Optical laminates and image display devices

Abstract

To provide an optical laminate that can realize an image display device with excellent visibility through an optical component having a polarizing effect, and that can suppress the occurrence and / or propagation of cracks. [Solution] The optical laminate according to an embodiment of the present invention includes a first phase difference film, a polarizer, and a second phase difference film in this order. The in-plane phase difference Re(550) of the first phase difference film is 80 nm or more and 160 nm or less. The average coefficient of linear expansion of the first phase difference film at -40°C to 85°C is 4.5 × 10⁻⁶ -5 It is below / ℃.

Description

[Technical Field]

[0001] This invention relates to an optical laminate and an image display device. [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. When a viewer looks at such an image display device through polarized sunglasses, depending on the viewer's viewing angle, the transmission axis direction of the polarized sunglasses and the transmission axis direction of the polarizer in the image display device may be crossed. In this case, the screen of the image display device may turn black, and the displayed image may not be visible. To solve these problems, it has been proposed that an optical laminate comprising a phase difference film and a polarizer be placed on the viewing side of the image display panel in an image display device (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

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

[0004] However, the image display device equipped with the optical laminate described in Patent Document 1 has the problem that cracks may occur in the optical laminate depending on the usage environment. The main objective of the present invention is to provide an optical laminate that can realize an image display device with excellent visibility through an optical element having a polarizing effect, and that can suppress the occurrence and / or propagation of cracks. [Means for solving the problem]

[0005] [1] An optical laminate according to an embodiment of the present invention comprises a first phase difference film, a polarizer, and a second phase difference film in this order. The in-plane phase difference Re(550) of the first phase difference film is 80 nm or more and 160 nm or less. The average coefficient of linear expansion of the first phase difference film at -40°C to 85°C is 4.5 × 10⁻⁶ -5 It is below / ℃. [2] In the optical laminate described in [1] above, the angle between the slow phase axis direction of the first phase difference film and the absorption axis direction of the polarizer may be 35° to 55°. [3] The optical laminate described in [1] or [2] above may have through holes. The through holes penetrate the optical laminate in the stacking direction. [4] In the optical laminate described in [3] above, the diameter of the through hole may be 6 mm or less. [5] In the optical laminate described in any of [1] to [4] above, the first phase difference film may contain a cellulose resin. [6] In any of the optical laminates described in [1] to [5] above, the distance from the surface of the polarizer on the first phase difference film side to the surface of the second phase difference film opposite to the polarizer in the lamination direction of the optical laminate may be less than the thickness of the first phase difference film. [7] In any of the optical laminates described in [1] to [6] above, the distance from the surface of the polarizer on the first phase difference film side to the surface of the second phase difference film opposite to the polarizer in the stacking direction of the optical laminate may be 5 μm to 15 μm. [8] In the optical laminate described in any of [1] to [7] above, the thickness of the first phase difference film may exceed 20 μm. The thickness of the second phase difference film may be less than 10 μm. [9] In the optical laminate described in any of [1] to [8] above, the second phase difference film may be attached to the polarizer via an adhesive layer.

[10] In the optical laminate described in any of [1] to [9] above, the second phase difference film may function as a λ / 4 plate.

[11] In the optical laminate according to any one of [1] to

[10] above, the second retardation film may contain an alignment and curing layer of a liquid crystal compound.

[12] An image display device according to another aspect of the present invention includes the optical laminate according to any one of [1] to

[11] above. In the image display device, the first retardation film may be disposed on the viewing side with respect to the polarizer. [Effects of the Invention]

[0006] According to an embodiment of the present invention, an image display device excellent in visibility through an optical member having a polarizing action can be realized, and the occurrence and / or expansion of cracks can be suppressed. [Brief Description of the Drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention. [Figure 3] FIG. 3 is a schematic plan view of the optical laminate of FIG. 1. [Figure 4] FIG. 4 is a schematic cross-sectional view of the first retardation film included in the optical laminate of FIG. 1. [Figure 5] FIG. 5 is a schematic cross-sectional view of the second retardation film included in the optical laminate of FIG. 1. [Modes 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. In addition, for the sake of clarity of explanation, the drawings may schematically show the widths, thicknesses, shapes, etc. of each part as compared with 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, where d (nm) is the thickness of the layer (film). (3) Retardation in the thickness direction (Rth) “Rth(λ)” is the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, “Rth(550)” is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, “45°” means ±45°.

[0010] A. Outline of the optical laminate FIG. 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 includes a first retardation film 1, a polarizer 3, and a second retardation film 2 in this order. The in-plane retardation Re(550) of the first retardation film 1 is 80 nm or more and 160 nm or less. The first retardation film 1 typically functions as a λ / 4 plate. The average linear expansion coefficient of the first retardation film 1 at -40°C to 85°C is 4.5×10 -5 / °C or less. While the inventors were considering miniaturizing and / or thinning image display devices, they encountered a new problem: cracks that were previously hidden by the bezel of the image display device could reach the display screen of the device. Therefore, the present inventors diligently investigated the occurrence and propagation of cracks in optical laminates and found that by adjusting the average coefficient of linear expansion (hereinafter sometimes referred to as CTE) of the phase difference film in the optical laminate to a predetermined range, the occurrence and / or propagation of cracks in the optical laminate can be suppressed. For more details, the average linear expansion coefficient of the first phase difference film at -40°C to 85°C is 4.5 × 10⁻⁶. -5 Because the temperature is below / °C, even when an image display device equipped with an optical laminate is used in various environments (especially in the temperature range of -40°C to 85°C), the occurrence and / or propagation of cracks in the optical laminate can be significantly suppressed. Therefore, even when the image display device is miniaturized, it is possible to prevent cracks that occur in the optical laminate from reaching the display screen of the image display device. Furthermore, since the in-plane phase difference Re(550) of the first phase difference film is between 80 nm and 160 nm, sufficient visibility of the image display device can be ensured through an optical element having a polarizing effect (hereinafter sometimes referred to as a polarizing element). Therefore, by applying an optical laminate according to one embodiment to an image display device, an image display device with excellent visibility via a polarizing member can be realized, and the occurrence and / or propagation of cracks in the optical laminate can be suppressed regardless of the operating environment of the image display device.

[0011] The first phase difference film 1 is located on the opposite side of the polarizer 3 from the second phase difference film 2. The first phase difference film 1 can typically function as a protective layer for the polarizer 3. In one embodiment, the first phase difference film 1 is positioned on the viewing side with respect to the polarizer 3 when the optical laminate 100 is applied to the image display device.

