JP2020095254A - Transparent member, imaging device, and method for manufacturing transparent member - Google Patents

Abstract

To provide a transparent member formed with a highly reliable film capable of maintaining hydrophilic performance by suppressing a haze rise for long time even when being exposed to an outdoor environment.SOLUTION: A transparent member has a porous layer on a resin base material. The porous layer has a network structure in which silica particles bonded together with a binder. The resin base material has a mixed layer into which the network structure enters at a side where the porous layer is formed. In the transparent member, a thickness of the mixed layer is 20 nm or more and 160 nm or less, a thickness variation of the cross-section of the mixed layer in a thickness direction is 15% or less in a range of 1 μm length along a surface of the resin base material.SELECTED DRAWING: Figure 1

Description

The present invention relates to a hydrophilic transparent member, a method for manufacturing the same, and an image pickup device using the transparent member as a protective cover.

In recent years, surveillance cameras have been installed in various places such as stores, hotels, banks, and stations for the purpose of crime prevention. The surveillance camera is installed by a method of mounting it on the ceiling, an outer wall, a pillar, or the like via a mounting part, or embedding it.

A transparent protective cover that does not interfere with imaging is attached to the surveillance camera body for the purpose of protecting it from the surrounding environment. For the protective cover, a resin material such as polycarbonate or acrylic resin having excellent transparency and impact resistance is used. For surveillance cameras installed outdoors, water droplets due to rain, condensation, etc. may adhere to the protective cover and distort or obscure the image.Therefore, a hydrophilic film should be provided on the protective cover to prevent water droplets from adhering. Prevention techniques are widely used.

Patent Document 1 proposes a hydrophilic film in which silica sol is infiltrated into a resin substrate to obtain a silica particle film having high hydrophilicity and high adhesion.

JP, 2013-203774, A

In general, a resin base material such as polycarbonate or acrylic resin used for a protective cover of a surveillance camera or the like is deteriorated by sunlight and cracks such as cracks are generated when it is installed outdoors for a long time. Therefore, even when the hydrophilic film is formed on the protective cover, cracks are generated in the hydrophilic film along with the occurrence of cracks in the resin base material, which is the protective cover, and the image taken is disturbed due to an increase in haze. There is. There is also a problem that when the crack extends, the hydrophilic film falls off from the protective cover and the hydrophilicity cannot be maintained.

Therefore, it is preferable that the hydrophilic film provided on the protective cover can suppress the occurrence of cracks, suppress the rise of haze, and maintain the hydrophilicity when it is installed outdoors for a long time. However, since the hydrophilic film having the configuration proposed in Patent Document 1 cannot suppress the deterioration of the base material due to sunlight when it is installed outdoors for a long time, it is possible to suppress the occurrence of cracks in the hydrophilic film. It is not possible to suppress the rise of haze for a long period of time and maintain the hydrophilicity.

The present invention has been made in view of the above problems, and suppresses the occurrence of cracks in the hydrophilic film when it is installed outdoors for a long period of time, suppresses an increase in haze, and is a hydrophilic film capable of maintaining hydrophilicity. And a transparent member having:

The transparent member according to the present invention is a transparent member having a porous layer on a resin substrate, the porous layer has a network structure in which silica particles are bonded to each other by a binder, the resin substrate, The mixed layer having the network structure invaded in the surface layer on the side where the porous layer is provided, the mixed layer has a film thickness of 20 nm or more and 160 nm or less, and the resin of the cross section in the thickness direction of the mixed layer. It is characterized in that the variation of the film thickness is 15% or less in the range of the length of 1 μm along the film surface on the surface of the base material.

Further, the image pickup apparatus according to the present invention includes an optical system and an image sensor that acquires an image via the optical system, in a space surrounded by the housing and the transparent member.

Further, the method for producing a transparent member according to the present invention is a method for producing a transparent member in which a layer containing silica is formed on a resin base material, and silica particles and a component serving as a binder are provided on the resin base material. A step of applying a dispersion liquid containing, and forming a mixed layer in which a network structure in which the silica particles are bonded to each other by a binder penetrates into the porous layer and the resin substrate by curing the dispersion liquid, The film thickness of the mixed layer is 20 nm or more and 160 nm or less, and the film thickness variation in a range of 1 μm along the film surface of the cross section in the direction intersecting the film surface of the mixed layer is 15% or less. Is characterized by.

According to the present invention, it is possible to provide a transparent member having a highly reliable hydrophilic film capable of suppressing haze increase for a long period of time and maintaining hydrophilicity even when exposed to an outdoor environment.

It is a schematic diagram which shows the cross section of the thickness direction of one Embodiment of the transparent member concerning this invention. It is a schematic diagram which shows one Embodiment of the imaging device concerning this invention. It is a schematic diagram which shows the structural example of the imaging device concerning this invention. 4 is an image observed by a scanning transmission electron microscope of a cross section of the transparent member created in Example 1.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and may be modified as appropriate without departing from the spirit of the present invention.

≪Transparent material≫
FIG. 1 is an embodiment of a transparent member according to the present invention, and is a schematic view showing a cross section in a thickness direction (direction parallel to a normal line of a substrate surface). In the same figure, the transparent member 10 according to the present invention has a hydrophilic coating comprising, on a resin base material 16, a porous layer 14 and a mixed layer 15 in which the porous layer penetrates into the resin base material 16. .. In the present invention, “transparent” means a characteristic that the transmittance for visible light is 20% or more.

