JP5653069B2 - Method for producing aluminum oxide precursor sol and method for producing optical member - Google Patents

Description

  The present invention relates to an aluminum oxide precursor sol having good coatability and capable of producing a high antireflection performance in a wide region including the visible region at a low temperature, a method for producing the aluminum oxide precursor sol, and an optical member using the same. It relates to the manufacturing method.

  It is known that an antireflection structure using a microstructure having a wavelength equal to or smaller than the wavelength in the visible light region exhibits excellent antireflection performance in a wide wavelength region by forming a microstructure with an appropriate pitch and height. . As a method for forming a fine structure, coating of a film in which fine particles having a particle size of a wavelength or less are dispersed is known.

  In addition, the pitch and height can be controlled in a method for forming a fine structure by pattern formation using a fine processing apparatus (electron beam drawing apparatus, laser interference exposure apparatus, semiconductor exposure apparatus, etching apparatus, etc.). It is also known that a fine structure having excellent antireflection properties can be formed (Patent Document 1).

  As another method, it is also known that boehmite, which is an aluminum hydroxide oxide, is grown on a substrate to obtain an antireflection effect. In these methods, an aluminum oxide (alumina) film formed by a vacuum film formation method or a liquid phase method (sol-gel method) is subjected to steam treatment or hot water immersion treatment to form a fine structure by boehmizing the surface layer, thereby preventing reflection. A film is obtained (Patent Document 2).

It is known that the method of forming an antireflection film using the fine structure of boehmite has extremely low reflectivity due to normal incidence and oblique incidence, and can provide excellent antireflection performance.
When a wet process such as a liquid phase method (sol-gel method) is used, the firing temperature during film formation is usually as high as 200 ° C. or higher (Patent Document 2). For this reason, there are problems in that the surface accuracy of the optical component and the peripheral members are adversely affected, and a film cannot be formed on a substrate that cannot withstand high temperatures such as a resin substrate.

  In addition, a stabilizer is added to the sol that forms an aluminum oxide film by the liquid phase method (sol-gel method) in order to prevent aluminum alkoxide from being rapidly hydrolyzed and clouded by the addition of moisture or water in the air. ing. As the stabilizer, compounds such as β-ketoester compounds, β-diketone compounds, alkanolamines are generally used.

  Stabilizers form chelates with aluminum to produce organoaluminum compounds. The organoaluminum compound may have a sublimation point of 150 ° C. or higher. Therefore, at a firing temperature lower than 200 ° C., organic components such as organoaluminum compounds cannot be completely removed from the aluminum oxide film by firing, and bond formation between particles obtained by hydrolyzing aluminum alkoxide is insufficient. It is estimated that If the bond formation between the particles is insufficient, the uneven structure of aluminum oxide boehmite is not sufficiently formed, and the antireflection performance deteriorates.

  In addition, when a film is formed by applying a sol using at least an aluminum-containing metal alkoxide and a stabilizer as raw materials on an optical component, aggregation of the organoaluminum compound occurs, resulting in a decrease in film uniformity and film unevenness. May cause poor appearance.

  Therefore, it is preferable to remove the organoaluminum compound from the aluminum oxide precursor sol and not leave it in the film.

  Therefore, a method is known in which the organic component in the film is eluted and removed by immersing the film in a water-containing solution before baking, and baking is performed while moisture is contained in the film (Patent Document 3). .

Japanese Patent Laid-Open No. 50-70040 JP-A-9-202649 JP 2009-015310 A

  However, in the liquid phase method (sol-gel method) in which an antireflection film is formed using the aluminum oxide precursor sol as described above, a highly hydrophobic organoaluminum compound is generated depending on the stabilizer used, There was a problem that it could not be removed. If a highly hydrophobic organoaluminum compound remains in the film, it was difficult to obtain an optical film having a high antireflection performance with suppressed appearance defects due to aggregation of the organoaluminum compound.

  The present invention has been made in view of such background art, and an aluminum oxide precursor sol and an aluminum oxide precursor capable of producing a high-performance antireflection film at a lower temperature without impairing the appearance of the optical member. A method for producing a sol and a method for producing an optical member are provided.

The method for producing an aluminum oxide precursor sol that solves the above problems includes (1) a step of dissolving an aluminum compound containing an aluminum alkoxide or an aluminum salt compound in a mixture of a β-ketoester compound or β-diketone compound and a solvent; ,
(2) The solution obtained in the step (1) is mixed with water or water containing a catalyst and hydrolyzed so that the condensate of the aluminum alkoxide or aluminum salt compound and the general formula (1) Forming a precipitate of an organoaluminum compound represented by:
(3) A step of removing the precipitate of the organoaluminum compound from the solution obtained in the step (2).

  R1 and R2 are each independently an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an alkoxyl group, or an allyl group; R3 is a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, A fluoroalkyl group, an allyl group, or an aryl group, and n is an integer of 1 to 3;

Method for producing an optical member for solving the aforementioned problem, on at least one side of the substrate, an aluminum oxide precursor aluminum oxide precursor produced by the method for producing a sol according to any one of claims 1 to 3 A step of supplying a body sol, a step of spreading the aluminum oxide precursor sol on a base material, a step of forming an aluminum oxide film by drying and / or firing the base material, and the aluminum oxide film at a temperature of 60 ° C. to 100 ° C. process ℃ was immersed in the following hot water to form a concavo-convex structure of aluminum oxide boehmite, and having a.

