Multilayer film, optical component, spectacles and method for producing multilayer film

Abstract

To provide a multilayer film having excellent antifogging properties and excellent antifogging retention properties by forming a low refractive index layer having a certain film thickness above a layer having a photocatalytic function.SOLUTION: A multilayer film has, directly on the surface of or via another layer on a substrate, a layer having a film thickness of 70-300 nm and containing cerium oxide having a cubic polycrystalline structure, has, above the layer containing cerium oxide, a layer having a film thickness of 50-240 nm and a refractive index at a wavelength of 500 nm of 1.46-1.65 and containing silicon oxide, and has, above the layer containing silicon oxide, a layer having a film thickness of 2-10 nm and a refractive index at a wavelength of 500 nm of 1.33-1.45 and containing porous silica.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a multilayer film having excellent anti-fogging properties and anti-fogging maintenance performance, an optical element having the multilayer film, eyeglasses having the optical element, and a method for manufacturing the multilayer film. [Background technology]

[0002] Optical components such as optical lenses, mirrors, and optical filters are coated with inorganic materials to increase or decrease light transmittance or reflectance. However, when moisture from steam or breath adheres to the surface of an optical component, it forms tiny droplets that cover the surface, causing the optical component to become cloudy. Several anti-fogging technologies have been proposed, including one known technique that prevents fogging by coating the surface of an optical component with a hydrophilic substance such as a silanol group (Si-OH) to allow water droplets to wet and spread evenly (Patent Document 1). However, while such hydrophilic surfaces are good in terms of anti-fogging performance, the adhesion of environmental contaminants reduces the surface free energy in a relatively short period of time. As a result, there is a problem that the hydrophilic performance decreases and the anti-fogging performance cannot be maintained.

[0003] To solve the above-mentioned problems, a hydrophilic film in which a thin film of silicon dioxide is formed on a thin film of crystalline titanium dioxide is used (Patent Document 2, Patent Document 3, Non-Patent Document 1). When the surface of crystalline titanium dioxide is irradiated with near-ultraviolet light, active oxygen is generated by the photocatalytic function, and the generated active oxygen decomposes organic matter on the surface of the hydrophilic film. As a result, the hydrophilicity of the hydrophilic film is restored, and dirt is washed away by rain, resulting in self-purification. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3435136 [Patent Document 2] Japanese Patent Application Publication No. 09-057912 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-053449 [Non-patent literature]

[0005] [Non-Patent Document 1] Miyashita, Yoshiyoshi, Kuroda, Shinichi, Tokuda, Keiji, Ubukata, Tsutomu, Kubota, Hitoshi, Journal of the Ceramic Society of Japan, Volume 110, Issue 1281, pp. 450-454 (2002)

[0006] However, when a silicon dioxide thin film is formed on a titanium dioxide thin film, the refractive index of titanium dioxide is high, so if the thickness of the low-refractive-index layer such as silicon dioxide on the surface is less than 50 nm, the reflectance increases and the transmittance decreases, which is a problem. Therefore, while this method can be applied to automotive door mirrors and other applications where a high reflectance does not cause any problems, it is not suitable for optical components such as lenses with anti-reflection coatings.

[0007] On the other hand, when the thickness of a low refractive index layer such as silicon dioxide on the surface is 50 nm or more, although it is suitable in terms of reducing reflectance, there is a problem that the hydrophilicity recovery function by the photocatalytic function is insufficient and anti-fogging performance cannot be maintained. In addition, the anti-fogging performance of silicon dioxide thin films is insufficient, and a thin film with even better anti-fogging performance was desired. Summary of the Invention [Problem to be solved by the invention]

[0008] The present disclosure provides a multilayer film that has excellent anti-fogging properties and excellent anti-fogging maintenance performance by forming a low refractive index layer having a specific thickness above a layer having a photocatalytic function. [Means for solving the problem]

