CN118151283A

CN118151283A - Polarizing plate with retardation layer and image display device

Info

Publication number: CN118151283A
Application number: CN202311667988.2A
Authority: CN
Inventors: 有贺草平
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2022-12-07
Filing date: 2023-12-07
Publication date: 2024-06-07
Also published as: JP2024082166A; KR20240085207A; TW202424549A

Abstract

The present invention relates to a polarizing plate with a retardation layer and an image display device. The present invention provides a polarizing plate with a retardation layer, which can realize excellent reflection color tone, more specifically, can realize neutral reflection color tone with suppressed coloring when applied to an organic EL display device. The polarizing plate with a retardation layer comprises, in order, a polarizing plate comprising a polarizer, a first retardation layer, a second retardation layer, a third retardation layer, and a fourth retardation layer, wherein the refractive index characteristics of the second retardation layer and the fourth retardation layer show a relationship of nx > ny > nz, the refractive index characteristics of the first retardation layer and the third retardation layer show a relationship of nz > nx=ny, re (550) of the second retardation layer is 200nm to 300nm, re (550) of the fourth retardation layer is 120nm to 170nm, the slow axis of the second retardation layer forms an angle of 5 DEG to 25 DEG with the absorption axis of the polarizer, and the slow axis of the fourth retardation layer forms an angle of 65 DEG to 85 DEG with the absorption axis of the polarizer.

Description

Polarizing plate with retardation layer and image display device

Technical Field

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

Background

In recent years, image display devices (organic EL display devices) having organic EL panels mounted thereon have been proposed as thin displays are becoming popular. Since the organic EL panel has a metal layer with high reflectivity, problems such as reflection of external light and reflection of background are likely to occur. Therefore, it is known to prevent these problems by providing a circular polarizer on the viewing side. As a general circularly polarizing plate, a retardation layer functioning as a λ/4 plate is known to be laminated such that its slow axis forms an angle of about 45 ° with respect to the absorption axis of the polarizer. Further, from the viewpoint of obtaining anti-reflection properties in a wide band and a wide viewing angle, there have been proposed circular polarizers further including a retardation layer functioning as a λ/2 plate and/or a retardation layer exhibiting refractive index properties of nz > nx=ny (for example, patent documents 1 and 2). However, there is still room for further improvement in the reflection tone when the circularly polarizing plate is applied to an organic EL display device.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 6786640

Patent document 2: japanese patent No. 5822006

Disclosure of Invention

Technical problem to be solved by the invention

The main object of the present invention is to provide a polarizing plate with a retardation layer, which can realize an excellent reflection color tone, more specifically, can realize a neutral reflection color tone suppressed when applied to an organic EL display device.

Means for solving the technical problems

[1] The polarizing plate with a retardation layer according to the embodiment of the present invention comprises, in order: comprising a polarizer, a first phase difference layer, a second phase difference layer, a third phase difference layer, and a fourth phase difference layer,

The refractive index characteristics of the second phase difference layer and the fourth phase difference layer show a relationship in which nx > ny.gtoreq.nz,

The refractive index characteristics of the first retardation layer and the third retardation layer show a relationship of nz > nx=ny,

Re (550) of the second phase difference layer is 200nm to 300nm,

Re (550) of the fourth phase difference layer is 120nm to 170nm,

The angle formed by the slow axis of the second phase difference layer and the absorption axis of the polarizer is 5-25 degrees,

The angle formed by the slow axis of the fourth phase difference layer and the absorption axis of the polarizer is 65-85 degrees.

[2] The polarizing plate with a retardation layer according to item [1], wherein Rth (550) of the first retardation layer is from-10 nm to-70 nm.

[3] The polarizing plate with a retardation layer according to [1] or [2], wherein Rth (550) of the third retardation layer is from-50 nm to-110 nm.

[4] The polarizing plate with a retardation layer according to any one of the above [1] to [3], wherein Rth (550) of the first retardation layer is from-10 nm to-70 nm, and Rth (550) of the third retardation layer is from-50 nm to-110 nm.

[5] The polarizing plate with a retardation layer according to any one of the above [1] to [4], which can be used in an organic EL display device.

[6] An image display device according to an embodiment of the present invention includes the polarizing plate with a retardation layer described in any one of [1] to [5] above.

Effects of the invention

According to the embodiment of the present invention, a polarizing plate with a retardation layer that can realize an excellent reflection color tone, more specifically, a neutral reflection color tone in which coloring is suppressed when applied to an organic EL display device can be provided.

Drawings

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

Fig. 2 is a schematic cross-sectional view showing a schematic configuration of an organic EL display device according to an embodiment of the present invention.

Symbol description

10. Polarizing plate

12. Polarizer

14. Protective layer

20. First phase difference layer

30. Second phase difference layer

40. Third phase difference layer

50. Fourth phase difference layer

60. Adhesive layer

100. Polarizing plate with phase difference layer

200. Organic EL display device

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The drawings are for clarity of description, and therefore, width, thickness, shape, and the like of each portion are shown schematically in comparison with the embodiment, but are merely examples, and do not limit the explanation of the present invention. In the present specification, (meth) acrylic acid means acrylic acid and/or methacrylic acid. In the present specification, "to" representing a range of values includes values of the upper limit and the lower limit thereof.

(Definition of terms and symbols)

The terms and symbols in the present specification are defined as follows.

(1) Refractive index (nx, ny, nz)

"Nx" is the refractive index in the direction in which the in-plane refractive index becomes maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

"Re (lambda)" is the in-plane retardation measured at 23℃by light of wavelength lambda nm. For example, "Re (550)" is the in-plane retardation measured at 23℃by light having a wavelength of 550 nm. Re (λ) is represented by the following formula when the thickness of the layer (film) is d (nm): re (λ) = (nx-ny) ×d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction measured at 23℃by light having a wavelength of λnm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23℃by light having a wavelength of 550 nm. Rth (λ) is represented by the following formula when the thickness of the layer (film) is d (nm): rth (λ) = (nx-nz) ×d.

(4) Nz coefficient

The Nz coefficient is obtained by using nz=rth/Re.

(5) Angle of

When referring to an angle in this specification, the angle includes both clockwise rotation and counterclockwise rotation relative to a reference direction. Thus, the method is applicable to a variety of applications. For example, "45" means 45 ° clockwise and 45 ° counterclockwise.

A. Polarizing plate with phase difference layer

The polarizing plate with a retardation layer according to the embodiment of the present invention comprises, in order: a polarizer including a polarizer, a first phase difference layer, a second phase difference layer, a third phase difference layer, and a fourth phase difference layer. The refractive index characteristics of the second phase difference layer and the fourth phase difference layer show a relationship in which nx > ny > nz; the refractive index characteristics of the first retardation layer and the third retardation layer show a relationship of nz > nx=ny; re (550) of the second phase difference layer is 200nm to 300nm; re (550) of the fourth phase difference layer is 120nm to 170nm; the angle formed by the slow axis of the second phase difference layer and the absorption axis of the polarizer is 5-25 degrees; the angle formed by the slow axis of the fourth phase difference layer and the absorption axis of the polarizer is 65-85 degrees. By combining the first phase difference layer and the third phase difference layer each having refractive index characteristics of nz > nx=ny with the second phase difference layer and the fourth phase difference layer each functioning as a λ/2 plate and a λ/4 plate so as to have the above-described configuration, a polarizing plate with a phase difference layer capable of realizing a very excellent reflection color tone when used in an image display device (for example, an organic EL display device) can be obtained.

