Optical laminate, and polarizing plate, surface plate, and image display device using the same

Abstract

Provided is an optical layered body capable of suppressing visibility degradation in a high-temperature environment. The optical layered body comprises a layer containing a metal oxide on a plastic film, wherein the optical layered body has an emissivity of 0.27 to 0.75 for light in a wavelength range of 2000 nm to 22000 nm, as measured from the side of the layer containing the metal oxide with respect to the plastic film.

Description

Technical Field

[0001] The present invention relates to an optical layered body, and a polarizing plate, a surface plate, and an image display device using the optical layered body. Background Art

[0002] In recent years, the use of image display devices such as liquid crystal display devices and organic EL display devices has been expanding, and they are being used in smartphones, car navigation systems, televisions, monitors, digital cameras, and the like.

[0003] Among image display devices, car navigation systems are often installed on the dashboard of a car, and portable image display devices such as smartphones are also often brought into cars.

[0004] In the summer, the temperature inside a car is very high, especially the temperature of the dashboard, which can reach nearly 80° C. Therefore, image display devices are sometimes exposed to high temperatures inside the car for a long time, and in such cases, there is a concern that various performance characteristics of the image display devices may be degraded.

[0005] As a means for suppressing temperature rise in a car interior, laminated glass including a heat ray shielding structure has been proposed (for example, Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. WO2019 / 167897 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The temperature rise inside the car can be suppressed to some extent if the window glass of the car is the laminated glass of Patent Document 1. However, in a car without taking measures to suppress the temperature rise, the image display device is exposed to high temperatures.

[0011] Therefore, it is considered that the cover glass of the image display device is laminated glass as disclosed in Patent Document 1.

[0012] However, when an image display device using laminated glass as its cover glass is exposed to a high-temperature environment, visibility of the image display device often decreases. Furthermore, when using laminated glass as its cover glass, the image display device also has the problem of increased thickness.

[0013] The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical layered body capable of suppressing a decrease in visibility in a high-temperature environment, and a polarizing plate, a surface plate, and an image display device using the optical layered body.

[0014] Means for solving problems

[0015] The present invention provides the following [1] to [4].

[0016] [1] An optical laminate comprising a layer containing a metal oxide on a plastic film, wherein the optical laminate has an emissivity of 0.27 to 0.75 for light having a wavelength in the range of 2000 nm to 22000 nm, as measured from the side of the layer containing the metal oxide with respect to the plastic film.

[0017] [2] A polarizing plate comprising a polarizing element, a first transparent protective plate disposed on one side of the polarizing element, and a second transparent protective plate disposed on the other side of the polarizing element, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate described in [1].

[0018] [3] A surface plate for an image display device, wherein the optical laminate according to [1] is laminated onto a resin plate or a glass plate.

[0019] [4] An image display device comprising the optical layered body described in [1] above on the light emitting surface side of a display element.

[0020] Effects of the Invention

[0021] According to the present invention, there are provided an optical layered body capable of suppressing a decrease in visibility in a high-temperature environment, and a polarizing plate, a surface plate, and an image display device using the optical layered body. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic cross-sectional view showing one embodiment of the optical layered body of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the optical layered body of the present invention, and a polarizing plate, a surface plate, and an image display device using the optical layered body will be described.

[0024] [Optical laminate]

[0025] The optical layered body of the present invention comprises a layer containing a metal oxide on a plastic film, and the emissivity of the optical layered body to light in a wavelength range of 2000 nm to 22000 nm, measured from the layer containing the metal oxide side with respect to the plastic film, is 0.27 to 0.75.

[0026] In this specification, the emissivity of the optical layered body to light in a wavelength range of 2000 nm to 22000 nm, measured from the layer side containing the metal oxide based on the plastic film, may be referred to as “emissivity α”.

[0027] Emissivity is a value expressed as a ratio of the energy of light emitted by an object due to thermal radiation to the energy of light emitted by a black body at the same temperature as 1.

[0028] Figure 1 This is a schematic cross-sectional view showing one embodiment of the optical layered body of the present invention.

[0029] Figure 1 The optical laminate 100 has a layer 30 containing a metal oxide on a plastic film 10. Figure 1 The optical laminate 100 includes a functional layer α ( 20 ) between the plastic film 10 and the layer 30 containing a metal oxide. Figure 1 The functional layer α (20) is a single layer of the hard coating layer 21. In addition, based on the layer 30 containing the metal oxide, Figure 1 The optical laminate 100 has a functional layer β ( 40 ) on the side opposite to the plastic film 10 . Figure 1 The functional layer β ( 40 ) is a single layer of the low refractive index layer 41 .

[0030] <Plastic film>

[0031] The plastic film serves as a support for the layer containing a metal oxide and the functional layer described later.

[0032] It should be noted that glass is an alternative support to plastic film. Glass itself has excellent heat resistance, but due to its thickness, heat easily accumulates. The thickness of glass is generally 0.5 mm or more. Therefore, when glass is used as a support, the temperature of the optical laminate tends to increase in a high-temperature environment, and layers comprising metal oxides and functional layers, or components of image display devices such as display elements, are susceptible to the effects of high temperatures, which can reduce visibility.

[0033] Examples of the plastic film include films formed from one or more selected from polyester, triacetyl cellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyetherketone, polymethyl methacrylate, polycarbonate, polyurethane, and amorphous olefin (COP). The plastic film may be a co-extruded film of two or more resins or a laminated film of two or more plastic films.

[0034] Among these plastic films, polyesters such as polyethylene terephthalate and polyethylene naphthalate that have been stretched, particularly biaxially stretched, are preferred due to their excellent mechanical strength and dimensional stability. Polyimides are also preferred due to their excellent bending resistance and ease of application in foldable and rollable image display devices. Furthermore, plastic films coextruded from polycarbonate and polymethyl methacrylate are preferred due to their excellent formability.

[0035] It should be noted that as the substrate for the optical laminate, a thin-film glass film having a thickness of 5 μm to 200 μm can be used instead of a plastic film. In recent years, thin-film glass films have been used, for example, in foldable image displays. Furthermore, the use of thin-film glass films improves the smoothness of the optical laminate, thereby reducing emissivity and suppressing heat intrusion, which in turn can improve optical properties.

[0036] Among plastic films, those with a retardation value of 3000 nm to 30000 nm or a 1 / 4 wavelength phase difference are suitable because they can prevent color unevenness from being observed on the display screen when viewing images through polarized sunglasses.

[0037] The surface of the plastic film may be subjected to a known adhesion-facilitating treatment such as a corona discharge treatment, a primer treatment, or a base treatment.

[0038] For reasons of handling and to suppress deformation due to heat, the thickness of the plastic film is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 25 μm or more.

[0039] On the other hand, if the plastic film is too thick, heat accumulates in the film, sometimes adversely affecting visibility. Furthermore, if heat accumulates in the film, even if the optical layered body is moved from a high-temperature environment to a normal-temperature environment, the temperature is difficult to decrease, and visibility may be reduced for a long time. Therefore, the thickness of the plastic film is preferably 350 μm or less, more preferably 150 μm or less, even more preferably 90 μm or less, and even more preferably 70 μm or less.

[0040] Examples of suitable ranges of the thickness of the plastic film include 5 μm to 350 μm, 5 μm to 150 μm, 5 μm to 90 μm, 5 μm to 70 μm, 10 μm to 350 μm, 10 μm to 150 μm, 10 μm to 90 μm, 10 μm to 70 μm, 25 μm to 350 μm, 25 μm to 150 μm, 25 μm to 90 μm, and 25 μm to 70 μm.

[0041] The thickness of each layer constituting the optical layered body, such as the plastic film, the layer containing a metal oxide, and the functional layer, can be calculated by averaging the values of 20 points selected at random in a cross-sectional photograph of the optical layered body obtained using a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM). The 20 points are selected so that their positions are not biased in one direction.

[0042] The acceleration voltage and magnification of the STEM may be set according to the layer to be measured.

[0043] <Layer Containing Metal Oxide>

[0044] The layer containing the metal oxide is a core layer for making the emissivity α of the optical layered body fall within the range described below.

[0045] Examples of the metal oxide include indium tin oxide (ITO); antimony oxides such as antimony trioxide, tin-doped antimony oxide (ATO), and antimony pentoxide; tin oxide; zinc oxides such as aluminum-doped zinc oxide and gallium-doped zinc oxide; and titanium oxide. Preferably, the metal oxide contains at least one selected from the group consisting of these.

