Optical laminate and image display device

Abstract

To provide an optical laminate with a prescribed resin layer disposed adjacent to a polarizer, the optical laminate inhibiting a crack in the polarizer under a high temperature environment.SOLUTION: An optical laminate includes: a polarization plate including a polarizer and a protective layer disposed on one side of the polarizer; a resin layer disposed adjacent to the polarizer; and a first adhesive layer disposed as an outermost layer on the resin layer side. The polarizer has a contraction coefficient of 2.5% or less in an absorption axis direction. The first adhesive layer has a thickness of 17 μm or less, and a storage modulus of 0.10 MPa or more at 23°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In image display devices (e.g., liquid crystal display devices, organic EL display devices, quantum dot display devices), a polarizing plate is often arranged on at least one side of the display panel due to the image formation method. Furthermore, for the purpose of thinning and high functionality, a protective layer may be provided only on one side of the polarizer in the polarizing plate, and a specific resin layer may be provided on the side where the protective layer is not provided. In polarizing plates having such a protective layer / polarizer / resin layer configuration, cracks often occur in the polarizer under high temperature environments. Furthermore, polarizing plates are often used integrally with a retardation layer (retardation film), and when a retardation layer is provided on such a polarizing plate, cracks in the polarizer often become more noticeable under high temperature environments. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-072951 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned problems in the conventional art, and a main object of the present invention is to provide an optical laminate in which a specific resin layer is arranged adjacent to a polarizer and in which cracking of the polarizer is suppressed in a high-temperature environment. [Means for solving the problem]

[0005] [1] The optical laminate according to an embodiment of the present invention includes a polarizer, a protective layer disposed on one side of the polarizer, a resin layer disposed adjacent to the polarizer, and a first adhesive layer disposed as the outermost layer on the resin layer side. The shrinkage rate in the absorption axis direction of the polarizer is 2.5% or less, the thickness of the first adhesive layer is 17 μm or less, and the storage elastic modulus at 23°C is 0.10 MPa or more. [2] In the above [1], the optical laminate further includes a retardation layer laminated via a second adhesive layer on the side of the resin layer opposite to the polarizer. The retardation layer has a circular polarization function or an elliptical polarization function. The thickness of the second adhesive layer is 7 μm or less, and the storage elastic modulus at 23°C is 0.12 MPa or more. [3] In the above [1] or [2], when the total thickness of the polarizer and the protective layer is A (μm) and the total thickness of the resin layer, the second adhesive layer, the retardation layer, and the first adhesive layer is B (μm), the optical laminate satisfies the relationship A < B. [4] In the above [2] or [3], the retardation layer is composed of a stretched film of a resin film, Re(550) thereof is 100 nm to 200 nm, the relationship Re(450) < Re(550) is satisfied, and the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is 40° to 50°. [5] In any one of the above [2] to [4], the optical laminate further has another retardation layer on the side of the resin layer of the retardation layer opposite thereto, and the refractive index characteristics thereof show the relationship nz > nx = ny. [6] In any one of the above [1] to [5], the resin layer contains a resin having a glass transition temperature of 85°C or higher and a weight average molecular weight Mw of 25,000 or higher. [7] In any one of the above [1] to [6], the indentation elastic modulus of the resin layer is 8 GPa or more. [8] In any one of the above [1] to [7], the thickness of the resin layer is 1 μm or less. [9] In any one of the above [1] to [8], the thickness of the polarizer is 8 μm or less, the indentation elastic modulus is 9.5 GPa or less, and the indentation hardness is 0.65 GPa or more.

[10] In any one of the above [1] to [9], the orientation function of the polarizer is 0.30 or more.

[11] In any one of the above [1] to

[10] , the polarizer has a shrinkage rate in the absorption axis direction of 2.0% or less.

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

[11] above bonded to the image display panel via the first pressure-sensitive adhesive layer. Effect of the Invention

[0006] According to an embodiment of the present invention, it is possible to realize an optical laminate in which a specific resin layer is disposed adjacent to a polarizer and in which cracks in the polarizer are suppressed in a high-temperature environment. [Brief description 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. [Diagram 2] 2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Representative embodiments of the present invention will be described below, 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 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 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.

[0010] A. Optical laminate FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 of the illustrated example has a polarizing plate 10, a resin layer 20, and a first adhesive layer 50 in this order from the top of the drawing. The top of the drawing may correspond to the viewing side when the optical laminate is applied to an image display device; the bottom of the drawing may correspond to the image display panel side. The polarizing plate 10 includes a polarizer 11 and a protective layer 12 arranged on one side (viewing side) of the polarizer 11. That is, in the embodiment of the present invention, the polarizing plate is a so-called one-sided protected polarizing plate. If necessary, the protective layer 12 may include a hard coat layer (not shown) on the side opposite to the polarizer 11. The resin layer 20 is arranged adjacent to the polarizer 11. In this specification, "arranged adjacent to the polarizer" means that the resin layer is directly formed on the polarizer, or that the resin layer is laminated on the polarizer via an adhesive layer (typically, an adhesive layer, an adhesive layer). In other words, this means that no optical functional layer is interposed between the polarizer and the resin layer. The first pressure-sensitive adhesive layer 50 is disposed as the outermost layer on the resin layer 20 side. The first pressure-sensitive adhesive layer 50 enables the optical laminate to be attached to an image display panel.

[0011] The resin layer 20 is typically a solidified or cured product of a coating film of an organic solvent solution of a resin. The resin contained in the resin layer 20 typically has a glass transition temperature of 85° C. or higher and a weight average molecular weight Mw of 25,000 or higher. The resin layer 20 may have a barrier function. The resin layer 20 may suppress the movement of moisture in a high-temperature, high-humidity environment, and may suppress the discoloration of the edge of the polarizer. The resin layer 20 may also suppress the movement of iodine that may be contained in the polarizer, and may reduce the influence that the polarizer may have on other members. For example, when the optical laminate is mounted on an image display device (e.g., an organic EL display device), the corrosion of the metal members of the image display device may be suppressed. By providing such a resin layer adjacent to the polarizer according to the embodiment of the present invention, the discoloration of the edge in a high-temperature, high-humidity environment can be further suppressed. By providing such a resin layer adjacent to the polarizer, a protective layer can be omitted. The resin layer is much thinner than the protective layer, and therefore can contribute to the thinning of the optical laminate while maintaining the function of protecting the polarizer well. Details of the resin layer will be described in Section C below. In the optical laminate in which such a specific resin layer is disposed adjacent to the polarizer, the effect of the embodiment of the present invention becomes remarkable.

