JP7555862B2 - Retardation film, polarizing plate with retardation layer, and image display device - Google Patents

Description

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

Image display devices (e.g., liquid crystal display devices, organic EL display devices, quantum dot display devices) often have a polarizing plate arranged on at least one side of the image display cell due to their image formation method. Furthermore, a retardation film may be laminated on the image display cell side of the polarizing plate arranged on the viewing side of the image display device for the purpose of preventing external light reflection and background reflection, improving color tone, etc. As a retardation film, so-called Z film, which shows refractive index characteristics of nx>nz>ny, is known. However, Z film has insufficient crack resistance, and has the problem that cracks are likely to occur in both solvent resistance tests and heat shock tests.

JP 2001-091743 A

The present invention has been made to solve the above problems, and its main objective is to provide a retardation film that exhibits refractive index characteristics of nx>nz>ny and has excellent crack resistance.

The retardation film according to an embodiment of the present invention includes a stretched film containing a cyclic olefin resin and exhibiting a refractive index characteristic of nx>nz>ny; a fragile layer formed on at least one surface of the stretched film; and a reinforcement layer provided on the outside of the fragile layer. The reinforcement layer is a cured layer of an active energy ray curable resin. In the retardation film, an intermediate layer is formed between the reinforcement layer and the fragile layer, which is a compatible region containing the components of the reinforcement layer and the components of the fragile layer.
In one embodiment of the present invention, the reinforcement layer of the retardation film is a cured layer of an active energy ray-curable adhesive.
In one embodiment, the retardation film has the fragile layer, the reinforcing layer and the intermediate layer on both sides of the stretched film.
In one embodiment, the thickness _T1 of the fragile layer before the intermediate layer is formed is between 200 nm and 300 nm.
In one embodiment, the ratio T ₂ /T ₁ of the thickness T ₁ to the thickness T ₂ of the intermediate layer is 0.1 to 0.7.
According to another aspect of the present invention, there is provided a polarizing plate with a retardation layer, the polarizing plate having a retardation layer, the polarizing plate having a polarizer and the above-mentioned retardation film.
According to yet another aspect of the present invention, there is provided an image display device, the image display device including the above-mentioned retardation layer-attached polarizing plate.

According to an embodiment of the present invention, in a retardation layer film having a refractive index characteristic of nx>nz>ny and having a fragile layer formed therein, a reinforced layer, which is a cured layer of an active energy ray curable resin, is provided on the outside of the fragile layer, and an intermediate layer, which is a compatible region containing the components of the reinforced layer and the components of the fragile layer, is formed between the reinforced layer and the fragile layer, thereby achieving excellent crack resistance.

1 is a schematic cross-sectional view of a retardation film according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a retardation film according to another embodiment of the present invention. 1 is a schematic cross-sectional view of a retardation layer-attached polarizing plate according to one embodiment of the present invention.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is calculated by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise angles with respect to a reference direction. Thus, for example, "45°" means ±45°.
(6) Substantially perpendicular or substantially parallel In this specification, the expressions "substantially perpendicular" and "approximately perpendicular" include the case where the angle between two directions is 90°±7°, preferably 90°±5°, and more preferably 90°±3°. The expressions "substantially parallel" and "approximately parallel" include the case where the angle between two directions is 0°±7°, preferably 0°±5°, and more preferably 0°±3°. Furthermore, when simply referring to "orthogonal" or "parallel" in this specification, it is understood that it can include a substantially perpendicular or substantially parallel state.

A. Retardation Film A-1. Overall Configuration of Retardation Film FIG. 1 is a schematic cross-sectional view of a retardation layer film according to one embodiment of the present invention. The retardation film 100 of the illustrated example has a stretched film 10, a fragile layer 20 formed on at least one surface of the stretched film (the visible side in the illustrated example, the upper side of the drawing), and a reinforced layer 30 provided on the outside of the fragile layer 20. The stretched film 10 contains a cyclic olefin resin and exhibits a refractive index characteristic of nx>nz>ny. Since the stretched film 10 exhibits a refractive index characteristic of nx>nz>ny, the retardation film 100 can also exhibit a refractive index characteristic of nx>nz>ny.

The fragile layer 20 can be formed when a stretched film is produced from a cyclic olefin resin film (i.e., by stretching). The inventors, through trial and error to solve the problem that cracks are likely to occur in so-called Z films that exhibit a refractive index characteristic of nx>nz>ny, have found that the cracks are mainly caused by the fragile layer and that the fragile layer can be formed by stretching. It is presumed that the fragile layer can be formed due to the difference in molecular orientation between the surface portion and the middle portion in the thickness direction of the stretched film. According to an embodiment of the present invention, by forming a reinforcing layer and an intermediate layer as described below, it is possible to achieve excellent crack resistance in the Z film. More specifically, by forming a reinforcing layer and an intermediate layer, it is possible to significantly suppress cracks in both solvent resistance tests and heat shock tests.

