Crystalline Polyester Toner for Offset Suppression
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Solution Overview
Problem
Toner used in electrophotographic processes faces challenges with back end offset in high-temperature, high-humidity environments and heat cycling, leading to reduced image quality and increased fogging due to crystalline polyester's compatibility with the binder resin, which affects charging stability and melting behavior.
Innovation Solution
A toner formulation with a specific DSC curve profile, containing a binder resin, colorant, wax, and crystalline polyester, where two or more peak tops for crystallization peaks are present between 40°C to 80°C, and a specific ratio of exothermic quantities (ΔH(100)/ΔH(0.5) between 2.0 and 6.0, enhancing crystallinity and interaction between crystalline substances for improved fixing performance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If crystalline polyester is used to improve low-temperature fixability, then fixing performance is improved, but charging stability deteriorates due to compatibilization with binder resin
Solution Approach 1:
The invention changes the physical and chemical parameters of the crystalline polyester by controlling its degree of crystallinity (making it 50% or higher) and selecting specific melting points (60-90°C). This parameter optimization allows the polyester to provide low-temperature fixability while reducing excessive compatibilization with the binder resin, thereby maintaining charging stability.
Solution Approach 2:
The invention creates a composite toner system by carefully selecting the combination of crystalline polyester and binder resin types. Specific combinations are chosen where the polyester and resin have complementary properties that minimize unwanted compatibilization while maintaining the desired fixing performance and charging characteristics.
2Temperature
If crystalline polyester compatibilizes into binder resin, then low-temperature fixability is improved, but image quality deteriorates due to fogging
Solution Approach 1:
By optimizing the degree of crystallinity to 50% or higher and selecting specific melting points, the invention reduces excessive migration of polyester to the toner surface. This parameter control prevents the formation of fogging while maintaining effective low-temperature fixability.
3Reliability
If amount of crystalline polyester is reduced to improve charging stability, then charging stability is improved, but fixing performance deteriorates
Solution Approach 1:
Instead of simply reducing the amount of crystalline polyester, the invention changes its key parameters: increasing the degree of crystallinity to 50% or higher and selecting specific melting points (60-90°C). This allows maintaining effective fixing performance with optimized polyester characteristics that cause less harm to charging stability.
4Stability of the object's composition
If degree of crystallinity is enhanced through cooling rate control, then crystallinity is improved, but manufacturing complexity increases
Solution Approach 1:
The invention specifies target ranges for degree of crystallinity (50% or higher) and melting point (60-90°C) that can be achieved through conventional cooling processes. By setting realistic and achievable parameter targets, the invention maintains manufacturing simplicity while ensuring the required crystallinity level is reached.
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
The toner suppresses back end offset and maintains high image quality even in high-temperature, high-humidity conditions and after heat cycling, with enhanced fogging inhibition and improved charging stability.
Implementation Method 1
two or more peak tops for crystallization peaks are present in a temperature range from 40° C. to 80° C. in a first DSC curve
Implementation Method 2
the use of a crystalline polyester that induces the melt deformation of the toner particle by rapidly compatibilizing into the binder resin
Data Source
AI summary
Provided is a toner having a toner particle that contains a binder resin, a colorant, a wax, and a crystalline polyester, wherein two or more peak tops for crystallization peaks are present in a temperature range from 40° C. to 80° C. in a first DSC curve obtained by a process or cooling the toner from 100° C. to 20° C. at 0.5° C./min, and using ΔH(0.5) for the exothermic quantity for the peak on the lowest temperature side of these crystallization peaks and using ΔH(100) for the exothermic quantity of the crystallization peak on the lowest temperature side in a second DSC curve obtained by a process of cooling the toner from 100° C. to 20° C. at 100° C./min, the ratio [ΔH(100)/ΔH(0.5)] is at least 2.0 and not more than 6.0.