JP7441611B2 - Polarizing plate with retardation layer and organic EL display device - Google Patents

Description

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

In recent years, with the spread of thin displays, image display devices equipped with organic EL panels (organic EL display devices) have been proposed. Organic EL panels have a highly reflective metal layer, which tends to cause problems such as reflection of external light and background reflection. Therefore, it is known that these problems can be prevented by providing a polarizing plate with a retardation layer (circularly polarizing plate) on the viewing side. However, as the retardation layer of such a polarizing plate with a retardation layer, a laminate in which two retardation layers containing a liquid crystal compound are bonded together with an adhesive is used. If it is bonded to an organic EL panel via a layer, the heat resistance is low, and problems such as cracks or unevenness in the retardation layer may occur.

Patent No. 3325560

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizing plate with a retardation layer having excellent heat resistance, and an organic EL using such a polarizing plate with a retardation layer. The purpose of this invention is to provide a display device.

The polarizing plate with a retardation layer of the present invention includes a polarizing plate, a first retardation layer, a first adhesive layer, a second retardation layer, and a second adhesive layer in this order. wherein the first retardation layer and the second retardation layer contain a liquid crystal compound, the first 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, and the second adhesive layer is composed of an adhesive containing 70% by weight or more of alkyl (meth)acrylate in the base polymer, and has an elastic modulus of 9.0 × 10 ⁴ Pa at 25°C. It is as follows.
According to another aspect of the invention, an organic EL display device is provided. This organic EL display device has the above polarizing plate with a retardation layer.

According to the present invention, the thickness of the first adhesive layer is 5 μm to 30 μm, the elastic modulus at 25° C. is 10 ⁵ Pa to 10 ⁶ Pa, and the second adhesive layer contains alkyl in the base polymer. By containing 70% by weight or more of (meth)acrylate and having an elastic modulus of 9.0×10 ⁴ Pa or less at 25° C., it was possible to realize a polarizing plate with a retardation layer having excellent heat resistance.

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

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

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, the polarizing plate 100 with a retardation layer includes a polarizing plate 10, a first retardation layer 20, a first adhesive layer 30, a second retardation layer 40, and a second retardation layer 40. adhesive layer 50 in this order. That is, the first retardation layer 20 and the second retardation layer 40 are laminated with the first adhesive layer 30 in between. The first retardation layer 20 and the second retardation layer 40 are configured to contain a liquid crystal compound. The first adhesive layer 30 has a thickness of 5 μm to 30 μm, and an elastic modulus of 10 ⁵ Pa to 10 ⁶ Pa at 25° C. 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 ⁴ Pa or less at 25°C. The polarizing plate 100 with a retardation layer has excellent heat resistance, and can suppress the occurrence of cracks and unevenness in the first retardation layer 20 and/or the second retardation layer 40.

Each layer constituting the polarizing plate 100 with a retardation layer will be described in detail below.

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 absorption polarizer. One of the first protective layer and the second protective layer may be omitted.

B-1. Polarizer Any suitable polarizer may be employed 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.

Specific examples of polarizers composed of single-layer resin films include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene/vinyl acetate copolymer films. Examples include those that have been dyed with dichroic substances such as iodine and dichroic dyes and stretched, and polyene-based oriented films such as dehydrated PVA and dehydrochloric acid treated polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching is used because it has excellent optical properties.

The above-mentioned staining with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching may be carried out after the dyeing process or may be carried out while dyeing. Alternatively, it may be dyed after being stretched. If necessary, the PVA film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing a PVA film in water and washing it with water before dyeing, you can not only wash dirt and anti-blocking agents from the surface of the PVA film, but also swell the PVA film and prevent uneven dyeing. It can be prevented.

Specific examples of polarizers obtained using a laminate include a laminate of a resin base material and a PVA resin layer (PVA resin film) laminated on the resin base material, or a laminate of a resin base material and the resin Examples include polarizers obtained using a laminate with a PVA-based resin layer coated on a base material. A polarizer obtained using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material can be obtained by, for example, applying a PVA-based resin solution to the resin base material and drying it. Forming a PVA-based resin layer thereon to obtain a laminate of a resin base material and the PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in the boric acid aqueous solution, if necessary. The obtained resin base material/polarizer laminate may be used as is (that is, the resin base material may be used as a protective layer for the polarizer), or the resin base material may be peeled from the resin base material/polarizer laminate. However, any appropriate protective layer may be laminated on the peeled surface depending on the purpose. Details of the method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Publication No. 2012-73580. The entire description of this publication is incorporated herein by reference.