In the embodiment of the present invention, as described above, the reinforcement layer 30 is provided on the outside of the fragile layer 20. The reinforcement layer 30 is a cured layer of an active energy ray curable resin, typically a cured layer of an active energy ray curable adhesive. The reinforcement layer 30 is formed by applying an active energy ray curable resin to the surface of the stretched film 10 (substantially the fragile layer 20) and curing the applied film by irradiating it with active energy rays. When the active energy ray curable resin is applied, the uncured resin component penetrates into the fragile layer, and as a result, an intermediate layer 40, which is a compatible region containing the components of the reinforcement layer and the components of the fragile layer, can be formed between the reinforcement layer 30 and the fragile layer 20. By forming the intermediate layer 40, the reinforcement layer and the fragile layer are firmly adhered to each other via the intermediate layer, and the fragile layer, which has insufficient mechanical strength and is prone to cracking, can be appropriately reinforced by the reinforcement layer. As a result, cracks (which can be assumed to be mainly caused by the fragile layer) can be significantly suppressed in the Z film. In the intermediate layer 40, preferably, the concentration of the fragile layer component (substantially, the stretched film component) increases continuously from the reinforced layer side to the fragile layer side. By continuously changing the concentration of the fragile layer component (in other words, the concentration of the reinforced layer component), it is possible to prevent the formation of an interface in the intermediate layer due to the change in concentration of the fragile layer component or the reinforced layer component. As a result, it is possible to suppress the interface reflection in the intermediate layer, and when the retardation film is applied to an image display device, it is possible to suppress the adverse effects of the interface reflection (for example, interference unevenness). More preferably, the concentration of the fragile layer component increases continuously from the reinforced layer to the intermediate layer, and also increases continuously from the intermediate layer to the fragile layer. That is, more preferably, a clear interface between the reinforced layer and the intermediate layer, and a clear interface between the intermediate layer and the fragile layer are not formed. With such a configuration, a retardation film with even less interference unevenness can be obtained.

In another embodiment, as in the retardation film 101 shown in FIG. 2, the fragile layers 20 may be formed on both sides of the stretched film 10. In this case, the reinforcement layers 30 are typically provided on the outside of each fragile layer, and an intermediate layer may be formed between each reinforcement layer and each fragile layer.

The MIT number of times of the retardation film is preferably 70 times or more, more preferably 80 times or more, and even more preferably 100 times or more. The upper limit of the MIT number of times can be, for example, 1000 times. According to the embodiment of the present invention, it is possible to realize the MIT number of times (break resistance) that could not be realized with conventional Z films. As a result, it is possible to realize excellent crack resistance as described above. The MIT test can be performed in accordance with JIS P 8115.

The breaking elongation of the resin film (before stretching) constituting the retardation film is preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more. The upper limit of the breaking elongation can be, for example, 30%. According to the embodiment of the present invention, it is possible to realize a breaking elongation that could not be achieved with conventional Z films. As a result, it is possible to realize excellent crack resistance as described above. The breaking elongation can be measured in accordance with JIS K 7161.

The components of the retardation film are explained in more detail below.

A-2. Stretched film The stretched film 10 is a so-called Z film that exhibits the refractive index characteristic of nx>nz>ny, as described above. The retardation layer has such a refractive index characteristic, so that the hue in the oblique direction of an image display device to which a retardation layer-attached polarizing plate is applied can be improved. Furthermore, such improvement in the hue in the oblique direction can be achieved without separately providing a retardation layer and a layer that performs optical compensation in the oblique direction, which can contribute to simplifying the design and/or reducing the number of parts.

The in-plane retardation Re(550) of the stretched film (and, as a result, the entire retardation film) is preferably 220 nm to 320 nm, more preferably 240 nm to 300 nm, and even more preferably 260 nm to 280 nm. If the in-plane retardation Re(550) of the stretched film is in this range, when the retardation film is applied to an image display device, the movement distance on the Poincaré sphere is short, so that excellent hue and brightness characteristics are realized, and the color shift of the image display panel and the deviation due to the retardation component of the TFT are also reduced.

The Nz coefficient of the stretched film is preferably 0.3 to 0.7, more preferably 0.4 to 0.6, and even more preferably 0.45 to 0.55. If the Nz coefficient is within this range, the hue in the oblique direction can be further improved.

Stretched films typically exhibit flat wavelength dispersion characteristics, with the phase difference value changing very little with the wavelength of the measurement light.

The absolute value of the photoelastic coefficient of the stretched film is preferably 1.0×10 ⁻¹² m ² /N to 12.0× ^{10 −12} m ² /N, more preferably 2.0×10 ⁻¹² m ² /N to 8.0× ^{10 −12} m ² /N, even more preferably 2.0×10 ⁻¹² m ² /N to 6.0×10 ⁻¹² m ² /N, and particularly preferably 3.0×10 ⁻¹² m ² /N to 4.0 ^{×10 −12} m ² /N. When the absolute value of the photoelastic coefficient of the retardation layer is in such a range, display unevenness of the image display device can be well suppressed.