A-1 integral Structure of polarizing plate with retardation layer

Fig. 1 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate with a retardation layer 100 has a polarizing plate 10, a first retardation layer 20, a second retardation layer 30, a third retardation layer 40, and a fourth retardation layer 50 in this order.

The polarizing plate 10 includes a polarizer 12, and further includes a protective layer 14 disposed on the opposite side of the polarizer 12 from the side on which the first retardation layer 20 is disposed. In the example of the figure, no protective layer is arranged between the polarizer 12 and the adjacent first retardation layer 20, and the first retardation layer 20 is arranged adjacent to the polarizer 12. By omitting the protective layer in this manner, the polarizing plate 100 with the retardation layer can be thinned. The polarizing plate 100 with a retardation layer is preferably used in an organic EL display device in which the polarizer 12 is disposed on the visible side of the first retardation layer 20.

The polarizing plate 100 with a phase difference layer further has an adhesive layer 60 on the side of the fourth phase difference layer 50 opposite to the side on which the third phase difference layer 40 is disposed. The polarizing plate 100 with a retardation layer may be attached to an optical member such as an organic EL panel by the adhesive layer 60, for example. Although not shown, a release liner is attached to the surface of the pressure-sensitive adhesive layer 60 from a practical standpoint. The release liner may be temporarily attached until the polarizing plate with the retardation layer is supplied for use. By using a release liner, for example, the polarizing plate 100 with a retardation layer can be formed in a roll while protecting the adhesive layer 60.

The polarizing plate 100 with a retardation layer may further have other functional layers not shown. The kind, characteristics, number, combination, arrangement, and the like of the other functional layers that the polarizing plate with a retardation layer may have can be appropriately set according to the purpose. For example, the polarizing plate with a retardation layer may further have a conductive layer or an isotropic substrate with a conductive layer. A polarizing plate with a retardation layer having a conductive layer or an isotropic substrate with a conductive layer is used, for example, in a so-called internal touch panel type input display device in which a touch sensor is incorporated in an image display panel. Further, as another example, the polarizing plate with a retardation layer may further have another retardation layer. The optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient, photoelastic coefficient), thickness, arrangement, and the like of the other retardation layers can be appropriately set according to the purpose. As a specific example, another retardation layer (typically, a layer imparting (elliptical) circularly polarized light function, a layer imparting ultra-high retardation) that improves visibility when viewed through polarized sunglasses may be provided on the visible side of the polarizer. By providing such a layer, excellent visibility can be achieved even when a display screen is visually recognized through a polarized lens such as a polarized sunglasses, and the present invention can be preferably applied to an image display device that can be used outdoors.

The components constituting the polarizing plate 100 with a retardation layer are typically laminated via any appropriate adhesive layer. Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. Although not shown, the protective layer 14 is attached to the polarizer 12 via an adhesive layer (preferably, an active energy ray-curable adhesive) for example. The polarizing plate 10 and each retardation layer are laminated via an adhesive layer (preferably, an active energy ray-curable adhesive) or via an adhesive layer (preferably, an acrylic adhesive). The thickness of the adhesive layer is, for example, 0.1 μm or more, preferably 0.3 μm to 5 μm, more preferably 0.5 μm to 3 μm. The thickness of the pressure-sensitive adhesive layer is, for example, 3 μm or more, preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm.

The total thickness of the laminated portion from the polarizing plate 10 to the adhesive layer 60 (including the thickness of the adhesive layer) is, for example, 200 μm or less, preferably 150 μm or less, and is, for example, 30 μm or more, preferably 50 μm or more. The thickness of the laminated portion of the polarizing plate 10 to the fourth phase difference layer 50 (the thickness after the adhesive layer 60 is removed from the entire thickness) is, for example, 100 μm or less, preferably 80 μm or less, and is, for example, 20 μm or more, preferably 40 μm or more.

The polarizing plate 100 with the retardation layer may be a single plate or a long plate. The term "elongated" as used herein refers to an elongated shape sufficiently long with respect to the width and length, and includes, for example, an elongated shape having a length of 10 times or more, preferably 20 times or more, with respect to the width and length. The elongated laminate may be wound into a roll.

A-2 polarizing plate

The polarizing plate 10 includes a polarizer 12, and preferably further includes a protective layer 14 on the opposite side of the polarizer 12 from the side on which the first retardation layer 20 is disposed. The polarizing plate 10 may include a protective layer on the side of the polarizer 12 where the first retardation layer 20 is disposed, as needed.

A-2-1 polarizer

The polarizer 12 is typically a resin film containing a dichroic substance (e.g., iodine). Examples of the resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene-vinyl acetate copolymer partially saponified films.

The thickness of the polarizer is, for example, 18 μm or less, preferably 15 μm or less, more preferably 12 μm or less, and still more preferably 8 μm or less. The thickness of the polarizer is preferably 1 μm or more.

The polarizer preferably exhibits absorption dichroism at any one of wavelengths 380nm to 780 nm. The polarizer has a single-body transmittance of, for example, 40.0% to 46.0%, preferably 41.0% to 45.0%, and more preferably 41.5% to 44.5%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

The polarizer may be fabricated using any suitable method. Specifically, the polarizer may be made of a single-layer resin film, or may be made of a laminate including a base material.

The method for producing a polarizer from the single-layer resin film typically includes subjecting the resin film to a dyeing treatment using a dichroic substance such as iodine or a dichroic dye, and a stretching treatment. As the resin film, for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized PVA film, or an ethylene-vinyl acetate copolymer partially saponified film is used. The method may further comprise an insolubilization treatment, a swelling treatment, a crosslinking treatment, and the like. Since such a manufacturing method is well known and commonly used in the art, a detailed description thereof will be omitted.

The polarizer obtained using the laminate including the base material may be produced using, for example, a laminate of a resin base material and a resin film or a resin layer (typically, PVA-based resin layer). Specifically, the method can be manufactured by the following steps: coating a PVA-based resin solution on a resin substrate, drying the same, and forming a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminated body, and making the PVA resin layer into a polarizer. In the present embodiment, it is preferable to form a PVA-based resin layer containing a halide and a PVA-based resin on one side of a resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, stretching may further include air stretching the laminate at a high temperature (for example, 95 ℃ or higher) before stretching in an aqueous boric acid solution, if necessary. Further, in the present embodiment, it is preferable that the laminate is subjected to a drying shrinkage process in which the laminate is heated while being conveyed in the longitudinal direction and is shrunk by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes sequentially subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment. By introducing the auxiliary stretching, even when PVA is coated on the thermoplastic resin, crystallinity of PVA can be improved, and high optical characteristics can be achieved. In addition, by simultaneously improving the orientation of PVA in advance, even when immersed in water in the subsequent dyeing step or stretching step, problems such as deterioration in the orientation of PVA or dissolution can be prevented, and high optical characteristics can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, disorder of orientation and decrease of orientation of PVA molecules can be suppressed, and high optical characteristics can be achieved, as compared with the case where the PVA-based resin layer does not contain a halide. Further, by shrinking the laminate in the width direction by the drying shrinkage treatment, high optical characteristics can be achieved. The protective layer is laminated on a release surface after the resin substrate is released from the obtained laminate of the resin substrate and the polarizer or on a surface opposite to the release surface, whereby a polarizing plate can be obtained. Details of such a method for producing a polarizer are described in, for example, japanese patent application laid-open No. 2012-73580 and japanese patent No. 6470455. The entire disclosures of these publications are incorporated by reference into this specification.

