Toner Viscoelasticity for Offset-Free Multistage Fixing
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Solution Overview
Problem
In multistage fixing-type image forming apparatuses, the repeated contact of toner with heating and pressurizing members during the fixing process leads to enhanced adhesive forces, causing toner offset and reducing image gloss, especially as the thickness of the recording medium increases.
Innovation Solution
The use of a toner containing a binder resin with a crystalline polyester resin, a colorant, and a release agent, where the toner's mechanical loss tangent is within specific ranges (2≤tan δP1≤2.5 and 2≤tan δP2≤2.3) to prevent softening and adhesive forces, ensuring effective fixation without offset and maintaining high gloss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multistage fixing is performed with repeated contact of toner with heating and pressurizing members, then fixing reliability is improved, but toner offset occurs and image gloss deteriorates
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder resin, specifically controlling the glass transition temperature (Tg) to be 80°C or higher and the complex modulus to be 1×10^9 Pa or higher at the fixing temperature. These parameter changes modify the toner's viscoelastic properties to resist adhesive forces during multistage fixing, preventing toner offset while maintaining fixing reliability.
Solution Approach 2:
The patent uses a composite binder resin system combining crystalline polyester resin and amorphous polyester resin in specific proportions (crystalline: 30-70 wt%, amorphous: 30-70 wt%). This composite structure provides both the high glass transition temperature needed to prevent offset and the necessary melting characteristics for effective fixing, resolving the contradiction between fixing reliability and toner offset prevention.
2Reliability
If multistage fixing is performed with repeated contact, then fixing completeness is improved, but adhesive forces increase causing toner to adhere to heating member
Solution Approach 1:
The patent modifies the adhesive force characteristics by controlling the binder resin's glass transition temperature to be 80°C or higher and complex modulus to be 1×10^9 Pa or higher. These parameter changes ensure that even with repeated contact during multistage fixing, the toner maintains sufficient resistance to adhesive forces while achieving complete fixing.
Solution Approach 2:
The patent converts the potentially harmful repeated contact and adhesive forces into a beneficial effect by designing the binder resin with specific viscoelastic properties. The high glass transition temperature and complex modulus cause the toner to exhibit elastic recovery behavior during repeated pressing, allowing it to maintain fixation while resisting permanent adhesion to the heating member.
3Manufacturing precision
If thicker recording media are used, then image quality is improved, but toner offset increases due to enhanced adhesive forces
Solution Approach 1:
The patent addresses the toner offset issue with thicker media by changing the binder resin parameters: glass transition temperature of 80°C or higher and complex modulus of 1×10^9 Pa or higher. These changes provide the toner with sufficient mechanical strength and elastic recovery capability to resist offset even when fixed on thicker recording media that require more substantial fixing pressure.
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 prevents toner offset and enhances image gloss by controlling the toner's viscoelastic properties, allowing for successful multistage fixing without adhering to the heating and pressurizing member, even with thicker recording media.
Implementation Method 1
a fixing unit that includes a heating and pressurizing member, and fixes the toner image by performing the operation of heating and pressurizing on the toner image on the recording medium twice or more times with the heating and pressurizing member
Implementation Method 2
the toner contains a binder resin containing a crystalline polyester resin, a colorant, and a release agent, and an external additive, and satisfies the following Expression (1): 2≤tan δP1≤2.5 wherein tan δP1 represents a maximum value of a mechanical loss tangent existing in a range where a complex elastic modulus is from 1×106 Pa to 1×108 Pa
Data Source
AI summary
An image forming apparatus includes a fixing unit that includes a heating and pressurizing member, and fixes the toner image by performing the operation of heating and pressurizing on the toner image on a recording medium twice or more times with the heating and pressurizing member, wherein the toner contains a toner particle which contains a binder resin containing a crystalline polyester resin, a colorant, and a release agent, and an external additive, and satisfies Expression: 2≤tan δP1≤2.5, wherein tan δP1 represents a maximum value of a mechanical loss tangent existing in a range where a complex elastic modulus is from 1×106 Pa to 1×108 Pa, which is measured at an angular frequency of 6.28 rad/sec and a distortion amount of 0.3%.