Electro-optical Device Insulating Layer Steps
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Solution Overview
Problem
In electro-optical devices with OLEDs, local thickness variations in the light-emitting layer lead to reduced resistance and unintended current flow between electrodes, causing peripheral light emission with colors different from the primary colors, resulting in decreased color reproducibility, especially during low-gradation displays.
Innovation Solution
An electro-optical device configuration featuring a transflective first electrode, first and second reflective layers, pixel electrodes, and an insulating layer with multiple steps on the light-emitting layer side, which extends between the pixel electrodes, allowing for gradual thickness changes in the light-emitting layer to prevent peripheral light emission and maintain color accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If distance adjustment layers are stacked at some sub-pixels to adjust optical distance, then optical resonance can be achieved for specific colors, but local thickness reduction occurs in peripheral regions causing unintended current flow and peripheral light emission
Solution Approach 1:
An insulating layer is introduced as an intermediary between the light-emitting layer and the distance adjustment layers. This insulating layer has higher insulating properties than the distance adjustment layers, preventing unintended current flow in peripheral regions while allowing the distance adjustment layers to maintain optical resonance in the light-emitting regions. The insulating layer effectively mediates between the electrical isolation requirement and the optical resonance requirement.
Solution Approach 2:
The insulating layer is selectively positioned in peripheral regions where thickness reduction occurs, providing localized electrical isolation where needed. The distance adjustment layers are positioned in light-emitting regions to provide localized optical distance adjustment. This local differentiation of material properties and positions resolves the contradiction between achieving optical resonance and preventing peripheral light emission.
2Ease of manufacture
If light-emitting layer thickness is reduced in peripheral regions to match different layer structures, then device integration is improved, but resistance decreases causing current leakage and color distortion
Solution Approach 1:
The insulating layer serves as a mediator that allows thin light-emitting layers in peripheral regions to maintain adequate resistance. By introducing this intermediate layer with high insulating properties, the structure accommodates thickness variations needed for integration with different sub-pixel configurations while preventing the resistance degradation that would otherwise occur.
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 configuration effectively suppresses peripheral light emission and enhances color reproducibility by maintaining consistent light-emitting layer thickness and resistance, ensuring accurate color representation across the display.
Implementation Method 1
a light-emitting layer provided between the first electrode, and the first pixel electrode and the second pixel electrode
Data Source
AI summary
An electro-optical device includes a transflective first electrode, a first reflective layer, a first pixel electrode provided between the first electrode and the first reflective layer, a second reflective layer, a second pixel electrode provided between the first electrode and the second reflective layer, a light-emitting layer provided between the first electrode, and the first pixel electrode and the second pixel electrode, and an insulating layer provided between the first pixel electrode and the first reflective layer. The insulating layer extends from the first pixel electrode and between the first pixel electrode and the second pixel electrode in plan view. A surface of the insulating layer on the light-emitting layer side includes a plurality of steps between the first pixel electrode and the second pixel electrode in plan view.