Optical laminates and image display devices

Abstract

To provide an optical laminate that can realize an image display device capable of reducing reflective brightness. [Solution] An optical laminate according to an embodiment of the present invention comprises, in this order: a polarizer; a first optical compensation layer whose refractive index characteristics are related to nz > nx = ny; a second optical compensation layer whose refractive index characteristics are related to nx > ny; and a third optical compensation layer whose refractive index characteristics are related to nx > ny. The refractive index characteristics of the second optical compensation layer and / or the third optical compensation layer are related to nx > ny ≥ nz, the in-plane phase difference of the second optical compensation layer and the third optical compensation layer is 10 nm or more and 220 nm or less, the absorption axis direction of the polarizer and the slow axis direction of the second optical compensation layer intersect without being substantially orthogonal, the Nz coefficient of the third optical compensation layer is -4 or more and 0 or less or 0.9 or more and 4 or less, and the first optical compensation layer, the second optical compensation layer and the third optical compensation layer satisfy a specific equation (1).

Description

Technical Field

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

Background Art

[0002] In image display devices, various optical laminates combining a polarizer and an optical compensation film are generally used to compensate for optical characteristics suitable for the application. As such an optical laminate, for example, an elliptical polarizing plate including a polarizer, a first birefringent layer that is a λ / 2 plate, a second birefringent layer that is a λ / 4 plate, and a third birefringent layer having a refractive index characteristic showing a relationship of nz > nx = ny in this order has been proposed (see, for example, Patent Document 1). In addition, in image display devices, external light reflection or background reflection by the display device itself or a reflector used in the display device (for example, a touch panel portion, metal wiring) may be a problem. In particular, an organic EL panel has a highly reflective metal layer, so problems such as external light reflection and background reflection are likely to occur. Therefore, it has been considered to arrange an optical laminate on the viewing side of the image display panel to reduce the reflection luminance of the image display device. However, even if the elliptical polarizing plate described in Patent Document 1 is adopted for an image display device, it is difficult to sufficiently reduce the reflection luminance, and there is room for improvement in reducing the reflection luminance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above conventional problems, and its main object is to provide an optical laminate capable of realizing an image display device with reduced reflection luminance.

Means for Solving the Problems

[0005] The optical laminate according to an embodiment of the present invention includes a polarizer; a first optical compensation layer having refractive index characteristics satisfying nz > nx = ny; a second optical compensation layer having refractive index characteristics satisfying nx > ny; and a third optical compensation layer having refractive index characteristics satisfying nx > ny, in this order. The refractive index characteristics of the second optical compensation layer and / or the third optical compensation layer satisfy nx > ny ≧ nz. The in-plane retardation Re 2 (550) of the second optical compensation layer and the in-plane retardation Re 3 (550) of the third optical compensation layer are each 10 nm or more and 220 nm or less. The absorption axis direction of the polarizer and the slow axis direction of the second optical compensation layer intersect without being substantially orthogonal. The Nz coefficient of the third optical compensation layer is -4 or more and 0 or less, or 0.9 or more and 4 or less. The first optical compensation layer, the second optical compensation layer, and the third optical compensation layer satisfy the following formula (1).

Equation

[0006] According to the optical laminate of the present invention, an image display device capable of reducing reflective brightness can be realized. [Brief explanation of the drawing]

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

[0008] The following describes representative embodiments of the present invention, but the present invention is not limited to these embodiments.

[0009] (Definitions of terms and symbols) The definitions of terms and symbols used in this specification are as follows: (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the refractive index is maximum in the plane (i.e., the slow phase axis direction), "ny" is the refractive index in the direction perpendicular to the slow phase axis in the plane (i.e., the fast phase axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23°C. Re(λ) can be calculated using the formula: Re(λ)=(nx-ny)×d, where d(nm) is the thickness of the layer (film). In this specification, "in-plane phase difference Re(λ) of the first optical compensation layer" is referred to as "Re 1 The term "(λ)" is used to refer to the "in-plane phase difference Re(λ) of the second optical compensation layer" as "Re 2 The term "(λ)" is used to refer to the "in-plane phase difference Re(λ) of the third optical compensation layer" as "Re 3 It is sometimes referred to as "(λ)". (3) Phase difference in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. Rth(λ) is calculated using the formula: Rth(λ)=(nx-nz)×d, where d(nm) is the thickness of the layer (film). In this specification, "Rth(λ)", which is the phase difference in the thickness direction of the first optical compensation layer, is referred to as "Rth 1 The term "(λ)" is used to refer to the "phase difference Rth(λ) in the thickness direction of the second optical compensation layer," and "Rth 2 The term "(λ)" is used to refer to the "phase difference Rth(λ) in the thickness direction of the third optical compensation layer," and "Rth 3 It is sometimes referred to as "(λ)". (4) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re. (5) substantially parallel or orthogonal The expressions "substantially orthogonal" and "approximately orthogonal" encompass the case where the angle between the two directions is 90°±3°, while the expressions "substantially parallel" and "approximately parallel" encompass the case where the angle between the two directions is 0°±3°. Furthermore, "intersecting without substantially orthogonal" means that the angle between the two directions is neither substantially orthogonal nor substantially parallel. More specifically, the expression "intersecting without substantially orthogonal" encompasses the case where the angle between the two directions is greater than 3° but less than 87°, and greater than 93° but less than 177°, preferably between 5° and 85°, or between 95° and 175°.

[0010] A. Overall configuration of the optical laminate Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The illustrated optical laminate 100 comprises, in this order: a polarizer plate 40 including a polarizer 41; a first optical compensation layer 10 whose refractive index characteristics are related to nz > nx = ny; a second optical compensation layer 20 whose refractive index characteristics are related to nx > ny; and a third optical compensation layer 30 whose refractive index characteristics are related to nx > ny. The refractive index characteristics of the second optical compensation layer 20 and / or the third optical compensation layer 30 are related to nx > ny ≥ nz. The in-plane phase difference Re of the second optical compensation layer 20 2 (550) and the in-plane phase difference Re of the third optical compensation layer 30 3 Each of (550) is between 10 nm and 220 nm, preferably between 30 nm and 200 nm. The absorption axis direction of the polarizer 41 and the slow axis direction of the second optical compensation layer 20 intersect without being substantially orthogonal. The Nz coefficient of the third optical compensation layer 30 is between -4 and 0, or between 0.9 and 4. The first optical compensation layer 10, the second optical compensation layer 20, and the third optical compensation layer 30 satisfy the following equation (1).

number

[0011] The value calculated in formula (1) above is, for example, -150 or more, preferably -100 or more, and for example, 150 or less, preferably 100 or less, and more preferably 60 or less. The refractive index characteristics of the first optical compensation layer 10 exhibit the relationship nz > nx = ny. Here, "nx = ny" includes not only the case where nx and ny are completely identical, but also the case where nx and ny are substantially identical. In-plane phase difference Re of the first optical compensation layer 10 1 (550) is, for example, 0 nm or more and 3.0 nm or less, and preferably 0 nm. Phase difference Rth in the thickness direction of the first optical compensation layer 10 1 (550) is, for example, -200 nm or more and less than 0 nm, preferably -5 nm or less.

