Optical laminate and image display device

Abstract

Provided is an optical laminate capable of reducing interference irregularities in an image display device. An optical laminate according to an embodiment of the present invention comprises: a polarizing plate that includes a polarizer; a first adhesive layer; a first phase-difference film; and a second adhesive layer, in that order. The optical laminate satisfies the formula (1). [(nθ1-nθ2)2+(nθ3-nθ2)2] X d1 X d2 < 1000 (1). (In the formula (1), nθ1 represents the refractive index of the first adhesive layer in the transmission axis direction of the polarizer, nθ2 represents the refractive index of the first phase-difference film in the transmission axis direction of the polarizer, nθ3 represents the refractive index of the second adhesive layer in the transmission axis direction of the polarizer, d1 represents the thickness (nm) of the first adhesive layer and d2 represents the thickness (nm) of the second adhesive layer. )

Description

Optical laminates and image display devices

[0001] This invention relates to an optical laminate and an image display device.

[0002] Conventionally, image display devices, such as liquid crystal displays and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), have rapidly become widespread. To impart desired optical properties to such image display devices, it is known that optical laminates comprising polarizing plates and phase difference films are applied. As such optical laminates, for example, an optical film has been proposed comprising a quarter-wave plate and a linear polarizing plate, wherein the quarter-wave plate is formed by bonding a half-wave phase difference layer and a quarter-wave phase difference layer with an adhesive layer, and the half-wave phase difference layer is attached to the linear polarizing plate with an adhesive layer (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2015-025947

[0004] Image display devices generally display black when not illuminated. However, in image display devices equipped with an optical film as described in Patent Document 1, when ambient light is incident on the optical film, the incident light is reflected at the interfaces of adjacent layers in the optical film, and the interference of this reflected light can cause interference unevenness that causes the black display to appear colored. The main object of the present invention is to provide an optical laminate that can reduce interference unevenness in an image display device.

[0005] [1] An optical laminate according to an embodiment of the present invention comprises, in this order, a polarizing plate containing a polarizer, a first adhesive layer, a first phase difference film, and a second adhesive layer. The optical laminate satisfies the following formula (1): [(nθ1 - nθ2)] ２ + (nθ3 - nθ2) ２] × d1 × d2 < 1000 ... (1) (In equation (1), nθ1 represents the refractive index of the first adhesive layer in the transmission axis direction of the polarizer, nθ2 represents the refractive index of the first phase difference film in the transmission axis direction of the polarizer, nθ3 represents the refractive index of the second adhesive layer in the transmission axis direction of the polarizer, d1 represents the thickness [nm] of the first adhesive layer, and d2 represents the thickness [nm] of the second adhesive layer.) [2] The optical laminate described in [1] above may satisfy the following equation (2). [(nθ1 - nθ2) ２ + (nθ3 - nθ2) ２] × d1 × d2 < 500 ... (2) (In equation (2), nθ1 represents the refractive index of the first adhesive layer in the transmission axis direction of the polarizer, nθ2 represents the refractive index of the first phase difference film in the transmission axis direction of the polarizer, nθ3 represents the refractive index of the second adhesive layer in the transmission axis direction of the polarizer, d1 represents the thickness [nm] of the first adhesive layer, and d2 represents the thickness [nm] of the second adhesive layer.) [3] In the optical laminate described in [1] or [2] above, the thickness d1 of the first adhesive layer may be less than 80 nm. [4] In the optical laminate described in any of [1] to [3] above, the thickness d2 of the second adhesive layer may be less than 80 nm. [5] In the optical laminate described in any of [1] to [4] above, the refractive index nθ2 of the first phase difference film in the transmission axis direction may be less than 1.60. [6] In the optical laminate described in any of [1] to [5] above, the first adhesive layer may be a first adhesive layer. [7] In the optical laminate described in [6] above, the first adhesive layer may contain a cured product of an aqueous adhesive containing an organosilicon compound. [8] In the optical laminate described in [7] above, the organosilicon compound may contain an amino silane coupling agent. [9] In the optical laminate described in [7] or [8] above, the organosilicon compound may contain an epoxy silane coupling agent.

[10] In the optical laminate described in any of [1] to [9] above, the second adhesive layer may be a second adhesive layer.

[11] In the optical laminate described in any of [1] to

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

[12] The optical laminate described in any of [1] to

[11] above may further comprise a second phase difference film. The second phase difference film is located on the opposite side of the second adhesive layer from the first phase difference film.

[13] In the optical laminate described in

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

[14] In the optical laminate described in

[12] or

[13] , the refractive indices of the first phase difference film and the second phase difference film may be in the relationship nx > ny.

[15] In the optical laminate described in any of [1] to

[14] above, the polarizer plate may further comprise a protective layer. The protective layer is located on the opposite side of the polarizer from the first phase difference film. The protective layer may have an in-plane phase difference.

[16] An optical laminate according to another aspect of the present invention comprises, in this order, a polarizer plate, a first adhesive layer, a first phase difference film, and a second adhesive layer. The refractive index nθ2 of the first phase difference film in the transmission axis direction of the polarizer is less than 1.60. At least one of the thickness d1 of the first adhesive layer and the thickness d2 of the second adhesive layer is less than 80 nm.

[17] An optical laminate according to yet another aspect of the present invention comprises, in this order, a polarizer plate, a first adhesive layer, a first phase difference film, and a second adhesive layer.

[18] An image display device according to yet another aspect of the present invention comprises an optical laminate as described in any of [1] to

[17] above, wherein the thickness d1 of the first adhesive layer and the thickness d2 of the second adhesive layer are each less than 80 nm.

[0006] According to embodiments of the present invention, an optical laminate capable of reducing interference unevenness in an image display device can be realized.

[0007] Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention.

[0008] The following describes representative embodiments of the present invention, but the present invention is not limited to these embodiments. Furthermore, in order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the embodiments; however, these are merely examples and do not limit the interpretation of the present invention.

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols used herein are as follows: (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the refractive index in the plane is maximum (i.e., in the direction of the slow axis), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., in the direction of the fast axis), and "nz" is the refractive index in the thickness direction. Equation of an ellipse (x ２ / a ２ ) + (y ２ / b ２When ( ) = 1, let a be nx, b be ny, x and y be the refractive indices in the x - direction and y - direction in the angular θ - direction on the ellipse. Solve the simultaneous equations from y = x(tanθ) and the above nx and ny. The "refractive index in the transmission - axis direction" is √(x ２ + y ２ ). The "average refractive index" is obtained by (nx + ny + nz) / 3. (2) In - plane retardation (Re) "Re(λ)" is the in - plane retardation measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in - plane retardation measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx - ny)×d when the thickness of the layer (film) is d (nm). (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ)=(nx - nz)×d when the thickness of the layer (film) is d (nm). (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, the angle includes both clockwise and counter - clockwise with respect to the reference direction. Thus, for example, "45°" means ±45°. (6) Substantially parallel or orthogonal The expressions "substantially parallel" and "substantially parallel" include the case where the angle formed by two directions is within 0°±3°. Also, the expressions "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed by two directions is 90°±3°.

[0010] A. Schematic Figure 1 of the optical laminate is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. In one embodiment, the optical laminate 100 comprises, in this order, a polarizing plate 3 including a polarizer 31, a first adhesive layer 4, a first phase difference film 1, and a second adhesive layer 5. The polarizer 31 has a transmission axis that transmits polarized light vibrating in a specific direction, and an absorption axis perpendicular to the transmission axis. Hereinafter, the direction in which the transmission axis extends may be referred to as the transmission axis direction, and the direction in which the absorption axis extends may be referred to as the absorption axis direction. The first adhesive layer 4 typically bonds the polarizing plate 3 and the first phase difference film 1, and is adjacent to both the polarizing plate 3 and the first phase difference film 1. The optical laminate 100 typically satisfies the following formula (1), and preferably satisfies the following formula (2). The left-hand sides of formulas (1) and (2) may be referred to as interference uniformity parameters. [(nθ1 - nθ2)] ２ + (nθ3 - nθ2) ２ ]×d1×d2<1000...(1) [(nθ1-nθ2) ２ + (nθ3 - nθ2) ２ ] × d1 × d2 < 500 ... (2) (In equations (1) and (2), nθ1 represents the refractive index of the first adhesive layer in the transmission axis direction of the polarizer, nθ2 represents the refractive index of the first phase difference film in the transmission axis direction of the polarizer, nθ3 represents the refractive index of the second adhesive layer in the transmission axis direction of the polarizer, d1 represents the thickness [nm] of the first adhesive layer, and d2 represents the thickness [nm] of the second adhesive layer.) On the other hand, the interference uniformity parameter exceeds, for example, 0 (i.e., 0 < [(nθ1 - nθ2) ２ + (nθ3 - nθ2) ２ ] × d1 × d2) and also, for example, 1 or more (i.e., 1 ≤ [(nθ1 - nθ2) ２ + (nθ3 - nθ2) ２] × d1 × d2). The refractive index nθ1 of the first adhesive layer, the refractive index nθ2 of the first phase difference film, and the refractive index nθ3 of the second adhesive layer are measured, for example, by a thin-film waveguide method (prism coupler) using light with a wavelength of 594 nm. The inventors have discovered that in an image display device to which an optical laminate comprising a polarizing plate and a phase difference film is applied, the refractive index of the phase difference film and the refractive index and thickness of the adhesive layers arranged on both sides of the thickness direction of the phase difference film affect the occurrence of interference unevenness. Therefore, the inventors have diligently investigated the relationship between the refractive index of the phase difference film and the refractive index and thickness of the adhesive layers, and have found that if they satisfy a specific relationship, interference unevenness in the image display device can be reduced. More specifically, if the optical laminate satisfies the above formula (1), it is possible to suppress the reflection of light (visible light) incident on the optical laminate at the interface between the first phase difference film and the layer adjacent to the first phase difference film (typically the first adhesive layer or the second adhesive layer), and to suppress the interference of the reflected light. Therefore, interference unevenness in image display devices to which optical laminates are applied can be sufficiently reduced.

[0011] The absolute value of the difference between the refractive index nθ1 of the first adhesive layer 4 and the refractive index nθ2 of the first phase difference film 1 in the transmission axis direction of the polarizer 31 (|nθ1 - nθ2|) is, for example, 0.30 or less, preferably 0.20 or less, more preferably 0.10 or less, and even more preferably 0.08 or less. On the other hand, the lower limit of |nθ1 - nθ2| is typically 0. When the refractive index difference between the first adhesive layer and the first phase difference film is within this range, even if the first adhesive layer and the first phase difference film are adjacent to each other, reflection of light (visible light) incident on the optical laminate at the interface between the first adhesive layer and the first phase difference film can be suppressed. As a result, interference unevenness in an image display device to which the optical laminate is applied can be suppressed more stably.

