Optical laminate and image display device using the same

Abstract

To provide an optical laminate which includes a liquid crystal alignment solidified layer, has an integrated front plate, and is capable of suppressing particular appearance defects when used in image display devices.SOLUTION: An optical laminate according to an embodiment of the present invention comprises a front plate, an adhesive layer, a polarizing plate including a polarizer, and a retardation layer arranged in the described order. The retardation layer comprises a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer laminated on the first liquid crystal alignment solidified layer via an adhesive layer in order from the polarizing plate side. A refractive index nLC1 of a polarizer of the first liquid crystal alignment solidified layer in a transmission axis direction, a refractive index nLC2 of a polarizer of the second liquid crystal alignment solidified layer in a transmission axis direction, and a refractive index nAD of a polarizer of the adhesive layer in a transmission axis direction satisfy the following expression (1): (nLC1-nAD)2+(nLC2-nAD)2<0.009 ...(1).SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices, inorganic EL display devices) have been rapidly spreading. In many cases, an optical laminate including a retardation film (for example, an antireflection film in which a polarizing plate and a retardation film are integrated) is used in the image display device. In recent years, as the demand for thinning of the image display device has increased, the demand for thinning of the optical laminate has also increased. For the purpose of thinning the optical laminate, the retardation layer (retardation film), which makes a large contribution to the thickness, has been thinned. As a typical example of the thin retardation film, a film in which a liquid crystal compound is aligned and its alignment state is fixed (hereinafter referred to as a liquid crystal film) can be mentioned. Since the liquid crystal compound has a much larger birefringence (Δn) than the resin, the liquid crystal film can have a much smaller thickness for obtaining a desired in-plane retardation than the stretched film of the resin film. On the other hand, in order to impart surface hardness and impact resistance to the image display device, a front panel (for example, cover glass) may be laminated on the outermost surface of the image display device. In this case, an optical laminate integrated with the front panel may be used. However, an image display device using an optical laminate including a front panel and a liquid crystal film may have an appearance defect (specifically, a phenomenon in which reflected light is visually recognized as undulating).

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 solidified layer, has an integrated front panel, and can suppress specific appearance defects when applied to an image display device.

Means for Solving the Problems

[0005] [1] The optical laminate according to an embodiment of the present invention has, in this order, a front panel, an adhesive layer, a polarizing plate including a polarizer, and a retardation 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 laminated to the first liquid crystal alignment solidified layer via an adhesive layer. The refractive index n LC1 in the transmission axis direction of the polarizer of the first liquid crystal alignment solidified layer, the refractive index n LC2 in the transmission axis direction of the polarizer of the second liquid crystal alignment solidified layer, and the refractive index n AD in the transmission axis direction of the polarizer of the adhesive layer satisfy the following formula (1): (n LC1 - n AD ) 2 + (n LC2 - n AD ) 2 < 0.009 ··· (1). [2] In the above [1], the above n LC1 is greater than 1.60. [3] In the above [1] or [2], the angle formed by the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer is 40° or less. [4] In any one of the above [1] to [3], the storage elastic modulus of the adhesive layer is 3 GPa or less. [5] In the above [4], the storage elastic modulus of the adhesive layer is 10 MPa or less. [6] In any one of the above [1] to [5], the front panel is made of antireflection glass. [7] According to another aspect of the present invention, an image display device is provided. The image display device includes the optical laminate according to any one of the above [1] to [6].

Effects of the Invention

[0006] According to an embodiment of the present invention, it is possible to realize an optical laminate including a liquid crystal alignment solidification layer, having an integrated front panel, and capable of suppressing specific appearance defects when applied to an image display device.

Brief Description of the Drawings

[0007]

Figure 1

Embodiments for Carrying Out the Invention

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

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

[0010] A. Optical laminate FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 in the illustrated example has a front panel 50, an adhesive layer 40, a polarizing plate 10, and a retardation layer 20 in this order. That is, in the optical laminate 100, the front panel 50 and the polarizing plate 10 are laminated via the adhesive layer 40. Further, the polarizing plate 10 and the retardation layer 20 are laminated via an arbitrary appropriate adhesive layer (for example, an adhesive layer, an adhesive layer: not shown). The polarizing plate 10 typically includes a polarizer 11 and protective layers 12 and 13 disposed on both sides of the polarizer 11. Depending on the purpose, at least one of the protective layers 12 and 13 may be omitted. Therefore, the polarizing plate may be a so-called double-protection polarizing plate, a so-called single-protection polarizing plate, or may be composed of only a polarizer.

[0011] The retardation layer 20 includes, in order from the polarizing plate 10 side, a first liquid crystal alignment cured layer 21 and a second liquid crystal alignment cured layer 22 laminated to the first liquid crystal alignment cured layer 21 via an adhesive layer 25. By using the liquid crystal alignment cured layer as the retardation layer, a desired in-plane retardation can be realized with a thickness significantly thinner than that of a stretched film of a resin film. As a result, a significant thinning of the optical laminate can be achieved. The retardation layer 20, in one embodiment, 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. The retardation layer, in one embodiment, as a whole, may have an Nz coefficient of, for example, 0.30 to 0.70. In this specification, the "liquid crystal alignment cured layer" refers to a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The "liquid crystal alignment cured layer" is a concept that includes an alignment cured layer obtained by curing a liquid crystal monomer.

[0012] In an embodiment of the present invention, the refractive index n in the transmission axis direction of the polarizer of the first liquid crystal alignment solidified layer LC1 , the refractive index n in the transmission axis direction of the polarizer of the second liquid crystal alignment solidified layer LC2 , and the refractive index n in the transmission axis direction of the polarizer of the adhesive layer AD satisfy the following formula (1). The left side of formula (1) may be referred to as an appearance parameter. In the following description of this specification, unless otherwise specified, "refractive index" means the refractive index in the transmission axis direction of the polarizer. Further, since the adhesive layer is substantially optically isotropic, the refractive index n AD is also substantially isotropic. (n LC1 - n AD ) 2 + (n LC2 - n AD ) 2 < 0.009 ···(1) The appearance parameter is preferably 0.007 or less, more preferably 0.005 or less, still more preferably 0.003 or less, and particularly preferably 0.001 or less. The smaller the appearance parameter, the more preferable, and it can be, for example, 0.000.

[0013] In considering further thinning of an optical laminate including a liquid crystal alignment cured layer as a retardation layer, the inventors have found a new problem that an image display device using an optical laminate including a liquid crystal alignment cured layer as a retardation layer and having an integrated front panel may have specific appearance defects depending on the viewing environment. Specifically, it has been found that a phenomenon in which reflected light (particularly, reflected light of an LED light) is visually recognized as undulating (which may be referred to as reflected light undulation) may occur. As a result of intensive studies on suppression of such reflected light undulation, the inventors have found that the reflected light undulation can be suppressed by suppressing the interference of the optical laminate. In addition, instead of individually adjusting the average refractive index, thickness, etc. of each layer constituting the optical laminate in order to suppress the interference of the optical laminate, the inventors have adjusted the refractive index in the transmission axis direction of the polarizers of the two liquid crystal alignment cured layers and the refractive index in the transmission axis direction of the polarizers of the adhesive layer for laminating them to make the above appearance parameters smaller than a predetermined value, and have found that the reflected light undulation can be comprehensively suppressed in a specific configuration of the optical laminate according to the purpose and / or constituent materials, etc., and thus have completed the present invention. That is, such an effect according to an embodiment of the present invention solves a newly found problem in considering further thinning of an optical laminate including a liquid crystal alignment cured layer as a retardation layer and having an integrated front panel, and is an unexpectedly excellent effect.

[0014] As the adhesive layer 25, any appropriate configuration may be adopted as long as the effects according to the embodiments of the present invention can be obtained (specifically, as long as the above appearance parameters can be made smaller than a predetermined value). For example, the adhesive layer may be composed of an adhesive or may be composed of an adhesive agent.

