Polarized LED Structure for Higher LCD Light Utilization
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Solution Overview
Problem
Liquid crystal display (LCD) devices using light emitting diodes (LED) backlights suffer from low light utilization due to the use of unpolarized light, which cannot pass through the polarizer effectively, reducing the overall efficiency of image formation.
Innovation Solution
A light emitting diode (LED) design incorporating a semiconductor layer sequence stack, a reflective polarizing layer, and a diffuse or specular reflection structure to generate linearly polarized light by reflecting and scattering light in specific directions, enhancing light extraction and utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If unpolarized light is used in LED backlight, then the light source can emit light in all directions, but most light cannot pass through the polarizer, reducing light utilization efficiency
Solution Approach 1:
The patent applies preliminary action by generating linearly polarized light at the LED light source before the light enters the LCD panel. The reflective polarizing layer is positioned to receive light from the semiconductor layer sequence stack and output linearly polarized light in a specific direction, ensuring that the light is already polarized before entering the liquid crystal layer, thereby eliminating the need for a separate polarizer and preventing light loss.
Solution Approach 2:
The patent extracts the polarizing function from the traditional LCD structure by integrating it into the LED backlight assembly. The reflective polarizing layer is disposed on the semiconductor layer sequence stack, separating the polarizing function from the liquid crystal display layer, and allowing the liquid crystal layer to focus solely on modulating the polarized light without the additional light loss from a separate polarizer.
2Use of energy by moving object
If a reflective polarizing layer is added to generate linearly polarized light, then light utilization improves, but the device structure becomes more complex
Solution Approach 1:
The patent merges the polarizing layer with the LED light source structure. The reflective polarizing layer is disposed directly on the semiconductor layer sequence stack, combining the light generation and polarizing functions into a single integrated assembly. This reduces the overall number of separate components and simplifies the system architecture compared to having a separate polarizer in the LCD stack.
Solution Approach 2:
The reflective polarizing layer serves multiple functions: it generates linearly polarized light, reflects light back through the semiconductor layers to improve extraction efficiency, and eliminates the need for a separate polarizer in the LCD panel. This multi-functionality reduces the overall device complexity while improving light utilization.
3Power
If diffuse reflection structure is used, then light extraction efficiency improves, but the optical path becomes more complex
Solution Approach 1:
The patent applies local quality by creating a non-planar surface with localized irregularities on the light emitting layer or adjacent structure. This non-planar surface provides diffuse reflection at specific locations where light is generated, scattering light in multiple directions to improve extraction efficiency without requiring the entire optical path to be complex or diffuse.
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 proposed LED design significantly improves light utilization and extraction, leading to increased efficiency in image formation and output power, particularly in LCD devices and projector systems.
Implementation Method 1
The reflective polarizing layer is disposed on the semiconductor layer sequence stack
Implementation Method 2
generate linearly polarized light by reflecting and scattering light in specific directions
Implementation Method 3
The diffuse reflection structure is disposed on the light emitting layer opposite to the reflective polarizing layer
Implementation Method 4
a specular reflection layer disposed on the semiconductor layer sequence stack opposite to the reflective polarizing layer
Data Source
AI summary
A light emitting diode includes a semiconductor layer sequence stack, a reflective polarizing layer and a diffuse reflection structure. The semiconductor layer sequence stack includes first and second semiconductor layers, and a light emitting layer disposed therebetween. The reflective polarizing layer is disposed on the semiconductor layer sequence stack. The diffuse reflection structure is disposed on the light emitting layer opposite to the reflective polarizing layer. A light emitting device including the light emitting diode, and a projector including the light emitting device are also provided.