Optical stack and optical components therein

Abstract

An optical stack comprises, in sequence, a first λ / 2 plate made solely of material M1, a second λ / 2 plate made solely of material M2, and a λ / 4 plate made solely of material M3, wherein the angle between the slow axis of the first λ / 2 plate and the slow axis of the second λ / 2 plate is 24.6° or more and 30.6° or less, the angle between the slow axis of the first λ / 2 plate and the slow axis of the λ / 4 plate is 90.5° or more and 96.5° or less, the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate respectively satisfy a specified formula, and the materials M1, M2, and M3 are specified materials.

Description

[Technical Field]

[0001] This invention relates to an optical stack and an optical component comprising the same. [Previous Technology]

[0002] A component with an in-plane delay Re(λ) of approximately λ / 2 at wavelength λ is also called a λ / 2 plate, and a component with an in-plane delay Re(λ) of approximately λ / 4 at wavelength λ is also called a λ / 4 plate.

[0003] For example, Patent Document 1 describes stacking a λ / 2 plate and a λ / 4 plate on each side of a glass plate to obtain a phase difference plate that imparts an in-plane delay to the transmitted light.

[0004] Furthermore, Patent Document 2 describes stacking two λ / 2 plates and one λ / 4 plate to obtain a phase difference plate.

[0005] 『Patent Documents』 《Patent Document 1》: Japanese Patent Publication No. 2003-344652 《Patent Document 2》: International Patent Publication No. 2020 / 209354 [Summary of the Invention]

[0006] In order for the phase retardation plate, which imparts an in-plane delay of λ / 4 to the transmitted light, to function in a wide wavelength range (especially the visible light range), the technology in Patent Document 2 stacks two λ / 2 plates and one λ / 4 plate to obtain the phase retardation plate.

[0007] Incidentally, retardation plates can be used as constituent elements of image display devices. In recent years, in order to install in the optical systems of stereoscopic image display devices that display stereoscopic images, there has been a search for high-performance retardation plates that can function as λ / 4 plates over a wide wavelength range.

[0008] Here, if the phase difference plate is deformed in order to combine it with the optical elements (e.g., pancake lens) included in the optical system of an image display device such as a stereoscopic image display device, the phase difference that the phase difference plate originally has will become uneven, which may sometimes affect the quality of the image display device.

[0009] Especially in stereoscopic image display devices, a slight decrease in the performance or quality of the phase difference plate can sometimes lead to a decrease in display performance (e.g., the display of unintended images (double images)).

[0010] It is sometimes difficult to obtain a phase difference plate that functions as a λ / 4 plate to reduce phase difference unevenness (phase difference spot) caused by deformation processing and to achieve excellent display performance when installed in a stereoscopic image display device, based on the technology of Patent Documents 1 and 2.

[0011] Therefore, there is a need for an optical stack that reduces phase difference inconsistency caused by deformation processing and achieves excellent display performance in a stereoscopic image display device, and an optical component comprising such an optical stack.

[0012] As a result of the inventors’ dedicated research to solving the aforementioned problems, they discovered that stacking two λ / 2 plates and one λ / 4 plate made of a specified material along the thickness direction with their respective slow axes clamping at a specified angle can solve the aforementioned problems and thus complete the present invention.

[0013] That is, the present invention provides the following content.

[0014] [1]An optical stack comprising, in sequence, a first λ / 2 plate made only of material M1, a second λ / 2 plate made only of material M2, and a λ / 4 plate made only of material M3, wherein the angle between the slow axis of the first λ / 2 plate and the slow axis of the second λ / 2 plate is 24.6° or more and 30.6° or less, the angle between the slow axis of the first λ / 2 plate and the slow axis of the λ / 4 plate is 90.5° or more and 96.5° or less, and the first λ / 2 plate satisfies any one of the following equations (1a), (1b), and (1c): nx1>ny1≒nz1 (1a)nx1>ny1>nz1 (1b)nx1>nz1>ny1 (1c) Here, nx1 represents the refractive index in the in-plane direction of the first λ / 2 plate that imparts the maximum refractive index, ny1 represents the refractive index in the in-plane direction of the first λ / 2 plate that is orthogonal to the direction of nx1, and nz1 represents the refractive index in the thickness direction of the first λ / 2 plate. The second λ / 2 plate satisfies any one of the following equations (2a), (2b), and (2c): nx2 > ny2 ≒ nz2 (2a) nx2 > ny2 > nz2 (2b) nx2 > nz2 > ny2 (2c) Here, nx2 represents the refractive index in the in-plane direction of the aforementioned second λ / 2 plate that imparts the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the aforementioned second λ / 2 plate that is orthogonal to the direction of nx2, and nz2 represents the refractive index in the thickness direction of the aforementioned second λ / 2 plate. The aforementioned λ / 4 plate satisfies any one of the following equations (3a), (3b), and (3c): nx3 > ny3 ≒ nz3 (3a) nx3 > ny3 > nz3 (3b) nx3 > nz3 > ny3 (3c) Here, nx3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate and the direction that imparts the maximum refractive index, ny3 represents the refractive index in the aforementioned in-plane direction of the aforementioned λ / 4 plate and the direction orthogonal to nx3, nz3 represents the refractive index in the thickness direction of the aforementioned λ / 4 plate, the aforementioned materials M1, M2 and M3 are each independently photoelastic coefficient of 10×10⁻¹³ cm² / dyn or less, and the aforementioned materials M1, M2 and M3 each contain more than 50% by weight of a specific polymer (P).

[0015] [2]The optical stack as described in [1], wherein the first λ / 2 plate satisfies the aforementioned formula (1a) or formula (1b), the aforementioned second λ / 2 plate satisfies the aforementioned formula (2a) or formula (2b), and the aforementioned λ / 4 plate satisfies the aforementioned formula (3a) or formula (3b).

[0016] [3]The optical stack as described in [1] or [2], wherein the first λ / 2 plate satisfies the aforementioned formula (1c), the second λ / 2 plate satisfies the aforementioned formula (2c), and the λ / 4 plate satisfies the aforementioned formula (3c).

[0017] [4]An optical stack as described in any of[1] to[3], wherein the NZ coefficient NZ1 of the aforementioned first λ / 2 plate satisfies 0.0<NZ1<1.0, the NZ coefficient NZ2 of the aforementioned second λ / 2 plate satisfies 0.0<NZ2<1.0, and the NZ coefficient NZ3 of the aforementioned λ / 4 plate satisfies 0.0<NZ3<1.0. Here, NZ1 is represented by the following formula: NZ1=(nx1-nz1) / (nx1-ny1), NZ2 is represented by the following formula: NZ2=(nx2-nz2) / (nx2-ny2), and NZ3 is represented by the following formula: NZ3=(nx3-nz3) / (nx3-ny3), where nx1, ny1, nz1, nx2, ny2, nz2, nx3, ny3 and nz3 are respectively synonyms of the aforementioned.

[0018] [5] An optical stack as described in any of [1] to [4], wherein the aforementioned polymer (P) is a polymer containing an alicyclic structure.

[0019] [6] An optical stack as described in any of [1] to [5] includes a first bonding layer between the first λ / 2 plate and the second λ / 2 plate, and a second bonding layer between the second λ / 2 plate and the λ / 4 plate.

[0020] [7]The optical stack as described in[6] satisfies the following equations (4), (5), (6) and (7). |I1-Ia1|≦0.02 (4)|I2-Ia1|≦0.02 (5)|I2-Ia2|≦0.02 (6)|I3-Ia2|≦0.02 (7) Here, I1 represents the refractive index of the aforementioned first λ / 2 plate, I2 represents the refractive index of the aforementioned second λ / 2 plate, I3 represents the refractive index of the aforementioned λ / 4 plate, Ia1 represents the refractive index of the aforementioned first bonding layer, and Ia2 represents the refractive index of the aforementioned second bonding layer.

[0021] [8] An optical component comprising a transparent component and an optical stack as described in any one of [1] to [7] disposed on the aforementioned transparent component.

[0022] [9] The optical component described in [8], wherein the aforementioned transparent component has a curved surface, and the aforementioned optical stack is disposed on the curved surface of the aforementioned transparent component.

[0023]

[10] An optical stack as described in any of[1] to[7], which is used to adhere to the aforementioned curved surface of a transparent component having a curved surface.

[0024] Furthermore, this disclosure provides the following content.

[0025] [2-1]An optical stack comprising, in sequence, a first λ / 2 plate made only of material M1, a second λ / 2 plate made only of material M2, and a λ / 4 plate made only of material M3, wherein the angle between the slow axis of the first λ / 2 plate and the slow axis of the second λ / 2 plate is 24.6° or more and 30.6° or less, the angle between the slow axis of the first λ / 2 plate and the slow axis of the λ / 4 plate is 90.5° or more and 96.5° or less, and the first λ / 2 plate satisfies the following formula (1a) or formula (1b): nx1>ny1≒nz1 (1a) nx1>ny1>nz1 (1b) Here, nx1 represents the refractive index in the in-plane direction of the first λ / 2 plate that imparts the maximum refractive index, ny1 represents the refractive index in the in-plane direction of the first λ / 2 plate that is orthogonal to the direction of nx1, and nz1 represents the refractive index in the thickness direction of the first λ / 2 plate. The second λ / 2 plate satisfies the following equation (2a) or equation (2b): nx2>ny2≒nz2 (2a) nx2>ny2>nz2 (2b) Here, nx2 represents the refractive index in the in-plane direction of the second λ / 2 plate that imparts the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the second λ / 2 plate that is orthogonal to the direction of nx2, and nz2 represents the refractive index in the thickness direction of the second λ / 2 plate. The λ / 4 plate satisfies the following equation (3a) or equation (3b): nx3>ny3≒nz3 (3a) nx3 > ny3 > nz3 (3b) Here, nx3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate and the direction that imparts the maximum refractive index, ny3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate and the direction orthogonal to the direction of nx3, and nz3 represents the refractive index in the thickness direction of the aforementioned λ / 4 plate. The aforementioned materials M1, M2 and M3 are each independently photoelastic coefficients of 10 × 10⁻¹³ cm² / dyn or less, and the aforementioned materials M1, M2 and M3 each contain more than 50% by weight of a specific polymer (P).

[0026] [2-2] The optical stack as described in [2-1], wherein the aforementioned polymer (P) is a polymer containing an alicyclic structure.

[0027] [2-3] The optical stack as described in [2-1] or [2-2] includes a first bonding layer between the first λ / 2 plate and the second λ / 2 plate, and a second bonding layer between the second λ / 2 plate and the λ / 4 plate.

[0028] [2-4]The optical stack as described in[2-3] satisfies the following equations (4), (5), (6) and (7). |I1-Ia1|≦0.02 (4)|I2-Ia1|≦0.02 (5)|I2-Ia2|≦0.02 (6)|I3-Ia2|≦0.02 (7) Here, I1 represents the refractive index of the aforementioned first λ / 2 plate, I2 represents the refractive index of the aforementioned second λ / 2 plate, I3 represents the refractive index of the aforementioned λ / 4 plate, Ia1 represents the refractive index of the aforementioned first bonding layer, and Ia2 represents the refractive index of the aforementioned second bonding layer.

[0029] [2-5] An optical component comprising a transparent component and an optical stack disposed on the aforementioned transparent component as described in any one of [2-1] to [2-4].

[0030] [2-6] The optical component described in [2-5] has a curved surface, and the aforementioned optical stack is disposed on the curved surface of the aforementioned transparent component.

[0031] [2-7]An optical stack as described in any of[2-1] to[2-4], which is used to adhere to the aforementioned curved surface of a transparent component having a curved surface.

