Light Emitting Device Phosphor Layer Reflection Structure
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Solution Overview
Problem
Existing light emitting devices face challenges in achieving uniform light emission and satisfactory light extraction efficiency due to differences in optical path lengths and light absorption by phosphor layers on conductive wiring patterns, leading to uneven light distribution and reduced light extraction efficiency.
Innovation Solution
A light emitting device with a substrate, a light emitting element, a phosphor layer covering the element and its peripheral conductive portion, and a reflection layer positioned below the light emitting element to control light extraction and prevent absorption by the conductive portion, formed using methods like electrodeposition or electrostatic coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphor particles are deposited on the conductive portion by electrodeposition, then the light emitting area is reduced and light distribution characteristics approach point light source, but the wiring pattern is covered with phosphor particles causing light absorption and uneven light emission
Solution Approach 1:
The conductive portion is divided into two functional zones: a light-emitting area covered with phosphor particles for light conversion, and a non-light-emitting wiring pattern area protected from phosphor deposition. This segmentation allows the same conductive structure to serve dual purposes while avoiding the contradiction between reducing light emitting area and preventing light absorption.
Solution Approach 2:
A protective coating is applied to the wiring pattern before the electrodeposition process. This preliminary action prevents phosphor particles from adhering to the wiring pattern during electrodeposition, eliminating the need for post-process removal and simplifying the overall manufacturing process.
2Loss of energy
If phosphor layer is formed on the wiring pattern to prevent light absorption, then light extraction efficiency is improved, but additional steps for forming and removing photoresist are required
Solution Approach 1:
The protective coating on the wiring pattern serves dual functions: it prevents phosphor deposition during electrodeposition and simultaneously acts as a reflective layer to improve light extraction efficiency. This self-service approach eliminates the need for separate protective and reflective layers, reducing manufacturing process steps.
3Object-affected harmful factors
If phosphor particles are used to fill the space between light emitting element and substrate, then light leakage is reduced, but density of phosphor particles is lower than other areas
Solution Approach 1:
Different regions of the device are assigned different phosphor particle densities according to their functional requirements. The bonding area between the light emitting element and substrate uses higher density phosphor particles to prevent light leakage, while other areas maintain appropriate density for light conversion. This local quality approach resolves the contradiction between preventing light leakage and maintaining density uniformity.
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 enables uniform light emission and improved light extraction efficiency by minimizing light absorption and leakage, resulting in a light distribution characteristic similar to a point light source, suitable for various applications including lighting and display devices.
Implementation Method 1
a wavelength of a portion of the blue light output from the light emitting element is converted by the phosphor, and yellow light resulting from the wavelength conversion is mixed with the blue light from the light emitting element, thereby emitting white light
Implementation Method 2
In the electrodeposition method, the phosphor particles deposit on a surface of the light emitting element by applying an electric field in a bath liquid containing phosphor particles deposits
Implementation Method 3
a reflection layer for covering at least an upper surface of a part of the phosphor layer formed on the peripheral surface area of the conductive portion
Data Source
Figure 1~2
Figure 3(a)~3(c)
Figure 4~5
AI summary
A light emitting device includes a substrate having a conductive portion; a light emitting element having one or more electrodes on a lower surface side thereof, the electrodes being positioned on the conductive portion of the substrate; a phosphor layer disposed on a surface of the light emitting element and on a peripheral surface area of the conductive portion next to the light emitting element; and a reflection layer covering a part of the phosphor layer disposed on the peripheral surface area of the conductive portion.