Optical laminate, image display device, and method for manufacturing an optical laminate

Abstract

To provide an optical laminate that can be stably formed on a three-dimensional curved surface, an image display device, and a method for manufacturing an optical laminate. [Solution] An optical laminate according to an embodiment of the present invention is used in an image display device having a three-dimensional curved surface. The optical laminate is equipped with a polarizer. In the optical laminate, the maximum value in the temperature range of 50°C to 95°C in the differential curve of the heating curve of differential scanning calorimetry (DDSC) is greater than 600 μW / min and less than 3000 μW / min.

Description

[Technical Field]

[0001] The present invention relates to an optical laminate, an image display device, and a method for manufacturing an optical laminate. [Background technology]

[0002] Conventionally, image display devices, such as liquid crystal displays and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), have rapidly become widespread. It is known that optical laminates comprising a phase difference film and a polarizer can be applied to such image display devices in order to impart desired optical properties (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-124169 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, the applications of image display devices have expanded. Consequently, the shapes of image display devices have diversified, and some may have three-dimensional curved surfaces that are not developable. The manufacture of optical laminates and image display devices with three-dimensional curved surfaces is being explored by attaching optical laminates to such image display devices, or by forming the three-dimensional curved surface after attaching the optical laminate to the image display device. However, it is difficult to form a three-dimensional curved surface using the optical laminate described in Patent Document 1, and if the optical laminate is forcibly attached to or formed on a three-dimensional curved surface, defects such as breakage, wrinkles, folds, bubbles, and peeling may occur in the optical laminate. The main objective of the present invention is to provide an optical laminate, an image display device, and a method for manufacturing an optical laminate that can be stably formed into a three-dimensional curved surface. [Means for solving the problem]

[0005] [1] An optical laminate according to an embodiment of the present invention is used in an image display device having a three-dimensional curved surface. The optical laminate is equipped with a polarizer. In the optical laminate, the maximum value in the temperature range of 50°C to 95°C in the differential curve of the heating curve of differential scanning calorimetry (DDSC) is greater than 600 μW / min and less than 3000 μW / min. [2] In the optical laminate described in [1] above, the average of the loss tangent tanδ at 95°C in the absorption axis direction of the polarizer and the loss tangent tanδ at 95°C in the transmission axis direction perpendicular to the absorption axis direction may be greater than 0.06 and less than 0.2. [3] In the optical laminate described in [1] or [2] above, the maximum value of the elastic modulus at 95°C in the absorption axis direction of the polarizer and the elastic modulus at 95°C in the transmission axis direction perpendicular to the absorption axis direction is 1000 N / mm 2 More than 3400N / mm 2 It is acceptable to be less than [a certain value]. [4] In the optical laminate described in any of [1] to [3] above, the minimum value of the fracture displacement at 95°C in the absorption axis direction of the polarizer and the fracture displacement at 95°C in the transmission axis direction perpendicular to the absorption axis direction may be greater than 1.7 and less than 4.0. [5] In the optical laminate described in any of [1] to [4] above, the minimum number of bends in the MIT test in the absorption axis direction of the polarizer and the minimum number of bends in the MIT test in the transmission axis direction perpendicular to the absorption axis direction may be greater than 80 and less than 200. [6] An image display device according to another aspect of the present invention has a three-dimensional curved surface. The image display device comprises an optical laminate as described in any of [1] to [5] above. The optical laminate is attached to the three-dimensional curved surface. [7] The image display device described in [6] above may further include an image display panel. The optical laminate has a first surface opposite to the image display panel and a second surface on the side of the image display panel. The radius of curvature of the first surface of the optical laminate may be greater than the radius of curvature of the second surface of the optical laminate. [8] In the image display device described in [7] above, the radius of curvature of the first surface of the optical laminate may be 4 mm or more and less than 100 mm. [9] In the image display device described in [7] or [8] above, the optical laminate may further comprise a first phase difference film. The first phase difference film is located on the opposite side of the polarizer from the image display panel. The first phase difference film may function as a λ / 4 plate. The radius of curvature of the first phase difference film may be greater than the radius of curvature of the polarizer.

[10] The image display device described in [9] above may further include a second phase difference film, the second phase difference film located on the opposite side of the polarizer from the first phase difference film. The second phase difference film may function as a λ / 4 plate. The radius of curvature of the second phase difference film may be smaller than the radius of curvature of the polarizer.

[11] In the image display device described in

[10] above, the second phase difference film may include an orientation solidification layer of a liquid crystal compound.

[12] A method for manufacturing an optical laminate according to another aspect of the present invention includes a preparation step for preparing a polarizer. The preparation step includes a coating step, a dyeing step, and a stretching step. In the coating step, a coating solution containing a polyvinyl alcohol-based resin is applied to a substrate to obtain a laminate comprising a polyvinyl alcohol-based resin layer and a substrate. In the dyeing step, the polyvinyl alcohol-based resin layer is dyed with a dichroic substance. In the stretching step, the laminate is stretched. The stretching ratio in the stretching step is 3.0 to 5.0 times the original length of the laminate.

[13] In the method for manufacturing an optical laminate described in

[12] above, the stretching ratio of the stretching step may be 3.0 to 4.5 times the original length of the laminate.

[14] An optical laminate according to another embodiment of the present invention is used in an image display device having a three-dimensional curved surface. The optical laminate comprises a polarizer. In the optical laminate, the average of the loss tangent tanδ at 95°C in the absorption axis direction of the polarizer and the loss tangent tanδ at 95°C in the transmission axis direction perpendicular to the absorption axis direction is greater than 0.06 and less than 0.2.

[15] An optical laminate according to yet another embodiment of the present invention is used in an image display device having a three-dimensional curved surface. The optical laminate comprises a polarizer. In the optical laminate, the maximum value of the elastic modulus of the polarizer at 95°C in the absorption axis direction and the elastic modulus at 95°C in the transmission axis direction perpendicular to the absorption axis direction is 1000 N / mm 2 More than 3400N / mm 2 It is less than.

[16] An optical laminate according to yet another embodiment of the present invention is used in an image display device having a three-dimensional curved surface. The optical laminate comprises a polarizer. In the optical laminate, the minimum value of the fracture displacement at 95°C in the absorption axis direction of the polarizer and the fracture displacement at 95°C in the transmission axis direction perpendicular to the absorption axis direction is greater than 1.7 and less than 4.0.

[17] An optical laminate according to yet another embodiment of the present invention is used in an image display device having a three-dimensional curved surface. The optical laminate comprises a polarizer. In the optical laminate, the minimum number of MIT test bends in the absorption axis direction of the polarizer and the minimum number of MIT test bends in the transmission axis direction perpendicular to the absorption axis direction is greater than 80 and less than 200. [Effects of the Invention]

[0006] According to embodiments of the present invention, it is possible to realize an optical laminate that can be stably molded onto a three-dimensional curved surface. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 2]Figure 2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention. [Figure 3] Figure 3 is a schematic cross-sectional view of an optical laminate according to yet another embodiment of the present invention. [Figure 4] Figure 4 is a schematic cross-sectional view of the second retardation film included in the optical laminate of Figure 1. [Figure 5] Figure 5 is a schematic configuration diagram of an image display device according to another aspect of the present invention. [Figure 6] Figure 6 is a schematic cross-sectional view of the optical laminate included in the image display device of Figure 5.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments. Further, for the sake of clarity in the explanation, in the drawings, the widths, thicknesses, shapes, etc. of each part may be schematically represented compared to the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] (Definitions of Terms and Symbols) The definitions of the terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) “nx” is the refractive index in the direction where the in-plane refractive index is maximum (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal 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 Retardation (Re) “Re(λ)” is the in-plane retardation measured with light of wavelength λ nm at 23°C. For example, “Re(550)” is the in-plane retardation measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ) = (nx - ny) × d when the thickness of the layer (film) is d (nm). (3) Retardation in the Thickness Direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. Rth(λ) can be calculated using the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re. (5)Angle In this specification, when an angle is referred to, it encompasses both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, "45°" means ±45°.

[0010] A. Overview of Optical Laminates Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. In one embodiment, the optical laminate 100 is used in an image display device 101 having a three-dimensional curved surface 90 (see Figure 5). The optical laminate 100 is equipped with a polarizer 3. In the optical laminate 100, the maximum value in the temperature range of 50°C to 95°C in the differential curve of the temperature rise curve of differential scanning calorimetry (DDSC, hereinafter sometimes simply referred to as DDSC) exceeds 600 μW / min and is less than 3000 μW / min. DDSC is typically an indicator of the thermal fluctuation of an optical laminate. In one embodiment, when forming an optical laminate into a three-dimensional curved surface (specifically, when attaching an optical laminate to a three-dimensional curved surface, or when forming an optical laminate into a three-dimensional curved surface after attaching it to a substrate), the optical laminate is heated to, for example, 50°C to 120°C. At this time, if the maximum value of the DDSC of the optical laminate in the temperature range of 50°C to 95°C exceeds 600 μW / min, the flexibility and / or conformability of the optical laminate can be improved. Therefore, when forming an optical laminate into a three-dimensional curved surface, it is possible to suppress the occurrence of breakage, wrinkles, folds, bubbles, peeling, etc. in the optical laminate, and to allow the optical laminate to stably conform to the three-dimensional curved surface. Furthermore, since the maximum value in the DDSC of the optical laminate in the temperature range of 50°C to 95°C is less than 3000 μW / min, the optical properties can be maintained even when heated. Therefore, the optical properties can be maintained when forming the optical laminate into a three-dimensional curved surface. As a result, the optical laminate can be stably formed into a three-dimensional curved surface (specifically, by attaching the optical laminate to a three-dimensional curved surface, and / or by attaching the optical laminate to a substrate and then forming it into a three-dimensional curved surface).

[0011] The maximum value in the DDSC of the optical laminate 100 within the 50°C to 95°C temperature range is preferably 650 μW / min or more, more preferably 750 μW / min or more, and even more preferably 800 μW / min or more. If the maximum value in the DDSC of the optical laminate within the 50°C to 95°C temperature range is above this lower limit, fracture of the optical laminate can be further suppressed, and the optical laminate can be made to follow the three-dimensional curved surface more stably. On the other hand, the maximum value in the DDSC of the optical laminate 100 in the 50°C to 95°C temperature range is preferably 2000 μW / min or less, more preferably 1500 μW / min or less, and even more preferably 1300 μW / min or less. If the maximum value in the DDSC of the optical laminate in the 50°C to 95°C temperature range is below this upper limit, the optical properties can be stably maintained. The DDSC of the optical laminate is, for example, the differential curve of the heating curve measured in accordance with JIS K 7121. The heating curve is determined from the heat flow measured by heating a 3 mg sample cut from the optical laminate at a predetermined rate. The heating rate may be 20°C / min. In addition, the maximum value in the temperature range of 50°C to 95°C for the DDSC of the optical laminate may be the median value obtained by calculating the DDSC of the optical laminate multiple times (typically 5 times). In this specification, DDSC (unit: μW / min) refers to the measurement value for a 3 mg sample unless otherwise specified.

