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

Abstract

Provided is an optical laminate which can suppress visibility from decreasing in a high-temperature environment.　The optical laminate comprises a metal oxide-containing layer on a plastic film, wherein the emissivity of the optical laminate for light having a wavelength range of 2000-22000 nm is 0.27 to 0.75 as measured from the metal oxide-containing layer side with reference to the plastic film.

Description

Technical Field

[0001] The present disclosure relates to an optical laminate, and a polarizing plate, a surface plate, and an image display device using the same.

Background Art

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

[0003] Among image display devices, car navigation systems are often installed on the dashboard of automobiles. In addition, portable image display devices such as smartphones are often brought into automobiles. The interior of a car in midsummer becomes hot, and especially the temperature of the dashboard may reach nearly 80°C. Therefore, an image display device may be exposed to high temperatures in the car for a long time, and in such a case, a decline in various performances of the image display device is a concern.

[0004] As a means for suppressing the temperature rise inside an automobile, laminated glass including a heat ray shielding structure has been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] If the window glass of an automobile is the laminated glass of Patent Document 1, the temperature rise inside the automobile can be suppressed to some extent. However, in an automobile where no countermeasure for suppressing the temperature rise is taken, an image display device will be exposed to high temperatures. Therefore, it is conceivable to use laminated glass, such as that described in Patent Document 1, for the protective glass of the image display device.

[0007] However, when the protective glass of an image display device, such as that of laminated glass as described in Patent Document 1, is exposed to high-temperature environments, a problem of reduced visibility of the image display device frequently occurs. In addition, when the protective glass of an image display device is made of laminated glass as described in Patent Document 1, there is also the problem of increased thickness.

[0008] This disclosure is made in view of the above circumstances and aims to provide an optical laminate, as well as a polarizing plate, a surface plate, and an image display device using the same, that can suppress the deterioration of visibility in high-temperature environments. [Means for solving the problem]

[0009] This disclosure provides the following [1] to [4]. [1] An optical laminate, wherein the optical laminate has a layer containing a metal oxide on a plastic film, and the emissivity of the optical laminate 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 plastic film, is 0.27 to 0.75. [2] A polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate described in [1]. [3] A surface plate for an image display device, comprising a resin plate or a glass plate on which the optical laminate described in [1] is bonded. [4] An image display device having the optical laminate described in [1] on the light-emitting surface side of the display element. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide an optical laminate that can suppress the decrease in visibility in high-temperature environments, as well as a polarizing plate, a surface plate, and an image display device using the same. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the optical laminate of the present disclosure. [Modes for carrying out the invention]

[0012] The following describes embodiments of the optical laminate of this disclosure, as well as a polarizing plate, a surface plate, and an image display device using the same.

[0013] [Optical laminate] The optical laminate of this disclosure has a layer containing a metal oxide on a plastic film, and the emissivity of the optical laminate 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 plastic film, is 0.27 to 0.75.

[0014] In this specification, the emissivity of the optical laminate for light in the wavelength range of 2000 nm to 22000 nm, measured from the layer containing the metal oxide with respect to the plastic film, may be referred to as "emissivity α". Emissivity is a value that expresses the ratio of the energy of light emitted by an object through thermal radiation to the energy of light emitted by a black body at the same temperature, with the latter being set to 1.

[0015] Figure 1 is a schematic cross-sectional view showing one embodiment of the optical laminate of the present disclosure. The optical laminate 100 in FIG. 1 has a layer 30 containing a metal oxide on a plastic film 10. Further, the optical laminate 100 in FIG. 1 has a functional layer α(20) between the plastic film 10 and the layer 30 containing a metal oxide. The functional layer α(20) in FIG. 1 is a single layer of a hard coat layer 21. Further, the optical laminate 100 in FIG. 1 has a functional layer β(40) on the side opposite to the plastic film 10 with respect to the layer 30 containing a metal oxide. The functional layer β(40) in FIG. 1 is a single layer of a low refractive index layer 41.

[0016] <Plastic film> The plastic film serves as a support for the layer containing a metal oxide and the functional layer, which will be described later. Note that glass is a support other than the plastic film. Glass itself has excellent heat resistance, but since it has a thick thickness, heat tends to be trapped. The thickness of the glass is usually 0.5 mm or more. Therefore, when glass is used as the support, the optical laminate tends to become hot in a high-temperature environment, and the layers constituting the optical laminate such as the layer containing a metal oxide and the functional layer, or the components of an image display device such as a display element are affected by the high temperature, and there is a problem that the visibility tends to decrease.

[0017] Examples of the plastic film include those 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, polyether ketone, polymethyl methacrylate, polycarbonate, polyurethane, and amorphous olefin (Cyclo-Olefin-Polymer: COP). The plastic film may be formed by coextruding two or more resins, or may be formed by laminating two or more plastic films. Among these plastic films, polyesters such as those subjected to stretching, particularly biaxially stretched polyethylene terephthalate and polyethylene naphthalate, are preferred in terms of excellent mechanical strength and dimensional stability. Also, polyimide is preferred in that it has good flex resistance and is easy to apply to foldable type image display devices and rollable type image display devices. Further, a plastic film obtained by co-extruding polycarbonate and polymethyl methacrylate is preferred in terms of good moldability.

[0018] Note that as the base material of the optical laminate, instead of a plastic film, a thin glass film with a thickness of 5 μm or more and 200 μm or less can be used. The thin glass film has, for example, recently attracted attention for use in foldable type image displays. Also, when using a thin glass film, since the smoothness of the optical laminate is improved, it is expected that the emissivity will decrease and heat intrusion will be suppressed, and further, an improvement in optical characteristics can be expected.

[0019] Also, among plastic films, a plastic film having a retardation value of 3000 nm or more and 30000 nm or less or a plastic film with a quarter-wave phase difference is suitable in that it can prevent uneven coloring of different colors from being observed on the display screen when observing an image through a polarizing sunglass.

[0020] The plastic film may be one that has been subjected to known adhesion promotion treatments such as corona discharge treatment, primer treatment, and undercoat treatment on its surface.

[0021] For ease 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. On the other hand, if the plastic film is too thick, heat can build up in the plastic film, which may negatively affect visibility. Also, if heat builds up in the plastic film, even if the optical laminate is moved from a high-temperature environment to a room-temperature environment, the temperature will not cool down easily, and the decrease in visibility may persist for a long time. For this reason, 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. Suitable thickness ranges for plastic films 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.

[0022] The thickness of each layer constituting an optical laminate, such as a plastic film, a layer containing a metal oxide, and a functional layer, can be calculated, for example, by selecting 20 arbitrary points from a cross-sectional image of the optical laminate taken with a scanning electron microscope (SEM) or scanning transmission electron microscope (STEM) and taking the average value. However, the 20 points should be selected so as not to be biased towards any particular location. The acceleration voltage and magnification of the STEM should be set according to the layer being measured.

[0023] <Layer containing metal oxides> The layer containing the metal oxide is the core layer for bringing the emissivity α of the optical stack to the range described later. Examples of metal oxides 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. It is preferable to include one or more selected from this group. Among the metal oxides mentioned above, ITO is preferred because it makes it easier to set the emissivity α of the optical laminate within the range described later. Furthermore, ITO is preferred because it can increase the refractive index of the layer containing the metal oxide, and by combining it with an arbitrarily formed low refractive index layer, it is easier to lower the reflectivity in the visible light region of the optical laminate. In addition, ITO is preferred because it has good transparency and high conductivity, making it easier to improve the antistatic properties of the optical laminate.