  According to the present invention, the appearance defect due to the aggregation of the organoaluminum compound during film formation can be suppressed by precipitating and removing the organoaluminum compound during preparation of the aluminum oxide precursor sol. Moreover, the manufacturing method of the aluminum oxide precursor sol and the aluminum oxide precursor sol which can produce the surface uneven structure which has antireflection performance at low temperature, and the manufacturing method of the optical member using the same can be provided.

It is process drawing which shows one Embodiment of the manufacturing method 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 optical member of this invention. It is the schematic which shows one embodiment of the optical member of this invention. It is a figure which shows the relationship of the absolute reflectance (%) with respect to the wavelength (nm) of the light of Example 1 and Comparative Example 1 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

The method for producing an aluminum oxide precursor sol according to the present invention comprises:
(1) A step of dissolving an aluminum compound containing an aluminum alkoxide or an aluminum salt compound in a mixture of a β-ketoester compound or a β-diketone compound and a solvent. (2) Water is added to the solution obtained in the step (1). Or the water containing the catalyst is mixed and hydrolyzed to form a condensate of the aluminum alkoxide or aluminum salt compound and a precipitate of the organoaluminum compound (3) obtained in the step (2) A step of removing a precipitate of the organoaluminum compound from the solution.

  The steps (1) to (3) are included in order. The organoaluminum compound represented by the general formula (1) is precipitated, and the precipitated organoaluminum compound is removed by filtration.

  R1 and R2 are an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an alkoxyl group, or an allyl group; R3 is a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, It is an allyl group or an aryl group, and n is an integer of 1 to 3.

  Hereinafter, the compound represented by the general formula (1) is referred to as an organoaluminum compound, and the precipitated organoaluminum compound is referred to as a precipitate of the organoaluminum compound.

  The organoaluminum compound precipitate is removed. Thereby, when the aluminum atom contained in the aluminum oxide precursor sol is 100 mol%, the organoaluminum compound contained in the aluminum oxide precursor sol is 7.5 mol% or more and 15.5 mol%. It can be as follows. Within this range, the stability and applicability of the aluminum oxide precursor sol can be balanced. If it is less than this, the stability of the aluminum oxide precursor sol is lowered, for example, the solution becomes cloudy, precipitates, or gels due to moisture in the air. If the amount is larger than this, the organoaluminum compound aggregates when the aluminum oxide precursor sol is applied to the base material, resulting in poor appearance.

  Moreover, in order to precipitate more organoaluminum compounds in the aluminum oxide precursor sol, the aluminum oxide precursor sol may be cooled.

The aluminum oxide precursor sol of the present invention contains, as a main component, a hydrolyzate and / or condensate thereof obtained by contacting an aluminum compound with water in a solvent. Here, the aluminum compound refers to Al—X ₃ (X represents an alkoxyl group, an acyloxyl group, a halogen group, or a nitrate ion). Further, the hydrolyzate of the aluminum compound will be referred to a _{Al-X 2 (OH),} Al-X (OH) 2, or Al- _(OH) compound represented by _3. In the hydrolyzate, the —OH groups or the —X group and —OH group react to form an Al—O—Al bond with the elimination of H ₂ O or XH. The resulting compound having one or more Al—O—Al bonds and having a linear structure or a branched structure is referred to as an aluminum compound condensate. The particles are preferably amorphous.

  For the aluminum oxide precursor sol, a small amount of a metal compound composed of 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, metal salt compounds such as chlorides and nitrates can be used. It is particularly preferable to use a metal alkoxide for the reason that the by-product during preparation of the sol has a small influence on the film forming property during coating. Further, the amount of the aluminum compound contained in the total amount of the metal compound of 100 mol% is preferably 90 mol% or more.

  The content of particles containing the hydrolyzate of the aluminum compound and / or the condensate thereof as a component in the aluminum oxide precursor sol of the present invention is 1% by weight or more and 7% by weight or less in terms of metal oxide. Preferably, it is 2.5 to 6% by weight.

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

  Examples of the aluminum compound include aluminum alkoxide, aluminum ethoxide, aluminum isopropoxide, aluminum-n-butoxide, aluminum-sec-butoxide, aluminum-tert-butoxide, aluminum acetylacetonate, and oligomers and aluminum salts thereof. Examples of the compound include aluminum nitrate, aluminum chloride, aluminum acetate, aluminum phosphate, aluminum sulfate, and aluminum hydroxide.

  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 compounds represented by the general formula Si (OR) ₄ can be used. R may be the same or different lower alkyl group such as methyl group, ethyl group, propyl group, isopropyl group, butyl group and isobutyl group.

  Examples of the titanium alkoxide include tetramethoxy titanium, tetraethoxy titanium, tetra n-propoxy titanium, tetraisopropoxy titanium, tetra n-butoxy titanium, and tetraisobutoxy titanium.