A-2-2. Protective layer

The protective layer 14 may be formed of any suitable resin film that can be used as a protective layer of a polarizer, for example. Specific examples of the resin that is the main component of the resin film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyether sulfone-based resins, polysulfone-based resins, cycloolefin-based resins such as polystyrene-based resins and polynorbornene-based resins, polyolefin-based resins, (meth) acrylic-based resins, and acetate-based resins.

The polarizing plate 100 with a retardation layer is typically disposed on the visible side of the image display device, and the protective layer 14 is disposed on the visible side. Therefore, the protective layer 14 may be subjected to surface treatments such as Hard Coat (HC) treatment, antireflection treatment, anti-blocking treatment, antiglare treatment, and the like, as necessary.

The thickness of the protective layer is, for example, 5 μm to 80 μm, preferably 10 μm to 50 μm, and more preferably 15 μm to 35 μm. When the surface treatment is performed, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer.

A-3 first phase difference layer

The first retardation layer 20 is a so-called positive C plate whose refractive index characteristics show a relationship of nz > nx=ny. Here, "nx=ny" includes not only the case where nx and ny are exactly equal but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the first retardation layer may be less than 10nm.

The thickness direction retardation Rth (550) of the first retardation layer is, for example, -10nm to-120 nm, preferably, -10nm to-100 nm, more preferably, -10nm to-70 nm, still more preferably, -20nm to-60 nm.

The first retardation layer preferably has a puncture elastic modulus of 50g/mm or more, more preferably 52g/mm or more, and still more preferably 55g/mm or more. The first retardation layer has a puncture elastic modulus of, for example, 200g/mm or less. When the puncture elastic modulus of the first retardation layer is in the above range, dimensional changes of the second retardation layer (for example, expansion, shrinkage, and the like of the second retardation layer composed of a stretched film of a resin film) can be preferably suppressed. In the present specification, the puncture elastic modulus is a value obtained by dividing a force (g) when the retardation film is broken (or split) immediately after the needle (puncture tool) is vertically inserted into the main surface of the retardation film (for example, the first retardation layer) by a deformation (mm) at that time. The needle may have a tip diameter of 1mm phi and 0.5R. The speed of the puncture needle may be 0.33 cm/sec. The measurement of the puncture elastic modulus can be performed by sandwiching the retardation film between 2 plates each having a circular hole of 15mm or less in diameter (for example, 11mm in diameter) through which a needle can pass. The measurement of the modulus of elasticity in puncture can be performed in an environment at a temperature of 23 ℃. For example, the puncture elastic modulus of 5 retardation films may be measured, and the average value thereof may be used as the puncture elastic modulus of the retardation film. The puncture elastic modulus can be measured by a commercially available device. Examples of the commercially available devices include a portable compression tester "KES-G5 (KES-G5 needle penetration measuring standard)" manufactured by Kato-tech, and a small-sized bench tester "EZ Test" manufactured by Shimadzu corporation.

The first phase difference layer is formed of any suitable material. In one embodiment, the first phase difference layer is composed of a resin film. In another embodiment, the first retardation layer is composed of an alignment cured layer of a liquid crystal compound.

As a material of the resin film constituting the first retardation layer, a resin material having negative birefringence is typically given. The resin having negative birefringence is a resin exhibiting a property that the refractive index in the direction perpendicular to the stretching direction becomes maximum when uniaxially stretched. Examples of the resin having negative birefringence include resins having a chemical bond or functional group having a large polarization anisotropy such as an aromatic ring or carbonyl group introduced into a side chain. Specific examples of the resin having negative birefringence include acrylic resins, styrene resins, maleimide resins, modified polyolefin resins, and fumarate resins. The above resin materials may be used alone or two or more kinds may be used in combination.

The acrylic resin can be obtained, for example, by addition polymerization of an acrylic monomer. Examples of the acrylic resin include polymethyl methacrylate (PMMA), polybutyl methacrylate, and polycyclohexyl methacrylate.

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

The maleimide resin can be obtained, for example, by addition polymerization of a maleimide monomer. Examples of maleimide monomers include N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-propylphenyl) maleimide, N- (2-isopropylphenyl) maleimide, N- (2, 6-dimethylphenyl) maleimide, N- (2, 6-dipropylphenyl) maleimide, N- (2, 6-diisopropylphenyl) maleimide, N- (2-methyl-6-ethylphenyl) maleimide, N- (2-chlorophenyl) maleimide, N- (2, 6-dichlorophenyl) maleimide, N- (2-bromophenyl) maleimide, N- (2, 6-dibromophenyl) maleimide, N- (2-biphenylyl) maleimide, and N- (2-cyanophenyl) maleimide. The maleimide monomer is available from Tokyo chemical industry Co.

In the addition polymerization, the birefringent properties of the resulting resin can be controlled by substituting side chains after polymerization, or by subjecting them to maleimide reaction, grafting reaction, or the like.

The above resin having negative birefringence may be copolymerized with other monomers. By copolymerizing other monomers, brittleness or molding processability, heat resistance can be improved. Examples of the other monomer include olefins such as ethylene, propylene, 1-butene, 1, 3-butadiene, 2-methyl-1-butene, 2-methyl-1-pentene, and 1-hexene; acrylonitrile; methyl acrylate, methyl methacrylate and other (meth) acrylates; maleic anhydride; vinyl esters such as vinyl acetate, and the like.

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

As the resin having negative birefringence, styrene-maleic anhydride copolymer, styrene-acrylonitrile copolymer, styrene- (meth) acrylate copolymer, styrene-maleimide copolymer, vinyl ester-maleimide copolymer, olefin-maleimide copolymer, and the like are preferably used. These may be used singly or in combination of two or more. These resins can exhibit high negative birefringence and are excellent in heat resistance. These resins are available, for example, from Novachem Japan or from the company of the chemical industry, inc. of Sichuan.

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

[ Chemical Structure 1]

In the general formula (I), R ₁～R₅ each independently represents hydrogen, a halogen atom, a carboxylic acid ester, a hydroxyl group, a nitro group, or a linear or branched alkyl or alkoxy group having 1 to 8 carbon atoms (wherein R ₁ and R ₅ are not simultaneously hydrogen atoms), R ₆ and R ₇ represent hydrogen or a linear or branched alkyl or alkoxy group having 1 to 8 carbon atoms, and n represents an integer of 2 or more.

The resin having negative birefringence is not limited to the above, and for example, resins having negative birefringence described in japanese patent application laid-open No. 2008-544304 and japanese patent application laid-open No. 2008-544317 can be used.

