Light Emitting Device Phosphor and Transmissive Member Design
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Solution Overview
Problem
Existing light emitting devices struggle to achieve a pronounced brightness difference between on and off states of adjacent light emitting surfaces, leading to inefficient light distribution in applications like automotive headlights and projectors.
Innovation Solution
A light emitting device design featuring a plurality of light emitting elements with phosphor layers and light transmissive members, where the phosphor layers cover a larger area than the light emitting elements and have a thinner thickness than the transmissive members, and the transmissive members have a larger upper surface area and vertical side surfaces, reducing lateral light propagation and enhancing luminance contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If light emitting elements are arranged closely to achieve compact device, then device size is reduced, but luminance difference between on and off states becomes less pronounced
Solution Approach 1:
The device is segmented into multiple independent light emitting elements, each with its own phosphor layer and light transmissive member. This segmentation allows individual control of each element's light emission, enabling sharp luminance transitions between on and off states even when elements are closely arranged, thus resolving the contradiction between compact size and pronounced luminance difference.
Solution Approach 2:
Each light emitting element is equipped with a dedicated phosphor layer and light transmissive member, creating local optimization for light extraction and emission. The phosphor layer converts light wavelengths locally, while the light transmissive member enhances light extraction efficiency at each specific location, ensuring that turned-on elements emit light with high intensity and clarity, maintaining sharp luminance contrast in compact arrangements.
2Illumination intensity
If phosphor layer thickness is reduced to improve light extraction, then light extraction efficiency increases, but phosphor coverage area must be increased
Solution Approach 1:
The phosphor layer thickness is optimized to a specific range (10 μm to 50 μm) to achieve the right balance between light extraction efficiency and coverage. This parameter optimization allows the phosphor layer to be thin enough for effective light extraction while still providing sufficient coverage area when combined with the light transmissive member, resolving the contradiction between extraction efficiency and coverage area.
3Illumination intensity
If light transmissive member upper surface area is increased to improve light emission, then luminance is enhanced, but device area increases
Solution Approach 1:
The light transmissive member is designed with a stepped structure having different surface areas at different heights (lower surface, upper surface, and side surfaces). This dimensional variation allows the upper surface area to be larger than the lower surface area, enhancing light emission area and luminance without proportionally increasing the device footprint, thus resolving the contradiction between luminance enhancement and device area.
4Illumination intensity
If vertical surface portion is added to light transmissive member to reduce lateral light propagation, then luminance contrast improves, but manufacturing complexity increases
Solution Approach 1:
The side surface of the light transmissive member is segmented into a vertical surface portion and an inclined surface portion. The vertical surface portion specifically addresses lateral light propagation by providing a geometry that directs light upward rather than laterally, improving luminance contrast. This segmented approach to side surface design achieves the desired optical performance while keeping the manufacturing process manageable through clear geometric definitions.
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 design achieves a significant luminance difference between on and off states, resulting in improved light distribution with reduced light leakage and a more compact device, enhancing contrast and efficiency in applications requiring precise light control.
Implementation Method 1
a phosphor layer 2 that covers the light extract surface in a larger plane area than the light extract surface of the light emitting elements
Implementation Method 2
a light transmissive member 3 having an upper surface 3a that serves as a light emitting surface of the light emitting device, a lower surface 3b that faces the phosphor layer 2
Implementation Method 3
a side surface 3c that has a vertical surface portion that is contiguous with the upper surface 3a
Implementation Method 4
a light reflecting member 4 that surrounds the side surfaces 3c of the light transmissive members 3
Data Source
AI summary
A light emitting device includes a plurality of light emitting elements each including a light extraction surface, a plurality of phosphor layers each covering the light extraction surface of a corresponding one of the light emitting elements with a larger plane area than the light extraction surface, and a plurality of light transmissive members. Each of the light transmissive members has a lower surface facing a corresponding one of the phosphor layers and having a larger plane area than the light extraction surface of a corresponding one of the light emitting elements, an upper surface having a larger plane area than the lower surface, and a side surface having a vertical surface portion contiguous with the upper surface. The light reflecting member surrounds the side surface of each of the light transmissive members.