[0032] According to the present invention, an optical stack can be provided for a stereoscopic image display device that reduces phase difference inconsistency caused by deformation processing and achieves excellent display performance, as well as an optical component comprising such an optical stack.

Implementation Method

[0037] The following describes embodiments and examples to illustrate the present invention in detail. However, the present invention is not limited to the embodiments and examples disclosed below, and can be implemented in any way without departing from the scope of the present invention and its equivalents. The constituent elements of the embodiments shown below can be appropriately combined. Furthermore, in the figures, the same symbols are sometimes used to refer to the same constituent elements and their descriptions are omitted.

[0038] In the following description, the terms "polarizing plate", "circular polarizing plate", "plate", "λ / 2 plate" and "λ / 4 plate" unless otherwise noted, include not only rigid components but also flexible components such as resin films.

[0039] In the following description, the slow axis of a film, layer or plate, unless otherwise noted, refers to the slow axis within the plane of the film, layer or plate.

[0040] In the following description, the angle between the optical axes (slow axis, penetration axis, absorption axis, etc.) of each layer in a multi-layered component, unless otherwise noted, refers to the angle when viewing the aforementioned layer from the thickness direction.

[0041] In the following description, the term λ / 2 plate refers to a plate with an in-plane delay Re(λ) of approximately λ / 2 at wavelength λ.

[0042] Furthermore, the so-called λ / 4 plate refers to a plate with an in-plane delay Re(λ) of approximately λ / 4 at wavelength λ.

[0043] The in-plane delay Re(λ) of the λ / 2 plate is preferably in the range of (λ / 2 ± 35) nm, preferably in the range of (λ / 2 ± 15) nm, and ideally λ / 2 nm.

[0044] The in-plane delay Re(λ) of the λ / 4 plate is preferably in the range of (λ / 4 ± 30) nm, more preferably in the range of (λ / 4 ± 10) nm, and ideally λ / 4 nm.

[0045] When λ is 550 nm, the in-plane delay Re(550) of the λ / 2 plate is preferably above 240 nm, more preferably above 260 nm, and preferably below 310 nm and more preferably below 290 nm.

[0046] When λ is 550 nm, the in-plane delay Re(550) of the λ / 4 plate is preferably above 110 nm, more preferably above 130 nm, and preferably below 170 nm and more preferably below 150 nm.

[0047] In the following description, the angular relationship between the direction of the in-plane optical axis (slow axis, transmission axis, absorption axis, etc.) and the geometric direction (long side direction and width direction of the thin film, etc.) of a certain product (optical stack, circular polarizer, etc.) is defined, unless otherwise noted, in the form that a deviation in one direction is positive and a deviation in the other direction is negative. These positive and negative directions are commonly defined in the constituent elements of the product. For example, in a circular polarizer, the statement "the angle between the absorption axis of the circular polarizer and the slow axis of the first λ / 2 plate is A°, the angle between the slow axis of the first λ / 2 plate and the slow axis of the second λ / 2 plate is B°, and the angle between the slow axis of the first λ / 2 plate and the slow axis of the λ / 4 plate is C°" represents the following two cases: If the circular polarizer is observed from one of its surfaces, the slow axis of the first λ / 2 plate is shifted clockwise by A° from the absorption axis of the circular polarizer, the slow axis of the second λ / 2 plate is shifted clockwise by B° from the slow axis of the first λ / 2 plate, and the slow axis of the λ / 4 plate is shifted clockwise by C° from the slow axis of the first λ / 2 plate. If the circular polarizer is observed from one of its surfaces, the slow axis of the first λ / 2 plate is shifted counterclockwise by A° from the absorption axis of the circular polarizer, the slow axis of the second λ / 2 plate is shifted counterclockwise by B° from the slow axis of the first λ / 2 plate, and the slow axis of the λ / 4 plate is shifted counterclockwise by C° from the slow axis of the first λ / 2 plate.

[0048] In the following description, the so-called front direction of a thin film, unless otherwise noted, means the normal direction of the principal surface of the thin film, specifically the direction of the polar angle 0° and azimuth angle 0° of the aforementioned principal surface.

[0049] In the following description, a material with positive intrinsic birefringence, unless otherwise noted, means a material whose refractive index becomes greater in the direction of extension than in the direction perpendicular to it. Furthermore, a material with negative intrinsic birefringence, unless otherwise noted, means a material whose refractive index becomes smaller in the direction of extension than in the direction perpendicular to it. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

[0050] Examples of materials with positive intrinsic birefringence include resins containing polymers having positive intrinsic birefringence. Examples of polymers having positive intrinsic birefringence include: polymers containing alicyclic structures; polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfides such as polyphenylene sulfide; polyvinyl alcohol; polycarbonate; polyarylene ester; cellulose ester; polyether ether; polyether ether; polyarylene ether; polyarylene ether; polyvinyl chloride; rod-shaped liquid crystal polymers; etc.

[0051] In the following description, the in-plane retardation Re of the layer, unless otherwise noted, is the value shown as Re = (nx - ny) × d. Furthermore, the thickness retardation Rth of the layer, unless otherwise noted, is the value shown as Rth = {[(nx + ny) / 2] - nz} × d. Moreover, the NZ coefficient NZ, unless otherwise noted, is the value shown as NZ = Rth / Re + 0.5, thus yielding NZ = (nx - nz) / (nx - ny). Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the layer (in-plane direction) and imparting the maximum refractive index. ny represents the refractive index in the aforementioned in-plane direction of the layer and orthogonal to the direction of nx. nz represents the refractive index in the thickness direction of the layer. d represents the thickness of the layer. The measurement wavelength, unless otherwise noted, is 550 nm.

[0052] In the following description, the orientation of an element is referred to as "parallel", "perpendicular" and "orthogonal". Unless otherwise noted, it may also include an error within the range of, for example, ±3°, ±2° or ±1° without impairing the effect of the present invention.

[0053] In the following description, the term "bonding agent" means, unless otherwise noted, not only bonding agents in the narrow sense (bonding agents with a shear storage modulus of 1 MPa to 500 MPa at 23°C after irradiation with an energy line or after heat treatment), but also adhesives with a shear storage modulus of less than 1 MPa at 23°C.

[0054] Therefore, the "bonding layer" includes not only the layer of the bonding agent in the narrow sense, but also the layer of the adhesive.

[0055] "Substantially the same" also includes cases where they are completely identical.

[0056] [1. Optical stacking body]

[0057] [1.1. First Implementation Type]

[0058] The optical stack body of the first embodiment of the present invention sequentially includes a first λ / 2 plate, a second λ / 2 plate and a λ / 4 plate.

[0059] Figure 1 is a cross-sectional schematic diagram of an optical stack related to the first embodiment of the present invention.

[0060] As shown in Figure 1, the optical stack 100 sequentially includes a first λ / 2 plate 10, a second λ / 2 plate 20 and a λ / 4 plate 30 along the thickness direction.

[0061] In addition to the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate, the optical stack may also include any layer. Examples of arbitrary layers include: bonding layer, support layer, and functional layer.

[0062] The optical stack may also contain one or more phase retardation layers as arbitrary layers. For example, a phase retardation layer (posC) that satisfies the following equation (8): nx4≒ny4<nz4 (8)

[0063] Here, nx4 represents the refractive index in the in-plane direction of the layer and the direction that imparts the maximum refractive index, ny4 represents the refractive index in the aforementioned in-plane direction of the layer and the direction orthogonal to nx4, and nz4 represents the refractive index in the thickness direction of the layer.

[0064] The layer body (posC) that satisfies equation (8) means that the layer system is called a positive C-plate.

[0065] In equation (8), nx4≒ny4 means that the value of nx4 is substantially the same as the value of ny4. Specifically, the value of |nx4-ny4| is usually below 15 nm, preferably below 10 nm, and usually above 0 nm, or it can be 0 nm.

[0066] Furthermore, the retardation layer (posC), which functions as a positive C-plate, can be disposed at any position in the optical stack. For example, the retardation layer (posC) can be disposed between the first λ / 2 plate and the second λ / 2 plate; and / or it can also be disposed between the second λ / 2 plate and the λ / 4 plate; and / or it can also be disposed on the side of the first λ / 2 plate opposite to the second λ / 2 plate; and / or it can even be disposed on the side of the λ / 4 plate opposite to the second λ / 2 plate.

[0067] As one embodiment, the optical stack includes three phase difference layers (posC), and the first λ / 2 plate, the first phase difference layer (posC), the second λ / 2 plate, the second phase difference layer (posC), the λ / 4 plate and the third phase difference layer (posC) are arranged in sequence.

[0068] If, in addition to the aforementioned first λ / 2 plate, second λ / 2 plate and λ / 4 plate, a phase difference layer that functions as a positive C plate is further included, the optical stack can function well as a 1 / 4 wavelength plate in a wide wavelength range (especially the visible light range), and its function as a broadband 1 / 4 wavelength plate in the tilt direction can be particularly enhanced.

[0069] In this embodiment, the first λ / 2 plate 10 and the second λ / 2 plate 20 are in direct contact without any intermediate layer between them, and the second λ / 2 plate 20 and the λ / 4 plate 30 are in direct contact without any intermediate layer between them.

[0070] In another embodiment, any layer may also exist between the first λ / 2 plate and the second λ / 2 plate.

[0071] Furthermore, any layer may also exist between the second λ / 2 plate and the λ / 4 plate.

[0072] Figure 2 is a three-dimensional exploded view of an optical stack related to the first embodiment of the present invention.

[0073] As shown in Figure 2, the slow axis D1 of the first λ / 2 plate 10 and the slow axis D2 of the second λ / 2 plate form an angle θ12. The range of angle θ12 is generally above 24.6°, preferably above 25.6°, more preferably above 26.6°, and even more preferably above 27.1°, and is generally below 30.6°, preferably below 29.6°, more preferably below 28.6°, and even more preferably below 28.1°.

[0074] Furthermore, the slow axis D1 of the first λ / 2 plate 10 and the slow axis D3 of the λ / 4 plate 30 form an angle θ 13. The angle θ 13 is typically 90.5° or more, preferably 91.5° or more, more preferably 92.5° or more, more preferably 93.1° or more, and typically 96.5° or less, preferably 95.5° or less, more preferably 94.5° or less, and more preferably 94.0° or less.

[0075] The first λ / 2 plate usually satisfies any one of the following equations (1a), (1b) and (1c). nx1>ny1≒nz1 (1a) nx1>ny1>nz1 (1b) nx1>nz1>ny1 (1c)

[0076] Here, nx1 represents the refractive index in the in-plane direction of the aforementioned first λ / 2 plate and the direction that imparts the maximum refractive index, ny1 represents the refractive index in the in-plane direction of the aforementioned first λ / 2 plate and the direction that is orthogonal to the direction of nx1, and nz1 represents the refractive index in the thickness direction of the aforementioned first λ / 2 plate.

[0077] The second λ / 2 plate usually satisfies any one of the following equations (2a), (2b) and (2c). nx2>ny2≒nz2 (2a)nx2>ny2>nz2 (2b)nx2>nz2>ny2 (2c)

[0078] Here, nx2 represents the refractive index in the in-plane direction of the aforementioned second λ / 2 plate and the direction that imparts the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the aforementioned second λ / 2 plate and the direction that is orthogonal to the direction of nx2, and nz2 represents the refractive index in the thickness direction of the aforementioned second λ / 2 plate.

[0079] The λ / 4 plate usually satisfies any one of the following equations (3a), (3b) and (3c).

[0080] nx3>ny3≒nz3 (3a)

[0081] nx3>ny3>nz3 (3b)

[0082] nx3>nz3>ny3 (3c)

[0083] Here, nx3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate that imparts the maximum refractive index, ny3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate that is orthogonal to the direction of nx3, and nz3 represents the refractive index in the thickness direction of the aforementioned λ / 4 plate.

