Sol-Gel Silica Coating on Polymer Substrates
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Solution Overview
Problem
Existing low emissivity coatings for glass surfaces, such as those with silver or ceramic layers, face issues with stability, hardness, durability, and moisture resistance, and cannot be applied to polymer substrates due to temperature limitations.
Innovation Solution
A method involving a sol-gel process to deposit a silica or silica-based layer on a polymer substrate with an adhesion promoting layer, using partially condensed alkoxide precursors and low-temperature processing to achieve a hard, scratch-resistant, and low-e coated polymer substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard polymer top layer is applied to protect silver low-e coatings, then scratch resistance and durability are improved, but IR heat absorption increases and emissivity deteriorates
Solution Approach 1:
The patent changes the material parameter from organic polymer to inorganic silica coating, achieving both hardness and low emissivity. The silica coating provides scratch resistance equivalent to or exceeding hard polymers while maintaining low IR emissivity (e < 0.1), thus resolving the contradiction between protection and thermal performance.
Solution Approach 2:
The patent creates a composite structure with multiple layers: polymer substrate, adhesion promoting layer, and silica low-e coating. This composite approach combines the flexibility and formability of polymer with the hardness and low emissivity of inorganic silica, achieving both scratch resistance and thermal performance.
2Reliability
If ceramic coatings are deposited on glass substrates at high temperatures, then durability and adhesion are improved, but polymer substrates cannot be used due to temperature limitations
Solution Approach 1:
The patent changes the processing temperature parameter from high temperature (ceramic synthesis) to low temperature (sol-gel process at <150°C). This enables the deposition of durable inorganic silica coatings on temperature-sensitive polymer substrates, achieving both durability and substrate compatibility.
Solution Approach 2:
The patent replaces the high-temperature ceramic synthesis mechanism with a low-temperature sol-gel chemical process. The sol-gel process uses chemical reactions (hydrolysis and condensation of alkoxide precursors) to form silica networks at low temperatures, substituting the thermal field with a chemical field to achieve the same durability goal without damaging polymer substrates.
3Reliability
If silver layers are used for low-e coatings, then IR light transmission is minimized, but stability, hardness, and moisture resistance deteriorate
Solution Approach 1:
The patent replaces the fragile but effective silver layer with a durable inorganic silica coating. While silver provides good low-e performance, it is unstable and delicate. The silica coating may have slightly different optical properties but provides superior long-term stability, hardness, and moisture resistance, making it suitable for practical applications where durability is critical.
4Adaptability or versatility
If sol-gel process is used to deposit silica layer at low temperatures, then polymer substrate is not damaged, but adhesion between coating and substrate deteriorates
Solution Approach 1:
The patent introduces an adhesion promoting layer as an intermediary between the polymer substrate and silica coating. This intermediate layer is specifically designed to bond chemically or physically with both the organic polymer substrate and the inorganic silica coating, ensuring strong adhesion while allowing the sol-gel process to proceed at low temperatures that protect the polymer substrate.
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 results in a coated polymer substrate with low emissivity (e < 0.1), high hardness (≥ 2H pencil), and excellent adhesion, suitable for use as a low-e film without damaging the polymer substrate.
Implementation Method 1
applying a silica or silica-based layer on said adhesion promoting layer by a sol-gel process starting from a mixture comprising at least one partially condensed alkoxide precursor
Implementation Method 2
sol-gel process starting from a mixture comprising at least one partially condensed alkoxide precursor
Implementation Method 3
applying an adhesion promoting layer on one side of said polymer substrate
Data Source
Figure 1
AI summary
The invention relates to a method of manufacturing a coated polymer substrate having low emissivity properties and a high hardness. The method comprises the steps of providing a polymer substrate; applying at least one adhesion promoting layer on one side of said polymer substrate; applying at least one silica or silica-based layer on said at least one adhesion promoting layer by a sol-gel process. The invention further relates to a coated polymer substrate having low emissivity properties, to a glass substrate provided with a coated polymer substrate and to the use of such a coated substrate as substrate having low emissivity properties.