OLED Subpixel Electrode Recesses to Suppress Coffee Ring Effect

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In organic EL display devices, the film thickness of the organic EL layer varies within subpixels due to the coffee ring effect during film application, leading to luminous unevenness and decreased efficiency.

Innovation Solution

A display device design featuring first and third electrodes with recessed portions and edge covers to stabilize the film thickness of the organic EL layer, reducing variations and enhancing luminosity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If solution coating method is used to form organic EL layer, then manufacturing process is simplified, but film thickness uniformity deteriorates due to coffee ring effect

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidfilm thickness uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The first electrode surface is segmented into multiple regions by forming recessed portions, which divide the coating area into distinct zones. This segmentation prevents the continuous flow of solution to the edges, reducing the coffee ring effect and improving film thickness uniformity while maintaining solution coating methodology

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The recessed portions are strategically positioned at specific locations on the first electrode surface where solution accumulation occurs. By modifying only these local areas rather than the entire surface, the invention addresses the coffee ring effect locally while preserving the overall simplicity of the solution coating process

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If recessed portions are formed on first electrode, then film thickness uniformity improves, but device structure becomes more complex

Engineering Contradiction:

Improvefilm thickness uniformityVSAvoidelectrode structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The recessed portions are formed on the first electrode before applying the organic EL layer. This preliminary structural modification prepares the surface to receive the coating solution uniformly, preventing edge accumulation before it occurs. The recesses act as pre-positioned barriers that guide solution distribution, achieving uniform film thickness without requiring complex post-processing or additional components

Inventive Principle:

Principle #10Preliminary action

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

The design suppresses film thickness variations and luminous unevenness, thereby improving luminous efficiency and brightness in each subpixel.

Implementation Method 1

solute components are likely to aggregate at the edge of an applied film due to a coffee ring effect in drying the applied film to be the organic EL layer

Methodology Applied

Scientific EffectCoffee ring effect: Coffee Ring Effect

Data Source

PatentUS20260068483A1Display device

Publication Date: 2026.03.05 SHARP DISPLAY TECHNOLOGY CORP

AI summary

A TFT layer is provided on a base substrate, a light-emitting element layer is provided on the TFT layer, a plurality of first electrodes, a first edge cover commonly provided, a plurality of third electrodes, a plurality of light-emitting function layers, and a second electrode commonly provided are layered in order in the light-emitting element layer, corresponding to a plurality of subpixels constituting a display region, each first electrode exposed from the first edge cover is provided with a first recessed portion, and a surface of each third electrode is provided with a second recessed portion corresponding to the first recessed portion.