[0012] The absolute value of the difference between the refractive index nθ3 of the second adhesive layer 5 and the refractive index nθ2 of the first phase difference film 1 in the transmission axis direction (|nθ3 - nθ2|) is, for example, 0.30 or less, preferably 0.20 or less, more preferably 0.10 or less, and even more preferably 0.08 or less. On the other hand, the lower limit of |nθ3 - nθ2| is typically 0. When the refractive index difference between the first phase difference film and the second adhesive layer is within this range, even if the first phase difference film and the second adhesive layer are adjacent to each other, reflection of light (visible light) incident on the optical laminate at the interface between the first phase difference film and the second adhesive layer can be suppressed. As a result, interference unevenness in an image display device to which the optical laminate is applied can be suppressed more stably.

[0013] The refractive index nθ2 of the first phase difference film 1 in the transmission axis direction is, for example, 1.45 or more, preferably 1.50 or more. On the other hand, the refractive index nθ2 of the first phase difference film 1 in the transmission axis direction is, for example, 1.70 or less, preferably less than 1.60, and more preferably 1.58 or less. When the refractive index of the first phase difference film is within this range, the optical laminate can stably satisfy the above-described formula (1), and the reflection of light (visible light) incident on the optical laminate can be stably suppressed.

[0014] The refractive index nθ1 of the first adhesive layer 4 in the transmission axis direction is, for example, 1.40 or more, preferably 1.43 or more, and more preferably 1.45 or more. On the other hand, the refractive index nθ1 of the first adhesive layer 4 in the transmission axis direction is, for example, 1.70 or less, and preferably 1.60 or less. When the refractive index of the first adhesive layer is within this range, the optical laminate can more stably satisfy the above-described formula (1).

[0015] The thickness d1 of the first adhesive layer 4 is, for example, 2000 nm or less, preferably 1200 nm or less, more preferably 120 nm or less, even more preferably less than 80 nm, particularly preferably 50 nm or less, especially preferably less than 40 nm, and most preferably 30 nm or less. When the thickness of the first adhesive layer is below such an upper limit, the first adhesive layer can be made sufficiently thin with respect to the wavelength of visible light. Therefore, interference of reflected light having a visible light wavelength can be stably suppressed on both sides in the thickness direction of the first adhesive layer. On the other hand, the thickness d1 of the first adhesive layer 4 is, for example, 1 nm or more, preferably 5 nm or more, and more preferably 10 nm or more. When the thickness of the first adhesive layer is above such a lower limit, the adhesive strength of the first adhesive layer can be improved, and adjacent layers (typically polarizing plates and first phase difference films) on both sides in the thickness direction of the first adhesive layer can be stably bonded together.

[0016] The first adhesive layer 4 may be an adhesive layer composed of an adhesive, or an adhesive layer composed of a tackifier. In one embodiment, the first adhesive layer 4 is a first adhesive layer 41 composed of an adhesive (more specifically, a cured product of the adhesive). In the adhesive layer, curing shrinkage of the adhesive, coating unevenness, coating repellency, drying unevenness, etc., can cause waviness and / or thickness unevenness in the adhesive layer. In this case, the waviness and / or thickness unevenness of the adhesive layer can cause unevenness in the optical path length of the optical laminate, and as a result, interference unevenness may occur in the image display device equipped with the optical laminate. In this regard, according to one embodiment, since the thickness d1 of the first adhesive layer 41 is within the range described above, the degree of curing shrinkage of the adhesive, coating unevenness, coating repellency, drying unevenness, etc. can be sufficiently reduced, and the occurrence of waviness and / or thickness unevenness in the first adhesive layer can be significantly suppressed. Therefore, it is possible to reduce the unevenness of the optical path length in the optical laminate and to more stably suppress interference unevenness in an image display device to which the optical laminate is applied.

[0017] The refractive index nθ3 of the second adhesive layer 5 in the transmission axis direction is, for example, 1.40 or more, preferably 1.43 or more, and more preferably 1.45 or more. On the other hand, the refractive index nθ1 of the second adhesive layer 5 in the transmission axis direction is, for example, 1.70 or less, preferably 1.60 or less, and more preferably 1.49 or less. When the refractive index of the second adhesive layer is within this range, the optical laminate can stably satisfy the above-described formula (1).

[0018] The thickness d2 of the second adhesive layer 5 is, for example, 2000 nm or less, preferably 1200 nm or less, more preferably 120 nm or less, even more preferably less than 80 nm, and particularly preferably 50 nm or less. When the thickness of the second adhesive layer is below such an upper limit, the second adhesive layer can be made sufficiently thin with respect to the wavelength of visible light. Therefore, interference of reflected light having a visible light wavelength can be stably suppressed on both sides in the thickness direction of the second adhesive layer. On the other hand, the thickness d2 of the second adhesive layer is, for example, 1 nm or more, preferably 5 nm or more, and more preferably 10 nm or more. When the thickness of the second adhesive layer is above such a lower limit, the adhesive strength of the second adhesive layer can be improved, and adjacent layers (typically the first phase difference film and the second phase difference film 2 (described later)) on both sides in the thickness direction of the second adhesive layer can be stably bonded together.

[0019] The second adhesive layer 5 may be an adhesive layer composed of an adhesive, or an adhesive layer composed of a tackifier. In one embodiment, the second adhesive layer 5 is a second adhesive layer 51 composed of an adhesive (more specifically, a cured product of the adhesive). Since the thickness d2 of the second adhesive layer 51 is within the range described above, the degree of curing shrinkage of the adhesive, coating unevenness, coating repellency, drying unevenness, etc. can be sufficiently reduced, and the occurrence of waviness and / or thickness unevenness in the second adhesive layer can be significantly suppressed. As a result, the unevenness of the optical path length in the optical laminate can be further reduced, and interference unevenness in an image display device to which the optical laminate is applied can be suppressed more stably.

[0020] In one embodiment, the optical laminate 100 further comprises a second phase difference film 2. The second phase difference film 2 is located on the opposite side of the second adhesive layer 5 from the first phase difference film 1. In the illustrated example, the second phase difference film 2 is attached to the first phase difference film 1 via the second adhesive layer 5, and the second adhesive layer 5 is adjacent to both the first phase difference film 1 and the second phase difference film 2.

[0021] The refractive index nθ4 of the second phase difference film 2 in the transmission axis direction is, for example, 1.45 or more, for example, 1.50 or more, for example, exceeding 1.60, and for example, 1.61 or more. On the other hand, the upper limit of the refractive index nθ4 of the second phase difference film 2 in the transmission axis direction is typically 1.70. The absolute value of the difference between the refractive index nθ4 of the second phase difference film 2 and the refractive index nθ3 of the second adhesive layer 5 in the transmission axis direction (|nθ4 - nθ3|) is, for example, 0.30 or less, preferably 0.20 or less. On the other hand, the lower limit of |nθ4 - nθ3| is typically 0. When the refractive index difference between the second phase difference film and the second adhesive layer is within this range, even if the second phase difference film and the second adhesive layer are adjacent to each other, reflection of light (visible light) incident on the optical laminate at the interface between the second phase difference film and the second adhesive layer can be suppressed.

[0022] B. Details of the Optical Laminate Next, with reference to Figure 1, details of an optical laminate according to one embodiment will be described. As shown in Figure 1, in one embodiment, the optical laminate 100 comprises a polarizing plate 3, a first adhesive layer 41, a first phase difference film 1, a second adhesive layer 51, and a second phase difference film 2 in this order.

[0023] B-1. Polarizing plate The polarizing plate 3 typically includes a polarizer 31. Any suitable polarizer can be used as the polarizer 31. The polarizer may be composed of, for example, a single layer of resin film, or it may be obtained using a laminate of two or more layers.

[0024] Specific examples of polarizers composed of a single layer of resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) resin films, partially formalized PVA resin films, and partially saponified ethylene-vinyl acetate copolymer films, which have been subjected to dyeing and stretching treatments with dichroic substances such as iodine or dichroic dyes, as well as polyene-based oriented films such as dehydrated PVA or dehydrochlorinated polyvinyl chloride. Preferably, polarizers obtained by dyeing a PVA resin film with iodine and uniaxially stretching are used because they have excellent optical properties.

[0025] Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate, drying it to form a PVA-based resin layer on the resin substrate, and obtaining a laminate of the resin substrate and the PVA-based resin layer; or by stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In one embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching may, if necessary, further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in one embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which it shrinks by 2% or more in the width direction by heating while being transported in the longitudinal direction. Typically, the manufacturing method of this embodiment includes applying an air-assisted stretching treatment, a dyeing treatment, a water-based stretching treatment, and a drying shrinkage treatment to the laminate in this order. By introducing auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is coated on a thermoplastic resin, making it possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, it is possible to prevent problems such as a decrease in the orientation of PVA and dissolution when immersed in water in the subsequent dyeing and stretching processes, making it possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain halides. This makes it possible to improve the optical properties of polarizers obtained through processing steps that involve immersing the laminate in a liquid, such as dyeing and water-based stretching. Furthermore, by shrinking the laminate in the width direction through a drying shrinkage treatment, the optical properties can be improved.The resulting resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate, and any appropriate protective layer may be laminated onto the peeled surface according to the purpose. Details of such polarizer manufacturing methods are described, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0026] The above-mentioned iodine dyeing is carried out, for example, by immersing a PVA resin film in an iodine aqueous solution. The stretching ratio for the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or during the dyeing process. Alternatively, dyeing may be performed after stretching. If necessary, the PVA resin film may be subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA resin film in water and washing it before dyeing, not only can dirt and blocking inhibitors on the surface of the PVA resin film be washed away, but the PVA resin film can also be swollen to suppress uneven dyeing.

[0027] The thickness of the polarizer 31 is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, and even more preferably 3 μm to 8 μm. Having such a thickness for the polarizer makes it possible to make the optical laminate thinner, and as a result, to make the image display device smaller.

[0028] The polarizer 31 typically exhibits absorbing dichroism at any wavelength between 380 nm and 780 nm. The single-unit transmittance of the polarizer 31 is, for example, 41.5% or more, preferably 43.0% or more, and more preferably 44.5% or more. On the other hand, the upper limit of the single-unit transmittance of the polarizer 31 is typically 46.0%. The degree of polarization of the polarizer 31 is, for example, 97.0% or more, preferably 99.0% or more, and more preferably 99.9% or more.

[0029] The average refractive index of the polarizer 31 at a wavelength of 550 nm is, for example, 1.40 to 1.65, preferably 1.45 to 1.60, and more preferably 1.50 to 1.60.

[0030] The polarizing plate 3 may include a protective layer 32 in addition to the polarizer 31. The protective layer 32 is provided on at least one side of the polarizer 31. That is, the protective layer 32 may be provided on only one side of the polarizer 31, or on both sides of the polarizer 31. In the illustrated example, the protective layer 32 is located on the side of the polarizer 31 opposite to the first phase difference film 1. Typically, the protective layer 32 is attached to the polarizer 31 via any suitable adhesive layer (not shown).

