Optical Clear Resin Coating for Low-Index Micro-LED Light Extraction
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Solution Overview
Problem
Micro-LED displays face challenges in luminous efficiency due to total reflection from large refractive index differences between light-emitting chips and air, and existing low-refractive layers suffer from haze, cracking, poor adhesion, and visibility issues under ambient light.
Innovation Solution
A low-refractivity optical clear resin comprising a polysiloxane composition and organic solvent mixture is used, allowing for a low-refractive index layer formation without cracking, with controlled yellowing and adequate thickness, enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large amount of hollow inorganic particles are used in the coating composition to achieve desired refractivity, then the refractive index of the low-refractive layer is reduced, but the haze increases and the coating cracks during curing
Solution Approach 1:
The patent employs a porous low-refractive layer with controlled porosity (30-70%) to achieve low refractive index (1.1-1.35) without using excessive hollow particles. The porous structure is formed through a sol-gel process using silane precursors that create a network with controlled void spaces, providing the necessary optical properties while maintaining coating integrity and avoiding cracking
Solution Approach 2:
The patent changes the physical and chemical parameters of the coating material by controlling the porosity, pore size distribution, and chemical composition of the low-refractive layer. By adjusting these parameters during the sol-gel process and curing conditions, the refractive index is optimized to 1.1-1.35 while maintaining adequate adhesion and preventing cracking
2Illumination intensity
If fluoropolymer is used in the coating composition to achieve low refractive index, then the refractive index is reduced, but the adhesion between the low-refractive layer and substrate deteriorates due to low surface energy
Solution Approach 1:
The patent creates a composite low-refractive layer combining inorganic silane-based porous matrix with organic functional groups. This composite structure achieves low refractive index through the porous inorganic network while the organic components and controlled pore filling provide adequate surface energy for adhesion, avoiding the adhesion problems of pure fluoropolymer coatings
Solution Approach 2:
The porous structure of the low-refractive layer provides a balance between optical properties and adhesion. The controlled porosity (30-70%) reduces the refractive index to 1.1-1.35, while the pore walls and surface chemistry can be optimized to provide adequate adhesion strength, avoiding both the cracking of particle-filled coatings and the poor adhesion of fluoropolymer coatings
3Ease of manufacture
If siloxane composition is cured at high temperature (>150°C) to form a low-refractive layer, then the coating is formed, but the porous structure cannot maintain low refractivity and desired yellow index with adequate thickness without cracking
Solution Approach 1:
The patent optimizes the curing temperature and time parameters to form the low-refractive layer at controlled temperatures (50-150°C) rather than high temperatures. This parameter change allows the porous structure to be formed and stabilized without collapsing, maintaining the refractive index (1.1-1.35) and yellow index (≤1.5) while achieving adequate thickness without cracking
4Area of stationary object
If the thickness of the low-refractive layer is increased to improve filling ability, then the filling ability improves, but the coating cracks and yellowing increases
Solution Approach 1:
The porous structure of the low-refractive layer provides excellent filling ability for the pixel gaps while maintaining coating integrity. The interconnected pore network allows the coating to conform to the substrate topography and fill gaps effectively, and the controlled porosity (30-70%) prevents cracking even at adequate thicknesses required for complete gap filling
Solution Approach 2:
The low-refractive layer can be applied as multiple thin layers or as a single layer with controlled thickness. The porous structure allows each layer to cure without cracking, and multiple layers can be stacked to achieve the required filling ability while maintaining optical properties (refractive index 1.1-1.35, yellow index ≤1.5) and preventing yellowing
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 resin achieves a refractive index of 1.1 to 1.35, limited yellowing, and adequate thickness without cracking, improving light extraction efficiency and display visibility in micro-LED devices.
Implementation Method 1
the organic solvent composition comprises a high boiling point solvent with a boiling point more than 180°C. and a low boiling point solvent with a boiling point less than 150°C
Implementation Method 2
The present optical clear resin, when be used in micro-LED display devices, shows limited yellowing after curing without affecting the hue and chroma of the display
Data Source
AI summary
A low-refractivity optical clear resin is disclosed. The low-refractivity optical clear resin comprises a polysiloxane composition and an organic solvent composition, wherein the polysiloxane composition comprises a polysiloxane and a hydroxyalkylsilane monomer, and the organic solvent composition comprises a high boiling point solvent with a boiling point more than 180° C. and a low boiling point solvent with a boiling point less than 150° C.; wherein the used amount of the organic solvent composition is 50 to 120 parts by weight per 10 parts by weight of the polysiloxane composition. The present low-refractivity optical clear resin can be used on the micro light emitting diode (micro-LED) display devices to enhance the light extracting efficiency thereof, and provide excellent optical properties on an adequate coating thickness.