Optical laminate and image display device using the same

Abstract

To provide an optical laminate which includes a liquid crystal alignment solidified layer and is capable of suppressing particular display unevenness when used in image display devices.SOLUTION: An optical laminate according to an embodiment of the present invention comprises a polarizing plate including a polarizer, and a retardation layer laminated on the polarizing plate via a first adhesive layer. The retardation layer comprises a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer laminated on the first liquid crystal alignment solidified layer via a second adhesive layer in order from the polarizing plate side. A refractive index nLC1 of a polarizer of the first liquid crystal alignment solidified layer in a transmission axis direction is greater than 1.60, and a distance D from the polarizer to the first adhesive layer is less than 0.5 μm.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 the 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 thinning of the retardation layer (retardation film) that contributes greatly to the thickness has been progressing. 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 the 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, in an image display device using an optical laminate including a liquid crystal film, display unevenness (specifically, a phenomenon in which a thin pink line that is particularly noticeable in the absorption axis direction of the polarizer is visually recognized) may occur depending on the viewing environment.

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 can suppress 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 a polarizing plate including a polarizer and a retardation layer laminated on the polarizing plate via a first adhesive layer; the retardation layer includes, in order from the polarizer side, a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer laminated on the first liquid crystal alignment cured layer via a second adhesive layer; the refractive index n of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer LC1 is greater than 1.60; the distance D from the polarizer to the first adhesive layer is less than 0.5 μm. [2] In the above [1], the polarizing plate includes a first protective layer disposed on the side opposite to the retardation layer of the polarizer and a second protective layer disposed on the retardation layer side of the polarizer; the thickness of the second protective layer is less than 0.5 μm. [3] In the above [2], the second protective layer is a cured product or a thermoset of a coating film of an organic solvent solution of a resin. [4] In the above [1], the polarizing plate includes only a first protective layer disposed on the side opposite to the retardation layer of the polarizer as a protective layer; the first liquid crystal alignment cured layer is laminated on the polarizer via the first adhesive layer. [5] In any one of the above [1] to [4], the angle formed by the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer is 40° or less. [6] In any one of the above [1] to [5], the first adhesive layer is composed of an active energy ray curable adhesive, and its thickness T AD1 is 0.4 μm to 2.0 μm. [7] In any one of the above [1] to [6], the second adhesive layer is composed of an adhesive, and its thickness T AD2 is 2 μm to 10 μm. [8] In any one of the above [1] to [7], the refractive index n of the second adhesive layer AD2 is greater than 1.60. [9] According to another aspect of the present invention, an image display device is provided. The image display device includes any one of the optical laminate bodies [1] to [8] described above. [Advantages of the Invention]

[0006] According to an embodiment of the present invention, it is possible to realize an optical laminate body that includes a liquid crystal alignment solidification layer and can suppress specific display unevenness when applied to an image display device. [Brief Description of the Drawings]

[0007]

Figure 1

Figure 2

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

[0009] (Definition of Terms and Symbols) The definitions of the 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 is the thickness of the film in nm. (3) Phase Difference in the Thickness Direction (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. When the thickness of the film is d (nm), Rth(λ) is obtained by the formula: Rth = (nx - nz) × d. (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 the 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 and a retardation layer 20 laminated on the polarizing plate 10 via a first adhesive layer 31. In the optical laminate 100 in the illustrated example, the polarizing plate 10 includes a polarizer 11, a first protective layer 12 disposed on the side of the polarizer 11 opposite to the retardation layer 20, and a second protective layer 13 disposed on the side of the polarizer 11 on the retardation layer 20 side. In the embodiment of the present invention, the distance D from the polarizer 11 to the first adhesive layer 31 is less than 0.5 μm. That is, in the embodiment shown in FIG. 1, the total thickness of the second protective layer and the adhesive layer (not shown) for laminating the second protective layer on the polarizer is less than 0.5 μm.

[0011] FIG. 2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention. In the optical laminate 101 in the illustrated example, the polarizing plate 10 includes only a first protective layer 12 disposed on the side of the polarizer 11 opposite to the retardation layer 20 as a protective layer. That is, the polarizing plate is a so-called single-protection polarizing plate. With such a configuration, the distance D from the polarizer 11 to the first adhesive layer 31 becomes 0.0 μm, which is less than 0.5 μm.

[0012] The retardation layer 20 includes, in order from the polarizer 10 side, a first liquid crystal alignment cured layer 21 and a second liquid crystal alignment cured layer 22 laminated on the first liquid crystal alignment cured layer 21 via a second adhesive layer 32. Therefore, in the embodiment of FIG. 1, in the retardation layer 20, the first liquid crystal alignment cured layer 21 is laminated on the second protective layer 13 via the first adhesive layer 31; in the embodiment of FIG. 2, in the retardation layer 20, the first liquid crystal alignment cured layer 21 is laminated on the polarizer 11 via the first adhesive layer 31. 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 has, in one embodiment, a circular polarization function or an elliptical polarization function as a whole (as a laminate of the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22). The retardation layer has, in one embodiment, an Nz coefficient of, for example, 0.30 to 0.70 as a whole. 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.