  Examples of the zinc compound include zinc acetate, zinc chloride, zinc nitrate, zinc stearate, zinc oleate, and zinc salicylate, with zinc acetate and zinc chloride being particularly preferred.

  Examples of the magnesium compound include magnesium alkoxides such as dimethoxy magnesium, diethoxy magnesium, dipropoxy magnesium and dibutoxy magnesium, 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, tetraisopropoxytitanium, tetran-butoxytitanium, di A metal alkoxide such as propoxymagnesium or dibutoxymagnesium is preferably used as a raw material.

  Among the metal compounds, aluminum, zirconium, and titanium alkoxides are particularly highly reactive with water, and are rapidly hydrolyzed by the addition of water and water in the air, resulting in cloudiness and precipitation of the solution. In addition, aluminum salt compounds, zinc salt compounds, and magnesium salt compounds are difficult to dissolve with only an organic solvent, and the stability of the solution is low. In order to prevent these, it is preferable to add a stabilizer to stabilize the solution.

  A β-ketoester compound and / or a β-diketone compound is used as the stabilizer. The stabilizer becomes an enolate due to the keto-enol phase variability in the solvent. The enolate coordinates to an aluminum atom with the elimination of the alcohol of the metal alkoxide to produce an organometallic compound. The stabilizer is coordinated to the metal alkoxide in the quantity, thereby suppressing rapid hydrolysis of the metal alkoxide. When the metal alkoxide is hydrolyzed and the particles grow, the liberated enolate further coordinates to the metal alkoxide already coordinated with the enolate.

  In this way, the stabilizer also forms a chelate with the aluminum alkoxide to produce an organoaluminum compound. The organoaluminum compound may have a sublimation point of 150 ° C. or higher. Therefore, in low-temperature firing at 200 ° C. or lower, organic components such as organoaluminum compounds cannot be completely removed from the aluminum oxide film by firing, and bond formation between particles obtained by hydrolyzing aluminum alkoxide is insufficient. It is estimated that If the bond formation between the particles is insufficient, the uneven structure of aluminum oxide boehmite is not sufficiently formed, and the antireflection performance deteriorates.

  In addition, if a film is formed by applying a sol using at least a metal alkoxide or metal salt compound containing aluminum and a stabilizer as raw materials on an optical component, aggregation of the organoaluminum compound occurs. It may lead to defects. Therefore, it is preferable to remove the organoaluminum compound from the aluminum oxide precursor sol as much as possible and not leave it in the film as much as possible.

  The aluminum oxide precursor sol of the present invention contains a condensate and a solvent obtained by hydrolyzing aluminum alkoxide. Furthermore, an organoaluminum compound is contained in an amount of 7.5 mol% to 15.5 mol% with respect to 100 mol% of aluminum atoms in the aluminum oxide precursor sol. Within this range, the stability and applicability of the aluminum oxide precursor sol can be balanced. If it is less than this, the stability of the aluminum oxide precursor sol is lowered, for example, the solution becomes cloudy, precipitates, or gels due to moisture in the air. If the amount is larger than this, the organoaluminum compound aggregates when the aluminum oxide precursor sol is applied to the base material, resulting in poor appearance.

  One method for measuring the amount of the organoaluminum compound contained in the aluminum oxide precursor sol is as follows. After the solvent of the aluminum oxide precursor sol is removed by vacuum drying, the organoaluminum compound is extracted with an extraction solvent such as chloroform. After removing the extraction solvent by vacuum drying, the weight of the organoaluminum compound is measured to determine the amount of the substance. The amount of aluminum atoms contained in the aluminum oxide precursor sol can be measured by inductively coupled high-frequency plasma spectroscopy (ICP) or the like to obtain an organoaluminum compound with respect to 1 mol of aluminum atoms in the aluminum oxide precursor sol.

  Stabilizers include methyl acetoacetate, ethyl acetoacetate, allyl acetoacetate, isopropyl acetoacetate, tert-butyl acetoacetate, isobutyl acetoacetate, 2-methoxyethyl acetoacetate, dimethyl malonate, diethyl malonate, allylmalon Β-ketoester compounds such as diethyl acid, diethyl methylmalonate, diethyl ethylmalonate, diisopropyl malonate, diethyl isopropylmalonate, and di-tert-butyl malonate. Acetyl acetone, 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, 3-butyl-2,4-pentanedione, 3-pentyl-2,4-pentanedione, 3-hexyl- 2,4-pentanedione, 3-isopropyl-2,4-pentanedione, 3-isobutyl-2,4-pentanedione, 3-isopentyl-2,4-pentanedione, 3-isohexyl-2,4-pentanedione 3-phenyl-2,4-pentanedione, 3-chloroacetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, 2,6-dimethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione And β-diketone compounds such as dipivaloylmethane.

