Developing Roller End Coating for Nonprinting Area Scumming
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Solution Overview
Problem
Electrophotographic devices experience scumming in nonprinting areas due to toner adherence caused by increased electrical resistance at the developing roller's end portions, resulting from insulating materials in coating liquids used for end portion treatments.
Innovation Solution
A developing roller with end portion coat layers containing conductive materials, having higher hardness than the coat layer, and a resistance value ratio of 1.6 or less between the end portion coat layer and the coat layer, suppresses electrical resistance increases, preventing toner adherence and scumming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If insulating material is used in the end portion coating liquid, then wear resistance at the end portions is improved, but electrical resistance increases causing toner adherence and scumming in nonprinting areas
Solution Approach 1:
The patent applies different material properties to different regions of the developing roller. The end portion coat layer contains conductive material (0.1-5 wt% metal powder or conductive polymer) to maintain low electrical resistance, while the main body coat layer focuses on wear resistance. This local differentiation allows the end portions to prevent toner adherence without compromising overall wear resistance.
Solution Approach 2:
The end portion coat layer is formulated as a composite material combining a binder resin with conductive additives (metal powder such as aluminum or copper, or conductive polymer). This composite structure provides both the electrical conductivity needed to prevent scumming and the mechanical properties required for durability at the end portions.
2Duration of action of stationary object
If end portion treatment is applied to improve wear resistance, then the developing roller life is extended, but toner adherence occurs at the peripheral edge portion
Solution Approach 1:
The patent implements local quality by making the end portion coat layer distinct from the main body coat layer in terms of material composition. The end portion layer includes conductive material specifically to prevent toner adherence, while maintaining wear resistance through the binder resin matrix. This localized modification ensures image quality is not compromised while extending roller life.
Solution Approach 2:
The patent changes the electrical resistance parameter of the end portion coat layer by incorporating conductive materials. The metal powder content is controlled at 0.1-5 wt% to achieve appropriate conductivity, preventing toner adherence while maintaining mechanical integrity. This parameter adjustment resolves the conflict between durability and image quality.
3Productivity
If spray coating is used for end portion treatment, then coating efficiency is improved, but scattering of droplets and impregnation occur increasing electrical resistance
Solution Approach 1:
The patent controls the composition parameters of the coating liquid to ensure proper conductivity even when spray coating causes some scattering. By incorporating 0.1-5 wt% conductive material in the end portion coat layer, the formulation compensates for potential coating inconsistencies, maintaining low electrical resistance and preventing toner adherence despite the efficiency of spray application.
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 conductive material in the end portion coat layers ensures uniform coating and excellent wear resistance, reducing toner adherence and scumming in nonprinting areas, while maintaining balanced electrical resistance values.
Implementation Method 1
the end portion coat layers contain a conductive material, wherein the end portion coat layers have a higher hardness than the coat layer, wherein a ratio (Ω1/Ω2) of a resistance value S21 at an axial central part of the end portion coat layer to a resistance value Ω2 at an axial central part of the coat layer is 1.6 or less
Data Source
Figure 1~2
Figure 3
AI summary
The purpose of the present invention is to provide a developing roller which is not prone to scumming in a nonprinting area. The solution is to provide a developing roller which has an elastic layer, a coat layer formed on the elastic layer, and end portion coat layers formed on outermost surfaces on two axial end portions, wherein the end portion coat layer contains a conductive material.