[0046] Among the above-mentioned metal oxides, ITO is preferred because it can easily adjust the emissivity α of the optical laminate to the range described below. Furthermore, ITO can increase the refractive index of the layer containing the metal oxide, and therefore, by combining it with an optionally formed low-refractive-index layer, it is easy to reduce the reflectivity of the optical laminate in the visible light region, making it preferred from this perspective. Furthermore, ITO has good transparency and high conductivity, making it preferred because it can easily improve the antistatic properties of the optical laminate.

[0047] It is difficult to reduce the emissivity of metal nitrides such as aluminum nitride and boron nitride, which are generally used as heat dissipation materials for heat sinks, to 0.75 or less.

[0048] In addition, it is difficult to achieve an emissivity of 0.27 or higher for the metals such as Au, Ag, Cu, and Al exemplified in Patent Document 1, leading to concerns about reduced transparency. Furthermore, the low refractive index of these metals makes it difficult to achieve a refractive index within the range described below for the layer containing the metal oxide. Furthermore, due to the excessively strong specular reflection of these metals, the background is reflected, reducing visibility. Furthermore, there is a migration problem with the Ag vapor-deposited film.

[0049] Examples of the embodiment of the layer containing a metal oxide include the following (1) and (2).

[0050] (1) Layer containing metal oxide particles and binder resin

[0051] (2) Metal oxide films formed by physical vapor deposition methods such as sputtering or chemical vapor deposition methods

[0052] The above-mentioned (1) is preferable from the viewpoint that it has better bending resistance than the above-mentioned (2) and can be easily applied to foldable image display devices and rollable image display devices.

[0053] <<(1) Layer containing metal oxide particles and binder resin>>

[0054] -Metal oxide particles-

[0055] Examples of metal oxide particles include: indium tin oxide (ITO) particles; antimony oxide particles such as antimony trioxide, tin-doped antimony oxide (ATO), and antimony pentoxide; tin oxide particles; zinc oxide particles such as aluminum-doped zinc oxide and gallium-doped zinc oxide; titanium oxide particles; etc., preferably comprising one or more selected from these groups, and more preferably comprising ITO particles.

[0056] The average particle size of the metal oxide particles is preferably from 2 nm to 200 nm, more preferably from 7 nm to 100 nm, further preferably from 8 nm to 80 nm, and even more preferably from 10 nm to 50 nm.

[0057] Preferred ranges of the average particle size of the metal oxide particles include 2 nm to 200 nm, 2 nm to 100 nm, 2 nm to 80 nm, 2 nm to 50 nm, 7 nm to 200 nm, 7 nm to 100 nm, 7 nm to 80 nm, 7 nm to 50 nm, 8 nm to 200 nm, 8 nm to 100 nm, 8 nm to 80 nm, 8 nm to 50 nm, 10 nm to 200 nm, 10 nm to 100 nm, 10 nm to 80 nm, and 10 nm to 50 nm.

[0058] In this specification, the average particle size of various particles can be calculated by, for example, the following operations (1) to (3).

[0059] (1) Photographing a cross section of the optical laminate using STEM: The STEM preferably has an accelerating voltage of 10 kV to 30 kV and a magnification of 50,000 to 300,000.

[0060] (2) After extracting 10 random particles from the observed image, calculate the particle size of each particle. The particle size is measured as the distance between two random parallel straight lines that maximize the distance between the two straight lines when the cross section of the particle is sandwiched between them.

[0061] (3) The same operation is repeated five times on another observation image of the same sample, and the value obtained by averaging a total of 50 pieces is taken as the average particle size of the particles.

[0062] The content of the metal oxide particles is preferably 150 parts by mass or more, more preferably 250 parts by mass or more, and even more preferably 400 parts by mass or more relative to 100 parts by mass of the binder resin. By setting the content of the metal oxide particles to 150 parts by mass or more, the emissivity α of the optical laminate can be easily reduced to 0.75 or less. In addition, by setting the content of high-refractive-index metal oxide particles such as ITO to 150 parts by mass or more, the refractive index of the layer containing the metal oxide can be increased, and by combining it with an optionally formed low-refractive-index layer, the reflectivity of the optical laminate in the visible light region can be reduced, which is preferable from this perspective.

[0063] In addition, relative to 100 parts by mass of the binder resin, the content of the metal oxide particles is preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, further preferably 1200 parts by mass or less, and even more preferably 1000 parts by mass or less. By making the content of the metal oxide particles 2000 parts by mass or less, it is possible to easily suppress the reduction in the coating strength of the layer containing the metal oxide. In addition, if the emissivity α of the optical laminate is too low, the heat generated inside the image display device is difficult to release to the outside. In order to prevent the emissivity α of the optical laminate from being too low, the content of the metal oxide particles is preferably 2000 parts by mass or less.

[0064] Preferred ranges of the content of the metal oxide particles relative to 100 parts by mass of the binder resin include 150 parts by mass to 2000 parts by mass, 150 parts by mass to 1500 parts by mass, 150 parts by mass to 1200 parts by mass, 150 parts by mass to 1000 parts by mass, 250 parts by mass to 2000 parts by mass, 250 parts by mass to 1500 parts by mass, 250 parts by mass to 1200 parts by mass, 250 parts by mass to 1000 parts by mass, 400 parts by mass to 2000 parts by mass, 400 parts by mass to 1500 parts by mass, 400 parts by mass to 1200 parts by mass, and 400 parts by mass to 1000 parts by mass.

[0065] -Silane coupling agent-

[0066] The layer containing the metal oxide particles and the binder resin preferably contains a silane coupling agent. The silane coupling agent may be a silane coupling agent serving as a surface treatment agent for the metal oxide particles or a silane coupling agent serving as the binder resin.

[0067] By surface-treating the metal oxide particles with a silane coupling agent, the affinity between the metal oxide particles and the binder resin is improved, and the metal oxide particles are easily dispersed uniformly.

[0068] Furthermore, even when a silane coupling agent is contained as a binder resin, this is preferred from the viewpoint of facilitating uniform dispersion of the metal oxide particles.

[0069] Examples of the silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-Triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, vinyltrimethoxysilane and vinyltriethoxysilane, etc. In particular, it is preferable to use one or more selected from the group consisting of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0070] -Binder resin-

[0071] The binder resin preferably comprises a cured product of a curable resin composition. Examples of the cured product of the curable resin composition include cured products of thermosetting resin compositions and cured products of ionizing radiation curable resin compositions. In order to further improve mechanical strength, a cured product of an ionizing radiation curable resin composition is preferred.

[0072] The ratio of the cured product of the curable resin composition to the total binder resin in the layer containing metal oxide particles is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and even more preferably 100% by mass.

[0073] The thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that is cured by heating.

[0074] Examples of the thermosetting resin include acrylic resins, urethane resins, phenolic resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, and silicone resins. A curing agent is added to these curable resins as needed in the thermosetting resin composition.

[0075] An ionizing radiation curable resin composition is a composition containing a compound having an ionizing radiation curable functional group. In this specification, a "compound having an ionizing radiation curable functional group" is sometimes referred to as an "ionizing radiation curable compound". As ionizing radiation curable functional groups, ethylenically unsaturated bond groups such as (meth)acryloyl, vinyl, and allyl groups, as well as epoxy groups, oxetane groups, and the like can be cited. As the ionizing radiation curable compound, a compound having an ethylenically unsaturated bond group is preferred, and a compound having two or more ethylenically unsaturated bond groups is more preferred, among which a (meth)acrylate compound having two or more ethylenically unsaturated bond groups is further preferred. As the (meth)acrylate compound having two or more ethylenically unsaturated bond groups, any one of a monomer and an oligomer can be used.

[0076] It should be noted that ionizing radiation refers to radiation in electromagnetic waves or charged particle beams that has an energy quantum that can cause molecules to polymerize or cross-link. Ultraviolet rays or electron beams are usually used, but in addition to these, electromagnetic waves such as X-rays and gamma rays, alpha rays, and charged particle beams such as ion beams can also be used.

[0077] In this specification, (meth)acrylate means acrylate or methacrylate, (meth)acrylic acid means acrylic acid or methacrylic acid, and (meth)acryloyl means acryloyl or methacryloyl.

[0078] -Photopolymerization initiator, photopolymerization accelerator-

[0079] When the ionizing radiation curable compound is an ultraviolet curable compound, the ionizing radiation curable composition preferably contains additives such as a photopolymerization initiator and a photopolymerization accelerator.

[0080] Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzoin dimethyl ether, benzoylbenzoate, α-acyloxime ester, and thioxanthones.

[0081] The photopolymerization accelerator can increase the curing rate by reducing polymerization hindrance caused by air during curing, and examples thereof include one or more selected from isoamyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, and the like.

