Optical laminate and image display unit

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 Art

[0002] In an image display device (for example, a liquid crystal display device, an organic EL display device, a quantum dot display device), in many cases, a polarizing plate is disposed on at least one side of a display panel due to its image formation method. Further, for the purpose of thinning and high functionality, a protective layer may be provided only on one side of a polarizer in the polarizing plate, and a specific resin layer may be provided on the side where the protective layer is not provided. In such a polarizing plate having a configuration of a protective layer / polarizer / resin layer, cracks often occur in the polarizer in a high temperature environment. Further, since the polarizing plate is often used integrally with a retardation layer (retardation film), when a retardation layer is provided on the polarizing plate as described above, cracks in the polarizer often become more prominent in a high temperature environment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above conventional problems, and its main object is to provide an optical laminate in which a specific resin layer is disposed adjacent to a polarizer and cracks in the polarizer are suppressed in a high temperature environment.

Means for Solving the Problems

[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 relationship A < B is satisfied. [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 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, the refractive index characteristics of which show the relationship nz > nx = ny. [6] In any 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 of the above [1] to [6], the indentation elastic modulus of the resin layer is 8 GPa or more. [8] In any of the above [1] to [7], the thickness of the resin layer is 1 μm or less. [9] In any 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 [1] to [9] above, the orientation function of the polarizer is 0.30 or more.

[11] In any one of [1] to

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

[12] According to another aspect of the present invention, an image display device is provided. This image display device includes an image display panel and any one of the optical laminates of [1] to

[11] above bonded to the image display panel via the first adhesive layer. [Effects of the Invention]

[0006] According to an embodiment of the present invention, an optical laminate can be realized in which a specific resin layer is disposed adjacent to a polarizer and cracks in the polarizer are suppressed in a high-temperature environment. [Brief Description of the Drawings]

[0007]

Figure 1

Figure 2

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

[0009] [Definitions of Terms and Symbols] The definitions of terms and symbols 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 the film measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation of the film measured with light of wavelength 550 nm at 23°C. Re(λ) can be obtained 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 the film measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction of the film measured with light of wavelength 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth = (nx - nz) × d, where d (nm) is the thickness of the film. (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both the 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 in the illustrated example has a polarizing plate 10, a resin layer 20, and a first adhesive layer 50 in this order from the upper side of the drawing. The upper side of the drawing may correspond to the viewing side when the optical laminate is applied to an image display device; the lower side of the drawing may correspond to the image display panel side. The polarizing plate 10 includes a polarizer 11 and a protective layer 12 disposed 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 single-protection 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 disposed adjacent to the polarizer 11. In the present specification, "disposed adjacent to the polarizer" means that the resin layer is directly formed on the polarizer or the resin layer is laminated on the polarizer via an adhesive layer (typically, an adhesive layer or a pressure-sensitive adhesive layer). In other words, it means that no optical functional layer is interposed between the polarizer and the resin layer. The first adhesive layer 50 is disposed as the outermost layer on the resin layer 20 side. The optical laminate can be attached to the image display panel by the first adhesive layer 50.

[0011] The resin layer 20 is typically a solidified or cured product of a coating film of a resin organic solvent solution. 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 can have a barrier function. The resin layer 20 can suppress the movement of moisture in a high-temperature and high-humidity environment and can suppress the end discoloration of the polarizer. Further, the resin layer 20 can suppress the movement of iodine that may be contained in the polarizer and can reduce the influence that the polarizer can exert on other members. For example, when the optical laminate is mounted on an image display device (e.g., an organic EL display device), it can suppress the corrosion of the metal members of the image display device. By providing such a resin layer adjacent to the polarizer according to the embodiment of the present invention, the end discoloration in a high-temperature and high-humidity environment can be suppressed even better. Further, by providing such a resin layer adjacent to the polarizer, the protective layer can be omitted. Since the resin layer is significantly thinner than the protective layer, it 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 Item C below. In the optical laminate in which such a specific resin layer is disposed adjacent to the polarizer, the effects according to the embodiment of the present invention become remarkable.

