Optical laminate and image display device using the optical laminate

Abstract

To provide an optical laminate capable of realizing an image display device in which light leakage and bright spots are suppressed even when a load exceeding a predetermined value is locally applied.SOLUTION: An optical laminate according to an embodiment of the present invention includes, in this order: a polarizing plate including a polarizer; a first retardation layer having a refractive index characteristic satisfying the relationship of nx>ny>nz; an adhesive layer; and a second retardation layer laminated on the first retardation layer via the adhesive layer, and having a refractive index characteristic satisfying the relationship of nz>nx>ny. When the thickness of the adhesive layer is t (μm), and the storage elastic moduli of the adhesive layer at 0°C, 25°C, and 40°C are E0 (MPa), E25 (MPa), and E40 (MPa), respectively, the following relationships are satisfied. E0 / t≥1.50. E25 / t≥0.30. E40 / t≥0.25.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical laminate and an image display device using the optical laminate. [Background technology]

[0002] Due to the image formation method used in image display devices (e.g., liquid crystal display devices, organic EL display devices, and quantum dot display devices), a polarizing plate is often disposed on at least one side of the display cell. Image display devices include those that require folding, such as laptop computers. When such laptop computers are folded with a foreign object present, a local load may be applied due to the foreign object. Depending on the configuration of the polarizing plate, the polarizing plate may be damaged by such a local load, resulting in light leakage or bright spots (so-called white dots) in the image display device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-160197 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned problems, and its main object is to provide an optical laminate that can realize an image display device in which light leakage and bright spots are suppressed even when a load of a predetermined value or more is applied locally. [Means for solving the problem]

[0005] [1] An optical laminate according to an embodiment of the present invention comprises, in this order: a polarizing plate including a polarizer; a first retardation layer having refractive index characteristics satisfying the relationship nx>ny>nz; an adhesive layer; and a second retardation layer laminated to the first retardation layer via the adhesive layer and having refractive index characteristics satisfying the relationship nz>nx>ny; and satisfies the following relationship when the thickness of the adhesive layer is t (μm) and the storage moduli of the adhesive layer at 0°C, 25°C, and 40°C are E0 (MPa), E25 (MPa), and E40 (MPa), respectively. E0 / t ≧1.50 E25 / t≧0.30 E40 / t≧0.25 [2] In the above [1], E0 / t is 5.00 or more, E25 / t is 2.20 or more, and E40 / t is 2.00 or more. [3] In the above [1] or [2], the E0 / t is 1500 or more, the E25 / t is 10.0 or more, and the E40 / t is 2.20 or more. [4] In any of [1] to [3] above, E0 / t is 4000 or more, E25 / t is 25.0 or more, and E40 / t is 5.00 or more. [5] In any one of the above items [1] to [4], the adhesive layer is made of an active energy ray-curable adhesive. [6] In the above [5], the active energy ray-curable adhesive contains 20 parts by weight or more of a monomer having a ring structure and 3 parts by weight or more of an oligomer or polymer having a weight-average molecular weight Mw of 1,000 or more, when the total amount of the film-forming components is 100 parts by weight. [7] In any one of the above items [1] to [6], the thickness of the adhesive layer is 2.0 μm or less. [8] In any of the above [1] to [7], the first retardation layer has an in-plane retardation Re(550) of 80 nm to 150 nm, an Nz coefficient of 1.1 to 3.0, and a slow axis direction of the first retardation layer that is substantially parallel to the absorption axis direction of the polarizer; and the second retardation layer has an in-plane retardation Re(550) of 10 nm to 60 nm, an Nz coefficient of -10 to -0.1, and a slow axis direction of the second retardation layer that is substantially perpendicular to the absorption axis direction of the polarizer. [9] In any one of the above [1] to [8], the second retardation layer is made of a polymer that does not contain fluorine atoms and has negative intrinsic birefringence, and has a thickness of 15 μm to 50 μm.

[10] In any one of the above [1] to [9], the optical laminate further includes an anti-glare layer on the side of the polarizing plate opposite to the first retardation layer.

[11] According to another aspect of the present invention, there is provided an image display device, comprising the optical laminate according to any one of [1] to

[10] above on a viewing side. [Effects of the Invention]

[0006] According to the embodiment of the present invention, an optical laminate can be obtained that can realize an image display device in which light leakage and bright spots are suppressed even when a load of a predetermined value or more is locally applied. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention.

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

[0009] (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 greatest (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 of a film measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation of a film measured with light of wavelength 550 nm at 23°C. Re(λ) is calculated by the formula: Re=(nx-ny)×d, where d(nm) is the thickness of the film. (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction of a film measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction of a film measured with light of wavelength 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth=(nx-nz)×d, where d (nm) is the thickness of the film. (4) Nz coefficient The Nz coefficient is calculated by Nz=Rth / Re. (5)Angle When angles are referred to herein, unless otherwise specified, the angles include angles in both clockwise and counterclockwise directions, so for example, "45°" includes ±45°. (6) Substantially parallel and nearly parallel In this specification, 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, in this specification, when the term "parallel" is simply used, it can also include a substantially parallel state. (7) Substantially orthogonal and nearly orthogonal 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°. Furthermore, in this specification, when the term "perpendicular" is simply used, it can also include a state where the direction is substantially perpendicular.

[0010] A. Overall structure of the optical laminate FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The illustrated optical laminate 100 includes a polarizing plate 20, a first retardation layer 21, an adhesive layer 30, and a second retardation layer 22, in this order from the top of the drawing. The top of the drawing corresponds to the viewing side, and the bottom of the drawing corresponds to the image display panel side. The first retardation layer 21 is a so-called negative B plate whose refractive index characteristics satisfy the relationship nx>ny>nz; the second retardation layer 22 is a so-called positive B plate whose refractive index characteristics satisfy the relationship nz>nx>ny. The second retardation layer 22 is laminated to the first retardation layer 21 via an adhesive layer 30. The adhesive layer 30 may be an adhesive layer or a pressure-sensitive adhesive layer. The polarizing plate 20 typically includes a polarizer 11 and a protective layer 13 disposed on at least one side of the polarizer 11 (the viewing side in the illustrated example). Depending on the purpose, another protective layer (inner protective layer: not shown) may be disposed between the polarizer 11 and the first retardation layer 21. Furthermore, depending on the purpose, the protective layer 13 may be omitted. Therefore, the polarizing plate may be a so-called double-protected polarizing plate, a so-called single-protected polarizing plate, or may be composed of a polarizer alone.