[0013] In an embodiment of the present invention, as described above, the distance D from the polarizer 11 to the first adhesive layer 31 is less than 0.5 μm. The distance D is preferably 0.4 μm or less, more preferably 0.3 μm or less, still more preferably 0.2 μm or less, particularly preferably 0.1 μm or less, and most preferably 0.0 μm (that is, a so-called single-protection polarizing plate without a second protective layer). When the present inventors considered further thinning of the optical laminate including the liquid crystal alignment cured layer as the retardation layer, they found a new problem that an image display device using the optical laminate including the liquid crystal alignment cured layer as the retardation layer may cause specific display unevenness depending on the viewing environment. Specifically, it was found that in the reflection under a three-wavelength light source, a phenomenon (sometimes referred to as line unevenness) in which a thin line with a particularly prominent pink color in the absorption axis direction of the polarizer is visually recognized over the entire area may occur. Further, when the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer are formed using a material having a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, even when the same material (therefore, a material having the same average refractive index) is used for each layer, the refractive index in the transmission axis direction of the polarizer changes depending on the angle between the transmission axis of the polarizer and the slow axis of the liquid crystal alignment cured layer, and the degree of line unevenness can change depending on the refractive index in the transmission axis direction of the polarizer. As a result of intensive studies on suppressing such line unevenness, the present inventors found that line unevenness can be suppressed by making the distance D from the polarizer to the first adhesive layer less than 0.5 μm, and thus completed the present invention. In addition, the present inventors found that the smaller the distance D is, the more preferable it is, and that line unevenness can be significantly suppressed by making the polarizing plate a so-called single-protection polarizing plate. Such an effect according to the embodiment of the present invention solves a newly found problem when considering further thinning of the optical laminate including the liquid crystal alignment cured layer as the retardation layer, and is an unexpectedly excellent effect. Needless to say, the embodiment of the present invention can suppress conventionally recognized display unevenness.

[0014] Furthermore, in an embodiment of the present invention, the refractive index n in the transmission axis direction of the polarizer of the first liquid crystal alignment cured layer LC1 is greater than 1.60. nLC1 In a configuration where [the value] is large, the effects according to the embodiments of the present invention become remarkable.

[0015] As the first adhesive layer 31 and the second adhesive layer 32, any appropriate configuration can be adopted as long as the effects according to the embodiments of the present invention can be obtained. For example, each of the first adhesive layer and the second adhesive layer may be composed of an adhesive or an adhesive agent. The specific configurations of the first adhesive layer and the second adhesive layer will be described in item D below.

[0016] In the optical laminate, the total thickness from the first liquid crystal alignment cured layer to the second liquid crystal alignment cured layer (i.e., the total thickness of the retardation layer) is preferably 15 μm or less, more preferably 3 μm to 10 μm. According to the embodiments of the present invention, it is possible to solve the problem of linear unevenness newly found in an optical laminate including a very thin liquid crystal alignment cured layer. Note that 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.

[0017] The optical laminate may be in a sheet form or a long strip form. In this specification, "long strip form" means an elongated shape in which the length is sufficiently longer than the width, for example, an elongated shape in which the length 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 each component (each layer) cut into a predetermined size. In the long strip-shaped optical laminate (particularly, a configuration including a single-side protective polarizer), the effects according to the embodiments of the present invention can be remarkable. The following mechanism can be speculated. However, the mechanism is merely a speculation and does not limit the present invention, nor does it restrict the present invention by the mechanism. Since the polarizer is typically a film uniaxially stretched at a high magnification in the long axis direction, even when the first adhesive layer is composed of a curable adhesive and the adhesive shrinks during curing, it is considered that it is difficult to shrink following the shrinkage of the adhesive, particularly in the width direction. Therefore, in a configuration including a single-side protective polarizer, the protective layer on the adhesive side is omitted, and the polarizer and the adhesive are in contact with each other, so it is considered that the shrinkage of the polarizer is small when the adhesive cures. As a result, it is considered that the thickness unevenness of the entire optical laminate is suppressed, and the linear unevenness due to interference is suppressed.

[0018] Practically, the optical laminate has an adhesive layer (not shown) as the outermost layer on the second liquid crystal alignment curing layer side (image display panel side) and can be attached 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 used. By temporarily attaching the release liner, the adhesive layer is protected and the optical laminate can be formed into a roll.

[0019] Hereinafter, the components of the optical laminate will be specifically described.

[0020] B. Polarizer B-1. Polarizer The polarizer 11 is typically composed of a polyvinyl alcohol (PVA)-based resin film containing a dichroic substance (e.g., iodine). Examples of PVA-based resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and ethylene-vinyl acetate copolymer-based partially saponified products.

[0021] 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.

[0022] The polarizer preferably contains an iodide or sodium chloride (sometimes collectively referred to as a halide). Examples of iodides 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 later, 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, achieving both high polarization degree and high single transmittance) can be realized.

[0023] 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 in the above range, the degree of polarization can be maintained in such a range.

[0024] 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, a remarkable thinning of the optical laminate can be achieved. Further, if the thickness of the polarizer is in the above range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0025] 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.

[0026] Specific examples of the polarizer composed of a single-layer resin film include those 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 with a dichroic substance such as iodine or a dichroic dye and a 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.

