Core-Shell Toner Particles with Amorphous Polyester Shell
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Solution Overview
Problem
Polyester EA ultra low melt toners exhibit poor charging characteristics and blocking due to crystalline resin migration and plasticization of amorphous resin, which existing core-shell approaches have not adequately addressed.
Innovation Solution
The development of toner particles with a core-shell configuration, where the shell comprises a high molecular weight amorphous polyester resin with a weight average molecular weight of 10,000 to 5,000,000, encapsulating a crystalline or amorphous resin core, improving charging and blocking properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If crystalline polyester resin is used in toner composition, then melting point is controlled, but crystalline resin migrates to surface during coalescence causing poor charging characteristics
Solution Approach 1:
The toner is divided into core and shell segments, with crystalline resin confined to the core and amorphous resin forming the shell. This segmentation prevents crystalline resin migration to the surface while maintaining the melting point control benefits of crystalline components.
Solution Approach 2:
Different regions of the toner particle are assigned different resin compositions: the core contains crystalline polyester resin for melting point control, while the shell contains amorphous polyester resin to prevent surface migration and improve charging characteristics. Each region has optimized local quality for its specific function.
2Temperature
If crystalline resin is used to control melting point, then melting behavior is improved, but amorphous resin is plasticized resulting in poor blocking
Solution Approach 1:
The toner structure is segmented into core and shell, isolating the plasticization effect of crystalline resin to the core region. The amorphous shell remains unaffected, maintaining its glass transition properties and blocking resistance.
Solution Approach 2:
The shell region is specifically designed with amorphous polyester resin having controlled glass transition temperature to provide blocking resistance, while the core region handles melting behavior. This local quality differentiation prevents the plasticization of amorphous resin throughout the entire particle.
3Reliability
If amorphous resin is used in shell, then charging characteristics improve, but glass transition temperature is low causing blocking
Solution Approach 1:
The glass transition temperature of the amorphous polyester resin in the shell is specifically adjusted to a range of 40°C to 80°C. This parameter optimization allows the shell to maintain charging characteristics while providing sufficient thermal resistance against blocking.
Solution Approach 2:
The toner uses a composite resin system combining crystalline polyester in the core with amorphous polyester in the shell. The crystalline component provides melting point control while the amorphous component with optimized Tg provides charging characteristics and blocking resistance, creating synergistic performance.
Data Source
AI summary
Toner particles are provided which may, in embodiments, include a core possessing at least one polyester resin in combination with a colorant, optional wax, and optional other additives, and a shell over the core including a high molecular weight amorphous polyester resin. The high molecular weight amorphous polyester resin in the shell may prevent any crystalline polyester resin in the core from migrating to the toner surface.