JP2020032719A - Component and manufacturing method of component - Google Patents

Abstract

To provide a component for reducing refractive index variation under high humidity (60%RH or more and less than 90%RH) and a manufacturing method therefor.SOLUTION: There is provided a component having a substrate and a porous layer on at least one surface of the substrate, in which the porous layer has open diameter dNwhen differential pore volume is maximum in a fine pore distribution in nitrogen adsorption of 5 nm to 20 nm, and open diameter dHO when differential pore volume is maximum in a fine pore distribution in steam adsorption of 25 nm to 75 nm, and contact angle to water of less than 60°.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a member excellent in moisture absorption performance, and more particularly to a member excellent in antifogging performance and optical performance and a method for manufacturing the member.

  When the substrate surface becomes lower than the dew point temperature, a transparent substrate such as glass or plastic is scattered by transmitted light due to fine water droplets adhering to the substrate surface, resulting in a loss of transparency and a so-called "cloudy" state.

  As means for preventing fogging, a method has been proposed in which a layer having a hygroscopic property is provided on the surface of the substrate to absorb moisture in the layer and to prevent generation of water droplets. Patent Literature 1 discloses a method of coating a substrate surface with a hygroscopic layer composed of inorganic fine particles and a water-soluble resin.

  A method of making the substrate surface easy to wet and suppressing the generation of water droplets has also been considered. Patent Literature 2 discloses a method of covering a substrate surface with an uneven film containing inorganic particles and increasing wettability of water to prevent fogging.

JP-A-11-281802 JP-A-11-100234

  However, the method of preventing the generation of water droplets by increasing the hygroscopicity or wettability has a problem that the refractive index changes due to moisture absorption or wetting under high humidity (60% RH or more and less than 90% RH).

  The present invention has been made in view of such background art, and provides a porous layer that reduces a change in refractive index under high humidity (60% RH or more and less than 90% RH), and a method for producing the same. It is.

The present invention is a member having a substrate and a porous layer on at least one surface of the substrate, wherein the porous layer has a maximum differential pore volume in a differential pore distribution in nitrogen adsorption. When the pore diameter dN ₂ is 5 nm or more and 20 nm or less, the pore diameter dH ₂ O when the differential pore volume is maximum in the differential pore distribution in water vapor adsorption is 25 nm or more and 75 nm or less, and the contact angle with water Is less than 60 °.

Further, the present invention is an imaging apparatus including a housing, a protection cover, and an imaging sensor arranged in an internal space surrounded by the housing and the protection cover, wherein the protection cover includes a base material. And a porous layer on the surface of the substrate on the side of the internal space, wherein the porous layer has a pore diameter dN ₂ when the differential pore volume is maximized in the differential pore distribution in nitrogen adsorption. Is 5 nm or more and 20 nm or less, the pore diameter dH ₂ O when the differential pore volume is maximized in the differential pore distribution in water vapor adsorption is 25 nm or more and 75 nm or less, and the contact angle with water is less than 60 °. The present invention relates to an imaging device characterized by the above.

Furthermore, the present invention provides an organic silane compound having a hydrophobic functional group, and silica particles, a step of preparing a silica particle dispersion containing the solvent in a solvent, and other steps formed on the substrate or on the substrate. Coating the silica particle dispersion on a layer, forming a coating film of the silica particle dispersion, and drying the coating film, wherein the average particle diameter of the silica particles is 8 nm or more. 25 nm or less, wherein the silica particle dispersion liquid contains the silane compound having a hydrophobic functional group in an amount of 1 wt% or more and 30 wt% or less in terms of SiO _{2 with} respect to the silica particles. About the method.

  According to the present invention, it is possible to provide a member having a porous layer on the surface of a base material, which has a reduced refractive index change under high humidity (60% RH or more and less than 90% RH) and is excellent in antifogging property.

It is a schematic diagram showing one embodiment of a member of the present invention. is a graph illustrating dN _2. is a graph illustrating the dH ₂ O. It is a schematic diagram showing one embodiment of a member of the present invention. It is a schematic diagram of an example of composition of an imaging device using a member of the present invention.

Hereinafter, the present invention will be described in detail.
[Element]
FIG. 1 is a schematic view showing an embodiment of the member of the present invention.
The member 1 of the present invention includes a substrate 2 and a porous layer 3.

  As shown in FIG. 1, the porous layer 3 is porous and includes an inorganic substance 4 and pores 5. The holes 5 are preferably connected to each other, and are connected to the surface of the porous layer 3.

  Since the porous layer 3 has a small amount of moisture absorption at a humidity of less than 90% RH, a change in the refractive index under a high humidity (60% RH or more and less than 90% RH) can be reduced, and under a super high humidity of 90% RH or more. , The amount of moisture absorption increases, so that fogging does not occur even when exposed to an environment where dew condensation occurs. Therefore, the member 1 of the present invention can be used for a wide range of uses such as a window glass, a mirror, a lens, and a transparent film using a transparent substrate. Also, since no distortion occurs in the image transmitted through the member 1, it is particularly suitable for optical applications such as an optical lens, an optical mirror, an optical filter, an eyepiece of an imaging system and a projection system, a flat cover and a dome cover for outdoor cameras and surveillance cameras. ing.