[0084] A board that satisfies formula (1a), formula (2a) or formula (3a) means a so-called positive A board, a board that satisfies formula (1b), formula (2b) or formula (3b) means a so-called negative B board, and a board that satisfies formula (1c), formula (2c) or formula (3c) means a so-called Z board.

[0085] In equation (1a), ny1≒nz1 means that the value of ny1 is substantially the same as the value of nz1. Specifically, the value of |ny1-nz1| is usually below 15 nm, preferably below 10 nm, and usually above 0 nm, but can also be 0 nm.

[0086] In equation (2a), ny2≒nz2 means that the value of ny2 is substantially the same as the value of nz2. Specifically, the value of |ny2-nz2| is usually below 15 nm, preferably below 10 nm, and usually above 0 nm, but can also be 0 nm.

[0087] In equation (3a), ny3≒nz3 means that the value of ny3 is substantially the same as the value of nz3. Specifically, the value of |ny3-nz3| is usually below 15 nm, preferably below 10 nm, and usually above 0 nm, but can also be 0 nm.

[0088] In one embodiment, the optical stack preferably has a first λ / 2 plate satisfying formula (1a) or formula (1b). And / or, it is preferable that the second λ / 2 plate satisfies formula (2a) or formula (2b). And / or, it is preferable that the λ / 4 plate satisfies formula (3a) or formula (3b).

[0089] It is preferable that the first λ / 2 plate satisfies formula (1a) or formula (1b), the second λ / 2 plate satisfies formula (2a) or formula (2b), and the λ / 4 plate satisfies formula (3a) or formula (3b).

[0090] This allows for the creation of an optical stack that functions particularly well as a λ / 4 plate over a wide wavelength range.

[0091] In another embodiment, the optical stack preferably has a first λ / 2 plate satisfying equation (1c). And / or, it is preferable that the second λ / 2 plate satisfies equation (2c). And / or, it is preferable that the λ / 4 plate satisfies equation (3c).

[0092] It is preferable that the first λ / 2 plate satisfies equation (1c), the second λ / 2 plate satisfies equation (2c), and the λ / 4 plate satisfies equation (3c).

[0093] In this way, the optical stack can function well as a λ / 4 plate in a wide wavelength range, and especially in the frontal direction and in all directions of the tilt direction.

[0094] Preferably, the NZ coefficient NZ1 of the first λ / 2 plate satisfies 0.0 < NZ1 ≤ 1.0, and / or preferably, the NZ coefficient NZ2 of the second λ / 2 plate satisfies 0.0 < NZ2 ≤ 1.0, and / or preferably, the NZ coefficient NZ3 of the λ / 4 plate satisfies 0.0 < NZ3 ≤ 1.0. This allows the optical stack to function particularly well as a λ / 4 plate over a wide wavelength range.

[0095] It is preferable that the NZ coefficient NZ1 of the first λ / 2 plate satisfies 0.0 < NZ1 ≦ 1.0, the NZ coefficient NZ2 of the second λ / 2 plate satisfies 0.0 < NZ2 ≦ 1.0, and the NZ coefficient NZ3 of the λ / 4 plate satisfies 0.0 < NZ3 ≦ 1.0.

[0096] It is preferable that the NZ coefficient NZ1 of the first λ / 2 plate satisfies 0.0 < NZ1 < 1.0, the NZ coefficient NZ2 of the second λ / 2 plate satisfies 0.0 < NZ2 < 1.0, and the NZ coefficient NZ3 of the λ / 4 plate satisfies 0.0 < NZ3 < 1.0. In this way, the optical stack can function well as a λ / 4 plate in a wide wavelength range, and especially in the frontal direction and in all directions of the tilt direction.

[0097] The NZ coefficient NZ1 of the first λ / 2 plate is preferably greater than 0, preferably greater than 0.4, even better than 0.45, preferably less than 1.0, preferably less than 1.0, even better than 0.6, and especially better than 0.55.

[0098] The NZ coefficient NZ2 of the second λ / 2 plate is preferably greater than 0, preferably greater than 0.4, even better than 0.45, preferably less than 1.0, preferably less than 1.0, even better than 0.6, and especially better than 0.55.

[0099] The NZ coefficient NZ3 of the λ / 4 plate is preferably greater than 0, preferably greater than 0.4, even better than 0.45, preferably less than 1.0, preferably less than 1.0, even better than 0.6, and especially better than 0.55.

[0100] The NZ coefficient can be appropriately adjusted by "adjusting the stretching conditions (stretching temperature, stretching ratio, etc.) of the resin film used to manufacture the first λ / 2 plate, the second λ / 2 plate, or the λ / 4 plate" and "adjusting the NZ coefficient of the resin film." The NZ coefficient of the resin film can be adjusted by contacting the resin film with a solvent. By contacting the resin film with a solvent, the NZ coefficient of the resin film can be adjusted to be less than 1. By stretching the resin film having the NZ coefficient adjusted in this way, a stretched film with an NZ coefficient greater than 0 and less than 1 can be manufactured. As a method for manufacturing a stretched film with an NZ coefficient greater than 0 and less than 1, the method described in International Patent Publication No. 2021 / 107108 can be cited as an example.

[0101] The first λ / 2 plate is usually made of only material M1 and contains only material M1.

[0102] The second λ / 2 plate is usually made of only material M2 and contains only material M2.

[0103] λ / 4 plate is usually made of only material M3, and contains only material M3.

[0104] As a material that can form a layer satisfying the aforementioned formula (1a), formula (1b), formula (1c), formula (2a), formula (2b), formula (2c), formula (3a), formula (3b) or formula (3c), there are a variety of materials that can be used as any of materials M1 to M3.

[0105] The photoelastic modulus of materials M1, M2, and M3 is typically below 10 × 10⁻¹³ cm² / dyn, preferably below 8 × 10⁻¹³ cm² / dyn, more preferably below 6 × 10⁻¹³ cm² / dyn, even better below 5 × 10⁻¹³ cm² / dyn, and even better below 4 × 10⁻¹³ cm² / dyn, with a value close to 0 cm² / dyn being preferable. The absolute value of the photoelastic modulus of materials M1, M2, and M3 is preferably below 10 × 10⁻¹³ cm² / dyn, more preferably below 8 × 10⁻¹³ cm² / dyn, even better below 6 × 10⁻¹³ cm² / dyn, even better below 5 × 10⁻¹³ cm² / dyn, and even better below 4 × 10⁻¹³ cm² / dyn. Materials M1, M2, and M3 are preferred to have a photoelasticity coefficient of 0 cm² / dyn or higher.

[0106] In this embodiment of the optical stack, the ranges of angle θ12 and angle θ13 are within the aforementioned ranges, and materials M1, M2, and M3 each independently possess photoelastic coefficients within the aforementioned ranges. Therefore, while the optical stack can function well as a λ / 4 plate over a wide wavelength range, even when used in a deformed state from its initial shape, phase difference changes are less likely to occur, and phase difference inhomogeneity (phase difference spots) is difficult to generate. Thus, even when the optical stack is processed along the curved surface of an optical component mounted to a stereoscopic image display device, it can function well as a λ / 4 plate over a wide wavelength range. As a result, a stereoscopic image display device with excellent display characteristics can be manufactured from the optical stack.

[0107] As a material having a photoelastic coefficient within the aforementioned range, there are various materials known that can be used as any of materials M1 to M3. Examples of materials having a photoelastic coefficient within the aforementioned range include: materials containing alicyclic polymers, polymethyl methacrylate, etc.

[0108] The absolute values ​​of the difference between the photoelastic coefficient C1 of material M1 and the photoelastic coefficient C2 of material M2, the absolute values ​​of the difference between the photoelastic coefficient C2 of material M2 and the photoelastic coefficient C3 of material M3, and the absolute values ​​of the difference between the photoelastic coefficient C1 of material M1 and the photoelastic coefficient C3 of material M3 are preferably below 10×10⁻¹³ cm² / dyn, preferably below 5×10⁻¹³ cm² / dyn, and preferably below 2×10⁻¹³ cm² / dyn. They are usually above 0 cm² / dyn, and ideally 0 cm² / dyn.

[0109] Accordingly, when the optical stack is deformed, since the in-plane delays of the first λ / 2 plate, the second λ / 2 plate and the λ / 4 plate change or remain unchanged to the same extent, the phase difference change of the optical stack can be effectively suppressed when the optical stack is deformed.

[0110] The photoelasticity of a material can be measured by the following method.

[0111] A thin film made of this material was manufactured and cut into rectangles of 100 mm × 10 mm to obtain test pieces. Tensile loads of 0 g, 100 g, 200 g, 300 g, 400 g, 500 g, and 600 g were applied to the long side of the obtained test pieces, and the retardation in the in-plane direction was measured. The aforementioned measurement of the retardation in the in-plane direction was performed using an ellipsometry at a measurement wavelength of 550 nm. The thickness of the thin film was defined as d, and the stress was calculated in the form of the load per cross-sectional area of ​​the thin film. The photoelastic coefficient was derived in the form of the rate of change of the ratio of the retardation Re(550) to the thickness d in the in-plane direction with respect to this stress, Re(550) / d.

[0112] The wavelength dispersion of the thin film is evaluated by the value of D = Re(450) / Re(550). Here, Re(450) represents the delay in the in-plane direction of the thin film at a measurement wavelength of 450 nm, and Re(550) represents the delay in the in-plane direction of the thin film at a measurement wavelength of 550 nm.

[0113] The first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate are all preferably characterized by reverse wavelength dispersion. Here, the reverse wavelength dispersion of a thin film means that the value of D = Re(450) / Re(550) of the thin film is less than or equal to 1.

[0114] The value of Re(450) / Re(550) of the first λ / 2 plate is defined as D1, the value of Re(450) / Re(550) of the second λ / 2 plate is defined as D2, and the value of Re(450) / Re(550) of the λ / 4 plate is defined as D3.

[0115] Good is D1≦1 and D2≦1 and D3≦1.

[0116] Preferably D1 < 1. Preferably D2 < 1. Preferably D3 < 1.

[0117] By utilizing the reverse wavelength dispersion of all the first λ / 2 plate, the second λ / 2 plate and the λ / 4 plate, the optical stack can function well as a λ / 4 plate in a wide wavelength range (especially the visible light range).

[0118] It is preferable that the aforementioned first λ / 2 plate, second λ / 2 plate and λ / 4 plate have substantially the same wavelength dispersion.

[0119] The wavelengths that are substantially the same are confirmed by the fact that D1 of the first λ / 2 plate, D2 of the second λ / 2 plate, and D3 of the λ / 4 plate are substantially the same.

[0120] The term "D1 to D3 are essentially the same" means that if the maximum value among D1 to D3 is defined as Dmax and the minimum value as Dmin, then the value of Dmax-Dmin is preferably 0.3 or less, more preferably 0.2 or less, even more preferably 0.1 or less, and usually above 0, ideally 0. By ensuring that the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate each have substantially the same wavelength dispersion, the optical stack can function well as a λ / 4 plate over a wide wavelength range.

[0121] It is preferable that any one of materials M1, M2 and M3 has positive intrinsic birefringence. By using materials with positive intrinsic birefringence, the first λ / 2 plate, the second λ / 2 plate and the λ / 4 plate can be easily made into plates that satisfy formula (1a), formula (2a), formula (3a), formula (1b), formula (2b), formula (3b), formula (1c), formula (2c) or formula (3c).

