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 and a refractive index nAD1 of a polarizer of the first adhesive layer in a transmission axis direction satisfy the following expression (1): (nAD1-nLC1)2<0.020 ...(1).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 represented by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices, 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, there has also been an increasing demand for thinning of optical laminates. For the purpose of thinning the optical laminate, the thinning of the retardation layer (retardation film) that makes a large contribution 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 significantly larger birefringence (Δn) than a resin, the liquid crystal film can have a significantly smaller thickness than a stretched film of a resin film to obtain a desired in-plane retardation. However, an image display device using an optical laminate including a liquid crystal film may exhibit display unevenness (specifically, a phenomenon in which a thin pink line is particularly visible in the absorption axis direction of the polarizer) 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 including a liquid crystal alignment cured layer and capable of suppressing 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 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 LC1 in the transmission axis direction of the polarizer of the first liquid crystal alignment cured layer, and the refractive index n AD1 of the first adhesive layer in the transmission axis direction of the polarizer satisfy the following formula (1): (n AD1 - n LC1 ) 2 < 0.020 ···(1). [2] In the above [1], the above n LC1 is greater than 1.60. [3] In the above [1] or [2], 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. [4] In any one of the above [1] to [3], the optical laminate satisfies the following formula (2): (n AD1 - n LC1 ) 2 < 0.007 ···(2). [5] In any one of the above [1] to [4], the first adhesive layer is composed of an adhesive, and its thickness T AD1 is 2 μm to 10 μm. [6] In any one of the above [1] to [5], the second adhesive layer is composed of an active energy ray curable adhesive, and its thickness T AD2 is 0.4 μm to 2.0 μm. [7] According to another aspect of the present invention, an image display device is provided. The image display device includes the optical laminate according to any one of the above [1] to [6].

Advantages of the Invention

[0006] According to an embodiment of the present invention, it is possible to realize an optical laminate including a liquid crystal alignment curing layer and capable of suppressing specific display unevenness when applied to an image display device.

Brief Description of the Drawings

[0007]

Figure 1

Embodiments for Carrying Out the Invention

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

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) “nx” is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction. (2) In-Plane Phase Difference (Re) “Re(λ)” is the in-plane phase difference of the film measured with light of wavelength λ nm at 23°C. For example, “Re(550)” is the in-plane phase difference of the film measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re = (nx - ny) × d, where d (nm) is the thickness of the film. (3) Phase Difference in the Thickness Direction (Rth) “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. Rth(λ) is obtained by the formula: Rth = (nx - nz) × d, where d (nm) is the thickness of the film. (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions. Thus, 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. The polarizing plate 10 typically includes a polarizer 11 and protective layers 12 and 13 disposed on both sides of the polarizer 11. Depending on the purpose, at least one of the protective layers 12 and 13 may be omitted. Thus, the polarizing plate may be a so-called double-protection polarizing plate, a so-called single-protection polarizing plate, or may be composed of only the polarizer.

[0011] The retardation layer 20 includes, in order from the polarizing plate 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. Thus, in the retardation layer 20, the first liquid crystal alignment cured layer 21 is laminated on the polarizing plate 10 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 a stretched film of a resin film. As a result, a significant 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 that can be, for example, 0.30 to 0.70 as a whole. In this 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 that includes an alignment cured layer obtained by curing a liquid crystal monomer.

[0012] 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 solidified layer LC1 and the refractive index n in the transmission axis direction of the polarizer of the first adhesive layer AD1 satisfy the following formula (1), and preferably satisfy the following formula (2). The left side of formulas (1) and (2) may be referred to as a display unevenness parameter. In the following description of this specification, unless otherwise specified, "refractive index" means the refractive index in the transmission axis direction of the polarizer. Further, since the first adhesive layer and the second adhesive layer are substantially optically isotropic, the refractive indices n AD1 and n AD2 are also substantially isotropic. (n AD1 - n LC1 ) 2 <0.020 ···(1) (n AD1 - n LC1 ) 2 <0.007 ···(2) The display unevenness parameter is more preferably 0.006 or less, still more preferably 0.005 or less, particularly preferably 0.004 or less, even more particularly preferably 0.003 or less, and most preferably 0.002 or less. The smaller the display unevenness parameter, the more preferable, and it may be 0.000.