[0012] In an embodiment of the present invention, the shrinkage rate in the absorption axis direction of the polarizer 11 is 2.5% or less, the thickness of the first adhesive layer 50 is 17 μm or less, and the storage elastic modulus at 23°C is 0.10 MPa or more. With such a configuration, in an optical laminate in which the above-described specific resin layer is disposed adjacent to the polarizer, cracks in the polarizer in a high-temperature environment can be significantly suppressed. Details are as follows. The resin layer as described above is very hard in relation to its properties (as will be described later, the indentation elastic modulus is, for example, 8 GPa or more), and as a result, it is very prone to cracking. The polarizer is also configured to enhance optical properties and suppress end discoloration, and as a result, it is very hard (as will be described later, the indentation hardness is, for example, 0.65 GPa or more) and prone to cracking. The inventors have found that in such an optical laminate, the resin layer cracks due to an external force or the like, and cracks occur in the polarizer following the crack in the resin layer, and the cracks progress in a high-temperature environment. As a result of intensive studies on solutions by the inventors, first, it is useful to suppress the deformation that causes cracks in the resin layer, and it has been found that the deformation of the resin layer can be favorably suppressed by optimizing the combination of the thickness and the storage elastic modulus of the first adhesive layer adjacent to the resin layer. Specifically, by setting the thickness of the first adhesive layer to 17 μm or less, deformation of the resin layer due to an external force or the like can be suppressed. Furthermore, it has been found that by setting the storage elastic modulus of the first adhesive layer to 0.10 MPa or more (by making it somewhat hard), deformation of the resin layer can be suppressed. As a countermeasure against impacts such as external forces, it is common technical knowledge that by making the adhesive layer soft, the external force or the like is absorbed to mitigate the impact. According to the embodiment of the present invention, in an optical laminate having the above-described specific configuration, by optimizing the combination of the thickness and the storage elastic modulus of the adhesive layer and making the storage elastic modulus somewhat hard, deformation of the resin layer can be suppressed, and as a result, cracks in the polarizer can be suppressed. Thus, the effect according to the embodiment of the present invention is achieved by means contrary to common technical 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 to follow such deformation or cracking, and as a result, cracks can be suppressed. Note that the above mechanism is merely an assumption and does not limit the present invention nor restrict the present invention by the mechanism.

[0013] In one embodiment, as in the optical laminate 101 shown in FIG. 2, a retardation layer 30 laminated via a second adhesive layer 60 may be further provided on the side opposite to the polarizer 11 of the resin layer 10. The retardation layer 30 typically has a circular polarization function or an elliptical polarization function. With such a configuration, an optical laminate having excellent antireflection characteristics can be obtained. In this case, as shown in the illustrated example, the optical laminate 101 may further have another retardation layer 40 having a refractive index characteristic of nz > nx = ny on the side opposite to the resin layer 20 of the retardation layer 30 (for example, between the retardation layer 30 and the first adhesive layer 50). By providing such another retardation layer, reflection in an oblique direction can be satisfactorily prevented, and a wide viewing angle of the antireflection function can be achieved. In this case, 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. It has been found that providing a retardation layer can promote cracking of the resin layer due to an external force or the like. On the other hand, as described above, by optimizing the combination of the thickness and the storage elastic modulus of the second adhesive layer adjacent to the resin layer, deformation (and as a result, cracking) of the resin layer can be satisfactorily suppressed. Here, the thickness of the second adhesive layer is 7 μm or less, thinner than the thickness of the above-described first adhesive layer, and the storage elastic modulus is 0.12 MPa or more and greater than the storage elastic modulus of the above-described first adhesive layer. Thereby, even when deformation (and as a result, cracking) of the resin layer can be promoted due to the retardation layer, such deformation and cracking can be satisfactorily suppressed. In addition, by setting the thickness and the storage elastic modulus of the first adhesive layer as described above, a synergistic effect with the effect of optimizing the combination of the thickness and the storage elastic modulus of the second adhesive layer can be obtained.

[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 includes an acetoacetyl-modified PVA-based resin. With such a configuration, a polarizer having a desired mechanical strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% by weight to 20% by weight, more preferably 8% by weight to 12% by weight, when the total amount of the PVA-based resin is 100% by weight. If the blending amount is within such a range, a polarizer having more excellent mechanical strength can be obtained.