[0027] The above iodine staining is carried out, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the above uniaxial drawing is preferably 3 to 7 times. The drawing may be carried out after the dyeing treatment or during the dyeing. Also, dyeing may be carried out after drawing. If necessary, the PVA-based film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt on the surface of the PVA-based film and the anti-blocking agent be washed, but also the PVA-based film can be swollen to prevent uneven dyeing and the like.

[0028] 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, if necessary, air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in the present embodiment, preferably, the laminate is subjected to a dry 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 water stretching treatment, and a dry shrinkage treatment in this order. By introducing the assisted 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 or 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. Thereby, the optical properties 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. Furthermore, by shrinking the laminate in the width direction by the dry 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 the protective layer of the polarizer), and an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface of the resin substrate peeled from the resin substrate / polarizer laminate or on the surface opposite to the peeled surface and used. 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 descriptions of these publications are incorporated herein by reference.

[0029] B-2. Protective Layer The first protective layer 12 is composed of an arbitrary appropriate resin film. Representative examples of the material 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 descriptions of these publications are incorporated herein by reference. From the viewpoint of ease of profile processing and the like, cellulose-based resins are preferable, and TAC is more preferable. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic-based resins are preferable.

[0030] The optical laminate is typically disposed on the viewing side of an image display device, and the first protective layer 12 is typically disposed on its viewing side. Therefore, the first 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 first protective layer 12 may be treated as necessary to improve visibility when viewed through polarized sunglasses (typically, imparting an (elliptical) polarization function and imparting an ultra-high retardation). By performing such treatment, excellent visibility can be achieved even when the display screen is viewed 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.

[0031] The thickness of the first protective layer 12 is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 35 μm. When the first protective layer 12 is surface-treated, the thickness of the first protective layer 12 is the thickness including the thickness of the surface treatment layer.

[0032] As described above, the second protective layer 13 can preferably be omitted. When the second protective layer 13 is provided, its thickness can be set such that the distance D is less than 0.5 μm. Considering the thickness of the adhesive layer that laminates the second protective layer on the polarizer, the thickness of the second protective layer is preferably 0.05 μm to 0.40 μm, more preferably 0.08 μm to 0.37 μm, and even more preferably 0.10 μm to 0.35 μm.

[0033] The second protective layer (when present) is typically a solidified or thermoset product of a coating film of an organic solvent solution of a resin. Typically, the glass transition temperature (Tg) of the resin is 85°C or higher, and the weight average molecular weight (Mw) is 25,000 or higher. The Tg of the resin is preferably 90°C or higher, more preferably 100°C or higher, still more preferably 110°C or higher, and particularly preferably 120°C or higher. The Tg can be, for example, 200°C or lower. Also, the Mw of the resin is preferably 30,000 or higher, more preferably 35,000 or higher, still more preferably 40,000 or higher. The Mw of the resin can be, for example, 200,000 or lower. As the resin, any suitable resin that can form a solidified or cured product (e.g., a thermoset product) of a coating film of an organic solvent solution can be used. As the resin, preferably, a thermoplastic resin or a thermosetting resin having the above-mentioned Tg and Mw is used, and more preferably, a thermoplastic resin is used. Only one type of the resin may be used, or two or more types may be used in combination. Examples of the above thermoplastic resin include acrylic resins and epoxy resins. An acrylic resin and an epoxy resin may be used in combination. Specific examples of the acrylic resin include the boron-containing acrylic resin and the acrylic resin containing a lactone ring, etc., described in JP-A No. 2021-117484

[0034] ~

[0056] . As the epoxy resin, preferably, an epoxy resin having an aromatic ring is used. The solidified or cured product of the coating film of the organic solvent solution is described, for example, in the above-mentioned JP-A No. 2021-117484. As the solidified or cured product of the coating film of the organic solvent solution of the resin, the configuration described in WO 2020 / 138329 may be used. The descriptions of these publications are incorporated herein by reference.

[0034] C. 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, simply referring to the "retardation layer" means describing it as a whole, and simply referring to the "liquid crystal alignment cured layer" means collectively describing the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer.

[0035] In one embodiment, Re(550) of the first liquid crystal alignment cured layer is preferably 150 nm to 300 nm, more preferably 200 nm to 270 nm, and still more preferably 220 nm to 260 nm; 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 still more preferably 110 nm to 130 nm. Thus, since both the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer have an in-plane retardation, they exhibit a refractive index characteristic of nx > ny. The first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer typically exhibit a refractive index characteristic of nx > ny = nz (positive A plate). Here, "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. That is, the Nz coefficients of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer can be 0.9 to 1.1, respectively.

[0036] 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, 1.5 μm to 2.5 μm. Thus, according to the embodiment of the present invention, linear unevenness can be suppressed while reducing the thickness of the first liquid crystal alignment cured layer compared to the conventional case. The thickness of the second liquid crystal alignment cured layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness can be, for example, 0.8 μm to 1.5 μm.

[0037] The angle formed between the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer is, for example, 40° or less, preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 14° to 16°; the angle formed between the slow axis of the second 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°. 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.

[0038] Examples of the liquid crystal compound used for the liquid crystal alignment cured layer include 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, the formed liquid crystal alignment cured layer, for example, does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to the liquid crystalline compound. 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.

[0039] In one embodiment, the liquid crystal alignment curing layer can be formed using a composition containing a polymerizable liquid crystal compound (polymerizable liquid crystal compound, i.e., liquid crystal monomer). As used herein, 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 a polymerization reaction, preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by active radicals, acids, etc. generated from a photopolymerization initiator. 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.

