Optical laminate and image display device using same

Abstract

Provided is an optical laminate which includes a liquid crystal alignment fixing layer, and which, when applied to an image display device, can achieve excellent visibility in an oblique direction and can suppress specific display unevenness. An 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 phase difference layer. The optical compensation layer exhibits a refractive index characteristic of nx > ny and a relationship of nx < 1.55, and a slow axis of the optical compensation layer is substantially orthogonal to an absorption axis of the polarizer. The retardation layer includes a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer in this order from the optical compensation layer side, and has a circular polarization function or an elliptical polarization function as a whole.

Description

Technical Field

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

[0002] In recent years, image display devices typified by liquid crystal display devices and electroluminescent (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have been rapidly spreading. In most cases, an optical laminate including a retardation film (for example, an antireflection film obtained by integrating a polarizer and a retardation film) is used in an image display device. In recent years, as the demand for thinning of image display devices has increased, there has also been an increasing demand for thinning of optical laminates. For the purpose of thinning the optical laminate, thinning of the retardation layer (retardation film) that contributes greatly to the thickness is being carried out. As a representative example of a thin retardation film, a film obtained by aligning a liquid crystal compound and fixing its alignment state (hereinafter, referred to as a liquid crystal film) can be cited. Since the birefringence (Δn) of a liquid crystal compound is significantly larger than that of a resin, the thickness of the liquid crystal film required to obtain a desired in-plane retardation can be significantly smaller than that of a stretched film of a resin film. However, in an image display device using an optical laminate including a liquid crystal film, display unevenness may sometimes occur depending on the viewing environment (specifically, a phenomenon in which a pink line is visually recognized particularly clearly in the absorption axis direction of the polarizer). In addition, an image display device using an optical laminate including a liquid crystal film may have a large reflectance in an oblique direction (insufficient visual recognition in an oblique direction).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Laid-Open No. 2014-222282 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] The present invention has been made to solve the above-described prior problems, and a main object thereof is to provide an optical laminate including a liquid crystal alignment fixing layer, which can achieve excellent visual recognition in an oblique direction and can suppress specific display unevenness when applied to an image display device.

[0008] Means for Solving the Problems

[0009] [1] The optical laminate according to an embodiment of the present invention sequentially includes 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. Moreover, its slow axis is substantially orthogonal to the absorption axis of the polarizer. The retardation layer sequentially includes a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer from the side of the optical compensation layer, and the whole has a circular polarization function or an elliptical polarization function.

[0010] [2] In the above [1], the optical compensation layer exhibits a refractive index characteristic of nx > ny ≥ nz.

[0011] [3] In the above [1] or [2], Re(550) of the optical compensation layer is 50 nm to 220 nm.

[0012] [4] In any one of the above [1] to [3], Re(550) of the optical compensation layer is 50 nm to 150 nm.

[0013] [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.

[0014] [6] In any one of the above [1] to [5], the whole retardation layer shows a relationship of Re(450) < Re(550).

[0015] [7] In any one of the above [1] to [6], the first liquid crystal alignment fixing layer exhibits a refractive index characteristic of nz ≥ nx > ny.

[0016] [8] In any one of the above [1] to [7], the second liquid crystal alignment fixing layer exhibits a refractive index characteristic of nx > ny ≥ nz.

[0017] [9] In any one of the above [1] to [8], the slow axis of the first liquid crystal alignment fixing layer intersects with the slow axis of the second liquid crystal alignment fixing layer.

[0018]

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

[0019]

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

[10] .

[0020] Advantages of the Invention

[0021] According to an embodiment of the present invention, an optical laminate including a liquid crystal alignment fixing layer can be realized, and when applied to an image display device, excellent visual recognition in an oblique direction can be achieved and specific display unevenness can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention.

[0023] SYMBOL DESCRIPTION

[0024] 10 Polarizer

[0025] 11 Polarizer

[0026] 12 Protective layer

[0027] 13 Protective layer

[0028] 20 Phase difference layer

[0029] 21 First liquid crystal alignment fixing layer

[0030] 22 Second liquid crystal alignment fixing layer

[0031] 30 Optical compensation layer

[0032] 100 Optical laminate DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0034] (Definition of Terms and Symbols)

[0035] The definitions of the terms and symbols in this specification are as follows.

[0036] (1) Refractive index (nx, ny, nz)

[0037] "nx" is the refractive index in the direction in which the in-plane refractive index becomes the 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.

[0038] (2) In-plane phase difference (Re)

[0039] "Re(λ)" is the in-plane phase difference of the film measured with light having a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane phase difference of the film measured with light having a wavelength of 550 nm at 23°C. When the thickness of the film is set to d (nm), Re(λ) is obtained by the formula: Re = (nx - ny) × d.

[0040] (3) Phase difference in the thickness direction (Rth)

[0041] "Rth(λ)" is the phase difference in the thickness direction of the film measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction of the film measured with light of wavelength 550 nm at 23°C. When the thickness of the film is set to d (nm), Rth(λ) is obtained by the formula: Rth = (nx - nz) × d.

[0042] (4) Nz coefficient

[0043] The Nz coefficient is obtained by Nz = Rth / Re.

[0044] (5) Angle

[0045] When an angle is mentioned in this specification, unless otherwise specifically stated, the angle includes angles in both the clockwise and counterclockwise directions. Therefore, for example, "45°" includes ±45°.

[0046] A. Optical laminate

[0047] Figure 1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention. The illustrated optical laminate 100 sequentially includes a polarizer 10, an optical compensation layer 30, and a retardation layer 20. The polarizer 10 and the optical compensation layer 30, and the optical compensation layer 30 and the retardation layer 20 are laminated via any suitable adhesive layer (e.g., an adhesive layer, a binder layer: not shown), respectively. The polarizer 10 typically includes a polarizer 11 and protective layers 12 and 13 disposed on both sides of the polarizer 11. At least one of the protective layers 12 and 13 may be omitted according to the purpose. Therefore, the polarizer may be a so-called double-protection polarizer, a so-called single-protection polarizer, or may be composed of only the polarizer.

