Contact Developing Toner Reduces Drum Contamination
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Solution Overview
Problem
In electrophotographic image forming, the use of spherical toners with releasing agents leads to contamination of the electrostatic latent image bearing member due to migration and adhesion, resulting in poor cleanability and image quality, especially in contact type one-component developing systems.
Innovation Solution
An image forming method with a contact type one-component developing system that controls the contact pressure between the electrostatic latent image bearing member and the toner bearing member within a specific range (2.0 × 10^4 to 7.5 × 10^4 N/m^2) and uses a toner with a binder resin and releasing agent, where the extracted amount of releasing agent is between 10 mg/g to 25 mg/g, measured by extraction with hexane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of releasing agent is added to the toner to improve fixability and prevent recording medium winding, then the electrostatic latent image bearing member becomes contaminated due to migration and adhesion of the releasing agent, deteriorating cleanability
Solution Approach 1:
The invention changes the physical state parameters of the releasing agent by controlling its crystallinity (specifically making it amorphous or having low crystallinity) and adjusting its glass transition temperature to be within a specific range (20°C to 80°C). This parameter modification prevents the releasing agent from migrating and adhering to the electrostatic latent image bearing member, thereby resolving the contamination issue while maintaining adequate fixability.
Solution Approach 2:
The invention creates a composite toner system where the releasing agent is combined with specific binder resins (polyester resin with specific glass transition temperature and hydroxyl value ranges) and external additives (silica with specific surface treatment). This composite structure controls the releasing agent's behavior and prevents contamination while maintaining fixability.
2Manufacturing precision
If spherical toner is used to faithfully reproduce electrostatic latent image, then the toner can be spheroidized and small-sized, but cleanability deteriorates due to the sphericity
Solution Approach 1:
The invention modifies the surface parameters of the spherical toner by controlling the glass transition temperature of the binder resin (30°C to 70°C) and the crystallinity of the releasing agent (amorphous or low crystallinity). These parameter changes reduce the adhesion strength between the spherical toner and the electrostatic latent image bearing member, improving cleanability while maintaining the spherical shape needed for faithful image reproduction.
3Productivity
If contact type one-component developing is used to respond to small-sizing demand, then the toner bearing member rotates faster causing strong rubbing stress, but this strongly adheres toner to the electrostatic latent image bearing member and causes contamination
Solution Approach 1:
The invention changes the friction and adhesion parameters at the interface between the toner and electrostatic latent image bearing member by controlling the glass transition temperature of the binder resin (30°C to 70°C) and the surface properties of external additives (silica with 50-200 m²/g specific surface area). These parameter modifications reduce the strong adhesion caused by rubbing stress, preventing contamination while maintaining the high-speed rotating capability needed for small-sizing.
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 method prevents contamination of the electrostatic latent image bearing member, reduces the occurrence of white voids, and maintains high image graininess over time, even with a large amount of releasing agent, enhancing the overall quality and longevity of the image forming process.
Implementation Method 1
an electrostatic latent image is formed by charging and exposing a surface of an electrostatic latent image bearing member
Implementation Method 2
a surface of an electrostatic latent image bearing member is in contact with a surface of a toner bearing member, and the toner bearing member rotates faster than the electrostatic latent image bearing member, which causes strong rubbing stress
Implementation Method 3
the toner image is transferred onto a recording medium, followed by applying heat and pressure at a fixing step to thereby fix the toner image on the recording medium
Implementation Method 4
During fixing, the recording medium may be wound around a fixing roller, which is problematic. This problem has been solved by adding a releasing agent into a toner
Implementation Method 5
The toner remaining on the electrostatic latent image bearing member without being transferred is removed by, for example, a cleaning blade
Data Source
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AI summary
An image forming apparatus, including: an electrostatic latent image bearing member; an electrostatic latent image forming unit configured to form an electrostatic latent image on the electrostatic latent image bearing member; and a developing unit containing a toner and configured to develop the electrostatic latent image with the toner to thereby form a visible image, wherein the developing unit is a contact type one-component developing unit which includes a toner bearing member being in contact with the electrostatic latent image bearing member, wherein a contact pressure between the electrostatic latent image bearing member and the toner bearing member is 2.0 × 104 N/m2 to 7.5 × 104 N/m2, wherein the toner contains a binder resin and a releasing agent, and wherein an extracted amount of the releasing agent extracted with hexane from the toner is 10 mg/g to 25 mg/g.