[0015] In the optical laminate, the total thickness from the first liquid crystal alignment cured layer to the second liquid crystal alignment cured layer (i.e., the total thickness of the retardation layer) is preferably 15 μm or less, more preferably 3 μm to 10 μm. According to an embodiment of the present invention, it is possible to solve the problem of reflected light undulation newly found in an optical laminate including a very thin liquid crystal alignment cured layer. Note that if the total thickness from the first liquid crystal alignment cured layer to the second liquid crystal alignment cured layer is within the above range, the total thickness from the polarizing plate to the second liquid crystal alignment cured layer (the substantial total thickness of the optical laminate excluding the thickness of the adhesive for bonding to the image display panel and the thickness of the front panel and the adhesive for bonding the front panel) can be, for example, 100 μm or less, or for example, 30 μm to 80 μm.

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

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

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

[0019] B. Front panel As the front panel 50, any appropriate film or plate can be adopted according to the purpose. For example, the front panel may be made of glass or resin. The light transmittance of the front panel at a wavelength of 550 nm is preferably 85% or more. The refractive index of the front panel at a wavelength of 550 nm is preferably 1.4 to 1.65.

[0020] As the glass plate, any appropriate configuration that can be used as the front panel of the image display device can be adopted. The thickness of the glass plate is, for example, 1 mm to 10 mm. By using a glass plate as the front panel, an optical laminate having extremely excellent mechanical strength and surface hardness can be obtained. Glasses include, according to classification by composition, for example, soda-lime glass, borate glass, aluminosilicate glass, fused silica, etc. Also, according to classification by alkali component, alkali-free glass and low-alkali glass can be mentioned. The content of the alkali metal component (for example, Na2O, K2O, Li2O) in the glass is preferably 15% by weight or less, and more preferably 10% by weight or less. The density of the glass is preferably 2.3 g / cm 3 ~3.0 g / cm 3 and more preferably 2.3 g / cm 3 ~2.7 g / cm 3 If the density of the glass is within such a range, the weight of the optical laminate can be reduced. In one embodiment, the front panel is composed of anti-reflection glass. The reflectance of the anti-reflection glass is preferably 10% or less, and more preferably 5% or less. If the reflectance is within such a range, the visibility of the display image of the image display device can be improved.

[0021] As the resin plate, any suitable configuration that can be used as the front panel of the image display device can be adopted. Examples of the material constituting the resin plate include acrylic resins, styrene resins, acrylonitrile-styrene resins (AS resins), polycarbonate resins, polyester resins, and polyolefin resins. The thickness of the resin plate is, for example, 1 mm to 10 mm. By using a predetermined resin plate as the front panel, a surface hardness without practical problems can be achieved, and the weight can be reduced compared to a glass plate. Furthermore, low power consumption can be achieved by using a resin with higher transparency than glass.

[0022] C. Adhesive layer The adhesive layer 40 can be composed of any suitable adhesive (adhesive composition) that can be used for bonding the front panel and an optical film (e.g., a polarizing plate). Examples of the base polymer of the adhesive composition include (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluorine polymers, rubber polymers such as natural rubber and synthetic rubber. Preferably, it is an acrylic adhesive composition containing a (meth)acrylic polymer as the base polymer. This is because it has excellent optical transparency, exhibits adhesive properties such as appropriate wettability, cohesiveness, and adhesiveness, and is also excellent in weather resistance and heat resistance.

[0023] (Meth)acrylic polymers preferably have a crosslinked structure. More specifically, the (meth)acrylic polymer contains a (meth)acrylic polymer chain into which a crosslinked structure has been introduced.

[0024] (Meth)acrylic polymers contain alkyl (meth)acrylate as a main monomer component. As the alkyl (meth)acrylate, alkyl (meth)acrylates in which the alkyl group has 1 to 20 carbon atoms are preferably used. The alkyl (meth)acrylate may have a branched alkyl group or a cyclic alkyl group. The amount of alkyl (meth)acrylate relative to the total amount of monomer components constituting the (meth)acrylic polymer chain is preferably 50% by weight or more, more preferably 55% by weight or more, and still more preferably 60% by weight or more. From the viewpoint of setting the glass transition temperature (Tg) of the polymer chain within an appropriate range, the amount of alkyl (meth)acrylate having a linear alkyl group with 4 to 10 carbon atoms relative to the total amount of monomer components constituting the (meth)acrylic polymer chain is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 55% by weight or more. Note that the monomer components constituting the (meth)acrylic polymer chain are those obtained by removing monomers used for forming a crosslinked structure (polyfunctional (meth)acrylates, urethane (meth)acrylates, etc. described later) and crosslinking agents from all the monomer components constituting the polymer.

[0025] (Meta)acrylic polymers may further contain any suitable copolymer monomer component as a monomer component according to the purpose. Specific examples of such monomer components include hydroxyl group-containing monomers, carboxyl group-containing monomers, nitrogen-containing monomers, acid anhydride group-containing monomers, caprolactone adducts of (meth)acrylic acid, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, vinyl-based monomers such as vinyl acetate, vinyl propionate, styrene, α-methylstyrene; cyano group-containing acrylic monomers such as acrylonitrile, methacrylonitrile; epoxy group-containing monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate; acrylic ester-based monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, 2-methoxyethyl (meth)acrylate. By adjusting the number, type, combination, and blending amount of the copolymer monomer components, an adhesive layer having desired properties according to the purpose can be obtained.

[0026] Polymers in which a crosslinked structure is introduced into the (meth)acrylic polymer chain can be obtained, for example, by (1) adding a crosslinking agent after polymerizing a (meth)acrylic polymer having a functional group capable of reacting with the crosslinking agent to react the (meth)acrylic polymer with the crosslinking agent; and (2) introducing a branched structure (crosslinked structure) into the polymer chain by including a polyfunctional compound in the polymerization components of the polymer, etc. These may be used in combination.

[0027] Specific examples of the crosslinking agent in the method of reacting the base polymer of (1) above with the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, metal chelate-based crosslinking agents, and the like. Among them, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with the hydroxyl groups and carboxyl groups of the base polymer and it is easy to introduce a crosslinked structure. These crosslinking agents react with functional groups such as hydroxyl groups and carboxyl groups introduced into the base polymer to form a crosslinked structure.

[0028] In the method of including a polyfunctional compound in the polymerization component of the base polymer of (2) above, the total amount of the monomer component constituting the (meth)acrylic polymer and the polyfunctional compound for introducing the crosslinked structure may be reacted at once, or polymerization may be carried out in multiple steps. As a method of carrying out polymerization in multiple steps, a monofunctional monomer constituting the (meth)acrylic polymer is polymerized (prepolymerized) to prepare a partial polymer (prepolymer composition), and a polyfunctional compound such as polyfunctional (meth)acrylate is added to the prepolymer composition, and the prepolymer composition and the polyfunctional monomer are polymerized (main polymerization). The prepolymer composition is a partial polymer containing a polymer of low degree of polymerization and unreacted monomers. Examples of the polyfunctional compound include compounds containing two or more polymerizable functional groups (ethylenically unsaturated groups) having an unsaturated double bond in one molecule. As the polyfunctional compound, polyfunctional (meth)acrylate is preferred because it is easy to copolymerize with the monomer component of the (meth)acrylic polymer. When introducing a branched (crosslinked) structure by active energy ray polymerization (photo polymerization), polyfunctional (meth)acrylate is preferred. Further, by using urethane (meth)acrylate having a (meth)acryloyl group at the end of the urethane chain as the polyfunctional (meth)acrylate, a crosslinked structure by the urethane segment can be introduced.

[0029] In one embodiment, the pressure-sensitive adhesive composition may contain an acrylic oligomer. In one embodiment, the pressure-sensitive adhesive composition may be photocurable. In this case, the pressure-sensitive adhesive composition contains, for example, a polyfunctional compound and a photopolymerization initiator.

[0030] The pressure-sensitive adhesive composition may contain additives. Specific examples of the additives 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, conductive agents, 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, blending amount, etc. of the additives can be appropriately set according to the purpose. By appropriately adjusting the type, combination, and blending amount, etc. of the monomer components, as well as the type, number, combination, and blending amount, etc. of the crosslinking agent, silane coupling agent, and additives, a pressure-sensitive adhesive composition (and as a result, a pressure-sensitive adhesive layer) having desired properties according to the purpose can be obtained.

[0031] Another example of the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer includes those described in JP-A-2016-94569. The description of this publication is incorporated herein by reference.