[0012] The CTE of the first phase difference film 1 is preferably 4.2 × 10 -5 / °C or lower, more preferably 4.0×10 -5 / °C or lower, still more preferably 3.8×10 -5 / °C or lower. When the first retardation film has such a CTE, generation and / or expansion of cracks in the optical laminate can be stably suppressed. On the other hand, the CTE of the first retardation film 1 is, for example, 1.0×10 -5 / °C or higher, and also for example 2.0×10 -5 / °C or higher, and also for example 3.0×10 -5 / °C or higher. The coefficient of thermal expansion (CTE) is measured, for example, in accordance with JIS K 7197. More specifically, the coefficient of thermal expansion (CTE) is calculated using the maximum and minimum values of the dimensions in a predetermined direction in the cycle of (1) cooling from 25°C to -40°C, (2) heating from -40°C to 85°C, (3) cooling from 85°C to -40°C, (4) heating from -40°C to 85°C, (5) cooling from 85°C to -40°C, (6) heating from -40°C to 85°C, and (7) cooling from 85°C to 25°C. In the case of a film in which molecules are oriented or stretched, such as a retardation film or a polarizer, the coefficient of thermal expansion may vary depending on the in-plane orientation. In such a case, the value in the orientation where the coefficient of thermal expansion is maximum is referred to. In many stretched films, the stretched orientation is the smallest and the orientation perpendicular to the stretching direction is the largest. However, the in-plane orientation difference can be minimized by adjusting the stretching conditions, typically the heat fixing conditions or the relaxation conditions.

[0013] The refractive index of the first retardation film 1 shows a relationship of, for example, nx > ny ≥ nz, and preferably shows 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 a range not impairing the effects of the present invention, ny > nz or ny < nz may occur.

[0014] The in-plane phase difference Re(550) of the first phase difference film 1 is preferably 145 nm or less, more preferably 130 nm or less, even more preferably 120 nm or less, and particularly preferably 110 nm or less. When the Re(550) of the first phase difference film is below this upper limit, the desired coloring can be stably achieved in an image display device equipped with an optical laminate. On the other hand, the in-plane phase difference Re(550) of the first phase difference film 1 is preferably 90 nm or more. If the Re(550) of the first phase difference film is above this lower limit, the visibility through the polarizing member can be stably improved in an image display device equipped with an optical laminate.

[0015] The phase difference Rth(550) in the thickness direction of the first phase difference film 1 is, for example, 90 nm to 200 nm, and preferably 100 nm to 150 nm. The Nz coefficient of the first phase difference film 1 is, for example, 0.9 to 1.5, and preferably 1.1 to 1.4.

[0016] The first phase difference film 1 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.

[0017] The thickness of the first phase difference film 1 is, for example, 15 μm or more, preferably exceeding 20 μm, more preferably 23 μm or more, and even more preferably 28 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.

[0018] 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.

[0019] The polarizer 3 is located between the first phase difference film 1 and the second phase difference film 2 in the stacking direction of the optical laminate 100 (hereinafter sometimes simply referred to as the stacking direction). The polarizer 3 has a first surface 3a on the first phase difference film 1 side and a second surface 3b on the second phase difference film 2 side in the stacking direction. The first surface 3a and the second surface 3b are separated from each other in the stacking direction.

[0020] The average coefficient of linear expansion (CTE) of polarizer 3 at -40°C to 85°C is, for example, 20 × 10⁻⁶. -5 / ℃ or lower, preferably 10 × 10 -5 It is below / ℃. On the other hand, the CTE of polarizer 3 is, for example, 0.1 × 10⁻⁶. -5 It is above / ℃, and also, for example, 0.5 × 10 -5 It is above / ℃. The absolute value of the difference between the CTE of the first phase difference film 1 and the CTE of the polarizer 3 is, for example, 5 × 10⁻¹⁰. -5 / ℃ or lower, preferably 4 × 10 -5 It is below / ℃. If the polarizer's CTE is within this range, the occurrence and / or propagation of cracks in the optical laminate can be reliably suppressed.

[0021] The polarizer 3 is typically thinner than the first phase difference film 1. 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.

[0022] In the illustrated example, the polarizer 3 is attached to the first phase difference film 1 via an adhesive layer 61. Hereafter, the adhesive layer that attaches the polarizer 3 and the first phase difference film 1 may be referred to as the first adhesive layer 61. The first adhesive layer 61 is in contact with the first surface 3a of the polarizer 3. The first adhesive layer 61 may be an adhesive layer or a tack layer.

[0023] 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.

[0024] The thickness of the first adhesive layer 61 is, for example, 10 μm or less, preferably 5 μm or less, and more preferably 2 μm or less. On the other hand, the lower limit of the thickness of the first adhesive layer 61 is typically 0.01 μm.

[0025] The second phase difference film 2 is located on the opposite side of the polarizer 3 from the first phase difference film 1. In one embodiment, the second phase difference film 2 is positioned on the opposite side of the polarizer 3 from the viewing side (i.e., the panel side) when the optical laminate 100 is applied to the image display device. The second phase difference film 2 has a first surface 2a on the polarizer 3 side and a second surface 2b on the opposite side of the polarizer 3 in the stacking direction. The first surface 2a and the second surface 2b are separated from each other in the stacking direction.

[0026] 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. The second phase difference film 2 may be a single-layer film or a multi-layer film. The second phase difference film 2 preferably has an in-plane phase difference. The in-plane phase difference Re(550) of the second phase difference film 2 is, for example, 100 nm to 300 nm. The Nz coefficient of the second phase difference film 2 is, for example, 0.9 to 1.5, preferably 0.9 to 1.3. In one embodiment, the second phase difference film 2 functions as a λ / 4 plate. When the second phase difference film functions as a λ / 4 plate, it can provide excellent anti-reflective properties to an image display device comprising an optical laminate. When the second phase difference film 2 functions as a λ / 4 plate, the in-plane phase difference Re(550) of the second phase difference film 2 is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm.

[0027] 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.

[0028] The average coefficient of linear expansion (CTE) of the second phase difference film 2 at -40°C to 85°C is, for example, 15 × 10⁻⁶. -5 The temperature is below / ℃, preferably 12 × 10 -5 It is below / ℃. On the other hand, the CTE of the second phase difference film 2 is, for example, 2 × 10 -5 / ℃ or higher, and for example, 5 × 10 -5 It is above / ℃. The absolute value of the difference between the CTE of the first phase difference film 1 and the CTE of the second phase difference film 2 is, for example, 10 × 10 -5 / ℃ or lower, preferably 8 × 10 -5 It is below / ℃. If the CTE of the second phase difference film is within this range, the occurrence and / or propagation of cracks in the optical laminate can be suppressed more stably.

[0029] The second phase difference film 2 is typically thinner than the first phase difference film 1. 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.

