Core-Shell Toner Particles with Segmented Shell Layers
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Solution Overview
Problem
Existing electrostatic latent image developing toners face challenges in achieving optimal low-temperature fixability and high-temperature preservability while maintaining image density and preventing filming, which are crucial for reliable image formation in electrophotographic processes.
Innovation Solution
The toner particles are designed with a core-shell structure, where the first shell particles and second shell particles are strategically attached to the toner core, with specific coverage and solubility parameter relationships to enhance adhesion strength and prevent separation, thereby improving fixability and preservability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shell particles are solidified on the toner core surface through partial phase dissolution, then adhesion strength is improved, but filming occurs and image density deteriorates over time
Solution Approach 1:
The shell layer is divided into multiple discrete shell particles rather than forming a continuous solidified layer. This segmentation prevents the formation of large continuous films while maintaining localized adhesion points between the toner core and shell particles, resolving the contradiction between adhesion strength and filming prevention
Solution Approach 2:
The shell particles are distributed non-uniformly on the toner core surface with varying coverage, creating different local properties. Some regions have higher shell particle concentration for adhesion, while other regions maintain lower concentration to prevent filming, allowing simultaneous achievement of both adhesion strength and filming resistance
2Temperature
If the shell layer coverage is increased to improve low-temperature fixability, then fixability is enhanced, but high-temperature preservability deteriorates
Solution Approach 1:
The invention optimizes the shell layer coverage within a specific range (10-40 wt%) rather than maximizing it. This parameter optimization allows sufficient coverage for low-temperature fixability while preventing excessive coverage that would cause high-temperature preservability issues, achieving a balance between the two opposing requirements
3Manufacturing precision
If shell particles are attached to toner core through wet mixing, then coverage is improved, but production complexity increases
Solution Approach 1:
The invention extracts and eliminates the wet mixing step from the production process, using only dry mixing methods. This simplifies the production process and reduces equipment complexity while still achieving adequate shell layer coverage through optimized dry mixing parameters and shell particle characteristics
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
This configuration ensures both low-temperature fixability and high-temperature preservability, maintaining image density over a long period and reducing filming issues, as the toner particles adhere effectively to the toner core and transfer media.
Implementation Method 1
The first shell particles and second shell particles are strategically attached to the toner core, with specific coverage and solubility parameter relationships to enhance adhesion strength
Implementation Method 2
A solubility parameter (SPT) of the binder resin contained in the toner core, a solubility parameter (SPF) of the binder resin contained in the first shell particles, and a solubility parameter (SPS) of the binder resin contained in the second shell particles satisfy the following expression (3)
Data Source
Figure 1
Figure 2
AI summary
An electrostatic latent image developing toner includes a plurality of toner particles each including a toner core (11) and a shell layer (12). The shell layer includes a plurality of first shell particles (12a) and a plurality of second shell particles (12b). The first shell particles cover the toner core at a coverage of at least 25% and no greater than 50%. The second shell particles additionally cover the toner cores at a coverage of at least 5% and no greater than 30%. An SP value of the toner core is greater than an SP value of the first shell particles. The SP value of the first shell particles is greater than an SP value of the second shell particles.