[0009] The multilayer film of the present disclosure is formed on the surface of a substrate directly or via another layer. a layer containing cerium oxide having a thickness of 70 nm or more and 300 nm or less and a cubic polycrystalline structure; a layer containing silicon oxide having a thickness of 50 nm or more and 240 nm or less and a refractive index at a wavelength of 500 nm of 1.46 or more and 1.65 or less, disposed on the upper side of the layer containing cerium oxide; The present invention is characterized in that it has, on the upper side of the silicon oxide-containing layer, a layer containing porous silica having a film thickness of 2 nm to 10 nm and a refractive index at a wavelength of 500 nm of 1.33 to 1.45. The method for producing a multilayer film according to the present disclosure includes the steps of: forming a layer containing cerium oxide having a thickness of 70 nm to 300 nm and a cubic polycrystalline structure; forming a silicon oxide-containing layer having a thickness of 50 nm or more and 240 nm or less and a refractive index at a wavelength of 500 nm of 1.46 or more and 1.65 or less on the upper side of the cerium oxide-containing layer; and forming an alkoxysilane layer on the upper side of the silicon oxide-containing layer, and hydrolyzing the layer to form a porous silica-containing layer having a thickness of 2 nm to 10 nm and a refractive index at a wavelength of 500 nm of 1.33 to 1.45. According to another aspect of the present disclosure, there is provided an optical member having the above multilayer film. Furthermore, according to another aspect of the present disclosure, eyeglasses are provided having the above optical member. [Effects of the Invention]

[0010] According to one aspect of the present disclosure, when a low refractive index layer having a specific thickness is formed on top of a layer having a photocatalytic function, a multilayer film having excellent anti-fogging properties and anti-fogging maintenance performance, an optical element having the multilayer film, and a method for manufacturing the multilayer film can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a first embodiment of a multilayer film according to the present disclosure. [Figure 2] 1 is a schematic diagram illustrating an embodiment (eyeglasses) of an optical member according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of the multilayer film, the optical member having the multilayer film, and the method for forming the multilayer film according to the present disclosure will be described. Furthermore, the present disclosure is not limited to the following embodiments. In the present disclosure, unless otherwise specified, the expressions [XX to YY] and [XX to YY] representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.

[0013] In this disclosure, a multilayer film refers to a configuration including two or more layers formed on the surface of a substrate. The multilayer film does not include the substrate. In the present disclosure, a substrate is a solid article. In the present disclosure, the optical member refers to an optical member having a substrate having the above-mentioned multilayer film, and examples of such optical members include optical filters, optical lenses, light collecting lenses, optical films, optical prisms, eyeglass lenses, photographic lenses, surveillance camera covers, in-vehicle camera covers, in-vehicle sensor covers, vehicle door mirrors, plate glass, condenser lenses, display cover glass, touch panels, and various films.

[0014] The multilayer film of the present disclosure is characterized by having, on the surface of a substrate directly or via another layer, a layer containing cerium oxide and having a thickness of 70 nm to 300 nm and a cubic polycrystalline structure; a layer containing silicon oxide and having a thickness of 50 nm to 240 nm and a refractive index at a wavelength of 500 nm of 1.46 to 1.65 above the cerium oxide layer; and a layer containing porous silica and having a thickness of 2 nm to 10 nm and a refractive index at a wavelength of 500 nm of 1.33 to 1.45 above the silicon oxide layer.

[0015] Before specifically describing the multilayer film according to the present disclosure, the mechanism by which the effects of the film are exhibited will be described below to facilitate understanding of the present disclosure. However, the following description is merely a hypothesis, and the present disclosure is not limited by the hypothesis. The present inventors have discovered that when a layer containing silicon oxide with a specific thickness is placed on the surface of a layer containing porous silica on the upper side, and a layer containing cerium oxide with a cubic polycrystalline structure is placed on the adjacent lower side, the self-cleaning properties and anti-fogging maintenance properties of the photocatalyst are exhibited. The following are thought to be the mechanism behind this.

[0016] When a near-ultraviolet light-responsive photocatalytic film is irradiated with near-ultraviolet light, holes and electrons are generated by photoexcitation. If the generated holes and electrons reach the film surface, a chemical reaction occurs, resulting in the self-cleaning properties and hydrophilicity recovery. However, if a low-refractive index layer having a specific thickness of 50 nm or more is formed on top of crystalline titanium dioxide, the holes and electrons generated by photoexcitation are blocked by the thickness and cannot reach the multilayer film surface. Therefore, the holes and electrons recombine and become inactivated, resulting in the failure to achieve self-cleaning properties and anti-fogging maintenance. On the other hand, if a low-refractive index layer having a thickness of 50 nm or more is formed on top of the cerium oxide-containing layer of the present disclosure, the proportion of holes and electrons that reach the multilayer film surface increases, causing a chemical reaction, resulting in the self-cleaning properties and anti-fogging maintenance. At the interface of the upper layer in contact with the cerium oxide-containing layer of the present disclosure, there is a region where the compounds or mixtures of the respective layers are interdiffused. In this region, trivalent and tetravalent cerium are more likely to coexist, making it easier to retain electrons generated by photoexcitation, which may have made it difficult for holes and electrons to recombine. In addition, the cubic polycrystalline structure has high conductivity and many interfaces, which may have made it easier for holes and electrons to move and make it difficult for them to recombine. Furthermore, the present inventors have found that in a case where a layer containing silicon oxide is disposed above a layer containing porous silica, by disposing a layer containing cerium oxide having a cubic polycrystalline structure below the layer containing silicon oxide, the anti-fogging performance is dramatically improved. The following is thought to be the mechanism behind this.

