OLED Emission Layer Height Control for Uniform Pixel Luminance
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Solution Overview
Problem
Organic light-emitting display apparatuses face issues with inconsistent luminance ratios between pixels emitting different colors, leading to image quality deterioration due to varying maximum-minimum surface differences in the emission layers.
Innovation Solution
The apparatus includes pixel electrodes with emission layers of specific wavelengths (450-495 nm, 495-570 nm, and 630-750 nm) formed by inkjet printing, with controlled surface height differences between 400 Å to 1500 Å, and pixel defining layers to ensure uniform luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If emission layers are formed with conventional methods, then manufacturing process is simple, but surface height difference becomes large causing luminance inconsistency
Solution Approach 1:
The patent applies parameter changes by controlling the surface height difference within a specific range (400-1500 Å) to optimize luminance uniformity. By adjusting the emission layer thickness and surface profile parameters, the invention achieves consistent luminance across different colored pixels while maintaining manufacturing feasibility through inkjet printing technology.
Solution Approach 2:
The patent implements preliminary action by pre-forming pixel defining layers with specific patterns before forming the emission layers. This preliminary structuring of the substrate with defined pixel boundaries and depth variations enables subsequent emission layer deposition to achieve uniform thickness and height control, preventing luminance inconsistency before it occurs.
2Ease of manufacture
If emission layers have large surface height difference, then material deposition is easier, but luminance ratio between pixels becomes inconsistent
Solution Approach 1:
The patent applies local quality by creating pixel defining layers with different depths in different regions, where the pixel electrode areas have greater depth than the pixel defining layer areas. This localized structural variation ensures that emission layers deposited over pixel electrodes achieve uniform thickness and appropriate height, while maintaining ease of material deposition through inkjet printing by accommodating the overall surface topology.
3Manufacturing precision
If inkjet printing is used for emission layer formation, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-forming pixel defining layers with specific patterns and depth variations before inkjet printing the emission layers. This preliminary structuring creates a prepared substrate topology that guides the inkjet printing process, ensuring uniform emission layer deposition and consistent surface height control while simplifying the printing process control through pre-established geometric constraints.
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 configuration maintains relative luminance at 0.9 or greater, ensuring uniform light emission and high-quality image display by minimizing luminance variations across pixels.
Implementation Method 1
An organic light-emitting display apparatus includes a first pixel electrode, a first color emission layer disposed over the first pixel electrode... a second pixel electrode, a second color emission layer disposed over the second pixel electrode... a third pixel electrode, and a third color emission layer disposed over the third pixel electrode
Data Source
AI summary
An organic light-emitting display apparatus capable of a high-quality image includings a substrate, a first pixel electrode over the substrate, and a first color emission layer disposed over the first pixel electrode and has an upper surface on which a distance in a direction perpendicular to a surface of the substrate between a highest point and a lowest point is about 400 Å to about 900 Å.