US-12619015-B2 - Method of manufacturing optical member

Abstract

A method of manufacturing an optical member includes forming a first layer on a light transmissive substrate by atomic layer deposition, converting a surface layer of the first layer into a boehmite layer, and forming a second layer by atomic layer deposition so as to cover the boehmite layer. The first layer includes aluminum oxide and has a first thickness. The second layer has a second thickness less than the first thickness.

Inventors

• Takaaki Tada

Assignees

• NICHIA CORPORATION

Dates

Publication Date

20260505

Application Date

20230809

Priority Date

20220818

Claims (18)

1. 1 . A method of manufacturing an optical member, the method comprising: forming a first layer on a light transmissive substrate by atomic layer deposition, the first layer comprising aluminum oxide and having a first thickness; converting a surface layer of the first layer into a boehmite layer; and after converting the surface layer of the first layer into the boehmite layer, forming a second layer on the boehmite layer by atomic layer deposition such that the second layer covers the boehmite layer and forms an outermost layer of the optical member, the second layer having a second thickness less than the first thickness.
2. 2 . The method of manufacturing the optical member according to claim 1 , wherein: the step of converting of the surface layer of the first layer into the boehmite layer comprises immersing the first layer in water having a temperature of 70° C. or more.
3. 3 . The method of manufacturing the optical member according to claim 1 , further comprising: before the step of forming the first layer, forming a third layer on the light transmissive substrate; wherein: the first layer is formed on the third layer; and a refractive index of the third layer is lower than a refractive index of the light transmissive substrate and is higher than a refractive index of the boehmite layer.
4. 4 . The method of manufacturing the optical member according to claim 2 , further comprising: before the step of forming the first layer, forming a third layer on the light transmissive substrate; wherein: the first layer is formed on the third layer; and a refractive index of the third layer is lower than a refractive index of the light transmissive substrate and is higher than a refractive index of the boehmite layer.
5. 5 . The method of manufacturing the optical member according to claim 3 , further comprising: before the step of forming the third layer, forming a fourth layer on the light transmissive substrate, the fourth layer comprising aluminum oxide; wherein: the third layer is formed on the fourth layer.
6. 6 . The method of manufacturing the optical member according to claim 4 , further comprising: before the step of forming the third layer, forming a fourth layer on the light transmissive substrate, the fourth layer comprising aluminum oxide; wherein: the third layer is formed on the fourth layer.
7. 7 . The method of manufacturing the optical member according to claim 1 , wherein: the first thickness is 5 nm or more and 17.5 nm or less.
8. 8 . The method of manufacturing the optical member according to claim 2 , wherein: the first thickness is 5 nm or more and 17.5 nm or less.
9. 9 . The method of manufacturing the optical member according to claim 3 , wherein: the first thickness is 5 nm or more and 17.5 nm or less.
10. 10 . The method of manufacturing the optical member according to claim 1 , wherein: the second thickness is 4 nm or more and 15 nm or less.
11. 11 . The method of manufacturing the optical member according to claim 2 , wherein: the second thickness is 4 nm or more and 15 nm or less.
12. 12 . The method of manufacturing the optical member according to claim 3 , wherein: the second thickness is 4 nm or more and 15 nm or less.
13. 13 . The method of manufacturing the optical member according to claim 1 , wherein: the second layer comprises at least one of silicon oxide, aluminum oxide, niobium pentoxide, tantalum pentoxide, hafnium oxide, zirconium oxide, titanium oxide, or zinc oxide.
14. 14 . The method of manufacturing the optical member according to claim 2 , wherein: the second layer comprises at least one of silicon oxide, aluminum oxide, niobium pentoxide, tantalum pentoxide, hafnium oxide, zirconium oxide, titanium oxide, or zinc oxide.
15. 15 . The method of manufacturing the optical member according to claim 3 , wherein: the second layer comprises at least one of silicon oxide, aluminum oxide, niobium pentoxide, tantalum pentoxide, hafnium oxide, zirconium oxide, titanium oxide, or zinc oxide.
16. 16 . The method of manufacturing the optical member according to claim 1 , wherein: the light transmissive substrate is a sapphire substrate.
17. 17 . The method of manufacturing the optical member according to claim 2 , wherein: the light transmissive substrate is a sapphire substrate.
