High Refractive Index Layer for Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light emitting devices suffer from low light extraction efficiency due to the total reflection condition at the interface between the light emitting element and the sealing material, which restricts the angle of light emission and reduces the effectiveness of light extraction.
Innovation Solution
A high-refractive index layer comprising transparent fine particles with a refractive index higher than the light emitting element and sealing material is applied to the emission surface, allowing incident light to be extracted without total reflection, and wavelength-converted light can be discharged towards the sealing material for enhanced extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent resin material with lower refractive index than the light emitting element surface is used as sealing material, then the light emitting element can be sealed, but total reflection occurs at the interface reducing light extraction efficiency
Solution Approach 1:
The patent changes the refractive index parameter of the sealing material by incorporating transparent fine particles with higher refractive index than the light emitting element surface. This parameter change eliminates the total reflection condition by ensuring n1 < n2 is not satisfied, thereby improving light extraction efficiency while maintaining sealing effectiveness.
Solution Approach 2:
The patent creates a composite sealing material by mixing transparent resin base material with transparent fine particles having different refractive index characteristics. This composite structure combines the sealing properties of the resin with the optical properties of the high refractive index particles, achieving both reliable sealing and improved light extraction.
2Illumination intensity
If a coating layer with phosphor particles and fine particles is formed on the light emitting element surface, then white light can be produced, but the region with thin fine particles allows resin sealing material to cover the surface reducing light extraction efficiency
Solution Approach 1:
The patent modifies the refractive index parameter of the sealing material layer by incorporating transparent fine particles throughout, ensuring that even in regions where the coating layer is thin, the underlying high refractive index particles prevent total reflection and maintain light extraction efficiency.
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 significantly enhances light extraction efficiency by preventing total reflection and ensuring that light is externally discharged, improving the overall performance of the light emitting device.
Implementation Method 1
since the surface portion (or a surface layer located on light extraction surface side thereof) of the light emitting element has a refractive index higher than that of the transparent resin material, a range of angle is defined within which the condition of total reflection can be satisfied at the interface of the light emitting element and the sealing material
Implementation Method 2
the fine particles comprise a refractive index higher than that of a material composing the emission surface of the light emitting element
Data Source
AI summary
A light emitting device has a light emitting element, and a high-refractive index layer that contacts an emission surface of the light emitting element. The high-refractive index layer has transparent fine particles uniformly arranged along the emission surface. The fine particles has a refractive index high than that of a material composing the emission surface of the light emitting element. Otherwise, a light emitting device has a light emitting element, a sealing material for sealing the light emitting element, and a high-refractive index layer that contacts an emission surface of the light emitting element. The fine particles has a refractive index high than that of a material composing the emission surface of the light emitting element and that of the sealing material. A phosphor may be included in the sealing material which is adapted to emit a wavelength-converted light by being excited by a light emitted from the light emitting element. The phosphor may have a same matrix as the fine particles, and it may be formed spherical. The light emitting element may be a face-up type light emitting element or a flip-chip type light emitting element.