Organic EL Display Electrode Reflectance and Insulating Layer
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Solution Overview
Problem
Organic EL display devices with high reflectance electrodes suffer from increased external light reflection, reduced contrast, and color shift due to light diffusion between pixels.
Innovation Solution
Incorporating a transparent electrode and a non-transparent electrode with a black insulating layer, where the non-transparent electrode has a reflectance of 25%±20% and the insulating layer has an optical density of 0.3 or more per 1.0 μm film thickness, to minimize external light reflection and light diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a metal electrode with high reflectance is used in the organic EL element, then light extraction efficiency is improved, but external light reflection increases and contrast is reduced
Solution Approach 1:
The patent changes the reflectance parameter of the electrode from high (conventional) to specifically 25%±20%, and controls the optical density of the insulating layer to be 0.3 or more per 1.0 μm thickness. This parameter optimization resolves the contradiction by achieving sufficient light extraction while minimizing external light reflection, thereby improving contrast
Solution Approach 2:
The patent employs a composite structure consisting of a non-transparent electrode with controlled reflectance (25%±20%) combined with a black insulating layer having specific optical density (0.3 or more per 1.0 μm). This composite approach allows the system to benefit from both light extraction and external light reflection suppression
2Illumination intensity
If a metal electrode with high reflectance is used in the organic EL element, then light emission is enhanced, but light diffusion to adjacent pixels increases and color shift occurs
Solution Approach 1:
The patent optimizes the electrode reflectance parameter to 25%±20%, which is sufficiently high to maintain bright light emission but low enough to prevent excessive light diffusion to adjacent pixels. This parameter control ensures color accuracy is maintained while preserving illumination intensity
Solution Approach 2:
The combination of the non-transparent electrode with controlled reflectance and the black insulating layer with specific optical density creates a composite system that confines light emission within pixels, preventing color shift while maintaining brightness
3Ease of manufacture
If a transparent insulating layer is used to separate pixels, then manufacturing is simplified, but external light passes through and reflects from the electrode, reducing contrast
Solution Approach 1:
The patent specifies that the insulating layer should have an optical density of 0.3 or more per 1.0 μm film thickness, transforming it from a conventional transparent layer to a black insulating layer. This parameter change maintains ease of manufacture through standard deposition processes while effectively blocking external light and preventing reflection-induced contrast loss
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 solution effectively reduces external light reflection, enhances contrast, and minimizes color shift, improving the display quality of organic EL display devices.
Implementation Method 1
The non-transparent electrode has a reflectance of 25%±20%
Implementation Method 2
the insulating layer has an optical density of 0.3 or more per 1.0 μm film thickness
Implementation Method 3
The organic EL display device is a self-luminous display device utilizing electroluminescence emitted from an organic compound
Data Source
AI summary
The organic EL display device includes at least a transparent electrode, an organic EL layer, and a non-transparent electrode in this order and further includes a black insulating layer, and the non-transparent electrode has a reflectance of 25%±20%.