[0012] The minimum heat flow in the DSC of the optical laminate 100 in the temperature range of 50°C to 95°C is, for example, -600 μW / mg or less, preferably -650 μW / mg or less, more preferably -700 μW / mg or less, and even more preferably -750 μW / mg or less. On the other hand, the minimum heat flow value in the DSC of the optical laminate 100 in the temperature range of 50°C to 95°C is, for example, -2000 μW / mg or more, preferably -1500 μW / mg or more, and more preferably -1000 μW / mg or more. When the heat flow at 95°C in the DDSC of an optical laminate is within this range, it is possible to stably suppress the occurrence of fracture, wrinkles, folds, bubbles, peeling, etc. in the optical laminate when it is heated to around 95°C and formed into a three-dimensional curved surface.

[0013] The loss tangent tanδ of the optical laminate 100 at 95°C is typically an indicator of the viscoelasticity of the optical laminate. In the optical laminate 100, the average value of the loss tangent tanδ at 95°C in the absorption axis direction of the polarizer 3 (hereinafter sometimes simply referred to as the absorption axis direction), and the average value of the loss tangent tanδ at 95°C in the transmission axis direction perpendicular to the absorption axis direction (hereinafter sometimes simply referred to as the transmission axis direction), is, for example, 0.055 or more, preferably 0.06 or more, more preferably exceeding 0.06, and even more preferably 0.07 or more. On the other hand, the average value of the loss tangent tanδ at 95°C in the absorption axis direction and the loss tangent tanδ at 95°C in the transmission axis direction is, for example, 0.3 or less, preferably less than 0.2, more preferably less than 0.1, and even more preferably 0.09 or less. If the average value of the loss tangent tanδ at 95°C in the optical laminate is within this range, the viscoelasticity of the optical laminate can be appropriately adjusted, allowing the optical laminate to more stably follow the three-dimensional curved surface of the image display device. The average value of the loss tangent tanδ of the optical laminate is measured, for example, in accordance with JIS K 7095. Also, the loss tangent tanδ of the optical laminate at 95°C may be the median value obtained by measuring the loss tangent tanδ of the optical laminate a plurality of times (typically 5 times).

[0014] In the optical laminate 100, the maximum value of the elastic modulus at 95°C in the absorption axis direction and the elastic modulus at 95°C in the transmission axis direction is, for example, 1000 N / mm 2 or more, preferably 1500 N / mm 2 or more, more preferably 1500 N / mm 2 exceeding, and even more preferably 2000 N / mm 2 or more. On the other hand, the maximum value of the elastic modulus at 95°C in the absorption axis direction and the elastic modulus at 95°C in the transmission axis direction is, for example, 3500 N / mm 2 or less, preferably 3400 N / mm 2 or less, more preferably 3400 N / mm 2 less than, and even more preferably 3300 N / mm 2 or less. If the maximum value of the elastic modulus at 95°C in the optical laminate is within such a range, breakage of the optical laminate can be more stably suppressed. The maximum value of the elastic modulus of the optical laminate is measured, for example, in accordance with JIS K 7161. Also, the elastic modulus of the optical laminate may be the median value obtained by measuring the elastic modulus of the optical laminate a plurality of times (typically 5 times).

[0015] In the optical laminate 100, the minimum value of the fracture displacement at 95°C in the absorption axis direction and the fracture displacement at 95°C in the transmission axis direction is, for example, 1.65 or more, preferably 1.7 or more, more preferably exceeding 1.7, and even more preferably 1.8 or more. On the other hand, the minimum value of the fracture displacement at 95°C in the absorption axis direction and the fracture displacement at 95°C in the permeation axis direction is, for example, 5.0 or less, preferably 4.0 or less, more preferably less than 4.0, and even more preferably 3.2 or less. If the minimum fracture displacement at 95°C in an optical laminate is within this range, then fracture of the optical laminate can be reliably suppressed when forming it into a three-dimensional curved surface. The minimum fracture displacement of the optical laminate is measured, for example, in accordance with JIS K 7161. Alternatively, the fracture displacement of the optical laminate may be the median value obtained by measuring the fracture displacement of the optical laminate multiple times (typically five times).

[0016] In the optical laminate 100, the minimum number of bends in the MIT test in the absorption axis direction and the minimum number of bends in the MIT test in the transmission axis direction is, for example, 70 times or more, preferably 80 times or more, more preferably more than 80 times, and even more preferably 90 times or more. On the other hand, the minimum number of bends in the MIT test in the absorption axis direction and the minimum number of bends in the MIT test in the transmission axis direction is, for example, 300 times or less, preferably 200 times or less, more preferably less than 200 times, and even more preferably 190 times or less. If the number of bending cycles in the MIT test of the optical laminate is within this range, the fracture of the optical laminate can be suppressed more stably. The MIT test is performed, for example, in accordance with JIS P 8115. Furthermore, the number of bends in the MIT test of the optical laminate may be the median value obtained by measuring the number of bends of the optical laminate multiple times (typically 5 times).

[0017] In one embodiment, the optical laminate 100 includes a first phase difference film 1 in addition to the polarizer 3.

[0018] The first phase difference film 1 is located on one side of the polarizer 3 in the stacking direction of the optical laminate 100 (hereinafter sometimes simply referred to as the stacking direction). The first retardation film 1 can typically function as a protective layer for the polarizer 3. The first retardation film 1 may have an in-plane retardation or a retardation in the thickness direction. The first retardation film 1 may function as a λ / 4 plate, or may function as a λ / 2 plate, λ / 5 plate, λ / 6 plate, or C-Plate.

[0019] In one embodiment, the first retardation film 1 has an in-plane retardation. The refractive indices of the first retardation film 1 exhibit, for example, a relationship of nx > ny ≧ nz, preferably a relationship of nx > ny > nz. Note that "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 the range that does not impair the effects of the present invention, ny > nz or ny < nz may occur. In the illustrated example, the first retardation film 1 functions as a λ / 4 plate. According to such a configuration, in an image display device including an optical laminate, it is possible to improve visibility through an optical member having a polarizing action (hereinafter sometimes referred to as a polarizing member).

[0020] The in-plane retardation Re(550) of the first retardation film 1 is, for example, 80 nm or more, and 90 nm or more. On the other hand, the in-plane retardation Re(550) of the first retardation film 1 is, for example, 160 nm or less, preferably 145 nm or less, more preferably 130 nm or less, still more preferably 120 nm or less, and particularly preferably 110 nm or less. When the first retardation film has such Re(550), in an image display device including an optical laminate, the visibility through the polarizing member can be stably improved, and a desired coloring can be stably exhibited.

[0021] The retardation Rth(550) in the thickness direction of the first retardation film 1 is, for example, 80 nm to 200 nm, preferably 90 nm to 160 nm. The Nz coefficient of the first retardation film 1 is, for example, 0.5 to 5.0, preferably 1.0 to 3.0.

[0022] The first phase difference film 1 having an in-plane phase difference may exhibit inverse wavelength dispersion characteristics in which the in-plane birefringence increases with the wavelength of the measurement light, or it may exhibit positive wavelength dispersion characteristics in which the in-plane birefringence decreases with the wavelength of the measurement light, or it may exhibit flat wavelength dispersion characteristics in which the in-plane birefringence hardly changes with the wavelength of the measurement light.

[0023] The thickness of the first phase difference film 1 is, for example, 10 μm or more, preferably 15 μm or more, and more preferably 20 μm or more. If the thickness of the first phase difference film is above this lower limit, the first phase difference film can function stably as a protective layer for the polarizer. On the other hand, the thickness of the first phase difference film 1 is, for example, 80 μm or less, preferably 60 μm or less, and more preferably 40 μm or less. If the thickness of the first phase difference film is below this upper limit, the optical laminate can be made thinner.

[0024] The angle between the slow phase axis direction of the first phase difference film 1 and the absorption axis direction of the polarizer 3 is, for example, 30° to 60°, preferably 35° to 55°, more preferably 40° to 50°, and even more preferably 43° to 47°. With this configuration, the visibility through the polarizing member can be more stably improved in an image display device equipped with an optical laminate.

[0025] The first phase difference film 1 is attached to the polarizer 3 via an adhesive layer 61. Hereinafter, the adhesive layer that bonds the first phase difference film 1 and the polarizer 3 may be referred to as the first adhesive layer 61. The first adhesive layer 61 may be an adhesive layer or a tack layer.

[0026] In one embodiment, the first adhesive layer 61 is an adhesive layer. In other words, the first adhesive layer 61 contains a cured product of any suitable adhesive. Examples of adhesives include water-based adhesives, thermosetting adhesives, moisture-curing adhesives, and active energy ray-curing adhesives such as ultraviolet-curing adhesives (UV adhesives), with active energy ray-curing adhesives being preferred. Adhesives can be used alone or in combination.

[0027] The thickness of the first adhesive layer 61 is, for example, 15 μm or less, preferably 10 μm or less, and more preferably 5 μm or less. On the other hand, the lower limit of the thickness of the first adhesive layer 61 is typically 0.5 μm.

[0028] In the illustrated example, the optical laminate 100 further comprises a second phase difference film 2. The second phase difference film 2 is located on the opposite side of the polarizer 3 from the first phase difference film 1.

[0029] The second phase difference film 2 may have an in-plane phase difference, or it may have a phase difference in the thickness direction. The second phase difference film 2 may function as a λ / 4 plate, or it may function as a λ / 2 plate, a λ / 3 plate, a λ / 5 plate, or a C-Plate.

[0030] In one embodiment, the second phase difference film 2 has an in-plane phase difference. The refractive index of the second phase difference film 2 exhibits, for example, the relationship nx > ny, preferably nx > nz ≥ ny. The second phase difference film 2 may be a combination of multiple phase difference films. Multiple phase difference films exhibiting the relationship nx > ny may be combined. Phase difference films exhibiting the relationships nx > ny and nx = ny may be combined. In the illustrated example, the second phase difference film 2 functions as a λ / 4 plate. With this configuration, excellent anti-reflective properties can be provided to an image display device equipped with an optical laminate.

