Optical laminate and display device using the same

Abstract

[Problem] To provide an optical laminate that uses a biaxially extended polyethylene terephthalate film as a substrate, has bending resistance, and suppresses rainbow unevenness, and an image display device using the same. [Solution] An optical laminate for use in an image display device comprises: a light-transmitting substrate composed of a biaxially extended polyethylene terephthalate film and having in-plane birefringence, and an optical functional layer disposed on one side of the light-transmitting substrate. The total haze of the optical laminate is 5% or more, and the in-plane retardation Re of the light-transmitting substrate, as defined by formula (1): Re=(nx-ny)×d, is 2,000 nm or more and 7,500 nm or less. Here, nx: refractive index in the slow axis direction, ny: refractive index in the fast axis direction, and d: thickness of the light-transmitting substrate.

Description

[Technical Field]

[0001] The present invention relates to an optical laminate disposed on the front surface side of an image display panel and a display device using the same. [Previous Technology]

[0002] Conventionally, triacetyl cellulose (TAC) films, which have no in-plane phase difference and excellent visual recognition, have been used as substrates for optical films disposed on the surface of image display devices. However, TAC films have the problem of warping of image display devices due to the absorption of moisture from the air. Therefore, polyethylene terephthalate (PET) films, which have low moisture absorption, have attracted attention, and in recent years, ultra-high retardation (ultra-high Re) PET films have been used (for example, see Patent Documents 1 and 2).

[0003] When visually recognizing an image display device through a polarizing plate such as polarized sunglasses, the image display device appears dark to the eye because the vibration surface of the light emitted from the image display device is orthogonal to the transmission axis of the polarizing plate, resulting in a phenomenon known as "blackout." As a solution to this blackout, Patent Document 3 describes, for example, setting the angle between the slow axis of the optical laminate and the absorption axis of the polarizer used in the liquid crystal display device to 45° ± 15°. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent No. 5304939 [Patent Document 2] Japanese Patent No. 6256385 [Patent Document 3] Japanese Patent No. 6044118 [Summary of the Invention]

[0005] [The problem the invention aims to solve]

[0006] When using ultra-high RePET film as a substrate, the occurrence of light blocking during the use of polarized sunglasses can be suppressed by the slow axis angle, but there is a problem of poor bending resistance due to the uniaxial stretching of the film. On the other hand, if a biaxial stretching PET film is used, the bending resistance is greatly improved, and the occurrence of light blocking can be suppressed regardless of the slow axis angle, but there is a problem of obvious rainbow unevenness due to in-plane phase difference.

[0007] Therefore, the object of the present invention is to provide an optical laminate that uses a biaxially stretched polyethylene terephthalate film as a substrate, has bending resistance, and suppresses iris spots, and an image display device using the same. [Means for solving the problem]

[0008] The optical laminate of the present invention comprises a light-transmitting substrate having birefringence in the plane, which is composed of a biaxially extended polyethylene terephthalate film, and an optical functional layer disposed on one side of the light-transmitting substrate. The total haze of the optical laminate is 5% or more, and the in-plane retardation Re of the light-transmitting substrate as defined in the following formula (1) is 2,000 nm or more and 7,500 nm or less. Re=(nx-ny)×d (1) Here, nx: refractive index in the slow axis direction; ny: refractive index in the fast axis direction; d: thickness of the light-transmitting substrate.

[0009] The image display device of the present invention includes an image display panel and the aforementioned optical laminate. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an optical laminate having flexural strength and suppressing iris spots by using a biaxially extended polyethylene terephthalate film as a substrate, and an image display device using the same.

Implementation Method

[0012] [Form for implementing the invention]

[0013] Figure 1 is a schematic cross-sectional view showing an example of an optical laminate in an embodiment.

[0014] The optical laminate 10 includes a light-transmitting substrate 1 and an anti-glare layer (AG layer) 2 laminated on one side of the light-transmitting substrate 1. The optical laminate 10 is an optical thin film (also called "AG film") that suppresses glare from external light by scattering incident light through the fine unevenness of the surface of the anti-glare layer 2 and the particles inside it. In the optical laminate 10 shown in FIG1, the anti-glare layer 2 is equivalent to an optical functional layer.

[0015] Figure 2 is a schematic cross-sectional view showing another example of an optical thin film in an embodiment.

[0016] The optical stack 20 comprises a light-transmitting substrate 1, an anti-glare layer 2 deposited on one side of the light-transmitting substrate 1, and a low-refractive-index layer (LR layer) 3 deposited on the surface of the anti-glare layer 2, having a lower refractive index than the anti-glare layer 2. The optical stack 20 is an optical thin film (also called "AGLR thin film") that suppresses glare and reflection of external light by utilizing the fine irregularities of the outermost surface and the scattering and optical interference of incident light caused by particles inside. In the optical stack 20 shown in Figure 2, the two layers, the anti-glare layer 2 and the low-refractive-index layer 3, are equivalent to optical functional layers.

[0017] The following describes the details of each layer.

[0018] The light-transmitting substrate is a transparent thin film that serves as the base for an optical laminate. For the light-transmitting substrate, a biaxially extended polyethylene terephthalate film with birefringence is used, and the in-plane retardation Re, as defined in equation (1) below, is 2,000 nm to 7,500 nm. Re = (nx - ny) × d (1) Here, nx: refractive index in the slow axis direction (direction with high refractive index) of the light-transmitting substrate; ny: refractive index in the fast axis direction of the light-transmitting substrate; d: thickness of the light-transmitting substrate.

[0019] When the in-plane retardation Re of the light-transmitting substrate is less than 2,000 nm, the thinner the light-transmitting substrate, the lower the processability or the insufficient surface hardness when forming an optical laminate, which is therefore less desirable. When the in-plane retardation Re of the light-transmitting substrate exceeds 7,500 nm, the thicker the light-transmitting substrate, the higher the raw material cost or the higher the total thickness when forming an optical laminate, which is also less desirable.

[0020] As a light-transmitting substrate, it is preferable to use one that meets the following condition (2): (nx-ny)<0.06 (2)

[0021] When the value of nx-ny is above 0.06, the mechanical properties, namely the resistance to cracks and fractures, are reduced due to excessive stretching, and therefore are not good.

[0022] Furthermore, as a light-transmitting substrate, it is preferable to use a light-transmitting substrate with a thickness direction retardation Rth' of 9,500 nm or more and 18,000 nm or less, as shown in the following formula (3). Rth'=(nx-nz)×d (3) Here, nz: refractive index in the thickness direction

[0023] When the thickness retardation Rth' of the light-transmitting substrate is less than 9,500 nm, the thickness of the light-transmitting substrate becomes thinner, which may result in insufficient mechanical strength when forming an optical laminate, and is therefore less desirable. Furthermore, when the thickness retardation Rth' of the light-transmitting substrate exceeds 18,000 nm, the thickness of the light-transmitting substrate becomes larger, which becomes unfavorable for the thinning of the optical laminate, and is therefore less desirable.