The resin film forming the first retardation layer may further contain any appropriate additive as required. Specific examples of the additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, tackifiers, and the like. The kind and content of the additive may be appropriately set according to the purpose. The content of the additive in the resin film is, for example, about 3 to 10% by weight.

As a method for producing the first retardation layer composed of the resin film, any suitable production method can be used. In one embodiment, the resin film including the above resin material may be used as the first retardation layer directly (i.e., in an unstretched state) after the film is formed. For example, when a film is formed by a solution film forming method using a resin solution containing the above resin material, stress is generated due to volume shrinkage when the resin solution is dried on a support, and the molecular chains of the polymer tend to be oriented in the in-plane direction. Thus, when a resin material having high birefringence and negative intrinsic birefringence is used, a coating film having large thickness-direction birefringence can be formed on the support by shrinkage during drying, and the coating film can be used as a positive C plate as it is.

The thickness of the first retardation layer as the resin film is, for example, 1 μm to 40 μm, preferably 3 μm to 35 μm, more preferably 5 μm to 30 μm.

The alignment cured layer of the liquid crystal compound is a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer, and the alignment state is fixed. Further, the "alignment cured layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer. As the alignment cured layer of the liquid crystal compound constituting the first phase difference layer, an alignment cured layer of a liquid crystal material fixed in a vertical alignment may be preferably exemplified. The liquid crystal material (liquid crystal compound) capable of vertically aligning the liquid crystal may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include those described in [0020] to [0028] of JP-A-2002-333642 and methods for forming the retardation layer.

The thickness of the first retardation layer as the alignment cured layer of the liquid crystal compound is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, still more preferably 0.5 μm to 5 μm.

A-4 second phase difference layer

The refractive index characteristics of the second phase difference layer 30 show a relationship of nx > ny.gtoreq.nz. In one embodiment, the second phase difference layer may function as a lambda/2 plate. The in-plane phase difference Re (550) of the second phase difference layer is, for example, 200nm to 300nm, preferably 220nm to 290nm, and more preferably 230nm to 280nm. Here, "ny=nz" includes not only the case where ny is strictly equal to nz but also the case where ny is substantially equal to nz. Therefore, ny < nz may be present within a range not impairing the effect of the present invention.

The Nz coefficient of the second phase difference layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained polarizing plate with a retardation layer is used in an image display device, a very excellent reflection color tone can be achieved.

The second phase difference layer is disposed such that its slow axis forms an angle of, for example, 5 ° to 25 °, preferably 10 ° to 20 °, and more preferably about 15 °, with the absorption axis of the polarizer 12. By such a constitution, a polarizing plate with a retardation layer having excellent circularly polarized light characteristics (as a result, excellent antireflection characteristics) can be obtained.

The second phase difference layer may exhibit an inverse dispersion wavelength characteristic in which the phase difference value increases with an increase in the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the phase difference value decreases with an increase in the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the second phase difference layer exhibits an inverse dispersive wavelength characteristic. In this case, re (450)/Re (550) of the second phase difference layer is, for example, 0.8 or more and less than 1, preferably 0.8 or more and 0.95 or less. With this configuration, extremely excellent antireflection characteristics can be achieved.

In one embodiment, the second phase difference layer comprises a resin having an absolute value of photoelastic coefficient of preferably 2×10 ^-11m²/N or less, more preferably 2.0×10 ^-13m²/N～1.5×10^-11m²/N, and still more preferably 1.0×10 ^-12m²/N～1.2×10^- ¹¹m²/N. When the absolute value of the photoelastic coefficient is in such a range, it is difficult to change the phase difference when shrinkage stress occurs during heating. As a result, thermal unevenness of the obtained image display device can be well prevented.

The second phase difference layer is formed of any suitable material that can satisfy the above characteristics. The second phase difference layer is constituted of, for example, a resin film or an alignment cured layer of a liquid crystal compound.

Examples of the resin contained in the resin film include polycarbonate-based resins, polyester-carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cycloolefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic-based resins. These resins may be used alone or in combination (e.g., blending, copolymerization). When the second phase difference layer exhibits the inverse dispersion wavelength characteristic, a resin film containing a polycarbonate-based resin or a polyester carbonate-based resin (hereinafter, may be simply referred to as a polycarbonate-based resin) may be preferably used. When the second phase difference layer exhibits flat wavelength dispersion characteristics, a resin film containing a cycloolefin resin can be preferably used.

Any suitable polycarbonate resin may be used as long as the effects of the present invention are obtained. For example, the polycarbonate resin includes: a structural unit derived from a fluorene-based dihydroxy compound; a structural unit derived from an isosorbide-based dihydroxy compound; and a structural unit derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanol, di-, tri-and polyethylene glycols, and alkylene glycols and spiro glycols. Preferably, the polycarbonate resin comprises: a structural unit derived from a fluorene-based dihydroxy compound; a structural unit derived from an isosorbide-based dihydroxy compound; and alicyclic dimethanol-derived structural units and/or di-, tri-or polyethylene glycol-derived structural units; further preferably comprises: a structural unit derived from a fluorene-based dihydroxy compound; a structural unit derived from an isosorbide-based dihydroxy compound; and structural units derived from di-, tri-or polyethylene glycols. The polycarbonate resin may contain other structural units derived from a dihydroxy compound, if necessary. Details of the polycarbonate resin that can be preferably used in the second phase difference layer are described in, for example, japanese patent application laid-open No. 2014-10291, japanese patent application laid-open No. 2014-26262, japanese patent application laid-open No. 2015-212816, japanese patent application laid-open No. 2015-212817, and Japanese patent application laid-open No. 2015-212818, and the descriptions of these publications are incorporated herein by reference.

The cycloolefin resin is a general term for a resin obtained by polymerizing cycloolefins as polymerization units, and examples thereof include resins described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Specific examples thereof include a ring-opened (co) polymer of cycloolefin, an addition polymer of cycloolefin, a copolymer (typically, a random copolymer) of cycloolefin and an α -olefin such as ethylene or propylene, a graft modified product obtained by modifying the copolymer with an unsaturated carboxylic acid or a derivative thereof, and a hydrogenated product thereof. Specific examples of cycloolefins include norbornene monomers. Examples of the norbornene monomer include norbornene and alkyl and/or alkylidene substituents thereof, for example, polar group substituents such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and halogen thereof; dicyclopentadiene, 2, 3-dihydro-dicyclopentadiene, and the like; polar group substituents such as dimethylbridged octahydronaphthalene, alkyl and/or alkylidene substituents thereof, and halogen, for example, 6-methyl-1, 4:5, 8-dimethylbridged-1, 4a,5,6,7,8 a-octahydronaphthalene 6-ethyl-1, 4:5, 8-dimethyl-1, 4a,5,6,7,8 a-octahydronaphthalene, 6-ethylidene-1, 4:5, 8-dimethyl-1, 4a,5,6,7,8 a-octahydronaphthalene 6-chloro-1, 4:5, 8-dimethylbridge-1, 4a,5,6,7,8 a-octahydronaphthalene, 6-cyano-1, 4:5, 8-dimethylbridge-1, 4a,5,6,7,8 a-octahydronaphthalene 6-pyridyl-1, 4:5, 8-dimethylbridge-1, 4a,5,6,7,8 a-octahydronaphthalene, 6-methoxycarbonyl-1, 4:5, 8-dimethylbridge-1, 4a,5,6,7,8 a-octahydronaphthalene, and the like; 3 to 4 polymers of cyclopentadiene, for example 4,9:5, 8-dimethyl-3 a, 4a,5, 8a,9 a-octahydro-1H-benzindene 4,11:5,10:6, 9-trimethyl-3 a, 4a, 5a,6, 9a,10 a,11 a-dodecahydro-1H-cyclopentaanthracene, and the like.