[0032] The glass transition temperature of the pressure-sensitive adhesive layer is preferably -3°C or lower, more preferably -5°C or lower, and even more preferably -6°C or lower. On the other hand, the glass transition temperature is preferably -20°C or higher, more preferably -15°C or higher, and even more preferably -13°C or higher. If the glass transition temperature is within such a range, a pressure-sensitive adhesive layer having excellent impact resistance can be realized.

[0033] The peak top value of the loss tangent tanδ of the adhesive layer (i.e., tanδ at the glass transition temperature) is preferably 1.5 or more, more preferably 1.6 or more, still more preferably 1.7 or more, and particularly preferably 1.75 or more. On the other hand, the upper limit of the peak top value of tanδ is preferably 3.0 or less, more preferably 2.5 or less, and still more preferably 2.3 or less. If the peak top value of tanδ is within such a range, the adhesive layer exhibits appropriate deformation behavior (viscoelastic behavior). For example, when a deformed portion such as a through hole is formed in the polarizing plate, it is less likely to form a gap when filling the deformed portion.

[0034] The gel fraction of the adhesive layer is preferably 50% to 95%, more preferably 55% to 93%, and still more preferably 60% to 90%. If the gel fraction is within such a range, the front panel and the polarizing plate can be firmly fixed. The gel fraction can be determined as the insoluble content in a solvent such as ethyl acetate. Specifically, the gel fraction is determined as the weight fraction (unit: wt%) of the insoluble component after immersing the adhesive constituting the adhesive layer in ethyl acetate at 23°C for 7 days with respect to the sample before immersion. The gel fraction can be adjusted by appropriately setting the types, combinations, and blending amounts of the monomer components constituting the base polymer of the adhesive, as well as the types and blending amounts of the crosslinking agents.

[0035] The storage modulus of the adhesive layer at 60°C is preferably 5.0×10 3 Pa to 5.0×10 5 Pa, more preferably 7.5×10 3 Pa to 4.0×10 5 Pa, and still more preferably 8.0×10 3 Pa to 3.0×10 5 Pa. If the storage modulus of the adhesive layer is within such a range, the gel elasticity of the adhesive layer becomes low and the residual stress becomes small.

[0036] The total light transmittance of the adhesive layer is preferably 85% or more, more preferably 90% or more. The haze value of the adhesive layer is preferably 1.5% or less, more preferably 1.0% or less.

[0037] The thickness of the adhesive layer is preferably 50 μm to 500 μm, more preferably 70 μm to 350 μm, still more preferably 80 μm to 250 μm, and particularly preferably 100 μm to 200 μm.

[0038] D. Polarizing plate D-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.

[0039] The PVA-based resin preferably includes an acetoacetyl-modified PVA-based resin. With such a configuration, a polarizer having a desired mechanical strength can be obtained. When the total amount of the PVA-based resin is 100% by weight, the blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% to 20% by weight, more preferably 8% to 12% by weight. If the blending amount is within such a range, a polarizer having more excellent mechanical strength can be obtained.

[0040] 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 to 20 parts by weight, more preferably 10 to 15 parts by weight, based on 100 parts by weight of the PVA-based resin. The halide can be blended 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 finally introduced into the polarizer. By introducing the halide into the polarizer, the orientation of PVA molecules in the polarizer can be enhanced, so that a polarizer having excellent optical properties (typically, achieving both high polarization degree and high single transmittance) can be realized.

[0041] 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.

[0042] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 to 8 μm, and even more preferably 3 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.

[0043] 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.

[0044] Specific examples of the polarizer composed of a single-layer resin film include hydrophilic polymer films such as PVA-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films, which are subjected to dyeing treatment with dichroic substances such as iodine and dichroic dyes and stretching treatment, and polyene-based 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.

[0045] The above-mentioned dyeing with iodine is performed, for example, by immersing a PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. Also, dyeing may be performed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, cross-linking 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 blocking inhibitor be washed, but also the PVA-based film can be swollen to prevent uneven dyeing.

[0046] As a specific example of a polarizer obtained using a laminate, there can be mentioned a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a polarizer obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material. A polarizer obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material can be produced, for example, by applying a PVA-based resin solution to the resin base material and drying it to form a PVA-based resin layer on the resin base material to obtain a laminate of the resin base material and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In the present embodiment, preferably, a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin base material. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include, if necessary, air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in the present embodiment, preferably, the laminate is subjected to a 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 assisted stretching, even when PVA is applied on a thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. Also, by simultaneously enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing process or stretching process can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. Thereby, the optical properties of the polarizer obtained through treatment steps such as a dyeing treatment and a stretching treatment in water, which are performed by immersing the laminate in a liquid, can be improved. Furthermore, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface of the resin substrate / polarizer laminate from which the resin substrate has been peeled, or on the surface opposite to the peeled surface. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. The entire descriptions of these publications are incorporated herein by reference.

[0047] D-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 descriptions of these publications are incorporated herein by reference. From the viewpoint of ease of profiling and the like, cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic-based resins are preferred.

[0048] The optical laminate is typically disposed on the viewing side of an image display device, and the protective layer 12 is typically disposed on its viewing side. Therefore, the protective layer 12 may be surface-treated as necessary. Examples of the surface treatment include hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment. Further / alternatively, the protective layer 12 may be treated as necessary to improve visibility when viewing through polarized sunglasses (typically, imparting an (elliptical) polarization function and imparting an extremely high retardation). By performing such treatment, excellent visibility can be achieved even when viewing the display screen through a polarizing lens such as polarized sunglasses. Therefore, the optical laminate can be suitably applied to an image display device that can be used outdoors.

[0049] 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.

[0050] 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.

[0051] E. Retardation layer As described above, the retardation layer 20 includes a first liquid crystal alignment cured layer 21 and a second liquid crystal alignment cured layer 22 in order from the polarizer side. Regarding the description of the retardation layer in this section, simply referring to the "retardation layer" means describing the entire retardation layer, and simply referring to the "liquid crystal alignment cured layer" means collectively describing the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer.

[0052] In one embodiment, Re(550) of the first liquid crystal alignment solidified layer is preferably 150 nm to 300 nm, more preferably 200 nm to 270 nm, and still more preferably 220 nm to 260 nm; Re(550) of the second liquid crystal alignment solidified layer is preferably 100 nm to 200 nm, more preferably 110 nm to 160 nm, and still more preferably 110 nm to 130 nm. Thus, since both the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer have an in-plane retardation, they exhibit a refractive index characteristic of nx > ny. The first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer typically exhibit a refractive index characteristic of nx > ny = nz (positive A plate). Here, "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where ny and nz are substantially equal. That is, the Nz coefficients of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer can be 0.9 to 1.1, respectively.

[0053] The thickness of the first liquid crystal alignment solidified layer can be adjusted so as to obtain the desired in-plane retardation. In one embodiment, the thickness of the first liquid crystal alignment solidified layer can be, for example, 1.5 μm to 2.5 μm. Thus, according to the embodiment of the present invention, it is possible to suppress the ripple of reflected light while making the thickness of the first liquid crystal alignment solidified layer thinner than before. The thickness of the second liquid crystal alignment solidified layer can also be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness can be, for example, 0.8 μm to 1.5 μm.

[0054] The angle formed by the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer is, for example, 40° or less, preferably 10° to 20°, more preferably 12° to 18°, and still more preferably 14° to 16°; the angle formed by the slow axis of the second liquid crystal alignment solidified layer and the transmission axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably 74° to 76°. Note that the angle formed by the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer and the angle formed by the slow axis of the second liquid crystal alignment solidified layer and the transmission axis of the polarizer may be reversed.

[0055] Examples of the liquid crystal compound used for the liquid crystal alignment cured layer include, for example, liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable (i.e., a liquid crystal monomer). When the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by polymerizing it after aligning the liquid crystal compound. Here, the polymer formed by polymerization is non-liquid crystalline. Therefore, the formed liquid crystal alignment cured layer, for example, does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to the liquid crystalline compound. As a result, the liquid crystal alignment cured layer becomes a retardation layer that is not affected by temperature changes and has extremely excellent stability.