[0012] The refractive index characteristics of at least one of the second optical compensation layer 20 and the third optical compensation layer 30 satisfy the relationship nx > ny ≥ nz. If the refractive index characteristics of the third optical compensation layer 30 satisfy the relationship nx > ny ≥ nz, then the refractive index characteristics of the second optical compensation layer 20 typically satisfy either nz ≥ nx > ny or nx > ny ≥ nz. Also, if the refractive index characteristics of the second optical compensation layer 20 satisfy the relationship nx > ny ≥ nz, then the refractive index characteristics of the third optical compensation layer 30 typically satisfy either nz ≥ nx > ny or nx > ny ≥ nz. Here, "nz = nx" includes not only the case where nz and nx are completely identical, but also the case where nz and nx are substantially identical. Similarly, "ny = nz" includes not only the case where ny and nz are completely identical, but also the case where ny and nz are substantially identical.

[0013] Of the second optical compensation layer 20 and the third optical compensation layer 30, the phase difference Rth(550) in the thickness direction of the optical compensation layer whose refractive index characteristics are such that nz=nx>ny is, for example, -3.0 nm or more and 3.0 nm or less, and preferably 0 nm. Of the second optical compensation layer 20 and the third optical compensation layer 30, the phase difference Rth(550) in the thickness direction of the optical compensation layer whose refractive index characteristics are in the relationship nz>nx>ny is, for example, -60 nm or more and less than 0 nm, preferably -50 nm or more and -5 nm or less. In this case, the Nz coefficient of the optical compensation layer is, for example, -1.0 or more and -0.1 or less, preferably -0.5 or more and -0.2 or less. Of the second optical compensation layer 20 and the third optical compensation layer 30, the phase difference Rth(550) in the thickness direction of the optical compensation layer whose refractive index characteristics are related to nx>ny≧nz is, for example, 10 nm to 220 nm, preferably 30 nm to 210 nm. In this case, the Nz coefficient of the optical compensation layer is, for example, 0.9 to 1.1.

[0014] In one embodiment, among the second optical compensation layer 20 and the third optical compensation layer 30, the Re(450) / Re(550) of the optical compensation layer whose refractive index characteristics are related to nx>ny≧nz is less than 1, and is typically 0.8 or greater.

[0015] In one embodiment, the absorption axis direction of the polarizer 41 and the slow phase axis direction of the third optical compensation layer 30 intersect without being substantially orthogonal.

[0016] The optical laminate may be in the form of a single sheet or a long length. In this specification, "long length" means an elongated shape in which the length is sufficiently longer than the width, and for example, includes an elongated shape in which the length is 10 times or more, preferably 20 times or more, than the width. The long optical laminate can be wound into a roll.

[0017] In practical terms, an adhesive layer (not shown) is provided on the side of the third optical compensation layer opposite the polarizing plate, allowing the optical laminate to be attached to an image display cell. Furthermore, it is preferable that a release liner is temporarily attached to the surface of the adhesive layer until the optical laminate is put into use. By temporarily attaching the release liner, the adhesive layer is protected and roll formation becomes possible.

[0018] The following describes specific combinations of the first optical compensation layer, the second optical compensation layer, and the third optical compensation layer in an optical laminate.

[0019] A-1. First optical laminate In one embodiment, the refractive index characteristics of the first optical compensation layer 10 exhibit the relationship nz > nx = ny, the refractive index characteristics of the second optical compensation layer 20 exhibit the relationship nz ≥ nx > ny, and the refractive index characteristics of the third optical compensation layer 30 exhibit the relationship nx > ny ≥ nz. An optical laminate including such a combination of the first optical compensation layer, the second optical compensation layer, and the third optical compensation layer may be referred to as the first optical laminate. In the first optical laminate, more preferably, the refractive index characteristics of the second optical compensation layer 20 exhibit the relationship nz = nx > ny, and the refractive index characteristics of the third optical compensation layer 30 exhibit the relationship nx > ny = nz. When the first optical compensation layer, the second optical compensation layer, and the third optical compensation layer are in such a combination, the reflectivity of the image display device can be further reduced.

[0020] In the first optical laminate, the phase difference Rth in the thickness direction of the first optical compensation layer 101 (550) is preferably -100 nm or more, more preferably -80 nm or more, even more preferably -60 nm or more, preferably -5 nm or less, and more preferably -20 nm or less. In the first optical stack, Rth 1 When (550) is within the above range, the reflected brightness can be further reduced in the image display device.

[0021] In the first optical laminate, the in-plane phase difference Re of the second optical compensation layer 20 2 (550) is preferably 40 nm or more, more preferably 50 nm or more, preferably 120 nm or less, and more preferably 90 nm or less. In the first optical stack, Re 2 If (550) is within the above range, the reflected brightness can be further reduced in the image display device. Furthermore, in the first optical laminate, the angle between the absorption axis direction of the polarizer 41 and the slow phase axis direction of the second optical compensation layer 20 is preferably 5° to 70°, more preferably 10° to 60°, and even more preferably 20° to 40°.

[0022] In the first optical laminate, the in-plane phase difference Re of the third optical compensation layer 30 3 (550) is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 110 nm or more, particularly preferably 140 nm or more, and preferably 195 nm or less. In the first optical laminate, the phase difference Rth in the thickness direction of the third optical compensation layer 30 3 (550) is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 110 nm or more, particularly preferably 140 nm or more, preferably 210 nm or less, and more preferably 195 nm or less. In the first optical stack, Re 3 (550) and / or Rth 3 If (550) is within the above range, the reflected brightness can be further reduced in the image display device. Furthermore, in the first optical laminate, the angle between the absorption axis direction of the polarizer 41 and the slow axis direction of the third optical compensation layer 30 is preferably 20° to 80° or 100° to 170°, more preferably 110° to 160°, and even more preferably 130° to 150°.

[0023] A-2. Second optical laminate In one embodiment, the refractive index characteristics of the first optical compensation layer 10 exhibit the relationship nz > nx = ny, the refractive index characteristics of the second optical compensation layer 20 exhibit the relationship nx > ny ≥ nz, and the refractive index characteristics of the third optical compensation layer 30 exhibit the relationship nz ≥ nx > ny. An optical laminate including such a combination of the first optical compensation layer, the second optical compensation layer, and the third optical compensation layer may be referred to as a second optical laminate. In the second optical laminate, more preferably, the refractive index characteristics of the second optical compensation layer 20 exhibit the relationship nx>ny=nz, and the refractive index characteristics of the third optical compensation layer 30 exhibit the relationship nz=nx>ny. When the first optical compensation layer, the second optical compensation layer, and the third optical compensation layer are in such a combination, the reflectivity of the image display device can be further reduced.

