Ultra Low E Silver Coating Infrared Absorption
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Solution Overview
Problem
Conventional conductive silver coatings face issues with insufficient sintering and adhesion to substrates during short firing cycles and high temperatures, leading to thermal stress between the coating and substrates like glass, silicon, or ceramic, as they are limited to a narrow firing range of about 510 °C to 593 °C (950 °F to 1100 °F).
Innovation Solution
A conductive silver coating composition incorporating silver metal, lead and/or zinc borosilicate glass frit, selenium and/or bismuth metal powder, carbon black, and inorganic black pigments, which allows for infrared absorption over an extended temperature range from 510 °C to 760 °C (950 °F to 1400 °F), ensuring consistent thermal absorption and reducing thermal stress by using borosilicate glass frits and maintaining infrared absorption beyond the decomposition temperature of carbon black.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is used to absorb infrared energy during firing, then adhesion and sintering are improved, but the coating cannot maintain infrared absorption above 593°C due to decomposition
Solution Approach 1:
The patent combines carbon black with inorganic black pigments (such as black iron oxide, black manganese oxide, or black chromium oxide) to create a composite infrared absorbing system. The carbon black provides effective absorption up to 593°C, while the inorganic pigments take over and maintain absorption capabilities at temperatures above 593°C, thus extending the overall operational temperature range without sacrificing adhesion properties.
Solution Approach 2:
The patent modifies the chemical composition parameters of the infrared absorbing agents by introducing inorganic black pigments with higher thermal stability. These pigments have decomposition temperatures significantly above 593°C, allowing the coating to maintain its infrared absorption function at elevated firing temperatures where carbon black alone would decompose.
2Productivity
If faster firing cycle times are used to increase productivity, then output is improved, but insufficient sintering and adhesion occur
Solution Approach 1:
The patent changes the chemical composition parameters of the glass frit by incorporating specific ratios of lead oxide, zinc oxide, and borosilicate components. This modified composition achieves optimal melt viscosity and reactivity that enables complete sintering and adhesion at lower temperatures and shorter times, thus supporting faster firing cycles without compromising sintering quality.
Solution Approach 2:
The patent replaces reliance on extended thermal exposure (time-based sintering) with chemically optimized glass frit that provides rapid melting and bonding. The enhanced chemical reactivity and controlled viscosity of the modified glass frit enable the sintering process to complete efficiently in shorter durations, substituting time-based mechanical sintering with chemistry-driven rapid bonding.
3Reliability
If higher firing temperatures are used to improve sintering, then adhesion is improved, but thermal stress differences increase between coating and substrate
Solution Approach 1:
The patent optimizes the glass frit composition parameters to achieve optimal melt viscosity and reactivity at moderate temperatures. This allows the coating to reach complete sintering and maximum adhesion at lower firing temperatures (avoiding excessive thermal gradients), while the extended infrared absorption capability ensures continued functionality even if higher temperatures are applied, thus providing a buffer against thermal stress issues.
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 enables wider firing ranges without inducing thermal stress, allowing for faster firing cycles and improved adhesion of the silver coating to substrates, maintaining infrared absorption consistency and reducing mechanical stress caused by temperature differences.
Implementation Method 1
carbon black, one or more inorganic black pigments... which, when firing the coating to a glass, silicon, ceramic or ceramic glass enamel substrate, provide infra-red absorption properties over an extended temperature range
Implementation Method 2
The fusion temperature range of the glass frit and melting temperatures of inorganic pigments and compounds set the upper limit of the firing temperatures needed to adequately fuse the silver metal and other inorganic materials together
Implementation Method 3
insufficient sintering of the coating may occur
Data Source
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AI summary
A silver conductive coating possessing infrared absorbing properties is disclosed. The coating is made from a blend of one or more micron size silver powders and/or flakes together with carbon black, inorganic pigment, glass frit, and powdered selenium or bismuth metal. The foregoing dry ingredients are pasted with an organic vehicle, applied to a substrate, and fired at a temperature of up to 1400° F. The coating absorbs infrared radiation beyond the decomposition of carbon black, thus allowing higher firing temperatures and hence shorter firing times.