White LED Light Extraction via Phosphor Embossing
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Solution Overview
Problem
Conventional white LEDs using phosphor layers suffer from reduced light emission efficiency due to light being re-absorbed by the LED chip surface, especially when phosphor materials are concentrated on the surface rather than uniformly distributed in the transparent resin.
Innovation Solution
A white LED design featuring a reflector cup with an LED chip surrounded by transparent resin, a phosphor layer formed on the resin, and spherical particles inserted into the phosphor layer to create an embossing pattern, which enhances light extraction efficiency by transmitting light upward and increasing the critical angle for refraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphor materials are concentrated on the surface of the LED chip, then the light extraction efficiency is improved, but the light is re-absorbed by the LED chip surface causing reduced emission efficiency
Solution Approach 1:
A transparent resin layer is introduced as an intermediary medium between the phosphor materials and the LED chip surface. This resin layer prevents direct contact between the phosphor-containing resin and the LED chip surface, thereby eliminating the re-absorption of emitted light by the chip surface while still allowing efficient light extraction. The transparent resin acts as a mediator that decouples the phosphor distribution benefit from the harmful re-absorption effect.
2Stability of the object's composition
If phosphor materials are uniformly distributed in transparent resin, then the light emission is more uniform, but the light extraction efficiency is reduced
Solution Approach 1:
The invention applies local quality by creating a specific spatial distribution of phosphor materials: concentrated in the upper portion of the transparent resin layer rather than uniformly distributed throughout. This localized concentration in the upper region allows photons to escape more efficiently before being re-absorbed, while still providing sufficient phosphor density in the extraction region to maintain good light emission uniformity.
3Device complexity
If phosphor layer is formed on the LED chip, then the structure is simpler, but light directed toward the LED chip is lost due to re-absorption
Solution Approach 1:
The invention transitions from a two-dimensional phosphor layer directly on the chip surface to a three-dimensional phosphor distribution within a transparent resin layer that surrounds the LED chip. This dimensional change allows phosphor materials to be positioned in multiple locations (including the upper portion and side regions) where they can convert light without being re-absorbed by the chip, while still maintaining a relatively simple overall structure.
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 increases light extraction efficiency by 5 to 30% compared to conventional designs, preventing total reflection and ensuring that more light is transmitted outward, thereby improving the overall brightness and uniformity of the white light emitted.
Implementation Method 1
phosphor which is excited by ultraviolet (UV) light so as to emit visible light from blue to red is coated on the LED chip which emits UV light, thereby obtaining white light. Alternately, on an LED chip which emits blue light, phosphor is distributed, the phosphor emitting yellow-green or yellow light by using the blue light as an excitation source.
Implementation Method 2
spherical particles are inserted into the surface of the phosphor layer such that an embossing pattern is provided on the surface. In the white LED, light directed from the phosphor layer toward the LED chip is transmitted upward, thereby enhancing light extraction efficiency.
Data Source
AI summary
Provided is a white LED including a reflector cup; an LED chip mounted on the bottom surface of the reflector cup; transparent resin surrounding the LED chip; a phosphor layer formed on the transparent resin; and a light transmitting layer that is inserted into the surface of the phosphor layer so as to form an embossing pattern on the surface, the light transmitting layer transmitting light, incident from the phosphor layer, in the upward direction.