Core-shell particles with steam-treated inorganic oxide shell
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Solution Overview
Problem
Porous anti-reflective coatings suffer from high optical fouling, water staining, and poor abrasion resistance due to their open pore structure and rough surface, making them difficult to clean and maintain.
Innovation Solution
The development of core-shell particles with a hollow organic polymer core and an inorganic oxide shell, featuring a limited number of enlarged pores that are treated with steam to create a more stable and resistant coating surface, enhancing stain resistance while maintaining optical and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If porous coatings are used to achieve anti-reflective properties with refractive index between 1 and 2%, then optical performance is improved, but the coatings become prone to water staining and optical fouling due to open pore structure and high surface roughness
Solution Approach 1:
The invention utilizes porous silica particles as the core component of the coating system. These particles provide the necessary low refractive index for anti-reflective properties while their controlled porosity allows for subsequent sealing treatment. The porous structure is intentionally created during particle synthesis and then modified through steam treatment to achieve both optical performance and stain resistance.
Solution Approach 2:
The invention changes the physical and chemical parameters of the porous coating through steam treatment. The steam treatment process modifies the pore structure by reducing pore size and decreasing surface roughness parameters (Ra from 100-150 nm to lower values), while maintaining the effective refractive index in the 1.0-1.5 range. This parameter transformation converts the coating from stain-prone to stain-resistant.
2Illumination intensity
If the coating surface is made rough with high specific surface area to enhance anti-reflective properties, then optical performance is improved, but cleanability and abrasion resistance deteriorate
Solution Approach 1:
The invention segments the coating function into two distinct components: porous silica particles providing the anti-reflective optical function, and a separate sealing layer providing the cleanability function. This segmentation allows each component to optimize its specific function without compromising the other - the porous particles maintain low refractive index while the sealing layer provides smooth, easily cleanable surface.
Solution Approach 2:
The invention creates a composite coating system consisting of porous silica particles embedded in a binder matrix, with an additional sealing layer. This composite structure combines the optical benefits of porous materials with the surface benefits of a sealed, smooth top layer, achieving both anti-reflective properties and improved cleanability.
3Illumination intensity
If conventional porous coatings are applied to achieve anti-reflective properties, then optical performance is improved, but stain resistance deteriorates due to accessible pores allowing organic material and water penetration
Solution Approach 1:
The invention performs preliminary sealing action during the coating formation process. The porous silica particles are pre-treated with steam before or during coating application, which partially seals the pores and reduces their accessibility. This preliminary action prevents stain-forming materials from penetrating deep into the coating structure, thereby improving stain resistance while maintaining optical performance.
Solution Approach 2:
The invention introduces a sealing layer as an intermediary between the porous silica particle core and the external environment. This sealing layer acts as a barrier that prevents direct access of water and organic materials to the porous structure, while still allowing the underlying particles to provide their anti-reflective optical function. The binder matrix also serves as an intermediary sealing component.
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 resulting coatings exhibit improved stain resistance, cleanability, and retention of mechanical and optical properties, with reduced water staining and enhanced durability compared to conventional coatings.
Implementation Method 1
Wu et al 'Properties of sol-gel derived scratch resistant nano-porous silica films by a mixed atmospheric treatment ', Journal of Non-Crystalline Solids, 275, (2000), pp 169-174, describes the treatment of the silica film with water and ammonia for 30 minutes at 400°C, resulting in a smoother surface and a densification of the silica structure.
Implementation Method 2
treatment of the silica film with water and ammonia for 30 minutes at 400°C, resulting in a smoother surface and a densification of the silica structure
Implementation Method 3
Typically these anti-reflective systems comprise a binder and nanoparticles. For example, US6.921,578 describes a method for preparing anti-reflective coating systems in which a binder (e.g. tetra-ethylorthosilicate TEOS) is hydrolyzed in the presence of the nanoparticles using an acid catalyst.
Implementation Method 4
a binder (e.g. tetra-ethylorthosilicate TEOS) is hydrolyzed in the presence of the nanoparticles using an acid catalyst
Data Source
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AI summary
The present invention relates to a particle having a core and a shell, said core being hollow or comprising an organic polymer composition and said shell comprising an inorganic oxide. The shell has a thickness in the range from 2 to 75 nm and has at least one and no more than five enlarged pores, each enlarged pore having a diameter of between 5 nm and 300 nm.