In order to precipitate and remove the organoaluminum compound from the aluminum oxide precursor sol, it is preferable to use β-diketone compounds having a symmetrical structure in order to increase the crystallinity of the organoaluminum compound. Although it varies depending on the type of metal compound, it is preferably 0.5 mol or more and 2 mol or less with respect to 1 mol of aluminum alkoxide. The content of the organoaluminum compound in the aluminum oxide precursor sol can be reduced by adding the stabilizer, but if the amount is less than 0.5 mole per mole of aluminum alkoxide, a stable aluminum oxide precursor sol is prepared. It becomes difficult. In addition, the stabilizer is effective 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 amount of water added is preferably 0.5 mol or more and less than 2 mol with respect to 1 mol of the aluminum compound.

  Further, water can be added for the purpose of promoting a part of the hydrolysis reaction. It is preferable to use an acid or base catalyst such as hydrochloric acid or phosphoric acid as a catalyst at a concentration of 0.1 mol / L or less.

  The solvent may be an organic solvent in which a raw material such as an aluminum compound is uniformly dissolved and 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 , 1-heptanol, 2-heptanol, 1-octanol, 2-octanol and the like monovalent alcohols: ethylene glycol, triethylene glycol and other divalent alcohols: methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxy Etano Ether alcohols such as 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol: dimethoxyethane, diglyme, tetrahydrofuran, dioxane, diisopropyl ether, cyclopentyl methyl ether Ethers such as: ethyl formate, ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, etc .: n-hexane, n -Various aliphatic or alicyclic hydrocarbons such as octane, cyclohexane, cyclopentane and cyclooctane: Torue , Xylene, ethylbenzene and other aromatic hydrocarbons: acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketones: chloroform, methylene chloride, carbon tetrachloride, tetrachloroethane and various chlorinated carbonizations Hydrogen: N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, aprotic polar solvent such as ethylene carbonate, and the like.

  Among the above solvents, monohydric alcohols having 5 or more and 8 or less carbon atoms are preferable in that the solubility of the aluminum compound is high and it is difficult to absorb moisture. When hydrolysis of the aluminum compound proceeds due to moisture absorption by the solvent, the particles are aggregated and the stability of the aluminum oxide precursor sol is lowered. Also, moisture absorption during coating impairs the stability of optical properties due to particle aggregation. On the other hand, the monohydric alcohol having 5 or more and 8 or less carbon atoms has high hydrophobicity, and water necessary for hydrolysis cannot be uniformly mixed, and it is difficult to make 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 here refers to a solvent having a solubility of water in a solvent at 23 ° C. of 80% by weight or more.

  The content of the solvent contained in the aluminum oxide precursor sol of the present invention is 50% by weight to 98% by weight, preferably 60% by weight to 93% by weight. As a mixing ratio of the solvent, a monohydric alcohol having 5 to 8 carbon atoms is 50% by weight to 90% by weight, and a water-soluble solvent having a boiling point of 110 ° C. to 170 ° C. is 10% to 50% by weight. It is preferable to contain by a ratio. The water-soluble solvent is a water-soluble solvent having a boiling point of 110 ° C. or higher and 170 ° C. or lower. When a water-soluble solvent having a boiling point of less than 110 ° C. is used, moisture absorption and whitening are likely to occur due to volatilization. If a water-soluble solvent having a boiling point exceeding 170 ° C. is used, it remains in the aluminum oxide film even after drying, resulting in a variation in reflectance. It is preferable that the water-soluble solvent is glycol ether.

  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. Although the heating temperature depends on the boiling point of the solvent, it is preferably 60 ° C. or higher and 150 ° C. or lower. By heating, the particles grow and the particle properties are improved.

  The aluminum oxide precursor sol of the present invention can form an uneven structure of aluminum oxide boehmite when coated on a substrate, dried and then immersed in warm water. Suitable for use.

  The method for producing the optical member of the present invention will be described in detail.

  The method for producing an optical member according to the present invention includes (a) supplying the aluminum oxide precursor sol onto at least one surface of a substrate, and (b) applying the aluminum oxide precursor sol onto the substrate. A step of spreading, (c) a step of forming an aluminum oxide film by drying and / or firing the substrate, and (d) aluminum oxide boehmite by immersing the aluminum oxide film in warm water of 60 ° C. or higher and 100 ° C. or lower. A step of forming a concavo-convex structure.

  It is preferable that the optical member has an antireflection film composed of a plate crystal layer formed of a plate crystal containing aluminum oxide boehmite as a component on at least one surface of the substrate.

  FIG. 1 is a process diagram showing one embodiment of a method for producing an optical member of the present invention.

  FIG. 1A shows a state in which the above-described aluminum oxide precursor sol 2 is supplied to the substrate 1 in the step (1). The method of supplying the aluminum oxide precursor sol 2 includes a method of supplying the aluminum oxide precursor sol 2 by dropping it from a narrow tube or one or a plurality of pores, and an aluminum oxide precursor on the substrate 1 through a slit. There is a method of attaching the sol 2. Alternatively, a method in which the aluminum oxide precursor sol 2 is once attached to the plate and then transferred to the substrate 1 may be used. Moreover, the sol 2 can be supplied to the base material 1 by immersing the base material 1 in the aluminum oxide precursor sol 2.