[0082] -Refractive index, film thickness-

[0083] The refractive index of the layer containing metal oxide particles and the binder resin is preferably from 1.53 to 2.30, more preferably from 1.57 to 2.00, more preferably from 1.60 to 1.80, and more preferably from 1.65 to 1.75. By setting the refractive index of the layer containing the metal oxide within the above range, the reflectivity of the optical layered body in the visible light region can be easily reduced by combining it with an optionally formed low refractive index layer.

[0084] Preferred ranges of the refractive index of the layer containing metal oxide particles and a binder resin include 1.53 or more and 2.30 or less, 1.53 or more and 2.00 or less, 1.53 or more and 1.80 or less, 1.53 or more and 1.75 or less, 1.57 or more and 2.30 or less, 1.57 or more and 2.00 or less, 1.57 or more and 1.80 or less, 1.57 or more and 1.75 or less, 1.60 or more and 2.30 or less, 1.60 or more and 2.00 or less, 1.60 or more and 1.80 or less, 1.60 or more and 1.75 or less, 1.65 or more and 2.30 or less, 1.65 or more and 2.00 or less, 1.65 or more and 1.80 or less, and 1.65 or more and 1.75 or less.

[0085] In this specification, the refractive index of each layer refers to the refractive index at a wavelength of 550 nm. In this specification, the refractive index of each layer can be calculated by, for example, fitting a reflection spectrum measured by a spectrophotometer with a reflection spectrum calculated from an optical model of a multilayer thin film using Fresnel coefficients.

[0086] In order to easily adjust the emissivity α to 0.75 or less, the thickness of the layer containing the metal oxide particles and the binder resin is preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 500 nm or more.

[0087] It should be noted that there is a limit to how much the emissivity α can be reduced by increasing the thickness of the layer containing metal oxide particles and a binder resin. Furthermore, if the thickness of the layer containing metal oxide particles and a binder resin is too thick, transparency tends to decrease. To achieve thin film thickness, the thickness of the layer containing metal oxide particles and a binder resin is preferably 5.0 μm or less, more preferably 2.0 μm or less, and even more preferably 1.5 μm or less.

[0088] Preferred ranges for the thickness of the layer containing metal oxide particles and the binder resin include 100 nm to 5.0 μm, 100 nm to 2.0 μm, 100 nm to 1.5 μm, 200 nm to 5.0 μm, 200 nm to 2.0 μm, 200 nm to 1.5 μm, 500 nm to 5.0 μm, 500 nm to 2.0 μm, and 500 nm to 1.5 μm.

[0089] In addition, in order to reduce the reflectivity in the visible light region by canceling interference waves in combination with an arbitrarily formed low refractive index layer, the thickness of the layer containing metal oxide particles and a binder resin is preferably determined in consideration of the refractive index n of the layer containing metal oxide particles and a binder resin. o Specifically, the thickness of the layer containing metal oxide particles and a binder resin is preferably adjusted to a thickness close to an integer multiple of "550 nm / 2n0". As described above, the thickness range of the layer containing metal oxide particles and a binder resin, which reduces the reflectivity in the visible light region, varies depending on the refractive index range and cannot be generalized. However, it is preferably 120 nm to 750 nm, more preferably 130 nm to 500 nm, and even more preferably 140 nm to 400 nm.

[0090] Preferred ranges for the thickness of the layer containing metal oxide particles and a binder resin for reducing the reflectivity in the visible light region include 120 nm to 750 nm, 120 nm to 500 nm, 120 nm to 400 nm, 130 nm to 750 nm, 130 nm to 500 nm, 130 nm to 400 nm, 140 nm to 750 nm, 140 nm to 500 nm, and 140 nm to 400 nm.

[0091] The layer containing the metal oxide particles and the binder resin may contain additives such as a leveling agent, a dispersant, a dye, an ultraviolet absorber, a light stabilizer, and an antioxidant within a range that does not inhibit the effects of the present invention.

[0092] The layer containing the metal oxide particles and the binder resin can be formed by, for example, applying a coating solution in which the components constituting the layer are dispersed or dissolved onto a plastic film, drying the coating solution, and then irradiating the plastic film with ionizing radiation as needed.

[0093] The layer containing the metal oxide particles and the binder resin is preferably subjected to a heat treatment after being formed as described above. The heat treatment can easily reduce the emissivity α.

[0094] The lower limit of the heat treatment temperature is preferably 90°C or higher, more preferably 95°C or higher, and even more preferably 100°C or higher, and the upper limit is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower.

[0095] The lower limit of the heat treatment time is preferably 30 minutes or longer, more preferably 45 minutes or longer, and even more preferably 50 minutes or longer, and the upper limit is preferably 200 minutes or shorter, more preferably 120 minutes or shorter, and even more preferably 80 minutes or shorter.

[0096] 《(2) Metal oxide film》

[0097] The metal oxide film is formed by forming a metal oxide film by, for example, physical vapor deposition such as sputtering, chemical vapor deposition, etc. Among the metal oxide films, an indium tin oxide film is preferred because it can easily reduce emissivity.

[0098] In order to easily achieve an emissivity α of 0.27 or greater in the optical laminate, the metal oxide film is preferably an amorphous film. That is, the metal oxide film is preferably not subjected to a crystallization treatment such as annealing. Furthermore, amorphous metal oxide films have excellent bending resistance and are readily applicable to foldable and rollable image display devices, making them preferred.

[0099] In summary, the metal oxide film is preferably an amorphous film of indium tin oxide.

[0100] -Refractive index, film thickness-

[0101] The refractive index of the metal oxide film is preferably 2.0 to 2.5, more preferably 2.1 to 2.2. By setting the refractive index of the metal oxide film within the above range, the reflectivity of the optical laminate in the visible light region can be easily reduced in combination with an optionally formed low refractive index layer.

[0102] Preferred ranges of the refractive index of the metal oxide film include, in addition to the above ranges, 2.0 to 2.2, and 2.1 to 2.5.

[0103] To easily keep the emissivity α below 0.75, the thickness of the metal oxide film is preferably 10 nm or greater, more preferably 20 nm or greater, and even more preferably 30 nm or greater. The degree to which a layer with low emissivity reflects radiant heat to the outside tends to increase with increasing thickness. Therefore, to suppress temperature rise in the optical layered body, the thickness of the metal oxide film is preferably 100 nm or greater.

[0104] It should be noted that if the thickness of the metal oxide film is too thick, there is a tendency for the transparency to decrease. In order to reduce the thickness of the film, the thickness of the metal oxide film is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less.

[0105] Preferred ranges of the thickness of the metal oxide film include 10 nm to 1000 nm, 10 nm to 500 nm, 10 nm to 300 nm, 20 nm to 1000 nm, 20 nm to 500 nm, 20 nm to 300 nm, 30 nm to 1000 nm, 30 nm to 500 nm, and 30 nm to 300 nm.

[0106] To improve bending resistance and facilitate application to foldable and rollable image display devices, the thickness of the metal oxide film is preferably from 30 nm to 250 nm, more preferably from 30 nm to 150 nm.

[0107] In order to reduce the reflectivity in the visible light region by combining with an optionally formed low refractive index layer, the thickness of the metal oxide film is preferably 100 nm to 200 nm, more preferably 100 nm to 170 nm, and even more preferably 100 nm to 140 nm.

[0108] <Functional layer α>

[0109] The optical layered body may have one or more functional layers α between the plastic film and the layer containing the metal oxide.

[0110] Examples of the functional layer α include a hard coat layer, a high refractive index layer, a medium refractive index layer, a low refractive index layer, an antiglare layer, an antistatic layer, and a circularly polarizing layer. A single hard coat layer is preferred.

[0111] Hard Coating

[0112] In order to improve scratch resistance and pencil hardness, the optical laminate preferably has a hard coat layer as the functional layer α.

[0113] The hard coat layer preferably comprises a resin component. The resin component of the hard coat layer preferably comprises a cured product of a curable resin composition as a main component. The main component refers to 50% by mass or more of the total resin of the hard coat layer, preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0114] Examples of the cured product of the curable resin composition include a cured product of a thermosetting resin composition and a cured product of an ionizing radiation curable resin composition. In order to further improve the mechanical strength, a cured product of an ionizing radiation curable resin composition is preferred.

[0115] Examples of the curable resin composition of the hard coat layer include the curable resin compositions exemplified for the layer containing the metal oxide.

[0116] The hard coat layer may contain additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, and a refractive index adjuster as needed.

