Planar Light Unit with Diffusing Side Surface for Bright Line Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional backlight systems for watch faces, particularly those using EL panels, suffer from high voltage requirements and limited chromaticity and emission efficiency, leading to unsatisfactory illumination, especially when trying to display various types of information beyond simple time indications.
Innovation Solution
A planar light unit incorporating an LED light source and a light guide plate with a diffusing surface on its side surfaces to prevent the appearance of bright lines when viewed from the side, utilizing electrical discharge processing or die machining to form the diffusing surface, which can be a prism or concave-convex surface, to scatter light uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide plate with a curved portion is used to achieve a non-rectangular emission surface shape, then the light distribution is improved, but a bright line appears on the emission surface
Solution Approach 1:
The patent applies different surface treatments to different regions of the light guide plate. Specifically, the side surface of the curved portion is treated with a diffusing surface having a specific roughness (Ra: 0.03μm to 0.3μm), while other surfaces may have different treatments. This local differentiation allows the curved portion to scatter light and eliminate bright lines without compromising the overall light distribution.
Solution Approach 2:
The patent controls the surface roughness parameter of the diffusing surface on the curved portion within a specific range (Ra: 0.03μm to 0.3μm). By precisely controlling this physical parameter, the patent achieves optimal light scattering to suppress bright lines while maintaining good light extraction efficiency. The incident surface is also controlled with specific roughness (Ra: 0.01μm to 0.1μm) to balance light input and distribution.
2Loss of energy
If the side surfaces of the light guide plate are mirror-finished to direct light toward the center, then light propagation efficiency is improved, but bright lines appear when viewed from the side of the emission surface
Solution Approach 1:
The patent selectively applies mirror-finishing to certain side surfaces while applying diffusing surface treatment to the side surface of the curved portion. This localized differentiation allows light to be directed toward the center through mirror surfaces while the curved portion's diffusing surface scatters light to prevent bright line formation when viewed from the side.
Solution Approach 2:
The patent utilizes the curved portion geometry combined with diffusing surface treatment to transform the optical path. The curvature itself, when combined with the diffusing surface, naturally scatters light in multiple directions, preventing the formation of concentrated bright lines that would occur with pure mirror surfaces.
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 the appearance of bright lines and enhances light distribution, providing improved illumination uniformity and efficiency even with curved light guide plates, thus addressing the limitations of traditional backlight systems.
Implementation Method 1
at least a part of the side surface is formed as a diffusing surface
Implementation Method 2
The side surfaces of the light guide plate other than the incident surface are mirror-finished so as to direct the light that has propagated through the light guide and reached the side surface toward the center of the light guide plate. Here, the mirror-finished surface refers to a planarized surface that causes total reflection.
Data Source
AI summary
A planar light unit is provided that suppresses appearance of a bright line when viewed from the side of the emission surface of the light guide plate. The planar light unit includes a light source, and a light guide plate including an incident surface for receiving light emitted from the light source, an emission surface from which the light introduced through the incident surface is emitted, an opposing surface disposed so as to oppose the emission surface, and a side surface disposed along an outer periphery of the emission surface and the opposing surface. The emission surface has a non-rectangular outer shape, and at least a part of the side surface is formed as a diffusing surface.