Core-Shell Toner Resolving Fixation and Heat Storage Trade-offs
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Solution Overview
Problem
Conventional toner preparation methods, such as pulverization, face challenges in controlling toner particle size, shape, and properties like charging, fixation, fluidity, and storage ability, which are crucial for high-quality, high-reliability digital color printing. Polymerized toners offer better control but require improvements in low-temperature fixation and heat storage ability.
Innovation Solution
A toner with a core layer containing a low molecular weight amorphous polyester resin and a shell layer made of high and low molecular weight amorphous polyester resins, combined with a crystalline polyester resin, exhibiting specific rheological behavior and a controlled mixing ratio to achieve low-temperature fixability, fluidity, and heat storage ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pulverization method is used to prepare toner, then manufacturing process is simple, but particle size control and shape control are difficult
Solution Approach 1:
The patent changes the fundamental parameter of toner preparation from mechanical pulverization to chemical polymerization. By controlling polymerization conditions (monomer composition, initiator type, reaction temperature, solvent selection), the invention achieves precise control over particle size (3-9 μm), particle size distribution (GSD ≤ 1.3), and spherical shape (circularity ≥ 0.96), while maintaining manufacturing feasibility through batch polymerization processes.
Solution Approach 2:
The invention uses composite material systems in the polymerization process, combining multiple monomers (styrene, acrylic acid, methyl acrylate) with initiators and solvents to create toner particles with specific properties. The core-shell structure formed through polymerization allows different functional components to be distributed in specific regions, achieving both manufacturing control and performance requirements.
2Temperature
If polymerized toner with low Tg binder resin is used, then low-temperature fixation is improved, but heat storage ability and gloss are insufficient
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains low Tg binder resin (acrylic acid-methyl acrylate copolymer, Tg = -20°C to 0°C) for low-temperature fixation, while the shell contains high Tg binder resin (styrene-acrylic acid copolymer, Tg = 50°C to 80°C) for heat storage ability and gloss. This spatial differentiation of resin properties allows simultaneous achievement of low-temperature fixation and adequate heat storage.
Solution Approach 2:
The invention combines binder resins with different glass transition temperatures in a composite core-shell structure. The low Tg resin in the core provides low-temperature fixation capability, while the high Tg resin in the shell provides heat storage ability and surface gloss, resolving the contradiction between fixation temperature and heat storage reliability.
3Ease of operation
If wax is added to improve fluidity, then fluidity is improved, but heat storage ability decreases due to plasticizing effect
Solution Approach 1:
The patent incorporates releasing agents (waxes such as polyethylene wax, polypropylene wax, or ester-based waxes) in controlled amounts (0.1-5 wt%) within the toner particle structure. These waxes provide fluidity improvement through lubrication effects during the fixing process, while the controlled quantity and distribution prevent excessive plasticizing that would reduce heat storage ability. The waxes also aid in releasing the fixed image from the fixing roller.
Data Source
AI summary
A toner for developing an electrostatic charge image includes a core layer including a first binder resin, a colorant and a releasing agent; and a shell layer coating the core layer and including a second binder resin. The first binder resin of the core layer includes a low molecular weight amorphous polyester resin having a weight-average molecular weight of about 6000 g/mol to about 20000 g/mol, a high molecular weight amorphous polyester resin having a weight-average molecular weight of about 25000 g/mol to about 100000 g/mol, and a crystalline polyester resin having a weight-average molecular weight of about 8000 g/mol to about 30000 g/mol. The second binder resin of the shell layer includes the low and high molecular weight amorphous polyester resins.