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

Abstract

To provide an optical laminate capable of suppressing degradation in visibility in a high-temperature environment.SOLUTION: An optical laminate has a layer containing a metal oxide on a plastic film, wherein an emissivity against light in a wavelength range of 2,000 or more and 22,000 nm or less in the optical laminate, as measured from a side of the layer containing the metal oxide with the plastic film as a reference is 0.27 or more and 0.75 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical laminate, 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, televisions, 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 an automobile in midsummer becomes hot, and in particular, the temperature of the dashboard may reach nearly 80°C. For this reason, an image display device may be exposed to high temperatures in the vehicle interior 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 a laminated glass such as that described in Patent Document 1 as the protective glass of the image display device.

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

[0008] The present disclosure has been made in view of such circumstances, and an object thereof is to provide an optical laminate 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 same.

Means for Solving the Problems

[0009] The present 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 with respect to light in the wavelength range of 2000 nm or more and 22000 nm or less, measured from the side of the layer containing the metal oxide with respect to the plastic film, is 0.27 or more and 0.75 or less. [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 according to [1]. [3] A surface plate for an image display device, in which the optical laminate according to [1] is laminated on a resin plate or a glass plate. [4] An image display device having the optical laminate according to [1] on the light-emitting surface side of a display element.

Effects of the Invention

[0010] According to the present disclosure, it is possible to provide an optical laminate 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 same.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the optical laminate of the present disclosure, and a polarizing plate, a surface plate, and an image display device using the same will be described.

[0013] [Optical Laminate] The optical laminate of the present disclosure has a layer containing a metal oxide on a plastic film, and the emissivity of the optical laminate with respect to light in a wavelength range of 2000 nm or more and 22000 nm or less, measured from the side of the layer containing the metal oxide with reference to the plastic film, is 0.27 or more and 0.75 or less.

[0014] In the present specification, the emissivity of the optical laminate with respect to light in a wavelength range of 2000 nm or more and 22000 nm or less, measured from the side of the layer containing the metal oxide with reference to the plastic film, may be referred to as "emissivity α". The emissivity means a value represented by the ratio of the energy of light emitted by an object by thermal radiation to the energy of light emitted by a black body at the same temperature, with the energy of light emitted by the black body being set to 1.

[0015] FIG. 1 is a schematic cross-sectional view showing an 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. Also, 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. In addition, glass is a support other than the plastic film. Although glass itself has excellent heat resistance, since its thickness is large, heat tends to be trapped. The thickness of glass is usually 0.5 mm or more. For this reason, 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, polyester films such as those obtained by stretching, particularly biaxially stretched polyethylene terephthalate and polyethylene naphthalate, are preferable in terms of excellent mechanical strength and dimensional stability. Further, polyimide is preferable in that it has good bend resistance and is easily applicable to foldable-type and rollable-type image display devices. Further, a plastic film obtained by co-extruding polycarbonate and polymethyl methacrylate is preferable in terms of good moldability.

[0018] Note that, as the base material of the optical laminate, instead of a plastic film, a glass film of a thin film having a thickness of 5 μm or more and 200 μm or less can be used. The glass film of the thin film has been attracting attention in recent years, for example, for foldable-type image display. Further, when a glass film of a thin film is used, since the smoothness of the optical laminate is improved, it can be expected that the emissivity is lowered and the intrusion of heat is suppressed, and further, an improvement in optical characteristics can be expected.

[0019] Further, among plastic films, a plastic film having a retardation value of 3000 nm or more and 30000 nm or less or a plastic film having a quarter-wave plate retardation is suitable in that it can prevent unevenness in color from being observed on the display screen when an image is observed through a polarizing sunglass.

[0020] The plastic film may be one subjected to a known adhesion-improving treatment such as corona discharge treatment, primer treatment, or undercoat treatment on its surface.

[0021] 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 for ease of handling and for suppressing deformation due to heat. On the one hand, if the thickness of the plastic film is too thick, heat may be trapped in the plastic film, which may have an adverse effect on visibility. Further, when heat is trapped in the plastic film, even if the optical laminate is moved from a high-temperature environment to a normal-temperature environment, the temperature is difficult to decrease, so the decrease in visibility may continue 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, still more preferably 90 μm or less, and even more preferably 70 μm or less. Suitable ranges for the thickness of the plastic film include 5 μm or more and 350 μm or less, 5 μm or more and 150 μm or less, 5 μm or more and 90 μm or less, 5 μm or more and 70 μm or less, 10 μm or more and 350 μm or less, 10 μm or more and 150 μm or less, 10 μm or more and 90 μm or less, 10 μm or more and 70 μm or less, 25 μm or more and 350 μm or less, 25 μm or more and 150 μm or less, 25 μm or more and 90 μm or less, 25 μm or more and 70 μm or less.

[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 photograph of the optical laminate by a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM), and taking the average value thereof. However, the 20 locations shall be selected so that the locations are not biased. The acceleration voltage and magnification of the STEM may be set according to the layer to be measured.

[0023] <Layer containing a metal oxide> The layer containing a metal oxide is a layer that serves as a core for making the emissivity α of the optical laminate fall within the range described later. Examples of the metal oxide include indium tin oxide (ITO); antimony trioxide, antimony tin-doped oxide (ATO), antimony pentoxide, etc. of antimony oxide; tin oxide; zinc oxide such as aluminum-doped zinc oxide, gallium-doped zinc oxide, etc.; titanium oxide; etc. It is preferable to contain one or more selected from these groups. Among the above metal oxides, ITO is preferable in that it easily makes the emissivity α of the optical laminate fall within the range described below. Further, since ITO can increase the refractive index of the layer containing the metal oxide, it is preferable in that it easily lowers the reflectance in the visible light region of the optical laminate in combination with a low refractive index layer formed arbitrarily. Further, since ITO has good transparency and high conductivity, it is preferable in that it easily improves the antistatic property of the optical laminate.

[0024] Heat dissipation materials such as metal nitrides such as aluminum nitride and boron nitride, which are widely used as heat dissipation materials for heat sinks and the like, have difficulty in making the emissivity 0.75 or less. In addition, metals such as Au, Ag, Cu, and Al exemplified in Patent Document 1 are difficult to make the emissivity 0.27 or more, and there is concern about a decrease in transparency. Further, the metal has a low refractive index, and it is difficult to make the refractive index of the layer containing the metal oxide fall within the range described below. Further, since the specular reflection of the metal is too strong, the background is reflected and the visibility is reduced. Further, the vapor deposition film of Ag has a problem of migration.

[0025] Examples of the embodiment of the layer containing a metal oxide include the following (1) and (2). (1) A layer containing metal oxide particles and a binder resin (2) A metal oxide film formed by a physical vapor deposition method such as sputtering, a chemical vapor deposition method, or the like to form a metal oxide

[0026] The above (1) is more preferable in that it has better bending resistance than (2) and is easily applicable to a foldable type image display device and a rollable type image display device.