As described above, the stretched film contains a cyclic olefin resin. A representative example of a cyclic olefin resin is a norbornene resin.

The norbornene-based resin is a resin polymerized using norbornene-based monomers as polymerization units. Examples of the norbornene-based monomers include norbornene and its alkyl and/or alkylidene substituted derivatives, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and polar group substituted derivatives thereof, such as halogen; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, and the like; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, and the like; Octahydronaphthalene, its alkyl and/or alkylidene substituted derivatives, and polar group substituted derivatives such as halogen, for example, 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7 ,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene norbornene-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; trimers and tetramers of cyclopentadiene, such as 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene, 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene, etc. The norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

The stretched film can be produced by stretching a film formed from the above cyclic olefin resin. Any appropriate method can be used to produce the stretched film. A typical example is a method in which a shrinkable film is attached to one or both sides of a resin film and then heated and stretched. The shrinkable film is used to impart a shrinkage force in a direction perpendicular to the stretching direction during heat stretching. By imparting such a shrinkage force, nz can be increased, and as a result, a Z film can be produced. Examples of materials used for the shrinkable film include polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, etc. Polypropylene film is preferably used because of its excellent shrink uniformity and heat resistance.

As the stretching method, any suitable stretching method can be adopted as long as it can impart tension in the stretching direction of the resin film and a shrinkage force in a direction perpendicular to the stretching direction in the film plane. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin film. This is because the retardation value of the resulting stretched film is likely to be uniform, and the film is less likely to crystallize (become cloudy). The stretching temperature is more preferably Tg+1°C to Tg+30°C of the polymer film, even more preferably Tg+2°C to Tg+20°C, particularly preferably Tg+3°C to Tg+15°C, and most preferably Tg+5°C to Tg+10°C. By setting the stretching temperature in such a range, uniform heating and stretching can be performed. Furthermore, it is preferable that the stretching temperature is constant in the film width direction. This is because a stretched film having good optical uniformity with small variation in retardation value can be produced.

The stretching ratio during the above stretching can be set to any appropriate value. It is preferably 1.05 to 2.00 times, more preferably 1.10 to 1.50 times, and particularly preferably 1.20 to 1.40 times. By setting the stretching ratio within such a range, a stretched film with little shrinkage in the film width and excellent mechanical strength can be obtained.

The thickness of the stretched film is preferably 80 μm to 200 μm, more preferably 100 μm to 180 μm, and even more preferably 120 μm to 160 μm. With such a thickness, the desired in-plane retardation value can be obtained.

A-3. Fragile layer The fragile layer 20 can be formed when preparing a stretched film from a cyclic olefin resin film (i.e., by stretching), as described above. In particular, the fragile layer can be formed by stretching when preparing a Z-film. The mechanism of formation of the fragile layer is not clear, but it is presumed that it may be related to laminating a shrinkable film during stretching to increase nz. According to the embodiment of the present invention, as described above, by forming a reinforced layer and an intermediate layer, cracks that may be caused by the fragile layer can be significantly suppressed in a Z-film in which an undesired fragile layer may be formed. The fragile layer can be typically formed on both sides of the stretched film. On the other hand, the effect of the embodiment of the present invention can be obtained by forming a reinforced layer and an intermediate layer for at least one of the fragile layers.

The thickness _T1 of the fragile layer before the intermediate layer is formed (i.e., the thickness before a portion of the fragile layer becomes the intermediate layer) is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, even more preferably 240 nm to 280 nm, and particularly preferably 250 nm to 270 nm.

A-4. Reinforcement layer As described above, the reinforcement layer 30 is a cured layer of an active energy ray curable resin, typically a cured layer of an active energy ray curable adhesive. Examples of active energy ray curable adhesives include ultraviolet ray curable adhesives and electron beam curable adhesives. In addition, from the viewpoint of the curing mechanism, examples of active energy ray curable adhesives include radical curable adhesives, cationic curable adhesives, anionic curable adhesives, and hybrids of radical curable adhesives and cationic curable adhesives. Typically, a radical curable ultraviolet ray curable adhesive can be used. This is because it has excellent versatility and the characteristics (composition) can be easily adjusted. Below, an adhesive will be described as a representative example.

The adhesive typically contains a curing component and a photopolymerization initiator. Typical examples of the curing component include monomers and/or oligomers having functional groups such as (meth)acrylate groups and (meth)acrylamide groups. Specific examples of the curing component include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, phenoxydiethylene glycol acrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO-modified diglycerin tetraacrylate, γ-butyrolactone acrylate, acryloylmorpholine, unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone, N-methylpyrrolidone, hydroxyethylacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, and N-ethoxymethylacrylamide. These curing components may be used alone or in combination of two or more.