[0117] To improve scratch resistance, the hard coat layer preferably has a thickness of 0.1 μm or greater, more preferably 0.5 μm or greater, more preferably 1.0 μm or greater, and even more preferably 2.0 μm or greater. Furthermore, to suppress heat buildup and curling, the hard coat layer preferably has a thickness of 100 μm or less, more preferably 50 μm or less, more preferably 30 μm or less, more preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0118] Preferred ranges of the thickness of the hard coat layer include 0.1 μm to 100 μm, 0.1 μm to 50 μm, 0.1 μm to 30 μm, 0.1 μm to 20 μm, 0.1 μm to 15 μm, 0.1 μm to 10 μm, 0.5 μm to 100 μm, 0.5 μm to 50 μm, 0.5 μm to 30 μm, 0.5 μm to 20 μm, 0.5 μm to 15 μm, and 0.5 μm to 100 μm. 10μm or more, 1.0μm or more and 10μm or less, 1.0μm or more and 100μm or less, 1.0μm or more and 50μm or less, 1.0μm or more and 30μm or less, 1.0μm or more and 20μm or less, 1.0μm or more and 15μm or less, 1.0μm or more and 10μm or less, 2.0μm or more and 100μm or less, 2.0μm or more and 50μm or less, 2.0μm or more and 30μm or less, 2.0μm or more and 20μm or less, 2.0μm or more and 15μm or less, 2.0μm or more and 10μm or less.

[0119] <Functional layer β>

[0120] The optical layered body may have one or more functional layers β on the side of the layer containing the metal oxide opposite to the plastic film.

[0121] As the functional layer β, a low refractive index layer, a high refractive index layer, an anti-glare layer, an antifouling layer, and a circular polarizing layer can be cited. The functional layer can have the above functions. For example, the low refractive index layer can have antifouling properties or anti-glare properties.

[0122] The total thickness of the one or more functional layers β is preferably 1000 nm or less, more preferably 500 nm or less, more preferably 350 nm or less, more preferably 200 nm or less, and more preferably 150 nm or less.

[0123] The layer located on the opposite side of the plastic film relative to the layer containing the metal oxide increases in temperature due to radiant heat from outside the image display device and radiant heat generated from within the image display device and transmitted through the layer containing the metal oxide. Therefore, the greater the total thickness of the one or more functional layers β, the more heat tends to accumulate in the one or more functional layers β. Therefore, by setting the total thickness of the one or more functional layers β to 350 nm or less, the temperature rise of the optical laminate can be easily suppressed. Furthermore, by setting the total thickness of the one or more functional layers β to 350 nm or less, the emissivity α can be easily reduced.

[0124] Furthermore, considering that the total thickness of one or more functional layers β is preferably thin, the functional layer β is preferably a single layer, and more preferably a single layer of a low refractive index layer.

[0125] Low refractive index layer

[0126] The low-refractive-index layer is preferably located on the outermost surface on the side opposite to the plastic film, based on the layer containing the metal oxide.

[0127] The refractive index of the low refractive index layer is preferably 1.10 to 1.48, more preferably 1.20 to 1.45, more preferably 1.26 to 1.40, more preferably 1.28 to 1.38, and more preferably 1.30 to 1.32.

[0128] Preferred ranges of the refractive index of the low refractive index layer include 1.10 to 1.48, 1.10 to 1.45, 1.10 to 1.40, 1.10 to 1.38, 1.10 to 1.32, 1.20 to 1.48, 1.20 to 1.45, 1.20 to 1.40, 1.20 to 1.38, 1.20 to 1.32, 1.26 to 1.48, 1.26 to 1.48, 5 or less, 1.26 or more and less than 1.40, 1.26 or more and less than 1.38, 1.26 or more and less than 1.32, 1.28 or more and less than 1.48, 1.28 or more and less than 1.45, 1.28 or more and less than 1.40, 1.28 or more and less than 1.38, 1.28 or more and less than 1.32, 1.30 or more and less than 1.48, 1.30 or more and less than 1.45, 1.30 or more and less than 1.40, 1.30 or more and less than 1.38, 1.30 or more and less than 1.32.

[0129] The thickness of the low refractive index layer is preferably 80 nm to 150 nm, more preferably 85 nm to 110 nm, and more preferably 90 nm to 105 nm. In addition, the thickness of the low refractive index layer is preferably greater than the average particle size of the low refractive index particles such as hollow particles.

[0130] As the preferred range of the thickness of low-refractive index layer, can enumerate more than 80nm and less than 150nm, more than 80nm and less than 110nm, more than 80nm and less than 105nm, more than 85nm and less than 150nm, more than 85nm and less than 110nm, more than 85nm and less than 105nm, more than 90nm and less than 150nm, more preferably more than 90nm and less than 110nm.More preferably the thickness of low-refractive index layer satisfies above-mentioned preferred range, and the thickness of low-refractive index layer is greater than the average grain diameter of low-refractive index particles such as hollow particle.

[0131] As the method for forming low-refractive index layer, can be roughly divided into wet method and dry method.As wet method, can enumerate the method that uses metal alkoxide etc. to form by sol-gel method, the method that is formed by coating the resin of low refractive index such as fluororesin, be coated on the method that the low-refractive index layer that contains low-refractive index particles in resin combination forms with coating fluid.As dry method, can enumerate the method that selects the particle with desired refractive index from low-refractive index particles and forms by physical vapor deposition method or chemical vapor deposition method.

[0132] The wet process is superior to the dry process in terms of production efficiency, suppression of oblique reflection tint, and chemical resistance. In this embodiment, the wet process is preferably formed from a low-refractive-index layer-forming coating liquid containing low-refractive-index particles in a binder resin composition for reasons of adhesion, water resistance, scratch resistance, and low refractive index. In other words, the low-refractive-index layer preferably contains a binder resin and low-refractive-index particles.

[0133] The binder resin of low-refractive index layer preferably comprises the cured product of curable resin composition.In addition, the cured product of curable resin composition is preferably more than 10 mass %, more preferably more than 30 mass %, more preferably more than 50 mass %, more preferably more than 70 mass %, more preferably more than 90 mass %, most preferably 100 mass %.

[0134] Examples of the curable resin composition of the low refractive index layer include the curable resin compositions exemplified for the layer containing the metal oxide.

[0135] The low refractive index particles preferably include one or more selected from hollow particles and non-hollow particles. In addition, in order to balance low reflection and scratch resistance, it is preferred to use one or more selected from hollow particles and one or more selected from non-hollow particles in combination.

[0136] The material of the hollow particles and the non-hollow particles may be any of inorganic compounds such as silicon dioxide and magnesium fluoride, or organic compounds, but silicon dioxide is preferred for reasons of lowering the refractive index and increasing strength.

[0137] Taking into account optical properties and mechanical strength, the average particle size of the hollow silica particles is preferably from 50 nm to 200 nm, more preferably from 60 nm to 80 nm. Preferred ranges for the average particle size of the hollow silica particles, in addition to the above ranges, include from 50 nm to 80 nm, and from 60 nm to 200 nm.

[0138] In order to prevent the aggregation of the non-hollow silica particles while taking dispersibility into consideration, the average particle size of the non-hollow silica particles is preferably from 5 nm to 100 nm, more preferably from 10 nm to 20 nm. Preferred ranges for the average particle size of the non-hollow silica particles, in addition to the above ranges, include from 5 nm to 20 nm, and from 10 nm to 100 nm.

[0139] The higher the content of the hollow silica particles, the higher the filling rate of the hollow silica particles in the binder resin, and the lower the refractive index of the low refractive index layer. Therefore, the content of the hollow silica particles is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, relative to 100 parts by mass of the binder resin.

[0140] On the other hand, if the content of hollow silica particles relative to the binder resin is too high, the amount of hollow silica particles exposed from the binder resin increases, and the amount of binder resin binding the particles decreases. Consequently, the hollow silica particles are easily damaged or fall off, and the mechanical strength of the low refractive index layer, such as its scratch resistance, tends to decrease. Therefore, the content of hollow silica particles is preferably 400 parts by mass or less, and more preferably 300 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0141] Preferred ranges of the content of the hollow silica particles per 100 parts by mass of the binder resin include 100 to 400 parts by mass, 100 to 300 parts by mass, 150 to 400 parts by mass, and 150 to 300 parts by mass.

[0142] If the content of non-hollow silica particles is small, even if non-hollow silica particles are present on the surface of the low-refractive index layer, sometimes the hardness rise will not be affected. In addition, if a large amount of non-hollow silica particles are contained, the influence of the shrinkage unevenness caused by the polymerization of the binder resin becomes smaller, and therefore the concavo-convexity generated on the surface of the low-refractive index layer after the resin is cured can be reduced. Therefore, relative to 100 mass parts of binder resin, the content of non-hollow silica particles is preferably more than 10 mass parts, more preferably more than 50 mass parts, more preferably more than 70 mass parts, and more preferably more than 100 mass parts.