[0013] In considering further thinning of an optical laminate including a liquid crystal alignment cured layer as a retardation layer, the inventors have found a new problem that an image display device using an optical laminate including a liquid crystal alignment cured layer as a retardation layer may exhibit specific display unevenness depending on the viewing environment. Specifically, in reflection under a three-wavelength light source, it has been found that a phenomenon may occur in which thin pink lines that are particularly prominent in the absorption axis direction of the polarizer are visually recognized over the entire area (which may be referred to as line unevenness). Further, when the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer are formed using a material exhibiting positive wavelength dispersion characteristics in which the retardation value decreases as the wavelength of the measurement light increases, even when the same material (and thus, 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 inventors have found that line unevenness can be suppressed by suppressing the interference of the optical laminate. In addition, instead of individually adjusting the average refractive index, thickness, etc. of each layer constituting the optical laminate in order to suppress the interference of the optical laminate, the refractive index in the transmission axis direction of each polarizer of the liquid crystal alignment cured layer on the polarizer side (for example, the first liquid crystal alignment cured layer) and the first adhesive layer that laminates the polarizer and the retardation layer is adjusted to make the above display unevenness parameter smaller than a predetermined value, and it has been found that line unevenness can be comprehensively suppressed in a specific configuration of the optical laminate according to the purpose and / or constituent materials, etc., and the present invention has been completed. That is, such an effect according to an embodiment of the present invention solves a newly found problem in considering further thinning of an optical laminate including a liquid crystal alignment cured layer as a retardation layer, and is an unexpectedly excellent effect. Needless to say, the embodiment of the present invention can suppress display unevenness that has been conventionally recognized.

[0014] As the first adhesive layer 31, any appropriate configuration can be adopted as long as the effects according to the embodiments of the present invention can be obtained (specifically, as long as the above display unevenness parameter can be made smaller than a predetermined value). Similarly, as 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 31 and the second adhesive layer 32 may be composed of an adhesive or an adhesive. In one embodiment, the first adhesive layer may be composed of an adhesive, and the second adhesive layer may be composed of an active energy ray curable adhesive. With such a configuration, it is possible to suppress the influence of dimensional changes of the polarizer on the liquid crystal alignment curing layer in a high temperature environment (for example, a durability test).

[0015] In the optical laminate, the total thickness from the first liquid crystal alignment curing layer to the second liquid crystal alignment curing layer (that is, 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 curing layer. Note that if the total thickness from the first liquid crystal alignment curing layer to the second liquid crystal alignment curing layer is within the above range, the total thickness from the polarizing plate to the second liquid crystal alignment curing 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.

[0016] The optical laminate may be in a sheet form or a long form. In this specification, "long form" means an elongated shape in which the length is sufficiently long with respect to the width, and includes, for example, an elongated shape in which the length is 10 times or more, preferably 20 times or more, the width. The long optical laminate can be wound into a roll. The long optical laminate can be produced, for example, by a so-called roll-to-roll process. The sheet-like optical laminate may be produced by cutting a long 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.

[0017] Practically, the optical laminate has an adhesive layer (not shown) as the outermost layer on the side of the second liquid crystal alignment cured layer (image display panel side) and is capable of being 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 put into use. By temporarily attaching the release liner, the adhesive layer is protected and the optical laminate can be formed into a roll.

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

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

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

[0021] The polarizer preferably contains iodide or sodium chloride (which may be collectively referred to as halide). Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 parts by weight to 20 parts by weight, more preferably 10 parts by weight to 15 parts by weight, based on 100 parts by weight of the PVA-based resin. The halide can be incorporated into the coating liquid for forming the PVA-based resin layer, which is a precursor of the polarizer, in the manufacturing method described later, and can ultimately be 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.

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

[0023] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 μm to 8 μm, and still more preferably 3 μm to 7 μm. By combining such a thin polarizer with the liquid crystal alignment curing layer, significant thinning of the optical laminate can be achieved. In addition, 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.

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

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

[0026] The above-mentioned dyeing with iodine is performed, for example, by immersing a 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 may be performed after the dyeing treatment, or may be performed while dyeing. Also, dyeing may be performed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt on the surface of the PVA-based film and the anti-blocking agent be washed away, but also the PVA-based film can be swollen to prevent uneven dyeing.

