can be used without particular limitation. The cyclic nitrogen structure preferably has a nitrogen atom within the cyclic structure. The content of the cyclic nitrogen-containing monomer is preferably 0.5 to 50 wt %, more preferably 0.5 to 40 wt %, and even more preferably 0.5 to 30 wt %, based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

[0034] The monomer components forming the (meth)acrylic polymer may contain other functional group-containing monomers. Examples of such monomers include carboxyl group-containing monomers and monomers having a cyclic ether group. When a carboxyl group-containing monomer is contained, the content is preferably 0.05 to 10 wt %, more preferably 0.1 to 8 wt %, and even more preferably 0.2 to 6 wt %. By containing a carboxyl group-containing monomer, the gel fraction of the pressure-sensitive adhesive layer can be adjusted to a value within a preferred range, and as a result, the occurrence of cracks in the retardation layer can be suppressed.

[0035] The monomer components may also contain a hydroxyl group-containing monomer. As the hydroxyl group-containing monomer, any monomer having a polymerizable functional group with an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, and a hydroxyl group can be used without particular limitation. To enhance adhesive strength and cohesive strength, the content of the hydroxyl group-containing monomer is preferably 1 wt % or more, more preferably 2 wt % or more, and even more preferably 3 wt % or more, based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer. On the other hand, the upper limit of the content of the hydroxyl group-containing monomer is preferably 30 wt %, more preferably 27 wt %, and even more preferably 25 wt %, based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer. If the amount of the hydroxyl group-containing monomer is too high, the pressure-sensitive adhesive layer may become hard, the adhesive strength may decrease, and the viscosity of the pressure-sensitive adhesive may become too high.

[0036] In addition to the monofunctional monomers described above, the monomer components forming the (meth)acrylic polymer may contain any appropriate polyfunctional monomer as needed to adjust the cohesive strength of the PSA.

[0037] The (meth)acrylic polymer typically has a weight-average molecular weight in the range of 500,000 to 3,000,000. Considering durability, particularly heat resistance, a weight-average molecular weight of 700,000 to 2,700,000 is preferred. A weight-average molecular weight of 800,000 to 2,500,000 is even more preferred. A weight-average molecular weight of less than 500,000 is undesirable in terms of heat resistance. A weight-average molecular weight of more than 3,000,000 is undesirable because a large amount of dilution solvent is required to adjust the viscosity to a level suitable for coating, resulting in increased costs. The weight-average molecular weight is measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene. The weight-average molecular weight of the (meth)acrylic polymer of the adhesive constituting the first pressure-sensitive adhesive layer is preferably 1,500,000 to 2,500,000, more preferably 1,800,000 to 2,300,000. The weight-average molecular weight of the (meth)acrylic polymer of the adhesive constituting the second pressure-sensitive adhesive layer is preferably 1,000,000 to 2,000,000, more preferably 1,200,000 to 1,800,000.

[0038] The (meth)acrylic polymer can be produced by any suitable method, such as solution polymerization, radiation polymerization such as ultraviolet (UV) polymerization, and various radical polymerization methods such as bulk polymerization and emulsion polymerization. The resulting (meth)acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0039] When producing a (meth)acrylic polymer by radical polymerization, polymerization can be carried out by appropriately adding a polymerization initiator, chain transfer agent, emulsifier, etc. used in radical polymerization to the monomer components. The polymerization initiator, chain transfer agent, emulsifier, etc. used in radical polymerization are not particularly limited and can be appropriately selected and used. The weight-average molecular weight of the (meth)acrylic polymer can be controlled by the amount of polymerization initiator and chain transfer agent used and the reaction conditions, and the amount used is adjusted appropriately depending on the type of these.

[0040] When a (meth)acrylic polymer is produced by radiation polymerization, it can be produced by polymerizing a monomer component by irradiating it with radiation such as an electron beam or ultraviolet (UV) light. Among these, ultraviolet polymerization is preferred. When performing ultraviolet polymerization, it is preferred to include a photopolymerization initiator in the monomer component, as this has the advantage of shortening the polymerization time.

