Dielectric Layer Resistivity via Carbon Nanotube Graphite Fillers
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Solution Overview
Problem
Existing electrophoretic display technologies face challenges in achieving the desired electrical resistivity for optimal performance, as available polymeric materials often have resistivity higher than required, and additives like dopant molecules or humectants can negatively impact display performance or make it moisture-dependent.
Innovation Solution
A dielectric layer composition incorporating a mixture of carbon nanotubes and graphite as conductive fillers, with specific weight percentages and possibly non-conductive fillers, to achieve the target resistivity range of 10^7 to 10^9 ohm·cm, while minimizing size distribution issues and moisture sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant molecules are added into the composition for forming the dielectric layer to reduce electrical resistivity, then the electrical resistivity decreases to the desired range, but the dopant molecules may travel into other components of the display device and negatively impact performance
Solution Approach 1:
The patent extracts the harmful dopant molecules from the system by replacing them with conductive fillers (carbon nanotubes and graphite) that achieve the desired electrical resistivity without the risk of migration into other components. This eliminates the harmful effect while maintaining the beneficial electrical property.
Solution Approach 2:
The patent introduces conductive fillers as an intermediary substance between the polymer matrix and the electrophoretic fluid. These fillers provide the necessary electrical conductivity through their inherent conductive properties rather than through reactive dopant molecules, preventing contamination while achieving the target resistivity range.
2Reliability
If humectants are added into the composition for forming the dielectric layer to raise moisture content and lower electrical resistivity, then the electrical resistivity decreases, but the display device becomes extremely moisture dependent and performance becomes sensitive to environmental changes
Solution Approach 1:
The patent removes humectants from the composition entirely, replacing them with conductive fillers that provide electrical conductivity through their inherent properties rather than through moisture content. This eliminates the moisture dependence issue while achieving the desired electrical resistivity range.
Solution Approach 2:
The patent changes the mechanism for achieving electrical conductivity from a moisture-dependent chemical process (humectants) to a physical property-based process (conductive fillers). This parameter change transforms the system from being sensitive to environmental moisture variations to being stable across different environmental conditions.
3Ease of manufacture
If polymeric materials are used for forming the dielectric layer, then the material is easy to process and form into layers, but the electrical resistivity is higher than the desired range of 10^7 to 10^10 ohm·cm
Solution Approach 1:
The patent creates a composite material by combining polymeric materials with conductive fillers (carbon nanotubes and graphite). This composite maintains the ease of processing and layer formation properties of the polymer while adding the electrical conductivity properties of the fillers, achieving both manufacturability and the desired electrical resistivity range.
Solution Approach 2:
The patent merges two materials with complementary properties: the polymer provides ease of manufacture and structural integrity, while the conductive fillers provide the necessary electrical properties. This combination allows the dielectric layer to be both easy to manufacture and have the required electrical resistivity.
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 combination of carbon nanotubes and graphite in the dielectric layer achieves the desired resistivity, reduces defects, and provides improved barrier properties, reduced temperature and moisture dependence, and anisotropic properties, leading to enhanced optical performance and stability.
Implementation Method 1
A dielectric layer composition incorporating a mixture of carbon nanotubes and graphite as conductive fillers, with specific weight percentages and possibly non-conductive fillers, to achieve the target resistivity range of 10^7 to 10^9 ohm·cm
Implementation Method 2
An electrophoretic display (EPD) is a non-emissive device based on the electrophoresis phenomenon influencing charged pigment particles dispersed in a solvent or solvent mixture
Data Source
AI summary
The present invention is directed to a composition for the dielectric layer, which composition comprises a mixture of conductive filler material wherein said mixture consists of carbon nanotubes and graphite, and the dielectric layer formed comprises 0.01% to 7% by weight of carbon nanotubes and 0.1% to 20% by weight of graphite. The composition of the present invention may form a dielectric layer which has the desired electrical resistivity. In addition, the dielectric layer is expected to show better barrier properties, less moisture and temperature dependence and improved anisotropic properties.