Toner Shell Layer Design for Fixability and Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional toners face a trade-off between low-temperature fixability and storage stability, as selecting a binder resin with a low glass transition temperature for low-temperature fixability compromises storage stability, and existing encapsulation methods either result in an inferior fixability or poor chargeability and residual monomer issues.
Innovation Solution
A toner is produced with an extremely thin, crosslinked shell layer formed by sequentially coating core particles with a water-soluble crosslinking agent and a water-soluble polymer in an aqueous dispersion medium, which enhances storage stability without compromising low-temperature fixability and improves chargeability by moderating the consumption of carboxyl groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a binder resin having a low glass transition temperature is selected for achieving low-temperature fixability, then the fixability at low temperature is improved, but the storage stability of the toner is deteriorated
Solution Approach 1:
The toner is divided into core particles and a shell layer, where the core contains the binder resin with low glass transition temperature for low-temperature fixability, and the shell provides storage stability. This segmentation allows each part to fulfill its specific function without compromising the other.
Solution Approach 2:
The toner combines core particles made of binder resin with low glass transition temperature and a shell layer formed by crosslinking polymerizable monomers. This composite structure enables the core to provide low-temperature fixability while the shell ensures storage stability.
2Reliability
If a shell layer with high thermal characteristic is formed by coating with resin particles of about 0.1 μm, then the storage stability is improved, but the low-temperature fixability becomes inferior due to the relatively thick shell layer
Solution Approach 1:
Instead of using thick resin particle coatings, the invention forms an extremely thin shell layer by reacting polymerizable monomers directly on the toner particle surface. This thin film approach provides the necessary storage stability without creating a thick barrier that would hinder low-temperature fixability.
Solution Approach 2:
The invention changes the formation method of the shell layer from physical coating of resin particles to chemical reaction of polymerizable monomers. This parameter change enables the formation of an extremely thin shell layer with appropriate thickness and structure that maintains both storage stability and low-temperature fixability.
3Reliability
If a polymerizable monomer is reacted on surfaces of toner particles to form an extremely thin shell layer, then the storage stability is improved, but the low-temperature fixability becomes inferior due to the dense crosslinked structure
Solution Approach 1:
The invention optimizes the molecular weight and chemical structure parameters of the polymerizable monomers to achieve an appropriate crosslinking density. By selecting monomers with specific properties and controlling reaction conditions, the shell layer achieves sufficient crosslinking for storage stability while maintaining enough flexibility for low-temperature fixability.
Solution Approach 2:
The shell layer has different properties from the core: it is crosslinked for storage stability but with controlled density to allow flexibility. The local quality of the shell differs from conventional dense crosslinked structures, providing both storage stability and acceptable low-temperature fixability.
4Length of stationary object
If a polymerizable monomer with low molecular weight is used for in situ polymerization, then an extremely thin shell layer is formed, but the resin develops a dense crosslinked structure that deteriorates low-temperature fixability and chargeability
Solution Approach 1:
The invention changes the parameter of monomer molecular weight from low to medium or high range. This parameter change prevents excessive crosslinking density while still forming a thin shell layer, thereby maintaining both low-temperature fixability and chargeability properties.
5Length of stationary object
If a polymerizable monomer is used for coating, then an extremely thin shell layer is formed, but the toner exhibits poor chargeability and residues of formaldehyde
Solution Approach 1:
The invention changes the chemical structure parameters of the polymerizable monomers, selecting those that do not produce harmful residues like formaldehyde. Additionally, the molecular weight parameter is adjusted to prevent excessive crosslinking that would impair chargeability, while still achieving thin shell formation.
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 resulting toner achieves both low-temperature fixability and improved storage stability with a strong capsule structure that withstands mechanical and chemical loads, while avoiding the safety issues associated with residual monomers.
Implementation Method 1
coating the core particles successively with a water-soluble crosslinking agent and a water-soluble polymer having a carboxyl group
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed is a toner obtained by coating surfaces of core particles including at least a binder resin having a carboxyl group and a coloring agent with successive coatings of a water-soluble crosslinking agent capable of crosslinking with a carboxyl group and a water-soluble polymer having a carboxyl group, which have been successively applied on the core particles and crosslinked with each other. The thus-formed toner is provided with a good harmony of favorable fixability represented by a low lowest fixable temperature and favorable storage stability represented by little aggregation after standing at 50°C for 8 hours.