[0012] In the embodiment of the present invention, the shrinkage rate of the polarizer 11 in the absorption axis direction is 2.5% or less, the thickness of the first pressure-sensitive adhesive layer 50 is 17 μm or less, and the storage modulus at 23° C. is 0.10 MPa or more. With such a configuration, in an optical laminate in which the specific resin layer as described above is disposed adjacent to the polarizer, cracks in the polarizer in a high-temperature environment can be significantly suppressed. Details are as follows. The above-mentioned resin layer is very hard in relation to its characteristics (as described later, the indentation modulus is, for example, 8 GPa or more), and as a result, it is very easy to crack. The polarizer is also very hard (as described later, the indentation hardness is, for example, 0.65 GPa or more) and is easily cracked as a result of being configured to enhance the optical characteristics and suppress edge discoloration. The present inventors have found that in such an optical laminate, the resin layer cracks due to external force or the like, and cracks occur in the polarizer following the cracks in the resin layer, and the cracks progress in a high-temperature environment. As a result of intensive research into a solution, the present inventors have found that it is useful to suppress deformation that causes cracking of the resin layer, and that deformation of the resin layer can be suppressed well by optimizing the thickness and storage modulus of the first pressure-sensitive adhesive layer adjacent to the resin layer in combination. Specifically, deformation of the resin layer caused by external forces and the like can be suppressed by setting the thickness of the first pressure-sensitive adhesive layer to 17 μm or less. Furthermore, it has been found that deformation of the resin layer can be suppressed by setting the storage modulus of the first pressure-sensitive adhesive layer to 0.10 MPa or more (by making it hard to a certain extent). As a measure against impacts such as external forces, it is technically common knowledge that the pressure-sensitive adhesive layer is softened to absorb external forces and to alleviate the impact. According to an embodiment of the present invention, in an optical laminate having a specific configuration as described above, the thickness and storage modulus of the pressure-sensitive adhesive layer are optimized in combination, and the storage modulus is hardened to a certain extent, thereby suppressing deformation of the resin layer, and as a result, cracking of the polarizer can be suppressed. In this way, the effect of the embodiment of the present invention is achieved by a means opposite to technical common knowledge, and is an unexpectedly excellent effect.In addition, according to an embodiment of the present invention, by setting the shrinkage rate in the absorption axis direction of the polarizer to 2.5% or less, even if the resin layer is deformed or cracked, it is possible to make it difficult for the resin layer to follow such deformation or cracking, and as a result, it is possible to suppress cracking. Note that the above-mentioned mechanism is merely an assumption, and is not intended to limit the present invention, and the present invention is not restricted by the mechanism.

[0013] In one embodiment, as in the optical laminate 101 shown in FIG. 2, a retardation layer 30 may be further provided on the opposite side of the resin layer 10 to the polarizer 11 via a second adhesive layer 60. The retardation layer 30 typically has a circular polarization function or an elliptically polarizing function. With such a configuration, an optical laminate having excellent antireflection properties can be obtained. In this case, the optical laminate 101 may further have another retardation layer 40 whose refractive index properties show the relationship nz>nx=ny on the opposite side of the resin layer 20 of the retardation layer 30 (for example, between the retardation layer 30 and the first adhesive layer 50) as shown in the illustrated example. By providing such another retardation layer, it is possible to effectively prevent reflection in an oblique direction, and it is possible to widen the viewing angle of the antireflection function. In this case, the thickness of the second adhesive layer is 7 μm or less, and the storage modulus at 23° C. is 0.12 MPa or more. It has been found that the provision of a retardation layer can promote cracking of the resin layer caused by external forces and the like. In contrast, similarly to the above, by optimizing the thickness and storage modulus of the second adhesive layer adjacent to the resin layer in combination, deformation of the resin layer (and consequently cracking) can be well suppressed. Here, the thickness of the second adhesive layer is 7 μm or less, which is thinner than the thickness of the first adhesive layer, and the storage modulus is 0.12 MPa or more, which is greater than the storage modulus of the first adhesive layer. This makes it possible to well suppress deformation and cracking even in cases where deformation of the resin layer (and consequently cracking) may be promoted due to the retardation layer. In addition, by setting the thickness and storage modulus of the first adhesive layer as described above, a synergistic effect can be obtained with the effect of optimizing the thickness and storage modulus of the second adhesive layer in combination.

[0014] In one embodiment, for the optical laminate, when the total thickness of the polarizer and the protective layer is A (μm) and the total thickness of the resin layer, the second adhesive layer, the retardation layer, and the first adhesive layer is B (μm), the relationship A < B is satisfied. It has been found that when the thickness of the resin layer is large on the side opposite to the visible side of the optical laminate, cracking of the resin layer is promoted. According to the embodiment of the present invention, even in such a case, deformation (and as a result, cracking) of the resin layer can be suppressed, and cracking of the polarizer can be suppressed. The absolute value of the difference between the thickness A and the thickness B is preferably 10 μm to 50 μm, more preferably 20 μm to 40 μm. Further, the ratio (B / A) of the thickness B to the thickness A is preferably 1.1 to 3.0, more preferably 1.2 to 2.5. When another retardation layer is provided, the total thickness B includes the thickness of the other retardation layer.

[0015] Practically, it is preferable that a release liner (not shown) is temporarily attached to the surface of the first adhesive layer 50 until the optical laminate is put into use. By temporarily attaching the release liner, the first adhesive layer is protected and the optical laminate can be formed into a roll.

[0016] Hereinafter, the components of the optical laminate will be described. The first adhesive layer and the second adhesive layer will be described together as the adhesive layer. When it is necessary to distinguish between the first adhesive layer and the second adhesive layer, "first" or "second" will be specified.

[0017] B. Polarizing plate B-1. Polarizer Typically, the polarizer is composed of a polyvinyl alcohol (PVA) - based resin film containing a dichroic substance (for example, iodine). Examples of the PVA - based resin include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene - vinyl alcohol copolymer, and a partially saponified ethylene - vinyl acetate copolymer.

[0018] The PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin. With this configuration, a polarizer having desired mechanical strength can be obtained. The amount of the acetoacetyl-modified PVA-based 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-based 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 halide). Examples of iodide 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, based on 100 parts by weight of the PVA-based resin. In the manufacturing method described below, the halide can be blended in a coating liquid that forms a PVA-based resin layer, which is a precursor of the polarizer, and finally introduced into the polarizer. By introducing a halide into the polarizer, the orientation of the PVA molecules in the polarizer can be increased, and therefore a polarizer having excellent optical properties (typically, both a high polarization degree and a high single transmittance) can be realized.

