Organic EL Panel Light-Shielding Layer Design
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Solution Overview
Problem
Existing organic EL panels face issues with light-induced degradation of thin film transistors and reduced contrast ratio due to light reflection from device separation layers, with existing light-shielding techniques either degrading transistor characteristics or failing to effectively cover lateral surfaces.
Innovation Solution
A top-emission type organic EL panel design featuring a light-shielding layer formed on a protective layer, covering lateral surfaces of the device separation layer and display regions other than light emitting sections, to prevent light exposure and minimize reflection, thereby maintaining drive characteristics and improving contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-shielding layer is formed directly on thin film transistors to prevent light-induced degradation, then transistor characteristics are protected from light damage, but the light-shielding layer creates capacitance when contacted with electro-conductive members, degrading transistor drive characteristics
Solution Approach 1:
The patent introduces a protective layer as an intermediary between the light-shielding layer and the thin film transistor. This protective layer physically separates the light-shielding layer from the electro-conductive members and transistor structures, preventing direct contact that would create harmful capacitance. The protective layer allows the light-shielding function to operate while eliminating the parasitic capacitance effect that would degrade transistor drive characteristics.
2Illumination intensity
If a black adhering member is arranged on the device separation layer to improve contrast ratio, then light reflection from lateral surfaces is reduced, but the tapered lateral surfaces of the device separation layer still allow light to strike and reflect, failing to fully improve contrast ratio
Solution Approach 1:
The patent extends the light-shielding function into the vertical dimension by forming a light-shielding layer that covers not only the planar display regions but also the lateral surfaces of the device separation layer. This three-dimensional light-shielding approach addresses the reflection problem from tapered lateral surfaces that two-dimensional planar black adhering members cannot fully solve.
3Object-affected harmful factors
If light-shielding material is used to cover thin film transistors, then light protection is achieved, but the light-shielding layer is sandwiched between thin film transistors and electro-conductive members, creating capacitance that changes transistor characteristics
Solution Approach 1:
The protective layer serves as a mediating structure that prevents the formation of the problematic sandwich structure. By placing the protective layer between the light-shielding layer and the thin film transistor/electro-conductive member assembly, it eliminates the direct electrical coupling that would create parasitic capacitance, thereby simplifying the electrical structure while maintaining light protection.
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 shields thin film transistors from light, maintains drive characteristics, and enhances contrast ratio by reducing light reflection on the device separation layer, while minimizing potential damage to the organic EL devices.
Implementation Method 1
a light-shielding layer formed on the protective layer in a display region other than light emitting sections of the organic EL devices so as to be held in contact with the protective layer and cover at least part of lateral surfaces of the device separation layer
Data Source
AI summary
A top-emission type organic EL panel has a substrate carrying thin film transistors formed thereon, a plurality of organic EL devices formed on the substrate, each of the organic EL devices including a reflecting electrode, organic compound layers and a transparent electrode arranged in this order from the substrate side, a device separation layer formed in a space separating adjacently located organic EL devices, a protective layer covering the organic EL devices and the device separation layer and a light-shielding layer formed on the protective layer in a display region other than light emitting sections of the organic EL devices so as to be held in contact with the protective layer and cover at least part of lateral surfaces of the device separation layer.