[0056] In one embodiment, the liquid crystal alignment cured layer can be formed using a composition containing a polymerizable liquid crystal compound (a polymerizable liquid crystal compound, i.e., a liquid crystal monomer). The polymerizable liquid crystal compound contained in the composition herein refers to a compound having a polymerizable group and having liquid crystallinity. The polymerizable group means a group involved in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by active radicals, acids, etc. generated from a photopolymerization initiator. Examples of the liquid crystal monomer include, for example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445, etc. 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.

[0057] The mechanism for the expression of liquid crystallinity of the liquid crystal compound may be thermotropic or lyotropic. Also, the constitution of the liquid crystal phase may be nematic liquid crystal or smectic liquid crystal. From the viewpoint of ease of production, thermotropic nematic liquid crystal is preferred for the liquid crystallinity.

[0058] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. Specifically, the temperature range is preferably from 40°C to 120°C, more preferably from 50°C to 100°C, and most preferably from 60°C to 90°C.

[0059] The birefringence Δn of the liquid crystal alignment curing layer is preferably 0.06 or more, more preferably 0.08 or more, still more preferably 0.09 or more, and particularly preferably 0.10 or more. The upper limit of Δn can be, for example, 0.13, or can be, for example, 0.12. If Δn is within such a range, a desired in-plane retardation can be realized with a very thin thickness. As a result, the liquid crystal alignment curing layer and the optical laminate can be made thinner, and ultimately can contribute to a significant thinning of the image display device.

[0060] The liquid crystal alignment curing layer may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light. In one embodiment, the liquid crystal alignment curing layer exhibits a positive wavelength dispersion characteristic. In such a case, the effects according to the embodiments of the present invention are remarkable.

[0061] In another embodiment, Re(550) of the first liquid crystal alignment curing layer 21 is preferably from 100 nm to 200 nm, more preferably from 110 nm to 180 nm, still more preferably from 120 nm to 160 nm, and particularly preferably from 130 nm to 150 nm. In this case, the second liquid crystal alignment curing layer 22 can typically be a positive C-plate. The thickness of the first liquid crystal alignment curing layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness can be, for example, from 1.0 μm to 1.6 μm, or can be, for example, from 1.1 μm to 1.3 μm. The angle formed by the slow axis of the first liquid crystal alignment curing layer and the transmission axis of the polarizer is preferably from 40° to 50°, more preferably from 42° to 48°, still more preferably from 44° to 46°, and particularly preferably about 45°.

[0062] In yet another embodiment, Re(550) of the first liquid crystal alignment cured layer 21 is preferably from 80 nm to 160 nm, more preferably from 90 nm to 150 nm, still more preferably from 100 nm to 140 nm, and particularly preferably from 110 nm to 130 nm. Also in this case, the second liquid crystal alignment cured layer 22 can typically be a positive C-plate. The thickness of the first liquid crystal alignment cured layer can be adjusted so as to obtain the desired in-plane retardation. Specifically, the thickness may be, for example, from 0.8 μm to 1.2 μm, or may be, for example, from 0.9 μm to 1.1 μm. The angle formed by the slow axis of the first liquid crystal alignment cured layer and the transmission axis of the polarizer is, for example, 40° or less, preferably from -10° to +10°, more preferably from -5° to +5°, still more preferably from -2° to +2°, and particularly preferably about 0°.

[0063] The second liquid crystal alignment cured layer (positive C-plate) 22 exhibits a refractive index characteristic of nz > nx = ny. The retardation Rth(550) in the thickness direction of the positive C-plate is preferably 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.

[0064] The positive C-plate can be formed, for example, using a composition containing a side-chain type thermotropic liquid crystal polymer. As the side-chain type thermotropic liquid crystal polymer, a copolymer having a liquid crystalline monomer unit represented by the general formula (I) and a non-liquid crystalline monomer unit represented by the general formula (II) is preferably used.

Chemical formula

Chemical formula

[0065] In formula (I), R 1 is a hydrogen atom or a methyl group, and R 2 is a cyano group, a fluoro group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and X 1 is -CO2- or -OCO-. a is an integer of 1 to 6, and b and c are each independently 1 or 2.

[0066] In formula (II), R 3 is a hydrogen atom or a methyl group, and R 4 is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or a group represented by the following general formula (III). [Chemical formula]

[0067] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0068] Specific examples of the method for forming the positive C plate include the methods described in

[0020] to

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

[0069] Even in the embodiment using the positive C plate, the arrangement order of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer may be reversed. In this case, the angle formed by the slow axis of the liquid crystal alignment solidified layer other than the positive C plate (the liquid crystal alignment solidified layer showing the refractive index characteristic of nx>ny) and the transmission axis of the polarizer can be appropriately set according to the purpose.

[0070] The refractive index of the liquid crystal alignment solidified layer (the refractive index in the direction of the transmission axis of the polarizer) is the refractive index n of the adhesive layer ADAs long as the above formula (1) is satisfied in relation to this, any appropriate refractive index can be adopted. As described above, when the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer are formed using a material exhibiting positive wavelength dispersion characteristics, even if the same material (therefore, a material having the same average refractive index) is used for each layer, the refractive index in the direction of the transmission axis of the polarizer changes depending on the angle formed by the transmission axis of the polarizer and the slow axis of the liquid crystal alignment solidified layer, and the degree of reflected light undulation can change depending on the refractive index in the direction of the transmission axis of the polarizer. Therefore, in an embodiment of the present invention, not the average refractive index of the liquid crystal alignment solidified layer, but the refractive index in the direction of the transmission axis of the polarizer can be optimized so as to satisfy the above formula (1). The refractive index n LC1 of the first liquid crystal alignment solidified layer and the refractive index n LC2 of the second liquid crystal alignment solidified layer may be the same or different from each other (the refractive index n LC1 of the first liquid crystal alignment solidified layer may be larger, or the refractive index n LC2 of the second liquid crystal alignment solidified layer may be larger). The refractive index n LC1 of the first liquid crystal alignment solidified layer and the refractive index n LC2 of the second liquid crystal alignment solidified layer are each preferably 1.50 or more, more preferably 1.52 to 1.68, and even more preferably 1.53 to 1.65. In one embodiment, the refractive index n LC1 of the first liquid crystal alignment solidified layer or the refractive index n LC2 of the second liquid crystal alignment solidified layer may be, for example, greater than 1.60. The average refractive index of the liquid crystal alignment solidified layer will typically conform to the composition of the composition for forming the liquid crystal alignment solidified layer in order to obtain desired optical characteristics. As a result, although reflected light undulation may occur, according to an embodiment of the present invention, the reflected light undulation can be suppressed by making the appearance parameter smaller than a predetermined value based on the refractive index in the direction of the transmission axis of the polarizer of the liquid crystal alignment solidified layer.

[0071] F. Adhesive layer As the subsequent layer 25, any appropriate configuration can be adopted as long as the appearance parameters can be made smaller than a predetermined value. Specifically, as described above, the adhesive layer may be composed of an adhesive or may be composed of a pressure-sensitive adhesive. Regardless of whether the adhesive layer is an adhesive layer or a pressure-sensitive adhesive layer, the refractive index n of the adhesive layer AD may be, for example, 1.45 or more, may be, for example, 1.50 or more, may be, for example, 1.53 or more, may be, for example, 1.55 or more, or may be, for example, 1.57 or more. On the other hand, the refractive index n of the adhesive layer AD may be, for example, 1.63 or less.

[0072] In one embodiment, the adhesive layer may be composed of an active energy ray-curable adhesive. In this case, the thickness T of the adhesive layer AD is preferably 0.4 μm to 2.0 μm, and more preferably 0.8 μm to 1.2 μm.

[0073] When the adhesive layer is composed of an active energy ray-curable adhesive, the storage elastic modulus of the adhesive layer at 25°C may be, for example, 3 GPa or less, may be, for example, 3 MPa to 3 GPa, may be, for example, 5 MPa to 100 MPa, or may be, for example, 7 MPa to 30 MPa.

[0074] As long as the appearance parameters can be made smaller than a predetermined value, any appropriate configuration can be adopted for the active energy ray-curable adhesive. By adjusting the number, type, combination, compounding amount, etc. of the resin component, curing component, photoinitiator, and additive in the adhesive (adhesive composition), an adhesive (adhesive composition) having a desired refractive index can be obtained to make the appearance parameters smaller than a predetermined value. In one embodiment, the adhesive (adhesive composition) may contain a (meth)acrylate containing an aromatic ring skeleton and / or metal oxide particles. Each will be briefly described below. Note that since well-known configurations can be adopted for other components (for example, curing components, photoinitiators) that can be included in the adhesive, specific descriptions are omitted.