[0020] The thickness of the polarizer is preferably 1 μm to 8 μm, more preferably 2 μm to 7 μm, and further preferably 3 μm to 6 μm. By controlling the shrinkage rate in the absorption axis direction in such a very thin and highly oriented polarizer, the effects of the embodiment of the present invention become remarkable. Furthermore, if the thickness of the polarizer is in this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0021] The shrinkage rate in the absorption axis direction of the polarizer is 2.5% or less, as described above, preferably 2.2% or less, more preferably 2.0% or less, and further preferably 1.8% or less. The smaller the shrinkage rate, the more preferable it is, and it may be, for example, 0.5% or more, or, for example, 0.8% or more. The shrinkage rate may be measured, for example, by thermomechanical analysis (TMA). More specifically, the shrinkage rate means the shrinkage rate at 95°C when measured by TMA under the following conditions. Temperature range: -50℃~120℃ Heating rate: 2℃ / min Modulation: ±5°C for 300 seconds / cycle Tensile load: 0.0196N

[0022] The indentation modulus of the polarizer is preferably 7.5 GPa to 9.4 GPa, more preferably 8.0 GPa to 9.3 GPa, still more preferably 8.2 GPa to 9.2 GPa, and particularly preferably 8.5 GPa to 9.2 GPa. The indentation hardness of the polarizer is preferably 0.65 GPa to 0.80 GPa, more preferably 0.66 GPa to 0.76 GPa, still more preferably 0.67 GPa to 0.74 GPa, and particularly preferably 0.68 GPa to 0.72 GPa. The polarizer used in the embodiment of the present invention has a feature that the indentation hardness is very large despite the relatively low indentation modulus. As a result, the polarizer according to the embodiment of the present invention can significantly suppress edge discoloration (particularly edge discoloration under a high temperature and high humidity environment) while being very thin. Such a polarizer tends to crack easily, but according to the embodiment of the present invention, the occurrence of cracks can be suppressed. The indentation hardness and the indentation modulus can be typically measured by a nanoindentation method using an indentation tester (typically, a nanoindenter). More specifically, the indentation hardness is calculated from the maximum load Pmax obtained from a displacement-load hysteresis curve obtained by pressing a probe (indenter) against the surface of the polarizer to be measured, and the contact projected area A between the indenter and the polarizer, according to the following formula: Indentation hardness (GPa) = Pmax / A The indentation elastic modulus is calculated from the above-mentioned contact projection area A, the slope of the tangent to the unloading curve of the displacement-load hysteresis curve (contact stiffness) S, and the circular constant π, according to the following formula: Indentation modulus (GPa) = (√π / 2) × (S / √A)

[0023] The orientation function of the polarizer is preferably 0.30 or more, more preferably 0.35 or more, even more preferably 0.37 or more, and particularly preferably 0.40 or more. If the orientation function of the polarizer is in such a range, it is easy to set the indentation elastic modulus and indentation hardness to the desired range. The upper limit of the orientation function of the polarizer can be, for example, 0.70. The orientation function (y) is determined, for example, by attenuated total reflection spectroscopy (ATR) measurement using a Fourier transform infrared spectrophotometer (FT-IR) and polarized light as the measurement light. Specifically, the measurement is performed with the stretching direction of the polarizer parallel and perpendicular to the polarization direction of the measurement light, and the 2941 cm of the obtained absorbance spectrum is measured. -1 The intensity I is calculated according to the following formula using the intensity of 3330 cm -1 is used as the reference peak, and 2941 cm -1 / 3330cm -1 The value is 2941 cm. Note that y=1 is perfect alignment, and y=0 is random. -1 The peak is considered to be an absorption caused by the vibration of the main chain (-CH2-) of PVA in the polarizer. y=(3 <cos 2 θ>-1) / 2 =(1-D) / [c(2D+1)] =-2×(1-D) / (2D+1) however, c = (3cos 2 β-1) / 2, 2941cm -1 For vibration, β=90°. θ: Angle of molecular chain to stretching direction β: Angle of the transition dipole moment with respect to the chain axis D=(I ⊥ ) / (I / / ) (In this case, the more the PVA molecules are oriented, the larger D becomes.) I ⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are perpendicular I / / : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are parallel

[0024] The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is, for example, 41.0% to 45.0%, preferably 41.5% to 43.5%, and more preferably 42.0% to 43.0%. 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 the embodiment of the present invention, even if the single transmittance is in the above-mentioned range, the degree of polarization can be maintained in such a range.

[0025] A polarizer can be obtained, typically, by using a laminate of a resin substrate and a PVA-based resin layer. Specific examples of polarizers obtained by 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 by using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by coating 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 to obtain a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. The stretching typically includes immersing the laminate in an aqueous boric acid solution to stretch it. Furthermore, the stretching may further include air-stretching the laminate at a high temperature (for example, 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 or dissolution of PVA 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 disturbance 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 by immersing the laminate in a liquid in a treatment process such as a dyeing process and an underwater stretching process, etc. 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 any suitable protective layer may be laminated on the peeled surface of the resin substrate / polarizer laminate after 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, JP2012-73580A and JP6470455A. The entire disclosures of these publications are incorporated herein by reference.

[0026] In the embodiment of the present invention, the stretching temperature in the auxiliary air stretching process is 140°C or higher, and the stretching ratio is 2.5 times or higher. The stretching temperature is preferably 145°C or higher, more preferably 150°C or higher, and further preferably 155°C or higher. The upper limit of the stretching temperature may be, for example, 170°C. The stretching ratio is preferably 2.5 times to 3.2 times, more preferably 2.6 times to 3.1 times, and further preferably 2.7 times to 3.0 times. In a conventional method for producing a thin polarizer, the auxiliary air stretching process is typically performed at a temperature that is a glass transition temperature (Tg) of a thermoplastic resin substrate (typically, polyethylene terephthalate (PET)) + 15°C or higher and that can suppress rapid crystallization of a PVA-based resin. Such a stretching temperature is specifically around 130°C. Moreover, the stretching ratio in the auxiliary air stretching process in a conventional method for producing a thin polarizer is usually set to 2.0 times to 2.4 times. Since the total stretching ratio of the auxiliary air stretching treatment and the underwater stretching treatment is preferably constant (for example, 5.5 to 6.0 times), when stretching is performed at around 130°C, the stretching ratio in the underwater stretching treatment needs to be reduced at a stretching ratio exceeding 2.5 times, and the optical properties may be deteriorated due to a decrease in the orientation of iodine. In addition, at a temperature exceeding 130°C, it is difficult to suppress the rapid crystallization of the PVA-based resin as described above, and further, it is difficult to control the stretchability. The present inventors have found that a hard thin polarizer can be realized while maintaining the desired optical properties (achieving both a high single transmittance and a high polarization degree) by performing the auxiliary air stretching treatment at a high temperature and a high stretching ratio that have not been performed in the past.