[0048] The retardation layer 20 includes a first liquid crystal alignment fixing layer 21 and a second liquid crystal alignment fixing layer 22 in this order from the side of the optical compensation layer 30. The first liquid crystal alignment fixing layer 21 and the second liquid crystal alignment fixing layer 22 are laminated via an arbitrary appropriate adhesive layer (for example, an adhesive layer, a binder layer: not shown). In one embodiment, the first liquid crystal alignment fixing layer 21 and the second liquid crystal alignment fixing layer 22 are laminated via an active energy ray-curable adhesive. By using the liquid crystal alignment fixing layer as the retardation layer, it is possible to achieve a desired in-plane retardation with a thickness significantly thinner than that of a stretched film of a resin film. As a result, significant thinning of the optical laminate can be achieved. The retardation layer 20 has a circular polarization function or an elliptical polarization function as a whole (as a laminate of the first liquid crystal alignment fixing layer 21 and the second liquid crystal alignment fixing layer 22). In one embodiment, the Nz coefficient of the retardation layer as a whole can be, for example, 0.30 to 0.70. In addition, in the present specification, the "liquid crystal alignment fixing layer" means a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state thereof is fixed. The "liquid crystal alignment fixing layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer.

[0049] In the optical laminate, the total thickness from the first liquid crystal alignment fixing layer to the second liquid crystal alignment fixing layer (that is, the total thickness of the retardation layer) is preferably 15 μm or less, more preferably 3 μm to 10 μm. In addition, if the total thickness from the first liquid crystal alignment fixing layer to the second liquid crystal alignment fixing layer is in the above range, the total thickness from the polarizing plate to the second liquid crystal alignment fixing layer (the substantial total thickness of the optical laminate excluding the thickness of the adhesive for attaching to the image display panel) can be, for example, 100 μm or less, and can also be, for example, 30 μm to 80 μm.

[0050] 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 (that is, the direction of this slow axis is substantially the transmission axis direction of the polarizer). Here, "substantially orthogonal" includes the case where the angle formed by 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 further preferably about 90°.

[0051] In an embodiment of the present invention, the optical compensation layer exhibits a relationship of nx < 1.55. The nx of the optical compensation layer is preferably 1.54 or less, more preferably 1.53 or less. The lower limit of nx of the optical compensation layer can be, for example, 1.48.

[0052] When the present inventors studied the further thinning of an optical laminate including a liquid crystal alignment fixing layer as a retardation layer, they found a new problem that an image display device using an optical laminate including a liquid crystal alignment fixing layer as a retardation layer sometimes exhibits specific display unevenness depending on the visual recognition environment. Specifically, in the reflection under a three-wavelength light source, a phenomenon was found in which a thin line with particularly obvious pink color was visually recognized as a whole in the absorption axis direction of the polarizer (sometimes referred to as line unevenness). The present inventors conducted in-depth research on suppressing such line unevenness, and as a result, found that by setting the liquid crystal alignment fixing layer on the polarizer side in the optical laminate to a specific configuration (representatively, a configuration showing a refractive index characteristic of nz ≥ nx > ny), the line unevenness can be well suppressed. On the other hand, the present inventors newly found that an image display device using such an optical laminate has a problem of large reflectance in the oblique direction (insufficient visual recognition in the oblique direction). The present inventors comprehensively studied the improvement of such visual recognition in the oblique direction and the suppression of the above-mentioned line unevenness, and as a result, found that by disposing an optical compensation layer showing a specific refractive index characteristic and having 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 and the visual recognition in the oblique direction can be improved. 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 less than a specified value, an optical laminate can be realized that can achieve excellent visual recognition in the oblique direction and suppress specific display unevenness when applied to an image display device. Thus, such an effect of the embodiment of the present invention solves the problem newly found when comprehensively studying the suppression of line unevenness and the improvement of visual recognition in the oblique direction in an optical laminate including a liquid crystal alignment fixing layer as a retardation layer, and is an excellent effect that cannot be expected. In addition, of course, the embodiment of the present invention can suppress the display unevenness recognized in the past.

[0053] The optical laminate may be in a single sheet form or in a long strip form. In this specification, "long strip form" means an elongated shape that is sufficiently long with respect to the width, for example, an elongated shape including a length that is 10 times or more, preferably 20 times or more, with respect to the width. The long strip-shaped optical laminate can be wound into a roll shape. The long strip-shaped optical laminate can be produced, for example, by a so-called roll-to-roll process. The single sheet-shaped optical laminate can be produced by cutting a long strip-shaped optical laminate into a specified size (representatively, a size corresponding to an image display device), or by laminating each constituent element (each layer) cut into a specified size.

[0054] In actual use, the optical laminate has an adhesive layer (not shown) as the outermost layer on the side of the second liquid crystal alignment fixing layer (image display panel side) and can be adhered to the image display panel. In this case, it is preferable that a release liner is temporarily adhered to the surface of the adhesive layer until the optical laminate is put into use. By temporarily adhering the release liner, the adhesive layer can be protected and a roll of the optical laminate can be formed.

[0055] Hereinafter, the components of the optical laminate will be specifically described.

[0056] B. Polarizer

[0057] B-1. Polarizer

[0058] The polarizer 11 is typically composed of a polyvinyl alcohol (PVA)-based resin film containing a dichroic substance (e.g., iodine). Examples of the PVA-based resin include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0059] The PVA-based resin preferably contains a PVA-based resin modified with acetoacetyl groups. If it has such a composition, a polarizer with desired mechanical strength can be obtained. When the total amount of the PVA-based resin is 100% by weight, the blending amount of the PVA-based resin modified with acetoacetyl groups is preferably 5% to 20% by weight, more preferably 8% to 12% by weight. If the blending amount is in such a range, a polarizer with more excellent mechanical strength can be obtained.

[0060] The polarizer preferably contains an iodide or sodium chloride (sometimes collectively referred to as halides). Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. With respect to 100 parts by weight of the PVA-based resin, the content of the halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight. The halide can be incorporated into the coating liquid for forming the PVA-based resin layer as a precursor of the polarizer in the manufacturing method described below and is finally introduced into the polarizer. By introducing the halide into the polarizer, the orientation of PVA molecules in the polarizer can be improved, and thus, a polarizer with excellent optical properties (typically, achieving both high polarization degree and high monomer transmittance) can be realized.

[0061] The polarizer preferably exhibits absorption dichroism at any wavelength in the range of 380 nm to 780 nm. The monomer transmittance of the polarizer is preferably 41.0% to 46.0%, more preferably 42.0% to 45.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more. According to the embodiments of the present invention, even if the monomer transmittance is in the above range, the polarization degree can be maintained in such a range.

[0062] 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 still more preferably 3 μm to 7 μm. By combining such a thin polarizer with the liquid crystal alignment fixing layer, significant thinning of the optical laminate can be achieved. In addition, if the thickness of the polarizer is within the above range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0063]

[0062] 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.

[0064] Specific examples of the polarizer composed of a single-layer resin film include polarizers obtained by subjecting a hydrophilic polymer film such as a PVA-based film, a partially formalized PVA-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film to a dyeing treatment and a stretching treatment using a dichroic substance such as iodine or a dichroic dye, polyene-based alignment films such as dehydrated products of PVA and dehydrochlorinated products of polyvinyl chloride. Due to excellent optical properties, a polarizer obtained by dyeing a PVA-based film with iodine and performing uniaxial stretching is preferably used.

