Backlight Unit Nanocrystal Light Converting Layer
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Solution Overview
Problem
Conventional LCD backlight units using cold cathode fluorescent lamps (CCFLs) face challenges in achieving uniform brightness and color purity, especially as display sizes increase, and white LEDs that convert light into white light have lower color purity and reproducibility compared to three-color LEDs, making them more expensive.
Innovation Solution
A backlight unit for LCD devices utilizing a light source with LEDs, a light converting layer containing semiconductor nanocrystals that converts light into white light, and a barrier layer to prevent moisture and oxygen penetration, ensuring high color reproducibility and purity while maintaining brightness over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If white LEDs are used as light source to reduce cost, then cost competitiveness is improved, but color purity and reproducibility deteriorate
Solution Approach 1:
A light converting layer containing semiconductor nanocrystals is introduced as an intermediary between the white LED light source and the liquid crystal panel. This layer converts the broad-spectrum white LED light into light with improved color purity and reproducibility, thereby maintaining cost competitiveness while enhancing optical performance.
Solution Approach 2:
The light converting layer utilizes composite materials including semiconductor nanocrystals dispersed in a polymer matrix, combined with barrier materials having specific moisture and oxygen transmission rates. This composite structure enables both color purification and protection against environmental degradation.
2Use of energy by moving object
If light converting layer is placed close to light source to improve efficiency, then energy efficiency is improved, but moisture and oxygen penetration increases causing degradation
Solution Approach 1:
Barrier materials with controlled moisture transmission rates (0.1-10 cc/m2/day) and oxygen transmission rates (0.1-100 cc/m2/day) are applied to the light converting layer, creating a protective environment that prevents moisture and oxygen penetration while maintaining the layer's proximity to the light source for efficient light conversion.
Solution Approach 2:
Thin barrier films are applied to the light converting layer, providing protection against moisture and oxygen penetration while maintaining close proximity to the light source. The barrier layer structure allows efficient light transmission while preventing environmental degradation.
3Reliability
If barrier material with very low transmission rate is used to prevent moisture penetration, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of using extremely low transmission rate materials that would complicate manufacturing, the patent optimizes the barrier material parameters to achieve balanced transmission rates (moisture: 0.1-10 cc/m2/day, oxygen: 0.1-100 cc/m2/day). This parameter optimization provides sufficient protection while maintaining manufacturing feasibility.
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 improves color reproducibility and purity, reduces the cost competitiveness of backlight units, and maintains brightness and color coordinates even after long-term operation, enhancing the reliability of the backlight unit.
Implementation Method 1
a light converting layer between the light source and the liquid crystal panel, and spaced apart from the light source. The light converting layer converts the light from the light source into white light and emits the white light toward the liquid crystal panel.
Implementation Method 2
a barrier material which restricts penetration of moisture or oxygen
Data Source
AI summary
A backlight unit for a liquid crystal display device including a liquid crystal panel, includes: a light source including a light-emitting diode (“ED”) which generates and emits light; and a light converting layer between the light source and the liquid crystal panel, spaced apart from the light source, and converting the light from the light source into white light and emitting the white light toward the liquid crystal panel. The light converting layer includes: semiconductor nanocrystals, and a barrier material which restricts penetration of moisture or oxygen.