[0024] It is difficult to reduce the emissivity of metal nitrides such as aluminum nitride and boron nitride, which are commonly used as heat dissipation materials in heat sinks and the like, to below 0.75. Furthermore, metals such as Au, Ag, Cu, and Al, as exemplified in Patent Document 1, are difficult to achieve an emissivity of 0.27 or higher, raising concerns about reduced transparency. Additionally, these metals have low refractive indices, making it difficult to bring the refractive index of the metal oxide-containing layer within the range described later. Moreover, these metals exhibit excessive specular reflection, resulting in background reflection and reduced visibility. Furthermore, Ag vapor-deposited films have migration problems.

[0025] Examples of embodiments of the layer containing the metal oxide include (1) and (2) below. (1) A layer containing metal oxide particles and binder resin. (2) Metal oxide film formed by physical vapor deposition methods such as sputtering, chemical vapor deposition, etc.

[0026] The above (1) is preferable because it has better bending resistance than the above (2) and is easier to apply to foldable type image display devices and rollable type image display devices.

[0027] (1) Layer containing metal oxide particles and binder resin -Metal oxide particles- 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; and titanium oxide particles. It is preferable to include one or more selected from this group, and more preferably to include ITO particles.

[0028] The average particle size of the metal oxide particles is preferably 2 nm to 200 nm, more preferably 7 nm to 100 nm, even more preferably 8 nm to 80 nm, and even more preferably 10 nm to 50 nm. Preferred ranges for the average particle diameter of 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.

[0029] In this specification, the average particle size of various particles can be calculated, for example, by the following steps (1) to (3). (1) The cross-section of the optical laminate is imaged using a STEM. Preferably, the acceleration voltage of the STEM is 10kV to 30kV, and the magnification is 50,000x to 300,000x. (2) After extracting any 10 particles from the observation image, the particle diameter of each particle is calculated. The particle diameter is measured as the distance between two parallel lines that maximizes the distance between the two lines when the cross-section of the particle is sandwiched between them. (3) After performing the same procedure five times on observation images of the same sample on different screens, the average particle diameter is taken from the numerical average of the total of 50 particles.

[0030] The content of 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, per 100 parts by mass of binder resin. By setting the content of metal oxide particles to 150 parts by mass or more, it is possible to make it easier to set the emissivity α of the optical laminate to 0.75 or less. Furthermore, 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 metal oxides is increased, and by combining it with a low refractive index layer that can be arbitrarily formed, it is preferable that the reflectivity in the visible light region of the optical laminate can be lowered. Furthermore, the content of metal oxide particles is preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, even more preferably 1200 parts by mass or less, and even more preferably 1000 parts by mass or less, per 100 parts by mass of binder resin. By limiting the content of metal oxide particles to 2000 parts by mass or less, it is easier to suppress the decrease in the coating strength of the layer containing metal oxides. Also, if the emissivity α of the optical laminate becomes too low, it becomes difficult for the heat generated inside the image display device to be released to the outside. In order to prevent the emissivity α of the optical laminate from becoming too low, it is preferable to limit the content of metal oxide particles to 2000 parts by mass or less. Preferred ranges for the content of metal oxide particles per 100 parts by mass of binder resin include 150 parts by mass or more and 2000 parts by mass or less, 150 parts by mass or more and 1500 parts by mass or less, 150 parts by mass or more and 1200 parts by mass or less, 150 parts by mass or more and 1000 parts by mass or less, 250 parts by mass or more and 2000 parts by mass or less, 250 parts by mass or more and 1500 parts by mass or less, 250 parts by mass or more and 1200 parts by mass or less, 250 parts by mass or more and 1000 parts by mass or less, 400 parts by mass or more and 2000 parts by mass or less, 400 parts by mass or more and 1500 parts by mass or less, 400 parts by mass or more and 1200 parts by mass or less, and 400 parts by mass or more and 1000 parts by mass or less.

[0031] -Silane coupling agent- The layer containing metal oxide particles and binder resin preferably contains a silane coupling agent. The silane coupling agent may be a silane coupling agent acting as a surface treatment agent for the metal oxide particles, or it may be a silane coupling agent acting as a binder resin. By surface-treating metal oxide particles with a silane coupling agent, the affinity between the metal oxide particles and the binder resin is improved, and the dispersion of the metal oxide particles becomes more uniform. Furthermore, even when a silane coupling agent is included as a binder resin, it is preferable in that the dispersion of metal oxide particles tends to be more uniform.

[0032] Examples of silane coupling agents 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-di Examples include methyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane. In particular, it is preferable to use one or more selected from 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0033] -Binder resin- The binder resin preferably contains a cured product of a curable resin composition. Examples of cured products of curable resin compositions include cured products of thermosetting resin compositions and cured products of ionizing radiation-curable resin compositions, and cured products of ionizing radiation-curable resin compositions are preferred in order to improve mechanical strength. The ratio of the cured product of the curable resin composition to the total binder resin of the layer containing metal oxide particles is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 100% by mass.

[0034] A thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that hardens upon heating. Examples of thermosetting resins 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 thermosetting resin compositions as needed.

[0035] 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" may be referred to as an "ionizing radiation-curable compound." Examples of ionizing radiation-curable functional groups include ethylenically unsaturated bonding groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy groups and oxetanyl groups. As the ionizing radiation-curable compound, a compound having an ethylenically unsaturated bonding group is preferred, a compound having two or more ethylenically unsaturated bonding groups is more preferred, and among these, a (meth)acrylate compound having two or more ethylenically unsaturated bonding groups is even more preferred. As the (meth)acrylate compound having two or more ethylenically unsaturated bonding groups, either monomers or oligomers can be used. Ionizing radiation refers to electromagnetic waves or charged particle beams that possess energy quanta capable of polymerizing or bridging molecules. While ultraviolet rays or electron beams are typically used, other electromagnetic waves such as X-rays and gamma rays, as well as charged particle beams such as alpha rays and ion beams, can also be used. In this specification, (meth)acrylate means acrylate or methacrylate, (meth)acrylic acid means acrylic acid or methacrylic acid, and (meth)acryloyl group means acryloyl group or methacryloyl group.

[0036] -Photopolymerization initiators, photopolymerization accelerators- When the ionizing radiation-curable compound is an ultraviolet-curable compound, the ionizing radiation-curable composition preferably contains additives such as photopolymerization initiators and photopolymerization accelerators. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler ketone, benzoin, benzyldimethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthones, etc. Furthermore, photopolymerization accelerators can accelerate the curing speed by reducing polymerization inhibition caused by air during curing, and examples include one or more selected from p-dimethylaminobenzoate isoamyl ester, p-dimethylaminobenzoate ethyl ester, etc.

