JP2019061137A - Optical element, optical device, method for producing optical element and coating - Google Patents

Abstract

To provide an optical element having high antireflection performance from the visible range to the infrared range, and a method for producing the optical element.SOLUTION: An optical element 10 has a particle layer 12 having particles 14 on a base material 11. The particle layer 12 has a fine rugged structure mainly composed of aluminum oxide, between the surface and the particles. Or, the particle layer 12 has a thickness of 100 nm or more and 145 nm or less, or the particles 14 are hollow particles.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical element having a wide band and a high antireflection effect, an optical apparatus using the same, a method of manufacturing an optical element, and a paint.

  An optical element such as a lens used for an optical system, which has an antireflection film having a fine concavo-convex structure of aluminum oxide, and which has high antireflection performance in the visible region to the near infrared region is known (patent document 1).

  In addition, there is known an optical element having an antireflective film having hollow particles and having excellent abrasion resistance and transparency (Patent Document 2).

JP 2008-233880 A JP 2012-108320 A

  However, although the antireflection film disclosed in Patent Document 1 has high antireflection performance in the visible region to the near infrared region, the reflectance is high in the infrared region of 1000 nm to 1600 nm.

  Moreover, although the anti-reflective film currently disclosed by patent document 2 is excellent in the reflection preventing performance in a visible region, a reflectance will become high in the infrared region of 1000 nm-1600 nm.

  The optical element of the present invention is an optical element having a particle layer having particles on a base material, wherein the particle layer has a fine uneven structure mainly composed of aluminum oxide on the surface and between the particles. It is characterized by

  An optical apparatus of the present invention is characterized by having the above-described optical element.

  The paint of the present invention comprises an aluminum oxide precursor sol containing, as components, a hydrolyzate of an aluminum compound and / or a condensate thereof, particles, and a solvent, wherein the aluminum oxide precursor sol and the dried solid of the particles It is characterized in that the mass ratio of minutes is 60:40 to 30:70.

  The method for producing an optical element of the present invention comprises the steps of forming a particle layer containing an aluminum oxide precursor sol between particles by applying the above-mentioned paint on a substrate, and an aluminum oxide precursor sol between the particles Forming aluminum oxide from said aluminum oxide precursor sol by drying and / or calcining a particle layer containing it, and immersing said aluminum oxide-containing particle layer in warm water or exposing it to steam Forming a fine structure of aluminum oxide between the particles, and forming a fine concavo-convex structure mainly composed of aluminum oxide on the particle layer.

  According to the present invention, it is possible to provide an optical element having high antireflection performance from the visible range to the infrared range, and a method of manufacturing the optical element.

It is a schematic diagram which shows one Embodiment of the anti-reflective film of this invention. It is process drawing which shows one Embodiment of the manufacturing method of the anti-reflective film of this invention. It is an observation photograph (magnification 200,000 times) of the cross section by the scanning transmission electron microscope of the anti-reflective film of this invention. It is a figure which shows the relationship of the reflectance (%) with respect to the wavelength (nm) of the light of the member for optics produced by Example 1, the comparative example 1, and the comparative example 2. FIG. It is a figure which shows the relationship of the reflectance (%) with respect to the wavelength (nm) of the light of the member for optics produced in Example 2. FIG. It is a figure which shows the relationship of the reflectance (%) with respect to the wavelength (nm) of the light of the member for optics produced by Example 1, the comparative example 1, and the comparative example 2. FIG. It is a figure which shows the relationship of the reflectance (%) with respect to the wavelength (nm) of the light of the member for optics produced in Example 3 and Example 4. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Optical equipment)
The optical apparatus of the present embodiment can be used for a telescope having an optical element, binoculars, a microscope, a camera, an endoscope, and the like.

  The optical apparatus of the present embodiment will be described below using an example of a camera. As shown in FIG. 1, the lens unit 101 of the camera is provided with a plurality of optical elements (lenses) 121 to 129 on the optical axis O. In the optical apparatus of the present embodiment, the optical elements described below can be used as the one or more optical elements 121 to 129.

(Optical element)
The optical element of the present embodiment can be used for a lens, a prism, a mirror, a diffraction grating, and a polarization element. Hereinafter, the optical element of the present embodiment will be described using a lens.

  FIG. 2 is a schematic view showing an embodiment of the optical element of the present embodiment.

  The optical element 10 has a particle layer 12 having particles, and a fine uneven structure 13 mainly composed of aluminum oxide on the surface of the particle layer 12 on a substrate 11. The particle layer 12 has voids (voids) 15 between the particles 14, and the particle layer 12 has a microstructure 16 mainly composed of aluminum oxide between the particles 14.

  As the substrate 11, a plastic substrate, a glass substrate, or a resin substrate can be used. The shape is not limited and may be flat, curved, concave, convex, or film-like.

  The particle layer 12 preferably has a thickness of 100 nm or more and 145 nm or less. When the thickness of the particle layer is thinner than 100 nm, the reflectance in the visible region decreases but the reflectance in the infrared region increases. In addition, when the thickness of the particle layer 12 is thicker than 145 nm, the reflectance in the infrared region decreases but the reflectance in the visible region increases.

