Conductive Sealing Layer Composition for Electrophoretic Microcells
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Solution Overview
Problem
Existing sealing layers for electrophoretic displays face challenges in balancing barrier properties for non-polar fluids, moisture absorption, and electrical resistivity, leading to inferior electro-optic performance.
Innovation Solution
A sealing layer composition comprising poly(vinyl alcohol) homopolymer or copolymer, polyurethane, and a conductive filler like carbon black, graphene, or carbon nanotubes, with specific surface energy ranges, forming a sealing layer with enhanced barrier properties and reduced moisture absorption while maintaining optimal electrical resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing layer is designed to provide good barrier properties for non-polar fluids, then fluid leakage is prevented, but moisture absorption increases and electrical resistivity deteriorates
Solution Approach 1:
The sealing layer uses a composite formulation combining poly(vinyl alcohol) homopolymer or copolymer with polyurethane and conductive filler. This composite structure allows the poly(vinyl alcohol) component to provide excellent barrier properties against non-polar fluids while the polyurethane component controls moisture absorption, and the conductive filler maintains electrical resistivity within the desired range of 10^6 to 10^9 ohm-cm.
2Use of energy by moving object
If conductive filler is added to maintain electrical resistivity, then power consumption is reduced, but barrier properties for non-polar fluids may deteriorate
Solution Approach 1:
The patent optimizes the concentration of conductive filler within specific ranges (carbon black: 1-30 wt%, graphene: 0.1-10 wt%, carbon nanotubes: 0.1-5 wt%) to achieve the desired electrical resistivity of 10^6 to 10^9 ohm-cm while maintaining barrier properties. The surface energy parameters are also controlled (total surface energy 20-50 mN/m, dispersive component 10-40 mN/m) to ensure compatibility with electrophoretic particles and maintain barrier functionality.
3Reliability
If poly(vinyl alcohol) content is increased to improve barrier properties, then fluid leakage is prevented, but moisture absorption increases
Solution Approach 1:
The sealing layer employs local quality differentiation by combining poly(vinyl alcohol) homopolymer or copolymer (providing barrier properties) with polyurethane (providing moisture resistance). This localized functional distribution allows each polymer component to excel at its specific function, with the poly(vinyl alcohol) content controlled at 30-70 wt% and polyurethane at 10-40 wt% to balance barrier performance and moisture absorption characteristics.
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 sealing layer achieves improved electro-optic performance by effectively preventing fluid leakage, reducing moisture ingress, and minimizing power consumption while maintaining image resolution.
Implementation Method 1
it must be a good barrier to the non-polar fluid, so that the non-polar fluid does not diffuse out form the microcells
Implementation Method 2
the sealing layer must not absorb significant amount of moisture from the environment
Implementation Method 3
it is very important that the sealing layer of an electrophoretic display has good electrical properties. The electric field, which is applied across the electrophoretic medium for the operation of the display, is transmitted through the sealing layer.
Data Source
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AI summary
The present invention is directed to a sealing layer that comprises a poly(vinyl alcohol) homopolymer or a poly(vinyl alcohol-co-ethylene) copolymer, a polyurethane, and a conductive filler. The sealing layer shows good barrier properties to a non-polar fluid. The sealing layer can be used to seal microcells of electro-optic devices, contributing to improved good electro-optic performance of the device, especially at low temperatures.