Display Panel Encapsulation with Planarized Inorganic Layers
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Solution Overview
Problem
Self-luminous display devices using organic electroluminescent or quantum dot materials face challenges in sealing light emitting elements due to vulnerability to environmental contaminants like oxygen and moisture, leading to issues with moisture permeability and optical properties.
Innovation Solution
A display panel design featuring a multi-layer encapsulation structure with inorganic layers and optional organic layers, where the top surfaces of these layers are planarized through polishing to enhance moisture resistance and optical properties, including a first encapsulation layer with a thickness of 1.0 μm to 5.0 μm, and a second encapsulation layer with similar characteristics, to protect the light emitting element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single encapsulation layer is used to seal the light emitting element, then the device complexity is reduced, but the moisture permeability resistance and optical properties are insufficient
Solution Approach 1:
The patent employs a composite encapsulation layer comprising multiple inorganic layers with different materials (e.g., SiO2, SiN, Al2O3, TiO2) and optionally organic layers. This multi-material composite structure provides superior moisture barrier properties and optical characteristics compared to single-layer encapsulation, directly resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The encapsulation layer is segmented into multiple discrete inorganic layers (first inorganic layer, second inorganic layer, third inorganic layer) with distinct functions. Each layer can be optimized for specific properties such as moisture barrier, adhesion, or optical transmission, allowing the system to achieve high reliability without excessive overall complexity.
2Reliability
If the encapsulation layer thickness is increased to improve moisture resistance, then the moisture permeability resistance improves, but the optical properties and light emission efficiency deteriorate
Solution Approach 1:
The composite inorganic layer structure enables achieving high moisture barrier performance with reduced total thickness compared to single-layer designs. By combining materials with different barrier properties and optical characteristics, the system maintains excellent moisture resistance while preserving light emission efficiency.
Solution Approach 2:
The patent optimizes the thickness parameters of each individual inorganic layer (e.g., first inorganic layer: 50-200 nm, second inorganic layer: 50-200 nm, third inorganic layer: 50-200 nm) to achieve the desired balance between moisture barrier and optical properties. This parameter optimization allows the total encapsulation thickness to be controlled within a range that maintains both reliability and illumination intensity.
3Reliability
If the top surfaces of the inorganic layers are left as-deposited, then the manufacturing process is simpler, but the moisture permeability resistance and optical properties are reduced
Solution Approach 1:
The patent incorporates surface planarization (polishing or CMP) as a preliminary action before final encapsulation layer formation. This pre-planarization of the inorganic layer surfaces ensures subsequent encapsulation layers can be deposited uniformly, improving both moisture barrier performance and optical properties while maintaining manufacturing feasibility.
4Reliability
If multiple inorganic layers are deposited to improve moisture resistance, then the moisture permeability resistance increases, but the manufacturing time and process complexity increase
Solution Approach 1:
The multi-layer inorganic composite structure achieves superior moisture barrier properties that would require much greater thickness in single-layer designs. This allows the manufacturing process to complete with thinner total deposits, reducing deposition time despite the increased number of layers.
Solution Approach 2:
By optimizing the thickness parameters of each inorganic layer to relatively thin ranges (50-200 nm per layer), the total deposition time is controlled. The parameter optimization ensures that while multiple layers are deposited, the cumulative thickness and associated manufacturing time remain reasonable for commercial production.
Data Source
AI summary
A display panel includes an emission area and a non-emission area. A light emitting element includes a first electrode, an emission layer on the first electrode, and a second electrode on the emission layer. A pixel defining layer includes a first opening defined therein and exposing the first electrode. A first encapsulation layer is on the second electrode to overlap the light emitting element. The first encapsulation layer includes a first inorganic layer on the second electrode and a second inorganic layer on the first inorganic layer. A top surface of the second electrode overlaps the first opening and includes at least one first stepped portion. A bottom surface of the second inorganic layer directly contacts a top surface of the first inorganic layer. At least one of the top surface of the first inorganic layer or a top surface of the second inorganic layer is a flat surface.