  The fine concavo-convex structure 13 on the surface of the particle layer 12 preferably contains aluminum oxide as a main component. In this specification, having aluminum oxide as a main component means containing 60 mass% or more of aluminum oxide. As for the fine concavo-convex structure 13, it is more preferable to contain aluminum oxide 80 mass% or more, and it is still more preferable to contain 90 mass% or more. The fine relief structure 13 is formed of crystals of aluminum oxide or hydroxide or their hydrates. Particularly preferred crystals are boehmite. In the present specification, an oxide or hydroxide of aluminum or a hydrate thereof is referred to as aluminum oxide.

  The fine concavo-convex structure 13 of aluminum oxide on the surface of the particle layer 12 has a smaller refractive index on the opposite side to the substrate 11 as compared with the refractive index on the base 11 side. Thereby, reflection of light from the surface can be prevented. Although the reflectance can be reduced by the presence of the fine concavo-convex structure 13, the thickness is preferably 150 nm or more and 280 nm. By having a thickness of 150 nm or more, it is possible to effectively reduce the reflectance in the infrared region. The thicker the fine uneven structure 13, the better optically, but in the fine uneven structure, dissolution and reprecipitation of aluminum oxide are repeated to grow projections, so dissolution and reprecipitation reach equilibrium at a height of 280 nm. . Therefore, since it is difficult to increase the thickness of the fine concavo-convex structure by stopping the growth of protrusions, the thickness is preferably 280 nm or less.

  The particles 14 in the particle layer 12 are preferably hollow particles. The refractive index of the fine concavo-convex structure 13 is preferably lower than the refractive index of the particle layer 12. Therefore, when the refractive index of the particle layer 12 becomes higher than the refractive index of the fine concavo-convex structure 13, the antireflection performance is lowered. Therefore, in order to make the refractive index of the particle layer 12 lower than the refractive index of the fine uneven structure 13 of aluminum oxide, it is preferable to use hollow particles as the particles 14.

Hollow particles have a void inside the particle and a shell around the outside of the void. The refractive index of the particle layer 12 can be reduced by the air (refractive index 1.0) contained in the pores. The pores may be single or porous and may be selected appropriately. The material constituting the hollow particles is preferably a low refractive index, SiO 2, _{MgF 2,} fluorine inorganic materials and such as can be used such as organic resin of the silicone resin. Among these, it is preferable to use SiO ₂ and MgF _2, and it is more preferable to use SiO ₂ which facilitates the production of hollow particles. As a method for producing hollow particles comprising a SiO _2, for example, JP-A-2001-233611, it is possible to produce by the method described in JP 2008-139581.

  The average particle diameter of the hollow particles is preferably 15 nm or more and 100 nm or less, and more preferably 15 nm or more and 60 nm or less. When the average particle size of the hollow particles is less than 15 nm, it is difficult to stably produce core particles. Moreover, when it exceeds 100 nm, it is not preferable because scattering occurs with the size of hollow particles.

  The average particle diameter of the hollow particles is the average Feret diameter. The mean Feret diameter can be measured by image processing as observed by a transmission electron microscope image. As the image processing method, a processing method using commercially available image analysis software such as image Pro PLUS (manufactured by Media Cybernetics) can be used. The average particle diameter of the hollow particles is determined by appropriately adjusting the contrast in a predetermined image area, if necessary, and calculating the average value from the Feret diameters of each of the about 30 hollow particles measured.

  The thickness of the shell of the hollow particle is preferably 10% to 50%, more preferably 20% to 35% of the average particle diameter of the hollow particle. If the thickness of the shell is less than 10%, the strength of the hollow particles is insufficient, which is not preferable. On the other hand, if it exceeds 50%, the refractive index is increased and the antireflection performance is lowered.

  In the particle layer 12 formed by stacking the particles 14 that are hollow particles, a void 15 is present between the particles 14 and the particles 14. That is, as shown in FIG. 2, in the case of spherical particles, voids 15 can be formed without being completely filled. The refractive index of the particle layer 12 can be lowered by utilizing the air gap 15.

  The refractive index of the base 11 side (root portion) of the fine concavo-convex structure 13 of the surface layer aluminum oxide is lower than the refractive index inherent to aluminum oxide due to the structure. Therefore, when the refractive index of the layer (on the side of the base 11) existing under the fine concavo-convex structure 13 of aluminum oxide is high, a smooth refractive index difference is obtained due to the difference of the refractive index with the fine concavo-convex structure 13 of aluminum oxide. It is difficult to obtain wide band anti-reflection characteristics. Therefore, it is preferable to use the particle 14 which is a hollow particle for the particle layer 12 as a layer which exists under the fine concavo-convex structure 13 of aluminum oxide whose apparent refractive index is low. By using the particles 14 which are hollow particles, the refractive index between the two layers can be made closer to each other, so that it is possible to obtain an antireflection characteristic of a wide band as a whole.

