Optical laminate and image display device using optical laminate

Abstract

To provide an optical laminate comprising a liquid crystal alignment solidified layer, capable of achieving superior visibility in an oblique direction and suppressing specific display unevenness when used in an image display device.SOLUTION: An optical laminate according to an embodiment of the present invention comprises, in this order, a polarizing plate including a polarizer, an optical compensation layer, and a retardation layer. The optical compensation layer exhibits a refractive index characteristic of nx>ny and a relation of nx<1.55, and its slow axis is substantially orthogonal to an absorption axis of the polarizer. The retardation layer includes, in order from the optical compensation layer side, a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer, and has, as a whole, a circular polarization capability or an elliptical polarization capability.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have been rapidly spreading. In many cases, an optical laminate including a retardation film (for example, an antireflection film in which a polarizing plate and a retardation film are integrated) is used for an image display device. In recent years, as the demand for thinning of image display devices has increased, the demand for thinning of optical laminates has also increased. For the purpose of thinning the optical laminate, the retardation layer (retardation film), which makes a large contribution to the thickness, has been thinned. As a typical example of a thin retardation film, a film in which a liquid crystal compound is aligned and its alignment state is fixed (hereinafter referred to as a liquid crystal film) can be mentioned. Since the liquid crystal compound has a much larger birefringence (Δn) than resin, the liquid crystal film can have a much smaller thickness than the stretched film of the resin film to obtain a desired in-plane retardation. However, an image display device using an optical laminate including a liquid crystal film may exhibit display unevenness (specifically, a phenomenon in which a thin pink line is particularly noticeable in the absorption axis direction of the polarizer) depending on the viewing environment. Furthermore, an image display device using an optical laminate including a liquid crystal film may have a large reflectance in an oblique direction (insufficient visibility in an oblique direction).

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-described conventional problems, and its main object is to provide an optical laminate that includes a liquid crystal alignment cured layer and realizes excellent visibility in an oblique direction and suppresses specific display unevenness when applied to an image display device.

Means for Solving the Problems

[0005] [1] The optical laminate according to an embodiment of the present invention has, in this order, a polarizing plate including a polarizer, an optical compensation layer, and a retardation layer; the optical compensation layer exhibits a refractive index characteristic of nx > ny, and shows a relationship of nx < 1.55, and its slow axis is substantially orthogonal to the absorption axis of the polarizer; the retardation layer includes a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer in this order from the optical compensation layer side, and has a circular polarization function or an elliptical polarization function as a whole. [2] In the above [1], the optical compensation layer exhibits a refractive index characteristic of nx > ny ≥ nz. [3] In the above [1] or [2], Re(550) of the optical compensation layer is 50 nm to 220 nm. [4] In any one of the above [1] to [3], Re(550) of the optical compensation layer is 50 nm to 150 nm. [5] In any one of the above [1] to [4], the optical compensation layer is composed of a stretched film of a resin film, and its thickness is 10 μm to 50 μm. [6] In any one of the above [1] to [5], the retardation layer shows a relationship of Re(450) < Re(550) as a whole. [7] In any one of the above [1] to [6], the first liquid crystal alignment cured layer exhibits a refractive index characteristic of nz ≥ nx > ny. [8] In any one of the above [1] to [7], the second liquid crystal alignment cured layer exhibits a refractive index characteristic of nx > ny ≥ nz. [9] In any one of the above [1] to [8], the slow axis of the first liquid crystal alignment cured layer and the slow axis of the second liquid crystal alignment cured layer intersect.

[10] In any one of [1] to [9] above, the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer are laminated via an active energy ray curable adhesive.

[11] According to another aspect of the present invention, an image display device is provided. The image display device includes the optical laminate according to any one of [1] to

[10] above.

Advantages of the Invention

[0006] According to an embodiment of the present invention, it is possible to realize an optical laminate that includes a liquid crystal alignment cured layer and can achieve excellent visibility in an oblique direction and suppress specific display unevenness when applied to an image display device.

Brief Description of the Drawings

[0007]

Figure 1

Embodiments for Carrying Out the Invention

[0008] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-Plane Phase Difference (Re) "Re(λ)" is the in-plane phase difference of the film measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane phase difference of the film measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re = (nx - ny) × d, where d (nm) is the thickness of the film. (3) Thickness Direction Retardation (Rth) "Rth(λ)" is the retardation in the thickness direction of the film measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction of the film measured with light of wavelength 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth = (nx - nz) × d, where d is the thickness of the film in nm. (4) Nz Coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions. Therefore, for example, "45°" includes ±45°.

[0010] A. Optical Laminate FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 in the illustrated example has a polarizing plate 10, an optical compensation layer 30, and a retardation layer 20 in this order. The polarizing plate 10 and the optical compensation layer 30, and the optical compensation layer 30 and the retardation layer 20 are each laminated via an arbitrary appropriate adhesive layer (for example, an adhesive layer, an adhesive layer: not shown). The polarizing plate 10 typically includes a polarizer 11 and protective layers 12 and 13 disposed on both sides of the polarizer 11. Depending on the purpose, at least one of the protective layers 12 and 13 may be omitted. Therefore, the polarizing plate may be a so-called double-protection polarizing plate, a so-called single-protection polarizing plate, or may be composed of only a polarizer.

[0011] The retardation layer 20 includes a first liquid crystal alignment cured layer 21 and a second liquid crystal alignment cured layer 22 in this order from the side of the optical compensation layer 30. The first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22 are laminated via any appropriate adhesive layer (for example, an adhesive layer, a pressure-sensitive adhesive layer: not shown). In one embodiment, the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22 are laminated via an active energy ray curable adhesive. By using the liquid crystal alignment cured layer as the retardation layer, a desired in-plane retardation can be realized with a thickness significantly thinner than that of the stretched film of the resin film. As a result, a remarkable thinning of the optical laminate can be achieved. The retardation layer 20 as a whole (as a laminate of the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22) has a circular polarization function or an elliptical polarization function. In one embodiment, the retardation layer as a whole may have an Nz coefficient of, for example, 0.30 to 0.70. In the present specification, the "liquid crystal alignment cured layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The "liquid crystal alignment cured layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer.

[0012] In the optical laminate, the total thickness from the first liquid crystal alignment cured layer to the second liquid crystal alignment cured layer (that is, the total thickness of the retardation layer) is preferably 15 μm or less, more preferably 3 μm to 10 μm. If the total thickness from the first liquid crystal alignment cured layer to the second liquid crystal alignment cured layer is within the above range, the total thickness from the polarizing plate to the second liquid crystal alignment cured layer (the substantial total thickness of the optical laminate excluding the thickness of the adhesive for bonding to the image display panel) can be, for example, 100 μm or less, or for example, 30 μm to 80 μm.

