Organic Light-Emitting Display Pixel-Defining Layer Thickness Collapse Prevention
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Solution Overview
Problem
In organic light-emitting display apparatuses, the thickness of the pixel-defining layer (PDL) surrounding the pixel electrode can collapse, affecting display quality and making it challenging to maintain a thin, planar structure necessary for efficient light emission.
Innovation Solution
The use of a planarization layer with offset grid patterns for via-holes and dummy via-holes, along with a thin pixel-defining layer of organic insulation material, helps maintain the thickness and planarity of the PDL, preventing collapse and ensuring accurate light emission area definition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pixel-defining layer (PDL) is made thin to improve display quality, then the light emission area can be more accurately defined, but the thickness of the PDL collapses near the via-holes
Solution Approach 1:
The patent introduces a planarization layer as an intermediary structure between the substrate and the pixel-defining layer. This planarization layer fills the via-holes and creates a flat surface, allowing the PDL to be formed with uniform thickness without collapsing into the via-hole depressions. The planarization layer mediates between the non-uniform via-hole structure and the requirement for uniform PDL thickness.
Solution Approach 2:
The patent solves the thickness uniformity problem by adding a vertical dimension solution - forming a planarization layer that fills the via-holes from below. This approach addresses the thickness issue in the vertical dimension rather than trying to modify the horizontal patterning of the PDL, allowing thin PDL with uniform thickness to be achieved.
2Measurement precision
If the pixel-defining layer thickness is reduced to define light emission area accurately, then display quality improves, but the structural stability of the PDL near via-holes deteriorates
Solution Approach 1:
The planarization layer serves as a mediator that provides structural support beneath the thin pixel-defining layer. By filling the via-holes and creating a planar surface, it prevents the thin PDL from collapsing into the via-hole regions, thereby maintaining both the accuracy of light emission boundary definition and the structural integrity of the PDL.
Solution Approach 2:
The planarization layer is formed beforehand to cushion and support the subsequent pixel-defining layer. This pre-prepared structural support prevents the PDL from experiencing stress or collapse in the via-hole regions, ensuring structural integrity is maintained before the thin PDL is formed.
3Area of stationary object
If via-holes are positioned closer to the pixel electrode to reduce spacing, then device area is reduced, but the PDL thickness collapses more significantly
Solution Approach 1:
The planarization layer acts as an intermediary that allows via-holes to be positioned closer to the pixel electrode without causing PDL collapse. By providing a filled, planar surface beneath the PDL, it enables tighter spacing while maintaining PDL thickness uniformity, thus reducing device area without sacrificing structural integrity.
Data Source
AI summary
An organic light-emitting display apparatus may include: a planarization layer disposed on a substrate and covering a plurality of thin film transistors; pixel electrodes, each comprising a light emission portion and anon-light emission portion, the light emission portion being arranged on the planarization layer in a first grid pattern; via-holes, each connecting one thin film transistor and one pixel electrode through the planarization layer, and arranged in a second grid pattern offset from the first grid pattern; dummy via-holes spaced apart from the via-holes; a pixel-defining layer (PDL) disposed on the planarization layer and covering the via-holes, the dummy via-holes, and the non-light emission portion of the pixel electrodes; an organic layer disposed on the light emission portion and comprising an emissive layer; and an opposite electrode disposed on the organic layer.