Backlight Optical Film Stack for Thin, Uniform LCD Illumination
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Solution Overview
Problem
Existing back light units for LCD displays face challenges in achieving a thin profile while delivering bright and uniform light while effectively hiding individual LEDs, as diffuser films used to enhance uniformity often result in overlapping light intensities and non-uniform regions.
Innovation Solution
Incorporating a pair of brightness enhancement films and at least two optical films with light splitting microstructures above an array of LEDs, including a color conversion layer, to split collimated beams into multiple beams with reduced on-axis intensity, thereby enhancing light uniformity and hiding LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional diffuser films are used to spread light from LEDs, then light uniformity is improved, but the back light unit thickness increases and individual LEDs remain visible
Solution Approach 1:
The patent divides the light spreading function into multiple thin optical films, each with specific microstructures, rather than using a single thick diffuser film. This segmentation allows light to be progressively redirected in small steps, achieving uniformity while maintaining a thin overall profile.
Solution Approach 2:
The patent transitions from using a thick film in one dimension to using multiple thin films stacked in another dimension (the thickness direction). Each thin film contributes a small amount of light redirection, and the cumulative effect of multiple films achieves the desired uniformity without increasing individual film thickness.
2Illumination intensity
If diffuser film thickness is increased to spread light further, then light uniformity improves, but brighter and darker regions persist and the profile becomes non-thin
Solution Approach 1:
The light redirection function is segmented across multiple thin optical films, each with specific microprism arrangements. This allows progressive light spreading without requiring any single film to be thick, thereby achieving uniformity while maintaining a thin profile.
Solution Approach 2:
The patent uses multiple optical films with different microprism orientations and configurations to dynamically control light distribution. Each film redirects light in specific directions, and the combination of multiple films creates a progressive, controlled spreading effect that achieves uniformity without excessive thickness.
3Illumination intensity
If individual LEDs are hidden using diffusers, then uniform light presentation is achieved, but light intensity and brightness are reduced
Solution Approach 1:
The patent segments the light modification function across multiple thin optical films with specific microstructures, rather than using a single thick diffuser. This segmentation allows light to be redirected with minimal loss, maintaining brightness while achieving uniformity.
Solution Approach 2:
The patent replaces the traditional mechanical diffusing mechanism (thick diffuser films that scatter and absorb light) with an optical redirection mechanism using microprisms. This substitution redirects light through refraction and reflection at microprism interfaces, preserving light intensity while achieving uniform distribution.
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 achieves brighter and more uniform light distribution by suppressing on-axis light and spreading it wider, maintaining a thin profile and improving overall light uniformity compared to traditional diffuser films.
Implementation Method 1
light splitting microstructures on at least one surface thereof. The light splitting microstructures are configured such that, when a collimated beam is directed on axis to the microstructure, the collimated beam is split into two or more beams with a region of lower relative intensity on axis
Implementation Method 2
a diffuser film 120, which may be a volumetric diffuser or a circular diffuser, a color conversion layer 130... a diffuser film 140, which may be a volumetric diffuser or a circular diffuser configured to spread or diffuse the light
Data Source
Figure 1
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Figure 2B
AI summary
A back light unit includes an array of light emitting diodes, at least two optical films positioned above the array of light emitting diodes, and a pair of brightness enhancement films positioned above the at least two optical films. A majority of the optical films are light splitting optical films having a plurality of light splitting microstructures on at least one surface thereof.