(Porous layer)
The contact angle of the porous layer 3 with water is less than 60 °. Here, the contact angle is a contact angle obtained when pure water is dropped on the porous layer 3 formed on the substrate 2. When the contact angle is less than 60 °, water molecules can sufficiently enter the inside of the porous layer 3, so that the moisture absorption of the porous layer 3 can be secured.

FIG. 2 shows the differential pore distribution obtained by the BJH method from the nitrogen adsorption isotherm of the porous layer 3 according to the present invention. In the differential pore distribution in nitrogen adsorption, the pore diameter at which the differential pore volume becomes maximum is defined as dN ₂ . dN ₂ takes a value close to the pore diameter obtained by SEM image observation or the like.

The pore diameter dN ₂ is desirably 5 nm or more and 20 nm or less in order to secure a moisture absorption amount. When dN ₂ is 5 nm or more, the porous layer 3 does not absorb moisture at low humidity (humidity less than 60% RH), and secures an amount of moisture absorption at high humidity (60% RH or more and less than 90% RH). Can be. When dN ₂ is 20 nm or less, water vapor easily aggregates, and the amount of moisture absorption can be secured. The volume of the pores (pore volume) is more preferably 0.37 cm ³ / g or more.

FIG. 3 shows the differential pore distribution obtained by the BJH method from the water vapor adsorption isotherm of the porous layer 3 according to the present invention. In the differential pore distribution in water vapor adsorption, the pore diameter when the differential pore volume becomes maximum is defined as dH ₂ O.

The dH ₂ O of the porous layer 3 is desirably 25 nm or more and 75 nm or less. When dH ₂ O is 25 nm or more, the pore surface does not become excessively hydrophilic, and capillary aggregation does not occur at high humidity (60% RH to less than 90% RH). (Less than RH), the refractive index does not change. When dH ₂ O is 75 nm or less, the surface of the pores does not become excessively hydrophobic, and the water vapor is easily aggregated, so that the moisture absorption can be secured. When dH ₂ O is 25 nm or more and 75 nm or less, moisture absorption below 90% RH can be suppressed to reduce the change in refractive index, and moisture can be absorbed at ultra-high humidity (90% RH or more) to secure the amount of moisture absorption. .

The pore diameter dH ₂ O indirectly represents the hydrophilicity / hydrophobicity of the pore surface as a distance, and the surface is more hydrophobic as the value of dH ₂ O is larger than the value of dN ₂ . Therefore, in the porous layer 3 according to the present invention, the value obtained by dividing dH ₂ O by dN ₂ is preferably 1.25 or more and 15 or less, more preferably 2.5 or more and 6.2 or less.

The reason why the change in the refractive index can be reduced and the amount of moisture absorption can be maintained as described above is considered as follows. When dH ₂ O is within the above range, if the humidity is lower than 90% RH, the pore surface of the porous layer 3 is hydrophobic, so that water vapor hardly aggregates. Therefore, when the humidity is lower than 90% RH, the porous layer 3 hardly absorbs moisture and the refractive index does not change. However, when the humidity approaches 90% RH, water molecules are gradually adsorbed on the pore surface of the porous layer 3, and the portion of the pore surface where the water molecules are adsorbed becomes hydrophilic. When the humidity becomes 90% RH or more, the entire surface of the pores becomes hydrophilic, and the water vapor easily aggregates inside the porous layer 3, and the amount of moisture absorption can be secured.

  The porous layer 3 may be a layer deposited in a vacuum or a layer formed by wet deposition of a precursor of the inorganic substance 4 by a sol-gel method or the like.

The inorganic substance 4 contained in the porous layer 3 may be any inorganic substance as long as it satisfies the contact angle with water, dN ₂ , and dH ₂ O. Specific examples of the inorganic substance 4 include silica and zirconia. In particular, it is preferable that the inorganic substance 4 contains silica as a main component in order to lower the refractive index of the porous layer 3 and improve the chemical stability.

FIG. 4 is a schematic view showing an embodiment of the member of the present invention.
In the member 1 illustrated in FIG. 4, the inorganic substance 4 includes the inorganic particles 6 in the porous layer 3, and preferably, the inorganic substance 4 is the inorganic particles 6. It is preferable that the inorganic substance 4 is the inorganic particles 6 because the pores 5 are easily connected to each other and the average pore diameter and the porosity can be made constant. The porous layer 3 in which the inorganic substance 4 is the inorganic particles 6 can be formed by wet film formation from a dispersion of the inorganic particles 6.
The amount of the inorganic particles 6 contained in the porous layer 3 is preferably at least 80 wt%.

  The shape of the inorganic particles 6 can be appropriately selected from various shapes such as a sphere, a chain, a disk, an ellipse, a bar, a needle, and a square. Spherical or chain-like is preferable, and chain-like is more preferable, since it is excellent in film-forming property and can increase porosity while obtaining sufficient film hardness.