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, particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is within such a range, curling during heating can be suppressed well, and good appearance durability during heating can be obtained.

B-2. Protective Layer The first and second protective layers are formed of any suitable protective film that can be used as a film to protect a polarizer. Specific examples of materials that are the main components of the protective film include cellulose resins such as triacetyl cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, and polysulfones. Examples include transparent resins such as polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Further, thermosetting resins or ultraviolet curable resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone resins may also be mentioned. Other examples include glassy polymers such as siloxane polymers. Furthermore, the polymer film described in JP-A-2001-343529 (WO01/37007) can also be used. Materials for this film include, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in its side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in its side chain. For example, a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile/styrene copolymer can be used. The polymer film may be, for example, an extrusion molded product of the resin composition.

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 closely (without an adhesive layer) on the polarizer. good. The adhesive layer is formed of any suitable adhesive. Examples of the adhesive include water-soluble adhesives containing polyvinyl alcohol resin as a main component. The water-soluble adhesive containing polyvinyl alcohol resin as a 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 charges of the fine particles, and may have permanent stability. . The average particle diameter of the fine particles forming the metal compound colloid can be any suitable value as long as it does not adversely affect optical properties such as polarization properties. The thickness 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 nicks. Note that the term "knick" refers to a local unevenness defect that occurs at the interface between the polarizer and the protective film. The adhesive layer is composed of any suitable adhesive.

C. Retardation Layer As described above, the first and second retardation layers contain a liquid crystal compound. Typically, the first and second retardation layers may be constituted by an alignment solidified layer of a liquid crystal composition containing a liquid crystal compound. As used herein, the term "orientation-fixed layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction and the orientation state is fixed. The alignment solidified layer of a liquid crystal compound is obtained by subjecting the surface of a predetermined base material to an alignment treatment, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, It can be formed by fixing the orientation state. In one embodiment, the base material is any suitable resin film, and the alignment solidified layer formed on the base material can be transferred to the surface of other layers constituting the polarizing plate with a retardation layer. . Specific examples of the liquid crystal compound and details of the method for forming the alignment solidified layer are described in JP-A No. 2006-163343. The description of the publication is incorporated herein by reference.

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 is 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°, 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°, 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 second retardation layer has an index ellipsoid of nz>nx=ny satisfies the relationship. 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°, particularly preferably about 45°.

C-1. First Retardation Layer In one embodiment, the first retardation layer may be constituted by an oriented solidified layer of a liquid crystalline composition containing a substantially vertically aligned discotic liquid crystal compound. In this specification, a "discotic liquid crystal compound" has a disc-shaped mesogenic group in its molecular structure, and the mesogenic group has 2 to 8 side gaps formed radially by ether bonds or ester bonds. Refers to things that are connected. 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 20 μm, more preferably 1 μm to 12 μm. The liquid crystal composition containing the discotic liquid crystal compound described above is not particularly limited as long as it contains the 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 and less than 100 parts by weight based on 100 parts by weight of the total solid content of the liquid crystal composition. The retardation film comprising an alignment solidified layer of a liquid crystal composition containing a substantially vertically aligned discotic liquid crystal compound can be obtained by the method described in JP-A No. 2001-56411.

In another embodiment, the first retardation layer may be constituted by an alignment solidified layer in which rod-shaped liquid crystal compounds are aligned in the slow axis direction of the retardation layer (homogeneous alignment). Examples of the liquid crystal compound include a liquid crystal compound whose liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for developing liquid crystallinity of a liquid crystal compound 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 suitable liquid crystal monomer may be employed as the liquid crystal monomer. For example, the Synthetic mesogenic compounds etc. can be used. Specific examples of such polymerizable mesogenic compounds include, for example, 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, more preferably 1 μm to 6 μm.

C-2. Second Retardation Layer The second retardation layer that can function as a λ/4 plate can be formed using the material and method described in Section C-1 above for the first retardation layer.