  FIG. 1B shows a state in which the aluminum oxide precursor sol 2 supplied in the step (1) is spread on the substrate 1 in the step (2). As a method of spreading the aluminum oxide precursor sol 2 on the substrate 1, a spin coating method that spreads the dropped sol 2 by rotating the substrate 1, a sol dropped by moving a blade or a roll on the substrate 1 For example, a blade coating method or a roll coating method can be used. Further, the aluminum oxide precursor sol 2 can be expanded while being supplied. While supplying the aluminum oxide precursor sol 2 from the slit, the slit coating method in which the slit or substrate 1 is moved to spread the sol 2 or the sol 2 once adhered to the plate is transferred while moving the plate or substrate 1. Printing method.

  A dip coating method in which the substrate 1 is once immersed in the aluminum oxide precursor sol 2 and then the substrate 1 is pulled up at a constant speed is also an example. When an optical member having a three-dimensionally complicated shape such as a concave surface is manufactured, the spin coating method is preferable because it is difficult to access the supply source of the aluminum oxide precursor sol 2.

  FIG.1 (c) represents the state which formed the aluminum oxide film 3 by drying and / or baking the base material 1 in a process (3). When the substrate 1 is heated and dried, the aluminum oxide precursor sol 2 spread on the substrate 1 in the step (2) volatilizes the solvent, and the aluminum oxide film 3 in which particles in the sol 2 are deposited is formed. The When further heated, the condensation reaction of unreacted alkoxide and hydroxyl group proceeds. The heating temperature is preferably 140 ° C. or higher, which is necessary for volatilization of the solvent, and preferably 200 ° C. or lower in consideration of the influence on the base material and other peripheral members. Examples of the heating method include a method of heating in a hot air circulating oven, a muffle furnace, an IH furnace, a method of heating with an IR lamp, and the like.

  FIG.1 (d) represents the state in which the layer 4 which has the uneven structure 5 of the aluminum oxide boehmite was formed on the base material 1 in the process (4). The concavo-convex structure 5 is formed by contacting the aluminum oxide film 3 obtained in the step (3) with warm water of 60 ° C. or more and 100 ° C. or less. The formed layer 4 having a concavo-convex structure of aluminum oxide boehmite consists of crystals of aluminum oxide or hydroxide or hydrates thereof, and the main crystals are boehmite. Examples of the method of bringing the aluminum oxide film 3 into contact with warm water include a method of immersing the base material 1 in warm water, a method of bringing warm water into running water or mist, and contacting the aluminum oxide film 3. Hereinafter, a crystal formed by contacting an aluminum oxide film with warm water is referred to as aluminum oxide boehmite.

  The layer 4 having the concavo-convex structure 5 of aluminum oxide boehmite is preferably a plate-like crystal layer formed from a plate-like crystal composed mainly of aluminum oxide boehmite. A schematic cross-sectional view showing the optical member according to the present embodiment in that case is shown in FIG.

  In FIG. 2, the optical member obtained by the manufacturing method of the present invention is obtained by laminating a plate-like crystal layer 6 formed of a plate-like crystal containing aluminum oxide boehmite as a main component on a substrate 1. The plate-like crystal layer 6 mainly composed of aluminum oxide boehmite is formed from crystals of aluminum oxide or hydroxide or hydrates thereof, and is mainly boehmite.

  In addition, by arranging these plate crystals, the end portions form fine uneven shapes 7, so that the plate crystals are selectively selected in order to increase the height of the fine unevenness and narrow the interval. It is arranged at a specific angle with respect to the surface of the substrate.

  When the surface of the substrate 1 is a flat surface such as a flat plate, a film, or a sheet, as shown in FIG. 3, the plate crystal is in relation to the surface of the substrate, that is, the inclination direction 8 of the plate crystal and the substrate surface. It is desirable that the angle θ1 be between 45 ° and 90 °. More preferably, it is desirable that the angle is 60 ° or more and 90 ° or less.

  Further, when the surface of the substrate 1 has a two-dimensional or three-dimensional curved surface, as shown in FIG. 4, the plate crystal is relative to the surface of the substrate, that is, the inclination direction 8 of the plate crystal and the base. It is desirable that the average angle of the angle θ2 between the material surface and the tangent line 9 is 45 ° or more and 90 ° or less. More preferably, it is desirable that the angle is 60 ° or more and 90 ° or less.

  The layer thickness of the plate crystal layer 6 is preferably 20 nm or more and 1000 nm or less, and more preferably 50 nm or more and 1000 nm or less. When the layer thickness for forming the unevenness is 20 nm or more and 1000 nm or less, the antireflection performance by the fine uneven structure is effective, and the mechanical strength of the uneven structure is eliminated, and the manufacturing cost of the fine uneven structure is advantageous. Become. Moreover, when the layer thickness is 50 nm or more and 1000 nm or less, the antireflection performance is further improved, which is more preferable.

  The surface density of the fine irregularities of the present invention is also important, and the average surface roughness Ra ′ value obtained by expanding the corresponding centerline average roughness is 5 nm or more, more preferably 10 nm or more, more preferably 15 nm or more and 100 nm or less, The surface area ratio Sr is 1.1 or more. More preferably, it is 1.15 or more, More preferably, it is 1.2 or more and 3.5 or less.

