Glass Coating Adhesion via Polymer Buffer Layers
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Solution Overview
Problem
The deposition of physical vapor deposition coatings onto glass substrates in electronic devices can cause excessive stress, leading to damage such as delamination and undesired waviness due to coefficient-of-thermal-expansion mismatch and lack of adhesion, which affects the performance and appearance of the coatings.
Innovation Solution
A buffer layer comprising a polymer with embedded silicon oxide particles and an adhesion promotion additive, such as siloxane, is interposed between the glass substrate and the coating to enhance adhesion and match the thermal expansion coefficient, thereby preventing delamination and improving the overall performance of the coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If physical vapor deposition coatings are deposited directly onto glass substrates, then the coating process is simple and direct, but excessive stress causes delamination and waviness due to thermal expansion mismatch and poor adhesion
Solution Approach 1:
An intermediate buffer layer comprising a polymer matrix with embedded inorganic particles is introduced between the glass substrate and the physical vapor deposition coating. This buffer layer acts as a mediator that reduces stress transfer and improves adhesion, preventing delamination and waviness while maintaining coating integrity
Solution Approach 2:
The buffer layer is formed as a composite material combining organic polymer matrix with embedded inorganic particles. This composite structure provides both the flexibility needed to accommodate thermal expansion differences and the adhesion properties required to bond effectively to both the glass substrate and the deposition coating
2Reliability
If a buffer layer with polymer and embedded particles is used to improve adhesion, then coating reliability and stress resistance are enhanced, but the device structure becomes more complex
Solution Approach 1:
The buffer layer is segmented into two functional components: a polymer matrix providing flexibility and stress absorption, and embedded inorganic particles providing adhesion and structural stability. This segmentation allows each component to perform its specific function optimally while working together to solve the adhesion problem
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 use of a polymer buffer layer with embedded silicon oxide particles and adhesion promotion additives enhances the reliability and appearance of coatings by preventing stress-induced damage and ensuring strong adhesion, resulting in improved coating performance and reliability on glass substrates in electronic devices.
Implementation Method 1
The deposition of physical vapor deposition coatings onto glass substrates
Implementation Method 2
coefficient-of-thermal-expansion mismatch
Data Source
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AI summary
An electronic device may have a display and a rear housing. A coating may be formed on an inner surface of a display cover layer for the display or on an inner surface of the rear housing. The coating may include one or more inorganic layers such as inorganic layers in a thin-film interference filter or other layer of material. A buffer layer having a polymer with adhesion promotion additive and embedded silicon oxide particles may be interposed between the coating and a glass layer forming the rear housing or between a patterned indium tin oxide coating on a display cover layer and an adhesive layer that attaches a pixel array to the display cover layer.