[0031] The in-plane phase difference Re(550) of the second phase difference film 2 is, for example, 100 nm to 300 nm, preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm. The Nz coefficient of the second phase difference film 2 is, for example, 0.3 to 1.5, and preferably 0.9 to 1.3.

[0032] The second phase difference film 2 having an in-plane phase difference may exhibit inverse wavelength dispersion characteristics in which the in-plane birefringence increases with the wavelength of the measurement light, or it may exhibit positive wavelength dispersion characteristics in which the in-plane birefringence decreases with the wavelength of the measurement light, or it may exhibit flat wavelength dispersion characteristics in which the in-plane birefringence hardly changes with the wavelength of the measurement light.

[0033] The thickness of the second phase difference film 2 is, for example, 15 μm or less, preferably less than 10 μm, and more preferably 5 μm or less. On the other hand, the lower limit of the thickness of the second phase difference film 2 is typically 1 μm. Having such a thickness in the second phase difference film allows for a thinner optical laminate.

[0034] In the illustrated example, the second phase difference film 2 is attached to the polarizer 3 via an adhesive layer 62. Hereafter, the adhesive layer that bonds the second phase difference film 2 and the polarizer 3 may be referred to as the second adhesive layer 62. The second adhesive layer 62 will be described in the same manner as the first adhesive layer 61 described above. Therefore, a detailed description of the second adhesive layer 62 will be omitted.

[0035] The optical laminate 100 has any suitable shape when viewed from the stacking direction. The shape of the optical laminate 100 as viewed from the stacking direction can be, for example, a polygonal shape such as a rectangle, a circular shape, an elliptical shape, or other irregular shapes. The shape of the optical laminate 100 is adjusted according to the shape of the image display device having a three-dimensional curved surface. Among the shapes of the optical laminate 100 as viewed from the stacking direction, a rectangular shape is preferred. The size of the optical laminate 100 can be adjusted arbitrarily and appropriately.

[0036] B. Details of the optical laminate Next, with reference to Figures 1 to 3, the details of an optical laminate according to one embodiment will be described. As shown in Figure 1, in one embodiment, the optical laminate 100 comprises the first phase difference film 1, the first adhesive layer 61, the polarizer 3, the second adhesive layer 62, and the second phase difference film 2 in this order. The optical laminate 100 has a first surface 100a and a second surface 100b in the stacking direction. The first surface 100a is one end surface of the optical laminate 100 in the stacking direction. In the illustrated example, the first surface 100a is the surface of the first phase difference film 1 opposite to the polarizer 3. The second surface 100b is the end face (other end face) of the optical laminate 100 opposite to the first surface 100a in the stacking direction. In the illustrated example, the second surface 100b is the surface of the second phase difference film 2 opposite to the polarizer 3.

[0037] B-1. First phase difference film The first phase difference film 1 has any suitable configuration. The first phase difference film 1 typically includes a stretched film prepared by stretching a resin film, and / or an orientation-solidified layer of a liquid crystal compound. In this specification, "orientation-solidified layer of liquid crystal compound" refers to a layer in which liquid crystal compounds are oriented in a predetermined direction within the layer, and this orientation state is fixed. Furthermore, the concept of "orientation-solidified layer" encompasses the orientation-cured layer obtained by curing liquid crystal monomers, as described later.

[0038] The first phase difference film 1 may have a single-layer structure or a laminated structure. In one embodiment, the first phase difference film 1 has a single-layer structure. The first phase difference film 1, which has a single-layer structure, is typically composed of a stretched film having the in-plane phase difference described above. Examples of materials for the stretched film include cycloolefin (COP) resins, cellulose resins, polycarbonate (PC) resins, and (meth)acrylic resins, with COP resins and cellulose resins being preferred. Polynorbornene resins are a specific example of COP-type resins. A specific example of a cellulosic resin is triacetylcellulose (TAC). The materials for the stretched film can be used individually or in combination. In one embodiment, the first phase difference film 1 having a single-layer structure contains a COP-based resin. With this configuration, the heat flow of the optical laminate at 95°C can be stably adjusted to the above-mentioned range.

[0039] A surface treatment layer is optionally provided on the surface of the first phase difference film 1 having a single-layer structure. Examples of surface treatment layers include a hard coat layer, an anti-reflective layer, an anti-sticking layer, and an anti-glare treatment layer. Preferably, the surface treatment layer is provided on the surface of the first phase difference film 1 opposite to the polarizer 3 (first surface 100a).

[0040] B-2.Polarizer The polarizer 3 has any suitable configuration. For example, the polarizer may be composed of a single layer of resin film, or it may be obtained using a laminate of two or more layers.

[0041] Specific examples of polarizers composed of a single layer of resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) resin films, partially formalized PVA resin films, and partially saponified ethylene-vinyl acetate copolymer films, which have been subjected to dyeing and stretching treatments with dichroic substances such as iodine or dichroic dyes, as well as polyene-based oriented films such as dehydrated PVA or dehydrochlorinated polyvinyl chloride. Preferably, polarizers obtained by dyeing a PVA resin film with iodine and uniaxially stretching are used because they have excellent optical properties.

[0042] Specific examples of polarizers obtained using laminates include polarizers obtained using a laminate of a substrate and a PVA-based resin layer (PVA-based resin film) laminated on the substrate, or polarizers obtained using a laminate of a substrate and a PVA-based resin layer coated on the substrate. The polarizer is preferably obtained using a laminate of a substrate and a PVA-based resin layer coated on the substrate. The method for preparing the polarizer will be described in detail later.

[0043] The thickness of the polarizer 3 is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, and even more preferably 3 μm to 7 μm. Having a polarizer of this thickness allows for stable thinning of the optical laminate.

[0044] Polarizer 3 typically exhibits absorption dichroism at wavelengths between 380 nm and 780 nm. The transmittance of polarizer 3 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of polarizer 3 is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0045] B-3. ​​Second phase difference film The second phase difference film 2 has any suitable configuration. The second phase difference film 2 typically includes a stretched film prepared by stretching a resin film, and / or an orientation solidified layer of a liquid crystal compound.

[0046] In one embodiment, the second phase difference film 2 includes an orientation solidification layer of a liquid crystal compound. If the second phase difference film contains an orientation solidification layer of a liquid crystal compound, the difference between nx and ny of the second phase difference film can be made significantly larger compared to non-liquid crystal materials, thus significantly reducing the thickness of the phase difference film having the desired in-plane phase difference. As a result, the optical laminate can be made even thinner.

[0047] The second phase difference film 2 may have a single-layer structure or a laminated structure. In one embodiment, the second phase difference film 2 has a laminated structure. More specifically, the second phase difference film 2 includes an orientation solidification layer of a plurality of liquid crystal compounds.

[0048] As shown in Figure 4, in one embodiment, the second phase difference film 2 comprises two orientation solidification layers of liquid crystal compounds. Hereinafter, the two orientation solidification layers of liquid crystal compounds in the second phase difference film 2 may be referred to as the first liquid crystal orientation solidification layer 21 and the second liquid crystal orientation solidification layer 22.

[0049] The first liquid crystal alignment solidification layer 21 is located between the polarizer 3 and the second liquid crystal alignment solidification layer 22 (see Figure 1). Therefore, the first liquid crystal alignment solidification layer 21 is typically attached to the polarizer 3 via the second adhesive layer 62. The second liquid crystal alignment solidification layer 22 is located on the opposite side of the polarizer 3 from the first liquid crystal alignment solidification layer 21 (see Figure 1).

[0050] The first liquid crystal alignment solidification layer 21 typically functions as a λ / 2 plate. The second liquid crystal alignment solidification layer 22 typically functions as a λ / 4 plate. With this configuration, the wavelength dispersion characteristics of the second phase difference film can be brought closer to ideal inverse wavelength dispersion characteristics. Therefore, excellent anti-reflective properties can be imparted to the optical laminate. Furthermore, the first liquid crystal alignment solidification layer 21 may function as a λ / 4 plate, and the second liquid crystal alignment solidification layer 22 may function as a λ / 2 plate.

[0051] The angle between the absorption axis direction of the polarizer 3 and the slow phase axis direction of the first liquid crystal alignment solidification layer 21 is, for example, 10° to 20°, preferably 12° to 18°, and more preferably 14° to 16°. Furthermore, the angle between the absorption axis direction of the polarizer 3 and the slow phase axis direction of the second liquid crystal alignment solidification layer 22 is, for example, 70° to 80°, preferably 72° to 78°, and more preferably 74° to 76°. With this configuration, the wavelength dispersion characteristics of the second phase difference film 2 can be brought closer to ideal inverse wavelength dispersion characteristics. Therefore, excellent anti-reflective properties can be stably imparted to the optical laminate. Furthermore, the range of angles between the absorption axis direction of the polarizer and the slow axis direction of the first liquid crystal alignment solidification layer may be reversed from the range of angles between the absorption axis direction of the polarizer and the slow axis direction of the second liquid crystal alignment solidification layer.

[0052] In the first liquid crystal alignment solidification layer 21, typically, rod-shaped liquid crystal compounds are oriented in a state where they are aligned along the slow phase axis direction of the first liquid crystal alignment solidification layer 21 (homogenous orientation). Examples of liquid crystal compounds include liquid crystal compounds in which the liquid crystal phase is a nematic phase (nematic liquid crystals). Examples of such liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. Liquid crystal polymers and liquid crystal monomers may be used individually or in combination. The mechanism by which liquid crystalline properties are expressed in liquid crystal compounds may be lyotropic or thermotropic.

[0053] When a liquid crystal compound contains a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinkable monomer. The orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After oriented the liquid crystal monomer, the orientation state can be fixed by polymerizing or crosslinking the liquid crystal monomers together, for example. Here, polymerization forms a polymer and crosslinking forms a three-dimensional network structure, but these are non-liquid crystal. Therefore, the formed first liquid crystal orientation solidified layer does not undergo transitions to liquid crystal phase, glass phase, or crystalline phase due to temperature changes, which is characteristic of liquid crystal compounds. As a result, the second phase difference film can have extremely excellent stability that is not affected by temperature changes.

[0054] Any suitable liquid crystal monomer can be used. Examples of liquid crystal monomers include polymerizable mesogenic compounds described in Japanese Patent Publication No. 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Specific examples of such polymerizable mesogenic compounds include BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767.