[0031] The protective layer is formed of any suitable film that can be used as a protective layer for a polarizer. Representative examples of the material that is the main component of the film include transparent resins. Specifically, cycloolefin (COP) resins such as polynorbornene-based resins; polyester resins such as polyethylene terephthalate (PET)-based resins; cellulose resins such as triacetyl cellulose (TAC); polycarbonate (PC)-based resins; (meth)acrylic resins; polyvinyl alcohol-based resins; polyamide resins; polyimide resins; polyethersulfone resins; polysulfone resins; polystyrene resins; polyolefin resins; acetate resins. Also, thermosetting resins or ultraviolet curable resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone resins can be mentioned. In this specification, "(meth)acrylic" includes acrylic and methacrylic. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Also, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used. For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the above resin composition. The materials of the resin film can be used alone or in combination. Among such materials of the resin film, preferably cellulose resins and COP resins can be mentioned, and preferably COP resins can be mentioned.

[0032] The protective layer 32 may have optical isotropy or may have optical anisotropy. In one embodiment, the protective layer 32 has an in-plane retardation. When the protective layer has an in-plane retardation, an arbitrary appropriate optical compensation function can be imparted to the optical laminate.

[0033] The refractive index of the protective layer 32 shows a relationship of, for example, nx > ny, and preferably shows a relationship of nx > ny ≥ nz. Note that in this specification, "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where they are substantially equal. Therefore, within a range that does not impair the effects of the present invention, ny > nz or ny < nz may occur.

[0034] In the illustrated example, the protective layer 32 functions as a λ / 4 plate. According to such a configuration, in an image display device, it is possible to improve visibility through an optical member having a polarization effect (hereinafter sometimes referred to as a polarization member). The in-plane retardation Re(550) of the protective layer 32 is, for example, 80 nm or more, and preferably 90 nm or more. On the other hand, the in-plane retardation Re(550) of the protective layer 32 is, for example, 160 nm or less, preferably 145 nm or less, more preferably 130 nm or less, still more preferably 120 nm or less, and particularly preferably 110 nm or less. When the protective layer has such Re(550), in an image display device, the visibility through the polarization member can be stably improved.

[0035] The retardation Rth(55) in the thickness direction of the protective layer 32 is, for example, 80 nm to 200 nm, and preferably 90 nm to 160 nm. The Nz coefficient of the protective layer 32 is, for example, 0.5 to 5.0, and preferably 1.0 to 3.0.

[0036] The protective layer 32 having an in-plane retardation may exhibit reverse wavelength dispersion characteristics in which the in-plane birefringence increases according to the wavelength of the measurement light, positive wavelength dispersion characteristics in which the in-plane birefringence decreases according to the wavelength of the measurement light, or flat wavelength dispersion characteristics in which the in-plane birefringence hardly changes depending on the wavelength of the measurement light.

[0037] The protective layer 32 having an in-plane retardation is prepared, for example, by stretching a film made of the above-described transparent resin. In other words, the protective layer 32 having an in-plane retardation is a stretched film of a transparent resin film. In one embodiment, the protective layer 32 is a stretched film of a COP-based resin film.

[0038] When the protective layer 32 has an in-plane phase difference, the angle between the slow axis direction of the protective layer 32 and the absorption axis direction of the polarizer 31 is, for example, 30° to 60°, preferably 35° to 55°, more preferably 40° to 50°, and even more preferably 43° to 47°. With such a configuration, the visibility through the polarizing member can be improved more stably in the image display device.

[0039] The thickness of the protective layer 32 is, for example, 100 μm or less, preferably 80 μm or less, more preferably 1 μm to 60 μm, and even more preferably 5 μm to 40 μm.

[0040] Furthermore, a surface treatment layer may be provided on the surface of the protective layer 32 as needed. Examples of surface treatment layers include a hard coat layer, an anti-reflective layer, an anti-sticking layer, and an anti-glare treatment layer. Preferably, the surface treatment layer is provided on the surface of the protective layer 32 opposite to the polarizer 31.

[0041] B-2. First phase difference film and second phase difference film B-2-1. First phase difference film The first phase difference film 1 is located between the polarizing plate 3 and the second phase difference film 2 in the stacking direction of the optical laminate 100. Typically, the first phase difference film 1 is attached to the polarizing plate 3 via the first adhesive layer 4. In the illustrated example, the first phase difference film 1 is attached to the polarizer 31 via the first adhesive layer 41.

[0042] The first phase difference film 1 may have an in-plane phase difference, or it may have a phase difference in the thickness direction. The first phase difference film 1 may function as a λ / 4 plate, or it may function as a λ / 2 plate, a λ / 5 plate, a λ / 6 plate, or a C-Plate.

[0043] In one embodiment, the first phase difference film 1 has an in-plane phase difference. In this case, the refractive index of the first phase difference film 1 exhibits, for example, the relationship nx > ny, preferably nx > ny ≥ nz. The in-plane phase difference Re(550) of the first phase difference film 1 exhibiting the relationship nx > ny is, for example, 80 nm or more and 300 nm or less. The Nz coefficient of the first phase difference film 1 exhibiting the relationship nx > ny is, for example, 0.9 or more and 1.5 or less. The first phase difference film 1 exhibiting the relationship nx > ny may exhibit inverse wavelength dispersion characteristics in which the in-plane birefringence increases with the wavelength of the measurement light, or it may exhibit positive wavelength dispersion characteristics in which the in-plane birefringence decreases with the wavelength of the measurement light, or it may exhibit flat wavelength dispersion characteristics in which the in-plane birefringence hardly changes with the wavelength of the measurement light.

[0044] In another embodiment, the first phase difference film 1 has a phase difference in the thickness direction and substantially no in-plane phase difference. In this case, the refractive index of the first phase difference film 1 exhibits, for example, the relationship nx = ny, preferably nz > nx = ny. In this specification, "nx = ny" includes not only the case where nx and ny are exactly equal, but also the case where they are substantially equal. Therefore, it is possible that nx > ny or nx < ny, to the extent that the effects of the present invention are not impaired. The in-plane phase difference Re(550) of the first phase difference film 1 exhibiting the relationship nx = ny is, for example, 0 nm or more and 3 nm or less, preferably 0 nm. The phase difference Rth(550) in the thickness direction of the first phase difference film 1 exhibiting the relationship nx = ny is, for example, -200 nm or more and 200 nm or less, preferably -200 nm or more and less than 0 nm, more preferably -140 nm or more and -100 nm or less.

[0045] The average refractive index of the first phase difference film 1 at a wavelength of 550 nm is, for example, 1.45 to 1.65, preferably 1.50 to 1.65, and more preferably 1.55 to 1.65.

[0046] The thickness of the first phase difference film 1 is arbitrarily and appropriately adjusted so that a desired phase difference is obtained. The thickness of the first phase difference film 1 is, for example, 10 μm or less, preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. On the other hand, the lower limit of the thickness of the first phase difference film 1 is typically 1 μm.

[0047] The first phase difference film 1 typically includes a stretched film prepared by stretching a film composed of the transparent resin described above, and / or an orientation-solidified layer of a liquid crystal compound. In this specification, "orientation-solidified layer of liquid crystal compound" refers to a layer in which the liquid crystal compound is oriented in a predetermined direction within the layer, and this orientation state is fixed. Note that "orientation-solidified layer" is a concept that includes orientation-cured layers obtained by curing liquid crystal monomers, as described later.

[0048] In one embodiment, the first phase difference film 1 includes an orientation solidified layer of a liquid crystal compound. In the illustrated example, the first phase difference film 1 has a single-layer structure of the orientation solidified layer of the liquid crystal compound. Hereinafter, the orientation solidified layer of the liquid crystal compound included in the first phase difference film 1 may be referred to as the first liquid crystal orientation solidified layer 11. When the first phase difference film includes the first liquid crystal orientation solidified layer, the difference between nx and ny of the first phase difference film can be made significantly larger compared to non-liquid crystal materials, so the thickness of the phase difference film having a desired phase difference can be made significantly smaller. As a result, the thickness of the first phase difference film (first liquid crystal orientation solidified layer) can be stably adjusted to the above range, and as a result, the optical laminate can be made thinner. On the other hand, light interference is more likely to occur in layers that are thinner and have stronger interfacial reflection. That is, light interference is likely to occur on the surface of layers that are thin and have a relatively large refractive index, such as the orientation solidified layer of a liquid crystal compound. In this regard, according to one embodiment, since the optical laminate satisfies formula (1) described above, even if the first phase difference film includes a first liquid crystal alignment solidification layer, interference of visible light in the optical laminate can be sufficiently suppressed.

[0049] In the first liquid crystal alignment solidification layer 11, rod-shaped liquid crystal compounds are oriented in a predetermined direction within the first liquid crystal alignment solidification layer 11 (homogeneous orientation). Examples of liquid crystal compounds include liquid crystal compounds in which the liquid crystal phase is a nematic phase (nematic liquid crystal). Examples of such liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. Liquid crystal polymers and liquid crystal monomers may be used individually or in combination. The mechanism by which the liquid crystal properties of the liquid crystal compound are expressed may be lyotropic or thermotropic.

[0050] When a liquid crystal compound contains a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinkable monomer. The orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After oriented the liquid crystal monomer, the orientation state can be fixed by polymerizing or crosslinking the liquid crystal monomers together, for example. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystal. Therefore, the formed first liquid crystal orientation solidified layer does not undergo transitions to the liquid crystal phase, glass phase, or crystalline phase due to temperature changes, which is characteristic of liquid crystal compounds. As a result, the first phase difference film can have extremely excellent stability that is not affected by temperature changes.

[0051] Any suitable liquid crystal monomer can be used. Examples of liquid crystal monomers include polymerizable mesogenic compounds described in Japanese Patent Publication No. 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Specific examples of such polymerizable mesogenic compounds include BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767.

[0052] An orientation-solidified layer of a liquid crystal compound can be formed by applying an appropriate orientation treatment to any suitable coated substrate, then applying a coating liquid containing the liquid crystal compound to the surface to orient the liquid crystal compound in a direction corresponding to the orientation treatment, and fixing the orientation state. Examples of orientation treatments include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of liquid crystal compounds and details of the method for forming the orientation-solidified layer are described in Japanese Patent Application Publication No. 2006-163343. The description in said publication is incorporated herein by reference.

[0053] The birefringence Δn of the first liquid crystal alignment solidification layer 11 is, for example, 0.06 or more, preferably 0.08 or more, more preferably 0.09 or more, and even more preferably 0.10 or more. On the other hand, the upper limit of the birefringence Δn of the first liquid crystal alignment solidification layer 11 is, for example, 0.13, and also, for example, 0.12. If Δn is within this range, a desired in-plane phase difference can be achieved with a very thin thickness.