[0143] On the other hand, if the content of non-hollow silica particles is too high, the non-hollow silica particles tend to aggregate, resulting in uneven shrinkage of the binder resin, which increases surface irregularities. Therefore, the content of non-hollow silica particles is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, per 100 parts by mass of the binder resin.

[0144] Preferred ranges of the content of the non-hollow silica particles relative to 100 parts by mass of the binder resin include 10 parts by mass to 200 parts by mass, 10 parts by mass to 150 parts by mass, 50 parts by mass to 200 parts by mass, 50 parts by mass to 150 parts by mass, 70 parts by mass to 200 parts by mass, 70 parts by mass to 150 parts by mass, 100 parts by mass to 200 parts by mass, and 100 parts by mass to 150 parts by mass.

[0145] By including hollow silica particles and non-hollow silica particles in the binder resin at the above ratio, the barrier properties of the low refractive index layer can be improved. This is presumably because the silica particles are uniformly dispersed at a high filling rate, which inhibits the permeation of gases and the like.

[0146] Furthermore, various cosmetics, such as sunscreens and hand creams, sometimes contain low-molecular-weight polymers with low volatility. Improving the barrier properties of the low-refractive index layer can inhibit the low-molecular-weight polymer from penetrating into the coating film of the low-refractive index layer, thereby preventing adverse effects such as abnormal appearance caused by the long-term retention of the low-molecular-weight polymer in the coating film. It should be noted that, in order to reduce the emissivity α, it is also preferable to inhibit the low-molecular-weight polymer from penetrating into the coating film of the low-refractive index layer.

[0147] <Emissivity>

[0148] The optical layered body of the present invention needs to have an emissivity of 0.27 to 0.75, measured from the side of the layer containing the metal oxide with respect to light in the wavelength range of 2000 nm to 22000 nm, based on the plastic film. As described above, this emissivity may be referred to as "emissivity α" in this specification.

[0149] When the emissivity α exceeds 0.75, the optical layered body absorbs radiant heat caused by the external environment such as the temperature inside the vehicle, and thus the visibility of the image display device including the optical layered body is reduced.

[0150] Furthermore, when the emissivity α is less than 0.27, radiant heat generated within the image display device is returned to the inner side of the image display device by the optical layered body, thereby increasing the temperature within the image display device and reducing the visibility of the image display device including the optical layered body. Radiant heat generated within the image display device includes radiant heat generated by the display element.

[0151] The emissivity α is preferably 0.35 to 0.70, more preferably 0.37 to 0.67, and even more preferably 0.40 to 0.60.

[0152] With the improvement of display technology in recent years, for example, in order to give the display curved surface and improve the appearance design, a flexible optical laminate is sometimes needed. If the emissivity α is less than 0.40, the layer containing the metal oxide is easy to harden, and the curved surface processability sometimes causes problems. Therefore, for the purpose of curved surface processability, it is preferred to make the emissivity α be 0.40 or more. In addition, the lower the emissivity α, the more the temperature rise caused by the external environment can be controlled, and thus it is good. Therefore, for example, if the emissivity α is less than 0.60, it is easy to reduce the surface temperature of the optical laminate to a degree that is easy to touch with the hand. In addition, it is easy to suppress the optical laminate itself from acting as a heat source, so it is preferred from the aspect of being easy to reduce the somatosensory temperature when the face or hand is close to the image display device for a long time.

[0153] Preferred ranges of the emissivity α include 0.27 to 0.75, 0.27 to 0.70, 0.27 to 0.67, 0.27 to 0.60, 0.35 to 0.75, 0.35 to 0.70, 0.35 to 0.67, 0.35 to 0.60, 0.37 to 0.75, 0.37 to 0.70, 0.37 to 0.67, 0.37 to 0.60, 0.40 to 0.75, 0.40 to 0.70, 0.40 to 0.67, and 0.40 to 0.60.

[0154] In this specification, examples of reduced visibility include: "various properties such as brightness, hue, and reflective directional characteristics become uneven in local areas within the display screen of the image display device", "the above-mentioned various properties become uneven near the center and near the ends of the display screen of the image display device", and "the above-mentioned various properties change in a high temperature environment compared to a normal temperature environment".

[0155] Such a reduction in visibility is considered to be caused by, for example, deformation of the optical layered body due to high temperature.

[0156] Image display devices typically include cooling mechanisms such as air cooling fans, but the cooling effect of these cooling mechanisms varies depending on the location of the image display device. Furthermore, since radiant heat is continuously generated, the differences in cooling effect gradually accumulate, resulting in temperature differences depending on the location within the image display device. Consequently, areas with different temperatures may sometimes occur within the surface of the optical layered body. In this case, due to localized changes in the physical properties of the optical layered body, it is believed that visibility may be reduced.

[0157] According to the optical layered body of the present invention, the reduction in visibility due to the above-mentioned reasons can be suppressed.

[0158] In this specification, the emissivity α refers to the emissivity at room temperature measured in accordance with JIS A1423: 1983. As an emissivity measuring device, for example, there is "TSS-5X-2" manufactured by JAPAN SENSOR CO., LTD.

[0159] It should be noted that, in this specification, unless otherwise stated, various physical properties such as emissivity, spectral transmittance, light reflectance Y value, total light transmittance and haze are measured after the sample for measurement is exposed to an environment with a temperature of 23±5°C and a relative humidity of 40% to 65% for more than 30 minutes and then measured in the same environment.

[0160] In this specification, unless otherwise specified, various physical properties such as emissivity, spectral transmittance, light reflectance Y value, total light transmittance, and haze are average values of 20 measurements.

[0161] <Various physical properties>

[0162] The average value of the spectral transmittance of the layer containing the metal oxide in the wavelength range of 8200 nm to 9000 nm is preferably 80% or less, more preferably 70% or less, and even more preferably 60% or less.

[0163] The following equation (1) is a formula that expresses the peak wavelength (λ) of radiation emitted by a black body at any temperature and is known as the Wien equation. In the equation, "T" represents temperature in degrees Celsius.

[0164] λ(nm)≈2897 / (T+273)(1)

[0165] For example, the temperature of the atmosphere and dashboard inside a car in summer, as well as the window temperature in a closed room in summer, is said to be approximately 50° C. to 80° C. Substituting 50 and 80 into T in the above formula (1), λ becomes approximately 9000 nm and 8200 nm.

[0166] Specifically, the wavelength range of the spectral transmittance is specifically set to 8200 nm to 9000 nm, taking into account the summer temperature of automobiles and the window temperature in enclosed rooms. Therefore, by setting the average spectral transmittance to 80% or less, the optical laminate effectively blocks infrared radiation emitted from the interior of a vehicle, thereby further suppressing temperature increases in the image display device and facilitating further reductions in visibility.

[0167] The lower limit of the average value of the spectral transmittance is not particularly limited, but is usually 30% or more, preferably 40% or more.

[0168] In this specification, the spectral transmittance of the layer containing a metal oxide refers to a value calculated by the following measurement (A1) and conversion processing (A2).

[0169] (A1) The absorbance of the layer containing the metal oxide at each wavelength is measured by FTIR reflection.

[0170] (A2) A process is performed to convert the absorbance at each wavelength in A1 into the transmittance at each wavelength.

[0171] In the measurement (A1) above, the measurement is performed from the side of the layer containing the metal oxide with the plastic film as the reference. Furthermore, even if the functional layer β is present on the layer containing the metal oxide, the measurement (A1) above can be performed with the functional layer β present if the total thickness of the functional layer β is approximately 250 nm or less. Furthermore, the absorbance of the layer containing the metal oxide measured with the functional layer β present can be converted in the above (A2) to calculate the spectral transmittance of the layer containing the metal oxide.

[0172] The optical layered body preferably has a light reflectance Y value measured from the layer side containing the metal oxide based on the plastic film, which is preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

[0173] In this specification, the light reflectance Y value refers to the light reflectance Y value of the CIE1931 standard colorimetric system, and is measured at an incident angle of 5 degrees.

[0174] The light reflectance Y value can be calculated using spectrophotometry. As a spectrophotometer, for example, there is a product name "UV-2450" manufactured by Shimadzu Corporation.

[0175] When measuring the light reflectance, it is preferable to attach a black plate to the back surface of the plastic film.