[0027] 《(1) A layer containing metal oxide particles and a binder resin》 - Metal oxide particles - Examples of the 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; and the like. It is preferable to include one or more selected from these groups, and it is more preferable to include ITO particles.

[0028] The average particle diameter of the metal oxide particles is preferably 2 nm or more and 200 nm or less, more preferably 7 nm or more and 100 nm or less, still more preferably 8 nm or more and 80 nm or less, and even more preferably 10 nm or more and 50 nm or less. Preferable ranges of the average particle diameter of the metal oxide particles include 2 nm or more and 200 nm or less, 2 nm or more and 100 nm or less, 2 nm or more and 80 nm or less, 2 nm or more and 50 nm or less, 7 nm or more and 200 nm or less, 7 nm or more and 100 nm or less, 7 nm or more and 80 nm or less, 7 nm or more and 50 nm or less, 8 nm or more and 200 nm or less, 8 nm or more and 100 nm or less, 8 nm or more and 80 nm or less, 8 nm or more and 50 nm or less, 10 nm or more and 200 nm or less, 10 nm or more and 100 nm or less, 10 nm or more and 80 nm or less, and 10 nm or more and 50 nm or less.

[0029] In this specification, the average particle diameter of various particles can be calculated, for example, by the following operations (1) to (3). (1) Image the cross-section of the optical laminate by STEM. The acceleration voltage of STEM is preferably 10 kV or more and 30 kV or less, and the magnification is preferably 50,000 times or more and 300,000 times or less. (2) After extracting any 10 particles from the observation image, calculate the particle diameter of each particle. The particle diameter is measured as the distance between two straight lines in a combination of two straight lines that sandwich the cross-section of the particle with any two parallel straight lines and maximize the distance between the two straight lines. (3) After performing the same operation 5 times on the observation images of different screens of the same sample, the value obtained from the number average of a total of 50 particles is taken as the average particle diameter of the particles.

[0030] 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 with respect 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 made 0.75 or less. Further, by setting the content of the metal oxide particles having a high refractive index such as ITO to 150 parts by mass or more, the refractive index of the layer containing the metal oxide can be increased, and in combination with a low refractive index layer formed arbitrarily, the reflectance in the visible light region of the optical laminate can be lowered, which is preferable. Also, the content of the 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 still more preferably 1000 parts by mass or less with respect to 100 parts by mass of the binder resin. By setting the content of the metal oxide particles to 2000 parts by mass or less, it is easy to suppress a decrease in the coating film strength of the layer containing the metal oxide. Further, if the emissivity α of the optical laminate becomes too low, the heat generated inside the image display device is difficult to be released to the outside. Therefore, it is preferable to set the content of the metal oxide particles to 2000 parts by mass or less so that the emissivity α of the optical laminate is not too low. Preferred ranges of the content of the metal oxide particles with respect to 100 parts by mass of the 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 a binder resin preferably contains a silane coupling agent. The silane coupling agent may be a silane coupling agent as a surface treatment agent for the metal oxide particles or a silane coupling agent as a binder resin. By subjecting the metal oxide particles to surface treatment with a silane coupling agent, the affinity between the metal oxide particles and the binder resin is improved, and the metal oxide particles are likely to be uniformly dispersed. Also, even when a silane coupling agent as a binder resin is included, it is preferable in that the metal oxide particles are likely to be uniformly dispersed.

[0032] 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-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and the like. 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. The cured product of the curable resin composition includes cured products of thermosetting resin compositions and cured products of radiation-curable resin compositions. Among them, the cured product of the radiation-curable resin composition is preferred in order to improve mechanical strength. The proportion 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, still 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 cures by heating. Examples of the thermosetting resin include acrylic resins, urethane resins, phenol resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, silicone resins, and the like. A curing agent is added to these curable resins to the thermosetting resin composition as necessary.

[0035] A radiation-curable resin composition is a composition containing a compound having a radiation-curable functional group. In this specification, the "compound having a radiation-curable functional group" may be referred to as a "radiation-curable compound". Examples of the radiation-curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl group, vinyl group, allyl group, and epoxy group, oxetanyl group, and the like. As the radiation-curable compound, a compound having an ethylenically unsaturated bond group is preferred, a compound having two or more ethylenically unsaturated bond groups is more preferred, and among them, a (meth)acrylate compound having two or more ethylenically unsaturated bond groups is still more preferred. As the (meth)acrylate compound having two or more ethylenically unsaturated bond groups, either a monomer or an oligomer can be used. Note that the ionizing radiation means an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or crosslinking molecules. Usually, ultraviolet rays or electron beams are used, but other electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-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] - Photoinitiator, Photopolymerization accelerator - When the radiation-curable compound is an ultraviolet-curable compound, the radiation-curable composition preferably contains additives such as a photoinitiator and a photopolymerization accelerator. Examples of the photoinitiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyldimethylketal, benzoyl benzoate, α-acyl oxime ester, thioxanthones, and the like. In addition, the photopolymerization accelerator can increase the curing rate by reducing the polymerization inhibition by air during curing. Examples thereof include one or more selected from isoamyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, and the like.

[0037] - Refractive index, Film thickness - The layer containing metal oxide particles and a binder resin preferably has a refractive index of 1.53 or more and 2.30 or less, more preferably 1.57 or more and 2.00 or less, still more preferably 1.60 or more and 1.80 or less, and even more preferably 1.65 or more and 1.75 or less. By setting the refractive index of the layer containing the metal oxide within the above range, it is easy to lower the reflectance of the optical laminate in the visible light region by combining it with a low refractive index layer formed arbitrarily. The preferable range of the refractive index of the layer containing metal oxide particles and a binder resin is 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, 1.65 or more and 1.75 or less.

[0038] In this specification, the refractive index of each layer means the refractive index at a wavelength of 550 nm. Further, in this specification, the refractive index of each layer can be calculated, for example, by fitting between the reflection spectrum measured by a spectrophotometer and the reflection spectrum calculated from the optical model of the multilayer thin film using the Fresnel coefficient.

[0039] The thickness of the layer containing metal oxide particles and a 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 make the emissivity α 0.75 or less. Note that there is a limit to the decrease in the emissivity α by increasing the thickness of the layer containing metal oxide particles and a binder resin. Further, when the thickness of the layer containing metal oxide particles and a binder resin is too thick, the transparency tends to decrease. For thinning, 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. The preferable range of the thickness of the layer containing metal oxide particles and a binder resin is 100 nm or more and 5.0 μm or less, 100 nm or more and 2.0 μm or less, 100 nm or more and 1.5 μm or less, 200 nm or more and 5.0 μm or less, 200 nm or more and 2.0 μm or less, 200 nm or more and 1.5 μm or less, 500 nm or more and 5.0 μm or less, 500 nm or more and 2.0 μm or less, 500 nm or more and 1.5 μm or less.