[0055] An orientation-solidified layer of liquid crystal compounds can be formed by applying an appropriate orientation treatment to the surface of any suitable coated substrate, then applying a coating liquid containing a liquid crystal compound to the surface to orient the liquid crystal compound in the direction corresponding to the orientation treatment, and fixing that orientation state. Orientation treatments include, for example, mechanical orientation treatments, physical orientation treatments, and chemical orientation treatments. Specific examples of liquid crystal compounds and details of the method for forming the orientation solidified layer are described in Japanese Patent Publication No. 2006-163343. The description in said publication is incorporated herein by reference.

[0056] The thickness of the first liquid crystal alignment solidification layer 21 is arbitrarily and appropriately adjusted so that a desired in-plane phase difference is obtained. The thickness of the first liquid crystal alignment solidification layer 21 is, for example, 5 μm or less, preferably 3 μm or less, and more preferably 2 μm or less. On the other hand, the lower limit of the thickness of the first liquid crystal alignment solidification layer 21 is typically 1.0 μm.

[0057] The second liquid crystal alignment solidification layer 22 will be described in the same manner as the first liquid crystal alignment solidification layer 21. Therefore, a detailed explanation of the second liquid crystal alignment solidification layer 22 will be omitted as appropriate. In the illustrated example, the second liquid crystal alignment solidification layer 22 is attached to the first liquid crystal alignment solidification layer 21 via an adhesive layer 23. The adhesive layer 23 will be described in the same way as the first adhesive layer 61 described above. Therefore, a detailed description of the adhesive layer 23 will be omitted.

[0058] B-4. Variations Next, a modified example of the optical laminate will be described with reference to Figures 2 and 3. As shown in Figure 2, the optical laminate 100 may include a protective layer 4 instead of the second phase difference film 2. With this configuration, the protective layer can stably protect the polarizer. In the illustrated example, the protective layer 4 is attached to the polarizer 3 via the adhesive layer 62. In other words, the optical laminate 100 shown in Figure 2 comprises the first phase difference film 1, the first adhesive layer 61, the polarizer 3, the second adhesive layer 62, and the protective layer 4 in that order. In such an optical laminate 100, the surface of the protective layer 4 opposite to the polarizer 3 functions as the second surface 100b.

[0059] The protective layer 4 contains any suitable transparent resin. Examples of transparent resins include cycloolefin (COP) resins such as polynorbornene; polyester resins such as polyethylene terephthalate (PET); cellulose resins such as triacetylcellulose (TAC); polycarbonate (PC) resins; (meth)acrylic resins; polyvinyl alcohol resins; polyamide resins; polyimide resins; polyethersulfone resins; polysulfone resins; polystyrene resins; polyolefin resins; and acetate resins. Note that "(meth)acrylic" refers to acrylic and / or methacrylic resins. Other examples include thermosetting resins such as (meth)acrylic, urethane, (meth)acrylic-urethane, epoxy, and silicone resins, as well as UV-curing resins. In addition, glassy polymers such as siloxane polymers can also be used. A polymer film described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As a material for the protective layer, for example, a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in its side chains and a thermoplastic resin having substituted or unsubstituted phenyl and nitrile groups in its side chains can be used. For example, a resin composition having an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be used. The polymer film may be, for example, an extruded product of the above resin composition. The protective layer materials can be used individually or in combination.

[0060] The thickness of the protective layer 4 is, for example, 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm.

[0061] As shown in Figure 3, the optical laminate 100 may include a second phase difference film 2 and a protective layer 4. In the illustrated example, the protective layer 4 is located between the polarizer 3 and the second phase difference film 2 in the lamination direction. Even with this configuration, the protective layer can stably protect the polarizer. On the other hand, from the viewpoint of thinning, the optical laminate 100 shown in Figures 1 and 2 is preferred over the optical laminate 100 shown in Figure 3. More specifically, the protective layer 4 is attached to the polarizer 3 via the adhesive layer 62, and the second phase difference film 2 is attached to the protective layer 4 via the adhesive layer 63. Hereafter, the adhesive layer that bonds the protective layer 4 and the second phase difference film 2 may be referred to as the third adhesive layer 63. The third adhesive layer 63 will be described in the same way as the first adhesive layer 61 described above. Therefore, a detailed explanation of the third adhesive layer 63 will be omitted.

[0062] Furthermore, while these embodiments have described in detail optical laminates in which the maximum temperature range of 50°C to 95°C in DDSC is within the range described above, the present invention is not limited thereto. In an optical laminate, instead of the maximum value in the temperature range of 50°C to 95°C in DDSC, if at least one of the following is within the range: the average value of the loss tangent tanδ at 95°C, the maximum value of the elastic modulus at 95°C, the minimum value of the fracture displacement at 95°C, and the minimum number of bending cycles in the MIT test, then the optical laminate can be stably formed into a three-dimensional curved surface.

[0063] C. Method for manufacturing optical laminates Next, with reference to Figure 1, a method for manufacturing an optical laminate according to one embodiment will be described. A typical method for manufacturing an optical laminate includes a preparation step for preparing the polarizer 3.

[0064] C-1. Preparation process In one embodiment, the preparation step includes a coating step, a dyeing step, and a stretching step.

[0065] C-1-1.Coating process In the coating process, first, the substrate is prepared, and then a coating solution containing a polyvinyl alcohol-based resin (hereinafter referred to as PVA-based resin) is applied to the substrate. This prepares a laminate comprising a PVA-based resin layer and a substrate.

[0066] The base material contains any suitable resin material. The substrate is typically a polyethylene terephthalate film. Examples of constituent materials for the substrate include amorphous (non-crystallized) polyethylene terephthalate resins, and preferably amorphous (difficult to crystallize) polyethylene terephthalate resins. Specific examples of amorphous polyethylene terephthalate resins include copolymers further containing isophthalic acid as a dicarboxylic acid, and copolymers further containing cyclohexanedimethanol as a glycol.

[0067] The glass transition temperature (Tg) of the substrate is, for example, 170°C or lower, preferably 120°C or lower. Having such a Tg in the substrate can suppress crystallization of the PVA-based resin and allow the stretching process to be carried out smoothly. On the other hand, the lower limit of the glass transition temperature (Tg) of the substrate is typically 60°C. This helps to suppress deformation of the substrate due to heat (e.g., the occurrence of unevenness, sagging, and wrinkles). The glass transition temperature (Tg) is measured according to, for example, JIS K 7121.

[0068] The thickness of the substrate before the stretching process is, for example, 20 μm to 300 μm, preferably 50 μm to 200 μm.

[0069] The surface of the substrate may be subjected to any appropriate surface treatment (e.g., corona treatment), and an easy-adhesion layer may be formed thereon.

[0070] The coating solution typically contains a solvent and a PVA-based resin. The solvent can dissolve the PVA resin. Examples of solvents include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide N-methylpyrrolidone, glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. Solvents can be used alone or in combination. Among the solvents, water is preferred.

[0071] Any suitable resin can be used for the PVA-based resin. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. The degree of saponification of PVA-based resins is typically 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%, and even more preferably 99.0 mol% to 99.5 mol%. The degree of saponification is measured according to, for example, JIS K 6726-1994.

[0072] The average degree of polymerization of the PVA resin can be appropriately selected depending on the purpose. For example, the average degree of polymerization of the PVA resin is 1000 or more, preferably 1500 or more, more preferably 2000 or more, and even more preferably 3000 or more. On the other hand, the average degree of polymerization of the PVA resin is 10000 or less, preferably 6000 or less, and more preferably 4300 or less. The average degree of polymerization is measured according to, for example, JIS K 6726-1994.

[0073] In one embodiment, the PVA-based resin includes acetoacetyl-modified PVA. The content of acetoacetyl-modified PVA in PVA-based resins is, for example, 5% by mass or more, preferably 8% by mass or more. On the other hand, the content of acetoacetyl-modified PVA in PVA-based resins is, for example, 20% by mass or less, preferably 12% by mass or less. If the PVA-based resin contains acetoacetyl-modified PVA, the mechanical strength of the polarizer can be improved.

[0074] The PVA-based resin content in the coating solution is, for example, 3 to 20 parts by mass per 100 parts by mass of solvent. With such a resin concentration, a uniform coating film that adheres closely to the substrate can be formed.

[0075] The coating solution preferably further contains a halide. The presence of a halide in the coating solution allows the PVA-based resin layer formed from the coating solution to also contain the halide. Therefore, even when the PVA-based resin layer is immersed in the liquid, disruption of the orientation of PVA molecules and a decrease in orientation can be suppressed. As a result, the optical properties of the polarizer manufactured in the preparation step can be improved.

[0076] Examples of halides include iodides and sodium chloride. In one embodiment, the coating solution contains iodide. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide, with potassium iodide being preferred. Halides can be used individually or in combination. The halogen content in the coating solution is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, per 100 parts by mass of PVA resin. On the other hand, the halogen content in the coating solution is, for example, 20 parts by mass or less, preferably 15 parts by mass or less. When the halogen content is within this range, the clouding of the final polarizer can be suppressed.

[0077] The coating solution may further contain any suitable additives. Examples of additives include plasticizers and surfactants.

[0078] Such a coating solution is applied to one side of the substrate in the thickness direction by any suitable method. This prepares a laminate comprising a PVA-based resin layer and a substrate. Subsequently, the PVA-based resin layer of the laminate is dried as needed. The thickness of the PVA-based resin layer before the stretching process is, for example, 3 μm to 40 μm, preferably 5 μm to 30 μm.

[0079] C-1-2. Dyeing process In the dyeing process, the PVA-based resin layer is dyed with a dichroic substance. More specifically, the dyeing solution is brought into contact with the PVA-based resin layer to adsorb the dichroic substance.

[0080] The staining solution contains a dichroic substance. This dichroic substance can form complexes with PVA-based resins. Examples of dichroic substances include iodine and organic dyes, with iodine being preferred. Dichroic substances can be used alone or in combination. The staining solution is typically an iodine aqueous solution. The iodine content in the staining solution is, for example, 0.05 to 3 parts by mass, preferably 0.5 to 3 parts by mass, per 100 parts by mass of water.

[0081] In one embodiment, the staining solution further contains an iodine compound. This can improve the solubility of iodine in water. Examples of iodine compounds include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide, with potassium iodide being preferred. Iodine compounds can be used alone or in combination. The mass ratio of iodine to iodine compound in the dyeing solution (iodine:iodine compound) is, for example, 1:5 to 1:20, preferably 1:5 to 1:10. This can impart excellent optical properties to the polarizer.