[0024] Furthermore, as a light-transmitting substrate, it is preferable to use one with a ratio Nz' of 1.5 or more and 5.5 or less, as shown in the following formula (4). Nz'=Rth' / Re (4)

[0025] When Nz' is within the above range, the birefringence and thickness of the light-transmitting substrate are within an appropriate range, which can take into account both the mechanical strength and iris suppression when constructing an optical laminate.

[0026] The thickness of the light-transmitting substrate 1 is not particularly limited, but is preferably 35 to 200 μm, more preferably 35 to 125 μm. For the surface of the light-transmitting substrate 1, a surface modification treatment may be performed to improve adhesion to other layers in the stack. Examples of surface modification treatments include: alkali treatment, corona treatment, plasma treatment, sputtering treatment, coating with surfactants, silane coupling agents, etc., and Si evaporation.

[0027] The anti-glare layer 2 is a functional layer that forms the outermost surface of the optical laminate 10 with a finely textured surface.

[0028] The anti-glare layer 2 is formed by coating a coating liquid containing an active energy line hardening compound, organic particles and / or inorganic particles (fillers) onto a light-transmitting substrate 1, thereby hardening the coating film.

[0029] For active energy line hardening compounds, for example, monofunctional, difunctional, or trifunctional (meth)acrylate monomers can be used. Furthermore, in this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryl" is a general term for both acrylonitrile and methacryl.

[0030] Examples of monofunctional (meth)acrylate compounds include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tributyl (meth)acrylate, glycidyl (meth)acrylate, acrylonitrile, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isocyanate (meth)acrylate. Esters, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, meth phosphate, ethylene oxide modified meth phosphate, phenoxy (meth)acrylate, ethylene oxide modified phenoxy (meth)acrylate, propylene oxide modified (meth)acrylate Phenoxy acrylate, nonylphenol (meth) acrylate, ethylene oxide modified nonylphenol (meth) acrylate, propylene oxide modified nonylphenol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, 2-(meth)acrylic acid ethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl acrylate, 2-(meth)acrylic acid ethyl phthalate, 2-hydroxy-3-phenoxypropyl phthalate (Meth)propenyloxypropyl ester, 2-(meth)propenyloxypropyl hexahydrophthalic acid, 2-(meth)propenyloxypropyl tetrahydrophthalic acid, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, and adamantane derivative mono(meth)acrylates such as adamantane acrylate derived from 2-adamantane or adamantanediol.

[0031] Examples of difunctional (meth)acrylates include: ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, hydroxytrimethylacetic acid neopentyl glycol di(meth)acrylate, and other di(meth)acrylates.

[0032] Examples of (meth)acrylates with three or more functions include: trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, triisocyanate tri-hydroxyethyl ester tri(meth)acrylate, glycerol tri(meth)acrylate, neopentyl tetraethanolamine tri(meth)acrylate, dinepentyl tetraethanolamine tri(meth)acrylate, di(trimethylolpropane)tri(meth)acrylate, and other trifunctional (meth)acrylates. Acid ester compounds, neopentyl tert-tetra(meth)acrylate, di(trimethylolpropane)tetra(meth)acrylate, dinepentyl tert-tetra(meth)acrylate, dinepentyl tert-pent(meth)acrylate, di(trimethylolpropane)pent(meth)acrylate, dinepentyl tert-hexa(meth)acrylate, di(trimethylolpropane)hexa(meth)acrylate and other polyfunctional (meth)acrylate compounds with 3 or more functions, and polyfunctional (meth)acrylate compounds formed by substituting a portion of such (meth)acrylates with alkyl groups or ε-caprolactones, etc.

[0033] Furthermore, as a multifunctional monomer, urethane (meth)acrylate can also be used. Examples of urethane (meth)acrylates include those obtained by reacting a hydroxyl-containing (meth)acrylate monomer with a product obtained by reacting an isocyanate monomer or a prepolymer with a polyester polyol.

[0034] Examples of urethane (meth)acrylates include: neopentyl tert-acrylate hexamethylene diisocyanate urethane prepolymer, dinepentyl tert-acrylate hexamethylene diisocyanate urethane prepolymer, neopentyl tert-acrylate toluene diisocyanate urethane prepolymer, dinepentyl tert-acrylate toluene diisocyanate urethane prepolymer, neopentyl tert-acrylate isoflavone diisocyanate urethane prepolymer, dinepentyl tert-acrylate isoflavone diisocyanate urethane prepolymer, etc.

[0035] One of the above-mentioned multifunctional monomers may be used, or two or more may be used in combination. Furthermore, the above-mentioned multifunctional monomers may be monomers in the coating liquid, or a portion of them may be oligomers formed by polymerization.

[0036] The organic microparticles are mainly materials that form fine irregularities on the surface of the anti-glare layer 2, giving it the function of diffusing external light. Regarding the organic microparticles, resin particles composed of light-transmitting resin materials such as acrylic resin, polystyrene resin, styrene-(meth)acrylate copolymer, polyethylene resin, epoxy resin, silicone resin, polyvinylidene fluoride, and polyvinyl fluoride resin can be used. To adjust the refractive index and the dispersion of the resin particles, two or more resin particles with different materials (refractive indices) can also be mixed and used. The average particle size of the organic microparticles is preferably 0.5 to 10 μm.

[0037] The inorganic microparticles added to the composition for forming the anti-glare layer are preferably nanoparticles with an average particle size of 10 to 200 nm.

[0038] The inorganic microparticles are mainly materials used to adjust the precipitation and aggregation of organic microparticles in the anti-glare layer 2. Regarding the inorganic microparticles, silica microparticles, metal oxide microparticles, and various mineral microparticles can be used. Regarding silica microparticles, examples include colloidal silica and silica microparticles surface-modified with reactive functional groups such as (meth)acrylic acid. Regarding metal oxide microparticles, examples include aluminum oxide, zinc oxide, tin oxide, antimony oxide, indium oxide, titanium dioxide, and zirconium oxide. Regarding mineral microparticles, examples include mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, bentonite, aluminum bentonite, soapstone, lithium bentonite, magnesia, chloroform, sodium silicate, illite, silicospore, layered titanate, bentonite, and synthetic bentonite. The mineral microparticles can be either natural or synthetic (including substitutes and derivatives), or a mixture of both. Layered organoclay is preferred among the mineral microparticles. Layered organoclay refers to bentonite formed by introducing organonium ions into the interlayer of bentonite. There are no restrictions on the organonium ions as long as they can utilize the cation exchange capacity of bentonite for organometallization. When using layered organoclay minerals as mineral microparticles, the aforementioned synthetic bentonite is suitable. Synthetic bentonite has the functions of increasing the viscosity of the anti-glare layer composition, inhibiting the precipitation of resin particles and inorganic microparticles, and adjusting the surface irregularity of the optical functional layer.

[0039] In order to harden the composition for forming the anti-glare layer by ultraviolet irradiation, a polymerization initiator may also be added. Regarding the polymerization initiator, polymerization initiators that generate free radicals by ultraviolet irradiation can be used. Regarding the polymerization initiator, free radical polymerization initiators such as acetophenone-based, diphenyl ketone-based, 9-oxosulfur-based, benzoin, benzoin methyl ether, and acetylphosphine oxide can be used. Examples of polymerization initiators that can be used include: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-phenylacetophenone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorodiphenyl ketone, p-methoxydiphenyl ketone, Michler's ketone, acetophenone, and 2-chloro9-oxosulfur. Of these, one can be used alone, or two or more can be used in combination.