[0019] The polarizer preferably contains an iodide or sodium chloride (which may be collectively referred to as a halide). Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 parts by weight to 20 parts by weight, more preferably 10 parts by weight to 15 parts by weight, based on 100 parts by weight of the PVA-based resin. The halide can be blended into the coating solution for forming the PVA-based resin layer, which is a precursor of the polarizer, in the manufacturing method described below, and finally introduced into the polarizer. By introducing the halide into the polarizer, the orientation of PVA molecules in the polarizer can be enhanced, so that a polarizer having excellent optical properties (typically, the coexistence of a high degree of polarization 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 even more 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 according to the embodiments of the present invention become remarkable. Furthermore, if the thickness of the polarizer is within such a 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 even more preferably 1.8% or less. The smaller the shrinkage rate, the more preferable it is. For example, it can be 0.5% or more, and for example, it can be 0.8% or more. The shrinkage rate can be measured by, for example, 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°C to 120°C Heating rate: 2°C / min Modulation: ±5°C at 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, even 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, even more preferably 0.67 GPa to 0.74 GPa, and particularly preferably 0.68 GPa to 0.72 GPa. The polarizer used in the embodiments of the present invention has the characteristic that although the indentation modulus is relatively low, the indentation hardness is very high. As a result, the polarizer according to the embodiments of the present invention can significantly suppress edge discoloration (particularly edge discoloration in a high-temperature and high-humidity environment) while being very thin. Although such a polarizer tends to crack easily, according to the embodiments of the present invention, the occurrence of cracks can be suppressed. Note that the indentation hardness and the indentation modulus can typically be measured by nanoindentation using an indentation tester (typically a nanoindenter). More specifically, the indentation hardness is calculated from the maximum load Pmax obtained from the 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 Further, the indentation elastic modulus is calculated by the following formula from the contact projected area A, the slope of the unloading curve of the displacement-load hysteresis curve (contact stiffness) S, and the pi (π). Indentation elastic 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, still more preferably 0.37 or more, and particularly preferably 0.40 or more. If the orientation function of the polarizer is within such a range, it is easy to make the indentation elastic modulus and the indentation hardness within the above desired ranges. The upper limit of the orientation function of the polarizer can be, for example, 0.70. The orientation function (y) is obtained, for example, by using a Fourier transform infrared spectrophotometer (FT-IR) and performing attenuated total reflection (ATR) measurement with polarized light as the measurement light. Specifically, the measurement is carried out in a state where the stretching direction of the polarizer is parallel and perpendicular to the polarization direction of the measurement light, and the intensity at 2941 cm -1 of the obtained absorbance spectrum is used to calculate according to the following formula. Here, the intensity I is based on the reference peak at 3330 cm -1 and is the value of 2941 cm -1 / 3330 cm -1 . Note that when y = 1, it is completely oriented, and when y = 0, it is random. Also, the peak at 2941 cm -1 is considered to be an absorption caused by the vibration of the main chain (-CH 2 -) 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, and in the case of the vibration at 2941 cm -1 , β = 90°. θ: Angle of the molecular chain with respect to the stretching direction β: Angle of the transition dipole moment with respect to the molecular chain axis D = (I ⊥ ) / (I / / ) (In this case, D increases as the PVA molecules become oriented.) I ⊥ : Absorption intensity when the polarization direction of the measurement light is perpendicular to the stretching direction of the polarizer I / / : Absorption intensity when the polarization direction of the measurement light is parallel to the stretching direction of the polarizer

[0024] The polarizer preferably exhibits absorption dichroism at any wavelength in the range 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 an embodiment of the present invention, even when the single transmittance is in the above range, the degree of polarization can be maintained within such a range.

[0025] A polarizer can typically be obtained using a laminate of a resin substrate and a PVA-based resin layer. Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. A polarizer obtained 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 it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In the present embodiment, preferably, a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include, if necessary, air stretching the laminate at a high temperature (for example, 95 °C or higher) before stretching in the aqueous boric acid solution. In addition, in the present embodiment, preferably, the laminate is subjected to a dry shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a water stretching treatment, and a dry shrinkage treatment in this order. By introducing auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in subsequent dyeing and stretching processes can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed. As a result, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and a water stretching treatment, in which the laminate is immersed in a liquid, can be improved. Furthermore, by shrinking the laminate in the width direction by dry shrinkage treatment, the optical properties can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may be used as the protective layer of the polarizer), or an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface of the resin substrate / polarizer laminate from which the resin substrate is peeled, or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described in, for example, JP-A-2012-73580 and Patent No. 6470455. The entire descriptions of these publications are incorporated herein by reference.

