Optical laminate and image display device using optical laminate

Abstract

To provide an optical laminate that includes a liquid crystal alignment cured layer and can suppress specific display non-uniformities when applied to an image display device.SOLUTION: An optical laminate according to an embodiment of the present invention includes: a polarizing plate that includes a polarizer; and a retardation layer that is laminated on the polarizing plate via an 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. The retardation layer, as a whole, has either circular or elliptical polarization functionality and has the relationship of Re(450)<Re(550)<Re(650). In the embodiment of the present invention, the adhesive layer satisfies the following relationship: (logG') / T>1.7, here, G' is the storage modulus (Pa) of the adhesive layer and T is the thickness (μm) of the adhesive layer.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 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 the resin, the liquid crystal film can have a significantly 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 line with a particularly noticeable pink color 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 an adhesive layer; the retardation layer includes a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer in order from the polarizing plate side; the retardation layer has a circular polarization function or an elliptical polarization function as a whole and has a relationship of Re(450) < Re(550) < Re(650); the adhesive layer satisfies the following relationship: (logG´) / T > 1.7 Here, G´ is the storage elastic modulus (Pa) of the adhesive layer, and T is the thickness (μm) of the adhesive layer. [2] In the above [1], the adhesive layer is composed of an active energy ray curable adhesive. [3] In the above [1], the adhesive layer is composed of an adhesive. [4] In any one of the above [1] to [3], the thickness of the first liquid crystal alignment cured layer is 1.7 μm or less. [5] According to another aspect of the present invention, an image display device is provided. The image display device includes the optical laminate according to the above [1] to [4].

Effects of the Invention

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

Brief Description of the Drawings

[0007]

Figure 1

Mode 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] (Definition 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 where 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 the clockwise and counterclockwise directions.

[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. The polarizing plate 10 and the retardation layer 20 are laminated via an adhesive layer 30. The polarizing plate 10 typically includes a polarizer 11 and protective layers 12 and 13 disposed on both sides of the polarizer 11. Depending on the purpose, at least one of the protective layers 12 and 13 may be omitted. Therefore, the polarizing plate may be a so-called double-protection polarizing plate, a so-called single-protection polarizing plate, or may be composed of only a polarizer. In one embodiment, the polarizing plate may be a single-protection polarizing plate with the protective layer 13 omitted.

[0011] 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 polarizing plate 10 side. The first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22 are laminated via an arbitrary appropriate adhesive layer (not shown: hereinafter may be referred to as an interlayer adhesive layer). 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, the optical laminate can be significantly thinned. The retardation layer 20 as a whole (as a laminate of the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22) has a circular polarization function or an elliptical polarization function and has a relationship of Re(450)<Re(550)<Re(650). In one embodiment, the retardation layer as a whole may have an Nz coefficient of, for example, 0.30 to 0.70. In the present specification, the “liquid crystal alignment cured layer” refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The “liquid crystal alignment cured layer” is a concept including an alignment cured layer obtained by curing a liquid crystal monomer.

[0012] In the embodiment of the present invention, the adhesive layer 30 satisfies the following relationship: (logG´) / T>1.7 Here, G' is the storage modulus (Pa) of the adhesive layer, and T is the thickness (μm) of the adhesive layer. Note that the left side of the above formula may be referred to as the "display unevenness parameter". The display unevenness parameter may be, for example, 2.0 or more, or may be, for example, 2.5 or more, or may be, for example, 3.5 or more, or may be, for example, 4.0 or more, or may be, for example, 4.5 or more, or may be, for example, 5.5 or more, or may be, for example, 6.0 or more, or may be, for example, 7.0 or more, or may be, for example, 8.0 or more, or may be, for example, 9.0 or more. The display unevenness parameter may be, for example, 15.0 or less, or may be, for example, 10.0 or less.

[0013] When the present inventors considered further thinning of an optical laminate including a liquid crystal alignment cured layer as a retardation layer, they found a new problem that an image display device using an optical laminate including a liquid crystal alignment cured layer as a retardation layer may exhibit specific display unevenness depending on the viewing environment. Specifically, they found that in reflection under a three-wavelength light source, a phenomenon (which may be referred to as line unevenness) in which thin pink lines that are particularly noticeable in the absorption axis direction of the polarizer are visually recognized over the entire area may occur. Furthermore, as a result of intensive studies on suppression of such line unevenness, the present inventors found that the line unevenness can be suppressed by suppressing the interference of the optical laminate. In addition, the present inventors found that if the adhesive layer 30 is suppressed from following such shrinkage even when curing shrinkage occurs in the interlayer adhesive layer, the interference of the optical laminate can be suppressed, and as a result, the line unevenness can be suppressed well, leading to the completion of the present invention. That is, such an effect according to an embodiment of the present invention solves a problem newly found when 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 embodiments of the present invention can suppress display unevenness that has been conventionally recognized.

[0014] The subsequent layer 30 can adopt any suitable configuration as long as it satisfies the above formula. Specifically, the adhesive layer may be composed of an adhesive or a pressure-sensitive adhesive. That is, the adhesive layer may be an adhesive layer or a pressure-sensitive adhesive layer. Examples of the adhesive include aqueous adhesives, solvent-based adhesives, emulsion adhesives, solventless adhesives, active energy ray (typically, electron beam, ultraviolet ray, visible light) curable adhesives, thermosetting adhesives, and hot melt adhesives. Preferably, it is a pressure-sensitive adhesive, an aqueous adhesive, or an active energy ray curable adhesive; more preferably, it is a pressure-sensitive adhesive, an aqueous adhesive, or a radical curable active energy ray curable adhesive. The radical curable active energy ray curable adhesive is preferred from the perspective of environmental consideration because it is solventless, and further has the advantage of being able to be thinned. The pressure-sensitive adhesive has the advantage that it can ensure smoothness because there is no curing shrinkage, and it can suppress unevenness of the retardation layer because it relaxes the dimensional shrinkage of the polarizer under a high-temperature environment. The aqueous adhesive is preferred from the perspective of environmental consideration because it does not use an organic solvent, and further has the advantage of being able to be thinned. In addition, examples of the active energy ray curable adhesive include adhesives that can be cured by light (visible light) with a wavelength of 380 nm to 440 nm. Such adhesives may be referred to as ultraviolet curable adhesives for convenience.

[0015] In the optical laminate, the total thickness from the first liquid crystal alignment cured layer to the second liquid crystal alignment cured layer is preferably 20 μm or less, more preferably 3 μm to 10 μm. According to the embodiment 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. In addition, 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 polarizer to the second liquid crystal alignment cured layer (the substantial total thickness of the optical laminate excluding the thickness of the pressure-sensitive 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] 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 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 put into use. By temporarily attaching the release liner, the adhesive layer is protected and the optical laminate can be formed into a roll.