[0082] The temperature of the staining bath is, for example, 10°C or higher, preferably 20°C or higher. On the other hand, the temperature of the staining bath is, for example, 50°C or lower, preferably 40°C or lower. The time required for the dyeing process (dyeing time) is, for example, 5 seconds or more, preferably 30 seconds or more. On the other hand, the dyeing time is, for example, 300 seconds or less, preferably 90 seconds or less, and more preferably 60 seconds or less.

[0083] In one embodiment, the laminate is immersed in a dyeing solution. However, the method of adsorbing the dichroic substance in the dyeing process is not limited to the immersion described above. For example, the dyeing solution may be coated onto the PVA resin layer, or the dyeing solution may be sprayed onto the PVA resin layer. As a result, the PVA-based resin layer of the laminate is stained by a dichroic substance.

[0084] C-1-3. Stretching process In the stretching process, the laminate is stretched. The stretching process may be carried out in one stage or in two or more stages. The stretching ratio in the stretching process is arbitrarily and appropriately adjusted according to the application of the polarizer. The stretching ratio in the stretching process is, for example, 3.0 to 6.0 times the original length of the laminate, preferably 3.0 to 5.0 times, and more preferably 3.0 to 4.5 times. If the stretching process is carried out in multiple stages, the stretching ratio in the stretching process is the product of the stretching ratios at each stage. If the stretching ratio in the stretching process is within this range, the DDSC of the manufactured optical laminate can be stably adjusted to the above range.

[0085] The stretching process typically includes a water stretching process that is carried out after the dyeing process. In the underwater stretching process, the laminate comprising the dyed PVA-based resin layer is stretched in a stretching bath (stretching solution) in a predetermined direction.

[0086] The stretching solution is typically an aqueous solution of boric acid. The boric acid content in the stretching solution is, for example, 1 part by mass or more, preferably 3 parts by mass or more, per 100 parts by mass of water. On the other hand, the boric acid content in the stretching solution is, for example, 10 parts by mass or less, preferably 8 parts by mass or less, per 100 parts by mass of water.

[0087] In one embodiment, the stretching solution further contains the iodine compound described above. The presence of an iodine compound in the stretching solution can suppress the elution of iodine adsorbed onto the PVA-based resin layer. The iodine compound content in the stretching solution is, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, per 100 parts by mass of water. On the other hand, the iodine compound content in the stretching solution is, for example, 10 parts by mass or less, preferably 6 parts by mass or less, per 100 parts by mass of water. The mass ratio of boric acid to iodine compound (boric acid:iodine compound) in the stretching solution is, for example, 1:0.5 to 1:1.2, and preferably 1:0.6 to 1:1.

[0088] The temperature of the stretching bath is, for example, 40°C or higher, preferably 60°C or higher. On the other hand, the temperature of the stretching bath is, for example, 85°C or lower, preferably 80°C or lower. The duration of the underwater stretching process is, for example, 15 to 300 seconds.

[0089] In one embodiment, the stretching process includes an air stretching process performed before the dyeing process, in addition to the underwater stretching process. In the air stretching process, the laminate comprising the PVA-based resin layer before dyeing is stretched in a predetermined direction. If the stretching process includes an air stretching process, the orientation of PVA molecules in the PVA resin layer can be improved before the dyeing process. Therefore, a decrease in the orientation of PVA molecules and dissolution of PVA can be suppressed during the dyeing process and / or the water stretching process, thereby improving the optical properties of the polarizer.

[0090] The stretching temperature in the air stretching process is typically above the glass transition temperature (Tg) of the PVA resin. The stretching temperature in the air stretching process is, for example, 95°C to 150°C, preferably 120°C to 140°C. The stretching ratio in the air stretching process is, for example, 1.5 times or more, preferably 2 times or more, relative to the original length of the laminate. On the other hand, the upper limit of the stretching ratio in the air stretching process is typically 3 times. This can improve the orientation of the PVA resin and suppress the dissolution of the PVA resin layer in the dyeing solution. If the stretching process includes both an underwater stretching process and an air stretching process, the stretching ratio in the underwater stretching process is, for example, 1.3 to 3.0 times the original length of the laminate, preferably 1.4 to 2.5 times.

[0091] C-1-4. Drying shrinkage process In one embodiment, the preparation step further includes a drying shrinkage step. In the drying shrinkage process, typically, the laminated material after the underwater stretching process is heated while being transported in the longitudinal direction.

[0092] The drying shrinkage process is carried out by any suitable heating and drying apparatus. The heating and drying apparatus may be a zone heating system in which the entire interior of the apparatus is heated, or a heated roll drying system in which the conveying rolls are heated. Preferably, the heating and drying apparatus performs both.

[0093] The internal temperature of the heating and drying apparatus is, for example, 70°C or higher, preferably 80°C or higher. On the other hand, the internal temperature of the heating and drying apparatus is, for example, 120°C or lower, preferably 100°C or lower. The surface temperature of the heating roll is, for example, 60°C or higher, preferably 70°C or higher. On the other hand, the surface temperature of the heating roll is, for example, 100°C or lower, preferably 80°C or lower. By drying using heated rolls, heat curling of the laminate can be efficiently suppressed, enabling the efficient production of polarizers with superior appearance. Furthermore, during the drying shrinkage process, the laminate shrinks in the width direction perpendicular to the length direction by contact with the heated rolls. The shrinkage rate in the width direction of the laminate during the drying shrinkage process is, for example, 2% or more, preferably 4% or more. When the laminate shrinks in this manner during the drying shrinkage process, the orientation of PVA and PVA / dichroic material complex (iodine complex) can be improved, and the optical properties of the polarizer can be further improved. On the other hand, the shrinkage rate in the width direction of the laminate is, for example, 10% or less, preferably 8% or less, and more preferably 6% or less. By adjusting the shrinkage rate in the width direction in this way, it is possible to suppress the occurrence of appearance defects such as wrinkles in the polarizer.

[0094] C-1-5. Immobilization process, crosslinking process The preparation step may further include an immobilization step and / or a crosslinking step. The immobilization step is typically performed before the dyeing step. In one embodiment, the immobilization step is performed after the air stretching step and before the dyeing step. In the immobilization process, the laminate is typically immersed in an aqueous boric acid solution, which serves as the immobilization solution. The boric acid content in the immobilization solution is, for example, 1 to 10 parts by mass per 100 parts by mass of water. The temperature of the insolubilizing solution is, for example, 10°C or higher, preferably 20°C or higher. On the other hand, the temperature of the insolubilizing solution is, for example, 60°C or lower, preferably 50°C or lower. The duration of the immobilization process is, for example, 10 seconds or more, preferably 20 seconds or more. On the other hand, the duration of the immobilization process is, for example, 200 seconds or less, preferably 60 seconds or less.

[0095] The crosslinking process is typically performed after the dyeing process. In one embodiment, the crosslinking process is performed after the dyeing process and before the underwater stretching process. In the crosslinking process, typically, the PVA resin layer is brought into contact with an aqueous boric acid solution, which serves as the crosslinking solution. When the PVA resin layer is brought into contact with the aqueous boric acid solution, the boric acid can bond with the PVA resin to form crosslinks. Examples of crosslinking include crosslinking by the formation of tetrahydroxyborate anions in the aqueous solution, which then form hydrogen bonds with the PVA resin, and crosslinking by the dehydration condensation of boric acid with the hydroxyl groups of the PVA resin to form boric acid esters. This can suppress the elution of the PVA resin and dichroic substances (preferably iodine). The range of boric acid content in the crosslinking solution is similar to, for example, the range of boric acid content in the insolubilization solution. In one embodiment, the crosslinking solution further contains the iodine compound described above. When the crosslinking solution contains the iodine compound, the elution of iodine adsorbed on the PVA resin can be stably suppressed. The content of the iodine compound in the crosslinking solution is, for example, 0.1 parts by mass or more, preferably 1 part by mass or more, per 100 parts by mass of water. On the other hand, the content of the iodine compound in the crosslinking solution is, for example, 8 parts by mass or less, preferably 5 parts by mass or less, per 100 parts by mass of water. The mass ratio of the iodine compound to boric acid in the crosslinking solution (iodine compound:boric acid) is, for example, 1:1 to 1:3, and preferably 1:1.5 to 1:2. The temperature of the crosslinking bath is, for example, 20°C or higher, preferably 30°C or higher. On the other hand, the temperature of the crosslinking bath is, for example, 60°C or lower, preferably 50°C or lower. The duration of the crosslinking process is, for example, 5 seconds or more, preferably 10 seconds or more. On the other hand, the duration of the crosslinking process is, for example, 200 seconds or less, preferably 60 seconds or less.

[0096] As described above, the polarizer 3 is prepared on the substrate.

[0097] C-2. First lamination process In one embodiment, the method for manufacturing the optical laminate includes a preparation step in addition to a first lamination step. In the first lamination step, the first phase difference film 1 described above is attached to the polarizer 3 prepared in the preparation step by any suitable method. More specifically, the polarizer 3 and the first phase difference film 1 are bonded together via the first adhesive layer 61 described above.

[0098] C-3.Second lamination process The method for manufacturing the optical laminate further includes a second bonding step, if necessary. In the second bonding step, first the substrate is peeled off from the polarizer 3, and then the second phase difference film 2 or protective layer 4 described above is attached to the peeled surface of the substrate on the polarizer 3 by any suitable method. More specifically, the polarizer 3 and the second phase difference film 2 or protective layer 4 are bonded together via the second adhesive layer 62 described above.

[0099] The optical laminate 100 described above is manufactured accordingly. The optical laminate 100 can be applied to any suitable image display device. Therefore, one embodiment of the present invention also includes an image display device using such an optical laminate. Examples of image display devices include liquid crystal displays and organic light-emitting diodes (EL displays).

[0100] D. Image display device As shown in Figure 5, the optical laminate 100 is typically applied to an image display device 101 that has a three-dimensional curved surface 90. In one embodiment, the image display device 101 includes an image display panel 92 and an optical laminate 100.

[0101] The optical laminate 100 is attached to the three-dimensional curved surface 90. More specifically, with the optical laminate 100 attached to the three-dimensional curved surface 90, the first surface 100a or the second surface 100b of the optical laminate 100 faces the three-dimensional curved surface 90 in the stacking direction.