The second retardation layer that can function as a positive C-plate may be made of any suitable liquid crystal compound as long as the index ellipsoid satisfies the relationship nz>nx=ny. Details of such liquid crystal compounds are described in Japanese Patent No. 4186980 and Japanese Patent No. 6055569. The description of the publication is incorporated herein by reference. In one embodiment, the second retardation layer has the following chemical formula (I) (numbers 65 and 35 in the formula indicate mol% of monomer units, and are conveniently expressed as a block polymer body: weight average It may be composed of a side chain type liquid crystal polymer having a molecular weight of 5,000) and a polymerizable liquid crystal exhibiting a nematic liquid crystal phase.

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

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

The gel fraction of the first and second adhesive layers is preferably 40% to 95%, more preferably 50% to 95%, still more preferably 65% to 93%, particularly preferably It is 80% to 93%. When the gel fraction of the adhesive layer is low, the cohesive force is poor and problems may arise in processability and handling. In addition, the gel fraction immediately after forming the adhesive layer is preferably 60% or more, more preferably 63% or more, and 66% or more from the viewpoint of preventing appearance defects such as glue dents. It is more preferable that it is, and it is especially preferable that it is 70% or more.

The adhesive constituting the first adhesive layer and/or the second adhesive layer may contain a crosslinking agent, an ultraviolet absorber, a pigment compound, etc. in the adhesive composition depending on the purpose and use.

D-1. Base polymer The adhesive constituting the first and second adhesive layers (hereinafter sometimes simply referred to as "adhesive layer") may be formed of any suitable material as long as it satisfies the above characteristics. . In one embodiment, examples of the base polymer of the adhesive constituting the adhesive layer include (meth)acrylic polymers, rubber polymers, and the like. Preferably, the base polymer is a (meth)acrylic polymer.

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

Regarding the adhesive constituting the first adhesive layer, the alkyl (meth)acrylate having an alkyl group having 1 to 24 carbon atoms at the ester end is added to the total amount of the monofunctional monomer component forming the (meth)acrylic polymer. It is preferably 40% by weight or more, more preferably 50% by weight or more, even more preferably 60% by weight or more. Regarding 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 the monofunctional monomer component forming the (meth)acrylic polymer.

The monomer component may include 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 component. The copolymerizable monomer may include, for example, a cyclic nitrogen-containing monomer. As the cyclic nitrogen-containing monomer, those having a polymerizable functional group having 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% by weight, more preferably 0.5 to 40% by weight based on the total amount of monofunctional monomer components forming the (meth)acrylic polymer. %, and even more preferably 0.5 to 30% by weight.

The monomer components forming the (meth)acrylic polymer may include other functional group-containing monomers. Examples of such monomers include carboxyl group-containing monomers and monomers having a cyclic ether group. When containing a carboxyl group-containing monomer, the content is preferably 0.05 to 10% by weight, more preferably 0.1 to 8% by weight, and even more preferably 0.2 to 6% by weight. . By including the carboxyl group-containing monomer, the gel fraction of the adhesive layer can be set within a preferable range, and as a result, the occurrence of cracks in the retardation layer can be suppressed.

Further, the monomer component may include a hydroxyl group-containing monomer. As the hydroxyl group-containing monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a hydroxyl group can be used without particular limitation. The content of the hydroxyl group-containing monomer is preferably 1% by weight or more, based on the total amount of monofunctional monomer components forming the (meth)acrylic polymer, from the viewpoint of increasing adhesive force and cohesive force. Preferably it is 2% by weight or more, more preferably 3% by weight or more. On the other hand, the upper limit of the content of the hydroxyl group-containing monomer is preferably 30% by weight, more preferably 27% by weight, based on the total amount of monofunctional monomer components forming the (meth)acrylic polymer, More preferably, it is 25% by weight. If the amount of the hydroxyl group-containing monomer increases too much, the adhesive layer may become hard and the adhesive force may decrease, and the viscosity of the adhesive may become too high.

In addition to the above-mentioned monofunctional monomers, the monomer component forming the (meth)acrylic polymer may contain any appropriate polyfunctional monomer as necessary to adjust the cohesive force of the adhesive. can do.