The porous layer 14 includes a plurality of silica particles (silicon oxide particles) 12 and a binder 11 interposed between the plurality of silica particles 12. The plurality of silica particles 12 are fixed to each other by a binder 11, and are made porous by voids 13 formed between the silica particles 12 and between the binders 11.

When a conventional hydrophilic film formed on a resin substrate is placed in an outdoor exposure environment, stress is applied to the hydrophilic film formed on the resin substrate due to the following two phenomena, and cracks occur.
(1) The surface of the resin base material is oxidized and deteriorated by sunlight and oxygen.
(2) The resin base material expands and contracts due to water absorption due to rain and temperature change due to sunlight.

On the other hand, with the above-described configuration, the resin base material 16 is first covered with the mixed layer 15, so that the surface area of the resin base material 16 exposed on the surface is reduced. It prevents oxidative deterioration and relieves the stress associated with the expansion and contraction of the resin base material 16. In addition, since the silica particles of the mixed layer 15 and the porous layer 14 have a network structure, the stress caused by the oxidative deterioration of the resin base material 16 is relaxed and the generation of cracks in the resin base material 16 is suppressed. As a result, the transparent member according to the present invention can suppress the occurrence of cracks in the hydrophilic film even when installed in an outdoor environment, suppress haze increase for a long period of time, and maintain hydrophilicity.

Hereinafter, each layer will be described in detail.
<Porous layer>
The porous layer 14 has a network structure in which the silica particles 12 are bonded to each other by the binder 11 and voids 13 are included between the silica particles 12 and in the binder 11. That is, the network structure is a structure formed by bonding silica particles to each other with a binder. 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, it is possible to suppress the occurrence of cracks in the film in an outdoor exposure environment by keeping the internal stress of the film to an appropriate level, suppress an increase in haze, and improve hydrophilicity. You can maintain sex. When the porosity of the porous layer 14 is 55% or less, the haze of the hydrophilic film can be reduced and the transparency can be maintained. Furthermore, since the binder 11 and the silica particles 12 are hydrophilic, the porous layer 14 has hydrophilicity, and the contact angle of water on the surface of the porous layer 14 is 30° or less. The thickness of the porous layer 14 is preferably 100 nm or more and 800 nm or less. When the film thickness of the porous layer 14 is smaller than 100 nm, the generation of cracks in the resin base material 16 due to the network structure of the mixed layer 15 and the porous layer 14 is not sufficiently suppressed, and cracks in the film occur. It may not be possible to suppress the increase in haze and maintain hydrophilicity. When the film thickness of the porous layer 14 is larger than 800 nm, the internal stress of the hydrophilic film increases, cracks occur in the film, haze is suppressed from increasing, and hydrophilicity is maintained. May not be possible.

Here, the porosity of the porous layer 14 is a value representing the ratio of the volume of the voids contained in the porous layer 14 to the porous layer 14. The porosity can be calculated using Equation 1 from the refractive index of the porous layer, the refractive index of silica of 1.46, and the refractive index of air of 1.00 using a spectroscopic ellipsometer.
(Equation 1) Porosity=100×(refractive index of porous layer-1.46)/(1.00-1.46)

Further, the surface average surface roughness Ra of the surface of the porous layer 14, that is, the surface of the transparent member according to the present invention on the side where the porous layer 14 is provided is preferably 2 nm or more and 10 nm or less. The surface average surface roughness Ra is calculated by the calculation method defined in JIS B 0601:2001, and when Ra is a small value, the porous layer 14 has a dense and uniform structure. Therefore, when Ra is 10 nm or less, even if the transparent member according to the present invention is placed outdoors for a long period of time, it is possible to suppress oxidative deterioration of the base material and generation of cracks in the hydrophilic coating, which is preferable. On the other hand, from the relationship with the porosity, Ra is preferably 2 nm or more.

[Silica particles]
The average particle diameter of the silica particles 12 is preferably 10 nm or more and 60 nm or less. When the average particle diameter of the silica particles 12 is 10 nm or more, the voids 13 formed between the particles can be appropriately increased, a desired porosity can be realized, and the internal stress of the film can be appropriately maintained. Therefore, it is possible to suppress the occurrence of cracks in the film in an outdoor exposure environment, suppress an increase in haze, and maintain hydrophilicity. Moreover, when the average particle diameter of the silica particles 12 is 60 nm or less, the size of the voids 13 formed between the particles can be appropriately reduced, and light does not scatter due to the voids 13 and the silica particles 12, and the haze can be reduced. Is preferable because it can suppress the increase of

Here, the average particle diameter of the silica particles 12 is an average Feret's diameter. This average ferret diameter can be measured by image processing of an observation image observed with a transmission electron microscope image. As the image processing method, commercially available image processing such as image Pro PLUS (manufactured by Media Cybernetics) can be used. In a predetermined image area, if necessary, the contrast may be appropriately adjusted, and the average Feret diameter of each particle may be measured with a commercially available particle measuring software to obtain the average value.