[0026] In an embodiment of the present invention, the stretching temperature in the air-assisted 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 still more preferably 155°C or higher. The upper limit of the stretching temperature can be, for example, 170°C. The stretching ratio is preferably 2.5 to 3.2 times, more preferably 2.6 to 3.1 times, and still more preferably 2.7 to 3.0 times. In the conventional method for manufacturing a thin polarizer, typically, the stretching is performed at a temperature of the glass transition temperature (Tg) of a thermoplastic resin substrate (typically polyethylene terephthalate (PET)) + 15°C or higher and at a temperature capable of suppressing rapid crystallization of the PVA-based resin in the air-assisted stretching process. Such a stretching temperature is specifically around 130°C. Also, the stretching ratio of the air-assisted stretching process in the conventional method for manufacturing a thin polarizer is usually set to 2.0 to 2.4 times. Since it is preferable that the total stretching ratio of the air-assisted stretching process and the water stretching process is constant (for example, 5.5 to 6.0 times), when stretching at around 130°C, if the stretching ratio exceeds 2.5 times, it is necessary to lower the stretching ratio of the water stretching process, and the optical properties may deteriorate due to a decrease in the orientation of iodine. Also, at temperatures exceeding 130°C, as described above, it is difficult to suppress rapid crystallization of the PVA-based resin, and furthermore, it is difficult to control the stretchability. The present inventors have found that by performing the air-assisted stretching process at a high temperature and a high stretching ratio, which has not been conventionally carried out, a hard thin polarizer can be realized while maintaining desired optical properties (compatibility of high single transmittance and high polarization degree).

[0027] The drying shrinkage treatment is typically performed by combining zone heating, which heats the entire zone, and heating roll drying, which heats the conveyance rolls (so-called using heating rolls). In the embodiments of the present invention, by controlling the temperature of the heating zone, the temperature of the heating roll, the time from the start of zone heating until contact with the heating roll, and the conveyance tension of the laminate, the shrinkage rate of the polarizer can be made 2.5% or less. 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 conveyance tension of the laminate is preferably 4 N / cm to 6 N / cm. The time from the start of zone heating until contact with the heating 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 the polarizer. Representative examples of the material constituting the resin film include cellulose-based resins such as triacetyl cellulose (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic-based 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 the (meth)acrylic-based resin include (meth)acrylic-based resins having a lactone ring structure. (Meth)acrylic-based resins having a lactone ring structure are described, for example, in 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 profiling and the like, 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-based resins are preferred.

[0029] The optical laminate is typically disposed on the viewing side of an image display device, and the protective layer 12 is typically disposed on its viewing side. Therefore, the protective layer 12 may be surface-treated as necessary. Examples of the surface treatment include hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment. In an embodiment of the present invention, hard coat treatment (formation of a hard coat layer) is preferred. The hard coat layer will be described later. The hard coat treatment may be combined with other surface treatments. Further / alternatively, the protective layer 12 may be treated as necessary to improve visibility when viewing through polarized sunglasses (typically, by imparting an (elliptical) polarization function or a very high retardation). By performing such treatment, excellent visibility can be achieved even when viewing the display screen through a polarizing lens such as polarized sunglasses. Therefore, the optical laminate can also 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 even more preferably 15 μm to 35 μm. When the surface treatment is performed, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

[0031] The hard coat layer is typically a cured layer of any suitable active energy ray (e.g., ultraviolet ray, visible ray, electron beam) curable resin. Examples of the active energy ray curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, epoxy resins, and the like. The hard coat layer may contain any suitable additive as necessary. Representative examples of the additive include inorganic fine particles and / or organic fine particles. The thickness of the hard coat layer can be, for example, 1 μm to 10 μm, or can 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, and more preferably 5H or less.

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

[0033] The resin layer is typically a solidified or cured product of a coating film of an organic solvent solution of a resin. According to such a configuration, excellent adhesion to the polarizer can be obtained. Specifically, the resin layer can be formed directly on the polarizer without an adhesive layer. Also, 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 still 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, still more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more.

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

[0035] As the resin constituting the resin layer, any suitable resin that can form a solidified product or a cured product (for example, a thermoset) of a coating film of an 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, and 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 above thermoplastic resin include acrylic resins and epoxy resins. An acrylic resin and an epoxy resin may be used in combination.

