JP2020166245A - Optical member, optical device, and coating liquid - Google Patents

Abstract

To provide an optical member with a low-scattering and mechanically strong porous layer.SOLUTION: An optical member is provided, having a porous layer, comprising a plurality of silicon oxide particles bound by an inorganic binder, provided on a substrate, and containing a fluorine-containing organic acid having 5 to 11 fluorine atoms, inclusive, in one molecule.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical member having an antireflection film having low scattering and excellent film strength, an optical device using the optical member, and a coating liquid for forming the antireflection film.

Conventionally, in order to suppress reflection at the light input / output interface of an optical member, it has been known to form an antireflection layer in which a single layer or a plurality of layers are laminated with a thickness of several tens to several hundreds nm of optical films having different refractive indexes. Has been done. In order to form these antireflection layers, a vacuum film forming method such as vapor deposition or sputtering or a wet film forming method such as dip coating or spin coating is used.

The material used for the outermost layer of the antireflection layer is a transparent material with a low refractive index, such as inorganic materials such as silica, magnesium fluoride, and calcium fluoride, and organic materials such as silicone resin and amorphous fluororesin. Is known to be used.

In recent years, in order to keep the reflectance lower, the refractive index has been reduced to 1.3 or less by forming voids in a layer such as silica or magnesium fluoride to include a region of air (refractive index 1.0). The development of a low refractive index layer that has been reduced to the above is in progress. A method of applying / drying a dispersion of silicon oxide particles is widely used for forming a low refractive index layer containing voids inside.

On the other hand, when silica particles are used for the optical member, it is known that problems occur in transparency and appearance. This is because the silica particles have a poor affinity with the organic solvent or the organic polymer to be mixed, and agglomerate during coating to generate scattering. Patent Document 1 discloses a method of forming a film with a coating material containing no organic polymer and suppressing aggregation to form a non-scattering porous layer in order to solve this problem.

JP-A-2009-73170

However, the porous layer described in Patent Document 1 does not contain a binder typified by an organic polymer in order to suppress scattering. The porous layer provided on the surface of the optical member as an antireflection film is required to have a low refractive index and transparency, while also being required to have strength as a film. Therefore, the film strength of the film not containing the binder is insufficient, and there is a problem that both low scattering and film strength cannot be achieved at the same time.

The present invention has been made in view of the above, and an optical member provided with a porous layer having low scattering and excellent film strength, an optical device using the optical member, and a coating liquid for forming the porous layer are provided. It is to provide.

The optical member for solving the above problems has a porous layer on a base material, and the porous layer has silicon oxide particles and an inorganic binder, and has a fluorine-containing organic acid.
Further, the coating liquid according to the present invention is a coating liquid for forming a porous layer, and contains silicon oxide particles, an inorganic binder and an organic solvent, and the silicon oxide particles are fluorine-containing organic on the surface. It is characterized by having an acid.

According to the present invention, it is possible to provide a porous layer having low scattering and excellent film strength, an optical device using the porous layer, and a coating liquid for forming the porous layer.

It is the schematic which shows one Embodiment of the optical member of this invention. It is the schematic which shows one Embodiment of the optical member of this invention. It is the schematic which shows one Embodiment of the optical member of this invention. It is the schematic which shows one Embodiment of the image pickup apparatus as an example of the optical apparatus of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.
(Porous layer)
FIG. 1 is a schematic view showing an embodiment of the optical member of the present invention. In the figure, the optical member 1 according to the present invention is an optical member 1 in which a porous layer 3 is formed as an antireflection film on a base material 2. The porous layer 3 has silicon oxide particles 4 and an inorganic binder 5. The silicon oxide particles 4 have a fluorine-containing organic acid 7 on the surface. Further, it is preferable that the silicon oxide particles 4 form a layer formed by stacking a plurality of layers on the surface of the base material 2.

2 and 3 are schematic views showing a partially enlarged state of the porous layer 3 of the optical member of the present invention. FIG. 2 shows a case where the silicon oxide particles 4 are hollow silicon oxide particles, and FIG. 3 shows a case where the silicon oxide particles 4 are made of chain silicon oxide particles (silicon oxide particle conjugate). As shown in FIGS. 2 and 3, the silicon oxide particles 4 constituting the porous layer 3 are bound to each other by an inorganic binder 5, and the porous layer 3 has a plurality of silicon oxide particles 4 among the plurality of silicon oxide particles 4. It contains a void 6. The porous layer 3 contains a fluorine-containing organic acid 7 in which the number of fluorine atoms in one molecule is 5 or more and 11 or less.

The porous layer 3 composed of the silicon oxide particles 4 is formed by stacking a plurality of silicon oxide particles 4 aligned on the surface of the base material 2.

In order to obtain the porous layer 3 having low scattering and excellent film strength, it is preferable that the silicon oxide particles 4 have a well-arranged arrangement. The difference in the arrangement of the silicon oxide particles 4 mainly changes depending on the dispersed state of the silicon oxide particles 4 in the coating liquid forming the porous layer 3 and the dispersed state of the silicon oxide particles 4 at the time of forming the coating film.

When the silicon oxide particles 4 in the coating liquid are not affected by the dispersion medium or the inorganic binder 5 and are sufficiently dispersed, the silicon oxide particles 4 are likely to be arranged. However, if the silicon oxide particles 4 are dispersed in a slightly aggregated state due to the influence of the dispersion medium and the inorganic binder 5, the arrangement property deteriorates.