Preferably, the adhesive contains a curing component having a heterocycle. Examples of the curing component having a heterocycle include acryloylmorpholine, γ-butyrolactone acrylate, unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone, and N-methylpyrrolidone. More preferred curing components are unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone and acryloylmorpholine, and particularly preferred curing component is acryloylmorpholine. The curing component having a heterocycle may be contained in the adhesive at a ratio of preferably 50 parts by weight or more, more preferably 60 parts by weight or more, and even more preferably 70 to 95 parts by weight, relative to 100 parts by weight of the curing component (the total of the curing component and the oligomer component when an oligomer component described below is present). The acryloylmorpholine may be contained in the adhesive at a ratio of preferably 5 to 60 parts by weight, more preferably 10 to 50 parts by weight, relative to 100 parts by weight of the curing component (the total of the curing component and the oligomer component when an oligomer component is present).

The adhesive may further contain an oligomer component in addition to the above-mentioned curing component. By using the oligomer component, the viscosity of the adhesive before curing can be reduced and the operability can be improved. A representative example of the oligomer component is a (meth)acrylic oligomer. Examples of (meth)acrylic monomers constituting the (meth)acrylic oligomer include (meth)acrylic acid (1 to 20 carbon atoms) alkyl esters, cycloalkyl (meth)acrylates (e.g., cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, etc.), aralkyl (meth)acrylates (e.g., benzyl (meth)acrylate, etc.), polycyclic (meth)acrylates (e.g., 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, etc.), hydroxyl group-containing (meth)acrylic acid esters (e.g., hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate, etc.), alkoxy group- or phenoxy group-containing (meth)acrylic acid esters (e.g., hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate, etc.), and the like. ) acrylic acid esters (2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), epoxy group-containing (meth)acrylic acid esters (for example, glycidyl (meth)acrylate, etc.), halogen-containing (meth)acrylic acid esters (for example, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, etc.), alkylaminoalkyl (meth)acrylates (for example, dimethylaminoethyl (meth)acrylate, etc.). Specific examples of (meth)acrylic acid (C1 to C20) alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate. These (meth)acrylates may be used alone or in combination of two or more.

As the photopolymerization initiator is a photopolymerization initiator well known in the industry and can be used in amounts well known in the industry, detailed explanation is omitted.

The thickness of the reinforcement layer (after curing) is preferably 0.1 μm to 7.0 μm, and more preferably 1.0 μm to 5.0 μm. By applying the adhesive to such a thickness, an intermediate layer of appropriate thickness can be formed.

A-5. Intermediate layer As described above, the intermediate layer 40 is a compatible region containing the components of the reinforcing layer and the components of the fragile layer. In other words, the intermediate layer is a permeation layer formed by the permeation of the reinforcing layer components (substantially uncured resin components) into the fragile layer. As described above, by forming the intermediate layer, the reinforcing layer and the fragile layer are firmly adhered to each other via the intermediate layer, and the fragile layer, which has insufficient mechanical strength and is prone to cracking, can be appropriately reinforced by the reinforcing layer. As a result, cracks (which can be assumed to be mainly caused by the fragile layer) can be significantly suppressed in the Z film.

The thickness _T2 of the intermediate layer is preferably 20 nm to 180 nm, more preferably 30 nm to 170 nm, even more preferably 40 nm to 160 nm, and particularly preferably 50 nm to 150 nm. The ratio _T2 / _T1 of the thickness _T1 of the brittle layer before the intermediate layer is formed to the thickness _T2 of the intermediate layer is preferably 0.1 to 0.7, more preferably 0.2 to 0.6. If _T2 or _T2 / _T1 is too small, cracks may easily occur. If _T2 or _T2 / _T1 is too large, the designed retardation may not be obtained.

The shear fracture strength per 1 μm of thickness of the intermediate layer may be, for example, 10 MPa or more, for example, 14 MPa or more, for example, 16 MPa or more, for example, 20 MPa or more, for example, 25 MPa or more, for example, 40 MPa or more, for example, 70 MPa or more, for example, 100 MPa or more, or for example, 120 MPa or more. The shear fracture strength per 1 μm of thickness of the intermediate layer may be, for example, 200 MPa or less. If the shear fracture strength per 1 μm of thickness of the intermediate layer is in such a range, cracks can be significantly suppressed. The shear fracture strength is the force required to cut (break) each layer of a single film or a laminate, and can be determined, for example, by SAICAS (Surface And Interfacial Cutting Analysis System). For example, the shear strength when a laminate having, from the top, a reinforcing layer, an intermediate layer, a brittle layer, and a stretched film is diagonally cut using a precision diagonal cutting device (e.g., "SAICAS DN-20" manufactured by Daipla Wintes Co., Ltd.) is the shear fracture strength. Diagonal cutting can be performed by biaxial movement of the cutting blade (horizontal and vertical movements). The shear fracture strength T (MPa) can be calculated from the following formula.
T (MPa)=F _H (kN)/(2×Wd(m ² )×cotφ)
Here, _FH is the horizontal load applied by the cutting blade, W is the width of the cutting blade (m), d is the vertical displacement of the cutting blade (m), and φ is the shear angle. The shear angle may vary depending on the cutting conditions, the material of the workpiece, etc., but is generally 45°.