  As one of the evaluation methods for the obtained fine uneven structure, there is observation of the surface of the fine uneven structure with a scanning probe microscope, and the average surface roughness Ra ′ obtained by extending the center line average roughness Ra of the film by the observation. The value and the surface area ratio Sr are determined. That is, the average surface roughness Ra ′ value (nm) is obtained by applying the centerline average roughness Ra defined in JIS B 0601 to the measurement surface and extending it three-dimensionally. The absolute value of the deviation up to the average value ”is expressed by the following equation (1).

Ra ′: average surface roughness value (nm),
S ₀ : Area when the measurement surface is ideally flat, | X _R −X _L | × | Y _T −Y _B |, F (X, Y): High at the measurement point (X, Y) X is the X coordinate, Y is the Y coordinate,
X _L to X _R : X coordinate range of the measurement surface,
Y _B to Y _T : Y coordinate range of the measurement surface,
Z ₀ : Average height in the measurement plane.

The surface area ratio Sr is Sr = S / S ₀ [S ₀ : Area when the measurement surface is ideally flat. S: Surface area of the actual measurement surface. ]. The actual surface area of the measurement surface is obtained as follows. First, it is divided into minute triangles composed of the three closest data points (A, B, C), and then the area ΔS of each minute triangle is obtained using a vector product. ΔS (ΔABC) = [s (s−AB) (s−BC) (s−AC)] 0.5 [where AB, BC, and AC are the lengths of each side, and s≡0.5 ( AB + BC + AC)], and the sum of ΔS is the surface area S to be obtained. When the surface density of the fine irregularities is Ra ′ is 5 nm or more and Sr is 1.1 or more, antireflection by the irregular structure can be expressed. If Ra ′ is 10 nm or more and Sr is 1.15 or more, the antireflection effect is higher than that of the former. When Ra ′ is 15 nm or more and Sr is 1.2 or more, the performance can withstand actual use. However, when Ra ′ is 100 nm or more and Sr is 3.5 or more, the effect of scattering by the concavo-convex structure is superior to the antireflection effect, and sufficient antireflection performance cannot be obtained.

  Between the base material 1 and the layer 4 having the concavo-convex structure 5 of aluminum oxide boehmite, a layer mainly composed of components other than aluminum oxide can be provided. FIG. 5 shows an example of an optical member in which a layer 10 containing as a main component other than aluminum oxide on a substrate 1 and a layer 4 having an uneven structure 5 of aluminum oxide boehmite formed thereon are formed.

  The layer 10 whose main component is other than aluminum oxide is provided mainly for the purpose of adjusting the refractive index difference between the substrate 1 and the layer 4 having the concavo-convex structure 5 of aluminum oxide boehmite. Therefore, it is preferable that the layer 6 mainly composed of other than aluminum oxide is a transparent film made of an inorganic material or an organic material.

Examples of the inorganic material used for the layer 10 whose main component is other than aluminum oxide include metal oxides such as SiO ₂ , TiO ₂ , ZrO ₂ , ZnO, and Ta ₂ O ₅ . Examples of the method for forming the layer 10 mainly composed of an inorganic material other than aluminum oxide include a vacuum film forming method such as vapor deposition and sputtering, and a sol-gel method by applying a metal oxide precursor sol.

  On the other hand, examples of organic materials used for the layer 10 mainly composed of other than aluminum oxide include acrylic resin, epoxy resin, oxetane resin, maleimide resin, melamine resin, benzoguanamine resin, phenol resin, resol resin, polycarbonate, polyester, Examples include organic polymers such as polyarylate, polyether, polyurea, polyurethane, polyamide, polyamideimide, polyimide, polyketone, polysulfone, polyphenylene, polyxylylene, and polycycloolefin. Examples of a method for forming the layer 10 mainly composed of an organic material other than aluminum oxide include a wet coating method in which the solution is mainly formed by coating.

In addition, the surface of the concavo-convex structure 5 of aluminum oxide boehmite can be treated to such an extent that the antireflection property is not impaired. In order to impart scratch resistance and antifouling properties, an example in which a very thin layer of SiO ₂ thin film, FAS (fluorinated alkylsilane) or fluororesin is provided can be given.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to such examples. The optical film having fine irregularities on the surface obtained in each example and comparative example was evaluated by the following method.

  In the preparation of the aluminum oxide precursor sol, the organoaluminum compound varies depending on the addition amount of the stabilizer, so the addition amount of the stabilizer relative to the aluminum alkoxide was 0.5 molar equivalent which is the lower limit of the preferred addition amount. . The aluminum oxide precursor sol on which the organoaluminum compound is precipitated was filtered.

