Flexible Polyimide Substrate for Organic Electronic Devices
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Solution Overview
Problem
Conventional light extraction technologies for organic electronic devices (OEDs) are ineffective on flexible substrates due to their rigid nature, leading to low light emission efficiency, and existing solutions fail to achieve suitable haze and refractive index adjustments for improved performance.
Innovation Solution
A polyimide film substrate with adjustable haze and refractive index is developed by combining different condensation and imidization units of tetracarboxylic acid dianhydrides and diamine compounds, allowing for the inclusion of high refractive index layers and inorganic material layers to enhance light extraction efficiency and surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional light extraction technology is applied to flexible substrates, then light extraction efficiency can be improved, but the rigid nature of conventional solutions makes them incompatible with flexible substrate properties
Solution Approach 1:
The patent modifies the refractive index parameter of the flexible substrate itself by incorporating a light scattering layer with controlled haze (2-50%) directly into the substrate structure. This changes the optical parameters of the flexible substrate to enable effective light extraction without requiring rigid external components, thereby resolving the contradiction between improving light extraction efficiency and maintaining flexibility compatibility.
2Loss of energy
If haze plastic film is used to increase light extraction, then light extraction efficiency improves, but surface smoothness deteriorates
Solution Approach 1:
The patent applies local quality by creating a light scattering layer with specific haze properties (2-50%) that is integrated into the substrate structure rather than using conventional haze plastic films. This localized optical modification provides sufficient light extraction enhancement while maintaining the overall surface smoothness required for high-quality OLED manufacturing, thus resolving the contradiction between light extraction efficiency and surface smoothness.
3Adaptability or versatility
If conventional plastic film is used as substrate, then flexibility is maintained, but refractive index adjustment capability is limited
Solution Approach 1:
The patent creates a composite substrate structure consisting of a flexible base film combined with a light scattering layer containing inorganic oxide particles (TiO2, SiO2, ZnO, etc.) dispersed in a binder resin. This composite material approach enables refractive index adjustment and enhanced light extraction efficiency while maintaining flexibility, resolving the contradiction between refractive index adjustability and device complexity by integrating multiple functions into a single composite substrate layer.
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 substrate achieves improved light extraction efficiency, surface smoothness, and refractive index control, resulting in enhanced luminous efficiency and device performance for flexible OEDs.
Implementation Method 1
a polyimide film as a base film... may generate a haze by using a minimum amount of light scattering particles
Implementation Method 2
an organic EL device comprising a light dispersion layer formed from a binder resin and light dispersion particles. The haze of the light dispersion layer may be 2-50.
Implementation Method 3
a part of the light incident at an interface of each layer at a critical angle or more is not emitted and trapped because of total internal reflection
Data Source
AI summary
Provided are a substrate for an OED and a use thereof. The substrate may be applied to manufacture a flexible device exhibiting a suitable haze to have an excellent physical property such as transmittance, and also have excellent physical properties such as surface smoothness and refractive index when needed.