[0037] Typically, the acrylic resin contains, as a main component, repeating units derived from (meth)acrylate monomers having a linear or branched structure. The acrylic resin may contain repeating units derived from any suitable comonomer according to the purpose. Examples of the comonomer (copolymer monomer) include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. By appropriately setting the type, number, combination, and copolymerization ratio of the monomer units, etc., 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 acrylic resin containing a lactone ring, etc., described in paragraphs

[0034] to

[0056] of JP-A-2021-117484.

[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. Further, when an adhesive layer is disposed adjacent to the resin layer, the anchoring force of the 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 resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; novolak type epoxy resins such as phenol novolak epoxy resin, cresol novolak epoxy resin, and hydroxybenzaldehyde phenol novolak epoxy resin; polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinylphenol; naphthol type epoxy resin, naphthalene type epoxy resin, and biphenyl type epoxy resin. Preferably, bisphenol A type epoxy resin, biphenyl type epoxy resin, and bisphenol F type epoxy resin are used. The epoxy resin may be used alone or in combination of two or more.

[0039] Typically, the resin layer can be formed by applying an organic solvent solution of the above resin to form a coating film, and then solidifying or thermosetting the obtained coating film. As the organic solvent, any suitable organic solvent capable of dissolving or uniformly dispersing the above resin can be used. 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 parts by weight to 20 parts by weight with respect 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 it is preferably applied to a polarizing plate (polarizer). When the solution is applied to a substrate, a 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, by applying the solution to the polarizing plate (polarizer), the resin layer can be directly formed and the adhesive layer can be omitted. As the coating method of the solution, any appropriate method can be adopted. Specific examples include roll coating method, spin coating method, wire bar coating method, dip coating method, die coating method, curtain coating method, spray coating method, knife coating method (comma coating method, etc.).

[0041] The heating temperature for solidification or thermosetting of the above coating film is preferably 100 °C or lower, more preferably 50 °C to 70 °C. If the heating temperature is within such a 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 (substantially the organic solvent solution of the above resin) may contain any appropriate additive according to the purpose. Specific examples of the additive include ultraviolet absorber; leveling agent; antioxidants such as hindered phenol-based, phosphorus-based, sulfur-based; stabilizers such as light stabilizer, weather stabilizer, heat stabilizer; reinforcing materials such as glass fiber, carbon fiber; near-infrared absorber; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents such as anionic, cationic, nonionic surfactants; colorants such as inorganic pigments, organic pigments, dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; flame retardants, etc. The type, number, combination, addition amount, etc. of the additive can be appropriately set according to 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, 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 of 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] Since the retardation layer typically exhibits the relationship nx > ny as described above, it has a slow axis. In one embodiment, the angle θ formed 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 within such a range, by using the retardation layer as a λ / 4 plate, an optical laminate having very excellent circular polarization characteristics (and as a result, very excellent antireflection characteristics) can be obtained.

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

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

[0049] Typical examples of the resin constituting the retardation layer (resin film) include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic 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 exhibiting reverse dispersion wavelength characteristics, a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be preferably used.

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

Chemical formula

Chemical formula

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

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

[0053] E. Another retardation layer Another retardation layer 40 can be a so-called positive C-plate whose refractive index characteristics exhibit the relationship of nz > nx = ny, as described above. By using a positive C-plate as another retardation layer, reflection in an oblique direction can be prevented well, and a wide viewing angle of the antireflection function can be achieved. In this case, the retardation Rth(550) in the thickness direction of another retardation layer is preferably from -50 nm to -300 nm, more preferably from -70 nm to -250 nm, still more preferably from -90 nm to -200 nm, and particularly preferably from -100 nm to -180 nm. Here, "nx = ny" includes not only the case where nx and ny are exactly equal but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of another retardation layer can be less than 10 nm.

[0054] Another retardation layer can be formed of any suitable material. Another retardation layer preferably comprises a film containing a liquid crystal material fixed in a homeotropic orientation. The liquid crystal material (liquid crystal compound) that can be homeotropically oriented 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 compounds and the method for forming the retardation layer described in paragraphs

[0020] to

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

[0055] F. Adhesive layer The first adhesive layer 50 has a storage elastic 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 still more preferably 0.11 MPa to 0.15 MPa. The second adhesive layer 60 has a storage elastic 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 still more preferably 0.13 MPa to 0.18 MPa. If the storage elastic moduli of the first adhesive layer and the second adhesive layer are within such ranges, the effects according to the above-described embodiments of the present invention can be even more remarkable. The storage elastic modulus can be obtained by dynamic viscoelasticity measurement.

