Glass Ceramic Substrate Reflectance Stabilization

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Solution Overview

Problem

Glass ceramic substrates for light emitting devices face issues with reflectance deterioration due to silver layer agglomeration and uneven firing shrinkage, leading to reduced reflectance and strength, especially when using α-alumina particles with a flat shape.

Innovation Solution

A glass ceramic body with a non-crystallized glass matrix and alumina particles having an α-alumina crystal structure and other crystal structures like θ-alumina, which suppresses blackening and firing shrinkage unevenness, thereby maintaining reflectance and strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a silver layer is formed in the glass ceramic substrate to improve reflectance or heat release, then reflectance or heat release property is improved, but silver melts into the glass ceramics during firing and forms colloids that cause blackening and reduce reflectance

Engineering Contradiction:

ImprovereflectanceVSAvoidblackening

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an intermediary substance (silicon oxide or boron oxide) that acts as a barrier between the silver layer and the glass ceramic matrix. This intermediary prevents direct contact and interaction between silver and the glass ceramic, thereby preventing silver dissolution and colloid formation during firing, while still allowing the silver layer to fulfill its reflectance and heat release functions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the potentially harmful effect of silver melting into a beneficial outcome by controlling the melting process. The silver does melt during firing, but instead of forming harmful colloids, it forms a controlled intermetallic compound with the intermediary substance, which stabilizes the silver in a non-harmful state while maintaining optical properties

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Manufacturing precision

If α-alumina particles with flat shape are used to suppress firing shrinkage, then firing shrinkage unevenness is suppressed, but blackening occurs more remarkably

Engineering Contradiction:

Improvefiring shrinkage uniformityVSAvoidblackening

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the glass ceramic substrate by adding specific amounts of silicon oxide (5-20 wt%) and/or boron oxide (5-20 wt%). This parameter change modifies the chemical environment during firing, preventing silver dissolution while maintaining the beneficial flat shape of α-alumina particles for suppressing firing shrinkage

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If high refractive index particles are incorporated to increase reflectance, then reflectance is increased, but sintering property deteriorates and glass composition design freedom is reduced

Engineering Contradiction:

ImprovereflectanceVSAvoidsintering property

Core Design Contradiction:

Illumination intensityVSEase of manufacture

Solution Approach 1:

The patent uses a composite material approach by combining multiple types of particles with different properties: α-alumina particles (for strength and reflectance), flat alumina particles (for firing shrinkage control), and high refractive index particles (for reflectance enhancement). The synergistic combination allows each particle type to contribute its specific function while maintaining overall sintering performance

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the particle size parameters of the high refractive index particles, specifying that they should be 0.5-5 μm in diameter. This parameter optimization ensures that the particles are small enough to maintain good sintering contact and dispersion, while still providing sufficient reflectance enhancement. The controlled particle size prevents aggregation and maintains manufacturability

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 solution effectively prevents reflectance deterioration and uneven firing shrinkage, enhancing the properties of the glass ceramic body, including high reflectance and strength, making it suitable for light emitting device substrates.

Implementation Method 1

a ceramic part composed of the dispersed alumina particles has an α-alumina crystal structure and a crystal structure other than the α-alumina crystal structure

Methodology Applied

Scientific EffectCrystal structure:

Data Source

PatentUS9024352B2Glass ceramic body, substrate for mounting light-emitting element, and light emitting device

Publication Date: 2015.05.05 AGC INC

AI summary

To provide a glass ceramic body wherein the deterioration of the reflectance due to black coloration is suppressed, and the unevenness of the firing shrinkage is suppressed.A glass ceramic body comprising a glass matrix and alumina particles dispersed therein, wherein the glass matrix is not crystallized, a ceramic part composed of the dispersed alumina particles has an α-alumina crystal structure and a crystal structure other than the α-alumina crystal structure.