[0040] The mechanism for the expression of liquid crystallinity of the liquid crystal compound may be thermotropic or lyotropic. Also, the structure of the liquid crystal phase may be nematic liquid crystal or smectic liquid crystal. From the viewpoint of ease of manufacture, thermotropic nematic liquid crystal is preferred for liquid crystallinity.

[0041] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

[0042] The birefringence Δn of the liquid crystal alignment cured 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, a desired in-plane retardation can be realized with a very thin thickness. As a result, the liquid crystal alignment cured layer and the optical laminate can be made thinner, and ultimately can contribute to a remarkable thinning of the image display device.

[0043] The liquid crystal alignment cured layer may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light. In one embodiment, the liquid crystal alignment cured layer exhibits a positive wavelength dispersion characteristic. In such a case, the effects according to the embodiments of the present invention are remarkable.

[0044] In another embodiment, Re(550) of the first liquid crystal alignment cured layer 21 is preferably 80 nm to 160 nm, more preferably 90 nm to 150 nm, still more preferably 100 nm to 140 nm, and particularly preferably 110 nm to 130 nm. In this case, the second liquid crystal alignment cured layer 22 can typically be a positive C plate. The thickness of the first liquid crystal alignment cured layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness can be, for example, 0.8 μm to 1.2 μm, or can be, for example, 0.9 μm to 1.1 μm. The angle formed by the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer is, for example, 40° or less, preferably -10° to +10°, more preferably -5° to +5°, still more preferably -2° to +2°, and particularly preferably about 0°.

[0045] In yet another embodiment, Re(550) of the first liquid crystal alignment solidified layer 21 is preferably 100 nm to 200 nm, more preferably 110 nm to 180 nm, still more preferably 120 nm to 160 nm, and particularly preferably 130 nm to 150 nm. Also in this case, the second liquid crystal alignment solidified layer 22 can typically be a positive C-plate. The thickness of the first liquid crystal alignment solidified layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness may be, for example, 1.0 μm to 1.6 μm, or may be, for example, 1.1 μm to 1.3 μm. The angle formed by the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, still more preferably 44° to 46°, and particularly preferably about 45°.

[0046] The second liquid crystal alignment solidified layer (positive C-plate) 22 exhibits a refractive index characteristic of nz > nx = ny. The retardation Rth(550) in the thickness direction of the positive C-plate is preferably -20 nm to -300 nm, more preferably -30 nm to -250 nm, still more preferably -40 nm to -200 nm, and particularly preferably -50 nm to -150 nm. Here, "nx = ny" includes not only the case where nx and ny are exactly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the positive C-plate can be less than 10 nm.

[0047] The positive C-plate can be formed, for example, using a composition containing a side-chain type thermotropic liquid crystal polymer. As the side-chain type thermotropic liquid crystal polymer, a copolymer having a liquid crystalline monomer unit represented by the general formula (I) and a non-liquid crystalline monomer unit represented by the general formula (II) is preferably used.

Chemical formula

Chemical formula

[0048] In formula (I), R 1 is a hydrogen atom or a methyl group, and R 2 is a cyano group, a fluoro group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and X 1 is -CO2- or -OCO-. a is an integer of 1 to 6, and b and c are each independently 1 or 2.

[0049] In formula (II), R 3 is a hydrogen atom or a methyl group, and R 4 is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or a group represented by the following general formula (III).

Chemical formula

[0050] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0051] Specific examples of the method for forming the positive C plate include the methods described in

[0020] to

[0028] of JP-A-2002-333642. In this case, the thickness of the positive C plate is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and still more preferably 0.5 μm to 5 μm.

[0052] Even in the embodiment using the positive C plate, the arrangement order of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer may be reversed. In this case, the angle formed by the slow axis of the liquid crystal alignment solidified layer (other than the positive C plate, the liquid crystal alignment solidified layer showing the refractive index characteristics of nx>ny) and the transmission axis of the polarizer can be appropriately set according to the purpose.

[0053] The refractive index (the refractive index in the transmission axis direction of the polarizer) n of the first liquid crystal alignment solidified layer LC1is greater than 1.60 as described above, preferably 1.61 to 1.68, and more preferably 1.63 to 1.66. The average refractive index of the liquid crystal alignment curing layer typically conforms to the composition of the composition for forming the liquid crystal alignment curing layer in order to obtain desired optical properties. As a result, linear unevenness may occur. According to an embodiment of the present invention, by making the distance D from the polarizer to the first adhesive layer less than 0.5 μm, linear unevenness can be suppressed. The refractive index (refractive index in the transmission axis direction with respect to the polarizer) n of the second liquid crystal alignment curing layer LC2 can adopt any appropriate refractive index.

