OLED Planarization Layer Tapered Edge Adhesion

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Solution Overview

Problem

Conventional organic light emitting displays (OLEDs) face issues with moisture and oxygen penetration due to poor adhesion between the passivation layer and the planarization layer, leading to ineffective protection of the driving and emission units, which can cause hydrogen generation and oxide layer formation, disrupting current flow.

Innovation Solution

The OLED design features a planarization layer with a normal tapered edge portion, matched by a passivation layer and sealant, enhancing adhesion and blocking moisture and oxygen penetration by maintaining a consistent taper angle of 15 to 60 degrees, primarily using polyacryl-based, polyimide-based, or benzocyclobutene-based resins.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the passivation layer is formed with a normal tapered edge portion on a planarization layer with perpendicular edges, then the passivation layer cannot be well deposited on the edge portions, but forming the passivation layer with tapered edges improves adhesion and prevents moisture penetration

Engineering Contradiction:

Improveprotection effectivenessVSAvoiddeposition quality

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The planarization layer is formed with a tapered edge portion at its edge regions, creating a local geometric modification that enables proper deposition of the passivation layer. This local quality change at the edges allows the passivation layer to be well-deposited without requiring changes to the entire structure, resolving the contradiction between deposition quality and protection effectiveness.

Inventive Principle:

Principle #3Local quality

2Reliability

If moisture penetrates through the passivation layer, then hydrogen is generated and bubbles form over the organic emitting layer, but the tapered edge configuration prevents moisture penetration

Engineering Contradiction:

Improveadhesion strengthVSAvoidmoisture penetration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The planarization layer is pre-formed with tapered edge portions before the passivation layer is deposited. This preliminary geometric configuration ensures that when the passivation layer is subsequently deposited, it properly adheres to the edge portions and creates an effective barrier against moisture penetration, preventing hydrogen generation and bubble formation.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If oxygen transmits through pin holes or edge portions, then oxide layers form on the cathode shielding current flow, but the tapered configuration blocks oxygen transmission

Engineering Contradiction:

Improvecurrent flow integrityVSAvoidoxide layer formation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The tapered edge portions of the planarization layer create a local geometric feature that enables the passivation layer to form a continuous, well-adhered barrier at critical edge regions. This local quality modification effectively blocks oxygen transmission paths that would otherwise lead to oxide layer formation on the cathode and current flow shielding.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7521718B2Organic light emitting display

Publication Date: 2009.04.21 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Provided is an organic light emitting display, comprising a substrate; a driving unit formed over the substrate; a planarization layer formed over the driving unit, the planarization layer comprising a normal tapered edge portion; and an emission unit formed over the planarization layer to be electrically connected to the driving unit.