Partition Walls for Inkjet Printed OLED Emission Layers
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Solution Overview
Problem
The inkjet printing process for forming emission layers in high-resolution display devices faces technical difficulties and increased costs due to the need for high-performance inkjet heads and precise ink placement, especially as pixel sizes decrease.
Innovation Solution
The implementation of a display device structure with specific partition walls, including an outer partition wall with lower surface energy and a thicker inner partition wall, allows for the formation of emission layers by inkjet printing, where the outer partition wall confines ink within pixel openings and the inner partition wall facilitates separate ink distribution between pixels, reducing the complexity and cost of the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inkjet printing is used to form emission layers in high-resolution display devices, then manufacturing flexibility is improved, but technical difficulty and cost increase due to the need for high-performance inkjet heads and precise ink placement
Solution Approach 1:
The partition walls are formed in advance before the inkjet printing process. The outer partition wall defines the pixel opening boundaries, and the inner partition wall is positioned within the pixel opening. This preliminary structuring allows subsequent inkjet printing to proceed more easily without requiring extremely high precision, as the partition walls provide physical guides for ink placement.
Solution Approach 2:
The inner partition wall acts as an intermediary structure between the pixel electrode and the emission layer. It facilitates ink distribution by providing a surface that guides ink flow and prevents ink from spreading to adjacent pixels, thereby reducing the technical difficulty of achieving precise ink placement without requiring excessively high-performance inkjet heads.
2Manufacturing precision
If pixel size is reduced to achieve high resolution, then display quality is improved, but inkjet printing precision requirements and cost increase
Solution Approach 1:
The pixel structure is segmented into multiple components: the pixel electrode, the outer partition wall, the inner partition wall, and the emission layer. The inner partition wall further segments the pixel opening into distinct regions. This segmentation allows each component to be optimized independently, enabling high resolution through precise structural definition rather than relying solely on inkjet printing precision.
Solution Approach 2:
Different regions of the pixel structure have different properties optimized for their specific functions. The outer partition wall has specific surface energy characteristics to confine ink within the pixel opening, while the inner partition wall has different surface energy to facilitate ink distribution. This local optimization of properties allows high-resolution patterning without requiring uniform high precision across the entire inkjet printing process.
3Reliability
If outer partition wall has lower surface energy to confine ink, then ink containment is improved, but contact angle increases requiring specific material selection
Solution Approach 1:
The surface energy of the outer partition wall is specifically adjusted to be lower than that of the inner partition wall. This parameter change ensures that the contact angle of ink on the outer partition wall is sufficiently large to confine ink within the pixel opening, while the inner partition wall maintains a smaller contact angle to allow ink distribution. This controlled parameter differentiation achieves reliable ink containment while allowing for material selection based on available low-surface-energy materials.
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
This approach enables the formation of emission layers across multiple pixels with a single discharge, simplifying the manufacturing process and reducing costs while maintaining high resolution.
Implementation Method 1
Surface energy of the outer partition wall may be lower than surface energy of the inner partition wall
Implementation Method 2
A contact angle of the outer partition wall may be higher than that of the inner partition wall
Data Source
AI summary
A display device includes: a substrate; a plurality of first electrodes positioned on the substrate; a lower partition wall configured to include a plurality of pixel openings that overlap the first electrodes; an outer partition wall positioned on at least a portion of the lower partition wall; an inner partition wall positioned on another portion of the lower partition wall; an emission layer disposed on each of the first electrodes; and a second electrode disposed on the emission layer.