Backlight Unit Quantum Dot Phosphor Heat Management
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Solution Overview
Problem
Backlight units using quantum dot phosphors face limitations in achieving a wide color gamut due to the narrow full width at half maximum (FWHM) of their optical spectrum, which is challenging to reduce due to material characteristics and manufacturing processes, and also suffer from reduced lifespan due to heat from the light source.
Innovation Solution
Incorporating a light cutting agent, such as dyes, pigments, or luminescent dyes, dispersed in a matrix or bead structure, to absorb specific wavelengths and reduce the FWHM of the optical spectrum, while positioning the quantum dot phosphor remotely from the light source to minimize heat-induced degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quantum dot phosphor is used to achieve wide color gamut, then color reproduction is improved, but FWHM is difficult to reduce due to material characteristics and manufacturing processes
Solution Approach 1:
A wavelength selective filter is introduced as an intermediary component between the quantum dot phosphor and the liquid crystal panel. This filter selectively transmits specific wavelength bands while blocking others, thereby narrowing the FWHM of the emitted light without requiring changes to the quantum dot phosphor material or manufacturing process. The filter acts as a mediator that achieves precise spectral control independently of the phosphor's inherent properties.
2Productivity
If quantum dot phosphor is positioned close to light source for efficient excitation, then light conversion efficiency is improved, but heat-induced degradation reduces lifespan
Solution Approach 1:
The system is segmented into distinct functional zones: the light source region, the quantum dot phosphor excitation region, and the light emission region. By positioning the quantum dot phosphor at a distance from the light source while maintaining optical coupling through the light guide plate, the design separates the high-temperature light source from the heat-sensitive phosphor material. This spatial segmentation allows efficient light conversion while protecting the phosphor from thermal degradation.
3Ease of manufacture
If yellow phosphor is used with blue LED to form white light, then manufacturing cost is reduced, but color reproduction is limited
Solution Approach 1:
The patent changes the key parameter of phosphor material from conventional yellow phosphor to quantum dot phosphor with specific size-controlled particle diameters (2-50 nm). This parameter change in material composition and particle size enables precise control over emission wavelength and FWHM, achieving wide color gamut (130% NTSC or higher) while maintaining manufacturing feasibility through established quantum dot synthesis and coating techniques.
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 approach enables the achievement of a wide color gamut without additional processing steps and helps in extending the lifespan of the quantum dot phosphor by reducing heat-related stress, thereby enhancing the performance and durability of the backlight unit.
Implementation Method 1
A quantum dot phosphor is excited by primary light provided from a light source to emit secondary light having a wavelength different from that of the primary light
Implementation Method 2
a light cutting agent (optical agent) absorbing light having a specific wavelength from the primary light or the secondary light
Data Source
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AI summary
The present invention provides a direct type backlight unit (120, 200, 620, 720, 800, 900, 1300, 1400) comprising: a light source (217, 542, 622, 810, 910, 1310, 1410) formed to provide primary light; a quantum dot phosphor film (840) comprising a quantum dot phosphor (841, 941, 1041, 1141, 1241) excited by the primary light provided from the light source (217, 542, 622, 810, 910, 1310, 1410) to emit secondary light having a wavelength different from a wavelength of the primary light and disposed to be spaced apart from the light source (217, 542, 622, 810, 910, 1310, 1410); and an optical agent (1044, 1144, 1244) absorbing light having a specific wavelength from the primary light or the secondary light.