[0030] 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 attaches 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 is in contact with the second surface 3b of the polarizer 3 and the first surface 2a of the second phase difference film 2. 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.

[0031] In one embodiment, the optical laminate 100 does not include an optical film (optical layer) thicker than the first phase difference film 1. With this configuration, the optical laminate can be made thin in a stable manner. Examples of optical films include polarizing plates, phase difference films, polarizing plate protective films, phase difference protective films, image display device protective films, ultraviolet light transmission suppression films, and infrared light transmission suppression films.

[0032] In the stacking direction, the distance from the first surface 3a of the polarizer 3 to the second surface 2b of the second phase difference film 2 may be greater than or equal to the thickness of the first phase difference film 1, or less than the thickness of the first phase difference film 1. In one embodiment, the distance from the first surface 3a of the polarizer 3 to the second surface 2b of the second phase difference film 2 in the stacking direction is smaller than the thickness of the first phase difference film 1. With this configuration, the thinning of the optical stack can be achieved more stably. The distance from the first surface 3a of the polarizer 3 to the second surface 2b of the second phase difference film 2 in the stacking direction is, for example, 5 μm to 25 μm, preferably 6 μm to 20 μm, and more preferably 7 μm to 15 μm.

[0033] In one embodiment, the optical laminate 100 further comprises an adhesive layer 5. The adhesive layer 5 is located on the opposite side of the polarizer 3 from the second phase difference film 2. With this configuration, the optical laminate can be attached to any suitable substrate (typically an image display panel) of the image display device by an adhesive layer.

[0034] The optical laminate 100 may further include a release liner 7. The release liner 7 is attached to the surface of the adhesive layer 5 opposite to the second phase difference film 2. Typically, the release liner 7 is temporarily attached to the adhesive layer 5 until the optical laminate is attached to the substrate, and is peeled off from the adhesive layer 5 when the optical laminate is attached.

[0035] In the optical laminate 100 shown in Figure 1, the second phase difference film 2 is attached to the polarizer 3 via the second adhesive layer 62. However, the configuration of the optical laminate is not limited to this. As shown in Figure 2, the optical laminate 100 may further include a protective layer 4. The protective layer 4 is located between the polarizer 3 and the second phase difference film 2 in the lamination direction. 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 Figure 1 is preferable to the optical laminate 100 shown in Figure 2. In the illustrated example, the protective layer 4 is attached to the polarizer 3 via an adhesive layer 63, and the second phase difference film 2 is attached to the protective layer 4 via an adhesive layer 64. Hereafter, the adhesive layer that bonds the polarizer 3 and the protective layer 4 may be referred to as the third adhesive layer 63, and the adhesive layer that bonds the protective layer 4 and the second phase difference film 2 may be referred to as the fourth adhesive layer 64. The third adhesive layer 63 and the fourth adhesive layer 64 will be described in the same manner as the first adhesive layer 61 described above. Therefore, a detailed description of the third adhesive layer 63 and the fourth adhesive layer 64 will be omitted.

[0036] As shown in Figure 3, 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, with a rectangular shape being preferred. In the illustrated example, the optical laminate 100 has a rectangular shape when viewed from the stacking direction. The size of the optical laminate 100 can be adjusted arbitrarily and appropriately. When the optical laminate 100 has a rectangular shape when viewed from the stacking direction, the dimensions of the optical laminate 100 in the longitudinal direction (long side direction) are, for example, 100 mm to 400 mm, and the dimensions of the optical laminate 100 in the width direction (short side direction) are typically 50 mm to 300 mm.

[0037] In one embodiment, the optical laminate 100 includes a shaped portion 10. Typically, the shaped portion 10 includes a portion that has an arc shape when viewed from the stacking direction. In this specification, "irregularly shaped part" refers to a part that has been processed into a special shape different from a general shape (for example, a rectangle or chamfered corners). Cracks tend to spread from the periphery of the irregularly shaped processed portion. However, according to one embodiment, since the CTE of the first phase difference film in the optical laminate is adjusted to the above range, the occurrence and / or spread of cracks can be sufficiently suppressed even if the optical laminate has an irregularly shaped processed portion. Examples of irregularly shaped processed parts 10 include through holes; recesses such as V-shaped notches and U-shaped notches. The optical laminate 100 may have one type of irregularly shaped section, or it may have two or more types of irregularly shaped sections.

[0038] In the illustrated example, the optical laminate 100 is provided with a through hole 10a as a shaped section. The through hole 10a penetrates the optical laminate 100 in the stacking direction. The through hole 10a may be located in the central part of the optical laminate 100 when viewed from the stacking direction, or it may be located closer to the edge than the center. The through-hole 10a is typically used as a hole for positioning cameras, sensors, physical switches, etc., within the plane of the image display device. The closer the through-hole is to the edge of the optical laminate 100 than to the center, the less it impairs the practicality of the image display device. On the other hand, the closer the through-hole 10a is to the center of the optical laminate 100 than to the edge, the less it impairs the practicality of the through-hole 10a. To improve industrial practicality, it is desirable that the user can position the through-hole 10a at any position. On the other hand, the closer the through-hole 10a is to the center, the greater the stress concentration in the plane, making it more prone to crack formation and / or propagation. To improve industrial practicality, it is desirable that crack formation and / or propagation do not occur even when the through-hole 10a is positioned in the central part. The distance between the center of the through-hole 10a and the edge of the optical laminate 100 is preferably 5 mm or more, more preferably 8 mm or more, even more preferably 10 mm or more, and particularly preferably 12 mm or more. The distance between the center of the through-hole 10a and the center of the optical laminate 100 is preferably 100 mm or less, more preferably 50 mm or less, even more preferably 30 mm or less, and particularly preferably 10 mm or less. If the optical laminate 100 is rectangular or has an irregularly shaped section, the distance between the optical laminate 100 and the end closest to the through-hole 10a is defined as the distance between the optical laminate 100 and the end of the optical laminate 100. The through-hole 10a has any suitable shape when viewed from the stacking direction. Examples of the shape of the through-hole 10a when viewed from the stacking direction include polygonal shapes such as rectangles, circular shapes, and elliptical shapes, with a circular shape being preferred. The diameter of the through hole 10a is, for example, 8 mm or less, preferably 6 mm or less. On the other hand, the lower limit of the diameter of the through hole 10a is typically 1 mm. Even if the optical laminate has through holes of such diameter, the occurrence and / or propagation of cracks can be reliably suppressed.

[0039] B. Details of the optical laminate Next, with reference to Figures 1 to 5, 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, the second phase difference film 2, the adhesive layer 5, and the release liner 7 in this order.