As the silica particles 12, solid silica particles or hollow silica particles can be used, but chain silica particles in which these are connected are particularly preferable. By using the chain-like silica particles, it is possible to increase the porosity without generating large voids. Solid silica particles or hollow silica particles may be mixed with chain silica particles for use. In the case of chain-like silica particles, it is preferable that the average particle diameter of individual particles connected to each other is 10 nm or more and 60 nm or less.

Although the silica particles 12 contain SiO ₂ as a main component, the particles may also contain metal oxides such as Al ₂ O ₃ , TiO ₂ , ZnO ₂ and ZrO ₂ . However, if 30% or more of the silanol (Si—OH) groups on the surface of the silica particles 12 are modified with an organic group or complexed with another metal, the hydrophilicity is lost. The porous layer 14 made of such silica particles has low hydrophilicity and also has a low self-cleaning property.

Therefore, in order to express good hydrophilicity in the porous layer 14, it is preferable to use silica particles in which a silanol (Si—OH) group remains in 70% or more of the particle surface, and 90% or more of the particle surface is used. It is more preferable to use silica particles in which silanol groups remain.

[binder]
The binder 11 can be appropriately selected depending on the abrasion resistance and environmental reliability of the hydrophilic coating and the adhesive force with the silica particles 12, but the binder 11 has a high affinity with the silica particles 12 and the abrasion resistance of the porous layer. It is preferable to use a silica binder that improves Among the silica (SiO ₂ ) binders, it is more preferable to use a hydrolytic condensate of silicate, and it is further preferable to use a hydrolytic condensate of a tetrafunctional silicate.

The content of the binder 11 is preferably 3% by mass or more and 20% by mass or less and more preferably 10% by mass or more and 20% by mass or less with respect to the total mass of the porous layer 14. When the content of the binder 11 is less than 3% by mass based on the total mass of the porous layer 14, the force for fixing the silica particles 12 is weak and the silica particles 12 may peel off. When the content of the binder 11 with respect to the porous layer 14 exceeds 20% by mass, the space between the silica particles 12 is filled with the binder, the porosity in the porous layer 14 decreases, and the internal stress of the hydrophilic coating increases. There is a tendency.

<Mixed layer>
The mixed layer 15 is a layer in which the resin base material 16 penetrates into voids of a network structure formed by bonding silica particles to each other with a binder, and is provided on the side of the resin base material 16 on which the porous layer 14 is provided. ing. The mixed layer 15 is a range from the uppermost part of the resin base material 16 that has entered the voids of the network structure formed of the binder and the silica particles to the lowermost part of the network structure. When installed in an outdoor environment, the resin base material 16 may be oxidatively deteriorated by sunlight and oxygen. However, since the surface area of the resin base material 16 in contact with oxygen can be reduced by the mixed layer, oxidative deterioration of the resin base material 16 can be suppressed. Further, since the mixed layer 15 and the porous layer 14 have a continuous network structure, the stress caused by the oxidative deterioration of the resin base material 16 is relaxed and the generation of cracks is suppressed.

The thickness of the mixed layer 15 is preferably 20 nm or more and 160 nm or less. When the film thickness of the mixed layer 15 is smaller than 20 nm, the resin base material 16 does not sufficiently penetrate into the network structure, and the stress due to the oxidative deterioration of the resin base material 16 cannot be relaxed. The generation of cracks cannot be suppressed. If the thickness of the mixed layer 15 is larger than 160 nm, scattering is caused by the resin base material 16 and the silica particles 12 and haze is increased, which is not preferable. The thickness of the mixed layer is preferably larger than the average particle size of silica particles. When the film thickness of the mixed layer is larger than the average particle diameter of the silica particles, the strength of the network structure of the mixed layer 15 can be increased, so that the occurrence of cracks can be suppressed more reliably. When chain-shaped silica particles are used, the thickness of the mixed layer is preferably larger than the average particle diameter of individual particles that are continuous with each other.

Further, the volume ratio of the network structure in the mixed layer 15 is preferably 20% or more and 80% or less, and more preferably 30% or more and 70% or less. When the volume ratio of the network structure in the mixed layer 15 is 20% or more, the oxidative deterioration of the resin base material 16 at the time of outdoor exposure can be sufficiently suppressed, and the generation of cracks can be suppressed. When the volume ratio of the network structure in the mixed layer 15 is 80% or less, the stress at the time of outdoor exposure can be relaxed and the generation of cracks can be suppressed.

Further, the mixed layer 15 relieves the stress of the resin base material 16 expanding and contracting due to water absorption due to rain and temperature change due to sunlight. Regarding the film thickness of the mixed layer 15, in the cross section in the thickness direction, the film thickness variation in the range of an arbitrary length of 1 μm along the surface of the resin substrate 16 is 15% or less. When the variation in the film thickness of the mixed layer in the film surface is larger than 15%, the stress due to the expansion/contraction of the resin base material concentrates on the portion where the film thickness of the mixed layer is smaller than the surroundings. The material 16 is cracked and the hydrophilic coating is cracked. Therefore, it is not possible to suppress an increase in haze and maintain hydrophilicity.