[0037] -Refractive index, film thickness- The layer containing metal oxide particles and binder resin preferably has a refractive index of 1.53 to 2.30, more preferably 1.57 to 2.00, more preferably 1.60 to 1.80, and more preferably 1.65 to 1.75. By setting the refractive index of the layer containing metal oxide within the above range, it is possible to easily lower the reflectance in the visible light region of the optical laminate by combining it with an arbitrarily formed low refractive index layer. Preferred ranges for the refractive index of the layer containing metal oxide particles and binder resin include 1.53 to 2.30, 1.53 to 2.00, 1.53 to 1.80, 1.53 to 1.75, 1.57 to 2.30, 1.57 to 2.00, 1.57 to 1.80, 1.57 to 1.75, 1.60 to 2.30, 1.60 to 2.00, 1.60 to 1.80, 1.60 to 1.75, 1.65 to 2.30, 1.65 to 2.00, 1.65 to 1.80, and 1.65 to 1.75.

[0038] In this specification, the refractive index of each layer refers to the refractive index at a wavelength of 550 nm. Furthermore, in this specification, the refractive index of each layer can be calculated, for example, by fitting the reflection spectrum measured by a spectrophotometer with the reflection spectrum calculated from an optical model of a multilayer thin film using Fresnel coefficients.

[0039] The thickness of the layer containing the metal oxide particles and binder resin is preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 500 nm or more, in order to easily reduce the emissivity α to 0.75 or less. However, 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 binder resin. Also, if the thickness of the layer containing metal oxide particles and binder resin is too thick, transparency tends to decrease. For thin film formation, the thickness of the layer containing metal oxide particles and 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. Preferred thickness ranges for the layer containing metal oxide particles and 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.

[0040] Furthermore, in order to reduce the reflectivity in the visible light region by canceling interference waves through a combination with an arbitrarily formed low refractive index layer, the thickness of the layer containing metal oxide particles and binder resin is n, which is the refractive index of the layer containing metal oxide particles and binder resin. o It is preferable to adjust the thickness of the layer containing metal oxide particles and binder resin with consideration to the above. Specifically, it is preferable to adjust the thickness of the layer containing metal oxide particles and binder resin to a thickness close to an integer multiple of "550 nm / 2n0". The range of thickness of the layer containing metal oxide particles and binder resin, taking into consideration the reduction of reflectance in the visible light region, is difficult to generalize as it varies depending on the range of refractive index as mentioned above, but it is preferably 120 nm to 750 nm, more preferably 130 nm to 500 nm, and even more preferably 140 nm to 400 nm. Preferred thickness ranges for the layer containing metal oxide particles and binder resin to lower the reflectance 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.

[0041] The layer containing metal oxide particles and binder resin may contain additives such as leveling agents, dispersants, dyes, ultraviolet absorbers, light stabilizers, and antioxidants, to the extent that they do not impair the effects of the present disclosure. A layer containing metal oxide particles and a binder resin can be formed, for example, by applying a coating solution in which the components constituting the layer are dispersed or dissolved onto a plastic film or the like, drying it, and then irradiating it with ionizing radiation as needed. The layer containing metal oxide particles and binder resin is preferably heat-treated after the layer is formed as described above. Heat treatment makes it easier to lower the emissivity α. The temperature for the heat treatment is preferably 90°C or higher at the lower limit, more preferably 95°C or higher, and even more preferably 100°C or higher. The upper limit is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower. The heat treatment temperature is preferably 30 minutes or more at the lower limit, more preferably 45 minutes or more, and even more preferably 50 minutes or more. The upper limit is preferably 200 minutes or less, more preferably 120 minutes or less, and even more preferably 80 minutes or less.

[0042] (2) Metal oxide film Metal oxide films are formed by depositing metal oxides using methods such as physical vapor deposition (VPM) or chemical vapor deposition (CVM). Among metal oxide films, indium tin oxide films are preferred because they tend to have low emissivity.

[0043] Amorphous metal oxide films are preferred because they facilitate achieving an emissivity α of 0.27 or higher in the optical laminate. Specifically, metal oxide films that have not undergone crystallization treatments such as annealing are preferred. Furthermore, amorphous metal oxide films are preferred because they have good flexibility and are easily applicable to foldable and rollable image display devices. Based on the above, an amorphous indium tin oxide film is preferred for the metal oxide film.

[0044] -Refractive index, film thickness- The metal oxide film preferably has a refractive index of 2.0 to 2.5, and more preferably 2.1 to 2.2. By setting the refractive index of the metal oxide film within the above range, it is possible to easily lower the reflectance in the visible light region of the optical laminate by combining it with an arbitrarily formed low refractive index layer. In addition to the range mentioned above, preferred ranges for the refractive index of the metal oxide film include 2.0 to 2.2 and 2.1 to 2.5.

[0045] The thickness of the metal oxide film is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more, in order to easily keep the emissivity α below 0.75. The degree to which a low-emissivity layer reflects radiant heat to the outside tends to increase with increasing thickness. For this reason, in order to suppress the temperature rise of the optical laminate, the thickness of the metal oxide film is preferably 100 nm or more. Furthermore, transparency tends to decrease if the metal oxide film is too thick. To achieve thinness, 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. Meritorious ranges for 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. To ensure good flexibility and facilitate application to foldable and rollable image display devices, the thickness of the metal oxide film is preferably 30 nm to 250 nm, and more preferably 30 nm to 150 nm.

[0046] Furthermore, in order to lower the reflectance in the visible light region by combining it with an arbitrarily 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.

[0047] <Functional Layer α> The optical laminate may have one or more functional layers α between the plastic film and the layer containing a metal oxide. Examples of functional layer α include a hard coat layer, a high refractive index layer, a medium refractive index layer, a low refractive index layer, an anti-glare layer, an antistatic layer, and a circular polarizing layer, with a single layer of hard coat being preferred.

[0048] Hard court layer To enhance scratch resistance and pencil hardness, the optical laminate preferably has a hard coat layer as the functional layer α.

[0049] The hard coat layer preferably contains a resin component. The resin component of the hard coat layer preferably consists mainly of a cured product of a curable resin composition. The main component means 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.

[0050] Examples of cured products of curable resin compositions include cured products of thermosetting resin compositions and cured products of ionizing radiation-curable resin compositions. Cured products of ionizing radiation-curable resin compositions are preferred in order to improve mechanical strength. Examples of curable resin compositions for the hard coat layer include the curable resin compositions exemplified by the layer containing a metal oxide.

[0051] The hard coat layer may contain additives such as UV absorbers, light stabilizers, antioxidants, and refractive index adjusters, as needed.

[0052] The thickness of the hard coat layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, more preferably 1.0 μm or more, and more preferably 2.0 μm or more, in order to easily improve scratch resistance. Furthermore, the thickness of the hard coat layer is preferably 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 more preferably 10 μm or less, in order to suppress heat buildup and curling. The preferred range for the hard coat layer thickness is 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 or less. Examples include 10 μm or less, 1.0 μm to 100 μm, 1.0 μm to 50 μm, 1.0 μm to 30 μm, 1.0 μm to 20 μm, 1.0 μm to 15 μm, 1.0 μm to 10 μm, 2.0 μm to 100 μm, 2.0 μm to 50 μm, 2.0 μm to 30 μm, 2.0 μm to 20 μm, 2.0 μm to 15 μm, and 2.0 μm to 10 μm.

[0053] <Functional layer β> The optical laminate may have one or more functional layers β on the side opposite to the plastic film of the layer containing the metal oxide. Examples of functional layers β include low refractive index layers, high refractive index layers, anti-glare layers, anti-fouling layers, and circularly polarizing layers. Functional layers may also serve multiple functions as described above. For example, a low refractive index layer may have anti-fouling or anti-glare properties.