[0040] In addition, in order to reduce the reflectance 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 n, which is the refractive index of the layer containing metal oxide particles and a binder resin. o It is preferably adjusted in consideration of 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". The range of the thickness of the layer containing metal oxide particles and a binder resin in consideration of reducing the reflectance in the visible light region varies depending on the refractive index range as described above, and thus cannot be generally stated, but it is preferably 120 nm or more and 750 nm or less, more preferably 130 nm or more and 500 nm or less, and even more preferably 140 nm or more and 400 nm or less. Preferred ranges of the thickness of the layer containing metal oxide particles and a binder resin for reducing the reflectance in the visible light region include 120 nm or more and 750 nm or less, 120 nm or more and 500 nm or less, 120 nm or more and 400 nm or less, 130 nm or more and 750 nm or less, 130 nm or more and 500 nm or less, 130 nm or more and 400 nm or less, 140 nm or more and 750 nm or less, 140 nm or more and 500 nm or less, and 140 nm or more and 400 nm or less.

[0041] The layer containing metal oxide particles and a binder resin may contain additives such as a leveling agent, a dispersant, a dye, an ultraviolet absorber, a light stabilizer, and an antioxidant as long as the effects of the present disclosure are not impaired. The 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, and then irradiating with ionizing radiation as necessary. After forming the layer as described above, the layer containing metal oxide particles and a binder resin is preferably heat-treated. Heat treatment can easily reduce the emissivity α. The lower limit of the heat treatment temperature is preferably 90 °C or higher, more preferably 95 °C or higher, still more preferably 100 °C or higher, and the upper limit is preferably 170 °C or lower, more preferably 160 °C or lower, still more preferably 150 °C or lower. The lower limit of the heat treatment time is preferably 30 minutes or longer, more preferably 45 minutes or longer, still more preferably 50 minutes or longer, and the upper limit is preferably 200 minutes or shorter, more preferably 120 minutes or shorter, still more preferably 80 minutes or shorter.

[0042] 《(2) Metal Oxide Film》 The metal oxide film is formed by, for example, physical vapor deposition methods such as sputtering or chemical vapor deposition methods to form a metal oxide film. Among metal oxide films, an indium tin oxide film with a low emissivity is preferred.

[0043] The metal oxide film is preferably amorphous in order to easily make the emissivity α of the optical laminate 0.27 or higher. That is, the metal oxide film is preferably one that has not been crystallized by heating such as annealing treatment. Also, the amorphous metal oxide film is preferred in that it has good flex resistance and is easily applicable to foldable type image display devices and rollable type image display devices. From the above, the metal oxide film is preferably an amorphous film of indium tin oxide.

[0044] - Refractive Index, Film Thickness - The refractive index of the metal oxide film is preferably 2.0 or higher and 2.5 or lower, more preferably 2.1 or higher and 2.2 or lower. By setting the refractive index of the metal oxide film within the above range, the reflectance in the visible light region of the optical laminate can be easily reduced by combining it with a low refractive index layer formed arbitrarily. Preferred ranges of the refractive index of the metal oxide film include, in addition to the above range, 2.0 or higher and 2.2 or lower, and 2.1 or higher and 2.5 or lower.

[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 facilitate making the emissivity α 0.75 or less. The degree to which the layer with low emissivity reflects back the radiant heat to the outside tends to increase as the thickness increases. Therefore, for suppressing the temperature rise of the optical laminate, the thickness of the metal oxide film is preferably 100 nm or more. Note that if the thickness of the metal oxide film is too thick, the transparency tends to decrease. For thinning, 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. Preferred ranges for the thickness of the metal oxide film include 10 nm or more and 1000 nm or less, 10 nm or more and 500 nm or less, 10 nm or more and 300 nm or less, 20 nm or more and 1000 nm or less, 20 nm or more and 500 nm or less, 20 nm or more and 300 nm or less, 30 nm or more and 1000 nm or less, 30 nm or more and 500 nm or less, and 30 nm or more and 300 nm or less. In order to have good flex resistance and be easily applicable to a foldable type image display device and a rollable type image display device, the thickness of the metal oxide film is preferably 30 nm or more and 250 nm or less, and more preferably 30 nm or more and 150 nm or less.

[0046] Also, in order to lower the reflectance 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 or more and 200 nm or less, more preferably 100 nm or more and 170 nm or less, and even more preferably 100 nm or more and 140 nm or less.

[0047] <Functional layer α> The optical laminate may have one or more functional layers α between the plastic film and the layer containing the metal oxide. 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, a circularly polarized layer, etc., and a single layer of the hard coat layer is preferred.

[0048] 《Hard Coat Layer》 In order 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 is preferably mainly composed 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 the cured product of the curable resin composition include the cured product of a thermosetting resin composition and the cured product of an ionizing radiation curable resin composition. In order to improve mechanical strength, the cured product of the ionizing radiation curable resin composition is preferred. Examples of the curable resin composition for the hard coat layer include the curable resin compositions exemplified for the layer containing a metal oxide.

[0051] The hard coat layer may contain additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, and a refractive index adjuster, if necessary.

[0052] The thickness of the hard coat layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, and even more preferably 2.0 μm or more in order to easily improve scratch resistance. Also, the thickness of the hard coat layer is preferably 100 μm or less, more preferably 50 μm or less, still more preferably 30 μm or less, even more preferably 20 μm or less, still more preferably 15 μm or less, and even more preferably 10 μm or less in order to suppress heat accumulation and curl suppression. The preferable range of the thickness of the hard coat layer is 0.1 μm or more and 100 μm or less, 0.1 μm or more and 50 μm or less, 0.1 μm or more and 30 μm or less, 0.1 μm or more and 20 μm or less, 0.1 μm or more and 15 μm or less, 0.1 μm or more and 10 μm or less, 0.5 μm or more and 100 μm or less, 0.5 μm or more and 50 μm or less, 0.5 μm or more and 30 μm or less, 0.5 μm or more and 20 μm or less, 0.5 μm or more and 15 μm or less, 0.5 μm or more and 10 μm or less, 1.0 μm or more and 100 μm or less, 1.0 μm or more and 50 μm or less, 1.0 μm or more and 30 μm or less, 1.0 μm or more and 20 μm or less, 1.0 μm or more and 15 μm or less, 1.0 μm or more and 10 μm or less, 2.0 μm or more and 100 μm or less, 2.0 μm or more and 50 μm or less, 2.0 μm or more and 30 μm or less, 2.0 μm or more and 20 μm or less, 2.0 μm or more and 15 μm or less, 2.0 μm or more and 10 μm or less.