[0017] Hereinafter, the components of the optical laminate will be specifically described.

[0018] B. Polarizing plate 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 the PVA-based resin include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and ethylene-vinyl acetate copolymer-based partially saponified products.

[0019] 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% to 20% by weight, more preferably 8% 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.

[0020] 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 blended in the coating solution 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.

[0021] 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 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 polarization degree can be maintained in such a range.

[0022] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 μm to 8 μm, and even more preferably 3 μm to 7 μm. By combining such a thin polarizer with the liquid crystal alignment curing layer, significant thinning of the optical laminate becomes possible. Further, if the thickness of the polarizer is in the above range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0023] 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.

[0024] 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.

[0025] 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 during the dyeing. Also, it may be dyed 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, but also the PVA-based film can be swollen to prevent uneven dyeing.

[0026] As specific examples of the polarizer obtained using the laminate, there may be mentioned a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In the present embodiment, preferably, a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution, if necessary. In addition, in the present embodiment, preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a stretching treatment in water, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing step or stretching step can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. As a result, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and a stretching treatment in water, in which the laminate is immersed in a liquid, can be improved. Further, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may also serve as a protective layer for the polarizer), or an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface of the resin substrate / polarizer laminate from which the resin substrate has been peeled, 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 disclosures of these publications are incorporated herein by reference.

[0027] B-2. Protective Layer The protective layers 12 and 13 are 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 profile processing and the like, cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic-based resins are preferred.

[0028] 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 a hard coat treatment, an antireflection treatment, an anti-sticking treatment, and an antiglare treatment. Further / alternatively, the protective layer 12 may be treated as necessary to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptical) polarization function or a very high retardation). By performing such a 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.

[0029] 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.

[0030] 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.

[0031] 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. Further, as described above, the retardation layer 20 as a whole (as a laminate of the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22) has a circular polarization function or an elliptical polarization function, and has a relationship of Re(450) < Re(550) < Re(650). Regarding the description of the retardation layer in this section, when simply referred to as the "retardation layer", it means to describe the entire retardation layer, and when simply referred to as the "liquid crystal alignment cured layer", it means to describe the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer together.

[0032] For the retardation layer 20, Re(550) is preferably 100 nm to 200 nm, more preferably 110 nm to 180 nm, still more preferably 120 nm to 170 nm, and particularly preferably 130 nm to 150 nm. If the Re(550) of the retardation layer is within such a range, the retardation layer can exhibit a good circular polarization function or elliptical polarization function in combination with a polarizer.

[0033] The retardation layer 20 has a relationship of Re(450) < Re(550) < Re(650). That is, the retardation layer 20 preferably exhibits an inverse dispersion wavelength dependence in which the retardation value increases according to the wavelength of the measurement light. With such a configuration, a good antireflection function can be realized in a very wide wavelength band. Re(450) / Re(550) is, for example, more than 0.5 and less than 1.0, preferably 0.7 to 0.95, more preferably 0.75 to 0.92, and still more preferably 0.8 to 0.9. Re(650) / Re(550) is preferably 1.0 or more and less than 1.15, more preferably 1.03 to 1.1.

[0034] In one embodiment, the retardation layer 20 may have an Nz coefficient of, for example, 0.30 to 0.70 as described above. Therefore, the retardation layer 20 exhibits a refractive index characteristic of nx > nz > ny. With such a configuration, reflection in an oblique direction can be favorably prevented, and the anti-reflection function can be widened in the viewing angle. The Nz coefficient is preferably 0.35 to 0.65, more preferably 0.40 to 0.60, and even more preferably 0.45 to 0.55.

[0035] Examples of the liquid crystal compound used for the liquid crystal alignment curing layer include a liquid crystal polymer and a liquid crystal monomer. 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 curing 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 curing layer becomes a retardation layer that is not affected by temperature changes and has extremely excellent stability.

[0036] 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.

[0037] 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 liquid crystallinity.

[0038] 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.

[0039] 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, the desired in-plane retardation can be achieved 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.

[0040] 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.

[0041] The first liquid crystal alignment cured layer 21 can typically function as a λ / 2 plate, and the second liquid crystal alignment cured layer 22 can typically function as a λ / 4 plate. Specifically, 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 even 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 even more preferably 120 nm to 140 nm. The thickness of the first liquid crystal alignment cured layer can be adjusted so as to obtain a desired in-plane retardation of the λ / 2 plate. In one embodiment, the thickness of the first liquid crystal alignment cured layer can be, for example, 2.0 μm to 4.0 μm. In another embodiment, the thickness of the first liquid crystal alignment cured layer is preferably 1.7 μm or less, more preferably 1.6 μm or less, and even more preferably 1.5 μm or less. In this case, the thickness of the first liquid crystal alignment cured layer can be, for example, 1.3 μm or more. 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 as compared with the conventional case. The thickness of the second liquid crystal alignment cured layer can be adjusted so as to obtain a desired in-plane retardation of the λ / 4 plate. Specifically, the thickness can be, for example, 0.8 μm to 2.5 μm. The angle formed by the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 14° to 16°; the angle formed by 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 arrangement order of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer may be reversed, and the angle formed by the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer and the angle formed by the slow axis of the second liquid crystal alignment cured layer and the transmission axis of the polarizer may be reversed.

[0042] The refractive index of the liquid crystal alignment cured layer can vary depending on the composition for forming the liquid crystal alignment cured layer (substantially, the type of liquid crystal compound, the type, number, combination, blending amount, etc. of additives). The refractive index n of the first liquid crystal alignment cured layer LC1 and the refractive index n of the second liquid crystal alignment cured layerLC2 They may be the same or different from each other (the refractive index n of the first liquid crystal alignment cured layer LC1 may be larger, and the refractive index n of the second liquid crystal alignment cured layer LC2 may be larger). The refractive index n of the first liquid crystal alignment cured layer LC1 is preferably 1.55 to 1.75, more preferably 1.60 to 1.70. The refractive index n of the second liquid crystal alignment cured layer LC2 is preferably 1.45 to 1.65, more preferably 1.50 to 1.60. The refractive index n of the first liquid crystal alignment cured layer LC1 and the refractive index n of the second liquid crystal alignment cured layer LC2 may be opposite. The refractive index n of the first liquid crystal alignment cured layer LC1 and the refractive index n of the second liquid crystal alignment cured layer LC2 The absolute value of the difference between them can be, for example, 0.00 to 0.20. The refractive index of the liquid crystal alignment cured layer typically conforms to the composition of the composition for forming the liquid crystal alignment cured layer in order to obtain desired optical properties. As a result, line-shaped unevenness may occur. According to an embodiment of the present invention, by making the display unevenness parameter greater than 1.7, line-shaped unevenness can be suppressed.

