OLED Pixel Defining Layer Thickness Gradient for Sealant Stability
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Solution Overview
Problem
The mechanical strength of OLED displays is compromised due to an empty space between the display substrate and encapsulation substrate, which can lead to damage from external impact, and filling this space with a filler interferes with the sealant's hardening process, causing instability in the bond between substrates.
Innovation Solution
A pixel defining layer with a stepwise or linearly increasing thickness is designed, featuring drop points and varying spacer lengths to control the diffusion of filler and prevent premature contact with the sealant, allowing for stable sealing and enhanced mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the empty space between the display substrate and encapsulation substrate is filled with a filler, then the mechanical strength is improved, but the sealant hardening process is interfered with
Solution Approach 1:
The pixel defining layer is designed with non-uniform thickness, being thicker at the edges and thinner at the center. This local variation in thickness creates a gradient structure that controls filler diffusion, allowing the filler to be contained in the central region while keeping the edge regions clear for proper sealant contact and hardening.
Solution Approach 2:
The pixel defining layer acts as an intermediary structure between the filler and the sealant. It provides a controlled interface that allows the filler to exist in the empty space while preventing direct contact between the filler and sealant, thus mediating the interaction to avoid interference with the sealant hardening process.
2Reliability
If the empty space is left empty, then the sealant can harden properly, but the mechanical strength is compromised
Solution Approach 1:
The pixel defining layer creates different functional zones: a central region with thinner layer thickness that accommodates the filler, and edge regions with thicker layer thickness that ensure proper sealant contact. This local differentiation allows both filler presence and sealant stability to coexist.
Solution Approach 2:
The pixel defining layer is formed in advance with a specific thickness profile before the filler is introduced. This preliminary structuring of the layer thickness prepares the system to control filler diffusion and ensure proper sealant positioning, preventing future bonding issues.
Data Source
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AI summary
An organic light emitting diode (OLED) display includes a display substrate including a display substrate including an organic light emitting element and a pixel defining layer having an opening defining a light emitting region of the organic light emitting element, an encapsulation substrate arranged opposite to the display substrate, a sealant arranged at an edge between the display substrate and the encapsulation substrate to seal a space between the display substrate and the encapsulation substrate from an outside and a filler filling the space between the display substrate and the encapsulation substrate, wherein the pixel defining layer has a thickness that varies by location, and a portion of the pixel defining layer closest to the sealant at edges of the display substrate having a thickness that is greater than a thickness of the pixel defining layer at all other portions of the display.