[0013] The optical compensation layer 30 exhibits a refractive index characteristic of nx > ny, and thus has a slow axis. More specifically, the optical compensation layer exhibits a refractive index characteristic of nx > ny ≥ nz. The slow axis of the optical compensation layer 30 is substantially orthogonal to the absorption axis of the polarizer 11 (i.e., the direction of the slow axis is substantially the direction of the transmission axis of the polarizer). Here, "substantially orthogonal" includes the case where the angle formed by the two directions (here, the slow axis direction of the optical compensation layer and the absorption axis direction of the polarizer) is 85° to 95°, preferably 87° to 93°, more preferably 89° to 91°, and even more preferably about 90°.

[0014] In an embodiment of the present invention, the optical compensation layer shows a relationship of nx < 1.55. The nx of the optical compensation layer is preferably 1.54 or less, and more preferably 1.53 or less. The lower limit of nx of the optical compensation layer can be, for example, 1.48.

[0015] When the present inventors considered further thinning of an optical laminate including a liquid crystal alignment cured layer as a retardation layer, they found a new problem that an image display device using an optical laminate including a liquid crystal alignment cured layer as a retardation layer may exhibit specific display unevenness depending on the viewing environment. Specifically, in the reflection under a three-wavelength light source, it was found that a phenomenon (sometimes referred to as line unevenness) in which a thin pink line that is particularly noticeable in the absorption axis direction of the polarizer is visually recognized over the entire area may occur. As a result of intensive studies on suppressing such line unevenness, the present inventors found that by configuring the liquid crystal alignment cured layer on the polarizer side in the optical laminate to have a specific configuration (typically, a configuration showing refractive index characteristics of nz ≧ nx > ny), the line unevenness can be suppressed well. On the other hand, the present inventors newly found that an image display device using an optical laminate having such a configuration has a problem that the reflectance in the oblique direction is large (the visibility in the oblique direction is insufficient). As a result of comprehensively studying the improvement of such oblique direction visibility and the suppression of the above-mentioned line unevenness, the present inventors found that by disposing an optical compensation layer having specific refractive index characteristics and a specific nx between the polarizer and the retardation layer such that its slow axis is substantially orthogonal to the absorption axis of the polarizer, the line unevenness can be suppressed while improving the visibility in the oblique direction. nx corresponds to the refractive index in the transmission axis direction of the polarizer in the optical compensation layer. That is, by making the refractive index in the transmission axis direction of the polarizer in the optical compensation layer smaller than a predetermined value, an optical laminate capable of realizing excellent visibility in the oblique direction and suppressing specific display unevenness when applied to an image display device can be realized. Thus, such an effect according to the embodiment of the present invention solves a newly found problem in comprehensively studying the suppression of line unevenness and the improvement of visibility in the oblique direction in an optical laminate including a liquid crystal alignment cured layer as a retardation layer, and is an unexpectedly excellent effect. Needless to say, the embodiment of the present invention can suppress conventionally recognized display unevenness.

[0016] The optical laminate may be in a sheet form or a long strip form. In this specification, "long strip form" means an elongated shape that is sufficiently long in length compared to the width, for example, an elongated shape with a length that is 10 times or more, preferably 20 times or more, the width. The long strip-shaped optical laminate can be wound into a roll. The long strip-shaped optical laminate can be produced, for example, by a so-called roll-to-roll process. The sheet-shaped optical laminate may be produced by cutting a long strip-shaped optical laminate into a predetermined size (typically, a size corresponding to an image display device), or may be produced by bonding together each component (each layer) cut into a predetermined size.

[0017] Practically, the optical laminate has an adhesive layer (not shown) as the outermost layer on the second liquid crystal alignment solidification layer side (image display panel side) and is configured to be attachable to the image display panel. In this case, 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 the optical laminate can be formed into a roll.

[0018] Hereinafter, the components of the optical laminate will be specifically described.

[0019] B. Polarizing plate B-1. Polarizer The polarizer 11 is typically composed of a polyvinyl alcohol (PVA)-based resin film containing a dichroic substance (for example, iodine). Examples of the PVA-based resin include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and an ethylene-vinyl acetate copolymer-based partially saponified product.

[0020] The PVA-based resin preferably includes an acetoacetyl-modified PVA-based resin. With such a configuration, a polarizer having a desired mechanical strength can be obtained. When the total amount of the PVA-based resin is 100% by weight, the blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% to 20% by weight, more preferably 8% to 12% by weight. If the blending amount is within such a range, a polarizer having more excellent mechanical strength can be obtained.

[0021] The polarizer preferably contains an iodide or sodium chloride (which may be collectively referred to as a halide). Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, based on 100 parts by weight of the PVA-based resin. The halide can be blended into the coating solution for forming the PVA-based resin layer, which is a precursor of the polarizer, in the manufacturing method described below, and finally introduced into the polarizer. By introducing the halide into the polarizer, the orientation of PVA molecules in the polarizer can be enhanced, so that a polarizer having excellent optical properties (typically, the coexistence of a high degree of polarization and a high single transmittance) can be realized.

[0022] The polarizer preferably exhibits absorption dichroism at any wavelength in the range of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 41.0% to 46.0%, more preferably 42.0% to 45.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more. According to the embodiment of the present invention, even when the single transmittance is within the above range, the degree of polarization can be maintained within such a range.

[0023] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 μm to 8 μm, and even more preferably 3 μm to 7 μm. By combining such a thin polarizer with the liquid crystal alignment curing layer, significant thinning of the optical laminate becomes possible. Further, if the thickness of the polarizer is within the above range, curling during heating can be favorably suppressed, and good appearance durability during heating can be obtained.

[0024] The polarizer can be produced by any suitable method. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0025] Specific examples of the polarizer composed of a single-layer resin film include hydrophilic polymer films such as PVA-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films, which are subjected to dyeing treatment with dichroic substances such as iodine and dichroic dyes and stretching treatment, and polyene-based alignment films such as dehydrated products of PVA and dehydrochlorinated products of polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used because of its excellent optical properties.

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

[0027] Specific examples of the polarizer obtained using the 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 formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In the present embodiment, preferably, a PVA-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. Further, stretching may further include air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution, if necessary. In addition, in the present embodiment, preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a stretching treatment in water, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA and dissolution when immersed in water in the subsequent dyeing process and stretching process can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. As a result, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and a stretching treatment in water, in which the laminate is immersed in a liquid, can be improved. Furthermore, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface obtained by peeling the resin substrate from the resin substrate / polarizer laminate, or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0028] B-2. Protective Layer The protective layers 12 and 13 are composed of an arbitrary appropriate resin film. Representative materials constituting the resin film include cellulose-based resins such as triacetyl cellulose (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic-based resins, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins. Representative examples of the (meth)acrylic-based resin include (meth)acrylic-based resins having a lactone ring structure. (Meth)acrylic-based resins having a lactone ring structure are described, for example, in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, and JP-A-2005-146084. The entire disclosures of these publications are incorporated herein by reference. From the viewpoint of ease of profile processing and the like, cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic-based resins are preferred.

