Transparent member and image pickup device, and method for manufacturing transparent member

Abstract

The present application provides a transparent member and an image pickup device, and a manufacturing method of the transparent member, on which a film with high reliability is formed, which is capable of suppressing an increase in its haze and maintaining its hydrophilicity for a long time even when exposed to an outdoor environment. The transparent member is a transparent member including a resin base material and a porous layer provided thereon, wherein the porous layer has a network structure in which silica particles are joined to each other by a binder, wherein the resin base material has a mixed layer into which the network structure has entered, wherein a thickness of the mixed layer is 20 nm or more and 160 nm or less, and wherein a thickness variation of a cross section of the mixed layer in a thickness direction thereof in a range of 1 μm in length along a surface of the resin base material is 15% or less.

Description

[0001] This application is a divisional application of Chinese patent application No. 201911218359.5, filed on December 3, 2019, entitled "Transparent Component and Image Picking Device, and Method for Manufacturing Transparent Component". Technical Field

[0002] This disclosure relates to a hydrophilic transparent component and a method for manufacturing the component, as well as an image acquisition device using the transparent component in a protective cover. Background Technology

[0003] In recent years, to prevent crime, surveillance cameras have been placed in various locations such as shops, hotels, banks, and train stations. For example, each surveillance camera is placed using methods such as mounting components to ceilings, exterior walls, pillars, etc., or being embedded within them.

[0004] A transparent protective cover that does not obstruct image capture is installed on the body of any such surveillance camera to protect it from the surrounding environment. The protective cover uses a resin material with excellent transparency and impact resistance, such as polycarbonate or acrylic resin. When the surveillance camera is placed outdoors, water droplets caused by rain, condensation, etc., can adhere to its protective cover, causing image distortion or blurriness. Therefore, technologies including incorporating a hydrophilic film on the protective cover to prevent water droplet adhesion are widely used.

[0005] Japanese Patent Application Publication No. 2013-203774 discloses a hydrophilic membrane in which silica sol is incorporated into a resin substrate to provide a silica particle membrane with high hydrophilicity and high adhesion.

[0006] Typically, when the resin substrate of a protective cover for surveillance cameras, such as polycarbonate or acrylic resin, is exposed outdoors for extended periods, the substrate deteriorates due to sunlight, resulting in cracks, such as fissures. Therefore, even when a hydrophilic film is formed on the protective cover, the following problems exist: as cracks form in the resin substrate serving as the protective cover, cracks also form in the hydrophilic film, causing distortion of the captured image due to increased haze. Furthermore, as the cracks propagate, the hydrophilic film may detach from the protective cover, thus compromising its hydrophilicity.

[0007] Therefore, the hydrophilic membrane to be installed on the protective cover preferably has the following characteristics: when the membrane is placed outdoors for a long time, it can suppress the formation of cracks and thus maintain its haze and hydrophilicity. However, when a hydrophilic membrane with the structure proposed in Japanese Patent Application Publication No. 2013-203774 is placed outdoors for a long time, it cannot suppress the degradation of its substrate caused by sunlight. Therefore, it cannot suppress the formation of cracks in the hydrophilic membrane, and thus cannot maintain its haze and hydrophilicity for a long time. Summary of the Invention

[0008] This disclosure is made in view of the above-mentioned problems and provides a transparent member including a hydrophilic membrane, the member having the following characteristics: when the member is placed outdoors for a long time, the member can suppress the formation of cracks in the hydrophilic membrane and thus suppress the increase of haze and maintain the hydrophilicity of the membrane.

[0009] According to one aspect of this disclosure, a transparent component is provided, comprising: a resin substrate; a porous layer disposed on the resin substrate, wherein the porous layer has a mesh structure in which silica particles are bonded to each other by an adhesive, wherein the resin substrate has a mixing layer in which the mesh structure extends into a surface layer of the resin substrate on one side on which the porous layer is disposed, wherein the thickness of the mixing layer is more than 20 nm and less than 160 nm, and wherein the thickness variation of the cross section of the mixing layer in its thickness direction within a range of 1 μm along the surface of the resin substrate is less than 15%.

[0010] Additionally, according to one aspect of this disclosure, an image acquisition device is provided, comprising: a housing; a transparent member; an optical system; and an image sensor configured to acquire an image (video) via the optical system, the optical system and the image sensor being disposed in a space surrounded by the housing and the transparent member.

[0011] Additionally, according to one aspect of this disclosure, a method for manufacturing a transparent component is provided, wherein a layer comprising silica is formed on a resin substrate. The method includes applying a dispersion comprising silica particles and a component as a binder onto the resin substrate, then curing the dispersion to form a porous layer, and a mixed layer in which a network structure in which silica particles are bonded to each other by the binder has entered the resin substrate, wherein the thickness of the mixed layer is 20 nm or more and 160 nm or less, and wherein the thickness variation of the cross section of the mixed layer in the direction intersecting the surface of the resin substrate is within a length of 1 μm along the surface is 15% or less.

[0012] According to one aspect of this disclosure, a transparent member may be provided on which a highly reliable hydrophilic membrane is formed, which is able to suppress the increase of its haze and maintain its hydrophilicity for a long time even when exposed to an outdoor environment.

[0013] Other features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1This is a schematic diagram illustrating a cross-section of a transparent member in its thickness direction according to one aspect of this disclosure.

[0015] Figure 2A and Figure 2B Each is a schematic diagram illustrating an image acquisition device according to one aspect of this disclosure.

