Light Diffusion Sheet Luminance Enhancers for LCD Backlight Uniformity
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Solution Overview
Problem
Conventional direct backlights in liquid crystal display devices experience a decrease in luminance in inter-light source regions due to reduced thickness or distance between light sources and light diffusion sheets, leading to luminance unevenness, which cannot be fully mitigated by existing methods.
Innovation Solution
A light diffusion sheet with a light diffuser having recesses and luminance enhancers, where the luminance enhancers are arranged in a gradation pattern with higher density in lower luminance regions, suppressing light diffusibility to increase perpendicular light travel and enhance luminance uniformity without decreasing overall screen luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the light diffusion sheet is reduced or the distance between the light source and the light diffusion sheet is reduced, then the overall device thickness is reduced, but the luminance in the inter-light source region decreases
Solution Approach 1:
The patent applies local quality by creating regions with different surface characteristics on the light diffusion sheet. Specifically, it forms light diffuser regions with recesses that scatter light, and light non-diffuser regions (luminance enhancers) that are flatter and allow more direct light transmission. By strategically positioning these different regions, the patent locally enhances luminance in inter-light source areas while maintaining thin overall structure.
Solution Approach 2:
The light diffusion sheet is segmented into multiple functional regions: light diffuser regions with recesses for general light scattering, and light non-diffuser regions (luminance enhancers) with flatter surfaces for enhancing luminance in specific areas. This segmentation allows different parts of the sheet to perform different functions, resolving the contradiction between thinness and luminance uniformity.
2Stability of the object's composition
If white ink is printed on the light diffusion sheet to reflect light in regions above light sources, then luminance unevenness between light source regions and inter-light source regions is reduced, but the luminance of the entire screen decreases
Solution Approach 1:
Instead of applying a uniform reflective layer across the entire light diffusion sheet (which would reduce overall luminance), the patent applies the light non-diffuser regions (luminance enhancers) only in specific locations corresponding to inter-light source areas. This localized approach enhances luminance uniformity without significantly impacting the overall screen luminance, as the majority of the sheet maintains its light-diffusing properties.
Solution Approach 2:
Rather than adding reflective material (white ink) to enhance luminance, the patent inverts the approach by creating regions that do NOT diffuse light (light non-diffuser regions). These flatter regions allow more direct light transmission, effectively enhancing luminance through the absence of light-diffusing structures rather than through additive reflective materials.
3Ease of manufacture
If the number of light sources is reduced for cost reduction, then manufacturing cost decreases, but luminance uniformity deteriorates
Solution Approach 1:
The patent compensates for reduced light source density by creating localized luminance enhancement regions (light non-diffuser regions) in the inter-light source areas. This allows fewer light sources to achieve adequate luminance uniformity, as the flat regions concentrate and enhance light transmission in areas that would otherwise be darkest.
Solution Approach 2:
By segmenting the light diffusion sheet into light diffuser regions and light non-diffuser regions, the patent creates a structure that passively enhances luminance in critical areas. This segmentation allows the system to maintain luminance uniformity even with fewer active light sources, as the structural segmentation itself contributes to light distribution optimization.
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 solution improves luminance uniformity across the screen while allowing for thinner backlights and reduced number of light sources, maintaining overall screen luminance and facilitating cost reduction.
Implementation Method 1
a light diffuser provided with a plurality of recesses arrayed two-dimensionally
Implementation Method 2
a plurality of luminance enhancers that is flatter than the light diffuser... light diffusibility is suppressed, and as a result, a proportion of a linear light traveling straight perpendicularly to the sheet surface increases
Data Source
AI summary
A first surface 21a of a light diffusion sheet 43 has a light diffuser 43A provided with a plurality of recesses 22 arrayed two-dimensionally and a plurality of luminance enhancers 43B that is flatter than the light diffuser 43A. The plurality of luminance enhancers 43B is provided in a gradation pattern such that the arrangement density is higher in a region where the luminance is lower in the luminance distribution generated by the plurality of point light sources 42 when the plurality of recesses 22 is formed all over the first surface 21a.