Core-Shell Toner Particles with Co-Emulsified Charge Control Agent
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Solution Overview
Problem
Existing toner formulations with crystalline polyester resins face issues with charging characteristics due to surface migration, and conventional charge control agents (CCAs) are difficult to use effectively in emulsion aggregation processes, especially when in solid powder form.
Innovation Solution
A process for preparing toner particles with a core-shell configuration, where the shell includes a charge control agent (CCA) co-emulsified with an amorphous polyester resin, allowing for efficient distribution and incorporation of CCAs, thereby improving charging properties and reducing the need for high CCA concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If crystalline polyester resin is used in toner formulation, then melting point and structural stability are improved, but charging characteristics deteriorate due to surface migration
Solution Approach 1:
The toner particle is divided into core and shell segments. The core contains the crystalline polyester resin for structural stability, while the shell contains the charge control agent for improved charging characteristics. This segmentation prevents the crystalline polyester from migrating to the surface while maintaining both structural stability and reliable charging.
Solution Approach 2:
Different regions of the toner particle are assigned different compositions: the core region contains crystalline polyester for stability, while the shell region contains charge control agents for charging performance. This local differentiation allows each region to optimize its specific function without interfering with the other.
2Reliability
If solid powder charge control agents are used, then charging effectiveness is improved, but ease of manufacture deteriorates due to difficulty in conversion to aqueous dispersions
Solution Approach 1:
The charge control agent is changed from solid powder form to aqueous dispersion form. This parameter change in physical state allows the CCA to be easily incorporated into the emulsion aggregation process without requiring conversion steps, significantly improving ease of manufacture while maintaining charging effectiveness.
Solution Approach 2:
An aqueous dispersion serves as an intermediary form of the charge control agent, bridging the gap between solid powder CCA and the emulsion aggregation process. This intermediary form allows efficient incorporation of CCAs into the toner shell during manufacturing.
3Reliability
If high concentration of charge control agents is used, then charging characteristics are improved, but loss of substance increases
Solution Approach 1:
The charge control agent is extracted from the bulk toner composition and concentrated specifically in the shell region. This extraction and localized placement allows for reduced overall CCA concentration while maintaining effective charging characteristics at the particle surface where charging occurs.
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 core-shell structure enhances charging characteristics, sensitivity to relative humidity, and cohesiveness of toner particles, while preventing crystalline polyester migration and reducing CCA requirements, leading to improved performance and cost-effectiveness.
Implementation Method 1
contacting the dispersion with an emulsion comprising at least one charge control agent in combination with at least one amorphous polyester resin emulsion
Implementation Method 2
aggregating the small particles to form a core
Implementation Method 3
coalescing the small particles possessing the shell to form toner particles
Data Source
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AI summary
Toner particles are provided which may, in embodiments, include a core and a shell. In embodiments, charge control agents may be co-emulsified with a resin utilized to form a shell. The shell may prevent a crystalline resin in the core from migrating to the toner surface. Inclusion of the charge control agent in the shell itself may provide the resulting toner particles with desirable charge characteristics and sensitivity to relative humidity.