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

[0057] As the adhesive constituting the adhesive layer, any appropriate configuration can be adopted. 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 blending ratio of the monomers forming the base resin of the adhesive, as well as the blending amount of the crosslinking agent, reaction temperature, reaction time, etc., 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, etc., 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 can be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more in the solid content of the adhesive composition. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a main component in monomer units. Note that (meth)acrylate refers to acrylate and / or methacrylate. The alkyl (meth)acrylate can be contained at a ratio of preferably 80% by weight or more, more preferably 90% by weight or more in the monomer components forming the (meth)acrylic polymer. 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 of the alkyl group is preferably 3 to 9, more preferably 3 to 6. A preferred alkyl (meth)acrylate is butyl acrylate. Examples of the monomers (copolymerization 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, heterocyclic ring-containing vinyl monomers, etc. Representative examples of the copolymerization monomers include acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone.The acrylic pressure-sensitive adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include epoxy group-containing silane coupling agents. Examples of the crosslinking agent include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Further, the acrylic pressure-sensitive adhesive composition may contain an antioxidant and / or a conductive agent. Details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described, for example, in JP-A-2006-183022, JP-A-2015-199942, JP-A-2018-053114, JP-A-2016-190996, and WO 2018 / 008712, 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, embodiments of the present invention also include an image display device using such an optical laminate. Representative examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to an 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 disposed on the viewing side of the image display panel such that the polarizing plate faces the viewing side.

Examples

[0059] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods for each property in the examples are as follows.

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

[0061] (2) Indentation elastic modulus and indentation hardness Using a nanoindenter (manufactured by Hysitron Inc, "Triboindenter"), the measurement was performed by the nanoindentation method 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 following formula was calculated from the displacement-load hysteresis curve. Indentation hardness (GPa) = Pmax / A Indentation elastic modulus (GPa) = (√π / 2) × (S / √A) Here, Pmax is the maximum load obtained from the displacement-load hysteresis curve, A is the contact projection area between the indenter and the polarizer, S is the slope of the unloading curve of the displacement-load hysteresis curve (contact stiffness), and π is the pi. (Measurement conditions) · Measurement method: Single indentation method · Measurement temperature: 25°C · Indentation speed: Approximately 2 nm / sec · Indentation depth: Approximately 300 nm · Indenter used: Diamond-made, Berkovich type (triangular pyramid type) Note that the indentation elastic modulus of the resin layer was also measured in the same manner.

[0062] (3) Crack The optical laminates obtained in the examples and comparative examples were cut into pieces measuring 80 mm × 150 mm. At this time, they were cut so that the absorption axis direction of the polarizer was in the short side direction. The cut pieces were bonded to a glass plate via a first adhesive layer, and cuts (2 mm in length) extending in the short side direction (the absorption axis direction of the polarizer) and penetrating to the glass plate were made at 10 equally spaced positions along the long side direction. 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 cuts was measured. The average of the lengths of the 10 cracks was taken as the crack propagation degree and evaluated according to the following criteria. A (excellent): The crack propagation degree is less than 20 mm B (good): The crack propagation degree is 20 mm or more and less than 40 mm C (medium): The crack propagation degree is 40 mm or more and less than 60 mm D (poor): The crack propagation degree is 60 mm or more Note that the above "A" to "D" are relative evaluation criteria. Practically, if the crack propagation degree is 30 mm or less, it is good, and if the crack propagation degree is 45 mm or less, it is acceptable.

[0063] [Production Example 1: Production of Polarizer] As a thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) in a long strip shape with a Tg of about 75°C was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") in a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). 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-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 (longitudinal direction) in an oven at 140°C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by blending iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer became a desired value (dyeing treatment). Next, the laminate was immersed in a crosslinking bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 64°C (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%), uniaxial stretching was performed in the longitudinal direction (lengthwise direction) between rolls with different peripheral speeds so that the total draw ratio became 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by blending 3 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment). Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry 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 contacted the heating roll was set to 5 seconds. In this way, a polarizer P1 with a thickness of 5.5 μm was formed on the resin substrate, and a polarizing plate having a structure of resin substrate / polarizer P1 was obtained. The shrinkage rate in the absorption axis direction of the polarizer P1 was 2.5%. Further, the single transmittance Ts of the polarizer P1 was 43.0%, the indentation elastic modulus was 8.77 GPa, and the indentation hardness was 0.688 GPa.