[0040] B-1. First phase difference film The first phase difference film 1 has any suitable configuration. The first phase difference film 1 typically contains a cellulose-based resin. When the first phase difference film contains a cellulose-based resin, the CTE of the first phase difference film can be stably adjusted to the range described above. Examples of cellulosic resins include triacetylcellulose (TAC) and diacetylcellulose, with triacetylcellulose (TAC) being preferred. Cellulose resins can be used alone or in combination.

[0041] The first phase difference film 1 may have a single-layer structure or a laminated structure.

[0042] 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. The stretched film is prepared by stretching a cellulose resin film (preferably a TAC film). 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.

[0043] As shown in Figure 4, in another embodiment, the first phase difference film 1 has a laminated structure. The first phase difference film 1 having a laminated structure typically comprises a substrate 11 and an orientation solidification layer 12 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. In the following, the orientation solidification layer of the liquid crystal compound in the first phase difference film 1 may be referred to as the first liquid crystal orientation solidification layer 12.

[0044] The substrate 11 may be located on the opposite side of the polarizer 3 from the first liquid crystal alignment solidification layer 12, or it may be located between the first liquid crystal alignment solidification layer 12 and the polarizer 3 (see Figure 1). When the substrate 11 is located on the opposite side of the polarizer 3 from the first liquid crystal alignment solidification layer 12, the first liquid crystal alignment solidification layer 12 is attached to the polarizer 3 via the first adhesive layer 61 (see Figure 1). When the substrate 11 is located between the first liquid crystal alignment solidification layer 12 and the polarizer 3, the substrate 11 is attached to the polarizer 3 via the first adhesive layer 61 (see Figure 1).

[0045] The base material 11 is typically composed of a cellulose resin film (preferably a TAC film).

[0046] In one embodiment, the substrate 11 is substantially optically isotropic. The in-plane phase difference Re(550) of the substrate 11 is, for example, 10 nm or less, preferably 8 nm or less, and more preferably 5 nm or less. On the other hand, the lower limit of the in-plane phase difference Re(550) of the substrate 11 is typically 0 nm.

[0047] The thickness of the substrate 11 is, for example, 10 μm to 50 μm, preferably 20 μm to 30 μm.

[0048] The surface of the substrate 11 is provided with the surface treatment layer described above, if necessary. Preferably, the surface treatment layer is provided on the surface of the substrate 11 opposite to the first liquid crystal alignment solidification layer 12.

[0049] The first liquid crystal alignment solidification layer 12 is supported by the substrate 11. In the first liquid crystal alignment solidification layer 12, typically, rod-shaped liquid crystal compounds are oriented in a state where they are aligned along the slow phase axis of the first phase difference film 1 (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.

[0050] 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 first phase difference film can have extremely excellent stability that is not affected by temperature changes.

[0051] 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.

[0052] 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.

[0053] The range of the in-plane phase difference Re(550) of the first liquid crystal alignment solidification layer 12 is, for example, the same as the range of the in-plane phase difference Re(550) of the first phase difference film 1 described above. The thickness of the first liquid crystal alignment solidification layer 12 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 12 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 12 is typically 0.5 μm. Having such a thickness in the first liquid crystal alignment solidification layer allows for even thinner optical laminates.

[0054] In the illustrated example, the first liquid crystal alignment solidification layer 12 is attached to the substrate 11 via the adhesive layer 13. In other words, the first phase difference film 1 in the illustrated example comprises the substrate 11, the adhesive layer 13, and the first liquid crystal alignment solidification layer 12 in this order.

[0055] The adhesive layer 13 may be an adhesive layer or a tack layer. In the illustrated example, the adhesive layer 13 is an adhesive layer 13a. The adhesive layer 13a is composed 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). Adhesives can be used alone or in combination.

[0056] In one embodiment, the adhesive layer 13a is formed by solidifying and / or curing a water-based adhesive. In other words, the adhesive layer 13a contains a solidified and / or cured product of a water-based adhesive. Such a configuration allows for a thinner adhesive layer.

[0057] Water-based adhesives have any suitable composition. Typically, water-based adhesives are liquid at room temperature (25°C) before solidification (curing). In one embodiment, the water-based adhesive contains a polyvinyl alcohol (PVA) resin. The PVA resin preferably contains acetoacetyl groups. The inclusion of acetoacetyl groups in the PVA resin of the water-based adhesive can improve the adhesion between the first liquid crystal alignment solidified layer and the adhesive layer.

[0058] The average degree of saponification of PVA resins containing acetoacetyl groups is, for example, 85 mol% or more, preferably 90 mol% or more. On the other hand, the average degree of saponification of PVA resins containing acetoacetyl groups is, for example, 100 mol% or less. The average degree of saponification is measured, for example, by NMR, or in accordance with JIS K6726.

[0059] The degree of acetoacetylation of a PVA resin containing an acetoacetyl group is, for example, 0.1 mol% or more, preferably 1 mol% or more, and more preferably 2 mol% or more. On the other hand, the degree of acetoacetylation of a PVA resin containing an acetoacetyl group is, for example, 40 mol% or less, preferably 20 mol% or less, and more preferably 7 mol% or less. The degree of acetoacetylation is calculated, for example, from the spectrum measured by NMR.

[0060] The average degree of polymerization of the PVA resin in the water-based adhesive is, for example, 100 or more, preferably 1000 or more. On the other hand, the average degree of polymerization of the PVA resin in the water-based adhesive is, for example, 5000 or less, preferably 4000 or less, and more preferably 2000 or less.

[0061] Water-based adhesives may contain any suitable additives. Examples of additives include crosslinking agents, refractive index modifiers, UV absorbers, antioxidants, and leveling agents. The additives can be used individually or in combination.

[0062] In one embodiment, the water-based adhesive contains a crosslinking agent as an additive in addition to the PVA-based resin described above. The crosslinking agent crosslinks the PVA-based resin and cures the water-based adhesive. Examples of crosslinking agents include melamine resins such as methylolmelamine; alkylenediamines; isocyanates; epoxys; and aldehydes. Crosslinking agents can be used alone or in combination. The proportion of the crosslinking agent in the water-based adhesive is, for example, 10 to 50 parts by mass, preferably 20 to 40 parts by mass, per 100 parts by mass of the PVA resin.

[0063] The thickness of such adhesive layer 13 is, for example, 1 μm or less, preferably 0.5 μm or less, more preferably 0.20 μm or less, even more preferably 0.15 μm or less, and particularly preferably 0.10 μm or less. On the other hand, the lower limit of the thickness of the adhesive layer 13 is typically 0.01 μm. The first liquid crystal alignment solidification layer 12 may be formed directly on the substrate 11 without an adhesive layer 13. The first liquid crystal alignment solidification layer 12 may be laminated on the substrate 11 via an alignment layer for aligning the liquid crystals.