[0027] The drying shrinkage treatment is typically performed by combining zone heating, which is performed by heating the entire zone, with a heated roll drying method, which is performed by heating a transport roll (using a so-called heated roll). In an embodiment of the present invention, the shrinkage rate of the polarizer can be set to 2.5% or less by controlling the temperature of the heating zone, the temperature of the heating roll, the time from the start of zone heating to contact with the heated roll, and the transport tension of the laminate. The temperature of the heating zone is preferably 80°C to 110°C. The temperature of the heating roll is preferably 60°C to 90°C. The transport tension of the laminate is preferably 4N / cm to 6N / cm. The time from the start of zone heating to contact with the heated roll is preferably 1 second to 10 seconds.

[0028] B-2.Protective layer The protective layer 12 is composed of any suitable resin film that can be used as a protective film for a polarizer. Representative 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. Representative examples of (meth)acrylic resins include (meth)acrylic resins having a lactone ring structure. (Meth)acrylic resins having a lactone ring structure are described in, for example, JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, and JP-A-2005-146084. These publications are incorporated herein by reference. From the viewpoint of ease of processing into irregular shapes, etc., cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate having low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic resins are preferred.

[0029] The optical laminate is typically placed on the viewing side of an image display device, and the protective layer 12 is typically placed on the viewing side. Therefore, the protective layer 12 may be subjected to a surface treatment as necessary. Examples of the surface treatment include hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment. In the embodiment of the present invention, hard coat treatment (formation of a hard coat layer) is preferable. The hard coat layer will be described later. The hard coat treatment may be combined with other surface treatments. In addition, the protective layer 12 may be subjected to a treatment for improving visibility when viewed through polarized sunglasses (typically, imparting an (elliptical) polarizing function or imparting an ultra-high phase difference) as necessary. By performing such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the optical laminate can be suitably applied to an image display device that can be used outdoors.

[0030] The thickness of the protective layer 12 is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and further preferably 15 μm to 35 μm. When a surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0031] The hard coat layer is typically a cured layer of any appropriate active energy ray (e.g., ultraviolet ray, visible light, electron beam) curable resin. Examples of active energy ray curable resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain any appropriate additives as necessary. Representative examples of the additives include inorganic fine particles and / or organic fine particles. The thickness of the hard coat layer may be, for example, 1 μm to 10 μm, and may be, for example, 3 μm to 7 μm. The hard coat layer preferably has a pencil hardness of H or more, more preferably 2H or more, and even more preferably 3H or more. On the other hand, the pencil hardness of the hard coat layer is preferably 6H or less, more preferably 5H or less.

[0032] C.Resin layer The resin layer 20 can have a barrier function as described above. In this regard, the resin layer is typically hard. Specifically, the indentation modulus of the resin layer is preferably 8 GPa or more, more preferably 10 GPa to 20 GPa, and further preferably 11 GPa to 15 GPa. According to the embodiment of the present invention, even though the resin layer is thus hard and prone to cracking, it is possible to suppress cracking of the polarizer adjacent to the resin layer.

[0033] The resin layer is typically a solidified or cured product of a coating film of a resin in an organic solvent solution. With such a configuration, the adhesion to the polarizer can be excellent. Specifically, the resin layer can be formed directly on the polarizer without an adhesive layer. In addition, the thickness of the resin layer can be made very thin. The thickness of the resin layer is, for example, 10 μm or less, preferably 5 μm or less, more preferably 1 μm or less, and even more preferably 0.7 μm or less. The thickness of the resin layer is preferably 0.05 μm or more, more preferably 0.08 μm or more, even more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more.

[0034] In one embodiment, the resin constituting the resin layer has a glass transition temperature (Tg) of 85° C. or more and a weight average molecular weight (Mw) of 25,000 or more. The Tg of the resin constituting the resin layer is preferably 90° C. or more, more preferably 100° C. or more, even more preferably 110° C. or more, and particularly preferably 120° C. or more. The Tg may be, for example, 200° C. or less. The Mw of the resin constituting the resin layer is preferably 30,000 or more, more preferably 35,000 or more, and even more preferably 40,000 or more. When the Tg and Mw of the resin constituting the resin layer are in such ranges, excellent barrier function can be achieved despite a very thin thickness.

[0035] As the resin constituting the resin layer, any suitable resin that can form a solidified or cured product (for example, a thermoset product) of the coating film of the organic solvent solution can be used. As the resin constituting the resin layer, preferably, a thermoplastic resin or a thermosetting resin having the above-mentioned Tg and Mw is used, more preferably, a thermoplastic resin is used. Only one type of resin may be used, or two or more types may be used in combination.

[0036] Examples of the thermoplastic resin include acrylic resins and epoxy resins. The acrylic resin and the epoxy resin may be used in combination.

[0037] The acrylic resin typically contains a repeating unit derived from a (meth)acrylic acid ester monomer having a linear or branched structure as the main component. The acrylic resin may contain a repeating unit derived from any appropriate copolymerization monomer according to the purpose. Examples of the copolymerization monomer (copolymerization monomer) include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, an aromatic ring-containing (meth)acrylate, and a heterocyclic ring-containing vinyl monomer. By appropriately setting the type, number, combination, and copolymerization ratio of the monomer units, an acrylic resin having the above-mentioned predetermined Mw can be obtained. Specific examples of the acrylic resin include the boron-containing acrylic resin and the lactone ring-containing acrylic resin described in

[0034] to

[0056] of JP 2021-117484 A.

[0038] As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. By using an epoxy resin having an aromatic ring as the epoxy resin, the adhesion between the resin layer and the polarizer can be improved. Furthermore, when a pressure-sensitive adhesive layer is disposed adjacent to the resin layer, the anchoring force of the pressure-sensitive adhesive layer can be improved. Examples of the epoxy resin having an aromatic ring include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; novolac-type epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, and hydroxybenzaldehyde phenol novolac epoxy resins; polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol, naphthol-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins. Preferably, bisphenol A-type epoxy resins, biphenyl-type epoxy resins, and bisphenol F-type epoxy resins are used. Only one type of epoxy resin may be used, or two or more types may be used in combination.

[0039] The resin layer can be typically formed by applying an organic solvent solution of the resin to form a coating film, and solidifying or thermally curing the resulting coating film. Any appropriate organic solvent capable of dissolving or uniformly dispersing the resin can be used as the organic solvent. Specific examples of the organic solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed.