[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 the functional layer β include a low refractive index layer, a high refractive index layer, an antiglare layer, an antifouling layer, and a circularly polarizing layer. The functional layer may also serve the functions described above. For example, the low refractive index layer may have antifouling or antiglare properties.

[0054] The total thickness of one or more functional layers β is preferably 1000 nm or less, more preferably 500 nm or less, still more preferably 350 nm or less, yet more preferably 200 nm or less, and even more preferably 150 nm or less. The layer located on the side opposite to the plastic film with respect to the layer containing the metal oxide has its temperature increased by the radiant heat from outside the image display device and the radiant heat generated inside the image display device and transmitted through the layer containing the metal oxide. Therefore, the thicker the total thickness of the one or more functional layers β, the more likely heat is to be trapped in the one or more functional layers β. For this reason, by setting the total thickness of the one or more functional layers β to 350 nm or less, it is easier to suppress the optical laminate from becoming high in temperature. Also, by setting the total thickness of the one or more functional layers β to 350 nm or less, it is easier to lower the emissivity α. Also, considering that it is preferable that the total thickness of the one or more functional layers β is thin, the functional layer β is preferably a single layer, and more preferably a single layer of a low refractive index layer.

[0055] 《Low refractive index layer》 The low refractive index layer is preferably located on the outermost surface on the side opposite to the plastic film with respect to the layer containing the metal oxide.

[0056] The refractive index of the low refractive index layer is preferably 1.10 or more and 1.48 or less, more preferably 1.20 or more and 1.45 or less, still more preferably 1.26 or more and 1.40 or less, still more preferably 1.28 or more and 1.38 or less, and most preferably 1.30 or more and 1.32 or less. Preferred ranges of the refractive index of the low refractive index layer include 1.10 or more and 1.48 or less, 1.10 or more and 1.45 or less, 1.10 or more and 1.40 or less, 1.10 or more and 1.38 or less, 1.10 or more and 1.32 or less, 1.20 or more and 1.48 or less, 1.20 or more and 1.45 or less, 1.20 or more and 1.40 or less, 1.20 or more and 1.38 or less, 1.20 or more and 1.32 or less, 1.26 or more and 1.48 or less, 1.26 or more and 1.45 or less, 1.26 or more and 1.40 or less, 1.26 or more and 1.38 or less, 1.26 or more and 1.32 or less, 1.28 or more and 1.48 or less, 1.28 or more and 1.45 or less, 1.28 or more and 1.40 or less, 1.28 or more and 1.38 or less, 1.28 or more and 1.32 or less, 1.30 or more and 1.48 or less, 1.30 or more and 1.45 or less, 1.30 or more and 1.40 or less, 1.30 or more and 1.38 or less, 1.30 or more and 1.32 or less.

[0057] The thickness of the low refractive index layer is preferably 80 nm or more and 150 nm or less, more preferably 85 nm or more and 110 nm or less, still more preferably 90 nm or more and 105 nm or less. Further, the thickness of the low refractive index layer is preferably larger than the average particle diameter of the low refractive index particles such as hollow particles. Preferred ranges for the thickness of the low refractive index layer include 80 nm or more and 150 nm or less, 80 nm or more and 110 nm or less, 80 nm or more and 105 nm or less, 85 nm or more and 150 nm or less, 85 nm or more and 110 nm or less, 85 nm or more and 105 nm or less, 90 nm or more and 150 nm or less, 90 nm or more and 110 nm or less, 90 nm or more and 105 nm or less. It is more preferable that the thickness of the low refractive index layer satisfies the above-mentioned preferred range and that the thickness of the low refractive index layer is larger than the average particle diameter of the low refractive index particles such as hollow particles.

[0058] The methods for forming the low refractive index layer can be broadly classified into a wet method and a dry method. Examples of the wet method include a method of forming by a sol-gel method using a metal alkoxide or the like, a method of forming by coating a low refractive index resin such as a fluororesin, and a method of forming by coating a coating liquid for forming a low refractive index layer containing low refractive index particles in a resin composition. Examples of the dry method include a method of selecting particles having a desired refractive index from among the low refractive index particles and forming by a physical vapor deposition method or a chemical vapor deposition method. The wet method is superior to the dry method in terms of production efficiency, suppression of the oblique reflection hue, and chemical resistance. In the present embodiment, among the wet methods, it is preferable to form by a coating liquid for forming a low refractive index layer containing low refractive index particles in a binder resin composition for the sake of adhesion, water resistance, scratch resistance, and reduction of the refractive index. In other words, the low refractive index layer preferably 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 the curable resin composition. Further, 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 the curable resin composition for the low refractive index layer include the curable resin compositions exemplified for the layer containing a metal oxide.

[0060] The low refractive index particles preferably contain one or more selected from hollow particles and non-hollow particles. Further, for the balance between low reflectance and scratch resistance, it is preferable to use in combination one or more selected from hollow particles and one or more selected from non-hollow particles. The materials of the hollow particles and the non-hollow particles may be any of inorganic compounds such as silica and magnesium fluoride and organic compounds, but silica is preferable for reducing the refractive index and improving the strength.

[0061] Considering the optical properties and mechanical strength, the average particle diameter of the hollow silica particles is preferably 50 nm or more and 200 nm or less, and more preferably 60 nm or more and 80 nm or less. Preferred ranges of the average particle diameter of the hollow silica particles include, in addition to the above range, 50 nm or more and 80 nm or less, and 60 nm or more and 200 nm or less. Considering the dispersibility while preventing aggregation of the non-hollow silica particles, the average particle diameter of the non-hollow silica particles is preferably 5 nm or more and 100 nm or less, and more preferably 10 nm or more and 20 nm or less. Preferred ranges of the average particle diameter of the non-hollow silica particles include, in addition to the above range, 5 nm or more and 20 nm or less, and 10 nm or more and 100 nm or less.

[0062] As the content of the hollow silica particles increases, the filling rate of the hollow silica particles in the binder resin increases, and the refractive index of the low refractive index layer decreases. Therefore, the content of the hollow silica particles is preferably 100 parts by mass or more, and more preferably 150 parts by mass or more with respect to 100 parts by mass of the binder resin. On the other hand, if the content of the hollow silica particles with respect to the binder resin is too high, the exposed hollow silica particles from the binder resin increase, and the binder resin that binds between the particles decreases. For this reason, the hollow silica particles are likely to be damaged or fall off, and the mechanical strength such as the scratch resistance of the low refractive index layer tends to decrease. Therefore, the content of the hollow silica particles is preferably 400 parts by mass or less, and more preferably 300 parts by mass or less with respect to 100 parts by mass of the binder resin. Preferred ranges of the content of the hollow silica particles with respect to 100 parts by mass of the 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 the non-hollow silica particles is low, even if non-hollow silica particles are present on the surface of the low refractive index layer, it may not affect the increase in hardness. Also, when a large amount of non-hollow silica particles are contained, the influence of shrinkage unevenness due to the polymerization of the binder resin becomes small, so the unevenness generated on the surface of the low refractive index layer after resin curing can be reduced. Therefore, the content of the non-hollow silica particles is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, still more preferably 70 parts by mass or more, and even more preferably 100 parts by mass or more with respect to 100 parts by mass of the binder resin. On the other hand, if the content of the non-hollow silica particles is too high, the non-hollow silica is likely to aggregate, and shrinkage unevenness of the binder resin occurs, so the surface unevenness becomes large. Therefore, the content of the non-hollow silica particles is preferably 200 parts by mass or less, and more preferably 150 parts by mass or less with respect to 100 parts by mass of the binder resin. The preferable range of the content of non-hollow silica particles with respect to 100 parts by mass of the binder resin is 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, 100 parts by mass or more and 150 parts by mass or less.