[0029] The optical laminate is typically disposed on the viewing side of an image display device, and the protective layer 12 is typically disposed on its viewing side. Therefore, the protective layer 12 may be surface-treated as necessary. Examples of the surface treatment include hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment. Further / Alternatively, the protective layer 12 may be treated as necessary to improve visibility when viewing through polarized sunglasses (typically, by imparting an (elliptical) polarization function or a very high retardation). By performing such treatment, excellent visibility can be achieved even when viewing the display screen through a polarizing lens such as polarized sunglasses. Therefore, the optical laminate can also be suitably applied to an image display device that can be used outdoors.

[0030] In one embodiment, the protective layer 13 is preferably optically isotropic. As used herein, "optically isotropic" means that the in-plane retardation Re(550) is from 0 nm to 10 nm and the retardation in the thickness direction Rth(550) is from -10 nm to +10 nm.

[0031] The thicknesses of the protective layers 12 and 13 are each preferably from 10 μm to 80 μm, more preferably from 12 μm to 40 μm, and still more preferably from 15 μm to 35 μm. When the protective layer 12 is surface-treated, the thickness of the protective layer 12 is the thickness including the thickness of the surface treatment layer.

[0032] C. Retardation layer C-1. Outline of the retardation layer As described above, the retardation layer 20 includes a first liquid crystal alignment cured layer 21 and a second liquid crystal alignment cured layer 22 in order from the polarizer side. Regarding the description of the retardation layer in this section, when simply referred to as the "retardation layer", it means an explanation of the entire retardation layer, and when simply referred to as the "liquid crystal alignment cured layer", it means an explanation of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer together.

[0033] As described above, the retardation layer 20 as a whole (as a laminate of the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22) has a circular polarization function or an elliptical polarization function. Therefore, Re(550) of the retardation layer is preferably 130 nm to 180 nm, more preferably 140 nm to 170 nm, still more preferably 150 nm to 160 nm, and particularly preferably 152 nm to 157 nm. The retardation layer preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. Re(450) / Re(550) of the retardation layer is preferably 0.85 to 0.98, more preferably 0.88 to 0.95, and still more preferably 0.90 to 0.93. The angle formed by the apparent slow axis of the retardation layer and the transmission axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and still more preferably 44° to 46°. In one embodiment, the retardation layer may exhibit a refractive index characteristic of nx > nz > ny. Therefore, the Nz coefficient of the retardation layer may be, for example, 0.30 to 0.70, or may be, for example, 0.40 to 0.60, or may be, for example, 0.45 to 0.55.

[0034] The liquid crystal alignment cured layer can adopt any appropriate configuration as long as the retardation layer exhibits the above characteristics. In one embodiment, the first liquid crystal alignment cured layer exhibits a refractive index characteristic of nz ≧ nx > ny, and the second liquid crystal alignment cured layer exhibits a refractive index characteristic of nx > ny ≧ nz.

[0035] Hereinafter, the respective configurations of the first liquid crystal alignment cured layer exhibiting a refractive index characteristic of nz ≧ nx > ny and the second liquid crystal alignment cured layer exhibiting a refractive index characteristic of nx > ny ≧ nz will be specifically described.

[0036] C-2. The First Liquid Crystal Alignment Cured Layer As described above, the first liquid crystal alignment cured layer exhibits refractive index characteristics of nz ≧ nx > ny. That is, the first liquid crystal alignment cured layer can be a negative A plate (nz = nx > ny) or a positive B plate (nz > nx > ny). The Re(550) of the first liquid crystal alignment cured layer is preferably 200 nm to 300 nm, more preferably 210 nm to 270 nm, and even more preferably 230 nm to 250 nm. The Nz coefficient of the first liquid crystal alignment cured layer is preferably -0.2 to 0, more preferably -0.1 to 0, and even more preferably -0.05 to 0. Note that "nz = nx" includes not only the case where nx and nz are exactly equal, but also the case where nx and nz are substantially equal. Therefore, the Nz coefficient of the first liquid crystal alignment cured layer can be less than 1.0 (for example, 0 or more and less than 1.0).

[0037] The thickness of the first liquid crystal alignment cured layer can be adjusted so as to obtain the desired in-plane retardation. In one embodiment, the thickness of the first liquid crystal alignment cured layer can be, for example, 1.0 μm to 3.0 μm.

[0038] The angle formed by the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 74° to 76°.

[0039] As long as the first liquid crystal alignment cured layer satisfies the above optical properties, any appropriate configuration can be adopted. The first liquid crystal alignment cured layer can typically be an alignment cured layer of a liquid crystalline composition containing a discotic liquid crystal compound aligned substantially vertically. In this specification, the "discotic liquid crystal compound" refers to a compound having a disc-shaped mesogenic group in its molecular structure, and 2 to 8 side chains are radially bonded to the mesogenic group via ether bonds or ester bonds. Examples of the above mesogenic group include those having the structure described in P.22, Figure 1 of the Liquid Crystal Dictionary (published by Baifukan). Specifically, benzene, triphenylene, turxene, pyran, rufigallol, porphyrin, metal complexes, etc. Ideally, a discotic liquid crystal compound aligned substantially vertically has an optical axis in one direction within the film plane. The "discotic liquid crystal compound aligned substantially vertically" refers to a state in which the disc plane of the discotic liquid crystal compound is perpendicular to the film plane and the optical axis is parallel to the film plane.

[0040] The liquid crystalline composition containing the above discotic liquid crystal compound is not particularly limited as long as it contains the discotic liquid crystal compound and exhibits liquid crystallinity. The content of the discotic liquid crystal compound in the above liquid crystalline composition is preferably 40 parts by weight or more and less than 100 parts by weight, more preferably 50 parts by weight or more and less than 100 parts by weight, and most preferably 70 parts by weight or more and less than 100 parts by weight based on 100 parts by weight of the total solid content of the liquid crystalline composition.

[0041] The alignment cured layer of the liquid crystalline composition containing the above discotic liquid crystal compound aligned substantially vertically can be obtained, for example, by the method described in JP-A-2001-56411. The discotic liquid crystal compound in the above liquid crystal composition can be aligned along the restraining force imparted by an alignment treatment such as a rubbing treatment or a photoalignment treatment. Therefore, by performing an alignment treatment so that the restraining force acts in a desired direction and coating the liquid crystal composition thereon, a liquid crystal alignment cured layer (negative A plate) having a slow axis in the desired direction can be produced without performing a stretching or shrinking treatment thereafter.