[0017] The porous silica-containing layer of the present disclosure has a large surface area due to its porosity, and contains more hydrophilic silanol groups (Si-OH) than non-porous silicon oxide, potentially resulting in excellent anti-fogging performance. Additionally, when a layer containing cerium oxide with a cubic polycrystalline structure is exposed to ultraviolet light or higher-energy light, electrical, chemical, and other energy is stored within the cerium oxide or at its interface. It is believed that the cerium oxide-containing layer of the present disclosure supplies the stored energy to the surface of the multilayer film, thereby maintaining the surface energy of the multilayer film at a high level and improving its anti-fogging performance. In particular, the cerium oxide-containing layer of the present disclosure formed by vacuum deposition is likely to contain a mixture of trivalent and tetravalent cerium, potentially making it more susceptible to energy storage.

[0018] First Embodiment FIG. 1 is a schematic cross-sectional view showing a first embodiment of a multilayer film according to the present disclosure formed on a substrate, showing an example of a configuration in which another layer 12 is formed on a substrate 11, a layer 13 containing cerium oxide according to the present disclosure is further formed, a layer 14 containing silicon oxide according to the present disclosure is further formed, and a layer 15 containing porous silica according to the present disclosure is further formed. Note that FIG. 1 is a schematic representation of the configuration of the multilayer film according to the present disclosure. Therefore, the areas and film thicknesses of each layer are not shown to exact proportions. Furthermore, the other layer 12 may or may not be present.

[0019] The substrate 11 will now be described. The substrate 11 may be made of any material, such as glass, ceramics, resin, or metal, as long as it can be laminated with the other layer 12 or the cerium oxide-containing layer 13 of the present disclosure. The shape of the substrate is not limited and may be flat, curved, concave, convex, or film-like. It may also have a hard coat layer or a barrier layer. Furthermore, the size and thickness are not particularly limited and can be appropriately set depending on the application.

[0020] The cerium oxide-containing layer 13 according to the present disclosure will be described. The multilayer film according to the present disclosure has a cerium oxide-containing layer 13 on the upper layer side of the substrate 11. The cerium oxide-containing layer 13 according to the present disclosure is a layer containing cerium oxide having a cubic polycrystalline structure. A layer made of cerium oxide with a polycrystalline structure is less likely to cause cracks in the multilayer film. Furthermore, when the cerium oxide-containing layer has a cubic polycrystalline structure, it has high photocatalytic self-purification function and anti-fogging maintenance performance. In the present disclosure, the definition of a polycrystalline structure is that a peak specific to cerium oxide appears when the thin film is subjected to X-ray diffraction (XRD) measurement after deposition.

[0021] The cerium oxide-containing layer 13 of the present disclosure has a thickness of 70 nm to 300 nm. A thickness of 70 nm or more provides high photocatalytic self-cleaning function and anti-fogging performance. A thickness of 300 nm or less prevents cracks from occurring and prevents excessive inhomogeneity and surface roughness, which has a positive effect on optical properties. The composition of the cerium oxide in the cerium oxide-containing layer 13 of the present disclosure is CeO x where x is preferably 1.5 or more and 2.0 or less. Within the above range, a thin film that is more transparent in the wavelength range from visible light to near-infrared light can be obtained. The content of cerium oxide in the total amount of materials constituting the cerium oxide-containing layer 13 of the present disclosure is preferably 85 mass % or more. If the content of cerium oxide is 85 mass % or more, the anti-fogging performance is further improved. The cerium oxide-containing layer 13 of the present disclosure may be disposed directly on the substrate 11 or may be disposed via another layer 12 .