  Since the air gap 15 is formed by stacking the hollow particles 14, the outermost surface of the particle layer 12 and the air gap 15 are spatially connected by the air gap 15.

  Inside the particles 14 in the particle layer 12 (voids 15), a microstructure 16 of aluminum oxide is present. The fine structure 16 of aluminum oxide is the same as the fine concavo-convex structure 13 of the aluminum oxide in the outermost layer, and is formed in the (void 15) between the particles 14 in the particle layer 12. In the present specification, the microstructure 16 of aluminum oxide refers to a crystalline structure formed between particles (voids 15) in the particle layer by dissolution and precipitation of aluminum oxide.

  The aluminum oxide sol contained in the coating liquid is formed between the particles after the coating. The aluminum oxide microstructure 16 is formed by the dissolution of the aluminum oxide from the aluminum oxide sol formed between the particles and the precipitation of the aluminum oxide in the voids 15. As described above, the particles 14 (voids 15) in the particle layer 12 are spatially connected to the surface layer of the particle layer 12. Therefore, the fine structure 16 of aluminum oxide repeats dissolution and precipitation in the voids 15 between the particles 14 in the particle layer 12 while receiving supply of aluminum ions from the aluminum oxide sol. Finally, the fine asperity structure 13 of aluminum oxide is formed by depositing on the surface of the particle layer 12. Furthermore, the fine uneven structure 13 can grow until dissolution and reprecipitation of the aluminum sol reach equilibrium while receiving supply of aluminum ions generated in the particle layer. Since the aluminum oxide microstructure 16 is formed based on such a mechanism, the aluminum oxide microstructure 16 in the particle layer 12 is located near the surface of the particle layer 12 on the side to which aluminum ions are supplied. There are more. Therefore, it is considered that the refractive index in the particle layer can be changed smoothly, and the optical member of the present embodiment can obtain wide-band anti-reflection characteristics.

(paint)
Next, the paint of the present embodiment will be described. The film produced by the paint of the present embodiment has high antireflection performance.

  The paint of the present embodiment includes an aluminum oxide precursor sol containing, as components, a hydrolyzate of an aluminum compound and / or a condensate thereof, particles, and a solvent. Furthermore, it is characterized in that a mass ratio of dry solid content of the aluminum oxide precursor sol and particles is 60:40 to 30:70.

  The aluminum oxide precursor sol contained in the paint can be applied and dried on the substrate 11 and then immersed in warm water to form the fine concavo-convex structure 13 and the fine structure 16 of aluminum oxide. It can be used for the manufacturing method.

The aluminum oxide precursor sol contains, as a main component, a hydrolyzate of an aluminum compound obtained by bringing an aluminum compound into contact with water in a solvent and / or a condensate thereof. When the aluminum compound is Al-X ₃ (X represents an alkoxyl group, an acyloxyl group, a halogen group, or a nitrate ion), the hydrolyzate is Al-X ₂ (OH), Al-X (OH) ₂ , Or it is a compound represented by Al- (OH) ₃ . The hydrolyzate thereof and -OH groups to each other or -X group and -OH group forms Al-O-Al bonds accompanied by elimination of _{H 2} O or XH react. The resulting compound having one or more Al-O-Al bonds and having a linear or branched structure is a condensate of an aluminum compound. The condensate of the aluminum compound is preferably amorphous.

  As the aluminum oxide precursor sol, a small amount of a metal compound including at least one of each of Zr, Si, Ti, Zn, and Mg can be used together with the aluminum compound. As these metal compounds, respective metal alkoxides and metal salt compounds such as chlorides and nitrates can be used. It is particularly preferable to use a metal alkoxide because the by-product at the time of preparation of the sol has a small influence on film formability at the time of coating. Further, the amount of the aluminum compound contained in the total 100 mol% of the metal compound is preferably 90 mol% or more.

  Specific examples of metal compounds such as aluminum compounds are illustrated below.

  As an aluminum compound, for example, aluminum ethoxide, aluminum isopropoxide, aluminum-n-butoxide, aluminum-sec-butoxide, aluminum-tert-butoxide, aluminum acetylacetonate, or an oligomer thereof, aluminum nitrate, aluminum chloride, Aluminum acetate, aluminum phosphate, aluminum sulfate, aluminum hydroxide and the like can be mentioned.

  Specific examples of the zirconium alkoxide include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetra n-propoxide, zirconium tetraisopropoxide, zirconium tetra n-butoxide, zirconium tetra t-butoxide and the like.

  As the silicon alkoxide, various ones represented by the general formula Si (OR) 4 can be used. R includes the same or different lower alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group and isobutyl group.

  Examples of the titanium alkoxide include tetramethoxytitanium, tetraethoxytitanium, tetra n-propoxytitanium, tetraisopropoxytitanium, tetra n-butoxytitanium, tetraisobutoxytitanium and the like.

  Examples of zinc compounds include zinc acetate, zinc chloride, zinc nitrate, zinc stearate, zinc oleate, zinc salicylate and the like, with zinc acetate and zinc chloride being particularly preferable.

