OLED Encapsulation Composition Cross-Linking Density
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) face reliability issues due to degradation from external moisture and oxygen, and existing encapsulation methods may not adequately prevent this, especially when forming inorganic layers through processes like chemical vapor deposition, which can cause wrinkles in the organic layers.
Innovation Solution
A composition for encapsulation of OLEDs is developed, comprising photocurable monomers with a Cross-Linking Density (CLD) of 50 or more, including a first photocurable monomer with at least two functional groups and a second monomer with one functional group, along with an initiator, to form a hard and reliable organic layer that can be alternately stacked with inorganic layers, enhancing the encapsulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic layers are formed by plasma process and vacuum process (sputtering, CVD, etc.), then the encapsulation layer provides good barrier properties, but wrinkles may form in the organic layers during repeated deposition
Solution Approach 1:
The patent changes the chemical composition parameters of the organic layer by using a specific ratio of multi-functional to mono-functional photocurable monomers (3:7 to 7:3 weight ratio), achieving a cross-linking density of 50 or more. This parameter optimization allows the organic layer to maintain flexibility and suppress wrinkle formation during repeated inorganic layer deposition while preserving encapsulation barrier properties.
Solution Approach 2:
The patent creates a composite encapsulation structure with alternating organic and inorganic layers, where the organic layer is formulated as a composite of different photocurable monomers (multi-functional and mono-functional). This composite approach allows the organic layer to provide both mechanical flexibility (preventing wrinkles) and chemical barrier properties (preventing moisture and oxygen penetration).
2Strength
If the organic layer is formed with high cross-linking density to increase hardness, then the layer provides better mechanical strength, but the viscosity may become unsuitable for ink-jet processes
Solution Approach 1:
The patent optimizes the composition parameters by combining multi-functional photocurable monomers (for high cross-linking density and hardness) with mono-functional photocurable monomers (for lower viscosity and better processability). The specific weight ratio range (3:7 to 7:3) balances these competing requirements, achieving CLD of 50 or more while maintaining viscosity suitable for ink-jet deposition.
3Reliability
If photocurable monomers with high cross-linking density are used to form hard organic layers, then the encapsulation reliability improves, but the composition complexity increases
Solution Approach 1:
The patent simplifies the composition design by focusing on a key parameter - the weight ratio of multi-functional to mono-functional photocurable monomers within the 3:7 to 7:3 range. This single parameter optimization achieves high cross-linking density (CLD ≥ 50) and reliable encapsulation without requiring complex multi-component formulations, making the composition easier to manufacture and control.
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 composition achieves high hardness and reliability for the organic layer, suppresses wrinkle formation during repeated inorganic layer deposition, and maintains suitable viscosity for ink-jet processes, ensuring a uniform surface and effective encapsulation of OLEDs.
Implementation Method 1
a composition for encapsulation of organic light emitting diodes, the composition comprising photocurable monomers and having a CLD of 50 or more
Implementation Method 2
The inorganic layers may be formed by a plasma process and a vacuum process, e.g., sputtering, chemical vapor deposition
Data Source
AI summary
A composition for encapsulation of organic light emitting diodes and an organic light emitting diode display apparatus, the composition including photocurable monomers and having a CLD of 50 or more, as calculated by Equation 1:CLD=∑Mx(Nx-1)Mtotal[Equation 1]wherein, in Equation 1, Mtotal is a total sum of a number of moles of the photocurable monomers in the composition, Mx is a number of moles of an xth photocurable monomer in the composition, Nx is a number of photocurable functional groups per mole of the xth photocurable monomer in the composition, and x is an integer of 1 or more.