[0054] The total thickness of 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. The layer located on the opposite side of the plastic film from the layer containing the metal oxide will experience a temperature increase due to radiant heat from outside the image display device and radiant heat generated from inside the image display device that passes through the layer containing the metal oxide. Therefore, the thicker the total thickness of one or more functional layers β, the more heat tends to accumulate in those layers. For this reason, by setting the total thickness of one or more functional layers β to 350 nm or less, it is possible to suppress the optical laminate from becoming too hot. Furthermore, by setting the total thickness of one or more functional layers β to 350 nm or less, it is possible to lower the emissivity α. Furthermore, considering that it is preferable for the total thickness of one or more functional layers β to be thin, it is preferable for the functional layer β to be a single layer, and more preferably a single layer of low refractive index.

[0055] Low refractive index layer The low refractive index layer is preferably located on the outermost surface opposite the plastic film, relative to the layer containing the metal oxide.

[0056] 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. The preferred ranges for the refractive index of the low refractive index layer are: 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, and 1.26 to 1.45. Examples include 1.26 to 1.40, 1.26 to 1.38, 1.26 to 1.32, 1.28 to 1.48, 1.28 to 1.45, 1.28 to 1.40, 1.28 to 1.38, 1.28 to 1.32, 1.30 to 1.48, 1.30 to 1.45, 1.30 to 1.40, 1.30 to 1.38, and 1.30 to 1.32.

[0057] The thickness of the low refractive index layer is preferably 80 nm to 150 nm, more preferably 85 nm to 110 nm, and even more preferably 90 nm to 105 nm. Furthermore, the thickness of the low refractive index layer is preferably greater than the average particle diameter of the low refractive index particles, such as hollow particles. Preferred thickness ranges for the low refractive index layer include 80 nm to 150 nm, 80 nm to 110 nm, 80 nm to 105 nm, 85 nm to 150 nm, 85 nm to 110 nm, 85 nm to 105 nm, 90 nm to 150 nm, 90 nm to 110 nm, and 90 nm to 105 nm. The thickness of the low refractive index layer satisfies the above preferred ranges, and it is more preferable that the thickness of the low refractive index layer is greater than the average particle diameter of the low refractive index particles such as hollow particles.

[0058] Methods for forming a low refractive index layer can be broadly classified into wet methods and dry methods. Wet methods include forming the layer by the sol-gel method using metal alkoxides, forming the layer by coating with a low refractive index resin such as fluororesin, and forming the layer by coating with a coating solution for low refractive index layer formation that contains low refractive index particles in a resin composition. Dry methods include selecting particles with a desired refractive index from among low refractive index particles and forming them by physical vapor deposition or chemical vapor deposition. The wet method is superior to the dry method in terms of production efficiency, suppression of oblique reflection hue, and chemical resistance. In this embodiment, among wet methods, it is preferable to form the layer using a coating solution for forming a low refractive index layer, which contains low refractive index particles in the binder resin composition, for adhesion, water resistance, scratch resistance, and low refractive index. In other words, it is preferable that the low refractive index layer contains a binder resin and low refractive index particles.

[0059] The binder resin of the low refractive index layer preferably contains a cured product of a curable resin composition. Furthermore, the ratio of the cured product of the curable resin composition to the total binder resin of the low refractive index layer is preferably 10% by mass or more, more preferably 30% by mass or more, more preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. Examples of curable resin compositions with a low refractive index layer include the curable resin composition exemplified by the layer containing a metal oxide.

[0060] The low refractive index particles preferably include one or more types selected from hollow particles and non-hollow particles. Furthermore, in order to balance low reflectivity and scratch resistance, it is preferable to use one or more types selected from hollow particles and one or more types selected from non-hollow particles in combination. The material of the hollow and non-hollow particles may be any inorganic compound such as silica and magnesium fluoride, or an organic compound, but silica is preferred due to its low refractive index and strength.

[0061] Considering optical properties and mechanical strength, the average particle diameter of hollow silica particles is preferably 50 nm to 200 nm, and more preferably 60 nm to 80 nm. In addition to the above range, preferred ranges for the average particle diameter of hollow silica particles include 50 nm to 80 nm and 60 nm to 200 nm. To prevent aggregation of non-hollow silica particles while considering dispersibility, the average particle diameter of the non-hollow silica particles is preferably 5 nm to 100 nm, and more preferably 10 nm to 20 nm. In addition to the above range, preferred ranges for the average particle diameter of non-hollow silica particles include 5 nm to 20 nm and 10 nm to 100 nm.

[0062] The higher the content of hollow silica particles, the higher the packing density of hollow silica particles in the binder resin, and the lower the refractive index of the low refractive index layer. For this reason, the content of hollow silica particles is preferably 100 parts by mass or more, and more preferably 150 parts by mass or more, per 100 parts by mass of binder resin. On the other hand, if the content of hollow silica particles relative to the binder resin is too high, the number of hollow silica particles exposed from the binder resin increases, and the amount of binder resin binding the particles together decreases. As a result, the hollow silica particles become more susceptible to damage and detachment, and the mechanical strength, such as scratch resistance, of the low refractive index layer tends to decrease. For this reason, the content of hollow silica particles is preferably 400 parts by mass or less, and more preferably 300 parts by mass or less, per 100 parts by mass of binder resin. Preferred ranges for the content of hollow silica particles per 100 parts by mass of binder resin include 100 parts by mass or more and 400 parts by mass or less, 100 parts by mass or more and 300 parts by mass or less, 150 parts by mass or more and 400 parts by mass or less, and 150 parts by mass or more and 300 parts by mass or less.

[0063] If the content of non-hollow silica particles is low, the presence of non-hollow silica particles on the surface of the low refractive index layer may not affect the hardness increase. Furthermore, if a large amount of non-hollow silica particles are included, the effect of shrinkage unevenness due to polymerization of the binder resin is reduced, thereby reducing the unevenness that occurs on the surface of the low refractive index layer after resin curing. For this reason, the content of non-hollow silica particles is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and most preferably 100 parts by mass or more, per 100 parts by mass of binder resin. On the other hand, if the content of non-hollow silica particles is too high, the non-hollow silica tends to aggregate, causing uneven shrinkage of the binder resin and resulting in larger surface irregularities. For this reason, the content of non-hollow silica particles is preferably 200 parts by mass or less, and more preferably 150 parts by mass or less, per 100 parts by mass of binder resin. Preferred ranges for the content of non-hollow silica particles per 100 parts by mass of binder resin include 10 parts by mass or more and 200 parts by mass or less, 10 parts by mass or more and 150 parts by mass or less, 50 parts by mass or more and 200 parts by mass or less, 50 parts by mass or more and 150 parts by mass or less, 70 parts by mass or more and 200 parts by mass or less, 70 parts by mass or more and 150 parts by mass or less, 100 parts by mass or more and 200 parts by mass or less, and 100 parts by mass or more and 150 parts by mass or less.