[0064] By containing hollow silica particles and non-hollow silica particles in the binder resin at the above ratios, the barrier property of the low refractive index layer can be improved. This is presumably because the silica particles are uniformly dispersed at a high filling rate, inhibiting the permeation of gases and the like. In addition, various cosmetics such as sunscreen and hand cream may contain low molecular weight polymers with low volatility. By improving the barrier property of the low refractive index layer, the penetration of the low molecular weight polymer into the coating film of the low refractive index layer can be suppressed, and defects such as appearance abnormalities caused by the long-term residual of the low molecular weight polymer in the coating film can be suppressed. Note that suppressing the penetration of the low molecular weight polymer into the coating film of the low refractive index layer is also preferable for reducing the emissivity α.

[0065] <Emissivity> The optical laminate of the present disclosure requires that the emissivity of the optical laminate with respect to light in the wavelength range of 2000 nm or more and 22000 nm or less, measured from the layer side containing the metal oxide with reference to the plastic film, is 0.27 or more and 0.75 or less. 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 takes in radiant heat caused by the external environment such as the temperature inside the vehicle, resulting in a decrease in the visibility of the image display device including the optical laminate. In addition, when 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, resulting in a high temperature inside the image display device and a decrease in the visibility of the image display device including the optical laminate. Examples of the radiant heat generated inside the image display device include the radiant heat generated from the display element. 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 the recent improvement in display technology, for example, in order to impart curvature to the display to enhance the design, a flexible optical laminate may be required. When the emissivity α is less than 0.40, the layer containing the metal oxide tends to become hard, and there may be problems in the formability of curved surfaces. Therefore, setting the emissivity α to 0.40 or more is preferable for the formability of curved surfaces. Also, the lower the emissivity α, the better because it can control the temperature rise caused by the external environment. For this reason, for example, when the emissivity α is 0.60 or less, it is easy to lower the surface temperature of the optical laminate to a level that can be easily touched by hand, and it is also easy to suppress the optical laminate itself from acting as a heat source. Thus, it is preferable in terms of easily lowering the perceived temperature when the face or hand is brought close to the image display device for a long time. Preferable ranges of the emissivity α include 0.27 or more and 0.75 or less, 0.27 or more and 0.70 or less, 0.27 or more and 0.67 or less, 0.27 or more and 0.60 or less, 0.35 or more and 0.75 or less, 0.35 or more and 0.70 or less, 0.35 or more and 0.67 or less, 0.35 or more and 0.60 or less, 0.37 or more and 0.75 or less, 0.37 or more and 0.70 or less, 0.37 or more and 0.67 or less, 0.37 or more and 0.60 or less, 0.40 or more and 0.75 or less, 0.40 or more and 0.70 or less, 0.40 or more and 0.67 or less, 0.40 or more and 0.60 or less.

[0067] In this specification, the decrease in visibility refers to, for example, "the non-uniformity of various performances such as brightness, color tone, and specular reflectance characteristics at a local location within the display screen of an image display device", "the non-uniformity of the above-mentioned various performances between the vicinity of the center and the vicinity of the edge of the display screen of the image display device", "the change in the above-mentioned various performances in a high-temperature environment compared to a normal-temperature environment", and the like. Such a decrease in visibility is considered to be caused, for example, by the deformation of the optical laminate due to high temperature. In addition, an image display device usually has a cooling means such as an air-cooling fan, but the cooling effect by the cooling means varies depending on the location of the image display device. And since radiant heat is continuously generated and the above-mentioned differences in cooling effect are gradually accumulated, a temperature difference occurs depending on the location within the image display device. For this reason, there may be a location where the temperature is different within the plane of the optical laminate, and in such a case, a local change in physical properties occurs in the optical laminate, which is considered to cause a decrease in visibility. According to the optical laminate of the present disclosure, it is possible to suppress the decrease in visibility caused by the above-mentioned causes.

[0068] In this specification, the emissivity α means the emissivity at normal temperature measured in accordance with JIS A1423:1983. Examples of the measuring device for emissivity include the product number "TSS-5X-2" manufactured by Japan Sensor Co., Ltd.

[0069] In addition, in this specification, various physical properties such as emissivity, spectral transmittance, visual reflectance Y value, total light transmittance, and haze are, unless otherwise specified, measured after exposing a measurement sample to an environment of a temperature of 23 ± 5°C and a relative humidity of 40% or more and 65% or less for 30 minutes or more, and then measured in the same environment. Also, in this specification, various physical properties such as emissivity, spectral transmittance, visual reflectance Y value, total light transmittance, and haze are, unless otherwise specified, the average value of 20 measurements.

[0070] <Various physical properties> The average spectral transmittance of the layer containing the metal oxide in the wavelength range of 8200 nm or more and 9000 nm or less is preferably 80% or less, more preferably 70% or less, and still more preferably 60% or less.

[0071] The following formula (1) shows the peak wavelength (λ) of the radiation wavelength emitted by a black body at any temperature, and is a formula called Wien's formula. In the formula, "T" represents the temperature, and the unit is °C. λ(nm)≒2897 / (T + 273) (1) For example, it is said that the temperature of the atmosphere and dashboard inside a car in summer, and the temperature near the window in a sealed room in summer, etc., are about 50°C or more and 80°C or less. When 50 and 80 are substituted into T in the above formula (1), λ becomes about 9000 nm and about 8200 nm. That is, the wavelength range of the above spectral transmittance is specified as 8200 nm or more and 9000 nm or less in consideration of the temperature of a car in summer and the temperature near the window in a sealed room in summer. Therefore, by setting the average of the above spectral transmittance to 80% or less, the optical laminate can efficiently cut the infrared rays emitted from inside the car, so that it is possible to more effectively suppress the increase in temperature of the image display device and more easily suppress the decrease in visibility. The lower limit of the average of the above spectral transmittance is not particularly limited, but is usually 30% or more, preferably 40% or more.

