Side-View LED Backlight Unit for Slim LCD Design
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Solution Overview
Problem
The existing liquid crystal display (LCD) devices face limitations in reducing the thickness of the backlight unit due to the constraints in minimizing the thickness of the LED package, which affects the luminous flux and increases the fabrication cost, and results in non-uniform luminance due to hot spots caused by the radial emission of light from LED packages.
Innovation Solution
A backlight unit design featuring a light guide plate, a side-view type LED assembly with an LED printed circuit board, spaced-apart LED chips, first and second lead frames for electrical connection, and an LED housing that surrounds the chips and lead frames, reducing the thickness by omitting the lower side surface and enhancing heat radiation, thus improving optical efficiency and luminance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the LED package is minimized, then the thickness of the backlight unit is reduced, but the luminous flux is decreased
Solution Approach 1:
The patent transitions from a top-view LED configuration to a side-view LED configuration, changing the dimensional orientation of light emission. This allows the LED chips to be positioned horizontally along the PCB edge, enabling light to exit through the side surface rather than the top surface, thereby reducing the vertical thickness of the backlight unit while maintaining adequate luminous flux through optimized chip placement and emission angle control
Solution Approach 2:
The patent modifies the emission angle parameter of the LED chips by adjusting their orientation and positioning. By changing the light emission direction from perpendicular (top-view) to parallel (side-view) relative to the PCB surface, the system achieves thinner backlight unit thickness while preserving luminous flux through optimized optical path design and chip arrangement parameters
2Length of stationary object
If the thickness of the LED package is minimized, then the thickness of the backlight unit is reduced, but the fabrication cost increases
Solution Approach 1:
The side-view LED configuration simplifies the packaging structure by eliminating the need for complex lens assemblies and precise top-surface alignment mechanisms. The LED chips can be mounted along the edge of the PCB with simpler fixation structures, reducing manufacturing complexity and cost while achieving the desired thickness reduction
Solution Approach 2:
The patent segments the LED assembly into discrete modules with individual LED chips positioned along the PCB edge. This modular approach facilitates easier assembly and quality control, reducing fabrication complexity and cost compared to integrated top-view LED packages that require more precise alignment and more complex packaging structures
3Illumination intensity
If light is emitted radially from LED packages, then the light distribution is enhanced, but hot spots are formed causing non-uniform luminance
Solution Approach 1:
The patent applies local quality control by positioning LED chips at specific intervals along the PCB edge rather than uniformly distributing them. This localized arrangement, combined with individual chip orientation control, allows optimization of light emission at each position to compensate for radial emission patterns, thereby achieving uniform overall luminance distribution while maintaining enhanced light distribution
Solution Approach 2:
The patent introduces an optical sheet as an intermediary component between the LED assembly and the liquid crystal panel. This optical sheet acts as a mediator that redistributes the radially emitted light from the side-view LEDs, converting the non-uniform light distribution into a more uniform illumination pattern across the display panel, thereby eliminating hot spots while preserving enhanced light distribution characteristics
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 solution reduces the thickness of the backlight unit, enhances optical efficiency, and prevents hot spots, resulting in a slim and uniformly lit LCD device with improved heat radiation properties.
Implementation Method 1
a light guide plate 1123, a light emitting diode (LED) assembly 1129 supplying a light to the light guide plate
Implementation Method 2
a reflecting plate 1125 under the light guide plate
Implementation Method 3
a plurality of LED chips 1129b over the LED PCB 1129a
Data Source
AI summary
A backlight unit according to an embodiment includes: a light guide plate; a light emitting diode (LED) assembly supplying a light to the light guide plate; and a reflecting plate under the light guide plate, wherein the LED assembly includes: an LED printed circuit board (PCB) disposed at a side of the light guide plate; a plurality of LED chips over the LED PCB, the plurality of LED chips spaced apart from each other; a plurality of first lead frames electrically connecting the LED PCB and the plurality of LED chips; and an LED housing surrounding the plurality of LED chips and the plurality of first lead frames.