[0064] By incorporating hollow silica particles and non-hollow silica particles into the binder resin in the above proportions, the barrier properties of the low refractive index layer can be improved. This is presumed to be because the silica particles are uniformly dispersed with a high packing density, thereby inhibiting the permeation of gases and other substances. Furthermore, various cosmetics such as sunscreens and hand creams may contain low-molecular-weight polymers with low volatility. By improving the barrier properties of the low-refractive-index layer, it is possible to suppress the penetration of low-molecular-weight polymers into the coating film of the low-refractive-index layer, thereby suppressing defects such as appearance abnormalities caused by the long-term persistence of low-molecular-weight polymers in the coating film. It is also preferable to suppress the penetration of low-molecular-weight polymers into the coating film of the low-refractive-index layer in order to lower the emissivity α.

[0065] <Emissivity> The optical laminate of this disclosure is required to have an emissivity of 0.27 to 0.75 for light in the wavelength range of 2000 nm to 22000 nm, measured from the layer containing the metal oxide with respect to the plastic film. As described above, in this specification, the emissivity may be referred to as "emissivity α".

[0066] When the emissivity α exceeds 0.75, the optical laminate absorbs radiant heat from external environmental factors such as the temperature inside the vehicle, which reduces the visibility of the image display device, including the optical laminate. Furthermore, if the emissivity α is less than 0.27, the radiant heat generated inside the image display device is returned to the inside of the image display device by the optical laminate, causing the inside of the image display device to become hot and reducing the visibility of the image display device including the optical laminate. Radiant heat generated inside the image display device can be seen from the display elements. The emissivity α is preferably 0.35 or more and 0.70 or less, more preferably 0.37 or more and 0.67 or less, and even more preferably 0.40 or more and 0.60 or less. With recent advancements in display technology, flexible optical laminates are sometimes required, for example, to enhance the design of displays by adding curved surfaces. When the emissivity α is less than 0.40, the layer containing metal oxides tends to harden, which can cause problems with curved surface processing. For this reason, it is preferable to have an emissivity α of 0.40 or higher for curved surface processing. Furthermore, the lower the emissivity α, the better it is because it is possible to control the temperature rise caused by the external environment. For this reason, for example, if the emissivity α is 0.60 or lower, it is easier to lower the surface temperature of the optical laminate to a level where it can be easily touched, and it is easier to suppress the optical laminate itself from acting as a heat source. This is preferable because it makes it easier to lower the perceived temperature when the face or hands are held close to the image display device for a long time. Preferred ranges for 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.

[0067] In this specification, a decrease in visibility refers to, for example, "non-uniformity of various performance characteristics such as brightness, color, and reflection directivity in localized areas within the display screen of an image display device," "non-uniformity of the aforementioned performance characteristics near the center and near the edges of the display screen of an image display device," and "changes in the aforementioned performance characteristics in a high-temperature environment compared to a normal temperature environment." This decrease in visibility is thought to be caused, for example, by deformation of the optical laminate due to high temperatures. Furthermore, while image display devices typically have cooling means such as air-cooling fans, the cooling effect of these means varies depending on the location within the image display device. Since radiant heat is generated continuously, the aforementioned differences in cooling effect gradually accumulate, resulting in temperature differences within the image display device. Consequently, areas with different temperatures may occur within the surface of the optical laminate, and in such cases, localized changes in the physical properties of the optical laminate occur, which is thought to lead to a decrease in visibility. The optical laminate of this disclosure can suppress the decrease in visibility caused by the above-mentioned factors.

[0068] In this specification, emissivity α refers to the emissivity at room temperature measured in accordance with JIS A1423:1983. An example of an emissivity measuring device is the "TSS-5X-2" manufactured by Japan Sensor Co., Ltd.

[0069] In this specification, unless otherwise specified, various physical properties such as emissivity, spectral transmittance, luminous reflectance Y value, total light transmittance, and haze shall be measured in an environment where the sample for measurement is exposed to a temperature of 23±5°C and a relative humidity of 40% to 65% for 30 minutes or more. Furthermore, in this specification, unless otherwise specified, various physical properties such as emissivity, spectral transmittance, luminous reflectance Y value, total light transmittance, and haze shall be the average values ​​of 20 measurements.

[0070] <Physical properties> The average 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.

[0071] Equation (1) below represents the peak wavelength (λ) of radiation emitted by a black body at any given temperature, and is known as Wien's equation. In the equation, "T" represents temperature, and its unit is °C. λ(nm) ≈ 2897 / (T+273) (1) For example, the temperature inside a car and on the dashboard during the summer, as well as the temperature near a window in a sealed room during the summer, are said to be between 50°C and 80°C. Substituting 50 and 80 for T in equation (1) above, λ becomes approximately 9000 nm and approximately 8200 nm. In other words, the wavelength range of the spectral transmittance described above was specified as 8200nm to 9000nm to take into account the temperature of a car in the summer and the temperature near a window in a sealed room in the summer. Therefore, by setting the average spectral transmittance to 80% or less, the optical laminate efficiently cuts out infrared rays emitted from inside the car, which further suppresses the image display device from becoming hot and makes it easier to suppress the decrease in visibility. The lower limit of the average spectral transmittance mentioned above is not particularly limited, but is usually 30% or more, and preferably 40% or more.

[0072] In this specification, the spectral transmittance of a layer containing a metal oxide refers to the value calculated by the measurement in (A1) and the conversion process in (A2) below. (A1) Measure the absorbance of the layer containing the metal oxide at each wavelength using FTIR reflection. (A2) The absorbance of A1 at each wavelength is converted into the transmittance of each wavelength. The measurement in (A1) above shall be performed from the side of the layer containing the metal oxide, with the plastic film as the reference. Furthermore, even if a functional layer β is present on the layer containing the metal oxide, the measurement in (A1) above can be performed with the functional layer β present, as long as the total thickness of the functional layer β is approximately 250 nm or less. Then, by converting the absorbance of the layer containing the metal oxide measured with the functional layer β present using the method in (A2) above, the spectral transmittance of the layer containing the metal oxide can be calculated.

[0073] The luminous reflectance Y value of the optical laminate, measured from the layer containing the metal oxide with respect to the plastic film, is preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.

[0074] In this specification, the luminous reflectance Y value refers to the luminous reflectance Y value of the CIE 1931 standard color system, and is assumed to be measured at an incident angle of 5 degrees. The luminous reflectance Y value can be calculated using a spectrophotometer. An example of such a spectrophotometer is the "UV-2450" manufactured by Shimadzu Corporation. When measuring luminous reflectance, it is preferable to attach a black plate to the back of the plastic film.

[0075] The optical laminate preferably has a total light transmittance of 70% or more, more preferably 80% or more, and even more preferably 90% or more, according to JIS K7361-1:1997. Furthermore, the optical laminate preferably has a haze of 5% or less according to JIS K7136:2000, more preferably 3% or less, and even more preferably 1% or less. It is preferable to measure the total light transmittance and haze with the plastic film side as the light incident surface, using the layer containing the metal oxide as the reference.

[0076] In the optical laminate, it is preferable that the surface roughness of the outermost surface of the side containing the metal oxide layer is within a predetermined range, relative to the plastic film. Specifically, the arithmetic mean roughness Ra of the outermost surface at a JIS B0601:2001 cutoff value of 2.5 mm is preferably 3 μm or less, more preferably 1 μm or less, and even more preferably 0.1 μm or less. By setting Ra to 3 μm or less, it becomes easier to set the emissivity α to 0.75 or less. When measuring Ra, it is preferable to set the measurement conditions of the measuring device to a horizontal magnification of 1000x and a vertical magnification of 20000x.

