Backlight Unit Wavelength Filter Layers for Luminance Uniformity
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Solution Overview
Problem
In liquid crystal display devices, the reduction in thickness leads to a reduced distance between light sources and diffusion plates, causing hot spots and lower luminance uniformity due to increased optical distance, which existing technologies fail to effectively address.
Innovation Solution
A backlight unit design featuring a substrate with light sources, a reflective film, and spaced-apart wavelength filter layers that vary transmittance based on incident angle, along with a wavelength conversion film and a diffusion plate, to diffuse light and improve luminance uniformity while reducing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the distance between light source and diffusion plate is reduced to decrease device thickness, then device thickness is reduced, but hot spots occur and luminance uniformity deteriorates
Solution Approach 1:
The wavelength filter layer is divided into multiple segments stacked in the thickness direction, with each segment having different transmittance characteristics for different incident angle ranges. This segmentation allows selective control of light transmission at different angles, diffusing hot spot light while maintaining overall device thinness.
Solution Approach 2:
Different portions of the wavelength filter layer are designed with different transmittance properties tailored to specific incident angle ranges. The first wavelength filter layer targets a first incident angle range with a specific transmittance, while the second wavelength filter layer targets a second incident angle range with a different transmittance, creating localized optical control to eliminate hot spots.
2Stability of the object's composition
If a wavelength filter layer is added to improve luminance uniformity, then luminance uniformity is improved, but device complexity and material cost increase
Solution Approach 1:
The stacked wavelength filter layers serve multiple functions simultaneously: they act as wavelength filters, incident angle selectors, and luminance uniformity controllers. By combining these functions into a single integrated structure, the patent avoids adding separate components for each function, thereby reducing overall device complexity despite the multi-layer design.
Solution Approach 2:
The patent controls luminance uniformity by changing the transmittance parameter of the wavelength filter layers for different incident angle ranges. By adjusting transmittance values in different angular zones through the stacked layers, the system achieves luminance uniformity control without requiring complex mechanical or structural modifications.
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 effectively reduces light output in the upward direction of the light source, increases light diffusion, and enhances luminance uniformity, while selectively patterning the wavelength filter layer reduces material costs and prevents light leakage.
Implementation Method 1
The wavelength filter layers may have a different transmittance according to a wavelength of incident light and an incident angle with respect to a normal direction
Implementation Method 2
a wavelength conversion film disposed above the wavelength filter layers to convert light of the first wavelength band into light of a second wavelength band different from the first wavelength band
Implementation Method 3
a first reflective film disposed on one surface of the substrate and including first openings
Data Source
AI summary
A backlight unit and a display device including the backlight unit are provided. A backlight unit includes a substrate, light sources disposed on one surface of the substrate, a first reflective film disposed on one surface of the substrate and including first openings, each of the first openings of the first reflective film exposing each of the light sources, and wavelength filter layers disposed above the first reflective film and disposed to correspond to the first openings, the wavelength filter layers are spaced apart from each other, and each of the wavelength filter layers covers at least one of the first openings.