[0024] In the second optical laminate, the phase difference Rth in the thickness direction of the first optical compensation layer 10 1 (550) is preferably -100 nm or more, more preferably -70 nm or more, preferably -10 nm or less, and more preferably -30 nm or less. In the second optical stack, Rth 1 When (550) is within the above range, the reflected brightness can be further reduced in the image display device.

[0025] In the second optical laminate, the in-plane phase difference Re of the second optical compensation layer 20 2 (550) is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, particularly preferably 140 nm or more, and preferably 195 nm or less. In the second optical laminate, the phase difference Rth in the thickness direction of the second optical compensation layer 20 2(550) is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, particularly preferably 140 nm or more, preferably 210 nm or less, and more preferably 195 nm or less. In the second optical stack, Re 2 (550) and / or Rth 2 If (550) is within the above range, the reflected brightness can be further reduced in the image display device. Furthermore, in the second optical laminate, the angle between the absorption axis direction of the polarizer 41 and the slow axis direction of the second optical compensation layer 20 is preferably 5° to 70° or 95° to 160°, more preferably 10° to 50°, and even more preferably 10° to 40°.

[0026] In the second optical laminate, the in-plane phase difference Re of the third optical compensation layer 30 3 (550) is preferably 40 nm or more, more preferably 60 nm or more, preferably 200 nm or less, more preferably 180 nm or less, and even more preferably 110 nm or less. In the second optical stack, Re 3 If (550) is within the above range, the reflected brightness can be further reduced in the image display device. Furthermore, in the second optical laminate, the angle between the absorption axis direction of the polarizer 41 and the slow phase axis direction of the third optical compensation layer 30 is preferably 10° to 85°, more preferably 30° to 85°, and even more preferably 60° to 85°.

[0027] A-3. Third optical laminate In one embodiment, the refractive index characteristics of the first optical compensation layer 10 exhibit the relationship nz > nx = ny, and the refractive index characteristics of the second optical compensation layer 20 and the third optical compensation layer 30 each exhibit the relationship nx > ny ≥ nz. An optical laminate including such a combination of the first optical compensation layer, the second optical compensation layer, and the third optical compensation layer may be referred to as a third optical laminate. In the third optical laminate, more preferably, the refractive index characteristics of the second optical compensation layer 20 and the third optical compensation layer 30 satisfy the relationship nx > ny = nz. When the first optical compensation layer, the second optical compensation layer and the third optical compensation layer are in such a combination, the reflectivity of the image display device can be further reduced.

[0028] In the third optical laminate, the phase difference Rth in the thickness direction of the first optical compensation layer 10 1 (550) is preferably -180 nm or more, more preferably -140 nm or more, preferably -10 nm or less, more preferably -80 nm or less, and even more preferably -100 nm or less. In the third optical stack, Rth 1 When (550) is within the above range, the reflected brightness can be further reduced in the image display device.

[0029] In the third optical laminate, the in-plane phase difference Re of the second optical compensation layer 20 2 (550) is preferably 40 nm or more, more preferably 50 nm or more, preferably 180 nm or less, more preferably 120 nm or less, and even more preferably 90 nm or less. In the third optical laminate, the phase difference Rth in the thickness direction of the second optical compensation layer 20 2 (550) is preferably 40 nm or more, more preferably 50 nm or more, preferably 180 nm or less, more preferably 120 nm or less, and even more preferably 90 nm or less. In the third optical laminate, Re 2 (550) and / or Rth 2 If (550) is within the above range, the reflected brightness can be further reduced in the image display device. Furthermore, in the third optical laminate, the angle between the absorption axis direction of the polarizer 41 and the slow axis direction of the second optical compensation layer 20 is preferably 5° to 60° or 110° to 170°, more preferably 10° to 50°, and even more preferably 20° to 40°.

[0030] In the third optical laminate, the in-plane phase difference Re of the third optical compensation layer 30 3 (550) is preferably 40 nm or more, more preferably 60 nm or more, even more preferably 130 nm or more, particularly preferably 170 nm or more, and preferably 195 nm or less. In the third optical laminate, the phase difference Rth in the thickness direction of the third optical compensation layer 30 3 (550) is preferably 40 nm or more, more preferably 60 nm or more, even more preferably 130 nm or more, particularly preferably 170 nm or more, preferably 210 nm or less, and more preferably 195 nm or less. In the third optical laminate, Re 3 (550) and / or Rth 3 If (550) is within the above range, the reflected brightness can be further reduced in the image display device. Furthermore, in the third optical laminate, the angle between the absorption axis direction of the polarizer 41 and the slow axis direction of the third optical compensation layer 30 is preferably 10° to 70°, or 95° to 170°, more preferably 110° to 160°, and even more preferably 130° to 150°.

[0031] The following describes each component that makes up the optical laminate.

[0032] B. Polarizing plate B-1.Polarizer Any suitable polarizer can be used as the polarizer 41. For example, the resin film forming the polarizer may be a single layer resin film or a laminate of two or more layers.

[0033] Specific examples of polarizers composed of a single layer of resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA 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 film with iodine and uniaxially stretching are used because they have excellent optical properties.

[0034] The above-mentioned iodine dyeing is carried out, for example, by immersing the PVA 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 film may be subjected to swelling, crosslinking, washing, drying, etc. For example, immersing the PVA film in water and washing it before dyeing can not only wash away dirt and blocking agents from the surface of the PVA film, but also swell the PVA film to prevent uneven dyeing.

[0035] 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 of the present invention, preferably, 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 optionally 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 of the present invention, 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.

[0036] The thickness of the polarizer is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, even more preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is within this range, curling during heating can be well suppressed, and good durability of the appearance during heating can be obtained.

[0037] The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0038] B-2.Protective layer The polarizing plate 40 may further include a protective layer. The protective layer is provided on at least one surface of the polarizer. In the illustrated example, the polarizing plate 40 includes a protective layer 42 provided on the viewing side of the polarizer 41.

[0039] The protective layer is formed from any suitable film that can be used as a protective layer for the polarizer. Specific examples of materials that make up the main component of the film include cellulosic resins such as triacetylcellulose (TAC), and transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Thermosetting resins or UV-curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone can also be used. In addition, glassy polymers such as siloxane polymers can also be used. Polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used.

[0040] If the polarizing plate 40 includes a protective layer located on the outermost surface of the image display device described later, the protective layer may be subjected to surface treatments such as hard coating, anti-reflective coating, anti-sticking coating, and anti-glare coating, as necessary.

