Positively Chargeable Toner Coating for Low-UFP Fixing
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Solution Overview
Problem
The issue of ultrafine particles (UFPs) generation due to thermal decomposition of binder resin and release agent components in toners with lower melting points during the fixing process in electrophotographic methods, leading to poor charge stability and transfer properties.
Innovation Solution
A positively chargeable toner with specific SP value differences (ΔSP1 and ΔSP2) between the release agent and resin particle, and binder resin and resin particle, along with a resin particle hardness of 1 µN, to enhance fixation and suppress thermal decomposition, improving charge stability and transfer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If toners with lower melting points are used, then fixing efficiency is improved, but thermal decomposition of binder resin and release agent occurs causing UFP generation
Solution Approach 1:
The patent introduces a shell layer as an intermediary between the toner base particle and the external environment. This shell layer, composed of specific resin materials with controlled thickness (5-50 nm), acts as a protective barrier that prevents direct thermal decomposition of the binder resin and release agent during fixing, thereby suppressing UFP generation while maintaining the low melting point characteristics for efficient fixing
Solution Approach 2:
The patent creates a composite structure consisting of a toner base particle surrounded by a shell layer. The shell layer is formed by coating the toner base particle with a resin composition that has different thermal properties than the core materials. This composite structure allows the toner to maintain low melting point for efficient fixing while the shell layer provides thermal stability to prevent decomposition and UFP generation
2Ease of operation
If release agent content is increased to improve release properties, then transfer properties are improved, but thermal decomposition increases leading to more UFP generation
Solution Approach 1:
The shell layer serves as an intermediary protective barrier that encloses the release agent within the toner base particle. This shell prevents direct exposure and thermal decomposition of the release agent during the fixing process, allowing the toner to maintain good release and transfer properties without the release agent decomposing and generating UFPs
3Productivity
If toner particles are heated during fixing, then image fixation is achieved, but binder resin and release agent undergo thermal decomposition
Solution Approach 1:
The shell layer is applied beforehand to the toner base particle as a protective cushioning layer. This shell, composed of thermally stable resin materials, absorbs and distributes the thermal stress during fixing, preventing direct thermal decomposition of the binder resin and release agent in the toner base particle while still allowing sufficient heat transfer for image fixation
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
Reduces UFP generation, enhances toner durability, and improves drum-cleaning properties by stabilizing charge and preventing resin particle release, ensuring high-quality image formation.
Implementation Method 1
The external additive attaches to the surface of the toner base particle
Implementation Method 2
a surface of an electrostatic latent image carrier is electrostatically charged by corona discharge or the like
Data Source
Figure 1
AI summary
A positively chargeable toner (101) includes toner particles each including a toner base particle (102) and an external additive (103). The toner base particle (102) contains, at least, a binder resin, a colorant, and a release agent. The external additive (103) includes an inorganic particle (104) and a resin particle (105). The resin particle (105) contains a cationic surfactant, has a volume average particle size of 40 nm or more but 110 nm or less, and has a hardness of 1 µN or higher when measured with a probe displacement of 40 nm. Where ΔSP1 is a difference between an SP value of the release agent and an SP value of the resin particle (105), and ΔSP2 is a difference between an SP value of the binder resin and the SP value of the resin particle (105), 0.8 ≦ ΔSP1 ≦ 1.1 (cal/cm3)1/2 and 1.3 ≦ ΔSP2 ≦ 1.6 (cal/cm3)1/2 are satisfied.