The variation in film thickness is the ratio of the height of the irregularities generated at the interface between the resin base material 16 and the mixed layer 15 to the average film thickness of the mixed layer 15. By thinning the transparent member of the present invention and observing the cross section with a scanning transmission electron microscope or the like, the average film thickness of the mixed layer 15 and the height of the irregularities generated at the interface between the resin base material 16 and the mixed layer 15 are obtained. Here, the height of the irregularities generated at the interface between the resin base material 16 and the mixed layer 15 means a portion consisting only of the resin base material 16 existing on the most mixed layer side at the interface and the mixed layer 15 located closest to the resin base material 16 side. It is the absolute value of the difference in height in the thickness direction from the portion. When calculating the film thickness variation, it is preferable to binarize the obtained image with image processing software so that the base material and the mixed layer (silica particles or binder) can be easily distinguished. As shown in FIG. 4, when an arbitrary length of 1 μm along the surface of the resin base material 16 in the cross section in the thickness direction is represented by the range of the solid line in the drawing, the resin base material 16 and the mixed layer 15 are The height of unevenness (film thickness variation) generated at the interface corresponds to the ratio of the height of unevenness to the average film thickness of the distance between two white broken lines (distance indicated by white arrow).

<Resin base material 16>
As the material of the resin base material 16, a transparent acrylic resin, polycarbonate, polyester, or other resin can be used. The shape of the resin base material 16 is not limited, and may be plate-like or film-like, and may be plate-like or have a curved surface, a concave surface or a convex surface, for example, a hemispherical shape. It may have a dome shape or the like. The visible light transmittance of the resin substrate is preferably 50% or more.

<Manufacturing method>
Next, an example of the method for manufacturing a transparent member according to the present invention will be described.
The method for producing a transparent member according to the present invention has a step of forming the porous layer 14 and the mixed layer 15 on the resin substrate 16.

As the step of forming the porous layer 14 and the mixed layer 15, a method of coating/drying the dispersion liquid of the silica particles 12 and the binder solution on the resin base material 16 in order, or a method of forming the silica particles 12 and the binder 11 A method of applying/drying the dispersion liquid containing both on the resin substrate 16 can be used. The method of applying the dispersion liquid containing both the silica particles 12 and the component to be the binder 11 is more preferable because the composition inside the porous layer 14 becomes uniform.

The dispersion liquid of the silica particles 12 is a liquid in which the silica particles 12 are dispersed in a solvent, and the content of the silica particles 12 is preferably 2% by mass or more and 10% by mass or less. A silane coupling agent or a surfactant may be added to the dispersion liquid of the silica particles 12 in order to improve the dispersibility of the silica particles 12. However, when these compounds react with many of the silanol groups on the surface of the silica particles 12, the bond between the silica particles 12 and the binder 11 is weakened and the abrasion resistance of the porous layer 14 is reduced, or The hydrophilicity of the layer 14 may be reduced. Therefore, the content of the additive such as the silane coupling agent and the surfactant in the dispersion is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less with respect to 100 parts by mass of the silica particles 12.

As the binder solution, it is preferable to use a solution of a silica binder that has a strong binding force with the silica particles 12. The silica binder solution contains silicate hydrolyzed condensate as a main component, which is produced by adding water, acid or base to silicic acid ester such as methyl silicate and ethyl silicate in a solvent and hydrolyzing and condensing the same. Solutions are preferred.

What kind of acid or base is to be used may be appropriately selected in consideration of solubility in a solvent and reactivity with a silicate ester. The acid used in the hydrolysis reaction is preferably hydrochloric acid or nitric acid, and the base is preferably ammonia or various amines. The silicate hydrolysis-condensation product can be prepared not only by silicic acid ester but also by neutralizing and condensing a silicate such as sodium silicate in water. Acids that can be used in the neutralization reaction are hydrochloric acid, nitric acid and the like. When preparing the silica binder solution, heating may be performed at a temperature of 80° C. or lower.

When a silica binder is used as the binder 11, a trifunctional silane alkoxide substituted with an organic group such as methyltriethoxysilane and ethyltriethoxysilane may be added to the silica binder solution for the purpose of improving solubility and coating properties. it can. The addition amount of the trifunctional silane alkoxide is preferably 10 mol% or less based on the whole silane alkoxide contained in the silica binder solution. If the amount added exceeds 10 mol %, the organic group inhibits hydrogen bonding between silanol groups in the binder, resulting in reduced wear resistance.

When the dispersion liquid containing both the silica particles 12 and the component to be the binder 11 is used, the dispersion liquid of the silica particles 12 and the binder solution may be prepared in advance and then mixed. Alternatively, the dispersion liquid may be prepared by adding a component to be the binder 11 to the dispersion liquid of the silica particles 12 and reacting them. In the case of using the latter method to obtain a dispersion liquid containing silica particles 12 and a silica binder as a component which becomes the binder 11, by adding a silicic acid ester, water and an acid catalyst to the dispersion liquid of the silica particles 12 and reacting them. It is possible to prepare. A method of preparing the binder solution in advance and then mixing the binder solution is preferable in that the reaction of the component to be the binder 11 can be controlled and the binder 11 can be prepared while confirming the reaction state.