Other cycloolefins which can be ring-opening polymerized may be used in combination within a range not to impair the object of the present invention. Specific examples of such cycloolefins include compounds having 1 reactive double bond such as cyclopentene, cyclooctene, and 5, 6-dihydrodicyclopentadiene.

The cycloolefin resin preferably has a number average molecular weight (Mn) of 25,000 ～ 200,000, more preferably 30,000 ～ 100,000, and still more preferably 40,000 ～ 80,000, as measured by Gel Permeation Chromatography (GPC) using a toluene solvent. When the number average molecular weight is in the above range, a resin film excellent in mechanical strength, solubility, formability, and casting workability can be obtained.

When the cycloolefin resin is obtained by hydrogenating a ring-opened polymer of a norbornene monomer, the hydrogenation ratio is preferably 90% or more, more preferably 95% or more, and still more preferably 99% or more. When the content is within this range, the heat deterioration resistance, the light deterioration resistance and the like are excellent.

Various products are commercially available as the cycloolefin resin. As a specific example of this, it is possible, examples thereof include "ZEONEX", "ZEONOR", which are tradenames of ZEON, JSR, TICONA, and Sanjing chemical, which are tradenames of TOPAS, APEL.

The second phase difference layer can be obtained by, for example, stretching the unstretched resin film. In the stretching, any suitable stretching method, stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction) may be employed. Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, and fixed end shrinkage may be used alone or simultaneously or sequentially. The stretching direction may be performed in various directions or dimensions such as a longitudinal direction, a width direction, a thickness direction, and an oblique direction. The stretching temperature is preferably from Tg to 30℃to Tg+60℃and more preferably from Tg to 10℃to Tg+50℃relative to the glass transition temperature (Tg) of the resin film.

By appropriately selecting the stretching method and the stretching conditions, a resin film having the desired optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient) can be obtained.

In one embodiment, the second phase difference layer is produced by uniaxially stretching or uniaxially stretching the unstretched resin film at the fixed end. As a specific example of the fixed-end uniaxial stretching, a method of stretching a resin film in the width direction (transverse direction) while advancing the resin film in the longitudinal direction is given. The stretching ratio is preferably 1.1 to 3.5 times.

The thickness of the second phase difference layer of the stretched film as the resin film is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, more preferably 10 μm to 60 μm, still more preferably 20 μm to 50 μm.

In the second phase difference layer composed of the alignment cured layer of the liquid crystal compound, typically, the rod-like liquid crystal compound is aligned (parallel alignment) in a state of being aligned in the slow axis direction of the second phase difference layer. Examples of the rod-like liquid crystal compound include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably capable of polymerization. When the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.

The alignment cured layer (liquid crystal alignment cured layer) of the above-mentioned liquid crystal compound can be formed by the following method: the method comprises the steps of applying an alignment treatment to a surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface, aligning the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. As the orientation treatment, any suitable orientation treatment may be employed. Specifically, there may be mentioned a mechanical alignment treatment, a physical alignment treatment, and a chemical alignment treatment. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical alignment treatment include a magnetic field alignment treatment and an electric field alignment treatment. Specific examples of the chemical alignment treatment include oblique vapor deposition and photo alignment treatment. The process conditions of the various orientation processes may employ any suitable conditions according to purposes.

The alignment of the liquid crystal compound is performed by performing a treatment at a temperature at which a liquid crystal phase is exhibited according to the kind of the liquid crystal compound. By performing such a temperature treatment, the liquid crystal compound is in a liquid crystal state, and the liquid crystal compound is aligned according to the alignment treatment direction of the substrate surface.

In one embodiment, the fixing of the alignment state is performed by cooling the liquid crystal compound aligned as above. When the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the liquid crystal compound which has been aligned as described above to polymerization treatment or crosslinking treatment.

As the liquid crystal compound, any suitable liquid crystal polymer and/or liquid crystal monomer is used. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination. Specific examples of the liquid crystal compound and a method for producing the liquid crystal alignment cured layer are described in, for example, japanese patent application laid-open No. 2006-163343, japanese patent application laid-open No. 2006-178389, and International publication No. 2018/123551. The descriptions of these publications are incorporated by reference into the present specification.

The thickness of the second phase difference layer as the liquid crystal alignment cured layer is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, still more preferably 1 μm to 4 μm.

A-5 third phase difference layer

The third phase difference layer 40 is a so-called positive C plate whose refractive index characteristics show a relationship of nz > nx=ny. Here, "nx=ny" includes not only the case where nx and ny are exactly equal but also the case where nx and ny are substantially equal. That is, the in-plane phase difference Re (550) of the third phase difference layer may be less than 10nm.

The thickness direction retardation Rth (550) of the third phase difference layer is, for example, -10nm to-120 nm, preferably, -30nm to-110 nm, more preferably, -50nm to-110 nm, and still more preferably, -60nm to-100 nm. In one embodiment, the sum of Rth (550) of the first phase difference layer and the third phase difference layer is, for example, -80nm to-160 nm, preferably, -100nm to-140 nm, more preferably, -110nm to-130 nm.

The third phase difference layer preferably has a puncture elastic modulus of 50g/mm or more, more preferably 52g/mm or more, and still more preferably 55g/mm or more. The third phase difference layer has a puncture elastic modulus of 200g/mm or less, for example. When the puncture elastic modulus of the third phase difference layer is within the above range, dimensional changes of the adjacent phase difference layers (for example, expansion, contraction, and the like of the second phase difference layer and/or the fourth phase difference layer made of a stretched film of a resin film) can be preferably suppressed.

The third phase difference layer is formed of any suitable material. In one embodiment, the third phase difference layer is composed of a resin film. In another embodiment, the third phase difference layer is composed of an alignment cured layer of a liquid crystal compound.

As a material of the resin film constituting the third phase difference layer, the same resin material as the resin film constituting the first phase difference layer can be used. For example, by adjusting the thickness of the resin film, a third phase difference layer having a desired thickness direction phase difference can be obtained.

The thickness of the third phase difference layer as the resin film is, for example, 1 μm to 40 μm, preferably 3 μm to 35 μm, more preferably 5 μm to 30 μm.

As the alignment cured layer of the liquid crystal compound constituting the third retardation layer and the method of forming the same, the alignment cured layer of the liquid crystal compound constituting the first retardation layer and the method of forming the same can be similarly applied. The first phase difference layer and the third phase difference layer may be made of the same material or different materials. For example, one of the layers may be formed of a resin film, and the other may be formed of a liquid crystal alignment cured layer. The first retardation layer formed of a resin film can also function as a protective layer for a polarizer when the protective layer on the first retardation layer side of the polarizer is omitted.

