Toner Eccentricity and Skewness for Offset Prevention
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Solution Overview
Problem
In image forming apparatuses, the occurrence of offset (where a portion of the fixed image adheres to the fixing device) is a persistent issue due to uneven nip pressure and insufficient release agent distribution, particularly during double-sided printing, leading to detachment problems and uneven gloss variations.
Innovation Solution
The use of toner particles with a sea and island structure, where the release agent is distributed with a maximum frequent value of eccentricity B between 0.75 and 0.95 and skewness between −1.10 and −0.50, ensuring adequate release agent bleeding even at low nip pressures, thereby enhancing detachability and preventing offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional toner with uniform release agent distribution is used, then manufacturing is simpler, but offset occurs during fixing due to insufficient release agent at low nip pressure areas
Solution Approach 1:
The release agent is distributed non-uniformly within the toner particle, with higher concentration at the peripheral portion compared to the internal portion. This local quality variation ensures that release agent is available at the toner surface where contact with the fixing device occurs, improving detachability and preventing offset during fixing operations.
2Reliability
If moving unit is added to move first member or second member, then offset is prevented during double-sided printing, but device complexity increases
Solution Approach 1:
The fixing device incorporates a moving unit that enables the first member or second member to move in a direction intersecting with the transport direction of the recording medium. This dynamic adjustment allows the nip position to be shifted, preventing offset during double-sided printing by ensuring proper positioning of the recording medium as it passes through the fixing nip.
3Reliability
If release agent content is increased to prevent offset, then detachability improves, but toner storage stability deteriorates
Solution Approach 1:
The release agent is distributed non-uniformly within the toner particle, with higher concentration at the peripheral portion and lower concentration at the internal portion. This localized distribution provides sufficient release agent at the toner surface for improved detachability while maintaining lower overall release agent content, thereby preserving toner storage stability and preventing aggregation during storage.
4Strength
If nip pressure is increased to improve fixing quality, then fixing strength improves, but offset increases due to reduced release agent effectiveness
Solution Approach 1:
The release agent is concentrated at the peripheral portion of the toner particle, ensuring availability at the contact surface with the fixing device. This localized concentration maintains effective detachability even under high nip pressure conditions, allowing high fixing strength to be achieved without increasing offset, as the release agent remains accessible at the toner surface despite compression.
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
This configuration effectively prevents offset by ensuring sufficient release agent distribution across the toner surface, maintaining high detachability during both single and double-sided printing, and reducing uneven gloss issues.
Implementation Method 1
ensuring adequate release agent bleeding even at low nip pressures
Implementation Method 2
fixes the toner image transferred on the surface of the recording medium while transporting the recording medium
Data Source
AI summary
An image forming apparatus includes a fixing unit that fixes a toner image on a surface of a recording medium while transporting the recording medium with a contact portion of a first member and a second member, and a moving unit that moves at least one of the first member and the second member toward a direction intersecting with a transport direction of the recording medium, wherein a toner has a sea and island structure of a sea portion containing a binder resin and an island portion containing a release agent, a maximum frequent value in distribution of the eccentricity B of the island portion containing the release agent is in a range of from 0.75 to 0.95, a skewness in the distribution of the eccentricity B is from −1.10 to −0.50, and the eccentricity B is defined in the specification.