[0054] D. Adhesive layer In this section, the first adhesive layer and the second adhesive layer are collectively described as the "adhesive layer". When it is necessary to distinguish between the first adhesive layer and the second adhesive layer, "first" and "second" are specified. Therefore, when expressing "n AD ", it means the refractive index when the first adhesive layer and the second adhesive layer are collectively regarded as the "adhesive layer"; when expressing "n AD1 " or "n AD2 ", it means the refractive index of the first adhesive layer or the second adhesive layer, respectively. As the adhesive layer, any appropriate configuration can be adopted as long as the display unevenness parameter can be set to a predetermined value or less. Specifically, as described above, the adhesive layer may be composed of an adhesive or an adhesive. Regardless of whether the adhesive layer is an adhesive layer or an adhesive layer, the refractive index n AD of the adhesive layer may be, for example, 1.45 or more, or may be, for example, 1.47 or more, or may be, for example, 1.49 or more. On the other hand, the refractive index n AD of the adhesive layer may be, for example, 1.62 or less, or may be, for example, 1.60 or less. In one embodiment, the refractive index n AD2 of the second adhesive layer may be, for example, greater than 1.60.

[0055] The first adhesive layer can typically be composed of an active energy ray-curable adhesive. In this case, the thickness T of the first adhesive layer AD1is preferably from 0.4 μm to 2.0 μm, more preferably from 0.8 μm to 1.2 μm. With such a configuration, even when an adhesive is used for the second adhesive layer, thinning of the optical laminate can be achieved.

[0056] The active energy ray-curable adhesive can adopt any suitable configuration as long as the display unevenness parameter can be made smaller than a predetermined value. 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 a desired refractive index can be obtained to make the display unevenness parameter smaller than the predetermined value. The adhesive (adhesive composition) may contain a (meth)acrylate containing an aromatic ring skeleton and / or metal oxide particles in one embodiment. Each will be briefly described below. Note that since well-known configurations can be adopted for other components that can be included in the adhesive (for example, curing components, photoinitiators), specific descriptions are omitted.

[0057] By containing a (meth)acrylate having an aromatic ring skeleton in the adhesive composition, an adhesive layer having a desired refractive index can be formed in the embodiments of the present invention. As the (meth)acrylate having an aromatic ring skeleton, it is preferable to use 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.

[0058] 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.

[0059] From the viewpoint 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.

[0060] 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 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.

[0061] 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.

[0062] The second adhesive layer may be composed of an adhesive or an active energy ray-curable adhesive. The active energy ray-curable adhesive is as described for the first adhesive layer.

[0063] The second adhesive layer can typically be composed of an adhesive. In this case, the thickness T of the adhesive layer AD2 is preferably 2 μm to 10 μm, more preferably 3 μm to 9 μm, still more preferably 4 μm to 7 μm, and particularly preferably 4.5 μm to 5.5 μm. If the thickness of the second adhesive layer is within such a range, thin film interference between the second adhesive layer and the first liquid crystal alignment cured layer and the second alignment cured layer can be suppressed. As a result, linear unevenness can be suppressed. Furthermore, since the adhesive is less likely to have thickness variation compared to the active energy ray-curable adhesive, even if interference occurs between the first liquid crystal alignment cured layer and the second alignment cured layer, linear unevenness can be suppressed.

[0064] The adhesive can adopt any suitable configuration as long as it can make the display unevenness parameter smaller than a predetermined value. By adjusting the type, number, combination, and blending amount of the monomer components of the base polymer in the adhesive (adhesive composition); the type, number, combination, and blending amount of the crosslinking agent; and the type, number, combination, and blending amount of the additive, an adhesive (adhesive composition) capable of realizing desired appearance parameters can be prepared. In one embodiment, the monomer components of the base polymer of the adhesive (adhesive composition) include heterocyclic ring-containing acrylates and / or aromatic ring-containing acrylates. Examples of the heterocyclic ring-containing acrylate include acryloylmorpholine. Examples of the aromatic ring-containing acrylate include benzyl acrylate and phenoxybenzyl acrylate.

[0065] E. Image display device The optical laminate described in the above Items A to D 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 D on its viewing side.

Examples

[0066] 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.

[0067] (1) Refractive index (1-1) Adhesive layer For the adhesive layers formed in the examples and comparative examples, measurement was performed using an Abbe refractometer (manufactured by ATAGO Co., Ltd., product name "DR-M2 / 1550"). The measurement wavelength was 589 nm and the measurement temperature was 25°C. (1-2) Adhesive layer and liquid crystal alignment curing layer The adhesives used in the examples and comparative examples were applied to a cycloolefin polymer film (COP film) (thickness: 100 μm), and the same COP film was laminated on the coated surface. Then, visible light was irradiated using an active energy ray irradiation device to obtain a cured product layer (single film). For the obtained cured product layer, the in-plane refractive index and the refractive index in the thickness direction were measured using a prism coupler (manufactured by Sirion Technologies, product name "SPA-4000"), and the average value of these was taken as the average refractive index of the adhesive layer. The measurement wavelength was 594 nm, and the measurement temperature was 23°C. Furthermore, for the liquid crystal alignment cured layer, the refractive index in the transmission axis direction was determined as follows. 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) Furthermore, in the equation of the ellipse (x 2 / a 2 )+(y 2 / b 2 ) = 1, nx was set as a, ny was set as b, x and y were set as the refractive indices in the x direction and y direction at the angle θ direction on the ellipse, and by solving the simultaneous equations from y = tanθ and the above nx and ny, the refractive index in the transmission axis direction was calculated.