[0011] In an embodiment of the present invention, adhesive layer 30 satisfies the following relationship when the thickness is t (μm) and the storage moduli at 0°C, 25°C, and 40°C are E0 (MPa), E25 (MPa), and E40 (MPa), respectively. E0 / t ≧1.50 E25 / t≧0.30 E40 / t≧0.25 This means that the adhesive layer 30 is very thin and very hard. Light leakage and bright spots (so-called white dots), which can occur when a load exceeding a predetermined value is applied locally to an image display device, are typically caused by scratches on optical components such as polarizing plates incorporated in the image display device. In this case, those skilled in the art will understand that attempts to absorb or buffer the load and suppress scratches can be made by making the components of the optical components soft and thick. Here, the material and thickness of the optical film, one of the components of the optical components, are specified to achieve the desired optical characteristics, and significant variations in softness and thickness may be restricted. Therefore, those skilled in the art will understand that attempts to soften and thicken the adhesive and pressure-sensitive adhesive constituting the adhesive layer for laminating the optical film are made possible. According to an embodiment of the present invention, a technical means completely opposite to conventional methods can suppress light leakage and bright spots, which can occur when a load exceeding a predetermined value is applied locally to an image display device. Controlling the relationship between the storage modulus and thickness of the adhesive layer at 0°C, 25°C, and 40°C as described above has the following technical significance. Generally, at low temperatures, the higher the elastic modulus of the adhesive, the higher the resistance to high-speed indentation; at high temperatures, the higher the elastic modulus of the adhesive, the higher the resistance to low-speed indentation. The inventors discovered that white dots tend to occur more significantly when indented at high speed, and realized an optical laminate capable of suppressing white dots by laminating the first retardation layer and the second retardation layer via an adhesive layer having a particularly high E / t at low temperatures. The configuration of the adhesive layer 30 will be specifically described in Section E below.

[0012] The optical laminate may further include various optical functional layers on the side of the protective layer 13 opposite the polarizer 11 (i.e., the viewing side). Specific examples of optical functional layers include an anti-glare layer, a hard coat layer, an anti-reflection layer, an anti-fouling layer, an anti-sticking layer, and an anti-glare layer. These optical functional layers may be disposed on the viewing side of the protective layer 13 as layers separate from the protective layer 13, or may be formed as surface-treated layers by surface-treating the viewing-side surface of the protective layer 13. The type, number, combination, arrangement position, and properties of the optical functional layers may be appropriately set depending on the purpose. In one embodiment, the optical laminate may include an anti-glare layer. In this case, the anti-glare layer may be typically incorporated into the optical laminate as a laminate with a substrate. Alternatively / additionally, the optical laminate may include a hard coat layer and / or an anti-reflection layer as the outermost layer on the viewing side. When both a hard coat layer and an anti-reflection layer are provided, the anti-reflection layer may typically be the outermost layer.

[0013] The optical laminate according to the embodiment of the present invention preferably exhibits no light leakage after a puncture test under a load of 3 kg; more preferably, the light leakage is 520 μm or less after a puncture test under a load of 5 kg; and even more preferably, no light leakage occurs after a puncture test under a load of 5 kg. The puncture test can be performed, for example, by attaching a predetermined needle to a compression tester and puncturing the optical laminate with the needle at a predetermined load. "No light leakage occurs" refers to a state in which no light leakage is observed when the optical laminate after the puncture test and a standard polarizing plate are arranged so that the polarizer of the optical laminate and the polarizer of the polarizing plate are in a cross-Nicol state and observed visually. "Light leakage of 520 μm or less" refers to the maximum diameter of the light leakage portion, which is determined by imaging the light leakage portion through a microscope (magnification: 5x) and processing the image obtained when light leakage is observed through the above visual observation.

[0014] The optical laminate may be in the form of a sheet or a long strip. In this specification, "long strip" means a long, narrow shape in which the length is sufficiently longer than the width, and includes, for example, a long, narrow shape in which the length is 10 times or more, preferably 20 times or more, the width. A long optical laminate can be wound into a roll. A long optical laminate can be produced, for example, by a so-called roll-to-roll process. A sheet-like optical laminate may be produced by cutting a long optical laminate into a predetermined size (typically, a size corresponding to an image display device), or by bonding together each component (each layer) cut into a predetermined size.

[0015] In practice, the optical laminate has a pressure-sensitive adhesive layer (not shown) as the outermost layer on the second retardation layer side (image display panel side), so that it can be attached to the image display panel. In this case, it is preferable that a release liner is temporarily attached to the surface of the pressure-sensitive adhesive layer until the optical laminate is used. Temporarily attaching the release liner protects the pressure-sensitive adhesive layer and enables the optical laminate to be rolled.

[0016] The components of the optical laminate will be specifically described below.

[0017] B. Polarizing plate B-1.Polarizer The polarizer 11 is typically made of a polyvinyl alcohol (PVA) resin film containing a dichroic substance (e.g., iodine). Examples of PVA resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0018] The PVA resin preferably contains an acetoacetyl-modified PVA resin. With this configuration, a polarizer having desired mechanical strength can be obtained. The amount of the acetoacetyl-modified PVA resin is preferably 5% by weight to 20% by weight, and more preferably 8% by weight to 12% by weight, based on 100% by weight of the entire PVA resin. If the amount is within this range, a polarizer having better mechanical strength can be obtained.

[0019] The polarizer preferably contains iodide or sodium chloride (sometimes collectively referred to as a halide). Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, relative to 100 parts by weight of the PVA-based resin. In the manufacturing method described below, the halide is blended into a coating liquid that forms a PVA-based resin layer, which is a precursor of the polarizer, and can be finally introduced into the polarizer. Introducing a halide into the polarizer can improve the orientation of PVA molecules in the polarizer, thereby achieving a polarizer with excellent optical properties (typically, both a high degree of polarization and a high single-unit transmittance).

[0020] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably 41.0% to 46.0%, and more preferably 42.0% to 45.0%. 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. According to an embodiment of the present invention, even if the single transmittance is within the above range, the degree of polarization can be maintained within this range.

[0021] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 μm to 8 μm, and even more preferably 3 μm to 7 μm. By combining such a thin polarizer with a liquid crystal alignment solidified layer, it is possible to significantly reduce the thickness of the optical laminate. Furthermore, if the thickness of the polarizer is within the above range, curling during heating can be effectively suppressed and good appearance durability during heating can be obtained.

