Resin-Coated Developing Roller Charge Control
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Solution Overview
Problem
Conventional developing devices in electrophotographic image forming apparatuses face issues with toner charge distribution, leading to image density deterioration and blurring due to partial charge-up of toner near the developing roller, especially during extended printing sessions, resulting in suboptimal image quality.
Innovation Solution
A developing device with a resin-coated developing roller that maintains an absolute charge difference of 6 μC/g or less between the upper and lower toner layers, preventing partial charge-up and ensuring uniform toner distribution, utilizing a magnetic roller and a silicone-modified urethane resin layer to manage toner charge effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional developing devices are used with extended printing, then productivity is maintained, but image quality deteriorates due to partial charge-up of toner near the developing roller
Solution Approach 1:
The invention changes the physical-chemical parameters of the developing roller surface by coating it with a resin layer having specific properties (volume resistivity of 10^5 to 10^7 Ω, specific glass transition temperature range). This parameter change controls the charge distribution of toner particles, preventing partial charge-up and maintaining image quality consistency during extended printing operations.
Solution Approach 2:
The invention uses a composite resin layer composed of specific polymer materials with controlled electrical and thermal properties. This composite material structure allows simultaneous control of toner charge distribution and adhesion, resolving the contradiction between maintaining image quality and enabling extended printing productivity.
2Productivity
If toner is conveyed by developing roller, then productivity is improved, but charge distribution becomes non-uniform leading to image density deterioration
Solution Approach 1:
By controlling the volume resistivity of the resin layer within 10^5 to 10^7 Ω and adjusting the glass transition temperature, the invention optimizes the electrical parameters that govern charge distribution. This allows uniform charge distribution across toner particles while maintaining efficient conveyance by the developing roller.
Solution Approach 2:
The resin layer acts as an intermediary between the developing roller and toner particles, mediating the charge transfer process. It provides a controlled interface that ensures uniform charge distribution to toner particles while maintaining effective conveyance, thus resolving the contradiction between productivity and charge uniformity.
3Manufacturing precision
If small-diameter toner particles are used, then image density should improve, but they accumulate on developing roller causing image blurring
Solution Approach 1:
The invention adjusts the surface electrical parameters of the developing roller through resin coating, creating optimal charge conditions that prevent accumulation of small-diameter toner particles. This allows small toner particles to be used for high image density while maintaining image clarity by preventing blurring from particle accumulation.
Solution Approach 2:
The invention converts the naturally high adhesive force of small-diameter toner particles to the developing roller into a beneficial effect by controlling charge distribution. The resin layer ensures that this adhesive force does not lead to problematic accumulation, allowing small particles to provide high image density without causing image blurring.
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 ensures high-quality image production over extended periods by preventing selective toner migration and utilizing small-diameter toners effectively, maintaining image density and preventing fog formation.
Implementation Method 1
a nonmagnetic mono-component developing device using a toner charged for example by corona charger, wherein at least the surface of the toner conveyer (developing roller) is made of a material containing a charge-controlling agent that is charged in the polarity same as that of the toner and that the frictional charge on the toner and that on the material for the toner conveyer have a particular relationship
Implementation Method 2
a magnetic roller carrying and conveying a two-component developer containing a toner and a carrier
Data Source
AI summary
A developing device is provided for visualizing an electrostatic latent image previously formed on the surface of an image carrier as a toner image. The developing device has a developing roller placed at a position facing the image carrier, carrying a toner on the surface thereof, conveying the toner and flying the conveyed toner onto the surface of the image carrier; and a resin layer coated on the surface of the developing roller. The absolute value of the difference in charge between the toners in the upper and lower layers of the toner layer formed on the developing roller as the toner carried on the developing roller is 6 μC/g or less.