The amount of the component serving as the binder 11 in the dispersion liquid containing both the silica particles 12 and the component serving as the binder 11 is preferably 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the component serving as the silica particles and the binder. It is more preferably 10 parts by mass or more and 20 parts by mass or less.

The solvent that can be used for the dispersion liquid of the silica particles 12 or the silica binder solution needs to be capable of uniformly dissolving or dispersing them and forming a film having a uniform thickness of the mixed layer 15. .. Therefore, it is desirable to combine a solvent having a relatively high solubility of the resin base material 16 and a solvent having a relatively low solubility. Further, it is desirable that the solvent having a relatively high solubility of the resin base material 16 has a higher boiling point than the solvent having a relatively low solubility of the resin base material 16. By selecting the solvent in such a manner, uniform alignment of silica particles is promoted in the initial stage of the film formation process, and a porous network structure having a high uniform alignment is formed. In the latter stage of the film formation process, the proportion of the solvent having a high boiling point and the relatively high solubility increases, and the resin substrate 16 is rapidly dissolved, so that the porous network formed in the initial stage of the film formation process. The structure penetrates into the resin base material 16 to form a uniform mixed layer 15.

Examples of the solvent having a relatively high solubility of the resin base material 16 include ethers such as dimethoxyethane, diglyme, dioxane, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether; ethyl acetate, n-butyl acetate, ethylene glycol monomethyl. Esters such as ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, and propylene glycol monomethyl ether acetate; various aliphatic compounds such as n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane Alicyclic hydrocarbons; various aromatic hydrocarbons such as toluene, xylene, ethylbenzene; various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, 2-heptanone, cyclohexanone; chloroform, Various chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, tetrachloroethane; aprotic such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, ethylene carbonate Examples include polar solvents. As the solvent having a relatively high solubility of the resin base material 16, diglyme, dibutyl ether, propylene glycol monomethyl ether acetate, and 2-heptanone are preferably used.

Examples of the solvent having a relatively low solubility of the resin base material 16 include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol, 1-pentanol, and 2 -Pentanol, cyclopentanol, 2-methylbutanol, 3-methylbutanol, 1-hexanol, 2-hexanol, 3-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2- Monohydric alcohols such as ethylbutanol, 2,4-dimethyl-3-pentanol, 3-ethylbutanol, 1-heptanol, 2-heptanol, 1-octanol and 2-octanol; ethylene glycol, triethylene glycol, etc. Dihydric or higher alcohols; ether alcohols such as methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol The kind is mentioned. 2-Propanol is preferably used as the solvent in which the resin substrate 16 has a relatively low solubility.

In order to obtain the transparent member according to the present invention, a solvent having a relatively high solubility of the resin base material 16 and a solvent having a relatively low solubility of the resin base material 16 are selected from these exemplified solvents. It may be selected and used so that the boiling points are different. In consideration of the boiling point of the solvent, a solvent having a relatively high solubility and a solvent having a relatively low solubility may be used as a mixture of two or more kinds.

When a solvent having a relatively high solubility and a solvent having a relatively low solubility are mixed and used, the proportion of the solvent having a relatively high solubility is 2% by mass or more and 30% by mass or less. It is preferably 10% by mass or more and 20% by mass or less. When it is 2% by mass or more, a sufficient mixed layer can be formed, and when it is 30% by mass or less, the film thickness of the mixed layer does not become too thick, and the haze can be kept good. ..

Examples of the method for applying the dispersion liquid of the silica particles 12 and the binder solution, or the dispersion liquid in which they are mixed include a spin coating method, a blade coating method, a roll coating method, a slit coating method, a printing method and a dip coating method. .. When manufacturing a transparent member having a three-dimensionally complicated shape such as a concave surface, the spin coating method is preferable from the viewpoint of film thickness uniformity.

After applying the dispersion liquid of the silica particles 12 and the binder solution or the dispersion liquid in which they are mixed, the amount of the solvent remaining in the porous layer and the mixed layer can be suppressed to improve the abrasion resistance. Therefore, it is preferable to form a porous layer and a mixed layer by providing a drying step and a curing step. The drying step and the curing step are steps for accelerating the removal of the solvent, the reaction of the component serving as the binder 11, or the reaction between the component serving as the binder 11 and the silica particles 12. The temperature of the drying step and the curing step is preferably 20° C. or higher and 200° C. or lower, and more preferably 60° C. or higher and 150° C. or lower. If the temperature of the drying process and the curing process is less than 20° C., the solvent remains and the abrasion resistance decreases. Further, when the temperature of the drying step and the curing step exceeds 200° C., the binder 11 is excessively hardened, and as a result, cracks are likely to occur in the porous layer 14.
The solvent remaining in the porous layer 14 is preferably 3.0 mg/cm ³ or less.

When the dispersion liquid of the silica particles 12 and the binder solution are applied in order, the dispersion liquid of the silica particles 12 is applied and the firing process is performed once, and then the binder solution is applied, and the drying process and the curing process are performed. It is also possible to form a porous layer and a mixed layer.

In order to make the porous layer 14 have a desired film thickness, the coating step, the drying step and the curing step may be alternately repeated a plurality of times.