[0016] Figure 3 This is a schematic diagram illustrating an example of the configuration of an image pickup device according to one aspect of this disclosure.

[0017] Figure 4 The image is a cross-sectional view of the transparent component manufactured in Example 1, obtained by observation using a scanning transmission electron microscope. Detailed Implementation

[0018] Preferred embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. The present disclosure is not limited to the embodiments described below, and modifications may be appropriately made without departing from the spirit of the present disclosure.

[0019] <<Transparent Components>>

[0020] Figure 1 This is a schematic diagram illustrating a cross-section of a transparent member according to one aspect of this disclosure in its thickness direction (the direction parallel to the normal to the surface of its substrate). Figure 1 In one aspect of this disclosure, the transparent member 10 includes a hydrophilic film formed of a porous layer 14 and a hybrid layer 15 on a resin substrate 16, wherein the porous layer extends into the resin substrate 16. In this disclosure, the term "transparent" refers to the property of having a transmittance of 20% or more for visible light.

[0021] The porous layer 14 comprises a plurality of silica particles (silica particles) 12 and an adhesive 11 between the plurality of silica particles 12. The plurality of silica particles 12 are fixed together by the adhesive 11, and the voids 13 formed between the silica particles 12 and some portions of the adhesive 11 make the layer porous.

[0022] When a hydrophilic film formed on a conventional resin substrate is placed in an outdoor environment, stress is applied to the hydrophilic film formed on the resin substrate through the following two phenomena, thereby causing cracks:

[0023] (1) The surface of the resin substrate is oxidatively degraded by sunlight and oxygen; and

[0024] (2) The resin substrate expands or contracts due to water absorption caused by rain or temperature changes caused by sunlight.

[0025] In contrast, when the above-described configuration is adopted, firstly, the resin substrate 16 is covered by the hybrid layer 15, thus reducing the surface area of ​​the resin substrate 16 exposed to the transparent member. Therefore, oxidative degradation of the resin substrate 16 is prevented, and the stress associated with the expansion and contraction of the resin substrate 16 is reduced. Furthermore, the silica particles of the hybrid layer 15 and the porous layer 14 have a network structure. Therefore, the stress associated with the oxidative degradation of the resin substrate 16 is reduced, and thus, crack formation in the resin substrate 16 is suppressed. Thus, even when the transparent member according to one aspect of this disclosure is placed in an outdoor environment, the member can suppress crack formation in the hydrophilic film, thereby suppressing the increase in haze and maintaining the hydrophilicity of the film for a long time.

[0026] The following describes each layer in detail.

[0027] <Porous layer>

[0028] The porous layer 14 has a mesh structure in which silica particles 12 are bonded together by an adhesive 11, and voids 13 exist between the silica particles 12 and in the adhesive 11. In other words, the mesh structure is a structure formed by bonding silica particles together with an adhesive. The porosity of the porous layer 14 is preferably 40% or more and 55% or less. When the porosity of the porous layer 14 is 40% or more, the internal stress of the membrane is properly maintained. Therefore, when the membrane is placed in an outdoor exposure environment, crack formation in the membrane can be suppressed, thereby suppressing the increase of its haze and maintaining its hydrophilicity. In addition, when the porosity of the porous layer 14 is 55% or less, the haze of the hydrophilic membrane can be reduced, thereby maintaining its transparency. Furthermore, the adhesive 11 and the silica particles 12 are hydrophilic. Therefore, the porous layer 14 is hydrophilic, and the contact angle between the surface of the porous layer 14 and water is 30° or less. Furthermore, the thickness of the porous layer 14 is preferably 100 nm or more and 800 nm or less. When the thickness of the porous layer 14 is 100 nm or more, the network structure of the mixed layer 15 and the porous layer 14 can sufficiently suppress the generation of cracks in the resin substrate 16, thereby suppressing the increase in haze and maintaining hydrophilicity. Furthermore, when the thickness of the porous layer 14 is 800 nm or less, the increase in internal stress of the hydrophilic film is suppressed. Therefore, the generation of cracks in the film can be suppressed, thereby suppressing the increase in haze and maintaining hydrophilicity.

[0029] Here, the porosity of the porous layer 14 is a value representing the ratio of voids in the porous layer 14 to the volume of the porous layer 14. The porosity can be calculated using Equation 1 by means of the refractive index of the porous layer, the refractive index of silica (i.e., 1.46), and the refractive index of air (i.e., 1.00), as measured by a spectroscopic ellipsometry.

[0030] (Equation 1) Porosity = 100 × (Refractive index of porous layer - 1.46) / (1.00 - 1.46)

[0031] Furthermore, the average surface roughness Ra of the surface of the porous layer 14, i.e., the side of the transparent member according to one aspect of the present disclosure on which the porous layer 14 is disposed, is preferably 2 nm or more and 10 nm or less. The average surface roughness Ra is calculated using the calculation method defined in JIS B 0601:2001, and when the value of Ra is small, the porous layer 14 has a dense and uniform structure. Therefore, it is preferable that Ra is 10 nm or less for the following reasons: even if the transparent member according to one aspect of the present disclosure is placed outdoors for a long time, the oxidation and deterioration of the substrate and the formation of cracks in the hydrophilic film can be suppressed. At the same time, Ra is preferably 2 nm or more in relation to porosity.