[0065]

[0063] The above-mentioned iodine dyeing is carried out, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching can be carried out after the dyeing treatment or while dyeing. In addition, dyeing can also be carried out after stretching. If necessary, a swelling treatment, a crosslinking treatment, a cleaning treatment, a drying treatment, etc. are carried out on the PVA-based film. For example, by immersing the PVA-based film in water before dyeing for water washing, not only can the dirt and anti-sticking agent on the surface of the PVA-based film be washed off, but also the PVA-based film can be swollen to prevent uneven dyeing.

[0066] As a specific example of a polarizer obtained using a laminate, a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be cited. A 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, as follows: A PVA-based resin solution is coated on the resin substrate and dried to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to form the PVA-based resin layer into a polarizer. In the present embodiment, it is preferable to form a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, if necessary, stretching may further include air stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. Further, in the present embodiment, it is preferable to heat the laminate while transporting it in the length direction to subject it to a dry shrinkage treatment that causes it to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes sequentially performing an air-assisted stretching treatment, a dyeing treatment, a water stretching treatment, and a dry shrinkage treatment on the laminate. By introducing the assisted stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical characteristics can be achieved. At the same time, by improving 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 characteristics 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 orientation disorder of polyvinyl alcohol molecules and the decrease in orientation can be suppressed. Thus, the optical characteristics of the polarizer obtained through treatment steps such as a dyeing treatment and a water stretching treatment in which the laminate is immersed in a liquid can be improved. Further, by shrinking the laminate in the width direction using the dry shrinkage treatment, the optical characteristics can be improved. The obtained laminate of the resin substrate / polarizer can be used directly (i.e., the resin substrate can be used as a protective layer of the polarizer), or an appropriate protective layer corresponding to the purpose can be laminated on the peeling surface after peeling the resin substrate from the laminate of the resin substrate / polarizer or on the surface opposite to the peeling surface. The details of such a method for manufacturing a polarizer are described, for example, in Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0067] B-2. Protective layer

[0068] The protective layers 12 and 13 are made of any suitable resin film. As materials for forming the resin film, typically, cellulose-based resins such as cellulose triacetate (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic resins, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins can be cited. As a representative example of the (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure can be cited. The (meth)acrylic resin having a lactone ring structure is described, for example, in Japanese Patent Laid-Open No. 2000-230016, Japanese Patent Laid-Open No. 2001-151814, Japanese Patent Laid-Open No. 2002-120326, Japanese Patent Laid-Open No. 2002-254544, and Japanese Patent Laid-Open No. 2005-146084. These publications are incorporated herein by reference. From the viewpoint of ease of profiling, etc., a cellulose-based resin is 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 resins are preferred.

[0069] The optical laminate is typically disposed on the visible side of the image display device, and the protective layer 12 is typically disposed on this visible side. Therefore, if necessary, a surface treatment can be performed on the protective layer 12. As the surface treatment, for example, hard coat treatment, antireflection treatment, anti-blocking treatment, and antiglare treatment can be cited. And / or if necessary, a treatment for improving the visibility when visually recognizing through a polarized sunglasses (typically, imparting an (elliptical) polarization function, imparting an ultra-high retardation) can be performed on the protective layer 12. By performing such a treatment, excellent visibility can be achieved even when visually recognizing the display screen through a polarized lens such as a polarized sunglasses. Therefore, the optical laminate can also be suitably used for an image display device that can be used outdoors.

[0070] In one embodiment, the protective layer 13 is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm, and the retardation in the thickness direction Rth(550) is -10 nm to +10 nm.

[0071] The thicknesses of the protective layers 12 and 13 are each preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and further preferably 15 μm to 35 μm. In addition, when a surface treatment is performed on the protective layer 12, the thickness of the protective layer 12 is the thickness including the thickness of the surface treatment layer.

[0072] C. Retardation layer

[0073] C-1. Outline of the retardation layer

[0074] As described above, the retardation layer 20 includes a first liquid crystal alignment fixing layer 21 and a second liquid crystal alignment fixing layer 22 in this order from the polarizer side. Regarding the description of the retardation layer in this item, when abbreviated as the "retardation layer", it means the description of the retardation layer as a whole, and when abbreviated as the "liquid crystal alignment fixing layer", it means the integrated description of the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer.

[0075] As described above, the retardation layer 20 as a whole (as a laminate of the first liquid crystal alignment fixing layer 21 and the second liquid crystal alignment fixing 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, further preferably 150 nm to 160 nm, and particularly preferably 152 nm to 157 nm. The retardation layer preferably exhibits an inverse wavelength dispersion characteristic in which the retardation value increases corresponding 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 further 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 further preferably 44° to 46°. In one embodiment, the retardation layer can exhibit a refractive index characteristic of nx > nz > ny. Therefore, the Nz coefficient of the retardation layer can be, for example, 0.30 to 0.70, can also be, for example, 0.40 to 0.60, and can also be, for example, 0.45 to 0.55.

[0076] As long as the retardation layer exhibits the characteristics described above, the liquid crystal alignment fixing layer can adopt any suitable configuration. In one embodiment, the first liquid crystal alignment fixing layer exhibits a refractive index characteristic of nz ≥ nx > ny, and the second liquid crystal alignment fixing layer exhibits a refractive index characteristic of nx > ny ≥ nz.

[0077] Hereinafter, the configurations of the first liquid crystal alignment fixing layer that exhibits a refractive index characteristic of nz ≥ nx > ny and the second liquid crystal alignment fixing layer that exhibits a refractive index characteristic of nx > ny ≥ nz will be specifically described.

[0078] C-2. The first liquid crystal alignment fixing layer

[0079] As described above, the first liquid crystal alignment fixing layer exhibits a refractive index characteristic of nz ≥ nx > ny. That is, the first liquid crystal alignment fixing 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 fixing layer is preferably from 200 nm to 300 nm, more preferably from 210 nm to 270 nm, and still more preferably from 230 nm to 250 nm. The Nz coefficient of the first liquid crystal alignment fixing layer is preferably from -0.2 to 0, more preferably from -0.1 to 0, and still more preferably from -0.05 to 0. In addition, "nz = nx" includes not only the case where nx and nz are strictly equal, but also the case where nx and nz are substantially equal. Therefore, the Nz coefficient of the first liquid crystal alignment fixing layer can be less than 1.0 (for example, 0 or more and less than 1.0).