[0022] A layer containing a metal, fluoride, oxide, carbide, or nitride can be disposed as the other layer 12. Specific examples of the other layer 12 include a metal layer containing elements such as aluminum (Al), chromium (Cr), gold (Au), silver (Ag), copper (Cu), silicon (Si), germanium (Ge), titanium (Ti), and nickel (Ni), a layer containing a fluoride such as magnesium fluoride (MgF2) and calcium fluoride (CaF2), and a layer containing silicon oxide (SiO2). x ), aluminum oxide (AlO x ), yttrium oxide (YO x ), zirconium oxide (ZrO x ), hafnium oxide (HfO x ), zinc oxide (ZnO x ), tantalum oxide (TaO x ), niobium oxide (NbO x ), indium oxide (In2O x ), tin oxide (SnO x ), tungsten oxide (WO x ), cerium oxide (CeO x ), titanium oxide (TiO x ), lanthanum titanate (La x Ti y O z ), aluminum titanate (La x Al y O z ), a layer containing an oxide such as alumina-added silicon dioxide (SiO2 + Al2O3), a layer containing a nitride such as silicon nitride (Si3N4), or a layer containing a carbide such as tungsten carbide (WC) can be used. The other layer 12 may be a single layer, or when it is a multilayer of two or more layers, the other layer 12 may be formed by combining multiple types of layers from the layers exemplified above. The other layer 12 may also be a layer containing a mixture of two or more types of compounds contained in the layers exemplified above.

[0023] There are no particular limitations on the method for forming the other layer 12. Examples of methods that can be used to form the other layer 12 include dry film formation methods such as sputtering, vacuum deposition, and ion plating, and wet film formation methods such as dipping, coating, spraying, spin coating, bar coating, printing, and flow coating. By adjusting the composition, refractive index, film thickness, number of layers, etc. of the other layers 12 according to the purpose and function, it is possible to create a multilayer film with specific functions added, such as an anti-reflection layer, a half mirror layer, a light absorbing layer, an alkali diffusion preventing layer, an adhesion layer, an anti-static layer, a heater layer, etc.

[0024] The silicon oxide-containing layer 14 according to the present disclosure will now be described. The multilayer film of the present disclosure has a silicon oxide-containing layer 14 on the upper side of the cerium oxide-containing layer 13. The thickness of the silicon oxide-containing layer 14 is 50 nm or more and 240 nm or less. If the thickness is 50 nm or more, the reflectance of the multilayer film does not become too high. On the other hand, if the thickness is 240 nm or less, a photocatalytic self-purification function is exhibited on the surface of the multilayer film. The refractive index of the silicon oxide-containing layer 14 is 1.46 to 1.65 at a light wavelength of 500 nm. If the refractive index exceeds 1.65, the reflectance of the multilayer film may become too high. On the other hand, if the refractive index is below 1.46, the anti-fogging performance deteriorates. The content of silicon oxide in the silicon oxide-containing layer 14 is preferably 65 mass % or more with respect to the entire silicon oxide-containing layer 14. If the content of silicon oxide in the silicon oxide-containing layer 14 is within the above range, the anti-fogging performance is further improved.

[0025] The silicon oxide-containing layer 14 has a composition of SiO x The composition of silicon oxide is SiO x If the value of x is within the above range, the refractive index of the silicon oxide-containing layer 14 can be made 1.65 or less. Also, a film with higher transparency in the wavelength range from visible light to near-infrared light can be obtained.

[0026] The porous silica-containing layer 15 according to the present disclosure will be described. The multilayer film according to the present disclosure has a porous silica-containing layer 15 on the upper side of the silicon oxide-containing layer 14. The porous silica-containing layer 15 has a thickness of 2 nm or more and 10 nm or less. A thickness of 2 nm or more and 10 nm or less can improve the anti-fogging performance of the multilayer film. The porous silica-containing layer 15 has a refractive index of 1.33 or more and 1.45 or less at a light wavelength of 500 nm. A refractive index of 1.33 or more and 1.45 or less can improve the anti-fogging performance of the multilayer film. If the refractive index exceeds 1.45, the number of pores decreases, and the anti-fogging performance decreases. On the other hand, if the refractive index is less than 1.33, the number of pores increases, and the strength of the porous silica-containing layer decreases. The porous silica-containing layer is preferably formed by the hydrolysis of an alkoxysilane, which has the general formula H 2n+1 C n O(Si(OC n H 2n+1 )2O) m C n H 2n+1 Preferably, n is 1 or more and 4 or less, and m is 1 or more and 100 or less. More preferably, m is 4 or more and 50 or less, and even more preferably 6 or more and 10 or less. Specific examples include methyl polysilicate (methyl silicate 53A manufactured by Colcoat Co., Ltd.), ethyl polysilicate (ethyl silicate 48 manufactured by Colcoat Co., Ltd.), propyl polysilicate, and butyl polysilicate.