[0122] Materials M1, M2, and M3 each contain more than 50% by weight of a specific polymer (P), and may contain any other components as required. Examples of specific polymers (P) contained in each of Materials M1, M2, and M3 include: alicyclic polymers such as cycloolefin polymers; cellulose polymers such as cellulose triacetate; polyimide; polyolefin; polyester; polyaryl sulfide; polyvinyl alcohol; polycarbonate; polyarylate; polyether sulfide; polysulfide; polyaryl sulfide; polyvinyl chloride; etc., among which alicyclic polymers are preferred.

[0123] A specific polymer (P) may be a crystalline polymer or an amorphous polymer. "Crystallized polymer" means a polymer with a melting point Tm. Resins containing crystalline polymers are hereinafter also referred to as crystalline resins. The melting point of a polymer with a melting point Tm can be observed using a differential scanning calorimeter (DSC).

[0124] The melting point Tm of a polymer can be measured by the following method. First, the polymer is melted by heating, and the melted polymer is rapidly cooled with dry ice. Next, this polymer is used as a sample, and the glass transition temperature Tg and melting point Tm of the polymer are measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode).

[0125] The alicyclic polymer is a polymer in which an alicyclic structure is contained in the repeating unit. As an alicyclic polymer, it can be used in either polymers containing an alicyclic structure in the main chain or polymers containing an alicyclic structure in the side chain. Examples of alicyclic structures include cycloalkane structures and cycloalkene structures, but from the viewpoint of thermal stability, cycloalkane structures are preferred. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, especially 6 or more, and preferably 30 or less, more preferably 20 or less, and especially preferably 15 or less.

[0126] In alicyclic polymers, the proportion of repeating alicyclic units is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. When the proportion of repeating alicyclic units is within the aforementioned range, an optical stack with excellent heat resistance can be obtained.

[0127] Examples of alicyclic polymers include: (1) norethene polymers, (2) monocyclic cyclic olefin polymers, (3) cyclic conjugated diene polymers, (4) ethylene alicyclic hydrocarbon polymers, and their hydrides. Among these, cyclic olefin polymers and norethene polymers are preferred, with norethene polymers being particularly preferred. Examples of norethene polymers include: ring-opening polymers containing monomers with a norethene structure, ring-opening copolymers containing monomers with a norethene structure and other monomers capable of ring-opening copolymerization, and their hydrides; addition polymers containing monomers with a norethene structure, addition copolymers containing monomers with a norethene structure and other monomers capable of copolymerization. Among these, from the viewpoint of transparency, ring-opening polymer hydrides containing monomers with a norethene structure are particularly preferred. The aforementioned alicyclic polymers may be selected from, for example, polymers disclosed in Japanese Patent Publication No. 2002-321302, or polymers obtained by the manufacturing method disclosed in International Patent Publication No. 2018 / 062067.

[0128] In one embodiment, the specific polymer (P) is preferably an amorphous polymer with an alicyclic structure.

[0129] In another embodiment, the specific polymer (P) is preferably a crystalline alicyclic polymer. Among crystalline alicyclic polymers, those that are crystalline and are ring-opening polymers of dicyclopentadiene, and those that are crystalline and are hydrides of ring-opening polymers of dicyclopentadiene, are preferred. Of these, those that are crystalline and are hydrides of ring-opening polymers of dicyclopentadiene are particularly preferred. Here, a ring-opening polymer of dicyclopentadiene is defined as a polymer in which the proportion of dicyclopentadiene-derived structural units relative to all structural units is typically 50% by weight or more—preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 100% by weight.

[0130] A high proportion of racemic binary units other than the repeating units in the hydride of the ring-opening polymer of dicyclopentadiene is preferred. Specifically, the proportion of racemic binary units other than the repeating units in the hydride of the ring-opening polymer of dicyclopentadiene is preferably 51% or more, preferably 70% or more, and especially preferably 85% or more. A high proportion of racemic binary units indicates a high degree of stereoregularity. Accordingly, the higher the proportion of racemic binary units, the higher the melting point of the hydride of the ring-opening polymer of dicyclopentadiene tends to be.

[0131] The proportion of racemic binary units can be determined based on the 13C-NMR spectral analysis described in the embodiments described later.

[0132] Each of the polymers (P) contained in materials M1, M2 and the aforementioned material M3 may be polymers with the same weight average molecular weight or polymers that are different from each other.

[0133] Each of the polymers (P) contained in materials M1, M2 and the aforementioned material M3 may be polymers with the same weight composition of the constituent units contained therein, or they may be polymers that are different from each other.

[0134] The proportions of the specific polymer (P) in material M1, material M2, and material M3 are preferably more than 50% by weight and less than 100% by weight, more preferably 70% by weight and less than 100% by weight, more preferably 90% by weight and less than 100% by weight, more preferably 95% by weight and less than 100% by weight, and more preferably 97% by weight and less than 100% by weight. When the proportions of the polymer (P) are within the aforementioned ranges, the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate included in the optical stack can be easily made into plates with substantially the same wavelength dispersion.

[0135] Materials M1, M2, and M3 may also be combined with the aforementioned specific polymer (P) to further include any other components. Examples of such components include: antioxidants, heat stabilizers, light stabilizers, weather stabilizers, ultraviolet absorbers, near-infrared absorbers, and other stabilizers; plasticizers; solvents; etc. These components may be used individually or in any combination of two or more.

[0136] Materials M1, M2, and M3 are preferably made of a polymer (P) containing more than 50% by weight of an alicyclic polymer, more preferably 70% by weight, more preferably 90% by weight, and more preferably 95% by weight or 97% by weight. This allows the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate to be easily fabricated into plates satisfying formulas (1a), (2a), (3a), (1b), (2b), (3b), (1c), (2c), or (3c), respectively. Furthermore, the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate can be easily fabricated into plates having substantially the same wavelength dispersion.

[0137] [1.2. Second Implementation Type]

[0138] The optical stack of the second embodiment of the present invention sequentially includes a first λ / 2 plate, a second λ / 2 plate, and a λ / 4 plate. Furthermore, the optical stack of this embodiment includes a first bonding layer between the first λ / 2 plate and the second λ / 2 plate, and a second bonding layer between the second λ / 2 plate and the λ / 4 plate.

[0139] Figure 3 is a cross-sectional schematic diagram of an optical stack related to the second embodiment of the present invention.

[0140] As shown in Figure 3, the optical stack 200 sequentially includes a first λ / 2 plate 10, a second λ / 2 plate 20, and a λ / 4 plate 30 along the thickness direction. Between the first λ / 2 plate 10 and the second λ / 2 plate 20, a first bonding layer 12 is configured to directly contact the main surfaces of the first λ / 2 plate and the second λ / 2 plate. Between the second λ / 2 plate 20 and the λ / 4 plate 30, a second bonding layer 23 is configured to directly contact the main surfaces of the second λ / 2 plate 20 and the λ / 4 plate 30.

[0141] In the optical stack 200, the angle θ12 between the slow axis of the first λ / 2 plate 10 and the slow axis of the second λ / 2 plate, and the angle θ13 between the slow axis of the first λ / 2 plate 10 and the slow axis of the λ / 4 plate 30, are respectively within the same range as the angles θ12 and θ13 in the optical stack 100.

[0142] The first bonding layer 12 and the second bonding layer 23 may be formed by an adhesive. Examples of adhesives used to form the bonding layers include: acrylate adhesives, carbamate adhesives, carbamate acrylate adhesives, epoxy adhesives, acrylic epoxy ester adhesives, polyolefin adhesives, ethylene vinyl alcohol adhesives, vinyl chloride adhesives, chloroprene rubber adhesives, cyanoacrylate adhesives, polyamide adhesives, polystyrene adhesives, polyvinyl butyral adhesives, and polyvinyl alcohol adhesives.

[0143] Commercially available adhesive sheets can be used as the bonding layer. For example, Nitto Denko Corporation's adhesive sheet "CS9621" (refractive index 1.477) is a commercially available product.

[0144] The optical stack 200 preferably satisfies the following equations (4), (5), (6) and (7). |I1-Ia1|≦0.02 (4)|I2-Ia1|≦0.02 (5)|I2-Ia2|≦0.02 (6)|I3-Ia2|≦0.02 (7)

[0145] Here, I1 represents the refractive index of the aforementioned first λ / 2 plate 10, I2 represents the refractive index of the aforementioned second λ / 2 plate 20, I3 represents the refractive index of the aforementioned λ / 4 plate 30, Ia1 represents the refractive index of the aforementioned first bonding layer 12, and Ia2 represents the refractive index of the aforementioned second bonding layer 23. I1, I2, I3, Ia1, and Ia2 are all refractive indices measured at a wavelength of 550 nm.

[0146] The optical stack 200 reduces reflection at the interface between layers by satisfying equations (4) to (7). Therefore, in an optical system equipped with the optical stack 200, the generation of unintended images can be effectively suppressed.

[0147] The refractive index I1 of the first λ / 2 plate 10 is preferably 1.40 or higher, preferably 1.50 or higher, preferably 1.60 or lower, and preferably 1.55 or lower.

[0148] The good range of the refractive index I2 of the second λ / 2 plate 20 is determined to be the same as the good range of the refractive index I1.

[0149] The good range of the refractive index I3 of λ / 4 plate 30 is determined to be the same as the good range of the refractive index I1.

[0150] The refractive index Ia1 of the first bonding layer 12 is preferably 1.40 or higher, preferably 1.50 or higher, preferably 1.60 or lower, and preferably 1.55 or lower.

[0151] The good range of the refractive index Ia2 of the second bonding layer 23 is determined to be the same as the good range of the refractive index Ia1.

[0152] The refractive index of each layer (i.e., the first λ / 2 plate 10, the second λ / 2 plate 20, the λ / 4 plate 30, the first bonding layer 12 and the second bonding layer 23) of the optical stack 200 can be measured by the following method.

[0153] First, using a refractive index film thickness measuring device (such as a "prism coupler" manufactured by Metricon Corporation), the refractive index of each layer of the optical stack 200 is measured at measurement wavelengths of 405 nm, 532 nm, and 633 nm. For the measurement values ​​obtained at these measurement wavelengths of 405 nm, 532 nm, and 633 nm, the Cauchy dispersion formula is fitted to calculate the refractive index at a measurement wavelength of 550 nm.

[0154] When the refractive index of the layer is anisotropic, the average refractive index can be obtained by the following method and defined as the refractive index of the layer.

[0155] The refractive index of the layer is measured at a wavelength of 550 nm in each of the extrusion direction, the in-plane direction perpendicular to the extrusion direction, and the thickness direction. Then, the average refractive index of the layer at a wavelength of 550 nm is obtained by taking the average of the refractive indices in the extrusion direction, the in-plane direction perpendicular to the extrusion direction, and the thickness direction, and is defined as the refractive index of the layer.

[0156] [1.3. Characteristics of optical stacks]

[0157] The aforementioned optical stack can function as a λ / 4 plate.

[0158] When a circular polarizer is formed by combining an optical stack and a linear polarizer, near-ideal circular polarized light with an ellipticity close to 1 or 1 can be obtained in a wide wavelength range (especially the visible light range of 450 nm to 650 nm).

[0159] The ellipticity of the circularly polarized light obtained by the aforementioned circularly polarizing plate containing optical stacks is preferably 0.80 or higher in the frontal direction and at a measurement wavelength of 550 nm, preferably 0.85 or higher, and ideally 1.

[0160] Furthermore, the ellipticity of the circularly polarized light obtained by means of the aforementioned circularly polarized plate containing optical stacks is preferably 0.7 or higher, more preferably 0.8 or higher, and ideally 1, in the tilt direction of a polar angle of 45° and a measurement wavelength of 550 nm.

[0161] The ellipticity of the circularly polarized light obtained at 450 nm, 550 nm and 650 nm by means of a circularly polarized plate containing optical stacks, in the front direction or the tilt direction with a polar angle of 45°, the difference between the maximum value Max and the minimum value Min (Max-Min) is preferably less than 0.20, less than 0.10, and ideally 0.