[0041] The thickness of the protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm. If a surface treatment is applied, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0042] C. First optical compensation layer In the illustrated example, the first optical compensation layer 10 is positioned adjacent to the polarizer 40. More specifically, the first optical compensation layer 10 is positioned adjacent to the polarizer 41. In this specification, "positioned adjacent" means either directly laminated or laminated only via an adhesive layer (e.g., an adhesive layer or a tack layer). That is, it means that no other optical functional layer is interposed between the polarizer 40 and the first optical compensation layer 10. The light transmittance of the first optical compensation layer 10 at a wavelength of 550 nm is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The theoretical upper limit of light transmittance is 100%, but due to surface reflection caused by the refractive index difference between air and the phase difference film, the achievable upper limit of light transmittance is approximately 94%. The thickness of the first optical compensation layer 10 can be set to obtain desired optical properties. The thickness of the first optical compensation layer 10 is typically 0.5 μm or more, typically 10 μm or less, preferably 8 μm or less, and more preferably 5 μm or less.

[0043] As described above, the refractive index characteristics of the first optical compensation layer 10 exhibit the relationship nz > nx = ny. A layer (film) exhibiting the refractive index characteristics nz > nx = ny is sometimes referred to as a "positive C plate," etc. The first optical compensation layer 10 is typically composed of a film containing a liquid crystal material fixed in a homeotropic orientation (hereinafter referred to as a homeotropic orientation liquid crystal film). The liquid crystal material (liquid crystal compound) that can be homeotropically oriented may be a liquid crystal monomer or a liquid crystal polymer. The liquid crystal material (liquid crystal compound) is preferably polymerizable, and more preferably photopolymerizable. Specific examples of such liquid crystal compounds include the liquid crystal compounds described in paragraphs

[0020] to

[0028] of Japanese Patent Application Publication No. 2002-333642.

[0044] Any suitable preparation method can be used to prepare such a homeotropically oriented liquid crystal film. For example, a coating solution containing liquid crystal material and a solvent is applied to a substrate (e.g., a resin substrate), and then the coating film is heated to cause the liquid crystal material to be in a liquid crystal state and homeotropically oriented. Subsequently, the homeotropically oriented liquid crystal material is irradiated with light (e.g., ultraviolet light) to polymerize or crosslink the liquid crystal material, thereby fixing the orientation of the liquid crystal material. This yields a homeotropically oriented liquid crystal film. Furthermore, by adjusting the orientation processing conditions (heating temperature, heating time), the Rth of the first optical compensation layer can be adjusted. 1 (550) can be adjusted to the range described above. The heating temperature is, for example, 60°C or higher, preferably 70°C or higher, and for example, 300°C or lower, preferably 200°C or lower. The heating time is, for example, 10 seconds or more, preferably 20 seconds or more, and for example, 2 hours or less, preferably 30 minutes or less. If the orientation treatment conditions are within the above range, homeotropic orientation can be stably formed.

[0045] D. Second optical compensation layer The second optical compensation layer 20 is positioned on the opposite side of the polarizer 40 from the first optical compensation layer 10. In the illustrated example, the second optical compensation layer 20 is positioned adjacent to the first optical compensation layer 10. This means that no other optical functional layer is interposed between the first optical compensation layer 10 and the second optical compensation layer 20. The range of light transmittance of the second optical compensation layer 20 at a wavelength of 550 nm is the same as the range of light transmittance of the first optical compensation layer 10 described above. The thickness of the second optical compensation layer 20 can be set to obtain desired optical properties. The thickness of the second optical compensation layer 20 is typically 1 μm or more, preferably 4 μm or more, typically 200 μm or less, preferably 150 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0046] The refractive index characteristics of the second optical compensation layer 20 show the relationship nx > ny as described above, and typically show the relationship nz ≥ nx > ny, or nx > ny ≥ nz. A layer (film) that shows the refractive index characteristics nz = nx > ny is sometimes called a "negative A plate," etc. A layer (film) that shows the refractive index characteristics nz > nx > ny is sometimes called a "positive B plate," etc. A layer (film) that shows the refractive index characteristics nx > ny = nz is sometimes called a "positive A plate," etc. A layer (film) that shows the refractive index characteristics nx > ny > nz is sometimes called a "negative B plate," etc. The second optical compensation layer 20 can be made of any suitable material, as long as the above-described characteristics are obtained.

[0047] D-1. Second optical compensation layer exhibiting the relationship nz≧nx>ny in refractive index characteristics. When the refractive index characteristics of the second optical compensation layer 20 exhibit the relationship nz≧nx>ny, the second optical compensation layer 20 is typically composed of a stretched polymer film mainly composed of a thermoplastic resin. Preferably, a polymer exhibiting negative birefringence is used as the thermoplastic resin. By using a polymer exhibiting negative birefringence, a phase difference film having a refractive index ellipsoid with nz≧nx>ny can be easily obtained. Here, "exhibiting negative birefringence" means that when the polymer is oriented by stretching or the like, the refractive index in the stretching direction becomes relatively small. In other words, it means that the refractive index in the direction perpendicular to the stretching direction becomes large. Examples of polymers exhibiting negative birefringence include polymers in which chemical bonds or functional groups with high polarization anisotropy, such as aromatic rings or carbonyl groups, are introduced into the side chains. Specifically, examples include acrylic resins, styrene resins, maleimide resins, etc.

[0048] The above-mentioned acrylic resins can be obtained, for example, by addition polymerization of acrylate monomers. Examples of acrylic resins include polymethyl methacrylate (PMMA), polybutyl methacrylate, and polycyclohexyl methacrylate.

[0049] The above-mentioned styrene-based resin can be obtained, for example, by addition polymerization of styrene-based monomers. Examples of styrene-based monomers include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene, 2,5-dichlorostyrene, and pt-butylstyrene.

[0050] The above maleimide-based resin can be obtained, for example, by addition polymerization of maleimide-based monomers. Examples of maleimide monomers include N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(2-ethylphenyl)maleimide, N-(2-propylphenyl)maleimide, N-(2-isopropylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2,6-dipropylphenyl)maleimide, N-(2,6-diisopropylphenyl)maleimide, N-(2-methyl-6-ethylphenyl)maleimide, N-(2-chlorophenyl)maleimide, N-(2,6-dichlorophenyl)maleimide, N-(2-bromophenyl)maleimide, N-(2,6-dibromophenyl)maleimide, N-(2-biphenyl)maleimide, and N-(2-cyanophenyl)maleimide.

[0051] In the addition polymerization described above, the birefringence properties of the resulting resin can also be controlled after polymerization by substituting side chains or by carrying out maleimidation or grafting reactions.