[0102] The three-dimensional curved surface 90 may be a concave surface or a convex surface. In the illustrated example, the three-dimensional curved surface 90 is a concave surface. The three-dimensional curved surface 90 is provided on any suitable member. Examples of components with three-dimensional curved surfaces include lenses, cover glass, mobile phones (smartphones), laptop computers, and furniture. By shaping the edges of mobile phones and laptop computers to have three-dimensional curved surfaces, the screen size can be maximized. Furniture generally has three-dimensional curved surfaces, and by combining it with an image display device that also has a three-dimensional curved surface, an image display function can be obtained without compromising practicality. In the illustrated example, the three-dimensional curved surface 90 is provided on the cover glass 91. In other words, the image display device 101 includes a cover glass 91 having the three-dimensional curved surface 90. The three-dimensional curved surface 90 is provided on the surface of the cover glass 91 on the side facing the image display panel 92. The radius of curvature of the three-dimensional curved surface 90 is, for example, 2 mm to 200 mm, and preferably 10 mm to 100 mm.

[0103] Since the optical laminate 100 has the above-described configuration, it can be stably attached to such a three-dimensional curved surface 90. As shown in Figures 5 and 6, in one embodiment, the optical laminate 100 is attached to a three-dimensional curved surface 90 via an adhesive layer 5. In the illustrated example, the adhesive layer 5 is provided on the first surface 100a of the optical laminate 100. The adhesive layer 5 is composed of any suitable optically transparent adhesive. Examples of optically transparent adhesives include (meth)acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. Optically transparent adhesives can be used alone or in combination.

[0104] The total light transmittance of the adhesive layer 5 at a wavelength of 590 nm is, for example, 80% or more, preferably 85% or more. On the other hand, the total light transmittance of the adhesive layer 5 at a wavelength of 590 nm is, for example, 95% or less, or for example, 93% or less.

[0105] The thickness of the adhesive layer 5 is, for example, 10 μm to 600 μm, preferably 30 μm to 500 μm.

[0106] With the optical laminate 100 attached to the three-dimensional curved surface 90, the first surface 100a of the optical laminate 100 is located on the opposite side from the image display panel 92, and the second surface 100b of the optical laminate 100 is located on the side of the image display panel 92.

[0107] Furthermore, when the optical laminate 100 is attached to the three-dimensional curved surface 90, at least a portion of each of the first surface 100a and the second surface 100b is curved along the three-dimensional curved surface 90. The radius of curvature of the first surface 100a (more specifically, the radius of curvature of the curved portion of the first surface 100a) is typically larger than the radius of curvature of the second surface 100b (more specifically, the radius of curvature of the curved portion of the second surface 100b). The radius of curvature of the first surface 100a (the radius of curvature of the curved portion of the first surface 100a) is, for example, 2 mm or more, preferably 4 mm or more, more preferably 10 mm or more, and even more preferably 20 mm or more. On the other hand, the radius of curvature of the first surface 100a (the radius of curvature of the curved portion of the first surface 100a) is, for example, 200 mm or less, preferably 100 mm or less, more preferably less than 100 mm, and even more preferably 50 mm or less. The radius of curvature of the second surface 100b (the radius of curvature of the curved portion of the second surface 100b) is, for example, 2 mm or more, preferably 4 mm or more, more preferably 10 mm or more, and even more preferably 20 mm or more. On the other hand, the radius of curvature of the second surface 100b (the radius of curvature of the curved portion of the second surface 100b) is, for example, 200 mm or less, and preferably 100 mm or less.

[0108] With the optical laminate 100 attached to the three-dimensional curved surface 90, the first phase difference film 1 is positioned on the opposite side of the image display panel 92 from the polarizer 3. At least a portion of both the first phase difference film 1 and the polarizer 3 is curved along the three-dimensional curved surface 90. The radius of curvature of the first phase difference film 1 (more specifically, the radius of curvature of the curved portion of the first phase difference film 1) is typically larger than the radius of curvature of the polarizer 3 (more specifically, the radius of curvature of the curved portion of the polarizer 3).

[0109] Furthermore, the illustrated optical laminate 100 includes a second phase difference film 2. At least a portion of the second phase difference film 2 is curved along the three-dimensional curved surface 90. The radius of curvature of the second phase difference film 2 (more specifically, the radius of curvature of the curved portion of the second phase difference film 2) is typically smaller than the radius of curvature of the polarizer 3 (more specifically, the radius of curvature of the curved portion of the polarizer 3).

[0110] The optical laminate 100 may also be attached to the three-dimensional curved surface 90 via an adhesive layer 5 provided on the second surface 100b. [Examples]

[0111] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows.

[0112] (1) Measurement of phase difference The in-plane phase difference of the first and second phase difference films used in the examples and comparative examples was automatically measured using a KOBRA-WPR manufactured by Oji Instruments Co., Ltd. The measurement wavelength was 550 nm and the measurement temperature was 25 °C.

[0113] (2) Measurement of DDSC The optical laminates obtained in the examples and comparative examples were placed in a differential scanning calorimeter (HITACHI DSC7000X) at a temperature of 0.1 MPa (approximately 3 mg) and heated from 20°C to 120°C at a heating rate of 20°C / min. The heat flow per unit time (unit: μW / 3 mg) of the optical laminate at each temperature was measured. A heating curve was obtained with heat flow per unit time on the vertical axis and temperature change on the horizontal axis. Furthermore, the differential curve of the heating curve, DDSC (unit: μW / min), was calculated. Subsequently, the maximum value in the range of 50°C to 95°C was read. The DDSC measurement of the optical laminate described above was repeated five times. This yielded five maximum values ​​for the DDSC of the optical laminate in the temperature range of 50°C to 95°C, and the median value was calculated. The results are shown in Table 1.

[0114] (3) Measurement of loss tangent tanδ The optical laminates obtained in the examples and comparative examples were cut to a length of 20 mm and a width of 5 mm to be used as measurement samples. Next, the measurement samples were set in a dynamic viscoelasticity measuring device (DVA-225, manufactured by IT Measurement Control Co., Ltd.) under normal pressure (0.1 MPa). Subsequently, the tanδ of the measurement samples at 95°C was measured in both the absorption axis direction (MD) and the transmission axis direction (TD) of the polarizer, at a frequency of 10 Hz and a heating rate of 10°C / min. The tanδ measurement of the sample described above was repeated five times. This yielded five tanδ values ​​at 95°C for the sample in the absorption axis direction, and the median value was calculated. Similarly, the median tanδ value at 95°C for the sample in the transmission axis direction was calculated. Subsequently, the median tanδ value at 95°C for the measurement samples in the absorption axis direction and the average value of the median tanδ value at 95°C for the measurement samples in the transmission axis direction were calculated. The results are shown in Table 1.

[0115] (4) Measurement of elastic modulus The optical laminates obtained in the examples and comparative examples were placed in a tensile testing machine with a heated bath (Shimadzu Corporation, product name "AG-1") under normal pressure (0.1 MPa). Then, with a chuck distance of 100 mm and a width of 10 mm, the elastic modulus of the optical laminate at 95°C was measured in both the absorption axis direction (MD) and the transmission axis direction (TD) of the polarizer, at a speed of 20 mm / min. The measurement of the elastic modulus of the optical laminate described above was repeated five times. This yielded five values ​​of the elastic modulus of the optical laminate at 95°C in the absorption axis direction, and the median value was calculated. Similarly, the median value of the elastic modulus of the optical laminate at 95°C in the transmission axis direction was calculated. Table 1 shows the maximum values ​​of the median elastic modulus of the optical laminate at 95°C in the absorption axis direction and the median elastic modulus of the optical laminate at 95°C in the transmission axis direction.

[0116] (5) Measurement of fracture displacement The optical laminates obtained in the examples and comparative examples were placed in a tensile testing machine with a heated bath (Shimadzu Corporation, product name "AG-1") under normal pressure (0.1 MPa). Then, with a chuck distance of 100 mm and a width of 10 mm, the fracture displacement of the optical laminate at 95°C was measured in both the absorption axis direction (MD) and the transmission axis direction (TD) of the polarizer, at a speed of 20 mm / min. The fracture displacement of the optical laminate described above was measured five times. This yielded five fracture displacements of the optical laminate at 95°C in the absorption axis direction, and the median value was calculated. Similarly, the median fracture displacement of the optical laminate at 95°C in the transmission axis direction was calculated. Table 1 shows the median fracture displacement of the optical laminate at 95°C in the absorption axis direction, and the minimum median fracture displacement of the optical laminate at 95°C in the transmission axis direction.

[0117] (6) Measurement of MIT flexion count The optical laminates obtained in the examples and comparative examples were subjected to MIT testing in accordance with JIS P 8115. Specifically, the optical laminates were cut to a length of 150 mm and a width of 15 mm to serve as test samples. The test samples were mounted on an MIT folding fatigue tester (manufactured by Tester Industries Co., Ltd.) (load 1.0 kgf, bending surface radius: 0.38 mm), and repeatedly bent at a test speed of 90 cpm and a bending angle of 90° in an environment of 25°C. The number of bends at which the test sample fractured was recorded as the test value. This allowed for the measurement of the test values ​​of the test samples in both the absorption axis direction (MD) and the transmission axis direction (TD) of the polarizer. The number of MIT bends of the sample described above was measured five times. This yielded five test values ​​for the sample in the absorption axis direction, and the median of these values ​​was calculated. Similarly, the median of the test values ​​for the sample in the transmission axis direction was calculated. Table 1 shows the median test values ​​for the measurement sample in the absorption axis direction and the minimum median test values ​​for the measurement sample in the transmission axis direction.

[0118] (7) Test of attachment of optical laminates to three-dimensional curved surfaces In the optical laminates obtained in the examples and comparative examples, the optically transparent adhesive film (thickness: 100 μm) obtained in Preparation Example 6 was attached to the surface of the first phase difference film. Next, the optical laminate was attached to a lens having a three-dimensional curved surface using an optically transparent adhesive film. The three-dimensional curved surface was concave, and its radius of curvature was 38.6 mm. More specifically, after setting the lens in a curved lens bonding device (TFH-0321-UD, manufactured by Asano Research Institute), the optical laminate was positioned so that the optically transparent adhesive film faced the three-dimensional curved surface of the lens with a gap between them. Next, a mold having a convex surface corresponding to the three-dimensional curved surface of the lens was brought into contact with the optical laminate from the side opposite the lens, and the lens was moved toward the optical laminate. The temperature of the mold was 95°C. This allowed the optical laminate to be attached to the three-dimensional curved surface of the lens via an optically transparent adhesive film. We visually inspected whether or not the optical laminate had fractured while it was attached to the three-dimensional curved surface of the lens. The results are shown in Table 1. Subsequently, the lens with the optical laminate attached was placed on a reflector, and the ratio of the bonded area to the three-dimensional curved surface was calculated using the image processing software ImageJ. The results are shown in Table 1.