[0075] By the adhesive composition containing a (meth)acrylate having an aromatic ring skeleton, an adhesive layer having a desired refractive index can be formed in an embodiment of the present invention. As the (meth)acrylate having an aromatic ring skeleton, it is preferable to use at least one selected from the group consisting of a (meth)acrylate having a polycyclic aromatic ring skeleton and a (meth)acrylate 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.

[0076] Examples of the metal oxide particles include silicon oxide, zirconium oxide, titanium oxide, zinc oxide, antimony pentoxide, tin oxide, aluminum oxide, indium oxide, indium tin oxide, ferric oxide, cerium oxide, yttrium oxide, manganese oxide, holmium oxide, copper oxide, bismuth oxide, cobalt oxide, cobalt tetroxide, iron tetroxide, magnesium oxide, lanthanum oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, tantalum pentoxide, niobium pentoxide, iridium oxide, rhodium oxide, ruthenium oxide, and composite oxides formed by combining these. Among these, zirconium oxide and titanium oxide are preferred, and zirconium oxide is particularly preferred. Note that the metal oxide particles may be composed only of the metal oxides listed above, or may contain other components, but it is preferable that the metal oxide occupies the maximum weight as a component in the particles. The shape of the metal oxide particles can be any shape such as spherical, ellipsoidal, cubic, rectangular parallelepiped, or pyramidal. Note that as the metal oxide particles, those surface-treated by any appropriate method may be used.

[0077] 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.

[0078] From the viewpoint of improving the stability of the metal oxide particles in the adhesive composition and the refractive index of the adhesive layer, the 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.

[0079] 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.

[0080] In another embodiment, the adhesive layer may be composed of an adhesive. In this case, the thickness T AD of the adhesive layer is preferably 2 μm to 10 μm, more preferably 3 μm to 9 μm, still more preferably 4 μm to 7 μm, and particularly preferably 4.5 μm to 5.5 μm.

[0081] When the adhesive layer is composed of an adhesive, the storage elastic modulus of the adhesive layer at 25°C may be, for example, 10 MPa or less, or may be, for example, 0.1 MPa to 3 MPa, or may be, for example, 0.2 MPa to 1 MPa, or may be, for example, 0.3 MPa to 0.7 MPa.

[0082] The adhesive can adopt any suitable configuration as long as it can make the appearance parameters smaller than the predetermined values. By adjusting the type, number, combination, and blending amount of the monomer components of the base polymer in the adhesive (adhesive composition); the type, number, combination, and blending amount of the cross-linking agent; and the type, number, combination, and blending amount of the additives, an adhesive (adhesive composition) capable of realizing the desired appearance parameters can be prepared. In one embodiment, the monomer components of the base polymer of the adhesive (adhesive composition) include heterocyclic ring-containing acrylates and / or aromatic ring-containing acrylates. Examples of the heterocyclic ring-containing acrylates include acryloylmorpholine. Examples of the aromatic ring-containing acrylates include benzyl acrylate and phenoxybenzyl acrylate.

[0083] G. Image display device The optical laminate described in the above items A to F 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 embodiment of the present invention typically includes the optical laminate described in the above items A to F on its viewing side. In one embodiment, the image display device has flexibility that can be curved or bent. There can be a trade-off relationship between flexibility and deformation in the vacuum lamination when laminating the front panel, and as a result, appearance defects are likely to occur in an image display device using an optical laminate integrated with the front panel. According to the embodiment of the present invention, appearance defects can be suppressed even in such a flexible image display device.

Examples

[0084] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by 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.

[0085] (1) Refractive index (1-1) Adhesive layer For the adhesive layers formed in the examples and comparative examples, measurements were taken using an Abbe refractometer (manufactured by ATAGO Co., Ltd., product name "DR-M2 / 1550"). The measurement wavelength was 589 nm and the measurement temperature was 25°C. (1-2) Adhesive layer and liquid crystal alignment curing layer The adhesives used in the examples and comparative examples were coated on a cycloolefin polymer film (COP film) (thickness 100 μm), the same COP film was laminated on the coated surface, and visible light was irradiated using an active energy ray irradiation device to obtain a cured product layer (single film). For the obtained cured product layer, the in-plane refractive index and the refractive index in the thickness direction were measured using a prism coupler (manufactured by Sirion Technologies, product name "SPA-4000"), and the average value of these was taken as the average refractive index of the adhesive layer. The measurement wavelength was 594 nm and the measurement temperature was 23°C. Furthermore, for the liquid crystal alignment curing layer, the refractive index in the transmission axis direction was determined as follows. The in-plane retardation Re(550) and the thickness direction retardation Rth(550) were measured using Axoscan (manufactured by Axometrics). From the following simultaneous equations, nx, ny, and nz were calculated. Re(550)=(nx - ny)×d Nz = Rth(550) / Re(550)=(nx - nz) / (nx - ny) Furthermore, in the equation of the ellipse (x 2 / a 2 )+(y 2 / b 2 ) = 1, let a be nx, b be ny, x and y be the refractive indices in the x direction and y direction at the angle θ direction on the ellipse, and from y = tanθ and the above nx and ny, solve the simultaneous equations to calculate the refractive index in the axis direction.

[0086] (2) Thickness Measured with an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0087] (3) Reflection light ripple The image display devices obtained in the examples and comparative examples were irradiated with LED light in the non-lighting state, and the reflected light was visually observed and evaluated according to the following criteria. ○ (Good): No undulation of the reflected light was observed. × (Bad): Undulation of the reflected light that was unacceptable in practical use was observed.

[0088] [Production Example 1: Preparation of the pressure-sensitive adhesive PSA constituting the pressure-sensitive adhesive layer] (Preparation of acrylic oligomer) First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas introduction tube, a mixture containing 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), 3.5 parts by mass of α-thioglycerol as a chain transfer agent, and 100 parts by mass of toluene as a polymerization solvent was stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture to prepare a reaction solution, and the reaction was carried out at 70°C for 2 hours and then at 80°C for 2 hours under a nitrogen atmosphere (polymerization reaction). Next, the reaction solution was heated at 130°C to volatilize and remove toluene, the chain transfer agent, and unreacted monomers. Thereby, an acrylic oligomer (solid form) was obtained. The weight average molecular weight of this acrylic oligomer was 5100.

[0089] (Preparation of prepolymer composition) In a flask, to a monomer mixture of 71 parts by mass of n-butyl acrylate (BA), 13 parts by mass of N-vinyl-2-pyrrolidone (NVP), 3 parts by mass of acryloylmorpholine (ACMO), and 13 parts by mass of 4-hydroxybutyl acrylate (4HBA), two types of first photopolymerization initiators (total 0.062 parts by mass) were added. Then, the mixture was irradiated with ultraviolet rays under a nitrogen atmosphere to polymerize a part of the monomer components in the mixture to obtain a prepolymer composition. The entanglement molecular weight of n-butyl acrylate (BA) was 15,000. As the first photopolymerization initiators, 0.031 parts by mass of "Omnirad184" (1-hydroxy-cyclohexyl-phenyl-ketone) manufactured by BASF and 0.031 parts by mass of "Omnirad651" (2,2-dimethoxy-2-phenylacetophenone) manufactured by BASF were used. The ultraviolet irradiation was continued until the viscosity of the composition reached about 20 Pa·s. This viscosity was the value measured by a B-type viscometer under the conditions of rotor No. 5, rotor rotation speed 10 rpm, and temperature 30°C. The obtained prepolymer composition is a partial polymer containing a photopolymer (photopolymerized polymer P1a) and monomer components (residual monomers) that have not undergone a polymerization reaction.