[0032] [Silica particles]

[0033] The average particle size of the silica particles 12 is preferably 10 nm or more and 60 nm or less. When the average particle size of the silica particles 12 is 10 nm or more, the size of the voids 13 formed between the particles can be appropriately increased. Therefore, the desired porosity can be achieved, and the internal stress of the membrane can be appropriately maintained. Therefore, when the membrane is placed in an outdoor exposure environment, crack formation in the membrane can be suppressed, thereby suppressing the increase in its haze and maintaining its hydrophilicity. In addition, it is preferable that the average particle size of the silica particles 12 is 60 nm or less for the following reasons: the size of the voids 13 formed between the particles can be appropriately reduced, thereby suppressing the increase in haze without causing light scattering caused by the voids 13 and the silica particles 12.

[0034] Here, the average particle size of the silica particles 12 is the average Ferrette diameter. The average Ferrette diameter can be measured by image processing of an image obtained by observing the particles using a transmission electron microscope. Commercial image processing software such as image Pro PLUS (manufactured by Media Cybernetics, Inc.) can be used as the image processing method. Contrast is adjusted appropriately as needed within a predetermined image area, and the average Ferrette diameter of each particle is measured using commercial particle size measurement software. In this way, the average value can be determined.

[0035] While solid or hollow silica particles can be used as silica particles 12, chain-like silica particles in which such particles are interconnected are particularly preferred. Using chain-like silica particles increases the porosity of the porous layer without creating any large voids. Particles obtained by mixing chain-like silica particles with solid or hollow silica particles can be used. In the case of chain-like silica particles, the average particle size of the interconnected individual particles is preferably 10 nm or more and 60 nm or less.

[0036] The silica particles 12 all contain SiO2 as the main component. In addition to this component, metal oxides such as Al2O3, TiO2, ZnO2, or ZrO2 can be introduced into each particle. However, when more than 30% of the silanol (Si-OH) groups on the surface of the silica particles 12 are modified with organic groups or combined with any other metal, the hydrophilicity of the porous layer is lost. The porous layer 14 formed from such silica particles has low hydrophilicity and reduced self-cleaning properties.

[0037] Therefore, in order for the porous layer 14 to exhibit satisfactory hydrophilicity, it is preferable to use silica particles in which more than 70% of the silanol (Si-OH) groups are retained on the surface of the particles, and more preferably to use silica particles in which more than 90% of the silanol groups are retained on the particle surface.

[0038] [Adhesive]

[0039] The adhesive 11 can be appropriately selected based on the abrasion resistance and environmental reliability of the hydrophilic film, as well as its adhesion to the silica particles 12. Preferably, a silica adhesive with high affinity for the silica particles 12 and improved abrasion resistance of the porous layer is used. Among such silica (SiO2) adhesives, hydrolysis condensates of silica esters are more preferred, and hydrolysis condensates of tetrafunctional silica esters are even more preferred.

[0040] The content of adhesive 11 relative to the total mass of porous layer 14 is preferably 3% by mass or more and 20% by mass or less, more preferably 10% by mass or more and 20% by mass or less. When the content of adhesive 11 relative to the total mass of porous layer 14 is less than 3% by mass, there is a risk that the adhesive 11 has a weak force in fixing the silica particles 12, and therefore the silica particles 12 may peel off. In addition, when the content of adhesive 11 relative to the total mass of porous layer 14 is greater than 20% by mass, the following trend is observed: the space between silica particles 12 is filled by adhesive, thereby reducing the porosity in porous layer 14, and thus increasing the internal stress of the hydrophilic membrane.

[0041] <Hybrid Layer>

[0042] The hybrid layer 15 is a layer in which the resin substrate 16 has been incorporated into the voids of a mesh structure formed by bonding silica particles together using an adhesive, and is disposed on the side of the resin substrate 16 on which the porous layer 14 is disposed. The hybrid layer 15 extends from the uppermost part of the resin substrate 16 into the voids of the mesh structure formed by the adhesive and silica particles to the lowermost part of the mesh structure. When placed in an outdoor environment, the resin substrate 16 can be oxidized and degraded by sunlight and oxygen. However, the hybrid layer can reduce the surface area of ​​the resin substrate 16 in contact with oxygen, thus suppressing the oxidative deterioration of the resin substrate 16. Furthermore, when the hybrid layer 15 and the porous layer 14 have a continuous mesh structure, the stress accompanying the oxidative deterioration of the resin substrate 16 can be alleviated, thus suppressing the formation of cracks in the resin substrate.

[0043] The thickness of the hybrid layer 15 is preferably 20 nm or more and 160 nm or less. When the thickness of the hybrid layer 15 is less than 20 nm, the resin substrate 16 cannot fully penetrate the network structure. Therefore, the stress accompanying the oxidative degradation of the resin substrate 16 cannot be alleviated, and thus crack formation in the resin substrate 16 cannot be suppressed. Furthermore, a thickness greater than 160 nm is not preferred because it generates light scattering due to the resin substrate 16 and the silica particles 12, thereby increasing the haze of the hydrophilic film. Additionally, the thickness of the hybrid layer is preferably greater than the average particle size of the silica particles. When the thickness of the hybrid layer is greater than the average particle size of the silica particles, the strength of the network structure of the hybrid layer 15 can be improved, thus more reliably suppressing crack formation. When chain-like silica particles are used, the thickness of the hybrid layer is preferably greater than the average particle size of each interconnected particle.

