Low Solar Absorbing Blue Glass Composition and Coating
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Solution Overview
Problem
Current glass compositions for insulating glass units face challenges in achieving a neutral blue-gray color with mid-range visible transmittance and low solar heat gain coefficient, as increasing iron content for reduced solar infrared absorption can lead to thermal stresses and aesthetically undesirable colors when coated with IR reflective coatings.
Innovation Solution
A soda-lime-silica glass composition with specific amounts of iron oxide, cobalt oxide, selenium, and optional colorants, balanced to provide chromaticity coordinates and visible light transmittance, combined with low emissivity coatings to achieve the desired color and solar control properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the total iron content in the glass is increased to reduce solar infrared transmittance, then the solar infrared absorption is improved, but the glass surface emissivity remains high causing heat flow to the building interior and thermal stresses leading to fracturing
Solution Approach 1:
The patent changes the chemical composition parameters of the glass by strictly limiting total iron content to 0.04-0.28 wt% (down from typical >0.3 wt%), and precisely controlling cobalt oxide (32-90 ppm) and selenium (1-5.5 ppm) concentrations to achieve the desired solar control and color properties without thermal stress fracturing
Solution Approach 2:
The patent creates a composite glass system combining multiple colorants (iron oxide, cobalt oxide, selenium) in specific proportions within a soda-lime-silica base glass, where each component contributes to different properties: iron for solar absorption, cobalt for blue color, and selenium for color enhancement, achieving synergistic effects
2Object-affected harmful factors
If IR reflective coatings are applied to reduce solar infrared absorption, then the solar heat gain is reduced, but the glass color becomes aesthetically undesirable (green, yellow, or too green/blue)
Solution Approach 1:
The patent performs preliminary coloration of the glass substrate itself with controlled iron, cobalt, and selenium content before applying the low emissivity coating, so that the glass body provides the primary color foundation (neutral blue-gray) and the coating only needs to provide solar reflection without compromising aesthetics
Solution Approach 2:
The patent assigns different functional roles to different components: the glass bulk (with controlled colorants) provides the aesthetic color and baseline solar absorption, while the thin surface coating provides the low emissivity and additional solar reflection, creating localized functional zones
3Object-affected harmful factors
If the total iron content is increased to reduce solar infrared transmittance, then the infrared absorption is improved, but the glass heats when exposed to sunlight causing thermal stresses
Solution Approach 1:
The patent changes the iron content parameter from typical >0.3 wt% to a controlled range of 0.04-0.28 wt%, and introduces precise amounts of cobalt oxide (32-90 ppm) and selenium (1-5.5 ppm) to compensate for reduced iron-based solar absorption, achieving similar solar control with lower heat storage
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 glass composition and coating combination results in a coated glass product with a neutral blue-gray color, mid-range visible light transmittance, and a solar heat gain coefficient of no greater than 0.50, effectively reducing thermal stresses and enhancing aesthetic appeal while maintaining low solar heat gain.
Implementation Method 1
apply an IR reflective coating... IR reflective coatings also typically have reduced surface emissivity, also referred to as 'low e' coatings, thereby reducing heat flow through the window
Implementation Method 2
a significant portion of the absorbed energy flows to the building interior... reduced surface emissivity... thereby reducing heat flow through the window
Data Source
AI summary
An insulating unit having a blue color and a solar heat gain coefficient less than 0.40 includes a clear glass sheet spaced from a coated glass sheet. The coated glass sheet includes a colored glass substrate having a solar infrared reflective coating. The composition of the coated substrate includes a base glass portion and a glass colorant portion, the glass colorant portion including total iron in the range of 0.04 to less than 0.28 weight percent; CoO in the range of 32 to 90 parts per million, and Se in the range of greater than 0 to less than 5.5 parts per million. In one non-limiting embodiment of the invention the glass substrate at a thickness of 0.223 inches has a* chromaticity coordinates of -3.5 to +2.5 and b* chromaticity coordinates of -1 to -15, and a visible light transmittance of 40 to 80%.