[0090] (Preparation of Adhesive Composition) Next, 100 parts by mass of the prepolymer composition, 3 parts by mass of the above acrylic oligomer, 0.6 parts by mass of a urethane acrylate oligomer (UAO) (product name "UN-350", manufactured by Negami Kogyo Co., Ltd.) as a second photopolymerizable polyfunctional compound, 0.4 parts by mass of a second photopolymerization initiator, 0.5 parts by mass of an antioxidant (product name "Irganox 1010", manufactured by BASF), 0.2 parts by mass of a rust inhibitor (product name "BT-120", 1,2,3-benzotriazole, manufactured by Johoku Chemical Industry Co., Ltd.), and 0.3 parts by mass of a silane coupling agent (product name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain an adhesive composition. The amount of the second photopolymerizable polyfunctional compound (crosslinking agent) per 100 parts by mass of the monomer components was 0.55 parts by mass. As the second photopolymerization initiator, "Omnirad819" (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) manufactured by BASF was used.

[0091] (Preparation of Base Adhesive Sheet) Next, an adhesive composition was applied onto the release-treated surface of a first release liner (product name: “Diafoil MRF”, thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. Next, the release-treated surface of a second release liner (product name: “Diafoil MRE”, thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was bonded onto the coating film on the first release liner. Next, the coating film between the release liners was irradiated with ultraviolet light from the second release liner side to photocure the coating film and form an adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light lamp (wavelength: 320 nm to 400 nm, manufactured by Toshiba Corporation) was used as the light source, the illuminance was set to 6.5 mW / cm 2 and the integrated light quantity of irradiation was set to 1500 mJ / cm 2 . In the ultraviolet irradiation step, in the coating film, a photopolymerization reaction proceeds in a reaction system containing the above-mentioned residual monomer, additional monomer, and second photopolymerizable polyfunctional compound (crosslinking agent), and a photopolymer P1b having a crosslinked structure is formed. Further, since the photopolymerization reaction proceeds around the photopolymer P1a, the photopolymer P1b is formed around the photopolymer P1a. The adhesive layer formed in this step contains such photopolymer P1a and photopolymer P1b as a base polymer P1. In the above manner, a base adhesive sheet with double-sided release liners (first release liner / base adhesive sheet (thickness: 100 μm) / second release liner) was prepared.

[0092] (Preparation of Post-Added Component Solution) 6.0 parts by mass of trimethylolpropane triacrylate (TMPTA) (product name: "Biscoat #295", manufactured by Osaka Organic Chemical Industry Co., Ltd.) as the first photopolymerizable polyfunctional compound, 1.2 parts by mass of ethoxylated bisphenol A diacrylate (BPAEODE) (product name: "ABE-300", manufactured by Shin-Nakamura Chemical Co., Ltd.) as another first photopolymerizable polyfunctional compound, 0.3 parts by mass of the third photoinitiator, 7.0 parts by mass of an ultraviolet absorber (product name: "Tinosorb S", manufactured by BASF), and 90.7 parts by mass of ethyl acetate as a solvent were mixed to prepare a post-addition component solution (components other than the solvent in the solution are post-addition components). As the third photoinitiator, "Omnirad 819" manufactured by BASF was used.

[0093] (Production of the optical adhesive sheet) First, after peeling off the second release liner from the above-mentioned base adhesive sheet with a release liner, the post-addition component solution was applied to the exposed surface of the base adhesive sheet thus exposed to a thickness of 20 μm (coating process). For the coating, a bar coater RDS No. 10 manufactured by R.D. SPECIALTIES was used. Next, it was dried in a dryer at 110 °C for 60 seconds. By the coating process and the drying process, the post-addition components (the first photopolymerizable polyfunctional compound, the third photoinitiator, the ultraviolet absorber) were infiltrated into the base adhesive sheet, and the solvent was vaporized. Due to the infiltration of the post-addition components into the base adhesive sheet, a photocurable optical adhesive sheet was formed. The addition amount of TMPTA per 100 parts by mass of the above-mentioned prepolymer composition was 6.0 parts by mass, the addition amount of BPAEODE was 1.2 parts by mass, the addition amount of the third photoinitiator (Omnirad 819) was 0.3 parts by mass, and the addition amount of the ultraviolet absorber (Tinosorb S) was 7.0 parts by mass. Next, the release-treated surface of a third release liner (product name: "Diafoil MRE", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was bonded to the adhesive sheet on the first release liner.

[0094] As described above, an adhesive sheet with a release liner (first release liner / adhesive sheet (thickness 100 μm) / third release liner) was produced. The adhesive sheet is a photocurable optical adhesive sheet containing a base polymer, a first photopolymerizable polyfunctional compound (TMPTA, BPAEODE), and a third photoinitiator. This optical adhesive sheet was used as the pressure-sensitive adhesive PSA.

[0095] [Production Example 2: Preparation of Adhesive A1 Constituting the Adhesive Layer] 25 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 10 parts of ε-caprolactone-modified 2-hydroxyethyl acrylate (trade name "PLACCEL FA1DDM", manufactured by Daicel Chemical Industries, Ltd.), 10 parts of lauryl acrylate (trade name "Light Acrylate L-A", manufactured by Kyoeisha Chemical Co., Ltd.), 20 parts of isostearyl acrylate (trade name "ISTA", manufactured by Osaka Organic Chemical Industry Co., Ltd.), 15 parts of 1,9-nonanediol diacrylate (trade name "Light Acrylate 1.9ND-A", manufactured by Kyoeisha Chemical Co., Ltd.), 15 parts of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), 1 part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 2 parts of diethylthiioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare Adhesive A1. The refractive index n AD of Adhesive A1 was 1.50, and the storage elastic modulus at 25°C was 7.0 MPa.

[0096] [Production Example 3: Preparation of Adhesive A2 Constituting the Adhesive Layer] 10 parts of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals Co., Ltd.), 4 parts of 2-acetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals Corporation), 60 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 11 parts of tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.), 1 part of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Corporation), 10 parts of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), 1 part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 1 part of diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare Adhesive A2. The refractive index n of Adhesive A2 AD was 1.52, and the storage modulus at 25°C was 1.3 GPa.

[0097] [Production Example 4: Preparation of Adhesive A3 Constituting the Adhesive Layer] 60 parts of Ogsool EA-F5710 (manufactured by Osaka Gas Chemical Co., Ltd.), 10 parts of Placcel FA1DDM (manufactured by Daicel Corporation), 20 parts of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.), 5 parts of ARFON UP-1190 (manufactured by Toagosei Co., Ltd.), 1 part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 2 parts of diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for 1 hour to prepare Adhesive A3. The refractive index n of Adhesive A3 AD was 1.56, and the storage modulus at 25°C was 2.5 GPa.

[0098] [Production Example 5: Preparation of Adhesive A4 Constituting the Adhesive Layer] (Preparation of Dispersant) 415 g (1 mol) of tristyrenated phenol and 1 g (0.018 mol) of potassium hydroxide were charged into an autoclave and mixed uniformly. While the reaction system was at 130°C, 352 g (8 mol) of ethylene oxide (EO) was dropped into the reaction system. After the dropping of ethylene oxide was completed, the pressure was maintained at 0.1 MPa at 130°C for 1 hour for aging to obtain an 8-mol adduct of EO to tristyrenated phenol. 767 g (1 mol) of the obtained 8-mol adduct of EO to tristyrenated phenol and 152 g (1.3 mol) of sodium monochloroacetate were put into a reactor and stirred to be uniform. Next, 52 g of sodium hydroxide was added under the condition that the reaction system was at 60°C, then the temperature was raised to 80°C and aged for 3 hours. After aging, it was cooled to 50°C, and 117 g (1.2 mol) of 98% sulfuric acid was dropped at the same temperature to obtain a white suspension solution. This white suspension solution was washed with distilled water, and the solvent was distilled off under reduced pressure to obtain a dispersant. (Preparation of Zirconia Dispersion) To 100 parts of a methanol dispersion of zirconium oxide (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-CM", average particle diameter (D50) based on dynamic light scattering method: 8 nm, zirconium oxide solid content concentration: 30%), 1.5 parts of the dispersant obtained above and 28.5 parts of m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added and mixed. Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain a zirconia dispersion which is a monomer dispersion of zirconium oxide. This zirconia dispersion contains zirconium oxide / dispersant / POB-A in a weight ratio of 50 / 2.5 / 47.5. (Preparation of Adhesive A4) 35 parts of zirconia dispersion, 40 parts of "POB-A", 10 parts of 4-hydroxybutyl acrylate, 10 parts of tripropylene glycol diacrylate (trade name "ARONIX M-220", manufactured by Toagosei Co., Ltd.), 1 part of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins B.V.), 2 parts of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), and 2 parts of diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50 °C for 1 hour to prepare Adhesive A4. The refractive index n of Adhesive A4 AD was 1.59, and the storage elastic modulus at 25 °C was 12.0 MPa.