[0040] The solution may be applied to a separately prepared substrate, but is preferably applied to a polarizing plate (polarizer). When the solution is applied to the substrate, the solidified or cured product (resin layer) of the coating film formed on the substrate is transferred to the polarizing plate (polarizer). Since the transfer is typically performed via an adhesive layer, the resin layer can be directly formed by applying the solution to the polarizing plate (polarizer), and the adhesive layer can be omitted. Any appropriate method can be adopted as the method for applying the solution. Specific examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating, etc.).

[0041] The heating temperature for solidifying or thermosetting the coating film is preferably 100° C. or less, and more preferably 50° C. to 70° C. If the heating temperature is within this range, adverse effects on the polarizer can be prevented. The heating time can be, for example, 1 minute to 10 minutes.

[0042] The resin layer (essentially, the organic solvent solution of the resin) may contain any suitable additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenols, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizers; lubricants; and flame retardants. The type, number, combination, and amount of additives can be appropriately set depending on the purpose.

[0043] D. Retardation layer As described above, the retardation layer 40 typically has a circular polarization function or an elliptical polarization function. The retardation layer may be a single layer or may have a laminated structure of two or more layers. When the retardation layer is composed of a single layer, the retardation layer can be a λ / 4 plate. When the retardation layer has a laminated structure, the retardation layer can be a laminate of a λ / 2 plate and a λ / 4 plate. The retardation layer can be composed of any suitable material. Specifically, the retardation layer may be an alignment cured layer of a liquid crystal compound, a resin film (typically, a stretched film), or a combination thereof. In an embodiment of the present invention, the retardation layer can typically be composed of a stretched film of a resin film. In this case, the retardation layer can typically be a single layer (λ / 4 plate). Hereinafter, the stretched film of the resin film that is a single layer will be briefly described.

[0044] The retardation layer can function as a λ / 4 plate as described above. In this case, the in-plane retardation Re(550) of the retardation layer is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. In this case, the retardation layer preferably exhibits a refractive index characteristic of nx > ny ≧ nz. Here, "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where they are substantially equal. Therefore, within a range that does not impair the effects according to the embodiments of the present invention, ny < nz may occur.

[0045] The Nz coefficient of the retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained optical laminate is used in an image display device, a very excellent reflected hue can be achieved.

[0046] The retardation layer typically has a slow axis since it has the relationship of nx>ny as described above. In one embodiment, the angle θ between the slow axis of the retardation layer and the absorption axis of the polarizer is, for example, 40° to 50°, preferably 42° to 48°, and more preferably about 45°. If the angle θ is in this range, the retardation layer is a λ / 4 plate, and an optical laminate having very good circular polarization properties (as a result, very good antireflection properties) can be obtained.

[0047] The thickness of the retardation layer can be set to a thickness that can function appropriately as a λ / 4 plate, typically. The thickness of the retardation layer can be, for example, 10 μm to 60 μm. If the thickness of the retardation layer is in such a range, the total thickness B of the resin layer, the second adhesive layer, the retardation layer, and the first adhesive layer is large. That is, the thickness of the resin layer on the side opposite to the viewing side in the optical laminate is large, and cracking of the resin layer due to external forces or the like can be promoted. According to the embodiment of the present invention, even when a retardation layer having such a thickness is provided, deformation of the resin layer (resulting in cracking) can be suppressed, and cracking of the polarizer can be suppressed.

[0048] The retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes according to the wavelength of the measurement light. In one embodiment, the retardation layer exhibits a reverse dispersion wavelength characteristic. In this case, Re(450) / Re(550) of the retardation layer is, for example, 0.8 or more and less than 1, and preferably 0.8 or more and 0.95 or less. With such a configuration, it is possible to realize very excellent antireflection properties.

[0049] Representative examples of the resin constituting the retardation layer (resin film) include polycarbonate-based resins, polyester carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cyclic olefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic-based resins. These resins may be used alone or in combination (for example, blended or copolymerized). When the retardation layer is composed of a resin film that exhibits reverse dispersion wavelength characteristics, polycarbonate-based resins or polyester carbonate-based resins (hereinafter may be simply referred to as polycarbonate-based resins) can be suitably used.

[0050] The polycarbonate-based resin contains at least one structural unit selected from the group consisting of structural units represented by the following general formula (1) and / or structural units represented by the following general formula (2). These structural units are structural units derived from divalent oligofluorene, and may be referred to as oligofluorene structural units hereinafter. Such polycarbonate-based resins have positive refractive index anisotropy. [ka] [ka]

[0051] The retardation layer typically further contains an acrylic resin, the content of which is 0.5% by mass to 1.5% by mass.

[0052] Details of polycarbonate-based resins that can be suitably used in the retardation layer and methods for forming the retardation layer are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, JP 2015-212818 A, WO 2015 / 159928 A, and JP 2021-67762 A, the descriptions of which are incorporated herein by reference.

[0053] E. Another retardation layer The separate retardation layer 40 may be a so-called positive C plate whose refractive index characteristics show the relationship nz>nx=ny, as described above. By using a positive C plate as the separate retardation layer, it is possible to effectively prevent reflection in an oblique direction, and the anti-reflection function can be made to have a wide viewing angle. In this case, the thickness direction retardation Rth(550) of the separate retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, further preferably -90 nm to -200 nm, and particularly preferably -100 nm to -180 nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the separate retardation layer may be less than 10 nm.

[0054] The separate retardation layer may be formed of any appropriate material. The separate retardation layer is preferably made of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compound and the method for forming the retardation layer described in

[0020] to

[0028] of JP-A-2002-333642. In this case, the thickness of the separate retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

[0055] F.Adhesive layer The first pressure-sensitive adhesive layer 50 has a storage modulus at 23°C of 0.10 MPa or more, as described above, preferably 0.10 MPa to 0.20 MPa, more preferably 0.11 MPa to 0.17 MPa, and even more preferably 0.11 MPa to 0.15 MPa. The second pressure-sensitive adhesive layer 60 has a storage modulus at 23°C of 0.12 MPa or more, as described above, preferably 0.12 MPa to 0.25 MPa, more preferably 0.13 MPa to 0.20 MPa, and even more preferably 0.13 MPa to 0.18 MPa. When the storage moduli of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are within such ranges, the effects of the above-described embodiment of the present invention can be more remarkable. The storage modulus can be obtained by dynamic viscoelasticity measurement.

[0056] The first pressure-sensitive adhesive layer 50 has a thickness of 17 μm or less, preferably 5 μm to 17 μm, more preferably 8 μm to 16 μm, and even more preferably 10 μm to 15 μm, as described above. The second pressure-sensitive adhesive layer 60 has a thickness of 7 μm or less, preferably 2 μm to 7 μm, more preferably 3 μm to 6 μm, and even more preferably 4 μm to 5 μm, as described above. If the thicknesses of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are within such ranges, the effects of the above-described embodiment of the present invention can become even more remarkable.