[0022] The polarizer can be produced by any appropriate method. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0023] Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as PVA films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it is preferred because of its excellent optical properties.

[0024] The dyeing with iodine is carried out, for example, by immersing the PVA film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the PVA film may be stretched and then dyed. If necessary, the PVA film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA film in water and washing it before dyeing, it is possible to wash away dirt and antiblocking agents on the surface of the PVA film, and also to swell the PVA film, thereby preventing uneven dyeing.

[0025] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, 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. The stretching typically involves immersing the laminate in a boric acid aqueous solution and stretching it. Furthermore, the stretching may further include, if necessary, in-air stretching of the laminate at an elevated temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution. Additionally, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment by heating while being transported 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 auxiliary in-air stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment, in this order. By introducing auxiliary stretching, it is possible to increase the crystallinity of PVA, even when PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of PVA in advance, problems such as a decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing or stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disordering 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 a polarizer obtained through treatment steps in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through the drying shrinkage treatment.The obtained resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or any suitable protective layer may be laminated on the surface obtained by peeling the resin substrate from the resin substrate / polarizer laminate or on the surface opposite to the peeled surface, depending on the purpose. Details of the method for producing such a polarizer are described in, for example, JP 2012-73580 A and Japanese Patent No. 6470455 A. The entire disclosures of these publications are incorporated herein by reference.

[0026] B-2.Protective layer The protective layer 13 is composed of any appropriate resin film. Typical materials for the resin film include cellulose-based resins such as triacetyl cellulose (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic resins, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins. From the viewpoint of ease of processing into profile shapes, cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic resins are preferred.

[0027] Examples of the (meth)acrylic resin include (meth)acrylic resins having a lactone ring structure and (meth)acrylic resins having a glutarimide structure. (Meth)acrylic resins having a lactone ring structure are described in, for example, JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, and JP 2005-146084 A. (Meth)acrylic resins having a glutarimide structure (hereinafter sometimes referred to as glutarimide resins) are described in, for example, JP 2006-309033 A, JP 2006-317560 A, JP 2006-328329 A, JP 2006-328334 A, JP 2006-337491 A, JP 2006-337492 A, JP 2006-337493 A, JP 2006-337569 A, JP 2007-009182 A, JP 2009-161744 A, and JP 2010-284840 A. These publications are incorporated herein by reference.

[0028] The thickness of the protective layer is typically 10 μm to 100 μm, preferably 12 μm to 40 μm, and more preferably 15 μm to 35 μm. The protective layer is typically laminated on the polarizer via an adhesive layer (specifically, an adhesive layer or a pressure-sensitive adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activation energy ray-curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive.

[0029] The indentation modulus of the protective layer is preferably 3.0 GPa or more, more preferably 3.5 GPa to 5.0 GPa. As described above, when the indentation modulus of the protective layer is within this range, the synergistic effect of the combined control of E0 / t, E25 / t, and E40 / t of the adhesive layer can suppress light leakage and bright spots even when a load of a predetermined value or more is locally applied to an image display device to which the optical laminate is applied. The indentation modulus can be measured in accordance with JIS Z 2255.

[0030] The inner protective layer (if present) is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm and the thickness direction retardation Rth(550) is -10 nm to +10 nm. The constituent material and thickness of the inner protective layer are as described above for protective layer 13.

[0031] C. First retardation layer The first retardation layer 21 may be made of a retardation film having any appropriate optical and / or mechanical properties depending on the purpose.

[0032] The in-plane retardation Re(550) of the first retardation layer is preferably 80 nm to 150 nm, more preferably 90 nm to 140 nm, and further preferably 100 nm to 130 nm.

[0033] The thickness of the first retardation layer is preferably 10 μm to 60 μm, and more preferably 30 μm to 50 μm.

[0034] As described above, the first retardation layer has refractive index characteristics that satisfy the relationship nx>ny>nz. The Nz coefficient of the first retardation layer is preferably 1.1 to 3.0, and more preferably 1.3 to 2.7.

[0035] The first retardation layer can be preferably disposed so that its slow axis is substantially parallel to the absorption axis of the polarizer.

[0036] The absolute value of the photoelastic coefficient of the first retardation layer is preferably 2×10 -11 m 2 / N or less, preferably 2.0 × 10 -13 m 2 / N~1.5×10 -11 m 2 / N, more preferably 1.0 × 10 -12 m 2 / N~1.2×10 -11 m 2 / N resin. If the absolute value of the photoelastic coefficient is in this range, the phase difference is unlikely to change when shrinkage stress occurs during heating. Therefore, by forming the first retardation layer using a resin having such an absolute value of the photoelastic coefficient, thermal unevenness can be effectively prevented when the optical laminate is applied to an image display device.

[0037] The first retardation layer may exhibit an inverse wavelength dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value changes little depending on the wavelength of the measurement light. The first retardation layer preferably exhibits a flat wavelength dispersion characteristic. Specifically, Re(450) / Re(550) of the first retardation layer is preferably 0.99 to 1.03, and Re(650) / Re(550) is preferably 0.98 to 1.02.

[0038] The first retardation layer may be made of any suitable resin film that satisfies the above-mentioned characteristics. Typical examples of such resins include cyclic olefin resins, polycarbonate resins, cellulose resins, polyester resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. Among these, cyclic olefin resins are preferably used. The first retardation layer can be obtained, for example, by stretching a film formed from the above-mentioned resin. Details of cyclic olefin resins and methods for stretching resin films (methods for forming retardation films) are described, for example, in JP 2015-210459 A and JP 2016-105166 A. The disclosures of these publications are incorporated herein by reference.

[0039] D. Second retardation layer The second retardation layer 22 may be made of a retardation film having any appropriate optical and / or mechanical properties depending on the purpose.

[0040] The in-plane retardation Re(550) of the second retardation layer is preferably 10 nm to 60 nm, more preferably 20 nm to 50 nm, and further preferably 30 nm to 40 nm.

[0041] The second retardation layer has refractive index characteristics that satisfy the relationship nz>nx>ny as described above. The Nz coefficient of the second retardation layer is preferably -10 to -0.1, and more preferably -5 to -1.

[0042] The second retardation layer can be preferably disposed so that its slow axis is substantially perpendicular to the absorption axis of the polarizer.