[0064] B-2.Polarizer As shown in Figure 1, the polarizer 3 has any suitable configuration. The polarizer may be composed of, for example, a single layer of resin film, or it may be obtained using a laminate of two or more layers.

[0065] 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.

[0066] Specific examples of polarizers obtained using laminates include polarizers obtained using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or polarizers obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. Polarizers obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate, drying it to form a PVA-based resin layer on the resin substrate, and obtaining a laminate of the resin substrate and the PVA-based resin layer; or by stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In one embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching may further include, if necessary, air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in one embodiment, the laminate is subjected to a drying shrinkage treatment in which it shrinks by 2% or more in the width direction by heating while being transported in the longitudinal direction. Typically, the manufacturing method of this embodiment includes applying an air-assisted stretching treatment, a dyeing treatment, a water-based stretching treatment, and a drying shrinkage treatment to the laminate in this order. By introducing auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is coated on a thermoplastic resin, making it possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, it is possible to prevent problems such as a decrease in the orientation of PVA and dissolution when immersed in water in the subsequent dyeing and stretching processes, making it possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain halides. This makes it possible to improve the optical properties of polarizers obtained through processing steps that involve immersing the laminate in a liquid, such as dyeing and water-based stretching. Furthermore, by shrinking the laminate in the width direction through the drying shrinkage treatment, the optical properties can be improved.The resulting resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate, and any appropriate protective layer may be laminated onto the peeled surface according to the purpose. Details of the manufacturing method of such polarizers are described, for example, in Japanese Patent Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0067] The above-mentioned iodine dyeing is carried out, for example, by immersing the PVA resin film in an iodine aqueous solution. The stretching ratio for the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or during the dyeing process. Alternatively, dyeing may be performed after stretching. If necessary, the PVA resin film may be subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA resin film in water and washing it before dyeing, not only can dirt and blocking inhibitors on the surface of the PVA resin film be washed away, but the PVA resin film can also be swollen to suppress uneven dyeing.

[0068] 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.

[0069] 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.

[0070] 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. The second phase difference film 2 may comprise one orientation solidification layer of liquid crystal compound, or it may comprise multiple orientation solidification layers of liquid crystal compound.

[0071] As shown in Figure 5, 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 second liquid crystal orientation solidification layer 22 and the third liquid crystal orientation solidification layer 23. The second liquid crystal alignment solidification layer 22 and the third liquid crystal alignment solidification layer 23 will be described in the same manner as the first liquid crystal alignment solidification layer 12. Therefore, detailed descriptions of the second liquid crystal alignment solidification layer 22 and the third liquid crystal alignment solidification layer 23 will be omitted as appropriate.

[0072] The second liquid crystal alignment solidification layer 22 is located between the polarizer 3 and the third liquid crystal alignment solidification layer 23 (see Figure 1). Therefore, the second liquid crystal alignment solidification layer 22 is typically attached to the polarizer 3 via the second adhesive layer 62. The third liquid crystal alignment solidification layer 23 is located on the opposite side of the polarizer 3 from the second liquid crystal alignment solidification layer 22 (see Figure 1).

[0073] The second liquid crystal alignment solidification layer 22 typically functions as a λ / 2 plate. The third liquid crystal alignment solidification layer 23 typically functions as a λ / 4 plate. 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 imparted to the optical laminate. Furthermore, the second liquid crystal alignment solidification layer 22 may function as a λ / 4 plate, and the third liquid crystal alignment solidification layer 23 may function as a λ / 2 plate.

[0074] 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, 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 third liquid crystal alignment solidification layer 23 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 second 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 third liquid crystal alignment solidification layer.

[0075] In the illustrated example, the second liquid crystal alignment solidification layer 22 and the third liquid crystal alignment solidification layer 23 are bonded together via an adhesive layer 24. The adhesive layer 24 will be described in the same way as the first adhesive layer 61 described above. Therefore, a detailed explanation of the adhesive layer 24 will be omitted.

[0076] B-4. Adhesive layer As shown in Figure 1, the adhesive layer 5 is typically provided on the second surface 2b of the second phase difference film 2. In one embodiment, the adhesive layer 5 is provided on the surface of the third liquid crystal alignment solidification layer 23 opposite to the second liquid crystal alignment solidification layer 22 (see Figure 5).

[0077] The adhesive layer 5 is composed of any suitable adhesive. Examples of adhesives include (meth)acrylic adhesives, urethane adhesives, and silicone adhesives. Note that "(meth)acrylic" refers to acrylic and / or methacrylic adhesives. The adhesives can be used alone or in combination. Among adhesives, (meth)acrylic adhesives are preferred.

[0078] The thickness of the adhesive layer 5 is, for example, 3 μm or more, preferably 5 μm or more, and preferably 10 μm or more. On the other hand, the thickness of the adhesive layer 5 is, for example, 50 μm or less, and preferably 30 μm or less.

[0079] B-5. Peel-off liner The release liner 7 contains any suitable resin material. Examples of resin materials include polyethylene terephthalate (PET), polyethylene, and polypropylene. Resin materials can be used alone or in combination.

[0080] In one embodiment, a release treatment layer is provided on the contact surface of the release liner 7 with the adhesive layer 5. The release layer typically contains a release agent. Examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents, with silicone-based release agents being preferred, and vinyl group-containing addition-type silicones being even more preferred. Release agents can be used alone or in combination. The thickness of the release layer is, for example, 50 nm to 400 nm.

[0081] B-6.Protective layer As shown in Figure 2, the optical laminate 100 may further include a protective layer 4. The protective layer 4 contains any suitable transparent resin. Examples of transparent resins include cycloolefin (COP) resins such as polynorbornene-based resins; polyester resins such as polyethylene terephthalate (PET)-based resins; cellulose resins such as triacetylcellulose (TAC); polycarbonate (PC) resins; (meth)acrylic resins; polyvinyl alcohol-based resins; polyamide resins; polyimide resins; polyethersulfone resins; polysulfone resins; polystyrene resins; polyolefin resins; and acetate resins. Thermosetting resins or UV-curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone resins can also be used. In addition, glassy polymers such as siloxane polymers can also be used. Polymer films 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 groups and nitrile groups in its side chains can be used. Examples include a resin composition having an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. 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.

[0082] 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.

[0083] B-7. Irregular processing section As shown in Figure 3, in one embodiment, the optical laminate 100 has the shaped portion 10 described above.