[0162] Furthermore, the difference in ellipticity Emax-Emin between all directions in the tilt direction of the circularly polarized light obtained by the circularly polarized plate containing the optical stack is small. The small difference in ellipticity Emax-Emin means that the optical stack contained in the circularly polarized plate functions as a λ / 4 plate with near homogeneity in a wide wavelength range and in all directions in the tilt direction.

[0163] The value of Emax-Emin is preferably below 0.4, better below 0.3, even better below 0.2, and ideally 0.

[0164] Here, the value of E max-E min is obtained by referring to the following content.

[0165] Within the range of 0° to 360° at 450 nm, the ellipticity calculated every 5° in the azimuth direction is defined as the largest ellipticity as E(450) max and the smallest ellipticity as E(450) min. Similarly, the largest ellipticity at 550 nm is defined as E(550) max and the smallest ellipticity as E(550) min, and the largest ellipticity at 650 nm is defined as E(650) max and the smallest ellipticity as E(650) min. The values ​​of each are calculated. The largest ellipticity among E(450) max, E(550) max, and E(650) max is defined as E max, and the smallest ellipticity among E(450) min, E(550) min, and E(650) min is defined as E min. The value of E max - E min is calculated.

[0166] The aforementioned optical stack has excellent heat resistance.

[0167] Specifically, the phase difference variation caused by heat in the aforementioned optical stack is small.

[0168] If “the in-plane delay of the optical stack at a wavelength of 550 nm before the heat resistance test of heating the optical stack at 85°C for 500 hours” is defined as Reb(550) and “the in-plane delay of the optical stack at a wavelength of 550 nm after the heat resistance test” is defined as Rea(550), then the absolute value |Reb(550)-Rea(550)| is preferably less than 10 nm, less than 5 nm is better, less than 3 nm is even better, less than 3 nm is even better, closer to 0 nm is better, but it can also be greater than 0.5 nm.

[0169] Regarding the optical stack related to this embodiment, the reason for the small phase difference change caused by heat is not to limit the present invention, but can be inferred as follows.

[0170] The materials M1, M2, and M3 forming the first λ / 2 plate, second λ / 2 plate, and λ / 4 plate included in the optical stack contain more than 50% by weight of a specific polymer (P). Since the included polymer (P) is common in the first λ / 2 plate, second λ / 2 plate, and λ / 4 plate, it is conceivable that if the optical stack is heated, the phase difference change state of each of the included first λ / 2 plate, second λ / 2 plate, and λ / 4 plate due to heating will be the same. It is conceivable that, given the angular relationship between the slow axis of the first λ / 2 plate, the slow axis of the second λ / 2 plate, and the slow axis of the λ / 4 plate in the optical stack in this embodiment, the phase difference variation in the first and second λ / 2 plates will cancel out the phase difference variation in the λ / 4 plate. Therefore, the phase difference variation of the entire optical stack caused by heat will be smaller than the phase difference variation caused by heat in the λ / 4 plate in the case of a single layer.

[0171] [2. Manufacturing method of optical stacks]

[0172] The aforementioned optical stack can be manufactured by any method. For example, a first λ / 2 plate with a slow axis in the transport direction or width direction, a second λ / 2 plate with a slow axis in either the non-transport direction or the width direction (obliquely), and a λ / 4 plate with a slow axis in the oblique direction are prepared, and layers of suitable adhesive are arbitrarily interposed to make the strips aligned and stacked along the thickness direction to manufacture a strip-shaped optical stack.

[0173] Furthermore, the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate, which are cut into sheets, are laminated together along the thickness direction in such an angular relationship as described above in the slow axis direction, thereby manufacturing an optical stack in the form of cut sheets.

[0174] The method of manufacturing the first λ / 2 plate, the second λ / 2 plate and the λ / 4 plate is not particularly limited, and examples include obtaining an extruded film by melt extrusion and stretching the extruded film.

[0175] The obtained extruded film can be extended, or it can be extended after any process at the extrusion site. As an example of any process, a process of contacting the extruded film with a solvent can be given. By contacting the extruded film with a solvent, the NZ coefficient of the extruded film can be changed.

[0176] Examples of solvents used for contacting the extruded film include hydrocarbon solvents such as toluene, benzoxene, and decahydronaphthalene, and carbon disulfide. When the extruded film is made of a resin containing a crystalline polymer, a hydrocarbon solvent is preferred from the viewpoint of making the crystalline polymer difficult to dissolve. One solvent or two or more solvents may be used. Examples of methods for contacting the extruded film with the solvent include: a spraying method where the solvent is sprayed onto the film; a coating method where the solvent is applied to the film; an immersion method where the film is immersed in a solvent; and so on.

[0177] [3. Applications of optical stacks]

[0178] [3.1. Circular polarizer]

[0179] The aforementioned optical stack can be used appropriately as a constituent element of a circular polarizer.

[0180] The circular polarizer may include the aforementioned optical stack and linear polarizer.

[0181] The aforementioned circular polarizer containing optical stacks can convert linearly polarized light into circularly polarized light over a wide wavelength range.

[0182] The aforementioned circular polarizing plate with optical stacking preferably includes, in sequence along the thickness direction, a linear polarizing element, a first λ / 2 plate, a second λ / 2 plate, and a λ / 4 plate. The angle between the absorption axis of the linear polarizing element and the slow axis of the first λ / 2 plate is preferably 2° or more, more preferably 4° or more, more preferably 12° or less, and more preferably 10° or less.

[0183] Alternatively, the angle between the penetration axis of the linear polarizer and the slow axis of the first λ / 2 plate is preferably 29° or more, more preferably 31° or more, and preferably 40° or less, and more preferably 38° or less.

[0184] Examples of linear polarizers included in a circular polarizer are not particularly limited, such as absorptive polarizers and reflective polarizers.

[0185] As an example of an absorptive polarizer, a polarizer manufactured by a manufacturing method including a process of adsorbing dichroic dyes onto a polyvinyl alcohol-based resin film can be cited.

[0186] Examples of reflective polarizers include: polarizers that are stacks of thin films with different birefringence; wire grid polarizers; and polarizers that are stacks of cholesterol-regular layers and λ / 4 plates that have the function of separating left and right circular polarized light.

[0187] [3.2. Image display device]

[0188] The aforementioned optical stack is suitable for use as a component of an image display device. For example, a circular polarizing plate containing an optical stack is suitable for use as a component of a flexible image display device or a stereoscopic image display device because it has less change in optical properties due to deformation.

[0189] Examples of image display devices include: organic electroluminescent image display devices and liquid crystal image display devices.

[0190] [4. Optical components]

[0191] (Third Implementation Type)

[0192] The optical component of the third embodiment of the present invention includes a transparent component and the aforementioned optical stack disposed on the aforementioned transparent component.

[0193] Figure 4 is a cross-sectional schematic diagram illustrating an optical component related to a third embodiment of the present invention. The optical component 1000 includes a transparent component 40 and an optical stack 100. In this embodiment, the transparent component 40 and the optical stack 100 are in direct contact without any intermediate layer such as a bonding layer. However, in another embodiment, the optical stack 100 may be disposed on the transparent component 40 through any intermediate layer (e.g., a third bonding layer). In this specification, the term "on the transparent component" includes not only the case where the layer is directly disposed on the transparent component, but also the case where the layer is indirectly disposed on the transparent component through any intermediate layer.

[0194] The transparent component 40 is typically a component with a total light transmittance of 80% or more in the visible light range. The total light transmittance is typically less than 100%, but can also be 100%.

[0195] In this embodiment, the transparent component 40 is lens-shaped and has a curved surface 40U, on which an optical stack 100 is disposed. As mentioned above, in another embodiment, the optical stack 100 may also be disposed on the curved surface 40U of the transparent component 40, with any layer (e.g., a bonding layer) intervening.

[0196] In another embodiment, the transparent component included in the optical component may also have any shape other than a lens (e.g., a flat plate, a prism, or a corrugated plate).

[0197] In another embodiment, the optical component may also include any optical stack related to the embodiment, such as optical stack 200, instead of optical stack 100.

[0198] The optical component may include, in sequence along the thickness direction, a transparent component, a first λ / 2 plate, a second λ / 2 plate and a λ / 4 plate, or it may include, in sequence along the thickness direction, a transparent component, a λ / 4 plate, a second λ / 2 plate and a first λ / 2 plate, but it is preferable that the optical component includes, in sequence along the thickness direction, a transparent component, a first λ / 2 plate, a second λ / 2 plate and a λ / 4 plate.

[0199] As described above, the phase difference change that occurs when the optical stack is deformed from its initial shape is reduced. Therefore, even if the optical stack is disposed on the curved surface of a transparent component with a curved surface, it is difficult to generate phase difference inhomogeneity (phase difference spot). As a result, an optical component with excellent homogeneity and desired optical properties can be obtained.

[0200] The optical components may be suitably used, for example, in a pancake optics system included in a stereoscopic image display device. Examples of pancake optics systems are not particularly limited, and examples include the optical system described in "Official journal of the CIOMP 2047-7538" and the optical system described in International Patent Publication No. 2020 / 209354 (Patent Document 2).

[0201] 『Example』

[0202] The following embodiments are disclosed to specifically illustrate the present invention. However, the present invention is not limited to the embodiments disclosed below, and may be implemented in any way without departing from the scope of the claims and their equivalents.

[0203] In the following description, the terms “%” and “parts” are by weight unless otherwise noted. Furthermore, the operations described below are performed at room temperature (20℃±15℃) and normal pressure (1 atm) unless otherwise noted.

[0204] [Evaluation Method]

[0205] (Method for measuring the hydrogenation rate of polymers)

[0206] The hydrogenation rate of the polymer was measured by 1H-NMR at 145°C using o-dichlorobenzene-d4 as a solvent.

[0207] (Methods for measuring glass transition temperature Tg and melting point Tm)

[0208] The glass transition temperature Tg and melting point Tm of the polymer were measured as follows. First, the polymer was melted by heating, and the melted polymer was rapidly cooled with dry ice. Next, this polymer was used as a sample, and the glass transition temperature Tg and melting point Tm of the polymer were measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode).

[0209] (Method for measuring the proportion of racemic binary units outside of polymers)

[0210] The proportion of the racemic binary unit group outside the polymer was measured as follows. Using o-dichlorobenzene-d4 as a solvent, the polymer was subjected to 13C-NMR measurements at 200°C using inverse-gated decoupling. In the 13C-NMR results, the peak at 127.5 ppm of o-dichlorobenzene-d4 was defined as the reference shift, and signals originating from the meso-racic binary unit group at 43.35 ppm and from the exo-racic binary unit group at 43.43 ppm were identified. The proportion of the racemic binary unit group outside the polymer was determined based on the intensity ratio of these signals.

[0211] (Thickness)

[0212] The thickness of each layer is measured using a film thickness measurement system (Filmetrics "F20").

[0213] (Photoelastic coefficient)

[0214] The photoelasticity coefficient is measured by the following method.

[0215] The material of the object to be measured is supplied to an extruder, and after passing through a polymer filter, it is extruded into a sheet shape from a T-die onto a casting roller and cooled to obtain an extruded film with a thickness of 40 μm (in the case of a norben-based resin (ZEONOR1430 manufactured by Japan)), 35 μm (in the case of a crystalline resin containing a ring-opening polymer of dicyclopentadiene as a hydride) or 16 μm (in the case of a polycarbonate resin (Iupilon E2000 manufactured by Mitsubishi Engineering Plastics)).