[0043] The second retardation layer may be composed of any appropriate resin film that satisfies the above-mentioned characteristics. Such a resin may typically be a polymer having negative intrinsic birefringence. A polymer having negative intrinsic birefringence refers to a polymer whose refractive index in the oriented direction becomes relatively small when oriented by stretching or the like. Examples of polymers having negative intrinsic birefringence include those in which atoms, chemical bonds, or functional groups with large polarization anisotropy are introduced into the main chain and / or side chain of the polymer. More specifically, such polymers include those in which fluorine atoms or functional groups such as aromatic or carbonyl groups are introduced into the main chain and / or side chain of the polymer. However, due to concerns about global environmental issues, it is preferable not to use polymers that use compounds containing fluorine atoms as monomers (so-called fluorine-based resins and fluorine-modified resins). Therefore, it is preferable that polymers having negative intrinsic birefringence do not contain fluorine atoms. Examples of such polymers include acrylic resins, styrene-based resins, maleimide-based resins, and fumaric acid ester-based resins. From the viewpoint of balancing environmental considerations with optical properties, a fumaric acid ester resin is preferred. The second retardation layer can be obtained, for example, by appropriately stretching a film formed from the above resin.

[0044] The thickness of the second retardation layer is preferably 15 μm to 50 μm, more preferably 20 μm to 40 μm. When the second retardation layer is formed using a polymer having negative intrinsic birefringence and not containing fluorine atoms, such a thickness (particularly 15 μm or more) is preferable to obtain desired optical properties in the embodiment of the present invention. When the second retardation layer is formed using a fluorine-modified resin, its thickness is typically 10 μm or less, more specifically 5 μm to 6 μm. Here, the problem of light leakage, which was not a problem in an optical laminate including a second retardation layer using a fluorine-modified resin, becomes significant in an optical laminate including a second retardation layer using a polymer having negative intrinsic birefringence and not containing fluorine atoms. The embodiment of the present invention solves a newly apparent problem in an optical laminate of a specific configuration by controlling the E0 / t, E25 / t, and E40 / t of the adhesive layer in combination.

[0045] E. Adhesive layer As described above, the adhesive layer 30 is used to laminate the first retardation layer 21 and the second retardation layer 22. Furthermore, as described above, the adhesive layer 30 has a thickness t and storage moduli E0, E25, and E40 at 0°C, 25°C, and 40°C that satisfy the following relationships: With such an adhesive layer configuration, light leakage and bright spots can be suppressed even when a load equal to or greater than a predetermined value is locally applied to an image display device to which the optical laminate is applied. The storage moduli E0, E25, and E40 can be determined by reading the values ​​at 0°C, 25°C, and 40°C when measured at a frequency of 1 Hz, in the range of -50°C to 150°C, and at a heating rate of 5°C / min, in accordance with the method described in JIS K7244-1 "Plastics - Testing methods for dynamic mechanical properties." E0 / t ≧1.50 E25 / t≧0.30 E40 / t≧0.25

[0046] E0 / t is preferably 5.00 or more, more preferably 500 or more, even more preferably 1000 or more, particularly preferably 1500 or more, particularly preferably 2500 or more, and most preferably 4000 or more. E0 / t can be, for example, 8000 or less, or, for example, 6000 or less. When E0 / t is in such a range, the above-mentioned effects can be more remarkable.

[0047] E25 / t is preferably 1.00 or more, more preferably 2.20 or more, even more preferably 5.00 or more, particularly preferably 10.0 or more, particularly preferably 15.0 or more, and most preferably 25.0 or more. E25 / t may be, for example, 100 or less, or, for example, 80 or less. When E25 / t is in this range, the above-mentioned effects may become more pronounced.

[0048] E40 / t is preferably 2.00 or more, more preferably 2.20 or more, even more preferably 2.50 or more, particularly preferably 3.00 or more, particularly preferably 4.00 or more, and most preferably 5.00 or more. E40 / t can be, for example, 20.0 or less, or, for example, 10.0 or less. When E40 / t is in this range, the above-mentioned effects can be more pronounced.

[0049] The storage modulus E0 of the adhesive layer at 0°C can be preferably set so that E0 / t is in the desired range. The storage modulus E0 is preferably 0.80 MPa or more, more preferably 1.50 MPa or more, even more preferably 5.00 MPa or more, particularly preferably 500 MPa or more, particularly preferably 1000 MPa or more, and most preferably 1500 MPa or more. The storage modulus E0 can be, for example, 3500 MPa or less, or, for example, 3000 MPa or less. If E0 is too small, it is difficult to set E0 / t in the desired range, and the above-mentioned effects of the embodiment of the present invention may not be obtained. If E0 is too large, the adhesion between the adhesive layer and the first retardation layer and the second retardation layer may be insufficient in a low-temperature environment.

[0050] The storage modulus E25 of the adhesive layer at 25°C is preferably set so that E25 / t falls within the desired range. The storage modulus E25 is preferably 0.17 MPa or more, more preferably 0.50 MPa or more, even more preferably 0.80 MPa or more, particularly preferably 1.00 MPa or more, particularly preferably 5.00 MPa or more, and most preferably 10.0 MPa or more. The storage modulus E25 may be, for example, 25.0 MPa or less, or, for example, 18.0 MPa or less. If E25 is too small, it may be difficult to achieve E25 / t within the desired range, and the effects of the present invention may not be achieved. If E25 is too large, the adhesion between the adhesive layer and the first and second retardation layers may be insufficient at room temperature.

[0051] The storage modulus E40 of the adhesive layer at 40°C is preferably set so that E40 / t falls within the desired range. The storage modulus E40 is preferably 0.15 MPa or more, more preferably 0.30 MPa or more, even more preferably 0.50 MPa or more, particularly preferably 0.80 MPa or more, particularly preferably 1.50 MPa or more, and most preferably 2.20 MPa or more. The storage modulus E40 may be, for example, 7.00 MPa or less, or, for example, 5.00 MPa or less. If E40 is too small, it may be difficult to achieve E40 / t within the desired range, and the effects of the present invention may not be achieved. If E40 is too large, the adhesion between the adhesive layer and the first and second retardation layers may be insufficient in a high-temperature environment.

[0052] The thickness t of the adhesive layer can be set so that E0 / t, E25 / t, and E40 / t fall within the desired ranges. The thickness t of the adhesive layer is preferably 0.01 μm to 2.0 μm, more preferably 0.03 μm to 1.8 μm, even more preferably 0.1 μm to 1.5 μm, and particularly preferably 0.4 μm to 1.3 μm. With such a thickness, it is easy to set E0 / t, E25 / t, and E40 / t within the desired ranges, and as a result, an optical laminate can be obtained that can realize an image display device in which light leakage and bright spots are suppressed even when a load of a predetermined value or more is locally applied.

