OLED Encapsulation Layer with Alternating Inorganic-Organic Stacks
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Solution Overview
Problem
Organic light emitting display devices face issues with moisture and oxygen permeability, leading to delamination and degradation of the encapsulation layer, which affects the light emission properties and reliability of the device.
Innovation Solution
A multilayer encapsulation structure is implemented, comprising alternately stacked inorganic and organic layers with specific thickness and refractive index ranges, using a photocurable monomer composition without aromatic hydrocarbons to enhance plasma resistance, surface flatness, and low permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an organic layer is used in the encapsulation structure, then flexibility and adhesion are improved, but plasma resistance and moisture barrier performance deteriorate
Solution Approach 1:
The patent employs a composite encapsulation structure consisting of alternating inorganic layers (SiOx, SiNx) and organic layers (photo-curable resin). This composite approach combines the plasma resistance and moisture barrier properties of inorganic materials with the flexibility and adhesion advantages of organic materials, resolving the contradiction between plasma resistance and adhesion.
Solution Approach 2:
The encapsulation layer is segmented into multiple thin layers (inorganic-organic-inorganic-organic-inorganic) rather than using a single thick layer. Each layer has a thickness of 50-200 nm, creating a multi-functional barrier structure where inorganic layers provide plasma resistance and organic layers provide adhesion and flexibility.
2Reliability
If plasma deposition is used to form inorganic layers, then encapsulation quality is improved, but the organic layer is etched and surface roughness increases
Solution Approach 1:
The organic layer is formed first as a base layer, then inorganic layers are deposited on top of it. This preliminary action of forming the organic layer before inorganic deposition allows the inorganic layers to be deposited with better control, reducing plasma-induced etching and surface roughness while maintaining encapsulation quality.
Solution Approach 2:
The patent specifies precise thickness parameters for each layer (50-200 nm) and controls the refractive index of the organic layer (1.4-1.65). By optimizing these parameters, the encapsulation quality is improved while minimizing plasma damage and surface roughness during deposition.
3Reliability
If multiple inorganic layers are stacked, then moisture and oxygen barrier performance is improved, but delamination between layers occurs
Solution Approach 1:
The organic layer acts as an intermediary between adjacent inorganic layers. This intermediate organic layer prevents direct contact between inorganic layers, reducing stress concentration and preventing delamination while maintaining the moisture and oxygen barrier performance of the multi-layer structure.
Solution Approach 2:
Different layers are assigned different functions: inorganic layers provide moisture and oxygen barrier properties, while organic layers provide adhesion and stress relief. This local quality differentiation ensures both barrier performance and layer stability throughout the encapsulation structure.
4Power
If the organic layer has high refractive index, then light extraction efficiency is improved, but transparency and color accuracy deteriorate
Solution Approach 1:
The patent optimizes the refractive index of the organic layer to be within 1.4-1.65, which balances light extraction efficiency and transparency. This parameter optimization ensures adequate light extraction while maintaining good color accuracy and transparency of the display device.
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 provides an organic light emitting display device with improved plasma resistance, low moisture and oxygen permeability, excellent transparency, and increased reliability, while maintaining efficient light extraction with reduced power consumption.
Implementation Method 1
the photocurable monomer including about 5 wt % to about 45 wt % of the monomer including substituted or non-substituted at least two phenyl groups and about 55 wt % to about 95 wt % of the monomer without an aromatic hydrocarbon
Implementation Method 2
The inorganic layer may be formed by plasma deposition
Implementation Method 3
The organic light emitting element may suffer from delamination at an interface between a metal field and a light emitting layer due to moisture
Data Source
AI summary
Disclosed is an organic light emitting display device including a substrate, an organic light emitting element formed on the substrate, and an encapsulation layer encapsulating the organic light emitting element, wherein the encapsulation layer has a structure in which at least two inorganic layers and at least one organic layer are alternately stacked one above another, each of the inorganic layers having a thickness of about 40 nm to about 1,000 nm and an index of refraction of about 1.41 to about 2.0, each of the organic layer having a thickness of about 0.2 μm to about 15 μm and an index of refraction of about 1.4 to about 1.65, the organic layer including a composition for encapsulating a display device, the composition for encapsulating a display device including a photocurable monomer and a photopolymerization initiator.