[0040] Furthermore, antifouling agents, leveling agents, oil-repellent agents, water-repellent agents, and anti-fingerprint adhesion agents may also be added to the composition for forming the anti-glare layer as components to enhance antifouling properties. Fluorinated compounds and silica compounds are suitable additives for use as such additives. In addition, various additives such as antistatic agents, defoamers, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers may also be added as needed.

[0041] Furthermore, solvents may be added to the composition for forming the anti-glare layer as needed. Regarding solvents, one or more of the following can be used: methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropanol, isobutanol, etc.; acetone, methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone, etc.; diacetone alcohol, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; diols such as ethylene glycol, propylene glycol, hexanediol, etc.; diol ethers such as ethyl celecoxib, butyl celecoxib, ethyl carbitol, butyl carbitol, diethyl celecoxib, diethyl carbitol, propylene glycol monomethyl ether, etc.; esters such as methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, amyl acetate, etc.; ethers such as dimethyl ether, diethyl ether, etc.; N-methylpyrrolidone, dimethylformamide, etc.

[0042] The low refractive index layer 3 is a functional layer that has a lower refractive index than the lower anti-glare layer 2 and suppresses reflection through optical interference.

[0043] The low refractive index layer 3 can be formed by coating a composition containing an active energy line hardening compound onto the surface of the anti-glare layer 2 and hardening the coating. The low refractive index layer 3 may also contain low refractive index particles to adjust the refractive index.

[0044] Regarding low-refractive-index microparticles, suitable materials include, for example, LiF, MgF, 3NaF, AlF or AlF (all with a refractive index of 1.4), or Na 3AlF 6 (cryolite, refractive index 1.33), as well as silica microparticles with internal pores. Silica microparticles with internal pores allow the pore portion to have a refractive index similar to air (approximately 1), thus benefiting the reduction of the refractive index of the low-refractive-index layer 3. Specifically, porous silica particles and shell-structured silica particles can be used. Furthermore, low-refractive-index microparticles are not necessarily required; if the refractive index of the hardened active energy line hardening compound is lower than the refractive index of the anti-glare layer 2, the low-refractive-index microparticles can be omitted.

[0045] For active energy line hardening compounds, the polymerizable compounds described in the anti-glare layer section can be used. Furthermore, the aforementioned polymerization initiator and solvent can also be appropriately added to the composition for forming a low refractive index layer.

[0046] Antifouling agents, leveling agents, oil-repellent agents, water-repellent agents, and anti-fingerprint adhesion agents may also be added to the composition for forming the low refractive index layer as components to enhance antifouling properties. Fluorinated compounds and silica compounds are suitable additives for use. In addition, various additives such as antistatic agents, defoamers, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, and photosensitizers may be added as needed.

[0047] Between the light-transmitting substrate 1 and the anti-glare layer 2, one or more layers of hard coating, high refractive index layer, medium refractive index layer, antistatic layer, electromagnetic wave blocking layer, infrared absorption layer, ultraviolet absorption layer, color correction layer and other functional layers may also be deposited.

[0048] The coating method for the composition for forming the anti-glare layer and the composition for forming the low refractive index layer described above is not particularly limited, and coating can be performed using, for example, a spin coater, a roller coater, a reverse roller coater, a gravure coater, a micro-gravure coater, a knife coater, a bar coater, a wire bar coater, a die coater, a dip coater, a spray coater, a coater, etc.

[0049] Here, the details of the surface irregularity of the optical laminate of this embodiment will be explained.

[0050] The total haze of the optical laminate of the present invention is preferably 5% or more. When the total haze is 5% or more, external light can be sufficiently diffused, suppressing iris spots originating from the light-transmitting substrate. The total haze is more preferably 22.0% to 71.6%. When the total haze is within the more preferred range, it is advantageous for suppressing iris spots.

[0051] The surface haze of the optical laminate of the present invention is preferably 3% or more. When the surface haze is 3% or more, external light can be sufficiently diffused, suppressing iris spots originating from the light-transmitting substrate. The surface haze is more preferably 12.0% to 68.6%. When the surface haze is within the more preferred range, it is advantageous for suppressing iris spots.

[0052] The internal haze of the optical laminate of the present invention is preferably 2% or more. When the internal haze is 2% or more, external light can be sufficiently diffused, suppressing iris spots originating from the light-transmitting substrate. The internal haze is more preferably 3.1% to 55.6%. When the internal haze is within the preferred range, it is advantageous for suppressing iris spots.

[0053] Furthermore, the total haze, surface haze and internal haze mentioned above are values ​​obtained by measurement according to JIS K7136.

[0054] In the optical laminate of the present invention, the value of Δn × total haze is preferably 0.2 or more (wherein Δn = nx - ny). If the value of Δn × total haze is 0.2 or more, it is advantageous in terms of suppressing rainbow spots in the optical laminate. From the viewpoint of suppressing rainbow spots in the optical laminate, within the above range, the value of Δn × total haze is more preferably 0.39 to 2.55, and the value of Δn × total haze is further preferably 0.78 to 2.55.

[0055] In the optical laminate of the present invention, the Re×total haze value is preferably 10,000 or more. When the Re×total haze value is 10,000 or more, it is advantageous in terms of rainbow spot suppression of the optical laminate. From the viewpoint of rainbow spot suppression of the optical laminate, within the above range, the Re×total haze value is more preferably 19,725 to 301,028, and the Re×total haze value is even more preferably 58,679 to 301,028.

[0056] Furthermore, in the optical laminate of the present invention, the value of Δn × surface haze is preferably 0.12 or higher. When the value of Δn × surface haze is 0.12 or higher, it is advantageous for suppressing rainbow spots in the optical laminate. From the viewpoint of suppressing rainbow spots in the optical laminate, within the above-mentioned range, the value of Δn × surface haze is more preferably 0.15 to 2.44, and the value of Δn × surface haze is even more preferably 0.37 to 2.44.

[0057] Furthermore, in the optical laminate of the present invention, the Re× surface haze value is preferably 6,000 or higher. A Re× surface haze value of 6,000 or higher is advantageous for suppressing iris spots in the optical laminate. From the viewpoint of suppressing iris spots in the optical laminate, within the above-mentioned range, the Re× surface haze value is more preferably 9,544 to 182,972, and even more preferably 32,007 to 182,972.

[0058] Furthermore, in the optical laminate of the present invention, the value of Δn × internal haze is preferably 0.08 or higher. When the value of Δn × internal haze is 0.08 or higher, it is advantageous in terms of suppressing rainbow spots in the optical laminate. From the viewpoint of suppressing rainbow spots in the optical laminate, within the above range, the value of Δn × internal haze is more preferably 0.11 to 1.98.

[0059] Furthermore, in the optical laminate of the present invention, the Re× internal haze value is preferably 4,000 or higher. When the Re× internal haze value is 4,000 or higher, it is advantageous in terms of rainbow spot suppression of the optical laminate. From the viewpoint of rainbow spot suppression of the optical laminate, within the above range, the Re× internal haze value is more preferably 8,268 to 207,991.