[0053] The adhesive layer may have any suitable configuration as long as the thickness t and the storage moduli E0, E25, and E40 satisfy the above relationships. Specifically, the adhesive layer may be an adhesive layer or a pressure-sensitive adhesive layer as described above. The adhesive layer is preferably composed of an adhesive, as this makes it easy to set E0 / t, E25 / t, and E40 / t within the desired ranges.

[0054] Representative examples of adhesives include water-based adhesives, solvent-based adhesives, emulsion-based adhesives, solventless adhesives, active energy ray-curable adhesives, and thermosetting adhesives. Active energy ray-curable adhesives are preferred. This is because active energy ray-curable adhesives have the advantage that they can easily achieve a more preferable relationship among the above relationships between thickness and storage modulus, and also that they are easily chemically stable (for example, solvent resistance and chemical resistance).

[0055] Any appropriate active energy ray-curable adhesive can be used as the active energy ray-curable adhesive. Examples of active energy ray-curable adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. In terms 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-curable adhesive can be used. This is because it has excellent versatility and its properties (composition) can be easily adjusted.

[0056] An active energy ray-curable adhesive typically contains a film-forming component and a photopolymerization initiator. Typical examples of the film-forming component include monofunctional monomers, polyfunctional monomers, oligomers, and polymers. The monofunctional monomers and polyfunctional monomers are typically radically polymerizable compounds. More specifically, the monofunctional monomers and polyfunctional monomers are compounds containing an ethylenically unsaturated group, and are preferably (meth)acrylic monomers. The monofunctional monomers, polyfunctional monomers, oligomers, and polymers may each be used alone or in combination of two or more. In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0057] Preferred monofunctional monomers include, for example, higher alkyl esters of (meth)acrylic acid, hydroxyl group-containing monomers, carboxyl group-containing monomers, nitrogen atom-containing monomers, cyclopolymerizable monomers, ring-opening polymerizable monomers, epoxy group-containing monomers, heterocycle-containing monomers, aromatic ring-containing monomers, and cyclic ester-based monomers. Specific examples of preferred monofunctional monomers include isostearyl (meth)acrylate, lauryl (meth)acrylate, isomyristyl (meth)acrylate, tridecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, (meth)acrylic acid, amide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-vinylpyrrolidone, alkoxyalkyl acrylate, glycidyl(meth)acrylate, methyl glycidyl(meth)acrylate, acryloylmorpholine, unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone, phenoxydiethylene glycol(meth)acrylate, 3-phenoxybenzyl(meth)acrylate, phenoxyethyl(meth)acrylate, γ-butyrolactone(meth)acrylate, N-methylpyrrolidone, hydroxyethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, 9-vinylcarbazole, 4-vinylphenylboronic acid, fluorene-based (meth)acrylates.More preferred examples include lauryl (meth)acrylate, acryloylmorpholine, 4-hydroxybutyl (meth)acrylate, unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone, phenoxydiethylene glycol (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0058] Examples of preferred polyfunctional monomers include polyethylene glycol di(meth)acrylate, trimethylpropane tri(meth)acrylate, glycerin tri(meth)acrylate, tripropylene glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, dioxane glycol di(meth)acrylate, EO-modified diglycerin tetra(meth)acrylate, and fluorene-based (meth)acrylate.Preferably, polyethylene glycol di(meth)acrylate and fluorene-based (meth)acrylate are mentioned.

[0059] Examples of the oligomer or polymer include (meth)acrylic oligomers or polymers and urethane (meth)acrylic oligomers or polymers. The weight-average molecular weight Mw of the oligomer or polymer is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more. The weight-average molecular weight Mw can be, for example, 5,000 or less, or, for example, 4,000 or less.

[0060] Examples of the photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2,4-diethylthioxanthone, and 2-methyl-1-(methylthiophenyl)-2-morphoninopropan-1-one.

[0061] The active energy ray-curable adhesive contains, when the total amount of the film-forming components is 100 parts by weight, preferably 20 parts by weight or more, preferably 30 parts by weight or more, more preferably 60 parts by weight or more, and even more preferably 70 parts by weight or more of a monomer having a ring structure. The content of the monomer having a ring structure may be, for example, 100 parts by weight (i.e., all of the film-forming components may be monomers having a ring structure), or may be, for example, 95 parts by weight or less, when the total amount of the film-forming components is 100 parts by weight.

[0062] The active energy ray-curable adhesive preferably contains 3 parts by weight or more of an oligomer or polymer, more preferably 5 parts by weight or more, even more preferably 7 parts by weight or more, and particularly preferably 10 parts by weight or more, based on 100 parts by weight of the total amount of the film-forming components. The content of the oligomer or polymer may be, for example, 25 parts by weight or less, or, for example, 20 parts by weight or less, based on 100 parts by weight of the total amount of the film-forming components.

[0063] F. Anti-glare layer The anti-glare layer is provided to prevent reflections of the face of a user of the image display device, the keyboard of the image display device, external light (e.g., fluorescent light), etc. The anti-glare layer is typically a layer of a liquid crystal compound with a fixed orientation. In this specification, the term "fixed orientation layer" refers to a layer in which the liquid crystal compound is oriented in a predetermined direction within the layer and the orientation state is fixed. The term "fixed orientation layer" encompasses a hardened orientation layer obtained by hardening a liquid crystal monomer. The anti-glare layer is typically formed by applying a composition containing a liquid crystal compound to the surface of an alignment film formed on a substrate and hardening and / or curing the applied layer. The liquid crystal compound may be a rod-shaped liquid crystal compound, a discotic (discotic) liquid crystal compound, or a combination thereof.

[0064] The thickness of the anti-glare layer is preferably 1 μm to 5 μm, and more preferably 1 μm to 3 μm.

[0065] Details of the constituent materials, optical properties, and formation method of the anti-glare layer are described, for example, in JP 2018-155998 A. The disclosure of this publication is incorporated herein by reference.

[0066] As described above, the anti-glare layer can be typically incorporated into the optical laminate as a laminate with a substrate. The substrate is used to form the anti-glare layer. The indentation modulus of the substrate is preferably 3.0 GPa or more, more preferably 3.5 GPa to 5.0 GPa. When the indentation modulus of the substrate is within this range, a synergistic effect with the effect achieved by controlling the E0 / t, E25 / t, and E40 / t of the adhesive layer in combination can suppress light leakage and bright spots, even when a load equal to or greater than a predetermined value is locally applied to an image display device to which the optical laminate is applied.