  Examples of the magnesium compound include magnesium alkoxides such as dimethoxymagnesium, diethoxymagnesium, dipropoxymagnesium, dibutoxymagnesium, magnesium acetylacetonate, magnesium chloride and the like.

  Among the above metal compounds, aluminum-n-butoxide, aluminum-sec-butoxide, zirconium tetraisopropoxide, zirconium tetra n-butoxide, tetramethoxysilane, tetraethoxysilane, tetraisopropoxy titanium, tetra n-butoxy titanium, di It is preferable to use metal alkoxides such as propoxy magnesium and dibutoxy magnesium as raw materials.

  Among the metal compounds, alkoxides of aluminum, zirconium and titanium in particular are highly reactive to water, and are rapidly hydrolyzed by the addition of water or moisture in the air to cause white turbidity and precipitation of the solution. Further, the aluminum salt compound, the zinc salt compound and the magnesium salt compound are difficult to dissolve only with the organic solvent, and the solution stability is low. In order to prevent these, it is preferable to add a stabilizer to stabilize the solution.

  As the stabilizing agent, for example, β-diketone compounds such as acetylacetone, dipyrroleylmethane, trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone and dibenzoylmethane. Methyl acetoacetate, ethyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, iso-propyl acetoacetate, tert-butyl acetoacetate, iso-butyl acetoacetate, 2-methoxyethyl acetoacetate, 3-keto-n -Beta-ketoester compounds such as methyl valeric acid. Further, alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and the like can be mentioned.

  Although the addition amount of a stabilizer changes with kinds of metal compound, 0.2 mol or more and 2 mol or less are preferable with respect to 1 mol of aluminum alkoxides. In addition, the stabilizer exerts an effect by mixing with the alkoxide for a certain period of time before adding water.

  In order to cause hydrolysis, it is necessary to add an appropriate amount of water. The amount of water added varies depending on the solvent and concentration. The addition amount of water is preferably 1.2 mol or more and less than 2 mol with respect to 1 mol of the aluminum compound.

  Also, after the addition of the stabilizing agent, a catalyst can be added to the water for the purpose of promoting a part of the hydrolysis reaction. Examples of the catalyst include nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, ammonia and the like, and when it is used at a concentration of 0.1 mol / L or less, hydrolysis and condensation can be promoted steadily.

  The particles contained in the paint of the present embodiment are preferably those whose surface is surface-modified with a methyl group or the like because the viscosity is lowered at the time of slurrying. Therefore, in the case of hollow silica particles, it is preferable to use a trifunctional silane modified with a methyl group such as methyltriethoxysilane or methyltrimethoxysilane as a precursor for forming the wall of the hollow particles. Moreover, as a material used for a precursor, you may mix and use said trifunctional silane and tetrafunctional silanes, such as a tetraethoxysilane, It is preferable to select the composition which can implement | achieve stable particle manufacture.

  It is preferable that dry solid content mass ratio of the said aluminum oxide precursor sol and a silica particle is 60: 40-30: 70. If the ratio of silica particles is less than this range, a particle layer can not be formed, and as a result, the thickness of a layer whose refractive index changes smoothly can not be increased, thus forming a broadband antireflection structure. It is difficult. In addition, when the ratio of silica particles exceeds this range, the amount of aluminum oxide precursor sol contained between particles after coating decreases, and the height of the aluminum oxide microstructure on the particle layer decreases, which is a broad band It is difficult to form an antireflective structure.

  The dry solid content mass of the antireflective coating is preferably from 1% by mass to 7% by mass in terms of metal oxide, and more preferably from 2.5% by mass to 6% by mass.

  The solvent may be an organic solvent in which a raw material such as an aluminum compound is uniformly dissolved, and the alumina precursor sol and the silica particles do not aggregate. 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, 2-octanol and the like: alcohols having 2 or more valences such as ethylene glycol and triethylene glycol: methoxyethanol (boiling point 125 ° C.), ethoxyethanol Boiling point 136 ° C), propoxy Tanol (boiling point 151 ° C.), isopropoxyethanol (boiling point 141 ° C.), butoxyethanol (boiling point 170 ° C.), 1-methoxy-2-propanol (boiling point 120 ° C.), 1-ethoxy-2-propanol (boiling point 132 ° C.), Glycol ethers such as 1-propoxy-2-propanol (boiling point 140 to 160 ° C.): Ethers such as dimethoxyethane, diglyme, tetrahydrofuran, dioxane, diisopropyl ether, cyclopentyl methyl ether: ethyl formate, ethyl acetate, n-acetate Butyl, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, etc. Kinds: Various aliphatic or alicyclic hydrocarbons such as n-hexane, n-octane, cyclohexane, cyclopentane, cyclooctane: Various aromatic hydrocarbons such as toluene, xylene, ethylbenzene: Various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone: Various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride and tetrachloroethane: N-methylpyrrolidone, N, N-dimethyl form And aprotic polar solvents such as amide, N, N-dimethylacetamide, ethylene carbonate and the like.