[0054] B-2-2. Second Phase Difference Film The second phase difference film 2 is located on the opposite side of the polarizing plate 3 from the first phase difference film 1 in the stacking direction of the optical laminate 100. In one embodiment, the second phase difference film 2 is attached to the first phase difference film 1 via a second adhesive layer 5. In the illustrated example, the second phase difference film 2 is attached to the first liquid crystal alignment solidification layer 11 via a second adhesive layer 51.

[0055] The second phase difference film 2 may have an in-plane phase difference, or it may have a phase difference in the thickness direction. The second phase difference film 2 may function as a λ / 4 plate, or it may function as a λ / 2 plate, a λ / 5 plate, a λ / 6 plate, or a C-Plate.

[0056] The second phase difference film 2 is described in the same manner as the first phase difference film 1 described above. Therefore, a detailed description of the second phase difference film 2 will be omitted as appropriate. The refractive index of the second phase difference film 2 may be in the relationship nx > ny or nx = ny. In one embodiment, the refractive indices of the first phase difference film 1 and the second phase difference film 2 each exhibit the relationship nx > ny. With such a configuration, it is possible to have wavelength dispersion characteristics better than the wavelength dispersion characteristics of each phase difference film. In addition, the viewing angle characteristics, i.e., the optical characteristics for any azimuth angle and polar angle, can also be improved. The ranges of the phase difference, average refractive index, and thickness in the second phase difference film 2 are, for example, the same as the ranges of the phase difference, average refractive index, and thickness in the first phase difference film 1 described above.

[0057] The second phase difference film 2 typically includes a stretched film and / or an orientation-solidified layer of a liquid crystal compound. In one embodiment, the second phase difference film 2 includes an orientation-solidified layer of a liquid crystal compound. In the illustrated example, the second phase difference film 2 has a single-layer structure of an orientation-solidified layer of a liquid crystal compound. Hereinafter, the orientation-solidified layer of the liquid crystal compound included in the second phase difference film 2 may be referred to as the second liquid crystal orientation-solidified layer 21. The second liquid crystal orientation-solidified layer 21 is described in the same way as the first liquid crystal orientation-solidified layer 11. When the second phase difference film includes the second liquid crystal orientation-solidified layer, the difference between nx and ny of the second phase difference film can be made significantly larger compared to non-liquid crystal materials, so the thickness of the phase difference film having the desired phase difference can be significantly reduced. As a result, the thickness of the second phase difference film (second liquid crystal orientation-solidified layer) can be stably adjusted to the above range, and the optical laminate can be made thinner. Furthermore, according to one embodiment, since the optical laminate satisfies formula (1) described above, even if the second phase difference film includes a second liquid crystal alignment solidification layer, interference of visible light in the optical laminate can be sufficiently suppressed.

[0058] B-2-3. Combination of First Phase Difference Film and Second Phase Difference Film In one embodiment, the first phase difference film 1 functions as a λ / 2 plate, and the second phase difference film 2 functions as a λ / 4 plate. Alternatively, the first phase difference film 1 may function as a λ / 4 plate, and the second phase difference film 2 may function as a λ / 2 plate. The combination of the two phase difference films being a λ / 2 plate and a λ / 4 plate is sometimes referred to as the first combination. With this configuration, the wavelength dispersion characteristics of the laminate of the first phase difference film and the second phase difference film can be brought closer to ideal inverse wavelength dispersion characteristics. Therefore, excellent anti-reflective properties can be imparted to the optical laminate.

[0059] In the first combination, the in-plane phase difference Re(550) of the phase difference film functioning as a λ / 4 plate is, for example, 90 nm to 180 nm, preferably 100 nm to 160 nm, and more preferably 110 nm to 150 nm. In the first combination, the in-plane phase difference Re(550) of the phase difference film functioning as a λ / 2 plate is, for example, 200 nm to 300 nm, preferably 220 nm to 290 nm, and even more preferably 230 nm to 280 nm.

[0060] In the first combination, the angle between the absorption axis direction of the polarizer 31 and the slow axis direction of the first phase difference film 1 is, for example, 10° to 20°, preferably 12° to 18°, and more preferably 14° to 16°. Also, in the first combination, the angle between the absorption axis direction of the polarizer 31 and the slow axis direction of the second phase difference film 2 is, for example, 70° to 80°, preferably 72° to 78°, and more preferably 74° to 76°. Note that in the first combination, the range of the angle between the absorption axis direction of the polarizer and the slow axis direction of the first phase difference film and the range of the angle between the absorption axis direction of the polarizer and the slow axis direction of the second phase difference film may be reversed. With such a configuration, the wavelength dispersion characteristics of the laminate of the first phase difference film and the second phase difference film can be brought closer to ideal inverse wavelength dispersion characteristics. Therefore, excellent anti-reflective properties can be stably imparted to the optical laminate.

[0061] The first phase difference film 1 may function as a λ / 4 plate, and the second phase difference film 2 may function as a C-Plate (i.e., nx = ny). Alternatively, the first phase difference film 1 may function as a C-Plate, and the second phase difference film 2 may function as a λ / 4 plate. When the combination of the two phase difference films is a λ / 4 plate and a C-Plate, this is sometimes referred to as the second combination. Even with this configuration, excellent anti-reflective properties can be imparted to the optical laminate. However, the first combination described above is preferred over the second combination. When the combination of the two phase difference films is a λ / 2 plate and a λ / 4 plate, interference unevenness in an image display device equipped with an optical laminate can be stably reduced.

[0062] In the second combination, the in-plane phase difference Re(550) of the phase difference film functioning as a λ / 4 plate is, for example, 90 nm to 190 nm, preferably 100 nm to 170 nm, and more preferably 110 nm to 160 nm. In the second combination, the range of the phase difference Rth(550) in the thickness direction of the phase difference film functioning as a C-Plate is, for example, the same as the range of the phase difference Rth(550) in the thickness direction of the first phase difference film 1 whose refractive index exhibits the relationship nx=ny. In the second combination, the angle between the slow axis direction of the phase difference film functioning as a λ / 4 plate and the absorption axis direction of the polarizer 31 is arbitrarily and appropriately adjusted. Even with such a configuration, excellent anti-reflective properties can be stably imparted to the optical laminate.

[0063] B-3. ​​First Adhesive Layer The first adhesive layer 41 is located between the polarizing plate 3 and the first phase difference film 1 in the stacking direction of the optical laminate 100, and bonds the polarizing plate 3 and the first phase difference film 1 together. Typically, the first adhesive layer 41 is in contact with both the polarizing plate 3 and the first phase difference film 1.

[0064] The first adhesive layer 41 contains a cured product of any suitable adhesive. Examples of adhesives include water-based adhesives; thermosetting adhesives; moisture-curing adhesives; and active energy ray-curing adhesives such as ultraviolet-curing adhesives (UV adhesives). The adhesives can be used alone or in combination.

[0065] In one embodiment, the first adhesive layer 41 contains a cured product of a water-based adhesive. When the adhesive layer contains a cured product of a water-based adhesive, the thickness d1 of the first adhesive layer can be stably adjusted to the above range, and the occurrence of interference unevenness in the optical laminate can be sufficiently suppressed.

[0066] Water-based adhesives typically contain a curing component and a solvent that includes water.

[0067] The curing components are typically soluble and / or dispersible in a solvent. The curing components can be cured by any suitable chemical reaction. Examples of curing components include combinations of polyvinyl alcohol (PVA) and crosslinking agents, and organosilane compounds. The curing components can be used alone or in combination.

[0068] Water-based adhesives containing PVA and a crosslinking agent as curing components may be referred to as PVA-containing water-based adhesives below. The crosslinking agent can crosslink the PVA and cure the water-based adhesive. Examples of crosslinking agents include melamine resins such as methylolmelamine; alkylenediamines; isocyanates; epoxys; and aldehydes. Crosslinking agents can be used alone or in combination. The content ratio of the crosslinking agent in the water-based adhesive is, for example, 10 to 50 parts by mass, preferably 20 to 40 parts by mass, per 100 parts by mass of PVA.

[0069] PVA-containing water-based adhesives may further contain a metal compound colloid in addition to PVA and a crosslinking agent. The metal compound colloid consists of fine particles of a metal compound dispersed in a solvent, and can be electrostatically stabilized due to the mutual repulsion of like charges among the fine particles, thereby possessing permanent stability.

[0070] Examples of metal compounds include metal oxides such as alumina, silica, zirconia, and titania; metal salts such as aluminum silicate, calcium carbonate, magnesium silicate, zinc carbonate, barium carbonate, and calcium phosphate; and minerals such as celite, talc, clay, and kaolin. These metal compounds can be used individually or in combination.

[0071] The average particle size of the fine particles forming the metal compound colloid can be adjusted arbitrarily and appropriately. For example, the average particle size of the fine particles is 1 nm to 100 nm, preferably 1 nm to 50 nm. When the average particle size of the fine particles is within this range, the fine particles can be uniformly dispersed in the adhesive layer. The content ratio of the metal compound colloid in the water-based adhesive can be adjusted arbitrarily and appropriately.

[0072] Water-based adhesives containing an organic silane compound as a curing component may be referred to as organic silane-containing water-based adhesives below. Organic silane compounds typically have an alkoxysilyl group and / or a silanol group (hydroxysilyl group). When an organic silane compound has an alkoxysilyl group and / or a silanol group, it can cure the water-based adhesive through a dehydration condensation reaction.

[0073] Examples of organosilane compounds include silane coupling agents having an alkoxysilyl group and / or a silanol group and an organic functional group. Examples of organic functional groups in silane coupling agents include an amino group, an epoxy group, and a methoxy group. A silane coupling agent may have one organic functional group or a combination of two or more organic functional groups. Having such organic functional groups in a silane coupling agent can improve the adhesion between the polarizing plate and the first phase difference film and the first adhesive layer. These silane coupling agents can be used individually or in combination.

[0074] In one embodiment, the organosilicon compound comprises an amino-based silane coupling agent containing an amino group and / or an epoxy-based silane coupling agent containing an epoxy group. With this configuration, the adhesion between the polarizing plate and the first phase difference film and the first adhesive layer can be stably improved, and the first adhesive layer can be made thinner.

[0075] The amino-based silane coupling agent has any suitable structure comprising an amino group and an alkoxysilyl group and / or a silanol group. Examples of amino silane coupling agents include N,N'-bis(2-aminoethyl)-6-(3-trihydroxysilylpropyl)amino-1,3,5-triazine-2,4-diamine, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and their hydrochloride salts.