[0057] Any suitable structure may be adopted as the adhesive constituting the adhesive layer. Specific examples of the adhesive constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and compounding ratio of the monomers forming the base resin of the adhesive, as well as the compounding amount of the crosslinking agent, reaction temperature, reaction time, and the like, an adhesive having desired properties according to the purpose can be prepared. The base resin of the adhesive may be used alone or in combination of two or more. From the viewpoints of transparency, processability, durability, and the like, an acrylic adhesive (acrylic adhesive composition) is preferred. The acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer may be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more of the solid content of the adhesive composition. The (meth)acrylic polymer contains alkyl (meth)acrylate as a monomer unit as a main component. Incidentally, (meth)acrylate refers to acrylate and / or methacrylate. The alkyl (meth)acrylate may be contained in the monomer components forming the (meth)acrylic polymer at a ratio of preferably 80% by weight or more, more preferably 90% by weight or more. Examples of the alkyl group of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3 to 9, more preferably 3 to 6. A preferred alkyl (meth)acrylate is butyl acrylate. Examples of monomers (copolymerizable monomers) constituting the (meth)acrylic polymer include, in addition to alkyl (meth)acrylates, carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. Representative examples of the copolymerizable monomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone.The acrylic adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent. Examples of the crosslinking agent include an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent. Furthermore, the acrylic adhesive composition may contain an antioxidant and / or a conductive agent. Details of the adhesive layer or the acrylic adhesive composition are described in, for example, JP 2006-183022 A, JP 2015-199942 A, JP 2018-053114 A, JP 2016-190996 A, and WO 2018 / 008712 A, and the descriptions in these publications are incorporated herein by reference.

[0058] G. Image display device The optical laminate described in the above items A to F can be applied to an image display device. Therefore, the embodiment of the present invention also includes an image display device using such an optical laminate. Representative examples of image display devices include a liquid crystal display device and an organic EL display device. The image display device according to the embodiment of the present invention includes an image display panel, and the optical laminate described in the above items A to F bonded to the image display panel via a first pressure-sensitive adhesive layer. The optical laminate is typically placed on the viewing side of the image display panel with the polarizing plate on the viewing side. EXAMPLES

[0059] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating each property in the examples are as follows.

[0060] (1) Shrinkage rate of polarizer A laminate of the polarizer and triacetyl cellulose (TAC) film used in the examples and comparative examples was prepared. This laminate was cut into a size of 4 mm x 16 mm to prepare a test sample. The long side of the test sample was aligned with the absorption axis direction of the polarizer. This test sample was attached to a TMA device (manufactured by TA Instruments, product name "Discovery TMA450EM"), and the shrinkage rate at 95°C measured under the following conditions was taken as the shrinkage rate of the polarizer. Temperature range: -50℃~120℃ Heating rate: 2℃ / min Modulation: ±5°C for 300 seconds / cycle Tensile load: 0.0196N

[0061] (2) Indentation modulus and indentation hardness Measurement was performed by a nanoindentation method using a nanoindenter (manufactured by Hysitron Inc., "Triboindenter") under the following measurement conditions. Specifically, the probe (indenter) of the nanoindenter was pressed into the surface of the polarizer of the polarizing plate, and the displacement-load hysteresis curve was used to calculate the following formula. Indentation hardness (GPa) = Pmax / A Indentation modulus (GPa) = (√π / 2) × (S / √A) where Pmax is the maximum load obtained from the displacement-load hysteresis curve, A is the contact projected area between the indenter and the polarizer, S is the slope of the tangent to the unloading curve of the displacement-load hysteresis curve (contact stiffness), and π is the circular constant. (Measurement conditions) Measurement method: Single indentation method ·Measurement temperature: 25℃ Push-in speed: approx. 2nm / sec Indentation depth: approx. 300 nm Indenter used: Diamond, Berkovich type (triangular pyramid type) The indentation elastic modulus of the resin layer was also measured in the same manner.

[0062] (3) Cracks The optical laminates obtained in the examples and comparative examples were cut to 80 mm x 150 mm. At this time, the cut pieces were cut so that the absorption axis direction of the polarizer was the short side direction. The cut pieces were attached to a glass plate via a first adhesive layer, and slits (length 2 mm) were made at 10 equally spaced locations along the long side direction, extending in the short side direction (absorption axis direction of the polarizer) and penetrating to the glass plate. This was used as a test sample. After placing this test sample in an oven at 95°C for 8 hours, the length of the cracks extending from the slits was measured. The average length of the cracks at 10 locations was taken as the crack progression degree and evaluated according to the following criteria. A (Excellent): Crack progression is less than 20mm B (Good): Crack progression is 20mm or more but less than 40mm C (medium): Crack progression is between 40mm and 60mm D (Poor): Crack progression is 60mm or more The above "A" to "D" are relative evaluation standards, and in practical terms, a crack progression of 30 mm or less is considered good, and a crack progression of 45 mm or less is acceptable.

[0063] [Manufacturing Example 1: Preparation of polarizer] As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used, and one side of the resin substrate was subjected to a corona treatment. A PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 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., product name "GOHSEFFIMER") in a ratio of 9:1, and dissolving the mixture in water. The above PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 3.0 times in the longitudinal direction (machine direction) in an oven at 140° C. (auxiliary 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 the desired value (dyeing treatment). Next, the piece was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment). Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 64°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 (an aqueous solution obtained by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment). Thereafter, while drying in an oven maintained at about 90° C., it was brought into contact with a SUS heated roll whose surface temperature was maintained at about 75° C. (drying shrinkage treatment). Here, the conveying tension of the laminate was set to 6 N / cm, and the time from the oven entrance until the laminate came into contact with the heated roll was set to 5 seconds. In this way, a polarizer P1 having a thickness of 5.5 μm was formed on the resin substrate, and a polarizing plate having a resin substrate / polarizer P1 structure was obtained. The shrinkage rate of the polarizer P1 in the absorption axis direction was 2.5%. Furthermore, the polarizer P1 had a single transmittance Ts of 43.0%, an indentation elastic modulus of 8.77 GPa, and an indentation hardness of 0.688 GPa.

[0064] [Production Example 2: Preparation of polarizer] A polarizing plate having a resin substrate / polarizer P2 structure was obtained in the same manner as in Production Example 1, except that the transport tension of the laminate in the heat shrinking treatment was set to 5 N / cm and the time from the oven entrance to the contact of the laminate with the heated roll was set to 3.5 seconds. The shrinkage rate of the polarizer P2 in the absorption axis direction was 1.5%. The single transmittance, indentation elastic modulus, and indentation hardness of the polarizer P2 were the same as those of the polarizer P1 in Production Example 1.