  Among the above-mentioned solvents, monohydric alcohols having 5 to 8 carbon atoms are preferable in that the solubility of the aluminum compound is high and moisture absorption is difficult. When the hydrolysis of the aluminum compound proceeds due to the moisture absorption of the solvent, it becomes difficult to control the particle size. In addition, moisture absorption at the time of coating causes aggregation of particles and impairs the stability of optical properties. Furthermore, when a general low-boiling alcohol is used, evaporation of the solvent is quick, and the above-mentioned stabilizer remains in the film to affect the optical properties. However, when a monohydric alcohol having 5 to 8 carbon atoms is used, the solvent volatilizes with the stabilizer during drying and / or calcining, so that the stabilizer hardly remains. On the other hand, the monohydric alcohol having 5 to 8 carbon atoms is highly hydrophobic, and water necessary for hydrolysis can not be uniformly mixed, making it difficult to keep the particle size constant. Therefore, it is preferable to use a water-soluble solvent in combination with a monohydric alcohol having 5 to 8 carbon atoms. The water-soluble solvent described herein refers to a solvent having a water solubility of 80% by mass or more in a solvent at 23 ° C.

  The mixing ratio of the solvent is a ratio of 10% by mass to 50% by mass of a water-soluble solvent having a boiling point of 110 ° C. to 170 ° C. and 50% by mass to 90% by mass of a C 5 to 8 monohydric alcohol. Is preferably contained. When a water-soluble solvent having a boiling point of less than 110 ° C. is used, moisture absorption and whitening due to volatilization are likely to occur. When a water-soluble solvent having a boiling point of 170 ° C. or more is used, it remains in the film after coating even after drying, resulting in variation in reflectance. It is preferable to use glycol ether as a water-soluble solvent.

  In preparing the aluminum oxide precursor sol of the present invention, heating can be performed to promote the hydrolysis and condensation reaction of the aluminum alkoxide. The heating temperature depends on the boiling point of the solvent, but is preferably 60 ° C. or more and 150 ° C. or less. By heating, the particles grow and the particle property is improved.

(Method of manufacturing optical element)
Next, a method of manufacturing the optical element of the present embodiment will be described. FIG. 3 is a process chart showing an embodiment of a method of manufacturing an optical element of the present invention.

  The method for producing the optical element of the present invention is as follows.

  By depositing the above-described paint, a particle layer 22 having particles 23 contained in the paint is formed on the base 21. In the particle layer 22, a void 24 is formed in a part between the particles 23 and the particles 23, and an aluminum oxide precursor sol 25 contained in the paint is formed in a part between the particles 23 and the particles 23 ( Fig. 3 (a).

  As the base 21, it is possible to use a glass base, a plastic base, a resin base or the like. Moreover, the shape is not limited and may be flat, curved, concave, convex, or film.

  As a method of apply | coating said coating material to the base material 21, known application methods, such as a dipping method, a spin coat method, a spray method, a printing method, a flow coat method, and these combined use, are employable, for example. Among these, it is preferable to use a spin coating method because a particle layer can be generated efficiently.

  Thereafter, by performing drying and / or firing, the solvent is volatilized from the aluminum oxide precursor sol 25 to form aluminum oxide 26 in which particles in the sol are deposited (FIG. 3 (b)). Further heating causes volatilization of the stabilizer, and condensation reaction of unreacted alkoxide and hydroxyl group proceeds.

  The temperature for drying and / or firing is preferably in the range of 120 ° C. or more and 230 ° C. or less. The higher the heat treatment temperature, the higher the density of the film. However, if the heat treatment temperature exceeds 230 ° C., the substrate 21 is easily damaged. The temperature of drying and / or firing is preferably in the range of 140 ° C. or more and 210 ° C. or less. Even when a stabilizer is used by heating at 140 ° C. or higher, impurities such as a stabilizer are unlikely to remain, and by heating at 210 ° C. or less, the influence on the substrate can be reduced. Although heating time is based also on heating temperature, 10 minutes or more are preferable. Examples of the heating method include a hot air circulation oven, a muffle furnace, a method of heating in an IH furnace, and a method of heating with an IR lamp.

  Thereafter, by immersion in warm water of 50 ° C. or higher and / or exposure to steam, the warm water or steam hydrates and dissolves aluminum oxide through the voids 23 in the particle layer 22, and the aluminum oxide is reprecipitated. The fine concavo-convex structure 28 of aluminum oxide is formed on the surface while the fine structure 27 of aluminum oxide is formed in the voids 24 in the particle layer 22 by reprecipitation of aluminum oxide (FIG. 3 (c)). Since the dissolution and precipitation of aluminum oxide are equilibrium reactions, the formation of the fine structure and the fine relief structure of aluminum oxide is completed when the dissolution and precipitation reach equilibrium, and an optical element is formed.

