OLED Flexible Substrate Silicon Nitride Barrier Adhesion
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Solution Overview
Problem
Organic light-emitting diode (OLED) displays with flexible substrates face challenges in maintaining low water vapor transmission rates and high adhesive strength, leading to potential damage from moisture and oxygen penetration, which can reduce the lifespan of the OLED and cause detachment defects during manufacturing.
Innovation Solution
The OLED display incorporates a flexible substrate with alternating layers of plastic and silicon nitride barrier layers, where the density and refractive index of silicon nitride in the barrier layers vary to enhance water vapor barrier properties and adhesive strength, and an intermediate layer is added between the barrier and plastic layers to improve adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flexible substrate with plastic layers is used in OLED display, then flexibility and ease of manufacture are improved, but water vapor transmission rate increases and adhesive strength decreases
Solution Approach 1:
The patent employs a composite structure consisting of alternating organic plastic layers and inorganic barrier layers (silicon nitride). This composite material approach combines the flexibility and ease of manufacture of organic materials with the low water vapor transmission properties of inorganic materials, resolving the contradiction between flexibility and moisture barrier performance.
Solution Approach 2:
The substrate is segmented into multiple thin layers (plastic layer 1, barrier layer 1, plastic layer 2, barrier layer 2, etc.) rather than using a single thick plastic layer. This segmentation creates multiple interfaces that collectively provide both flexibility and effective moisture barrier properties, as each layer contributes specific functional characteristics.
2Ease of manufacture
If a flexible substrate with plastic layers is used in OLED display, then flexibility and ease of manufacture are improved, but adhesive strength decreases
Solution Approach 1:
The alternating organic-inorganic layered structure creates a composite material system where the different materials complement each other's properties. The plastic layers provide flexibility while the barrier layers provide adhesion, resolving the contradiction between ease of manufacture and adhesive strength.
Solution Approach 2:
Different layers are assigned different local qualities: plastic layers are optimized for flexibility and organic-inorganic interface compatibility, while barrier layers are optimized for adhesion and moisture barrier properties. This local differentiation allows each layer to excel at its specific function without compromising the overall structure.
3Reliability
If barrier layers are added to reduce water vapor transmission, then moisture protection is improved, but device complexity increases
Solution Approach 1:
The moisture barrier function is segmented across multiple thin alternating layers rather than requiring a single complex thick barrier. This segmentation achieves effective moisture protection through the cumulative effect of multiple interfaces while keeping each individual layer simple and manageable.
Solution Approach 2:
The patent uses thin film structures for both the plastic and barrier layers, creating a flexible multi-layered shell structure. This approach provides effective moisture barrier properties through the thin-film stack while maintaining flexibility and avoiding the complexity of thick rigid barriers.
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
This configuration increases the average water vapor transmission path, reduces detachment defects, and improves the characteristics of the thin-film transistor (TFT) by maintaining a low water vapor transmission rate while enhancing adhesive strength between the barrier and plastic layers, thus extending the OLED's lifespan and manufacturing reliability.
Implementation Method 1
a flexible substrate that has a low water vapor transmission rate... The first barrier layer may include silicon nitride... The silicon nitride may be present within the first barrier layer at a density of equal to or more than 2.2 g/cm3 and less than or equal to 2.4 g/cm3
Implementation Method 2
a first intermediate layer each positioned between the first and second plastic layers... enhancing adhesive strength... improves the characteristics of the thin-film transistor (TFT) by maintaining a low water vapor transmission rate while enhancing adhesive strength between the barrier and plastic layers
Data Source
AI summary
Provided is an organic light-emitting diode (OLED) display including: first and second plastic layers; a first barrier layer and a first intermediate layer each positioned between the first and second plastic layers; and an OLED layer formed on the second plastic layer. The first barrier layer comprises silicon nitride.