The thickness of the third phase difference layer as the alignment cured layer of the liquid crystal compound is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, still more preferably 0.5 μm to 5 μm.

A-6 fourth phase difference layer

The refractive index characteristics of the fourth phase difference layer 50 show a relationship of nx > ny.gtoreq.nz. In one embodiment, the fourth phase difference layer may function as a lambda/4 plate. The in-plane phase difference Re (550) of the fourth phase difference layer is, for example, 120nm to 170nm, preferably 130nm to 160nm, and more preferably 140nm to 150nm. Here, "nx=ny" includes not only the case where ny is strictly equal to nz but also the case where ny is substantially equal to nz. Therefore, ny < nz may be present within a range not impairing the effect of the present invention.

The Nz coefficient of the fourth phase difference layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained polarizing plate with a retardation layer is used in an image display device, a very excellent reflection color tone can be achieved.

The fourth phase difference layer is disposed such that the slow axis thereof forms an angle with the absorption axis of the polarizer 12, for example, 65 ° to 85 °, preferably 70 ° to 80 °, and more preferably about 75 °. The angle between the slow axis of the fourth phase difference layer and the slow axis of the second phase difference layer is, for example, 50 ° to 70 °, preferably 55 ° to 65 °, and more preferably about 60 °. By such a constitution, a polarizing plate with a retardation layer having excellent circularly polarized light characteristics (as a result, excellent antireflection characteristics) can be obtained.

The fourth phase difference layer may exhibit an inverse dispersion wavelength characteristic in which the phase difference value increases with an increase in the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the phase difference value decreases with an increase in the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the fourth phase difference layer exhibits an inverse dispersive wavelength characteristic. In this case, re (450)/Re (550) of the fourth phase difference layer is, for example, 0.8 or more and less than 1, preferably 0.8 or more and 0.95 or less. With this configuration, extremely excellent antireflection characteristics can be achieved.

In one embodiment, the fourth phase difference layer contains a resin having an absolute value of a photoelastic coefficient of preferably 2×10 ^-11m²/N or less, more preferably 2.0×10 ^-13m²/N～1.5×10^-11m²/N, and still more preferably 1.0×10 ^-12m²/N～1.2×10^- ¹¹m²/N. If the absolute value of the photoelastic coefficient is in such a range, it is difficult to change the phase difference when stress is generated during heating. As a result, thermal unevenness of the obtained image display device can be well prevented.

The fourth phase difference layer is formed of any appropriate material that can satisfy the above characteristics. The fourth phase difference layer is constituted of, for example, a resin film or an alignment cured layer of a liquid crystal compound.

The resin contained in the resin film may be the same as the resin contained in the resin film constituting the second phase difference layer. The fourth phase difference layer can be obtained, for example, by stretching an unstretched resin film. As described in connection with the second phase difference layer, any suitable stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) may be used in stretching. By appropriately selecting the stretching method and stretching conditions, a resin film having the above-described desired optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient) can be obtained.

The thickness of the fourth phase difference layer, which is a stretched film of the resin film, is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, more preferably 10 μm to 60 μm, still more preferably 20 μm to 50 μm.

As the liquid crystal compound contained in the alignment cured layer of the liquid crystal compound, any suitable liquid crystal polymer and/or liquid crystal monomer is used. Specifically, the same liquid crystal compound as that contained in the liquid crystal alignment cured layer constituting the second phase difference layer can be exemplified, and the production method thereof is as described above.

The thickness of the fourth phase difference layer as the liquid crystal alignment cured layer is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, still more preferably 1 μm to 4 μm.

A-7 adhesive layer

The adhesive layer 60 is provided on the side of the fourth phase difference layer 50 opposite to the side on which the third phase difference layer 40 is provided. As described above, the polarizing plate 100 with the retardation layer can be attached to a member such as an organic EL panel via the adhesive layer 60.

The adhesive layer 60 may be composed of any suitable adhesive. Specific examples thereof include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the kind, amount, combination and ratio of the monomers forming the base resin of the adhesive, and the amount of the crosslinking agent, the reaction temperature, the reaction time, and the like, an adhesive having desired characteristics corresponding to the purpose can be produced. The base resin of the adhesive may be used alone, or two or more kinds may be used in combination. As the base resin, an acrylic resin is preferably used. Specifically, the adhesive layer is preferably composed of an acrylic adhesive.

The adhesive layer may be formed by coating an adhesive composition containing an additive such as a base resin and a crosslinking agent and a solvent, and drying. For example, the adhesive composition may be directly coated on the adherend to form the adhesive layer. Alternatively, for example, the adhesive composition may be coated on a substrate such as a base film prepared separately to form an adhesive layer, and then transferred to an adherend. Drying is typically performed by heating.

The thickness of the pressure-sensitive adhesive layer is, for example, 5 μm or more, preferably 10 μm or more, and is, for example, 100 μm or less, preferably 80 μm or less.

A-8 release liner

Examples of the release liner include a plastic film having flexibility. Examples of the plastic film include polyethylene terephthalate film, polyethylene film, polypropylene film, and polyester film. The thickness of the release liner is, for example, 3 μm or more and, for example, 200 μm or less. The surface of the release liner is coated with a release agent. Specific examples of the release agent include silicone release agents, fluorine release agents, and long-chain alkyl acrylate release agents.

B. Image display device

The polarizing plate with a retardation layer described in item a is typically applicable to an image display device, preferably an image display device having a metal layer, and more preferably an organic electroluminescence (organic EL) display device. Accordingly, the image display device according to the embodiment of the present invention includes the above-described polarization with the retardation layer. The organic EL display device according to the embodiment of the present invention typically includes an organic EL panel and the polarizing plate with the retardation layer disposed on the visible side thereof.

The organic EL display device 200 illustrated in fig. 2 includes an organic EL panel 120 and a polarizing plate 100 with a retardation layer disposed on the visible side thereof. The polarizing plate 100 with a retardation layer is disposed so that the first retardation layer 20 is located closer to the organic EL panel 120 than the polarizer 12, and is adhered to the organic EL panel 120 through the adhesive layer 60. The organic EL panel 120 includes metal members (e.g., electrodes, sensors, wirings, metal layers), but since the polarizing plate 100 with a phase difference layer has excellent anti-reflection characteristics, reflection caused by the metal members can be preferably prevented.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, various measurement methods are described below. Unless otherwise specified, "parts" and "%" in examples and comparative examples are weight standards.

1. Thickness of (L)

The thickness of 1 μm or less was measured by a scanning electron microscope (product name "JSM-7100F" manufactured by Japanese electronics Co., ltd.). The thickness exceeding 1 μm was measured using a digital micrometer (product name "KC-351C", manufactured by Anritsu Co., ltd.).

2. In-plane retardation Re (lambda) and thickness direction retardation Rth (lambda)

The in-plane retardation and the thickness-direction retardation at each wavelength at 23℃were measured using Mueller Matrix Polarimeter (manufactured by Axmetrics Co., ltd., product name "Axoscan").

3. Refractive index

The average refractive index was measured using an Abbe refractometer manufactured by Atago, and the refractive indices nx, ny, nz were calculated from the above-mentioned phase difference values.