The thickness and shear fracture strength of the intermediate layer can be adjusted by appropriately combining and setting the constituent materials of the reinforced layer, the composition of the constituent materials of the reinforced layer (e.g., solids concentration, solvent composition, or type, number or amount of additives), and the formation conditions of the reinforced layer (e.g., drying or heating conditions of the coating film, amount or method of ultraviolet irradiation) depending on the composition of the fragile layer, etc.

B. Retardation Layer-Attached Polarizing Plate B-1. Overall Configuration of Retardation Layer-Attached Polarizing Plate The retardation film described in the above item A may be provided as a laminate with other optical films and/or optical members. In one embodiment, the retardation film may be provided as a laminate (representatively, a retardation layer-attached polarizing plate) with a polarizer (substantially, a polarizing plate). Thus, an embodiment of the present invention encompasses a retardation layer-attached polarizing plate including the above retardation film. FIG. 3 is a schematic cross-sectional view of a retardation layer-attached polarizing plate according to one embodiment of the present invention. The retardation layer-attached polarizing plate 200 of the illustrated example includes a polarizer 110 and a retardation layer 100. The retardation layer 100 is the retardation film described in the above item A. A protective layer may be disposed on at least one side of the polarizer 110. In the illustrated example, a protective layer 120 is disposed on the viewing side of the polarizer 110. The protective layer may be disposed on both sides of the polarizer, or may be disposed only between the polarizer and the retardation layer. Hereinafter, the protective layer 120 may be referred to as a viewer-side protective layer, and a protective layer (not shown) disposed between the polarizer and the retardation layer may be referred to as an inner protective layer.

The retardation layer-attached polarizing plate 200 may further have any appropriate functional layer on the side of the retardation layer 100 opposite to the polarizer 110 (image display panel side) according to the purpose (not shown). Representative examples of the functional layer include another retardation layer and a conductive layer. The type, number, combination, arrangement position, and characteristics of the functional layer (for example, the optical characteristics of another retardation layer: specifically, the refractive index characteristics, in-plane retardation, thickness direction retardation, and Nz coefficient) can be appropriately set according to the purpose. By the retardation layer-attached polarizing plate further having a conductive layer, the retardation layer-attached polarizing plate can be suitably used in an inner touch panel type input display device. Furthermore/alternatively, the visible side of the protective layer 120 may be treated, as necessary, to improve visibility when viewed through polarized sunglasses. Representative examples of such treatments include imparting an (elliptical) circular polarization function (arranging a λ/4 plate) and imparting an ultra-high retardation (arranging an ultra-high retardation film). By carrying out such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the polarizing plate with a retardation layer can be suitably applied to image display devices that can be used outdoors.

The polarizing plate with a retardation layer may be in the form of a sheet or a long sheet. In this specification, "long sheet" means a long and narrow shape whose length is sufficiently longer than its width, and includes, for example, a long and narrow shape whose length is 10 times or more, preferably 20 times or more, larger than its width. A long polarizing plate with a retardation layer can be wound into a roll.

For practical purposes, an adhesive layer (not shown) is provided on the side of the retardation layer 100 opposite the polarizing plate 110 (i.e., as the outermost layer on the side opposite the viewing side), so that the polarizing plate with a retardation layer can be attached to an image display panel. Furthermore, it is preferable that a separator (not shown) is temporarily attached to the surface of the adhesive layer until the polarizing plate with a retardation layer is used. Temporarily attaching the separator protects the adhesive layer and enables the polarizing plate with a retardation layer to be formed into a roll.

The polarizer and protective layer are described in detail below.

B-2. Polarizer The polarizer 110 is typically made of a resin film containing a dichroic material.

As the resin film, any suitable resin film that can be used as a polarizer can be used. The resin film is typically a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

Any suitable resin can be used as the PVA-based resin forming the PVA-based resin film. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer is obtained by saponifying ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be determined in accordance with JIS K 6726-1994. By using a PVA-based resin with such a saponification degree, a polarizer with excellent durability can be obtained. If the saponification degree is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

Examples of dichroic substances contained in the resin film include iodine and organic dyes. These can be used alone or in combination of two or more. Iodine is preferably used.

The resin film may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers made of a single-layer resin film include a PVA-based resin film that has been dyed with iodine and stretched (typically, uniaxially stretched). The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing process or while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based resin film may be subjected to a swelling process, a crosslinking process, a washing process, a drying process, or the like. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can dirt and antiblocking agents on the surface of the PVA-based film be washed off, but the PVA-based resin film can also be swelled to prevent uneven dyeing, etc.

Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate and drying the substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, the stretching may further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution, as necessary. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is applied onto a thermoplastic resin, and it is possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution can be prevented when the PVA is immersed in water in the subsequent dyeing step or stretching step, and it is possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the polarizer obtained by immersing the laminate in a liquid in a treatment process such as a dyeing process and an underwater stretching process. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by a drying shrinkage process. The obtained resin substrate/polarizer laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate/polarizer laminate and any suitable protective layer may be laminated on the peeled surface according to the purpose. Details of the manufacturing method of such a polarizer are described in, for example, JP 2012-73580 A and JP 6470455 A. The entire disclosures of these publications are incorporated herein by reference.

The thickness of the polarizer is, for example, 30 μm or less, for example, 20 μm or less, for example, 1 μm to 18 μm, for example, 3 μm to 12 μm, or for example, 3 μm to 8 μm.

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

B-3. Protective layer The viewing side protective layer and the inner protective layer (if present) are each formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that are the main components of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates. Other examples include thermosetting resins or ultraviolet-curing resins such as (meth)acrylics, urethanes, (meth)acrylic urethanes, epoxys, and silicones. Other examples include glassy polymers such as siloxane polymers. Polymer films described in JP-A-2001-343529 (WO01/37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, and 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 can be, for example, an extrusion molded product of the above resin composition. As the material for the protective layer, TAC and (meth)acrylic resins can be preferably used.

The (meth)acrylic resin preferably has a Tg (glass transition temperature) of 115°C or higher, more preferably 120°C or higher, even more preferably 125°C or higher, and particularly preferably 130°C or higher. This is because it can have excellent durability. There is no particular upper limit to the Tg of the (meth)acrylic resin, but from the viewpoint of moldability, etc., it is preferably 170°C or lower.

As the (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure is particularly preferred because it has high heat resistance, high transparency, and high mechanical strength. Examples of (meth)acrylic resins having a lactone ring structure include (meth)acrylic resins having a lactone ring structure described in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, etc.

The polarizing plate with a retardation layer is typically placed on the viewing side of the image display device, and the viewing-side protective layer 120 is placed on the viewing side. Therefore, the viewing-side protective layer 120 may be subjected to surface treatments such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment, as necessary.

The thickness of the viewer-side protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and even more preferably 30 μm to 60 μm. When the viewer-side protective layer is subjected to a surface treatment to form a surface treatment layer, the thickness of the viewer-side protective layer includes the thickness of the surface treatment layer.

The inner protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm, and the retardation in the thickness direction Rth(550) is -10 nm to +10 nm. The thickness of the inner protective layer is preferably 5 μm to 80 μm, more preferably 20 μm to 70 μm, and even more preferably 20 μm to 40 μm.

C. Image display device The retardation layer-attached polarizing plate according to the embodiment of the present invention can be applied to an image display device. Typically, the retardation layer-attached polarizing plate is arranged on the viewing side of the image display device so that the polarizing plate is on the viewing side. Representative examples of the image display device include a liquid crystal display device, an organic electroluminescence (EL) display device, and a quantum dot display device. A liquid crystal display device is preferred, and an IPS mode liquid crystal display device is more preferred. This is because the hue improvement in the oblique direction is more remarkable.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. Note that "parts" and "%" in the examples are by weight unless otherwise specified.

(1) Thickness of the fragile layer The Z-films (films before the formation of the reinforcing layer and intermediate layer) used in the examples and comparative examples were subjected to SAICAS, and the thickness was calculated from the vertical movement of the cutting edge to the position where the shear fracture strength changes (the position corresponding to the layer interface).
(2) Thickness of intermediate layer For the retardation films obtained in the examples and comparative examples, a cross section was observed by ultrathin sectioning including heavy metal staining using a transmission electron microscope (TEM), and the thickness was calculated from the image. The TEM used was "HT7820" manufactured by Hitachi. The accelerating voltage was 100 kV.
(3) Elongation at break The retardation films obtained in the examples and comparative examples were punched out into a dumbbell shape so as to be stretched in the fast axis direction to prepare samples. The samples were attached to an "Autograph" manufactured by Shimadzu Corporation with a chuck distance of 100 mm, and a tensile test was performed in the fast axis direction at 0.5 mm/min to measure the stress and elongation at break.
(4) MIT Test The retardation films obtained in the examples and comparative examples were punched out to a width of 15 mm and a length of about 100 mm to prepare samples. The samples were subjected to a folding endurance test using a "BE-201" MIT folding endurance tester manufactured by Tester Sangyo Co., Ltd., and the number of times until the sample broke was measured. The test conditions were as follows.
Tensile load weight: 2N
Bending angle: 135° left and right
Bending speed: 175 times/min. Folding clamp radius: 5.00 mm
Folding clamp opening: 0.25 mm
(5) Heat Shock Test An adhesive layer was placed on the retardation film obtained in the examples and comparative examples, and the retardation film was laser-cut into a butterfly of 40 mm length x 75 mm width (slow axis direction is 40 mm), and the adhesive layer was bonded to an alkali glass of 250 mm length x 180 mm width x 1.3 mm thickness to prepare a sample. This sample was subjected to a heat shock test in which the sample was repeatedly held at -40°C for 30 minutes and then held at 85°C for 30 minutes, and the presence or absence of cracks was visually checked every 10 cycles, and the number of cycles until cracks occurred was used as the evaluation criterion.
(6) Solvent Resistance Test The retardation layer-attached polarizing plate obtained in the Examples and Comparative Examples was cut to 100 mm long x 100 mm wide, and attached to an alkali-free glass of 350 mm long x 250 mm wide x 0.7 mm thick via an adhesive layer to prepare a sample. This sample was preheated in a thermostatic chamber at 95°C for 3 hours, then removed and left at room temperature for 1 hour. Thereafter, the entire circumference of the end was wiped with a cloth soaked in hexane, the length of the cracks that occurred was measured, and the evaluation was performed according to the following criteria.
○: The maximum crack length is 30 mm or less. ×: The maximum crack length exceeds 30 mm.

