Edge-Lit Backlight Prism Structures for 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 an improved light management diffuser film with angular light distribution matching 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 a conventional diffuser film is used in the back light unit, then the structure is simple and easy to manufacture, but the light efficiency is low and viewing brightness is insufficient
Solution Approach 1:
The diffuser film is segmented into multiple functional layers: a first diffuser layer with first prism microstructures and a second diffuser layer with second prism microstructures. Each layer has different apex directions that work together to optimize light distribution in specific angular ranges, improving viewing brightness while maintaining manufacturing feasibility through modular design
Solution Approach 2:
Different regions of the diffuser film have different optical properties tailored to specific functions. The first prism microstructures are configured with apex directions within 0-30 degrees relative to the light guide film's light direction to optimize one angular range, while the second prism microstructures have apex directions within 30-60 degrees to optimize another angular range, creating localized optical quality variations that enhance overall light efficiency
2Loss of energy
If the apex direction of prism microstructures is aligned with the light direction of the light guide film, then light coupling efficiency is improved, but the angular distribution does not match the acceptance angles of brightness enhancement films
Solution Approach 1:
The apex direction parameter of the prism microstructures is changed and distributed across different ranges. Instead of a single fixed apex direction, the patent specifies first prism microstructures with apex directions of 0-30 degrees and second prism microstructures with apex directions of 30-60 degrees relative to the light guide film's light direction. This parameter variation optimizes both light coupling efficiency and angular distribution matching with brightness enhancement films
Solution Approach 2:
The patent introduces an additional dimensional parameter - the apex direction angle distribution - to the traditional single-direction prism design. By distributing prism apex directions across multiple angular ranges (0-30 degrees and 30-60 degrees), the system achieves better angular matching with crossed brightness enhancement films while maintaining overall light efficiency
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 higher viewing brightness without increasing 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
a specular reflector and an edge-lit light guide film positioned above the specular reflector, wherein a combination of the edge-lit light guide film and the specular reflector is configured to provide a peak optical distribution and a full width half maximum angle of diffusion along a light propagation direction
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.