[0076] Any suitable commercially available amino silane coupling agent can be used. Examples of commercially available amino silane coupling agents include KBM-602, KBM-603, KBM-903, KBE-603, KBE-903, X-12-972F (all manufactured by Shin-Etsu Chemical Co., Ltd.), Z-6011, Z-6020, Z-6026, Z-6032, Z-6094, Z-6610 (all manufactured by Toray Dow Corning Co., Ltd.), and A-1100, A-1110, A-1120, A-2120, Y-9669 (all manufactured by Momentive Performance Materials).

[0077] Epoxy silane coupling agents have any suitable structure having an epoxy group and an alkoxysilyl group and / or a silanol group. Examples of epoxy silane coupling agents include 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0078] Any suitable commercially available epoxy silane coupling agent can be used. Examples of commercially available epoxy silane coupling agents include KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KR-516, X-12-981S (all manufactured by Shin-Etsu Chemical Co., Ltd.), SH6040, Z-6040, Z-6042, Z-6043, Z-6044 (all manufactured by Toray Dow Corning Co., Ltd.), and A-186, A-187, A-1871 (all manufactured by Momentive Performance Materials).

[0079] When the organosilicon compound contains both an amino-based silane coupling agent and an epoxy-based silane coupling agent, the amino groups of the amino-based silane coupling agent can react with the epoxy groups of the epoxy-based silane coupling agent. This allows for stable curing of the water-based adhesive and further thinning of the adhesive layer. The molar ratio of the amino-based silane coupling agent to the epoxy-based silane coupling agent (amino-based silane coupling agent: epoxy-based silane coupling agent) is, for example, 8:92 to 60:40, and preferably 10:90 to 55:45. If the molar ratio of the amino-based silane coupling agent to the epoxy-based silane coupling agent is within this range, the adhesive layer can be made thinner and more stable.

[0080] The content of the curing component in the water-based adhesive is, for example, less than 50% by mass, preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, especially preferably 5% by mass or less, and most preferably 2% by mass or less. On the other hand, the content of the curing component in the water-based adhesive is, for example, 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, and particularly preferably 0.5% by mass or more.

[0081] As mentioned above, the solvent for water-based adhesives contains water. In addition to water, the solvent may also contain an organic solvent. Examples of organic solvents include esters, ketones, cyclic ethers, aliphatic or alicyclic hydrocarbons, aromatic hydrocarbons, aliphatic or alicyclic alcohols, glycol ethers, and glycol ether acetates. Organic solvents can be used alone or in combination.

[0082] The water content in the solvent of the aqueous adhesive is, for example, 50% by mass or more, preferably 80% by mass or more, and more preferably 95% by mass or more. On the other hand, the upper limit of the water content in the solvent is typically 100% by mass. In one embodiment, the solvent of the aqueous adhesive contains substantially no organic solvent. In other words, the water content in the solvent is, for example, 98% by mass or more and 100% by mass or less. When the water content in the solvent of the aqueous adhesive is within this range, the solvent can be smoothly evaporated when the aqueous adhesive is applied and dried, and the thinning of the adhesive layer can be stably achieved. Furthermore, since water causes little damage to the polarizer and phase difference film, optical laminates with excellent quality can be stably manufactured.

[0083] The solvent content in water-based adhesives is arbitrarily and appropriately adjusted according to the curing component content. Water-based adhesives may contain any suitable additives as needed. Examples of additives include amino compounds, epoxy compounds, binder resins, surfactants, plasticizers, tackifiers, low molecular weight polymers, polymerizable monomers, surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, UV absorbers, polymerization inhibitors, titanium coupling agents, inorganic or organic fillers, metal powders, particulate matter, and foils. Additives may be used alone or in combination. Among the additives, surfactants are preferred.

[0084] The content ratio of the additive is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, and especially preferably 0.5 parts by mass or less, per 1 part by mass of the hardening component. On the other hand, the lower limit of the content ratio of the additive is typically 0 parts by mass per 1 part by mass of the hardening component.

[0085] B-4. Second Adhesive Layer The second adhesive layer 51 is located between the first phase difference film 1 and the second phase difference film 2 in the stacking direction of the optical laminate 100, and bonds the first phase difference film 1 and the second phase difference film 2 together. The second adhesive layer 51 is in contact with each of the first phase difference film 1 and the second phase difference film 2. In one embodiment, the contact surface of the first phase difference film 1 with the second adhesive layer 51, and / or the contact surface of the second phase difference film 2 with the second adhesive layer 51 is an activated surface that has undergone an activation treatment. With this configuration, polar groups such as hydroxyl groups can be introduced to the surface of the phase difference film, and as a result, the adhesion between the phase difference film and the second adhesive layer can be improved. Examples of activation treatments include corona treatment, plasma treatment, saponification treatment, and low-pressure UV treatment. The activation treatments can be carried out alone or in combination.

[0086] The second adhesive layer 51 will be described in the same manner as the first adhesive layer 41 described above. Therefore, a detailed description of the second adhesive layer 51 will be omitted as appropriate. The second adhesive layer 51 contains a cured product of any suitable adhesive. Examples of adhesives include water-based adhesives; thermosetting adhesives; moisture-curing adhesives; and active energy ray-curing adhesives such as ultraviolet-curing adhesives (UV adhesives). The adhesives can be used alone or in combination.

[0087] In one embodiment, the second adhesive layer 51 contains the cured product of the water-based adhesive described above. When the adhesive layer contains the cured product of the water-based adhesive, the thickness d2 of the second adhesive layer can be stably adjusted to the above range, and the occurrence of interference unevenness in the optical laminate can be sufficiently suppressed. Furthermore, when each of the first adhesive layer 41 and the second adhesive layer 51 contains the cured product of the water-based adhesive described above, each of the first adhesive layer and the second adhesive layer can be sufficiently thinned, and as a result, unevenness in the optical path length in the optical laminate can be significantly suppressed. In this case, the cured product of the water-based adhesive contained in the first adhesive layer 41 and the cured product of the water-based adhesive contained in the second adhesive layer 51 may be the same as or different from each other. In one embodiment, the cured product of the water-based adhesive contained in the first adhesive layer 41 and the cured product of the water-based adhesive contained in the second adhesive layer 51 are the same as each other. This allows the refractive index nθ1 of the first adhesive layer 41 in the transmission axis direction and the refractive index nθ3 of the second adhesive layer 51 in the transmission axis direction to be adjusted to be substantially the same.

[0088] B-5. Adhesive Layer In one embodiment, the optical laminate 100 further comprises an adhesive layer 6. The adhesive layer 6 is located on the side of the second phase difference film 2 opposite to the first phase difference film 1. In the illustrated example, the adhesive layer 6 is laminated on the surface of the second liquid crystal alignment solidification layer 21 opposite to the first phase difference film 1. With this configuration, the optical laminate can be attached by the adhesive layer 6 to any suitable substrate (typically an image display panel) provided by an image display device.

[0089] The adhesive layer 6 is composed of any suitable adhesive. Examples of adhesives include (meth)acrylic adhesives, urethane adhesives, and silicone adhesives. The adhesives can be used alone or in combination. Among the adhesives, (meth)acrylic adhesives are preferred.

[0090] The thickness of the adhesive layer 6 is, for example, 3 μm or more, preferably 5 μm or more, and preferably 10 μm or more. On the other hand, the thickness of the adhesive layer 6 is, for example, 50 μm or less, and preferably 30 μm or less.

[0091] B-6. The peel-off liner optical laminate 100 may further include a peel-off liner 7. The peel-off liner 7 is attached to the surface of the adhesive layer 6 opposite to the second phase difference film 2. Typically, the peel-off liner 7 is temporarily attached to the adhesive layer 6 until the optical laminate is attached to the substrate, and is peeled off from the adhesive layer 6 when the optical laminate is attached.

[0092] The release liner 7 contains any suitable resin material. Examples of resin materials include polyethylene terephthalate (PET), polyethylene, and polypropylene. The resin materials can be used alone or in combination.

[0093] In one embodiment, a release layer is provided on the contact surface of the release liner 7 with the adhesive layer 6. The release layer typically contains a release agent. Examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents, with silicone-based release agents being preferred, and vinyl group-containing addition-type silicones being even more preferred. The release agents can be used alone or in combination. The thickness of the release layer is, for example, 50 nm to 400 nm.

[0094] C. Method for Manufacturing an Optical Laminate Next, a method for manufacturing an optical laminate 100 according to one embodiment will be described. In one embodiment, the method for manufacturing an optical laminate includes a step of bonding a first phase difference film 1 and a second phase difference film 2 (first bonding step), and a step of bonding the first phase difference film 1 and a polarizing plate 3 (second bonding step). In one embodiment, the method for manufacturing an optical laminate includes the first bonding step and the second bonding step in this order.

[0095] C-1. First Lamination Process In one embodiment, first, the first phase difference film 1 and the second phase difference film 2 described above are prepared. The first phase difference film 1 and the second phase difference film 2 each preferably have an elongated shape. If the first phase difference film 1 and / or the second phase difference film 2 include a liquid crystal alignment solidification layer, the liquid crystal alignment solidification layer is prepared in a state supported on the coated substrate. Furthermore, if necessary, the activation treatment described above is performed on the surface of the first phase difference film 1 and / or the second phase difference film 2 in the thickness direction.

[0096] Next, the first phase difference film 1 and the second phase difference film 2 are bonded together by any suitable means. In one embodiment, the first phase difference film 1 and the second phase difference film 2 are bonded together by roll-to-roll such that their longitudinal directions are substantially parallel. More specifically, the adhesive described above is applied to at least one surface (preferably the activated surface) of the first phase difference film 1 and the second phase difference film 2 by any suitable method. Examples of adhesive application methods include dip coating, curtain coating, spray coating, bar coating, rod coating, roll coating, die coating, and gravure coating, with gravure coating being preferred.

[0097] Next, the first phase difference film 1 and the second phase difference film 2 are overlapped so as to sandwich the adhesive coating film. Then, the adhesive is cured by an appropriate method depending on the adhesive. For example, if the adhesive contains a water-based adhesive, the adhesive coating film is heated and dried. The heating temperature is, for example, 35°C to 120°C. The heating time is, for example, 30 seconds to 10 minutes. At this time, the solvent contained in the coating film volatilizes and the curing component contained in the coating film hardens. As a result, a second adhesive layer 51 containing the cured product of the water-based adhesive is formed, and the first phase difference film 1 and the second phase difference film 2 are bonded together by the second adhesive layer 51. Also, if the first phase difference film 1 and / or the second phase difference film 2 contains a liquid crystal alignment solidification layer, the coated substrate is peeled off and removed from the liquid crystal alignment solidification layer as necessary. By the above, an intermediate laminate having a laminated structure of first phase difference film 1 / second adhesive layer 51 / second phase difference film 2 is prepared.

