Light Mixing Chamber for LCD Backlight Uniformity
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Solution Overview
Problem
Standard backlights using white LEDs for liquid crystal displays (LCDs) face inefficiencies and color uniformity issues due to the scattering and reflection of light as it passes through color converting materials, leading to suboptimal display performance.
Innovation Solution
A light mixing chamber design incorporating discrete higher frequency LEDs and a capillary filled with color converting materials, such as quantum dots, where an appropriate optical system optimally injects light into a light guide plate, balancing efficiency and color uniformity by varying the distance between the LED and capillary, and using scattering particles and coatings to manage light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If light passes from the LED through the color converting material to the light guide plate, then color conversion occurs, but light is multiply scattered and reflected leading to loss of efficiency and distortion of color uniformity
Solution Approach 1:
The patent introduces a light mixing chamber as an intermediary component between the LED and light guide plate. This chamber contains scattering particles that redistribute light paths, allowing light to undergo multiple scattering events in a controlled environment before reaching the light guide plate, thereby reducing the harmful scattering and reflection that occurs when light directly passes through the color converting material.
Solution Approach 2:
The light mixing chamber adds a spatial dimension to the light path by creating a three-dimensional mixing zone. Light from the LED is distributed throughout the chamber volume containing scattering particles, transforming the direct one-dimensional light path into a multi-dimensional scattering medium that enables more uniform light distribution before injection into the light guide plate.
2Illumination intensity
If light passes from the LED through the color converting material to the light guide plate, then color conversion occurs, but distortion of backlight color uniformity results
Solution Approach 1:
The light mixing chamber serves as a mediator that decouples the color conversion process from the light injection process. By allowing light to mix and uniformize within the chamber before entering the light guide plate, the system achieves better color uniformity without compromising the efficiency of the color conversion that occurs in the liquid crystal layer.
3Reliability
If an appropriate optical system is designed to improve efficiency and color uniformity, then display performance improves, but device complexity increases
Solution Approach 1:
The light mixing chamber is implemented as a thin, flexible component that can be easily integrated into the existing backlight structure. Rather than introducing complex optical systems with multiple lenses and mirrors, the chamber uses a simple enclosed space containing scattering particles, maintaining structural simplicity while achieving the desired optical effects.
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
This configuration enhances the efficiency and color uniformity of backlights, providing a wider color gamut and improved display performance by optimizing the injection and distribution of light, thereby overcoming the limitations of standard white LED solutions.
Implementation Method 1
The light from an LED is injected into a light guide plate which distributes the light evenly in the backplane of the backlight. The white LED is typically an assembly including a light emitting semiconductor die emitting at higher frequency (e.g., ultraviolet or blue) together with a color converting material which converts some portion of the higher frequency light to lower frequency visible light (e.g., green and red).
Implementation Method 2
The light generating portion of the backlight utilizes one or more discrete LEDs emitting at higher frequencies (e.g., ultraviolet or blue) that excite a remotely located color converting material containing color converting elements, such as quantum dots (semiconductor nanocrystals), which convert some portion of the higher frequency light to lower frequency visible light (e.g., green and red). The narrow spectral bandwidth of the emission peaks of the quantum dots enables higher efficiency and/or wider color gamut backlights
Implementation Method 3
A capillary is positioned in the channel and has an interior cavity containing a matrix formulation which contains a color converting material and scattering elements
Data Source
AI summary
A light mixing chamber of a backlight includes a housing having a channel and a chamber exposed to the channel, an LED positioned within the chamber, and a capillary containing quantum dots positioned in the channel. A light guide plate is positioned adjacent the housing and adjacent the capillary. Relative dimensions of the elements of the light mixing chamber, as well as features added to the elements of the light mixing chamber, can be varied to balance efficiency and uniformity of light generated in the backlight.