Anodic Oxidation Mold for Antireflection Without Joint Lines
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Solution Overview
Problem
Producing large area molds or roll molds with microscopic patterns smaller than the wavelength of visible light is challenging due to issues like joint line remnants, low yield, and high production costs, as well as macroscopic unevenness from existing methods.
Innovation Solution
A process involving anodic oxidation of aluminum to create a mold with a regular microscopic pattern without joint lines or visible unevenness, using a combination of first and second anodic oxidation steps and pore diameter enlargement to achieve a smooth, tapered pore structure suitable for antireflection applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large area mold or roll mold with microscopic pattern is produced by conventional lithography or assembly methods, then the mold can be used for mass production, but joint lines remain visible and yield is low
Solution Approach 1:
The invention divides the mold production process into two independent stages: (1) producing a master mold with microscopic pattern by lithography on a small substrate, and (2) replicating this pattern onto a large area mold or roll mold through contact copying. This segmentation allows the master mold to be small and free of joint lines, while the replicated large mold inherits the pattern without introducing joint line defects.
Solution Approach 2:
The invention uses a contact copying process where a master mold with the microscopic pattern is pressed against a larger substrate to transfer the pattern. This copying method eliminates the need to directly fabricate the large mold with lithography, thereby avoiding joint line issues and improving yield through simpler, more reliable pattern transfer.
2Manufacturing precision
If lithography is used to form microscopic pattern not larger than visible light wavelength over large area, then the pattern resolution is sufficient, but the process complexity and production cost increase significantly
Solution Approach 1:
The invention separates the high-precision pattern formation step from the large area coverage step. The master mold is fabricated with the required sub-wavelength precision using lithography on a small, manageable substrate. Subsequently, this precise pattern is replicated onto large substrates through simple contact copying, which does not require lithographic precision but achieves large area coverage efficiently.
Solution Approach 2:
The contact copying process transfers the high-resolution pattern from the master mold to large area substrates without requiring the copying process itself to have lithographic precision. This dramatically simplifies the overall process complexity and reduces production costs while maintaining the required pattern resolution.
3Ease of manufacture
If anodic oxidation is used to create microscopic pattern on aluminum, then the process is simple and economical, but macroscopic unevenness from rolling marks or crystal grain boundaries becomes visible
Solution Approach 1:
The invention performs preliminary surface treatment of the aluminum substrate before anodic oxidation to eliminate macroscopic unevenness. The substrate undergoes mechanical polishing, chemical polishing, or electropolishing to remove rolling marks and level crystal grain boundaries. This preliminary action ensures that the subsequent anodic oxidation produces a uniform microscopic pattern without visible macroscopic defects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for the simple and economical production of molds and sheets with microscopic patterns, ensuring high yield and optical quality by eliminating joint lines and macroscopic unevenness, thereby enhancing antireflection properties.
Implementation Method 1
anodic oxidation of aluminum to create a mold with a regular microscopic pattern
Implementation Method 2
a steric structure called as a moth-eye structure is known as an effective antireflection means due to gradual increase from a refractive index of air to a refractive index of a material
Data Source
AI summary
A mold comprising alumina having a microscopic pattern, in which distances between adjacent recesses or salients therein are not longer than wavelength of visible light, formed by anodic oxidation on a surface of an alminum pre-mold without a rolling mark, wherein height or depth difference at a crystal grain boundary is 300 nm or less.