Back Light Unit Uniformity via Diffuser and BEF
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Solution Overview
Problem
Existing back light units for liquid crystal displays face challenges in achieving uniform light distribution and maintaining a thin profile while providing high brightness and contrast ratios, especially in thinner displays where individual LEDs need to be hidden and local dimming capabilities are essential.
Innovation Solution
The use of double-sided diffuser layers, air gaps, and transparent material layers in conjunction with high-index cross brightness enhancement films and a polarizer reflector film to manage light distribution and achieve uniformity, with the option of using volumetric diffuser layers for stronger hiding properties, allowing for efficient light management and local dimming in thin back light units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If individual LEDs are used to provide high brightness and contrast ratios, then local dimming capability is improved, but the LEDs become visible and uniform light distribution deteriorates
Solution Approach 1:
A diffuser layer is introduced as an intermediary component between the LED array and the display panel. This diffuser layer scatters and redistributes the light from individual LEDs, creating a uniform illumination pattern while preserving the high brightness and contrast ratios enabled by the LED architecture. The diffuser acts as a mediator that reconciles the conflicting requirements of LED visibility and uniform light distribution.
2Length of moving object
If a thin profile is maintained for display applications, then device thickness is reduced, but achieving uniform light distribution becomes more difficult
Solution Approach 1:
The patent employs a diffuser layer with specific optical parameters (scattering coefficient, refractive index) that are optimized to achieve uniform light distribution within a thin profile. By carefully selecting and tuning these optical parameters, the system achieves uniform illumination without requiring excessive thickness, thus resolving the contradiction between thin profile and uniform light distribution.
3Device complexity
If fewer LEDs are used to maintain thin profile, then device complexity is reduced, but achieving sufficient brightness and uniformity becomes more challenging
Solution Approach 1:
The diffuser layer serves as a light management intermediary that enables fewer LEDs to achieve sufficient brightness and uniformity. By scattering and redistributing light from a reduced number of LEDs, the diffuser layer creates a uniform illumination pattern that would otherwise require many more LEDs to achieve, thus reducing device complexity while maintaining optical performance.
Solution Approach 2:
The patent optimizes optical parameters of the diffuser layer (scattering properties, refractive index, thickness) to maximize light redistribution efficiency. These parameter optimizations enable a reduced LED array to achieve the same brightness and uniformity as a larger LED array without the diffuser, thus reducing device complexity while maintaining performance.
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 results in a highly uniform and efficient light output that hides individual LEDs, enhances brightness, and supports local dimming operations, maintaining a thin profile while achieving excellent contrast ratios and brightness, even with fewer LEDs.
Implementation Method 1
double-sided diffuser layers... to manage light distribution and achieve uniformity
Implementation Method 2
transparent material layers... to manage light distribution
Implementation Method 3
high-index cross brightness enhancement films
Implementation Method 4
polarizer reflector film
Data Source
AI summary
A BLU includes a 2D array of LEDs producing light with an angular distribution of nominally ±90 degrees around a center. A transparent solid material layer is positioned with a bottom surface over the 2D array of LEDs and configured to transform the light produced by the 2D array into light having an angular distribution of nominally less than ±90 degrees around the at a top surface of the transparent solid material layer. A diffuser film is positioned over the top surface of the transparent solid material layer configured to provide a FWHM of greater than 60 degrees and configured to diffuse the light produced at the top surface of the transparent solid material layer to produce diffused light at a top surface of the diffuser film. A BEF positioned over the top surface of the diffuser film and comprising a plurality of prism microstructures, where at least some prism microstructures have an apex angle of approximately ninety degrees. The BEF configured to narrow an angular optical distribution of the diffused light produced at the top surface of the diffuser film, thereby providing uniform and high brightness light output from the back light unit.