[Production Example 1: Preparation of Z film]
A 60 μm thick shrinkable film [manufactured by Toray Industries, Inc., product name "Trefan BO2873"] was attached to both sides of a 130 μm thick norbornene resin film via an acrylic adhesive layer (thickness 15 μm). Then, the film was held in the longitudinal direction by a roll stretching machine and stretched 1.38 times in an air circulating oven at 146 ° C. After stretching, the shrinkable film was peeled off together with the acrylic adhesive layer to produce a retardation film (stretched film). The obtained retardation film showed a refractive index characteristic of nx>nz>ny, Re (550) = 270 nm, Nz coefficient = 0.5, and thickness was 138 μm. A fragile layer having a thickness of 260 nm was formed on both sides of the obtained retardation film. This retardation film was used as a stretched film.

[Production Example 2: Preparation of Z film]
A retardation film (stretched film) was produced in the same manner as in Production Example 1, except that the stretching temperature was changed to 143 ° C. and the stretching ratio was changed to 1.23 times. The obtained retardation film showed a refractive index characteristic of nx>nz>ny, Re (550) = 270 nm, Nz coefficient = 0.5, and thickness was 138 μm. A fragile layer having a thickness of 120 nm was formed on both sides of the obtained retardation film. This retardation film was used as a stretched film.

[Production Example 3: Preparation of polarizing plate]
A polyvinyl alcohol film having a thickness of 45 μm was stretched to 3 times between rolls having different speed ratios while being dyed in a 0.3% concentration iodine solution at 30° C. for 1 minute. Thereafter, the film was stretched to a total stretch ratio of 6 times while being immersed in an aqueous solution containing 4% concentration boric acid and 10% concentration potassium iodide at 60° C. for 0.5 minutes. The film was then washed by being immersed in an aqueous solution containing 1.5% concentration potassium iodide at 30° C. for 10 seconds, and then dried at 50° C. for 4 minutes to obtain a polarizer having a thickness of 18 μm.
An HC-TAC film (thickness 49 μm) was bonded to one surface of the polarizer obtained above. The HC-TAC film was a film in which a hard coat (HC) layer (thickness 9 μm) was formed on a triacetyl cellulose (TAC) film (thickness 40 μm), and the films were bonded so that the TAC film was on the polarizer side. Furthermore, an acrylic resin film (thickness 30 μm) containing a lactone ring structure was bonded to the other surface of the polarizer. In this way, a polarizing plate was obtained.

[Production Example 4: Preparation of adhesive constituting reinforcing layer]
An ultraviolet-curable adhesive was prepared by mixing 50 parts of unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone (Daicel Corporation's "Placcel FA1DDM"), 40 parts of acryloylmorpholine (Kojin Co., Ltd.'s "ACMO (registered trademark)"), 10 parts of an acrylic oligomer (Toagosei Co., Ltd.'s "ARFON UP-1190"), and 3 parts of "KAYACURE DETX-S" (Nippon Kayaku Co., Ltd.) and 3 parts of OMNIRAD907 (IGM Resins Italia S.r.l.) as photopolymerization initiators. This ultraviolet-curable adhesive was used to form the reinforcing layer.

[Production Example 5: Preparation of hard coat composition constituting reinforcing layer]
As a film-forming component of the hard coat layer, 100 parts by weight of an ultraviolet-curable acrylate resin (manufactured by DIC Corporation, product name "Luxidia 17-806", solid content 80%) was prepared. Per 100 parts by weight of the resin solid content, 3 parts by weight of a photopolymerization initiator (manufactured by BASF Corporation, product name "OMNIRAD907") and 0.01 parts by weight of a leveling agent (manufactured by DIC Corporation, product name "GRANDIC PC4100", solid content 10%) were mixed. This mixture was diluted with a PGME/cyclopentanone mixed solvent (weight ratio 65/35) so that the solid content concentration was 36%, to prepare a hard coat composition. This hard coat composition was used to form a reinforcing layer.

