Precursor sol of aluminum oxide and method for manufacturing the same, method for manufacturing optical member, optical member, and optical system
A precursor sol of aluminum oxide includes particles containing a hydrolysate and/or a condensate of an aluminum compound, a solvent, and an organo aluminum compound. When a pulsed-NMR T 2 relaxation curve of nuclide 1 H of the precursor sol of aluminum oxide includes two components with different T 2 relaxation times and the component with the longer T 2 relaxation time has an abundance level of C L (%) and the component with the shorter T 2 relaxation time has an abundance level of C S (%), the relative proportion R CS (%) defined by [{C S /(C S +C L )}×100] is in the range of 23.5% to 50.0%, both inclusive.
1. A precursor sol of aluminum oxide including particles containing a hydrolysate or a condensate of an aluminum compound, a solvent, and an organo aluminum compound represented by general formula (1), wherein when a pulsed-NMR T 2 relaxation curve of nuclide 1 H of the precursor sol of aluminum oxide includes two components with different T 2 relaxation times and the component with the longer T 2 relaxation time has an abundance level of C L (%) and the component with the shorter T 2 relaxation time has an abundance level of C S (%), a relative proportion R CS (%) of C S determined by equation (1) is in a range of 23.5% to 50.0%, both inclusive:
where R 1 and R 2 denote an alkyl, perfluoroalkyl, or allyl group of one to six carbon atoms, R 3 denotes a hydrogen atom, a halogen atom, or an alkyl, perfluoroalkyl, allyl, or aryl group of one to six carbon atoms, and n denotes an integer of 1 to 3, both inclusive
R
cs
=
C
S
C
S
+
C
L
×
100.
(
1
)
2. The precursor sol of aluminum oxide according to claim 1 , wherein the particles containing a hydrolysate or a condensate of an aluminum compound have an average particle size of 7.5 nm to 35 nm, both inclusive.
3. A method for manufacturing an optical member, comprising (a) supplying the precursor sol of aluminum oxide according to claim 1 to at least either side of a base, (b) drying or baking the precursor sol of aluminum oxide supplied to the base to form an aluminum oxide film, and (c) bringing the aluminum oxide film into contact with hot water or steam at 60° C. to 100° C., both inclusive, to make a crystalline matter containing aluminum oxide separate out, thereby forming a textured structure containing aluminum oxide crystals.
4. The method for manufacturing an optical member according to claim 3 , wherein the precursor sol of aluminum oxide is supplied to the base by spin coating.
5. The method for manufacturing an optical member according to claim 3 , wherein the aluminum oxide film has a thickness of 160 nm to 300 nm, both inclusive.
6. An optical member produced by the method for manufacturing an optical member according to claim 3 .
7. The optical member according to claim 6 , wherein the textured structure is an aluminum oxide nanostructure.
8. An optical system comprising the optical member according to claim 6 .