[0072] In this specification, the spectral transmittance of the layer containing the metal oxide means the value calculated by the measurement of the following (A1) and the conversion process of (A2). (A1) Measure the absorbance of each wavelength of the layer containing the metal oxide by the reflection of FTIR. (A2) Perform a process of converting the absorbance of each wavelength in A1 into the transmittance of each wavelength. The measurement of the above (A1) shall be made from the side of the layer containing the metal oxide with reference to the plastic film. Even when the functional layer β exists on the layer containing the metal oxide, if the total thickness of the functional layer β is about 250 nm or less, the measurement of the above (A1) can be carried out in the state having the functional layer β. Then, by subjecting the absorbance of the layer containing the metal oxide measured in the state having the functional layer β to the conversion treatment in the above (A2), the spectral transmittance of the layer containing the metal oxide can be calculated.

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

[0074] In this specification, the visual reflectance Y value refers to the visual reflectance Y value in the CIE1931 standard colorimetric system, and is measured at an incident angle of 5 degrees. The visual reflectance Y value can be calculated using a spectrophotometer. Examples of the spectrophotometer include the product name "UV-2450" manufactured by Shimadzu Corporation. When measuring the visual reflectance, it is preferable to bond a black plate to the back surface of the plastic film.

[0075] Preferably, the total light transmittance of the optical laminate is 70% or more, more preferably 80% or more, and even more preferably 90% or more in accordance with JIS K7361-1:1997. Also, preferably, the haze of the optical laminate is 5% or less, more preferably 3% or less, and even more preferably 1% or less in accordance with JIS K7136:2000. Preferably, the total light transmittance and the haze are measured with the surface on the plastic film side as the light incident surface with reference to the layer containing the metal oxide.

[0076] Preferably, with reference to the plastic film, the roughness of the outermost surface on the side having the layer containing the metal oxide of the optical laminate is within a predetermined range. Specifically, the arithmetic mean roughness Ra at a cut-off value of 2.5 mm of JIS B0601:2001 on the outermost surface 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 make the emissivity α 0.75 or less. When measuring Ra, it is preferable to set the horizontal magnification to 1000 times and the vertical magnification to 20000 times as the measurement conditions of the measuring device.

[0077] <Layer structure> The overall layer structure of the optical laminate of the present disclosure is not particularly limited, but the following (1) to (6) can be mentioned. Note that " / " indicates the interface of the layer. (1) Plastic film / layer containing metal oxide (2) Plastic film / hard coat layer / layer containing metal oxide (3) Plastic film / layer containing metal oxide / 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 improve mechanical strength. Further, 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 still more preferably 75 μm or less in order to be easily applicable to a foldable type image display device and a rollable type image display device. The preferred range of the total thickness of the optical laminate is 10 μm or more and 130 μm or less, 10 μm or more and 100 μm or less, 10 μm or more and 90 μm or less, 10 μm or more and 75 μm or less, 30 μm or more and 130 μm or less, 30 μm or more and 100 μm or less, 30 μm or more and 90 μm or less, 30 μm or more and 75 μm or less, 45 μm or more and 130 μm or less, 45 μm or more and 100 μm or less, 45 μm or more and 90 μm or less, 45 μm or more and 75 μm or less. By setting the total thickness of the optical laminate within the above range, it is possible to easily achieve φ10 mm or less in the evaluation using an outer bending mandrel test bar. Among the above ranges, for an optical laminate with a total thickness of 75 μm or less, it is also possible to easily achieve φ6 mm or less. That is, by setting the total thickness of the optical laminate within the above range, the optical laminate can be easily applied to a foldable type image display device and a rollable type image display device. Note that "outer bending" means bending such that the side having the layer containing the metal oxide faces outward with respect to the plastic film. Also, "outer side" means "the side farther from the mandrel bar".

[0079] [Polarizer] The polarizer of the present disclosure is a polarizer 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 the polarizer include sheet type polarizers such as polyvinyl alcohol films dyed with iodine or the like and stretched, polyvinyl formal films, polyvinyl acetal films, saponified ethylene-vinyl acetate copolymer films, wire grid type polarizers composed of a large number of metal wires arranged in parallel, coated type polarizers coated with lyotropic liquid crystals and dichroic guest-host materials, multilayer thin film type polarizers, etc. These polarizers may be reflective polarizers having a function of reflecting polarization components that do not pass through.

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

[0082] Examples of the first transparent protective plate and the second transparent protective plate other than the optical laminate include plastic films and glass, and a plastic film is preferred. Examples of the plastic film include polyester film, polycarbonate film, cycloolefin polymer film, acrylic film, and triacetyl cellulose film, etc. For mechanical strength, these stretched films are preferred. The polarizer and the transparent protective plate are preferably bonded via an adhesive. A general-purpose adhesive can be used as the adhesive, and a PVA-based adhesive is preferred.

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

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

[0085] The optical laminate is preferably arranged such that the surface on the plastic film side faces the resin plate or the glass plate side with respect to the layer containing the metal oxide. Further, it is preferable that the front plate for the image display device is arranged such that the surface on which the optical laminate is bonded faces the front side. In other words, it is preferable that the front plate for the image display device is arranged such that the surface on which the optical laminate is bonded faces the side opposite to the display element.

[0086] As the resin plate or the glass plate, a resin plate or a glass plate that is generally used as the front plate of the image display device can be used.

[0087] The thickness of the resin plate or the glass plate is preferably 10 μm or more in order to improve the strength. The upper limit of the thickness of the resin plate or the glass plate is usually 5000 μm or less. However, in recent years, since thinning of the image display device is preferred, it is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 100 μm or less. Preferable ranges of the thickness of the resin plate or the glass plate include 10 μm or more and 5000 μm or less, 10 μm or more and 1000 μm or less, 10 μm or more and 500 μm or less, and 10 μm or more and 100 μm or less.

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

[0089] Preferably, the optical laminate is arranged such that the surface on the layer containing the metal oxide side faces the side opposite to the display element with respect to the plastic film. Further, it is preferable that the optical laminate is arranged on the outermost surface of the image display device. Further, in order to suppress heat conduction, it is preferable to arrange the image display device such that air is interposed between the display element and the optical laminate.

[0090] Examples of the display element include EL display elements such as liquid crystal display elements, organic EL display elements, and inorganic EL display elements, plasma display elements, etc., 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. Examples of the liquid crystal display method of the liquid crystal display element include the IPS method, VA method, multi-domain method, OCB method, STN method, TSTN method, etc. When the display element is a liquid crystal display element, a backlight is required. The backlight is disposed on the side opposite to the side having the optical laminate of the liquid crystal display element. The image display device may be a foldable image display device or a rollable image display device. Further, the image display device may be an image display device with a touch panel. Note that a portable image display device and an image display device incorporated in an automobile dashboard are likely to be exposed to a high-temperature environment, so they are preferable in terms of easily exhibiting the effects of the present disclosure.