[0027] As specific examples of the polarizer obtained using the laminate, there may be mentioned a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a polarizer obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material. The polarizer obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material can be produced, for example, by applying a PVA-based resin solution to the resin base material and drying it to form a PVA-based resin layer on the resin base material to obtain a laminate of the resin base material 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 base material. 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 auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA and dissolution when immersed in water in the subsequent dyeing step and stretching step can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, the disturbance of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. Thereby, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and a water stretching treatment, which are performed by immersing the laminate 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 obtained by peeling the resin substrate from the resin substrate / polarizer laminate or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0028] B-2. Protective Layer The protective layers 12 and 13 are each 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 disclosures of these publications are incorporated herein by reference. From the viewpoint of ease of profiling and the like, cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic-based resins are preferred.

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

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

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

[0032] C. Retardation layer 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 the entire retardation layer, and simply referring to the "liquid crystal alignment cured layer" means describing the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer together.

[0033] In one embodiment, Re(550) of the first liquid crystal alignment curing 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 curing 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 curing layer and the second liquid crystal alignment curing layer have in-plane retardation, they exhibit a refractive index characteristic of nx > ny. The first liquid crystal alignment curing layer and the second liquid crystal alignment curing 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 curing layer and the second liquid crystal alignment curing layer can be 0.9 to 1.1, respectively.

[0034] The thickness of the first liquid crystal alignment curing layer can be adjusted so as to obtain the desired in-plane retardation. In one embodiment, the thickness of the first liquid crystal alignment curing 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 making the thickness of the first liquid crystal alignment curing layer thinner than before. The thickness of the second liquid crystal alignment curing layer can also 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.

[0035] The angle formed by the slow axis of the first liquid crystal alignment curing layer and the transmission axis of the polarizer is, for example, 40° or less, preferably 10° to 20°, more preferably 12° to 18°, and still more preferably 14° to 16°; the angle formed by the slow axis of the second liquid crystal alignment curing layer and the transmission axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably 74° to 76°. Note that the angle formed by the slow axis of the first liquid crystal alignment curing layer and the transmission axis of the polarizer and the angle formed by the slow axis of the second liquid crystal alignment curing layer and the transmission axis of the polarizer may be reversed.

[0036] Examples of the liquid crystal compound used for the liquid crystal alignment cured layer include, for example, liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable (i.e., a liquid crystal monomer). When the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by polymerizing it after aligning the liquid crystal compound. Here, the polymer formed by polymerization is non-liquid crystalline. Therefore, in the formed liquid crystal alignment cured layer, for example, 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 does not occur. As a result, the liquid crystal alignment cured layer becomes a retardation layer that is not affected by temperature changes and has extremely excellent stability.

[0037] In one embodiment, the liquid crystal alignment cured layer can be formed using a composition containing a polymerizable liquid crystal compound (a polymerizable liquid crystal compound, i.e., a liquid crystal monomer). The polymerizable liquid crystal compound contained in the composition herein refers to a compound having a polymerizable group and having liquid crystallinity. The polymerizable group means a group involved 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 active radicals, acids, etc. generated from a photopolymerization initiator. Examples of the liquid crystal monomer include polymerizable mesogenic compounds described in, for example, JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Specific examples of such polymerizable mesogenic compounds include, for example, LC242 with the trade name of BASF, E7 with the trade name of Merck, and LC-Sillicon-CC3767 with the trade name of Wacker-Chem.

[0038] The mechanism for the expression of liquid crystallinity of the liquid crystal compound may be thermotropic or lyotropic. Also, the configuration of the liquid crystal phase may be nematic liquid crystal or smectic liquid crystal. From the viewpoint of ease of production, thermotropic nematic liquid crystal is preferred for the liquid crystallinity.

[0039] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably from 40°C to 120°C, more preferably from 50°C to 100°C, and most preferably from 60°C to 90°C.

[0040] The birefringence Δn of the liquid crystal alignment curing layer is preferably 0.06 or more, more preferably 0.08 or more, still more preferably 0.09 or more, and particularly preferably 0.10 or more. The upper limit of Δn can be, for example, 0.13 or can be, for example, 0.12. If Δn is in such a range, a desired in-plane retardation can be realized with a very thin thickness. As a result, it becomes possible to further thin the liquid crystal alignment curing layer and the optical laminate, and ultimately contribute to a remarkable thinning of the image display device.

[0041] The liquid crystal alignment curing 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 curing layer exhibits a positive wavelength dispersion characteristic. In such a case, the effects according to the embodiments of the present invention are remarkable.