  The chain-like particles that can be used as the inorganic particles 6 in the present invention are an aggregate of particles in which a plurality of particles are connected in a chain or bead shape while being linear or bent. The shape of each particle that forms the chain-like inorganic particles may be a shape that can be clearly observed, or a shape that cannot be clearly observed because the shape has collapsed due to fusion or the like, and when forming a layer, It is only necessary that the structure of the chain-like particles is maintained. In this case, the voids between the particles can be expanded as compared with the case where spherical particles or the like are used, so that the porous layer 3 having a high porosity can be formed.

The average particle diameter of the inorganic particles 6 is preferably from 8 nm to 25 nm. Since the average particle size has a value close to the dN _2, the value of the average long diameter is at 8nm than 25nm or less dN ₂ can be secured to the moisture absorption becomes 5nm or 20nm or less.

  When the inorganic particles 6 are chain-shaped, rod-shaped, or needle-shaped, the inorganic particles 6 are particles having a minor axis and a major axis, and the ratio of major axis / minor axis is preferably 3 or more and 12 or less. When the ratio of the major axis / minor axis is 3 or more, it is easy to obtain the effect of increasing the porosity, and when it is 12 or less, the average pore diameter becomes a certain range, and it is possible to suppress light scattering and maintain transparency. it can. A more preferred ratio of major axis / minor axis is 4 or more and 10 or less. The ratio of the major axis to the minor axis can be calculated by observing with a transmission electron microscope image.

Here, the average particle diameter of the inorganic particles is a particle diameter (BET particle diameter) calculated using the BET method. The BET particle diameter can be calculated from the specific surface area calculated by BET analysis of a nitrogen adsorption isotherm measured by a nitrogen gas adsorption method. The calculation method is represented by Expression (1), where the BET particle diameter, the specific surface area, and the density of the elements constituting the inorganic particles are d (nm), A (m ² / g), and ρ (g / cm ³ ), respectively. You.
d = 6000 / (A × ρ) (1)

  As the inorganic particles 6, particles other than chain-like particles, such as perfectly circular, elliptical, disk-like, rod-like, needle-like, and square-like particles other than chain-like shapes, may be appropriately mixed and used. The ratio at which particles having a shape other than the chain shape can be mixed with the entire porous layer 3 is preferably 40 wt% or less, and more preferably 20 wt% or less.

  The main components of the inorganic particles 6 include, for example, silica and zirconia. In order to lower the refractive index of the porous layer 3 and improve the chemical stability, the inorganic particles 6 preferably contain silica as a main component.

  In order to enhance the scratch resistance of the porous layer 3, the silica particles can be bonded to each other. Examples of the method for bonding the silica particles include a method for physically bonding the silica particles using a binder and a method for chemically bonding the silica particles through a silanol group having enhanced activity. Examples of a method of chemically binding the silica particles include a method of treating the surface of the silica particles with a strong acid or the like, and a method of attaching a silanol group to the surface of the silica particles.

  The binder added for bonding the silica particles is preferably a silane compound. A preferred example of the silane compound is a silicon oxide oligomer obtained by hydrolyzing and condensing a silicate ester.

The amount of the silane compound in the porous layer 3 is preferably from 1 wt% to 30 wt% in terms of SiO _{2 with} respect to the silica particles as the inorganic particles 6. When the amount of the silane compound is 1 wt% or more, the abrasion resistance of the porous layer 3 becomes sufficient. When the amount is 30 wt% or less, part of the pores 5 is not filled with the silane compound, and the antifogging of the porous layer 3 is prevented. Performance can be maintained. A more preferred amount of the silane compound is 4 wt% or more and 20 wt% or less in terms of SiO ₂ .

  The layer thickness of the porous layer 3 is preferably from 100 nm to 5 μm, more preferably from 500 nm to 3 μm. When the layer thickness is 100 nm or more, it becomes easy to secure a moisture absorption amount. When the layer thickness is 5 μm or less, the occurrence of light scattering can be suppressed, which is preferable.

(Base material)
As the base material 2, glass, resin, or the like can be used. When the member 1 is used as an optical member, a transparent substrate (transparent substrate) having a light transmittance of 70% or more in a visible light region is used. The shape is not limited, and may be a flat surface, a curved surface, a concave surface, a convex surface, or a film shape.

  As glass, inorganic materials containing zirconium oxide, titanium oxide, tantalum oxide, niobium oxide, hafnium oxide, lanthanum oxide, gadolinium oxide, silicon oxide, calcium oxide, barium oxide, sodium oxide, potassium oxide, boron oxide, aluminum oxide, etc. Glass can be used. As the glass substrate, a glass substrate formed by grinding and polishing, molding, float molding, or the like can be used.

  Examples of the resin include polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, acrylic resin, polycarbonate, cycloolefin polymer, and polyvinyl alcohol.