[0077] <Layer configuration> The overall layer configuration of the optical laminate described herein is not particularly limited, but includes the following (1) to (6). Note that " / " indicates a layer interface. (1) Plastic film / layer containing metal oxide (2) Plastic film / hard coat layer / layer containing metal oxide (3) Plastic film / Metal oxide-containing layer / Low refractive index layer (4) Plastic film / hard coat layer / layer containing metal oxide / low refractive index layer (5) Plastic film / Layer containing metal oxide / High refractive index layer / Low refractive index layer (6) Plastic film / hard coat layer / layer containing metal oxide / high refractive index layer / low refractive index layer

[0078] <Total Thickness> The total thickness of the optical laminate is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 45 μm or more, in order to ensure good mechanical strength. Furthermore, the total thickness of the optical laminate is preferably 130 μm or less, more preferably 100 μm or less, even more preferably 90 μm or less, and even more preferably 75 μm or less, in order to facilitate application to foldable and rollable image display devices. Preferred ranges for 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. By setting the total thickness of the optical laminate within the above range, it becomes easier to achieve a diameter of φ10 mm or less in evaluation using an outward-bending mandrel test rod. Furthermore, within the above range, it also becomes easier to achieve a diameter of φ6 mm or less for optical laminates with a total thickness of 75 μm or less. In other words, by setting the total thickness of the optical laminate within the above range, it becomes easier to apply the optical laminate to foldable-type and rollable-type image display devices. Note that "outward bending" means bending the plastic film so that the side containing the metal oxide layer faces outwards. Also, "outside" means "the side farther from the mandrel rod."

[0079] [Polarizing plate] The polarizing plate of the present disclosure is a polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate of the present disclosure described above.

[0080] <Polarizer> Examples of polarizers include sheet-type polarizers such as polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, and ethylene-vinyl acetate copolymer saponified film dyed with iodine or the like and stretched; wire grid-type polarizers consisting of numerous parallel metal wires; coated polarizers coated with lyotropic liquid crystal and dichroic guest-host materials; and multilayer thin-film polarizers. These polarizers may also be reflective polarizers that have the function of reflecting polarization components that do not transmit through them.

[0081] <Transparent protection plate> A first transparent protective plate is placed on one side of the polarizer, and a second transparent protective plate is placed on the other side. At least one of the first and second transparent protective plates is the optical laminate of the present disclosure described above. The optical laminate is preferably arranged such that the plastic film side faces the polarizer side, with respect to the layer containing the metal oxide.

[0082] Examples of the first and second transparent protective plates other than the optical laminate include plastic film and glass, with plastic film being preferred. Examples of plastic films include polyester film, polycarbonate film, cycloolefin polymer film, acrylic film, and triacetylcellulose film, and stretched films of these are preferred due to their mechanical strength. It is preferable to bond the polarizer and the transparent protective plate together using an adhesive. A general-purpose adhesive can be used, and a PVA-based adhesive is preferred.

[0083] In the polarizing plate of this disclosure, both the first transparent protective plate and the second transparent protective plate may be the optical laminate of this disclosure described above, but it is preferable that one of the first transparent protective plate and the second transparent protective plate is the optical laminate of this disclosure described above. Furthermore, when the polarizing plate of this disclosure is used as a polarizing plate placed on the light-emitting surface side of a display element, it is preferable that the transparent protective plate on the light-emitting surface side of the polarizer is the optical laminate of this disclosure described above.

[0084] [Surface plate for image display device] The surface plate for the image display device of this disclosure is formed by bonding the optical laminate of this disclosure described above onto a resin plate or a glass plate.

[0085] In the optical laminate, it is preferable to arrange the layers so that the plastic film side faces the resin plate or glass plate side, with respect to the layer containing the metal oxide. Furthermore, it is preferable that the surface plate for the image display device be positioned such that the side to which the optical laminate is bonded faces the surface side. In other words, it is preferable that the surface plate for the image display device be positioned such that the side to which the optical laminate is bonded faces away from the display element.

[0086] As the resin plate or glass plate, a resin plate or glass plate commonly used as a surface plate for image display devices can be used.

[0087] The thickness of the resin or glass plate is preferably 10 μm or more to ensure good strength. The upper limit of the thickness of the resin or glass plate is usually 5000 μm or less, but in recent years, as thinner image display devices are preferred, it is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 100 μm or less. Preferred thickness ranges for 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.

[0088] [Image display device] The image display device of this disclosure has the optical laminate of this disclosure described above on the light-emitting surface side of the display element.

[0089] The optical laminate is preferably arranged such that the side containing the metal oxide layer faces away from the display element, relative to the plastic film. Furthermore, it is preferable that the optical laminate is placed on the outermost surface of the image display device. Furthermore, in order to suppress heat conduction, it is preferable to arrange the display elements and the optical laminate within the image display device so that air is interposed between them.

[0090] Examples of display elements include liquid crystal display elements, organic EL display elements, inorganic EL display elements, and other EL display elements, as well as plasma display elements. Furthermore, LED display elements such as micro-LED display elements and mini-LED display elements are also included. These display elements may have a touch panel function inside the display element. Examples of liquid crystal display methods for liquid crystal display elements include IPS, VA, multi-domain, OCB, STN, and TSTN methods. When the display element is a liquid crystal display element, a backlight is required. The backlight is positioned on the side of the liquid crystal display element opposite to the side with the optical laminate. The image display device may be a foldable image display device or a rollable image display device. Furthermore, the image display device may be an image display device with a touch panel. Furthermore, portable image display devices and image display devices incorporated into the dashboards of automobiles are prone to being exposed to high-temperature environments, making them preferable in that the effects of this disclosure can be easily demonstrated.

[0091] 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 general-purpose heat dissipation mechanisms include cooling fans, heat fins, heat pumps, and Peltier elements. [Examples]

[0092] The present disclosure will be described in detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the forms described in the examples.

[0093] 1. Evaluation and Measurement The optical laminates obtained in the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 1. Unless otherwise specified, the atmosphere during each measurement and evaluation was a temperature of 23±5°C and a relative humidity of 40% to 65%. Before starting each measurement and evaluation, the target sample was exposed to the aforementioned atmosphere for at least 30 minutes. Note that the optical laminate of Comparative Example 2 does not have a layer containing a metal oxide. Therefore, for Comparative Example 2, the following evaluation and measurements will be performed assuming that the heat dissipation layer of Comparative Example 2 contains a metal oxide.