[0042] In another embodiment, Re(550) of the first liquid crystal alignment curing layer 21 is preferably from 100 nm to 200 nm, more preferably from 110 nm to 180 nm, still more preferably from 120 nm to 160 nm, and particularly preferably from 130 nm to 150 nm. In this case, the second liquid crystal alignment curing layer 22 can typically be a positive C-plate. The thickness of the first liquid crystal alignment curing layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness can be, for example, from 1.0 μm to 1.6 μm or can be, for example, from 1.1 μm to 1.3 μm. The angle formed by the slow axis of the first liquid crystal alignment curing layer and the transmission axis of the polarizer is preferably from 40° to 50°, more preferably from 42° to 48°, still more preferably from 44° to 46°, and particularly preferably about 45°.

[0043] In yet another embodiment, Re(550) of the first liquid crystal alignment solidification 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. Also in this case, the second liquid crystal alignment solidification layer 22 can typically be a positive C-plate. The thickness of the first liquid crystal alignment solidification layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness may be, for example, 0.8 μm to 1.2 μm, or may be, for example, 0.9 μm to 1.1 μm. The angle formed by the slow axis of the first liquid crystal alignment solidification 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°.

[0044] The second liquid crystal alignment solidification 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.

[0045] 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

[0046] 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.

[0047] 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]

[0048] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0049] 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.

[0050] 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) showing the refractive index characteristics of nx>ny and the transmission axis of the polarizer can be appropriately set according to the purpose.

[0051] The refractive index (refractive index in the direction of the transmission axis of the polarizer) n of the first liquid crystal alignment solidified layer LC1 is the refractive index n of the first adhesive layer AD1As long as the above formula (1) is satisfied in the relationship, any appropriate refractive index can be adopted. The refractive index n of the first liquid crystal alignment solidified layer LC1 is preferably 1.50 or more, more preferably 1.52 to 1.68, and still more preferably 1.53 to 1.65. In one embodiment, the refractive index n of the first liquid crystal alignment solidified layer LC1 may be, for example, greater than 1.60. The average refractive index of the liquid crystal alignment solidified layer will typically conform to the composition of the composition for forming the liquid crystal alignment solidified layer in order to obtain desired optical properties. As a result, line unevenness may occur. According to an embodiment of the present invention, by setting the display unevenness parameter to a predetermined value or less based on the refractive index and thickness in the transmission axis direction of the polarizer of the first liquid crystal alignment solidified layer, line unevenness can be suppressed. The refractive index (refractive index in the transmission axis direction of the polarizer) n of the second liquid crystal alignment solidified layer LC2 Any appropriate refractive index can be adopted.

[0052] D. Adhesive layer D-1. First adhesive layer As the first adhesive layer 31, any appropriate configuration can be adopted as long as the display unevenness parameter can be set to a predetermined value or less. Therefore, the first adhesive layer may be composed of an adhesive or an adhesive. As described above, in one embodiment, the first adhesive layer can be composed of an adhesive. Regardless of whether the first adhesive layer is an adhesive layer or an adhesive layer, the refractive index n of the first adhesive layer AD1 may be, for example, 1.45 or more, or may be, for example, 1.50 or more, or may be, for example, 1.52 or more. The refractive index n of the first adhesive layer AD1 is preferably 1.54 or more, more preferably 1.55 or more, still more preferably 1.57 or more, and particularly preferably 1.60 or more. On the other hand, the refractive index n of the first adhesive layer AD1 can be, for example, 1.63 or less.

[0053] When the first adhesive layer is an adhesive layer, the thickness T of the first adhesive layer AD1is preferably from 2 μm to 10 μm, more preferably from 3 μm to 9 μm, still more preferably from 4 μm to 7 μm, and particularly preferably from 4.5 μm to 5.5 μm. When the first adhesive layer is an adhesive layer, the thickness T of the first adhesive layer AD1 is preferably from 0.4 μm to 2.0 μm, more preferably from 0.8 μm to 1.2 μm.

[0054] Hereinafter, the adhesive and the adhesive constituting the first adhesive layer will be described respectively.

[0055] D-2. Adhesive Constituting the First Adhesive Layer The adhesive can adopt any suitable configuration as long as the display unevenness parameter can be made 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.

[0056] D-3. Adhesive Constituting the First Adhesive Layer The adhesive can also adopt any appropriate configuration as long as it satisfies the above characteristics. Examples of the adhesive include active energy ray curable adhesives. 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 a predetermined value. In one embodiment, the adhesive (adhesive composition) may contain (meth)acrylate containing an aromatic ring skeleton and / or metal oxide particles. Each will be briefly described below. Note that since well-known configurations can be adopted for other components (for example, curing components, adhesives) that can be included in the adhesive, specific descriptions are omitted.