[Example 1]
The ultraviolet-curing adhesive prepared in Production Example 4 was applied to both sides of the stretched film obtained in Production Example 1, and ultraviolet rays (accumulated light amount 300 mJ/cm ² ) were irradiated to form a reinforced layer with a thickness of 5 μm, to produce a retardation film. In the obtained retardation film, an intermediate layer (compatible region) with a thickness of 60 nm was formed between the reinforced layer and the fragile layer. Furthermore, the obtained retardation film was bonded to the acrylic resin film surface of the polarizing plate obtained in Production Example 3 via an acrylic adhesive (thickness 20 μm) to obtain a polarizing plate with a retardation layer. Here, the polarizing plate and the retardation film were bonded so that the absorption axis of the polarizer and the slow axis of the retardation film were substantially perpendicular to each other. The obtained retardation film or the polarizing plate with a retardation layer was subjected to the above evaluations (3) to (6). The results are shown in Table 1.

[Example 2]
A retardation film was produced in the same manner as in Example 1, except that the applied stretched film was placed in a thermostatic chamber at 30° C. for 1 minute after applying the ultraviolet-curing adhesive and before irradiating with ultraviolet light. In the obtained retardation film, an intermediate layer (compatible region) having a thickness of 140 nm was formed between the reinforced layer and the fragile layer. A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that this retardation film was used. The obtained retardation film or polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A retardation film was produced in the same manner as in Example 1, except that a reinforced layer (thickness 5 μm) was formed using the hard coat composition prepared in Production Example 5 instead of the ultraviolet-curing adhesive. In the obtained retardation film, no intermediate layer (compatible region) was formed between the reinforced layer and the fragile layer. A retardation layer-attached polarizing plate was obtained in the same manner as in Example 1, except that this retardation film was used. The obtained retardation film or retardation layer-attached polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
The retardation film (stretched film) of Production Example 1 was used as it was. That is, the reinforcing layer (and necessarily the intermediate layer) was not formed. A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that this retardation film was used. The obtained retardation film or polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
The retardation film (stretched film) of Production Example 2 was used as it was. That is, the reinforcing layer (and necessarily the intermediate layer) was not formed. A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that this retardation film was used. The obtained retardation film or polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
The norbornene-based resin film (unstretched film) used in Production Example 1 was used as is. That is, a reinforcing layer (and necessarily an intermediate layer) was not formed. In addition, no fragile layer was formed in this unstretched film. A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that this unstretched film was used. The unstretched film or the polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[evaluation]
As is clear from Table 1, according to the embodiment of the present invention, in the retardation layer film showing the refractive index characteristic of nx>nz>ny in which the fragile layer is formed, a reinforcement layer which is a cured layer of active energy ray curable resin is provided on the outside of the fragile layer, and an intermediate layer which is a compatible region containing the components of the reinforcement layer and the components of the fragile layer is formed between the reinforcement layer and the fragile layer, thereby achieving excellent crack resistance. Specifically, the retardation film and the retardation layer-attached polarizing plate of the embodiment show remarkable suppression of cracks in both the heat shock test and the solvent resistance test, and show excellent crack resistance. Furthermore, it can be seen that the active energy ray curable adhesive is preferable as the active energy ray curable resin.

The retardation film and retardation layer-attached polarizing plate of the present invention can be suitably used in image display devices such as liquid crystal display devices, organic EL display devices, and quantum dot display devices, and can be particularly suitably used in liquid crystal display devices.

10 Stretched film 20 Weak layer 30 Reinforced layer 40 Intermediate layer (compatible region)
100 Retardation film 110 Polarizing plate 120 Protective layer 200 Retardation layer-attached polarizing plate

Claims (7)

A stretched film containing a cyclic olefin resin and exhibiting a refractive index characteristic of nx>nz>ny; a fragile layer formed on at least one surface of the stretched film and substantially composed of components of the stretched film ; and a reinforcing layer provided on the outside of the fragile layer;
the reinforcing layer is a cured layer of an active energy ray curable resin,
Between the reinforcing layer and the fragile layer, an intermediate layer is formed which is a compatible region containing the components of the reinforcing layer and the components of the fragile layer.
Phase contrast film. The retardation film according to claim 1, wherein the reinforcement layer is a cured layer of an active energy ray-curable adhesive. The retardation film according to claim 1 or 2, which has the fragile layer, the reinforcing layer, and the intermediate layer on both sides of the stretched film. The retardation film according to any one of claims 1 to 3, wherein the fragile layer has a thickness _T1 of 200 nm to 300 nm before the intermediate layer is formed. 5. The retardation film according to claim 4, wherein a ratio T ₂ /T ₁ of the thickness T ₁ to the thickness T ₂ of the intermediate layer is 0.1 to 0.7. A polarizing plate with a retardation layer, comprising a polarizer and the retardation film according to any one of claims 1 to 5. An image display device comprising the retardation layer-attached polarizing plate according to claim 6 .

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