Toner Core-Shell Structure for Durability and Fixability
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Solution Overview
Problem
Existing toners face challenges in maintaining long-term durability and low-temperature fixability, particularly on rough paper, due to the migration and embedding of external additives, which affect image density and fixability over time.
Innovation Solution
A toner composition with inorganic fine particles and an external additive where the external additive has a specific particle size and adhesion index, ensuring strong adherence to the toner surface and minimal migration, thereby maintaining image density and fixability even after long-term use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large amounts of inorganic fine particles are externally added to improve long-term durability, then image density stability is improved, but low-temperature fixability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where inorganic fine particles are concentrated in the core region while the shell layer has different composition and properties. This spatial differentiation allows the core to provide durability while the shell maintains low-temperature fixability, resolving the contradiction between these two opposing requirements.
Solution Approach 2:
The patent uses composite materials by combining organic binder resin with inorganic fine particles in a specific core-shell configuration. This composite structure allows the inorganic core to provide long-term durability and image density stability while the organic shell layer preserves low-temperature fixability, thus resolving the technical contradiction.
2Reliability
If external additives are added to improve durability, then chargeability is improved, but embedding of external additives occurs over time causing image density to decrease
Solution Approach 1:
The patent applies preliminary action by pre-embedding inorganic fine particles within the toner particle core before the toner is used in the developing device. This preliminary incorporation prevents the external additives from migrating and embedding onto the toner surface during use, thereby maintaining image density while providing durability.
Solution Approach 2:
The patent uses the nesting principle by placing inorganic fine particles inside the core of the toner particle, which is itself surrounded by an organic shell. This nested core-shell structure protects the inorganic particles from migrating to the surface, preventing embedding while maintaining their durability-enhancing function.
3Reliability
If spacer particles are used to suppress embedding, then particle size is increased, but spacer particles migrate from toner surface over time
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of placing spacer particles on the outer surface of the toner, the inorganic fine particles are placed in the core. This inverted core-shell structure prevents migration while maintaining the spacer function, resolving the contradiction between embedding suppression and positional stability.
Data Source
Figure 1~1(c)
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AI summary
A toner comprising an external additive and a toner particle including a binder resin, a colorant and inorganic fine particles A, wherein the external additive contains an external additive B, a number average particle diameter of primary particles of the external additive B is 30 to 200 nm, an adhesion index of the external additive B to the toner particle is 0.00 to 3.00, a number average particle diameter of primary particles of the inorganic fine particles A is greater than that of the external additive B, and in SEM observations of the toner under specific condiiton, the number of particles (Na) of the external additive B in a 2 µm square region of the toner surface and the number of particles (Nb) of the external additive B observed in a state of overlapping with the inorganic fine particles A in the region satisfy Nb/Na of 0.20 or more.