[0060] In the optical laminate of the present invention, it is preferable that the arithmetic mean roughness Ra of the surface of the optical functional layer is 0.04 μm or more, and the average tilt angle θa of the unevenness on the surface of the optical functional layer is 0.30° or more. When the arithmetic mean roughness Ra and the average tilt angle θa are within the above ranges, external light can be sufficiently diffused, and iris spots originating from the light-transmitting substrate can be suppressed. From the viewpoint of iris spot suppression of the optical laminate, within the above ranges, the arithmetic mean roughness Ra is preferably 0.070 to 0.391 μm, and the average tilt angle θa is preferably 0.39 to 4.58°.

[0061] Furthermore, in the optical laminate of the present invention, the maximum height Rz of the unevenness existing on the surface of the optical functional layer is preferably 0.2 μm or more. When the maximum height Rz is 0.2 μm or more, external light can be sufficiently diffused, suppressing iris spots originating from the light-transmitting substrate. From the viewpoint of iris spot suppression in the optical laminate, the maximum height Rz is more preferably 0.280 to 2.982 μm within the above range.

[0062] Furthermore, in the optical laminate of the present invention, the value of Ra×Rsm is preferably 1.6 or higher. Here, Rsm is the average length of the profile curve element. A value of Ra×Rsm of 1.6 or higher is advantageous in terms of rainbow spot suppression in the optical laminate. From the viewpoint of rainbow spot suppression in the optical laminate, the value of Ra×Rsm is more preferably 1.77 to 23.09 within the above range.

[0063] Furthermore, in the optical laminate of the present invention, the value of Ra×θa is preferably 0.018 or higher. When the value of Ra×θa is 0.018 or higher, it is advantageous in terms of rainbow spot suppression of the optical laminate. From the viewpoint of rainbow spot suppression of the optical laminate, the value of Ra×θa is more preferably 0.027 to 2.457 within the above range.

[0064] Furthermore, in the optical laminate of the present invention, the value of Ra×Rsm×θa is preferably 1.6 or higher. When the value of Ra×Rsm×θa is 1.6 or higher, it is advantageous in terms of rainbow spot suppression of the optical laminate. From the viewpoint of rainbow spot suppression of the optical laminate, within the above range, the value of Ra×Rsm×θa is more preferably 1.79105.78.

[0065] Furthermore, in the optical laminate of the present invention, the value of Δn×Ra is preferably 0.002 to 0.02. A value of Δn×Ra of 0.002 to 0.02 is advantageous in terms of rainbow spot suppression in the optical laminate. From the viewpoint of rainbow spot suppression in the optical laminate, within the above range, the value of Δn×Ra is more preferably 0.0025 to 0.0191.

[0066] Furthermore, in the optical laminate of the present invention, the Re×Ra value is preferably 140 to 1,500. A Re×Ra value of 140 to 1,500 is advantageous in terms of rainbow spot suppression in the optical laminate. From the viewpoint of rainbow spot suppression in the optical laminate, within the above range, the Re×Ra value is more preferably 159 to 1,431.

[0067] Furthermore, in the optical laminate of the present invention, the value of Δn×θa is preferably 0.01 to 0.17. A value of Δn×θa of 0.01 to 0.17 is advantageous in terms of rainbow spot suppression in the optical laminate. From the viewpoint of rainbow spot suppression in the optical laminate, within the above range, the value of Δn×θa is more preferably 0.014 to 0.163.

[0068] Furthermore, in the optical laminate of the present invention, the value of Re×θa is preferably 800 to 12,500. A value of Re×θa of 800 to 12,500 is advantageous in terms of rainbow spot suppression in the optical laminate. From the viewpoint of rainbow spot suppression in the optical laminate, within the above range, the value of Re×θa is more preferably 886 to 12,218.

[0069] The optical laminate of this embodiment can be used to form an image display device by being laminated to the outermost surface of an image display panel such as a liquid crystal panel or an organic EL panel. A touch panel can also be disposed between the optical laminate and the image display panel. Because the optical laminate of this embodiment uses a biaxially stretched PET film as the light-transmitting substrate, it exhibits excellent moisture resistance and bending resistance. Furthermore, the light diffusion caused by the anti-glare layer suppresses iris spots originating from the biaxially stretched PET film, making it suitable as an optical film disposed on the outermost surface of an image display device. The optical laminate also possesses bending resistance, thus it can also be used as an optical film for foldable image display devices.

[0070] As explained above, the optical laminate system of this embodiment uses a biaxially stretched PET film with an in-plane retardation Re of 2,000 to 7,500 nm as the light-transmitting substrate. When using a biaxially stretched PET film, there is a problem of obvious iris spots, but the occurrence of iris spots can be suppressed by controlling the overall optical properties (anti-glare, anti-reflection) of the optical laminate through optical functional layers. When using a biaxially stretched PET film with an in-plane retardation Re of less than 2000, the surface hardness is easily reduced due to the thinning of the light-transmitting substrate. However, in this embodiment, by using a biaxially stretched PET film with an in-plane retardation Re of 2,000 to 7,500 nm, the surface hardness required for the optical laminate can be ensured. Furthermore, when a PET film, referred to as an ultra-high RePET film, is used in the light-transmitting substrate, the light-blocking problem during the use of polarized sunglasses can be solved by adjusting the angle of the slow axis of the light-transmitting substrate. However, the ultra-high RePET film is a uniaxially stretched film, and therefore has the problem of weak bending resistance. In this embodiment, the light-transmitting substrate is a biaxially stretched PET film, thus exhibiting good bending resistance. Even in applications where visual recognition is performed through polarizing plates such as polarized sunglasses, it still offers the advantage of solving light-blocking issues regardless of the slow axis angle of the light-transmitting substrate. In other words, the optical laminate of this embodiment simultaneously addresses the problems encountered when using PET films with low in-plane retardation Re (less than 2,000 nm) and those encountered when using PET films with high in-plane retardation Re (more than 7,500 nm), making it suitable for applications in image display devices where visual recognition is performed through polarizing plates such as polarized sunglasses. [Example]

[0071] Hereinafter, specific embodiments of the present invention will be described.

[0072] First, the manufacturing method of the light-transmitting substrate will be explained.

[0073] <Unstretched Film> Polyethylene terephthalate (PET) raw material, dissolved at 285°C, is filtered through a stainless steel sintered filter media (nominal filtration accuracy: 95% cutoff for 10μm particles). Two types of three-layer aggregates are laminated, extruded from a die into a sheet, and then electrostatically cast onto a casting roller at a surface temperature of 30°C to cool and solidify, resulting in an unstretched film. At this point, the output of each extruder is adjusted so that the thickness ratio of the three layers is 10:80:10. Next, using a reverse roller method, an adhesion-modifying coating solution is applied to both sides of the unstretched PET film at a dry coating weight of 0.08 g / m², and then dried at 80°C for 20 seconds.

[0074] <Uniaxially Stretched Film> The unstretched film with the coating layer formed is guided to a tenter frame, the ends of the film are held by clamps, and simultaneously guided to a hot air zone at a temperature of 125°C, where it is stretched to 4.0 times its original width. Then, while maintaining the width stretched in the width direction, it is treated at a temperature of 225°C for 30 seconds, and further treated with a 3% easing in the width direction to obtain a uniaxially stretched PET film with a film thickness of 80 μm.