[0216] The obtained extruded film was cut into rectangles of 100 mm × 10 mm to obtain test pieces. The cutting was carried out with the long side of the test piece parallel to the film conveying direction. Tensile loads of 0 g, 100 g, 200 g, 300 g, 400 g, 500 g and 600 g were applied along the long side of the obtained test pieces at 25°C, and the retardation in the in-plane direction was measured. The aforementioned measurement of the retardation in the in-plane direction was performed using an ellipsometry at a measurement wavelength of 550 nm. The thickness of the film was defined as d, and the stress was calculated in the form of the load per cross-sectional area of ​​the film. The photoelastic coefficient was derived in the form of the rate of change of the ratio of the retardation Re(550) to the thickness d in the in-plane direction with respect to this stress, Re(550) / d.

[0217] (Measurement of refractive index)

[0218] The refractive index of the thin film was measured at 25°C using a refractive index film thickness measuring device (a "prism coupler" manufactured by Metricon Corporation) at measurement wavelengths of 405 nm, 532 nm, and 633 nm. The measured values ​​obtained at these measurement wavelengths of 405 nm, 532 nm, and 633 nm were fitted to the Cauchy dispersion formula to calculate the refractive index at a measurement wavelength of 550 nm.

[0219] The refractive index at a wavelength of 550 nm was measured in the extrusion direction, the in-plane direction perpendicular to the extrusion direction, and the thickness direction of the sample film. Then, the average refractive index of the film at a wavelength of 550 nm was calculated as the average of the refractive indices in the extrusion direction, the in-plane direction perpendicular to the extrusion direction, and the thickness direction, and this was defined as the refractive index of the film.

[0220] Furthermore, the in-plane retardation Re and the retardation Rth in the thickness direction of the thin film are measured. From these values, the NZ coefficient NZ of the thin film is calculated using the formula: NZ = Rth / Re + 0.5.

[0221] (Heat resistance of optical stacks) Re change after treatment at 85°C for 500 hours

[0222] A 50 mm × 50 mm square sample was cut from the optical stack. The cutting was performed with each side of the sample parallel to the width or length of the strip-shaped optical stack. For the cut optical stack sample, the in-plane delay (Reb(550)) at a wavelength of 550 nm was measured using a phase difference meter (Axometrics, Inc. "AxoScan"). Afterward, the sample was placed in a thermostat at 85°C for 500 hours and then removed from the thermostat to measure the phase difference (Rea(550)) at a wavelength of 550 nm. The heat resistance was evaluated by calculating the absolute value of the difference in phase difference before and after the heat resistance test.

[0223] When |Reb(550)-Rea(550)| is less than 3 nm, the in-plane delay Re change is evaluated as "small" and when it is more than 3 nm, the in-plane delay Re change is evaluated as "large".

[0224] (Phase difference spot during curved surface processing)

[0225] A mold with one of concave or convex surfaces and a radius of curvature of 125 mm was fabricated. The optical stack of the embodiment and the comparative example was sandwiched between two fluoropolymer (Teflon (registered trademark)) films as release films and placed in the mold. The flat optical stack was hot-pressed at 110°C for 1 minute to process it into a curved shape. The obtained curved optical stack was placed between two polarizing plates and observed under backlight. At this time, the observation was performed while arbitrarily rotating either of the two polarizing plates. Those with color spots observed in the plane were defined as "having" phase difference spots, and those without color spots were defined as "not having" phase difference spots. The optical stack without observed color spots indicates that the phase difference change generated when processed into a curved shape is reduced.

[0226] (Using the simulation method to calculate ellipticity)

[0227] Using "LCD Master" manufactured by SHINTECH Co., Ltd. as simulation software, the optical stacks manufactured in each embodiment and comparative example were modeled. In the simulation model, the structure of the optical stacks of the embodiments and comparative examples with the linear polarizer attached was set as a circular polarizer. Therefore, in this model, the polarizer, the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate of the optical stack were arranged sequentially in the thickness direction, and the structure was set such that the absorption axis direction of the linear polarizer and the slow axis of the first λ / 2 plate of the optical stack were aligned at an angle θ01 as shown in Tables 1 and 2. Then, in the aforementioned model, the ellipticity of the light transmitted when light from the D65 light source is irradiated onto the circular polarizer was calculated in the front direction and the tilt direction with an epipolar angle of 45°. Here, in the front direction, calculations were performed every 5° in the azimuth direction within the range of 0° to 360° at an epipolar angle of 0°, and the average of these calculated values ​​was used as the ellipticity in the front direction. The ellipticity, in circular or elliptical polarization, is the ratio of the amplitude of the minor axis to the amplitude of the major axis, ranging from 0 to 1. A value closer to 1 indicates a more perfectly circular polarization, resulting in superior performance for circular polarizers. Ellipticity was calculated at wavelengths of 450 nm, 550 nm, and 650 nm. Furthermore, to evaluate the reduction in color shift, the difference between the maximum and minimum ellipticity values ​​at 450 nm, 550 nm, and 650 nm (Max-Min) was calculated. The smaller this value, the more homogeneous the characteristics of the circular polarizer become across a wide wavelength range.

[0228] Next, calculations are performed every 5° in the azimuth direction within the range of 0° to 360° at a polar angle of 45°, and the average of these calculated values ​​is used as the ellipticity in the tilt direction. The ellipticity in the tilt direction is calculated at wavelengths of 450 nm, 550 nm, and 650 nm. Furthermore, to evaluate the reduction in color shift, the maximum minus the minimum ellipticity at 450 nm, 550 nm, and 650 nm (Max-Min) is calculated. The smaller this value, the closer the characteristics of the circular polarizer become to homogeneity over a wide wavelength range.

[0229] Next, within the azimuth range of 0° to 360° at 450 nm, the ellipticity calculated every 5° in the azimuth direction is defined as the largest ellipticity as E(450) max and the smallest ellipticity as E(450) min. Similarly, the largest ellipticity at 550 nm is defined as E(550) max and the smallest ellipticity as E(550) min, and the largest ellipticity at 650 nm is defined as E(650) max and the smallest ellipticity as E(650) min. The values ​​of each are calculated. The largest ellipticity among E(450) max, E(550) max, and E(650) max is defined as E max, and the smallest ellipticity among E(450) min, E(550) min, and E(650) min is defined as E min. E max - E min is calculated. The smaller the value of Emax-Emin, the closer the reduction in color shift is to uniformity across all tilt directions and across all measured wavelengths. This means that the characteristics of the circular polarizer observed from the tilt direction become more homogeneous across all tilt directions and across all measured wavelengths. In other words, it implies that the optical stack contained in the circular polarizer functions well as a λ / 4 plate across all tilt directions and over a wide wavelength range.

[0230] (Visual evaluation of the performance of circular polarizer)

[0231] An absorptive linear polarizer is prepared by stretching a strip of polyvinyl alcohol resin film dyed with iodine.

[0232] The aforementioned linear polarizer and the optical stack obtained in each embodiment and comparative example are bonded together with an optically isotropic adhesive (Nitto Denko Corporation "CS9621") intervening between the linear polarizer and the first λ / 2 plate of the optical stack, so as to obtain a circular polarizer. The bonding is performed such that the absorption axis direction of the linear polarizer and the slow axis of the first λ / 2 plate of the optical stack are aligned at the angle θ01 shown in Tables 1 and 2. The obtained circular polarizer sequentially comprises a linear polarizer, a first λ / 2 plate, a second λ / 2 plate, and a λ / 4 plate.

[0233] Prepare an Apple "iPad" (registered trademark) as the image display device. Attach the obtained circular polarizing plate to this image display device using an adhesive (Nitto Denko Corporation "CS9621"). Display a white image on the image display device and observe it from the front. At this time, place the polarizing plate between the image display device and the observer's eyes, and observe while rotating the polarizing plate. Check the brightness and color cast of the image; if low brightness or color cast is detected, it is rated as "poor"; if neither is detected, it is rated as "good".

[0234] (The presence or absence of double images in a stereoscopic image display optical system)

[0235] Two optical stacks (designated as optical stack (1) and optical stack (2)) obtained in the various embodiments and comparative examples were mounted to a head-mounted display device equipped with a pancake-type optical system. The mounting was performed in the manner of including the display device, the first linear polarizer, the optical stack (1), the beam diffuser which is a half-mirror, the optical stack (2), the polarizing beam diffuser (DBEF (registered trademark)) and the second linear polarizer in sequence. Furthermore, the direction of the absorption axis of the first linear polarizer was aligned with the slow axis of the first λ / 2 plate included in the optical stack (1) at the angle θ 01 shown in Tables 1 and 2, and the direction of the absorption axis of the first linear polarizer was aligned with the slow axis of the first λ / 2 plate included in the optical stack (2) at the angle θ 01 shown in Tables 1 and 2.

[0236] The image is displayed on a head-mounted display device equipped with two optical stacks to visually confirm the existence of unnecessary images (double images). When a double image is confirmed, it is evaluated as "present", when a double image can be slightly confirmed, it is evaluated as "slightly present", and when a double image is almost impossible to confirm, it is evaluated as "absent".

[0237] [Wavelength plate and bonding layer]

[0238] The wavelength plate and bonding layer used in the various embodiments and comparative examples are disclosed below.

[0239] [COP(λ / 2)1】

[0240] The following operation is performed to manufacture and use a COP(λ / 2)1 of a 1 / 2 wavelength plate.

[0241] Particles of a northoene-based resin (ZEONOR 1430, manufactured by Zeon Corporation, Japan) were dried at 100°C for 5 hours. After drying, the particles were fed to an extruder, passed through a polymer filter, and extruded from a T-die onto a casting roller to form a sheet. The sheet was then cooled to obtain an unstretched film with a thickness of 80 μm. This unstretched film was fed to a roller stretcher and subjected to uniaxial stretching along the long side of the film at a temperature of 139°C and a magnification of 2.0, to obtain a 1 / 2 wavelength film (λ / 2 plate) with a thickness of 56 μm. The obtained 1 / 2 wavelength film had an in-plane retardation Re of 275 nm and a thickness retardation Rth of 138 nm. The refractive index exhibited a relationship of nx > ny = nz.

[0242] [COP(λ / 2)2】

[0243] The following operation is used to manufacture and use a COP(λ / 2)2 of a 1 / 2 wavelength plate.

[0244] (1) Manufacturing of a crystalline resin containing a ring-opening polymer of dicyclopentadiene as a hydride

[0245] After thoroughly drying the metal pressure reactor, it is purged with nitrogen. 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution containing dicyclopentadiene (with an internal isomer content of 99% or more) (30 parts as the amount of dicyclopentadiene), and 1.9 parts of 1-hexene are added to this metal pressure reactor, and the mixture is heated to 53°C.

[0246] A solution was prepared by dissolving 0.014 parts of tetrachlorophenylimine (tetrahydrofuran) tungsten complex in 0.70 parts of toluene. A catalyst solution was prepared by adding 0.061 parts of a 19% diethylaluminum ethoxide / n-hexane solution to this solution and stirring for 10 minutes. This catalyst solution was added to a pressure reactor to initiate the ring-opening polymerization reaction. The reaction was then maintained at 53°C for 4 hours to obtain a solution of the ring-opening polymer of dicyclopentadiene. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the obtained ring-opening polymer of dicyclopentadiene were 8,750 and 28,100, respectively, and the molecular weight distribution (Mw / Mn) was calculated to be 3.21.

[0247] 0.037 parts of 1,2-ethylene glycol were added to 200 parts of the obtained dicyclopentadiene ring-opening polymer solution as a terminator, and the mixture was heated to 60°C and stirred for 1 hour to stop the polymerization reaction. Then, 1 part of a hydrotalcite-like compound (KYOWAAD 2000, manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was heated to 60°C and stirred for 1 hour. Afterwards, 0.4 parts of a filter aid (RADIOLITE #1500, manufactured by Showa Chemical Industry Co., Ltd.) were added, and the adsorbent and solution were filtered out using a PP pleated filter (TCP-HX, manufactured by ADVANTEC Toyo Co., Ltd.).