[0119] <Preparation of polarizers: Preparation steps> <<Preparation Example 1>> As a thermoplastic resin substrate, an amorphous isophthalic copolymer polyethylene terephthalate film (thickness: 100 μm) in a long length with a Tg of approximately 75°C was used, and one side of the film was subjected to corona treatment. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by mass of a PVA-based resin, which was prepared 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 "Gosephymer") in a 9:1 ratio, with 13 parts by mass of potassium iodide. A 13 μm thick PVA-based resin layer was formed on the thermoplastic resin substrate by applying the above PVA aqueous solution to the corona-treated surface of the thermoplastic resin substrate and drying it at 60°C. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (air-assisted stretching). Next, the laminate was immersed for 30 seconds in an insolubilization bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 4 parts by mass of boric acid with 100 parts by mass of water) (insolubilization treatment). Next, the laminate was immersed for 60 seconds in a staining bath at a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by mass of water) while adjusting the concentration so that the final transmittance (Ts) of the polarizer obtained would be the desired value (staining treatment). Next, the laminate was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with 100 parts by mass of water) (crosslinking treatment). Subsequently, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4% by weight, potassium iodide concentration 5% by weight) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to achieve a total stretch ratio of 4.0 times (underwater stretching treatment). Subsequently, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by mass of potassium iodide with 100 parts by mass of water) (washing treatment). Subsequently, the laminate was dried in an oven maintained at approximately 90°C while being brought into contact with a SUS (stainless steel) heated roll whose surface temperature was maintained at approximately 75°C (drying shrinkage treatment). In this way, a polarizer with a thickness of approximately 6 μm was formed on a thermoplastic resin substrate. The polarization degree of the obtained polarizer was 99%.

[0120] <<Preparation Example 2>> A polarizer was formed on a thermoplastic resin substrate in the same manner as in Preparation Example 1, except that the total stretching ratio in the aerial and underwater stretching treatments was changed to 5.5 times. The thickness of the polarizer was 5.0 μm. The polarization degree of the obtained polarizer was 99.99%.

[0121] <Preparation of the first phase difference film> <<Preparation Example 3>> As the first phase difference film, a cycloolefin (COP) resin film (manufactured by Zeon Corporation, trade name: ZD12, thickness: 25 μm) having an in-plane phase difference Re(550) was prepared. The first phase difference film in Preparation Example 3 had a single-layer structure of a stretched film containing COP. The first phase difference film of Preparation Example 3 had a refractive index of nx>ny>nz, and the in-plane phase difference Re(550) was 99 nm.

[0122] <<Preparation Example 4>> As the first phase difference film, a triacetylcellulose (TAC) film (manufactured by Konica Minolta, trade name: KC2UGR-HC, thickness: 36 μm) having an in-plane phase difference Re(550) was prepared. The first phase difference film of Preparation Example 4 had a stretched film containing TAC and a hard coat layer. Furthermore, the first phase difference film of preparation example 4 had a refractive index of nx>ny>nz, and the in-plane phase difference Re(550) was 103 nm.

[0123] <Preparation of the second phase difference film> <<Preparation Example 5>> A liquid crystal composition (coating solution) was prepared by dissolving 10 parts by mass of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (BASF: trade name "Paliocolor LC242", represented by the following formula) and 3 parts by mass of a photopolymerization initiator for the polymerizable liquid crystal compound (BASF: trade name "Irgacure 907") in 40 parts by mass of toluene. [ka] The surface of a polyethylene terephthalate (PET) film (38 μm thick) used as a coating substrate was rubbed with a rubbing cloth and subjected to orientation treatment. The direction of the orientation treatment was set so that when bonded to a polarizer (described later), it was at a 15° angle from the viewing side with respect to the absorption axis of the polarizer. The liquid crystal coating solution was applied to this orientation-treated surface using a bar coater, and the liquid crystal compound was oriented by heating and drying at 90°C for 2 minutes. In the liquid crystal layer formed in this manner, a metal halide lamp is used to apply 1 mJ / cm³ of liquid crystal. 2 A first liquid crystal alignment solidification layer was formed on the PET film by irradiating it with light and curing the liquid crystal layer. The thickness of the first liquid crystal alignment solidification layer was 2 μm. The first liquid crystal alignment solidification layer had a refractive index of nx > ny = nz. The in-plane phase difference Re(550) of the first liquid crystal alignment solidification layer was 270 nm. In other words, the first liquid crystal alignment solidification layer can function as a λ / 2 plate.

[0124] Furthermore, a second liquid crystal alignment solidification layer (λ / 4 plate) was formed on the PET film in the same manner as described above, except that the orientation processing direction was changed to a 75° direction relative to the absorption axis axis of the polarizer when viewed from the viewing side. The in-plane phase difference Re(550) of the second liquid crystal alignment solidification layer was 140 nm. In other words, the second liquid crystal alignment solidification layer can function as a λ / 4 plate.

[0125] Next, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer were bonded together using an ultraviolet-curing adhesive. Then, the ultraviolet-curing adhesive was cured by irradiating it with ultraviolet light. This formed a UV adhesive layer containing the cured product of the ultraviolet-curing adhesive. The thickness of the UV adhesive layer was 1 μm. Next, the PET film (coated substrate) was peeled off from the first liquid crystal alignment solidification layer. This allowed us to prepare a second phase difference film having a laminated structure consisting of a first liquid crystal alignment solidification layer (λ / 2 plate) / UV adhesive layer / second liquid crystal alignment solidification layer (λ / 4 plate) / PET film (coated substrate).

[0126] <Preparation of optically transparent adhesive film> <<Preparation Example 6>> (Preparation of acrylic oligomers) First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), 3.5 parts by mass of α-thioglycerol as a chain transfer agent, and 100 parts by mass of toluene as a polymerization solvent was stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture to prepare a reaction solution, which was reacted under a nitrogen atmosphere at 70°C for 2 hours, and then at 80°C for 2 hours (polymerization reaction). Next, the reaction solution was heated to 130°C to volatilize and remove toluene, chain transfer agent, and unreacted monomers. This yielded an acrylic oligomer (solid form). The weight-average molecular weight of this acrylic oligomer was 5100.

[0127] (Preparation of prepolymer composition) In a flask, a monomer mixture consisting of 71 parts by mass of n-butyl acrylate (BA), 13 parts by mass of N-vinyl-2-pyrrolidone (NVP), 3 parts by mass of acryloylmorpholine (ACMO), and 13 parts by mass of 4-hydroxybutyl acrylate (4HBA) was mixed with two types of first photopolymerization initiators (totaling 0.062 parts by mass). The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere to polymerize a portion of the monomer components in the mixture and obtain a prepolymer composition. The inter-entanglement molecular weight of n-butyl acrylate (BA) was 15000. As the first photopolymerization initiators, 0.031 parts by mass of BASF's "Omnirad 184" (1-hydroxycyclohexyl-phenyl-ketone) and 0.031 parts by mass of BASF's "Omnirad 651" (2,2-dimethoxy-2-phenylacetophenone) were used. Ultraviolet irradiation was continued until the viscosity of the composition reached approximately 20 Pa·s. This viscosity was measured using a B-type viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The resulting prepolymer composition is a partially polymerized product containing a photopolymerized product (photopolymerized polymer P1a) and monomer components that have not undergone polymerization (residual monomer).

[0128] (Preparation of adhesive composition) Next, 100 parts by mass of the prepolymer composition, 3 parts by mass of the above-mentioned acrylic oligomer, 0.6 parts by mass of urethane acrylate oligomer (UAO) (product name "UN-350", manufactured by Negami Kogyo Co., Ltd.) as a second photopolymerizable polyfunctional compound, 0.4 parts by mass of a second photopolymerization initiator, 0.5 parts by mass of an antioxidant (product name "Irganox 1010", manufactured by BASF), 0.2 parts by mass of a rust inhibitor (product name "BT-120", 1,2,3-benzotriazole, manufactured by Johoku Chemical Industry Co., Ltd.), and 0.3 parts by mass of a silane coupling agent (product name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain an adhesive composition. The amount of the second photopolymerizable polyfunctional compound (crosslinking agent) per 100 parts by mass of monomer components was 0.55 parts by mass. As the second photopolymerization initiator, we used "Omnirad819" (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) manufactured by BASF.

[0129] (Preparation of the base adhesive sheet) Next, an adhesive composition was applied to the peel-treated surface of a first peel-treated liner (product name "Diafoil MRF", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation), which has a peel-treated surface on one side, to form a coating film. Next, the peel-treated surface of a second peel-treated liner (product name "Diafoil MRE", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation), which also has a peel-treated surface on one side, was bonded onto the coating film on the first peel-treated liner. Next, ultraviolet light was irradiated onto the coating film between the peel-treated liners from the side of the second peel-treated liner to photo-cur the coating film and form an adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). For ultraviolet irradiation, a black light lamp (wavelength 320 nm to 400 nm, manufactured by Toshiba Corporation) was used as the light source, and the illuminance was set to 6.5 mW / cm². 2 The integrated irradiation light dose is 1500 mJ / cm². 2In the ultraviolet irradiation step, a photopolymerization reaction proceeds in the coating film in a reaction system containing the aforementioned residual monomer, additional monomer, and a second photopolymerizable polyfunctional compound (crosslinking agent), forming a photopolymerizable polymer P1b having a crosslinked structure. Furthermore, since this photopolymerization reaction proceeds around the photopolymerizable polymer P1a, the photopolymerizable polymer P1b is formed around the photopolymerizable polymer P1a. The adhesive layer formed in this step contains such photopolymerizable polymers P1a and P1b as the base polymer P1. In this manner, a base adhesive sheet with double-sided peel-off liners (first peel-off liner / base adhesive sheet (thickness 100 μm) / second peel-off liner) was prepared.

