High Refractive Index Glass for OLED Light Extraction
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Solution Overview
Problem
Conventional OLED devices face inefficiencies in light extraction due to refractive index differences between substrates and ITO films, leading to high reflectance and uneven illumination.
Innovation Solution
A high refractive index glass with specific composition ranges, including SiO2, Al2O3, B2O3, BaO, La2O3, Nb2O5, TiO2, and ZrO2, is developed to match the refractive indices of organic light-emitting elements and ITO films, enhancing light extraction and denitrification resistance, and allowing for unpolished surfaces with low surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional substrate with refractive index of about 1.5 is used, then the manufacturing process is simple, but the reflectance at the interface between substrate and ITO film is high, leading to poor light extraction efficiency
Solution Approach 1:
The patent changes the refractive index parameter of the substrate material from the conventional 1.5 to a higher range of 1.65-2.2 by adjusting the glass composition (specific ratios of SiO2, B2O3, Al2O3, and metal oxides like BaO, La2O3, Nb2O5, TiO2, ZrO2). This parameter change reduces the refractive index difference at the substrate-ITO interface, thereby reducing reflectance and improving light extraction efficiency without complicating the manufacturing process
Solution Approach 2:
The patent uses a composite glass material containing multiple components (SiO2, B2O3, Al2O3, and various metal oxides) to achieve the desired refractive index. This composite material approach allows precise control over the refractive index while maintaining good manufacturing properties and chemical stability, resolving the contradiction between manufacturing simplicity and optical performance
2Loss of energy
If the refractive index of the substrate is increased to match the organic light-emitting element and ITO film, then light extraction efficiency is improved, but the glass composition becomes more complex
Solution Approach 1:
The patent systematically adjusts the composition parameters of the glass, establishing specific ratio ranges for different oxide components. By controlling the ratios of network formers (SiO2, B2O3), network modifiers (metal oxides), and intermediates (Al2O3), the patent achieves the target refractive index while maintaining a manageable composition complexity through defined proportion relationships rather than arbitrary combinations
3Manufacturing precision
If polishing is applied to reduce surface roughness, then the surface quality is improved, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent enables the glass material to self-provide good surface quality through its inherent properties. By optimizing the glass composition and manufacturing parameters, the glass naturally forms with low surface roughness (Ra ≤ 5 nm) without requiring additional polishing steps. The material essentially serves itself to achieve the desired surface quality, eliminating the need for complex post-processing
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 high refractive index glass improves light extraction efficiency, reduces reflectance, and enhances denitrification resistance, while also simplifying the manufacturing process by allowing for unpolished surfaces and reducing production costs.
Implementation Method 1
a difference in refractive index between the substrate and the ITO film at their interface leads to a high reflectance, and hence light emitted from the organic light-emitting element cannot be extracted efficiently
Implementation Method 2
The emitted light enters a substrate via the transparent conductive film such as an ITO film and is released out while repeating reflection in the substrate
Data Source
AI summary
Provided is a high refractive index glass, comprising, as a glass composition in terms of mass %, 0.1 to 60% of SiO2+Al2O3+B2O3, having a mass ratio (BaO+La2O3+Nb2O5+TiO2+ZrO2)/(SiO2+Al2O3+B2O3) of 0.1 to 50, amass ratio (MgO+CaO+SrO+BaO)/(BaO+La2O3+Nb2O5+TiO2+ZrO2) of 0 to 10, and a mass ratio (TiO2+ZrO2)/(BaO+La2O3+Nb2O5) of 0.001 to 40, and having a refractive index nd of 1.55 to 2.3.