[0176] The total light transmittance of the optical layered body according to JIS K7361-1:1997 is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more.

[0177] The haze of the optical layered body according to JIS K7136:2000 is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

[0178] The total light transmittance and haze are preferably measured with the layer containing the metal oxide as a reference and the surface on the plastic film side as the light incident surface.

[0179] The optical layered body preferably has a surface roughness within a predetermined range on the outermost side of the layer containing the metal oxide based on the plastic film.

[0180] Specifically, the arithmetic mean roughness Ra of the outermost surface at a sampling length of 2.5 mm according to JIS B0601:2001 is preferably 3 μm or less, more preferably 1 μm or less, and even more preferably 0.1 μm or less. Setting Ra to 3 μm or less facilitates setting the emissivity α to 0.75 or less.

[0181] When measuring Ra, it is preferable that the measurement conditions of the measuring device be set to 1000 times in the transverse direction and 20000 times in the longitudinal direction.

[0182] <Layer Structure>

[0183] The overall layer structure of the optical layered body of the present invention is not particularly limited, and examples thereof include the following (1) to (6): In addition, “ / ” indicates the interface between layers.

[0184] (1) Plastic film / layer containing metal oxide

[0185] (2) Plastic film / hard coat layer / layer containing metal oxide

[0186] (3) Plastic film / layer containing metal oxide / low refractive index layer

[0187] (4) Plastic film / hard coat layer / layer containing metal oxide / low refractive index layer

[0188] (5) Plastic film / layer containing metal oxide / high refractive index layer / low refractive index layer

[0189] (6) Plastic film / hard coat layer / layer containing metal oxide / high refractive index layer / low refractive index layer

[0190] <Total Thickness>

[0191] In order to improve mechanical strength, the total thickness of the optical laminate is preferably 10 μm or more, more preferably 30 μm or more, and further preferably 45 μm or more. In addition, in order to facilitate application to foldable image display devices and rollable image display devices, the total thickness of the optical laminate is preferably 130 μm or less, more preferably 100 μm or less, further preferably 90 μm or less, and further preferably 75 μm or less.

[0192] Preferred ranges of the total thickness of the optical laminate include 10 μm to 130 μm, 10 μm to 100 μm, 10 μm to 90 μm, 10 μm to 75 μm, 30 μm to 130 μm, 30 μm to 100 μm, 30 μm to 90 μm, 30 μm to 75 μm, 45 μm to 130 μm, 45 μm to 100 μm, 45 μm to 90 μm, and 45 μm to 75 μm.

[0193] By setting the total thickness of the optical layered body within the above range, it is possible to easily achieve the following in the evaluation using an outwardly bent mandrel test bar: In addition, within the above range, an optical laminate having a total thickness of 75 μm or less can also be easily realized. The following. That is, by setting the total thickness of the optical laminate within the above range, the optical laminate can be easily applied to foldable image display devices and rollable image display devices. It should be noted that "bending outward" means that the side having the layer containing the metal oxide is bent outward with respect to the plastic film. In addition, "outside" refers to "the side away from the core rod."

[0194] [Polarizing plate]

[0195] The polarizing plate of the present invention comprises a polarizing element, a first transparent protective plate arranged on one side of the polarizing element, and a second transparent protective plate arranged on the other side of the polarizing element, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate of the present invention.

[0196] <Polarizing Element>

[0197] Examples of polarizing elements include sheet-type polarizing elements such as polyvinyl alcohol films, polyvinyl formal films, polyvinyl acetal films, and saponified films of ethylene-vinyl acetate copolymers dyed with iodine or the like and stretched; wire-grid polarizing elements composed of a large number of parallel metal wires; coated polarizing elements coated with lyotropic liquid crystals or dichroic host-guest materials; and multilayer thin-film polarizing elements. These polarizing elements may be reflective polarizing elements that reflect polarized components that are not transmitted.

[0198] <Transparent protective plate>

[0199] A first transparent protective plate is placed on one side of the polarizing element, and a second transparent protective plate is placed on the other side. At least one of the first transparent protective plate and the second transparent protective plate is the optical laminate of the present invention.

[0200] The optical layered body is preferably arranged so that the surface on the plastic film side faces the polarizing element side based on the layer containing the metal oxide.

[0201] Examples of the first transparent protective plate and the second transparent protective plate other than the optical laminate include plastic films and glass, and plastic films are preferred.

[0202] Examples of the plastic film include polyester films, polycarbonate films, cycloolefin polymer films, acrylic films, and triacetylcellulose films. Stretched films of these are preferred for mechanical strength.

[0203] The polarizing element and the transparent protective plate are preferably bonded together with an adhesive. A general-purpose adhesive can be used, and a PVA-based adhesive is preferred.

[0204] The polarizer of the present invention may be a polarizer in which both the first transparent protective plate and the second transparent protective plate are the optical laminate of the present invention, but preferably one of the first transparent protective plate and the second transparent protective plate is the optical laminate of the present invention. In addition, when the polarizer of the present invention is used as a polarizer disposed on the light-emitting surface side of a display element, the transparent protective plate on the light-emitting surface side of the polarizing element is preferably the optical laminate of the present invention.

[0205] [Surface panel for image display device]

[0206] The surface plate for an image display device of the present invention is obtained by laminating the above-mentioned optical layered body of the present invention to a resin plate or a glass plate.

[0207] The optical laminate is preferably arranged so that the surface on the plastic film side faces the resin plate or the glass plate side based on the layer containing the metal oxide.

[0208] The surface sheet for an image display device is preferably arranged so that the surface on which the optical layered body is bonded faces the front side. In other words, the surface sheet for an image display device is preferably arranged so that the surface on which the optical layered body is bonded faces the side opposite to the display element.

[0209] As the resin plate or the glass plate, those commonly used as surface plates of image display devices can be used.

[0210] To improve strength, the thickness of the resin plate or glass plate is preferably 10 μm or more. The upper limit of the thickness of the resin plate or glass plate is generally 5000 μm or less. However, in recent years, thinner image display devices have become popular. Therefore, the thickness is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 100 μm or less.

[0211] Preferred ranges of the thickness of the resin plate or glass plate include 10 μm to 5000 μm, 10 μm to 1000 μm, 10 μm to 500 μm, and 10 μm to 100 μm.

[0212] [Image Display Device]

[0213] The image display device of the present invention includes the optical layered body of the present invention on the light emitting surface side of a display element.

[0214] The optical laminate is preferably arranged so that the surface of the layer containing the metal oxide faces the opposite side to the display element with respect to the plastic film.

[0215] Furthermore, the optical layered body is preferably disposed on the outermost surface of the image display device.

[0216] Furthermore, in order to suppress heat conduction, it is preferable to arrange the image display device so that air is interposed between the display element and the optical laminate.

[0217] Examples of display elements include liquid crystal display elements, organic EL display elements, inorganic EL display elements, and other EL display elements, plasma display elements, and further include LED display elements such as Micro LED display elements and Mini LED display elements. These display elements may have a touch panel function inside the display element.

[0218] As the display mode of the liquid crystal of the liquid crystal display element, IPS mode, VA mode, multi-domain mode, OCB mode, STN mode, TSTN mode, etc. can be mentioned. In the case where the display element is a liquid crystal display element, a backlight is required. The backlight is arranged on the side of the liquid crystal display element opposite to the side having the optical laminate.

[0219] The image display device may be a foldable image display device or a rollable image display device. In addition, the image display device may be an image display device with a touch panel.

[0220] Note that portable image display devices and image display devices incorporated into a car instrument panel are likely to be exposed to high-temperature environments and are therefore preferred from the perspective of easily exhibiting the effects of the present invention.

[0221] The image display device preferably has a general-purpose heat dissipation mechanism on the side opposite to the light emitting surface of the display element. Examples of the general-purpose heat dissipation mechanism include an air cooling fan, a heat sink, a heat pump, and a Peltier element.

[0222] Example

[0223] The present invention will be described in detail below with reference to Examples and Comparative Examples. However, the present invention is not limited to the embodiments described in the Examples.

[0224] 1. Evaluation and measurement

[0225] The optical layered products obtained in the Examples and Comparative Examples were subjected to the following measurements and evaluations. The results are shown in Table 1. Unless otherwise stated, the atmosphere during each measurement and evaluation was a temperature of 23±5°C and a relative humidity of 40% to 65%. Prior to each measurement and evaluation, the sample was exposed to this atmosphere for at least 30 minutes before the start of the measurement and evaluation.

[0226] In addition, the optical layered body of Comparative Example 2 does not have a layer containing a metal oxide. Therefore, regarding Comparative Example 2, the following evaluation and measurement were performed assuming that the heat release layer of Comparative Example 2 is a layer containing a metal oxide.