[0067] The substrate may be made of any suitable resin film that satisfies the desired indentation modulus. Examples of materials for forming the resin film include polyester resins such as polyethylene terephthalate (PET), cellulose resins such as triacetyl cellulose (TAC), and acrylic resins.

[0068] The thickness of the substrate can be appropriately set depending on the purpose, and is typically 20 μm to 200 μm, and preferably 25 μm to 100 μm.

[0069] The anti-glare layer (effectively a laminate of the anti-glare layer and the substrate) can typically be laminated to the protective layer 13 via a pressure-sensitive adhesive layer. In this case, the substrate side can be laminated to the protective layer 13. The thickness of the pressure-sensitive adhesive layer is preferably 10 μm to 30 μm, and more preferably 12 μm to 25 μm. The storage modulus of the pressure-sensitive adhesive layer at 25° C. is preferably 0.05 MPa to 0.25 MPa, more preferably 0.10 MPa to 0.22 MPa, and more preferably 0.13 MPa to 0.20 MPa. When the pressure-sensitive adhesive layer has such a configuration, it can contribute to suppressing light leakage and bright spots when a load of a predetermined value or more is locally applied to an image display device to which the optical laminate is applied.

[0070] G. Hard Coat Layer The hard coat layer preferably has sufficient surface hardness, excellent mechanical strength, and excellent light transmittance. The hard coat layer can be formed from any appropriate resin as long as it has such desired properties. Specific examples of the resin include thermosetting resins, thermoplastic resins, ultraviolet curing resins, electron beam curing resins, and two-component resins. Ultraviolet curing resins are preferred because they allow the hard coat layer to be formed with simple operation and high efficiency.

[0071] Specific examples of ultraviolet-curable resins include polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based ultraviolet-curable resins. Examples of ultraviolet-curable resins include ultraviolet-curable monomers, oligomers, and polymers. Examples of preferred ultraviolet-curable resins include resin compositions containing acrylic monomer or oligomer components having preferably two or more, and more preferably three to six, ultraviolet-polymerizable functional groups. Typically, ultraviolet-curable resins contain a photopolymerization initiator.

[0072] The hard coat layer can be formed by any appropriate method. For example, the hard coat layer can be formed by coating a resin composition for forming a hard coat layer on a substrate, drying the coating, and curing the dried coating film by irradiating it with ultraviolet light.

[0073] The thickness of the hard coat layer is, for example, 0.5 μm to 20 μm, and preferably 1 μm to 15 μm.

[0074] H.Anti-reflection layer The antireflection layer is provided to prevent reflection of external light (e.g., fluorescent light) and the like. Any appropriate configuration can be adopted as the configuration of the antireflection layer. Typical configurations of the antireflection layer include: (1) a single layer of a low refractive index layer having an optical film thickness of 120 nm to 140 nm and a refractive index of about 1.35 to 1.55; (2) a laminate having, from the substrate side, a medium refractive index layer, a high refractive index layer, and a low refractive index layer; and (3) an alternating multilayer laminate of a high refractive index layer and a low refractive index layer.

[0075] Examples of materials that can form a low refractive index layer include silicon oxide (SiO2) and magnesium fluoride (MgF2). The refractive index of a low refractive index layer is typically about 1.35 to 1.55. Examples of materials that can form a high refractive index layer include titanium oxide (TiO2), niobium oxide (Nb2O3 or Nb2O5), tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), and ZrO2-TiO2. The refractive index of a high refractive index layer is typically about 1.60 to 2.20. Examples of materials that can form a medium refractive index layer include titanium oxide (TiO2) and a mixture of a material that can form a low refractive index layer and a material that can form a high refractive index layer (for example, a mixture of titanium oxide and silicon oxide). The refractive index of a medium refractive index layer is typically about 1.50 to 1.85. The thicknesses of the low refractive index layer, the medium refractive index layer and the high refractive index layer can be set so as to achieve an appropriate optical film thickness depending on the layer structure of the antireflection layer, the desired antireflection performance and the like.

[0076] The antireflection layer is typically formed by a dry process. Specific examples of the dry process include PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition). PVD methods include vacuum deposition, reactive vapor deposition, ion beam assisted deposition, sputtering, and ion plating. CVD methods include plasma CVD. The dry process for forming the antireflection layer is preferably sputtering.

[0077] The thickness of the antireflection layer as described above is, for example, about 20 nm to 300 nm.

[0078] The antireflection layer may be a cured layer of a curable resin composition. The curable resin composition typically contains a binder resin and, if necessary, a photopolymerization initiator. The binder resin typically contains a curable compound. Examples of the curable compound include a polyfunctional monomer, and an oligomer or prepolymer derived from the polyfunctional monomer. In this case, the thickness of the antireflection layer may be, for example, 1 μm to 10 μm.

[0079] The difference between the maximum reflectance and the minimum reflectance of the antireflection layer in the wavelength range of 400 nm to 700 nm is preferably 2.0% or less, more preferably 1.9% or less, and even more preferably 1.8% or less. If the difference between the maximum reflectance and the minimum reflectance is in this range, coloring of reflected light can be effectively prevented.

[0080] I. Image display device The optical laminate according to the embodiment of the present invention can be applied to an image display device. Accordingly, the embodiment of the present invention also encompasses such an image display device. An image display device typically includes the above-described optical laminate on the viewing side. The optical laminate is typically arranged so that the polarizing plate is on the viewing side. Representative examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, and quantum dot display devices. The image display device according to the embodiment of the present invention suppresses light leakage and bright spots even when a load equal to or greater than a predetermined value is locally applied. In other words, according to the embodiment of the present invention, the so-called white dot phenomenon can be prevented. Therefore, if the image display device is a notebook computer, the effects of the present invention can be significant. [Example]

[0081] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement and evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are by weight.

[0082] (1) Light leakage The optical laminates obtained in the examples and comparative examples were cut into 5 cm x 5 cm pieces to serve as test samples. Next, the test samples were attached to a 1.2 mm-thick glass plate via an adhesive sheet to prepare measurement samples. The measurement samples of the examples and comparative examples were placed on the stage of an indenter CMS tester (Instron, product name "5581") equipped with a piercing jig. The piercing jig had a rounded, pointed tip. The radius of curvature R of the tip of the piercing jig was 550 μm. The piercing jig was pierced into the test sample on the stage with a load of 5 kg at room temperature (23°C ± 3°C). The optical laminate after the piercing test was positioned so that the polarizer of the optical laminate and the polarizer attached to the microscope were in a crossed Nicol position. Light leakage at this time was observed under a microscope (objective lens magnification: 5x), and the diameter of the light leakage was measured.