[0042] In another embodiment, the first liquid crystal alignment cured layer can be an alignment cured layer of a lyotropic liquid crystal compound-containing liquid crystal composition that is homogeneously aligned. As used herein, the term "lyotropic liquid crystal compound" refers to a liquid crystal compound in which a liquid crystal phase is exhibited depending on the concentration of a solute in a solution state. Any suitable lyotropic liquid crystal compound can be used. Specific examples of the lyotropic liquid crystal compound include amphiphilic compounds having a hydrophilic group and a hydrophobic group at both ends of a molecule, chromonic compounds having an aromatic ring imparted with water solubility, and polymer compounds such as cellulose derivatives, polypeptides, and nucleic acids whose main chains have a rod-like skeleton. Preferably, it is an alignment cured layer of a liquid crystal composition containing a homogeneously aligned lyotropic liquid crystal compound, and the lyotropic liquid crystal compound is a chromonic compound having an aromatic ring imparted with water solubility.

[0043] The liquid crystal composition containing the above-mentioned lyotropic liquid crystal compound is not particularly limited as long as it contains a lyotropic liquid crystal compound and exhibits liquid crystallinity. The content of the discotic liquid crystal compound in the liquid crystal composition is preferably 40 parts by weight or more and less than 100 parts by weight, more preferably 50 parts by weight or more and less than 100 parts by weight, and most preferably 70 parts by weight or more and less than 100 parts by weight with respect to 100 of the total solid content of the liquid crystal composition.

[0044] The retardation film composed of the alignment cured layer of the liquid crystal composition containing the above-mentioned homogeneously aligned lyotropic liquid crystal compound can be obtained, for example, by the method described in JP-A-2002-296415. The lyotropic liquid crystal compound in the liquid crystal composition can be aligned along the regulating force imparted by an alignment treatment such as a rubbing treatment or a photoalignment treatment. Therefore, by performing an alignment treatment so that a regulating force acts in a desired direction and then coating the liquid crystal composition thereon, a liquid crystal alignment cured layer having a slow axis in the desired direction can be produced without performing a stretching or shrinking treatment thereafter.

[0045] C-3. Second Liquid Crystal Alignment Cured Layer As described above, the second liquid crystal alignment cured layer exhibits refractive index characteristics of nx > ny ≥ nz. That is, the second liquid crystal alignment cured layer can be a positive A plate (nx > ny = nz) or a negative B plate (nx > ny > nz). The Re(550) of the second liquid crystal alignment cured layer is preferably 100 nm to 200 nm, more preferably 110 nm to 160 nm, and even more preferably 110 nm to 130 nm. The Nz coefficient of the second liquid crystal alignment cured layer is preferably 1.0 to 1.3, more preferably 1.0 to 1.2, and even more preferably 1.0 to 1.1. Note that "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where ny and nz are substantially equal. Therefore, the Nz coefficient of the second liquid crystal alignment cured layer can be less than 1.0 (for example, 0.95 or more and less than 1.0).

[0046] The thickness of the second liquid crystal alignment cured layer can be adjusted so as to obtain the desired in-plane retardation. In one embodiment, the thickness of the second liquid crystal alignment cured layer can be, for example, 0.8 μm to 1.5 μm.

[0047] The angle formed between the slow axis of the second liquid crystal alignment cured layer and the transmission axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 14° to 16°. Therefore, the slow axis of the first liquid crystal alignment cured layer and the slow axis of the second liquid crystal alignment cured layer intersect. The angle formed between the slow axis of the first liquid crystal alignment cured layer and the slow axis of the second liquid crystal alignment cured layer is preferably 55° to 65°, more preferably 57° to 63°, and even more preferably 59° to 61°. Note that the angle formed between the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer and the angle formed between the slow axis of the second liquid crystal alignment cured layer and the transmission axis of the polarizer may be reversed.

[0048] Examples of the liquid crystal compound used for the second liquid crystal alignment cured layer include, for example, liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable (i.e., a liquid crystal monomer). When the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by polymerizing it after aligning the liquid crystal compound. Here, the polymer formed by polymerization is non-liquid crystalline. Therefore, in the formed second liquid crystal alignment cured layer, for example, the transition from the liquid crystal phase, glass phase, and crystal phase due to the temperature change peculiar to the liquid crystalline compound does not occur. As a result, the liquid crystal alignment cured layer becomes a retardation layer that is not affected by temperature changes and has extremely excellent stability. In one embodiment, in the second liquid crystal alignment cured layer, rod-shaped liquid crystal compounds are arranged in the direction of the slow axis (homogeneous alignment).

[0049] In one embodiment, the second liquid crystal alignment cured layer can be formed using a composition containing a polymerizable liquid crystal compound (polymerizable liquid crystal compound, i.e., liquid crystal monomer). In this specification, the polymerizable liquid crystal compound contained in the composition refers to a compound having a polymerizable group and having liquid crystallinity. The polymerizable group means a group involved in the polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in the polymerization reaction by active radicals, acids, etc. generated from a photopolymerization initiator. Examples of the liquid crystal monomer include, for example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Specific examples of such polymerizable mesogenic compounds include, for example, LC242 (trade name of BASF), E7 (trade name of Merck), and LC-Sillicon-CC3767 (trade name of Wacker-Chem).

[0050] The mechanism of the manifestation of the liquid crystallinity of the liquid crystal compound may be thermotropic or lyotropic. Also, as the constitution of the liquid crystal phase, it may be a nematic liquid crystal or a smectic liquid crystal. From the viewpoint of ease of production, thermotropic nematic liquid crystals are preferred for the liquid crystallinity.

[0051] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably from 40°C to 120°C, more preferably from 50°C to 100°C, and most preferably from 60°C to 90°C.

[0052] The birefringence Δn of the liquid crystal alignment fixing layer is preferably 0.06 or more, more preferably 0.08 or more, still more preferably 0.09 or more, and particularly preferably 0.10 or more. The upper limit of Δn can be, for example, 0.13, or can be, for example, 0.12. If Δn is in such a range, a desired in-plane retardation can be realized with a very thin thickness. As a result, the second liquid crystal alignment fixing layer and the optical laminate can be made thinner, and ultimately can contribute to a significant thinning of the image display device.

[0053] D. Optical compensation layer As described above, nx of the optical compensation layer is less than 1.55, preferably 1.54 or less, and more preferably 1.53 or less. The lower limit of nx of the optical compensation layer can be, for example, 1.48 as described above. If nx of the optical compensation layer is in such a range, the first liquid crystal alignment fixing layer can be appropriately optically compensated, and light leakage in the oblique direction can be suppressed. As a result, the visibility in the oblique direction can be improved. At the same time, line-like unevenness can be well suppressed.