[0043] A side-chain type thermotropic liquid crystal polymer may be introduced into the first liquid crystal alignment cured layer and / or the second liquid crystal alignment cured layer (substantially, the liquid crystal composition for forming them). By introducing a side-chain type thermotropic liquid crystal polymer, an action of homeotropically aligning (vertically aligning) the liquid crystal monomer can occur. As a result, the nz of the first liquid crystal alignment cured layer and / or the second liquid crystal alignment cured layer can be increased, and as a result, the Nz coefficient of the first liquid crystal alignment cured layer and / or the second liquid crystal alignment cured layer can be set within the above-described desired range. Finally, the Nz coefficient of the retardation layer can be set within the above-described desired range without providing a positive C plate described later.

[0044] As the side-chain type thermotropic liquid crystal polymer, typically, a copolymer having a monomer unit containing a thermotropic liquid crystal fragment side chain and a monomer unit containing a non-liquid crystal fragment side chain is used. Since the polymer has a thermotropic liquid crystal fragment in the side chain, when the liquid crystal composition is heated to a predetermined temperature, the side-chain type liquid crystal polymer can be oriented. Further, since the side-chain type polymer has a non-liquid crystal fragment in the side chain, the non-liquid crystal fragment can interact with the photopolymerizable liquid crystal monomer to cause an action of homeotropically orienting the photopolymerizable liquid crystal monomer.

[0045] As the side-chain type thermotropic liquid crystal polymer, a copolymer having a liquid crystal monomer unit represented by the general formula (I) and a non-liquid crystal 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, 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, X 1 is -CO 2 - 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, 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] The ratio of the liquid crystalline monomer unit and the non-liquid crystalline monomer unit in the side-chain type liquid crystal monomer can be appropriately set according to the purpose. The ratio (molar ratio) of the non-liquid crystalline monomer to the total of the liquid crystalline monomer unit and the non-liquid crystalline monomer unit is preferably 0.05 to 0.8, more preferably 0.1 to 0.6, and still more preferably 0.15 to 0.5. With such a configuration, a liquid crystal alignment cured layer exhibiting desired refractive index characteristics (Nz coefficient) can be obtained.

[0050] The ratio of the liquid crystal monomer and the side-chain type liquid crystal polymer in the liquid crystal composition can be appropriately set according to the purpose. When the content of the side-chain type liquid crystal polymer is large, the Nz coefficient tends to be small; when the content of the liquid crystal monomer is large, the Nz coefficient also tends to be small. The content of the liquid crystal monomer is preferably 1.2 to 20 times, more preferably 1.3 to 10 times, still more preferably 1.4 to 9 times, and particularly preferably 1.5 to 8 times that of the content of the side-chain type liquid crystal polymer. With such a configuration, a liquid crystal alignment cured layer exhibiting desired refractive index characteristics (Nz coefficient) can be obtained.

[0051] Details of the method for forming a side-chain type liquid crystal polymer and a liquid crystal alignment cured layer having an Nz coefficient of less than 1.0 are described in Japanese Patent No. 6769921. The description of the said patent is incorporated herein by reference.

[0052] The retardation layer 20 may further include a positive C plate. The positive C plate exhibits a refractive index characteristic of nz > nx = ny. The retardation Rth(550) in the thickness direction of the positive C plate is preferably from -20 nm to -300 nm, more preferably from -30 nm to -250 nm, still more preferably from -40 nm to -200 nm, and particularly preferably from -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.

[0053] The positive C plate can be formed, for example, using a composition containing the above side-chain type liquid crystal polymer. Specific examples of the method for forming the positive C plate include the methods described in paragraphs

[0020] to

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

[0054] D. Adhesive layer The adhesive layer 30 can adopt any suitable configuration as long as the desired display unevenness parameter is realized. The adhesive layer 30 can preferably be composed of an adhesive, an aqueous adhesive, or an active energy ray-curable adhesive (particularly, an ultraviolet ray-curable adhesive) as described above.

[0055] The active energy ray-curable adhesive typically contains a monofunctional component, a polyfunctional component (curing component), and a photopolymerization initiator. The monofunctional component and the polyfunctional component are each typically a radically polymerizable compound. Preferred monofunctional components include, for example, higher alkyl esters of (meth)acrylic acid and modified products thereof. Specifically, isostearyl acrylate, lauryl acrylate, acryloylmorpholine, unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone, and the like can be mentioned. By using a monofunctional component having a large molecular weight per functional group, an adhesive with a small curing shrinkage rate can be obtained. As a result, an adhesive layer with small thickness variation can be obtained. Preferred polyfunctional components include, for example, monomers and / or oligomers having two or more functional groups such as (meth)acrylate groups and (meth)acrylamide groups. Specifically, polyethylene glycol diacrylate, trimethylolpropane triacrylate, glycerin triacrylate can be mentioned. Specific examples of monofunctional components or polyfunctional components other than the above include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, phenoxydiethylene glycol acrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO-modified diglycerin tetraacrylate, γ-butyrolactone acrylate, N-methylpyrrolidone, hydroxyethyl acrylamide, N-methylol acrylamide, N-methoxymethyl acrylamide, N-ethoxymethyl acrylamide, 9-vinylcarbazole, 4-vinylphenylboronic acid, fluorene-based acrylate. In one embodiment, the monofunctional component or the polyfunctional component has a ring structure. Specifically, acryloylmorpholine, γ-butyrolactone acrylate, unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone, N-methylpyrrolidone, 9-vinylcarbazole, fluorene-based acrylate can be mentioned. Compounds having a ring structure have a small free volume (high density), and by using such compounds, an adhesive with a small curing shrinkage rate can be obtained. As a result, an adhesive layer with small thickness variation can be obtained.The monofunctional component or polyfunctional component may each be used alone or in combination of two or more.

[0056] The active energy ray-curable adhesive may further contain a cationic polymerizable compound, if necessary. The cationic polymerizable compound may be monofunctional or polyfunctional. Examples of the monofunctional cationic polymerizable compound include p-tert-butylphenyl glycidyl ether and 3-ethyl-3-[(2-ethylhexyl)oxy]oxetane. Examples of the polyfunctional cationic polymerizable compound include 3-ethyl-3-{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane. A silane coupling agent may be used as the cationic polymerizable compound. Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane.

[0057] The active energy ray-curable adhesive may further contain an acrylic oligomer, if necessary. The molecular weight of the acrylic oligomer can be appropriately set according to the purpose. By using an acrylic oligomer that does not form further bonds, an adhesive with a small curing shrinkage rate can be obtained. As a result, an adhesive layer with a small thickness variation can be obtained.

[0058] The active energy ray-curable adhesive may further contain a photoinitiator, if necessary. Examples of the photoinitiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, and diethylthioxanthone.