[0099] [Production Example 6: Preparation of Adhesive A5 Constituting the Adhesive Layer] 55 parts of zirconia dispersion, 25 parts of "POB-A", 10 parts of 4-hydroxybutyl acrylate, 10 parts of "ARONIX M-220", 1 part of "Omnirad 819", 2 parts of "Omnirad 184", and 2 parts of "KAYACURE DETX-S" were stirred at 50 °C for 1 hour to prepare Adhesive A5. The refractive index n of Adhesive A5 AD was 1.61, and the storage elastic modulus at 25 °C was 11.7 MPa.

[0100] [Production Example 7: Preparation of Pressure-Sensitive Adhesive PS1 Constituting the Adhesive Layer] A monomer mixture containing 91 parts of butyl acrylate, 6 parts of acryloylmorpholine, 2.7 parts of acrylic acid, and 0.3 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate per 100 parts of this monomer mixture, and nitrogen gas was introduced while gently stirring for nitrogen substitution. Then, the liquid temperature in the flask was maintained at around 55 °C, and a polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer P1 having a weight average molecular weight (Mw) of 2.7 million. To 100 parts of the solid content of the acrylic polymer P1 solution, 0.1 part of an isocyanate-based crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 part of a peroxide crosslinking agent (benzoyl peroxide: manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 part of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were added to obtain an adhesive PS1. The polymer concentration of the adhesive PS1 was adjusted to 8%. The refractive index n AD1 was 1.47, and the storage elastic modulus at 25 °C was 0.39 MPa.

[0101] [Production Example 8: Preparation of Adhesive PS2 Constituting the Adhesive Layer] A monomer mixture containing 30 parts of butyl acrylate, 69 parts of m-phenoxybenzyl acrylate, and 1 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate per 100 parts of this monomer mixture. After introducing nitrogen gas while gently stirring for nitrogen substitution, the liquid temperature in the flask was maintained at around 60 °C, and a polymerization reaction was carried out for 6 hours to prepare a solution of an acrylic polymer P2 having a weight average molecular weight (Mw) of 650,000. To 100 parts of the solid content of the acrylic polymer P2 solution, 0.1 part of an isocyanate-based crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Mitsui Chemicals, Inc., trade name "D101E") and 0.3 part of a peroxide crosslinking agent (benzoyl peroxide: manufactured by NOF Corporation, trade name "Niper BMT") were added to obtain an adhesive PS2. The refractive index n AD1 was 1.56, and the storage elastic modulus at 25 °C was 0.30 MPa.

[0102] [Production Example 9: Preparation of Adhesive PS3 Constituting the Adhesive Layer] A solution of an acrylic polymer P3 with a weight average molecular weight (Mw) of 650,000 was prepared in the same manner as in Production Example 8, except that a monomer mixture containing 19 parts of butyl acrylate, 80 parts of m-phenoxybenzyl acrylate, and 1 part of 4-hydroxybutyl acrylate was used. An adhesive PS3 was obtained in the same manner as in Production Example 8, except that the acrylic polymer P3 was used. The refractive index n AD1 of the adhesive PS3 was 1.58, and the storage elastic modulus at 25 °C was 0.45 MPa.

[0103] [Example 1] 1. Preparation of a polarizing plate 1-1. Preparation of a polarizer An amorphous isophthalic copolyethylene terephthalate film (thickness: 100 μm) that is long and has a Tg of about 75 °C was used as a thermoplastic resin substrate, and one side of the resin substrate was subjected to a corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") in a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The above PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60 °C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (lengthwise direction) in an oven at 130 °C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilizing 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 (insolubilizing treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 30 °C (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment). Next, it was immersed in a crosslinking bath at a liquid temperature of 40 °C (an aqueous boric acid solution obtained by adding 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 70 °C (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight), uniaxial stretching was performed in the longitudinal direction (length direction) between rolls with different peripheral speeds so that the total draw ratio became 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a cleaning bath at a liquid temperature of 20 °C (an aqueous solution obtained by adding 4 parts by weight of potassium iodide to 100 parts by weight of water) (cleaning treatment). 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 having a thickness of about 5 μm was formed on the resin substrate, and a long polarizing plate having a resin substrate / polarizer structure was obtained. The single transmittance Ts of the polarizer was 43.3%. The polarizer had an absorption axis in the long direction. Hereinafter, the absorption axis direction (long direction) is referred to as the "0° direction", and the transmission axis direction (width direction) is referred to as the "90° direction".

[0104] 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-based 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, and a triacetyl cellulose (TAC) film (thickness: 25 μm) was bonded to the peeled surface via an ultraviolet curable adhesive. In this way, a polarizing plate having a structure of HC layer / COP film (protective layer) / polarizer / TAC film (protective layer) was obtained.

[0105] 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. To this solution, a surfactant (manufactured by BYK Chemie, "BYK-360") and a photopolymerization initiator (manufactured by IGM Resins, "Omnirad907") were added to prepare a liquid crystal composition solution. The addition amounts of the surfactant and the polymerization initiator were 0.01 part by weight and 3 parts by weight, respectively, based on 100 parts by weight of the photopolymerizable liquid crystal compound. As a substrate, a biaxially stretched norbornene-based film (Zeonor film manufactured by Zeon Corporation, thickness 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition was coated on this substrate with a bar coater so that Re(550) became 240 nm, and heated at 100 °C for 3 minutes to align the liquid crystal. After cooling to room temperature, under a nitrogen atmosphere, ultraviolet rays with an integrated light amount of 400 mJ / cm 2 were irradiated to perform photocuring, and a long laminated body having a structure of a substrate / First liquid crystal alignment cured layer was obtained. The First liquid crystal alignment cured layer was homogeneously aligned, and its thickness was 2.0 μm. The direction of the slow axis of the First liquid crystal alignment cured layer was the 75° direction. A long laminated body of a substrate / Second liquid crystal alignment cured layer (homogeneous alignment, thickness 1.0 μm, Re(550) = 120 nm) was obtained in the same manner as above except that the coating thickness was changed. The direction of the slow axis of the Second liquid crystal alignment cured layer was the 15° direction.

Chemical formula

[0106] 3. Fabrication of the optical laminate After laminating the first liquid crystal alignment cured layer on the TAC film surface of the polarizing plate via the adhesive A2 (thickness: 1 μm) of Production Example 3, the substrate was peeled off. Next, the second liquid crystal alignment cured layer was laminated on the surface of the first liquid crystal alignment cured layer via the adhesive A3 (thickness: 1 μm) of Production Example 4, and the substrate was peeled off to obtain a long optical laminate having a structure of polarizing plate / first liquid crystal alignment cured layer / adhesive layer / second liquid crystal alignment cured layer. The lamination and peeling were performed by a roll-to-roll process. The average refractive index of each of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer was 1.59. The second liquid crystal alignment cured layer side of this optical laminate was laminated on an acrylic resin film (thickness: 40 μm) via a normal adhesive. On the other hand, the cover glass and the optical film on the viewing side of a commercially available organic EL display device (manufactured by Samsung Electronics Co., Ltd., trade name "Galaxy (registered trademark) A41") were removed, the removal surface was cleaned, and an organic EL panel was obtained. On one surface of the cover glass removed from the organic EL display device, the polarizing plate side of the laminate of the optical laminate / acrylic resin film obtained above was laminated via the pressure-sensitive adhesive PSA (thickness: 100 μm) of Production Example 1 using a vacuum laminator. The conditions of the vacuum lamination were as follows: pressure bonding at 0.5 MPa and 25 °C (standby time: 5 seconds) in a vacuum of 100 Pa. In this way, the optical laminate of this example having a structure of front panel (cover glass) / pressure-sensitive adhesive layer / polarizing plate / first liquid crystal alignment cured layer / adhesive layer / second liquid crystal alignment cured layer was obtained. In the obtained optical laminate, the refractive index n LC1 of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer was 1.65, and the refractive index n LC2 of the second liquid crystal alignment cured layer was 1.54. Furthermore, the refractive index n AD of the adhesive layer was 1.56, and as a result, the appearance parameter was 0.008.

