Anodized Layer Formation with Sloped Surfaces
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Solution Overview
Problem
The existing methods for forming anodized porous alumina layers result in antireflection films with stepped lateral surfaces, leading to higher light reflectance at specific wavelengths and a visible hue, which can be mitigated but at the cost of reduced throughput by repeating anodization and etching steps with short intervals.
Innovation Solution
An anodized layer formation method involving anodization of an aluminum base with a gradually increased forming voltage and subsequent etching to create minute recessed portions with sloped lateral surfaces, free from steps, by controlling the forming voltage and accumulated electricity during the anodization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional anodization methods are used to form porous alumina layers, then micropores with regular arrangement are formed, but the lateral surfaces of recessed portions become stepped, causing increased light reflectance at specific wavelengths and visible hue
Solution Approach 1:
The patent applies periodic action by repeating the anodization process multiple times with progressively increased voltage. Each anodization cycle creates micropores, and subsequent etching removes the barrier layer and portions of the porous layer. By cycling through anodization at different voltage levels, the method transforms the stepped lateral surfaces into continuously sloped surfaces, eliminating the harmful step effects while preserving micropore regularity.
Solution Approach 2:
The patent employs parameter changes by systematically varying the forming voltage across multiple anodization cycles. The voltage is increased from cycle to cycle (e.g., 40V, 60V, 80V, 100V), which changes the morphology of the porous alumina layer formed in each cycle. This progressive parameter change enables the transformation of stepped surfaces into continuously sloped surfaces, resolving the contradiction between regularity and harmful reflectance.
2Object-affected harmful factors
If multiple anodization and etching steps are repeated with short intervals to eliminate stepped surfaces, then hue appearance is reduced, but manufacturing throughput decreases
Solution Approach 1:
The patent structures the manufacturing process as periodic cycles of anodization and etching, where each cycle serves a specific purpose in transforming the surface morphology. By optimizing the number of cycles and the duration of each step, the method achieves continuously sloped surfaces that eliminate hue appearance while maintaining reasonable manufacturing throughput, balancing quality improvement with production efficiency.
Solution Approach 2:
The patent ensures continuity of useful action by designing a process where each anodization-etching cycle builds upon the previous one, progressively transforming the surface morphology toward the desired continuously sloped structure. This continuous transformation approach eliminates the need for excessive intermediate steps, thereby maintaining manufacturing throughput while achieving the quality improvement of eliminating hue appearance.
3Shape
If forming voltage is increased progressively during anodization, then continuously sloped lateral surfaces are formed, but process control complexity increases
Solution Approach 1:
The patent segments the voltage increase into discrete steps across multiple anodization cycles, with each cycle operating at a specific voltage level. This segmentation transforms the complex continuous voltage control problem into a series of simpler discrete voltage settings, reducing process control complexity while still achieving continuously sloped lateral surfaces through the cumulative effect of multiple cycles.
Solution Approach 2:
The patent applies preliminary action by pre-planning the voltage sequence for multiple anodization cycles before actual manufacturing. The voltage levels for each cycle are determined in advance based on the desired final surface morphology. This preliminary planning simplifies real-time process control, as the complex voltage progression is predetermined, reducing the actual control complexity during manufacturing.
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
This method effectively forms anodized layers with continuously sloped lateral surfaces, reducing light reflectance across the visible spectrum and preventing hue appearance in antireflection films, while maintaining a simple and efficient process.
Implementation Method 1
An aluminum base is immersed in an acidic electrolytic solution of sulfuric acid, oxalic acid, phosphoric acid, or the like, or an alkaline electrolytic solution, and this is used as an anode in application of a voltage (which is referred to as 'forming voltage'), which causes oxidation and dissolution.
Implementation Method 2
The oxidation and the dissolution concurrently advance over a surface of the aluminum base to form an oxide film which has micropores over its surface.
Implementation Method 3
A porous alumina layer which has minute recessed portions is formed by immersing an aluminum base or an aluminum film deposited on a support in an electrolytic solution and applying a voltage thereon
Implementation Method 4
a porous alumina layer is brought into contact with an etching solution, whereby the minute recessed portion is enlarged and a lateral surface of the minute recessed portion is sloped
Implementation Method 5
The refractive index for light that is incident on the substrate is continuously changed along the depth direction of the recessed portions or raised portions, from the refractive index of a medium on which the light is incident to the refractive index of the substrate, whereby reflection of a wavelength band that is subject to antireflection is prevented.
Data Source
AI summary
An anodized layer formation method includes: (a) providing an aluminum base or an aluminum film deposited on a support; anodization step (b) in which a forming voltage is increased to a predetermined first voltage level under a predetermined condition with a surface of the aluminum base or a surface of the aluminum film being kept in contact with an electrolytic solution, and thereafter, the forming voltage is maintained at the first voltage level for a predetermined period of time, whereby a porous alumina layer which has a minute recessed portion is formed; and etching step (c) in which, after step (b), the porous alumina layer is brought into contact with an etching solution, whereby the minute recessed portion is enlarged and a lateral surface of the minute recessed portion is sloped.