Light Guide Plate Prism Protrusions for LCD Backlight Uniformity
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Solution Overview
Problem
Existing backlight units for liquid crystal display devices face issues with hot spots and bright/dark lines due to the placement of prisms on the light guide plate, leading to impaired uniformity and reduced light use efficiency, as well as increased power consumption and screen quality deterioration.
Innovation Solution
A light guide plate design featuring a flat surface portion adjacent to the incident surface and prism protrusions extending orthogonal to the incident surface, with specific configurations of prism grooves and protrusions to control light propagation and reduce hot spots and bright/dark lines, while maintaining efficient light use and emission properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If prism sheets are used to converge light to visual directions, then luminance is improved, but the number of component parts increases and assembly becomes complicated
Solution Approach 1:
The patent combines the light-converging function previously performed by separate prism sheets into the light guide plate itself by forming prism protrusions directly on its outgoing surface. This integration eliminates the need for additional prism sheet components while maintaining the light convergence function, thus improving luminance without increasing device complexity
Solution Approach 2:
The light guide plate is designed to perform multiple functions: guiding light from the incident surface, diffusing light through scattered dots, and converging light to visual directions through prism protrusions on the outgoing surface. This multi-functionality replaces what previously required separate components, reducing assembly complexity while maintaining luminance performance
2Ease of operation
If prisms are placed in regular array on the light guide plate, then light direction control is improved, but hot spots and bright/dark lines occur impairing uniformity
Solution Approach 1:
The patent creates different surface regions with different properties: a flat surface portion adjacent to the incident surface that prevents hot spots, and a prism portion with regular array prism protrusions that provides light direction control. This local differentiation allows each region to perform its specific function optimally without the uniformity problems of completely regular arrays
Solution Approach 2:
The outgoing surface is segmented into distinct functional zones: a flat surface portion and a prism portion with regular array prism protrusions. This segmentation allows the light guide plate to simultaneously achieve uniform light distribution (from the flat portion) and directed light output (from the prism portion), resolving the contradiction between direction control and uniformity
3Manufacturing precision
If scattered dots are printed on the bottom face to control luminance distribution, then uniformity is improved, but light orientation distribution spreads to wide angle making direction control difficult
Solution Approach 1:
The patent addresses the wide-angle light distribution problem by adding vertical dimension features (prism protrusions extending orthogonal to the incident surface) on the outgoing surface. These three-dimensional structures redirect the widely distributed light from the scattered dots back toward visual directions, effectively controlling light orientation without compromising the uniformity achieved by the scattered dots
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 suppresses hot spots and bright/dark lines, enhances light uniformity, and improves light use efficiency without impairing the split light-emission property, allowing for efficient light extraction and reduced power consumption.
Implementation Method 1
a reflection-and-propagation surface at which the light incident from the incident surface is reflected so as to propagate the light toward the outgoing surface
Implementation Method 2
a plurality of prism protrusions extending orthogonal to the incident surface are formed in a prism portion provided in a region of the outgoing surface adjacent to the flat surface portion
Data Source
AI summary
A light guide plate includes an incident surface on which light outputted from point light sources is incident and an outgoing surface for outputting light incident from the incident surface. A reflection-and-propagation surface for reflecting light toward the outgoing surface is formed in a back surface opposite to the outgoing surface. The outgoing surface is made up of a propagation region adjacent to the incident surface, a propagation auxiliary region adjacent to the propagation region, a first diffusion-and-propagation region adjacent to the propagation auxiliary region, and a second diffusion-and-propagation region adjacent to the first diffusion-and-propagation region. The propagation region, the propagation auxiliary region, and the first diffusion-and-propagation region control hot spots and bright/dark lines in vicinities of the incident surface, while the second diffusion-and-propagation region controls viewing-angle characteristics of the light guide plate.