[0080] The thickness of the first liquid crystal alignment fixing layer can be adjusted in such a manner as to obtain the above-described desired in-plane retardation. In one embodiment, the thickness of the first liquid crystal alignment fixing layer can be, for example, from 1.0 μm to 3.0 μm.

[0081] The angle formed by the slow axis of the first liquid crystal alignment fixing layer and the transmission axis of the polarizer is preferably from 70° to 80°, more preferably from 72° to 78°, and still more preferably from 74° to 76°.

[0082] As long as the above-described optical characteristics are satisfied, the first liquid crystal alignment fixing layer can adopt any suitable configuration. The first liquid crystal alignment fixing layer can typically be an alignment fixing layer of a liquid crystalline composition containing a discotic liquid crystal compound that is substantially vertically aligned. In this specification, a "discotic liquid crystal compound" means a compound having a disc-shaped mesogenic group in its molecular structure and having 2 to 8 side chains radially bonded thereto through ether bonds or ester bonds on the mesogenic group. As the above mesogenic group, for example, groups having the structures described on P.22 of the Liquid Crystal Dictionary (published by Baifukan) can also be cited. Figure 1 Specifically, benzene, triphenylene, truxene, pyran, gallic acid, porphyrin, metal complexes, etc. Ideally, the discotic liquid crystal compound that is substantially vertically aligned has an optical axis in one direction in the film plane. A "discotic liquid crystal compound that is substantially vertically aligned" means a discotic liquid crystal compound in a state where 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.

[0083] The liquid crystalline composition containing the above-mentioned discotic liquid crystal compound is not particularly limited as long as it contains the discotic liquid crystal compound and exhibits liquid crystallinity. With respect to 100 parts by weight of all solid components of the liquid crystalline composition, 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.

[0084] The alignment fixing layer of the liquid crystalline composition containing the above-mentioned substantially vertically aligned discotic liquid crystal compound can be obtained, for example, by the method described in Japanese Patent Application Laid-Open No. 2001-56411. The discotic liquid crystal compound in the above liquid crystal composition can be aligned along the restraining force imparted by alignment treatment such as rubbing treatment or photo-alignment treatment. Thus, by performing alignment treatment in such a manner that the restraining force acts in a desired direction, applying a liquid crystal composition thereon, and then not performing stretching or shrinking treatment, a liquid crystal alignment fixing layer (negative A plate) having a slow axis in the desired direction can be fabricated.

[0085] In another embodiment, the first liquid crystal alignment fixing layer may be an alignment fixing layer of a liquid crystalline composition containing a lyotropic liquid crystal compound that is uniformly aligned. In the present specification, the "lyotropic liquid crystal compound" refers to a liquid crystal compound that exhibits a liquid crystal phase depending on the concentration of the solute in a solution state. As the above lyotropic liquid crystal compound, any suitable lyotropic liquid crystal compound can be used. Specific examples of the above lyotropic liquid crystal compound include amphiphilic compounds having hydrophilic groups and hydrophobic groups at both ends of the molecule, chromonic compounds having an aromatic ring imparted with water solubility, and polymer compounds having a rod-like backbone such as cellulose derivatives, polypeptides, and nucleic acids. Preferably, it is an alignment fixing layer of a liquid crystalline composition containing a lyotropic liquid crystal compound that is uniformly aligned, and the lyotropic liquid crystal compound is a chromonic compound having an aromatic ring imparted with water solubility.

[0086] The liquid crystalline composition containing the above-mentioned lyotropic liquid crystal compound is not particularly limited as long as it contains the lyotropic liquid crystal compound and exhibits liquid crystallinity. With respect to 100 parts by weight of all solid components of the liquid crystalline composition, 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.

[0087] A retardation film formed from an alignment fixing layer of a liquid crystalline composition containing the above-described lyotropic liquid crystal compound aligned uniformly can be obtained, for example, by the method described in Japanese Patent Application Laid-Open No. 2002-296415. The lyotropic liquid crystal compound in the above liquid crystal composition can be aligned along the restraining force imparted by an alignment treatment such as rubbing treatment or photo-alignment treatment. Thus, by performing the alignment treatment in such a manner that the restraining force acts in a desired direction, applying the liquid crystal composition thereon, and then not performing stretching or shrinking treatment, a liquid crystal alignment fixing layer having a slow axis in the desired direction can be fabricated.

[0088] C-3. Second Liquid Crystal Alignment Fixing Layer

[0089] As described above, the second liquid crystal alignment fixing layer exhibits a refractive index characteristic of nx > ny ≥ nz. That is, the second liquid crystal alignment fixing 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 fixing layer is preferably from 100 nm to 200 nm, more preferably from 110 nm to 160 nm, and still more preferably from 110 nm to 130 nm. The Nz coefficient of the second liquid crystal alignment fixing 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. In addition, "ny = nz" includes not only the case where ny and nz are strictly equal but also the case where ny and nz are substantially equal. Therefore, the Nz coefficient of the second liquid crystal alignment fixing layer can be less than 1.0 (for example, 0.95 or more and less than 1.0).

[0090] The thickness of the second liquid crystal alignment fixing layer can be adjusted in such a manner as to obtain the above-described desired in-plane retardation. In one embodiment, the thickness of the second liquid crystal alignment fixing layer can be, for example, from 0.8 μm to 1.5 μm.

[0091] The angle formed by the slow axis of the second liquid crystal alignment fixing layer and the transmission axis of the polarizer is preferably from 10° to 20°, more preferably from 12° to 18°, and still more preferably from 14° to 16°. Therefore, the slow axis of the first liquid crystal alignment fixing layer intersects with the slow axis of the second liquid crystal alignment fixing layer. The angle formed by the slow axis of the first liquid crystal alignment fixing layer and the slow axis of the second liquid crystal alignment fixing layer is preferably from 55° to 65°, more preferably from 57° to 63°, and still more preferably from 59° to 61°. In addition, the angle formed by the slow axis of the first liquid crystal alignment fixing layer and the transmission axis of the polarizer and the angle formed by the slow axis of the second liquid crystal alignment fixing layer and the transmission axis of the polarizer can also be reversed.

[0092] As the liquid crystal compound for the second liquid crystal alignment fixing layer, for example, liquid crystal polymers and liquid crystal monomers can be cited. The liquid crystal compound is preferably capable of polymerization (i.e., a liquid crystal monomer). If the liquid crystal compound is capable of polymerization, the alignment state of the liquid crystal compound can be fixed by polymerizing it after the liquid crystal compound is aligned. Here, the polymer formed by polymerization is non-liquid crystalline. Therefore, the formed second liquid crystal alignment fixing layer, for example, does not undergo a transition to a liquid crystal phase, a glass phase, or a crystalline phase due to a temperature change peculiar to a liquid crystalline compound. As a result, the liquid crystal alignment fixing layer becomes a retardation layer with extremely excellent stability that is not affected by temperature changes. In one embodiment, in the second liquid crystal alignment fixing layer, rod-shaped liquid crystal compounds are arranged side by side in the slow axis direction (homogeneous alignment).