Further, the volatilization and drying of the solvent when the coating liquid is applied onto the base material 2 to form the coating film, and the flow of the silicon oxide particles 4 due to concentration also greatly affect the arrangement. Even if the dispersed state of the silicon oxide particles 4 in the coating liquid is good, if the silicon oxide particles 4 aggregate during the drying of the coating film formation, the arrangement of the silicon oxide particles 4 is disturbed, and when the coating film is formed. The gap between the silicon oxide particles 4 becomes large, and the void in the substrate surface direction becomes large. Therefore, the scattering becomes large in visible light. Further, since the silicon oxide particles 4 are formed in a shifted state rather than in an aligned and deposited state, the stress distribution of the coating film becomes non-uniform and the strength of the film cannot be sufficiently maintained.

As described above, by using the silicon oxide particles 4 having the fluorine-containing organic acid 7 added to the surface, the porous silicon oxide particles 4 of the present invention are arranged and deposited without disturbing the arrangement of the silicon oxide particles 4. A coating film to be layer 3 can be formed.

The fluorine-containing organic acid 7 not only improves the dispersibility of the silicon oxide particles 4 in the coating liquid, but also coats the silicon oxide particles 4 while maintaining the aligned and deposited state at the time of forming the coating film. It is possible to form a film, and it is possible to realize a porous layer 3 having low scattering and excellent film strength.

The fluorine-containing organic acid 7 contained in the coating liquid or the porous layer 3 can be obtained by elemental analysis in silicon oxide particles or the porous layer, separation and quantitative analysis of the organic acid by ion exclusion chromatography or the like.

Examples of the fluorine-containing organic acid 7 suitable for the present invention include 2,2,3,3-tetrafluoropropionic acid, pentafluoropropionic acid, heptafluorobutyric acid, nonafluorovaleric acid, undecafluorohexanoic acid, and dodecafluorosveric acid. Examples include tridecafluoroheptanic acid.

The fluorine-containing organic acid 7 is preferably an organic acid having a fluorine atom number in one molecule (hereinafter, may be simply referred to as a fluorine number) of 5 or more and 11 or less. When the porous layer 3 contains an organic acid having 5 or more and 11 or less fluorine atoms in one molecule, low scattering and excellent film strength can be realized.
If the number of fluorines is less than 5, the dispersibility of the silicon oxide particles 4 in the coating liquid can be improved, but the reaction promotion between Si—OH is insufficient, so that oxidation during coating film formation It is difficult to form a coating film in a state where the silicon particles 4 are aligned and deposited, and the scattering tends to be aggravated. If the number of fluorines exceeds 11, the coatability of the coating liquid and the stability over time deteriorate, and the appearance quality of the obtained porous layer 3 may deteriorate. On the other hand, when the number of fluorines exceeds 11, the repulsive force of the CF group becomes too large, and the silicon oxide particles 4 at the time of forming the coating film are not uniformly arranged, and the scattering and the film strength tend to deteriorate.

Examples of the shape of the silicon oxide particles 4 include a true sphere, a cocoon shape, a bale shape, a disk shape, a rod shape, a needle shape, a square shape, and a chain shape. Among them, hollow silicon oxide particles which are hollow particles having pores inside and shells around the outside of the pores as shown in FIG. 2 and chains which are hydrophilic particle conjugates as shown in FIG. It is preferably composed of silicon oxide particles (chain particles).

The hollow silicon oxide particles can lower the refractive index of the porous layer 3 by the air (refractive index 1.0) contained in the pores. The pores may be either single pores or porous, and can be appropriately selected. As a method for producing the hollow silicon oxide particles, for example, it can be produced by the method described in JP-A-2001-233611, JP-A-2008-139581, and the like. The hollow silicon oxide particles make it possible to reduce the refractive index of a layer formed by stacking a plurality of layers of silicon oxide particles 4 aligned in a direction parallel to the surface of the base material 2.

The inorganic binder 5 in the present invention is preferably a silicon oxide binder.

(Coating liquid that forms a porous layer)
The coating liquid according to the present invention is a coating liquid that forms the porous layer 3, and contains silicon oxide particles 4 having a fluorine-containing organic acid 7 on the surface, an inorganic binder 5, and an organic solvent.

The organic solvent that can be used in the coating liquid may be any solvent that does not cause silicon oxide particles to precipitate or the coating liquid to rapidly thicken. Specifically, for example, the following solvents can be mentioned. 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, Monohydric alcohols such as 1-heptanol, 2-heptanol, 1-octanol and 2-octanol. Divalent or higher alcohols such as ethylene glycol and triethylene glycol. Ether alcohols such as methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol, dimethoxyethane, diglime ( Ethers such as diethylene glycol dimethyl ether), tetrahydrofuran, dioxane, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether. Esters such as ethyl formate, ethyl acetate, n-butyl acetate, methyl lactate, ethyl lactate, 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, tetrachloroethane. Aprotic polar solvents such as N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, ethylene carbonate and the like. Of these solvents, two or more kinds of solvents can be mixed and used.

From the viewpoint of dispersibility and coatability of the silicon oxide particles 4, the solvent contained in the coating liquid is preferably a water-soluble solvent in which 30% or more has a hydroxyl group having 4 or more and 6 or less carbon atoms. Among them, one or more selected from ethoxyethanol, propoxyethanol, isopropanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propanol-2-propanol, and ethyl lactate are included. Solvents are particularly preferred.

