Metal Substrate Buffer Layer Adhesion in OLED Displays
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Solution Overview
Problem
In organic light emitting display devices with metal substrates, surface protrusions and thermal expansion coefficient differences lead to partial separation of buffer layers, causing electrical shorts and increased leakage currents.
Innovation Solution
A metal thin film with a specific thermal expansion coefficient is interposed between the substrate and the buffer layer, made of materials like molybdenum, tungsten, or titanium, to absorb stress and enhance adhesion, preventing separation and electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal substrate is used for flexibility and heat-resistance, then the substrate has good mechanical properties and thermal stability, but surface protrusions cause poor adhesion and buffer layer separation
Solution Approach 1:
A metal thin film is introduced as an intermediary layer between the metal substrate and the buffer layer. This intermediate metal film has a thermal expansion coefficient between that of the substrate and the buffer layer, acting as a stress-absorbing mediator that prevents buffer layer separation while maintaining the mechanical strength and flexibility of the metal substrate.
2Reliability
If a metal thin film is added between substrate and buffer layer, then adhesion is improved and separation is prevented, but device structure becomes more complex
Solution Approach 1:
The solution changes the physical parameter (thermal expansion coefficient) of the intermediate layer to resolve the adhesion problem. By selecting a metal film with an intermediate thermal expansion coefficient between the substrate and buffer layer, the patent achieves stress compatibility and prevents separation, while the thin film nature keeps the added complexity minimal.
3Reliability
If the metal thin film has intermediate thermal expansion coefficient, then thermal stress is absorbed and adhesion is enhanced, but material selection becomes more restricted
Solution Approach 1:
The patent employs composite material strategy by combining the metal substrate with a metal thin film of intermediate thermal expansion properties. This composite structure achieves thermal stress absorption and enhanced adhesion. The specific materials mentioned (molybdenum, tungsten, titanium, and their alloys) provide the necessary intermediate thermal expansion coefficients while maintaining compatibility with the overall device structure.
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 metal thin film effectively prevents buffer layer separation and electrical shorts, reducing leakage currents by reinforcing adhesion and smoothing the substrate surface, thereby improving the reliability of the organic light emitting display device.
Implementation Method 1
The metal thin film may have a third thermal expansion coefficient between the first and second thermal expansion coefficients
Data Source
AI summary
An organic light emitting display device which can prevent separation of a buffer layer, thereby reducing an electrical short is disclosed. One embodiment of the organic light emitting display device includes a substrate made of a metal, a metal thin film formed on the substrate, a buffer layer formed on the metal thin film, and an organic light emitting diode formed on the buffer layer. Accordingly, a leakage current caused by an electrical short can be effectively prevented by preventing the separation of the buffer layer.