[0093] In one embodiment, the second liquid crystal alignment fixing layer can be formed using a composition containing a liquid crystal compound capable of polymerization (a polymerizable liquid crystal compound, i.e., a liquid crystal monomer). In the present 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 refers to a group participating in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by an active radical generated by a photoinitiator or an acid, etc. As the liquid crystal monomer, for example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, GB2280445, etc. can be used. Specific examples of such polymerizable mesogenic compounds include, for example, LC242 with the trade name of BASF, E7 with the trade name of Merck, and LC-Sillicon-CC3767 with the trade name of Wacker-Chem.

[0094] The mechanism of manifestation of liquid crystallinity of the liquid crystal compound can be thermotropic or lyotropic. In addition, as the constitution of the liquid crystal phase, it can be a nematic liquid crystal or a smectic liquid crystal. From the viewpoint of ease of manufacture, the liquid crystallinity is preferably a thermotropic nematic liquid crystal.

[0095] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, this temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

[0096] 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 within such a range, the desired in-plane retardation can be achieved with a very thin thickness. As a result, the second liquid crystal alignment fixing layer and the optical laminate can be further thinned, and ultimately, it can contribute to significant thinning of the image display device.

[0097] D. Optical compensation layer

[0098] As described above, nx of the optical compensation layer is less than 1.55, preferably 1.54 or less, more preferably 1.53 or less. As described above, the lower limit of nx of the optical compensation layer can be, for example, 1.48. If nx of the optical compensation layer is within 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 visual recognition in the oblique direction can be improved. At the same time, line-like unevenness can be well suppressed.

[0099] As described above, the optical compensation layer exhibits a refractive index characteristic 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 50 nm to 220 nm, more preferably 60 nm to 200 nm, still more preferably 70 nm to 190 nm. Re(550) of the optical compensation layer can be, for example, 50 nm to 150 nm, or can be, for example, 70 nm to 140 nm. The Nz coefficient of the optical compensation layer is preferably 1.0 to 1.3, more preferably 1.0 to 1.2, still more preferably 1.0 to 1.1. In addition, "ny = nz" includes not only the case where ny and nz are strictly 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).

[0100] As long as the optical compensation layer exhibits a relationship of nx < 1.55, any appropriate configuration can be adopted. Specifically, the optical compensation layer can be a stretched film of a resin film or a liquid crystal alignment fixing layer. It is preferably a stretched film of a resin film. This is because it is easy to achieve the desired nx. On the other hand, by using a liquid crystal compound having an appropriate birefringence Δn (= nx - ny), a liquid crystal alignment fixing layer having the desired nx can be obtained.

[0101] As the resin film, any suitable resin film can be used. Representative examples of the resin constituting the resin film include cyclic olefin resins. Cyclic olefin resins are a general term for resins obtained by polymerizing cyclic olefins as polymerization units. For example, resins described in Japanese Patent Laid-Open No. 1-240517, Japanese Patent Laid-Open No. 3-14882, Japanese Patent Laid-Open No. 3-122137, etc. can be cited. As specific examples, there can be cited: ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (representatively random copolymers), graft-modified products obtained by modifying them with unsaturated carboxylic acids and their derivatives, and their hydrides. As specific examples of cyclic olefins, norbornene-based monomers can be cited. As norbornene-based monomers, monomers described in Japanese Patent Laid-Open No. 2015-210459, etc. can be cited.

[0102] As long as the effects of the embodiments of the present invention can be obtained, other cycloolefins capable of ring-opening polymerization can be used in combination. As specific examples of such cycloolefins, for example, compounds having 1 reactive double bond such as cyclopentene, cyclooctene, 5,6-dihydrodicyclopentadiene, etc. can be cited.

[0103] The number average molecular weight (Mn) of the above-mentioned cyclic olefin resin obtained by measurement using gel permeation chromatography (GPC) with toluene solvent is preferably 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, excellent mechanical strength, good solubility, formability, and casting operability can be achieved.

[0104] There are various commercially available products of the above-mentioned cyclic olefin resins. As specific examples, there can be cited products with the trade names "ZEONEX" and "ZEONOR" manufactured by Zeon Corporation, products with the trade name "Arton" manufactured by JSR Corporation, products with the trade name "TOPAS" manufactured by Ticona Corporation, and products with the trade name "APEL" manufactured by Mitsui Chemicals, Inc.

[0105] The optical compensation layer is 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 forming process can be used. In addition, since there are a large number of commercially available film products of the above-mentioned cyclic olefin resins, these commercially available films can be directly subjected to stretching treatment.

[0106] The stretching method and stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction) can be appropriately set according to the purpose and the desired optical properties of the optical compensation layer. For example, by uniaxially stretching the above resin film, a positive A plate (nx > ny = nz) can be obtained, and by biaxially stretching, a negative B plate (nx > ny > nz) can be obtained.

[0107] E. Adhesive layer

[0108] As described above, the polarizer 10 and the optical compensation layer 30, and the optical compensation layer 30 and the retardation layer 20 are laminated via any appropriate adhesive layer, respectively. That is, the adhesive layer can be an adhesive layer or an adhesive agent layer. When the adhesive layer is an adhesive layer, the adhesive layer is typically composed of an active energy ray-curable adhesive. In addition, as described above, the first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing layer are typically laminated via an active energy ray-curable adhesive. Hereinafter, the active energy ray-curable adhesive and the adhesive agent will be specifically described.

[0109] The active energy ray-curable adhesive can adopt any appropriate composition. By adjusting the amount, type, combination, compounding 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 (meth)acrylate containing an aromatic ring skeleton and / or metal oxide particles. Hereinafter, they will be briefly described separately. In addition, regarding other components (e.g., curing component, photoinitiator) that can be contained in the adhesive, well-known compositions can be adopted, so the specific description is omitted.

[0110] By making the adhesive composition contain 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, a (meth)acrylate containing at least one selected from (meth)acrylates having a polycyclic aromatic ring skeleton and (meth)acrylates having two or more aromatic rings is preferably used. Examples of such (meth)acrylates include: benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, phenoxybenzyl (meth)acrylate, ethylene oxide-modified o-phenylphenol (meth)acrylate, and a reaction product of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and (meth)acrylic acid. Among these, phenoxybenzyl (meth)acrylate and phenoxyethyl (meth)acrylate are more preferably used, and phenoxybenzyl (meth)acrylate is particularly preferably used. 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% by mass to 90% by mass, and more preferably 30% by mass to 80% by mass.