[0094] 1-1.Emissivity The emissivity of the optical laminates of the examples and comparative examples was measured at room temperature in accordance with JIS A1423:1983. Specifically, the emissivity of the optical laminate for light in the wavelength range of 2000 nm to 22000 nm was measured, measured from the layer containing the metal oxide with respect to the substrate. As described above, in this specification, the emissivity may be referred to as "emissivity α". Materials with an emissivity α exceeding 0.75 were given a C rating. Materials with an emissivity α less than 0.27 were given a B rating. Materials with an emissivity α between 0.27 and 0.75 were given an A rating or higher, and among those with an emissivity α between 0.37 and 0.60, were given an AA rating. If the emissivity α is too high, the optical laminate absorbs radiant heat from the external environment, causing the image display device to overheat. On the other hand, if the emissivity α is too low, the optical laminate absorbs less radiant heat from the external environment, but the radiant heat generated inside the image display device is returned to the inside of the image display device by the optical laminate, which is expected to cause the inside of the image display device to become hot. The emissivity meter used was the "TSS-5X-2" model manufactured by Japan Sensor Co., Ltd. The emissivity reference strips included with the meter come in two types: emissivity values ​​of 0.06 and 0.97. The main specifications of the meter are as follows: <Specifications> ·Measurement area: Φ15mm • Measurement distance: 12mm

[0095] 1-2.Spectral transmittance The spectral transmittance of the metal oxide-containing layer in the optical laminates of the examples and comparative examples was measured in the wavelength range of 8200 nm to 9000 nm. As described in the main text of the specification, the spectral transmittance of the metal oxide-containing layer in the wavelength range of 8200 nm to 9000 nm was calculated by measuring the absorbance at each wavelength of the metal oxide-containing layer using FTIR reflection, and then converting the absorbance at each wavelength to the transmittance at each wavelength. The FIIR analyzer used was a Thermo Fisher SCIENTIFIC "NICOLET iS10" model. A Thermo Fisher SCIENTIFIC "Single-Reflection Ge ATR Accessory Foundation" was used as an accessory. The measurement conditions were as follows: the measurement surface was pointed towards the Ge crystal plane, the sample was compressed and fixed using a Pressure Tower, then the incident light was a single pass, at a 45° angle, with 32 scans, a resolution of 8, a DTGS KBr detector, a mirror velocity of 0.6329, an open aperture, and a measurement range of 680 cm. -1 More than 4000cm -1 The measurements were taken under the following conditions. The measured absorbance was converted to transmittance, and the result was calculated in cm². -1 By converting to nm, the average transmittance in the wavelength range was calculated.

[0096] 1-3. Luminous reflectance Y value Samples were prepared by laminating a black plate (Kuraray Co., Ltd., product name: Comoglass DFA2CG 502K (black), 2 mm thick) to the opposite side of the metal oxide-containing layer of the optical laminate substrate of the examples and comparative examples, via a 25 μm thick transparent adhesive layer (Panac Co., Ltd., product name: Panaclean PD-S1). The luminous reflectance Y value was measured for the above samples by incident light at an incidence angle of 5 degrees from the metal oxide-containing layer side, with the substrate as the reference. The luminous reflectance Y value was determined by measuring the 5° specular reflectance using a spectrophotometer (Shimadzu Corporation, product name: UV-2450) under the conditions of a field of view of 2 degrees, a C light source, and a wavelength range of 380 nm to 780 nm. The value representing the luminous reflectance was then calculated using software (built-in UVPC color measurement Version 3.12) that converts this value to the brightness perceived by the human eye.

[0097] 1-4. Total light transmittance and haze The total light transmittance (JIS K7361-1:1997) and haze (JIS K7136:2000) of the optical laminates of the examples and comparative examples were measured using a haze meter (HM-150, manufactured by Murakami Color Technology Laboratory). The light incident surface was the substrate side.

[0098] 1-5.Surface temperature A simulated liquid crystal display was fabricated by placing the optical laminates of the examples and comparative examples on a commercially available liquid crystal display device (Amazon product name Kindle Fire HDX) so that the substrate side faces the display device side. Assuming the conditions inside a car during summer, a simulated liquid crystal display was placed in an 80°C oven and removed after 10 minutes. Immediately after removing the simulated liquid crystal display, the temperature was measured from the surface using an IR camera (FLIR Systems, product name FLIR E4). 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 acceptable. Considering actual image display scenarios, a maximum temperature of 60°C or less is more preferable, and 57°C or less is even more preferable.

[0099] 1-6. Visibility (non-uniformity) The simulated liquid crystal display device prepared in steps 1-5 was placed in an 80°C oven and removed after 10 minutes. Immediately after removing the simulated liquid crystal display device, the screen of the liquid crystal display device was displayed in solid green, and the evaluators visually assessed whether there were any areas of uneven brightness and color within the display screen. Ten evaluators with a visual acuity of 0.7 or higher were selected. This includes corrected visual acuity. The distance between the evaluators and the liquid crystal display device was 50 cm. Devices where 8 or more evaluators answered that there were no areas of uneven brightness and color were classified as "A," and devices where 7 or fewer evaluators answered that there were no areas of uneven brightness and color were classified as "C."

[0100] 2. Fabrication of optical stacks [Example 1] A hard coat layer with a thickness of 5 μm was formed on a substrate (triacetylcellulose film, 60 μm thick) by applying the following hard coat coating solution, drying, and irradiating with ultraviolet light. Next, the following coating solution 1 for metal oxide layers was applied to the hard coat layer, dried, and irradiated with ultraviolet light to form a layer containing ITO particles as a metal oxide with a thickness of 350 nm. Next, the following low refractive index layer coating solution was applied to the metal oxide layer, dried, and irradiated with ultraviolet light to form a low refractive index layer with a thickness of 100 nm, thereby obtaining the optical laminate of Example 1.

[0101] <Coating liquid for hard coat layers> The following components were mixed to prepare a composition for forming a hard coat layer. Pentaerythritol triacrylate 46 parts by mass (Nippon Kayaku Co., Ltd., Product name: KAYARAD PET-30) • Photopolymerization initiator 4 parts by mass (IGM Resins BV, product name: Omnirad 184) • Methyl ethyl ketone 50 parts by mass

[0102] <Coating solution for metal oxide layer 1> The following components were mixed to prepare coating solution 1 for the metal oxide layer. • Pentaerythritol triacrylate 1 part by mass (Nippon Kayaku Co., Ltd., Product name: KAYARAD PET-30) ·ITO particles 8.5 parts by mass (Average particle size 30nm) • Photopolymerization initiator 0.4 parts by mass (IGM Resins BV, product name: Omnirad 184) • Leveling agent 0.03 parts by mass (DIC Corporation MegaFac F-477) • Methyl isobutyl ketone 89 parts by mass

[0103] <Coating solution for low refractive index layers> The following components were mixed to prepare a coating solution for the low refractive index layer. Pentaerythritol triacrylate 0.4 parts by mass (Nippon Kayaku Co., Ltd., Product name: KAYARAD PET-30) • Fluorine-containing polymer 0.2 parts by mass (solids) (Manufactured by JSR, product name: JN35) • Fluorine-containing monomer 0.7 parts by mass (solids) (Manufactured by Kyoeisha Chemical Co., Ltd. Product name: LINC3A) • Hollow silica particles 1.7 parts by mass (Average particle size 75 nm, refractive index 1.212) • Solid silica particles 0.6 parts by mass (Average particle size 15nm) • Leveling agent 0.06 parts by mass (Shin-Etsu Silicone Co., Ltd., Product name: X-22-164E) • Photopolymerization initiator 0.09 parts by mass (IGM Resins BV, product name: Omnirad 127) • Solvent 97 parts by mass (A 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, prepared according to the desired thickness.)

[0104] [Example 2] An optical laminate 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.

[0105] [Example 3] An optical laminate 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.

[0106] [Example 4] An optical laminate of Example 4 was obtained in the same manner as in Example 1, except that the base material (triacetylcellulose film, 60 μm thick) was changed to a biaxially oriented polyethylene terephthalate film with a thickness of 100 μm.