[0044] Furthermore, the volume ratio of the mesh structure in the hybrid layer 15 is preferably 20% or more and 80% or less, more preferably 30% or more and 70% or less. When the volume ratio of the mesh structure in the hybrid layer 15 is 20% or more, the oxidative degradation of the resin substrate 16 during outdoor exposure can be sufficiently suppressed, thus preventing crack formation therein. When the volume ratio of the mesh structure in the hybrid layer 15 is 80% or less, the stress during outdoor exposure can be reduced, thus suppressing crack formation.

[0045] Furthermore, the hybrid layer 15 mitigates the stress associated with the expansion and contraction of the resin substrate 16 due to water absorption caused by rain or temperature changes caused by sunlight. The thickness of the hybrid layer 15 exhibits a thickness variation of less than 15% in any section along a length of 1 μm from the surface of the resin substrate 16 in its thickness direction. When the thickness variation of the hybrid layer on the membrane surface exceeds 15%, the stress associated with the expansion and contraction of the resin substrate concentrates in the portion of the hybrid layer where its thickness is less than the surrounding thickness. This causes cracks to form in the resin substrate 16, and consequently, in the hydrophilic membrane. Therefore, the increase in haze cannot be suppressed, and the hydrophilicity of the membrane cannot be maintained.

[0046] The thickness variation is the ratio of the height of the unevenness at the interface between the resin substrate 16 and the hybrid layer 15 to the average thickness of the hybrid layer 15. The average thickness of the hybrid layer 15 and the height of the unevenness at the interface between the resin substrate 16 and the hybrid layer 15 are determined by thinning a transparent member according to one aspect of this disclosure and observing the cross-section of the resulting sheet using a scanning transmission electron microscope or the like. Here, the height of the unevenness at the interface between the resin substrate 16 and the hybrid layer 15 is the absolute value of the height difference in the thickness direction between the portion of the interface closest to the hybrid layer side formed solely by the resin substrate 16 and the portion of the hybrid layer 15 closest to the resin substrate 16 side. When calculating the thickness variation, it is preferable to binarize the image obtained through observation using image processing software, as this makes it easier to distinguish between the substrate and the hybrid layer (silica particles or adhesive). Figure 4 As shown, an arbitrary range with a length of 1 μm along the surface of the resin substrate 16 in the thickness direction section is defined as... Figure 4 The range shown by the solid line in the figure represents the height (thickness variation) of the unevenness at the interface between the resin substrate 16 and the hybrid layer 15, which is equivalent to the ratio of the height of the unevenness to the average value of the distance between the two white dashed lines (the distance indicated by the white arrow).

[0047] <Resin substrate 16>

[0048] Resins such as transparent acrylic resins, polycarbonate, or polyester can be used as the material for the resin substrate 16. The shape of the resin substrate 16 is not limited and can be plate-like or film-like. Alternatively, the shape can be a flat plate or a shape with curved, concave, or convex surfaces, such as a hemispherical dome. The transmittance of the resin substrate to visible light is preferably 50% or more.

[0049] <Manufacturing Method>

[0050] Next, an example of a method for manufacturing a transparent component according to one aspect of this disclosure will be described.

[0051] A method for manufacturing a transparent component according to one aspect of the present disclosure includes the following steps: forming a porous layer 14 and a mixed layer 15 on a resin substrate 16.

[0052] Methods including sequentially coating a dispersion of silica particles 12 and an adhesive solution onto a resin substrate 16 and then drying, or methods including coating a dispersion containing both silica particles 12 and a component as an adhesive 11 onto a resin substrate 16 and then drying, can be used as steps to form the porous layer 14 and the mixed layer 15. A method including coating a dispersion containing both silica particles 12 and a component as an adhesive 11 is more preferred because the composition in the porous layer 14 becomes more uniform.

[0053] The dispersion of silica particles 12 is a liquid obtained by dispersing silica particles 12 in a solvent, and the content of silica particles 12 is preferably 2% by mass or more and 10% by mass or less. A silane coupling agent or a surfactant can be added to the dispersion of silica particles 12 to improve the dispersibility of the silica particles 12. However, when any such compound reacts with the numerous silanol groups on the surface of the silica particles 12, the bond between the silica particles 12 and the binder 11 weakens, thereby reducing the wear resistance or hydrophilicity of the porous layer 14. Therefore, the content of additives such as silane coupling agents or surfactants in the dispersion is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of silica particles 12.

[0054] Preferably, a silica adhesive solution having strong adhesion to silica particles 12 is used as the adhesive solution. The silica adhesive solution is preferably a solution containing a silicate hydrolysis condensate as a major component, which is manufactured by adding water and an acid or base to a silicate (e.g., methyl silicate or ethyl silicate) in a solvent to cause the silicate to undergo hydrolysis condensation.

[0055] The choice of acid or base should be appropriately selected considering its solubility in solvents and its reactivity with silicates. The preferred acid for the hydrolysis reaction is hydrochloric acid or nitric acid, and the preferred base is ammonia or any of various amines. Silicate hydrolysis condensates can be prepared not only by using silicates but also by neutralizing and condensing silicates such as sodium silicate in water. Acids that can be used for the neutralization reaction are, for example, hydrochloric acid or nitric acid. When preparing silica binder solutions, the materials can be heated at temperatures below 80°C.