[0111] Examples of the metal oxide particles include: silica, zirconia, titania, zinc oxide, antimony pentoxide, tin oxide, alumina, indium oxide, indium tin oxide, iron 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 them. Among these, zirconia and titania are preferred, and zirconia is particularly preferred. In addition, the metal oxide particles may be composed only of the metal oxides listed above, or may contain other components. As the components in the particles, the metal oxide preferably accounts for the largest weight. The shape of the metal oxide particles can take any shape such as spherical, ellipsoidal, cubic, cuboid, or pyramidal. In addition, as the metal oxide particles, metal oxide particles surface-treated by any appropriate method can be used.

[0112] From the viewpoints of improving the stability of metal oxide particles in the adhesive composition and increasing the refractive index of the adhesive layer, the average particle diameter of the metal oxide particles is preferably from 1 nm to 150 nm, more preferably from 1 nm to 50 nm. The average particle diameter of the metal oxide particles can be obtained, for example, by the following method: Particles can be 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. For example, 1000 particles are randomly selected, the maximum length thereof is measured, and the arithmetic mean thereof is calculated.

[0113] From the viewpoints of improving the stability of metal oxide particles in the adhesive composition and increasing the refractive index of the adhesive layer, when the total amount of the adhesive composition is 100% by mass, the compounding amount of the metal oxide particles is preferably from 10% by mass to 50% by mass, more preferably from 15% by mass to 40% by mass.

[0114] The adhesive composition may further contain a hydroxy group-containing (meth)acrylate. If such a configuration is adopted, the adhesive force of the adhesive layer can be further improved. When the total amount of the adhesive composition is 100% by mass, the compounding amount of the hydroxy group-containing (meth)acrylate is preferably from 1% by mass to 30% by mass, more preferably from 3% by mass to 20% by mass.

[0115] In addition, the binder may adopt any suitable configuration. By adjusting the types, amounts, combinations, and compounding amounts of the monomer components of the base polymer in the binder (binder composition); the types, amounts, combinations, and compounding amounts of the crosslinking agents; and the types, amounts, combinations, and compounding amounts of the additives, a binder (binder composition) having desired characteristics can be prepared. In one embodiment, the monomer components of the base polymer of the binder (binder composition) include a heterocyclic group-containing acrylate and / or an aromatic ring-containing acrylate. Examples of the heterocyclic group-containing acrylate include acryloylmorpholine. Examples of the aromatic ring-containing acrylate include benzyl acrylate and phenoxybenzyl acrylate.

[0116] F. Image display device

[0117] The optical laminate described in the above items A to E can be applied to an image display device. Therefore, an embodiment of the present invention also includes an image display device using such an optical laminate. As a representative example of the image display device, a liquid crystal display device and an organic EL display device can be cited. The image display device according to the embodiment of the present invention typically includes the optical laminate described in the above items A to E on its visible side.

[0118] Examples

[0119] 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 described below. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

[0120] (1) Refractive index nx

[0121] For 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). nx, ny, and nz were calculated from the following simultaneous equations.

[0122] Re(550) = (nx - ny) × d

[0123] Nz = Rth(550) / Re(550) = (nx - nz) / (nx - ny)

[0124] (2) Thickness

[0125] Measurement was performed using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0126] (3) Linear non-uniformity

[0127] The image display devices obtained in the examples and comparative examples were observed visually under a 3-wavelength fluorescent lamp in the non-lighting state and evaluated according to the following criteria.

[0128] ◎ (Excellent): No linear non-uniformity was confirmed even when a polarizing plate was installed on the 3-wavelength fluorescent lamp and observed.

[0129] ○ (Good): No linear non-uniformity was confirmed in the normal observation using a 3-wavelength fluorescent lamp.

[0130] △ (Not allowable): Linear non-uniformity was confirmed in the normal observation using a 3-wavelength fluorescent lamp.

[0131] × (Poor): Linear non-uniformity was significant in the normal observation using a 3-wavelength fluorescent lamp.

[0132] (4) Reflectance

[0133] The optical laminates obtained in the examples and comparative examples were adhered 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).

[0134] [Production Example 1: Production of Polarizing Plate]

[0135] 1. Production of Polarizer

[0136] As the thermoplastic resin substrate, an amorphous isophthalic acid copolyethylene terephthalate film (thickness: 100 μm) in the shape of a long strip with a Tg of about 75°C was used, and one side of the resin substrate was subjected to corona treatment.

[0137] In 100 parts by weight of a PVA-based resin obtained 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 “Gosefaimer”) in a ratio of 9:1, 13 parts by weight of potassium iodide was added, and the resulting substance was dissolved in water to prepare a PVA aqueous solution (coating solution).

[0138] The above-mentioned PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60°C, whereby a PVA-based resin layer with a thickness of 13 μm was formed to produce a laminate.

[0139] The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (length direction) in an oven at 130°C (air-assisted stretching treatment).

[0140] Next, the laminate was immersed in an insolubilization bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by adding 4 parts by weight of boric acid to 100 parts by weight of water) for 30 seconds (insolubilization treatment).

[0141] Next, in a dyeing bath at a liquid temperature of 30°C (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water), while adjusting the concentration so that the monomer transmittance (Ts) of the finally obtained polarizer becomes a desired value, it was immersed for 60 seconds (dyeing treatment).

[0142] Next, it was immersed in a crosslinking bath at a liquid temperature of 40°C (an aqueous boric acid solution obtained by adding 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water) for 30 seconds (crosslinking treatment).

[0143] Then, 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%), it was uniaxially stretched in the longitudinal direction (length direction) between rollers with different circumferential speeds so that the total stretching ratio reached 5.5 times (in-water stretching treatment).

[0144] Then, the laminate was immersed in a cleaning bath at a liquid temperature of 20°C (an aqueous solution obtained by adding 4 parts by weight of potassium iodide to 100 parts by weight of water) (cleaning treatment).

[0145] Then, while drying in an oven maintained at about 90°C, it is brought into contact with a SUS heating roll having a surface temperature maintained at about 75°C (dry shrinkage treatment).

[0146] In this way, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a long polarizing plate having a structure of resin substrate / polarizer was obtained. The monomer transmittance Ts of the polarizer was 43.3%. The polarizer has an absorption axis in the length direction. Hereinafter, the absorption axis direction (length direction) is defined as the "0° direction", and the transmission axis direction (width direction) is defined as the "90° direction".