[0052] The polymer exhibiting the negative birefringence described above may be copolymerized with other monomers. Copolymerization with other monomers can improve brittleness, moldability, and heat resistance. Examples of such other monomers include olefins such as ethylene, propylene, 1-butene, 1,3-butadiene, 2-methyl-1-butene, 2-methyl-1-pentene, and 1-hexene; acrylonitrile; (meth)acrylates such as methyl acrylate and methyl methacrylate; maleic anhydride; and vinyl esters such as vinyl acetate.

[0053] When the polymer exhibiting negative birefringence is a copolymer of the styrene monomer and the other monomer, the blending ratio of the styrene monomer is preferably 50 mol% to 80 mol%. When the polymer exhibiting negative birefringence is a copolymer of the maleimide monomer and the other monomer, the blending ratio of the maleimide monomer is preferably 2 mol% to 50 mol%. By blending within these ranges, a polymer film with excellent toughness and moldability can be obtained.

[0054] Preferred polymers exhibiting the negative birefringence described above include styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-(meth)acrylate copolymers, styrene-maleimide copolymers, vinyl ester-maleimide copolymers, and olefin-maleimide copolymers. These can be used individually or in combination of two or more. These polymers exhibit high negative birefringence and can have excellent heat resistance. These polymers can be obtained, for example, from Nova Chemical Japan or Arakawa Chemical Industries, Ltd.

[0055] As a polymer exhibiting the negative birefringence described above, a polymer having repeating units represented by the following general formula (I) is also preferably used. Such polymers exhibit even higher negative birefringence and can have excellent heat resistance and mechanical strength. Such polymers can be obtained, for example, by using an N-phenyl-substituted maleimide in which a phenyl group having a substituent at least in the ortho position is introduced as the N substituent of the starting material maleimide monomer. [ka]

[0056] In the above general formula (I), R1 to R5 each independently represent hydrogen, a halogen atom, a carboxylic acid, a carboxylic acid ester, a hydroxyl group, a nitro group, or a linear or branched alkyl or alkoxy group having 1 to 8 carbon atoms (provided that R1 and R5 are not simultaneously hydrogen atoms), R6 and R7 represent hydrogen or a linear or branched alkyl or alkoxy group having 1 to 8 carbon atoms, and n represents an integer of 2 or more.

[0057] The polymer exhibiting negative birefringence is not limited to those described above, and for example, cyclic olefin copolymers such as those disclosed in Japanese Patent Application Publication No. 2005-350544 can also be used. Furthermore, compositions containing polymers and inorganic fine particles, such as those disclosed in Japanese Patent Application Publication No. 2005-156862 and Japanese Patent Application Publication No. 2005-227427, can also be suitably used. In addition, one type of polymer exhibiting negative birefringence may be used alone, or two or more types may be used in mixture form. Furthermore, these can also be modified by copolymerization, branching, crosslinking, molecular end modification (or encapsulation), and stereoregular modification before use.

[0058] Any suitable molding method can be used to form such polymer films. The molding conditions can be appropriately set depending on the composition and type of resin used, the molding process, etc.

[0059] A phase difference film (stretched film) corresponding to the second optical compensation layer whose refractive index characteristics are such that nz≧nx>ny can be obtained by stretching the above polymer film under any appropriate stretching conditions. Specific examples of stretching methods include longitudinal uniaxial stretching, transverse uniaxial stretching, longitudinal and transverse sequential biaxial stretching, and longitudinal and transverse simultaneous biaxial stretching. Preferably, longitudinal uniaxial stretching, longitudinal and transverse sequential biaxial stretching, and longitudinal and transverse simultaneous biaxial stretching are used. In polymers exhibiting negative birefringence as described above, the refractive index in the stretching direction becomes relatively small, so in the case of longitudinal uniaxial stretching, the polymer film has a fast-advancing axis in the transport direction (the refractive index in the direction perpendicular to the transport direction becomes nx). In the case of longitudinal and transverse sequential biaxial stretching and longitudinal and transverse simultaneous biaxial stretching, the transport direction and the width direction can both be made slow-advancing axes depending on the ratio of the longitudinal and transverse stretching ratios. Specifically, if the stretching ratio in the longitudinal (transport) direction is made relatively large, the transverse (width) direction becomes the slow-advancing axis, and if the stretching ratio in the transverse (width) direction is made relatively large, the longitudinal (transport) direction becomes the slow-advancing axis.

[0060] Furthermore, by adjusting the thickness of the polymer film (raw material thickness), the stretching temperature, and the stretching ratio, the Re of the second optical compensation layer can be adjusted. 2 (550) and Rth 2 (550) can be adjusted to the range described above. The thickness of the polymer film (raw material thickness) is typically 5 μm or more, preferably 10 μm or more, and typically 50 μm or less, preferably 40 μm or less. The stretching temperature (the temperature inside the stretching oven when stretching the polymer film) is preferably near the glass transition temperature (Tg) of the polymer film. Specifically, it is preferably (Tg-10)°C to (Tg+30)°C, more preferably Tg to (Tg+25)°C, and particularly preferably (Tg+5)°C to (Tg+20)°C. If the stretching temperature is too low, the phase difference value and the direction of the slow axis may become non-uniform, or the polymer film may crystallize (become cloudy). On the other hand, if the stretching temperature is excessively high, the polymer film may melt or the development of the phase difference may be insufficient. Typically, the stretching temperature is between 120°C and 170°C. The glass transition temperature can be determined by the DSC method in accordance with JIS K7121-1987. The stretching ratio can be set to any appropriate value depending on the composition of the polymer film, the type of volatile components, the residual amount of volatile components, the desired phase difference value, etc. Preferably, it is between 1.1 and 3.0 times. Furthermore, the feed rate during stretching is preferably between 0.5 m / min and 20 m / min from the viewpoint of the mechanical accuracy and stability of the stretching apparatus.

[0061] The above describes a method for obtaining a phase difference film using a polymer exhibiting negative birefringence, but a phase difference film can also be obtained using a polymer exhibiting positive birefringence. As a method for obtaining a phase difference film using a polymer exhibiting positive birefringence, for example, a stretching method that increases the refractive index in the thickness direction can be used, as disclosed in Japanese Patent Publication No. 2000-231016, Japanese Patent Publication No. 2000-206328, and Japanese Patent Publication No. 2002-207123. Specifically, one method involves adhering a heat-shrinkable film to one or both sides of a film containing a polymer exhibiting positive birefringence and then performing a heat treatment. By shrinking the film under the action of the shrinkage force of the heat-shrinkable film due to the heat treatment, the refractive index in the thickness direction can be increased, and a phase difference film having a refractive index ellipsoid with nz>nx>ny can be obtained.