[0098] C-2. Second Lamination Step Next, prepare the polarizing plate 3 described above. The polarizing plate 3 preferably has a long shape. Then, the intermediate laminate prepared in the first lamination step described above and the polarizing plate 3 are bonded together by any suitable means. In one embodiment, the intermediate laminate and the polarizing plate 3 are bonded together by roll-to-roll so that their longitudinal directions are substantially parallel. More specifically, the adhesive described above is applied to the surface of the first phase difference film 1 in the intermediate laminate and / or the surface of the polarizing plate 3 (the surface of the polarizer 31 in the illustrated example) by any suitable method. As an example of the method for applying the adhesive, the same application method as in the first lamination step described above can be used.

[0099] Next, the intermediate laminate and the polarizing plate 3 are stacked on top of each other, with the adhesive coating film in between. Then, the adhesive is cured using an appropriate method depending on the adhesive. For example, if the adhesive contains a water-based adhesive, the adhesive coating film is heated and dried in the same manner as described above. At this time, the solvent contained in the coating film evaporates, and the curing component contained in the coating film hardens. As a result, a first adhesive layer 41 containing the cured product of the water-based adhesive is formed, and the polarizing plate 3 and the first phase difference film 1 are bonded together by the first adhesive layer 41.

[0100] As described above, an optical laminate 100 having a laminated structure of polarizing plate 3 / first adhesive layer 41 / first phase difference film 1 / second adhesive layer 51 / second phase difference film 2 is prepared. Subsequently, if necessary, the adhesive described above may be applied to the surface of the second phase difference film 2 opposite to the second adhesive layer 51 by any appropriate method to form an adhesive layer 6.

[0101] D. Another Embodiment The optical laminate 100 in the above embodiment satisfies formula (1) above. This suppresses the reflection of visible light incident on the optical laminate at the interface between the first phase difference film and the adjacent layer (typically the first adhesive layer or the second adhesive layer), and suppresses interference of the reflected light. However, the present invention is not limited thereto. In one embodiment, the refractive index nθ2 of the first phase difference film 1 in the transmission axis direction is less than 1.60, and at least one of the thickness d1 of the first adhesive layer 4 and the thickness d2 of the second adhesive layer 5 is less than 80 nm. With such a configuration, even if the optical laminate does not satisfy formula (1) above, it is possible to stably suppress the reflection of visible light incident on the optical laminate at the interface between the first phase difference film and the adjacent layer (typically the first adhesive layer or the second adhesive layer), and suppress interference of the reflected light. In another embodiment, the thickness d1 of the first adhesive layer 4 and the thickness d2 of the second adhesive layer 5 are both less than 80 nm. This also allows for sufficient suppression of visible light reflection and reflected light interference, even if the optical laminate does not satisfy formula (1) above.

[0102] E. Image Display Device The optical laminates described in sections A to D above can be applied to any suitable image display device. Therefore, one embodiment of the present invention also includes an image display device using such an optical laminate. Examples of image display devices include liquid crystal displays and organic EL displays, and preferably organic EL displays. An image display device according to an embodiment of the present invention comprises an image display panel and the optical laminate 100 described above. The image display panel typically includes an image display cell. The optical laminate 100 is positioned on the viewing side of the image display panel. The optical laminate 100 is typically attached to the image display panel by an adhesive layer 6. In the image display device, the polarizing plate 3 is located on the viewing side, i.e., opposite to the image display panel, with respect to the first phase difference film 1, and the second phase difference film 2 is located between the first phase difference film 1 and the image display panel. The optical laminate 100 has any suitable shape depending on the image display device to which it is applied. The size of the optical laminate 100 is adjusted arbitrarily and appropriately. Since such an image display device is equipped with an optical laminate that can suppress the reflection of visible light and the interference of reflected light, it can significantly suppress interference unevenness that causes black displays to appear colored.

[0103] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows.

[0104] (1) The adhesives used in the refractive index measurement examples and comparative examples were coated onto a cycloolefin polymer film (COP film) (thickness 100 μm), and after laminating the same COP film onto the coated surface, it was cured to obtain a cured layer (single film). The coating films composed of the water-based adhesives in Preparation Examples 1 and 2 were cured by heating and drying at 60°C for 10 minutes. On the other hand, the coating films composed of the UV-curable adhesives in Preparation Examples 3A to 3E were cured by irradiation with ultraviolet light. The refractive index in the plane and the refractive index in the thickness direction of the obtained cured layer were measured using a prism coupler (Sylon Technology Co., Ltd., product name "SPA-4000"). The measurement wavelength was 594 nm and the measurement temperature was 25°C. The adhesive layer was optically isotropic. The refractive index in the plane of the adhesive layer was defined as the refractive index of the adhesive layer in the transmission axis direction nθ. Furthermore, the phase difference of the phase difference films (liquid crystal alignment solidification layers) used in the examples and comparative examples was automatically measured using Axoscan (manufactured by Axometrics). The measurement wavelength was 550 nm or 594 nm, and the measurement temperature was 25°C. nx, ny, and nz were calculated from the following simultaneous equations: Re(594) = (nx - ny) × d Nz = Rth(594) / Re(594) = (nx - nz) / (nx - ny) In addition, the equation of the ellipse (x ２ / a ２ ) + (y ２ / b ２ In the equation ) = 1, let a be nx and b be ny, and let x and y be the refractive indices in the x and y directions at the angle θ on the ellipse. Solve the simultaneous equations from y = x(tanθ) and the above nx and ny, and √(x ２ +y ２ The refractive index nθ of the phase difference film (liquid crystal alignment solidification layer) in the width direction (direction perpendicular to the length direction and thickness direction) was calculated using the following method. These results are shown in Tables 1 to 4.

[0105] (2) Measurement of the thickness of the adhesive layer The cross-sections of the optical laminates obtained in the examples and comparative examples were observed using a transmission electron microscope (TEM) with a Hitachi HT7820 instrument by the freeze ultrathin sectioning method including heavy metal staining. The acceleration voltage during measurement was 100 kV. The thickness of the first adhesive layer and the second adhesive layer were measured using this method. The results are shown in Tables 1 to 4.

[0106] (3) Evaluation of the Visibility of Interference Unevenness An organic EL display device (Samsung Galaxy A41) was disassembled, and the cover glass and polarizer were removed from the organic EL display device. Then, the optical laminates obtained in the examples and comparative examples were bonded to the organic EL panel with an adhesive layer to prepare samples. Next, the obtained samples were placed under a three-wavelength fluorescent lamp, and polarizers were placed between the fluorescent lamp and the sample, and between the sample and the observer, creating a crossed nicol relationship (the absorption axis directions of the two polarizers are orthogonal to each other). Then, with the organic EL panel turned off, the samples were observed visually, and interference unevenness was evaluated according to the following criteria: Level 1 (Excellent): No interference unevenness is visible. Level 2 (Good): Slight interference unevenness is visible. Level 3 (Poor): Weak interference unevenness is visible. Level 4 (Poor): Strong interference unevenness is visible. The results are shown in Tables 1 to 4.

[0107] <Preparation of Adhesives> <<Preparation Example 1>> An aqueous solution of silane coupling agents was prepared by adding an amino-based silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603") and an epoxy-based silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403") to water. In the aqueous solution of silane coupling agents, the mass ratio of the amino-based silane coupling agent to the epoxy-based silane coupling agent was 1:1 (molar ratio 51.5:48.5), and the total concentration of the amino-based silane coupling agent and the epoxy-based silane coupling agent was 1.0% by mass. Subsequently, 0.2 parts by mass of a surfactant (manufactured by Nisshin Chemical Co., Ltd., product name "EXP4200") was added to 100 parts by mass of the aqueous solution of silane coupling agents to prepare an aqueous adhesive.

[0108] <<Preparation Example 2>> An aqueous solution of the amino-silane coupling agent (N,N'-bis(2-aminoethyl)-6-(3-trihydroxysilylpropyl)amino-1,3,5-triazine-2,4-diamine, manufactured by Iou Chemical Research Institute) was added to water to prepare an aqueous solution of the amino-silane coupling agent. The concentration of the aqueous solution of the amino-silane coupling agent was 1.0% by mass. Next, 0.2 parts by mass of a surfactant (manufactured by Nisshin Chemical Co., Ltd., trade name "EXP4200") was added to 100 parts by mass of the aqueous solution of the amino-silane coupling agent to prepare an aqueous adhesive.

[0109] <<Preparation Example 3A>> 25 parts by mass of acryloyl morpholine (trade name "ACMO", manufactured by KJ Chemicals), 10 parts by mass of ε-caprolactone 1 mol modified 2-hydroxyethyl acrylate (trade name "PLACCEL FA1DDM", manufactured by Daicel Chemicals), 10 parts by mass of lauryl acrylate (trade name "Light Acrylate L-A", manufactured by Kyoeisha), 20 parts by mass of isostearyl acrylate (trade name "ISTA", manufactured by Osaka Organic Chemical Industry Co., Ltd.), 15 parts by mass of 1,9-nonanediol diacrylate (trade name "Light Acrylate 1.9ND-A", manufactured by Kyoeisha Chemicals Co., Ltd.), 15 parts by mass of acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad One part by mass of 819 (manufactured by IGM Resins B.V.), two parts by mass of 1-hydroxycyclohexylphenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and two parts by mass of diethylthioxanthone (trade name "KAYACRE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for one hour to prepare an ultraviolet-curing adhesive.

[0110] <<Preparation Example 3B>> 10 parts by mass of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals), 4 parts by mass of 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals), 60 parts by mass of acryloyl morpholine (trade name "ACMO", manufactured by KJ Chemicals), 11 parts by mass of tripropylene glycol diacrylate (trade name "Aronics M-220", manufactured by Toagosei Co., Ltd.), 1 part by mass of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 10 parts by mass of acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", IGM Resins One part by mass of (manufactured by B.V. Co.), two parts by mass of 1-hydroxycyclohexylphenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V. Co.), and one part by mass of diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for one hour to prepare an ultraviolet-curing adhesive.

[0111] <<Preparation Example 3C>> 60 parts by mass of Ogusol EA-F5710 (manufactured by Osaka Gas Chemical Co., Ltd.), 10 parts by mass of Praxel FA1DDM (manufactured by Daicel Corporation), 20 parts by mass of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 5 parts by mass of ARFON UP-1190 (manufactured by Toagosei Co., Ltd.), 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and diethylthioxanthone (trade name "KAYACURE Two parts by mass of "DETX-S" (manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for one hour to prepare an ultraviolet-curing adhesive.

