Organic EL Display Panel Insulating Layer for Contrast
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Solution Overview
Problem
In organic EL display panels, position shifts during alignment lead to decreased display contrast due to external light reflection at the outer edges of reflective electrode layers, and increasing the width of the light shielding layer to prevent this interferes with light extraction efficiency and uniformity.
Innovation Solution
An organic EL display panel with a top-emission type configuration, featuring a substrate with pixel electrode layers, an insulating layer with an optical density of 0.5 to 1.5, and a counter electrode layer made of light-transmissive material, which suppresses external light reflection at the outer edges of the reflective pixel electrode layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the width of the light shielding layer is increased to prevent external light reflection at the outer edges of reflective electrode layers, then display contrast is improved, but light extraction efficiency decreases and luminance/chromaticity nonconformity occurs
Solution Approach 1:
The insulating layer is applied selectively only at the outer edges of the reflective pixel electrode layers rather than uniformly across the entire electrode surface. This localized application provides light shielding exactly where external light reflection occurs (at the edges) while leaving the central light-emitting regions uncovered, thus maintaining high light extraction efficiency and uniform luminance distribution.
2Manufacturing precision
If the width of the light shielding layer is increased to prevent position shift effects, then alignment tolerance is improved, but aperture ratio per unit pixel decreases
Solution Approach 1:
The insulating layer is confined to the peripheral edges of the pixel electrode layers, providing alignment tolerance and preventing light leakage only at the boundaries between pixels. The central aperture regions remain fully open, maximizing the aperture ratio for light emission while still protecting against misalignment effects.
3Object-affected harmful factors
If the optical density of the insulating layer is increased to suppress external light reflection, then display contrast is improved, but light absorption by the insulating layer increases
Solution Approach 1:
The insulating layer with optimized optical density (0.5 to 1.5) is applied only at the edge regions where external light reflection is problematic, while the central light-emitting areas remain uncovered. This ensures that the insulating layer blocks external light at boundaries without absorbing light from the light-emitting regions, thus improving contrast while maintaining high light extraction efficiency.
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 effectively maintains high contrast and light extraction efficiency while preventing light leakage and luminance/chromaticity nonconformity, even as resolution increases, by strategically placing insulating layers and light-emitting layers to control external light reflection.
Implementation Method 1
the insulating layer has an optical density of 0.5 to 1.5 in a direction of the substrate when viewed in plan
Implementation Method 2
the light-emitting layers causing organic electroluminescence
Implementation Method 3
a plurality of pixel electrode layers that are made of a light-reflective material
Data Source
AI summary
An organic electroluminescence (EL) display panel including pixels arranged in a matrix, the organic EL display panel includes: a substrate; pixel electrode layers made of a light-reflective material and arranged on the substrate in a matrix; an insulating layer provided at least above row and column outer edges of the pixel electrode layers and above inter-regions on the substrate between the row and column outer edges; an organic functional layer provided above the pixel electrode layers; and a counter electrode layer made of a light-transmissive material and is provided above the organic functional layer, wherein the organic functional layer includes light-emitting layers that are provided in regions above the pixel electrode layers where the insulating layer is not provided, the light-emitting layers causing organic electroluminescence, and the insulating layer has an optical density of 0.5 to 1.5 in a direction of the substrate when viewed in plan.