[0062] Thus, a second optical compensation layer exhibiting the relationship nz≧nx>ny in refractive index characteristics can be manufactured using any polymer exhibiting negative birefringence. Generally, using a polymer exhibiting positive birefringence has the advantage of offering a wide variety of polymers to choose from, while using a polymer exhibiting negative birefringence has the advantage of easily obtaining a phase difference film with excellent uniformity in the slow axis direction, due to the stretching method, compared to using a polymer exhibiting positive birefringence.

[0063] D-2. Second optical compensation layer exhibiting the relationship nx>ny≧nz in refractive index characteristics. When the refractive index characteristics of the second optical compensation layer 20 satisfy the relationship nx > ny ≥ nz, the second optical compensation layer 20 is typically composed of a phase difference film (a stretched polymer film). Any suitable resin can be used as the resin forming the polymer film. Specific examples include resins that constitute positive birefringence films, such as norbornene resins, polycarbonate resins, cellulose resins, polyvinyl alcohol resins, and polysulfone resins. Among these, norbornene resins and polycarbonate resins are preferred.

[0064] The norbornene-based resin described above is a resin polymerized using norbornene-based monomers as polymerization units. Examples of the norbornene-based monomers include norbornene and its alkyl and / or alkylidene-substituted derivatives, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., and their halogen- and other polar group-substituted derivatives; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc. Tanooctahydronaphthalene, its alkyl and / or alkylidene substituted derivatives, and polar group substituted derivatives such as halogens, e.g., 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7 ,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano Examples include tano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, and tripers or tetramers of cyclopentadiene, such as 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene. The above norbornene-based resin may also be a copolymer of norbornene-based monomers and other monomers.

[0065] The polycarbonate resin described above includes, for example, structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanol, di, tri, or polyethylene glycols, and alkylene glycols or spiroglycols. Preferably, the polycarbonate resin includes structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from spiroglycols. The polycarbonate resin may optionally contain structural units derived from other dihydroxy compounds. Further details regarding polycarbonate resins suitably used in the present invention are described, for example, in Japanese Patent Publication No. 2014-10291, Japanese Patent Publication No. 2014-26266, Japanese Patent Publication No. 2015-212816, Japanese Patent Publication No. 2015-212817, and Japanese Patent Publication No. 2015-212818, and such descriptions are incorporated herein by reference.

[0066] A phase difference film (stretched film) corresponding to a second optical compensation layer whose refractive index characteristics exhibit the relationship nx > ny ≥ nz can be obtained by stretching the polymer film under any appropriate stretching conditions. Specifically, by appropriately selecting the type of polymer, stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction), and stretching method (e.g., longitudinal uniaxial stretching), a phase difference film (second optical compensation layer) having the desired optical properties (e.g., refractive index characteristics, in-plane phase difference, phase difference in the thickness direction) can be obtained. In particular, by adjusting the thickness of the polymer film (raw material thickness), stretching temperature, and stretching ratio, the Re of the second optical compensation layer can be adjusted. 2 (550) and Rth 2 (550) can be adjusted to the range described above. The thickness of the polymer film (raw material thickness) is typically 5 μm or more, preferably 10 μm or more, typically 210 μm or less, preferably 160 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. The stretching temperature is preferably 120°C to 170°C, and more preferably 130°C to 160°C. The stretching ratio is preferably 1.1 to 3.0 times, and more preferably 1.3 to 2.0 times.

[0067] E. Third optical compensation layer The third optical compensation layer 30 is positioned on the opposite side of the first optical compensation layer 10 from the second optical compensation layer 20. In the illustrated example, the third optical compensation layer 30 is positioned adjacent to the second optical compensation layer 20. This means that no other optical functional layer is interposed between the second optical compensation layer 20 and the third optical compensation layer 30. The range of light transmittance of the third optical compensation layer 30 at a wavelength of 550 nm is the same as the range of light transmittance of the first optical compensation layer 10 described above. The thickness of the third optical compensation layer 30 can be set to obtain desired optical properties. The thickness of the third optical compensation layer 30 is typically 1 μm or more, preferably 4 μm or more, typically 200 μm or less, preferably 150 μm or less, more preferably 40 μm or less, and preferably 30 μm or less.

[0068] The refractive index characteristics of the third optical compensation layer 30 exhibit the relationship nx > ny as described above, and typically, the relationship nz ≥ nx > ny, or nx > ny ≥ nz. If the refractive index characteristics of the third optical compensation layer 30 satisfy the relationship nz≧nx>ny, the third optical compensation layer 30 is formed in the same manner as the second optical compensation layer (refractive index characteristics; nz≧nx>ny) described in section D-1 above. If the refractive index characteristics of the third optical compensation layer 30 satisfy the relationship nx > ny ≥ nz, the third optical compensation layer 30 is formed in the same manner as the second optical compensation layer (refractive index characteristics; nx > ny ≥ nz) described in section D-2 above.

[0069] F. Image display device The optical laminates described in items A to E above can be applied to image display devices. Therefore, one embodiment of the present invention also includes an image display device using such an optical laminate. Typical examples of image display devices include liquid crystal display devices and organic EL display devices. In particular, the optical laminate described above can reduce the reflectivity of the image display device and is therefore suitably applied to organic EL display devices. An image display device according to an embodiment of the present invention comprises an image display cell and an optical laminate described in items A to E above. Typically, an image display device comprises an image display panel including an image display cell and the optical laminate disposed on its viewing side. Note that an image display device may be referred to as an optical display device, an image display panel may be referred to as an optical display panel, and an image display cell may be referred to as an optical display cell. [Examples]

[0070] 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.

[0071] (1) Measurement of phase difference The phase difference values ​​of the first optical compensation layer, second optical compensation layer, and third optical compensation layer used in the examples and comparative examples were automatically measured using a KOBRA-WPR manufactured by Oji Instruments. The measurement wavelength was 450 nm or 550 nm, and the measurement temperature was 23°C. (2) Reflectance (luminance) The reflective luminance of the image display devices obtained in the examples and comparative examples was measured using a luminance meter (Instrument Systems, product name "DMS505") at an extreme angle of 60°, in increments of 5° azimuth (unit: cd / m²). 2 The ) value was measured, and the maximum value was defined as the reflectance. The results are shown in Tables 1 to 4.