A fluorine-containing organic acid having a fluorine number of 5 or more and 11 or less in one molecule is added to the surface of the silicon oxide particles 4. More specifically, a fluorine-containing organic acid is added to some OH groups existing on the surface of the silicon oxide particles 4. In the silicon oxide particles 4 contained in the coating liquid, the distance between the silicon oxide particles 4 is maintained by the fluorine-containing organic acid 7 added to the surface thereof, aggregation is suppressed, and the dispersibility is improved. Then, at the time of forming the coating film, the state in which the silicon oxide particles 4 are aligned and deposited is maintained by the fluorine-containing organic acid, so that the porous layer 3 having low scattering and excellent film strength can be obtained.

The fluorine-containing organic acid 7 is preferably contained in the range of 0.1 phr or more and 8 phr or less, and more preferably 0.2 phr or more and 2.0 phr or less with respect to silicon oxide. Here, "phr" represents a part by weight of the fluorine-containing organic acid with respect to the weight of silicon oxide of 100. When the fluorine-containing organic acid 7 is contained in a range less than 0.1 phr with respect to silicon oxide, the silicon oxide particles 4 at the time of forming the coating film may be aligned and deposited to form a coating film. Scattering worsens because it cannot be done sufficiently. Further, due to the influence of the dispersion medium and the binder, the dispersion stability of the silicon oxide particles 4 in the coating liquid deteriorates, which may cause the coating liquid to thicken or gel over time. When the fluorine-containing organic acid 7 is contained in a range of more than 8 phr with respect to silicon oxide, the silicon oxide particles 4 are likely to be densely clogged, and the voids 6 are reduced, so that the refractive index of the coating film itself is likely to increase. Become.

The acid dissociation constant of the fluorine-containing organic acid 7 is preferably 0 pKa or more and 0.5 pKa or less, and more preferably 0.1 pKa or more and 0.3 pKa or less. When the acid dissociation constant is smaller than 0 pKa, the arrangement of the silicon oxide particles 4 at the time of forming the coating film is disturbed, and the scattering tends to be deteriorated. When the acid dissociation constant is larger than 0.5 pKa, the strength of the coating film is lowered, so that linear scratches are likely to occur when the coating film is wiped off, and the appearance quality of the obtained porous layer 3 is slightly poor. May become.

The molecular weight of the fluorine-containing organic acid 7 is preferably 100 or more and 360 or less. If the molecular weight is less than 100, the scattering tends to worsen. If the molecular weight is larger than 360, the stability of the coating liquid over time may deteriorate.

When the silicon oxide particles 4 are hollow silicon oxide particles, the average particle diameter is preferably 15 nm or more and 100 nm or less, preferably 15 nm or more and 60 nm or less. When the average particle size of the hollow silicon oxide particles is less than 15 nm, it is difficult to stably produce the core particles necessary for producing the hollow particles, and it is difficult to produce the hollow silicon oxide particles themselves. Further, when the average particle diameter of the hollow silicon oxide particles exceeds 100 nm, the size of the voids 6 between the hollow silicon oxide particles becomes large, so that large voids are likely to occur, and scattering due to the size of the hollow silicon oxide particles occurs. Therefore, it is not preferable.

Here, the average particle size of the hollow silicon oxide particles is the average ferret diameter. The average ferret diameter can be measured by image processing of a plurality of hollow silicon oxide particles contained in the coating liquid observed by a transmission electron microscope image. As the image processing method, a commercially available image processing such as image Pro PLUS (manufactured by Media Cybernetics) can be used. In a predetermined image region, if necessary, the contrast is adjusted as appropriate, the average ferret diameter of each particle is measured by particle measurement, and the average value can be calculated and obtained.

The thickness of the shell of the hollow silicon oxide particles is preferably 10% or more and 50% or less, preferably 20% or more and 35% or less of the average particle diameter. If the thickness of the shell is less than 10%, the strength of the particles is insufficient, which is not preferable. Further, if the thickness of the shell exceeds 50%, the hollow effect does not appear remarkably in the refractive index, which is not preferable.

Next, a case where the silicon oxide particles 4 are chain silicon oxide particles will be described. The chain silicon oxide particles are secondary particles in which a plurality of solid silicon oxide particles, which are primary particles, are connected in a straight line or while being bent. The size of the chain silicon oxide particles can be represented by a minor axis and a major axis.

The minor axis of the chain silicon oxide particles corresponds to the thickness of the chain silicon oxide particles, that is, the average particle size of one primary particle constituting the chain silicon oxide particles, and is a chain shape extracted from the coating liquid. It can be calculated from the specific surface area obtained by the nitrogen adsorption method for the silicon oxide particles. The average minor axis of the chain silicon oxide particles is preferably 8 nm or more and 20 nm or less. If the minor axis is less than 8 nm, the surface area of the silicon oxide particles 4 increases too much, and the possibility of reliability deterioration due to the uptake of moisture and chemical substances in the atmosphere increases. Further, if the average minor diameter exceeds 20 nm, the dispersion in the solvent becomes unstable and there is a concern that the coatability deteriorates.

On the other hand, the major axis of the chain silicon oxide particles corresponds to the length of the secondary particles, that is, the average particle diameter of the conjugate, and can be obtained by a dynamic light scattering method. The major axis of the chain silicon oxide particles is preferably 4 times or more and 8 times or less the minor axis. If the major axis is less than 4 times the minor axis, the refractive index may not decrease sufficiently when the film is formed, and if it exceeds 8 times, the coatability and leveling property deteriorate due to thickening, making it difficult to form the film. Become.