4. Monomer transmittance and polarization degree

The single transmittance Ts, the parallel transmittance Tp, and the orthogonal transmittance Tc of the polarizer were measured using a spectrophotometer (manufactured by Katsukamu electronic corporation, "LPF-200"). These Ts, tp, and Tc are Y values measured by using a 2-degree field of view (C light source) of JIS Z8701, and subjected to sensitivity correction. From the obtained Tp and Tc, the degree of polarization of the polarizing plate (polarizer) was calculated using the following formula.

Degree of polarization (%) = { (Tp-Tc)/(tp+tc) } ^1/2 ×100

Production example 1: production of polarizing plate A ]

(Production of polarizer)

As the thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness 100 μm) having a long shape and a Tg of about 75 ℃ was used, and one side of the resin substrate was subjected to corona treatment.

At 9:1 to 100 parts by weight of a PVA-based resin mixed with polyvinyl alcohol (polymerization degree: 4200, saponification degree: 99.2 mol%) and acetoacetyl-modified PVA (trade name: gohsenx Z, manufactured by Mitsubishi Chemical Co., ltd.), 13 parts by weight of potassium iodide was added, and these were dissolved in water to prepare a PVA aqueous solution (coating liquid).

The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

The resulting laminate was uniaxially stretched to 2.4 times in the longitudinal direction (length direction) in an oven at 130 ℃.

Subsequently, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insolubilization treatment).

Next, the polarizer was immersed in a dyeing bath (aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the polarizer finally obtained reached a desired value (dyeing treatment).

Then, the resultant solution was immersed in a crosslinking bath (aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water and 5 parts by weight of boric acid) at a liquid temperature of 40℃for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4 wt% and potassium iodide concentration: 5 wt%) at a liquid temperature of 70 ℃ and uniaxially stretched (in-water stretching treatment) between rolls having different peripheral speeds so that the total stretching ratio in the longitudinal direction (longitudinal direction) became 5.5 times.

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 100 parts by weight of water with 4 parts by weight of potassium iodide) at a liquid temperature of 20 ℃ (washing treatment).

After that, while drying in an oven maintained at about 90 ℃, a SUS-made heating roller (drying shrinkage treatment) was maintained at a contact surface temperature of about 75 ℃.

Thus, a polarizer having a thickness of 5 μm was formed on the resin substrate.

(Production of polarizing plate A)

An HC-TAC film was adhered to the surface of the resulting polarizer (the surface opposite to the resin substrate) as a protective layer via an ultraviolet curable adhesive. Specifically, the ultraviolet curable adhesive was coated so that the thickness of the adhesive became 1.0 μm, and the adhesive was applied by a roll press. Then, UV light is irradiated from the protective layer side to cure the adhesive. Further, the HC-TAC film is a film in which a Hard Coat (HC) layer (thickness of 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness of 25 μm), and is attached so that the TAC film is on the polarizer side. Next, the resin-based was peeled off to obtain a polarizing plate a having a configuration of [ polarizer/TAC protective layer with HC ]. The monomer transmittance of the polarizing plate a was 43% and the degree of polarization was 99.9%.

Production example 2A: production of positive C plate A ]

48 Parts by weight of hydroxypropyl methylcellulose (trade name: METOLOSE 60SH-50, manufactured by Xin Yue chemical Co., ltd.), 15601 parts by weight of distilled water, 8161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethyl-3-oxetanyl methyl acrylate and 45 parts by weight of t-butyl peroxypivalate as a polymerization initiator were charged into an autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube and a thermometer, and after 1 hour of nitrogen bubbling, the mixture was stirred and kept at 49℃for 24 hours, to thereby carry out radical suspension polymerization. Then, the mixture was cooled to room temperature, and the suspension containing the polymer particles was centrifuged. The resultant polymer was washed 2 times with distilled water and 2 times with methanol, followed by drying under reduced pressure. The obtained fumarate resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene/methyl ethyl ketone, 50 wt%/50 wt%) to prepare a 20% solution. Further, 5 parts by weight of tributyl trimellitate as a plasticizer was added to 100 parts by weight of the fumarate-based resin to prepare a thick slurry. As the support film, a biaxially stretched film (thickness 75 μm) of polyester (polyethylene terephthalate/polyethylene isophthalate copolymer) was used. The prepared slurry was applied to a support film so that the film thickness after drying became 8. Mu.m, and dried at 140 ℃. Thus, a resin film (positive C plate a) exhibiting refractive index characteristics of nz > nx=ny was obtained. The positive C plate A had a thickness of 8 μm and an in-plane retardation Re (550) ≡0nm and a thickness direction retardation Rth (550) of-40 nm.

Production example 2B: production of positive C plate B ]

A resin film (positive C plate B) exhibiting refractive index characteristics of nz > nx=ny was obtained in the same manner as in production example 2A, except that the coating thickness of the resin solution was changed. The positive C plate B has a thickness of 17 μm and an in-plane retardation Re (550) ≡0nm and a thickness direction retardation Rth (550) of-80 nm.

Production example 2C: production of positive C plate C

A resin film (positive C plate C) exhibiting refractive index characteristics of nz > nx=ny was obtained in the same manner as in production example 2A, except that the coating thickness of the resin solution was changed. The positive C plate C has a thickness of 26 μm and an in-plane retardation Re (550) ≡0nm and a thickness direction retardation Rth (550) of-120 nm.

Production example 3: production of lambda/2 plate A (second phase difference layer)

A liquid crystal composition (coating liquid) was prepared by dissolving 10g of a polymerizable liquid crystal (product name: paliocolor LC242, manufactured by BASF corporation) exhibiting a nematic liquid crystal phase and 3g of a photopolymerization initiator (product name: irgacure 907, manufactured by BASF corporation) for the polymerizable liquid crystal compound in 40g of toluene.

[ Chemical Structure 2]

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth to perform an orientation treatment. The orientation treatment direction was a direction of 15 ° viewed from the visual side with respect to the absorption axis direction of the polarizer when the polarizing plate was attached. The liquid crystal coating liquid was coated on the alignment treated surface by a bar coater, and the liquid crystal compound was aligned by drying at 90℃for 2 minutes. On the liquid crystal layer thus formed, a light of 1mJ/cm ² was irradiated using a metal halide lamp, and the liquid crystal layer was cured, thereby forming a liquid crystal alignment cured layer (λ/2 plate A) on the PET film. The thickness of the lambda/2 plate A was 2.5 μm and the in-plane retardation Re (550) was 270nm. Furthermore, λ/2 plate a shows refractive index characteristics of nx > ny=nz.

Production example 4: production of lambda/4 plate A (fourth phase difference layer)

A liquid crystal alignment cured layer (λ/4 plate a) was formed on a PET film in the same manner as in production example 3, except that the coating thickness was changed and the alignment treatment direction was changed to a direction of 75 ° from the visual side with respect to the direction of the polarizer absorption axis. The lambda/4 plate A had a thickness of 1.5 μm and an in-plane retardation Re (550) of 140nm. Furthermore, λ/4 plate a shows refractive index characteristics of nx > ny=nz.