[0057] When the adhesive composition contains (meth)acrylate having an aromatic ring skeleton, an adhesive layer having a desired refractive index can be formed in the embodiment 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)acrylate having a polycyclic aromatic ring skeleton and (meth)acrylate having two or more aromatic rings. Examples of such (meth)acrylate 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 preferable, and zirconium oxide is particularly preferable. 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 viewpoints of improving the stability of the metal oxide particles in the adhesive composition and improving the refractive index of the adhesive layer, the average particle diameter of the metal oxide particles is preferably 1 nm to 150 nm, and more preferably 1 nm to 50 nm. The average particle diameter of the metal oxide particles can be derived, for example, by the following method: The particles are magnified and observed using a transmission electron microscope (TEM), a field emission transmission electron microscope (FE-TEM), a field emission scanning electron microscope (FE-SEM), etc., and, for example, 1000 particles are randomly selected, their maximum length is measured, and the arithmetic mean is calculated.

[0060] From the viewpoints of improving the stability of the metal oxide particles in the adhesive composition and increasing 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] D-4. Second Adhesive Layer As 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. Therefore, the second adhesive layer may be composed of a pressure-sensitive adhesive or an adhesive. As described above, in one embodiment, the second adhesive layer can be composed of an active energy ray-curable adhesive. Since a well-known configuration can be adopted for the active energy ray-curable adhesive, a specific description thereof is omitted.

[0063] Refractive index n of the second adhesive layer AD2 may be, for example, 1.48 to 1.60, or may be, for example, 1.50 to 1.58, or may be, for example, 1.51 to 1.57. Thickness T of the second adhesive layer AD2 is preferably 0.4 μm to 2.0 μm, more preferably 0.8 μm to 1.2 μm.

[0064] E. Image Display Device The optical laminate described in Items A to D above 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 Items A to D above on its viewing side.

Examples

[0065] 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.

[0066] (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), the same COP film was laminated on the coated surface, and the coated surface was irradiated with visible light 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 Co., Ltd., 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 curing 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, the equation of the ellipse (x 2 / a 2 )+(y 2 / b 2)=1, set a as nx, b as ny, x and y as the refractive indices in the x - direction and y - direction at the angle θ on the ellipse, solve the simultaneous equations from y = tanθ and the above - mentioned nx and ny, and calculate the refractive index in the direction passing through the axis.

[0067] (2) Thickness It was measured with an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0068] (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 - lit state and evaluated according to the following criteria. ◎ (Excellent): No linear unevenness was observed even when observing with a polarizing plate attached to the three - wavelength fluorescent lamp. ○ (Good): No linear unevenness was observed in the normal observation with a three - wavelength fluorescent lamp. △ (Unacceptable): Linear unevenness was observed in the normal observation with a three - wavelength fluorescent lamp. × (Poor): Linear unevenness was significant in the normal observation with a three - wavelength fluorescent lamp.

[0069] [Production Example 1: Preparation of the adhesive PS1 constituting the first adhesive layer] Into a four - necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, a monomer mixture containing 91 parts of butyl acrylate, 6 parts of acryloylmorpholine, 2.7 parts of acrylic acid, and 0.3 parts of 4 - hydroxybutyl acrylate was charged. 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. After introducing nitrogen gas while gently stirring for nitrogen substitution, the liquid temperature in the flask was maintained at around 55 °C and a polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer P1 with a weight - average molecular weight (Mw) of 2.7 million. To 100 parts by solid content of the acrylic polymer P1 solution, 0.1 part of an isocyanate crosslinking agent (trimethylolpropane / tolylene 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 an adhesive PS1. The polymer concentration of the adhesive PS1 was adjusted to 8%. The refractive index n AD1 was 1.47.

[0070] [Production Example 2: Preparation of Adhesive PS2 Constituting the First Adhesive Layer] A monomer mixture containing 19 parts of butyl acrylate, 80 parts of benzyl acrylate, and 1 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. After introducing nitrogen gas while gently stirring for nitrogen substitution, the liquid temperature in the flask was maintained at around 60°C and a polymerization reaction was carried out for 6 hours to prepare a solution of an acrylic polymer P2 having a weight average molecular weight (Mw) of 1.9 million. To 100 parts by solid content of the acrylic polymer P2 solution, 0.1 part of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Mitsui Chemicals, Inc., trade name "D101E") and 0.3 part of a peroxide crosslinking agent (benzoyl peroxide: manufactured by NOF Corporation, trade name "Niper BMT") were blended to obtain an adhesive PS2. The refractive index n AD1 was 1.54.