  In order to improve the adhesion, strength, flatness and the like of the base material 2 and to provide functions such as anti-reflection and anti-glare properties, the base material surface is washed, polished, An adhesive layer, a hard coat layer, a refractive index adjusting layer, and the like can be provided between the substrate and the base material 2.

(Production method)
As a method for manufacturing a member according to the present invention, as an example, a member 1 having a porous silica layer as a porous layer 3 using silica as an inorganic substance 4 will be described.

  The method for manufacturing the member 1 in which the porous layer 3 is formed on at least one surface of the base material 2 includes a silica particle dispersion containing an organic silane compound having a hydrophobic functional group and silica particles in a solvent. Preparing a silica particle dispersion, coating the silica particle dispersion on the substrate 2 or another layer formed on the substrate 2 to form a coating film of the silica particle dispersion, And drying the coating film to form the porous layer 3.

  The step of forming the porous layer 3 is preferably a step of using a dispersion in which inorganic particles 6 containing silica as a main component are dispersed.

  A dispersion of silica particles used for forming the porous layer 3 is prepared by diluting a dispersion of silica particles prepared by a wet method such as a sol-gel method or a hydrothermal method with water or a solvent, or a similar dispersion. It is prepared by a method in which the solvent is replaced with a desired solvent by distillation or ultrafiltration, or a method in which silica particles synthesized by a dry method such as fumed silica are dispersed in water or a solvent by ultrasonic waves or a bead mill.

  The binder added to bond the silica particles is preferably an organic silane compound. A preferred example of the organic silane compound is a silicon oxide oligomer obtained by hydrolyzing and condensing a silicate ester.

  The silicon oxide oligomer is prepared by mixing a silicon oxide oligomer solution prepared in advance in water or a solvent with a dispersion of silica particles, or a method of mixing the raw material of the silicon oxide oligomer with the dispersion of silica particles and then converting the mixture into the silicon oxide oligomer. Is mentioned. The silicon oxide oligomer is prepared by adding water, an acid, or a base to a silicate ester such as methyl silicate or ethyl silicate in a solvent or a dispersion, followed by hydrolysis and condensation. Acids that can be used for hydrolytic condensation of silicate esters include hydrochloric acid, nitric acid, methanesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, phosphoric acid, p-toluenesulfonic acid, and the like. Is selected in consideration of solubility in a solvent and reactivity of a silicate ester. When preparing the binder solution, heating at a temperature of 80 ° C. or less is also possible.

  The weight average molecular weight of the silicon oxide condensate contained in the binder solution is preferably 500 or more and 3000 or less in terms of polystyrene. When the weight average molecular weight is 500 or more, generation of cracks after curing can be suppressed, and the stability of a binder solution as a coating material can be maintained. When the weight average molecular weight is 3,000 or less, an increase in the viscosity of the binder solution can be suppressed, so that the voids inside the binder tend to be uniform.

In order to make dH ₂ O 25 nm or more and 75 nm or less, it is necessary to introduce a hydrophobic functional group on the surface of the pore. Examples of such a method include a method of introducing silica particles during synthesis, a method of introducing silica particles after synthesis, and a method of introducing silica particles into the surface of pores after film formation.

  Examples of the treating agent used when introducing the hydrophobic functional group include organic silane compounds, for example, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, Ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, benzyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, diethoxymethylphenylsilane, allyltriethoxysilane , Vinyltriethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, hexamethyldisilazane, etc. Alkoxysilanes having a substituted alkyl group, a phenyl group, a vinyl group and the like; chlorosilanes such as trimethylchlorosilane and diethyldichlorosilane, and the like, preferably methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane An organic silane compound having a hydrophobic functional group having 1 to 3 carbon atoms such as silane, hexamethyldisilazane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, and propyltriethoxysilane is used. When the number of carbon atoms in the hydrophobic functional group is 1 to 3, the pore surface is likely to change from hydrophobic to hydrophilic due to a change in humidity.

The solvent that can be used for the dispersion of silica particles may be any solvent in which the raw materials are uniformly dissolved and the reactants do not precipitate. For example, 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 And monohydric alcohols such as 1-heptanol, 2-heptanol, 1-octanol and 2-octanol. Dihydric or higher alcohols such as ethylene glycol and triethylene glycol. Methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ether alcohols such as 1-propoxy-2-propanol, dimethoxyethane, diglyme, Ethers such as tetrahydrofuran, dioxane, diisopropyl ether, dibutyl ether and cyclopentyl methyl ether. Esters such as ethyl formate, 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 and cyclohexanone. Various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, and tetrachloroethane. Non-protonic polar solvents such as N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, ethylene carbonate and the like are preferable, and 1-methoxy-2-propanol, 1-ethoxy is preferable. Branched structure having 5 to 7 carbon atoms such as -2-propanol, 1-propoxy-2-propanol, 1-butoxy-2-propanol, 2-isopropoxyethanol, 3-methoxy-1-butanol, methyl lactate and ethyl lactate Use alcohol with. Due to the steric hindrance of the alcohol having a branched structure having 5 to 7 carbon atoms, a part of the hydroxyl groups on the surface of the silica particles remains without reacting with the organosilane compound, so that the surface density of the hydrophobic functional group can be easily controlled. Can be As the chain length (carbon number) of an alcohol having a branched structure having 5 to 7 carbon atoms increases, the boiling point of the solvent increases. Therefore, a high drying temperature and / or a sintering temperature is required to vaporize the alcohol, and depending on the base material on which the porous layer 3 is formed, the porous layer 3 may be damaged by the high temperature, causing deformation or discoloration. Therefore, as the alcohol having a branched structure having 5 to 7 carbon atoms, a solvent having a lower boiling point is preferable. However, if the boiling point is too low, voids are widened due to rapid vaporization of the solvent, and dN ₂ exceeds 20 nm, which causes a problem that it is difficult for the porous layer to secure a sufficient amount of moisture absorption. Although the dispersibility of the silica particles may decrease depending on the surface density of the hydrophobic functional group, it is considered that the dispersibility can be maintained by using an alcohol having a branched structure having 5 to 7 carbon atoms. The solvent may be used as a mixture of two types.