The shape of the primary particles constituting the chain silicon oxide particles may be in a state where they can be clearly observed or in a state where the particles are fused to each other and lose their shape, but the shape of each primary particle is clear. It is preferable that the particles can be observed. The individual primary particles constituting the chain silicon oxide particles may be spherical, cocoon-shaped, or bale-shaped. The particles are preferably cocoon-shaped or bale-shaped, and more preferably particles having a minor axis of 8 nm or more and 20 nm or less and a major axis of 1.5 times or more and 3.0 times or less of the minor axis. If the minor axis and the relationship between the major axis and the minor axis are within the above range, in addition to the chain silicon oxide particles, a true sphere, a cocoon shape, a bale shape, a disk, a rod shape, and a needle shape are included in the coating liquid. , Square-shaped particles may be mixed.

Further, it is preferable that the chain silicon oxide particles have a surface state in which they can be bound to each other. The chain silicon oxide particles originally have many silanol (Si-OH) groups on the surface, but by further increasing the number of silanol groups on the surface by a method of mixing with silica sol, the chain silicon oxide particles can be formed. It is possible to make the surface states that can be bonded to each other. When the coating composition is applied and dried so that the plurality of chain silicon oxide particles 4 are in contact with each other and the chain silicon oxide particles are bound to each other, a layer having high scratch resistance can be realized. it can.

The inorganic binder 5 for binding the particles in the present invention is preferably a silicon oxide oligomer obtained by hydrolyzing and condensing a silicic acid ester.

In the present invention, the content of the inorganic binder 5 is preferably 1.0 phr or more and 20 phr or less, and more preferably 3.0 phr or more and 15 phr or less with respect to the silicon oxide particles 4. When the content of the inorganic binder 5 is less than 1.0 phr with respect to the silicon oxide particles 4, sufficient film strength cannot be obtained. Further, when the content of the inorganic binder 5 is more than 20 phr with respect to the silicon oxide particles 4, the scattering in visible light may be deteriorated or the refractive index may be increased.

(Optical member and its manufacturing method)
The method for producing the optical member 1 of the present invention includes a step of applying a coating liquid for forming a porous layer 3 on a base material 2 to form a coating film, and a base material 1 on which the coating film is formed. , Drying and / or firing to form a porous layer.

Examples of the method for applying the coating liquid 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 an optical 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.

In order to form the porous layer 3 of the present invention, a coating liquid is applied onto a substrate and dried and / or cured. Drying and / or curing is a step of removing the solvent and depositing the silicon oxide particles while binding them together without disturbing the arrangement to form the porous layer 3. The drying and / or curing temperature depends on the heat resistant temperature of the base material 2, but is preferably 20 ° C. or higher and 200 ° C. or lower. The drying and / or curing time may be a time that does not affect the substrate and allows the organic solvent in the layer to evaporate, but is preferably 10 minutes or more and 200 hours or less, and more preferably 30 minutes or more. It is less than 24 hours.

The optical member 1 of the present invention obtained by the above method has at least a base material 2 and a porous layer 3 on the base material 2.

As the base material 2, glass, resin, or the like can be used. Further, the shape is not limited, and may be a flat surface, a curved surface, a concave surface, a convex surface, or a film shape.

Inorganic glass 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 base material, a glass base material formed by grinding and polishing, molding, float molding or the like can be used.

As the resin, polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, acrylic resin, polycarbonate, cycloolefin polymer, polyvinyl alcohol and the like can be used.

The refractive index of the porous layer 3 of the present invention is preferably 1.20 or more and 1.30 or less, and more preferably 1.20 or more and 1.24 or less. When the refractive index is less than 1.20, the proportion of voids contained in the film is large, so that the abrasion resistance of the porous layer may be insufficient. If the refractive index exceeds 1.30, the difference in refractive index between the air and the base material 2 cannot be sufficiently reduced, and the antireflection effect may not be sufficiently obtained.

Further, the amount of Na contained in the porous layer 3 of the present invention is suppressed to 10 ppm or less. This is because the Na content of the coating liquid used for the porous layer 3 of the present invention is suppressed to 1 ppm or less.

Further, the surface of the porous layer 3 of the present invention is preferably hydrophilic. Specifically, the contact angle of pure water at room temperature of 23 ° C. and humidity of 40 to 45% RH is preferably 3 ° or more and 20 ° or less, and more preferably 5 ° or more and 10 ° or less. If the contact angle of pure water is less than 3 °, moisture or the like easily enters the membrane from the surface of the porous layer 3, which may impair environmental stability. If the contact angle of pure water exceeds 20 °, the binding between the silicon oxide particles is weak, and the abrasion resistance of the porous layer 3 may not be sufficient.

Further, an antifouling layer or the like may be provided on the surface of the porous layer 3 of the present invention, if necessary. Examples of the antifouling layer include a fluoropolymer layer, a fluorosilane monolayer, and a titanium oxide particle layer.

The optical member 1 according to the present invention may be provided with an intermediate layer between the base material 2 and the porous layer 3. The intermediate layer plays a role of preventing the diffusion of impurities from the glass base material and enhancing the antireflection performance of the porous layer 3. Suitable examples of the intermediate layer include a high refractive index layer containing zirconium oxide, titanium oxide, tantalum oxide, niobium oxide and hafnium oxide, a low refractive index layer containing silicon oxide and magnesium fluoride, aluminum oxide and a polymer. And so on. The intermediate layer may be a single layer or a plurality of layers may be laminated, but a layer in which a high refractive index layer and a low refractive index layer are alternately laminated is preferable.

The optical member 1 of the present invention can be used as an optical lens, an optical mirror, a filter, and an optical film. Above all, it is particularly preferable to use it as an optical lens. Further, the optical member 1 according to the present invention is not limited to members constituting semiconductor elements and liquid crystal panels (or displays) that require high purity, and can be used in various optical devices. In particular, it is suitable as a lens for an imaging optical system included in an imaging device that requires high antireflection performance.

