Precursor Antifog Coating for Optical Articles Resolving Cleanability Trade-offs
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Solution Overview
Problem
Existing anti-fog coatings for optical articles, such as ophthalmic lenses, often suffer from inadequate cleanability and insufficient anti-fog performance, with permanent coatings losing mechanical resistance due to water absorption and temporary coatings having limited durability.
Innovation Solution
A precursor anti-fog coating is developed with a surface having a static contact angle greater than 90° and a polar component surface energy greater than 1.5 mJ/m², achieved by depositing a combination of hydrophilic and hydrophobic compounds on the substrate, allowing for improved anti-fogging performance while enhancing cleanability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a permanent hydrophilic coating is applied to prevent fogging, then anti-fog performance is improved, but mechanical resistance is reduced due to water absorption and swelling
Solution Approach 1:
The coating is divided into two distinct layers: a permanent hydrophobic precursor coating providing mechanical strength and cleanliness, and a temporary hydrophilic surfactant layer providing anti-fog performance. This segmentation allows each layer to fulfill its specific function without compromising the other, resolving the contradiction between mechanical resistance and anti-fog performance.
Solution Approach 2:
The system transitions from a static permanent hydrophilic coating to a dynamic combination where a permanent hydrophobic coating is temporarily modified by applying and later removing a hydrophilic surfactant layer. This dynamic approach allows the coating to switch between hydrophobic (cleanable) and hydrophilic (anti-fog) states, resolving the contradiction between mechanical resistance and anti-fog performance.
2Ease of operation
If a hydrophobic coating is applied to improve cleanability, then ease of cleaning is improved, but anti-fog performance deteriorates
Solution Approach 1:
The permanent hydrophobic precursor coating is applied in advance to provide excellent cleanability and serve as a stable base layer. Later, when anti-fog performance is needed, a hydrophilic surfactant layer is temporarily applied over this hydrophobic base. This preliminary action allows the system to maintain cleanability while temporarily gaining anti-fog properties when required.
Solution Approach 2:
The permanent hydrophobic coating acts as an intermediary layer between the substrate and the temporary hydrophilic surfactant. This intermediary provides a stable, cleanable surface that can temporarily accept hydrophilic surfactants for anti-fog performance, then release them for cleaning, resolving the contradiction between cleanability and anti-fog performance.
3Reliability
If a surfactant composition is applied to a precursor coating to form an anti-fog coating, then anti-fog performance is improved, but cleanability worsens
Solution Approach 1:
The hydrophilic surfactant layer is designed as a temporary, disposable coating that provides anti-fog performance only during its presence on the substrate. When cleaning is needed, this temporary layer is easily removed, revealing the permanent hydrophobic precursor coating underneath. This disposable approach allows temporary anti-fog performance without permanent loss of cleanability.
Solution Approach 2:
The system discards the temporary hydrophilic surfactant layer when cleaning is required, recovering the permanent hydrophobic precursor coating's cleanability. The surfactant layer is applied only when anti-fog performance is needed and is subsequently removed, allowing the underlying coating to be cleaned and reused, resolving the contradiction between anti-fog performance and cleanability.
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 solution maintains satisfactory anti-fogging performance while significantly improving the ability to clean the coating, ensuring effective fog prevention and resistance to soiling, as demonstrated by improved visual acuity and reduced haze under fogging conditions.
Implementation Method 1
a surface having a static contact angle with water greater than 90°
Implementation Method 2
achieved by depositing a combination of hydrophilic and hydrophobic compounds on the substrate
Data Source
Figure 1~3
AI summary
The present invention relates to an optical article having a substrate coated with a coating that is a precursor of an antifog coating, the surface of which has a static contact angle with water larger than 90° and a polar surface energy component higher than 1.5 mJ/m2. The precursor of the antifog coating, which furthermore possesses antifouling properties, is converted into an actual antifog coating by applying a surfactant film to its surface.