Siloxane Encapsulant for High-Index LED Light Output
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Solution Overview
Problem
Current LED encapsulant materials face challenges in achieving high luminance due to limitations in relative light output, heat resistance, and color fastness, with existing materials either being high in refractive index but low in heat and light resistance, or vice versa.
Innovation Solution
A polymer-based encapsulant material with a refractive index of 1.55 or more, incorporating units with specific functional groups, such as phenyl and alkyloxy groups, is developed to enhance relative light output, heat resistance, and color fastness, utilizing a siloxane bond structure that maintains transparency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a polymer with high refractive index (e.g., acrylic resin, epoxy resin) is used to increase relative light output, then the relative light output improves, but heat resistance and light resistance deteriorate
Solution Approach 1:
The invention uses a copolymer composed of a siloxane backbone unit and a high refractive index unit (such as phenyl-containing or carbonyl-containing groups). This composite structure combines the thermal stability and light resistance of siloxane bonds with the high refractive index properties of aromatic or carbonyl groups, achieving both high relative light output and excellent heat/light resistance simultaneously
Solution Approach 2:
The invention changes the chemical composition parameters of the polymer by introducing specific functional groups (phenyl groups, carbonyl groups) into the siloxane backbone. By controlling the types and proportions of monomer units in the copolymer, the refractive index is increased while maintaining the inherent stability of the siloxane bond structure, thus improving light output without sacrificing reliability
2Illumination intensity
If phenyl groups are introduced into the side chain of polysiloxane to increase refractive index, then the refractive index improves, but color fastness deteriorates due to yellowing
Solution Approach 1:
The invention changes the molecular structure by introducing phenyl groups directly into the main chain positions (alpha positions) of the siloxane backbone rather than as side chain substituents. This structural parameter change allows the phenyl groups to contribute to high refractive index while the siloxane backbone provides steric protection and chemical stability, preventing yellowing and maintaining color fastness
Solution Approach 2:
The siloxane backbone acts as an intermediary structure that mediates between the high refractive index requirement and color fastness requirement. The siloxane bonds provide a stable, yellowing-resistant framework that allows phenyl groups to be incorporated in a way that enhances refractive index without compromising color stability
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 encapsulant material significantly increases relative light output while maintaining heat resistance and color fastness, preventing yellowing and degradation, thus improving the performance of LED devices.
Implementation Method 1
a polysiloxane being a polymer having a siloxane bond as the skeleton is not easily decomposed because it has a large bonding energy of Si—O (Si—O: 444 kJ/mol)
Implementation Method 2
the relative light output of an encapsulant material is nearly proportional to the refractive index n of the encapsulant material and as the refractive index n is higher, the relative light output (%) is higher
Data Source
AI summary
A light-emitting device is provided which uses an encapsulant material made from a polymer having a high relative light output. The light-emitting device includes a light-emitting element and a member sealing the light-emitting element. The encapsulant material has one or more than two kinds of units given by the following formula (1) and a refractive index of 1.55 or more.where R is a hydrogen atom, alkyl group or phenyl group, Y is an alkyl group of which the carbon number is 1 to 6 or an alkyloxy group of which the carbon number is 1 to 6 and Z is an aromatic compound that meets predetermined requirements.