When the optical member 1 of the present invention is used in the image pickup optical system, the reflection of light on the surface of the optical member 1 is suppressed until the light from the outside is imaged on the image pickup element via the image pickup optical system. Since the light transmittance is improved and flare and ghost are significantly reduced, it is possible to acquire a high-quality image.

(Optical equipment)
The optical member of the present invention can be used as various optical lenses, microlenses, and glass for a liquid crystal panel, and the optical device provided with the optical member of the present invention can be applied to an image pickup device, a liquid crystal projector, an image sensor, a liquid crystal panel, and the like. ..

FIG. 4 shows an example of a preferred embodiment of the image pickup apparatus of the present invention, and shows a configuration example of a single-lens reflex digital camera to which a lens barrel (interchangeable lens), which is an example of the optical device of the present invention, is coupled. ..
The optical device of the present invention is an optical device including a housing and an optical system composed of a plurality of lenses in the housing. For example, an optical member of the present invention such as binoculars, a microscope, a semiconductor exposure device, an interchangeable lens, etc. A device equipped with an optical system that includes it. Alternatively, it refers to an interchangeable lens of a so-called camera, which is a device that generates an image by light passing through an optical member of the present invention.

Further, the image pickup device of the present invention refers to an electronic device including a camera system such as a digital still camera or a digital video camera, or an image pickup element that receives light that has passed through an optical member of the present invention such as a mobile phone. In some cases, a modular form mounted on an electronic device, for example, a camera module may be used as an image pickup device.

In FIG. 4, in the image pickup apparatus 400, the camera body 402 and the lens barrel 401, which is an optical device, are coupled, and the lens barrel 401 is a so-called interchangeable lens that can be attached to and detached from the camera body 402.
The light from the subject passes through an optical system including a plurality of lenses 403 and 405 arranged on the optical axis of the photographing optical system in the housing 420 of the lens barrel 401, and is received by the image sensor. The optical member of the present invention is arranged as a lens constituting an optical system such as a lens 403.

Here, the lens 405 is supported by the inner cylinder 404, and is movably supported with respect to the outer cylinder of the lens barrel 401 for focusing and zooming.

During the observation period before shooting, the light from the subject is reflected by the main mirror 407 in the housing 421 of the camera body, passes through the prism 411, and then the shot image is projected to the photographer through the finder lens 412. The main mirror 407 is, for example, a half mirror, and the light transmitted through the main mirror is reflected by the sub mirror 408 in the direction of the AF (autofocus) unit 413, and the reflected light is used for distance measurement, for example. Further, the main mirror 407 is attached and supported on the main mirror holder 440 by adhesion or the like. At the time of photographing, the main mirror 407 and the sub mirror 408 are moved out of the optical path via a drive mechanism (not shown), the shutter 409 is opened, and the image pickup element 410 is imaged with a photographed light image incident from the lens barrel 401. Further, the aperture 406 is configured so that the brightness and the depth of focus at the time of shooting can be changed by changing the aperture area.

As described above, in the optical device and the imaging apparatus according to the present invention, the reflection of light passing through the optical system is reduced. Therefore, when imaging is performed using these, a sharp image with reduced flare and ghost is obtained. be able to.

Hereinafter, the present invention will be specifically described with reference to Examples. The present invention can be appropriately modified without exceeding the gist thereof, and the examples described below do not limit the invention to these.

<Evaluation of coatability during film formation of porous layer>
The applicability of the coating liquid for forming the porous layer was evaluated as follows. When a coating liquid is dropped on the polished surface side of a glass substrate (φ30 mm, 1 mm thick synthetic quartz) so that the thickness of the porous layer is about 120 nm, and a spin coater is used to form a film, the porous layer is porous. The appearance was evaluated to see if there were any defects on the stratum.

The one (A) in which no defects in appearance are observed has very good coatability, and the one in which no defects in appearance are observed, but the one in which some dripping marks are generated (B) has excellent coatability. Good, those with dripping marks and some foreign matter (C), those with normal coatability, streaky defects due to unevenness and foreign matter, etc., and those with clearly bad appearance (D) are painted It was evaluated as having poor workability.
A: Very good coatability B: Good coatability C: Normal coatability D: Poor coatability In the present invention, when the coatability is evaluated as A, B, C, coatability is applied. It was assumed that there was no problem with sex.

<Scattering evaluation of porous layer>
The evaluation of the scattering of the porous layer was performed as follows. First, the base material holder was installed so that the glass substrate (φ30 mm, thickness 1 mm, both sides polished synthetic quartz) on which the porous layer was formed was always in the same position. Next, an illuminance meter (manufactured by T-10M Konica Minolta Sensing Co., Ltd.) was installed in the base material holder, and while measuring the illuminance, white light was irradiated to the base material surface side so that the illuminance from the vertical direction was 4000 lux. Next, a glass substrate on which the porous layer was formed was installed so that the white light irradiation side became the film-forming surface of the porous layer. The installed glass substrate was tilted at 45 °, and a camera (lens: EF50mm F2.5 Compact Macro Canon Inc., camera: EOS-70D Canon Inc.) was used to shoot from the normal direction of the opposite surface of the irradiation surface. .. The shooting conditions of the camera were ISO400, white balance sunny, aperture 10 and shutter speed 10 seconds. Scattering was evaluated using the calculated average luminance values of 700 pix × 700 pix of any four points on the glass substrate surface in the photographed image as the scattering value.
In the present invention, the coating film having a scattering value of 25 or less calculated by the above method was used as a porous layer that realized low scattering.

