Aqueous Sol-Gel Spray Coating for Defect-Free Thin Films
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Solution Overview
Problem
Existing sol-gel thin layer deposition methods face challenges such as the use of flammable solvents, limited precision in thickness control, defects like cracks on large substrates, and inability to achieve uniform, optical-grade coatings with high transmission.
Innovation Solution
A method utilizing a spray-coating technique with aqueous colloidal or polymeric suspensions, where the solvent comprises at least 95% water, and drying is performed in a static atmosphere without air circulation, allowing for precise control of solvent evaporation and elimination of defects, enabling uniform and defect-free thin layers on large substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flammable solvents like ethanol are used in sol-gel deposition, then fast drying and good deposition quality are achieved, but safety risks due to flammability increase
Solution Approach 1:
The patent changes the solvent parameter from flammable organic solvents (ethanol) to non-flammable aqueous solvents (water-based). This substitution maintains the sol-gel process functionality while eliminating flammability risks. The aqueous colloidal suspensions or polymeric suspensions in water enable safe processing without compromising the deposition quality or requiring high-temperature heat treatment steps.
2Manufacturing precision
If conventional sol-gel methods are used, then thin layers can be deposited, but thickness control precision and uniformity are limited
Solution Approach 1:
The patent replaces conventional deposition techniques (dip-coating, spin-coating, spray-coating) with a novel method using aqueous colloidal or polymeric suspensions. This substitution enables precise thickness control through controlled evaporation in static atmosphere, achieving uniform coatings with thickness precision better than 5 nm and excellent uniformity across large substrates (400×400 mm²).
Solution Approach 2:
The patent employs a static atmosphere environment during drying to control solvent evaporation. This controlled environment prevents defects like cracks and ensures uniform thickness distribution across the substrate surface, achieving optical-grade coating quality with high transmission properties.
3Loss of substance
If spray-coating technique is used with conventional solvents, then material consumption is reduced, but defects like cracks appear on large substrates
Solution Approach 1:
The patent changes the solvent parameter from conventional organic solvents to aqueous solvents in colloidal or polymeric suspensions. This change enables spray-coating to produce defect-free coatings on large substrates while maintaining low material consumption. The aqueous-based suspensions prevent crack formation during drying, achieving optical-grade quality with high transmission.
Solution Approach 2:
The patent uses a static atmosphere during the drying process to control evaporation and prevent defect formation. This controlled environment allows spray-coating to achieve uniform, crack-free coatings on large substrates while maintaining efficient material utilization.
4Manufacturing precision
If dip-coating, spin-coating or laminar-coating are used, then precise thickness control is achieved, but flammable solvents and limited substrate size applicability are required
Solution Approach 1:
The patent creates a universal deposition method using aqueous colloidal or polymeric suspensions that can be applied to substrates of any size (including large 400×400 mm² substrates) and various geometries. The method combines the advantages of different coating techniques while eliminating their limitations, achieving precise thickness control (better than 5 nm) without flammable solvents.
Solution Approach 2:
The patent changes the solvent system from flammable organic solvents to non-flammable aqueous solvents. This parameter change enables the deposition method to be applied to large substrates without safety concerns, while maintaining precise thickness control and uniform coating quality across the entire substrate surface.
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 approach eliminates flammability risks, achieves high-quality, uniform thin layers with optical-grade properties and high transmission, even on large substrates, while reducing material consumption and enabling varied coating thicknesses on complex shapes.
Implementation Method 1
spraying onto a surface of a substrate: a colloidal suspension comprising solid nanoparticles (or colloids) of an inorganic compound dispersed in a solvent, whereby a wet layer of the colloidal suspension is obtained on the surface
Implementation Method 2
drying the wet layer... whereby the thin layer is obtained
Data Source
AI summary
A thin film on a surface of a solid substrate, including: a) spraying on the surface: —a colloidal suspension including solid nanoparticles (or colloids) of an inorganic compound dispersed in a solvent to obtain a wet layer of the colloidal suspension on the surface; or —a suspension including an inorganic compound in polymeric form in a solvent, to obtain a wet layer of the suspension of the inorganic compound in polymeric form on the surface; or —a solution or suspension of an organic polymer in a solvent, to obtain a wet layer of the solution or suspension of the organic polymer on the surface; b) drying the wet layer; c) optionally, heat-treating the wet layer that has undergone the drying step, whereby the thin film is obtained; wherein: the solvent comprises at least 95% by weight of water, and the drying is carried out in a static atmosphere.