Backlight Assembly Prismatic Film Angle for Cross-Hatching
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Solution Overview
Problem
Backlight assemblies for LCDs, particularly those with in-plane switching (IPS) type displays, suffer from a cross-hatching pattern of bright and dark alternating squares when two brightness enhancement films (BEFs) are aligned with their prismatic elements vertical and horizontal axes, respectively, leading to reduced display brightness and visibility.
Innovation Solution
The solution involves positioning a first brightness enhancement film with prismatic elements at an angle of between 5 to 15 degrees offset from the polarized transmission axis of the display and a second film with elements substantially perpendicular to the first, thereby reducing the cross-hatching effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two brightness enhancement films are aligned with their prismatic elements vertical and horizontal axes respectively, then the display structure is simple and manufacturing is easy, but a cross-hatching pattern of bright and dark alternating squares appears reducing display brightness and visibility
Solution Approach 1:
The patent applies asymmetry by rotating the first brightness enhancement film at an angle of 5-15 degrees relative to the polarized transmission axis of the display, rather than aligning it perfectly perpendicular. This asymmetric angular offset breaks the cross-hatching pattern caused by the interaction between the two BEFs and the polarizer, eliminating the harmful visual artifact while maintaining brightness enhancement functionality.
2Illumination intensity
If the first brightness enhancement film is rotated at an angle offset from the polarized transmission axis, then the cross-hatching pattern is reduced and display brightness is improved, but the alignment complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a precise angular parameter range of 5-15 degrees for rotating the first brightness enhancement film relative to the polarized transmission axis. This parameter change optimizes the balance between eliminating cross-hatching patterns and maintaining manufacturability, providing a specific design guideline that reduces the precision burden compared to requiring exact angular positioning.
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 brightness in both dimensions of the display, minimizing the cross-hatching pattern and improving visibility by optimizing the alignment of prismatic elements relative to the polarized transmission axis, thus enhancing the overall display performance.
Implementation Method 1
a first brightness enhancement film having a plurality of prismatic elements extending in a first direction, and positioned to receive light emitted from the light source
Data Source
AI summary
A backlight assembly for a display having a polarized transmission axis is provided including a light source for emitting light; a first brightness enhancement film having a plurality of prismatic elements extending in a first direction, and positioned to receive light emitted from the light source; and a second brightness enhancement film having a plurality of prismatic elements extending in a second direction and positioned to receive light exiting the first brightness enhancement film, wherein the first direction extends at an angle of between about 5 degrees and about 15 degrees offset from the polarized transmission axis of the display and the second direction is substantially perpendicular to the first direction.