Backlight Module Stray Light Suppression via Absorbing Sheet
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Solution Overview
Problem
Existing high light collection backlight modules suffer from stray light issues due to manufacturing defects in light guide plates, leading to reduced light collection and anti-peep performance, especially at oblique viewing angles.
Innovation Solution
A backlight module design incorporating a light guide plate with micro lens structures, a prism sheet with prism structures parallel to the light incident surface, and a light absorbing sheet with high visible light absorption (>70%) to suppress stray light and enhance light collection and anti-peep effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reverse prism sheet is used to improve light collection, then total light output near normal viewing angle is improved, but stray light increases due to multiple reflections and refractions
Solution Approach 1:
A light absorbing sheet is introduced as an intermediary component between the light guide plate and the rear surface to intercept and absorb stray light before it can reflect back into the optical path. This mediator prevents the harmful stray light from completing its unwanted optical path while allowing the primary light transmission path to remain intact.
Solution Approach 2:
The harmful stray light is extracted and removed from the optical system by placing the light absorbing sheet at the rear surface, which selectively absorbs the scattered light that deviates from the desired optical path, thereby separating the useful light from the harmful stray light.
2Illumination intensity
If multiple brightness enhancement films are stacked to guide light, then light intensity near normal viewing angle is improved, but light collection efficiency decreases
Solution Approach 1:
The dual-layer BEF structure is replaced by extracting only the essential light-guiding function and implementing it through a single prism sheet combined with a light absorbing sheet, thereby removing the excessive light loss associated with multiple film layers while maintaining the desired light distribution.
Solution Approach 2:
The light absorbing sheet serves as a mediator that compensates for the reduced light guidance effect of using fewer films, by actively managing stray light and preventing it from degrading overall light collection efficiency.
3Illumination intensity
If light guide plate is used for light transmission, then light distribution is improved, but manufacturing defects cause stray light scattering
Solution Approach 1:
The light absorbing sheet is positioned at the rear surface to preemptively counteract the stray light scattering caused by manufacturing defects in the light guide plate, preventing the scattered light from affecting the final image quality before it can cause harm.
Solution Approach 2:
The light absorbing sheet converts the harmful effect of stray light from manufacturing defects into a controlled absorption process, where the stray light is deliberately intercepted and absorbed at a specific location, transforming an uncontrolled harmful phenomenon into a managed optical control mechanism.
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 effectively reduces stray light influence, improving light collection and anti-peep performance by absorbing unwanted light and focusing it near the normal viewing angle, thereby enhancing the overall light output and viewing angle luminance ratio.
Implementation Method 1
A light absorbing sheet is disposed on a side of the bottom surface of the light guide plate. An absorbance of the light absorbing sheet within a wavelength range of visible light is higher than 70%.
Implementation Method 2
At least one of the light emitting surface and the bottom surface of the light guide plate is disposed with a plurality of micro lens structures.
Implementation Method 3
The prism sheet is overlapped with the light emitting surface of the light guide plate and has a plurality of prism structures facing the light emitting surface.
Data Source
AI summary
A backlight module including a light guide plate, a light source, a prism sheet and a light absorbing sheet is provided. The light guide plate has a light incident surface, a light emitting surface connected to the light incident surface and a bottom surface opposite to the light emitting surface. At least one of the light emitting surface and the bottom surface of the light guide plate is disposed with a plurality of micro lens structures. The light source is disposed on a side of the light incident surface of the light guide plate. The prism sheet is overlapped with the light emitting surface of the light guide plate and has a plurality of prism structures facing the light emitting surface with an extending direction parallel to the light incident surface. The light absorbing sheet is disposed on a side of the bottom surface of the light guide plate.