  Examples of a method for applying the dispersion for forming the porous layer 3 on a substrate include a spin coating method, a spraying method, a blade coating method, a roll coating method, a slit coating method, a printing method and a dip coating method. Can be When manufacturing a member having a three-dimensionally complicated shape such as a concave surface, a spin coating method or a spraying method is preferred from the viewpoint of uniformity of the layer thickness.

  After applying the dispersion to form the porous layer 3, drying and curing are performed. Drying and curing are steps for removing the solvent and for promoting the reaction between the silicon oxide binders or between the silicon oxide binder and the silica particles. The drying and curing temperature is preferably from 20 ° C to 200 ° C, more preferably from 60 ° C to 150 ° C. If the drying and curing temperature is lower than 20 ° C., the solvent remains and the abrasion resistance decreases. On the other hand, when the drying and curing temperature exceeds 200 ° C., the curing of the binder proceeds excessively, and the binder is liable to crack. The drying and curing time is preferably from 5 minutes to 24 hours, more preferably from 15 minutes to 5 hours. If the drying and curing time is less than 5 minutes, the solvent partially remains and the film becomes partially cloudy. If the drying and curing time is more than 24 hours, the layer easily cracks.

(Application example)
As an example in which the member according to the present invention is suitably used, an example in which the member is used as a protective cover of an imaging device will be described. FIG. 5 shows an outline of a configuration example of the imaging apparatus.

  The imaging device 30 has an internal space surrounded by a protective cover 31 which is a member according to the present invention and a housing 37, and a lens 32, an image sensor 33, a video engine 34, a compression output A circuit 35 is arranged, and an output unit 36 is provided inside or outside the space.

  An image incident from the outside is guided to the image sensor 33 by the protective cover 31 and the lens 32, and is converted into a video analog signal (electric signal) by the image sensor 33 and output. The video analog signal output from the image sensor 33 is converted into a video digital signal by a video engine 34, and the video digital signal output from the video engine 34 is compressed by a compression output circuit 35 into a digital file. In the process of converting the video analog signal into the video digital signal, the video engine 34 may perform processing for adjusting the image quality such as luminance, contrast, color correction, and noise removal. The signal output from the compression output circuit 35 is output from the output unit 36 to an external device via wiring and / or a network.

  The protective cover 31 has a configuration in which a porous layer 312 is provided on at least one surface of the base material 311. In the configuration example of the imaging device illustrated in FIG. 5, the surface on which the porous layer 312 is provided is a housing. It is installed so as to be on the inner space side of 37. The base material 311 is a transparent member that transmits an image incident on the image sensor 33. Here, "transparent" means that the light transmittance in the visible light region is 70% or more.

  According to such a configuration, in the internal space surrounded by the protective cover 31 and the housing 37, the ingress and egress of air between the outside and the outside are restricted, and following the temperature change of the outside environment is delayed. . For example, if the temperature of the outside suddenly drops, the temperature of the protective cover 31 located at the boundary between the outside and the inside of the housing 37 may be lower than the dew point temperature inside the housing. In such a case, if the protective cover 31 does not have the anti-fogging function, water drops adhere to the surface of the protective cover 31 inside the housing 37, and fogging occurs. However, in the case of the protective cover 31 according to the present invention, even if the temperature of the protective cover 31 becomes lower than the dew point temperature inside the housing 37, moisture inside the housing is adsorbed inside the holes of the porous layer 312. . Therefore, water droplets that cause fogging are not formed on the surface of the protective cover 31, and fogging can be suppressed.

  As a modification of FIG. 5, the porous layer 312 may not be provided on the surface of the protective cover 31, and the porous layer 312 may be provided on the inner wall using the inner wall of the housing 37 as a base material. As in the case where the protective cover is provided, the fogging of the lens can be suppressed. Further, a porous layer 312 may be provided on the inner wall of the housing 37 in addition to the surface of the protective cover 31. According to such a configuration, the moisture inside the housing can be absorbed by the porous layer 312 provided on the surface of the protective cover 31 and the inner wall of the housing 37, so that clouding of the lens can be further suppressed. it can.