[0072] <Fabrication of a phase difference film (positive C plate) with refractive index properties nz>nx=ny> <<Manufacturing Example 1>> A liquid crystal coating solution was prepared by dissolving 20 parts by mass of a side-chain liquid crystal polymer represented by the following chemical formula (II) (the numbers 65 and 35 in the formula indicate the mole percent of monomer units and are conveniently represented as a block polymer: weight-average molecular weight 5000), 80 parts by mass of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (BASF: trade name Paliocolor LC242), and 5 parts by mass of a photopolymerization initiator (Ciba Specialty Chemicals: trade name Irgacure 907) in 200 parts by mass of cyclopentanone. [ka] Then, the coating solution was applied to the base film (norbornene-based resin film: manufactured by Zeon Corporation, product name "Zeonex") using a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. By irradiating this liquid crystal layer with ultraviolet light and curing the liquid crystal layer, a phase difference film (thickness: 1 μm) was formed on the base material. The phase difference film obtained in this manner exhibited a refractive index characteristic of nz > nx = ny. The in-plane phase difference Re (550) and the thickness-direction phase difference Rth (550) of the phase difference film (positive C plate) are shown in Tables 1 to 4. <<Manufacturing Example 2-8>> A phase difference film (positive C plate) was obtained in the same manner as in Manufacturing Example 1, except that the orientation processing conditions were changed so that the phase difference Rth(550) in the thickness direction was the value shown in Tables 1 to 4.

[0073] <Fabrication of a phase difference film (negative A plate) with refractive index properties nz=nx>ny> <<Manufacturing Example 9>> A pelletized resin of styrene-maleic anhydride copolymer (manufactured by Nova Chemical Japan, trade name "Dailark D232") was extruded at 270°C using a single-screw extruder and T-die, and the molten resin in sheet form was cooled in a cooling drum to obtain a film with a thickness of 40 μm. This film was stretched longitudinally in the conveying direction using a roll stretcher at a temperature of 130°C and a stretching ratio of 1.1 times to obtain a phase difference film having a phase-advancing axis in the conveying direction. The phase difference film obtained in this manner exhibited a refractive index characteristic of nz = nx > ny. The in-plane phase difference Re(550), the phase difference Rth(550) in the thickness direction, and Re(450) / Re(550) of the phase difference film (negative A plate) are shown in Tables 1 and 2. <<Manufacturing Example 10-16>> The unstretched film (thickness 40 μm) obtained in the same manner as in Production Example 9 was longitudinally stretched at 130°C to obtain a phase difference film (negative A plate) such that the in-plane phase difference Re(550) was the value shown in Tables 1 and 2.

[0074] <Fabrication of a phase difference film (positive B plate) with refractive index properties nz>nx>ny> <<Manufacturing Examples 17 and 18>> A pre-stretched film (thickness 40 μm) obtained in the same manner as in Production Example 9 was longitudinally stretched at 130°C in the transport direction with a fixed end so that the in-plane phase difference Re(550) and the phase difference Rth(550) in the thickness direction were the values ​​shown in Tables 1 and 2, thereby obtaining a phase difference film. The phase difference film obtained in this manner exhibited a refractive index characteristic of nz > nx > ny. The in-plane phase difference Re(550), the phase difference Rth(550) in the thickness direction, Re(450) / Re(550), and the Nz coefficient of the phase difference film (positive B plate) are shown in Tables 1 and 2.

[0075] <Fabrication of a phase difference film (positive A plate) with refractive index properties nx>ny=nz> <<Manufacturing Example 19>> Long norbornene-based resin film (manufactured by Zeon Corporation, product name Zeonor, thickness 40 μm, photoelastic modulus 3.10 × 10) -12 m 2 A phase difference film with a thickness of 35 μm was obtained by stretching the free-end longitudinal section of ( / N) 1.4 times at 135°C. The phase difference film obtained in this manner exhibited a refractive index characteristic of nx > ny = nz. The in-plane phase difference Re(550), the phase difference Rth(550) in the thickness direction, Re(450) / Re(550), and the Nz coefficient of the phase difference film (positive A plate) are shown in Tables 1 to 4. <<Manufacturing Examples 20-30>> A norbornene-based resin film (manufactured by Zeon Corporation, trade name Zeonor, thickness 40 μm) was stretched longitudinally at the free edge at 135°C to obtain a phase difference film (positive A plate) such that the in-plane phase difference Re(550) was the value shown in Tables 1 to 4. The phase difference film of Production Example 29 has an Re(550) of 270 nm and functions as a λ / 2 plate. The phase difference film of Production Example 30 has an Re(550) of 135 nm and functions as a λ / 4 plate.

[0076] <<Manufacturing Example 31>> A batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled to 100°C was used to prepare the reactor. The mixture contained 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), 42.28 parts by mass (0.139 mol) of spiroglycol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19 × 10⁻¹⁶ calcium acetate monohydrate as a catalyst. -2 Part of mass (6.78×10 -5A mol (mol) of polymer was added. After purging the reactor with reduced pressure using nitrogen, the reactor was heated with a heat transfer medium, and stirring was started when the internal temperature reached 100°C. Forty minutes after the start of heating, the internal temperature was raised to 220°C, and while controlling the pressure to maintain this temperature, the pressure was reduced to 13.3 kPa 90 minutes after reaching 220°C. The phenol vapor produced as a by-product of the polymerization reaction was directed to a reflux condenser at 100°C, and the monomer components contained in the phenol vapor were returned to the reactor. The uncondensed phenol vapor was directed to a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor to restore the pressure to atmospheric pressure, and then the oligomerized reaction mixture in the first reactor was transferred to the second reactor. Next, heating and depressurization in the second reactor were started, and the internal temperature reached 240°C and the pressure 0.2 kPa in 50 minutes. Polymerization was then allowed to proceed until the predetermined stirring power was reached. Once the predetermined power level was reached, nitrogen was introduced into the reactor to restore pressure, and the resulting polyester carbonate resin was extruded into water. The strands were then cut to obtain pellets. The obtained polyester carbonate resin (pellets) was vacuum-dried at 80°C for 5 hours. Then, a long resin film with a thickness of 130 μm was produced using a film-making apparatus equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width 200 mm, setting temperature: 250°C), a chill roll (setting temperature: 120~130°C), and a winding machine. The obtained long resin film was stretched 1.4 times at the free end longitudinally at 140°C to obtain a phase difference film (positive A plate) with a thickness of 110 μm. <<Manufacturing Examples 32 and 33>> A resin film (thickness 130 μm) obtained before stretching in the same manner as in Manufacturing Example 31 was stretched longitudinally at the free edge at 140°C so that the in-plane phase difference Re(550) was the value shown in Tables 1 to 4 to obtain a phase difference film (positive A plate). The phase difference film of Manufacturing Example 33 has an Re(550) of 140 nm and functions as a λ / 4 plate.

[0077] <Fabrication of a phase difference film (negative B plate) with refractive index characteristics nx>ny>nz> <<Manufacturing Examples 34 and 35>> A norbornene-based resin film (manufactured by Zeon Corporation, trade name Zeonor, thickness 40 μm) was stretched transversely at a fixed edge at 135°C to obtain a phase difference film, such that the in-plane phase difference Re(550) and the phase difference Rth(550) in the thickness direction were the values ​​shown in Tables 1 to 3. The phase difference film obtained in this manner exhibited a refractive index characteristic of nx > ny > nz. The in-plane phase difference Re(550), the phase difference Rth(550) in the thickness direction, Re(450) / Re(550), and the Nz coefficient of the phase difference film (negative B plate) are shown in Tables 1 to 3.