[0068] (2) Thickness It was measured with an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0069] (3) Linear 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. 1 (excellent): No linear unevenness was observed even when observed with a polarizing plate attached to the three-wavelength fluorescent lamp. 2 (good): No linear unevenness was observed in the normal observation with a three-wavelength fluorescent lamp. 3 (Acceptable): Slight linear unevenness was observed in normal observation with a three-wavelength fluorescent lamp. 4 (Unacceptable): Practically unacceptable linear unevenness was observed in normal observation with a three-wavelength fluorescent lamp. 5 (Defective): Linear unevenness was prominent in normal observation with a three-wavelength fluorescent lamp.

[0070] [Production Example 1: Preparation of Adhesive A1 Constituting the First Adhesive Layer or the Second Adhesive Layer] 10 parts of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals Co., Ltd.), 4 parts of 2-acetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals Corporation), 60 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 11 parts of tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.), 1 part of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Corporation), 10 parts of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), 1 part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 1 part of diethylthiioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50 °C for 1 hour to prepare Adhesive A1. The refractive index n AD of Adhesive A1 was 1.52.

[0071] [Production Example 2: Preparation of Adhesive A2 Constituting the Second Adhesive Layer] 55 parts of zirconia dispersion, 25 parts of "POB-A", 10 parts of 4-hydroxybutyl acrylate, 10 parts of tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.), 1 part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 2 parts of diethylthiioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50 °C for 1 hour to prepare Adhesive A2. The refractive index n of Adhesive A2 AD was 1.61.

[0072] [Production Example 3: Preparation of Pressure-Sensitive Adhesive PS1 Constituting the Second Adhesive Layer] A monomer mixture containing 91 parts of butyl acrylate, 6 parts of acryloylmorpholine, 2.7 parts of acrylic acid, and 0.3 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate per 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring for nitrogen substitution. Then, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55 °C to prepare a solution of acrylic polymer P1 having a weight average molecular weight (Mw) of 2.7 million. To 100 parts of the solid content of the acrylic polymer P1 solution, 0.1 part of an isocyanate-based crosslinking agent (trimethylolpropane / toluene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 part of a peroxide crosslinking agent (benzoyl peroxide: manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 part of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended to obtain pressure-sensitive adhesive PS1. The polymer concentration of pressure-sensitive adhesive PS1 was adjusted to 8%. The refractive index n of pressure-sensitive adhesive PS1 AD was 1.47.

[0073] [Production Example 4: Resin Film Constituting the Second Protective Layer] A commercially available acrylic resin film (manufactured by Toyo Kohan Co., Ltd., thickness: 30 μm) was used as it was.

[0074] [Production Example 5: Resin Film Constituting the Second Protective Layer] A commercially available triacetyl cellulose (TAC) film (manufactured by Fuji Film Co., Ltd., thickness: 25 μm) was used as it was.

[0075] [Production Example 6: Resin Film Constituting the Second Protective Layer] A commercially available cycloolefin-based resin (COP) film (manufactured by Nippon Zeon Co., Ltd., product name "ZF14", thickness: 13 μm) was used as it was.

[0076] [Production Example 7: Preparation of Resin Solution for Forming the Second Protective Layer (Solidified Layer)] 97.0 parts of methyl methacrylate (MMA, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., trade name "methyl methacrylate monomer"), 3.0 parts of copolymerizable monomer represented by the following formula (1e), and 0.2 part of polymerization initiator (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., trade name "2,2'-azobis(isobutyronitrile)") were dissolved in 200 parts of toluene. Subsequently, a polymerization reaction was carried out for 5.5 hours while heating to 70 °C under a nitrogen atmosphere to obtain a boron-containing acrylic resin solution (solid content concentration: 33%). The Tg of the obtained boron-containing acrylic polymer (resin) was 110 °C and the Mw was 80,000. 20 parts of the obtained boron-containing acrylic resin was dissolved in 80 parts of methyl ethyl ketone to obtain a resin solution (20%). [Chemical Formula]

[0077] [Example 1] 1. Production of Polarizing Plate 1-1. Production of Polarizer As a thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) that was long and had a Tg of about 75 °C was used, and one side of the resin substrate was subjected to corona treatment. 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gohsei Chemical Industry Co., Ltd., trade name "Gosefimer") at a ratio of 9:1, with 13 parts by weight of potassium iodide added, 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 mixing 4 parts by weight of boric acid with 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 mixing iodine and potassium iodide at a weight ratio of 1:7) 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 mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 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 became 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 mixing 4 parts by weight of potassium iodide with 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".

[0078] 1-2. 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 (thickness 1 μm). 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 laminated so that the COP film was on the polarizer side. The Re(550) of the COP film was 135 nm. Next, the resin substrate was peeled off, and the resin solution of Production Example 7 was applied to the peeled surface using a wire bar, and then the coating film was dried at 60°C for 5 minutes to form a solidified layer (second protective layer, thickness 300 nm) of the coating film of the organic solvent solution of the resin. In this way, a polarizing plate having a structure of HC layer / COP resin film (first protective layer) / polarizer / solidified layer (second protective layer: thickness 0.3 μm) was obtained.

