Core-Shell Toner with Segmented Polyester Resins
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Solution Overview
Problem
Toner formulations face challenges in achieving low-temperature fixability while maintaining heat-resistant storage stability and durability, particularly during stress conditions such as stirring in the developing device, due to issues like blocking and pulverization.
Innovation Solution
A toner with a core-shell structure comprising a binder resin with crystalline and non-crystalline polyester resins, where the mass ratio of crystalline to non-crystalline polyester resin ranges from 5/95 to 75/25, and a hardness ratio of the shell to core between 1.05 and 1.50, ensuring optimal durability and fixability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If toners are formulated with low-softening-point resin and wax to achieve low-temperature fixability, then low-temperature fixability is improved, but heat resistant storage stability deteriorates due to blocking phenomenon
Solution Approach 1:
The toner is divided into core and shell segments with distinct functional compositions. The core contains low-softening-point resin for low-temperature fixability, while the shell contains high-melting-point crystalline polyester for heat resistance and blocking prevention. This segmentation allows each part to perform its specialized function without compromising the other.
Solution Approach 2:
The toner employs a composite structure combining different resin materials with complementary properties. The core uses soft resin (low Tg) for ease of fusion at low temperatures, while the shell uses hard crystalline polyester (high Tm) for thermal stability and blocking resistance. The composite structure synergistically achieves both low-temperature fixability and heat resistant storage stability.
2Reliability
If toners are encapsulated to incorporate crystalline polyester for heat resistant storage stability, then heat resistant storage stability is improved, but durability deteriorates due to soft core pulverization under stress
Solution Approach 1:
The toner structure is segmented into a soft core and a hard shell. The core contains the crystalline polyester for heat resistance, while the shell provides a protective hardened layer. This segmentation allows the core to maintain its heat-resistant properties while the shell protects it from mechanical stress and pulverization during development.
Solution Approach 2:
The shell acts as a protective film or coating over the soft core. This shell layer is sufficiently thin to allow the toner to maintain its functional properties but thick enough to provide mechanical protection against stress, stirring, and pulverization during the development process.
3Temperature
If toners are formulated with specific deformation characteristics (1.0-3.0 μm at 1 mN, 3.0-5.0 μm at 5 mN) and surface roughness (0.02-0.40 μm Ra) for low-temperature fixability and heat resistant storage stability, then low-temperature fixability and heat resistant storage stability are improved, but durability under stress in the developing device deteriorates
Solution Approach 1:
The toner is segmented into core and shell regions with different mechanical properties. The core is designed with specific deformation characteristics for low-temperature fixability, while the shell is designed with higher hardness and strength for durability under stress. This segmentation allows the toner to exhibit both softness for easy fixing and hardness for stress resistance.
Data Source
AI summary
A toner including a binder resin and a colorant, the toner having a core-shell structure containing a core and a shell, wherein the binder resin contains a crystalline polyester resin and a non-crystalline polyester resin, wherein a ratio (A/B) of a mass (A) of the crystalline polyester resin to a mass (B) of the non-crystalline polyester resin is 5/95 to 75/25, and wherein a ratio (Ds/Dc) of a hardness (Ds) of the shell to hardness (Dc) of the core is 1.05 to 1.50 where the hardnesses (Ds) and (Dc) are measured with a scanning probe microscope.