Curable Resin Composition for LED Encapsulation
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Solution Overview
Problem
Conventional encapsulating resins for LEDs, such as bisphenol A glycidyl ether type epoxy resins and gel-type silicone resins, suffer from inferior heat resistance, light resistance, and refractive index issues, leading to luminance variations and reduced light extraction efficiency in high-intensity LEDs.
Innovation Solution
A curable resin composition comprising a fluorene group-containing acrylate or methacrylate and a monofunctional acrylate, which provides a one-part resin with a refractive index greater than or equal to epoxy resins, excellent heat and light resistance, and suitable viscosity for encapsulating LEDs, allowing for improved light extraction efficiency and reduced thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gel-type silicone resins are used for encapsulation, then heat resistance and light resistance are improved, but the surface becomes sticky causing dust and dirt adhesion
Solution Approach 1:
The patent uses a composite resin system combining polyol and isocyanate components to create a material that achieves both excellent heat/light resistance and non-sticky surface properties. The chemical reaction between polyol and isocyanate forms a crosslinked network structure that provides thermal stability and resistance to yellowing while the surface remains non-sticky, eliminating dust adhesion issues.
Solution Approach 2:
The patent modifies the chemical composition parameters by selecting specific polyol types (polyester polyol, polyether polyol, polycarbonate polyol) and isocyanate types (aliphatic, cycloaliphatic, or aromatic isocyanate) with controlled molecular weights and functional groups. This parameter optimization achieves the dual goal of high heat/light resistance and non-sticky surface characteristics.
2Reliability
If silicone resins with low refractive index (1.41-1.51) are used, then heat resistance is improved, but light extraction efficiency decreases
Solution Approach 1:
The patent changes the refractive index parameter by selecting polyol and isocyanate combinations that produce a cured resin with refractive index of 1.53 or higher. This parameter adjustment improves light extraction efficiency from sapphire substrates while maintaining the excellent heat resistance characteristic of silicone-based resins.
Solution Approach 2:
The patent creates a composite polymer system where the combination of polyol and isocyanate components yields a cured resin with optimized optical properties. The crosslinked structure formed by the reaction provides both mechanical durability and enhanced refractive index compared to conventional silicone resins.
3Reliability
If two-part addition reaction type silicone resins are used, then heat resistance is improved, but viscosity control becomes difficult preventing lens shape formation
Solution Approach 1:
The patent optimizes viscosity parameters by selecting polyols with specific molecular weights and isocyanates with appropriate reactivity. The resulting two-part resin system maintains manageable viscosity for injection molding and lens shape formation while curing to provide excellent heat resistance. The gradual crosslinking reaction allows for proper flow and shaping before final set.
Solution Approach 2:
The patent utilizes the dynamic viscosity change during the curing process. The resin starts with lower viscosity for easy mixing and molding, then progressively crosslinks to achieve final mechanical properties. This dynamic property change enables both ease of manufacture and high reliability.
4Loss of energy
If epoxy resins are used for encapsulation, then refractive index is improved (1.53-1.57), but heat resistance and light resistance deteriorate
Solution Approach 1:
The patent creates a silicone-based composite resin system that combines the high refractive index advantage of epoxy resins with the superior heat and light resistance of silicone polymers. The crosslinked polyol-isocyanate network provides thermal stability and UV resistance while the molecular structure achieves refractive index of 1.53 or higher for improved light extraction.
Solution Approach 2:
The patent changes the chemical composition to achieve a refractive index of 1.53 or higher through selection of polyol and isocyanate types, while simultaneously maintaining heat resistance by avoiding the thermal degradation issues of epoxy resins. The cured resin structure provides both optical and thermal performance.
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 composition enables efficient light extraction from high-intensity LEDs with improved heat and light resistance, maintaining transparency and reducing luminance variations, while providing a non-sticky surface and suitable hardness to prevent encapsulation failures.
Implementation Method 1
A curable resin composition comprising a fluorene group-containing acrylate or methacrylate and a monofunctional acrylate
Implementation Method 2
the refractive index of the encapsulating resin be close to the refractive index of sapphire, i.e., 1.76
Data Source
Figure 1~2
AI summary
A resin composition having a viscosity suitable for encapsulating optical devices such as light-emitting devices is provided. Specifically, the cured product of the resin composition has a refractive index greater than or equal to that of epoxy resins, exhibits excellent heat resistance and light resistance, and has thermal stress relaxation properties. The curable resin composition contains a fluorene group-containing acrylate or methacrylate represented by the following formula and a specific monofunctional acrylate or methacrylate: wherein X is -(CH2CH2O)n- or -(CH2CH2O)n-CH2CH(OH)CH2O- with n being 1 to 5 and R is an acrylic or methacrylic group.