[0054] As described above, the optical compensation layer exhibits refractive index characteristics of nx > ny ≥ nz. That is, the optical compensation layer can be a positive A plate (nx > ny = nz) or a negative B plate (nx > ny > nz). As described above, the slow axis of the optical compensation layer is substantially orthogonal to the absorption axis of the polarizer. Re(550) of the optical compensation layer is preferably from 50 nm to 220 nm, more preferably from 60 nm to 200 nm, and still more preferably from 70 nm to 190 nm. Re(550) of the optical compensation layer may be, for example, from 50 nm to 150 nm, or may be, for example, from 70 nm to 140 nm. The Nz coefficient of the optical compensation layer is preferably from 1.0 to 1.3, more preferably from 1.0 to 1.2, and still more preferably from 1.0 to 1.1. Note that "ny = nz" includes not only the case where ny and nz are exactly equal, but also the case where ny and nz are substantially equal. Therefore, the Nz coefficient of the optical compensation layer can be less than 1.0 (for example, 0.95 or more and less than 1.0).

[0055] As long as the optical compensation layer shows a relationship of nx < 1.55, any suitable configuration can be adopted. Specifically, the optical compensation layer may be a stretched film of a resin film or a liquid crystal alignment solidified layer. Preferably, it is a stretched film of a resin film because a desired nx can be easily realized. On the other hand, by using a liquid crystal compound having an appropriate birefringence Δn (= nx - ny), a liquid crystal alignment solidified layer having a desired nx can be obtained.

[0056] As the resin film, any suitable resin film can be adopted. Representative examples of the resin constituting the resin film include cyclic olefin resins. The cyclic olefin resin is a general term for resins polymerized with cyclic olefins as polymerization units, and examples include resins described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, etc. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), graft-modified products obtained by modifying these with unsaturated carboxylic acids or their derivatives, and hydrogenated products thereof. Specific examples of cyclic olefins include norbornene-based monomers. Examples of norbornene-based monomers include monomers described in JP-A-2015-210459, etc.

[0057] As long as the effects according to the embodiments of the present invention can be obtained, other cycloolefins capable of ring-opening polymerization may be used in combination. Specific examples of such cycloolefins include, for example, compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

[0058] The above cyclic olefin resin preferably has a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) using a toluene solvent of 25,000 to 200,000, more preferably 30,000 to 100,000, and most preferably 40,000 to 80,000. If the number average molecular weight is within the above range, a product excellent in mechanical strength, solubility, moldability, and casting operability can be obtained.

[0059] Various products of the above cyclic olefin resins are commercially available. Specific examples include the product names "Zeonex" and "Zeonor" manufactured by Nippon Zeon Co., Ltd., "Arton" manufactured by JSR Corporation, "Topas" manufactured by Ticona, and "APEL" manufactured by Mitsui Chemicals, Inc.

[0060] The optical compensation layer can be obtained, for example, by stretching a film formed from the above-mentioned cyclic olefin resin. As a method for forming a film from a cyclic olefin resin, any suitable molding process can be employed. Since many film products made of the cyclic olefin resin are commercially available, the commercially available film may be directly subjected to a stretching process.

[0061] The stretching method and stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction) can be appropriately set according to the purpose and the optical properties desired for the optical compensation layer. For example, a positive A plate (nx > ny = nz) can be obtained by uniaxially stretching the resin film, and a negative B plate (nx > ny > nz) can be obtained by biaxially stretching the resin film.

[0062] E. Adhesive layer As described above, the polarizing plate 10 and the optical compensation layer 30, and the optical compensation layer 30 and the retardation layer 20 are each laminated via an arbitrary appropriate adhesive layer. That is, the adhesive layer may be an adhesive layer or a pressure-sensitive adhesive layer. When the adhesive layer is an adhesive layer, the adhesive layer is typically composed of an active energy ray-curable adhesive. Further, as described above, the first liquid crystal alignment curing layer and the second liquid crystal alignment curing layer are typically laminated via an active energy ray-curable adhesive. Hereinafter, the active energy ray-curable adhesive and the pressure-sensitive adhesive will be specifically described.

[0063] The active energy ray-curable adhesive can adopt any appropriate configuration. By adjusting the number, type, combination, blending amount, etc. of the resin component, curing component, photoinitiator, and additive in the adhesive (adhesive composition), an adhesive (adhesive composition) having desired properties can be obtained. In one embodiment, the adhesive (adhesive composition) may contain a (meth)acrylate containing an aromatic ring skeleton and / or metal oxide particles. Hereinafter, each will be briefly described. Note that since well-known configurations can be adopted for other components (e.g., curing component, photoinitiator) that can be contained in the adhesive, specific descriptions are omitted.

[0064] By the adhesive composition containing a (meth)acrylate having an aromatic ring skeleton, an adhesive layer having a desired refractive index can be formed in an embodiment of the present invention. As the (meth)acrylate having an aromatic ring skeleton, it is preferable to use one containing at least one selected from the group consisting of (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings. Examples of such (meth)acrylates include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 1-naphthalenemethyl (meth)acrylate, phenoxybenzyl (meth)acrylate, ethylene oxide-modified orthophenylphenol (meth)acrylate, and the reaction product of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and (meth)acrylic acid. Among these, it is more preferable to use phenoxybenzyl (meth)acrylate and phenoxyethyl (meth)acrylate, and it is particularly preferable to use phenoxybenzyl (meth)acrylate. When the total amount of the adhesive composition is 100% by mass, the blending amount of the (meth)acrylate having an aromatic ring skeleton is preferably 20% to 90% by mass, and more preferably 30% to 80% by mass.

[0065] Examples of the metal oxide particles include silicon oxide, zirconium oxide, titanium oxide, zinc oxide, antimony pentoxide, tin oxide, aluminum oxide, indium oxide, indium tin oxide, ferric oxide, cerium oxide, yttrium oxide, manganese oxide, holmium oxide, copper oxide, bismuth oxide, cobalt oxide, cobalt tetroxide, iron tetroxide, magnesium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, tantalum pentoxide, niobium pentoxide, iridium oxide, rhodium oxide, ruthenium oxide, and composite oxides formed by combining these. Among these, zirconium oxide and titanium oxide are preferred, and zirconium oxide is particularly preferred. Note that the metal oxide particles may be composed only of the metal oxides listed above, or may contain other components, but it is preferable that the metal oxide occupies the maximum weight as a component in the particles. The shape of the metal oxide particles can be any shape such as spherical, ellipsoidal, cubic, rectangular parallelepiped, or pyramidal. Note that as the metal oxide particles, those surface-treated by any appropriate method may be used.

[0066] From the viewpoints of improving the stability of the metal oxide particles in the adhesive composition and improving the refractive index of the adhesive layer, the average particle diameter of the metal oxide particles is preferably 1 nm to 150 nm, and more preferably 1 nm to 50 nm. The average particle diameter of the metal oxide particles can be derived, for example, by the following method: The particles are magnified and observed using a transmission electron microscope (TEM), a field emission transmission electron microscope (FE-TEM), a field emission scanning electron microscope (FE-SEM), etc., and, for example, 1000 particles are randomly selected, their maximum length is measured, and the arithmetic mean is calculated.