[0065] [Production Example 3: Preparation of polarizer] A polarizing plate having a resin substrate / polarizer P3 structure was obtained in the same manner as in Production Example 1, except that the conveying tension of the laminate in the heat shrinking treatment was set to 7 N / cm. The shrinkage rate of the polarizer P3 in the absorption axis direction was 3.0%. The single transmittance, indentation elastic modulus, and indentation hardness of the polarizer P3 were the same as those of the polarizer P1 in Production Example 1.

[0066] [Production Example 4: Preparation of coating solution for forming resin layer] 97.0 parts of methyl methacrylate (MMA, Fujifilm Wako Pure Chemical Industries, Ltd., trade name "methyl methacrylate monomer"), 3.0 parts of a copolymerization monomer represented by the following formula (1e), and 0.2 parts of a polymerization initiator (Fujifilm Wako Pure Chemical Industries, Ltd., trade name "2,2'-azobis(isobutyronitrile)") were dissolved in 200 parts of toluene. Next, a polymerization reaction was carried out for 5.5 hours while heating to 70°C under a nitrogen atmosphere, to obtain a boron-containing acrylic resin solution (solid content concentration: 33%). The obtained boron-containing acrylic polymer (resin) had a Tg of 110°C and an Mw of 80000. 20 parts of the obtained boron-containing acrylic resin were dissolved in 80 parts of methyl ethyl ketone to obtain a coating liquid for forming a resin layer (20% resin solution). [ka]

[0067] [Production Example 5: Preparation of a laminate of a retardation layer / another retardation layer] 1. Preparation of retardation film that constitutes the retardation layer Into a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled at 100°C, 29.60 parts by weight (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by weight (0.200 mol) of isosorbide (ISB), 42.28 parts by weight (0.139 mol) of spiroglycol (SPG), 63.77 parts by weight (0.298 mol) of diphenyl carbonate (DPC), and 1.19 x 10 calcium acetate monohydrate as a catalyst were added. -2 Weight part (6.78×10 -5 mol) was charged. After the inside of the reactor was purged with nitrogen under reduced pressure, heating was performed with a heat medium, and stirring was started when the inside temperature reached 100 ° C. 40 minutes after the start of the temperature increase, the inside temperature was reached 220 ° C., and while controlling to maintain this temperature, the pressure was reduced and 90 minutes after reaching 220 ° C., the pressure was reduced to 13.3 kPa. Phenol vapor by-produced with the polymerization reaction was led to a reflux condenser at 100 ° C., a small amount of monomer components contained in the phenol vapor were returned to the reactor, and the uncondensed phenol vapor was led to a condenser at 45 ° C. and recovered. Nitrogen was introduced into the first reactor to restore the pressure to atmospheric pressure, and the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and the inside temperature was set to 240 ° C. and the pressure to 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until the specified stirring power was reached. When the specified power was reached, nitrogen was introduced into the reactor to restore pressure, and 100 parts by weight of the produced polyester carbonate resin were melt-kneaded with 0.7 part by mass of PMMA, which was then extruded into water and the strands were cut to obtain pellets. The obtained polyester carbonate resin (pellets) was vacuum-dried at 80°C for 5 hours, and then a long resin film with a thickness of 105μm was produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width 200mm, setting temperature: 250°C), a chill roll (setting temperature: 120-130°C) and a winder. The obtained long resin film was stretched 2.8 times in the width direction at 138°C while adjusting so as to obtain a predetermined retardation, to obtain a retardation film (λ / 4 plate) with a thickness of 38μm. The Re(550) of the obtained retardation film was 144nm, and Re(450) / Re(550) was 0.86.

[0068] 2. Preparation of a laminate of a retardation layer and another retardation layer A liquid crystal coating liquid was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (3) (the numbers 65 and 35 in the formula indicate the mole percent of the monomer unit, and are conveniently represented as a block polymer: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) in 200 parts by weight of cyclopentanone. The coating liquid was then applied to a PET substrate that had been subjected to a vertical alignment treatment using a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. This liquid crystal layer was irradiated with ultraviolet light to harden the liquid crystal layer, thereby forming a positive C plate (thickness 3 μm) exhibiting a refractive index characteristic of nz>nx=ny on the substrate. The obtained positive C plate was transferred to the above-mentioned retardation film via an adhesive layer, and a laminate of a λ / 4 plate and a positive C plate was obtained. [ka]

[0069] [Production Example 6: Preparation of first adhesive layer] (Preparation of Acrylic Polymer A1) A monomer mixture containing 94.9 parts of butyl acrylate, 0.1 parts of hydroxyethyl acrylate, and 5 parts of acrylic acid was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate for 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A1 with a weight average molecular weight (Mw) of 2.2 million and Mw / Mn=3.9.

[0070] (Preparation of adhesive PSA1) 0.6 parts of trimethylolpropane / tolylene diisocyanate adduct (manufactured by Tosoh Corporation, product name "Coronate L"), 0.3 parts of a peroxide crosslinking agent (manufactured by Nippon Oil & Fats Corporation, product name "Niper BMT"), and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were blended with 100 parts of the solid content of the acrylic polymer A1 solution to obtain adhesive PSA1.

[0071] [Production Example 7: Preparation of first adhesive layer] (Preparation of Acrylic Polymer A2) A monomer mixture containing 87.9 parts of butyl acrylate, 10 parts of 2-ethylhexyl acrylate, 0.1 parts of hydroxyethyl acrylate, and 2 parts of acrylic acid was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 90 parts of ethyl acetate for 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A2 with a weight average molecular weight (Mw) of 2.2 million and Mw / Mn=4.0.

[0072] (Preparation of adhesive PSA2) 0.6 parts of trimethylolpropane / tolylene diisocyanate adduct (manufactured by Tosoh Corporation, product name "Coronate L"), 0.3 parts of peroxide crosslinking agent (manufactured by Nippon Oil & Fats Corporation, product name "Niper BMT"), and 0.2 parts of epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were blended with 100 parts of the solid content of the acrylic polymer A2 solution to obtain adhesive PSA2.

[0073] [Production Example 8: Preparation of second adhesive layer] (Preparation of Acrylic Polymer A3) 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 was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate for 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A3 with a weight average molecular weight (Mw) of 2.7 million and Mw / Mn=3.8.

[0074] (Preparation of adhesive PSA3) 0.1 parts of trimethylolpropane / tolylene diisocyanate adduct (manufactured by Tosoh Corporation, product name "Coronate L"), 0.3 parts of peroxide crosslinking agent (manufactured by Nippon Oil & Fats Corporation, product name "Niper BMT"), and 0.2 parts of epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were blended with 100 parts of the solid content of the acrylic polymer A3 solution to obtain adhesive PSA3.