[0075] <Biaxially Stretched Film> The unstretched film with the coating layer formed thereon is heated to 105°C using a heated roller assembly and an infrared heater. Then, using a roller assembly with a circumferential speed difference, it is stretched 2.6 times in the travel direction and 4.0 times in the width direction to obtain biaxially stretched PET films with thicknesses of 38, 50, 75, 125, and 188 μm. Furthermore, stretching it 1.4 times in the travel direction and 4.0 times in the width direction yields a biaxially stretched PET film with a thickness of 23 μm.

[0076] Tables 1-4 below show the compositions of the anti-glare layer forming coating liquid and the low refractive index layer forming coating liquid used in the embodiments and comparative examples. Furthermore, each coating liquid was diluted to a suitable coating concentration using the solvents listed in Tables 1-4. Also, the addition ratio of each component shown in Tables 1-4 is the percentage (mass%) of the total solid components of the coating liquid. Here, the term "total solid components of the optical functional layer forming coating liquid" refers to the components after the solvent has been removed. Therefore, the mixing ratio (mass%) of resin particles and inorganic particles in the total solid components of the optical functional layer forming coating liquid is equal to the content ratio (mass%) of resin particles and inorganic particles in the optical functional layer of the hardened film of the optical functional layer forming coating liquid. "-" in Table 1 indicates unmixed materials.

[0077] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Anti-glare layer UV / EB curable resin Light Acrylate PE-3A 86.88% 86.88% 86.88% 86.93% 68.35% 68.35% Photopolymerization initiator 4.57% 4.57% 4.57% 4.58% 3.60% 3.60% resin particles (Organic spherical packing material) Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.515) 3.00% 3.00% 3.00% - - - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.565) 3.00% 3.00% 3.00% 2.50% 4.67% 4.67% Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.555) - - - 4.50% - - polystyrene - - - - - - Acrylic acid / styrene copolymer (Average particle size 2.0µm, n=1.595) - - - - - - Amorphous silicon dioxide particles (Average particle size 2.7µm, n=1.45) - - - - - - Synthetic bentonite (layered organic clay) 2.00% 2.00% 2.00% 1.00% 1.17% 1.17% Leveling agent 0.05% 0.05% 0.05% 0.50% 0.04% 0.04% Nanoparticles (organic silica sol) 0.50% 0.50% 0.50% - 22.17% 22.17% Solvent (toluene) low refractive index layer Adhesive resin Light Acrylate PE-3A 26.81% 26.81% - - - - Fluorinated acrylates 16.09% 16.09% - - - - Photopolymerization initiator 2.70% 2.70% - - - - Hollow silicon dioxide (Porous silica microparticles) (dispersion) Average particle size 60nm - - - - - - Average particle size 75nm 45.50% 45.50% - - - - Leveling agent 8.90% 8.90% - - - - Solvent (methyl isobutyl ketone)

[0078] [Table 2] Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Anti-glare layer UV / EB curable resin Light Acrylate PE-3A 83.89% 81.47% 64.04% 64.04% 75.46% 85.72% Photopolymerization initiator 2.72% 2.64% 3.37% 3.37% 2.45% 4.51% resin particles (Organic spherical packing material) Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.515) - - - - - - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.565) 11.00% 13.50% - - 13.50% - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.555) - - - - - - polystyrene - - 7.67% 7.67% - - Acrylic acid / styrene copolymer (Average particle size 2.0µm, n=1.595) - - - - 6.20% - Amorphous silicon dioxide particles (Average particle size 2.7µm, n=1.45) - - - - - 9.49% Synthetic bentonite (layered organic clay) 1.84% 1.84% 1.53% 1.53% 1.84% - Leveling agent 0.05% 0.05% 0.04% 0.04% 0.05% 0.28% Nanoparticles (organic silica sol) 0.50% 0.50% 23.35% 23.35% 0.50% - Solvent (toluene) low refractive index layer Adhesive resin Light Acrylate PE-3A 38.40% 38.40% - - 37.40% - Fluorinated acrylates - - - - - - Photopolymerization initiator 2.70% 2.70% - - 2.70% - Hollow silicon dioxide (Porous silica microparticles) (dispersion) Average particle size 60nm 50.00% 50.00% - - 51.00% - Average particle size 75nm - - - - - - Leveling agent 8.90% 8.90% - - 8.90% - Solvent (methyl isobutyl ketone)

[0079] [Table 3] Example 13 Example 14 Example 15 Example 16 Example 17 Anti-glare layer UV / EB curable resin Light Acrylate PE-3A ​​​​​​67.93% 64.04% 64.04% 64.04% 64.04% Photopolymerization initiator 3.58% 3.37% 3.37% 3.37% 3.37% resin particles (Organic spherical packing material) Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.515) - - - - - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.565) - - - - - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.555) - - - - - polystyrene - 7.67% 7.67% 7.67% 7.67% Acrylic acid / styrene copolymer (Average particle size 2.0µm, n=1.595) 26.00% - - - - Amorphous silicon dioxide particles (Average particle size 2.7µm, n=1.45) - - - - - Synthetic bentonite (layered organic clay) 2.00% 1.53% 1.53% 1.53% 1.53% Leveling agent 0.50% 0.04% 0.04% 0.04% 0.04% Nanoparticles (organic silica sol) - 23.35% 23.35% 23.35% 23.35% Solvent (toluene) low refractive index layer Adhesive resin Light Acrylate PE-3A - - - - - Fluorinated acrylates - - - - - Photopolymerization initiator - - - - - Hollow silicon dioxide (Porous silica microparticles) (dispersion) Average particle size 60nm - - - - - Average particle size 75nm - - - - - Leveling agent - - - - - Solvent (methyl isobutyl ketone)

[0080] [Table 4] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Anti-glare layer (Comparative Examples 1 and 2 are HC layers) UV / EB curable resin Light Acrylate PE-3A 92.93% 92.93% 88.45% 64.04% Photopolymerization initiator 4.57% 4.57% 4.66% 3.37% resin particles (Organic spherical packing material) Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.515) - - 3.15% - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.565) - - 0.35% - Acrylic acid / styrene copolymer (Average particle size 3.5µm, n=1.555) - - - - polystyrene - - - 7.67%​​​​​ Acrylic acid / styrene copolymer (Average particle size 2.0µm, n=1.595) - - - - Amorphous silicon dioxide particles (Average particle size 2.7µm, n=1.45) - - - - Synthetic bentonite (layered organic clay) 2.00% 2.00% 2.00% 1.53% Leveling agent 0.50% 0.50% 0.40% 0.04% Nanoparticles (organic silica sol) - - 1.00% 23.35% Solvent (toluene) low refractive index layer Adhesive resin Light Acrylate PE-3A - - 26.81% - Fluorinated acrylates - - 16.09% - Photopolymerization initiator - - 2.70% - Hollow silicon dioxide (Porous silica microparticles) (dispersion) Average particle size 60nm - - - - Average particle size 75nm - - 45.50% - Leveling agent - - 8.90% - Solvent (methyl isobutyl ketone)

[0081] The materials used in Tables 1 to 4 are as follows.