[0071] [Production Example 3: Preparation of Adhesive PS3 Constituting the First Adhesive Layer] A solution of an acrylic polymer P3 with a weight average molecular weight (Mw) of 650,000 was prepared in the same manner as in Production Example 2, except that a monomer mixture containing 30 parts of butyl acrylate, 69 parts of m-phenoxybenzyl acrylate, and 1 part of 4-hydroxybutyl acrylate was used. An adhesive PS3 was obtained in the same manner as in Production Example 2, except that the acrylic polymer P3 was used. The refractive index n AD1 was 1.56.

[0072] [Production Example 4: Preparation of Adhesive PS4 Constituting the First Adhesive Layer] A solution of an acrylic polymer P4 with a weight average molecular weight (Mw) of 650,000 was prepared in the same manner as in Production Example 2, except that a monomer mixture containing 19 parts of butyl acrylate, 80 parts of m-phenoxybenzyl acrylate, and 1 part of 4-hydroxybutyl acrylate was used. An adhesive PS4 was obtained in the same manner as in Production Example 2, except that the acrylic polymer P4 was used. The refractive index n AD1 was 1.58.

[0073] [Production Example 5: Preparation of Adhesive PS5 Constituting the First Adhesive Layer] A solution of an acrylic polymer P5 with a weight average molecular weight (Mw) of 650,000 was prepared in the same manner as in Production Example 2, except that a monomer mixture containing 6 parts of butyl acrylate, 93 parts of m-phenoxybenzyl acrylate, and 1 part of 4-hydroxybutyl acrylate was used. An adhesive PS5 was obtained in the same manner as in Production Example 2, except that the acrylic polymer P5 was used. The refractive index n AD1 was 1.59.

[0074] [Production Example 6: Preparation of Adhesive PS6 Constituting the First Adhesive Layer] To 100 parts by solid content of the acrylic polymer P5 of Production Example 5, 0.1 part of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Mitsui Chemicals, Inc., trade name "D101E"), 0.3 part of a peroxide crosslinking agent (benzoyl peroxide: manufactured by NOF Corporation, trade name "Niper BMT"), and 10 parts of a refractive index improver (6-acryloyloxymethyldinaphthothiophene: manufactured by Suga Chemical Industry Co., Ltd., trade name "6MDNTA") were blended to obtain an adhesive PS6. The refractive index n AD1 was 1.61.

[0075] [Production Example 7: Preparation of Adhesive A1 Constituting the Second Adhesive Layer] 10 parts of hydroxyethylacrylamide (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 diethylthioketone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare an adhesive A1. The refractive index n AD2 was 1.52.

[0076] [Production Example 8: Preparation of Adhesive A2 Constituting the Second Adhesive Layer] 60 parts of Ogsoal EA-F5710 (manufactured by Osaka Gas Chemicals Co., Ltd.), 10 parts of Plaxel FA1DDM (manufactured by Daicel Corporation), 20 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 5 parts of ARFON 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 2 parts of diethylthioxanthone (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 AD2 of Adhesive A2 was 1.56.

[0077] [Example 1] 1. Production of polarizing plate 1-1. Production of polarizer As a thermoplastic resin substrate, an amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) in a long strip shape with a Tg of about 75 °C was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") at a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The above PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60 °C to form a PVA-based resin layer with a thickness of 13 μm, and a laminate was produced. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130 °C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath with 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, it was immersed for 60 seconds in a dyeing bath at a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water), while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer became a desired value (dyeing treatment). Next, it was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40°C (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) (crosslinking treatment). Thereafter, while immersing the laminate in a boric acid aqueous 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 (longitudinal direction) between rolls with different peripheral speeds so that the total draw ratio became 5.5 times (stretching treatment in water). 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 respect to 100 parts by weight of water) (washing treatment). Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a long polarizing plate having a resin substrate / polarizer configuration was obtained. The single transmittance Ts of the polarizer was 43.3%. The polarizer had an absorption axis in the long direction. Hereinafter, the absorption axis direction (long 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. Production of polarizing plate An HC-COP film was laminated onto the surface of the obtained polarizer (the surface opposite to the resin substrate) via an ultraviolet-curing adhesive. 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 was laminated such that the COP film faced the polarizer side. The Re(550) of the COP film was 100 nm. Here, the HC-COP film was laminated such that the angle between the slow axis of the COP film and the absorption axis of the polarizer was 45°. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness: 25 μm) was laminated onto the peeled surface via an ultraviolet-curing adhesive. In this way, a polarizing plate having a structure of HC layer / COP film (protective layer) / polarizer / TAC film (protective layer) was obtained.