[0059] The active energy ray-curable adhesive may further contain a plasticizer (e.g., oligomer component), a crosslinking agent, a diluent, etc., according to the purpose. Note that commercially available products may be used for each of the above components.

[0060] The refractive index of the active energy ray-curable adhesive is preferably such that the absolute value of the difference from the refractive index of the adjacent layer (particularly, the first liquid crystal alignment curing layer) is small.

[0061] Details of the active energy ray curable adhesive are described, for example, in JP-A-2018-017996. The description of this publication is incorporated herein by reference.

[0062] The aqueous adhesive typically contains a polyvinyl alcohol (PVA)-based resin. The adhesive layer can typically be formed by applying and drying an aqueous solution of a PVA-based resin. The average degree of polymerization of the PVA-based resin contained in the aqueous solution is preferably about 100 to 5000, more preferably 1000 to 4000. The average degree of saponification is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%. If the average degree of polymerization and the average degree of saponification are in such ranges, an adhesive layer (substantially, the first adhesive layer) excellent in adhesiveness to the polarizer can be formed.

[0063] The PVA-based resin preferably contains an acetoacetyl group. This is because an optical laminate excellent in adhesion to the polarizer and the protective layer and excellent in durability can be obtained. The acetoacetyl group-containing PVA-based resin can be obtained, for example, by reacting a PVA-based resin with diketene by any method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA-based resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol%, more preferably 1 mol% to 20 mol%, particularly preferably 2 mol% to 7 mol%. The degree of acetoacetyl group modification is a value measured by NMR.

[0064] The resin concentration in the aqueous PVA-based resin solution is preferably 0.1 wt% to 15 wt%, more preferably 0.5 wt% to 10 wt%. The viscosity of the aqueous solution is preferably 1 to 50 mPa·s. The pH of the aqueous solution is preferably 2 to 6, more preferably 2.5 to 5, further preferably 3 to 5, particularly preferably 3.5 to 4.5. If the resin concentration and the viscosity of the aqueous PVA-based resin solution are in such ranges, an adhesive layer having a desired thickness can be formed in the embodiment of the present invention.

[0065] The PVA-based resin aqueous solution (which results in the adhesive layer) may contain a metal compound colloid in one embodiment. The metal compound colloid is one in which metal compound fine particles are dispersed in a dispersion medium, and is electrostatically stabilized due to the mutual repulsion of the same charges of the fine particles and can have permanent stability.

[0066] The average particle diameter of the fine particles forming the metal compound colloid is set to any appropriate value as long as it does not adversely affect optical properties such as transparency and polarization characteristics. Preferably, it is 1 nm to 100 nm, and more preferably 1 nm to 50 nm. This is because the fine particles can be uniformly dispersed in the adhesive layer.

[0067] As the metal compound, any appropriate compound is used. For example, metal oxides such as alumina, silica, zirconia, and titania; metal salts such as aluminum silicate, calcium carbonate, magnesium silicate, zinc carbonate, barium carbonate, and calcium phosphate; minerals such as celite, talc, clay, and kaolin. A metal compound colloid having a positive charge is preferably used. Examples of the metal compound include alumina and titania, and alumina is particularly preferred.

[0068] When the adhesive layer is an adhesive layer, the storage elastic modulus of the adhesive constituting the adhesive layer at 25°C is preferably 5.0×10 6 Pa to 3.0×10 9 Pa, preferably 1.0×10 7 Pa to 2.0×10 9 Pa, and more preferably 1.5×10 7 Pa to 1.5×10 9 Pa. If the storage elastic modulus of the adhesive is within such a range, the desired display unevenness parameter can be achieved.

[0069] When the subsequent layer is an adhesive layer, the thickness of the adhesive layer can vary according to the storage elastic modulus of the adhesive constituting the adhesive layer. The thickness of the adhesive layer may be, for example, from 0.05 μm to 7.0 μm, or may be, for example, from 0.1 μm to 6.0 μm, or may be, for example, from 0.5 μm to 5.0 μm, or may be, for example, from 1.0 μm to 3.0 μm.

[0070] Specific examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. By adjusting the type, number, combination, and blending ratio of the monomers forming the base polymer of the pressure-sensitive adhesive, as well as the blending amount of the crosslinking agent, reaction temperature, reaction time, etc., a pressure-sensitive adhesive having desired properties according to the purpose can be prepared. The base polymer of the pressure-sensitive adhesive may be used alone or in combination of two or more. From the viewpoints of transparency, processability, and durability, etc., acrylic pressure-sensitive adhesives (acrylic pressure-sensitive adhesive compositions) are preferred. An acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a main component as the base polymer. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a main monomer component. Note that (meth)acrylic refers to acrylic and / or methacrylic.

[0071] The alkyl (meth)acrylate can be contained in a proportion of preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, particularly preferably 80% by weight or more, and especially preferably 90% by weight or more in all the monomer components forming the (meth)acrylic polymer.

[0072] As the alkyl (meth)acrylate, those having a linear or branched alkyl group with 1 to 18 carbon atoms are preferably mentioned. The number of carbon atoms of the alkyl group is more preferably 2 to 10, and even more preferably 3 to 8. Examples of the alkyl (meth)acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate. The alkyl (meth)acrylate can be used alone or in combination.

[0073] (Meta)acrylic polymers may contain copolymerizable monomers that can copolymerize with alkyl (meth)acrylates as monomer components. Examples of copolymerizable monomers include carboxyl group-containing monomers and hydroxyl group-containing monomers. Carboxyl group-containing monomers are compounds that contain a carboxyl group in their structure and also contain polymerizable unsaturated double bonds such as (meth)acryloyl groups and vinyl groups. Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Acrylic acid is preferred. Hydroxyl group-containing monomers are compounds that contain a hydroxyl group in their structure and also contain polymerizable unsaturated double bonds such as (meth)acryloyl groups and vinyl groups. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. 2-Hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred. From the perspective of adjusting the properties of the adhesive layer, copolymerizable monomers other than those described above may also be used. Examples of such copolymerizable monomers include amino group-containing monomers, amide group-containing monomers, polyfunctional monomers, cyclopolymerizable monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, (meth)acrylic acid esters having an alicyclic hydrocarbon group, (meth)acrylic acid esters having an aromatic hydrocarbon group, vinyl esters, aromatic vinyl compounds, olefins, dienes, and vinyl ethers. Copolymerizable monomers can be used alone or in combination.

[0074] The adhesive composition may contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent, a polyfunctional metal chelate, etc. can be used. Examples of the organic crosslinking agent include an isocyanate-based crosslinking agent, a peroxide-based crosslinking agent, an epoxy-based crosslinking agent, and an imine-based crosslinking agent. The polyfunctional metal chelate is one in which a polyvalent metal is covalently bonded or coordinately bonded to an organic compound.