[0147] 2. Fabrication of Polarizing Plate

[0148] The HC-COP film was adhered to the surface of the obtained polarizer (the side opposite to the resin substrate) via an ultraviolet curable adhesive. In addition, the HC-COP film is a film in which an HC layer (thickness 4 μm) is formed on a cycloolefin-based resin (COP) film (thickness 25 μm), and it was adhered in such a manner that the COP film faces the polarizer side. In addition, Re(550) of the COP film is 100 nm. Here, the HC-COP film was adhered in such a manner that the angle formed by the slow axis of the COP film and the absorption axis of the polarizer reaches 45°. Then, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness 25 μm) was adhered to 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.

[0149] [Production Example 2-1: Production of a stretched film (phase difference film) constituting an optical compensation layer]

[0150] A commercially available cycloolefin-based resin film (manufactured by Zeon Corporation, product name "ZEONOR 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, and a phase difference film 2-1 was obtained. The phase difference film 2-1 exhibits a refractive index characteristic of nx > ny = nz (positive A plate), has a thickness of 37 μm, Re(550) of 80 nm, nx of 1.52, and the slow axis in the 0° direction.

[0151] [Production Example 2-2: Production of a stretched film (phase difference film) constituting an optical compensation layer]

[0152] The stretching ratio was changed to 1.35 times, and otherwise, a phase difference film 2-2 was obtained in the same manner as in Production Example 2-1. The phase difference film 2-2 exhibits a refractive index characteristic of nx > ny = nz (positive A plate), has a thickness of 34 μm, Re(550) of 130 nm, nx of 1.52, and the slow axis in the 0° direction.

[0153] [Production Example 2-3: Production of a stretched film (phase difference film) constituting an optical compensation layer]

[0154] The stretching ratio was changed to 1.52 times, and otherwise, the phase difference film 2-3 was obtained in the same manner as in Production Example 2-1. The phase difference film 2-3 exhibited refractive index characteristics of nx > ny = nz (positive A plate), had a thickness of 32 μm, Re(550) of 180 nm, nx of 1.52, and the slow axis in the 0° direction.

[0155] [Production Example 3-1: Production of a stretched film (phase difference film) constituting an optical compensation layer]

[0156] A commercially available cycloolefin-based resin film (manufactured by Zeon Corporation, product name "ZEONOR ZF14", thickness 40 μm) was subjected to transverse stretching with a stretching ratio of 1.18 times in the direction orthogonal to the transport direction and a stretching temperature of 135°C, obtaining the phase difference film 3-1. The phase difference film 3-1 exhibited refractive index characteristics of nx > ny > nz (negative B plate), had 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.

[0157] [Production Example 3-2: Production of a stretched film (phase difference film) constituting an optical compensation layer]

[0158] The stretching ratio in the direction orthogonal to the transport direction was changed to 1.35 times, and otherwise, the phase difference film 3-2 was obtained in the same manner as in Production Example 3-1. The phase difference film 3-2 exhibited refractive index characteristics of nx > ny > nz (negative B plate), had 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.

[0159] [Production Example 3-3: Production of a stretched film (phase difference film) constituting an optical compensation layer]

[0160] The stretching ratio in the direction orthogonal to the transport direction was changed to 1.52 times, and otherwise, the phase difference film 3-3 was obtained in the same manner as in Production Example 3-1. The phase difference 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 in the 90° direction.

[0161] [Production Example 4-1: Production of a liquid crystal alignment fixing layer constituting an optical compensation layer]

[0162] The photopolymerizable liquid crystal compound ("Paliocolor LC242" manufactured by BASF, the following chemical formula) showing a nematic liquid crystal phase was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. A surfactant ("BYK-360" manufactured by Bick Chemi Corporation) and a photopolymerization initiator ("Omnirad907" manufactured by IGM Resins Corporation) were added to the solution to prepare a liquid crystal composition solution. The amount of surfactant and polymerization initiator added was set to 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound. As a substrate, a biaxially stretched cycloolefin film ("ZEONOR film" manufactured by Japan Zeon, with a thickness of 33μm and Re(550)=135nm) was prepared. The above-mentioned liquid crystal composition was applied to the substrate by a rod coater so that Re(550) reached 80nm, and heated at 100°C for 3 minutes to orient the liquid crystal. After cooling to room temperature, the sample was irradiated with a cumulative light dose of 400 mJ / cm in a nitrogen atmosphere. 2 The optical laminate was cured by ultraviolet light to obtain a laminate having a structure of substrate / liquid crystal orientation fixing layer 4-1. The liquid crystal orientation fixing layer 4-1 was uniformly oriented and showed a refractive index characteristic of nx>ny=nz (positive A plate), with a thickness of 0.7μm, nx of 1.65, and a slow axis of 90°. In the preparation of the optical laminate, the liquid crystal orientation fixing layer 4-1 was transferred to the polarizer via an acrylic adhesive (thickness 5μm).

[0163] [Chemical formula 1]

[0164]

[0165] [Manufacturing Example 4-2: Preparation of a Liquid Crystal Alignment Fixing Layer Constituting an Optical Compensation Layer]

[0166] The coating thickness of the liquid crystal composition was changed so that Re (550) became 130 nm. In addition, a laminate having a structure of a substrate / liquid crystal orientation fixing layer 4-2 was obtained in the same manner as in Manufacturing Example 4-1. The liquid crystal orientation fixing layer 4-2 was uniformly oriented and showed a refractive index characteristic of nx>ny=nz (positive A plate), with a thickness of 1.1 μm, nx of 1.65, and a slow axis of 90°. In the preparation of the optical laminate, the liquid crystal orientation fixing layer 4-2 was transferred to the polarizer in the same manner as the liquid crystal orientation fixing layer 4-1.

[0167] [Manufacturing Example 4-3: Preparation of a Liquid Crystal Alignment Fixing Layer Constituting an Optical Compensation Layer]

[0168] The coating thickness of the liquid crystal composition was changed so that Re(550) became 180 nm. Other than that, a laminate having the structure of substrate / liquid crystal alignment fixing layer 4-3 was obtained in the same manner as in Production Example 4-1. The liquid crystal alignment fixing layer 4-3 was uniformly aligned, showing a refractive index characteristic of nx > ny = nz (positive A plate), having a thickness of 1.5 μm, nx of 1.65, and a slow axis in the 90° direction. In the production of the optical laminate, the liquid crystal alignment fixing layer 4-3 was transferred to the polarizing plate in the same manner as the liquid crystal alignment fixing layer 4-1.

