Edge-Lit Backlight Prism Diffuser for Higher On-Axis Brightness
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Solution Overview
Problem
Existing edge-lit back light units for displays face challenges in maximizing viewing brightness without increasing electric power consumption.
Innovation Solution
The use of a diffuser film with angular light distribution matched to the light acceptance angles of crossed brightness enhancement films, combined with a specular reflector and edge-lit light guide film, to optimize optical distribution and diffusion angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional diffuser film is used in edge-lit back light unit, then light distribution is achieved, but light efficiency and viewing brightness are insufficient
Solution Approach 1:
The diffuser film incorporates prism microstructures with different apex directions at different locations - bottom-side prisms have apex directions generally along the light propagation direction while top-side prisms have apex directions generally perpendicular to the light propagation direction. This local differentiation optimizes light extraction and distribution efficiency at each location, improving overall viewing brightness without increasing power consumption.
Solution Approach 2:
The patent uses a composite structure combining diffuser film with prism microstructures and crossed brightness enhancement films. The diffuser film itself acts as a composite element integrating both bottom-side and top-side prism structures, which work together with the brightness enhancement films to maximize light efficiency and viewing brightness while maintaining low power consumption.
2Illumination intensity
If light is coupled out of light guide film with conventional structures, then light extraction occurs, but angular distribution is directed away from optimal viewing angles
Solution Approach 1:
The diffuser film employs prism microstructures with spatially varying apex directions - bottom-side prisms oriented along the light propagation direction for efficient light extraction, and top-side prisms oriented perpendicular to redirect light toward optimal viewing angles. This localized optimization enhances on-axis brightness without requiring complex additional optical components.
Solution Approach 2:
The patent introduces a new dimensional aspect by rotating the apex direction of top-side prisms perpendicular to the light propagation direction, whereas conventional designs use uniform or single-direction prisms. This dimensional change in prism orientation enables superior angular light distribution and on-axis brightness enhancement while maintaining relatively simple film structure.
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 enhances on-axis brightness by aligning prism microstructures and film orientations to improve light propagation efficiency, achieving increased viewing brightness without additional power consumption.
Implementation Method 1
The diffuser film has a plurality of parallel prism microstructures on the bottom-side, wherein at least some of the plurality of parallel prism microstructures on the bottom-side have an apex direction that is generally along the light propagation direction
Implementation Method 2
The diffuser film has a plurality of parallel prism microstructures on the top-side having an apex direction that is rotated with respect to the apex direction of the plurality of parallel prism microstructures on the bottom-side such that the apex direction of the parallel prism microstructures on the top-side is generally perpendicular to the light propagation direction
Implementation Method 3
A pair of crossed brightness enhancement films are positioned above the diffuser film. At least one of the brightness enhancement films has a plurality of parallel prism microstructures on one side thereof and facing away from the diffuser film, wherein the plurality of parallel micro prisms of one of the brightness enhancement films is oriented perpendicular to the plurality of micro prisms of the other brightness enhancement film
Implementation Method 4
The edge-lit back light unit includes a specular reflector and an edge-lit light guide film positioned above the specular reflector
Data Source
AI summary
An edge-lit back light unit includes a specular reflector and an edge-lit light guide film positioned above the specular reflector, both configured to provide peak optical distribution and FWHM angle of diffusion along a light propagation direction. A diffuser film above the edge-lit light guide film has a bottom-side that faces the edge-lit light guide film and a top-side that faces away from the edge-lit light guide film, and has a plurality of parallel prism microstructures on the bottom-side, some have an apex direction that is generally along the light propagation direction. The diffuser film has a plurality of parallel prism microstructures on the top-side having an apex direction that is rotated with respect to the apex direction of the plurality of parallel prism microstructures on the bottom-side such that the apex direction of the parallel prism microstructures on the top-side is generally perpendicular to the light propagation direction. A pair of crossed BEFs above the diffuser film have a plurality of parallel prism microstructures on one side and face away from the diffuser film, wherein the plurality of parallel micro prisms of one of the BEFs is oriented perpendicular to the plurality of micro prisms of the other BEF. The apex direction of the plurality of parallel prism microstructures on the bottom side of the diffuser film is substantially aligned with the plurality of parallel micro prisms of at least one of the brightness enhancement films.