[0082] <Coating liquid for forming anti-glare layer (hard coating)> .UV / EB curable resin Light Acrylate PE-3A (neopentyl terephthalol triacrylate), manufactured by Kyoei Chemical Co., Ltd. .Photopolymerization initiator Omnirad (registered trademark) 184 (1-hydroxycyclohexyl-phenyl ketone), IGM Resins BV .Resin particles (organic spherical filler) (1) Acrylic acid / styrene copolymer, average particle size 3.5μm, n=1.515 (2) Acrylic acid / styrene copolymer, average particle size 3.5μm, n=1.565 (3) Acrylic acid / styrene copolymer, average particle size 3.5μm, n=1.555 (4) Polystyrene, average particle size 3.5μm, n=1.595 (5) Acrylic acid / styrene copolymer, average particle size 2.0μm, n=1.595 . Amorphous silica particles, average particle size 2.7 μm, n=1.45, FUJI SILYSIA Co., Ltd. Leveling agent F565, DIC Co., Ltd. Nanoparticles (organic silica sol) MEK-ST-40, Nissan Chemical Co., Ltd.

[0083] <Coating solution for forming low refractive index layer> . Adhesive resin Light Acrylate PE-3A (neopentyl terephthalol triacrylate), Kyoei Chemical Co., Ltd. . Photopolymerization initiator Omnirad (registered trademark) 184 (1-hydroxycyclohexyl-phenyl ketone), IGM Resins BV . Hollow silica (porous silica microparticle dispersion) (1) Average particle size 60nm (2) Average particle size 75nm . Leveling agent RS-75, DIC Co., Ltd. ​​​​

[0084] (Examples 1, 2, 7, 8, 11, and Comparative Example 3) A coating liquid for forming an anti-glare layer having the compositions described in Tables 1-4 was prepared and coated onto a biaxially stretched PET film as shown in Table 5. After the coating was dried, it was polymerized and hardened by irradiation with ultraviolet light to form an anti-glare layer. Next, a coating liquid for forming a low refractive index layer having the compositions described in Tables 1-4 was prepared and coated onto the anti-glare layer. After the coating was dried, it was polymerized and hardened by irradiation with ultraviolet light to form a low refractive index layer. Through the above steps, an optical laminate (AGLR film) was obtained.

[0085] (Examples 3-6, 9, 10, 12-16, Comparative Examples 4, 5) No low refractive index layer was formed on the anti-glare layer. Otherwise, the process was carried out in the same manner as in Example 1 to obtain an optical laminate (AG film).

[0086] (Comparative Example 1) A coating liquid for forming a hard coating with the composition shown in Table 4 was adjusted and coated onto a uniaxially stretched PET film as described in Table 5 with a hardened film thickness of 5 μm. After the coating was dried, it was polymerized and hardened by irradiation with ultraviolet light to form a hard coating. Through the above steps, an optical laminate (HC film) was obtained.

[0087] (Comparative Example 2) The biaxially stretched PET film described in Table 5 was used as the light-transmitting substrate, and otherwise the same procedure as in Comparative Example 1 was performed to obtain an optical laminate (HC film).

[0088] (Haze) The haze value was measured according to JIS K7136 using a haze meter (NDH4000, manufactured by Nippon Denshoku Kogyo Co., Ltd.). Here, the haze value of the optical laminate is defined as the total haze. Furthermore, the internal haze of the optical laminate is defined as the value obtained by subtracting the haze value of the transparent sheet with adhesive from the haze value measured on the surface of the optical functional layer of the optical laminate where the adhesive-coated transparent sheet is attached. In addition, the transparent sheet with adhesive is obtained by coating an acrylic adhesive (10 μm thick) onto a polyethylene terephthalate film (38 μm thick). Furthermore, the surface haze is calculated using the following formula: Surface haze (%) = Total haze (%) - Internal haze (%)

[0089] (Delay) The in-plane phase difference and thickness direction phase difference of the fabricated uniaxial or biaxially stretched PET film were measured using a phase difference film / optical material inspection device (RETS-100, manufactured by Otsuka Electronics Co., Ltd.). The measurement conditions are as follows: [Measurement Conditions] . Delay measurement method: Rotation analyzer method . Measurement spot diameter: ϕ5mm . Tilting angle range: 0° . Measurement wavelength range: 400nm to 800nm ​​. Average refractive index N of the light-transmitting substrate: The value calculated using the formula N=(nx+ny+nz) / 3 based on nx, ny, and nz. In the case of PET film, N=1.660. In addition, the in-plane delay Re and the thickness direction delay Rth' are values ​​at a wavelength of 589nm.

[0090] [Surface Shape Analysis] The surface irregularities of the optical functional layers of the optical laminates of each embodiment and comparative example were measured using a non-contact surface / layer profile shape measurement system (measurement device: Bartscan R3300FL-Lite-AC, analysis software: VS-Viewer6, manufactured by Ryoka System Co., Ltd.) by optical interferometry. The measurement data were analyzed using the device's particle analysis software to measure the arithmetic mean roughness Ra, maximum height Rz, and average length Rsm and average tilt angle θa of the low refractive index layer surface.

[0091] Furthermore, under the analysis conditions of the VS-Viewer's profile profile (multi-line), an average roughness is generated. The arithmetic mean roughness Ra, maximum height Rz, average length Rsm of the curve element, and average tilt angle θa obtained from the profile profile obtained by averaging the profile profile of the set 6-point measuring vernier are defined as the arithmetic mean roughness Ra, maximum height Rz, average length Rsm of the curve element, and average tilt angle θa of the roughness of the present invention.

[0092] The measurement software of the device performs measurements under the following conditions to obtain image files of the surface unevenness measurement results. • Optical Conditions: Camera: Sony HR-50 1 / 3-inch; Objective Lens: 10XDI (10x); Imaging Lens (Tube): 0.5x; Zoom Lens: 1x; Light Source / Wavelength Filter: 520nm; ND Filter: Not Used; A-Stop (Aperture Stop): Not Used (Fully Open); F-Stop (Field of View Aperture): Not Used (Fully Open). • Measurement Conditions: Measurement Device: Piezoelectric; Measurement Mode: Phase Scanning Speed: 4μm / sec; Scanning Range: -10~10μm; Effective Pixel Count: 50%; Measurement Area: 704.192μm × 938.923μm

[0093] The acquired image files are analyzed using the device's analysis software under the following conditions. • Analysis Conditions (VS-Viewer6): Surface Correction: 4th order S-filter: Automatic L-filter: Not used. • Particle Analysis Conditions (VS-Viewer6): Analysis Type: Protrusion Analysis; Image Correction: None; Height Threshold: 0.1μm; Particle Shaping: None.

[0094] (Calculation method of Ra, Rz, Rsm and θa) In the acquired image after applying surface correction (4 times) and S-filter, the measuring vernier is set at positions of 200μm, 500μm and 800μm in the longitudinal direction (X direction) and at positions of 200μm, 400μm and 600μm in the transverse direction (Y direction). The values ​​of Ra, Rz, Rsm and θa of each vernier position (a total of 6 points, 3 points parallel to the X direction and 3 points parallel to the Y direction) are obtained using the profile contour of VS-Viewer. The average value (arithmetic mean) of the obtained values ​​is set as the measurement result.

