Silicon Dioxide Coated Phosphor Sheet for Chromaticity Stability
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Solution Overview
Problem
Sulfide phosphor particles in liquid crystal display backlight systems deteriorate due to oxygen and water vapor, leading to chromaticity shift and corrosion, which shortens the lifespan of LED elements and reduces light extraction efficiency.
Innovation Solution
Coating sulfide phosphor particles with a silicon dioxide film containing metal oxide powders, such as zinc oxide, to prevent water ingress and sulfur-based gas release, while also coating non-sulfide phosphor particles with a silicon dioxide film to enhance durability and prevent chromaticity shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sulfide phosphor particles are used to emit green light when irradiated with blue light, then the white light generation efficiency is improved, but the phosphor particles deteriorate due to oxygen and water vapor causing chromaticity shift and corrosion
Solution Approach 1:
A protective coating layer comprising a silane compound and a sulfur-atom containing gas adsorbent is applied to the surface of sulfide phosphor particles. This intermediary layer prevents direct contact between the phosphor particles and harmful substances (oxygen and water vapor), while allowing the phosphor to maintain its light-emitting function. The coating acts as a mediator that protects the phosphor particles from deterioration.
Solution Approach 2:
The protective coating is formed as a composite material combining a silane compound (which provides water vapor barrier properties) and a sulfur-atom containing gas adsorbent (which adsorbs sulfur-based gases). This composite structure provides dual protection: preventing water-induced deterioration and adsorbing sulfur-based gases that cause chromaticity shift, thereby maintaining both the stability and optical properties of the phosphor particles.
2Ease of manufacture
If the phosphor particles are exposed to oxygen and water vapor, then the manufacturing process is simplified, but the phosphor particles deteriorate causing chromaticity shift and corrosion
Solution Approach 1:
The protective coating is applied to the phosphor particles before they are incorporated into the resin composition and before the final product is used. This preliminary protection prevents deterioration during storage and handling, ensuring chromaticity uniformity is maintained throughout the product lifecycle without requiring complex manufacturing controls.
3Duration of action of stationary object
If a protective layer is formed on phosphor particles, then the lifetime of LED elements is extended, but the device structure becomes more complex
Solution Approach 1:
The protective coating is formed as a thin film on the surface of phosphor particles using silane compounds. This thin film structure provides effective protection against oxygen and water vapor without significantly increasing the size or complexity of the phosphor particles. The coating can be applied uniformly and maintains the particles' optical and physical properties while extending LED element lifetime.
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 coating significantly suppresses chromaticity shift and corrosion of sulfide phosphor particles, extending the lifespan of LED elements and maintaining light emission intensity by preventing sulfur-based gas release and water-induced deterioration.
Implementation Method 1
coating a sulfide phosphor particle with a silicon dioxide film
Implementation Method 2
the silicon dioxide film of the coated sulfide phosphor particle containing powders of a sulfur-atom containing gas adsorbent made of a metal oxide
Implementation Method 3
a sulfide phosphor particle that emits green light when irradiated with blue light
Data Source
AI summary
In order to suppress the chromaticity shift and corrosion associated with the deterioration of a sulfide phosphor particle, this phosphor sheet is produced using a phosphor particle-containing resin composition which comprises: covered phosphor particles; polymerizable compound; and a polymerization initiator. The covered phosphor particles are obtained by covering phosphor particles with silicon dioxide films, wherein among the phosphor particles, at least sulfide phosphor particles are covered with silicon dioxide films that contain a metal oxide powder. Thus, the phosphor sheet can be inhibited from emitting a sulfur-based gas, and exhibits a minimized chromaticity shift, even when the phosphor sheet is present in such a manner that the edge of the phosphor layer of the sheet is in an exposed state.