[0027] <Optical components> Fig. 2 is a schematic diagram showing the configuration of one embodiment using the optical element of the present disclosure. Fig. 2 shows eyeglasses, which are composed of eyeglass lenses 21, which are the optical element of the present disclosure, and eyeglass frames 22. The multilayer films of the present disclosure are formed on both sides of the eyeglass lenses 21. The multilayer film of the present disclosure can be used for optical thin films such as anti-reflection films, various optical filter multilayer films, and optical mirror multilayer films. It can also be used for optical components such as optical lenses, light collecting lenses, optical films, optical prisms, camera sensors, and infrared sensors, as well as covers for protecting these optical components. Furthermore, by applying a coating with a composition, refractive index, film thickness, number of layers, etc., depending on the purpose and function to the back side of the substrate 11, optical components with specific functions can be created, such as a mirror layer, half mirror layer, light absorption layer, transparent heater layer, and anti-reflection layer.

[0028] <Manufacturing method of multilayer film> The method for producing a multilayer film according to the present disclosure is characterized in that the film is formed by a method including at least the following steps (A), (B), and (C): (A) A step of forming a layer 13 containing cerium oxide on the surface of a substrate directly or via another layer by a vacuum deposition method. (B) A step of forming a silicon oxide-containing layer 14 on the cerium oxide-containing layer 13 of the present disclosure by vacuum deposition. (C) A step of forming a layer 15 containing porous silica on the upper side of the layer 14 containing silicon oxide by vacuum deposition of alkoxysilane, followed by hydrolysis.

[0029] The cerium oxide-containing layer 13 formed in step (A) contains cerium oxide having a cubic polycrystalline structure, and the thickness of the cerium oxide-containing layer 13 formed in step (A) is 70 nm to 300 nm. The silicon oxide-containing layer 14 formed in step (B) has a thickness of 50 nm to 240 nm, and the refractive index of the silicon oxide-containing layer 14 formed in step (B) at a light wavelength of 500 nm is 1.46 to 1.65. The porous silica-containing layer 15 formed in step (C) has a thickness of 2 nm to 10 nm, and the refractive index of the porous silica-containing layer 15 formed in step (C) at a light wavelength of 500 nm is 1.33 to 1.45. In this case, high anti-fogging properties and high anti-fogging retention properties are obtained.

[0030] The substrate temperature during vacuum deposition is preferably a temperature at which the cerium oxide-containing layer crystallizes. Although it depends on the heat resistance temperature of the substrate used and other deposition conditions, the temperature can usually be selected within the range of 0°C or higher and 500°C or lower. The evaporation method of the thin film forming material in vacuum deposition is not limited as long as the thin film forming material is evaporated. For example, evaporation means such as an electron gun, resistance heating, or laser can be used. Furthermore, the above evaporation means can be used in combination with ion-assisted or plasma-assisted evaporation, if necessary.

[0031] The multilayer film of the present disclosure can be suitably produced by the above method. [Example]

[0032] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples in any way.

[0033] (base material) The following flat substrates were used: · Made of borosilicate glass, 3mm thick ·Made of synthetic quartz, thickness 3mm Polycarbonate resin, 2mm thick Made of polymethyl methacrylate resin, 2mm thick

[0034] (Thin film forming material) The following materials were used: CeO2 cylindrical, 99.9% purity ·Sm2O3 granular purity 99.9% Granular SiO2, 99.9% purity ·Al2O3 granular purity 99.9% ·Ti3O5 granular purity 99.9% O2 gas purity 99.999% Methyl Silicate 53A Liquid Purity 97.0% Ethyl Silicate 48 Liquid Purity 94.0% Methyl Silicate 53A and Ethyl Silicate 48 are product names of Colcoat Co., Ltd.