[0056] When silica binder is used as binder 11, trifunctional silane oxides substituted with organic groups, such as methyltriethoxysilane or ethyltriethoxysilane, can be added to the silica binder solution to improve the solubility of the silica binder and the suitability of the solution. The amount of trifunctional silane oxide added is preferably less than 10 mol% of the total silane oxides in the silica binder solution. When the amount added is greater than 10 mol%, the organic groups inhibit hydrogen bonding between silanol groups in the binder, thus reducing the wear resistance of the porous layer.

[0057] When using a dispersion containing both silica particles 12 and a component as binder 11, the dispersion of silica particles 12 and the binder solution can be prepared separately before mixing. Alternatively, the dispersion can be prepared by adding the component as binder 11 to the dispersion of silica particles 12 and reacting the component with the particles. When obtaining a dispersion containing silica particles 12 and silica binder (which is the component as binder 11) using the latter method, the dispersion can be prepared by adding silicate ester, water, and an acid catalyst to the dispersion of silica particles 12 and reacting the silicate ester and water with the particles. A method that includes pre-preparing the binder solution and then mixing it with the dispersion of silica particles is preferred because the reaction of the component as binder 11 can be controlled, and the target dispersion can be prepared while observing the reaction state.

[0058] In the dispersion containing both silica particles 12 and the component as binder 11, the amount of the component as binder 11 is preferably 3 parts by mass or more and 20 parts by mass or less, more preferably 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of silica particles and the component as binder.

[0059] The solvent used in the dispersion of silica particles 12 or the silica binder solution needs to be able to uniformly dissolve or disperse the particles or binder therein, and to form a film in which the mixed layer 15 has a uniform thickness. Therefore, it is desirable to combine a solvent with a high solubility for the resin substrate 16 with a solvent with a low solubility for it. In addition, it is desirable that the boiling point of the solvent with a relatively high solubility for the resin substrate 16 is higher than that of the solvent with a relatively low solubility for the resin substrate 16. When the solvent is selected as described above, in the early stage of the film formation process, uniform alignment of silica particles is promoted, thus forming a uniform porous network structure with high alignment properties. In the later stage of the film formation process, the proportion of solvents with high boiling points and high solubility increases, thus the resin substrate 16 dissolves rapidly. Therefore, the porous network structure formed in the early stage of the film formation process enters the resin substrate 16, thus forming a uniform mixed layer 15.

[0060] Examples of solvents with high solubility in resin substrate 16 include: ethers, such as dimethoxyethane, diethylene glycol dimethyl ether, dioxane, diisopropyl ether, dibutyl ether, and cyclopentylmethyl ether; esters, such as ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, and propylene glycol monomethyl ether acetate; various aliphatic or alicyclic hydrocarbons, such as n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane; various aromatic hydrocarbons, such as toluene, xylene, and ethylbenzene; various ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, 2-heptanone, and cyclohexanone; various chlorinated hydrocarbons, such as chloroform, dichloromethane, carbon tetrachloride, and tetrachloroethane; and aprotic polar solvents, such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and ethylene carbonate. Among them, diethylene glycol dimethyl ether, dibutyl ether, propylene glycol monomethyl ether acetate and 2-heptanone are preferred solvents as having high solubility for resin substrate 16.

[0061] Examples of solvents with low solubility in the resin substrate 16 include: monohydric alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol, 1-pentanol, 2-pentanol, cyclopentanol, 2-methylbutanol, 3-methylbutanol, 1-hexanol, 2-hexanol, 3-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2-ethylbutanol, 2,4-dimethyl-3-pentanol, 3-ethylbutanol, 1-heptanol, 2-heptanol, 1-octanol, and 2-octanol; dihydric or higher alcohols, such as ethylene glycol and triethylene glycol; and ether alcohols, such as methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1-propoxy-2-propanol. Among these, 2-propanol is preferably used as a solvent with low solubility in the resin substrate 16.

[0062] To obtain a transparent component according to one aspect of this disclosure, it is only necessary to select, for example, from the listed solvents, a solvent with relatively high solubility for the resin substrate 16 and a solvent with relatively low solubility for the resin substrate 16, such that their boiling points may differ from each other. Furthermore, considering the boiling points of the solvents, two or more solvents selected from each of the groups of solvents with high solubility and the groups of solvents with low solubility can be used as a mixture.

[0063] When a solvent with higher solubility and a solvent with lower solubility are used as a mixture, the proportion of the solvent with higher solubility is preferably 2% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 20% by mass or less. When this proportion is 2% by mass or more, a sufficiently uniform mixed layer can be formed, and when this proportion is 30% by mass or less, the thickness of the mixed layer is prevented from becoming too large, and thus the increase in haze of the hydrophilic film can be satisfactorily suppressed.

[0064] Methods for coating a dispersion of silica particles 12 and a binder solution, or methods for coating a dispersion obtained by mixing a dispersion of silica particles and the solution, include spin coating, doctor blade coating, roller coating, slot coating, printing, and dip coating. When manufacturing transparent components with complex three-dimensional shapes (e.g., concave surfaces), spin coating is preferred from the viewpoint of film thickness uniformity.

[0065] After coating a dispersion of silica particles 12 and an adhesive solution, or coating a dispersion obtained by mixing a dispersion of silica particles and the solution, the wear resistance of the porous layer can be improved by suppressing the amount of solvent remaining in each of the porous layer and the mixed layer. Therefore, a drying step and a curing step are preferably provided to form the porous layer and the mixed layer. The drying step and the curing step are respectively steps for accelerating solvent removal, the reaction of the component as adhesive 11, or the reaction between the component as adhesive 11 and the silica particles 12. The temperature of each of the drying step and the curing step is preferably 20°C or higher and 200°C or lower, more preferably 60°C or higher and 150°C or lower. When the temperature of each of the drying step and the curing step is lower than 20°C, solvent residue reduces wear resistance. In addition, when the temperature of each of the drying step and the curing step is higher than 200°C, the curing of adhesive 11 proceeds excessively, resulting in easy cracking in the porous layer 14.

