Developing Roller Resin Layer for Charge Leakage Suppression
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Solution Overview
Problem
Existing image forming apparatuses using a cleaner-less system face issues with irregular-shaped toner charge failure, leading to fogging and image density unevenness, particularly under high temperature and humidity conditions, due to charge leakage and insufficient triboelectric charge imparting.
Innovation Solution
A process cartridge with a developing roller having a conductive outer surface and a resin layer containing polyurethane with a polycarbonate structure, equipped with a metal film and surface particles, ensures effective triboelectric charge imparting by maintaining high impedance and controlled surface potential, preventing charge leakage and excess charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the developing roller uses a conventional low-resistance structure to facilitate charge transfer, then charge transfer efficiency is improved, but charge leakage increases causing fogging and image density unevenness
Solution Approach 1:
The patent changes the electrical resistance parameter of the developing roller surface by introducing a polycarbonate structure into the resin layer, achieving high resistance (1.00×10^6Ω or more) to prevent charge leakage while maintaining reliable image formation without fogging
Solution Approach 2:
The patent uses a composite resin layer containing both polycarbonate structure and polyurethane components, combining the high resistance properties of polycarbonate with the desirable surface characteristics of polyurethane to achieve both charge isolation and effective triboelectric charging
2Object-generated harmful factors
If the developing roller resistance is increased to prevent charge leakage, then fogging is suppressed, but triboelectric charge imparting to irregular-shaped toner becomes insufficient
Solution Approach 1:
The patent creates local quality differentiation by having the polycarbonate structure concentrated in the resin layer to provide high resistance, while the surface particles and metal film provide localized conductive pathways that enable effective triboelectric charging of irregular-shaped toner particles at the contact interface
Solution Approach 2:
The patent optimizes the impedance parameter to be 1.00×10^6Ω or more at specific frequencies, creating a frequency-dependent resistance characteristic that blocks DC charge leakage while allowing AC triboelectric charging to occur effectively during the dynamic contact between developing roller and toner
3Device complexity
If a cleaner-less system is used to reduce size and eliminate waste toner, then device size is reduced and waste is eliminated, but foreign substances accumulate causing charge failure
Solution Approach 1:
The patent adopts a disposable process cartridge design where the developing roller with its specialized high-resistance coating is intended for limited use cycles. The roller maintains reliable toner charging performance throughout its service life without requiring cleaning mechanisms, and is replaced rather than maintained, eliminating the need for complex cleaning devices while ensuring consistent image quality
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 imparts triboelectric charge to irregular-shaped toner, suppressing fogging and image density unevenness, ensuring stable image quality under varying environmental conditions.
Implementation Method 1
the toner passing through the contact portion between the developing roller and the developing blade is rubbed, and a desired triboelectric charge is imparted
Implementation Method 2
it is possible to suppress charge leakage to the developing roller and a decrease in the triboelectric charge of the toner by increasing the resistance of the developing roller
Data Source
AI summary
Provided is a process cartridge including a developing roller having a resin layer formed on an outer surface of a conductive substrate, wherein the resin layer of the developing roller contains a polyurethane having a polycarbonate structure, when a specific AC voltage is applied to an outer surface of the developing roller while being varied within a specific frequency range, an impedance at a certain frequency is 1.0×106Ω or more, when a corona discharger is relatively moved along an axial direction of the developing roller at a speed of 400 mm/sec to charge the outer surface of the developing roller, and a potential of the outer surface is measured 0.06 seconds after the outer surface passes through a grid portion, a maximum value of the potential is less than 20.0 V.