Method of making an article with anti-reflective properties and article obtainable therefrom.
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Solution Overview
Problem
Anti-reflective coatings made with nano-particles and metal oxide binders suffer from property deterioration over time, especially when applied to float glass substrates, due to hygroscopic compounds like sodium that migrate and fill the coating's pores, affecting their optical performance.
Innovation Solution
A method involving reacting nano-particles with a surface modifying agent, pre-hydrolysing a binder, mixing the modified particles with the binder, applying the coating to a substrate, curing it, and washing the coating with water to remove hygroscopic materials, resulting in a porous coating with reduced sodium content and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous anti-reflective coating is applied to a float glass substrate, then the coating initially exhibits good anti-reflective properties, but the properties deteriorate over time due to sodium migration and pore filling
Solution Approach 1:
The patent removes hygroscopic compounds (sodium) from the coating system by treating the float glass substrate with hydrofluoric acid before coating application. This extraction of harmful substances prevents their subsequent migration into the porous coating structure, thereby eliminating the root cause of property deterioration and extending the coating's service life while maintaining reliable anti-reflective performance
Solution Approach 2:
The patent applies a preliminary treatment step using hydrofluoric acid to etch the glass substrate surface and remove sodium compounds before the anti-reflective coating is applied. This preliminary anti-action prevents the harmful migration of sodium that would otherwise occur during the coating's service life, thereby preventing future deterioration and ensuring long-term stability of the anti-reflective properties
2Stability of the object's composition
If the coating is washed with water after curing, then hygroscopic materials are removed and stability is improved, but additional processing steps are required
Solution Approach 1:
The patent combines the substrate preparation step (sodium removal via hydrofluoric acid treatment) with the initial coating application process, eliminating the need for a separate post-curing washing step. By merging the removal of hygroscopic materials into the pre-coating treatment phase, the method achieves improved coating stability without adding complex additional processing steps after curing
3Ease of manufacture
If sodium content in the substrate is high, then the substrate is easier to manufacture, but the coating properties deteriorate due to sodium migration
Solution Approach 1:
The patent introduces hydrofluoric acid treatment as an intermediary step between substrate manufacturing and coating application. This intermediary process selectively removes sodium from the glass substrate surface without requiring changes to the substrate manufacturing process itself, thereby maintaining ease of substrate production while preventing sodium migration that would compromise coating performance stability
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 produces a coating with enhanced stability and anti-reflective properties, maintaining low reflection levels and mechanical resistance, with sodium content minimized in the top 10nm of the coating, effectively preventing deterioration and maintaining performance over time.
Implementation Method 1
reacting nano-particles with an amount of surface modifying agent
Implementation Method 2
pre-hydrolysing a binder
Implementation Method 3
washing the cured coating with water
Implementation Method 4
The optical function is achieved by the effective refractive index of the coating being lower than that of the substrate leading to a gradient of refractive index from that of air to that of the substrate
Data Source
AI summary
The invention relates to an article comprising a substrate and a nano-porous coating, wherein the reflectivity of the article is less then 2 %, and whereby the amount of sodium measured in the coating by XPS is less then 1 wt%, and further to a method of making the article.