[0035] (Fabrication of multilayer films) The film formation method and film formation conditions common to the examples and comparative examples in the production of multilayer films will be explained. A vacuum deposition device (dome diameter Φ900 mm, deposition distance 890 mm) was used as the film formation device. The thin film forming materials and various clean substrates were set in the device, and the vacuum level (7.0 × 10) at which film formation was started was set. -4 The chamber was evacuated to a pressure of 1000 kJ / cm² (Pa). The substrate temperature during film formation was between -10°C and 60°C. After that, thin film forming materials were vacuum evaporated onto the set substrate to form a multilayer film as listed in Table 1, to obtain a test specimen. Each layer was evaporated at a deposition rate of approximately 0.5 nm / sec. Thin films consisting of two components, such as CeO2 + Al2O3 or SiO2 + Al2O3, were deposited using the binary evaporation method, in which two types of thin film forming materials are placed on two heating sources, respectively, and evaporated simultaneously. The substrate on which the film was formed was immersed in 50 ml of hydrochloric acid with a concentration of 0.01 mol / l for 16 hours to promote the hydrolysis reaction of the alkoxysilane, and a layer containing porous silica was formed from the alkoxysilane layer. In each of Examples 1 to 7 and Comparative Examples 1 to 4, the multilayer films obtained by changing the type of substrate were essentially the same except for the type of substrate, so only one example is shown in Table 1. In Table 1, "polycrystalline" means a cubic polycrystalline structure.

[0036] The individual conditions for fabricating the multilayer film in each of the examples and comparative examples will be described below. [Examples 1 to 3] A CeO2 thin film (a layer containing cerium oxide) was formed on various substrates using a CeO2 sintered body as the thin film forming material. Then, a SiO2 thin film (a layer containing silicon oxide) was formed on top of that using a SiO2 melt as the thin film forming material. Next, a layer containing porous silica was formed on top of that using methyl silicate 53A as the thin film forming material, producing a multilayer film. Other film formation conditions were as described in (Production of multilayer films).

[0037] [Example 4] CeO2 sintered body and metallic cerium were used as thin film forming materials on various substrates. 1.8 A thin film was formed on the substrate. Subsequently, a SiO2 thin film was formed on the substrate using SiO2 melt as the thin film forming material. Subsequently, a layer containing porous silica was formed on the thin film using methyl silicate 53A as the thin film forming material, thereby producing a multilayer film. Other film forming conditions were as described in (Production of multilayer film).

[0038] [Example 5] CeO2 sintered body and Al2O3 melt were used as thin film forming materials on various substrates. 1.8 A thin film of Al2O3 (85%) + Al2O3 (15%) was formed. Subsequently, a thin SiO2 film was formed on the thin film using SiO2 melt as the thin film forming material. Subsequently, a layer containing porous silica was formed on the thin film using methyl silicate 53A as the thin film forming material, thereby producing a multilayer film. Other film formation conditions were as described in (Production of multilayer film).

[0039] [Example 6] CeO2 sintered body and Sm2O3 sintered body were used as thin film forming materials on various substrates. 1.8 A thin film of SmO (85%) + SmO (15%) was formed. Next, a thin SiO film was formed on top of this using SiO melt as the thin film forming material. Next, a layer containing porous silica was formed on top of this using methyl silicate 53A as the thin film forming material, thereby producing a multilayer film. Other film formation conditions were as described in (Production of multilayer film).

[0040] [Example 7] A CeO2 polycrystalline thin film was formed on various substrates using sintered CeO2 as the thin film forming material. A SiO2 (65%) + CeO2 (35%) thin film was then formed on top of this using molten SiO2 and sintered CeO2 as the thin film forming materials. A porous silica-containing layer was then formed on top of this using methyl silicate 53A as the thin film forming material, producing a multilayer film. Other film formation conditions were as described in (Preparation of multilayer films).

[0041] [Comparative Example 1] In order to obtain an anatase TiO layer instead of the cubic polycrystalline CeO layer used in Example 2, the thin film forming material was changed to a TiO material, and the film was formed while introducing O gas. Otherwise, a multilayer film was fabricated in the same manner as in Example 2.

[0042] Comparative Example 2 The substrate temperature was changed to -10°C to form an amorphous CeO layer instead of the cubic polycrystalline CeO layer used in Example 2. Otherwise, a multilayer film was fabricated in the same manner as in Example 2.

[0043] Comparative Example 3 The CeO2 layer and the SiO2 layer were formed to have a thinner film thickness than in Example 1. Other than that, the multilayer film was fabricated in the same manner as in Example 1.

[0044] Comparative Example 4 The CeO2 layer and the SiO2 layer were formed to have a thickness greater than that of Example 3. Otherwise, the multilayer film was fabricated in the same manner as in Example 3.