  A case in which an anti-reflection layer or an anti-reflection structure is provided on the inner wall of the housing 37 in order to suppress the light incident through the protective cover 31 from being reflected on the inner wall of the housing 37 and deteriorating the image. There are many. Therefore, when the configuration of the present invention is used for the inner wall of the housing 37, the absorption of moisture below 90% RH can be suppressed and the change in the refractive index of the porous layer 312 can be reduced. (90% RH or more), which is preferable because the amount of moisture absorption can be secured.

  The imaging device 30 includes a pan / tilt for adjusting the angle of view, a controller for controlling imaging conditions and the like, a storage device for storing the acquired video data, a transfer unit for transferring data output from the output unit 36 to the outside, and the like. An imaging system can be configured.

  Hereinafter, the present invention will be described specifically with reference to examples. However, the present invention is not limited by the following examples unless it exceeds the gist.

(1) Preparation of Particle Dispersion (Preparation of Silica Particle Dispersion 1)
In a mixed solution A consisting of 750 g of pure water, 138 g of 25% aqueous ammonia, and 4112 g of 1-propoxy-2-propanol, an ammonia concentration of 0.69 wt%, 375 g of tetramethoxysilane, 125 g of 1-propoxy-2-propanol, and a hydrophobic functional group A mixed solution B consisting of 37 g of methyltriethoxysilane as a treating agent was added dropwise with stirring over 30 minutes while maintaining the temperature at 10 ° C. After the dropwise addition, the mixture was stirred at 50 ° C. for 5 hours to prepare a sol solution. The particle solution was heated and concentrated under reduced pressure, and the concentrated solution was passed through an ion exchange resin (Amberlite IR120B HAG manufactured by Organo Co., Ltd.) to remove ammonia, and the pH of the sol solution was adjusted to 8 or less. Thereafter, distillation was continued while 1-propoxy-2-propanol was added dropwise until the water content became 1% or less, and filtration was performed using a 3 μm membrane filter to prepare a silica particle dispersion 1 having a solid content concentration of 15 wt%.

(Preparation of silica particle dispersion liquid 2)
A silica particle dispersion 2 was prepared in the same manner as the silica particle dispersion 1, except that the hydrophobic functional group treating agent of the mixture B was propyltriethoxysilane and 22 g was added.

(Preparation of silica particle dispersion 3)
Silica particle dispersion 3 was prepared in the same manner as silica particle dispersion 1, except that 25 g of dimethyldimethoxysilane was used as the hydrophobic functional group treating agent of mixture B.

(Preparation of silica particle dispersion liquid 4)
Silica particle dispersion liquid 4 was prepared in the same manner as silica particle dispersion liquid 1 except that 185 g of 25% aqueous ammonia and 4065 g of 1-propoxy-2-propanol were used so that the ammonia concentration of mixed liquid A was 0.92 wt%. Was prepared.

(Preparation of silica particle dispersion 5)
Silica particle dispersion liquid 5 was prepared in the same manner as silica particle dispersion liquid 1 except that 111 g of 25% aqueous ammonia and 4139 g of 1-propoxy-2-propanol were used so that the ammonia concentration of mixed liquid A was 0.56 wt%. Was prepared.

(Preparation of silica particle dispersion 6)
Using a 2-propanol (IPA) dispersion liquid of chain silica particles (IPA-ST-UP (registered trademark) manufactured by Nissan Chemical Industries, Ltd., particle diameter 12 nm; BET method, solid content concentration 15 wt%) using an evaporator. -Propanol was distilled off and replaced with 1-propoxy-2-propanol to prepare 1212 g of a 1-propoxy-2-propanol dispersion of solid silica particles (solid content concentration: 33 wt%).

  548 g of 1-propoxy-2-propanol and 907 g of ethyl lactate were added to a dispersion of 1-propoxy-2-propanol of the chain silica particles, and the mixture was stirred for 10 minutes. 27 g of an aqueous solution was added, and the mixture was stirred in an oil bath at 50 ° C. for 5 hours to prepare a silica particle dispersion 6 having a solid content of 15 wt%.

(Preparation of silica particle dispersion liquid 7)
192 g of 25% ammonia water and 4058 g of 1-propoxy-2-propanol so that the ammonia concentration of the mixed solution A becomes 0.96 wt%, and when the mixed solution B is dropped into the mixed solution A, the temperature is maintained at 50 ° C. Except for the above, a silica particle dispersion 7 was prepared in the same manner as the silica particle dispersion 1.

(Preparation of silica particle dispersion liquid 8)
A silica particle dispersion 8 was prepared in the same manner as the silica particle dispersion 1, except that the hydrophobic functional group treating agent was not added.

(Preparation of silica particle dispersion liquid 9)
A silica particle dispersion 9 was prepared in the same manner as the silica particle dispersion 1, except that the hydrophobic functional group treating agent of the mixture B was changed to propyltriethoxysilane and 43 g was added.