[0075] [Production Example 9: Preparation of second adhesive layer] (Preparation of Acrylic Polymer A4) A monomer mixture containing 82.7 parts of butyl acrylate, 10 parts of 2-ethylhexyl acrylate, 6 parts of acryloylmorpholine, 1 part of acrylic acid, and 0.3 parts of 4-hydroxybutyl acrylate was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 90 parts of ethyl acetate for 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at around 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A4 with a weight average molecular weight (Mw) of 2.6 million and Mw / Mn=3.9.

[0076] (Preparation of adhesive PSA4) 0.1 parts of trimethylolpropane / tolylene diisocyanate adduct (manufactured by Tosoh Corporation, product name "Coronate L"), 0.3 parts of a peroxide crosslinking agent (manufactured by Nippon Oil & Fats Corporation, product name "Niper BMT"), and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") were mixed with 100 parts of the solid content of the acrylic polymer A4 solution to obtain adhesive PSA4.

[0077] [Example 1] An HC-TAC film was attached to the surface (opposite side to the resin substrate) of the polarizer P1 of the polarizing plate obtained in Production Example 1 via an ultraviolet-curing adhesive. The HC-TAC film was a film in which an HC layer (7 μm thick) was formed on a triacetyl cellulose (TAC) film (25 μm thick), and the TAC film was attached to the polarizer side. Next, the resin substrate was peeled off to obtain a polarizing plate having a configuration of HC layer / TAC film (protective layer) / polarizer P1. Next, the resin layer forming coating liquid of Production Example 4 was applied to the surface of the polarizer P1 using a wire bar, and the coating film was dried at 60° C. for 5 minutes to form a resin layer (400 nm thick) constituted as a solidified coating film of the organic solvent solution of the resin. Next, the first adhesive layer PSA1 (15 μm thick) obtained in Production Example 6 was placed on the surface of the resin layer to obtain an optical laminate having a configuration of HC layer / TAC film (protective layer) / polarizer P1 / resin layer / first adhesive layer PSA1. The obtained optical laminate was subjected to the evaluation of "(3) Crack" above. The results are shown in Table 1.

[0078] [Examples 2 to 7, Comparative Examples 1 to 7, and Reference Examples 1 to 2] An optical laminate was obtained in the same manner as in Example 1, except that the polarizer, resin layer, retardation layer, first pressure-sensitive adhesive layer, and second pressure-sensitive adhesive layer were combined as shown in Table 1. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1. Note that the "protective layer" of Reference Examples 1 and 2 in the "resin layer" column in the table indicates that a TAC film was used instead of a resin layer.

[0079] [Table 1]

[0080] [evaluation] As is clear from Table 1, according to the examples of the present invention, in an optical laminate in which a specific resin layer is disposed adjacent to a polarizer, cracks in the polarizer in a high temperature environment can be suppressed when compared with the same configuration (configurations that do not include a retardation layer, or configurations that include a retardation layer). Furthermore, it can be seen that the cracks become more noticeable by providing a retardation layer. In addition, as is clear from Reference Examples 1 and 2, it can be seen that cracks become more noticeable in an optical laminate in which a specific resin layer is disposed adjacent to a polarizer. [Industrial Applicability]

[0081] The optical laminate according to the embodiment of the present invention can be suitably used in image display devices (typically, liquid crystal display devices and organic EL display devices). [Explanation of symbols]

[0082] 10 Polarizing plate 11 Polarizer 12 Protective layer 20 Resin layer 30 Retardation layer 40 Another retardation layer 50 First adhesive layer 60 Second adhesive layer 100 Optical laminate 101 Optical laminate

Claims

1. a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, a resin layer formed directly on the polarizer or laminated on the polarizer via an adhesive layer, and a first pressure-sensitive adhesive layer disposed as an outermost layer on the resin layer side; the polarizer has a shrinkage rate in the absorption axis direction of 2.5% or less at 95° C., an indentation elastic modulus of 9.5 GPa or less, and an indentation hardness of 0.65 GPa or more; The resin layer has a thickness of 5 μm or less and an indentation elastic modulus of 8 GPa or more; the resin layer contains a resin having a glass transition temperature of 85° C. or higher and a weight average molecular weight Mw of 25,000 or higher, the first pressure-sensitive adhesive layer has a thickness of 17 μm or less and a storage modulus at 23° C. of 0.10 MPa or more; The polarizer further includes a retardation layer laminated on the opposite side of the resin layer from the polarizer via a second pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer has a thickness of 7 μm or less, and a storage modulus at 23° C. that is greater than the storage modulus at 23° C. of the first pressure-sensitive adhesive layer and is 0.12 MPa or greater; Optical laminate.

2. the retardation layer is a λ / 4 plate, the retardation layer is laminated with the polarizer such that the angle between the slow axis of the retardation layer and the absorption axis of the polarizer is 40° to 50°, and the retardation layer has a circular polarization function or an elliptically polarizing function; The optical laminate according to claim 1 .

3. 3. The optical laminate according to claim 2, wherein the total thickness of the polarizer and the protective layer is A (μm) and the total thickness of the resin layer, the second pressure-sensitive adhesive layer, the retardation layer and the first pressure-sensitive adhesive layer is B (μm), satisfying the relationship A<B.

4. The optical laminate according to claim 3, wherein the retardation layer is composed of a stretched resin film, the Re(550) is 100 nm to 200 nm, the relationship of Re(450)<Re(550) is satisfied, and the angle between the slow axis of the retardation layer and the absorption axis of the polarizer is 40° to 50°. Here, Re(450) and Re(550) are in-plane retardations measured at 23° C. using light with wavelengths of 450 nm and 550 nm, respectively.

5. The optical laminate according to claim 4 , further comprising another retardation layer on the opposite side of the retardation layer to the resin layer, the another retardation layer having refractive index characteristics that satisfy the relationship nz>nx=ny.

6. The optical laminate according to claim 1 , wherein the resin layer has a thickness of 1 μm or less.

7. The optical laminate according to claim 6 , wherein the polarizer has a thickness of 8 μm or less.

8. The optical laminate according to claim 7 , wherein the orientation function of the polarizer is 0.30 or more.

9. The optical laminate according to claim 1 , wherein the shrinkage rate at 95° C. in the absorption axis direction of the polarizer is 2.0% or less.

10. An image display device comprising: an image display panel; and the optical laminate according to claim 1 attached to the image display panel via the first pressure-sensitive adhesive layer.

Images