(1) Preparation of aluminum oxide precursor sols 1 to 6 14.8 g of aluminum-sec-butoxide (ASBD, manufactured by Kawaken Fine Chemicals) and 0.5 molar equivalent of stabilizer relative to aluminum-sec-butoxide And 2-ethylbutanol were mixed and stirred until uniform. After 0.01M dilute hydrochloric acid was dissolved in a mixed solvent of 2-ethylbutanol / 1-ethoxy-2-propanol, it was slowly added to the aluminum-sec-butoxide solution and stirred for a while. The solvent was finally adjusted so that the mixing ratio of 2-ethylbutanol and 1-ethoxy-2-propanol was 7/3. Furthermore, aluminum oxide precursor sols 1 to 6 were prepared by stirring in an oil bath at 120 ° C. for 2 to 3 hours or more. Table 1 shows the stabilizer used in the preparation, the amount of each raw material used, and the content of the organoaluminum compound in the aluminum oxide precursor sol. For aluminum oxide precursor sols 1 to 3, a precipitate of organoaluminum compound was formed in the aluminum oxide precursor sol. The formed organoaluminum compound precipitate was removed by filtration.

(2) Preparation of SiO ₂ —TiO ₂ Sol Solution 7 3.15 g of 0.01 M diluted hydrochloric acid [HClaq. ] And 17.2 g of 2-propanol mixed solvent were slowly added, followed by stirring at room temperature. After stirring for 6 hours, it was diluted with a mixed solvent of 91.5 g of 4-methyl-2-pentanol and 46.4 g of 2-ethylbutanol to obtain a solution A. 6.7 g of tetra n-butoxy titanium was dissolved in a mixed solution of 2.6 g of ethyl 3-oxobutanoate and 16.8 g of 4-methyl-2-pentanol. This solution was stirred at room temperature for 3 hours to obtain a liquid B. The solution B was slowly added while stirring the solution A, and further stirred at room temperature for 3 hours to prepare a SiO ₂ —TiO ₂ sol solution 9 having a Si / Ti molar ratio of 78/22.

(3) Cleaning of base material Only one side is polished, and the other side is ground glass-like size φ30 mm, thickness of about 1 mm disc-shaped glass substrate ultrasonically washed in an alkaline detergent and then dried in an oven .

(4) Reflectance measurement Using an absolute reflectance measuring apparatus (USPM-RU, manufactured by Olympus), reflectance measurement was performed at an incident angle of 0 ° in the range of 400 nm to 700 nm. Evaluation was made with the average reflectance of the measurement range.

(5) Surface observation of substrate The surface of the substrate was visually observed. When film unevenness was observed, it was classified as follows.

Film unevenness 1: Annular film unevenness seen in the periphery of the substrate Film unevenness 2: Film unevenness extending from the center toward the periphery of the substrate

  (Note 1) * Stabilizer amount (molar equivalent) indicates the molar equivalent of stabilizer relative to aluminum-sec-butoxide.

  (Note 2) * Aluminum-sec-butoxide amount (% by weight) indicates the weight% of the raw material aluminum-sec-butoxide with respect to the aluminum oxide precursor sol.

  (Note 3) * Catalyst water (molar equivalent) indicates the molar equivalent of catalytic water relative to aluminum-sec-butoxide.

  (Note 4) * The amount (mol%) of the organoaluminum compound indicates the mol% of the organoaluminum compound relative to the aluminum atom in the aluminum oxide precursor sol.

Example 1
An appropriate amount of SiO ₂ —TiO ₂ sol solution 9 was dropped onto S-LAH55 (n550 nm = 1.83) flat glass washed by the above method, and spin coating was performed at 3000 rpm for 20 seconds. This substrate was baked in a hot air circulating oven at 200 ° C. for 12 hours to produce a lens with a SiO ₂ —TiO ₂ layer on the concave surface of the lens.

An appropriate amount of the aluminum oxide precursor sol 1 is dropped on a flat glass with a SiO ₂ —TiO ₂ layer, spin-coated at 3500 rpm for 20 seconds, and then baked in a hot air circulating oven at 140 ° C. for 2 hours to form an amorphous aluminum oxide film Was coated.

  Next, after being immersed in hot water at 75 ° C. for 20 minutes, it was dried at 60 ° C. for 20 minutes.

Example 2
The same operation as in Example 1 was performed except that the aluminum oxide precursor sol 2 was used in place of the aluminum oxide precursor sol 1 and an amorphous aluminum oxide film was formed.

Example 3
The same operation as in Example 1 was performed except that the aluminum oxide precursor sol 3 was used in place of the aluminum oxide precursor sol 1 to form an amorphous aluminum oxide film.

  When the reflectance was measured, it was confirmed that the average reflectance of the optical film made of the aluminum oxide precursor sol having a low organoaluminum compound content was lowered. Moreover, the film nonuniformity by aggregation was not seen.

Example 4
The same operation as in Example 3 was performed except that the firing conditions were changed to firing in a hot air circulating oven at 160 ° C. for 2 hours.

  When the reflectance was measured, it was confirmed that bond formation was promoted and the antireflection performance was improved due to the high firing temperature. Moreover, the film nonuniformity by aggregation was not seen.

Comparative Example 1
The same operation as in Example 1 was performed except that an aluminum oxide precursor sol 4 was used instead of the aluminum oxide precursor sol 1 and an amorphous aluminum oxide film was formed.