[0066] The density of the solvent remaining in the porous layer 14 is preferably 3.0 mg / cm³. 3 the following.

[0067] When the dispersion of silica particles 12 and the binder solution are applied sequentially, a porous layer and a mixed layer can be formed as follows: the dispersion of silica particles 12 is applied and a firing step is performed; then, the binder solution is applied and a drying step and a curing step are performed.

[0068] To set the thickness of the porous layer 14 to the desired value, the above coating step can be repeated multiple times, alternating with the drying and curing steps.

[0069] <<Image Picking Device>>

[0070] Figure 2A and Figure 2B Each is a schematic diagram illustrating an image acquisition device according to one aspect of this disclosure. Figure 2A This is an explanatory diagram of a fixed-point observation type surveillance camera. Figure 2B This is an illustration of a rotatable surveillance camera capable of pan-tilt-zoom drive.

[0071] Figure 2Aand Figure 2B The image acquisition device shown includes, within device bodies 1 and 2, a transparent member (protective cover) 3 according to one aspect of this disclosure (this member serves as a protective cover), and device bodies 1 and 2 include an optical system configured to acquire image data. Furthermore, the transparent member 3 at least covers the optical system of device bodies 1 and 2 to protect the system from external dust and impacts. Although Figure 2A The protective cover 3 is a flat box shape. Figure 2B The protective cover 3 is hemispherical dome-shaped, but the shape of the protective cover 3 is not limited to this.

[0072] exist Figure 3 The image acquisition device 30 is shown as an example of its configuration according to one aspect of the present disclosure. The image acquisition device 30 includes a space surrounded by a transparent member 10 and a frame 36, in which an optical system 31, an image sensor 32, a video engine 33, a compression output circuit 34, and an output unit 35 are included. The transparent member 10 includes a porous layer 14, a hybrid layer 15, and a resin substrate 16.

[0073] The image acquired through the transparent component 10 is guided by the optical system (lens) 31 to the image sensor 32, and converted by the image sensor 32 into a video analog signal (electrical signal) for output. The video analog signal output from the image sensor 32 is converted into a video digital signal by the image engine 33, and the video digital signal output from the image engine 33 is compressed into a digital file by the compression output circuit 34. The image engine 33 can perform image quality adjustment (e.g., brightness, contrast, color correction, and noise removal) during the conversion of the video analog signal into a video digital signal. The signal output from the compression output circuit 34 is output to an external device via wiring from the output unit 35.

[0074] A transparent member 10 is placed such that the surface of the porous layer 14 disposed thereon is exposed to the outside. This configuration protects the image acquisition device from external dust and impacts. Furthermore, water droplets adhering to the surface of the transparent member 10 due to changes in the external environment turn into a liquid film, thereby suppressing distortion of the image acquired by the image sensor 32.

[0075] Furthermore, the image acquisition device 30 can be combined with a pan-tilt unit configured to adjust the viewing angle, a controller configured to control image acquisition conditions, a storage device configured to store the acquired image data, and a transmission unit configured to transmit the data output from the output unit 35 to the outside to form an image acquisition system.

[0076] Example

[0077] The following describes a specific method for manufacturing a transparent component according to one aspect of this disclosure.

[0078] (Preparation of coating solution)

[0079] First, a coating liquid for manufacturing a transparent component according to one aspect of this disclosure is described.

[0080] (1) Preparation of silica adhesive solution

[0081] 13.82 g of ethanol and nitric acid aqueous solution (concentration: 3%) was added to 12.48 g of ethyl silicate, and the mixture was stirred at room temperature for 10 hours to prepare a silica adhesive solution (solid content concentration: 12.0% by mass).

[0082] (2-1) Preparation of silica particle coating solution A

[0083] A 20.00 g dispersion of 2-propanol (IPA) containing chain silica particles (product name: IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration: 15.5% by mass) was diluted with 85.00 g of IPA (boiling point: 82.5 °C) and 15.00 g of diethylene glycol dimethyl ether (boiling point: 162.0 °C) as solvents. Then, 2.60 g of the silica binder solution prepared in part (1) was added to the diluent, and the mixture was stirred at room temperature for 10 minutes. The mixture was then stirred at 50 °C for 1 hour to prepare silica particle coating solution A. Particle size distribution measurements using dynamic light scattering (the device used in the measurements is a ZETASIZER NANO ZS, manufactured by Malvern Panalytical Ltd.) confirmed that when chain-like silica particles were dispersed in silica particle coating liquid A, the silica particles with an average particle size of 15 nm were interconnected to have an average spherical equivalent diameter of 95 nm.

[0084] (2-2) Preparation of silica particle coating solution B

[0085] Except that 85.00 g IPA and 15.00 g dibutyl ether (boiling point: 140.8 °C) were used as solvents, silica particle coating solution B was prepared in the same manner as silica particle coating solution A.

[0086] (2-3) Preparation of silica particle coating solution C

[0087] Except that 85.00 g IPA and 15.00 g propylene glycol monomethyl ether acetate (boiling point: 140.0 °C) were used as solvents, silica particle coating solution C was prepared in the same manner as silica particle coating solution A.