<<Imaging device>>
2A and 2B are schematic diagrams showing an embodiment of the image pickup apparatus of the present invention. FIG. 2A is a fixed-point observation type surveillance camera, and FIG. 2B is a swivel type capable of pan/tilt/zoom driving. Surveillance camera. The image pickup apparatus shown in FIGS. 2A and 2B has a transparent member (protective cover) 3 according to the present invention, which functions as a protective cover, in the apparatus main bodies 1 and 2, and the apparatus main bodies 1 and 2 are provided with an image. An optical system for acquiring data is provided. Further, the transparent member 3 covers at least the optical system of the apparatus main bodies 1 and 2 and protects it from dust and shock from the outside. The protective cover 3 in FIG. 2A is a box-shaped planar shape, and the protective cover 3 in FIG. 2B is a hemispherical dome shape, but the shape of the protective cover 3 is not limited to these.

FIG. 3 shows a configuration example of the image pickup apparatus according to the present invention. The imaging device 30 has a space surrounded by the transparent member 10 including the porous layer 14, the mixed layer 15 and the resin base material 16 and the housing 36, and the optical system 31, the image sensor 32, and the inside of the space. A video engine 33, a compression output circuit 34, and an output unit 35 are provided.

The image acquired via the transparent member 10 is guided to the image sensor 32 by the optical system (lens) 31, converted into a video analog signal (electrical signal) by the image sensor 32, and output. The video analog signal output from the image sensor 32 is converted into a video digital signal by the video engine 33, and the video digital signal output from the video engine 33 is compressed into a digital file by the compression output circuit 34. The video engine 33 may perform processing of adjusting image quality such as brightness, contrast, color correction, and noise removal in the process of converting a video analog signal into a video digital signal. The signal output from the compression output circuit 34 is output from the output unit 35 to the external device via the wiring.

The transparent member 10 is installed so that the surface on which the porous layer 14 is provided is on the outside. With such a configuration, it protects against dust and shock from the outside, and also makes water droplets adhering to the surface of the transparent member 10 into a liquid film due to changes in the external environment, and suppresses distortion of the image acquired by the image sensor 32. be able to.

Further, the imaging device 30 includes a pan/tilt for adjusting the angle of view, a controller for controlling the imaging conditions, a storage device for storing the acquired video data, a transfer unit for transferring the data output from the output unit 35 to the outside, and the like. , An imaging system can be configured.

Hereinafter, a specific method for manufacturing the transparent member according to the present invention will be described.
(Preparation of coating liquid)
First, the coating liquid used for producing the transparent member according to the present invention will be described.

(1) Preparation of silica binder solution To 12.48 g of ethyl silicate, 13.82 g of ethanol and an aqueous nitric acid solution (concentration 3%) were added, and the mixture was stirred at room temperature for 10 hours to obtain a silica binder solution (solid content concentration 12.0% by mass). Was prepared.

(2-1) Preparation of silica particle coating liquid A 2-propanol (IPA) dispersion liquid of chain silica particles (trade name: IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 15.5 mass) %) 20.00 g was diluted with 85.00 g of IPA (boiling point: 82.5° C.) and 15.00 g of diglyme (boiling point: 162.0° C.) as a solvent, and then the silica binder solution 2 prepared in (1) .60 g was added and the mixture was stirred at room temperature for 10 minutes. Then, it stirred at 50 degreeC for 1 hour, and prepared the silica particle coating liquid A. By the particle size distribution measurement by the dynamic light scattering method (trade name: Zetasizer Nano ZS, manufactured by Malvern Co., Ltd.), silica particles having an average particle diameter of 15 nm were continuously connected to an average equivalent circle diameter of 95 nm in the silica particle coating liquid A. It was confirmed that the chain silica particles were dispersed.

(2-2) Preparation of silica particle coating liquid B Silica particle coating liquid A was coated in the same manner as the silica particle coating liquid A except that 85.00 g of IPA and 15.00 g of dibutyl ether (boiling point: 140.8° C.) were used as the solvent. A working solution B was prepared.

(2-3) Preparation of silica particle coating liquid C In the same manner as the silica particle coating liquid A, except that 85.00 g of IPA and 15.00 g of propylene glycol monomethyl ether acetate (boiling point: 140.0° C.) were used as the solvent. A silica particle coating liquid C was prepared.

(2-4) Preparation of silica particle coating liquid D Silica particles in the same manner as the silica particle coating liquid A except that 70.00 g of IPA and 30.00 g of 2-heptanone (boiling point: 151.0°C) are used as the solvent. A coating liquid D was prepared.

(2-5) Preparation of Silica Particle Coating Liquid E A silica particle coating liquid E was prepared in the same manner as the silica particle coating liquid A except that 70.00 g of IPA and 30.00 g of diglyme were used as the solvent.

(2-6) Preparation of silica particle coating liquid F A silica particle coating liquid F was prepared in the same manner as the silica particle coating liquid A except that 100.00 g of IPA was used as the solvent.

(2-7) Preparation of silica particle coating liquid G Silica particle coating liquid A was prepared in the same manner as the silica particle coating liquid A except that 70.00 g of IPA and 30.00 g of tetrahydrofuran (boiling point: 66.0° C.) were used as the solvent. Liquid G was prepared.