[0075] The blending amount of the crosslinking agent is, for example, 0.01 parts by weight to 5 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer.

[0076] The adhesive composition may contain a silane coupling agent. The silane coupling agent preferably contains a reactive functional group. The reactive functional group-containing silane coupling agent is one in which the reactive functional group is typically a functional group other than an acid anhydride group. Examples of the functional group other than the acid anhydride group include, for example, an epoxy group, a mercapto group, an amino group, an isocyanate group, an isocyanurate group, a vinyl group, a styryl group, an acetoacetyl group, a ureido group, a thiourea group, a (meth)acrylic group, a heterocyclic group, and combinations thereof. The reactive functional group-containing silane coupling agent can be used alone or in combination.

[0077] The blending amount of the reactive functional group-containing silane coupling agent is usually 0.001 parts by weight to 2 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer.

[0078] The adhesive composition may contain an additive. Specific examples of the additive include powders such as colorants and pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particulate materials, and foils. Also, within a controllable range, a redox system by adding a reducing agent may be adopted. The type, number, combination, content, etc. of the additive can be appropriately set according to the purpose.

[0079] When the intermediate layer is an adhesive layer, the storage elastic modulus of the adhesive constituting the adhesive layer at 25°C is preferably 8.0×10 4 Pa to 1.0×10 6 Pa, preferably 9.0×10 4 Pa to 5.0×10 5 Pa, more preferably 1.0×10 5 Pa to 2.0×10 5 Pa, and particularly preferably 1.1×10 5 Pa to 1.5×10 5 Pa. If the storage elastic modulus of the adhesive is within such a range, the desired display unevenness parameter can be achieved.

[0080] When the intermediate layer is an adhesive layer, the thickness of the adhesive layer can vary according to the storage elastic modulus of the adhesive constituting the adhesive layer. The thickness of the adhesive layer may be, for example, 0.7 μm to 5.0 μm, or may be, for example, 0.8 μm to 3.0 μm, or may be, for example, 1.0 μm to 3.0 μm.

[0081] E. Intermediate Adhesive Layer E-1. Overview As described above, the intermediate adhesive layer (not shown) is an adhesive layer for laminating the first liquid crystal alignment cured layer 21 and the second liquid crystal alignment cured layer 22. The intermediate adhesive layer may be composed of an adhesive or an adhesive agent.

[0082] In one embodiment, the refractive index n LC1 of the first liquid crystal alignment cured layer, the refractive index n LC2 of the second liquid crystal alignment cured layer, and the refractive index n AD of the intermediate adhesive layer, as well as the thickness T AD of the intermediate adhesive layer and the thickness variation TV AD satisfy the following formula (1). Note that the "refractive index" of the liquid crystal alignment cured layer in this specification means the refractive index in the transmission axis direction of the polarizer unless otherwise specified. Since the adhesive layer is substantially optically isotropic, the refractive index n AD is also isotropic. |{(n LC1 + n LC2 ) / 2 - n AD}|×(TV AD / T AD )×1000 ≤ 3.0 ···(1) The left side of formula (1) is preferably 2.5 or less, more preferably 2.0 or less, still more preferably 1.8 or less, particularly preferably 1.2 or less, and most preferably 0.7 or less. The smaller the absolute value of the left side of formula (1), the more preferable, and it can be, for example, 0.0.

[0083] Regardless of whether the interlayer adhesion layer is an adhesive layer or an adhesive agent layer, the refractive index n of the interlayer adhesion layer AD 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 interlayer adhesion layer AD 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 interlayer adhesion layer AD can be, for example, 1.63 or less.

[0084] When the interlayer adhesion layer is an adhesive agent layer, the thickness T of the interlayer adhesion layer AD is, for example, 3 μm or more, preferably 4 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and particularly preferably 15 μm or more. On the other hand, the thickness T of the interlayer adhesion layer AD can be, for example, 30 μm or less. When the interlayer adhesion layer is an adhesive layer, the thickness T of the interlayer adhesion layer AD is preferably 0.5 μm to 2.0 μm, more preferably 0.8 μm to 1.2 μm. The thickness variation TV of the interlayer adhesion layer AD is preferably 0.20 μm or less, more preferably 0.18 μm or less, still more preferably 0.16 μm or less. On the other hand, the thickness variation TV of the interlayer adhesion layer AD can be, for example, 0.03 μm or more.

[0085] Hereinafter, the adhesive agent and the adhesive that constitute the interlayer adhesion layer will be described respectively.

[0086] E-2. Adhesive As the adhesive, any appropriate configuration can be adopted as long as the above characteristics are satisfied. Specific examples of the adhesive include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and blending ratio of the monomers forming the base polymer of the adhesive, as well as the blending amount of the cross-linking agent, reaction temperature, reaction time, etc., an adhesive having desired characteristics according to the purpose can be prepared. The base polymer of the adhesive may be used alone or in combination of two or more. From the viewpoints of transparency, processability, and durability, etc., acrylic adhesives (acrylic adhesive compositions) are preferred. An acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component as the base polymer. The (meth)acrylic polymer can be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more in the solid content of the adhesive composition.

[0087] (Meth)acrylic polymers preferably contain an aromatic ring-containing monomer (m1) as a monomer component. As the monomer (m1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule can be used. As the monomer (m1), such a compound may be used alone or in combination of two or more. The aromatic ring and the ethylenically unsaturated group may be directly bonded or bonded via a linking group.

[0088] Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. From the viewpoint of polymerization reactivity, the (meth)acryloyl group is preferred, and from the viewpoints of flexibility and adhesiveness, the acryloyl group is more preferred. From the viewpoint of suppressing a decrease in the flexibility of the adhesive, as the monomer (m1), a compound in which the number of ethylenically unsaturated groups contained in one molecule is 1 (i.e., a monofunctional monomer) is preferably used.

[0089] The number of aromatic rings contained in one molecule of the compound used as monomer (m1) may be 1 or may be 2 or more. The upper limit of the number of aromatic rings contained in monomer (m1) is not particularly limited and may be, for example, 16 or less. In some embodiments, from the viewpoints of ease of preparation of the (meth)acrylic polymer and transparency of the adhesive, the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, may be 5 or less, may be 4 or less, may be 3 or less, or may be 2 or less.

[0090] The aromatic ring possessed by the compound used as monomer (m1) may be, for example, a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); a condensed ring such as a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, or a phenanthrene ring; etc., and may be a carbocyclic ring. For example, it may be a heterocyclic ring such as a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, or a thiophene ring. The heteroatom contained as a ring-constituting atom in the above heterocyclic ring may be 1 or more selected from the group consisting of, for example, nitrogen, sulfur, and oxygen. In some embodiments, the heteroatom constituting the heterocyclic ring may be one or both of nitrogen and sulfur. Monomer (m1) may have a structure in which one or more carbocyclic rings and one or more heterocyclic rings are condensed, such as a dinaphthothiophene structure.