<Evaluation of film strength of porous layer>
The film strength of the porous layer was evaluated as follows. First, a polyester wiper (Alpha wiper TX1009 manufactured by Texwipe) in which a porous layer was formed on the polished surface side of a glass substrate (φ30 mm, 1 mm thick synthetic quartz with one surface polished) and soaked with ethanol. After applying a load of 1000 g / cm ² and reciprocating on the porous layer 10 times, the appearance was evaluated to see if any defects were generated on the porous layer.

Those with almost no change in appearance (A) are films with very good film strength, and those with slight changes in appearance (B) are films with good film strength and appearance. (C) is a film with normal film strength, and the appearance of the film is significantly changed, and line scratches and peeling of the film are occurring (D). It was evaluated as a film with poor film strength.
A: Film with very good film strength B: Film with good film strength C: Film with normal film strength D: Film with poor film strength In the present invention, when the evaluation of film strength is A, B, C A film having no problem in film strength was used.

<Evaluation of refractive index of porous layer>
The refractive index was evaluated as follows. First, a porous layer is formed on the polished surface side of a glass substrate (φ30 mm, synthetic quartz having a thickness of 1 mm and one surface is polished), and a spectroscopic ellipsometer (VASE, manufactured by JA Woolam Japan) is used to obtain wavelength. It was measured from 380 nm to 800 nm. The refractive index was defined as the refractive index at a wavelength of 550 nm. The refractive index was evaluated according to the following criteria.
A: 1.24 or less B: more than 1.24 and 1.30 or less C: more than 1.30 In the present invention, when the evaluation of the refractive index is A or B, the porous layer has a low refractive index. The film had no problem.
The coating liquid for forming the porous layer and the formation of the porous layer in Examples 1 to 9 were prepared by the following methods.

<Preparation of coating liquid and formation of porous layer>
[Example 1]
1-ethoxy-2-propanol (1-ethoxy-2-propanol) in 580 g of an isopropyl alcohol dispersion of hollow silicon oxide particles (Thruria 1110 manufactured by Nikki Catalyst Kasei Co., Ltd., average particle diameter of about 50 nm, shell thickness of about 10 nm, solid content concentration of 20.5% by mass). Hereinafter, isopropyl alcohol was heated and distilled off while adding 1E2P). Isopropyl alcohol was distilled off until the solid content concentration reached 19.5% by mass to prepare 610 g of a 1E2P solvent replacement solution (hereinafter referred to as solvent replacement solution 1) of hollow silicon oxide particles. Fluorine-containing organic acid is added to the obtained solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (pentafluoropropionic acid, fluorine number 5 manufactured by Tokyo Chemical Industry Co., Ltd.) is 100/1. Then, the dispersion liquid 1 was obtained.

To another container, slowly add 11.4 g of 1-propanol-2-propanol and 4.5 g of methyl polysilicate (methyl silicate 53A manufactured by Corcote Co., Ltd.) and stir at room temperature for 120 minutes to prepare silica sol (hereinafter, silica sol 1). did.
The dispersion 1 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 1 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 1 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 1. An optical member 1 to have was obtained. The contact angle of pure water in the porous layer 1 is 10 °.

[Example 2]
Fluorine-containing organic acid is added to the solvent replacement solution 1 so that the ratio of the components of hollow silicon oxide particles: fluorine-containing organic acid (heptafluorobutyric acid, Tokyo Chemical Industry Co., Ltd., fluorine number 7) is 100/1, and the dispersion liquid is added. I got 2.

The dispersion 2 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 2 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 2 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 2. An optical member 2 to have was obtained. The contact angle of pure water in the porous layer 2 is 9 °.

[Example 3]
Hollow silicon oxide particles: Fluorine-containing organic acid (Nonafluorovaleric acid manufactured by Tokyo Chemical Industry Co., Ltd., fluorine number 9) is added to the solvent replacement solution 1 so that the ratio of the components is 100/1, and the dispersion liquid is added. I got 3.

The dispersion 3 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 3 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 3 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 3. An optical member 3 to have was obtained. The contact angle of pure water in the porous layer 3 is 11 °.

[Example 4]
A fluorine-containing organic acid was added to the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (undecafluorohexanoic acid fluorine number 11 manufactured by Tokyo Chemical Industry Co., Ltd.) was 100/2. The dispersion liquid 4 was obtained.

The dispersion 4 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 4 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 4 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 4. An optical member 4 to have was obtained. The contact angle of pure water in the porous layer 4 is 10 °.

[Example 5]
1-methoxy-2 in 500 g of an aqueous dispersion of hydrophilic silicon oxide particles (PL-1, manufactured by Fuso Chemical Industry Co., Ltd., average particle diameter of about 15 nm, major / minor diameter = 2.6, solid content concentration: 12% by mass) -Water was heated and distilled off while adding propanol (hereinafter abbreviated as PGME). Water was distilled off until the solid content concentration reached 17% by mass to prepare 350 g of a PGME solvent substitution solution (hereinafter referred to as solvent substitution solution 2) of hydrophilic silicon oxide particles. Hydrophilic organic acid containing hydrophilic silicon oxide particles: fluorine-containing organic acid (undecafluorohexanoic acid manufactured by Tokyo Kasei Kogyo Co., Ltd., number of fluorine 11) so that the ratio of the components to the obtained solvent replacement solution 2 is 100/3. Was added to obtain a dispersion liquid 5.