The (meth)acrylic polymer used usually has a weight average molecular weight in the range of 500,000 to 3,000,000. Considering durability, especially heat resistance, it is preferable to use a material having a weight average molecular weight of 700,000 to 2,700,000. More preferably, it is 800,000 to 2,500,000. If the weight average molecular weight is less than 500,000, it is unfavorable in terms of heat resistance. Furthermore, if the weight average molecular weight is greater than 3 million, a large amount of diluting solvent will be required to adjust the viscosity to a level suitable for coating, which is undesirable as it will increase costs. Note that the weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated based on polystyrene conversion. The weight average molecular weight of the (meth)acrylic polymer of the adhesive constituting the first adhesive layer is preferably 1.5 million to 2.5 million, more preferably 1.8 million to 2.3 million. The weight average molecular weight of the (meth)acrylic polymer of the adhesive constituting the second adhesive layer is preferably 1 million to 2 million, more preferably 1.2 million to 1.8 million.

As a method for producing the (meth)acrylic polymer, any suitable method can be employed, such as solution polymerization, radiation polymerization such as ultraviolet (UV) polymerization, various radical polymerizations such as bulk polymerization, and emulsion polymerization. Further, the (meth)acrylic polymer obtained may be a random copolymer, a block copolymer, a graft copolymer, or the like.

When producing a (meth)acrylic polymer by radical polymerization, polymerization can be carried out by appropriately adding a polymerization initiator, a chain transfer agent, an emulsifier, etc. used for 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 amounts of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amounts used are adjusted as appropriate depending on the types of these.

When producing a (meth)acrylic polymer by radiation polymerization, it can be produced by irradiating a monomer component with radiation such as an electron beam or ultraviolet (UV) to polymerize it. Among these, ultraviolet polymerization is preferred. When carrying out ultraviolet polymerization, it is preferable to include a photopolymerization initiator in the monomer component due to the advantage that the polymerization time can be shortened.

Although the photopolymerization initiator is not particularly limited, it 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"), 2,4,6-trimethylbenzoyl-diphenyl-phosphine Examples include fin oxide (manufactured by BASF, "LUCIRIN TPO").

The photopolymerization initiator may contain a photopolymerization initiator having an absorption band at a wavelength of less than 400 nm. Such a photopolymerization initiator is not particularly limited as long as it generates radicals by ultraviolet rays and initiates photopolymerization and has an absorption band at a wavelength of less than 400 nm. Any agent can be suitably used. For example, benzoin ether photoinitiator, acetophenone photoinitiator, α-ketol photoinitiator, photoactive oxime photoinitiator, benzoin photoinitiator, benzyl photoinitiator, benzophenone. A type photopolymerization initiator, a ketal type photopolymerization initiator, a thioxanthone type photopolymerization initiator, an acylphosphine oxide type photopolymerization initiator, etc. can be used.

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

In the adhesive, the content of the isocyanate crosslinking agent based on 100 parts by weight of the base polymer is preferably 0.1 parts by weight to 12 parts by weight.

The isocyanate crosslinking agent refers to a compound having two or more isocyanate groups (including isocyanate regenerating functional groups in which isocyanate groups are temporarily protected by blocking agents, quantization, etc.) in one molecule. Examples of the isocyanate crosslinking agent include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

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, 2,4-tolylene diisocyanate, Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, and polymethylene polyphenylisocyanate, trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industries Co., Ltd., product name "Coronate L") , trimethylolpropane/hexamethylene diisocyanate trimer adduct (made by Japan Polyurethane Industries Co., Ltd., product name "Coronate HL"), isocyanurate of hexamethylene diisocyanate (manufactured by Japan Polyurethane Industries Co., Ltd., product name "Coronate HX") ), trimethylolpropane adduct of xylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "D110N"), trimethylolpropane adduct of hexamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name "D160N") ); Examples include polyether polyisocyanates, polyester polyisocyanates, adducts of these with various polyols, polyisocyanates polyfunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among them, trimethylolpropane tolylene diisocyanate is preferably used as a crosslinking agent for the adhesive constituting the first adhesive layer, and trimethylolpropane xylene is preferably used as a crosslinking agent for the adhesive constituting the second adhesive layer. Diisocyanates are preferably used, and trimethylolpropane xylene diisocyanate is preferably used.

