White Anodized Aluminum Films With Diffuse Light Scattering
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Solution Overview
Problem
Conventional methods for producing anodized films with a white appearance often result in off-white, muted grey, or milky white finishes, failing to achieve a crisp and clean white appearance that is aesthetically appealing.
Innovation Solution
The methods involve varying current density during aluminum oxide layer formation on an aluminum substrate, creating a porous structure with irregular pore walls, forming micro-cracks using a pulsed laser beam, depositing a reflective layer, and infusing light reflective particles within the anodized film to achieve diffuse reflection of visible wavelengths, resulting in a white appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anodizing methods are used to form an anodized film, then the film provides corrosion resistance and wear resistance, but the film appears off-white, muted grey, or milky white instead of a crisp and clean white
Solution Approach 1:
The patent applies parameter changes by systematically varying anodizing conditions including electrolyte composition (sulfuric acid with additives like ammonium fluoride), temperature (0-25°C), voltage (12-24V), and time (15-60 minutes) to achieve a crisp white appearance while maintaining corrosion resistance. The specific parameter range of 12-24V and 15-60 minutes produces the desired optical properties without compromising protective functionality.
2Illumination intensity
If the anodized film is made more opaque to achieve white appearance, then light reflection improves, but the film may lose transparency needed for certain cosmetic effects
Solution Approach 1:
The patent applies local quality by creating a porous anodized film structure where the pore walls provide light scattering for white appearance in specific regions, while the overall film maintains controlled opacity. The porous structure with interconnected pores creates localized light interaction that produces crisp white appearance without complete opacity, allowing cosmetic effects to be achieved through selective light reflection and scattering.
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
These techniques produce anodized films that diffusely reflect nearly all visible wavelengths, imparting a bright, opaque, and cosmetically appealing white appearance, suitable for protective and attractive surfaces on consumer products.
Implementation Method 1
The method includes forming a pattern of melted portions within the porous structure by scanning a pulsed laser beam over a top surface of the anodized film
Implementation Method 2
The method also includes forming a pattern of crystallized metal oxide portions within the anodized film by allowing the pattern of melted portions to cool and transform into crystalline form
Implementation Method 3
The micro-cracks diffusely reflect nearly all visible wavelengths of light incident the crystallized metal oxide portions
Implementation Method 4
Anodizing is an electrolytic passivation process used to increase the thickness of a natural oxide layer on a surface of metal parts where the part to be treated forms the anode electrode of an electrical circuit
Data Source
AI summary
The embodiments described herein relate to forming anodized films that have a white appearance. In some embodiments, an anodized film having pores with light diffusing pore walls created by varying the current density during an anodizing process is described. In some embodiments, an anodized film having light diffusing micro-cracks created by a laser cracking procedure is described. In some embodiments, a sputtered layer of light diffusing aluminum is provided below an anodized film. In some embodiments, light diffusing particles are infused within openings of an anodized layer.