Comparative Example 2
The same operation as in Example 1 was performed except that an aluminum oxide precursor sol 5 was used instead of the aluminum oxide precursor sol 1 and an amorphous aluminum oxide film was formed.

Comparative Example 3
The same operation as in Example 1 was performed except that an aluminum oxide precursor sol 6 was used instead of the aluminum oxide precursor sol 1 and an amorphous aluminum oxide film was formed.

  When the reflectance was measured, it was confirmed that the average reflectance was inferior to the optical film made of the aluminum oxide precursor sol according to the present case. Further, when the aluminum oxide precursor sol was spin-coated, film unevenness 1 was observed in Comparative Examples 1 and 2, and film unevenness 2 was observed in Comparative Example 2.

Comparative Example 4
The same operation as in Comparative Example 1 was performed except that the firing conditions were changed to firing for 2 hours in a 160 ° C. hot air circulating oven.

  When the reflectance was measured, bond formation was promoted and the antireflection performance was improved due to the high baking temperature, but the same high antireflection performance as that of the optical film made of the aluminum oxide precursor sol according to the present case was obtained. It was confirmed that it was difficult to realize under firing conditions. Moreover, the film nonuniformity 1 was seen.

  (Note 5) * The amount (mol%) of the organoaluminum compound indicates the mol% of the organoaluminum compound relative to the aluminum atom in the aluminum oxide sol.

  (Note 6) * Average reflectance (%) indicates an average value of reflectance at an incident angle of 0 ° in a light wavelength range of 400 nm to 700 nm.

[Performance evaluation]
From the results of Examples 1 to 4 and the results of FIG. 6, it was found that the examples had higher antireflection performance even under the same low-temperature firing conditions as compared with the comparative examples. Further, the organoaluminum compound of the present invention is precipitated and removed so that the content of the organoaluminum compound is 7.5 mol% or more and 15.5 mol% or less with respect to 100 mol% of aluminum atoms in the aluminum oxide precursor sol did. This has been found to be important in obtaining a film with high reflectivity prevention performance. Moreover, the film nonuniformity by the aggregate was not seen. On the other hand, in Comparative Examples 1 to 4, film unevenness due to aggregation was observed after spin coating, and an optical film with deteriorated average reflectance was obtained.

  The optical member produced according to the present invention can correspond to a transparent substrate having an arbitrary refractive index, exhibits an antireflection effect excellent for visible light, and has long-term weather resistance. Therefore, various displays such as word processors, computers, televisions, plasma display panels, etc .: polarizing plates used in liquid crystal display devices, sunglasses lenses made of various optical glass materials and transparent plastics, prescription eyeglass lenses, camera finder lenses, prisms, fly eyes Optical members such as lenses, toric lenses, various optical filters and sensors: Furthermore, photographing optical systems using them, observation optical systems such as binoculars, projection optical systems used for liquid crystal projectors, etc .: scanning optical systems used for laser beam printers, etc. Various optical lenses such as: Covers for various instruments, optical members such as windows for automobiles, trains, etc.

DESCRIPTION OF SYMBOLS 1 Base material 2 Aluminum oxide precursor sol 3 Aluminum oxide film 4 Layer which has uneven structure of aluminum oxide boehmite 5 Uneven structure of aluminum oxide boehmite 6 Plate-like crystal formed from the plate-like crystal which has aluminum oxide boehmite as a main component Layer 7 Concave and convex shape 8 Inclination direction 9 Tangent line of substrate surface 10 Layer mainly composed of other than aluminum oxide

Claims (4)

(1) a step of dissolving an aluminum compound containing an aluminum alkoxide or an aluminum salt compound in a mixture of a β-ketoester compound or a β-diketone compound and a solvent;
(2) The solution obtained in the step (1) is mixed with water or water containing a catalyst and hydrolyzed so that the condensate of the aluminum alkoxide or aluminum salt compound and the general formula (1) Forming a precipitate of an organoaluminum compound represented by:
(3) A method for producing an aluminum oxide precursor sol, comprising: removing a precipitate of the organoaluminum compound from the solution obtained in the step (2).

R1 and R2 are an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an alkoxyl group, or an allyl group; R3 is a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, It is an allyl group or an aryl group, and n is an integer of 1 to 3.   The method for producing an aluminum oxide precursor sol according to claim 1, wherein the solvent is a monohydric alcohol having 5 to 8 carbon atoms.   The method for producing an aluminum oxide precursor sol according to claim 1 or 2, wherein an acid or base catalyst is used as the catalyst. The method for producing an optical member, (a) on at least one side of the substrate, an aluminum oxide precursor which is produced by the manufacturing method of the aluminum oxide precursor sol according to any one of claims 1 to 3 A step of supplying a sol, (b) a step of spreading the aluminum oxide precursor sol on a substrate, (c) a step of forming an aluminum oxide film by drying and / or firing the substrate, (d) A method for producing an optical member , comprising a step of immersing an aluminum oxide film in warm water of 60 ° C. or higher and 100 ° C. or lower to form an uneven structure of aluminum oxide boehmite.