Toner Shell Charge Density Control for Back Side Contamination
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Solution Overview
Problem
Toner used in electrophotographic methods experiences back side contamination and electrostatic offset when stored in high-temperature, high-humidity environments, leading to suboptimal low-temperature fixability and heat-resistant stability.
Innovation Solution
A toner with a core particle comprising a binder resin and wax, and a shell with a specific functional group, where the surface charge density of the wax is adjusted between -0.0080 and -0.0025, and the absolute difference between the wax and shell surface charge densities is minimized to control wax exudation and affinity, maintaining a uniform toner surface composition and charge distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a toner with oxazoline group-containing shell layer is used to improve charge retention, then heat-resistant storability and low-temperature fixability are improved, but back side contamination occurs after long-term storage in high-temperature, high-humidity environment
Solution Approach 1:
The invention changes the chemical composition parameters of the shell layer by introducing specific functional groups (carboxyl, hydroxyl, or amine groups) with controlled content ratios. This parameter modification allows the shell to maintain charge retention properties while gaining resistance to back side contamination through enhanced stability in humid environments.
Solution Approach 2:
The invention creates a composite shell structure combining oxazoline groups with additional functional groups (carboxyl, hydroxyl, or amine). This composite approach integrates the charge retention capability of oxazoline with the environmental stability of the additional functional groups, resolving the contradiction between charge retention and back side contamination resistance.
2Temperature
If a toner with diester compound as softening agent is used to improve low-temperature fixability, then low-temperature fixability and heat-resistant storability are improved, but electrostatic offset occurs after long-term storage in high-temperature, high-humidity environment
Solution Approach 1:
The invention modifies the shell layer composition by incorporating functional groups (carboxyl, hydroxyl, or amine) that regulate wax exudation behavior. This parameter change allows the toner to maintain low-temperature fixability while preventing excessive wax migration that causes electrostatic offset during long-term storage.
3Temperature
If wax exudation is increased to improve low-temperature fixability, then low-temperature fixability is improved, but toner aggregation and back side contamination occur during storage
Solution Approach 1:
The invention optimizes the functional group content ratio in the shell layer to precisely control wax exudation. This parameter optimization enables sufficient wax migration for low-temperature fixing while maintaining adequate shell integrity to prevent toner aggregation during storage.
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 effectively suppresses back side contamination and electrostatic offset, while maintaining excellent low-temperature fixability and heat-resistant stability, even after long-term storage in challenging environments.
Implementation Method 1
an absolute difference |DA−DB| between the surface charge density DA of the wax A and a surface charge density DB of the functional group B is not more than 0.0025
Data Source
AI summary
A toner comprising a toner particle comprising a core particle comprising a binder resin and a wax, and a shell formed on a surface of the core particle, wherein the wax comprises a wax A, the shell comprises a resin comprising a functional group B, the wax A has a surface charge density DA of −0.0080 to −0.0025, and an absolute difference |DA−DB| between the surface charge density DA of the wax A and a surface charge density DB of the functional group B is not more than 0.0025.