[0045] (Thickness measurement) The thickness of each layer in the multilayer films in the examples and comparative examples was measured using spectroscopic ellipsometry (ESM300 manufactured by JA WOOLLAM Co., Ltd.). When the number of layers and film thickness were complicated and analysis was difficult, the analysis was performed using the refractive index of a single layer film obtained separately from the same batch of film formation.

[0046] (Composition Measurement) The compositions of layers consisting of two components, such as SiO2+CeO2 and SiO2+Al2O3, in the multilayer films of the examples and comparative examples were measured and determined using a wavelength dispersive X-ray fluorescence spectrometer (ZSX Primus II, manufactured by Rigaku Corporation).

[0047] (Measurement of crystallinity) The multilayer films of the examples and comparative examples were measured in the range of 2θ=20° to 100° using an XRD diffractometer (Smart Lab, manufactured by Rigaku Corporation), and the layers were identified and their crystallinity was confirmed based on the diffraction intensity.

[0048] (Evaluation of anti-fogging and anti-fogging maintenance performance) On the day of preparation of the multilayer film, the haze difference was measured according to the following method. Then, the prepared multilayer film was placed in an airtight container with the film surface facing up and the lid was closed. The airtight container was left standing in the laboratory with the lid closed. After 180 days, the lid was opened and the multilayer film was taken out, and the haze difference was measured according to the following method. A CM-5 spectrophotometer manufactured by Konica Minolta, Inc. was used as a measuring device for the haze difference. Steam at approximately 100°C was sprayed onto the multilayer film using a humidifier, and the haze difference was measured 3 seconds later. The anti-fogging performance was evaluated on a 4-point scale based on the measured haze difference. Here, the haze difference is the value obtained by subtracting the haze value when no humidifier was used and no steam was sprayed on the substrate without a multilayer film from the haze value 3 seconds after the multilayer film was sprayed with steam at approximately 100°C using a humidifier. A: Haze difference less than 1 B: Haze difference 1 or more and less than 15 C: Haze difference 15 or more and less than 35 D: Haze difference 35 or more The results are shown in Table 1 below.

[0049] [Table 1]

[0050] [Example 8] The substrate used was a resin substrate (MR-8 manufactured by Mitsui Chemicals) coated with a silicon-based hard coat. An Al2O3 film (82 nm thick) was formed as the first layer using an Al2O3 melt. A CeO2 film (119 nm thick) was formed as the second layer using a CeO2 sintered compact. A SiO2 (95%) + CeO2 (5%) film (79 nm thick) was formed as the third layer using a SiO2 melt and a CeO2 sintered compact. The fourth and final layer was a multilayer film, fabricated by forming an alkoxysilane layer using ethyl silicate 48 and promoting a hydrolysis reaction to form a porous silica-containing layer (5 nm thick). During film formation, the substrate was heated to 60°C and the multilayer film was deposited at a deposition rate of 0.5 nm / s. The resulting multilayer-coated substrate was then processed and attached to an eyeglass frame to fabricate eyeglasses. The eyeglasses were stored in a dark eyeglass case for three months. When water droplets were then placed on the lens, the droplets spread across the lens, maintaining good visibility. The contact angle of the water was 5°. Even after the water dried, no traces remained, and good visibility was maintained. [Industrial Applicability]

[0051] The multilayer film of the present disclosure can be used for optical components such as optical filters, optical lenses, light-collecting lenses, optical films, optical prisms, eyeglass lenses, photographic lenses, vehicle door mirrors, plate glass, condenser lenses, display cover glass, touch panels, and various films, as well as covers for protecting optical components such as surveillance camera covers, in-vehicle camera covers, and in-vehicle sensor covers. In addition, the optical member of the present disclosure can be used as optical devices such as digital cameras, digital video cameras, action cameras, endoscopes, lens barrels, eyeglasses, sensors, binoculars, telescopes, surveillance cameras, in-vehicle cameras, smartphones, tablet PCs, weather cameras, live cameras, protective goggles, underwater goggles, head-mounted displays, sunglasses, smart glasses, face shields, helmet shields, vehicle mirrors, and bathroom mirrors, as well as covers for protecting these devices.