[0112] <<Preparation Example 3D>> (Preparation of Dispersant) 415 g (1 mol) of tristyrenated phenol and 1 g (0.018 mol) of potassium hydroxide were charged into an autoclave and mixed uniformly. Under conditions of 130°C, 352 g (8 mol) of ethylene oxide (EO) was added dropwise to the reaction system. After the addition of ethylene oxide was completed, the mixture was aged for 1 hour at 130°C while maintaining a pressure of 0.1 MPa to obtain an 8 mol EO adduct of tristyrenated phenol. 767 g (1 mol) of the obtained 8 mol EO adduct of tristyrenated phenol and 152 g (1.3 mol) of sodium monochloroacetate were placed in a reactor and stirred until homogenized. Next, under conditions of 60°C, 52 g of sodium hydroxide was added, and then the temperature was raised to 80°C and aged for 3 hours. After aging, the mixture was cooled to 50°C, and 117 g (1.2 moles) of 98% sulfuric acid was added dropwise at the same temperature to obtain a white suspension. This white suspension was washed with distilled water, and the solvent was removed by vacuum distillation to obtain a dispersant. (Preparation of Zirconia Dispersion) 100 parts by mass of a methanol dispersion of zirconium oxide (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-CM", average particle size (D50) based on dynamic light scattering method: 8 nm, zirconium oxide solid content concentration: 30%) was mixed with 1.5 parts by mass of the dispersant obtained above and 28.5 parts by mass of m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A"). The mixture was then mixed. Next, the solvent was removed by vacuum using a rotary evaporator to obtain a zirconia dispersion, which is a monomer dispersion of zirconium oxide. This zirconia dispersion contained zirconium oxide / dispersant / POB-A in a mass ratio of 50 / 2.5 / 47.5.(Preparation of adhesive) 35 parts by mass of zirconia dispersion, 40 parts by mass of "POB-A", 10 parts by mass of 4-hydroxybutyl acrylate, 10 parts by mass of tripropylene glycol diacrylate (trade name "Aronics M-220", manufactured by Toagosei Co., Ltd.), 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 2 parts by mass of diethylthioxanthone (trade name "KAYACRE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare an ultraviolet-curable adhesive.

[0113] <<Preparation Example 3E>> 55 parts by mass of zirconia dispersion, 25 parts by mass of "POB-A", 10 parts by mass of 4-hydroxybutyl acrylate, 10 parts by mass of "Aronics M-220", 1 part by mass of "Omnirad 819", 2 parts by mass of "Omnirad 184", and 2 parts by mass of "KAYACURE DETX-S" were stirred at 50°C for 1 hour to prepare an ultraviolet-curable adhesive.

[0114] <Preparation of Liquid Crystal Alignment Solidification Layer> <<Preparation Example 4>> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242", chemical formula below) was dissolved in cyclopentanone to prepare a solution with a solid content of 30% by mass. A surfactant (BYK-361N, manufactured by BYK Chemie) and a photopolymerization initiator (Omnirad907, manufactured by IGM Resins) were added to this solution to prepare a liquid crystal coating solution. The amount of surfactant added was 0.01 parts by mass per 100 parts by mass of the photopolymerizable liquid crystal compound. The amount of polymerization initiator added was 3 parts by mass per 100 parts by mass of the photopolymerizable liquid crystal compound. As an orientation substrate, the surface of a long polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth to perform an orientation treatment. The direction of the orientation treatment was set so that when the film was bonded to a polarizing plate, it was 15° from the viewing side relative to the absorption axis of the polarizer. In other words, the angle between the long direction of the orientation substrate and the direction of the orientation treatment was 15°. Next, the liquid crystal coating solution described above was applied to the orientation-treated surface using a bar coater, and the liquid crystal compound was oriented by heating and drying at 100°C for 3 minutes. The liquid crystal layer thus formed was cooled to room temperature (25°C), and then exposed to a nitrogen atmosphere with an integrated light intensity of 400 mJ / cm². ２ The liquid crystal layer was cured by irradiation with ultraviolet light. This formed a liquid crystal alignment solidified layer on the alignment substrate. The liquid crystal alignment solidified layer was elongated. The thickness of the liquid crystal alignment solidified layer was 2 μm. The liquid crystal alignment solidified layer had a refractive index of nx > ny = nz. In the liquid crystal alignment solidified layer, the in-plane phase difference Re(550) was 240 nm, and the phase difference Rth(550) in the thickness direction was 240 nm. In other words, the liquid crystal alignment solidified layer can function as a λ / 2 plate.

[0115] <<Preparation Example 5>> A liquid crystal alignment solidification layer was formed on the alignment substrate in the same manner as in Preparation Example 4, except that the direction of the alignment treatment was changed to a 75° direction relative to the absorption axis axis of the polarizer (longitudinal direction of the alignment substrate) as viewed from the viewing side. The thickness of the liquid crystal alignment solidification layer was 2 μm. The liquid crystal alignment solidification layer had a refractive index of nx > ny = nz. In the liquid crystal alignment solidification layer, the in-plane phase difference Re(550) was 240 nm, and the phase difference Rth(550) in the thickness direction was 240 nm. In other words, the liquid crystal alignment solidification layer can function as a λ / 2 plate.

[0116] <<Preparation Example 6>> A liquid crystal alignment solidification layer was formed on the alignment substrate in the same manner as in Preparation Example 4, except that the direction of the alignment treatment was changed to a 75° direction relative to the polarizer's absorption axis axis (longitudinal direction of the alignment substrate) as viewed from the viewing side, and the coating thickness was changed. The thickness of the liquid crystal alignment solidification layer was 1 μm. The liquid crystal alignment solidification layer had a refractive index of nx > ny = nz. In the liquid crystal alignment solidification layer, the in-plane phase difference Re(550) was 120 nm, and the phase difference Rth(550) in the thickness direction was 120 nm. In other words, the liquid crystal alignment solidification layer can function as a λ / 4 plate.

[0117] <<Preparation Example 7>> A liquid crystal alignment solidification layer was formed on the alignment substrate in the same manner as in Preparation Example 6, except that the direction of the alignment treatment was changed to a 15° direction relative to the polarizer's absorption axis axis (longitudinal direction of the alignment substrate) as viewed from the viewing side. The thickness of the liquid crystal alignment solidification layer was 1 μm. The liquid crystal alignment solidification layer had a refractive index of nx > ny = nz. In the liquid crystal alignment solidification layer, the in-plane phase difference Re(550) was 120 nm, and the phase difference Rth(550) in the thickness direction was 120 nm. In other words, the liquid crystal alignment solidification layer can function as a λ / 4 plate.

[0118] <Preparation of Polarizing Plate> <<Preparation Example 8>> As a thermoplastic resin substrate, an amorphous isophthalic copolymer polyethylene terephthalate film (thickness: 100 μm) in a long length with a Tg of approximately 75°C was used, and one side of the film was subjected to corona treatment. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by mass of a PVA-based resin, which was a mixture of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosephymer") in a 9:1 ratio, with 13 parts by mass of potassium iodide added, in water. The PVA aqueous solution was applied to the corona-treated surface of the thermoplastic resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm on the thermoplastic resin substrate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (air-assisted stretching treatment). Next, the laminate was immersed for 30 seconds in an insolubilization bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 4 parts by mass of boric acid with 100 parts by mass of water) (insolubilization treatment). Next, the laminate was immersed for 60 seconds in a staining bath at a liquid temperature of 30°C (a iodine aqueous solution obtained by mixing iodine and potassium iodide in a mass ratio of 1:7 with 100 parts by mass of water) while adjusting the concentration so that the final transmittance (Ts) of the polarizer obtained would be the desired value (staining treatment). Next, the laminate was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with 100 parts by mass of water) (crosslinking treatment). Subsequently, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4% by mass, potassium iodide concentration 5% by mass) at a liquid temperature of 70°C and uniaxially stretched between rolls with different peripheral speeds to achieve a total stretch ratio of 5.5 times in the longitudinal direction (water stretching treatment). After that, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by mass of potassium iodide with 100 parts by mass of water) (washing treatment). After that, the laminate was dried in an oven maintained at approximately 90°C while being brought into contact with a heated roll made of stainless steel with a surface temperature maintained at approximately 75°C (drying shrinkage treatment). In this way, a polarizer was formed on the thermoplastic resin substrate. The thickness of the polarizer was approximately 5.0 μm.

[0119] A stretched film containing COP (ZD12, manufactured by Nippon Zeon Co., Ltd.) was prepared as a protective layer. The protective layer had a refractive index of nx > ny > nz. The in-plane phase difference Re(550) of the protective layer was 99 nm. The thickness of the protective layer was 25 μm. Next, the polarizer and the protective layer were bonded together with an ultraviolet-curing adhesive. Then, the ultraviolet-curing adhesive was irradiated with ultraviolet light to cure it, forming a UV adhesive layer containing the cured product of the ultraviolet-curing adhesive. The thickness of the UV adhesive layer was 1 μm. Next, the thermoplastic resin substrate was peeled off and removed from the polarizer. This prepared a polarizer plate having a laminated structure of protective layer / polarizer. The polarizer plate was elongated. The angle between the longitudinal direction of the polarizer plate and the absorption axis direction of the polarizer was 0°, and the angle between the longitudinal direction of the polarizer plate and the transmission axis direction of the polarizer was 90°. In the polarizing plate, the angle between the absorption axis direction of the polarizer (i.e., the longitudinal direction of the polarizing plate) and the slow phase axis direction of the protective layer was 45°.

[0120] [Comparative Examples 1-5] The liquid crystal alignment solidification layer obtained in Preparation Example 4 was used as the first phase difference film (i.e., the first liquid crystal alignment solidification layer), and the liquid crystal alignment solidification layer obtained in Preparation Example 6 was used as the second phase difference film (i.e., the second liquid crystal alignment solidification layer). The surface of the first liquid crystal alignment solidification layer obtained in Preparation Example 4 and the surface of the second liquid crystal alignment solidification layer obtained in Preparation Example 6 were treated using a corona treatment machine at a treatment density of 50 W・min / m ２Corona treatment was performed. Next, while the first liquid crystal alignment solidified layer was conveyed in the longitudinal direction, the ultraviolet-curable adhesive obtained in Preparation Example 3A was applied to the corona-treated surface of the first liquid crystal alignment solidified layer using an MCD coater (manufactured by Fuji Machinery Co., Ltd., cell shape: honeycomb, gravure roll line count: 1000 lines / inch, rotation speed 130% / line speed) to form a coating film on the first liquid crystal alignment solidified layer. Similarly, the ultraviolet-curable adhesive obtained in Preparation Example 3A was applied to the corona-treated surface of the second liquid crystal alignment solidified layer. After that, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer were bonded together using a bonding roll machine so that their longitudinal directions were substantially parallel. More specifically, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer were passed through the bonding roll machine so that the coating film on the first liquid crystal alignment solidified layer and the coating film on the second liquid crystal alignment solidified layer were in contact with each other. The line speeds for the first liquid crystal alignment solidification layer and the second liquid crystal alignment solidification layer were 15 m / min. At this time, the angle between the slow axis direction of the first liquid crystal alignment solidification layer and the slow axis direction of the second liquid crystal alignment solidification layer was 60°. Subsequently, the coating film was irradiated with ultraviolet light to cure the ultraviolet-curable adhesive and form a second adhesive layer as the second adhesive layer. Next, the alignment substrate was peeled off and removed from both the first and second liquid crystal alignment solidification layers. This prepared an intermediate laminate having a laminated structure of first liquid crystal alignment solidification layer / second adhesive layer / second liquid crystal alignment solidification layer.