[0091] Examples of compounds that may be preferably employed as monomer (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and the aromatic ring-containing vinyl compounds can each be used alone or in combination of two or more. One or more aromatic ring-containing (meth)acrylates and one or more aromatic ring-containing vinyl compounds may be used in combination.

[0092] The content of monomer (m1) in the monomer components constituting the (meth)acrylic polymer can be set so as to realize an adhesive layer that can achieve, for example, a desired refractive index and adhesive properties (such as peel strength, flexibility, etc.) and / or optical properties (such as total light transmittance, haze value, etc.). In some embodiments, the content of monomer (m1) in the monomer components may be, for example, 30% by weight or more, preferably 50% by weight or more, may be 60% by weight or more, and may be 70% by weight or more. From the perspective of making it easier to obtain a higher refractive index, in some embodiments, the content of monomer (m1) may be, for example, more than 70% by weight, may be 75% by weight or more, may be 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more. The upper limit of the content of monomer (m1) in the monomer components is 100% by weight. From the perspective of achieving a good balance between high refractive index and adhesive properties and / or optical properties, it is advantageous that the content of the above monomer (m1) is less than 100% by weight, for example, preferably approximately 99% by weight or less, more preferably 98% by weight or less, may be 97% by weight or less, and may be 96% by weight or less. In some embodiments, the content of monomer (m1) may be 93% by weight or less, may be 90% by weight or less, may be 80% by weight or less, and may be 75% by weight or less. In some embodiments that place more emphasis on adhesive properties and / or optical properties, the content of monomer (m1) in the monomer components may be 70% by weight or less, may be 60% by weight or less, and may be 45% by weight or less.

[0093] In some embodiments, as the monomer (m1), a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be preferably employed because a high refractive index increasing effect is easily obtained. Examples of the monomer having two or more aromatic rings in one molecule (hereinafter also referred to as "aromatic ring multi-containing monomer") include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly chemically bonded (i.e., without intervening other atoms), a monomer having a condensed aromatic ring structure, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, and the like. The aromatic ring multi-containing monomer may be used alone or in combination of two or more kinds.

[0094] As at least a part of the monomer (m1), a high refractive index monomer can be preferably employed. Here, the "high refractive index monomer" refers to a monomer having a refractive index of, for example, about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, but from the viewpoints of ease of preparation of the pressure-sensitive adhesive composition and ease of compatibility with flexibility suitable for a pressure-sensitive adhesive, it is, for example, 3.000 or less, may be 2.500 or less, may be 2.000 or less, may be 1.900 or less, may be 1.800 or less, or may be 1.700 or less. The high refractive index monomer may be used alone or in combination of two or more kinds. The refractive index of the monomer can be measured, for example, using an Abbe refractometer under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, the model "DR-M4" manufactured by ATAGO Co., Ltd. or its equivalent can be used. When the nominal value of the refractive index at 25°C is provided by the manufacturer or the like, that nominal value can be adopted.

[0095] As the high refractive index monomer, a compound having a corresponding refractive index can be appropriately selected from among the compounds (for example, the compounds and compound groups exemplified above) included in the concept of the aromatic ring-containing monomer (m1). Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, Tg of homopolymer: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, Tg of homopolymer: 31°C), ethoxylated o-phenylphenol acrylate (number of repeating units of oxyethylene unit: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, Tg of homopolymer: 6°C), phenoxyethyl acrylate (refractive index (nD20): 1.517, Tg of homopolymer: 2°C), phenoxydiethylene glycol acrylate (refractive index: 1.510, Tg of homopolymer: -35°C), 6-acryloyloxymethyldinaphthothiophene (6MDNTA, refractive index: 1.75), 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6-acryloyloxyethyldinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1.793).

[0096] The content of the high refractive index monomer (i.e., an aromatic ring-containing monomer having a refractive index of about 1.510 or more, preferably about 1.530 or more, more preferably about 1.550 or more) in the monomer (m1) is not particularly limited, and may be, for example, 5% by weight or more, may be 25% by weight or more, may be 35% by weight or more, or may be 40% by weight or more. In some embodiments, from the perspective of facilitating obtaining a higher refractive index, the content of the high refractive index monomer in the monomer (m1) may be, for example, 50% by weight or more, preferably 70% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. Substantially 100% by weight of the monomer (m1) may be the high refractive index monomer. Also, in some embodiments, for example, from the perspective of achieving a good balance between a high refractive index and adhesive properties and / or optical properties, the content of the high refractive index monomer in the monomer (m1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, or may be 65% by weight or less. In some embodiments, considering the adhesive properties and / or optical properties, the content of the high refractive index monomer in the monomer (m1) may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, may be 15% by weight or less, or may be 10% by weight or less. Embodiments of the present invention may be practicable even if the content of the high refractive index monomer in the monomer (m1) is less than 5% by weight. It is not necessary to use the high refractive index monomer.

[0097] (Meth)acrylic polymers may contain, as monomer components, monomers copolymerizable with the aromatic ring-containing monomer (m1) (copolymerizable monomers). Examples of the copolymerizable monomers include aliphatic alkyl (meth)acrylates, alicyclic alkyl (meth)acrylates, carboxyl group-containing monomers, hydroxyl group-containing monomers, and amide group-containing monomers. The type, number, combination, and content in the monomer component of the copolymerizable monomers can be appropriately set according to the purpose.

[0098] The acrylic pressure-sensitive adhesive (acrylic pressure-sensitive adhesive composition) may contain a refractive index improver according to the purpose. In this specification, the refractive index improver refers to a material that can increase the refractive index of the pressure-sensitive adhesive layer by its use. As the refractive index improver, a material having a higher refractive index than the refractive index of the pressure-sensitive adhesive layer containing the refractive index improver can be preferably used. Also, as the refractive index improver, a material having a higher refractive index than the base polymer (for example, acrylic polymer) of the pressure-sensitive adhesive layer containing the refractive index improver can be preferably used. By appropriately using the refractive index improver, it is possible to preferably achieve both a higher refractive index and practical pressure-sensitive adhesive performance. In some embodiments, the refractive index improver is preferably an organic material. The organic material used as the refractive index improver may be a polymer or a non-polymer. Also, it may or may not have a polymerizable functional group. The refractive index improver may be used alone or in combination of two or more kinds.