[0052] The present disclosure includes the following embodiments. (1) Directly or through another layer on the surface of the substrate, a layer containing cerium oxide having a thickness of 70 nm or more and 300 nm or less and a cubic polycrystalline structure; a layer containing silicon oxide having a thickness of 50 nm or more and 240 nm or less and a refractive index at a wavelength of 500 nm of 1.46 or more and 1.65 or less, disposed on the upper side of the layer containing cerium oxide; A multilayer film characterized by having, on the upper side of the silicon oxide-containing layer, a layer containing porous silica, the layer having a thickness of 2 nm or more and 10 nm or less and a refractive index at a wavelength of 500 nm of 1.33 or more and 1.45 or less. (2) The cerium oxide in the cerium oxide-containing layer has a composition of CeO x (x is 1.5 or more and 2.0 or less). (3) The multilayer film according to (1) or (2), wherein the content of cerium oxide in the total amount of materials constituting the cerium oxide-containing layer is 85 mass % or more. (4) The multilayer film according to any one of (1) to (3), wherein the content of silicon oxide in the total amount of materials constituting the silicon oxide-containing layer is 65 mass % or more. (5) The multilayer film according to any one of (1) to (4), wherein the porous silica is formed by a hydrolysis reaction of an alkoxysilane. (6) The multilayer film according to (5), wherein the alkoxysilane is methyl polysilicate, ethyl polysilicate, propyl polysilicate, or butyl polysilicate. (7) An optical member having the multilayer film according to any one of (1) to (6). (8) (7) Eyeglasses having the optical element according to the present invention. (9) forming a layer containing cerium oxide having a thickness of 70 nm to 300 nm and a cubic polycrystalline structure on the surface of a substrate directly or via another layer; forming a silicon oxide-containing layer having a thickness of 50 nm or more and 240 nm or less and a refractive index at a wavelength of 500 nm of 1.46 or more and 1.65 or less on the upper side of the cerium oxide-containing layer; and forming a layer containing porous silica having a thickness of 2 nm to 10 nm and a refractive index at a wavelength of 500 nm of 1.33 to 1.45 by forming a film of alkoxysilane on an upper layer side of the layer containing silicon oxide and hydrolyzing the film. [Explanation of symbols]

[0053] 11 Base material 12 Other layers 13 Cerium oxide-containing layer 14 Silicon oxide-containing layer 15 Layer containing porous silica 21 Eyeglass lens having the multilayer film of the present disclosure 22 Eyeglass frame having an optical element of the present disclosure

Claims

1. Directly or through another layer on the surface of the substrate, a layer containing cerium oxide having a thickness of 70 nm to 300 nm and a cubic polycrystalline structure; a layer containing silicon oxide having a thickness of 50 nm or more and 240 nm or less and a refractive index at a wavelength of 500 nm of 1.46 or more and 1.65 or less, disposed on an upper side of the layer containing cerium oxide; A multilayer film comprising a layer containing porous silica, the layer having a thickness of 2 nm or more and 10 nm or less and a refractive index at a wavelength of 500 nm of 1.33 or more and 1.45 or less, on the upper side of the layer containing silicon oxide.

2. The cerium oxide in the cerium oxide-containing layer has a composition of CeO ｘ 2. The multilayer film according to claim 1, wherein x is 1.5 or more and 2.0 or less.

3. 2. The multilayer film according to claim 1, wherein the content of cerium oxide in the total amount of materials constituting the cerium oxide-containing layer is 85 mass % or more.

4. 2. The multilayer film according to claim 1, wherein the content of silicon oxide in the total amount of materials constituting said silicon oxide-containing layer is 65 mass % or more.

5. 2. The multilayer film according to claim 1, wherein the porous silica is formed by a hydrolysis reaction of an alkoxysilane.

6. 6. The multilayer film according to claim 5, wherein the alkoxysilane is methyl polysilicate, ethyl polysilicate, propyl polysilicate, or butyl polysilicate.

7. An optical member comprising the multilayer film according to any one of claims 1 to 6.

8. Eyeglasses comprising the optical element according to claim 7.

9. forming a layer containing cerium oxide having a thickness of 70 nm to 300 nm and a cubic polycrystalline structure on the surface of a substrate directly or via another layer; forming a silicon oxide-containing layer having a thickness of 50 nm or more and 240 nm or less and a refractive index at a wavelength of 500 nm of 1.46 or more and 1.65 or less on the upper side of the cerium oxide-containing layer; and forming a layer containing porous silica having a thickness of 2 nm to 10 nm and a refractive index at a wavelength of 500 nm of 1.33 to 1.45 on an upper side of the layer containing silicon oxide by forming a film of alkoxysilane on the upper side of the layer containing silicon oxide and hydrolyzing the film.

Images