Laminated Glazing Busbar Expansion Design
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Solution Overview
Problem
Laminated glazings with functional films face distortion or wrinkling during the lamination process due to vacuum, pressure, and heating, particularly in curved applications like automotive windshields, and electrically conductive coatings can lead to premature failure from wrinkles causing hot or cold spots.
Innovation Solution
Incorporating a busbar with an expansion portion, such as a bridging busbar portion or a gap, and a cut-out portion in the film, along with polymer plies for adhesion, to reduce wrinkling and ensure electrical connectivity while accommodating thermal expansion differences during the autoclave process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If vacuum, pressure and heating are applied during lamination to bond the polymer, then the bonding polymer softens and flows to form a transparent clear film, but the functional film distorts or wrinkles
Solution Approach 1:
The functional film is divided into multiple segments or zones with different properties. The busbar region has a different expansion characteristic than the rest of the film, allowing it to accommodate differential thermal expansion during lamination without causing wrinkles across the entire film surface.
Solution Approach 2:
The expansion characteristic of the functional film is modified in specific regions (where busbars are located) to have a higher expansion coefficient than the busbar material. This parameter change allows the film to expand more during heating, accommodating the busbar's lower expansion and preventing wrinkles.
2Area of stationary object
If the functional film is made co-extensive with the glazing material plies, then complete coverage is achieved, but wrinkling and distortion increase during lamination
Solution Approach 1:
The functional film has different properties in different regions. In the busbar regions, the film has modified expansion characteristics to match or exceed the busbar's thermal expansion, while other regions maintain standard properties for optimal optical and functional performance.
3Reliability
If busbars are made rigid to ensure electrical connectivity, then electrical connection is maintained, but wrinkles and cracks form during lamination
Solution Approach 1:
The functional film's expansion characteristic is made dynamically adaptable in the busbar regions, allowing it to accommodate the rigid busbar's lower thermal expansion during heating cycles. This dynamic parameter adjustment prevents stress concentration that would cause cracks while maintaining electrical connectivity.
4Stability of the object's composition
If the functional film has standard thermal expansion characteristics, then material consistency is maintained, but wrinkles form near busbars during autoclaving
Solution Approach 1:
The functional film has different properties in different regions. In the busbar regions, the film has modified expansion characteristics to match or exceed the busbar's thermal expansion, while other regions maintain standard properties for optimal optical and functional performance.
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 effectively reduces wrinkling and the risk of hot or cold spots, thereby preventing premature failure of the laminated glazing by allowing for relative movement and maintaining electrical conductivity.
Implementation Method 1
a film having an electrically conductive coating... When functional films are required to be electrically conductive e.g. to provide heating for a glazing
Implementation Method 2
heating the plies of the laminate in an autoclave to a temperature at which the bonding polymer softens and can flow to form a transparent clear film
Implementation Method 3
the use of an expansion portion appears to reduce the effect of the relative movement of the busbar, film and other components of the laminated glazing (many or all of which have different thermal expansion characteristics) during the autoclave process
Data Source
AI summary
A laminated glazing comprising, a first ply of a glazing material, a second ply of a glazing material, a film having an electrically conductive coating, the film being located between the first ply and the second ply, and a first busbar in electrical contact with the electrically conductive coating, the first busbar comprising an expansion portion, the expansion portion comprising a bridging busbar portion or a gap in the first busbar. Methods for producing the laminated glazing are also described.