[0169] [Production Example 5-1: Production of a retardation layer]

[0170] 1. Production of the first liquid crystal alignment fixing layer

[0171] A photo-alignment film was coated on the surface of a long strip-shaped 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 length direction. On the other hand, 10 parts by weight of a polymerizable discotic liquid crystal compound described in

[0111] of Japanese Patent No. 5186150 and 3 parts by weight of a photo-polymerization initiator for the polymerizable liquid crystal monomer (manufactured by BASF: trade name Irgacure 907) were dissolved in 40 parts by weight of toluene to prepare a liquid crystal coating solution. After coating this coating solution on the photo-alignment-treated surface of the PET substrate with a bar coater, it was heated and dried at 80 °C for 4 minutes to orient the liquid crystal. By irradiating ultraviolet rays to this liquid crystal layer, the liquid crystal layer was cured, and a long strip-shaped laminate having the first liquid crystal alignment fixing layer 5-1-1 formed on the PET substrate was obtained. The first liquid crystal alignment fixing layer 5-1-1 was uniformly aligned, showing a refractive index characteristic of nx = nz > ny (positive A plate), having 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 a slow axis in the 75° direction.

[0172] 2. Production of the second liquid crystal alignment fixing layer

[0173] An alignment treatment was performed so that the slow axis became the -15° direction, and the coating thickness of the liquid crystal composition was changed so that Re(550) became 120 nm. Other than that, a laminate having the structure of substrate / second liquid crystal alignment fixing layer 5-1-2 was obtained in the same manner as in Production Example 4-1. The second liquid crystal alignment fixing layer 5-1-2 was uniformly aligned, showing a refractive index characteristic of nx > ny = nz (positive A plate), having a thickness of 1.0 μm, and a slow axis in the -15° direction.

[0174] [Production Example 5-2: Production of a retardation layer]

[0175] 1. Fabrication of the first liquid crystal alignment fixing layer

[0176] A photo-alignment film was coated on the surface of a strip-shaped 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 length direction. On the other hand, 10 parts by weight of a polymerizable discotic liquid crystal compound described in

[0111] of Japanese Patent No. 5186150 and 3 parts by weight of a photoinitiator for the polymerizable liquid crystal monomer (manufactured by BASF: trade name Irgacure 907) were dissolved in 40 parts by weight of toluene to prepare a liquid crystal coating solution. After coating this coating solution on the photo-aligned surface of the PET substrate with a bar coater, it was heated and dried at 80°C for 4 minutes to orient the liquid crystal. By irradiating the liquid crystal layer with ultraviolet rays, the liquid crystal layer was cured, and thus a strip-shaped laminate having the first liquid crystal alignment fixing layer 5-2-1 formed on the PET substrate was obtained. The first liquid crystal alignment fixing layer 5-2-1 was uniformly aligned, showing a refractive index characteristic of nx = nz > ny (positive A plate), having 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 a slow axis in the -15° direction.

[0177] 2. Fabrication of the second liquid crystal alignment fixing layer

[0178] An 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. Other than this, a laminate having a structure of substrate / second liquid crystal alignment fixing layer 5-2-2 was obtained in the same manner as in Production Example 4-1. The second liquid crystal alignment fixing layer 5-2-2 was uniformly aligned, showing a refractive index characteristic of nx > ny = nz (positive A plate), having a thickness of 1.0 μm, and a slow axis in the 75° direction.

[0179] [Example 1]

[0180] 1. Fabrication of the optical laminate

[0181] The first liquid crystal alignment fixing layer 5-1-1 and the second liquid crystal alignment fixing layer 5-1-2 were bonded via an energy ray curable adhesive (thickness: 1 μm), and the substrate of the first liquid crystal alignment fixing layer 5-1-1 was peeled off. Next, an optical compensation layer (phase difference film 2-1) was bonded to the first liquid crystal alignment fixing layer 5-1-1 via an ultraviolet curable adhesive to obtain a phase difference 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 fixing layer 5-1-1 was -75° (105°), and the slow axis angle of the second liquid crystal alignment fixing layer 5-1-2 was -15° (165°). Next, the phase difference film with an optical compensation layer was bonded to the TAC film surface of the polarizing plate obtained in Production Example 1 via 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 fixing layer was peeled off to obtain an optical laminate having a configuration of polarizing plate / adhesive layer (adhesive layer) / optical compensation layer / adhesive layer (adhesive layer) / first liquid crystal alignment fixing layer / adhesive layer (adhesive layer) / second liquid crystal alignment fixing layer. The obtained optical laminate was subjected to the above-described evaluation of "reflectance". The results are shown in Table 1.

[0182] 2. Fabrication of Image Display Device

[0183] The cover glass and the optical film on the visible side of a commercially available organic EL display device ( manufactured by Samsung Corporation, trade name "Galaxy (registered trademark) A41") were removed, and after cleaning the removal surface, the second liquid crystal alignment fixing layer side of the above-obtained optical laminate was bonded to this cleaning surface via an acrylic adhesive (thickness: 10 μm) to obtain an image display device. The obtained image display device was subjected to the above-described evaluation of "line unevenness". The results are shown in Table 1.

[0184] [Examples 2 to 3]

[0185] The configuration of the optical compensation layer was changed as shown in Table 1, and otherwise, an optical laminate and an image display device were obtained in the same manner as in Example 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.

[0186] [Examples 4 to 6 and Comparative Examples 1 to 4]

[0187] The configuration of the optical compensation layer was changed as shown in Table 1, and the bonding and peeling of each layer constituting the optical laminate were all performed by a roll-to-roll process, and otherwise, an optical laminate and an image display device were obtained in the same manner as in Example 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.

[0188]

[0189] In Table 1, for example, "Ex. 1" refers to Example 1, and "Comp. 1" refers to Comparative Example 1. Further, "Positive A" refers to the positive A plate, "Negative A" refers to the negative A plate, and "Negative B" refers to the negative B plate. In addition, for example, "Stretch 2-1" refers to the retardation film 2-1 of Production Example 2-1, "LC 4-1" refers to the liquid crystal alignment fixing layer 4-1 of Production Example 4-1, and "Negative A (15)" refers to the negative A plate having a slow axis in the 15° direction.

[0190] Industrial Applicability

[0191] The optical laminate of the embodiment of the present invention can be suitably used for an image display device (typically a liquid crystal display device or an organic EL display device).

Claims

1. An optical laminate having, 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 sequentially includes a first liquid crystal alignment fixing layer and a second liquid crystal alignment fixing layer from the side of the optical compensation layer, and the whole has a circular polarization function or an elliptical polarization function.

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 whole retardation layer shows a relationship of Re(450) < Re(550).

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

8. The optical laminate according to claim 7, wherein, The second liquid crystal alignment fixing 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 fixing layer intersects the slow axis of the second liquid crystal alignment fixing layer.

10. The optical laminate according to claim 1, wherein, The first liquid crystal alignment fixing layer and the second liquid crystal alignment fixing 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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