Flexible PI Substrate With Refractive Index Gradient for OLED Light Extraction
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Solution Overview
Problem
Current methods for improving the external quantum efficiency of flexible OLED displays through anti-reflection techniques are complex and costly, often involving deposition of inorganic or organic materials or microstructures on substrates.
Innovation Solution
A flexible polyimide substrate with a refractive index gradient is achieved by controlling the ratio of heteroatoms in a multilayer structure, formed through a continuous film forming process using sulfur-containing diamine and dianhydride monomers, reducing light reflection at the ITO interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If inorganic or organic materials are deposited on the substrate by CVD or PVD to reduce light reflection, then the anti-reflection effect is improved, but the process complexity and manufacturing cost increase
Solution Approach 1:
The patent changes the refractive index parameter of the substrate material itself by using polyimide with a refractive index of 1.74, which is higher than conventional substrates (1.52). This parameter change in the base material reduces the refractive index difference at the ITO/organic layer interface, thereby reducing light reflection without requiring additional anti-reflection coating processes
Solution Approach 2:
The patent uses a composite structure consisting of the polyimide substrate combined with the ITO layer and organic light-emitting layers. By integrating the anti-reflection function into the substrate material itself rather than adding separate anti-reflection coatings, the system achieves reduced light reflection while simplifying the overall device structure and manufacturing process
2Illumination intensity
If a multilayer structure is deposited to achieve anti-reflection effect, then the light transmission is improved, but the manufacturing cost and process complexity increase
Solution Approach 1:
The patent modifies the refractive index parameter of the substrate material to 1.74, which optimizes the optical matching between layers. This single parameter change in the substrate material achieves improved light transmission by reducing interfacial reflection, eliminating the need for complex multilayer anti-reflection coatings and associated manufacturing costs
3Ease of manufacture
If conventional substrate with refractive index 1.52 is used, then the manufacturing process is simple, but the light reflection loss is high
Solution Approach 1:
The patent changes the refractive index parameter of the substrate from the conventional 1.52 to 1.74 by using polyimide material. This parameter optimization reduces the refractive index mismatch at the ITO/organic layer interface, thereby reducing light reflection loss while maintaining manufacturing simplicity through the use of a single integrated substrate material
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 approach enhances light transmission and extraction efficiency without the need for complex processes, improving the external quantum efficiency of OLED displays.
Implementation Method 1
the χ depends on the refractive index of each layer. That is, it presents a ratio of the emitted light which is reflected and lost in the device. As for the organic light emitting diode devices, the light emission can be mainly divided into three categories such as direct emission into the air, internal reflection in the substrate, and the light is reflected in the indium tin oxide (ITO)/organic layer.
Implementation Method 2
the light is reflected in the indium tin oxide (ITO)/organic layer. According to the calculation, the ratio of the three modes is 0.19, 0.36, and 0.46, thereby reducing the reflection of light in the ITO/organic layer, which is the key to improving the external quantum efficiency of the organic light emitting diode device.
Data Source
AI summary
A flexible substrate, a method of manufacturing thereof, and display panel are provided. The flexible substrate includes a glass substrate, a first flexible base layer disposed on the glass substrate, a second flexible base layer disposed on the first flexible base layer, and a third flexible base layer disposed on the second flexible base layer.