[0078] <Fabrication of polarizing plates> <<Manufacturing Example 36>> 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 resin substrate was subjected to corona treatment. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by mass of a PVA-based resin, which was prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosephymer") in a 9:1 ratio, with 13 parts by mass of potassium iodide. A PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60°C to form a 13 μm thick PVA-based resin layer, thereby creating a laminate. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (air-assisted stretching). Next, the laminate was immersed for 30 seconds in an insolubilization bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 4 parts by mass of boric acid with 100 parts by mass of water) (insolubilization treatment). Next, the polarizers were immersed for 60 seconds in a staining bath at a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by mass of water) while adjusting the concentration so that the final transmittance (Ts) of the polarizers obtained would be the desired value (staining treatment). Next, the material was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with 100 parts by mass of water) (crosslinking treatment). Subsequently, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4% by weight, potassium iodide concentration 5% by weight) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to achieve a total stretch ratio of 5.5 times (underwater stretching treatment). Subsequently, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by mass of potassium iodide with 100 parts by mass of water) (washing treatment). Subsequently, the material was dried in an oven maintained at approximately 90°C while being brought into contact with a SUS (stainless steel) heated roll whose surface temperature was maintained at approximately 75°C (drying shrinkage treatment). In this way, a polarizer with a thickness of approximately 5 μm was formed on the resin substrate, and a laminate having a resin substrate / polarizer configuration was obtained. A protective layer of HC-TAC film (20 μm thick) was bonded to the polarizer surface (the side opposite to the resin substrate) of the resulting laminate. Next, the resin substrate was peeled off to obtain a polarizing plate having a protective layer / polarizer configuration.

[0079] <Preparing the image display panel (OLED panel)> After removing the OLED panel with a polarizing film attached from an OLED display (manufactured by Samsung, product name "Galaxy A41"), the polarizing film was removed to obtain the image display panel (OLED panel).

[0080] [Examples 1-8] The phase difference films from the manufacturing examples shown in Table 1 and the polarizing plates from manufacturing example 36 were punched out to the size corresponding to the image display cells. Furthermore, the phase difference films from each manufacturing example were classified as follows, as shown in Table 1: a first phase difference film corresponding to the first optical compensation layer, a second phase difference film corresponding to the second optical compensation layer, and a third phase difference film corresponding to the third optical compensation layer. Next, a third phase difference film (third optical compensation layer), a second phase difference film (second optical compensation layer), a first phase difference film (first optical compensation layer), and a polarizer were stacked on the viewing side of the OLED panel in this order. The stacking was performed so that the angle between the absorption axis direction of the polarizer and the slow axis direction of the optical compensation layers (the second and third optical compensation layers, respectively) was as shown in Table 1. In this manner, an image display device was fabricated. Next, the image display device was subjected to the reflectance luminance measurement described above.

[0081] [Table 1]

[0082] [Examples 9-16] An image display device was fabricated in the same manner as in Example 1, except that the first phase difference film (first optical compensation layer), the second phase difference film (second optical compensation layer), and the third phase difference film (third optical compensation layer) were each replaced with the phase difference films shown in Table 2. The image display device was then subjected to the reflectance luminance measurement described above.

[0083] [Table 2]

[0084] [Examples 17-23] An image display device was fabricated in the same manner as in Example 1, except that the first phase difference film (first optical compensation layer), the second phase difference film (second optical compensation layer), and the third phase difference film (third optical compensation layer) were each replaced with the phase difference films shown in Table 3. The image display device was then subjected to the reflectance luminance measurement described above.

[0085] [Table 3]

[0086] [Comparative Examples 1 and 2] An image display device was manufactured in the same manner as in Example 1, except that the first phase difference film (first optical compensation layer) and the second phase difference film (second optical compensation layer) were replaced with the phase difference films shown in Table 4, and the third phase difference film (third optical compensation layer) was omitted. The image display device was then subjected to the reflectance luminance measurement described above. [Comparative Example 3] An image display device was fabricated in the same manner as in Example 1, except that the first phase difference film (first optical compensation layer), the second phase difference film (second optical compensation layer), and the third phase difference film (third optical compensation layer) were each replaced with the phase difference films shown in Table 4. The image display device was then subjected to the reflectance luminance measurement described above.

[0087] [Table 4]

[0088] [evaluation] As is clear from Tables 1-4, the refractive index characteristics of the first optical compensation layer show the relationship nz > nx = ny, and the refractive index characteristics of the second optical compensation layer and / or the third optical compensation layer show the relationship nx > ny ≥ nz, Re 2 (550) and Re 3 Each of (550) is between 10 nm and 220 nm, the Nz coefficient of the third optical compensation layer is between -4 and 0 or between 0.9 and 4, and the first optical compensation layer, the second optical compensation layer and the third optical compensation layer satisfy the above equation (1), thereby enabling the realization of an image display device (organic EL display device) with significantly low reflectivity. [Industrial applicability]

[0089] The optical laminate according to the embodiment of the present invention can be suitably applied to image display devices (typically liquid crystal display devices and organic EL display devices). [Explanation of symbols]

[0090] 10 First optical compensation layer 20 Second optical compensation layer 30 Third optical compensation layer 40 Polarizing plates 41 Polarizer 100 Optical laminate

Claims

[Claim 1] Polarizer and, A first optical compensation layer whose refractive index characteristics exhibit the relationship nz > nx = ny, A second optical compensation layer exhibiting the relationship nx > ny in refractive index characteristics, A third optical compensation layer exhibiting the relationship nx > ny in refractive index characteristics is provided in this order, The refractive index characteristics of the second optical compensation layer and / or the third optical compensation layer satisfy the relationship nx > ny ≥ nz, The in-plane phase difference Re of the second optical compensation layer ２ (550) and the in-plane phase difference Re of the third optical compensation layer ３ Each of (550) is between 10 nm and 220 nm, The absorption axis direction of the polarizer and the slow phase axis direction of the second optical compensation layer intersect without being substantially orthogonal. The Nz coefficient of the third optical compensation layer is -4 or greater and 0 or less, or 0.9 or greater and 4 or less. The first optical compensation layer, the second optical compensation layer, and the third optical compensation layer are optical laminates that satisfy the following formula (1): [Math 1] (In formula (1), Rth １ (550) represents the phase difference in the thickness direction of the first optical compensation layer; Rth ２ (550) represents the phase difference in the thickness direction of the second optical compensation layer; Rth ３ (550) represents the phase difference in the thickness direction of the third optical compensation layer; Re ２ (550) represents the in-plane phase difference of the second optical compensation layer; Re ３ (550) represents the in-plane phase difference of the third optical compensation layer.

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