Light-Reflective Anisotropic Conductive Adhesive for LED Efficiency
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Solution Overview
Problem
Conventional light-emitting devices with LED elements experience reduced light-emitting efficiency due to absorption of light by gold wires and die bond adhesives, and the production cost is increased by the need for a light-reflective layer in flip-chip mounting techniques, while anisotropic conductive adhesives without a light-reflective layer have brown or dark surfaces that further reduce efficiency.
Innovation Solution
A light-reflective anisotropic conductive adhesive is developed containing thermosetting resin, conductive particles, and titanium oxide particles with a surface treatment using metal oxides like Al2O3, SiO2, and ZnO2, which reflect light without direct contact with organic substances, preventing photodegradation and improving light-emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light-reflective layer is provided on the LED element through metal deposition method, then light-emitting efficiency is improved, but production cost increases
Solution Approach 1:
The patent merges the light-reflective function and the adhesive function into a single integrated layer. The anisotropic conductive adhesive contains both adhesive components and light-reflective particles (such as titanium oxide, aluminum oxide, or silicon oxide), eliminating the need for a separate light-reflective layer and reducing production costs while maintaining high light-emitting efficiency
Solution Approach 2:
The anisotropic conductive adhesive performs multiple functions simultaneously: it provides adhesive bonding, electrical conduction in specific directions, and light reflection. This multi-functional design replaces what would traditionally require multiple separate components, thereby reducing manufacturing complexity and cost while improving optical performance
2Ease of manufacture
If no light-reflective layer is provided, then production cost is reduced, but light-emitting efficiency is reduced due to brown or dark brown surface of conductive particles
Solution Approach 1:
The patent changes the optical parameters of the adhesive by incorporating light-reflective particles with high refractive indices (such as titanium oxide with refractive index of 2.6-2.9, aluminum oxide with 1.7-1.8, or silicon oxide with 1.4-1.5). These particles reflect incident light effectively, giving the cured adhesive a white or light-colored appearance and maintaining high light-emitting efficiency without requiring additional light-reflective layers
3Loss of energy
If titanium oxide particles with high photocatalytic action are used, then light reflection is improved, but photodegradation of organic substances in cured adhesive occurs
Solution Approach 1:
The patent introduces inert inorganic particles (such as aluminum oxide, silicon oxide, or zinc oxide) as intermediary substances that do not exhibit strong photocatalytic activity. These particles serve as light-reflective agents without causing photodegradation of the organic adhesive components, thereby maintaining both light reflection capability and chemical stability of the cured adhesive
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 adhesive enhances light-emitting efficiency by reflecting light without the need for a costly light-reflective layer, maintains the original color of the LED element, and ensures the stability of the organic substances in the cured adhesive.
Implementation Method 1
the light-reflective insulating particles have a particle diameter of 0.2 to 0.3 μm... most of the light output downward reflects on the light-reflective layer 40
Implementation Method 2
there is a concern of photodegradation of an organic substance contained in a cured adhesive. However, the present inventors have found that such a concern is solved by treating the surface of titanium oxide particles so that the surface is coated with a metal oxide
Data Source
Figure 1A
Figure 1B~2
Figure 3
AI summary
A light-reflective anisotropic conductive adhesive used for anisotropic conductive connection of a light-emitting element to a wiring substrate includes a thermosetting resin composition, conductive particles, and light-reflective insulating particles. The light-reflective insulating particles are formed by subjecting titanium oxide particles to a surface treatment with one kind selected from the group consisting of Al2O3, SiO, SiO2, ZnO, ZnO2, and ZrO2. The amount of the titanium oxide contained in the light-reflective insulating particles is 85 to 93%. The particle diameter of the light-reflective insulating particles is 0.2 to 0.3 µm, and the particle diameter of the conductive particles is 2 to 10 µm.