[0227] 1-1. Emissivity

[0228] The emissivity of the optical layered bodies of the Examples and Comparative Examples at room temperature was measured in accordance with JIS A1423:1983. Specifically, the emissivity of the optical layered body for light in the wavelength range of 2000 nm to 22000 nm, measured from the side of the layer containing the metal oxide with respect to the substrate, was measured. As described above, this emissivity may be referred to as "emissivity α" in this specification.

[0229] When the emissivity α exceeded 0.75, it was evaluated as C. When the emissivity α was less than 0.27, it was evaluated as B. When the emissivity α was 0.27 or more and 0.75 or less, it was evaluated as A or higher, and when the emissivity α was 0.37 or more and 0.60 or less, it was evaluated as AA.

[0230] If the emissivity α is too high, the optical layered body absorbs radiant heat generated by the external environment, causing an increase in the temperature of the image display device. On the other hand, if the emissivity α is too low, the optical layered body is less likely to absorb radiant heat generated by the external environment. However, radiant heat generated inside the image display device is returned to the inside of the image display device by the optical layered body, and an increase in the temperature inside the image display device is expected.

[0231] The emissivity meter used was a TSS-5X-2 manufactured by Japan Sensor Co., Ltd. The emissivity reference sheets included with the meter were two types: 0.06 and 0.97. The main specifications of the meter were as follows.

[0232] <Specifications>

[0233] Measuring area: Φ15mm

[0234] Measuring distance: 12mm

[0235] 1-2. Spectral transmittance

[0236] The spectral transmittance of the metal oxide-containing layer of the optical layered bodies of Examples and Comparative Examples in the wavelength range of 8200 nm to 9000 nm was measured. As described in the main text of the specification, the absorbance of the metal oxide-containing layer at each wavelength was measured by FTIR reflectance. The absorbance at each wavelength was then converted into transmittance at each wavelength, and the spectral transmittance of the metal oxide-containing layer in the wavelength range of 8200 nm to 9000 nm was calculated.

[0237] The FIIR measuring instrument used was the "NICOLET iS10" manufactured by Thermo Fisher Scientific. In addition, the "Single Reflection Ge ATR Accessory Base" manufactured by the same company was used as an accessory. Regarding the measurement conditions, the measuring surface was oriented toward the Ge crystal surface, and the sample was fixed by pressure using a pressure tower. The measurement conditions were: 1 incidence, 45°, 32 scans, 8 resolution, DTGS KBr detector, mirror speed 0.6329, aperture open, and a measurement range of 680 cm. -1 More than 4000cm -1 The absorbance was converted to transmittance and the cm -1 The average value of the transmittance in the wavelength range was calculated by converting the result to nm.

[0238] 1-3. Light reflectivity Y value

[0239] Samples were prepared by laminating a black plate (Comoglass DFA2CG 502K (black), 2 mm thick, manufactured by KURARAY Co., Ltd.) to the side of the substrate opposite the metal oxide layer of the optical laminates of Examples and Comparative Examples via a 25 μm thick transparent adhesive layer (Panaclean PD-S1, manufactured by Panac). Light was incident on these samples at an incident angle of 5 degrees from the metal oxide layer side relative to the substrate, and the light reflectance Y value was measured.

[0240] Regarding the light reflectance Y value, the 5° regular reflectance was measured using a spectrophotometer (manufactured by Shimadzu Corporation, trade name: UV-2450) at a viewing angle of 2 degrees, illuminant C, and a wavelength range of 380 nm to 780 nm. The value representing the light reflectance was then determined as the reflectance. This value was calculated using software (UVPC Color Measurement Version 3.12 built into the device) that converts it to the brightness perceived by the human eye.

[0241] 1-4. Total light transmittance and haze

[0242] The optical laminates of Examples and Comparative Examples were measured for total light transmittance according to JIS K7361-1: 1997 and haze according to JIS K7136: 2000 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory).

[0243] 1-5. Surface temperature

[0244] The optical laminates of Examples and Comparative Examples were arranged on a commercially available liquid crystal display device (manufactured by Amazon, trade name Kindle Fire HDX) with the substrate side facing the display device side to prepare a simulated liquid crystal display device.

[0245] Assuming the interior of a car in summer, a simulated liquid crystal display device was placed in an oven at 80°C and taken out after 10 minutes. Immediately after taking out the simulated liquid crystal display device, the temperature was measured from the surface side using an IR camera (manufactured by FLIR Systems, trade name FLIRE4). The distance between the optical film and the IR camera was 30 cm. The maximum temperature on the optical laminate is shown in Table 1. A maximum temperature of 65°C or less is considered an acceptable level. Considering the actual processing of image display, the maximum temperature is more preferably 60°C or less, and even more preferably 57°C or less.

[0246] 1-6. Visibility (unevenness)

[0247] The simulated liquid crystal display device prepared in 1-5 was placed in an oven at 80°C and taken out after 10 minutes. After taking out the simulated liquid crystal display device, the screen of the liquid crystal display device was immediately displayed in green monochrome, and the brightness and hue of the display screen were visually evaluated to see whether there were any uneven areas. The evaluators were 10 people with a visual acuity of 0.7 or above. The above visual acuity includes corrected visual acuity. The distance between the evaluators and the liquid crystal display device was 50 cm. If 8 or more people answered that there were no uneven areas in brightness and hue, it was recorded as "A", and if 7 or fewer people answered that there were no uneven areas in brightness and hue, it was recorded as "C".

[0248] 2. Preparation of optical laminates

[0249] [Example 1]

[0250] The following hard coat coating liquid was applied onto a substrate (triacetylcellulose film, thickness 60 μm), dried, and irradiated with ultraviolet rays to form a hard coat layer having a thickness of 5 μm.

[0251] Next, the following coating liquid 1 for a metal oxide layer was applied onto the hard coat layer, dried, and irradiated with ultraviolet rays to form a layer containing ITO particles as a metal oxide with a film thickness of 350 nm.

[0252] Next, the following low-refractive index layer coating liquid was applied onto the layer containing the metal oxide, dried, and irradiated with ultraviolet light to form a low-refractive index layer having a thickness of 100 nm. This gave an optical layered body of Example 1.

[0253] <Hard Coating Liquid>

[0254] The following components were mixed to prepare a hard coat layer-forming composition.

[0255] Pentaerythritol triacrylate 46 parts by mass

[0256] (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30)

[0257] 4 parts by mass of photopolymerization initiator

[0258] (IGM Resins BV, trade name: Omnirad 184)

[0259] 50 parts by mass of methyl ethyl ketone

[0260] <Metal Oxide Layer Coating Liquid 1>

[0261] The following components were mixed to prepare a coating liquid 1 for a metal oxide layer.

[0262] 1 part by mass of pentaerythritol triacrylate

[0263] (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30)

[0264] 8.5 parts by mass of ITO particles

[0265] (Average particle size 30nm)

[0266] 0.4 parts by mass of photopolymerization initiator

[0267] (IGM Resins BV, trade name: Omnirad 184)

[0268] 0.03 parts by mass of leveling agent

[0269] (DIC Corporation's MEGAFAC F-477)

[0270] 89 parts by mass of methyl isobutyl ketone

[0271] <Coating Liquid for Low Refractive Index Layer>

[0272] The following components were mixed to prepare a coating liquid for a low refractive index layer.

[0273] Pentaerythritol triacrylate 0.4 parts by mass

[0274] (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30)

[0275] 0.2 parts by mass of fluorinated polymer (solid content)

[0276] (JSR Corporation, trade name: JN35)

[0277] 0.7 parts by mass of fluorinated monomer (solid content)

[0278] (Manufactured by Kyoeisha Chemical Co., Ltd., trade name: LINC3A)

[0279] 1.7 parts by mass of hollow silica particles

[0280] (average particle size 75nm, refractive index 1.212)

[0281] 0.6 parts by mass of solid silica particles

[0282] (average particle size 15nm)

[0283] 0.06 parts by mass of leveling agent

[0284] (Shin-Etsu Silicone Co., Ltd., trade name: X-22-164E)

[0285] 0.09 parts by mass of photopolymerization initiator

[0286] (IGM Resins BV, trade name: Omnirad 127)

[0287] 97 parts by mass of solvent

[0288] (Mixed solvent of methyl isobutyl ketone and propylene glycol monomethyl ether acetate in a mass ratio of 70:30, with a solid content of 2% by mass and a thickness of 100 μm)

[0289] [Example 2]

[0290] An optical layered body of Example 2 was obtained in the same manner as in Example 1 except that the thickness of the layer containing the metal oxide was changed to 700 nm.

