Liquid Electrophotographic Ink Conductive Pattern Printing
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Solution Overview
Problem
Printing electrically conductive ink particles via liquid electrophotographic processes is challenging due to increased viscosity and electrostatic disruptions caused by conductive pigments, leading to issues such as high background noise and low ink film thickness.
Innovation Solution
The development of liquid electrophotographic inks comprising a conductive toner with a conductive pigment and polymeric binder, along with a charge director, which are formulated to maintain specific weight percentages and ratios, and heated to reduce viscosity, allowing for effective printing of electrically conductive patterns with controlled electrostatic transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive pigments are added to LEP ink to achieve electrical conductivity, then the electrical conductivity is improved, but the viscosity increases above a desirable range
Solution Approach 1:
The patent applies parameter changes by heating the LEP ink to elevated temperatures (e.g., 40-60°C) to reduce viscosity to a workable range. This temperature control allows the ink to maintain low viscosity during printing operations while still achieving the desired electrical conductivity through conductive pigment incorporation.
2Reliability
If conductive pigments are added to LEP ink, then electrical conductivity is improved, but electrostatic disruptions occur causing high background noise and low ink film thickness
Solution Approach 1:
The patent uses a charge director as an intermediary substance to mediate between the conductive pigment particles and the electrostatic field. The charge director (e.g., metal salts of fatty acids or sulfonates) provides controlled charge to the conductive toner particles, enabling them to respond to electrostatic fields during printing while maintaining their electrical conductivity for the final conductive pattern.
3Reliability
If conductive toner particles are used in LEP printing, then the desired conductive pattern is achieved, but the ink formulation becomes complex requiring specific weight ratios and heating procedures
Solution Approach 1:
The patent specifies precise parameter ranges for the ink formulation, including conductive toner content (0.1-5 wt%), charge director content (0.01-7.5 wt%), and operating temperature (40-60°C). By defining these parameters within specific ranges rather than fixed values, the patent simplifies formulation while maintaining performance, allowing flexibility within the specified windows.
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 enables the successful printing of electrically conductive patterns with improved digitization and thickness, minimizing electrostatic disruptions and achieving desired conductivity levels, suitable for various substrates and applications.
Implementation Method 1
The charged toner particles adhere to the image areas of the latent image while the background areas remain clean
Implementation Method 2
heating the ink dispersion to a temperature of about 38°C to about 48°C to prepare a heated ink dispersion
Implementation Method 3
adding a charge director to the heated ink dispersion
Data Source
Figure 1
Figure 2~3
AI summary
A liquid electrophotographic (LEP) ink can include a liquid ink vehicle, a conductive toner including a conductive pigment and a polymeric binder, and a charge director. The liquid electrophotographic ink can have a conductivity of from 150 to 2000 picoSiemens.