[0083] (2) Panel characteristics An LCD display device was prepared by peeling off the optical film laminated on the viewing side of an Apple notebook computer (MacBook Pro). The optical laminates obtained in the examples and comparative examples were laminated on the LCD display device with the anti-glare layer on the viewing side, to produce an LCD display device with the optical laminate. A black screen was displayed on the LCD display device with the optical laminate obtained in the examples and comparative examples, and the brightness was measured at a polar angle of 60° and an azimuth angle of 45° using a luminance meter (product name "Conoscope", manufactured by AUTRONIC-MELCHERS).

[0084] [Production Example 1: Preparation of Adhesive A] 20 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 10 parts of unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone (trade name "Placcel FA1DDM", manufactured by Daicel Corporation), 60 parts of fluorene-based acrylate (trade name "Oxol EA-F5710", manufactured by Osaka Gas Chemicals Co., Ltd.), 5 parts of acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd., weight average molecular weight Mw: 1900), 3 parts of 2-methyl-1-(methylthiophenyl)-2-morpholinopropan-1-one (trade name "Omnirad 907", manufactured by IGM Resins BV), and 2 parts of 2,4-diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50 ° C. for 1 hour to prepare adhesive A. The E0 of adhesive A was 2290 MPa, E25 was 12.8 MPa, and E40 was 2.81 MPa.

[0085] [Production Example 2: Preparation of Adhesive B] Adhesive B was prepared by stirring 10 parts of 4-hydroxybutyl acrylate, 35 parts of n-lauryl acrylate (trade name "Light Acrylate LA", manufactured by Kyoeisha Chemical Co., Ltd.), 40 parts of phenoxyethyl acrylate (trade name "Viscoat #192", manufactured by Kyoeisha Chemical Co., Ltd.), 1 part of polyethylene glycol diacrylate (trade name "Light Acrylate 9EG-A", manufactured by Kyoeisha Chemical Co., Ltd.), 14 parts of unsaturated urethane acrylate (trade name "EBECRYL4491", manufactured by Daicel Allnex Co., Ltd., weight average molecular weight Mw: 7000), 3 parts of 2-methyl-1-(methylthiophenyl)-2-morphoninopropan-1-one (trade name "Omnirad 907", manufactured by IGM Resins BV), and 2 parts of 2,4-diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) at 50 ° C. for 1 hour. The E0 of adhesive B was 2.80 MPa, E25 was 1.14 MPa, and E40 was 1.01 MPa.

[0086] [Production Example 3: Preparation of Adhesive C] 15 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 15 parts of unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone (trade name "Placcel FA1DDM", manufactured by Daicel Corporation), 50 parts of phenoxydiethylene glycol acrylate (trade name "Light Acrylate P2H-A", manufactured by Kyoeisha Chemical Co., Ltd.), 2 parts of polyethylene glycol diacrylate (trade name "Light Acrylate 9EG-A", manufactured by Kyoeisha Chemical Co., Ltd.), 18 parts of acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd., weight average molecular weight Mw: 1900), 3 parts of 2-methyl-1-(methylthiophenyl)-2-morphoninopropan-1-one (trade name "Omnirad 907", manufactured by IGM Resins BV), and 2,4-diethylthioxanthone (trade name "KAYACURE Two parts of "DETX-S" (manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for one hour to prepare adhesive C. The E0 of adhesive C was 0.945 MPa, the E25 was 0.195 MPa, and the E40 was 0.167 MPa.

[0087] [Production Example 4: Preparation of Adhesive D] A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 91 parts of butyl acrylate, 6 parts of acryloylmorpholine, 2.7 parts of acrylic acid, and 0.3 parts of 4-hydroxybutyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were charged to 100 parts of this monomer mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the temperature in the flask was maintained at around 55°C for 8 hours to produce a solution of acrylic polymer P4 with a weight-average molecular weight (Mw) of 2.7 million. 0.1 parts of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 parts of a peroxide crosslinking agent (benzoyl peroxide: manufactured by Nippon Oil & Fats Corporation, trade name "Niper BMT"), and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended with 100 parts of the solids content of the acrylic polymer P4 solution to obtain adhesive D. The E0 of adhesive D was 0.318 MPa, the E25 was 0.132 MPa, and the E40 was 0.116 MPa.

[0088] [Production Example 5: Preparation of Adhesive E] A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 94.9 parts of butyl acrylate, 5 parts of acrylic acid, and 0.1 parts of hydroxyethyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were charged to 100 parts of this monomer mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the temperature in the flask was maintained at around 55°C for 8 hours to produce a solution of acrylic polymer P5 with a weight average molecular weight (Mw) of 2.2 million. 0.6 parts of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.2 parts of a peroxide crosslinking agent (benzoyl peroxide: manufactured by Nippon Oil & Fats Corporation, trade name "Niper BMT"), and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended with 100 parts of the solids content of the acrylic polymer P5 solution to obtain adhesive E. The E0 of adhesive E was 0.165 MPa, the E25 was 0.113 MPa, and the E40 was 0.104 MPa.

[0089] [Example 1] 1. Preparation of Polarizing Plates A long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used as the thermoplastic resin substrate, and one side of the resin substrate was subjected to a corona treatment. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by weight of a PVA-based resin made by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFFIMER") in a 9:1 ratio, to which 13 parts by weight of potassium iodide was added, in water. The above PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60° C. to form a PVA resin layer with a thickness of 13 μm, thereby producing a laminate. The resulting laminate was uniaxially stretched 2.4 times in the machine direction (longitudinal direction) in an oven at 130°C (auxiliary in-air stretching treatment). Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilizing treatment). Next, the film was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment). Next, the sample was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). The laminate was then immersed in a boric acid aqueous solution (boric acid concentration 4 wt %, potassium iodide concentration 5 wt %) at a liquid temperature of 70°C and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment). Thereafter, the film was dried in an oven maintained at about 90°C, and brought into contact with a heated roll made of SUS whose surface temperature was maintained at about 75°C (drying shrinkage treatment). In this way, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a long polarizing plate having a resin substrate / polarizer structure was obtained. The single transmittance Ts of the polarizer was 43.3%. An acrylic resin film (40 μm thick) was attached to the surface of the obtained polarizer (the surface opposite to the resin substrate) via a UV-curable adhesive. The resin substrate was then peeled off to obtain a polarizing plate having a configuration of acrylic resin film (protective layer) / polarizer.