(2-8) Preparation of silica particle coating liquid H A silica particle coating liquid H was prepared in the same manner as the silica particle coating liquid A, except that 105.00 g of IPA and 30.00 g of diglyme were used as the solvent.

(Example 1)
An appropriate amount of the silica particle coating solution A is dropped on a polycarbonate substrate (nd=1.58, νd=30.2) having a diameter (φ) of 50 mm and a thickness of 4 mm and a light transmittance of about 80%, and 2000 rpm for 20 seconds. Spin coating was performed. Then, it heated at 90 degreeC for 15 minutes in a hot-air circulation oven, and produced the transparent member in which the porous layer and the mixed layer were formed. The average Feret diameter of the silica particles was 15 nm.

FIG. 4 is a cross-sectional observation image of the transparent member created in Example 1. It can be seen from the bottom of the observed image that three layers of the resin substrate 16, the mixed layer 15 of the resin substrate and silica particles, and the porous layer 14 are formed. The calculation of the film thickness variation of the mixed layer 15, which will be described later, was performed using this cross-section observation image, and the film thickness variation was 8%.

(Example 2)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid B was used in place of the silica particle coating liquid A.

(Example 3)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid C was used in place of the silica particle coating liquid A.

(Example 4)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid D was used in place of the silica particle coating liquid A.

(Example 5)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid E was used instead of the silica particle coating liquid A.

(Example 6)
The transparent member prepared in the same manner as in Example 1 was further coated with the silica particle coating liquid F. As the coating, a suitable amount of the silica particle coating liquid F was dropped, spin coating was performed at 2000 rpm for 20 seconds, and a series of steps of heating at 90° C. for 15 minutes in a hot air circulation oven was repeated twice to prepare a transparent member.

(Comparative Example 1)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid F was used in place of the silica particle coating liquid A.

(Comparative example 2)
The transparent member with a hydrophilic coating formed in the same manner as in Example 1 was further coated with the silica particle coating liquid F. For the coating, an appropriate amount of the silica particle coating liquid F is dropped, spin coating is performed at 2000 rpm for 20 seconds, and a series of steps of heating at 90° C. for 15 minutes in a hot air circulation oven is repeated 3 times to create a transparent member with a hydrophilic coating. did.

(Comparative example 3)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid G was used in place of the silica particle coating liquid A.

(Comparative example 4)
A transparent member was prepared in the same manner as in Example 1 except that the silica particle coating liquid H was used instead of the silica particle coating liquid A.

(Evaluation method of transparent member)
Next, a method for evaluating the transparent member created in Examples and Comparative Examples will be described.
(1) Measurement of film thickness of porous layer and mixed layer The thickness of the porous layer and the mixed layer was measured by using a spectroscopic ellipsometer (trade name: VASE, manufactured by JA Woollam Japan) in the wavelength range of 380 nm to 800 nm. The film thickness was calculated.

(2) Measurement of Porosity of Porous Layer Using a spectroscopic ellipsometer (trade name: VASE, manufactured by JA Woollam Japan), the wavelength was measured from 380 nm to 800 nm, and the refractive index of the porous layer was determined by analysis. The porosity of the porous layer was calculated using Equation 1.

(3) Measurement of variation in film thickness of mixed layer The film was cut out by a focused ion beam device (trade name: SMI3050, manufactured by SII Nanotechnology), and thinned so that a cross section in the film thickness direction of the mixed layer could be observed. The cross-sectional state of the mixed layer in the film thickness direction was subjected to bright-field observation with a scanning transmission electron microscope (trade name: S-5500 manufactured by Hitachi High-Technology) at a magnification of 100,000. Then, image processing of the observed image was performed. As the image processing method, commercially available image processing software such as image Pro PLUS (manufactured by Media Cybernetics) was used. In the predetermined image area, if necessary, contrast adjustment was appropriately performed to calculate the film thickness of the mixed layer, and the film thickness variation in the length range of 1 μm was calculated.

(4) Measurement of contact angle Using a fully automatic contact angle meter (trade name: DM-701, manufactured by Kyowa Interface Science Co., Ltd.), the contact angle at the time of contacting a droplet of 2 μl of pure water at 23° C. and 50% RH was measured. It was measured.

(5) Measurement of haze Haze was measured using a haze meter (trade name: NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

(6) Outdoor exposure test The transparent member was put into a xenon weather meter (trade name: Super Xenon Weather Meter SX75, manufactured by Suga Test Instruments Co., Ltd.). The light irradiation intensity was set to 180 W/m ² , light irradiation and water discharge were set to 18 minutes, and only light irradiation was set to 1 cycle for 1 hour and 42 minutes. A total of 300 cycles were tested for 600 hours for evaluation. The contact angle of the transparent member after the test was measured in the same manner as in (4) measurement of contact angle. This outdoor exposure test corresponds to 100 hours of actual outdoor exposure for one year.

(7) Evaluation If the contact angle is 30° or less, it is possible to sufficiently suppress the formation of water droplets on the surface of the transparent member. If the haze is 1 or less, a clear image can be obtained at the time of shooting. Therefore, in both cases, the initial value and the value after the outdoor exposure test are evaluated as good if the contact angle is 30° or less and the haze is 1 or less, and either contact angle is greater than 30° or haze is greater than 1. If it was large, it was determined to be defective.