[0248] 100 parts of cyclohexane and 0.0043 parts of ruthenium hydrogen chloride carbonyl succinate (triphenylphosphine) were added to 200 parts of a solution of the filtered ring-opening polymer of dicyclopentadiene (30 parts of polymer) and hydrogenation reaction was carried out at a hydrogen pressure of 6 MPa and 180°C for 4 hours. This yielded a reaction solution containing the hydride of the ring-opening polymer of dicyclopentadiene. The hydride precipitated from this reaction solution became a slurry solution.

[0249] The hydride contained in the aforementioned reaction solution was separated from the solution using a centrifuge and dried under reduced pressure at 60°C for 24 hours to obtain 28.5 parts of a hydride of a crystalline dicyclopentadiene ring-opening polymer. This hydride had a hydrogenation rate of over 99%, a glass transition temperature (Tg) of 93°C, a melting point (Tm) of 262°C, and a racemic binary fraction of 89%.

[0250] 100 parts of the obtained dicyclopentadiene ring-opening polymer hydride, mixed with 1.1 parts of antioxidant (tetra{3-[3′,5′-di(tributyl)-4′-hydroxyphenyl]propionic acid methylene}methane, manufactured by BASF Japan, "Irganox (registered trademark) 1010"), were placed into a biaxial extruder (product name "TEM-37B", manufactured by Toshiba Machine Co., Ltd.) with four 3 mm inner diameter dies. The mixture of the dicyclopentadiene ring-opening polymer hydride and antioxidant was formed into a strand by hot melt extrusion, and then finely chopped using a strand pelletizer to obtain granular crystalline resin. This crystalline resin has a positive intrinsic birefringence value.

[0251] The operating conditions of the twin-shaft extruder are described below: • Barrel set temperature = 270~280℃ • Die set temperature = 250℃ • Screw speed = 145 rpm

[0252] (2) Thin film manufacturing

[0253] The crystalline resin particles manufactured in (1) were dried at 100°C for 5 hours. After drying, the particles were fed to an extruder, passed through a polymer filter, extruded from a T-die onto a casting roller, and cooled to obtain an unstretched resin film with a thickness of 35 μm. The unstretched resin film was passed through a bath filled with toluene as a solvent, so that the toluene came into contact with the resin film. The contact time with the solvent was 7 seconds. The resin film in contact with the solvent was passed through an oven heated to 110°C for about 1 minute to obtain a solvent-treated resin film. The resin film was then fed to a roller longitudinal stretching machine and subjected to longitudinal uniaxial stretching along the long side of the film at a temperature of 130°C and a magnification of 1.5 times to obtain a 1 / 2 wavelength film (λ / 2 plate) with a thickness of 34 μm. The obtained 1 / 2 wavelength film had an in-plane retardation Re of 275 nm and a thickness direction retardation Rth of 0 nm. The refractive index exhibits a relationship of nx > nz > ny.

[0254] [COP(λ / 4)1】

[0255] is a 1 / 4 wavelength plate COP(λ / 4)1 manufactured and used through the following operation.

[0256] In the manufacturing of COP(λ / 2)1, the extrusion conditions were changed. Except for the above, following the manufacturing operation of COP(λ / 2)1, an unstretched film with a thickness of 40 μm was obtained. This unstretched film was supplied to a roll-type longitudinal stretcher and subjected to longitudinal uniaxial stretching along the long side of the film at a temperature of 139°C and a magnification of 2.0, obtaining a 1 / 4 wavelength film (λ / 4 plate) with a thickness of 28 μm. The obtained 1 / 4 wavelength film has an in-plane retardation Re of 138 nm and a thickness direction retardation Rth of 69 nm. The refractive index exhibits a relationship of nx > ny = nz.

[0257] [COP(λ / 4)2】

[0258] is a 1 / 4 wavelength plate COP(λ / 4)2 manufactured and used through the following operation.

[0259] In the manufacturing of COP(λ / 2)1, the extrusion conditions were changed. Except for the above, following the manufacturing operation of COP(λ / 2)1, an unstretched film with a thickness of 40 μm was obtained. This unstretched film was supplied to a roll-type longitudinal stretcher and subjected to longitudinal uniaxial stretching along the long side of the film at a temperature of 139°C and a magnification of 2.0, to obtain a 1 / 4 wavelength film (λ / 4 plate) with a thickness of 28 μm. The obtained 1 / 4 wavelength film has an in-plane retardation Re of 141 nm and a thickness direction retardation Rth of 70 nm. The refractive index exhibits a relationship of nx > ny = nz.

[0260] [COP(λ / 4)3】

[0261] is a 1 / 4 wavelength plate COP(λ / 4)3 manufactured and used through the following operation.

[0262] In the manufacture of COP(λ / 2)2, the extrusion conditions were changed. Except as described above, an unstretched resin film with a thickness of 18 μm was obtained by following the manufacturing operation of COP(λ / 2)2. This unstretched resin film was passed through a bath filled with toluene as a solvent, bringing the toluene into contact with the resin film. The contact time with the solvent was 7 seconds. The resin film in contact with the solvent was then passed through an oven heated to 110°C for approximately 1 minute to obtain a solvent-treated resin film. The resin film was then supplied to a roller stretcher and subjected to longitudinal uniaxial stretching along the long side of the film at a temperature of 130°C and a magnification of 1.5 times, obtaining a 1 / 4 wavelength film (λ / 4 plate) with a thickness of 15 μm. The obtained 1 / 4 wavelength film had an in-plane retardation Re of 138 nm and a thickness direction retardation Rth of 0 nm. The refractive index exhibited a relationship of nx > nz > ny.

[0263] [PC(λ / 2)】

[0264] is a PC (λ / 2) of 1 / 2 wavelength plate manufactured and used through the following operations.

[0265] In the manufacture of COP(λ / 2)1, polycarbonate resin particles (Mitsubishi Engineering Plastics Co., Ltd. "Iupilon E2000", glass transition temperature 151°C) were used instead of norethene resin particles, and the extrusion conditions were changed. Except for the above, following the manufacturing operation of COP(λ / 2)1, an unstretched film with a thickness of 32 μm was obtained. This unstretched film was supplied to a roll-type longitudinal stretching machine and subjected to longitudinal uniaxial stretching along the long side of the film at a temperature of 155°C and a magnification of 1.5 times, to obtain a 26 μm thick half-wavelength film (λ / 2 plate). The obtained half-wavelength film has an in-plane retardation Re of 275 nm and a thickness direction retardation Rth of 138 nm. The refractive index exhibits a relationship of nx > ny = nz.

[0266] [PC(λ / 4)】

[0267] is a PC (λ / 4) of 1 / 4 wavelength plate manufactured and used through the following operations.

[0268] In the manufacture of COP(λ / 2)1, polycarbonate resin particles (Mitsubishi Engineering Plastics Co., Ltd. "Iupilon E2000", glass transition temperature 151°C) were used instead of norethene resin particles, and the extrusion conditions were changed. Except for the above, following the manufacturing operation of COP(λ / 2)1, an unstretched film with a thickness of 16 μm was obtained. This unstretched film was supplied to a roll-type longitudinal stretcher and subjected to longitudinal uniaxial stretching along the long side of the film at a temperature of 155°C and a magnification of 1.5 times, to obtain a 1 / 4 wavelength film (λ / 4 plate) with a thickness of 13 μm. The obtained 1 / 4 wavelength film has an in-plane retardation Re of 138 nm and a thickness direction retardation Rth of 69 nm. The refractive index exhibits a relationship of nx > ny = nz.

[0269] [Joint Layer 1]

[0270] Nitto Denko Corporation's adhesive sheet "CS9621" (an acrylic adhesive layer with a refractive index of 1.477) is used as bonding layer 1.

[0271] [Joint Layer 2]

[0272] The bonding layer 2 is manufactured and used through the following operations.

[0273] (Fabrication of Bonding Layer 2)

[0274] In a reaction vessel equipped with a cooling pipe, a nitrogen inlet pipe, a thermometer, and a stirrer, 210 parts of ethyl acetate as a solvent, 70 parts of phenoxyethyl acrylate, 20 parts of butyl acrylate, 3 parts of hydroxyethyl acrylate, and 0.3 parts of benzoyl peroxide were added. Polymerization was carried out under a nitrogen gas flow to obtain a solution of an adhesive copolymer with a solid content of approximately 30% by weight. For every 100 parts of the solid content in this solution, 3 parts of a polyfunctional isocyanate crosslinking agent were uniformly mixed to prepare a solution of an acrylic adhesive composition. Next, this solution was coated onto a release liner and dried at 130°C for 5 minutes to form an adhesive layer with a thickness of 50 μm on the release liner, thus creating adhesive layer 2. The refractive index of adhesive layer 2 was measured, and the result showed a refractive index of 1.535 at 550 nm.

[0275] [Examples 1, 3 to 6, 7, Comparative Examples 1 to 6] Manufacturing of optical stacks

[0276] Prepare the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate as shown in Tables 1 and 2.

[0277] An intermediate stack is obtained by bonding the first λ / 2 plate and the second λ / 2 plate together with an intermediate bonding layer 2. An optical stack is obtained by bonding the second λ / 2 plate of the intermediate stack together with an intermediate bonding layer 2. The bonding is performed such that the angle θ12 between the first λ / 2 plate and the second λ / 2 plate and the angle θ13 between the first λ / 2 plate and the λ / 4 plate are the angles shown in Tables 1 and 2. The obtained optical stack is evaluated using the aforementioned method.

[0278] [Example 2]

[0279] Prepare the first λ / 2 plate, the second λ / 2 plate, and the λ / 4 plate as shown in Tables 1 and 2.

[0280] Except that bonding layer 1 is used instead of bonding layer 2, the optical stack is obtained by operating in accordance with Example 1. The obtained optical stack is evaluated by the aforementioned method.

[0281] [Comparative Example 7]

[0282] COP(λ / 4)2 was used instead of the optical stack for evaluation.

[0283] [Result]

[0284] The results are shown in the table below.

[0285] In the table below, the abbreviations have the following meanings: "θ01": Angle between the absorption axis of the linear polarizer and the slow axis of the first λ / 2 plate "θ02": Angle between the absorption axis of the linear polarizer and the slow axis of the second λ / 2 plate "θ03": Angle between the absorption axis of the linear polarizer and the slow axis of the λ / 4 plate "θ12": Angle between the slow axis of the first λ / 2 plate and the slow axis of the second λ / 2 plate "θ13": Angle between the slow axis of the first λ / 2 plate and the slow axis of the λ / 4 plate "Re": In-plane retardation (nm) "Rth": Thickness direction retardation (nm) "NZ1", "NZ2" and "NZ3": NZ coefficients of the first λ / 2 plate, the second λ / 2 plate and the λ / 4 plate, respectively.