D-3. Ultraviolet Absorber Any suitable ultraviolet absorber can be used as the ultraviolet absorber. The ultraviolet absorber preferably has 0 to 3 hydroxyl groups in its molecular structure. Specifically, triazine-based UV absorbers, benzotriazole-based UV absorbers, benzophenone-based UV absorbers, oxybenzophenone-based UV absorbers, salicylic acid ester-based UV absorbers, cyanoacrylate-based UV absorbers, etc. can be mentioned. , 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, and triazine-based ultraviolet absorbers having two or less hydroxyl groups in one molecule, and benzotriazole-based ultraviolet absorbers having one benzotriazole skeleton in one molecule. The at least one UV absorber selected from the group consisting of triazole UV absorbers has good solubility in the monomer used for forming the acrylic pressure-sensitive adhesive composition, and has a wavelength of around 380 nm. It is preferable because of its high ultraviolet absorption ability. The ultraviolet absorbers may be used alone or in combination of two or more.

D-4. Dye Compound The dye compound preferably has an absorption spectrum with a maximum absorption wavelength in a wavelength range of 380 nm to 430 nm. By using such a dye compound and an ultraviolet absorber in combination, it is possible to sufficiently absorb light in a region (wavelength 380 nm to 430 nm) that does not affect the light emission of the organic EL element, and also to reduce the light emission of the organic EL element. The region (longer wavelength side than 430 nm) can be sufficiently transmitted.

The half 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. Thereby, light in a region that does not affect the light emission of the organic EL element can be sufficiently absorbed, while light with wavelengths longer than 430 nm can be sufficiently transmitted.

D-5. Other Components The adhesive composition may contain other components such as a silane coupling agent, an antioxidant, an anti-aging agent, and a plasticizer, as necessary. Examples of the antioxidant include phenol-based, phosphorus-based, sulfur-based, and amine-based antioxidants. Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, and 3-acryloxypropyl Examples include (meth)acrylic group-containing silane coupling agents such as trimethoxysilane, isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane, and acetoacetyl group-containing silane coupling agents.

E. Organic EL Display Device The polarizing plate with a retardation layer described in items A to D above can be used in an image display device. Therefore, the present invention also includes an image display device using such an optical laminate. Typical 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 sections A to D above.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. The method for measuring each characteristic is as follows.
(1) Thickness The thickness of the retardation layer was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., MCPD2000). Further, the thickness of layers other than the retardation layer was 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 using an automatic birefringence measurement device (Automatic birefringence meter KOBRA-WPR, manufactured by Oji Scientific Instruments Co., Ltd.), and the in-plane retardation Re and The thickness direction retardation Rth was calculated.
(3) Elastic modulus of adhesive layer For the adhesives used in the examples and comparative examples, the temperature dependence of the storage elastic modulus G' was measured using a dynamic viscoelasticity measuring device (trade name: ARES, manufactured by Rheometrics). The measured value G' (25°C) was taken as the elastic modulus.

<Manufacture example 1>
(Preparation of polarizing plate)
A long roll of polyvinyl alcohol film (manufactured by Kuraray, product name "PE3000") with a thickness of 30 μm was uniaxially stretched in the longitudinal direction to a length of 5.9 times using a roll stretching machine, while at the same time swelling, dyeing, A polarizer with a thickness of 12 μm was produced by crosslinking, washing, and finally drying.
Specifically, in the swelling treatment, the film was stretched 2.2 times while being treated with pure water at 20°C. Next, the dyeing process was carried out in an aqueous solution at 30 °C in which the weight ratio of iodine and potassium iodide was 1:7, and the iodine concentration was adjusted so that the transmittance of the polarizing film to be produced was 45.0%. However, it was stretched 1.4 times. Furthermore, a two-stage crosslinking process was adopted for the crosslinking process, and the first crosslinking process was performed in an aqueous solution containing boric acid and potassium iodide at 40°C, and was stretched to 1.2 times. The boric acid content of the aqueous solution for the first stage crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage of crosslinking treatment, the film was stretched to 1.6 times while being treated in an aqueous solution containing boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution for the second stage crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Further, the cleaning treatment was performed using a potassium iodide aqueous solution at 20°C. The potassium iodide content of the aqueous solution for cleaning treatment was 2.6% by weight. Finally, the drying process was performed 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 layer having an HC layer on one side of the TAC film were applied to both sides of the obtained polarizer via a polyvinyl alcohol adhesive, respectively. A TAC film (thickness: 32 μm) was bonded to obtain a polarizing plate 1 in which protective films were bonded to both sides of a polarizer.