[0130] (Preparation of post-addition component solution) A solution of added components was prepared by mixing 6.0 parts by mass of trimethylolpropane triacrylate (TMPTA) (product name "Viscote #295", manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a first-order photopolymerizable polyfunctional compound, 1.2 parts by mass of ethoxylated bisphenol A diacrylate (BPAEODE) (product name "ABE-300", manufactured by Shin Nakamura Chemical Industry Co., Ltd.) as another first-order photopolymerizable polyfunctional compound, 0.3 parts by mass of a third-order photopolymerization initiator, 7.0 parts by mass of an ultraviolet absorber (product name "Tinosorb S", manufactured by BASF), and 90.7 parts by mass of ethyl acetate as a solvent (all components except the solvent in the solution are added later). "Omnirad 819" manufactured by BASF was used as the third-order photopolymerization initiator.

[0131] (Preparation of optical adhesive sheets) First, the second release liner was peeled off the base adhesive sheet with the release liner described above. Then, the post-addition component solution was applied to the exposed surface of the base adhesive sheet to a thickness of 20 μm (coating treatment). A bar coater RDS No. 10 manufactured by RDSPECIALTIES was used for coating. Next, it was dried in a drying oven at 110°C for 60 seconds. Through the coating and drying treatments, the post-addition components (first photopolymerizable polyfunctional compound, third photopolymerization initiator, ultraviolet absorber) were permeated into the base adhesive sheet, and the solvent was vaporized. The penetration of the post-addition components into the base adhesive sheet formed a photocurable optical adhesive sheet. Per 100 parts by mass of the above-mentioned prepolymer composition, the amount of TMPTA added was 6.0 parts by mass, the amount of BPAEODE added was 1.2 parts by mass, the amount of third photopolymerization initiator (Omnirad819) added was 0.3 parts by mass, and the amount of ultraviolet absorber (Tinosorb S) added was 7.0 parts by mass. Next, the peel-treated side of a third peel-off liner (product name "Diafoil MRE", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation), which has a peel-treated surface on one side, was attached to the adhesive sheet on the first peel-off liner.

[0132] As described above, an adhesive sheet with a release liner (first release liner / adhesive sheet (thickness 100 μm) / third release liner) was prepared. The adhesive sheet is a photocurable optical adhesive sheet containing a base polymer, a first photopolymerizable polyfunctional compound (TMPTA, BPAEODE), and a third photopolymerization initiator. This optical adhesive sheet was used as an optically transparent adhesive film.

[0133] [Example 1] The polarizer obtained in Preparation Example 1 and the first phase difference film obtained in Preparation Example 3 were bonded together using an ultraviolet-curing adhesive. Subsequently, the ultraviolet-curing adhesive was irradiated with ultraviolet light to cure it, forming a UV adhesive layer containing the cured product of the ultraviolet-curing adhesive. The thickness of the UV adhesive layer was 1 μm. Next, the thermoplastic resin substrate was peeled off and removed from the polarizer. Subsequently, a TAC film (manufactured by Fujifilm Corporation, product name: TJ25UL, thickness: 25 μm, Re(550): 0 nm) was applied as a protective layer to the surface of the polarizer opposite to the first phase difference film. Then, the UV-curable adhesive was irradiated with ultraviolet light to cure it, forming a UV adhesive layer containing the cured product of the UV-curable adhesive. The thickness of the UV adhesive layer was 1 μm. This resulted in the preparation of a polarizing plate having a laminated structure of a first phase difference film / UV adhesive layer / polarizer / UV adhesive layer / protective layer. In the polarizing plate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the first phase difference film was 45°.

[0134] Next, the protective layer of the polarizing plate and the first liquid crystal alignment solidification layer of the second phase difference film obtained in Preparation Example 5 were bonded together with an ultraviolet-curable adhesive. Subsequently, the ultraviolet-curable adhesive was irradiated with ultraviolet light to cure it, forming a UV adhesive layer containing the cured product of the ultraviolet-curable adhesive. The thickness of the UV adhesive layer was 1 μm. Subsequently, the PET film (coated substrate) was peeled off from the second liquid crystal alignment solidification layer. This allowed us to prepare an optical laminate having a laminated structure of a first phase difference film / UV adhesive layer / polarizer / UV adhesive layer / protective layer / UV adhesive layer / second phase difference film. In the optical laminate, the angle between the absorption axis direction of the polarizer and the slow axis direction of the first liquid crystal alignment solidification layer was 15°, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the second liquid crystal alignment solidification layer was 75°.

[0135] [Example 2] An optical laminate (polarizing plate) having a laminated structure of first phase difference film / UV adhesive layer / polarizer / UV adhesive layer / protective layer was prepared in the same manner as in Example 1, except that a second phase difference film was not attached to the protective layer of the polarizing plate.

[0136] [Example 3] The polarizer obtained in Preparation Example 1 and the first phase difference film obtained in Preparation Example 3 were bonded together in the same manner as in Example 1, and then the thermoplastic resin substrate was peeled off and removed from the polarizer. Next, the first liquid crystal alignment solidified layer of the second phase difference film obtained in Preparation Example 5 was attached to the surface of the polarizer opposite to the first phase difference film using an ultraviolet-curable adhesive. Subsequently, the ultraviolet-curable adhesive was irradiated with ultraviolet light to cure it, forming a UV adhesive layer containing the cured product of the ultraviolet-curable adhesive. The thickness of the UV adhesive layer was 1 μm. Subsequently, the PET film (coated substrate) was peeled off from the second liquid crystal alignment solidification layer. This allowed us to prepare an optical laminate having a laminated structure of a first phase difference film / UV adhesive layer / polarizer / UV adhesive layer / second phase difference film. In the optical laminate, the angle between the absorption axis direction of the polarizer and the slow axis direction of the first liquid crystal alignment solidification layer was 15°, and the angle between the absorption axis direction of the polarizer and the slow axis direction of the second liquid crystal alignment solidification layer was 75°.

[0137] [Example 4] An optical laminate was prepared in the same manner as in Example 3, except that the first phase difference film obtained in Preparation Example 3 was replaced with the first phase difference film obtained in Preparation Example 4.

[0138] [Comparative Example 1] An optical laminate was prepared in the same manner as in Example 1, except that the polarizer obtained in Preparation Example 1 was replaced with the polarizer obtained in Preparation Example 2.

[0139] [Comparative Example 2] An optical laminate was prepared in the same manner as in Example 2, except that the polarizer obtained in Preparation Example 1 was replaced with the polarizer obtained in Preparation Example 2.

[0140] [Table 1]

[0141] [evaluation] As is clear from Table 1, when the maximum value in the DDSC temperature range of 50°C to 95°C exceeds 600 μW / min but is less than 3000 μW / min, it is possible to suppress fracture during three-dimensional curved surface molding of optical laminates and to significantly improve the adhesion rate of optical laminates to three-dimensional curved surfaces. [Industrial applicability]

[0142] The optical laminate manufactured according to the embodiments of the present invention can be used in image display devices (typically liquid crystal display devices and organic EL display devices), and is particularly suitable for use in image display devices having a three-dimensional curved surface. [Explanation of symbols]

[0143] 1. First phase difference film 2. Second phase difference film 21. First liquid crystal alignment solidification layer 22 Second liquid crystal alignment solidification layer 3 Polarizer 4 protective layer 90 Three-dimensional curved surface 100 Optical laminate 101 Image display device

Claims

1. An optical laminate used in an image display device having a three-dimensional curved surface, Equipped with a polarizer, An optical laminate in which the maximum value in the temperature range of 50°C to 95°C in the differential curve of the heating curve of differential scanning calorimetry (DDSC) exceeds 600 μW / min and is less than 3000 μW / min.

2. The optical laminate according to claim 1, wherein the average value of the loss tangent tanδ at 95°C in the absorption axis direction of the polarizer and the average value of the loss tangent tanδ at 95°C in the transmission axis direction orthogonal to the absorption axis direction is greater than 0.06 and less than 0.

2.

3. The maximum value of the elastic modulus at 95°C in the absorption axis direction of the polarizer, and the elastic modulus at 95°C in the transmission axis direction perpendicular to the absorption axis direction, is 1000 N / mm². ２ More than 3400N / mm ２ The optical laminate according to claim 1, wherein the optical laminate is less than [amount missing].

4. The optical laminate according to claim 1, wherein the minimum value of the fracture displacement at 95°C in the absorption axis direction of the polarizer and the fracture displacement at 95°C in the transmission axis direction perpendicular to the absorption axis direction is greater than 1.7 and less than 4.

0.

5. The optical laminate according to claim 1, wherein the minimum number of bends in the MIT test in the absorption axis direction of the polarizer, and the minimum number of bends in the MIT test in the transmission axis direction perpendicular to the absorption axis direction, is greater than 80 and less than 200.

6. An image display device having a three-dimensional curved surface, The optical laminate comprises the optical laminate according to any one of claims 1 to 5, The optical laminate is attached to the three-dimensional curved surface, and is an image display device.

7. It also features an image display panel, The optical laminate has a first surface opposite to the image display panel and a second surface on the side of the image display panel. The image display device according to claim 6, wherein the radius of curvature of the first surface of the optical laminate is greater than the radius of curvature of the second surface of the optical laminate.

8. The image display device according to claim 7, wherein the radius of curvature of the first surface of the optical laminate is 4 mm or more and less than 100 mm.

9. The optical laminate further comprises a first phase difference film located on the opposite side of the polarizer from the image display panel, The first phase difference film functions as a λ / 4 plate, The image display device according to claim 7, wherein the radius of curvature of the first phase difference film is greater than the radius of curvature of the polarizer.

10. The polarizer further comprises a second phase difference film located on the opposite side from the first phase difference film, The second phase difference film functions as a λ / 4 plate, The image display device according to claim 9, wherein the radius of curvature of the second phase difference film is smaller than the radius of curvature of the polarizer.

11. The image display device according to claim 10, wherein the second phase difference film includes an orientation solidification layer of a liquid crystal compound.

12. This includes a preparation step for preparing the polarizer, The aforementioned preparation process is, A coating step involves applying a coating solution containing a polyvinyl alcohol-based resin to a substrate to obtain a laminate comprising a polyvinyl alcohol-based resin layer and a substrate, A dyeing step of dyeing the polyvinyl alcohol-based resin layer with a dichroic substance, The process includes stretching the laminate, A method for manufacturing an optical laminate, wherein the stretching ratio of the stretching step is 3.0 to 5.0 times the original length of the laminate.

13. The method for manufacturing an optical laminate according to claim 12, wherein the stretching ratio of the stretching step is 3.0 to 4.5 times the original length of the laminate.

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