[0095] (Evaluation of Iris) Assuming the observation of the iris using polarized sunglasses is performed as follows: An observation sample is prepared and arranged on a display equipped with backlight (brightness approximately 5,000 cd / m²) in the following order: a first polarizing lens, the optical laminate of the embodiment or comparative example, and a second polarizing lens (assuming it is polarized sunglasses). The first polarizing lens is arranged such that its absorption axis is orthogonal to the vertical direction of the display, and the absorption axis of the second polarizing lens is orthogonal to the absorption axis of the first polarizing lens. Furthermore, with the vertical direction of the display parallel to the slow axis of the light-transmitting substrate of the optical laminate as a reference rotation position (0°), the optical laminate is rotated 45° clockwise, and then further rotated 45° from that position (90° from the reference rotation position) to visually observe the iris in various orientations. In addition, the observer observes from a position 50-60cm away from the monitor, directly in front of it, and from a position 50-60cm away from the monitor, tilted at a 45° angle to the left and right relative to the normal direction when observing from the front. The iris pattern is evaluated based on the observation results using the following criteria: -: Light blocking occurs, making iris pattern determination impossible (unusable) ×: Iris pattern occurs, unusable △: Iris pattern occurs, but to a degree that is not a problem in practical use ○: Slight iris pattern occurs, but is not a problem in practical use ◎: No iris pattern occurs (significantly good)

[0096] (Bending Resistance) A planar unloaded U-shaped expansion test fixture (DMX-FS) was mounted on a benchtop durability testing machine (manufactured by Yuasa System Co., Ltd.) to ensure each sample was flat. Bending operations were performed continuously with the optical functional layer facing outwards and the interfacial distance between opposing surfaces at 2 mm. After 50,000 and 200,000 consecutive bending operations, the presence or absence of breakage at the bending points was visually confirmed, and the following criteria were used for evaluation: ○: No breakage occurred at the bending points in any consecutive folding test. ×: Breakage occurred at the bending points in any consecutive folding test.

[0097] (Pencil Hardness) Pencil hardness is evaluated according to JIS K5400-1900. The pencil hardness of the protective layer surface is measured using a pencil (uni, Mitsubishi Pencil Corporation) and a Clemens scratch tester (HA-301, TESTER SANGYO Corporation). The test is repeated while changing the pencil hardness, and the change in appearance due to damage is visually observed. The highest hardness at which no damage is observed is set as the evaluation value. A pencil hardness of H or higher is considered acceptable.

[0098] Table 5 shows the optical properties of the light-transmitting substrate, such as type, thickness, and delay, and the layer composition of the optical laminate for each embodiment and comparative example.

[0099] [Table 5] PET substrate thickness Δn Re(nm) Rth'(nm) NZ' Layer composition d(um) (nx-ny) (nx-ny)×d (nx-nz)×d (Rth' / Re) Example 1 Dual-axis extension 50 0.045 2,272 9,541 4.2 PET / AG / LR Example 2 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG / LR Example 3 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG Example 4 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG Example 5 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG Example 6 Dual-axis extension 125 0.043 5,347 17,842 3.3 PET / AG Example 7 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG / LR Example 8 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG / LR Example 9 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG Example 10 Dual-axis extension 125 0.043 5,347 17,842 3.3 PET / AG Example 11 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG / LR Example 12 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG Example 13 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG Example 14 Dual-axis extension 75 0.044 3,290 14,568 4.4 PET / AG Example 15 Dual-axis extension 100 0.042 4,150 15,015 3.6 PET / AG Example 16 Dual-axis extension 188 0.039 7,257 12,297 1.7 PET / AG Example 17 Dual-axis extension 38 0.053 2,027 7,929 3.9 PET / AG Comparative Example 1 Dual-axis extension 80 0.104 8,347 2,339 0.3 PET / HC Comparative Example 2 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / HC Comparative Example 3 Dual-axis extension 75 0.036 2,667 13,761 5.2 PET / AG / LR Comparative Example 4 Dual-axis extension twenty three 0.086 1,980 7,554 3.8 PET / AG

[0100] Table 6 shows the measured values ​​of surface roughness of the optical laminates of each embodiment and each comparative example.

[0101] [Table 6] Roughness parameters Ra(μm) Rz(μm) Rsm(μm) θa(deg) Ra×Rsm Ra×θa Ra×Rsm ×θa Δn×Ra Re×Ra Δn×θa Re×θa Example 1 0.070 0.280 67 0.39 4.70 0.027 1.83 0.0032 159 0.018 886 Example 2 0.070 0.280 67 0.39 4.70 0.027 1.83 0.0025 187 0.014 1,040 Example 3 0.090 0.470 44 0.78 3.99 0.070 3.11 0.0032 240 0.028 2,080 Example 4 0.100 0.530 48 0.91 4.79 0.091 4.36 0.0036 267 0.032 2,427 Example 5 0.090 0.540 twenty two 1.47 1.94 0.132 2.85 0.0032 240 0.052 3,921 Example 6 0.085 0.506 twenty four 1.28 2.06 0.109 2.63 0.0037 457 0.055 6,846 Example 7 0.099 0.424 71 0.59 7.03 0.059 4.17 0.0035 264 0.021 1,581 Example 8 0.161 0.748 62 1.06 9.93 0.171 10.54 0.0057 430 0.038 2,831 Example 9 0.070 0.410 25 1.01 1.77 0.071 1.79 0.0025 187 0.036 2,694 Example 10 0.100 0.510 28 1.10 2.80 0.110 3.08 0.0043 535 0.047 5,882 Example 11 0.391 1.673 39 3.00 15.15 1.173 45.49 0.0139 1,042 0.107 8,007 Example 12 0.536 2.982 43 4.58 23.09 2.457 105.78 0.0191 1,431 0.163 12,218 Example 13 0.286 1.282 43 2.32 12.32 0.665 28.63 0.0102 764 0.083 6,197 Example 14 0.100 0.510 28 1.10 2.80 0.110 3.08 0.0044 329 0.048 3,620 Example 15 0.100 0.510 28 1.10 2.80 0.110 3.08 0.0042 415 0.046 4,565 Example 16 0.100 0.510 28 1.10 2.80 0.110 3.08 0.0039 726 0.042 7,983 Example 17 0.100 0.510 28 1.10 2.80 0.110 3.08 0.0053 203 0.059 2,230 Comparative Example 1 0.003 0.004 86 0.01 0.23 0.000 0.00 0.0003 twenty two 0.001 112 Comparative Example 2 0.006 0.006 127 0.02 0.72 0.000 0.01 0.0002 15 0.001 45 Comparative Example 3 0.034 0.183 44 0.28 1.47 0.009 0.41 0.0012 89 0.010 734 Comparative Example 4 0.100 0.510 28 1.10 2.80 0.110 3.08 0.0086 198 0.095 2,179

[0102] Table 7 shows the measured values ​​of haze of the optical laminates of each embodiment and each comparative example.