[0107] 4. Fabrication of Image Display Device The optical laminate obtained above was disposed on the cleaned surface of the organic EL panel to obtain an image display device. The obtained image display device was subjected to the above "reflection light undulation" evaluation. The results are shown in Table 1.

[0108] [Examples 2 to 5 and Comparative Examples 1 to 3] An optical laminate and an image display device were obtained in the same manner as in Example 1, except that the structure of the subsequent layer was changed as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0109] [Example 6] 1. Production of a polarizing plate A polarizing plate was produced in the same manner as in Example 1.

[0110] 2. Production of a retardation layer 2-1. Production of the first liquid crystal alignment cured layer Using the same photopolymerizable liquid crystal compound as in Example 1, a long laminate having a structure of substrate / first liquid crystal alignment cured layer (Re(550)=144 nm) was obtained in the same manner as in Example 1. The first liquid crystal alignment cured layer was in a homogeneous alignment, and its thickness was 1.2 μm. The slow axis direction of the first liquid crystal alignment cured layer was in the 45° direction. 2-2. Production of the second liquid crystal alignment cured layer 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (n = 0.35, shown as a block polymer for convenience), 80 parts by weight of a polymerizable liquid crystal showing a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator ("Irgacure 907" manufactured by BASF) were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating solution. Then, the coating solution was applied to a PET substrate subjected to vertical alignment treatment with a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. The liquid crystal layer was irradiated with ultraviolet rays to cure the liquid crystal layer, thereby obtaining a long laminate having a structure of substrate / second liquid crystal alignment cured layer (positive C plate, thickness 1.0 μm).

Chemical formula

[0111] 3. Production of an optical laminate and an image display device Except for using the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer obtained above and using the adhesive A2 (thickness: 1 μm) of Production Example 3, a long optical laminate having a configuration of polarizing plate / first liquid crystal alignment cured layer / adhesive layer / second liquid crystal alignment cured layer was obtained in the same manner as in Example 1. In the obtained optical laminate, the refractive index n LC1 of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer was 1.59, and the refractive index n LC2 of the second liquid crystal alignment cured layer was 1.53. Furthermore, the refractive index n AD of the adhesive layer was 1.52, and as a result, the appearance parameter was 0.005. An image display device was obtained in the same manner as in Example 1 except for using this optical laminate. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0112] [Examples 7 to 11 and Comparative Examples 4 to 5] An optical laminate and an image display device were obtained in the same manner as in Example 4 except that the configuration of the adhesive layer was changed as shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0113] [Example 12] 1. Production of polarizing plate A polarizing plate was produced in the same manner as in Example 1.

[0114] 2. Production of retardation layer 2-1. Production of the first liquid crystal alignment cured layer Using the same photopolymerizable liquid crystal compound as in Example 1, a long laminate having a configuration of substrate / first liquid crystal alignment cured layer (Re(550) = 120 nm) was obtained in the same manner as in Example 1. The first liquid crystal alignment cured layer was homogeneously aligned, and its thickness was 1.0 μm. The slow axis direction of the first liquid crystal alignment cured layer was the 90° direction. 2-2. Production of the second liquid crystal alignment cured layer In the same manner as in Example 4, a long laminate having a configuration of substrate / second liquid crystal alignment cured layer (positive C plate) was obtained.

[0115] 3. Production of optical laminate An elongated optical laminate having a structure of polarizing plate / 1st liquid crystal alignment cured layer / adhesive layer / 2nd liquid crystal alignment cured layer was obtained in the same manner as in Example 1, except that the 1st liquid crystal alignment cured layer and the 2nd liquid crystal alignment cured layer obtained above were used, and the adhesive A4 (thickness: 1 μm) of Production Example 5 was used. The 2nd liquid crystal alignment cured layer side of this optical laminate was bonded to an acrylic resin film (thickness: 40 μm) via a normal adhesive. On the other hand, the cover glass and the optical film on the viewing side of a commercially available liquid crystal display device (manufactured by Apple Inc., trade name "iPad (registered trademark)", IPS mode) were removed, the removal surface was cleaned, and a liquid crystal panel was obtained. The polarizing plate side of the laminate of the optical laminate / acrylic resin film obtained above was bonded to one surface of the cover glass removed (taken out) from the liquid crystal display device by vacuum lamination in the same manner as in Example 1. In this way, the optical laminate of this Example having a structure of front panel (cover glass) / adhesive layer / polarizing plate / 1st liquid crystal alignment cured layer / adhesive layer / 2nd liquid crystal alignment cured layer was obtained. In the obtained optical laminate, the refractive index n LC1 of the 1st liquid crystal alignment cured layer in the transmission axis direction of the polarizer LC2 was 1.65, and the refractive index n AD of the 2nd liquid crystal alignment cured layer was 1.53. Furthermore, the refractive index n

[0116] 4. Fabrication of Image Display Device The optical laminate obtained above was placed on the cleaned surface of the above liquid crystal panel to obtain an image display device. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0117] [Examples 13 to 14 and Comparative Examples 6 to 10] An optical laminate and an image display device were obtained in the same manner as in Example 12, except that the configuration of the adhesive layer was changed as shown in Table 2. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0118] [Example 15] An optical laminate was produced in the same manner as in Example 12, except that the order of arrangement of the first and second liquid crystal alignment cured layers was reversed, the slow axis direction of the second liquid crystal alignment cured layer was set to the 0° direction, and the adhesive A1 (thickness 1 μm) of Production Example 2 was used. In the obtained optical laminate, the refractive index n LC1 of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer was 1.53, and the refractive index n LC2 of the second liquid crystal alignment cured layer was 1.53. Furthermore, the refractive index n AD of the adhesive layer was 1.50, and as a result, the appearance parameter was 0.002. An image display device was obtained in the same manner as in Example 12, except that this optical laminate was used. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0119] [Examples 16 to 21 and Comparative Example 11] An optical laminate and an image display device were obtained in the same manner as in Example 15, except that the configuration of the adhesive layer was changed as shown in Table 2. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 2.

[0120]

Table 1

[0121]

Table 2

[0122] In Tables 1 and 2, for example, "Ex. 1" means Example 1, and "Comp. 1" means Comparative Example 1. Also, "Posi A" means a positive A plate, and "Posi C" means a positive C plate.

Industrial Applicability

[0123] The optical laminate according to the embodiment of the present invention can be suitably used in an image display device (typically, a liquid crystal display device, an organic EL display device).

Explanation of Signs

[0124] 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 25 Adhesive layer 40 Adhesive layer 50 Front panel 100 Optical laminate

Claims

Claim 1 comprising a front panel, an adhesive layer, a polarizing plate including a polarizer, and a retardation layer, in this order; the retardation layer including, in order from the polarizing plate side, a first liquid crystal alignment cured layer and a second liquid crystal alignment cured layer laminated to the first liquid crystal alignment cured layer via an adhesive layer; The refractive index n in the transmission axis direction of the polarizer of the first liquid crystal alignment cured layer ＬＣ１ , the refractive index n in the transmission axis direction of the polarizer of the second liquid crystal alignment cured layer ＬＣ２ , and the refractive index n in the transmission axis direction of the polarizer of the adhesive layer ＡＤ satisfy the following formula (1), an optical laminate: (n ＬＣ１ - n ＡＤ ) ２ +(n ＬＣ２ - n ＡＤ ) ２ < 0.009...(1). Claim 2 The said n ＬＣ１ The optical laminate according to claim 1, wherein n is greater than 1.

60. Claim 3 The optical laminate according to claim 1, wherein an angle formed by a slow axis of the first liquid crystal alignment cured layer and a transmission axis of the polarizer is 40° or less. Claim 4 The optical laminate according to claim 1, wherein a storage elastic modulus of the adhesive layer is 3 GPa or less. Claim 5 The optical laminate according to claim 1, wherein a storage elastic modulus of the adhesive layer is 10 MPa or less. Claim 6 The optical laminate according to claim 1, wherein the front panel is made of an antireflection glass. Claim 7 An image display device including the optical laminate according to any one of claims 1 to 6.

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