[0079] 2. Fabrication of Retardation Layer 2-1. Fabrication of First Liquid Crystal Alignment Solidified 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 the substrate, a biaxially stretched norbornene-based film (Zeonoa Film manufactured by Nippon Zeon, thickness 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition was applied onto this substrate by a bar coater so that Re(550) became 120 nm, and heated at 100 °C for 3 minutes to align the liquid crystal. After cooling to room temperature, under a nitrogen atmosphere, ultraviolet rays with an integrated light amount of 400 mJ / cm 2 were irradiated to perform photocuring, and a long laminated body having a structure of a substrate / First Liquid Crystal Alignment and Solidification Layer was obtained. The First Liquid Crystal Alignment and Solidification Layer was homogeneously aligned, and its thickness was 1.0 μm. The slow axis direction of the First Liquid Crystal Alignment and Solidification Layer was in the 90° direction. [Chemical formula]

[0080] 2-2. Preparation of the Second Liquid Crystal Alignment and Solidification Layer 20 parts by weight of a side-chain type liquid crystal polymer with the following chemical formula (n = 0.35, shown as a block polymer for convenience), 80 parts by weight of a polymerizable liquid crystal showing a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (Irgacure 907 manufactured by BASF) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. Then, after applying the coating solution onto a PET substrate subjected to vertical alignment treatment by a bar coater, it was 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 laminated body having a structure of a substrate / Second Liquid Crystal Alignment and Solidification Layer (positive C plate, thickness 1.0 μm). [Chemical formula]

[0081] 3. Fabrication of the optical laminate After laminating the first liquid crystal alignment cured layer via the adhesive A1 (thickness: 1 μm) of Production Example 1 as the first adhesive layer on the surface of the cured layer (second protective layer) of the polarizing plate and then peeling off the substrate, the second liquid crystal alignment cured layer was laminated on the surface of the first liquid crystal alignment cured layer via the pressure-sensitive adhesive PS1 (thickness: 5 μm) of Production Example 3 as the second adhesive layer, and the substrate was peeled off to obtain a long optical laminate having a structure of polarizing plate / first liquid crystal alignment cured layer / adhesive layer / second liquid crystal alignment cured layer. The lamination and peeling were performed by a roll-to-roll process. In the obtained optical laminate, the refractive index n of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer LC1 was 1.65, and the refractive index n of the second liquid crystal alignment cured layer LC2 was 1.53. Further, the refractive index n of the first adhesive layer AD1 was 1.52, and the refractive index n of the second adhesive layer AD2 was 1.47.

[0082] 4. Fabrication of the image display device The cover glass and the optical film on the viewing side of a commercially available liquid crystal display device (manufactured by Apple Inc., trade name “iPad (registered trademark)”, IPS mode) were removed, and after cleaning the removal surface, the second liquid crystal alignment cured layer side of the optical laminate obtained above was laminated on the cleaning surface via an acrylic pressure-sensitive adhesive (thickness: 10 μm) to obtain an image display device. The obtained image display device was subjected to the above “linear unevenness” evaluation. The results are shown in Table 1.

[0083] [Example 2 and Comparative Examples 1 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 second protective layer was as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0084] [Example 3] An optical laminate and an image display device were obtained in the same manner as in Example 1, except that the adhesive A1 of Production Example 1 was used instead of the adhesive PS1 of Production Example 3 as the second adhesive layer. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0085] [Examples 4 and Comparative Examples 4 to 7] An optical laminate and an image display device were obtained in the same manner as in Example 3, except that the second protective layer was configured as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0086] [Examples 5 to 6] An optical laminate and an image display device were obtained in the same manner as in Example 1, except that the second adhesive layer was configured as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0087] [Reference Example 1] An optical laminate and an image display device were obtained in the same manner as in Example 1, except that the arrangement order of the first liquid crystal alignment curing layer and the second liquid crystal alignment curing layer was reversed, the slow axis direction of the second liquid crystal alignment curing layer was set to the 0° direction, and the second adhesive layer was configured as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0088] [Example 7] 1. Production of polarizing plate A polarizing plate was produced in the same manner as in Example 1.

[0089] 2. Production of retardation layer Using a photopolymerizable liquid crystal compound similar to that in Example 1, a long laminate having the structure of a substrate / First Liquid Crystal Alignment and Solidification Layer (Re(550) = 240 nm) was obtained in the same manner as in Example 1. The First Liquid Crystal Alignment and Solidification Layer had a homogeneous alignment, and its thickness was 2.0 μm. The slow axis direction of the First Liquid Crystal Alignment and Solidification Layer was the 75° direction. A long laminate of a substrate / Second Liquid Crystal Alignment and Solidification Layer (homogeneous alignment, thickness 1.0 μm, Re(550) = 120 nm) was obtained in the same manner as above except that the coating thickness was changed. The slow axis direction of the Second Liquid Crystal Alignment and Solidification Layer was the 15° direction.

[0090] 3. Fabrication of the optical laminate A long optical laminate having the structure of a polarizing plate / First Liquid Crystal Alignment and Solidification Layer / adhesive layer / Second Liquid Crystal Alignment and Solidification Layer was obtained in the same manner as in Example 1 except that the First Liquid Crystal Alignment and Solidification Layer and the Second Liquid Crystal Alignment and Solidification Layer obtained above were used.