[0064] [Production Example 2: Production of Polarizer] Except that the conveying tension of the laminate was set to 5 N / cm in the heat shrinkage treatment and the time from the oven entrance until the laminate contacted the heating roll was set to 3.5 seconds, a polarizing plate having a resin substrate / polarizer P2 structure was obtained in the same manner as in Production Example 1. The shrinkage rate in the absorption axis direction of the polarizer P2 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: Production of Polarizer] Except that the conveying tension of the laminate was set to 7 N / cm in the heat shrinkage treatment, a polarizing plate having a resin substrate / polarizer P3 structure was obtained in the same manner as in Production Example 1. The shrinkage rate in the absorption axis direction of the polarizer P3 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 Liquid for Resin Layer Formation] 97.0 parts of methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Corporation, trade name "methyl methacrylate monomer"), 3.0 parts of a copolymerizable monomer represented by the following formula (1e), and 0.2 part of a polymerization initiator (manufactured by Fujifilm Wako Pure Chemical Corporation, 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 Tg of the obtained boron-containing acrylic polymer (resin) was 110°C and the Mw was 80,000. 20 parts of the obtained boron-containing acrylic resin was dissolved in 80 parts of methyl ethyl ketone to obtain a coating liquid for resin layer formation (20% resin solution). [Chemical Formula]

[0067] [Production Example 5: Production of a Laminate of a Retardation Layer / Another Retardation Layer] 1. Production of a Retardation Film Constituting the Retardation Layer Into a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100 °C, 29.60 parts by weight (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluorene-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 1.19×10 -2 parts by weight (6.78×10 -5 mol) of calcium acetate monohydrate as a catalyst were charged. After replacing the inside of the reactor with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature reached 100 °C. Forty minutes after the start of temperature increase, the internal temperature reached 220 °C, and while controlling to maintain this temperature, reduced pressure was started and it was made 13.3 kPa in 90 minutes after reaching 220 °C. The phenol vapor by-produced along with the polymerization reaction was led to a reflux condenser at 100 °C, the monomer components contained in a small amount in the phenol vapor were returned to the reactor, and the phenol vapor that did not condense was led to a condenser at 45 °C and recovered. Nitrogen was introduced into the first reactor to once restore the pressure to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, heating and reduced pressure in the second reactor were started, and the internal temperature was made 240 °C and the pressure was made 0.2 kPa in 50 minutes. Thereafter, the polymerization was allowed to proceed until a predetermined stirring power was obtained. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and 0.7 part by mass of PMMA was melt-kneaded with 100 parts by weight of the produced polyester carbonate resin, 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 film forming apparatus equipped with a single screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 °C), a T-die (width 200 mm, set temperature: 250 °C), a chill roll (set temperature: 120 - 130 °C) and a winder was used to produce a long resin film with a thickness of 105 μm. The obtained long resin film was stretched 2.8 times in the width direction at 138 °C while adjusting to obtain a predetermined retardation, and a retardation film (quarter-wave plate) with a thickness of 38 μm was obtained. The Re(550) of the obtained retardation film was 144 nm, and Re(450) / Re(550) was 0.86.

[0068] 2. Preparation of a laminate of a retardation layer / another retardation layer 20 parts by weight of a side-chain type liquid crystal polymer represented by the following chemical formula (3) (the numbers 65 and 35 in the formula represent mol% of monomer units and are represented as a block polymer for convenience: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal showing 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) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. Then, the coating solution was applied to a PET substrate subjected to vertical alignment treatment by a bar coater, and the liquid crystal was aligned by heating and drying at 80 °C for 4 minutes. The liquid crystal layer was irradiated with ultraviolet rays to cure the liquid crystal layer, thereby forming a positive C-plate (thickness 3 μm) showing 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 to obtain a laminate of a quarter-wave plate and a positive C-plate.

Chemical formula

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

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

[0071] [Production Example 7: Preparation of the first pressure-sensitive 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 part of hydroxyethyl acrylate, and 2 parts of acrylic acid was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 90 parts of ethyl acetate per 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring for nitrogen substitution. After that, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55°C to prepare a solution of acrylic polymer A2 having a weight average molecular weight (Mw) of 2.2 million and Mw / Mn = 4.0.