(8) Measurement of surface roughness Using SPM (trade name: L-trace & NanoNaviII, manufactured by SII Nanotechnology Inc.), the surface shape in the range of 2 μm×2 μm was measured, and Ra was calculated therefrom.
Table 1 shows the measurement results and evaluation results of Examples 1 to 6 and Comparative Examples 1 to 4.

As shown in Table 1, it is confirmed that the contact angle is 30° or less and the haze is 1 or less, and the hydrophilicity and the haze can be maintained, both in the initial value and after the outdoor exposure, by the configuration of this example. Was confirmed. On the other hand, Comparative Example 1 in which the mixed layer is not provided is out of the range of the present invention, Comparative Example 2 in which the thickness of the porous layer is thicker than the range specified in the present invention, and the thickness of the porous layer is the same. Comparative Example 4, which is thinner than the range specified by the invention, and Comparative Example 3, in which the variation in the thickness of the mixed layer is larger than the range specified by the present invention, maintains the hydrophilicity after outdoor exposure and suppresses an increase in haze. I couldn't.

INDUSTRIAL APPLICABILITY The transparent member according to the present invention is not limited to the use of an image pickup device such as a flat cover or a dome cover for an outdoor camera or a surveillance camera, but is also used in general applications such as a window glass, a mirror, a lens and a transparent film, and an image pickup system or a projection system It can be used for optical lenses, optical mirrors, optical filters, eyepieces, and optical parts.

10 Transparent Member 11 Binder 12 Silica Particle 13 Void 14 Porous Layer 15 Mixed Layer 16 Resin Base Material 1 Device Main Body 2 Device Main Body 3 Transparent Member (Protective Cover)
30 Imaging Device 31 Optical System (Lens)
32 image sensor 33 video engine 34 compression output circuit 35 output unit 36 housing

Claims (17)

A transparent member having a porous layer on a resin substrate,
The porous layer has a network structure in which silica particles are bonded to each other with a binder,
The resin substrate has a mixed layer in which the network structure penetrates on the side where the porous layer is provided,
The thickness of the mixed layer is 20 nm or more and 160 nm or less,
A transparent member having a variation in film thickness of 15% or less in a range of a length of 1 μm along a surface of the resin substrate in a cross section in the thickness direction of the mixed layer. The transparent member according to claim 1, wherein a surface average surface roughness Ra of a surface of the porous layer opposite to a side on which the resin base material is provided is 2 nm or more and 10 nm or less. The transparent member according to claim 1, wherein the thickness of the mixed layer is larger than the average particle diameter of the silica particles. The transparent member according to any one of claims 1 to 3, wherein the average ferret diameter of the silica particles is 10 nm or more and 60 nm or less. The transparent member according to any one of claims 1 to 4, wherein the binder is a silica binder. The film thickness of the said porous layer is 100 nm or more and 800 nm or less, The transparent member of any one of Claim 1 to 5 characterized by the above-mentioned. The transparent member according to any one of claims 1 to 6, wherein the resin substrate has a visible light transmittance of 50% or more. The transparent member according to claim 7, wherein the material of the resin base material is one or more selected from the group consisting of acrylic resin, polycarbonate, and polyester. 9. The transparent member according to claim 1, wherein a contact angle of water on a surface of the porous layer opposite to a side on which the resin base material is provided is 30° or less. .. An imaging device comprising an optical system and an image sensor for acquiring an image via the optical system in a space surrounded by the housing and the transparent member according to claim 1. A method for producing a transparent member in which a layer containing silica is formed on a resin substrate,
A dispersion containing silica particles and a component serving as a binder was applied onto the resin substrate, and the silica particles were bonded to each other by a binder on the porous layer and the resin substrate by curing the dispersion. Having a step of forming a mixed layer where the network structure has invaded,
The thickness of the mixed layer is 20 nm or more and 160 nm or less,
The variation in film thickness in the range of the length of 1 μm along the surface of the resin substrate in the cross section in the thickness direction of the mixed layer is 15% or less,
A method for manufacturing a transparent member, comprising: The method for producing a transparent member according to claim 11, wherein the average Feret diameter of the silica particles is smaller than the film thickness of the mixed layer. The method for producing a transparent member according to claim 11 or 12, wherein the thickness of the porous layer is 100 nm or more and 800 nm or less. The silica particles are chain silica particles,
The method for producing a transparent member according to any one of claims 11 to 13, wherein the average Feret diameter of each particle constituting the chain silica particles is smaller than the film thickness of the mixed layer. 15. The dispersion liquid contains a solvent having a relatively high solubility of the resin base material and a solvent having a relatively low solubility of the resin base material. Item 6. A method for producing a transparent member according to item. The method for producing a transparent member according to claim 15, wherein the solvent having a relatively high solubility of the resin substrate has a boiling point higher than that of a solvent having a relatively low solubility of the resin substrate. .. The resin base material is a polycarbonate base material, and the solvent having a relatively high solubility of the resin base material is selected from diglyme, dibutyl ether, propylene glycol monomethyl ether acetate, and 2-heptanone, and the resin base material is dissolved. The method for producing a transparent member according to claim 15 or 16, wherein the solvent having a relatively low property is 2-propanol.