ポリエチレンテレフタレート（ＰＥＴ）フィルム（厚み３８μｍ）の表面を、ラビング布を用いてラビングし、配向処理を施した。配向処理の条件は、ラビング回数（ラビングロール個数）は１、ラビングロール半径ｒは７６．８９ｍｍ、ラビングロール回転数ｎｒは１５００ｒｐｍ、フィルム搬送速度ｖは８３ｍｍ／ｓｅｃであり、ラビング強度ＲＳおよび押し込み量Ｍは表１に示すような５種類の条件（ａ）～（ｅ）で行った。 <Manufacture example 2>
(Preparation of retardation layer A)
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 a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by Ciba Specialty Chemicals, trade name "Paliocolor LC242", represented by the following formula). A liquid crystal composition (coating liquid) was prepared by dissolving 3 g of Irgacure 907'') in 40 g of toluene.

The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed using a rubbing cloth to perform orientation treatment. The conditions for the orientation treatment are: the number of rubbings (number of rubbing rolls) is 1, the rubbing roll radius r is 76.89 mm, the rubbing roll rotation speed nr is 1500 rpm, the film conveyance speed v is 83 mm/sec, the rubbing strength RS and the pushing amount. M was conducted under five conditions (a) to (e) as shown in Table 1.

The direction of the alignment treatment was set to be −75° when viewed from the viewing side with respect to the direction of the absorption axis of the polarizer when it was attached to the polarizing plate. The above-mentioned coating liquid was applied to this alignment-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. Although some disorder occurred in the orientation of the liquid crystal compound under conditions (d) and (e), it was at a level that caused no problem in practical use. A retardation layer A was formed on the PET film by irradiating the thus formed liquid crystal layer with light of 1 mJ/cm ² using a metal halide lamp and curing the liquid crystal layer. The thickness of the retardation layer A was 2 μm, and the in-plane retardation Re was 270 nm. Furthermore, the retardation layer A had a refractive index distribution of nx>ny=nz.

<Manufacture example 3>
(Preparation of retardation layer B)
The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed using a rubbing cloth to perform orientation treatment. The direction of the alignment treatment was set to be −15° when viewed from the viewing side with respect to the direction of the absorption axis of the polarizer when it was attached to the polarizing plate. A liquid crystal coating liquid similar to that described 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 thickness of the retardation layer B was 1.2 μm, and the in-plane retardation Re was 140 nm. Furthermore, the retardation layer B had a refractive index distribution of nx>ny=nz.

<Manufacture example 4>
(Preparation of adhesive layer A)
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirring device, 94.9 parts of butyl acrylate, 5 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, and dibenzoyl peroxide were added as monomers. After adding 0.3 parts to 100 parts (solid content) together with ethyl acetate and reacting at 60°C for 7 hours under a nitrogen gas stream, ethyl acetate was added to the reaction solution to obtain a weight average molecular weight of 2.2 million. A solution containing an acrylic polymer (solid content concentration 30% by weight) was obtained. Per 100 parts of the solid content of the acrylic polymer solution, 0.6 part of trimethylolpropane tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Coronate L") and 0.075 part of γ-glycidoxypropylmethoxy. Silane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") was blended to obtain an adhesive composition (solution).
The above adhesive composition was applied to a separator made of a polyester film whose surface had been treated with a silicone release agent, and heat treated at 155° C. for 3 minutes to obtain an adhesive layer A having a thickness of 20 μm. The elastic modulus of adhesive layer A at 25° C. was 1.4×10 ⁵ Pa.