  By contacting with warm water, the aluminum oxide 26 is peptized and so on, and some components are eluted. In the present invention, plate-like crystals mainly composed of aluminum oxide precipitate and grow in the gaps 24 between the surface layer of the fine particle layer and the particles 23 due to the difference in the solubility of various metal oxide-derived hydroxides in hot water. Can be formed. The temperature of hot water is preferably 40 ° C. or more and 100 ° C. or less, and the temperature of water vapor is preferably 100 ° C. or more and 120 ° C. or less. The exposure time of the hot water treatment or the steam is preferably 5 minutes to 24 hours.

  The refractive index of the particle layer 22 depends on the particles 23, the voids 24 and the microstructure 27 of aluminum oxide. After the water treatment, a binder may be applied which penetrates into the voids 24 between the particles 23 for the purpose of adjusting the refractive index to adjust the wavelength dependency of the particle layer 22 and for preventing dirt and the like.

  In the coating of the binder or the component for producing the binder, it is possible to fill the binder in the voids 24 between the hollow particles 23 and the hollow particles 23 while maintaining the alignment of the particle layer 22.

  As a component of the binder, a metal alkoxide, a resin paint, a fluorine compound and the like can be formed into a film, and a binder having the same properties as the material of the particles 23 of the particle layer 22 is preferable. For example, when the material of the particles 23 in the particle layer 22 is silica, it is preferable to use a silane alkoxide as a component of the binder. As the binder concentration, the film may be formed at a concentration that provides a desired content for the desired function such as the refractive index of the formed particle layer 22 and dirt prevention, and the concentration depends on the binder component, the solvent, and the film forming conditions. Can be selected as appropriate. Moreover, as a solvent used for coating of a binder, it is preferable to select suitably a thing with favorable affinity with a binder.

  The coating method of the binder is not preferable because, since the film formation is performed again after the particles 23 are applied, in the case of the immersion type such as dip coating, the attached particles 23 are missing. There is no particular limitation other than that, and it is possible to use a general coating method of a liquid coating liquid such as a spin coating method and a spray coating method. The coating material is preferably applied by spin coating from the viewpoint of the lack of the particles 23 described above and the point that the film thickness can be uniformly formed on the substrate 21 having a curved surface such as a lens. Moreover, coating of a binder may coat a several coating liquid according to desired function expression.

  Although the particle layer 22 is directly provided on the substrate 21 in the above embodiment, one or more layers of another metal oxide may be provided between the substrate 21 and the aluminum oxide layer 22. When a plurality of metal oxide layers are provided, alternating layers of a high refractive index layer having a refractive index higher than that of the particle layer 22 and a middle refractive index layer can be used. For the high refractive index layer 103, a material having a refractive index of 1.75 to 2.7 can be used. Specifically, zirconium oxide, tantalum oxide, niobium oxide, titanium oxide, silicon nitride or the like can be used as the high refractive index material. For the middle refractive index layer 104, a low refractive index material having a refractive index of 1.35 or more and less than 1.75 can be used. Specifically, silicon oxide, aluminum oxide or the like can be used as the middle refractive material.

  The metal oxide layer can be formed by vapor deposition, vacuum evaporation, sputtering, CVD, dip coating, spin coating, spray coating, or the like.

  According to the manufacturing method of the present embodiment, the supply of ions is received from the aluminum oxide sol contained between the particle layers 12 formed after coating. When the aluminum oxide sol is contained in the particle layer, unlike the layer obtained by coating the aluminum oxide sol alone, the surface area of the aluminum oxide sol is increased, and the dissolution of the aluminum oxide sol tends to occur. Therefore, since the aluminum oxide sol layer does not remain alone, it is possible to make the refractive index change of the aluminum oxide microstructure 13 smooth as compared with the case of coating alone.

  EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples. However, the present invention is not limited by the following examples as long as the gist thereof is not exceeded.

Example 1
In Example 1, the optical element was produced and evaluated by the following method.

(Preparation of alumina precursor sol)
14.8 g of aluminum-sec-butoxide (ASBD, manufactured by Kawaken Fine Chemicals Co., Ltd.) and 0.5 molar equivalent of 3-methyl-2,4-pentanedione as a stabilizer with respect to the aluminum-sec-butoxide, It mixed and stirred until it became uniform with 2-ethyl butanol. 0.01 M dilute hydrochloric acid was dissolved in a mixed solvent of 2-ethylbutanol / 1-ethoxy-2-propanol, and then slowly added to the solution of aluminum-sec-butoxide, and stirred for a while. The solvent was adjusted so that the mixed solvent of the mixture ratio of 7/3 of 2-ethyl butanol and 1-ethoxy 2-propanol finally became 59.3 g. The aluminum oxide precursor sol was prepared by further stirring in an oil bath at 120 ° C. for 2 hours.

  When 5 g of this paint was taken and heated to 1000 ° C. to measure the solid content mass concentration, it was 8.0%.

(Preparation of hollow particle dispersion)
1. First step: 50 g of 1-ethoxy-2-propanol (hereinafter, 1E2P) was put in a 500 cc flask in advance, and then the hollow particle had a solid concentration of 20.5% by mass, and the solvent was isopropyl alcohol (hereinafter, IPA). An additional 200 g of silica sol (Surelia 1110, manufactured by JGC Corporation) was added, and an additional 136 g of 1E2P was added. The mixture was depressurized to 60 hPa and concentrated by heating to 45 ° C. When concentration was continued for 30 minutes, the solution weight was 205 g.

