Light Directing Film With Variable Height Microstructures
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Solution Overview
Problem
Conventional light directing films in backlit displays fail to effectively hide small-scale defects and reduce optical coupling, leading to non-uniform display appearances, especially in hand-held devices with increased LCD panel transmission and thin backlight structures.
Innovation Solution
A light directing film with a microstructured surface featuring a combination of first and second regions, where the second regions have a non-constant height greater than the first regions, reducing optical coupling while maintaining optical gain, and are designed to minimize 'wet-out' effects by controlling the proximity of adjacent surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional light directing films are used, then brightness enhancement is achieved, but optical coupling and wet-out defects occur causing non-uniform display appearance
Solution Approach 1:
The patent applies local quality by creating a microstructured surface where different regions have different heights. Specifically, the surface comprises a plurality of microstructures with first regions at a first height and second regions at a second height greater than the first height. This local variation in height creates zones of different optical coupling strength, allowing the film to maintain brightness enhancement while reducing wet-out defects and improving display uniformity.
2Illumination intensity
If multiple light directing films are placed adjacent to each other, then light direction along viewing axis is improved, but optical coupling between films causes wet-out effects
Solution Approach 1:
The patent uses local quality to create a hierarchical microstructured surface with multiple height levels. The second regions extend to a greater height than the first regions, creating localized zones that control optical coupling between adjacent films. This allows the films to be placed closely together for improved light direction while the height variations prevent excessive optical coupling that would cause wet-out effects.
3Reliability
If microstructured surfaces are made with complex randomized patterns, then optical coupling reduction is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the microstructured surface into distinct regions with different heights. The surface is segmented into first regions at a first height and second regions at a second height, creating a systematic pattern rather than a completely randomized one. This segmented approach maintains effectiveness in reducing optical coupling while simplifying manufacturing compared to fully randomized patterns.
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 film effectively reduces visible defects and maintains brightness by concentrating optical coupling in specific areas, enhancing the uniformity and appearance of displays, particularly in small form factor devices.
Implementation Method 1
light incident upon the smooth surface 14 of this film at relatively high incidence angles is refracted at the smooth surface 14 and the structured surface 12 of the film and is redirected toward an axis which is perpendicular to the smooth surface 14
Implementation Method 2
light which strikes the structured surface 12 at greater than the critical angle undergoes total internal reflection from both side surfaces, or facets, 20 of a prism element 16 and is directed back
Data Source
AI summary
A light directing film includes a structured major surface with a plurality of microstructures extending along a first direction. Each microstructure has a first region and a second region different from the first region, a substantially constant height in the first region and a non-constant maximum height in the second region greater than the substantially constant height in the first region, and a same lateral cross sectional shape in the first region and the second region.