[0041] The photopolymerization initiator is not particularly limited, but is preferably a photopolymerization initiator having an absorption band at a wavelength of 400 nm or more. Examples of such photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by BASF, product name "Irgacure 819") and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (manufactured by BASF, "LUCIRIN TPO").

[0042] The photopolymerization initiator may contain a photopolymerization initiator having an absorption band at a wavelength of less than 400 nm. Such photopolymerization initiators are not particularly limited as long as they generate radicals when exposed to ultraviolet light and initiate photopolymerization, and have an absorption band at a wavelength of less than 400 nm. Any commonly used photopolymerization initiator can be suitably used. For example, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators can be used.

[0043] D-2. Crosslinking agent Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more. Among these, isocyanate-based crosslinking agents are preferably used.

[0044] In the pressure-sensitive adhesive, the content of the isocyanate crosslinking agent relative to 100 parts by weight of the base polymer is preferably 0.1 to 12 parts by weight.

[0045] An isocyanate crosslinking agent is a compound having two or more isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate group is temporarily protected by a blocking agent or oligomerization, etc.) per molecule. Examples of isocyanate crosslinking agents include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

[0046] More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate and polymethylene polyphenyl isocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L"), Examples of suitable polyisocyanates include isocyanate adducts such as an isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate HL") and an isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate HX"), a trimethylolpropane adduct of xylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "D110N") and a trimethylolpropane adduct of hexamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "D160N"); polyether polyisocyanates, polyester polyisocyanates, and adducts of these with various polyols; and polyisocyanates that have been multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among these, trimethylolpropane tolylene diisocyanate is preferably used as a crosslinking agent for the adhesive that constitutes the first adhesive layer, and trimethylolpropane xylene diisocyanate is preferably used as a crosslinking agent for the adhesive that constitutes the second adhesive layer, and trimethylolpropane xylene diisocyanate is preferably used.

[0047] D-3. UV absorbers Any appropriate ultraviolet absorber can be used as the ultraviolet absorber. The ultraviolet absorber preferably has 0 to 3 hydroxyl groups in its molecular structure. Specific examples include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, oxybenzophenone-based ultraviolet absorbers, salicylic acid ester-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. These can be used alone or in combination of two or more. Among these, triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers are preferred. At least one ultraviolet absorber selected from the group consisting of triazine-based ultraviolet absorbers having two or less hydroxyl groups per molecule and benzotriazole-based ultraviolet absorbers having one benzotriazole skeleton per molecule is preferred because it has good solubility in the monomers used to form the acrylic pressure-sensitive adhesive composition and has high ultraviolet absorption capacity at a wavelength of around 380 nm. The ultraviolet absorbers may be used alone or in combination of two or more.

[0048] D-4. Pigment compounds The dye compound preferably has a maximum absorption wavelength in the absorption spectrum in the wavelength range of 380 nm to 430 nm. By using such a dye compound in combination with an ultraviolet absorber, it is possible to sufficiently absorb light in the range (wavelengths of 380 nm to 430 nm) that does not affect the light emission of the organic EL element, and to sufficiently transmit light in the light emission range of the organic EL element (wavelengths longer than 430 nm).

[0049] The half-value width of the dye compound is preferably 80 nm or less, more preferably 5 nm to 70 nm, and even more preferably 10 nm to 60 nm, which allows the dye compound to sufficiently absorb light in a range that does not affect the light emission of the organic EL device, while allowing the dye compound to sufficiently transmit light in wavelengths longer than 430 nm.

[0050] D-5. Other ingredients The PSA composition may contain other components, such as a silane coupling agent, an antioxidant, an antiaging agent, and a plasticizer, as needed. Examples of antioxidants include phenol-based, phosphorus-based, sulfur-based, and amine-based antioxidants. Examples of silane coupling agents include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane, and acetoacetyl group-containing silane coupling agents.