2. Second Step To the liquid obtained in the first step, 1E2P, 1-butoxy-2-propanol (hereinafter, 1B2P), 2-ethyl-1-butanol (hereinafter, 2E1B), and the amount of each solvent added is 1E2P: 1B2P: 2E1B was added so as to be 38: 31: 31. The diluted solution was stirred for 30 minutes to form a hollow particle dispersion for film formation. 5 g of this paint was taken and heated at 1000 ° C. to measure the solid content weight concentration, it was 3.80%.

(Adjustment of paint)
5 g of the above-mentioned aluminum oxide precursor sol and 5 g of a dispersion of hollow particles were mixed and stirred to obtain a paint of this example in which the ratio of dry solid content was hollow particle: aluminum oxide precursor sol of 32:68.

(Coating of paint)
The glass material was polished only on one side of BK7, and the other side was cleaned by ultrasonic cleaning in alkali detergent in a disk-like glass substrate of about 40 mm in diameter and about 2 mm in thickness, and then dried in an oven. An appropriate amount of the antireflective coating is dropped on the polished surface of the cleaned disk-like glass substrate, and coating is performed at 1500 rpm for 120 seconds by a spin coating method, and then heat treated in a hot air circulation oven at 140 ° C. for 30 minutes. A film containing amorphous aluminum oxide in the layer was obtained. As a result of measuring the film thickness of the obtained film with an ellipsometer, it was 102 nm. The film was immersed in warm water at 75 ° C. for 20 minutes to obtain an optical element.

  The reflectance at an incident angle of 5 ° in the wavelength range of 400 nm to 1600 nm of the optical element of Example 1 was measured by a spectrophotometer (U-4000 manufactured by Hitachi High-Technologies Corporation). At that time, the ground side was painted black with an oil-based pen, and measurement was performed in the state without back reflection.

  Cross-sectional observation of the optical element of Example 1 was performed. The fractured surface of the optical element in the direction perpendicular to the substrate was observed with an electron microscope (trade name: XL30-SFEG; manufactured by Philips) in a field of view of 800000 magnifications. The result is shown in FIG.

  In the optical element of Example 1, the particle layer was formed on the base material, and it was confirmed that the microstructure was formed in the particle layer. Furthermore, it was confirmed that a fine uneven structure was formed on the surface of the particle layer.

(Comparative example 1)
In the comparative example 1, the optical element which provided the multilayer film on the base material was produced. In the same manner as in Example 1, an antireflective film was formed on the substrate of BK7 by sequentially forming a multilayer film of MgF ₂ , SiO ₂ , Ta ₂ O ₅ , and Al ₂ O ₃ by vapor deposition on the substrate of BK7. . The reflectance of the optical element formed by the vapor deposition method was measured in the same manner as in Example 1.

(Comparative example 2)
In Comparative Example 2, as compared with Example 1, an optical element having no particle layer was produced. That is, film formation was performed using an alumina oxide precursor sol as a paint.

  After preparing a substrate in the same manner as in Example 1, an alumina oxide precursor sol was formed into a film by spin coating at 4500 rpm for 60 seconds. The optical element of Comparative Example 2 was obtained by immersing the substrate in warm water at 75 ° C. for 20 minutes.

(Evaluation)
The reflectance measurement result of the optical element produced by Example 1, the comparative example 1, and the comparative example 2 is shown in FIG. As compared with the optical elements of Comparative Example 1 and Comparative Example 2, it was confirmed that the optical element of Example 1 had good reflectance characteristics in the wide wavelength range of visible to infrared.

(Example 2)
An optical element was produced in the same manner as in Example 1 except that a paint in which the mixing ratio of the silica fine particles and the alumina precursor sol was changed was used.

  In Example 2, after the hollow particle dispersion and the alumina precursor sol are prepared, 5 g of the aluminum oxide precursor sol and 15 g of the hollow particle dispersion are mixed and stirred, and the ratio of the dry solid is hollow particles: aluminum oxide precursor The paint of this Example 2 whose body sol is 59:41 was obtained. As shown in Table 1, the optical element of Example 2 was obtained using this paint.

(Comparative example 3)
In Comparative Example 3, an optical element was produced in the same manner as Example 1 except that a paint in which the mixing ratio of the silica fine particles and the alumina precursor sol was changed was used.

  In Comparative Example 3, after preparing the hollow particle dispersion and the alumina precursor sol, 12 g of the aluminum oxide precursor sol and 6 g of the hollow particle dispersion are mixed and stirred, and the ratio of the dry solid is hollow particles: aluminum oxide precursor The paint of this comparative example 3 with a body sol of 19:81 was obtained. As shown in Table 1, an optical element of Comparative Example 3 was obtained using this paint.

(Comparative example 4)
In Comparative Example 4, an optical element was produced in the same manner as in Example 1 except that a paint in which the mixing ratio of the silica fine particles and the alumina precursor sol was changed was used.