18.0 g of pure water and 20.0 g of ethyl silicate were slowly added to another container and stirred at room temperature for 120 minutes to prepare a silica sol (hereinafter referred to as silica sol 2).
After diluting the dispersion 5 with 1-propoxy-2-propanol so that the solid content concentration becomes 4.5% by mass, the silica sol so that the ratio of the hydrophilic silicon oxide particles: silica sol component becomes 100/12. 2 was added. Further, the coating liquid 5 containing the hydrophilic silicon oxide particle conjugate was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 5 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 5. An optical member 5 to have was obtained. The contact angle of pure water in the porous layer 5 is 10 °.

[Example 6]
A fluorine-containing organic acid was added to the solvent replacement solution 2 so that the ratio of the hydrophilic silicon oxide particles: fluorine-containing organic acid (Undecafluorohexanoic acid, Tokyo Chemical Industry Co., Ltd., fluorine number 11) was 100/8. , The dispersion liquid 6 was obtained.

After diluting the dispersion 6 with 1-propoxy-2-propanol so that the solid content concentration becomes 4.5% by mass, the silica sol has a ratio of hydrophilic silicon oxide particles: silica sol component of 100/12. 2 was added. Further, the mixture was mixed and stirred at room temperature for 2 hours to obtain a coating liquid 6 containing a conjugate of hydrophilic silicon oxide particles.

The obtained coating liquid 6 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 6. An optical member 6 to have was obtained. The contact angle of pure water in the porous layer 6 is 11 °.

[Example 7]
A fluorine-containing organic acid was added to the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (heptafluorobutyric acid, fluorine number 7 manufactured by Tokyo Chemical Industry Co., Ltd.) was 100 / 0.2. A dispersion 7 was obtained.

The dispersion 7 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 7 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 7 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 7. An optical member 7 to have was obtained. The contact angle of pure water in the porous layer 7 is 8 °.

[Example 8]
A fluorine-containing organic acid was added to the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (heptafluorobutyric acid, Tokyo Chemical Industry Co., Ltd., fluorine number 7) was 100 / 0.1. The dispersion liquid 8 was obtained.

The dispersion 8 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 8 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 8 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form the porous layer 8. An optical member 8 to have was obtained. The contact angle of pure water in the porous layer 8 is 9 °.

[Example 9]
A fluorine-containing organic acid was added to the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (heptafluorobutyric acid, Tokyo Chemical Industry Co., Ltd., fluorine number 7) was 100/0.05. The dispersion liquid 9 was obtained.

The dispersion 9 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 9 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 9 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 9. An optical member 9 to have was obtained. The contact angle of pure water in the porous layer 9 is 10 °.

[Comparative Example 1]
An inorganic acid was added to the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: inorganic acid (Tokyo Kasei Kogyo Co., Ltd., hydrochloric acid number 0) was 100/1 to obtain a dispersion solution 10.

The dispersion 10 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 10 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 10 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 10. An optical member 10 to have was obtained. The contact angle of pure water in the porous layer 10 is 28 °.

[Comparative Example 2]
After diluting the solvent substitution solution 1 with ethyl lactate so that the solid content concentration becomes 4.5% by mass to obtain the dispersion solution 11, the ratio of the hollow silicon oxide particles: silica sol component becomes 100/12. , Silica sol 1 was added. Further, the coating liquid 11 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 11 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired at 140 ° C. for 30 minutes in a constant temperature furnace to form the porous layer 11. An optical member 11 to have was obtained. The contact angle of pure water in the porous layer 11 is 9 °.

[Comparative Example 3]
A fluorine-containing organic acid was added to the solvent replacement solution 2 so that the ratio of hydrophilic silicon oxide particles: fluorine-containing organic acid (difluoroacetic acid, fluorine number 2 manufactured by Tokyo Chemical Industry Co., Ltd.) was 100/0.05. A dispersion liquid 12 was obtained.
After diluting the solvent replacement solution 2 with 1-propoxy-2-propanol so that the solid content concentration becomes 4.5% by mass, the ratio of the hydrophilic silicon oxide particles: silica sol component becomes 100/12. Silica sol 2 was added. Further, by mixing and stirring at room temperature for 2 hours, a coating liquid 12 containing a conjugate of hydrophilic silicon oxide particles was obtained.

The obtained coating liquid 12 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 12. An optical member 12 to have was obtained. The contact angle of pure water in the porous layer 12 is 17 °.

[Comparative Example 4]
Hollow silicon oxide particles in the solvent replacement solution 1: Fluorine-containing organic acid (2,2,3,3-tetrafluoropropionic acid, fluorine number 4 manufactured by Tokyo Chemical Industry Co., Ltd.) , Fluorine-containing organic acid was added to obtain a dispersion liquid 13.

The dispersion 13 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 13 containing the hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 13 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 13. An optical member 13 to have was obtained. The contact angle of pure water in the porous layer 13 is 14 °.

[Comparative Example 5]
Fluorine-containing organic acid is added and dispersed in the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (Dodecafluorosuberic acid, Tokyo Chemical Industry Co., Ltd., fluorine number 12) is 100/1. Liquid 14 was obtained.

The dispersion 14 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 14 containing the hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 14 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 14. An optical member 14 to have was obtained. The contact angle of pure water in the porous layer 14 is 10 °.

[Comparative Example 6]
A fluorine-containing organic acid was added to the solvent replacement solution 1 so that the ratio of the hollow silicon oxide particles: fluorine-containing organic acid (tridecafluoroheptanic acid, fluorine number 13 manufactured by Tokyo Chemical Industry Co., Ltd.) was 100/9. The dispersion liquid 15 was obtained.

The dispersion 15 was diluted with ethyl lactate so that the solid content concentration was 4.5% by mass, and then silica sol 1 was added so that the ratio of the hollow silicon oxide particles: silica sol component was 100/12. Further, the coating liquid 15 containing hollow silicon oxide particles was obtained by mixing and stirring at room temperature for 2 hours.