[0088] (2-4) Preparation of silica particle coating solution D

[0089] Except that 70.00 g of IPA and 30.00 g of 2-heptanone (boiling point: 151.0 °C) were used as solvents, silica particle coating solution D was prepared in the same manner as silica particle coating solution A.

[0090] (2-5) Preparation of silica particle coating solution E

[0091] Except that 70.00 g IPA and 30.00 g diethylene glycol dimethyl ether were used as solvents, silica particle coating solution E was prepared in the same manner as silica particle coating solution A.

[0092] (2-6) Preparation of silica particle coating liquid F

[0093] Except for using 100.00g of IPA as a solvent, silica particle coating solution F was prepared in the same manner as silica particle coating solution A.

[0094] (2-7) Preparation of silica particle coating liquid G

[0095] Except for using 70.00 g IPA and 30.00 g tetrahydrofuran (boiling point: 66.0 °C) as solvents, silica particle coating solution G was prepared in the same manner as silica particle coating solution A.

[0096] (2-8) Preparation of silica particle coating solution H

[0097] Except for using 105.00g IPA and 30.00g diethylene glycol dimethyl ether as solvents, silica particle coating solution H was prepared in the same manner as silica particle coating solution A.

[0098] (Example 1)

[0099] A suitable amount of silica particle coating solution A was dropped onto a polycarbonate substrate (nd = 1.58, νd = 30.2) with a diameter (φ) of 50 mm, a thickness of 4 mm, and a light transmittance of approximately 80%, and spin-coated at 2,000 rpm for 20 seconds. The resulting material was then heated in a circulating hot air oven at 90°C for 15 minutes. This process produced a transparent component in which porous and mixed layers were formed. The average Freette diameter of the silica particles was 15 nm.

[0100] Figure 4This is an observation image of a cross-section of the transparent component manufactured in Example 1. Three layers are observed: a resin substrate 16, a mixed layer of resin substrate and silica particles 15, and a porous layer 14, forming from the bottom of the observation image. The thickness variation of the mixed layer 15, described later, is calculated in this cross-sectional observation image; the thickness variation is 8%.

[0101] (Example 2)

[0102] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid B was used instead of silica particle coating liquid A.

[0103] (Example 3)

[0104] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid C was used instead of silica particle coating liquid A.

[0105] (Example 4)

[0106] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid D was used instead of silica particle coating liquid A.

[0107] (Example 5)

[0108] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid E was used instead of silica particle coating liquid A.

[0109] (Example 6)

[0110] The transparent component, manufactured in the same manner as in Example 1, was further coated with silica particle coating liquid F. The coating was performed twice by repeating the following series of steps: an appropriate amount of silica particle coating liquid F was dropped onto the transparent component and spin-coated at 2,000 rpm for 20 seconds; the resulting material was then heated in a circulating hot air oven at 90°C for 15 minutes. Thus, the transparent component was manufactured.

[0111] (Comparative Example 1)

[0112] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid F was used instead of silica particle coating liquid A.

[0113] (Comparative Example 2)

[0114] The transparent component with a hydrophilic film, manufactured in the same manner as in Example 1, was further coated with silica particle coating liquid F. The coating was performed three times by repeating the following series of steps: an appropriate amount of silica particle coating liquid F was dropped onto the transparent component and spin-coated at 2,000 rpm for 20 seconds; the result was heated at 90°C for 15 minutes in a circulating hot air oven. Thus, a transparent component with a hydrophilic film was manufactured.

[0115] (Comparative Example 3)

[0116] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid G was used instead of silica particle coating liquid A.

[0117] (Comparative Example 4)

[0118] The transparent component was manufactured in the same manner as in Example 1, except that silica particle coating liquid H was used instead of silica particle coating liquid A.

[0119] (Evaluation methods for transparent components)

[0120] Next, the evaluation methods for the transparent components manufactured in the embodiments and comparative examples will be described.

[0121] (1) Measure the thickness of the porous layer and the hybrid layer

[0122] The thickness of the porous and hybrid layers of each transparent component was determined by measuring in the wavelength range of 380 nm to 800 nm using a spectroscopic ellipsometry (trade name: VASE, manufactured by JAWoollam Japan).

[0123] (2) Measuring the porosity of porous layers

[0124] The refractive index of the porous layer of each transparent component was determined by analyzing the values ​​obtained from measurements using a spectroscopic ellipsometer (trade name: VASE, manufactured by JAWoollam Japan) in the wavelength range of 380 nm to 800 nm, and the porosity of the porous layer was calculated using Equation 1.

[0125] (3) Measure the thickness change of the hybrid layer

[0126] The film was sliced ​​from each transparent component using a focused ion beam apparatus (product name: SMI-3050, manufactured by SII NanoTechnology Inc.) and thinned to allow observation of the cross-section of the hybrid layer in the thickness direction of the transparent component. The cross-sectional state of the hybrid layer in the thickness direction was observed in bright field at 100,000x magnification using a scanning transmission electron microscope (product name: S-5500, manufactured by Hitachi High-Technologies Corporation). The observed images were then image-processed. Commercial image processing software, such as image Pro PLUS (manufactured by MediaCybernetics, Inc.), was used as the image processing method. Contrast adjustment was performed appropriately in a predetermined image area as needed, and the thickness of the hybrid layer was calculated, followed by its thickness variation over a length of 1 μm.