[0103] [Table 7] Haze parameters Total Hz (%) Surface Hz (%) Internal Hz (%) Δn×total Hz Re×total Hz Δn× Surface Hz Re× Surface Hz Δn× Internal Hz Re× Internal Hz Example 1 8.7 4.2 4.5 0.39 19,725 0.19 9,544 0.20 10,226 Example 2 8.7 4.2 4.5 0.31 23,152 0.15 11,202 0.16 12,003 Example 3 10.5 5.6 4.8 0.37 27,873 0.20 14,936 0.17 12,803 Example 4 17.7 9.9 7.8 0.63 47,210 0.35 26,406 0.28 20,804 Example 5 22.0 12.0 10.0 0.78 58,679 0.43 32,007 0.36 26,672 Example 6 24.2 13.0 11.2 1.04 129,409 0.56 69,517 0.48 59,892 Example 7 25.0 10.5 14.5 0.89 66,681 0.37 28,006 0.52 38,675 Example 8 38.0 17.0 21.0 1.35 101,355 0.60 45,343 0.75 56,012 Example 9 41.5 12.8 28.7 1.48 110,636 0.46 34,194 1.02 76,443 Example 10 39.9 13.8 26.9 1.71 213,526 0.59 74,009 1.15 143,794 Example 11 61.0 29.5 31.5 2.17 162,701 1.05 78,683 1.12 84,018 Example 12 71.6 68.6 3.1 2.55 190,973 2.44 182,972 0.11 8,268 Example 13 70.8 15.2 55.6 2.52 188,840 0.54 40,542 1.98 148,298 Example 14 41.5 12.8 28.7 1.82 136,489 0.56 42,184 1.26 94,305 Example 15 41.5 12.8 28.7 1.72 172,146 0.53 53,204 1.19 118,942 Example 16 41.5 12.8 28.7 1.60 301,028 0.49 93,037 1.11 207,991 Example 17 41.5 12.8 28.7 2.21 84,086 0.68 25,988 1.53 58,098 Comparative Example 1 0.8 Approximately 0 0.8 or less 0.09 6,928 Approximately 0 Approximately 0 0.08 or less Below 6,678 Comparative Example 2 0.8 Approximately 0 0.8 or less 0.03 2,009 Approximately 0 Approximately 0 0.03 or less 2,134 or less Comparative Example 3 3.2 2.2 1.0 0.11 8,535 0.08 5,868 0.04 2,667 Comparative Example 4 41.5 12.8 28.7 3.57 82,150 1.10 25,390 2.47 56,761

[0104] Table 8 shows the evaluation results of the iris, flexural toughness and pencil hardness of the optical laminates of each embodiment and comparative example.

[0105] [Table 8] Iris evaluation Flexural strength Pencil hardness Direction of light-transmitting substrate Direction of light-transmitting substrate 0° 45° 90° MD TD Example 1 △ △ △ ○ ○ H Example 2 △ △ △ ○ ○ 2H Example 3 △ △ △ ○ ○ 2H Example 4 △ △ △ ○ ○ 2H Example 5 ○ ○ ○ ○ ○ 2H Example 6 ○ ○ ○ ○ ○ 3H Example 7 ○ ○ ○ ○ ○ 2H Example 8 ○ ○ ○ ○ ○ 2H Example 9 ○ ○ ○ ○ ○ 2H Example 10 ◎ ◎ ◎ ○ ○ 3H Example 11 ◎ ◎ ◎ ○ ○ 2H Example 12 ◎ ◎ ◎ ○ ○ 2H Example 13 ◎ ◎ ◎ ○ ○ 2H Example 14 ○ ○ ○ ○ ○ 2H Example 15 ○ ○ ○ ○ ○ 2H Example 16 ◎ ◎ ◎ △ △ 3H Example 17 ○ ○ ○ ○ ○ H Comparative Example 1 - ○ - × (fracture) ○ 2H Comparative Example 2 × × × ○ ○ 2H Comparative Example 3 × × × ○ ○ 2H Comparative Example 4 ○ ○ ○ ○ ○ HB The optical laminates in Examples 1-16 all use a biaxially stretched PET film with an in-plane retardation (Re) of 2,000-7,500 nm as the light-transmitting substrate. Therefore, even under the assumption of using polarized sunglasses, no light blocking occurs regardless of the slow axis direction of the light-transmitting substrate, and iris spots are suppressed by the optical functional layer. Furthermore, since the optical laminates in Examples 1-16 all use a biaxially stretched PET film, they have good surface hardness and flexural strength.

[0106] In contrast, the optical laminate of Comparative Example 1 uses a uniaxially extended PET film with high in-plane retardation Re as the light-transmitting substrate. Therefore, it blocks light according to the slow axis direction of the light-transmitting substrate, which is not suitable for the application of polarized sunglasses.

[0107] Furthermore, the optical laminates of Comparative Examples 2 and 3 are unable to suppress iris spots and are not suitable for the intended use of polarized sunglasses.

[0108] The optical laminate in Comparative Example 4 uses a biaxially stretched PET film with an in-plane retardation Re of less than 2,000 nm. Therefore, the iris is suppressed, but the pencil hardness is not sufficient. [Potential for Industrial Application]

[0109] The present invention can utilize an optical laminate disposed on the front surface side of an image display panel. [Simplified Explanation of the Diagram]

[0011] FIG1 is a schematic cross-sectional view showing an example of an optical laminate according to an embodiment. FIG2 is a schematic cross-sectional view showing another example of an optical laminate according to an embodiment.

Claims

1. An optical stack for use in an image display device, comprising: a light-transmitting substrate formed of a biaxially extended polyethylene terephthalate film and having in-plane birefringence; and an optical functional layer disposed on one side of the light-transmitting substrate; the total haze of the optical stack being 8.7% or more; the in-plane retardation Re of the light-transmitting substrate as defined by the following formula (1) being 2,000 nm or more and 7,500 nm or less; the average tilt angle θa of the unevenness of the surface of the optical functional layer being 0.30° or more; Re=(nx-ny)×d (1) where, nx: refractive index in the slow axis direction, ny: refractive index in the fast axis direction, and d: thickness of the light-transmitting substrate.

2. The optical laminate of claim 1 has a surface haze of 3% or more.

3. The optical laminate of request item 1 has an internal haze of 2% or more.

4. The optical laminate of claim 1 satisfies the following condition (2): (nx-ny) < 0.06 (2).

5. The optical laminate of claim 1, wherein the thickness direction delay Rth' of the light-transmitting substrate as shown in the following formula (3) is 9,500 nm or more and 18,000 nm or less; Rth'=(nx-nz)×d (3) Here, nz: refractive index in the thickness direction.

6. The optical laminate as claimed in claim 1, wherein the ratio Nz' shown in the following formula (4) is 1.5 or more and 5.5 or less; Nz'=Rth' / Re (4).

7. The optical laminate of claim 1, which did not break when subjected to 200,000 repeated 180° folding tests with the optical functional layer on the outside and the distance between the opposite surfaces being 2 mm.

8. An image display device comprising: an image display panel, and an optical laminate disposed on the front surface of the image display panel as claimed in any one of claims 1 to 7.

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