[0067] From the viewpoint of improving the stability of the metal oxide particles in the adhesive composition and the refractive index of the adhesive layer, the compounding amount of the metal oxide particles is preferably 10% by mass to 50% by mass, more preferably 15% by mass to 40% by mass, when the total amount of the adhesive composition is 100% by mass.

[0068] The adhesive composition may further contain a hydroxyl group-containing (meth)acrylate. With such a configuration, the adhesive strength of the adhesive layer can be further improved. The compounding amount of the hydroxyl group-containing (meth)acrylate is preferably 1% by mass to 30% by mass, more preferably 3% by mass to 20% by mass, when the total amount of the adhesive composition is 100% by mass.

[0069] The pressure-sensitive adhesive can also adopt any suitable configuration. By adjusting the type, number, combination, and compounding amount of the monomer components of the base polymer in the pressure-sensitive adhesive (pressure-sensitive adhesive composition); the type, number, combination, and compounding amount of the crosslinking agent; and the type, number, combination, and compounding amount of the additives, a pressure-sensitive adhesive (pressure-sensitive adhesive composition) having desired characteristics can be prepared. In one embodiment, the monomer components of the base polymer of the pressure-sensitive adhesive (pressure-sensitive adhesive composition) include a heterocyclic ring-containing acrylate and / or an aromatic ring-containing acrylate. Examples of the heterocyclic ring-containing acrylate include acryloylmorpholine. Examples of the aromatic ring-containing acrylate include benzyl acrylate and phenoxybenzyl acrylate.

[0070] F. Image display device The optical laminate described in the above items A to E can be applied to an image display device. Therefore, the embodiments of the present invention also include an image display device using such an optical laminate. Representative examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to the embodiments of the present invention typically includes the optical laminate described in the above items A to E on its viewing side.

Examples

[0071] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

[0072] (1) Refractive index nx Regarding the optical compensation layers used in the examples and comparative examples, the in-plane retardation Re(550) and the thickness-direction retardation Rth(550) were measured using Axoscan (manufactured by Axometrics). From the following simultaneous equations, nx, ny, and nz were calculated. Re(550)=(nx - ny)×d Nz = Rth(550) / Re(550)=(nx - nz) / (nx - ny)

[0073] (2) Thickness Measured with an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0074] (3) Line pattern unevenness The image display devices obtained in the examples and comparative examples were visually observed under a three-wavelength fluorescent lamp in the non-lighting state and evaluated according to the following criteria. ◎(Excellent): No line pattern unevenness was observed even when observed with a polarizing plate attached to the three-wavelength fluorescent lamp. ○(Good): No line pattern unevenness was observed in the normal observation with a three-wavelength fluorescent lamp. △(Unacceptable): Line pattern unevenness was observed in the normal observation with a three-wavelength fluorescent lamp. ×(Poor): Line pattern unevenness was prominent in the normal observation with a three-wavelength fluorescent lamp.

[0075] (4) Reflectance The optical laminate obtained in the examples and comparative examples was bonded to an aluminum reflector via an acrylic adhesive, and the reflectance (Y value) at a polar angle of 50° was measured using a spectrophotometer CM-26d (manufactured by Konica Minolta).

[0076] [Production Example 1: Production of a polarizing plate] 1. Production of a polarizer As the thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) in a long strip shape with a Tg of about 75°C was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gohsei Chemical Industry Co., Ltd., trade name "Gosefimer") at a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The above PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (lengthwise direction) in an oven at 130°C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer becomes a desired value (dyeing treatment). Next, the laminate was immersed in a crosslinking bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 70°C (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%), uniaxial stretching was performed in the longitudinal direction (lengthwise direction) between rolls with different peripheral speeds so that the total stretching ratio becomes 5.5 times (in-water stretching treatment). Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 20°C (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment). Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a long polarizing plate having a resin substrate / polarizer structure was obtained. The single transmittance Ts of the polarizer was 43.3%. The polarizer had an absorption axis in the longitudinal direction. Hereinafter, the absorption axis direction (longitudinal direction) is referred to as the "0° direction", and the transmission axis direction (width direction) is referred to as the "90° direction".

[0077] 2. Fabrication of Polarizing Plate An HC-COP film was laminated on the surface of the obtained polarizer (the surface opposite to the resin substrate) via an ultraviolet curable adhesive. The HC-COP film is a film in which an HC layer (thickness 4 μm) is formed on a cycloolefin resin (COP) film (thickness 25 μm), and it was laminated so that the COP film was on the polarizer side. The Re(550) of the COP film was 100 nm. Here, the HC-COP film was laminated so that the angle between the slow axis of the COP film and the absorption axis of the polarizer was 45°. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness 25 μm) was laminated on the peeled surface via an ultraviolet curable adhesive. In this way, a polarizing plate having a structure of HC layer / COP film (protective layer) / polarizer / TAC film (protective layer) was obtained.

[0078] [Production Example 2-1: Fabrication of Stretched Film (Phase Difference Film) Constituting Optical Compensation Layer] A commercially available cycloolefin resin film (manufactured by Nippon Zeon Co., Ltd., product name "Zeonoa ZF14", thickness 40 μm) was subjected to roll stretching (free-end uniaxial stretching) with a stretching ratio of 1.18 times and a stretching temperature of 135 °C to obtain a phase difference film 2-1. The phase difference film 2-1 exhibited refractive index characteristics of nx > ny = nz (positive A plate), the thickness was 37 μm, Re(550) was 80 nm, nx was 1.52, and the slow axis was in the 0° direction.

[0079] [Production Example 2-2: Fabrication of Stretched Film (Phase Difference Film) Constituting Optical Compensation Layer] A retardation film 2-2 was obtained in the same manner as in Production Example 2-1 except that the draw ratio was changed to 1.35 times. The retardation film 2-2 exhibited refractive index characteristics of nx > ny = nz (positive A plate), a thickness of 34 μm, Re(550) of 130 nm, nx of 1.52, and the slow axis in the 0° direction.

[0080] [Production Example 2-3: Production of a stretched film (retardation film) constituting an optical compensation layer] A retardation film 2-3 was obtained in the same manner as in Production Example 2-1 except that the draw ratio was changed to 1.52 times. The retardation film 2-3 exhibited refractive index characteristics of nx > ny = nz (positive A plate), a thickness of 32 μm, Re(550) of 180 nm, nx of 1.52, and the slow axis in the 0° direction.