[0107] [Example 5] An optical laminate of Example 5 was obtained in the same manner as in Example 1, except that the coating solution 1 for the metal oxide layer was changed to the coating solution 2 for the metal oxide layer described below, and the thickness was changed to 900 nm.

[0108] <Coating solution for metal oxide layer 2> • Pentaerythritol triacrylate 1 part by mass (Nippon Kayaku Co., Ltd., Product name: KAYARAD PET-30) • Al-doped ZnO particles: 9.6 parts by mass • Photopolymerization initiator 0.4 parts by mass (IGM Resins BV, product name: Omnirad 184) • Leveling agent 0.03 parts by mass (DIC Corporation MegaFac F-477) • Methyl isobutyl ketone 89 parts by mass

[0109] [Example 6] The coating solution 1 for the metal oxide layer was changed to the coating solution 3 for the metal oxide layer described below, and the thickness of the layer containing the metal oxide was changed to 900 nm. Furthermore, a step was added in which the coating solution for the metal oxide layer was applied, dried, and irradiated with ultraviolet light, followed by heating at 100°C for 60 minutes. Except for the changes and additions described above, the optical laminate of Example 6 was obtained in the same manner as in Example 1.

[0110] [Example 7] A hard coat layer with a thickness of 5 μm was formed on a substrate (cycloolefin polymer film, 47 μm thick) by applying the above-mentioned hard coat coating solution, drying it, and irradiating it with ultraviolet light. Next, the following coating solution 3 for metal oxide layers was applied to the hard coat layer, dried, and irradiated with ultraviolet light to form a layer containing ITO particles as a metal oxide with a thickness of 900 nm, and then heated at 150°C for 60 minutes. Next, the above-mentioned coating solution for low refractive index layers was applied to the layer containing the metal oxide, dried, and irradiated with ultraviolet light to form a low refractive index layer with a thickness of 100 nm, thereby obtaining the optical laminate of Example 7.

[0111] <Coating solution for metal oxide layer 3> The following components were mixed to prepare coating solution 3 for the metal oxide layer. • Pentaerythritol triacrylate 0.5 parts by mass (Nippon Kayaku Co., Ltd., Product name: KAYARAD PET-30) ·ITO particles 9 parts by mass (Average particle size 30nm) • Photopolymerization initiator 0.4 parts by mass (IGM Resins BV, product name: Omnirad 184) • Leveling agent 0.03 parts by mass (DIC Corporation MegaFac F-477) • Methyl isobutyl ketone 89 parts by mass

[0112] [Example 8] A hard coat layer was formed on a substrate (a biaxially oriented polyethylene terephthalate film with a thickness of 100 μm) in the same manner as in Example 1. Next, a metal oxide film with a thickness of 130 nm was formed on the hard coat layer by sputtering using an ITO target while introducing argon mixed with oxygen gas. The ITO target had a mass ratio of indium to tin of 90:10. The metal oxide film was an amorphous ITO film. Next, corona discharge treatment was performed on the metal oxide film side, and then a low refractive index layer similar to that in Example 1 was formed on the metal oxide film to obtain the optical laminate of Example 8.

[0113] [Comparative Example 1] A metal oxide film with a thickness of 140 nm was formed on a 0.7 mm thick glass substrate by sputtering using an ITO target while introducing argon mixed with oxygen gas. The ITO target had an indium-to-tin mass ratio of 90:10. Subsequently, by annealing treatment by heating at 200°C for 30 minutes, an optical laminate of Comparative Example 1 was obtained, having a 140 nm thick ITO crystalline film on the glass substrate.

[0114] [Comparative Example 2] A heat dissipation layer with a thickness of 1 μm was formed by applying the following heat dissipation layer coating solution to a substrate (triacetylcellulose film, 60 μm thick), drying it, and irradiating it with ultraviolet light, thereby obtaining the optical laminate of Comparative Example 2.

[0115] <Coating liquid for heat dissipation layer> The following components were mixed to prepare a coating solution for the heat dissipation layer. Pentaerythritol triacrylate 3.2 parts by mass (Nippon Kayaku Co., Ltd., Product name: KAYARAD PET-30) • Boron nitride particles 6.4 parts by mass (Average particle size 700nm) • Photopolymerization initiator 0.4 parts by mass (IGM Resins BV, product name: Omnirad 184) Methyl ethyl ketone 90 parts by mass

[0116] [Table 1]

[0117] The results in Table 1 confirm that the optical laminate of this disclosure can suppress the decrease in visibility in high-temperature environments. Furthermore, mandrel tests were performed on the optical laminates of Examples 1 to 8 in accordance with JIS K5600-5-1:1999. Specifically, 100 mm x 25 mm test pieces were cut from the optical laminates of Examples 1 to 8, and the short side of the test piece was wrapped around the mandrel rod so that it was parallel to the mandrel rod. The test piece was wrapped around the mandrel rod with an outward bend. Mandrel rods with diameters of φ10 mm and φ6 mm were used. The results of the mandrel tests described above showed that no cracks were observed in the metal oxide layer and the low refractive index layer of the optical laminates of Examples 1-8 at a diameter of φ10 mm. Furthermore, no cracks were observed in the metal oxide layer and the low refractive index layer of the optical laminates of Examples 1-3 and 5-7 at a diameter of φ6 mm. These results indicate that the optical laminates of Examples 1-8 have good flexibility and are easy to apply to foldable and rollable image display devices. In addition, among the examples, the optical laminates of Examples 1-3 and 5-7 exhibited extremely good flexibility. [Explanation of symbols]

[0118] 10: Plastic film 20: Functional layer α 21: Hard coat layer 30: Layer containing metal oxide 40: Functional layer β 41: Low refractive index layer 100: Optical laminate

Claims

1. An optical laminate, The optical laminate has a layer containing a metal oxide on a plastic film, The layer containing the metal oxide comprises metal oxide particles as the metal oxide and a binder resin. An optical laminate in which the emissivity of the optical laminate for light in the wavelength range of 2000 nm to 22000 nm is 0.27 to 0.75, measured from the layer containing the metal oxide with respect to the plastic film.

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

3. The optical laminate according to claim 1 or 2, wherein the metal oxide particles include indium tin oxide particles.

4. The optical laminate according to any one of claims 1 to 3, wherein one or more functional layers α are provided between the plastic film and the layer containing the metal oxide.

5. The optical laminate according to claim 4, wherein the functional layer α has a hard coat layer.

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

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

8. The optical laminate according to claim 6 or 7, wherein the functional layer β includes a low refractive index layer.

9. The optical laminate according to any one of claims 1 to 8, wherein the luminous reflectance Y value of the optical laminate, measured from the layer containing the metal oxide with respect to the plastic film, is 2.0% or less.

10. A polarizing plate having a polarizer, a first transparent protective plate disposed on one side of the polarizer, and a second transparent protective plate disposed on the other side of the polarizer, wherein at least one of the first transparent protective plate and the second transparent protective plate is an optical laminate according to any one of claims 1 to 9.

11. A surface plate for an image display device, comprising an optical laminate according to any one of claims 1 to 9 bonded to a resin plate or a glass plate.

12. An image display device having an optical laminate according to any one of claims 1 to 9 on the light-emitting surface side of a display element.

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