CNT String Emitter for Field Emission Display Shield Effect
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Solution Overview
Problem
Field emission displays (FEDs) face challenges in manufacturing controllable color pixel elements with high luminous efficiency due to the small size of single carbon nanotubes (CNTs) and the shield effect caused by adjacent CNTs, leading to low luminous efficiency.
Innovation Solution
A color pixel element for FEDs is designed with a sealed container housing CNT strings, phosphor layers, and anodes, where the CNT strings are electrically connected to the cathode and form a tooth-shaped emission structure to prevent the shield effect, enhancing luminous efficiency and ease of fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single CNTs are used as electron emitters, then the field enhancement factor is high due to small tip-surface area, but the controllability of manufacturing is poor and the shield effect from adjacent CNTs reduces luminous efficiency
Solution Approach 1:
Multiple carbon nanotubes are bundled together to form a CNT string with a unified support structure. This merging approach maintains the high field enhancement factor of individual CNTs while improving manufacturing controllability through a single integrated emitter unit that can be precisely positioned and controlled during fabrication.
Solution Approach 2:
The electron emission function is segmented into discrete CNT strings, each with its own support structure and emission portion. This segmentation allows for controlled spacing between emitters, reducing the shield effect from adjacent CNTs while maintaining the high efficiency benefits of nanoscale tip structures.
2Productivity
If adjacent CNTs are placed close together, then the device density is high, but the shield effect caused by adjacent CNTs reduces luminous efficiency
Solution Approach 1:
The CNT string structure extends the emission geometry into a vertical dimension with a tooth-shaped profile. This dimensional change allows adjacent strings to be positioned closer together horizontally while the vertical segmentation of emission portions prevents lateral shield effects, maintaining both high device density and luminous efficiency.
3Power
If conventional CNT emitters are used, then the electron emission capability is strong, but the manufacturing complexity and difficulty of controlling emitter positions increase
Solution Approach 1:
The support structure for the CNT string is prepared in advance as an integrated component before CNT attachment. This preliminary preparation establishes precise positioning features and structural support upfront, simplifying subsequent CNT placement and reducing the overall manufacturing complexity while maintaining strong electron emission capability.
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 use of CNT strings as electron emitters improves the luminous efficiency and manufacturing ease of color pixel elements, reducing the shield effect and enhancing emission performance at lower voltages, allowing for the production of various color light beams.
Implementation Method 1
Field emission displays (FEDs) are based on emission of electrons in vacuum. Electrons are emitted from micron-sized tips in a strong electric field
Implementation Method 2
the electrons are accelerated and collide with a fluorescent material, and then the fluorescent material emits visible light
Data Source
AI summary
A color pixel element for field emission display includes a sealed container having a light permeable portion, at least two anodes, a cathode, at least two phosphor layers formed on the end surfaces of the anodes, and at least two CNT strings electrically connected to and in contact with the cathode with the emission portions of the CNT strings suspending. The phosphor layers are opposite to the light permeable portion, and one emission portion is corresponding to one phosphor layer. In each CNT string, some of CNT bundles are taller than and project over the adjacent CNT bundles, and each of projecting CNT bundles functions as an electron emitter. The anodes, the cathode, the phosphor layers and the CNT strings are enclosed in the sealed container. The luminance of the color pixel element is enhanced at a relatively low voltage.