[0081] [Production Example 3-1: Production of a stretched film (retardation film) constituting an optical compensation layer] A commercially available cycloolefin-based resin film (manufactured by Nippon Zeon Co., Ltd., product name "Zeonex ZF14", thickness 40 μm) was subjected to transverse stretching with a draw ratio of 1.18 times and a stretching temperature of 135°C in a direction perpendicular to the conveyance direction to obtain a retardation film 3-1. The retardation film 3-1 exhibited refractive index characteristics of nx > ny > nz (negative B plate), a thickness of 34 μm, Re(550) of 80 nm, Rth(550) of 90 nm, nx of 1.52, and the slow axis in the 90° direction.

[0082] [Production Example 3-2: Production of a stretched film (retardation film) constituting an optical compensation layer] A retardation film 3-2 was obtained in the same manner as in Production Example 3-1 except that the draw ratio in the direction perpendicular to the conveyance direction was changed to 1.35 times. The retardation film 3-2 exhibited refractive index characteristics of nx > ny > nz (negative B plate), a thickness of 30 μm, Re(550) of 130 nm, Rth(550) of 145 nm, nx of 1.52, and the slow axis in the 90° direction.

[0083] [Production Example 3-3: Production of a stretched film (retardation film) constituting an optical compensation layer] A retardation film 3-3 was obtained in the same manner as in Production Example 3-1, except that the stretching magnification in the direction perpendicular to the conveying direction was changed to 1.52 times. The retardation film 3-3 exhibited refractive index characteristics of nx > ny > nz (negative B plate), had a thickness of 26 μm, Re(550) of 180 nm, Rth(550) of 198 nm, nx of 1.52, and the slow axis was in the 90° direction.

[0084] [Production Example 4-1: Preparation of a Liquid Crystal Alignment Solidified Layer Constituting an Optical Compensation Layer] A photopolymerizable liquid crystal compound showing a nematic liquid crystal phase (BASF's "Paliocolor LC242", the following chemical formula) was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. To this solution, a surfactant (BYK-360 manufactured by BYK Chemie) and a photopolymerization initiator (Omnirad907 manufactured by IGM Resins) were added to prepare a liquid crystal composition solution. The addition amounts of the surfactant and the polymerization initiator were 0.01 part by weight and 3 parts by weight, respectively, based on 100 parts by weight of the photopolymerizable liquid crystal compound. As a substrate, a biaxially stretched cycloolefin-based film (Zeonoa Film manufactured by Nippon Zeon, thickness 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition was coated on this substrate with a bar coater so that Re(550) became 80 nm, and heated at 100 °C for 3 minutes to align the liquid crystal. After cooling to room temperature, in a nitrogen atmosphere, ultraviolet rays with an integrated light amount of 400 mJ / cm 2 were irradiated to perform photocuring, and a laminate having the structure of the substrate / liquid crystal alignment solidified layer 4-1 was obtained. The liquid crystal alignment solidified layer 4-1 was homogeneously aligned and exhibited refractive index characteristics of nx > ny = nz (positive A plate), had a thickness of 0.7 μm, nx of 1.65, and the slow axis was in the 90° direction. In the production of the optical laminate, the liquid crystal alignment solidified layer 4-1 was transferred to a polarizing plate via an acrylic adhesive (thickness 5 μm). [Chemical formula]

[0085] [Production Example 4-2: Preparation of a Liquid Crystal Alignment Solidified Layer Constituting an Optical Compensation Layer] A laminate having a substrate / liquid crystal alignment solidified layer 4-2 structure was obtained in the same manner as in Production Example 4-1, except that the coating thickness of the liquid crystal composition was changed so that Re(550) was 130 nm. The liquid crystal alignment solidified layer 4-2 was homogeneously aligned, exhibiting refractive index characteristics of nx>ny=nz (positive A plate), a thickness of 1.1 μm, nx of 1.65, and a slow axis oriented at 90°. In producing the optical laminate, the liquid crystal alignment solidified layer 4-2 was transferred to a polarizing plate in the same manner as the liquid crystal alignment solidified layer 4-1.

[0086] [Production Example 4-3: Preparation of liquid crystal alignment solidified layer constituting optical compensation layer] A laminate having a substrate / liquid crystal alignment solidified layer 4-3 structure was obtained in the same manner as in Production Example 4-1, except that the coating thickness of the liquid crystal composition was changed so that Re(550) was 180 nm. The liquid crystal alignment solidified layer 4-3 was homogeneously aligned, exhibiting refractive index characteristics of nx>ny=nz (positive A plate), a thickness of 1.5 μm, nx of 1.65, and a slow axis oriented at 90°. In producing the optical laminate, the liquid crystal alignment solidified layer 4-3 was transferred to a polarizing plate in the same manner as the liquid crystal alignment solidified layer 4-1.

[0087] [Production Example 5-1: Preparation of Retardation Layer] 1. Preparation of the first liquid crystal alignment layer A photosensitive alignment film was coated on the surface of a long polyethylene terephthalate substrate (PET substrate) with a thickness of 100 μm, and a photo-alignment treatment was performed in a direction 5° with respect to the long direction. On the other hand, 10 parts by weight of a polymerizable discotic liquid crystal compound described in

[0111] of Patent No. 5186150 and 3 parts by weight of a photoinitiator (manufactured by BASF: trade name Irgacure 907) for the polymerizable liquid crystal monomer were dissolved in 40 parts by weight of toluene to prepare a liquid crystal coating solution. The coating solution was coated on the photo-alignment treated surface of the PET substrate using a bar coater, and then heated and dried at 80°C for 4 minutes to align the liquid crystal. The liquid crystal layer was irradiated with ultraviolet rays to cure the liquid crystal layer, thereby obtaining a long laminate in which a first liquid crystal alignment cured layer 5-1-1 was formed on the PET substrate. The first liquid crystal alignment cured layer 5-1-1 was homogeneously aligned, showed refractive index characteristics of nx = nz > ny (positive A plate), had a thickness of 2 μm, an in-plane retardation Re(550) of 220 nm, Re(450) / Re(550) of 1.08, Re(650) / Re(550) of 0.96, and the slow axis was in the 75° direction.

[0088] 2. Preparation of the second liquid crystal alignment cured layer A laminate having a structure of a substrate / second liquid crystal alignment cured layer 5-1-2 was obtained in the same manner as in Production Example 4-1, except that the alignment treatment was performed so that the slow axis was in the -15° direction and the coating thickness of the liquid crystal composition was changed so that Re(550) was 120 nm. The second liquid crystal alignment cured layer 5-1-2 was homogeneously aligned, showed refractive index characteristics of nx > ny = nz (positive A plate), had a thickness of 1.0 μm, and the slow axis was in the -15° direction.

