Partial Wavelength Conversion for Edge-Light Backlight Color Uniformity
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Solution Overview
Problem
Edge-light type backlights using a light guide plate with a wavelength conversion layer on the entire light-extraction or rear surface suffer from color non-uniformity due to repeated reflections and wavelength conversions, leading to a yellowish tint, especially at positions farther from the light-emitting element.
Innovation Solution
A lighting device design featuring a light-emitting component, a light guide plate with recesses in the edge region, and a partial wavelength conversion member, where the light-emitting element is accommodated in the recess and the wavelength conversion member covers only the edge region of the light guide plate, reducing repeated reflections and wavelength conversions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the entire light-extraction surface or rear surface of the light guide plate is covered with a wavelength conversion layer, then the light guide plate can convert blue light to yellow light to produce white light, but the light undergoes repeated wavelength conversions causing color non-uniformity and yellowish tint
Solution Approach 1:
The light guide plate is divided into two distinct regions: a first region with a wavelength conversion layer that converts blue light to yellow light, and a second region without a wavelength conversion layer that transmits blue light directly. This segmentation allows different portions of the light guide plate to perform different functions, preventing excessive repeated wavelength conversions and maintaining color uniformity across the entire plate.
Solution Approach 2:
Different regions of the light guide plate are assigned different optical properties: the first region has wavelength conversion capability while the second region has direct transmission capability. This local differentiation ensures that blue light is converted to yellow light only in specific areas, avoiding the problem of uniform yellowish tint across the entire plate while still achieving overall white light output.
2Illumination intensity
If the wavelength conversion layer covers the entire surface, then white light can be produced through blue and yellow light mixing, but light traveling longer distances experiences more reflections and wavelength conversions
Solution Approach 1:
The light guide plate is segmented into a first region with wavelength conversion layer and a second region without it. This segmentation creates multiple light extraction paths: some light undergoes wavelength conversion in the first region, while other light travels through the second region with fewer reflections, maintaining color consistency regardless of travel distance.
Solution Approach 2:
Instead of applying wavelength conversion across the entire light guide plate surface, the invention applies it only partially to the first region. This partial action prevents excessive wavelength conversions for light traveling long distances, as some light can exit through the second region before undergoing multiple conversions, thereby maintaining color reliability.
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 design minimizes color non-uniformity by ensuring that light exiting the light guide plate maintains a consistent color across the extraction region, reducing the yellowish tint and improving light extraction efficiency.
Implementation Method 1
a blue light-emitting element and to cover the entire light-extraction surface or entire rear surface of the light guide plate with an yellow phosphor layer (a wavelength conversion layer)
Implementation Method 2
light entering the light guide plate is spread across the entire light guide plate while repeatedly reflecting between a light-extraction surface and a rear surface of the light guide plate
Data Source
AI summary
A lighting device includes a light-emitting component including at least one light-emitting element mounted on a base, a light guide plate guiding light emitted from the light-emitting element, a wavelength conversion member partially covering the light guide plate, and a first reflective member covering the wavelength conversion member. The light guide plate comprises two main surfaces, which include a light-extraction surface allowing light emitted from the light-emitting element to exit and a rear surface opposite to the light-extraction surface. One of two main surfaces comprises at least one recess formed in an edge region thereof. The other main surface of the light guide plate includes a part covered by the wavelength conversion member and a part exposed from the wavelength conversion member. The light-emitting element is accommodated in the recess such that a light-emitting surface of the light-emitting element faces the wavelength conversion member.