[0051] E. Organic EL display device The polarizing plate with a retardation layer described in the above items A to D can be used in an image display device. Therefore, the present invention also encompasses an image display device using such an optical laminate. Representative examples of image display devices include liquid crystal display devices and organic electroluminescence (EL) display devices. An image display device (organic EL display device) according to an embodiment of the present invention includes the optical laminate described in the above items A to D. [Example]

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. (1) Thickness The thickness of the retardation layer was measured using an interference film thickness meter (MCPD2000, manufactured by Otsuka Electronics Co., Ltd.) The thicknesses of layers other than the retardation layer were measured using a digital micrometer (KC-351C, manufactured by Anritsu Corporation). (2) Phase difference value The refractive indices nx, ny and nz of the retardation layer were measured by an automatic birefringence measuring device (Oji Scientific Instruments, Automatic Birefringence Meter KOBRA-WPR), and the in-plane retardation Re and thickness direction retardation Rth were calculated. (3) Elastic modulus of adhesive layer For the adhesives used in the examples and comparative examples, the temperature dependence of the storage modulus G' was measured using a dynamic viscoelasticity measuring device (product name: ARES, manufactured by Rheometrics), and the measured value G' (25°C) at 25°C was taken as the modulus of elasticity.

[0053] <Production Example 1> (Preparation of polarizing plate) A long roll of 30 μm-thick polyvinyl alcohol film (manufactured by Kuraray, product name "PE3000") was uniaxially stretched in the longitudinal direction by a roll stretching machine to 5.9 times its original size while simultaneously undergoing swelling, dyeing, crosslinking, and washing treatments, and finally drying treatment to produce a 12 μm-thick polarizer. Specifically, the film was stretched 2.2 times while being swelled in pure water at 20°C. Then, the film was stretched 1.4 times while being dyed in a 30°C aqueous solution containing iodine and potassium iodide in a weight ratio of 1:7, with the iodine concentration adjusted so that the resulting polarizing film would have a transmittance of 45.0%. The crosslinking process was a two-stage process. In the first stage, the film was stretched 1.2 times while being treated in a 40°C aqueous solution containing boric acid and potassium iodide. The boric acid content of the aqueous solution used in the first stage was 5.0 wt % and the potassium iodide content was 3.0 wt %. In the second stage, the film was stretched 1.6 times while being treated in a 65°C aqueous solution containing boric acid and potassium iodide. The boric acid content of the aqueous solution used in the second stage was 4.3 wt % and the potassium iodide content was 5.0 wt %. The cleaning treatment was carried out with an aqueous potassium iodide solution at 20° C. The potassium iodide content of the aqueous solution used for the cleaning treatment was 2.6 wt %. Finally, the film was dried at 70° C. for 5 minutes to obtain a polarizer. A TAC film manufactured by Konica Minolta, Inc. (product name: KC2UA, thickness: 25 μm) and an HC-TAC film (thickness: 32 μm) having an HC layer on one side of the TAC film were bonded to both sides of the obtained polarizer via a polyvinyl alcohol-based adhesive, thereby obtaining polarizing plate 1 in which protective films were bonded to both sides of the polarizer.

[0054] <Production Example 2> (Preparation of Retardation Layer A) A liquid crystal composition (coating liquid) was prepared by dissolving 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name "Paliocolor LC242", represented by the following formula) and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by Ciba Specialty Chemicals, trade name "Irgacure 907") in 40 g of toluene. [ka] The surface of a polyethylene terephthalate (PET) film (38 μm thick) was rubbed with a rubbing cloth to perform an alignment treatment. The alignment treatment conditions were: number of rubbings (number of rubbing rolls) 1, rubbing roll radius r 76.89 mm, rubbing roll rotation speed nr 1500 rpm, film transport speed v 83 mm / sec, and rubbing strength RS and pressing depth M under five conditions (a) to (e) as shown in Table 1.

