Sintered Ceramic Optical Element for LED Adhesion
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Solution Overview
Problem
Optical elements for light emitting devices with both wavelength converting and scattering layers face challenges such as mechanical failure due to lack of adhesion, thermal instability, and chemical degradation, which affect light intensity distribution and durability.
Innovation Solution
A sintered ceramic body with a wavelength converting layer and a scattering layer, where both layers are made of ceramic materials with matched thermal expansion coefficients and refractive indices, eliminating the need for adhesives and ensuring intimate contact for efficient optical coupling and high durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an additional adhesive layer is used to achieve sufficient adhesion of the layers, then physical contact between the wavelength converting layer and the scattering layer is improved, but the device complexity increases and thermal stability deteriorates due to heat-induced stresses from different thermal expansion properties
Solution Approach 1:
The patent merges the adhesive layer function into the scattering layer by making the scattering layer itself adhesive through ceramic material composition and sintering process optimization. This eliminates the separate adhesive layer while maintaining strong bonding between the wavelength converting layer and scattering layer, reducing device complexity and improving thermal stability.
Solution Approach 2:
The patent uses composite ceramic materials in the scattering layer that provide both structural integrity and adhesive properties. The composite material composition enables the scattering layer to bond effectively with the wavelength converting layer without requiring a separate adhesive layer, resolving the contradiction between adhesion strength and device complexity.
2Strength
If an additional adhesive layer is used to achieve sufficient adhesion of the layers, then physical contact between the wavelength converting layer and the scattering layer is improved, but thermal stability worsens due to heat-induced stresses caused by different thermal expansion properties
Solution Approach 1:
The patent merges the adhesive layer function into the scattering layer, eliminating the interface between adhesive and ceramic layers that would experience thermal expansion mismatch. The scattering layer itself provides adhesive bonding through its ceramic material properties, eliminating the source of thermal stress and improving thermal stability.
Solution Approach 2:
The patent uses homogeneous ceramic materials for both the wavelength converting layer and scattering layer, ensuring matched thermal expansion coefficients. This material homogeneity eliminates thermal expansion mismatches at interfaces, preventing heat-induced stresses and improving thermal stability while maintaining strong adhesion.
3Ease of manufacture
If a very fine gap exists between the wavelength converting layer and the scattering layer, then manufacturing ease is improved, but optical contact deteriorates causing light leakage at the sides in undesired angles
Solution Approach 1:
The patent employs self-aligning features in the sintering process where the ceramic particles and green body structure automatically ensure intimate contact between layers during sintering. The viscous behavior of the green body at sintering temperatures allows the layers to conform to each other, eliminating gaps without requiring precision assembly, thus maintaining both manufacturing ease and optimal optical contact.
Solution Approach 2:
The patent changes the physical state and properties of the material during the sintering process. The green body exhibits viscous flow at sintering temperatures, allowing layers to deform and eliminate gaps. After sintering, the material becomes rigid with permanent intimate contact. This parameter change enables gap elimination through the manufacturing process itself rather than requiring precision assembly.
4Device complexity
If chemical interactions occur between the wavelength converting layer and the scattering layer, then manufacturing simplicity is maintained, but the function of the optical element deteriorates due to destroyed luminescence or emission color change
Solution Approach 1:
The patent carefully controls sintering parameters including temperature, atmosphere, and duration to prevent harmful chemical interactions between layers. By optimizing these parameters, the patent achieves intimate physical contact while maintaining chemical stability and preserving the luminescence function of the wavelength converting layer, thus maintaining both manufacturing simplicity and functional reliability.
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 provides a robust, thermally stable optical element with high reflectivity and efficient light emission, reducing mechanical failures and chemical interactions, thereby enhancing the longevity and performance of light emitting devices.
Implementation Method 1
a wavelength converting layer comprising a phosphor and/or a layer that redirects the emitted light. Thereby, the primary light emitted from the LED can be influenced in various ways.
Implementation Method 2
a scattering layer, wherein the porosity of the second layer is higher than the porosity of the first layer, and pores in the second layer are arranged to provide scattering of a light beam
Implementation Method 3
an optical element for a light emitting device, wherein the optical element comprises a sintered ceramic body
Data Source
Figure 1
AI summary
The present invention relates to an optical element for a light emitting device, wherein the optical element comprises a sintered ceramic body (3) comprising a wavelength converting layer (4) and a scattering layer (5), and to a method of manufacturing thereof. More specifically, the invention relates to an optical element, comprising a sintered ceramic body (3) of a first layer (4) and a second layer (5) arranged on the first layer, wherein the first layer comprises a wavelength converting material, the porosity of the second layer is higher than the porosity of the first layer, and pores in the second layer are arranged to provide scattering of a light beam. The method for manufacturing of the optical element comprises providing a green body comprising a first layer of a first material and a second layer of a second material; and co-sintering said layers into a sintered ceramic body; the compositions of the first and second layer are adapted such that after sintering, the porosity of the second layer is higher than the porosity of the first layer, and pores in said second layer are arranged to provide scattering of a light beam.