[0090] 2. Preparation of optical laminates A cyclic olefin film (refractive index characteristics: nx>ny>nz, Re(550): 116nm, Rth(550): 139nm, thickness: 18μm) was attached to the polarizer surface of the polarizing plate obtained above via a conventional ultraviolet curing adhesive (thickness 1μm). Furthermore, a fumaric acid ester resin film (refractive index characteristics: nz>nx>ny, Re(550): 33nm, Rth(550): -85nm, thickness: 21μm) was attached to the surface of the first retardation layer via adhesive A (thickness: 0.5μm). In this way, an optical laminate having a configuration of protective layer / polarizer / first retardation layer / adhesive layer (adhesive A) / second retardation layer was prepared.

[0091] An anti-glare laminate was produced by forming an alignment film and an alignment / solidification layer of a liquid crystal compound (anti-glare layer, total thickness with the alignment film: 2 μm) on one side of a TAC film (product name: TG40UL, thickness: 40 μm) manufactured by Fujifilm Corporation as a first substrate, according to the method described in Example 1 of JP 2014-214177 A. The anti-glare layer had an in-plane retardation Re(550) of 270 nm and was formed so that its slow axis was at an angle of 45° with respect to the absorption axis of the polarizer. Meanwhile, a hard coat layer and an anti-reflection layer were sequentially formed by standard methods on one side of a TAC film (product name: TD80UL, thickness: 80 μm) manufactured by Fujifilm Corporation as a second substrate, to produce a hard coat laminate. The total thickness of the hard coat layer and the anti-reflection layer was 4 μm. The anti-reflection layer of the anti-reflection laminate was bonded to the protective layer of the optical laminate obtained above via an acrylic adhesive (thickness: 23 μm). Next, the second substrate of the hard coat laminate was bonded to the opposite side of the anti-reflection layer of the first substrate via an acrylic adhesive (thickness: 23 μm). In this way, an optical laminate having a configuration of anti-reflection layer / hard coat layer / second substrate / first substrate / anti-reflection layer / protective layer / polarizer / first retardation layer / adhesive layer (adhesive A) / second retardation layer was obtained. The obtained optical laminate was subjected to the above evaluations (1) and (2). The results are shown in Table 1.

[0092] [Examples 2 to 4 and Comparative Examples 1 to 3] An optical laminate was produced in the same manner as in Example 1, except that the adhesive layer had the structure shown in Table 1. The obtained optical laminate was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0093] [Reference example 1] An optical laminate was produced in the same manner as in Comparative Example 1, except that the second retardation layer was changed to a fluorinated polystyrene resin film (refractive index characteristics: nz>nx>ny, Re(550): 33 nm, Rth(550): -80 nm, thickness: 6 μm). The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0094] [Table 1]

[0095] In Table 1, "Negative B" means a negative B plate (first retardation layer), and "Positive B" means a positive B plate (second retardation layer).

[0096] As is clear from Table 1, the optical laminates of the examples of the present invention can suppress light leakage even when a load of a predetermined value or more is locally applied while maintaining the display characteristics of the image display device. Furthermore, although Reference Example 1 has the same configuration as Comparative Example 1 except that the second retardation layer (positive B plate) is made of a fluorinated polystyrene-based resin film, it has good panel characteristics and light leakage is comparable to Example 4. This shows that the effects of the embodiments of the present invention are remarkable in optical laminates including a second retardation layer (positive B plate) made of a polymer that does not contain fluorine atoms. [Industrial Applicability]

[0097] The optical laminate of the present invention is suitably used in image display devices such as liquid crystal display devices, organic EL display devices, and quantum dot display devices. [Explanation of symbols]

[0098] 20 Polarizing plate 11 Polarizer 13 Protective layer 21 First retardation layer 22 Second retardation layer 30 Adhesive layer 100 Optical laminate

Claims

1. a polarizing plate including a polarizer; a first retardation layer having a refractive index characteristic that satisfies the relationship of nx>ny>nz; an adhesive layer; and a second retardation layer laminated on the first retardation layer via the adhesive layer and having a refractive index characteristic that satisfies the relationship of nz>nx>ny, in this order; When the thickness of the adhesive layer is t (μm) and the storage moduli of the adhesive layer at 0° C., 25° C. and 40° C. are E0 (MPa), E25 (MPa) and E40 (MPa), respectively, an optical laminate that satisfies the following relationship: E0 / t≧1.50 E25 / t≧0.30 E40 / t≧0.

25.

2. 2. The optical laminate according to claim 1, wherein E0 / t is 5.00 or more, E25 / t is 2.20 or more, and E40 / t is 2.00 or more.

3. 3. The optical laminate according to claim 2, wherein E0 / t is 1500 or more, E25 / t is 10.0 or more, and E40 / t is 2.20 or more.

4. The optical laminate according to claim 3, wherein E0 / t is 4000 or more, E25 / t is 25.0 or more, and E40 / t is 5.00 or more.

5. The optical laminate according to claim 1 , wherein the adhesive layer is made of an active energy ray-curable adhesive.

6. 6. The optical laminate according to claim 5, wherein the active energy ray-curable adhesive contains 20 parts by weight or more of a monomer having a ring structure and 3 parts by weight or more of an oligomer or polymer having a weight average molecular weight Mw of 1000 or more, when the total amount of the film-forming components is 100 parts by weight.

7. The optical laminate according to claim 6 , wherein the adhesive layer has a thickness of 2.0 μm or less.

8. the first retardation layer has an in-plane retardation Re(550) of 80 nm to 150 nm, an Nz coefficient of 1.1 to 3.0, and a slow axis direction of the first retardation layer substantially parallel to an absorption axis direction of the polarizer; the second retardation layer has an in-plane retardation Re(550) of 10 nm to 60 nm, an Nz coefficient of −10 to −0.1, and a slow axis direction of the second retardation layer that is substantially perpendicular to an absorption axis direction of the polarizer; The optical laminate according to any one of claims 1 to 4.

9. The optical laminate according to any one of claims 1 to 4, wherein the second retardation layer is made of a polymer having negative intrinsic birefringence that does not contain fluorine atoms, and has a thickness of 15 μm to 50 μm.

10. The optical laminate according to claim 1 , further comprising an anti-glare layer on the polarizing plate opposite to the first retardation layer.

11. An image display device comprising the optical laminate according to claim 1 on a viewing side.

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