[0099] The amount of the refractive index improver used with respect to 100 parts by weight of the base polymer (when a plurality of types of refractive index improvers are used, the total amount thereof) can be appropriately set according to the purpose. From the viewpoint of increasing the refractive index of the pressure-sensitive adhesive, the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, advantageously 3 parts by weight or more, preferably 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, or may be 20 parts by weight or more. Further, in some embodiments, the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less, and from the viewpoint of achieving a good balance between increasing the refractive index of the pressure-sensitive adhesive and suppressing the deterioration of the adhesive properties and optical properties, it is advantageously 60 parts by weight or less, and preferably 45 parts by weight or less. In some embodiments that place more emphasis on the adhesive properties and optical properties, the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer may be, for example, 30 parts by weight or less, may be 20 parts by weight or less, may be 15 parts by weight or less, may be 10 parts by weight or less, may be 5 parts by weight or less, or may be 3 parts by weight or less. Embodiments of the present invention can be implemented even when the amount of the refractive index improver used with respect to 100 parts by weight of the base polymer in the pressure-sensitive adhesive layer is less than 1 part by weight, or when the refractive index improver is not substantially used. Here, not substantially using means not using at least intentionally.

[0100] (Additive (H RO )) In some embodiments, as the refractive index improver, an organic material having a higher refractive index than the base polymer can be preferably employed. Hereinafter, such an organic material may be referred to as "additive (H RO )". Here, "H RO " represents an organic material having a high refractive index. The additive (H RO ) may be used alone or in combination of two or more.

[0101] Additive (H RO) Examples of the organic materials that can be an option include, for example, organic compounds having an aromatic ring and organic compounds having a heterocyclic ring (which may be an aromatic ring or a non-aromatic heterocyclic ring). Additive (H RO ) The aromatic ring of the organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") used as can be selected from the same ones as the aromatic ring of the compound used as the monomer (m1).

[0102] Additive (H RO ) Non-limiting specific examples of the aromatic ring-containing compound that can be used as include aromatic ring-containing monomers such as benzyl acrylate, m-phenoxybenzyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, the monomer having the above-mentioned fluorene structure, the monomer having a dinaphthothiophene structure, the monomer having a dibenzothiophene structure; aromatic ring-containing compounds having no ethylenically unsaturated group such as 3-phenoxybenzyl alcohol, dinaphthothiophene and its derivatives (for example, compounds having a structure in which one or more substituents selected from a hydroxy group, a methanol group, a diethanol group, a glycidyl group, etc. are bonded to the dinaphthothiophene ring by 1 or 2 or more);

[0103] The acrylic pressure-sensitive adhesive composition may preferably contain a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include epoxy group-containing silane coupling agents. Examples of the crosslinking agent include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Further, the acrylic pressure-sensitive adhesive composition may contain additives. Specific examples of the additives include antioxidants, conductive agents, colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softening agents, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foils. Also, within a controllable range, a redox system with the addition of a reducing agent may be adopted. The type, number, combination, content, etc. of the silane coupling agent, crosslinking agent, and / or additives can be appropriately set according to the purpose.

[0104] E-3. Adhesive The adhesive (adhesive composition) may typically contain a (meth)acrylate containing an aromatic ring skeleton and metal oxide particles. Each will be briefly described below. Note that for other components that may be included in the adhesive (e.g., curing components, pressure-sensitive adhesives), well-known configurations may be adopted, so specific descriptions are omitted.

[0105] By the adhesive composition containing a (meth)acrylate having an aromatic ring skeleton, an adhesive layer having a desired refractive index can be formed in 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.

[0106] 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 pyramid shape. Note that as the metal oxide particles, those surface-treated by any appropriate method may be used.

[0107] 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.

[0108] 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 blending 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.

[0109] 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 blending 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.

[0110] F. Image display device The optical laminate described in the above items A to E can be applied to an image display device. Therefore, the embodiments of the present invention also include an image display device using such an optical laminate. Representative examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to the embodiments of the present invention typically includes the optical laminate described in the above items A to E on its viewing side.

Examples

[0111] 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.

[0112] (1) Storage elastic modulus (1-1) Actinic energy ray-curable adhesives and aqueous adhesives The active energy ray-curable adhesive used in the examples and comparative examples was applied to a cycloolefin polymer film (COP film: manufactured by Nippon Zeon Co., Ltd., product name "ZF14") (thickness 100 μm), and the same COP film was laminated on the coated surface to obtain a laminate. An active energy ray irradiator (manufactured by Heraeus, "Light HAMMER10 Mark III", valve: V valve) was used to irradiate this laminate with a peak illuminance of 1600 mW / cm 2 , an integrated irradiation dose of 1000 / mJ / cm 2 (wavelength 380 nm to 440 nm) to obtain a cured product layer (single film) of the active energy ray-curable adhesive. The illuminance of the active energy ray was measured using a "Sola-Check system" manufactured by Solatell Co., Ltd. The storage elastic modulus at 25 °C of the obtained cured product layer (single film) of the active energy ray-curable adhesive was measured using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, product name "RSA-G2") under the following conditions. (Load mode): Tension (Temperature increase rate): 5 °C / min (Frequency): 1 Hz (Initial strain): 0.1% The aqueous adhesive was also measured in the same manner as above.

[0113] (1-2) Adhesive The solution of the acrylic adhesive composition used in the examples and comparative examples was applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., thickness: 38 μm), and dried at 150 °C for 3 minutes to prepare an adhesive sheet (thickness 1 mm). This adhesive sheet was punched into a disk shape with a diameter of 8 mm and used as a measurement sample. Using this measurement sample, the storage elastic modulus at 25 °C of the adhesive was measured using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, product name "ARES-G2") under the following conditions. (Load mode): Torsion (Temperature increase rate): 5 °C / min (Frequency): 1 Hz (Measurement temperature): -70 °C to 150 °C

[0114] (2) Thickness It was measured with an interference thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0115] (3) Linear unevenness A normal acrylic adhesive was placed on the second liquid crystal alignment cured layer side of the optical laminate obtained in the examples and comparative examples, and the optical laminate was bonded to a V3 reflector (manufactured by NEODIS) through the acrylic adhesive to obtain a test sample. The obtained test sample was visually observed under a three-wavelength fluorescent lamp and evaluated according to the following criteria. 1: No linear unevenness was observed 2: Slight linear unevenness was observed 3: Linear unevenness was observed, but it was within an acceptable level for practical use 4: Linear unevenness that was unacceptable for practical use was observed 5: Linear unevenness was prominent

[0116] [Production Example 1: Preparation of Adhesive] Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 94.9 parts of butyl acrylate, 0.1 part of 2-hydroxyethyl acrylate, 5 parts of acrylic acid, and 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator were charged together with 100 parts of ethyl acetate. After gently stirring while introducing nitrogen gas for nitrogen substitution, 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 an acrylic polymer. To 100 parts of the solid content of the obtained acrylic polymer solution, 0.6 part of an isocyanate crosslinking agent (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd., an adduct of tolylene diisocyanate and trimethylolpropane), 0.2 part of benzoyl peroxide (Niper BMT manufactured by NOF Corporation), and 0.2 part of γ-glycidoxypropylmethoxysilane (KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.) were blended to prepare a solution of an acrylic pressure-sensitive adhesive composition. This solution of the acrylic pressure-sensitive adhesive composition was applied to one side of a polyethylene terephthalate film (separator film: manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) treated with a silicone-based release agent, and dried at 150°C for 3 minutes to form an adhesive layer with a predetermined thickness on the surface of the separator film. The storage elastic modulus of the pressure-sensitive adhesive was 1.1×10 5 (Pa).