[0055] [Table 1]

[0056] The orientation direction was set to be -75° from the viewing side with respect to the direction of the absorption axis of the polarizer when attached to the polarizing plate. The above-mentioned coating liquid was applied to this orientation-treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. Under conditions (a) to (c), the alignment state of the liquid crystal compound was very good. Under conditions (d) and (e), some disturbance occurred in the alignment of the liquid crystal compound, but this was at a level that would not cause any practical problems. The liquid crystal layer thus formed was irradiated with 1 mJ / cm using a metal halide lamp. 2 The liquid crystal layer was cured by irradiating the PET film with light, thereby forming a retardation layer A on the PET film. The retardation layer A had a thickness of 2 μm and an in-plane retardation Re of 270 nm. Furthermore, the retardation layer A had a refractive index profile of nx>ny=nz.

[0057] <Production Example 3> (Preparation of Retardation Layer B) The surface of a polyethylene terephthalate (PET) film (38 μm thick) was rubbed with a rubbing cloth to perform an alignment treatment. The alignment direction was set to a -15° angle from the viewing side relative to the absorption axis of the polarizer when attached to a polarizing plate. The same liquid crystal coating solution as above was applied to this alignment-treated surface, and the liquid crystal was aligned and cured in the same manner as above to form a retardation layer B on the PET film. The retardation layer B had a thickness of 1.2 μm and an in-plane retardation Re of 140 nm. Furthermore, the retardation layer B had a refractive index distribution of nx > ny = nz.

[0058] <Production Example 4> (Preparation of adhesive layer A) A reaction vessel equipped with a condenser, nitrogen inlet, thermometer, and stirrer was charged with 94.9 parts butyl acrylate, 5 parts acrylic acid, 0.1 parts 2-hydroxyethyl acrylate, and 0.3 parts dibenzoyl peroxide (solids content: 100 parts) together with ethyl acetate. The reaction was allowed to proceed under a nitrogen gas flow at 60°C for 7 hours. Ethyl acetate was then added to the reaction mixture to obtain a solution containing an acrylic polymer with a weight-average molecular weight of 2.2 million (solids concentration: 30 wt%). Per 100 parts of the solids content of the acrylic polymer solution, 0.6 parts trimethylolpropane tolylene diisocyanate (product name: "Coronate L" manufactured by Nippon Polyurethane Co., Ltd.) and 0.075 parts γ-glycidoxypropyl methoxysilane (product name: "KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) were blended to obtain a pressure-sensitive adhesive composition (solution). The pressure-sensitive adhesive composition was applied to a separator made of a polyester film surface-treated with a silicone-based release agent and heat-treated at 155°C for 3 minutes to obtain a pressure-sensitive adhesive layer A having a thickness of 20 µm. The modulus of elasticity of the pressure-sensitive adhesive layer A at 25°C was 1.4 × 10 5 It was Pa.

[0059] <Production Example 5> (Preparation of adhesive layer B) A reaction vessel equipped with a condenser, nitrogen inlet, thermometer, and stirrer was charged with 99 parts butyl acrylate, 1.0 part 4-hydroxybutyl acrylate, and 0.3 parts 2,2'-azobisisobutyronitrile together with ethyl acetate. The mixture was reacted under nitrogen gas flow at 60°C for 4 hours. Ethyl acetate was then added to the reaction mixture to obtain a solution containing an acrylic polymer with a weight-average molecular weight of 1.65 million (30% solids). Per 100 parts of the solids of the acrylic polymer solution, 0.15 parts dibenzoyl peroxide (Niper BO-Y, manufactured by Nippon Oil & Fats Corporation), 0.1 parts trimethylolpropane xylene diisocyanate (Takenate D110N, manufactured by Mitsui Takeda Chemicals, Inc.), and 0.2 parts silane coupling agent (A-100, manufactured by Soken Chemical & Engineering Co., Ltd., an acetoacetyl-containing silane coupling agent) were blended to obtain a pressure-sensitive adhesive composition (solution). The pressure-sensitive adhesive composition was applied to a separator made of a polyester film surface-treated with a silicone-based release agent and heat-treated at 155°C for 3 minutes to obtain a 20µm-thick pressure-sensitive adhesive layer B. The modulus of elasticity of the pressure-sensitive adhesive layer B at 25°C was 8.1 × 10 4 It was Pa.