[0286] 『Table 1』 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 First λ / 2 plate COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)2 Re(nm) 275 275 275 275 275 275 275 Rth(nm) 138 138 138 138 138 138 0 NZ1 1.0 1.0 1.0 1.0 1.0 1.0 0.5 θ01 (°) 6.9 6.9 9.4 4.4 6.9 6.9 6.9 Photoelasticity coefficient (×10) -13 cm 2 / dyn) 4 4 4 4 4 4 4 Refractive index 1.534 1.534 1.534 1.534 1.534 1.534 1.534 Second λ / 2 plate COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)2 Re(nm) 275 275 275 275 275 275 275 Rth(nm) 138 138 138 138 138 138 0 NZ2 1.0 1.0 1.0 1.0 1.0 1.0 0.5 θ02 (°) 34.5 34.5 34.5 34.5 37 32 34.5 Photoelasticity coefficient (×10) -13 cm 2 / dyn) 4 4 4 4 4 4 4 Refractive index 1.534 1.534 1.534 1.534 1.534 1.534 1.534 λ / 4 plate COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)3 Re(nm) 138 138 138 138 138 138 138 Rth(nm) 69 69 69 69 69 69 0 NZ3 1.0 1.0 1.0 1.0 1.0 1.0 0.5 θ03 (°) 100.4 100.4 100.4 100.4 100.4 100.4 100.4 Photoelasticity coefficient (×10) -13 cm 2 / dyn) 4 4 4 4 4 4 4 Refractive index 1.534 1.534 1.534 1.534 1.534 1.534 1.534 θ 12 (°) 27.6 27.6 25.1 30.1 30.1 25.1 27.6 θ 13 (°) 93.5 93.5 91 96 93.5 93.5 93.5 The refractive index of the first and second bonding layers 1.535 1.477 1.535 1.535 1.535 1.535 1.535 Changes in Re after treatment at 85℃ for 500 hours Small Small Small Small Small Small Small Phase difference spots during curved surface machining none none none none none none none Ellipticity (0°) simulation 450 nm 0.98 0.98 0.84 0.86 0.85 0.85 0.98 550 nm 1.00 1.00 0.84 0.84 0.84 0.84 1.00 650 nm 0.97 0.97 0.83 0.85 0.84 0.84 0.97 Max-Min 0.03 0.03 0.01 0.01 0.01 0.01 0.03 Ellipticity (45°) simulation 450 nm 0.72 0.72 0.72 0.68 0.70 0.70 0.89 550 nm 0.73 0.73 0.75 0.68 0.70 0.72 0.92 650 nm 0.72 0.72 0.72 0.69 0.70 0.71 0.93 Max-Min 0.01 0.01 0.03 0.01 0.01 0.03 0.04 E max -E min 0.28 0.28 0.42 0.42 0.38 0.37 0.16 Visual evaluation of circular polarizing plate good good good good good good good The presence or absence of double images none Slightly none none none none none

[0287] 『Table 2』 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 First λ / 2 plate PC(λ / 2) COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 — Re(nm) 275 275 275 275 275 275 — Rth(nm) 138 138 138 138 138 138 — NZ1 1.0 1.0 1.0 1.0 1.0 1.0 — θ 01 (°) 6.9 6.9 11.9 1.9 6.9 6.9 — Optical elasticity coefficient (×10) - 13 cm 2 / dyn) 70 4 4 4 4 4 — Refractive index 1.591 1.534 1.534 1.534 1.534 1.534 — Second λ / 2 plate PC(λ / 2) PC(λ / 2) COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 COP(λ / 2)1 — Re(nm) 275 275 275 275 275 275 — Rth(nm) 138 138 138 138 138 138 — NZ2 1.0 1.0 1.0 1.0 1.0 1.0 — θ 02 (°) 34.5 34.5 34.5 34.5 39.5 29.5 — Optical elasticity coefficient (×10) - 13 cm 2 / dyn) 70 70 4 4 4 4 — Refractive index 1.591 1.591 1.534 1.534 1.534 1.534 — λ / 4 plate PC(λ / 4) COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)1 COP(λ / 4)2 Re(nm) 138 138 138 138 138 138 141 Rth(nm) 69 69 69 69 69 69 70 NZ3 1.0 1.0 1.0 1.0 1.0 1.0 1.0 θ 03 (°) 100.4 100.4 100.4 100.4 100.4 100.4 45 Optical elasticity coefficient (×10) - 13 cm 2 / dyn) 70 4 4 4 4 4 4 Refractive index 1.591 1.534 1.534 1.534 1.534 1.534 1.534 θ 12 (°) 27.6 27.6 22.6 32.6 32.6 22.6 — θ 13 (°) 93.5 93.5 88.5 98.5 93.5 93.5 — The refractive index of the first and second bonding layers 1.535 1.535 1.535 1.535 1.535 1.535 — Changes in Re after treatment at 85℃ for 500 hours Small big Small Small Small Small big Phase difference spots during curved surface machining have have none none none none none Ellipticity (0°) simulation 450 nm 0.98 0.84 0.71 0.72 0.72 0.72 0.65 550 nm 0.99 1.00 0.70 0.70 0.70 0.70 0.96 650 nm 0.98 0.95 0.70 0.71 0.71 0.71 0.81 Max-Min 0.02 0.16 0.02 0.02 0.02 0.02 0.31 Ellipticity (45°) simulation 450 nm 0.72 0.73 0.68 0.61 0.63 0.63 0.58 550 nm 0.74 0.74 0.70 0.61 0.63 0.66 0.59 650 nm 0.73 0.73 0.69 0.63 0.64 0.67 0.57 Max-Min 0.02 0.02 0.03 0.03 0.01 0.04 0.02 E max -E min 0.36 0.44 0.50 0.53 0.49 0.47 0.45 Visual evaluation of circular polarizing plate good bad bad bad bad bad bad The presence or absence of double images have have have have have have have

[0288] The results above show that the optical stacks related to the embodiments did not exhibit phase difference inconsistencies (phase difference spots) when processed along curved surfaces and have excellent heat resistance. Furthermore, the results of ellipticity simulations show that the optical stacks related to the embodiments function well as λ / 4 plates in a wide visible light range of at least 450 nm to 650 nm.

[0289] In particular, the E max-E min values ​​of the optical stack associated with Example 7 are significantly low, demonstrating that it functions as a nearly homogeneous λ / 4 plate over a wide wavelength range and in all directions of the tilt direction.

[0290] Furthermore, when the optical stack related to the embodiment is installed in a stereoscopic image display optical system, no ghosting or only slight ghosting is observed, making it suitable for use in optical systems seeking high performance.

[0291] On the other hand, it is known that the optical stack of the comparative example cannot fully function as a λ / 4 plate, the visual evaluation of the circular polarizer is poor, and / or phase aberration spots exist during the surface processing. Furthermore, when the optical stack of the comparative example is installed in a stereoscopic image display optical system, ghosting is observed, indicating that it is sometimes unsuitable for optical systems seeking high performance. [Simplified Explanation of the Diagram]

[0033] 〈Fig. 1〉Fig. 1 is a cross-sectional schematic diagram of an optical stack related to the first embodiment of the present invention.

[0034] <Figure 2> Figure 2 is a three-dimensional exploded view of an optical stack related to the first embodiment of the present invention.

[0035] 〈Fig. 3〉Fig. 3 is a cross-sectional schematic diagram of an optical stack related to the second embodiment of the present invention.

[0036] 〈Fig. 4〉Fig. 4 is a cross-sectional schematic diagram of an optical component related to the third embodiment of the present invention.

Claims

1. An optical stack comprising, sequentially, a first λ / 2 plate made solely of material M1, a second λ / 2 plate made solely of material M2, and a λ / 4 plate made solely of material M3, wherein the angle between the slow axis of the first λ / 2 plate and the slow axis of the second λ / 2 plate is 24.6° or more and 30.6° or less, the angle between the slow axis of the first λ / 2 plate and the slow axis of the λ / 4 plate is 90.5° or more and 96.5° or less, and the first λ / 2 plate satisfies any one of the following equations (1a), (1b), and (1c): nx1 > ny1 ≒ nz1 (1a) nx1 > ny1 > nz1 (1b) nx1 > nz1 > ny1 (1c) Here, nx1 represents the refractive index in the in-plane direction of the first λ / 2 plate that imparts the maximum refractive index, ny1 represents the refractive index in the in-plane direction of the first λ / 2 plate that is orthogonal to the direction of nx1, and nz1 represents the refractive index in the thickness direction of the first λ / 2 plate. The second λ / 2 plate satisfies any one of the following equations (2a), (2b), and (2c): nx2 > ny2 ≒ nz2 (2a) nx2 > ny2 > nz2 (2b) nx2 > nz2 > ny2 (2c) Here, nx2 represents the refractive index in the in-plane direction of the aforementioned second λ / 2 plate that imparts the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the aforementioned second λ / 2 plate that is orthogonal to the direction of nx2, and nz2 represents the refractive index in the thickness direction of the aforementioned second λ / 2 plate. The aforementioned λ / 4 plate satisfies any one of the following equations (3a), (3b), and (3c): nx3 > ny3 ≒ nz3 (3a) nx3 > ny3 > nz3 (3b) nx3 > nz3 > ny3 (3c) Here, nx3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate and the direction that imparts the maximum refractive index, ny3 represents the refractive index in the in-plane direction of the aforementioned λ / 4 plate and the direction orthogonal to the nx3 direction, nz3 represents the refractive index in the thickness direction of the aforementioned λ / 4 plate, the aforementioned materials M1, M2 and M3 are each independently photoelastic coefficient of 10×10⁻¹³ cm² / dyn or less, and the aforementioned materials M1, M2 and M3 each contain more than 50% by weight of a specific polymer (P).

2. The optical stack as claimed in claim 1, wherein the first λ / 2 plate satisfies the aforementioned formula (1a) or formula (1b), the aforementioned second λ / 2 plate satisfies the aforementioned formula (2a) or formula (2b), and the aforementioned λ / 4 plate satisfies the aforementioned formula (3a) or formula (3b).

3. The optical stack as described in claim 1, wherein the first λ / 2 plate satisfies the aforementioned equation (1c), the second λ / 2 plate satisfies the aforementioned equation (2c), and the λ / 4 plate satisfies the aforementioned equation (3c).

4. The optical stack as described in claim 1, wherein the NZ coefficient NZ1 of the aforementioned first λ / 2 plate satisfies 0.0 < NZ1 < 1.0, the NZ coefficient NZ2 of the aforementioned second λ / 2 plate satisfies 0.0 < NZ2 < 1.0, and the NZ coefficient NZ3 of the aforementioned λ / 4 plate satisfies 0.0 < NZ3 < 1.0, wherein NZ1 is represented by the following formula: NZ1 = (nx1 - nz1) / (nx1 - ny1), NZ2 is represented by the following formula: NZ2 = (nx2 - nz2) / (nx2 - ny2), and NZ3 is represented by the following formula: NZ3 = (nx3 - nz3) / (nx3 - ny3), where nx1, ny1, nz1, nx2, ny2, nz2, nx3, ny3, and nz3 are all synonyms of the aforementioned.

5. The optical stack as described in claim 1 or 4, wherein the aforementioned polymer (P) is an alicyclic polymer.

6. The optical stack as described in claim 1 or 4, comprising a first bonding layer between the first λ / 2 plate and the second λ / 2 plate, and a second bonding layer between the second λ / 2 plate and the λ / 4 plate.

7. The optical stack as described in claim 6 satisfies the following equations (4), (5), (6) and (7): |I1-Ia1|≦0.02 (4) |I2-Ia1|≦0.02 (5) |I2-Ia2|≦0.02 (6) |I3-Ia2|≦0.02 (7) where I1 represents the refractive index of the first λ / 2 plate, I2 represents the refractive index of the second λ / 2 plate, I3 represents the refractive index of the λ / 4 plate, Ia1 represents the refractive index of the first bonding layer, and Ia2 represents the refractive index of the second bonding layer.

8. An optical component comprising a transparent component and an optical stack disposed on the aforementioned transparent component as described in any one of claims 1 to 7.

9. The optical component as claimed in claim 8, wherein the aforementioned transparent component has a curved surface, and the aforementioned optical stack is disposed on the curved surface of the aforementioned transparent component.

10. Use of an optical stack as described in any one of claims 1 to 7, which is fitted to the aforementioned curved surface of a transparent component having a curved surface.

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