[0079] 2. Production of the retardation layer 2-1. Production of the first liquid crystal alignment cured 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. A surfactant (BYK-360 manufactured by BYK-Chemie) and a photopolymerization initiator (Omnirad907 manufactured by IGM Resins) were added to this solution 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, with respect to 100 parts by weight of the photopolymerizable liquid crystal compound. As the substrate, a biaxially stretched norbornene-based film (Zeonoar film manufactured by Nippon Zeon, thickness: 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition was coated on this substrate with a bar coater so that Re(550) was 120 nm, and heated at 100 °C for 3 minutes to align the liquid crystal. After cooling to room temperature, ultraviolet light with an integrated light amount of 400 mJ / cm 2 was irradiated in a nitrogen atmosphere to perform photocuring, and a long laminated body having a structure of substrate / first liquid crystal alignment cured layer was obtained. The first liquid crystal alignment cured layer was homogeneously aligned, and its thickness was 1.0 μm. The direction of the slow axis of the first liquid crystal alignment cured layer was the 90° direction. [Chemistry]

[0080] 2-2. Preparation of the Second Liquid Crystal Alignment and Curing Layer 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (where n = 0.35 and 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, the coating solution was applied to a PET substrate subjected to vertical alignment treatment using a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. 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 curing layer (positive C plate, thickness 1.0 μm). [Chemistry]

[0081] 3. Preparation of the Optical Laminate The first liquid crystal alignment and curing layer was bonded to the surface of the TAC film of the polarizing plate via the adhesive PS2 (thickness 5 μm) of Production Example 2 as the first adhesive layer, and then the substrate was peeled off. Next, the second liquid crystal alignment and curing layer was bonded to the surface of the first liquid crystal alignment and curing layer via the adhesive A1 (thickness 1 μm) of Production Example 7 as the second adhesive layer, and the substrate was peeled off to obtain a long optical laminate having a structure of a polarizing plate / first adhesive layer / first liquid crystal alignment and curing layer / second adhesive layer / second liquid crystal alignment and curing layer. The bonding and peeling were performed by a roll-to-roll process. In the obtained optical laminate, the refractive index n LC1 of the first liquid crystal alignment and curing layer in the transmission axis direction of the polarizer was 1.65, and the refractive index n LC2 of the second liquid crystal alignment and curing layer was 1.53. Furthermore, the refractive index n AD1 of the first adhesive layer was 1.54, and as a result, the display unevenness parameter was 0.012.

[0082] 4. Preparation 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., product 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 bonded to the 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 "linear unevenness" evaluation. The results are shown in Table 1.

[0083] [Examples 2 to 5 and Comparative Example 1] An optical laminate and an image display device were obtained in the same manner as in Example 1 except that the configuration of the first adhesive layer was changed 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 6] An optical laminate was produced in the same manner as in Example 1 except that the arrangement order of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer was reversed, the slow axis direction of the second liquid crystal alignment cured layer was set to the 0° direction, and the adhesive PS1 (thickness 5 μm) of Production Example 1 was used as the first adhesive layer. 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 1.53, and the refractive index n of the second liquid crystal alignment cured layer LC2 was 1.53. Furthermore, the refractive index n of the first adhesive layer AD1 was 1.47, and as a result, the display unevenness parameter was 0.004. An image display device was obtained in the same manner as in Example 1 except that this optical laminate was used. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0085] [Examples 7 to 11] An optical laminate and an image display device were obtained in the same manner as in Example 6 except that the configuration of the first adhesive layer was changed 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] [Example 12] 1. Production of polarizing plate A polarizing plate was produced in the same manner as in Example 1.

[0087] 2. Production of the retardation layer Using the same photopolymerizable liquid crystal compound as in Example 1 and in the same manner as in Example 1, a long laminate having a structure of a substrate / First liquid crystal alignment cured layer (Re(550) = 240 nm) was obtained. The first liquid crystal alignment cured layer was homogeneously aligned, and its thickness was 2.0 μm. The slow axis direction of the first liquid crystal alignment cured layer was the 75° direction. Except for changing the coating thickness, in the same manner as above, a long laminate of a substrate / Second liquid crystal alignment cured layer (homogeneous alignment, thickness 1.0 μm, Re(550) = 120 nm) was obtained. The slow axis direction of the second liquid crystal alignment cured layer was the 15° direction.