[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 the general-purpose heat dissipation mechanism include an air-cooling fan, heat dissipation fins, a heat pump, and a Peltier element.

Example

[0092] Hereinafter, the present disclosure will be specifically described with reference to examples and comparative examples. Note that the present disclosure is not limited to the forms described in the examples.

[0093] 1. Evaluation and measurement The following measurements and evaluations were performed on the optical laminates obtained in the examples and comparative examples. 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% or more and 65% or less. Before starting each measurement and evaluation, the target sample was exposed to the above atmosphere for 30 minutes or more and then the measurement and evaluation were performed. 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 evaluations and measurements shall be performed by fictitiously assuming that the heat dissipation layer of Comparative Example 2 is a layer containing a metal oxide.

[0094] 1-1. Emissivity Regarding the optical laminates of the examples and comparative examples, the emissivity at room temperature was measured in accordance with JIS A1423:1983. Specifically, “the emissivity of the optical laminate with respect to light in the wavelength range of 2000 nm or more and 22000 nm or less, measured from the side of the layer containing a metal oxide with the base material as a reference” was measured. As described above, in this specification, the emissivity may be referred to as “emissivity α”. Those with an emissivity α exceeding 0.75 were given a C evaluation. Those with an emissivity α less than 0.27 were given a B evaluation. Those with an emissivity α of 0.27 or more and 0.75 or less were given an A evaluation or higher, and among them, those with an emissivity α of 0.37 or more and 0.60 or less were given an AA evaluation. When the emissivity α is too high, the optical laminate takes in radiant heat caused by the external environment, resulting in a temperature rise of the image display device. On the other hand, when the emissivity α is too low, although the optical laminate is less likely to take in radiant heat caused by the external environment, the radiant heat generated inside the image display device is returned to the inside of the image display device by the optical laminate, so it is assumed that the inside of the image display device becomes high temperature. As the emissivity measuring device, the product number “TSS-5X-2” manufactured by Japan Sensor Co., Ltd. was used. The emissivity reference pieces attached to the measuring device are two types with emissivities of 0.06 and 0.97. The main specifications of the measuring device are as follows. <Specifications> · Measurement area: Φ15 mm · Measurement distance: 12 mm

[0095] 1-2. Spectral transmittance The spectral transmittance of the layer containing a metal oxide in the optical laminate of the examples and comparative examples was measured in the wavelength range of 8200 nm or more and 9000 nm or less. As described in the main text of the specification, after measuring the absorbance at each wavelength of the layer containing a metal oxide by reflection of FTIR, the spectral transmittance of the layer containing a metal oxide in the wavelength range of 8200 nm or more and 9000 nm or less was calculated by converting the absorbance at each wavelength into the transmittance at each wavelength. As the FIIR measuring instrument, the product number "NICOLET iS10" manufactured by Thermo Fisher SCIENTIFIC was used. Also, as an accessory, the "One-reflection type Ge ATR accessory foundation" manufactured by the same company was used. Further, the measurement conditions were as follows: after facing the measurement surface to the Ge crystal plane and crimping and fixing the sample with a Pressure Tower, the incident type was once, 45°, the number of scans was 32 times, the resolution was 8, the detector was DTGS KBr, the mirror speed was 0.6329, the aperture was open, and the measurement range was 680 cm -1 to 4000 cm -1 The measurement was performed under the following conditions. The measured absorbance was converted into transmittance, and cm -1 was converted into nm to calculate the average value of the transmittance in the wavelength range.

[0096] 1-3. Visual reflectance Y value A sample was prepared by laminating a black plate (manufactured by Kuraray Co., Ltd., trade name: Komoglas DFA2CG 502K (black), thickness 2 mm) via a transparent adhesive layer with a thickness of 25 μm (manufactured by Panac Co., Ltd., trade name: Panaclean PD-S1) on the side opposite to the layer containing a metal oxide of the base material of the optical laminate of the examples and comparative examples. For the said sample, the visual reflectance Y value was measured by irradiating light at an incident angle of 5 degrees from the side of the layer containing a metal oxide with the base material as a reference. The visual reflectance Y value was measured using a spectrophotometer (manufactured by Shimadzu Corporation, trade name: UV-2450) under the conditions of a viewing angle of 2 degrees, a C light source, and a wavelength range of 380 nm or more and 780 nm or less to measure the 5° regular reflectance, and then the value indicating the visual reflectance calculated by software (built-in UVPC color measurement Version 3.12 in the device) that converts it into the brightness felt by the human eye was obtained as the reflectance.

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

[0098] 1-5. Surface temperature A simulated liquid crystal display device was fabricated by disposing the optical laminates of the examples and comparative examples on a commercially available liquid crystal display device (manufactured by Amazon, product name Kindle Fire HDX) such that the substrate side faced the display device side. Assuming the interior of a car in summer, the 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, 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 lower is the pass level. Considering the actual handling of image display, the maximum temperature is more preferably 60°C or lower, and even more preferably 57°C or lower.

[0099] 1-6. Visibility (non-uniformity) The simulated liquid crystal display device fabricated in 1-5 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 screen of the liquid crystal display device was displayed in solid green, and it was visually evaluated whether there were any areas with non-uniform brightness and hue within the display screen. Ten evaluators with a visual acuity of 0.7 or higher were used. The visual acuity includes the corrected visual acuity. The distance between the evaluator and the liquid crystal display device was 50 cm. Those for which 8 or more people answered that there were no areas with non-uniform brightness and hue were rated as "A", and those for which 7 or fewer people answered that there were no areas with non-uniform brightness and hue were rated as "C".

[0100] 2. Fabrication of optical laminate [Example 1] On a substrate (triacetyl cellulose film, thickness 60 μm), the following coating solution for a hard coat layer was applied, dried, and irradiated with ultraviolet rays to form a hard coat layer with a film thickness of 5 μm. Next, on the hard coat layer, the following coating solution 1 for a metal oxide layer was applied, dried, and irradiated with ultraviolet rays to form a layer containing ITO particles as a metal oxide with a film thickness of 350 nm. Next, on the layer containing the metal oxide, the following coating solution for a low refractive index layer was applied, dried, and irradiated with ultraviolet rays to form a low refractive index layer with a film thickness of 100 nm, and the optical laminate of Example 1 was obtained.