18. 18 . The method of manufacturing the optical member according to claim 3 , wherein: the light transmissive substrate is a sapphire substrate.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based on and claims priority to Japanese Patent Application No. 2022-130499, filed on Aug. 18, 2022, the entire contents of which are incorporated herein by reference. FIELD The present disclosure relates to a method of manufacturing an optical member. BACKGROUND As a method of manufacturing a member having an antireflection function, a method of forming an aluminum oxide film on a base by atomic layer deposition and subjecting the aluminum oxide film to hydrothermal treatment so as to form a fine uneven structure is proposed in Japanese Patent Publication No. 2015-114381. The fine uneven structure formed by subjecting the aluminum oxide film to hydrothermal treatment is composed of boehmite. The strength of the fine uneven structure composed of boehmite is low, and thus the fine uneven structure is easily damaged. The fine uneven structure may be damaged by, for example, being rubbed with a finger. Therefore, it is difficult for an optical member having a fine uneven structure as described above to obtain stable optical characteristics. SUMMARY According to the present disclosure, it is desirable to provide a method of manufacturing an optical member that can reduce damage to a boehmite layer. According to an aspect of the present disclosure, a method of manufacturing an optical member includes forming a first layer on a light transmissive substrate by atomic layer deposition, converting a surface layer of the first layer into a boehmite layer, and forming a second layer by the atomic layer deposition so as to cover the boehmite layer. The first layer includes aluminum oxide and has a first thickness. The second layer has a second thickness less than the first thickness. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: FIG. 1 is a cross-sectional view (part 1) illustrating a method of manufacturing an optical member according to a first embodiment; FIG. 2 is a cross-sectional view (part 2) illustrating the method of manufacturing the optical member according to the first embodiment; FIG. 3 is a cross-sectional view (part 3) illustrating the method of manufacturing the optical member according to the first embodiment; FIG. 4 is a cross-sectional view (part 4) illustrating the method of manufacturing the optical member according to the first embodiment; FIG. 5 is a schematic view illustrating an example of the shape of the surface of a boehmite layer; FIG. 6 is a drawing illustrating an example of a scanning electron microscope image of the surface of the boehmite layer; FIG. 7 is a drawing illustrating an example of a scanning electron microscope image of the surface of a silicon oxide layer; FIG. 8 is a cross-sectional view (part 1) illustrating a method of manufacturing an optical member according to a second embodiment; FIG. 9 is a cross-sectional view (part 2) illustrating the method of manufacturing the optical member according to the second embodiment; FIG. 10 is a cross-sectional view (part 3) illustrating the method of manufacturing the optical member according to the second embodiment; FIG. 11 is a drawing illustrating an example of a light emitting device including an optical member; and FIG. 12 is a graph illustrating the relationship between the thickness of each silicon oxide layer and the reflectance. DETAILED DESCRIPTION Embodiments of the present disclosure will be described below with reference to the accompanying drawings. The following description is provided for the purpose of embodying the technical idea of the present invention, and the present invention is not limited to the embodiments in the following description. In the drawings, components having the same function may be denoted by the same reference numerals. Although configurations may be illustrated in separate embodiments for the sake of convenience in consideration of ease of explanation or ease of understanding of key points, such configurations illustrated in different embodiments or examples can be partially substituted or combined with one another. A description of an embodiment given after a description of another embodiment will be focused mainly on matters different from those of the already described embodiment, and a duplicate description of matters common to the already described embodiment may be omitted. The sizes, positional relationships, and the like of components illustrated in the drawings may sometimes be exaggerated for clearer illustration. First Embodiment A first embodiment will be described. The first embodiment relates to a method of manufacturing an optical member. FIG. 1 through FIG. 4 are cross-sectional views illustrating a method of manufacturing an optical member according to the first embodiment. An optical member 1 according to the first embodiment includes a light tran