[0084] The irregularly shaped section 10 is formed by any appropriate processing means. Examples of processing methods include cutting and thermal cutting, with thermal cutting being preferred. Specific examples of thermal cutting processes include laser cutting, plasma cutting, and gas cutting.

[0085] In one embodiment, the irregularly shaped section 10 is formed by laser processing. The peak wavelength of the laser light used in laser processing is, for example, 1500 nm or less, preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 680 nm or less. On the other hand, the wavelength of the laser light is, for example, 100 nm or more, preferably 220 nm or more. When laser light has such a peak wavelength, the smoothness of the end face of the irregularly shaped processed part in the optical laminate can be improved, and as a result, the propagation of cracks from the end face of the irregularly shaped processed part can be stably suppressed.

[0086] The laser light irradiation conditions are adjusted arbitrarily and appropriately. The frequency of the laser light is, for example, 1 kHz to 300 kHz, preferably 20 kHz to 100 kHz. The processing speed using laser light is, for example, 1 mm / s to 1000 mm / s, preferably 10 mm / s to 100 mm / s.

[0087] C. Image display device The optical laminates described in sections A and B above can be applied to any suitable image display device. Therefore, one embodiment of the present invention also includes image display devices using such optical laminates. Examples of image display devices include liquid crystal displays and organic light-emitting diodes (EL displays). An image display device according to an embodiment of the present invention comprises an image display panel and the optical laminate 100 described above. The image display panel typically includes an image display cell. The optical laminate 100 is positioned on the viewing side of the image display panel. In the optical laminate 100, the first phase difference film 1 is positioned on the viewing side, i.e., the side opposite to the image display panel, with respect to the polarizer 3. In such an image display device, the first phase difference film of the optical laminate has the in-plane phase difference described above and the CTE described above, so it has excellent visibility through a polarizing member (typically polarized sunglasses), and the occurrence and / or propagation of cracks in the optical laminate can be suppressed regardless of the usage environment of the image display device.

[0088] Furthermore, the image display device may also include a camera unit. In this case, the optical laminate 100 preferably includes a shaped processing unit 10. When the optical laminate 100 is applied to the image display device, the shaped processing unit 10 is typically positioned to face the camera unit. [Examples]

[0089] 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.

[0090] (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.

[0091] (2) Measurement of the mean coefficient of thermal expansion The dimensional changes of the first phase difference film obtained in the preparation example, and the protective layers used in the examples and comparative examples, were measured using a TMA analyzer (TMA7100E, Hitachi High-Tech Science Corporation) under the following conditions. More specifically, a sample of the first phase difference film or protective layer was placed in the TMA analyzer and operated in the following cycles: (1) cooling from 25°C to -40°C, (2) heating from -40°C to 85°C, (3) cooling from 85°C to -40°C, (4) heating from -40°C to 85°C, (5) cooling from 85°C to -40°C, (6) heating from -40°C to 85°C, and (7) cooling from 85°C to 25°C. The maximum and minimum lengths of the sample were measured. The obtained values ​​were substituted into equation (A) below to calculate the dimensional change rate. Then, the obtained dimensional change rate was substituted into equation (B) below to calculate the average linear expansion coefficient ( / °C) of the first phase difference film and the protective layer, respectively. The results are shown in Table 1. Furthermore, in the case of films in which molecules are oriented or stretched, such as phase difference films and polarizers, the average coefficient of linear thermal expansion may differ depending on the orientation within the plane. In such cases, the value of the orientation with the maximum average coefficient of linear thermal expansion was used as the reference. <Measurement conditions> Environmental humidity: 50%RH Low temperature: -40℃ High temperature side temperature: 85℃ Heating rate: 5°C / min Dimensional change rate = (ΔL / L) × 100···(A) ΔL: Dimensional change during measurement (maximum sample length in cycle operation - minimum sample length in cycle operation) L: Sample length at 25℃ Average linear expansion coefficient ( / °C) = (dimensional change rate / ΔT) / 100 ... (B) ΔT: Temperature change (high temperature - low temperature)

[0092] (3) Sunglasses evaluation (visibility) An organic EL display device (manufactured by Samsung, product number "Galaxy A41") was disassembled and the organic EL panel was removed. The optical laminates obtained in the examples and comparative examples were attached to the organic EL panel using an adhesive layer to prepare test samples. Next, a white image was displayed on the OLED panel, and the color rendering when the image was observed through polarized sunglasses was evaluated according to the following criteria. The results are shown in Table 1. Good: Visible from all directions. Defect: An angle occurred where it was not visible.

[0093] (4) Crack evaluation The optical laminates obtained in the examples and comparative examples were attached to a glass plate using an adhesive layer to prepare test samples. Next, the test samples were subjected to a heat shock test, in which they were held at -40°C for 30 minutes, followed by 85°C for 30 minutes, and this cycle was repeated 300 times. Subsequently, the occurrence of cracks near through-holes in the optical laminate was evaluated according to the following criteria. The results are shown in Table 1. Excellent: No cracks larger than 50 μm were observed. Good: Cracks exceeding 50 μm are present, but no cracks exceeding 200 μm are present. Defect: Cracks exceeding 200 μm were present.

[0094] <Preparation of the first phase difference film> <<Preparation Example 1>> 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 45° angle to the absorption axis of the polarizer as viewed from the viewing side. 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 1 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 100 nm. In other words, the first liquid crystal alignment solidification layer can function as a λ / 4 plate.

[0095] In addition, a triacetylcellulose (TAC) film (manufactured by Fujifilm Corporation, product name: TJ25UL, thickness: 25 μm) was prepared as a substrate. The in-plane phase difference Re(550) of this substrate was 0 nm. Furthermore, a water-based adhesive was prepared by dissolving and / or dispersing a polyvinyl alcohol resin containing acetoacetyl groups (average degree of polymerization: 1,200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) and methylolmelamine in water in a mass ratio of 3:1. Next, the liquid crystal alignment solidification layer was attached to the TAC film with a water-based adhesive and dried at 60°C for 5 minutes. This cured the water-based adhesive, forming a water-based adhesive layer containing the cured adhesive material. The thickness of the water-based adhesive layer was 0.1 μm. Subsequently, the PET film was peeled off from the liquid crystal alignment solidification layer. Based on the above, a first phase difference film having a laminated structure of a first liquid crystal alignment solidification layer / water-based adhesive layer / substrate (TAC film) was prepared. The in-plane phase difference Re(550) of the first phase difference film in Preparation Example 1 was 100 nm.

[0096] <<Preparation Example 2>> A first phase difference film having a laminated structure of a first liquid crystal alignment solidification layer / adhesive layer / substrate (TAC film) was prepared in the same manner as in Preparation Example 1, except that the in-plane phase difference Re(550) of the first liquid crystal alignment solidification layer was changed to 140 nm.