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

[0073] [Production Example 8: Preparation of the second pressure-sensitive 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 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate per 100 parts of this monomer mixture. After introducing nitrogen gas while gently stirring for nitrogen substitution, the liquid temperature in the flask was maintained at around 55 °C and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A3 having a weight average molecular weight (Mw) of 2.7 million and Mw / Mn = 3.8.

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

[0075] [Production Example 9: Preparation of the second pressure-sensitive adhesive layer] (Preparation of acrylic polymer A4) Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 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 part of 4-hydroxybutyl acrylate was charged. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 90 parts of ethyl acetate per 100 parts of this monomer mixture. After introducing nitrogen gas while gently stirring to perform nitrogen substitution, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55°C to prepare a solution of acrylic polymer A4 having a weight average molecular weight (Mw) of 2.6 million and Mw / Mn = 3.9.

[0076] (Preparation of Pressure Sensitive Adhesive PSA4) To 100 parts of the solid content of the acrylic polymer A4 solution, 0.1 part of trimethylolpropane / tolylene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 part of a peroxide crosslinking agent (manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 part of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended to obtain a pressure sensitive adhesive PSA4.

[0077] [Example 1] An HC-TAC film was laminated on the surface of the polarizer P1 of the polarizing plate obtained in Production Example 1 (the surface opposite to the resin base material) via an ultraviolet curable adhesive. The HC-TAC film is a film in which an HC layer (thickness: 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness: 25 μm), and it was laminated so that the TAC film was on the polarizer side. Next, the resin base material was peeled off to obtain a polarizing plate having a configuration of HC layer / TAC film (protective layer) / polarizer P1. Next, after applying the coating liquid for forming a resin layer of Production Example 4 on the surface of the polarizer P1 using a wire bar, the coating film was dried at 60°C for 5 minutes to form a resin layer (thickness: 400 nm) configured as a solidified product of the coating film of the organic solvent solution of the resin. Next, the first pressure-sensitive adhesive layer PSA1 (thickness: 15 μm) obtained in Production Example 6 was disposed 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 pressure-sensitive adhesive layer PSA1. The obtained optical laminate was subjected to the above-mentioned evaluation of "(3) Crack". 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, the resin layer, the retardation layer, the first pressure-sensitive adhesive layer, and the 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 "protective layer" in Reference Examples 1 and 2 in the "resin layer" column of 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 embodiments of the present invention, in an optical laminate in which a specific resin layer is disposed adjacent to a polarizer, when comparing the same configurations (configurations without a retardation layer or configurations with a retardation layer), it is possible to suppress cracks in the polarizer in a high-temperature environment. Furthermore, it can be seen that cracks become prominent by providing a retardation layer. In addition, as is clear from Reference Examples 1 and 2, it can be seen that cracks become prominent 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 embodiments of the present invention can be suitably used in an image display device (typically, a liquid crystal display device or an organic EL display device).

Explanation of Signs

[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 at 95°C in the absorption axis direction of 2.5% or less, an indentation modulus of 9.5 GPa or less, and an indentation hardness of 0.65 GPa or more; The thickness of the resin layer is 5 μm or less, 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; a retardation layer laminated on the resin layer on the opposite side to 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 polarization function; The optical laminate according to claim 1 .

3. An optical laminate as described in claim 2, which satisfies the relationship A < B 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).

4. The optical laminate according to claim 3, wherein the retardation layer is composed of a stretched resin film, has Re(550) of 100 nm to 200 nm, satisfies the relationship Re(450)<Re(550), 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. An optical laminate as described in claim 4, further having another retardation layer on the opposite side of the resin layer of the retardation layer, the refractive index characteristics of which exhibit the relationship nz > nx = ny.

6. An optical laminate as described in claim 1, wherein the thickness of the resin layer is 1 μm or less.

7. An optical laminate as described in Claim 6, wherein the thickness of the polarizer is 8 μm or less.

8. An optical laminate as described in claim 7, wherein the orientation function of the polarizer is 0.30 or more.

9. An optical laminate as described in 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 an optical laminate described in any one of claims 1 to 9 bonded to the image display panel via the first adhesive layer.

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