The obtained coating liquid 15 is dropped onto a glass substrate to form a film with a spin coater so as to have a thickness of about 120 nm, and then fired in a constant temperature furnace at 140 ° C. for 30 minutes to form a porous layer 15. An optical member 15 to have was obtained. The contact angle of pure water in the porous layer 15 is 13 °.

Table 1 shows the evaluation results of the coating liquids 1 to 15 prepared in Examples and Comparative Examples.

From the results in Table 1, the following was found.
It was found that the coating liquid 11 of Comparative Example 2 had a problem in coatability because ring-shaped defects and dripping marks were conspicuous during coating, and many streak-shaped defects were also generated radially. Although the inorganic acid can disperse the silicon oxide particles in the coating liquid, it is difficult to maintain the dispersed state of the silicon oxide particles at the time of forming the coating film, and a lot of particle aggregation occurs in the film forming process. Is estimated. In addition, the coating liquids 12 and 13 of Comparative Examples 3 and 4 also have many streaky defects that are assumed to be caused by the inclusion of precipitates and foreign substances, and the defects are the starting point when the coating film is wiped off. It was found that linear scratches are likely to occur.

Next, Table 2 shows the results of evaluating the porous layers of the optical members 1 to 15 produced in Examples and Comparative Examples as antireflection films.

From the results in Table 2, it was found that the optical members 1 to 9 were provided with a film having low scattering of 25 or less and excellent film strength. It was also found that sufficient performance can be realized as an antireflection film having a low refractive index.

It was confirmed that the porous layers of the optical members 10 to 15 produced as a comparative example are difficult to have excellent characteristics in both scattering and film strength, and the performance as an antireflection film is not sufficient.

1 ... Optical member 2 ... Base material 3 ... Porous layer 4 ... Silicon oxide particles 5 ... Inorganic binder 6 ... Voids 7 ... Fluorine-containing organic acid 400 ... Imaging device 401 ... Lens barrel 402 ... Camera body 403,405 ... Lens 404 ... Inner cylinder 406 ... Aperture 407 ... Main mirror 408 ... Sub mirror 409 ... Shutter 410 ... Imaging element 411 ... Prism 412 ... Finder lens 413 ... AF unit 420 ... Housing 421 ... Camera body housing 440 ... Main mirror holder

Claims (20)

An optical member having a porous layer in which a plurality of silicon oxide particles are bonded with an inorganic binder on a base material, and the porous layer contains fluorine in which the number of fluorine atoms in one molecule is 5 or more and 11 or less. An optical member characterized by containing an organic acid. The optical member according to claim 1, wherein the fluorine-containing organic acid is contained in an amount of 0.1 phr or more and 8 phr or less with respect to the silicon oxide particles. The optical member according to claim 1 or 2, wherein the fluorine-containing organic acid has an acid dissociation constant of 0 pKa or more and 0.5 pKa or less. The optical member according to any one of claims 1 to 3, wherein the fluorine-containing organic acid has a molecular weight of 100 or more and 360 or less. The optical member according to any one of claims 1 to 4, wherein the inorganic binder is a silicon oxide binder. An optical device including a housing and an optical system composed of a plurality of lenses in the housing.
An optical device according to any one of claims 1 to 5, wherein the lens is an optical member. The optical device according to claim 6, wherein the optical device is an image pickup device further including an image pickup element that receives light that has passed through the optical system. The optical device according to claim 7, wherein the imaging device is a camera. A coating liquid for forming a porous layer, which contains silicon oxide particles, an inorganic binder, and an organic solvent, and the silicon oxide particles have a fluorine-containing organic acid. The coating liquid according to claim 9, wherein the number of fluorine atoms in one molecule of the fluorine-containing organic acid is in the range of 5 or more and 11 or less. The coating liquid according to claim 9 or 10, wherein the fluorine-containing organic acid is contained in the silicon oxide particles in an amount of 0.1 phr or more and 8 phr or less. The coating liquid according to any one of claims 9 to 11, wherein the fluorine-containing organic acid has an acid dissociation constant of 0 pKa or more and 0.5 pKa or less. The coating liquid according to any one of claims 9 to 12, wherein the fluorine-containing organic acid has a molecular weight of 100 or more and 360 or less. The coating liquid according to any one of claims 9 to 13, wherein the silicon oxide particles are hollow particles or chain particles. The coating liquid according to any one of claims 9 to 14, wherein the inorganic binder is a silicon oxide oligomer. The coating liquid according to any one of claims 9 to 15, wherein the inorganic binder is contained in the silicon oxide particles at 1.0 phr or more and 20 phr or less. A method for manufacturing an optical member having a porous layer in which a plurality of silicon oxide particles are bonded with an inorganic binder.
A step of forming a coating film by applying a coating liquid containing silicon oxide particles, an inorganic binder and an organic solvent on a base material and having a fluorine-containing organic acid on the surface of the silicon oxide particles.
The step of drying and / or firing the coating film to form a porous layer, and
A method for manufacturing an optical member, which comprises. The method for producing an optical member according to claim 17, wherein the number of fluorine atoms in one molecule of the fluorine-containing organic acid is in the range of 5 or more and 11 or less. The method for producing an optical member according to claim 18, wherein the fluorine-containing organic acid is contained in the silicon oxide particles in an amount of 0.1 phr or more and 8 phr or less. The method for producing an optical member according to claim 18, wherein the fluorine-containing organic acid has a molecular weight of 100 or more and 360 or less.