<Manufacture example 5>
(Preparation of adhesive layer B)
99 parts of butyl acrylate, 1.0 part of 4-hydroxybutyl acrylate, and 0.3 part of 2,2'-azobisisobutyronitrile were placed in a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirring device. After adding 50% of the acrylic polymer with ethyl acetate and reacting for 4 hours at 60°C under a nitrogen gas stream, ethyl acetate was added to the reaction solution to prepare a solution containing an acrylic polymer with a weight average molecular weight of 1.65 million (solid content concentration 30 %) was obtained. Per 100 parts of the solid content of the acrylic polymer solution, 0.15 parts of dibenzoyl peroxide (manufactured by NOF Corporation, product name "Niper BO-Y") and 0.1 part of trimethylolpropane xylene diisocyanate (manufactured by Mitsui Takeda Chemical Co., Ltd., product name "Takenate D110N") and 0.2 parts of a silane coupling agent (manufactured by Soken Chemical Co., Ltd., product name "A-100", acetoacetyl group-containing silane coupling agent). A pressure-sensitive adhesive composition (solution) was obtained.
The above adhesive composition was applied to a separator made of a polyester film whose surface had been treated with a silicone release agent, and heat treated at 155° C. for 3 minutes to obtain an adhesive layer B having a thickness of 20 μm. The elastic modulus of adhesive layer B at 25° C. was 8.1×10 ⁴ Pa.

[Example 1]
The TAC film surface of the above polarizing plate and retardation layer A were bonded together via an ultraviolet curable adhesive so that the angle between the absorption axis of the polarizing plate and the slow axis of retardation layer A was 75°. . Next, the retardation layer A and the retardation layer B were bonded together via the 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, by bonding the adhesive layer B to the surface of the retardation layer B, a polarizing plate 1 with a retardation layer was obtained.

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

[Comparative example 2]
Except that the retardation layer A and the retardation layer B were bonded together using an ultraviolet curable adhesive (elastic modulus at 25° C.: greater than 1.0×10 ⁶ Pa) instead of the adhesive layer A. A polarizing plate 3 with a retardation layer was obtained in the same manner as in Example 1.

(evaluation)
The following evaluations were performed on the polarizing plates with retardation layers obtained in Examples and Comparative Examples. The results are shown in Table 2.
<Heat shock resistance>
The polarizing plate with a retardation layer was cut into a size of 120 mm x 60 mm and bonded to glass via the adhesive layer B on the outermost surface to prepare a test sample. This test sample was placed in a heat shock tester, and a heat shock test was performed by holding it at -40°C for 30 minutes and then holding it at 85°C for 30 minutes for 100 cycles. After that, cracks in the retardation layer were detected using an optical microscope. I checked to see if it was there.
In the polarizing plate 2 with a retardation layer, cracks were observed in the retardation layer, but in the polarizing plate 1 with a retardation layer, no retardation cracks were observed.
<Heat resistance>
The polarizing plate with a retardation layer was cut into a size of 120 mm x 60 mm and bonded to glass via the adhesive layer B on the outermost surface to prepare a test sample. This test sample was placed in an oven at 85° C. and stored for 500 hours, and then placed on a reflective plate to visually confirm the presence or absence of unevenness.
In the polarizing plate 3 with a retardation layer, unevenness in which the peripheral color turned red was strongly visible, but in the polarizing plate 1 with a retardation layer, no unevenness was observed.

As is clear from Table 2, in the polarizing plate with a retardation layer of the example, cracks in the retardation layer are suppressed and occurrence of unevenness is suppressed.

The optical laminate of the present invention is suitably used for image display devices such as organic EL display devices.

10 Polarizing plate 20 First retardation layer 30 Adhesive layer 40 Second retardation layer 50 Adhesive layer 100 Polarizing plate with retardation layer

Claims (2)

It has a polarizing plate, a first retardation layer, a first adhesive layer, a second retardation layer, and a second adhesive layer in this order,
The polarizing plate and the first retardation layer are bonded together via an ultraviolet curable adhesive,
The first retardation layer and the second retardation layer contain a liquid crystal compound,
The first adhesive layer has a thickness of 5 μm to 30 μm and an elastic modulus of 10 ⁵ Pa to 10 ⁶ Pa at 25° C.,
The second adhesive layer is composed 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 ⁴ Pa or less at 25° C.
Polarizing plate with retardation layer. An organic EL display device comprising the polarizing plate with a retardation layer according to claim 1.

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