[0097] <<Preparation Example 3>> 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 in Preparation Example 3 had a single-layer structure of a stretched film containing TAC, with a hard coat layer having a thickness of 5 μm. Furthermore, 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 103 nm.

[0098] <<Preparation Example 4>> 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 of Preparation Example 4 had a single-layer structure of a stretched film containing COP. 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 99 nm.

[0099] <Preparation of polarizers> <<Preparation Example 5>> 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. 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). 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. 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). 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 between rolls with different peripheral speeds to achieve a total stretch ratio of 5.5 times in the longitudinal direction. 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). Subsequently, the laminate was dried in an oven maintained at approximately 90°C while being brought into contact with a SUS (stainless steel) heating roll whose surface temperature was maintained at approximately 75°C. In this way, a polarizer with a thickness of approximately 5 μm was formed on a thermoplastic resin substrate. The polarizer had the same shape and size as the first phase difference film of Preparation Example 1 when viewed from the thickness direction.

[0100] <Preparation of the second phase difference film> <<Preparation Example 6>> A second liquid crystal alignment solidification layer (λ / 2 plate) was formed on a PET film in the same manner as in Preparation Example 1, except that the coating thickness was changed and the orientation processing direction was changed to 15° relative to the polarizer's absorption axis when viewed from the viewing side. The in-plane phase difference Re(550) of the second liquid crystal alignment solidification layer was 270 nm. In other words, the second liquid crystal alignment solidification layer can function as a λ / 2 plate. The thickness of the second liquid crystal alignment solidification layer was 2 μm. Furthermore, a third liquid crystal alignment solidification layer (λ / 4 plate) was formed on a PET film in the same manner as in Preparation Example 2, 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 third liquid crystal alignment solidification layer was 140 nm. In other words, the third liquid crystal alignment solidification layer can function as a λ / 4 plate. Next, the second liquid crystal alignment solidification layer and the third liquid crystal alignment solidification 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 second liquid crystal alignment solidification layer. This allowed us to prepare a second phase difference film having a laminated structure consisting of a second liquid crystal alignment solidification layer (λ / 2 plate) / UV adhesive layer / third liquid crystal alignment solidification layer (λ / 4 plate) / PET film (coated substrate). The second phase difference film had the same shape and size as the first phase difference film of Preparation Example 1 when viewed from the thickness direction.

[0101] [Example 1] The first liquid crystal alignment solidified layer of the first phase difference film obtained in Preparation Example 1 and the polarizer 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. This allowed us to prepare a polarizing plate having a laminated structure consisting of a substrate, a water-based adhesive layer, a first liquid crystal orientation solidification layer, a UV adhesive layer, a polarizer, and a thermoplastic resin substrate. In the polarizing plate, the angle between the absorption axis direction of the polarizer and the slow phase axis direction of the first liquid crystal alignment solidification layer was 45°.

[0102] Next, the thermoplastic resin substrate was peeled off and removed from the polarizer. Next, the polarizer of the polarizing plate and the second liquid crystal alignment solidification layer of the second phase difference film obtained in Preparation Example 6 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. Next, the PET film (coated substrate) was peeled off from the third liquid crystal alignment solidification layer. Subsequently, a (meth)acrylic adhesive was applied to the surface of the second phase difference film opposite to the polarizer, or more specifically, to the surface of the third liquid crystal alignment solidification layer opposite to the second liquid crystal alignment solidification layer, to form an adhesive layer with a thickness of 15 μm. This allowed us to prepare an optical laminate having a laminated structure of substrate / water-based adhesive layer / first liquid crystal alignment solidification layer / UV adhesive layer / polarizer / UV adhesive layer / second liquid crystal alignment solidification layer / UV adhesive layer / third liquid crystal alignment solidification layer / acrylic adhesive layer. The total thickness of the optical laminate is shown in Table 1. In the optical laminate, the angle between the absorption axis direction of the polarizer and the slow axis direction of the second 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 third liquid crystal alignment solidification layer was 75°.

[0103] Next, the optical laminate was cut to have a roughly rectangular shape when viewed from the thickness direction, and a through hole was formed in the central part of the optical laminate, penetrating the laminate in the stacking direction. At room temperature (25°C) and atmospheric pressure (0.1 MPa), the length of the optical laminate was 155 mm and the width was 77 mm. The slow phase axis of the first phase difference film was parallel to the length direction, and the absorption axis of the polarizer was at 45° with respect to the length direction. More specifically, through-holes were formed in the polarizing plate using a laser processing device (manufactured by Takei Electric Industry Co., Ltd., product name: TLSM-301) under the following processing conditions. The center of the through-hole substantially coincided with the center of the optical laminate. The through-hole had a roughly circular shape when viewed from the stacking direction of the optical laminate. The diameter of the through-hole was 4 mm. <Processing conditions> Laser wavelength: 355nm Output: 0.6W Machining speed: 38mm / s Frequency: 60000Hz The number of scans was set to an optimal value according to the optical laminate.

[0104] [Example 2] An optical laminate was prepared in the same manner as in Example 1, except that the substrate of the first phase difference film obtained in Preparation Example 2 and the polarizer obtained in Preparation Example 5 were bonded together with an ultraviolet-curing adhesive. The optical laminate prepared in Example 2 had a laminated structure consisting of a first liquid crystal alignment solidification layer / water-based adhesive layer / substrate / UV adhesive layer / polarizer / UV adhesive layer / second liquid crystal alignment solidification layer / UV adhesive layer / third liquid crystal alignment solidification layer / acrylic adhesive layer.

[0105] [Example 3] An optical laminate was prepared in the same manner as in Example 1, except that the first phase difference film obtained in Preparation Example 1 was replaced with the first phase difference film obtained in Preparation Example 3. The optical laminate prepared in Example 3 had a laminated structure consisting of a hard coat layer, a TAC film with an in-plane phase difference Re(550), a UV adhesive layer, a polarizer, a UV adhesive layer, a second liquid crystal alignment solidification layer, a UV adhesive layer, a third liquid crystal alignment solidification layer, and an acrylic adhesive layer.

