Direct-Lit Backlight Unit with Light Spreading Layers
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Solution Overview
Problem
Direct-lit backlight units in electronic devices can be bulky and produce non-uniform illumination due to inadequate light distribution and reflection, leading to suboptimal display performance.
Innovation Solution
A backlight unit design incorporating an array of light-emitting diodes, a printed circuit board, light spreading layers, a partially reflective layer, a color conversion layer, a collimating layer, a brightness enhancement film, and a diffuser, which work together to distribute and enhance light uniformity across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If direct-lit backlight units use arrays of light-emitting diodes to illuminate the display, then the backlight can provide sufficient illumination, but the unit becomes bulky and produces non-uniform backlight illumination
Solution Approach 1:
The patent introduces a light guide plate that redirects light from vertically emitted LEDs to laterally distributed illumination across the display. This dimensional transformation of light propagation converts the bulky direct-lit approach into a thin, uniform backlight system by changing the direction and distribution of light travel through the light guide structure
Solution Approach 2:
The light guide plate serves as an intermediary component between the light-emitting diodes and the display panel. It receives light from the LEDs and redistributes it uniformly across the display area, mediating the transition from point-source vertical illumination to area-wide lateral illumination while reducing overall unit thickness
2Illumination intensity
If direct-lit backlight units emit light vertically through the display, then illumination is provided, but non-uniform backlight illumination results without additional optical layers
Solution Approach 1:
The patent segments the backlight system into multiple functional layers including light guide plate, diffuser layer, and reflective layer. Each layer performs a specific function in light distribution, collectively transforming the non-uniform vertical light emission into uniform lateral illumination across the display surface
Solution Approach 2:
The patent changes the physical parameters of light propagation by introducing optical layers with different refractive indices and light scattering properties. The light guide plate changes light direction from vertical to lateral, while the diffuser layer changes light distribution from concentrated to uniform, achieving homogeneous illumination through parameter transformation
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 ensures uniform and efficient backlight illumination, reducing bulkiness and improving display performance by optimizing light distribution and reflection, resulting in enhanced image quality and reduced thermal gradients.
Implementation Method 1
Direct-lit backlight units have arrays of light-emitting diodes that emit light vertically through the display
Implementation Method 2
a light reflector that helps reflect light from the light-emitting diodes through the pixel array
Implementation Method 3
a color conversion layer formed over the partially reflective layer
Data Source
AI summary
A display may have a pixel array such as a liquid crystal pixel array. The pixel array may be illuminated with backlight illumination from a backlight unit. The backlight unit may include a printed circuit board, a plurality of light-emitting diodes mounted on the printed circuit board, at least one light spreading layer formed over the printed circuit board that spreads light received from the plurality of light-emitting diodes, a partially reflective layer formed over the at least one light spreading layer, a color conversion layer formed over the partially reflective layer, a collimating layer formed over the color conversion layer, a brightness enhancement film formed over the collimating layer, and a diffuser formed over the brightness enhancement film. The at least one light spreading layer may include two light spreading layers with elongated protrusions that are rotated relative to each other.