[0089] [Production Example 5-2: Preparation of the retardation layer] 1. Preparation of the first liquid crystal alignment cured layer A photo-alignment film was coated on the surface of a long polyethylene terephthalate substrate (PET substrate) with a thickness of 100 μm, and a photo-alignment treatment was performed in a direction of -85° with respect to the long direction. On the other hand, 10 parts by weight of a polymerizable discotic liquid crystal compound described in

[0111] of Patent No. 5186150 and 3 parts by weight of a photoinitiator (manufactured by BASF: trade name Irgacure 907) with respect to the polymerizable liquid crystal monomer were dissolved in 40 parts by weight of toluene to prepare a liquid crystal coating solution. The coating solution was coated on the photo-alignment treated surface of the PET substrate using a bar coater, and then heated and dried at 80°C for 4 minutes to align the liquid crystal. The liquid crystal layer was irradiated with ultraviolet rays to cure the liquid crystal layer, thereby obtaining a long laminate having a first liquid crystal alignment cured layer 5-2-1 formed on the PET substrate. The first liquid crystal alignment cured layer 5-2-1 is homogeneously aligned, exhibits refractive index characteristics of nx = nz > ny (positive A plate), has a thickness of 2 μm, an in-plane retardation Re(550) of 220 nm, Re(450) / Re(550) of 1.08, Re(650) / Re(550) of 0.96, and the slow axis is in the -15° direction.

[0090] 2. Preparation of the second liquid crystal alignment cured layer A laminate having a structure of substrate / second liquid crystal alignment cured layer 5-2-2 was obtained in the same manner as in Production Example 4-1, except that the alignment treatment was performed so that the slow axis was in the 75° direction and the coating thickness of the liquid crystal composition was changed so that Re(550) was 120 nm. The second liquid crystal alignment cured layer 5-2-2 is homogeneously aligned, exhibits refractive index characteristics of nx > ny = nz (positive A plate), has a thickness of 1.0 μm, and the slow axis is in the 75° direction.

[0091] [Example 1] 1. Preparation of the optical laminate The first liquid crystal alignment cured layer 5-1-1 and the second liquid crystal alignment cured layer 5-1-2 were bonded together through an active energy ray curable adhesive (thickness 1 μm), and the substrate of the first liquid crystal alignment cured layer 5-1-1 was peeled off. Next, an optical compensation layer (retardation film 2-1) was bonded to the first liquid crystal alignment cured layer 5-1-1 through an ultraviolet curable adhesive to obtain a retardation film with an optical compensation layer. The bonding and peeling were performed by a roll-to-roll process. The slow axis angle of the optical compensation layer was 0°, the slow axis angle of the first liquid crystal alignment cured layer 5-1-1 was -75° (105°), and the slow axis angle of the second liquid crystal alignment cured layer 5-1-2 was -15° (165°). Next, a retardation film with an optical compensation layer was bonded to the surface of the TAC film of the polarizing plate obtained in Production Example 1 through an acrylic adhesive (thickness 5 μm) so as to have the axis angles described in Table 1. Finally, the substrate of the second liquid crystal alignment cured layer was peeled off to obtain an optical laminate having a structure of polarizing plate / adhesive layer (adhesive layer) / optical compensation layer / adhesive layer (adhesive layer) / first liquid crystal alignment cured layer / adhesive layer (adhesive layer) / second liquid crystal alignment cured layer. The obtained optical laminate was subjected to the above-mentioned "reflectance" evaluation. The results are shown in Table 1.

[0092] 2. Fabrication of Image Display Device The cover glass and the optical film on the viewing side of a commercially available organic EL display device (manufactured by Samsung Electronics Co., Ltd., trade name "Galaxy (registered trademark) A41") were removed, and after washing the removal surface, the second liquid crystal alignment cured layer side of the optical laminate obtained above was bonded to the washed surface through an acrylic adhesive (thickness 10 μm) to obtain an image display device. The obtained image display device was subjected to the above-mentioned "line unevenness" evaluation. The results are shown in Table 1.

[0093] [Examples 2 to 3] An optical laminate and an image display device were obtained in the same manner as in Example 1 except that the configuration of the optical compensation layer was changed as shown in Table 1. The obtained optical laminate and image display device were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0094] [Examples 4 to 6 and Comparative Examples 1 to 4] An optical laminate and an image display device were obtained in the same manner as in Example 1, except that the configuration of the optical compensation layer was changed as shown in Table 1, and all the lamination and peeling of the respective layers constituting the optical laminate were performed by a roll-to-roll process. The obtained optical laminate and image display device were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0095]

Table 1

[0096] In Table 1, for example, "Ex. 1" means Example 1, and "Comp. 1" means Comparative Example 1. Also, "Pos. A" means a positive A plate, "Neg. A" means a negative A plate, and "Neg. B" means a negative B plate. Further, for example, "Stretched 2-1" means the retardation film 2-1 of Production Example 2-1, "Liquid Crystal 4-1" means the liquid crystal alignment cured layer 4-1 of Production Example 4-1, and "Neg. A(15)" means a negative A plate having a slow axis in the 15° direction.

Industrial Applicability

[0097] The optical laminate according to the embodiment of the present invention can be suitably used for an image display device (typically, a liquid crystal display device, an organic EL display device).

Explanation of Signs

[0098] 10 Polarizing plate 11 Polarizer 12 Protective layer 13 Protective layer 20 Retardation layer 21 First liquid crystal alignment cured layer 22 Second liquid crystal alignment cured layer 30 Optical compensation layer 100 Optical laminate

Claims

1. A polarizing plate including a polarizer, an optical compensation layer, and a retardation layer, in this order, wherein the optical compensation layer exhibits a refractive index characteristic of nx > ny and satisfies the relationship of nx < 1.55, and its slow axis is substantially orthogonal to the absorption axis of the polarizer, the retardation layer includes a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer in this order from the optical compensation layer side, and has a circular polarization function or an elliptical polarization function as a whole, an optical laminate.

2. The optical laminate according to Claim 1, wherein the optical compensation layer exhibits a refractive index characteristic of nx > ny ≥ nz.

3. The optical laminate according to Claim 2, wherein Re(550) of the optical compensation layer is 50 nm to 220 nm.

4. The optical laminate according to Claim 3, wherein Re(550) of the optical compensation layer is 50 nm to 150 nm.

5. The optical laminate according to Claim 4, wherein the optical compensation layer is composed of a stretched film of a resin film, and its thickness is 10 μm to 50 μm.

6. The optical laminate according to Claim 1, wherein the retardation layer as a whole shows a relationship of Re(450) < Re(550).

7. The optical laminate according to Claim 6, wherein the first liquid crystal alignment cured layer exhibits a refractive index characteristic of nz ≥ nx > ny.

8. The optical laminate according to Claim 7, wherein the second liquid crystal alignment cured layer exhibits a refractive index characteristic of nx > ny ≥ nz.

9. The optical laminate according to Claim 8, wherein the slow axis of the first liquid crystal alignment cured layer and the slow axis of the second liquid crystal alignment cured layer intersect.

10. The optical laminate according to Claim 1, wherein the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer are laminated via an active energy ray curable adhesive.

11. An image display device including the optical laminate according to any one of Claims 1 to 10.

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