Crystalline Polyester Toner for Charge Stability
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Solution Overview
Problem
In image forming apparatuses, low-temperature fixable toners experience charge reduction and fogging issues due to the embedding of external additives into toner particles, especially in long-term operation at temperatures around 40° C. to 50° C.
Innovation Solution
A toner configuration with toner particles made of crystalline polyester resin and wax, and external additives comprising a first additive with a primary particle size of 10 nm to 35 nm and a second additive with a size of 38 nm to 120 nm, achieving a loose bulk density of 0.3 g/cm3 to 0.35 g/cm3 and a stress relaxation ratio of 27% or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external additive is added to low-temperature fixable toner particles, then low-temperature fixability is improved, but external additive embeds into toner particles during long-term operation causing charge reduction and fogging
Solution Approach 1:
The patent changes the physical and chemical parameters of the toner particle surface by controlling the softening point of the binder resin (80°C to 100°C) and the glass transition temperature (Tg) within 0°C to 50°C. This parameter optimization creates a surface that maintains external additives during long-term operation while preserving low-temperature fixability, preventing charge reduction and fogging
Solution Approach 2:
The patent uses a composite binder resin system combining crystalline polyester resin and amorphous polyester resin with specific Tg ranges. This composite material structure provides both the low-temperature fixing capability and the surface stability needed to prevent external additive embedding, resolving the contradiction between fixability and charge stability
2Temperature
If external additive is added to increase surface area coverage, then low-temperature fixability is improved, but external additive embeds into toner particles causing image quality degradation
Solution Approach 1:
The patent optimizes the glass transition temperature (Tg) of the binder resin to be within 0°C to 50°C and controls the softening point between 80°C to 100°C. These parameter changes create a surface morphology that securely holds external additives, preventing embedding during operation and maintaining image quality while achieving low-temperature fixability
3Reliability
If stress relaxation ratio is increased to suppress external additive embedding, then charge stability is improved, but toner compression characteristics may be affected
Solution Approach 1:
The patent carefully balances the glass transition temperature (Tg) and softening point parameters to achieve a stress relaxation ratio of 20% or more while maintaining appropriate compression characteristics. This parameter optimization ensures that the toner surface relaxes stress to prevent external additive embedding without compromising the structural integrity needed for proper toner compression and transfer
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 solution effectively suppresses charge reduction and fogging in image forming apparatuses during long-term operation without compromising low-temperature fixability.
Implementation Method 1
the toner particles include a crystalline polyester resin and a wax and have an apparent viscosity at 90° C. in a range from 100000 Pa*s to 200000 Pa*s
Implementation Method 2
an external additive adhering to the surface of the toner particles
Implementation Method 3
When the toner is compressed at 50° C. and 1.2 N/cm2, a compression degree of the toner is 50% or less, and a stress relaxation ratio of the toner is 27% or more
Data Source
AI summary
A toner including toner particles and an external additive adhering to a surface of the toner particles has the following configuration. The toner particles include a crystalline polyester resin and a wax and have an apparent viscosity at 90° C. in a range from 100000 Pa*s to 200000 Pa*s. The external additive includes a first external additive and a second external additive having an average primary particle size larger than that of the first external additive. A loose bulk density of the toner is in a range from 0.3 g/cm3 to 0.35 g/cm3. When the toner is compressed at 50° C. and 1.2 N/cm2, a compression degree of the toner is 50% or less, and a stress relaxation ratio of the toner is 27% or more.