Production example 5: production of adhesive layer A ]

A four-necked flask equipped with a stirring wing, a thermometer, a nitrogen inlet tube, and a cooler was charged with a monomer mixture containing 91.5 parts of butyl acrylate, 3 parts of acrylic acid, 0.5 part of 4-hydroxybutyl acrylate, and 5 parts of acryloylmorpholine. Further, 0.1 part of 2,2' -azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate with respect to 100 parts of the monomer mixture, nitrogen was introduced while stirring slowly, the inside of the flask was replaced with nitrogen, and then the liquid temperature in the flask was kept at about 55℃to carry out a polymerization reaction for 8 hours. Further, ethyl acetate was added to the obtained reaction solution to adjust the solid content to 12% by weight, thereby preparing a solution of an acrylic polymer having a weight average molecular weight (Mw) of 250 ten thousand.

An acrylic adhesive was prepared by blending 100 parts of the solid content of the obtained acrylic polymer solution with 0.3 part of benzoyl peroxide (trade name: NYPER BMT, manufactured by Japanese fat and oil Co., ltd.), 0.2 part of trimethylolpropane/toluene diisocyanate adduct (trade name: coronate L, manufactured by Tosoh Co., ltd.), and 0.2 part of a silane coupling agent (trade name: KBM403, manufactured by Xinyue chemical Co., ltd.).

The obtained acrylic pressure-sensitive adhesive was applied to a release surface of a 38 μm thick PET Film (MRF 38, manufactured by Mitsubishi chemical Polyester Film Co., ltd.) having a release liner treated with silicone as a release surface, and dried to form a pressure-sensitive adhesive layer A having a thickness of 20. Mu.m.

Example 1

The positive C plate a is stuck as a first retardation layer on the polarizer side of the polarizing plate a, and then the λ/2 plate a is transferred from the PET film as a second retardation layer on the positive C plate a. Next, the positive C plate a was stuck on the λ/2 plate a side of the obtained laminate as a third phase difference layer, and the λ/4 plate a was transferred from the PET film as a fourth phase difference layer thereon. At this time, transfer (pasting) was performed such that the slow axis of the λ/2 plate a and the slow axis of the λ/4 plate a were rotated clockwise by 15 ° and 75 ° with respect to the absorption axis of the polarizer, respectively, from the visual side. The retardation layers were all adhered via an ultraviolet curable adhesive (thickness: about 1 um).

The adhesive layer a was adhered together with a release liner on the λ/4 plate a side of the obtained laminate to obtain a polarizing plate with a retardation layer having a constitution of [ polarizing plate a/positive C plate a/λ/2 plate a/positive C plate a/λ/4 plate a/adhesive layer a/release liner ].

Examples 2 to 6 and comparative examples 1 to 6

Polarizing plates with retardation layers of examples 2 to 6 were obtained in the same manner as in example 1, except that different combinations selected from positive C plates a to C were used as the first retardation layer and the third retardation layer. Polarizing plates with retardation layers of comparative examples 1 to 6 were obtained in the same manner as in example 1, except that either one of the first retardation layer and the third retardation layer, or only one of the first retardation layer and the third retardation layer selected from the positive C plates a to C, was not used.

The combinations of positive C plates a to C used in the polarizing plates with retardation layers obtained in examples and comparative examples are shown in table 1.

TABLE 1

	Example 1	Example 2	Example 3
				First phase difference layer	Positive C-A	Positive C-A	Positive C-B
Third phase difference layer	Positive C-A	Positive C-B	Positive C-A
					Example 4	Example 5	Example 6
First phase difference layer	Positive C-B	Positive C-C	Positive C-C
				Third phase difference layer	Positive C-B	Positive C-A	Positive C-B
	Comparative example 1	Comparative example 2	Comparative example 3
				First phase difference layer	Without any means for	Positive C-A	Positive C-B
Third phase difference layer	Without any means for	Without any means for	Without any means for
					Comparative example 4	Comparative example 5	Comparative example 6
First phase difference layer	Positive C-C	Without any means for	Without any means for
				Third phase difference layer	Without any means for	Positive C-A	Positive C-B

< Evaluation of reflection color tone >

The organic EL display device (product model "Galaxy a41" manufactured by Samsung corporation) was decomposed and the organic EL panel was taken out. The release liners were peeled off from the polarizing plates with retardation layers obtained in examples and comparative examples, and the exposed adhesive layers a were adhered to the organic EL panels to prepare measurement samples. Light was irradiated from the polarizer a side of the measurement sample using a display measurement system (manufactured by KONICA MINOLTA corporation, "DMS 505") at an azimuth angle: 0-360 degrees (15 degree scale), polar angle: the L ^*a^*b^* value (SCE mode) was measured at 45 ℃. Using the obtained L ^*a^*b^* value, the reflection hue Δe00 is calculated by the following formulas (1) to (7). The maximum value of Δe00 obtained in each measurement is shown in table 2. Further, the smaller the value of Δe00, the smaller the coloration due to reflection, and the more excellent the reflection hue.

(1)C^*＝√(a^*＾2+b^*＾2)

(2)G＝0.5×(1-√((C^*/2)＾7/((C^*/2)＾7+25＾7)))

(3)a’＝a^*(1+G)

(4)C’＝√(a’＾2+b^*＾2)

(5)SL＝1+0.015×(L^*/2-50)＾2/√(20+(L^*/2-50)＾2)

(6)SC＝1+0.045×C’/2

(7)ΔE00＝√((L^*/SL)＾2+(C’/SC)＾2)

TABLE 2

As shown in table 2, in the polarizing plate with the retardation layer having the polarizer, the λ/2 plate, and the λ/4 plate in this order, by disposing 1 positive C plate between the polarizer and the λ/2 plate or between the λ/2 plate and the λ/4 plate, coloring of the reflection tone can be suppressed, and by disposing 1 positive C plate so as to be a constitution of [ polarizer/positive C plate/λ/2 plate/positive C plate/λ/4 plate ], more preferable suppression of the reflection tone of coloring can be achieved.

Industrial applicability

The polarizing plate with a retardation layer according to the embodiment of the present invention can be used in, for example, an image display device. As the image display device, a liquid crystal display device, an organic EL display device, and an inorganic EL display device are typically exemplified, and an organic EL display device is preferable.

Claims

1. A polarizing plate with a retardation layer, which comprises, in order, a polarizing plate comprising a polarizer, a first retardation layer, a second retardation layer, a third retardation layer, and a fourth retardation layer,

The refractive index characteristics of the second phase difference layer and the fourth phase difference layer show a relationship in which nx > ny > nz,

Re (550) of the second phase difference layer is 200 nm-300 nm,

Re (550) of the fourth phase difference layer is 120 nm-170 nm,

2. The polarizing plate with a retardation layer as claimed in claim 1, wherein Rth (550) of the first retardation layer is-10 nm to-70 nm.

3. The polarizing plate with a retardation layer according to claim 1, wherein Rth (550) of the third retardation layer is-50 nm to-110 nm.

4. The polarizing plate with a retardation layer according to claim 1, wherein Rth (550) of the first retardation layer is-10 nm to-70 nm, and Rth (550) of the third retardation layer is-50 nm to-110 nm.

5. The polarizing plate with a retardation layer as claimed in claim 1, which is used in an organic EL display device.

6. An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 5.