[0106] [Example 4] The first liquid crystal alignment solidification layer of the first phase difference film obtained in Preparation Example 1 and the polarizer obtained in Preparation Example 5 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. 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 using an ultraviolet-curing adhesive. Then, the coating was irradiated with ultraviolet light to cure the ultraviolet-curing adhesive, forming a UV adhesive layer containing the cured product of the ultraviolet-curing adhesive. The thickness of the UV adhesive layer was 1 μm. This allowed us to prepare a polarizing plate having a laminated structure of a substrate / water-based adhesive layer / first liquid crystal orientation solidification layer / UV adhesive layer / polarizer / UV adhesive layer / protective layer. Next, the protective layer of the polarizing plate and the second liquid crystal alignment solidification layer of the second phase difference film obtained in Preparation Example 6 were bonded together in the same manner as in Example 1, and then the PET film was peeled off from the third liquid crystal alignment solidification layer. Subsequently, an acrylic adhesive layer was formed on the surface of the second phase difference film opposite to the polarizer, in the same manner as in Example 1. This allowed us to prepare an optical laminate having a laminated structure of substrate / water-based adhesive layer / first liquid crystal alignment solidification layer / UV adhesive layer / polarizer / UV adhesive layer / protective layer / UV adhesive layer / second liquid crystal alignment solidification layer / UV adhesive layer / third liquid crystal alignment solidification layer / acrylic adhesive layer. Table 1 shows the mean coefficient of thermal expansion (CTE) of the protective layer.

[0107] [Example 5] An optical laminate was prepared in the same manner as in Example 4, except that the protective TAC film was replaced with a cycloolefin (COP) resin film (manufactured by Zeon Corporation, product name: ZF14, thickness: 13 μm, Re(550): 0 nm).

[0108] [Comparative Example 1] An optical laminate was prepared in the same manner as in Example 1, except that the first phase difference film obtained in Preparation Example 1 was replaced with the first phase difference film obtained in Preparation Example 4. The optical laminate prepared in Comparative Example 1 had a laminated structure consisting of a COP-based resin film with an in-plane phase difference Re(550) / UV adhesive layer / polarizer / UV adhesive layer / second liquid crystal alignment solidification layer / UV adhesive layer / third liquid crystal alignment solidification layer / acrylic adhesive layer.

[0109] [Comparative Example 2] An optical laminate was prepared in the same manner as in Example 1, except that the first phase difference film obtained in Preparation Example 1 was replaced with a cycloolefin (COP) resin film (manufactured by Zeon Corporation, product name: ZF14, thickness: 23 μm, Re(550): 0 nm) as a protective layer. The optical laminate prepared in Comparative Example 2 had a laminated structure consisting of a COP-based resin film, a UV adhesive layer, a polarizer, a UV adhesive layer, a second liquid crystal alignment solidification layer, a UV adhesive layer, a third liquid crystal alignment solidification layer, and an acrylic adhesive layer, without an in-plane phase difference Re(550).

[0110] [Comparative Example 3] An optical laminate was prepared in the same manner as in Example 5, except that the first phase difference film obtained in Preparation Example 1 was replaced with the first phase difference film obtained in Preparation Example 4, and the protective layer was changed to a cycloolefin (COP) resin film (manufactured by Zeon Corporation, product name: ZF14, thickness: 23 μm, Re(550): 0 nm). The optical laminate prepared in Comparative Example 3 had a laminated structure consisting of a COP-based resin film with an in-plane phase difference Re(550) / UV adhesive layer / polarizer / UV adhesive layer / protective layer / UV adhesive layer / second liquid crystal alignment solidification layer / UV adhesive layer / third liquid crystal alignment solidification layer / acrylic adhesive layer.

[0111] [Comparative Example 4] An optical laminate was prepared in the same manner as in Example 1, except that the first phase difference film obtained in Preparation Example 1 was replaced with a TAC film (manufactured by Fujifilm Corporation, product name: TJ25UL, thickness: 25 μm, Re(550): 0 nm) as a protective layer. The optical laminate prepared in Comparative Example 4 had a laminated structure of TAC film / UV adhesive layer / polarizer / UV adhesive layer / second liquid crystal alignment solidification layer / UV adhesive layer / third liquid crystal alignment solidification layer / acrylic adhesive layer that did not have an in-plane phase difference Re(550).

[0112] [Table 1]

[0113] [evaluation] As is clear from Table 1, the in-plane phase difference Re(550) of the first phase difference film in the optical laminate is between 80 nm and 160 nm, and the average coefficient of thermal expansion of the first phase difference film is 4.5 × 10⁻⁶. -5 It can be seen that when the temperature is below / ℃, the visibility through polarized sunglasses can be improved when the optical laminate is applied to an image display device, and the occurrence of cracks in the heat shock test can be suppressed. [Industrial applicability]

[0114] The optical laminate manufactured according to the embodiments of the present invention can be suitably used in image display devices (typically liquid crystal display devices and organic EL display devices). [Explanation of Symbols]

[0115] 1. First phase difference film 11 Base material 12. First liquid crystal alignment solidification layer 2. Second phase difference film 22 Second liquid crystal alignment solidification layer 23 Third liquid crystal alignment solidification layer 3 Polarizer 4 protective layer 5. Adhesive layer 100 Optical laminate

Claims

1. It includes a first phase difference film, a polarizer, and a second phase difference film in this order. The in-plane phase difference Re(550) of the first phase difference film is 80 nm or more and 160 nm or less. The average linear expansion coefficient of the first phase difference film at -40°C to 85°C is 4.5 × 10⁻⁶ －５ An optical laminate that is below / ℃.

2. The optical laminate according to claim 1, wherein the angle between the slow phase axis direction of the first phase difference film and the absorption axis direction of the polarizer is 35° to 55°.

3. The optical laminate according to claim 1, having through holes that penetrate in the stacking direction of the optical laminate.

4. The optical laminate according to claim 3, wherein the diameter of the through hole is 6 mm or less.

5. The optical laminate according to claim 1, wherein the first phase difference film comprises a cellulose-based resin.

6. The optical laminate according to claim 1, wherein, in the stacking direction of the optical laminate, the distance from the surface of the polarizer on the first phase difference film side to the surface of the second phase difference film opposite to the polarizer is smaller than the thickness of the first phase difference film.

7. The optical laminate according to claim 1, wherein, in the stacking direction of the optical laminate, the distance from the surface of the polarizer on the first phase difference film side to the surface of the second phase difference film opposite to the polarizer is 5 μm to 15 μm.

8. The thickness of the first phase difference film exceeds 20 μm. The optical laminate according to claim 7, wherein the thickness of the second phase difference film is less than 10 μm.

9. The optical laminate according to claim 1, wherein the second phase difference film is attached to the polarizer via an adhesive layer.

10. The optical laminate according to claim 1, wherein the second phase difference film functions as a λ / 4 plate.

11. The optical laminate according to claim 1, wherein the second phase difference film includes an orientation solidification layer of a liquid crystal compound.

12. The optical laminate comprises the optical laminate according to any one of claims 1 to 11, The first phase difference film is positioned on the viewing side relative to the polarizer in an image display device.

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