(Preparation of silica particle dispersion liquid 10)
Silica particle dispersion 10 was prepared in the same manner as silica particle dispersion 3 except that 192 g of 25% ammonia water and 4058 g of 1-propoxy-2-propanol were used so that the ammonia concentration of mixture A was 0.96 wt%. Was prepared.

(Preparation of silica particle dispersion liquid 11)
Silica particle dispersion liquid 11 was prepared in the same manner as silica particle dispersion liquid 1, except that 105 g of 25% aqueous ammonia and 4145 g of 1-propoxy-2-propanol were used so that the ammonia concentration of mixed liquid A became 0.52 wt%. Was prepared.

(2) Creation of member (Example 1)
In Example 1, an appropriate amount of the silica particle dispersion liquid 1 was dropped on a flat glass substrate (S-BSL7, nd = 1.52, manufactured by OHARA) having a diameter of 30 mm, spin-coated at 1000 rpm for 30 seconds, and then heated in a hot air circulating oven at 140 ° C. By baking for 30 minutes at, the member of Example 1 was produced. The thickness of the porous layer of the member of Example 1 was 2.6 μm.

(Examples 2 to 6 and Comparative Examples 1 to 5)
Members of Examples 2 to 6 and Comparative Examples 1 to 5 were prepared in the same manner as in Example 1 except that the silica particle dispersion 1 was changed to the silica particle dispersion shown in Table 1. Table 1 shows the thickness of the porous layers of the members of Examples 2 to 6 and Comparative Examples 1 to 5.

(3) Evaluation The members obtained in the examples and comparative examples were evaluated by the following methods. The results are shown in Table 1.

(3-1) Measurement of dN ₂ Nitrogen adsorption isotherm at −196 ° C. was measured using an automatic vapor adsorption measuring device (BELSORP-MAX manufactured by Bell Japan Co., Ltd.), and the differential pore distribution was obtained by the BJH method. . In the obtained differential pore distribution, the pore diameter at the time when the differential pore volume was the maximum was defined as dN ₂ .

(3-2) Measurement of dH ₂ O The adsorption isotherm at 25 ° C. was measured using an automatic vapor adsorption amount measuring device (BELSORP18 manufactured by Nippon Bell Co., Ltd.), and the differential pore distribution was obtained by the BJH method. In the obtained differential pore distribution, the pore diameter at the time when the differential pore volume became maximum was defined as dH ₂ O.

(3-3) Measurement of pore volume Nitrogen adsorption isotherm at -196 ° C was measured using an automatic vapor adsorption measuring device (BELSORP-MAX manufactured by Japan Bell Co., Ltd.), and the pore volume was determined by the BJH method. .

(3-4) Measurement of average particle diameter Using an automatic vapor adsorption amount measuring apparatus (BELSORP-MAX manufactured by Bell Japan Co., Ltd.), the nitrogen adsorption isotherm at -196 ° C was measured, and the specific surface area A (m ² / G). Thereafter, the average particle diameter and the density of silicon oxide constituting the inorganic particles are set to d (nm) and 202 (g / cm ³ ), respectively, and the average particle diameter (BET particle diameter) by the BET method is calculated from the following equation (2). Was.
d = 6000 / (A × 2.2) (2)

(3-5) Evaluation of Contact Angle Using a fully automatic contact angle meter (DM-701, manufactured by Kyowa Interface Science Co., Ltd.), the contact angle at the time of contacting a 2 μl droplet of pure water in an environment of 23 ° C. and 40% RH. It was measured.

(3-6) Measurement of Refractive Index After the members were allowed to stand for 1 hour in an environment at a temperature of 25 ° C. and a humidity of 60, 80, 90, and 95% RH, a reflectometer (manufactured by Ushio Inc.) under each humidity was used. The reflectance was measured using URE-50). The refractive index at a wavelength of 550 nm was determined from the reflectance data using analysis software (WVASE manufactured by JA Woollam). From the obtained refractive index, the change in the refractive index was evaluated according to the following criteria.
A: The difference in refractive index between the members at a humidity of 60% RH and 95% RH is less than 0.015. B: The difference in the refractive index at a humidity of 60% RH and 90% RH is less than 0.015, and the humidity is 60%. Difference in refractive index between RH and 95% RH is 0.015 or more C: Difference in refractive index between 60% RH and 90% RH is 0.015 or more

(3-7) Evaluation of antifogging property The amount of moisture absorption when the relative humidity was changed from 60% RH to 98% RH was measured using an automatic vapor adsorption amount measuring device (BELSORP18 manufactured by Bell Japan Co., Ltd.). The obtained moisture absorption was evaluated based on the following criteria.
A: 350 (cm ³ / g) or more B: 250 (cm ³ / g) or more and less than 350 (cm ³ / g) C: less than 250 (cm ³ / g)

(Evaluation of Examples and Comparative Examples)
From the comparison of the evaluation results of the members of Examples 1 to 6, when dH ₂ O is 25 nm or more and 75 nm or less, the change in the refractive index can be reduced by suppressing the moisture absorption below the humidity of 90% RH. It can be seen that moisture can be absorbed and a sufficient amount of moisture can be secured. It was also found that the larger the dH ₂ O, the more the change in the refractive index can be reduced. On the other hand, it can be seen that the member of Comparative Example 1 cannot secure a moisture absorption amount because dH ₂ O is larger than 75 nm. In addition, since the member of Comparative Example 2 has dH ₂ O of less than 25 nm, it can be seen that the change in the refractive index at high humidity (60% RH or more and less than 90% RH) is large.

