Phenoxyphenylsilane Polymers for High Refractive Index LED Encapsulation

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Solution Overview

Problem

Conventional encapsulating materials for LEDs, such as PDMS, have a low refractive index, leading to internal reflections and reduced light output and efficiency, and lack stability under intense light flux and heat, necessitating the development of high refractive index materials that do not yellow over time.

Innovation Solution

Phenoxyphenylsilanes and bis-phenoxyphenylsilanes are used as monomers for synthesizing polymers with higher refractive indices through hydrolysis and polymerization, offering improved thermal stability and resistance to UV-A and blue light, with specific formulations and polymerization methods ensuring high refractive index and low water and oxygen transmission rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PDMS is used as encapsulant, then durability and resistance to yellowing are improved, but refractive index is too low causing internal reflections

Engineering Contradiction:

Improvedurability and resistance to yellowingVSAvoidrefractive index

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent changes the chemical composition parameters of the silicone polymer by incorporating phenyl groups and heteroatoms (nitrogen, oxygen, sulfur) into the polymer chain. This modifies the refractive index parameter from ~1.4 of conventional PDMS to higher values while maintaining the durability and yellowing resistance of silicone materials.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite polymer structure combining silicone backbone with aromatic phenyl groups and heteroatom-containing side chains. This composite approach integrates the high refractive index contribution from phenyl groups with the stability and yellowing resistance of the silicone matrix, achieving both improved optical and durability properties.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If phenyl silicones are used to increase refractive index, then light output is improved, but thermal stability and resistance to yellowing deteriorate

Engineering Contradiction:

Improverefractive indexVSAvoidthermal stability and resistance to yellowing

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent modifies the polymer composition by incorporating heteroatoms (nitrogen, oxygen, sulfur) into the side chains of the phenyl-containing silicone polymer. This chemical parameter change enhances thermal stability and yellowing resistance while preserving the high refractive index provided by the phenyl groups.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite structure where phenyl groups provide high refractive index, while heteroatom-containing chains (nitrogen, oxygen, sulfur) contribute thermal stability and yellowing resistance. This multi-component composite approach simultaneously achieves improved optical properties and enhanced durability under LED operating conditions.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional encapsulants are used, then manufacturing is simple, but light flux and heat management become problematic under intense LED conditions

Engineering Contradiction:

Improveencapsulation process simplicityVSAvoidheat resistance under intense light flux

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent changes the thermal and optical parameters of the encapsulant material by incorporating phenyl groups and heteroatoms into the polymer structure. These compositional changes enable the material to withstand higher temperatures and intense light flux from modern LEDs while maintaining processability for standard encapsulation manufacturing.

Inventive Principle:

Principle #35Parameter changes

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 resulting polymers exhibit refractive indices higher than phenylsiloxanes, with enhanced thermal stability and reduced water and oxygen transmission rates, addressing the limitations of existing materials by improving light output and durability in LED applications.

Implementation Method 1

The present disclosure provides a siloxane monomer having the formula p-PhOPh-Si(X)3 wherein each X is a hydrolysable group independently selected from hydrogen and an alkoxy group

Methodology Applied

Scientific EffectHydrolysis: Hydrolysis

Implementation Method 2

many of the polymers derived from phenoxyphenylsilane and/or bis-phenoxyphenylsilanes, for example by conventional hydrolysation and polymerization procedures

Methodology Applied

Scientific EffectCondensation polymerization:

Implementation Method 3

These polymers are resistant to UV-A and blue light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentEP3271366B1High-ri siloxane monomers, their polymerization and use

Publication Date: 2020.10.14 INKRON OY

Figure 1~3

AI summary

Phenoxyphenylsilane monomers were synthesized and polymerized. The polymers have high refractive indices and excellent UV and thermal stability. Their water and oxygen permeability is lower than commercial phenyl silicone elastomers. They show good compatibility with metal oxide nanoparticles. The polymers of the invention are suitable as LED encapsulant, as light guide material in CMOS image sensors, in OLED devices, lasers and in other optical applications.