[0101] <Coating solution for hard coat layer> 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., trade name: KAYARAD PET-30) · Photoinitiator 4 parts by mass (IGM Resins B.V., trade name: Omnirad 184) · Methyl ethyl ketone 50 parts by mass

[0102] <Coating solution 1 for metal oxide layer> The following components were mixed to prepare coating solution 1 for a metal oxide layer. · Pentaerythritol triacrylate 1 part by mass (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30) · ITO particles 8.5 parts by mass (Average particle diameter 30 nm) · Photoinitiator 0.4 part by mass (IGM Resins B.V., trade name: Omnirad 184) · Levelling agent 0.03 part by mass (Manufactured by DIC Corporation, Megafac F-477) · Methyl isobutyl ketone 89 parts by mass

[0103] <Coating solution for low refractive index layer> The following components were mixed to prepare a coating solution for a low refractive index layer. · Pentaerythritol triacrylate: 0.4 parts by mass (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30) · Fluorine-containing polymer: 0.2 parts by mass (solid content) (manufactured by JSR Corporation, trade name: JN35) · Fluorine-containing monomer: 0.7 parts by mass (solid content) (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LINC3A) · Hollow silica particles: 1.7 parts by mass (average particle diameter 75 nm, refractive index 1.212) · Solid silica particles: 0.6 parts by mass (average particle diameter 15 nm) · Levelling agent: 0.06 parts by mass (manufactured by Shin-Etsu Silicone Co., Ltd., trade name: X-22-164E) · Photoinitiator: 0.09 parts by mass (manufactured by IGM Resins B.V., trade name: Omnirad 127) · Solvent: 97 parts by mass (a mixed solvent of methyl isobutyl ketone and propylene glycol monomethyl ether acetate with a mass ratio of 70:30, prepared according to the thickness with a solid content of 2% by mass)

[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 substrate (triacetyl cellulose film, thickness 60 μm) was changed to a biaxially stretched 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 liquid 1 for the metal oxide layer was changed to the following coating liquid 2 for the metal oxide layer and the thickness was changed to 900 nm.

[0108] [Coating Liquid 2 for Metal Oxide Layer] · 1 part by mass of pentaerythritol triacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30) · 9.6 parts by mass of Al-doped ZnO particles · 0.4 part by mass of a photopolymerization initiator (manufactured by IGM Resins B.V., trade name: Omnirad 184) · 0.03 part by mass of a leveling agent (manufactured by DIC Corporation, Megafac F-477) · 89 parts by mass of methyl isobutyl ketone

[0109] [Example 6] The coating liquid 1 for the metal oxide layer was changed to the following coating liquid 3 for the metal oxide layer, and the thickness of the layer containing the metal oxide was changed to 900 nm. Further, a step of heating at 100 °C for 60 minutes was added after coating, drying, and ultraviolet irradiation of the coating liquid for the metal oxide layer. An optical laminate of Example 6 was obtained in the same manner as in Example 1 except for the above-described changes and additions.

[0110] [Example 7] A hard coat layer with a film thickness of 5 μm was formed on a substrate (cycloolefin polymer film, thickness 47 μm) by coating, drying, and ultraviolet irradiation of the above-described coating liquid for the hard coat layer. Next, the following coating liquid 3 for the metal oxide layer was coated, dried, and ultraviolet irradiated on the hard coat layer to form a layer containing ITO particles as a metal oxide with a film thickness of 900 nm, and then heated at 150 °C for 60 minutes. Next, the above-described coating liquid for the low refractive index layer was coated, dried, and ultraviolet irradiated on the layer containing the metal oxide to form a low refractive index layer with a film thickness of 100 nm, and an optical laminate of Example 7 was obtained.

[0111] <Coating Liquid 3 for Metal Oxide Layer> Coating Liquid 3 for metal oxide layer was prepared by mixing the following components. · Pentaerythritol triacrylate: 0.5 parts by mass (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30) · ITO particles: 9 parts by mass (average particle diameter: 30 nm) · Photoinitiator: 0.4 parts by mass (manufactured by IGM Resins B.V., trade name: Omnirad 184) · Levelling agent: 0.03 parts by mass (manufactured by DIC Corporation, Megafac F-477) · Methyl isobutyl ketone: 89 parts by mass

[0112] [Example 8] A hard coat layer was formed on a substrate (biaxially stretched polyethylene terephthalate film with a thickness of 100 μm) in the same manner as in Example 1. Next, while introducing argon mixed with oxygen gas, sputtering was performed using an ITO target to form a metal oxide film with a thickness of 130 nm on the hard coat layer. The ITO target has a mass ratio of indium to tin of 90:10. The metal oxide film is an amorphous film of ITO. Next, after performing corona discharge treatment on the surface on the metal oxide film side, 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] While introducing argon mixed with oxygen gas, sputtering was performed using an ITO target to form a metal oxide film with a thickness of 140 nm on a glass substrate with a thickness of 0.7 mm. The ITO target has a mass ratio of indium to tin of 90:10. Next, by heating at 200 °C for 30 minutes and performing annealing treatment, an optical laminate of Comparative Example 1 having a crystalline film of ITO with a thickness of 140 nm on the glass substrate was obtained.

[0114] [Comparative Example 2] On a substrate (triacetyl cellulose film, thickness 60 μm), the following coating liquid for a heat dissipation layer was applied, dried, and irradiated with ultraviolet rays to form a heat dissipation layer with a film thickness of 1 μm, 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 liquid for a heat dissipation layer. · Pentaerythritol triacrylate 3.2 parts by mass (Nippon Kayaku Co., Ltd., trade name: KAYARAD PET-30) · Boron nitride particles 6.4 parts by mass (Average particle diameter 700 nm) · Photoinitiator 0.4 parts by mass (IGM Resins B.V., trade name: Omnirad 184) · Methyl ethyl ketone 90 parts by mass

[0116]

Table 1

[0117] From the results in Table 1, it was confirmed that the optical laminate of the present disclosure can suppress a decrease in visibility in a high-temperature environment. In addition, a mandrel test in accordance with JIS K5600-5-1:1999 was performed on the optical laminates of Examples 1 to 8. Specifically, test pieces of 100 mm × 25 mm were cut out from the optical laminates of Examples 1 to 8, and wound around a mandrel bar so that the short sides of the test pieces were parallel to the mandrel bar. The test pieces were wound around the mandrel bar by outer bending. As the mandrel bars, φ10 mm and φ6 mm were used. As a result of the above mandrel test, in the optical laminates of Examples 1 to 8, cracks were not confirmed in the layer containing a metal oxide and the low refractive index layer at φ10 mm. Further, in the optical laminates of Examples 1 to 3 and 5 to 7, cracks were not confirmed in the layer containing a metal oxide and the low refractive index layer even at φ6 mm. From these results, it can be seen that the optical laminates of Examples 1 to 8 have good flex resistance and are suitable for application to foldable type image display devices and rollable type image display devices. Also, among the examples, it can be seen that the optical laminates of Examples 1 to 3 and 5 to 7 have extremely good flex resistance.

Explanation of Signs

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

Claims

【Claim 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 with respect to light in the wavelength range of 2000 nm or more and 22000 nm or less, measured from the side of the layer containing the metal oxide with reference to the plastic film, is 0.27 or more and 0.75 or less.

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