[0127] (4) Measurement of contact angle

[0128] The contact angle of a 2 μl droplet of pure water was measured using a fully automated contact angle meter (product name: DM-701, manufactured by Kyowa Interface Science Co., Ltd.) at a temperature of 23°C and a humidity of 50% RH.

[0129] (5) Measurement of fog

[0130] The haze of each transparent component was measured using a haze meter (product name: NDH 2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0131] (6) Outdoor exposure test

[0132] Each transparent component was placed into a xenon weathering tester (product name: SUPER XENON WEATHER METER SX75, manufactured by Suga Test Instruments Co., Ltd.). The light intensity was set to 180 W / m². 2 The following steps are defined as one cycle: 18 minutes of light exposure and drainage; and only 1 hour and 42 minutes of light exposure. The transparent component is tested and evaluated by repeating this cycle a total of 300 times, or a total of 600 hours. The contact angle of the transparent component after testing is measured in the same manner as in section “(4) Measurement of Contact Angle”. 100 hours of outdoor exposure testing is equivalent to one year of actual outdoor exposure.

[0133] (7) Assessment

[0134] When the contact angle of the transparent component is 30° or less, the formation of water droplets on the surface of the transparent component can be effectively suppressed. Furthermore, when the haze is 1 or less, a clear image can be obtained during photography. Therefore, a case where the initial contact angle and the value after outdoor exposure testing are both 30° or less, and the initial haze and the value after testing are both 1 or less, is considered satisfactory. A case where either the initial contact angle or the value after testing is greater than 30°, or either the initial haze or the value after testing is greater than 1, is considered unsatisfactory.

[0135] (8) Measurement of surface roughness

[0136] The surface shape of each transparent component within a 2μm × 2μm range was measured using an SPM (product name: L-trace & NanoNavi II, manufactured by SII NanoTechnology Inc.), and its Ra was calculated from the measured values.

[0137] The measurement and evaluation results of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Table 1.

[0138] Table 1

[0139]

[0140] As shown in Table 1, it was confirmed that, through the configuration of each embodiment, the initial value of the contact angle and its value after outdoor exposure were both 30° or less, and the initial value of the haze and its value after exposure were both 1 or less. Therefore, it was confirmed that the hydrophilicity of each transparent component could be maintained and the increase in haze of each transparent component could be suppressed. Meanwhile, in each of Comparative Example 1 (which deviates from the scope of this disclosure due to the absence of any mixing layer), Comparative Example 2 (where the thickness of the porous layer is greater than the range determined in this disclosure), Comparative Example 4 (where the thickness of the porous layer is less than the range determined in this disclosure), and Comparative Example 3 (where the thickness variation of the mixing layer is greater than the range determined in this disclosure), the hydrophilicity could not be maintained after outdoor exposure and the increase in haze could not be suppressed.

[0141] The transparent component according to one aspect of this disclosure is not limited to applications in image pickup devices, such as planar covers and dome covers for outdoor cameras and surveillance cameras, but can also be used in optical components, such as optical lenses, optical mirrors, optical filters and eyepieces for image pickup systems and projection systems, as well as in general applications such as window glass, mirrors, lenses and transparent films.

[0142] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A coating liquid comprising: Silica particles; Silicate hydrolysis condensates; and solvent, The solvent comprises: At least one first solvent, which is selected from diethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, and 2-heptanone; and At least one second solvent, selected from monohydric alcohols, dihydric alcohols, and ether alcohols, Wherein the boiling point of the first solvent is higher than the boiling point of the second solvent, and The ratio of the first solvent to the total solvent is 2% by mass or more and 20% by mass or less. The silicate ester hydrolysis condensate is 3 parts by mass or more and 20 parts by mass or less relative to the total amount of the silica particles and the silicate ester hydrolysis condensate (100 parts by mass).

2. The coating liquid according to claim 1, comprising at least one selected from methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol, 1-pentanol, 2-pentanol, cyclopentanol, 2-methylbutanol, 3-methylbutanol, 1-hexanol, 2-hexanol, 3-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2-ethylbutanol, 2,4-dimethyl-3-pentanol, 3-ethylbutanol, 1-heptanol, 2-heptanol, 1-octanol, 2-octanol, ethylene glycol, triethylene glycol, methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1-propoxy-2-propanol as the second solvent.

3. The coating liquid according to claim 1 or 2, wherein the silica particles are chain-like silica particles.

4. The coating liquid according to claim 1 or 2, wherein the average Freret diameter of the silica particles is 10 nm or more and 60 nm or less.

5. A method for manufacturing a component, comprising: Apply the coating liquid according to any one of claims 1 to 4 to the substrate; as well as The coating liquid is cured to form a hybrid layer on the substrate. The thickness of the hybrid layer is greater than 20 nm and less than 160 nm, and The thickness variation of the cross-section of the hybrid layer in its thickness direction within a range of 1 μm along the surface of the substrate is less than 15%. The thickness variation is the ratio of the height of the unevenness at the interface between the substrate and the hybrid layer to the average thickness of the hybrid layer.

6. The method for manufacturing a component according to claim 5, wherein a porous layer is formed on the hybrid layer, the thickness of the porous layer being 100 nm or more and 800 nm or less.

7. The method for manufacturing a component according to claim 5, wherein the substrate is a resin substrate.

8. A component manufactured by the manufacturing method of any one of claims 5 to 7.

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