[0060] [Example 1] The TAC film surface of the polarizing plate and the retardation layer A were bonded together via an ultraviolet-curing adhesive so that the angle between the absorption axis of the polarizing plate and the slow axis of the retardation layer A was 75°. Next, the retardation layer A and the retardation layer B were bonded together via an adhesive layer A so that the angle between the absorption axis of the polarizing plate and the slow axis of the retardation layer B was 15°. Furthermore, the adhesive layer B was bonded to the surface of the retardation layer B, thereby obtaining a polarizing plate 1 with a retardation layer.

[0061] [Comparative Example 1] A polarizing plate 2 with a retardation layer was obtained in the same manner as in Example 1, except that the retardation layer A and the retardation layer B were bonded together using the pressure-sensitive adhesive layer B instead of the pressure-sensitive adhesive layer A.

[0062] Comparative Example 2 Instead of adhesive layer A, a UV-curable adhesive (elastic modulus at 25°C: 1.0 × 10 6A polarizing plate 3 with a retardation layer was obtained in the same manner as in Example 1, except that the retardation layer A and the retardation layer B were bonded together using a film having a resistivity greater than Pa.

[0063] (evaluation) The polarizing plates with a retardation layer obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Table 2. <Heat shock resistance> The polarizing plate with the retardation layer was cut to a size of 120 mm × 60 mm and attached to glass via the outermost pressure-sensitive adhesive layer B to prepare a test sample. This test sample was placed in a heat shock tester and subjected to a heat shock test in which 100 cycles of holding at -40°C for 30 minutes and then at 85°C for 30 minutes were repeated, and the presence or absence of cracks in the retardation layer was confirmed using an optical microscope. In the polarizing plate 2 with a retardation layer, cracks were found in the retardation layer, but in the polarizing plate 1 with a retardation layer, no cracks were found in the retardation layer. <Heat resistance> The polarizing plate with a retardation layer was cut into a size of 120 mm × 60 mm and attached to glass via the outermost pressure-sensitive adhesive layer B to prepare a test sample. This test sample was placed in an oven at 85°C and stored for 500 hours, after which it was visually inspected for the presence or absence of unevenness while placed on a reflector. In the polarizing plate 3 with a retardation layer, strong irregularities in which the color of the periphery turned red were visually recognized, but in the polarizing plate 1 with a retardation layer, no irregularities were visually recognized.

[0064] [Table 2]

[0065] As is clear from Table 2, in the polarizing plates with a retardation layer of the examples, cracks in the retardation layer are suppressed, and the occurrence of unevenness is also suppressed. [Industrial Applicability]

[0066] The optical laminate of the present invention is suitably used in image display devices such as organic EL display devices. [Explanation of symbols]

[0067] 10 Polarizing plate 20 First retardation layer 30 adhesive layer 40 Second retardation layer 50 adhesive layer 100 Polarizing plate with retardation layer

Claims

[Claim 1] a polarizing plate, a first retardation layer, a first pressure-sensitive adhesive layer, a second retardation layer, and a second pressure-sensitive adhesive layer in this order; the first retardation layer and the second retardation layer contain a liquid crystal compound, The first pressure-sensitive adhesive layer has a thickness of 5 μm to 30 μm and a modulus of elasticity at 25° C. of 10 ５ Pa to 10 ６ Pa, The second adhesive layer is made of an adhesive containing 70% by weight or more of alkyl (meth)acrylate in a base polymer, and has an elastic modulus of 9.0 × 10 at 25 ° C. ４ A polarizing plate with a retardation layer, wherein the retardation layer has a modulus of 1 Pa or less.

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