[0121] Next, the polarizing plate obtained in Preparation Example 8 and the intermediate laminate obtained above were bonded together using an ultraviolet-curing adhesive obtained in any of Preparation Examples 3A to 3E shown in Table 1 (hereinafter sometimes referred to as the ultraviolet-curing adhesive shown in Table 1). More specifically, while the polarizing plate was transported in the longitudinal direction, the ultraviolet-curing adhesive shown in Table 1 was applied to the surface of the polarizer opposite to the protective layer using an MCD coater (manufactured by Fuji Machinery Co., Ltd., cell shape: honeycomb, gravure roll line count: 1000 lines / inch, rotation speed 130% / line speed) to form a coating film on the polarizer. Similarly, the ultraviolet-curing adhesive shown in Table 1 was applied to the surface of the first liquid crystal alignment solidification layer opposite to the second liquid crystal alignment solidification layer. After that, the polarizing plate and the intermediate laminate were bonded together using a bonding roll machine so that their longitudinal directions were substantially parallel. More specifically, the polarizing plate and the intermediate laminate were passed through a lamination roll machine so that the coating on the polarizer and the coating on the first liquid crystal alignment solidification layer were in contact with each other. Next, the coating was irradiated with ultraviolet light to cure the ultraviolet-curable adhesive and form the first adhesive layer. Subsequently, a (meth)acrylic adhesive was applied to the surface of the second liquid crystal alignment solidification layer opposite to the second adhesive layer to form an adhesive layer. The thickness of the adhesive layer was 25 μm.

[0122] Based on the above, an optical laminate having a laminated structure of protective layer / polarizer / first adhesive layer / first liquid crystal alignment solidification layer (λ / 2 plates) / second adhesive layer / second liquid crystal alignment solidification layer (λ / 4 plates) / adhesive layer was manufactured. The optical laminate had a long shape. The longitudinal direction of the optical laminate and the absorption axis direction of the polarizer were substantially parallel, and the width direction of the optical laminate and the transmission axis direction of the polarizer were substantially parallel. The refractive index nθ1 of the first adhesive layer in the transmission axis direction of the polarizer, the refractive index nθ2 of the first liquid crystal alignment solidification layer in the transmission axis direction, the refractive index nθ3 of the second adhesive layer in the transmission axis direction, the refractive index nθ4 of the second liquid crystal alignment solidification layer in the transmission axis direction, the thickness d1 of the first adhesive layer, the thickness d2 of the second adhesive layer 51, and the interference uniformity parameter (value calculated from the above formula (1)) are shown in Table 1.

[0123] [Examples 1-4] Optical laminates were manufactured in the same manner as in Comparative Example 1, except that the ultraviolet-curable adhesive constituting the first adhesive layer was changed to the water-based adhesive obtained in Preparation Example 1, the thickness of the coating film of the water-based adhesive was adjusted, and the coating film was heated and dried at 60°C for 10 minutes to form the first adhesive layer.

[0124] [Examples 5-7] Optical laminates were manufactured in the same manner as in Examples 2-4, except that the ultraviolet-curing adhesive constituting the first adhesive layer was changed to the water-based adhesive obtained in Preparation Example 2.

[0125] [Examples 8-19] Optical laminates were manufactured in the same manner as Comparative Examples 1-5 and Examples 1-7, except that the UV-curable adhesive constituting the second adhesive layer was changed to the water-based adhesive obtained in Preparation Example 1, the thickness of the coating film of the water-based adhesive was adjusted, and the coating film was heated and dried at 60°C for 10 minutes to form the second adhesive layer. The refractive index nθ1 of the first adhesive layer in the transmission axis direction of the polarizer, the refractive index nθ2 of the first liquid crystal alignment solidification layer in the transmission axis direction, the refractive index nθ3 of the second adhesive layer in the transmission axis direction, the refractive index nθ4 of the second liquid crystal alignment solidification layer in the transmission axis direction, the thickness d1 of the first adhesive layer, the thickness d2 of the second adhesive layer 51, and the interference uniformity parameter (value calculated from the above formula (1)) are shown in Table 2.

[0126] [Examples 20-22 and Comparative Examples 6-14] Optical laminates were manufactured in the same manner as Comparative Examples 1-5 and Examples 1-7, except that the liquid crystal alignment solidification layer obtained in Preparation Example 5 was used as the first phase difference film, and the liquid crystal alignment solidification layer obtained in Preparation Example 7 was used as the second phase difference film. The refractive index nθ1 of the first adhesive layer in the transmission axis direction of the polarizer, the refractive index nθ2 of the first liquid crystal alignment solidification layer in the transmission axis direction, the refractive index nθ3 of the second adhesive layer in the transmission axis direction, the refractive index nθ4 of the second liquid crystal alignment solidification layer in the transmission axis direction, the thickness d1 of the first adhesive layer, the thickness d2 of the second adhesive layer 51, and the interference uniformity parameter (value calculated from the above formula (1)) are shown in Table 3.

[0127] [Examples 23-29 and Comparative Examples 15-19] Optical laminates were manufactured in the same manner as in Examples 8-19, except that the liquid crystal alignment solidification layer obtained in Preparation Example 5 was used as the first phase difference film, and the liquid crystal alignment solidification layer obtained in Preparation Example 7 was used as the second phase difference film. The refractive index nθ1 of the first adhesive layer in the transmission axis direction of the polarizer, the refractive index nθ2 of the first liquid crystal alignment solidification layer in the transmission axis direction, the refractive index nθ3 of the second adhesive layer in the transmission axis direction, the refractive index nθ4 of the second liquid crystal alignment solidification layer in the transmission axis direction, the thickness d1 of the first adhesive layer, the thickness d2 of the second adhesive layer 51, and the interference uniformity parameter (value calculated from the above formula (1)) are shown in Table 4.

[0128]

[0129]

[0130]

[0131]

[0132] [Evaluation] As is clear from Tables 1 to 4, if the optical laminate satisfies the above formula (1), interference unevenness can be reduced in an image display device equipped with the optical laminate. Furthermore, if the refractive index nθ2 of the first phase difference film in the transmission axis direction is less than 1.60, and at least one of the thickness d1 of the first adhesive layer and the thickness d2 of the second adhesive layer is less than 80 nm, interference unevenness can be stably reduced in an image display device. Moreover, if the thickness d1 of the first adhesive layer and the thickness d2 of the second adhesive layer are both less than 80 nm, interference unevenness can be stably reduced in an image display device.

[0133] The optical laminate manufactured according to the embodiments of the present invention can be suitably used in image display devices (typically liquid crystal display devices and organic EL display devices).

[0134] 1. First phase difference film 11. First liquid crystal alignment solidification layer 2. Second phase difference film 21. Second liquid crystal alignment solidification layer 3. Polarizing plate 31. Polarizer 32. Protective layer 4. First adhesive layer 41. First adhesive layer 5. Second adhesive layer 51. Second adhesive layer 6. Adhesive layer 100. Optical laminate

Claims

1. An optical laminate comprising a polarizing plate containing a polarizer, a first adhesive layer, a first phase difference film, and a second adhesive layer in this order, satisfying the following formula (1): [(nθ1 - nθ2)] ２ + (nθ3 - nθ2) ２ ] × d1 × d2 < 1000 ... (1) (In equation (1), nθ1 represents the refractive index of the first adhesive layer in the transmission axis direction of the polarizer; nθ2 represents the refractive index of the first phase difference film in the transmission axis direction of the polarizer; nθ3 represents the refractive index of the second adhesive layer in the transmission axis direction of the polarizer; d1 represents the thickness [nm] of the first adhesive layer; d2 represents the thickness [nm] of the second adhesive layer.) 2. The optical laminate according to claim 1, satisfying the following formula (2): [(nθ1 - nθ2)] ２ + (nθ3 - nθ2) ２ ] × d1 × d2 < 500 ... (2) (In equation (2), nθ1 represents the refractive index of the first adhesive layer in the transmission axis direction of the polarizer; nθ2 represents the refractive index of the first phase difference film in the transmission axis direction of the polarizer; nθ3 represents the refractive index of the second adhesive layer in the transmission axis direction of the polarizer; d1 represents the thickness [nm] of the first adhesive layer; d2 represents the thickness [nm] of the second adhesive layer.) 3. The optical laminate according to claim 1, wherein the thickness d1 of the first adhesive layer is less than 80 nm.

4. The optical laminate according to claim 1, wherein the thickness d2 of the second adhesive layer is less than 80 nm.

5. The optical laminate according to claim 1, wherein the refractive index nθ2 of the first phase difference film in the transmission axis direction is less than 1.

60.

6. The optical laminate according to claim 1, wherein the first adhesive layer is a first adhesive layer.

7. The optical laminate according to claim 6, wherein the first adhesive layer comprises a cured product of an aqueous adhesive containing an organosilicon compound.

8. The optical laminate according to claim 7, wherein the organosilicon compound comprises an amino-based silane coupling agent.

9. The optical laminate according to claim 7, wherein the organosilicon compound comprises an epoxy-based silane coupling agent.

10. The optical laminate according to claim 1, wherein the second adhesive layer is a second adhesive layer.

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

12. The optical laminate according to claim 1, further comprising a second phase difference film located on the opposite side of the second adhesive layer from the first phase difference film.

13. The optical laminate according to claim 12, wherein the second phase difference film includes an orientation solidification layer of a liquid crystal compound.

14. The optical laminate according to claim 12, wherein the refractive indices of the first phase difference film and the second phase difference film respectively satisfy the relationship nx > ny.

15. The optical laminate according to claim 1, wherein the polarizing plate further comprises a protective layer located on the opposite side of the polarizer from the first phase difference film, and the protective layer has an in-plane phase difference.

16. An optical laminate comprising, in this order, a polarizing plate containing a polarizer, a first adhesive layer, a first phase difference film, and a second adhesive layer, wherein the refractive index nθ2 of the first phase difference film in the transmission axis direction of the polarizer is less than 1.60, and at least one of the thickness d1 of the first adhesive layer and the thickness d2 of the second adhesive layer is less than 80 nm.

17. An optical laminate comprising, in this order, a polarizing plate containing a polarizer, a first adhesive layer, a first phase difference film, and a second adhesive layer, wherein the thickness d1 of the first adhesive layer and the thickness d2 of the second adhesive layer are each less than 80 nm.

18. An image display device comprising an optical laminate according to any one of claims 1 to 17.

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