[0117] [Production Example 2: Preparation of Adhesive A] 10 parts of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals), 50 parts of phenoxydiethylene glycol acrylate (trade name "Light Acrylate P2H-A", manufactured by Kyoeisha Chemical Co., Ltd.), 25 parts of 1,9-nonanediol diacrylate (trade name "Light Acrylate 1,9NDA", manufactured by Kyoeisha Chemical Co., Ltd.), 10 parts of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), 3 parts of a photopolymerization initiator (trade name "Omnirad 907", manufactured by IGM Resins B.V.), and 2 parts of a photopolymerization accelerator (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare Adhesive A (an active energy ray-curable adhesive). The storage elastic modulus of Adhesive A was 1.8×10 7 (Pa).

[0118] [Production Example 3: Preparation of Adhesive B] 11 parts of hydroxyethylacrylamide (trade name "HEAA", manufactured by KJ Chemicals), 1 part of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 4 parts of 2-acetoxyacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals), 59 parts of tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei), 1 part of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 10 parts of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei), 3 parts of a photopolymerization initiator (trade name "Omnirad 907", manufactured by IGM Resins B.V.), and 1 part of a photopolymerization accelerator (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50 °C for 1 hour to prepare Adhesive B (an active energy ray-curable adhesive). The storage elastic modulus of Adhesive B was 1.3×10 9 (Pa).

[0119] [Production Example 4: Preparation of Adhesive C] 6.02 parts of acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6%, degree of saponification 99.0 mol% or more, solid content concentration 4%, manufactured by Mitsubishi Chemical Corporation, trade name "Gosenex Z-200"), 25 parts of an aqueous solution containing a positively charged alumina colloid (average particle diameter 15 nm) at a solid content concentration of 3.2%, and 18.98 parts of pure water were mixed to prepare Adhesive C (an aqueous adhesive). The storage elastic modulus of Adhesive C was 1.5×10 9 (Pa).

[0120] [Example 1] 1. Preparation of Polarizing Plate 1-1. Preparation of Polarizer As a thermoplastic resin substrate, an amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100 μm) that is long and has 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 acetylacetylated 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 thereto, 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). Subsequently, 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). Subsequently, 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). Subsequently, 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 the laminate was immersed 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 polarizing plate having a resin substrate / polarizer structure was obtained. The single transmittance Ts of the polarizer was 43.3%.

[0121] 1-2. Production of Polarizing Plate An HC-COP film was bonded to the surface of the obtained polarizer (the surface opposite to the resin substrate) via an ultraviolet curable adhesive. The HC-COP film is a film in which an HC layer (thickness 4 μm) is formed on a cycloolefin resin (COP) film (thickness 25 μm), and it was bonded 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 to obtain a polarizing plate having a structure of HC layer / COP film (protective layer) / polarizer.

[0122] 2. Production of Retardation 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 (BIG CHEMIE's "BYK-360") and a photopolymerization initiator (IGM Resins' "Omnirad907") 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, based on 100 parts by weight of the photopolymerizable liquid crystal compound. As the substrate, a biaxially stretched norbornene-based film (Zeon's "Zeonoa Film" in Japan, thickness 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition was applied onto this substrate with a bar coater so that Re(550) was 240 nm, and heated at 100 °C for 3 minutes to orient 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 laminate having a structure of substrate / First Liquid Crystal Alignment and Curing Layer was obtained. The First Liquid Crystal Alignment and Curing Layer was homogeneously aligned, and its thickness was 1.7 μm. A laminate of substrate / Second Liquid Crystal Alignment and Curing Layer (homogeneous alignment, thickness 0.92 μm, Re(550) = 130 nm) was obtained in the same manner as above except that the coating thickness was changed.

Chemical Formula

[0123] 3. Production of Optical Laminate After bonding a first liquid crystal alignment cured layer via the adhesive of Production Example 1 (thickness: 1 μm) to the polarizer surface of a polarizing plate, the substrate was peeled off. Next, a second liquid crystal alignment cured layer was bonded via an acrylic adhesive (5 μm) to the surface of the first liquid crystal alignment cured layer, and the substrate was peeled off to obtain an optical laminate having a structure of polarizing plate / adhesive layer / first liquid crystal alignment cured layer / interlayer adhesive layer / second liquid crystal alignment cured layer. In the optical laminate, the angle formed between the transmission axis of the polarizer of the polarizing plate and the slow axis of the first liquid crystal alignment cured layer was 15°, and the angle formed between the transmission axis of the polarizer of the polarizing plate and the slow axis of the second liquid crystal alignment cured layer was 75°. The obtained optical laminate was subjected to the above-described "linear unevenness" evaluation. The results are shown in Table 1.

[0124] [Examples 2 to 7 and Comparative Examples 1 to 4] An optical laminate was obtained in the same manner as in Example 1 except that the configuration of the adhesive layer was changed as shown in Table 1. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0125]

Table 1

[0126] [Evaluation] As is clear from Table 1, linear unevenness can be suppressed by controlling the display unevenness parameter.

Industrial Applicability

[0127] 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 Signs

[0128] 10 Polarizing plate 11 Polarizer 12 Protective layer 13 Protective layer 20 Retardation layer 21 First liquid crystal alignment cured layer 22 Second liquid crystal alignment cured layer 30 Adhesive layer 100 Optical laminate

Claims

1. A polarizing plate including a polarizer and a retardation layer laminated on the polarizing plate via an adhesive layer, the retardation layer includes, in order from the polarizing plate side, a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer, the retardation layer as a whole has a circular polarization function or an elliptically polarizing function and has a relationship of Re(450)<Re(550)<Re(650); An optical laminate, wherein the adhesive layer satisfies the following relationship: (logG') / T>1.7 Here, G' is the storage modulus of the adhesive layer (Pa), and T is the thickness of the adhesive layer (μm).

2. The optical laminate according to claim 1 , wherein the adhesive layer is made of an active energy ray-curable adhesive.

3. The optical laminate according to claim 1 , wherein the adhesive layer is made of a pressure-sensitive adhesive.

4. The optical laminate according to claim 1 , wherein the first liquid crystal alignment solidified layer has a thickness of 1.7 μm or less.

5. An image display device comprising the optical laminate according to claim 1 .

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