[0091] 4. Fabrication of the image display device The cover glass and the viewing-side optical film of a commercially available organic EL display device (manufactured by Samsung, trade name "Galaxy (registered trademark) A41") were removed, and the removal surface was washed. Then, the Second Liquid Crystal Alignment and Solidification Layer side of the optical laminate obtained above was bonded to the washed surface via an acrylic adhesive (thickness 10 μm) to obtain an image display device. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0092] [Examples 8 and Comparative Examples 8 to 10] An optical laminate and an image display device were obtained in the same manner as in Example 7 except that the configuration of the second protective layer was as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0093] [Example 9] An optical laminate and an image display device were obtained in the same manner as in Example 7 except that Adhesive A1 of Production Example 1 was used instead of Adhesive PS1 of Production Example 3 as the second adhesive layer. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0094] [Example 10 and Comparative Examples 11 to 14] An optical laminate and an image display device were obtained in the same manner as in Example 9, except that the second protective layer was configured as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0095] [Examples 11 to 12] An optical laminate and an image display device were obtained in the same manner as in Example 9, except that the second protective layer was configured as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0096] [Reference Example 2] A polarizing plate was produced in the same manner as in Example 1. Further, using the same photopolymerizable liquid crystal compound as in Example 1, a long laminate having a structure of a substrate / first liquid crystal alignment cured layer (Re(550) = 144 nm) was obtained in the same manner as in Example 1. The first liquid crystal alignment cured layer was homogeneously aligned, and its thickness was 1.2 μm. The slow axis direction of the first liquid crystal alignment cured layer was the 45° direction. Further, a first liquid crystal alignment cured layer (positive C plate) was produced in the same manner as in Example 1. An optical laminate and an image display device were obtained in the same manner as in Example 9, except that the polarizing plate, the first liquid crystal alignment cured layer, and the second liquid crystal alignment cured layer thus obtained were used. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0097]

Table 1

[0098] In Table 1, for example, "Ex 1" means Example 1, "Comp 1" means Comparative Example 1, and "Ref 1" means Reference Example 1. Also, "Pos A" means a positive A plate, and "Pos C" means a positive C plate. Further, the notations of the second protective layer in Table 1 are as follows. Acrylic: Acrylic resin film of Production Example 4 (thickness: 30 μm, distance D from the polarizer to the first adhesive layer: 31 μm) TAC: TAC film of Production Example 5 (thickness: 25 μm, distance D: 26 μm) COP: COP film of Production Example 6 (thickness: 13 μm, distance D: 14 μm) Solidified layer: Solidified layer of Production Example 7 (thickness: 0.3 μm or 0.7 μm, distance D: 0.3 μm or 0.7 μm) None: Without providing the second protective layer, the first liquid crystal alignment solidified layer is bonded to the polarizer via the first adhesive layer (distance D: 0.0 μm) Note that the acrylic resin film, TAC film, and COP film were each obtained by peeling the resin substrate from HC layer / COP resin film (first protective layer) / polarizer / resin substrate, and bonding them to the peeled surface via an ultraviolet curable adhesive (thickness 1 μm).

Industrial Applicability

[0099] The optical laminate according to the embodiment of the present invention can be suitably used in an image display device (typically, a liquid crystal display device or an organic EL display device).

Explanation of Reference Numerals

[0100] 10 Polarizing plate 11 Polarizer 12 First protective layer 13 Second protective layer 20 Retardation layer 21 First liquid crystal alignment solidified layer 22 Second liquid crystal alignment solidified layer 31 First adhesive layer 32 Second adhesive layer 100 Optical laminate 101 Optical laminate

Claims

1. A polarizing plate including a polarizer, and a retardation layer laminated on the polarizing plate via a first adhesive layer, wherein the retardation layer includes, in order from the polarizing plate side, a first liquid crystal alignment cured layer, and a second liquid crystal alignment cured layer laminated on the first liquid crystal alignment cured layer via a second adhesive layer, The refractive index n in the transmission axis direction of the polarizer of the first liquid crystal alignment curing layer ＬＣ１ is greater than 1.60, and a distance D from the polarizer to the first adhesive layer is less than 0.5 μm, an optical laminate.

2. The polarizing plate includes a first protective layer disposed on the side opposite to the retardation layer of the polarizer, and a second protective layer disposed on the retardation layer side of the polarizer, and a thickness of the second protective layer is less than 0.5 μm, the optical laminate according to Claim 1.

3. The optical laminate according to Claim 2, wherein the second protective layer is a cured product or a thermoset product of a coating film of an organic solvent solution of a resin.

4. The polarizing plate includes only a first protective layer disposed on the side opposite to the retardation layer of the polarizer as a protective layer, and the first liquid crystal alignment cured layer is laminated on the polarizer via the first adhesive layer, the optical laminate according to Claim 1.

5. The optical laminate according to Claim 1, wherein an angle formed by a slow axis of the first liquid crystal alignment cured layer and a transmission axis of the polarizer is 40° or less.

6. The first adhesive layer is composed of an active energy ray-curable adhesive, and its thickness T ＡＤ１ is from 0.4 μm to 2.0 μm. The optical laminate according to claim 1.

7. The second adhesive layer is composed of an adhesive, and its thickness T ＡＤ２ is 2 μm to 10 μm. The optical laminate according to claim 1.

8. The refractive index n of the second adhesive layer ＡＤ２ The optical laminate according to claim 1, wherein the refractive index n is greater than 1.

60.

9. An image display device including the optical laminate according to any one of Claims 1 to 8.

Images