[0291] [Example 3]

[0292] An optical layered body of Example 3 was obtained in the same manner as in Example 1 except that the thickness of the layer containing the metal oxide was changed to 200 nm.

[0293] [Example 4]

[0294] An optical layered body of Example 4 was obtained in the same manner as in Example 1 except that the substrate (triacetylcellulose film, 60 μm in thickness) was changed to a biaxially oriented polyethylene terephthalate film having a thickness of 100 μm.

[0295] [Example 5]

[0296] An optical layered body of Example 5 was obtained in the same manner as in Example 1 except that the coating liquid 1 for a metal oxide layer was changed to the coating liquid 2 for a metal oxide layer described below and the thickness was changed to 900 nm.

[0297] <Metal Oxide Layer Coating Liquid 2>

[0298] 1 part by mass of pentaerythritol triacrylate

[0299] (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30)

[0300] 9.6 parts by mass of Al-doped ZnO particles

[0301] 0.4 parts by mass of photopolymerization initiator

[0302] (IGM Resins BV, trade name: Omnirad 184)

[0303] 0.03 parts by mass of leveling agent

[0304] (DIC Corporation's MEGAFAC F-477)

[0305] 89 parts by mass of methyl isobutyl ketone

[0306] [Example 6]

[0307] The metal oxide layer coating liquid 1 was replaced with the following metal oxide layer coating liquid 3, and the thickness of the metal oxide layer was changed to 900 nm. Furthermore, the metal oxide layer coating liquid was applied and dried, and then irradiated with ultraviolet light, followed by heating at 100°C for 60 minutes. An optical layered body of Example 6 was obtained in the same manner as in Example 1, except for the above changes and additions.

[0308] [Example 7]

[0309] The hard coat layer coating liquid was applied onto a substrate (cycloolefin polymer film, 47 μm in thickness), dried, and then irradiated with ultraviolet light to form a hard coat layer having a thickness of 5 μm.

[0310] Next, the following coating liquid 3 for a metal oxide layer was applied on the hard coat layer, dried, and irradiated with ultraviolet light to form a 900 nm thick layer containing ITO particles as a metal oxide. The layer was then heated at 150° C. for 60 minutes.

[0311] Next, the low-refractive index layer coating liquid was applied onto the layer containing the metal oxide, dried, and irradiated with ultraviolet light to form a low-refractive index layer having a thickness of 100 nm. This gave an optical layered body of Example 7.

[0312] <Metal Oxide Layer Coating Liquid 3>

[0313] The following components were mixed to prepare a coating liquid 3 for a metal oxide layer.

[0314] Pentaerythritol triacrylate 0.5 parts by mass

[0315] (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30)

[0316] 9 parts by mass of ITO particles

[0317] (Average particle size 30nm)

[0318] 0.4 parts by mass of photopolymerization initiator

[0319] (IGM Resins BV, trade name: Omnirad 184)

[0320] 0.03 parts by mass of leveling agent

[0321] (DIC Corporation's MEGAFAC F-477)

[0322] 89 parts by mass of methyl isobutyl ketone

[0323] [Example 8]

[0324] A hard coat layer was formed on a substrate (a biaxially oriented polyethylene terephthalate film having a thickness of 100 μm) in the same manner as in Example 1.

[0325] Next, while introducing argon mixed with oxygen, sputtering was performed using an ITO target to form a 130 nm thick metal oxide film on the hard coat layer. The mass ratio of indium to tin in the ITO target was 90:10. The metal oxide film was an amorphous film of ITO.

[0326] Next, the surface on the metal oxide film side was subjected to corona discharge treatment, and then the same low refractive index layer as in Example 1 was formed on the metal oxide film to obtain an optical layered body of Example 8.

[0327] [Comparative Example 1]

[0328] While introducing argon mixed with oxygen, sputtering was performed using an ITO target to form a 140 nm thick metal oxide film on a 0.7 mm thick glass substrate. The mass ratio of indium to tin in the ITO target was 90:10. Subsequently, annealing was performed by heating at 200°C for 30 minutes, resulting in an optical laminate of Comparative Example 1 having a 140 nm thick ITO crystal film on the glass substrate.

[0329] [Comparative Example 2]

[0330] The following heat release layer coating liquid was applied to a substrate (triacetylcellulose film, 60 μm thick), dried, and irradiated with ultraviolet light to form a heat release layer having a thickness of 1 μm, thereby obtaining an optical layered body of Comparative Example 2.

[0331] <Coating Liquid for Heat Release Layer>

[0332] The following components were mixed to prepare a coating liquid for a heat release layer.

[0333] 3.2 parts by mass of pentaerythritol triacrylate

[0334] (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30)

[0335] 6.4 parts by mass of boron nitride particles

[0336] (average particle size 700nm)

[0337] 0.4 parts by mass of photopolymerization initiator

[0338] (IGM Resins BV, trade name: Omnirad 184)

[0339] 90 parts by mass of methyl ethyl ketone

[0340] [Table 1]

[0341] Table 1

[0342]

[0343] From the results in Table 1, it was confirmed that the optical layered body of the present invention can suppress a decrease in visibility under a high-temperature environment.

[0344] In addition, for the optical laminates of Examples 1 to 8, a mandrel test was performed in accordance with JIS K5600-5-1:1999. Specifically, a 100 mm × 25 mm test piece was cut out from the optical laminates of Examples 1 to 8, and the test piece was wound onto the mandrel in such a manner that the short side of the test piece was parallel to the mandrel. The test piece was wound onto the mandrel in such a manner that it was bent outward. As the mandrel, and

[0345] The results of the mandrel test showed that the optical layered bodies of Examples 1 to 8 No cracks were found in the metal oxide layer and the low refractive index layer. No cracks were observed in the metal oxide layer or the low refractive index layer. These results indicate that the optical layered bodies of Examples 1 to 8 exhibit excellent flexural resistance and are readily applicable to foldable and rollable image display devices. Furthermore, among the examples, the optical layered bodies of Examples 1 to 3 and 5 to 7 exhibited extremely excellent flexural resistance.

[0346] Explanation of symbols

[0347] 10: Plastic film

[0348] 20: Functional layer α

[0349] 21: Hard coating

[0350] 30: Layer containing metal oxide

[0351] 40: Functional layer β

[0352] 41: Low refractive index layer

[0353] 100: Optical laminate

Claims

1. An optical laminate, wherein: The optical laminate comprises a layer containing a metal oxide on a plastic film. The layer containing metal oxide contains a binder resin and metal oxide particles as the metal oxide, The content of the metal oxide particles is 150 parts by mass or more and 2000 parts by mass or less relative to 100 parts by mass of the binder resin. The optical layered body has an emissivity of 0.27 to 0.75 for light in a wavelength range of 2000 nm to 22000 nm, measured from the side of the layer containing the metal oxide with reference to the plastic film. The emissivity is the emissivity at room temperature measured in accordance with JIS A1423:1983.

2. The optical laminate according to claim 1, wherein The layer containing the metal oxide has an average value of spectral transmittance of 80% or less in a wavelength range of 8200 nm to 9000 nm.

3. The optical laminate according to claim 1, wherein The metal oxide particles include indium tin oxide particles.

4. The optical layered body according to any one of claims 1 to 3, wherein There is one or more functional layers α between the plastic film and the layer containing metal oxide. The optical layered body according to claim 4 , wherein: A hard coating layer is provided as the functional layer α.

6. The optical layered body according to any one of claims 1 to 5, wherein One or more functional layers β are provided on the side of the layer containing the metal oxide opposite to the plastic film.

7. The optical layered body according to claim 6, wherein The total thickness of the one or more functional layers β is 1000 nm or less.

8. The optical layered body according to claim 6 or 7, wherein A low-refractive-index layer is included as the functional layer β.

9. The optical layered body according to any one of claims 1 to 8, wherein The optical layered body has a light reflectance Y value of 2.0% or less, as measured from the side of the layer containing the metal oxide based on the plastic film.

10. A polarizing plate comprising a polarizing element, a first transparent protective plate disposed on one side of the polarizing element, and a second transparent protective plate disposed on the other side of the polarizing element, wherein: At least one of the first transparent protective plate and the second transparent protective plate is the optical laminate according to any one of claims 1 to 9. 11 . A surface plate for an image display device, comprising the optical layered body according to claim 1 laminated onto a resin plate or a glass plate. 12 . An image display device comprising the optical layered body according to claim 1 on a light emitting surface side of a display element.

Images