Backlight Unit Edge LED Sizing for Luminance Uniformity
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Solution Overview
Problem
The existing backlight units for liquid crystal display devices face challenges in achieving uniform luminance and brightness, and in reducing the bezel width, due to the use of phosphor films that increase manufacturing costs and can lead to decreased color reproduction rates if the light emitted from light emitting diodes is not sufficiently excited.
Innovation Solution
A backlight unit design featuring a substrate with light emitting elements, a reflector with holes, a light conversion sheet with a light conversion pattern, and a phosphor sheet, where the size of light emitting elements on the edge is larger than those in the center, enhancing luminance uniformity and allowing for a narrower bezel by adjusting the light distribution and color conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a phosphor film containing a large amount of phosphor is disposed on the light emitting diode, then color reproduction is improved, but manufacturing cost increases
Solution Approach 1:
The phosphor layer is segmented into multiple distinct layers: a first phosphor layer (Y3Al5O12:Ce) disposed directly on the blue LED, and a second phosphor layer (BaMgAl10O17:Eu) disposed on the red color filter. This segmentation allows each phosphor layer to be optimized independently for its specific function, reducing the total phosphor quantity needed while maintaining color reproduction quality and lowering manufacturing costs.
Solution Approach 2:
Different phosphor materials with specific properties are placed at different locations: the first phosphor layer converts blue light to yellow-green light near the LED source, while the second phosphor layer converts blue light to red light at the color filter position. This local optimization of phosphor placement and composition achieves effective color reproduction with reduced phosphor quantities, thereby lowering manufacturing costs.
2Ease of manufacture
If the light emitted from the light emitting element is not sufficiently excited, then manufacturing cost is reduced, but color reproduction rate decreases
Solution Approach 1:
The patent changes the phosphor material parameters by selecting specific phosphors with appropriate excitation characteristics: Y3Al5O12:Ce (yttrium aluminum garnet doped with cerium) for the first layer and BaMgAl10O17:Eu (barium magnesium aluminate doped with europium) for the second layer. These phosphors have optimal excitation wavelengths matching the blue LED emission, ensuring efficient light conversion and high color reproduction rates without requiring excessive phosphor quantities, thus reducing manufacturing costs.
3Ease of manufacture
If light emitting elements of uniform size are used across the substrate, then manufacturing is simplified, but luminance uniformity decreases
Solution Approach 1:
The patent applies local quality by differentiating light emitting element sizes based on position: larger light emitting elements are placed at the edge regions of the substrate where light output is naturally lower, and smaller light emitting elements are placed at the center region where light output is naturally higher. This positional differentiation compensates for the non-uniform light distribution, achieving uniform luminance across the display area while maintaining manufacturing simplicity through a standardized sizing scheme.
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 design achieves uniform luminance and brightness across the display area, reduces the bezel width, and improves color reproduction by optimizing light emission and conversion, thereby enhancing the overall image quality and manufacturing efficiency.
Implementation Method 1
a light conversion sheet disposed on the substrate and having a light conversion pattern disposed at a position overlapping the light emitting element; and a phosphor sheet having a first phosphor disposed on the substrate
Implementation Method 2
a first reflector disposed on the substrate and including a plurality of holes, one of the plurality of light emitting elements being disposed in each hole
Data Source
AI summary
Embodiments of the present disclosure provides with a backlight unit and a display device with the backlight unit including a plurality of light emitting elements disposed on a substrate, a first reflector disposed on the substrate and including a plurality of holes, one of the plurality of light emitting elements being disposed in each hole, a light conversion sheet disposed on the substrate and having a light conversion pattern disposed at a position overlapping the light emitting element, and a phosphor sheet having a first phosphor disposed on the substrate, wherein a size of first light emitting elements disposed on the edge of the substrate among the plurality of light emitting elements is larger than size of second light emitting elements disposed in the center of the substrate.