ZnO Phosphor Layer Structure to Prevent Peeling and Contamination
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Solution Overview
Problem
Conventional wavelength conversion devices face issues with foreign substances attaching during fabrication, which affect optical characteristics and heat dissipation, leading to undesirable temperature rises and peeling of the phosphor layer from the substrate.
Innovation Solution
A wavelength conversion device with a substrate, phosphor layer embedded in a zinc oxide matrix, a seed crystal layer, a protective layer with an isoelectric point of 7 or higher, and a dielectric layer, which prevents foreign substance attachment and peeling by acting as a barrier between the phosphor layer and the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional wavelength conversion device structure is used, then the device can be manufactured with standard processes, but foreign substances attach during fabrication affecting optical characteristics and heat dissipation
Solution Approach 1:
A protective layer with isoelectric point of 7 or higher is introduced between the dielectric layer and phosphor layer to act as a barrier that prevents foreign substances from attaching to critical surfaces during fabrication, thereby maintaining optical characteristics without compromising manufacturing feasibility
2Stability of the object's composition
If foreign substances attach to the phosphor layer, then the device structure remains intact, but heat dissipation efficiency decreases causing temperature rise and peeling
Solution Approach 1:
The protective layer serves as an intermediary barrier that prevents foreign substances from settling on the phosphor layer and dielectric layer interfaces, ensuring maintained thermal pathways and preventing temperature-induced peeling while keeping the layered structure intact
3Device complexity
If no protective layer is used, then the device structure is simpler, but foreign substances attach causing peeling of the phosphor layer from the substrate
Solution Approach 1:
A protective layer with isoelectric point of 7 or higher is introduced as a thin intermediary barrier between the dielectric layer and phosphor layer, preventing foreign substance attachment that would cause peeling, while adding minimal structural complexity to the overall device
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 suppresses foreign substance attachment and peeling, maintaining desired optical characteristics and ensuring efficient heat dissipation, thereby enhancing the stability and performance of the wavelength conversion device.
Implementation Method 1
the protective layer having an isoelectric point equal to or larger than 7
Implementation Method 2
a seed crystal layer disposed between the substrate and the phosphor layer and functioning as a seed crystal for the matrix of the phosphor layer
Implementation Method 3
The phosphor particles are irradiated with excitation light from the light emitting element, and light having a wavelength longer than the wavelength of the excitation light is radiated from the phosphor
Implementation Method 4
ZnO is an inorganic material having a refractive index close to the refractive indexes of various phosphors, and exhibits excellent translucency and thermal conductivity. In the wavelength conversion device of PTL 1, light scattering at an interface between each phosphor particle and the ZnO matrix is suppressed and high optical output can be achieved
Implementation Method 5
ZnO layer 418 functions as a seed crystal in a crystal growth process of the matrix of phosphor layer 420
Implementation Method 6
ZnO is an inorganic material having a refractive index close to the refractive indexes of various phosphors, and exhibits excellent translucency and thermal conductivity
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3E
AI summary
A wavelength conversion device of the present disclosure includes a substrate, a phosphor layer that has a matrix containing zinc oxide and phosphor particles embedded in the matrix and that is supported by the substrate, a dielectric layer disposed between the substrate and the phosphor layer, and a protective layer that is disposed between the phosphor layer and the dielectric layer and that has an isoelectric point equal to or larger than 7. A main surface of the substrate includes, for example, first and second regions. The phosphor layer covers, for example, only the first region out of the first and second regions.