  In Comparative Example 4, after the hollow particle dispersion and the alumina precursor sol are prepared, 4 g of the aluminum oxide precursor sol and 16 g of the hollow particle dispersion are mixed and stirred, and the ratio of the dry solid is hollow particles: aluminum oxide precursor The paint of this comparative example 4 whose body sol is 66:33 was obtained. As shown in Table 1, an optical element of Comparative Example 4 was obtained using this paint.

(Evaluation)
The reflectance was measured in the same manner as in Example 1. The reflectance measurement result of the optical element produced by Example 2, the comparative example 3, and the comparative example 4 is shown in FIG. In Example 2, it was confirmed that good reflectance characteristics were obtained in the wide wavelength range of visible to infrared. On the other hand, in Comparative Example 3, the optical member had a high reflectance in the infrared region. Moreover, in the comparative example 4, it became an optical member with the high reflectance of a visible region.

(Example 3)
In Example 3, an optical element was produced in the same manner as in Example 1 except that the rotation speed of the spin coating was changed. In Example 3, as shown in Table 2, the same paint as in Example 1 was subjected to film formation at a rotational speed of 1000 rpm. As a result of measuring the film thickness of the obtained film with an ellipsometer, it was 122 nm. The optical element of Example 3 was obtained by immersing the obtained film in warm water of 75 ° C. for 20 minutes as in Example 1.

(Example 4)
In Example 3, an optical element was produced in the same manner as in Example 1 except that the rotation speed of the spin coating was changed. In Example 3, as shown in Table 2, the same paint as in Example 1 was subjected to film formation at a rotational speed of 700 rpm. As a result of measuring the film thickness of the obtained film with an ellipsometer, it was 140 nm. The optical element of Example 4 was obtained by immersing the obtained film in warm water of 75 ° C. for 20 minutes as in Example 1.

(Evaluation)
The reflectance measurement result of the optical element produced in Example 3 and Example 4 is shown in FIG. It was confirmed that good reflectance characteristics were obtained in the visible to infrared wide wavelength range in both Example 3 and Example 4.

  The optical element manufactured according to the present invention exhibits an excellent antireflection effect over a wide band. The optical element of the present invention can be used for a lens, a prism, a mirror, a diffraction grating, and a polarizing element. In addition, the optical apparatus of the present invention can be used for a telescope, a binocular, a microscope, a camera, an endoscope and the like having the optical element of the present invention.

DESCRIPTION OF SYMBOLS 10 optical element 11 base 12 particle layer 13 fine uneven structure 14 particle 15 void (void)
Reference Signs List 16 microstructure 21 base material 22 particle layer 23 particle 24 void 25 aluminum oxide precursor sol 26 aluminum oxide 27 microstructure 28 fine asperity structure 101 camera lens unit 121 to 129 optical element

Claims (12)

An optical element comprising a particle layer having particles on a substrate,
The optical element characterized in that the particle layer has a fine structure mainly composed of aluminum oxide on the surface and between the particles.   The thickness of the said particle layer is 100 nm or more and 145 nm or less, The optical element of Claim 1 characterized by the above-mentioned.   The optical element according to claim 1, wherein the particles are hollow particles.   The optical element according to claim 3, wherein the particles are hollow silica particles. An optical apparatus having an optical element,
The optical element has a particle layer having particles on a substrate,
The optical device, wherein the particle layer has a fine concavo-convex structure containing aluminum oxide as a main component between the surface and the particles.   The optical apparatus according to claim 5, wherein the optical apparatus is a lens unit having a plurality of optical elements.   An aluminum oxide precursor sol containing a hydrolyzate of an aluminum compound and / or a condensate thereof as components, particles, and a solvent, wherein the mass ratio of the aluminum oxide precursor sol to the dry solid content of the particles is 60 The paint characterized by being: 40 to 30: 70.   The paint according to claim 7, wherein the particles are hollow particles.   The paint according to claim 8, wherein the particles are hollow silica particles.   10. The solvent according to any one of claims 7 to 9, wherein the solvent comprises a C5 to C8 monohydric alcohol and a water-soluble solvent having a boiling point of 110 ° C to 170 ° C. paint.   The solvent contains 50% by mass to 90% by mass of a C 5 to 8 monohydric alcohol, and 10% by mass to 50% by mass of a water-soluble solvent having a boiling point of 110 ° C. to 170 ° C. The paint according to any one of claims 7 to 10, characterized in that: Forming a particle layer containing an aluminum oxide precursor sol between particles by applying the paint according to any one of claims 7 to 11 on a substrate;
Forming an aluminum oxide from the aluminum oxide precursor sol by drying and / or calcining a particle layer containing the aluminum oxide precursor sol between the particles;
By immersing the particle layer containing the aluminum oxide in warm water or exposing it to steam, an aluminum oxide microstructure is formed between the particles, and a microrelief structure mainly composed of aluminum oxide is formed on the particle layer. And a forming step of forming an optical element.