  From the comparison of the evaluation results of the members of Example 3 and Comparative Example 3, when the contact angle is 60 ° or more, water molecules penetrating into the inside of the layer are greatly reduced, so that the member of Comparative Example 3 can secure the moisture absorption. It can be seen that the antifogging property was poor.

From a comparison of the evaluation results of the members of Example 4 and Comparative Example 4, it can be seen that when dN ₂ is 20 nm or more, water vapor hardly aggregates in the pores in the porous layer, and the moisture absorption decreases. From the comparison of the evaluation results of the members of Example 5 and Comparative Example 5, when dN ₂ is 5 nm or less, moisture is absorbed at low humidity (less than 60% RH), so that the pores in the porous layer are buried. It can be seen that the amount of moisture absorption cannot be secured at high humidity (60% RH or more and less than 90% RH).

From the evaluation results of the member of Example 6, it was found that dN ₂ was 5 nm or more and 20 nm or less, the contact angle was less than 60 °, and dH ₂ O was 25 nm or more and 75 nm by introducing a hydrophobic functional group into the chain particles. It can be seen that the following can be performed. In the member of Example 6, since dN ₂ , dH ₂ O, and the contact angle are in the above ranges, the change in the refractive index and the maintenance of the moisture absorption at high humidity (60% RH or more and less than 90% RH) can be achieved. You can see what you can do.

  From the above, it was shown that the member of the example having the porous layer satisfying the requirements of the present invention was superior to the member of the comparative example in reducing the change in the refractive index and maintaining the moisture absorption.

  The members of the present invention can be used for general purposes such as window glass, mirrors, lenses, and transparent films, and for optical lenses, optical mirrors, optical filters, eye filters, eyepieces, outdoor cameras and surveillance cameras for imaging and projection systems. It can be preferably used for optical parts such as covers.

Reference Signs List 1 member 2 base material 3 porous layer 4 inorganic substance 5 pore 6 inorganic particle

Claims (13)

A member having a base material and a porous layer on at least one surface of the base material, wherein the porous layer is vacant when a differential pore volume is maximized in a differential pore distribution in nitrogen adsorption. The pore diameter dN ₂ is 5 nm or more and 20 nm or less, the pore diameter dH ₂ O when the differential pore volume is maximum in the differential pore distribution in water vapor adsorption is 25 nm or more and 75 nm or less, and the contact angle with water is less than 60 °. A member, characterized in that: The member according to claim 1, wherein the pore volume is 0.37 cm ³ / g or more.   The member according to claim 1, comprising silica particles.   The member according to claim 3, wherein the silica particles are chain silica particles. A housing,
A protective cover,
An image sensor arranged in an internal space surrounded by the housing and the protective cover,
An imaging device comprising:
The protective cover has a base material and a porous layer on the surface of the base material on the inner space side,
The porous layer, differential pore volume in the differential pore distribution in nitrogen adsorption is less than 20nm pore diameter dN ₂ is 5nm or more when the maximum, maximum differential pore volume in the differential pore distribution in water vapor adsorption Wherein the pore diameter dH ₂ O is 25 nm or more and 75 nm or less, and the contact angle with water is less than 60 °. The pore volume of the porous layer is characterized in that it is 0.37 cm 3 / ^g or more, the image pickup apparatus according to claim 5.   The imaging device according to claim 5, wherein the porous layer includes silica particles.   The imaging device according to claim 7, wherein the silica particles are chain silica particles. An organic silane compound having a hydrophobic functional group, and silica particles, and a step of preparing a silica particle dispersion containing the solvent in a solvent,
On the substrate or on another layer formed on the substrate, coated with the silica particle dispersion,
A step of forming a coating film of the silica particle dispersion,
Drying the coating film,
Including
The average particle diameter of the silica particles is 8 nm or more and 25 nm or less,
_2. The member according to claim 1, wherein the silica particle dispersion contains the silane compound having the hydrophobic functional group in an amount of 1 wt% or more and 30 wt% or less in terms of SiO _{2 with} respect to the silica particles. 3. Method.   The method according to claim 9, wherein the silica particles are chain silica.   The method according to claim 9, wherein the silica particle dispersion further includes a binder.   The method according to any one of claims 9 to 11, wherein the silica particle dispersion further contains an alcohol having a branched structure having 5 to 7 carbon atoms.   The method according to claim 12, wherein the alcohol having a branched structure having 5 to 7 carbon atoms is 1-propoxy-2-propanol.

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