[0088] 3. Production of the optical laminate Using the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer obtained above, using the pressure-sensitive adhesive PS2 (thickness 5 μm) of Production Example 2 as the first adhesive layer, and using the adhesive A2 (thickness 1 μm) of Production Example 8 as the second adhesive layer, in the same manner as in Example 1, a long optical laminate having a structure of a polarizing plate / First adhesive layer / First liquid crystal alignment cured layer / Second adhesive layer / Second liquid crystal alignment cured layer was obtained. In the obtained optical laminate, the refractive index n LC1 of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer was 1.65, and the refractive index n LC2 of the second liquid crystal alignment cured layer was 1.54. Furthermore, the refractive index n AD1 of the first adhesive layer was 1.54, and as a result, the display unevenness parameter was 0.012.

[0089] 4. Production 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 after cleaning the removal surface, the second liquid crystal alignment cured layer side of the optical laminate obtained above was bonded to the cleaned 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 same evaluation as in Example 1. The results are shown in Table 1.

[0090] [Examples 13 to 16 and Comparative Example 2] An optical laminate and an image display device were obtained in the same manner as in Example 12, except that the configuration of the first adhesive layer was changed 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.

[0091] [Example 17] 1. Production of polarizing plate A polarizing plate was produced in the same manner as in Example 1.

[0092] 2. Production of retardation layer 2-1. Production of first liquid crystal alignment cured layer Using the same photopolymerizable liquid crystal compound as in Example 1 and in the same manner as in Example 1, a long laminate having a structure of substrate / first liquid crystal alignment cured layer (Re(550)=144 nm) was obtained. 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. 2-2. Production of second liquid crystal alignment cured layer In the same manner as in Example 1, a long laminate having a structure of substrate / second liquid crystal alignment cured layer (positive C plate) was obtained.

[0093] 3. Production of optical laminate and image display device A long optical laminate having a structure of polarizing plate / first adhesive layer / first liquid crystal alignment cured layer / second adhesive layer / second liquid crystal alignment cured layer was obtained in the same manner as in Example 1, except that the above-obtained first liquid crystal alignment cured layer and second liquid crystal alignment cured layer were used, and the adhesive PS1 (thickness 5 μm) of Production Example 1 was used as the first adhesive layer. 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 1.59, 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 1.47, and as a result, the display unevenness parameter was 0.014. An image display device was obtained in the same manner as in Example 12, except that this optical laminate was used. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0094] [Examples 18 to 22] An optical laminate and an image display device were obtained in the same manner as in Example 17, except that the composition of the first adhesive layer was changed 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]

Table 1

[0096] In Table 1, for example, "Ex. 1" means Example 1, and "Comp. 1" means Comparative Example 1. Also, "Posi A" means a positive A plate, and "Posi C" means a positive C plate.

Industrial Applicability

[0097] 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, an organic EL display device).

Explanation of Signs

[0098] 10 Polarizing plate 11 Polarizer 12 Protective layer 13 Protective layer 20 Retardation layer 21 First liquid crystal alignment cured layer 22 Second liquid crystal alignment cured layer 31 First adhesive layer 32 Second adhesive layer 100 Optical laminate

Claims

Claim 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 cured layer ＬＣ１ , and the refractive index n in the transmission axis direction of the polarizer of the first adhesive layer ＡＤ１ satisfy the following formula (1), an optical laminate: (n ＡＤ１ - n ＬＣ１ ) ２ < 0.020... (1). Claim 2 the above-mentioned n ＬＣ１ The optical laminate according to claim 1, wherein n is greater than 1.

60. Claim 3 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. Claim 4 The optical laminate according to claim 1, which satisfies the following formula (2): (n ＡＤ１ - n ＬＣ１ ) ２ < 0.007... (2). Claim 5 The first adhesive layer is composed of an adhesive, and its thickness T ＡＤ１ is 2 μm to 10 μm. The optical laminate according to claim 1. Claim 6 The second adhesive layer is composed of an active energy ray-curable adhesive, and its thickness T ＡＤ２ is from 0.4 μm to 2.0 μm. The optical laminate according to claim 1. Claim 7 An image display device including the optical laminate according to any one of claims 1 to 6.

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