Developing Roller Carbon Black Gradient for Ghost Image Reduction
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Solution Overview
Problem
Developing rollers with conductive elastic layers and surface layers often experience ghost images due to residual electric charges at the interface between the two layers, leading to non-uniform electrical conductivity and contamination issues.
Innovation Solution
A developing roller with a conductive shaft member, a conductive elastic layer containing silicone rubber and carbon black, and a surface layer, where the carbon black ratio is higher near the interface, ensuring uniform electrical conductivity and preventing ghost images by controlling the carbon black distribution and particle size for optimal electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a surface layer is provided on the conductive elastic layer to prevent contamination, then the surface protection is improved, but ghost images occur due to residual electric charges at the interface
Solution Approach 1:
The patent applies local quality by creating a gradient in carbon black concentration within the conductive elastic layer. The carbon black content is higher near the interface with the surface layer and decreases toward the shaft member. This non-uniform distribution optimizes the electrical conductivity specifically at the interface region where residual charges accumulate, thereby reducing ghost images while maintaining the protective function of the surface layer.
Solution Approach 2:
The patent changes the physical parameter of carbon black concentration distribution within the elastic layer. By controlling the carbon black content to be 10-30% by mass near the interface and decreasing toward the shaft member, the electrical conductivity is optimized at the critical interface region. This parameter change resolves the contradiction by enabling the surface layer to protect against contamination while the modified elastic layer prevents charge accumulation and ghost image formation.
2Ease of manufacture
If carbon black is uniformly distributed in the conductive elastic layer, then the manufacturing process is simplified, but non-uniform electrical conductivity occurs causing image defects
Solution Approach 1:
The patent implements local quality by establishing a non-uniform carbon black distribution within the conductive elastic layer. The carbon black concentration is deliberately higher near the interface with the surface layer and decreases toward the shaft member. This localized variation in material composition ensures optimal electrical conductivity at the interface region where charge accumulation occurs, while maintaining adequate conductivity throughout the layer, thus achieving uniform electrical performance without requiring complex manufacturing processes.
3Reliability
If the carbon black content is increased to improve electrical conductivity, then the conductivity is improved, but the particle size distribution becomes critical causing non-uniform dispersion
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: carbon black content (10-30% by mass near the interface), particle size distribution (d10: 0.01-0.1 μm, d50: 0.1-1.0 μm, d90: 1.0-5.0 μm), and density (1.01-1.07 g/cm³). This multi-parameter optimization ensures uniform dispersion of carbon black particles while achieving the desired electrical conductivity. The controlled particle size distribution prevents agglomeration and ensures homogeneous electrical properties throughout the elastic layer.
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 reduces ghost images and contamination by ensuring uniform electrical conductivity and preventing residual charges from accumulating at the interface, enabling the formation of high-grade electrophotographic images with fewer defects.
Implementation Method 1
a conductive elastic layer which covers the shaft member on its peripheral surface... in which a conductive agent such as carbon black has been dispersed in silicone rubber
Implementation Method 2
the carbon black in the elastic layer has at least two peaks in its particle size number distribution... the ratio of carbon atoms to silicon atoms (C/Si) in the vicinity of the surface of the elastic layer is represented by X, the ratio of carbon atoms to silicon atoms at a depth of 100 μm from the surface of the elastic layer by Y, and the ratio of carbon atoms to silicon atoms at a depth of 200 μm from the surface of the elastic layer by Z
Data Source
AI summary
A developing roller has a conductive shaft member, a conductive elastic layer formed around the shaft member in a thickness of 0.5 mm to 6.0 mm, and a surface layer. The elastic layer contains carbon black and silicone rubber. The carbon black is in a content of 7% to 17% by mass and has at least two peaks in its particle size number distribution. The minimum diameter peak center in the particle size number distribution is within the range of 10 nm to 40 nm. The elastic layer has density within the range of 1.01 g/cm3 to 1.07 g/cm3. Where the ratios of carbon atoms to silicon atoms (C/Si), in the vicinity of the surface of the elastic layer, at depths of 100 μm and 200 μm from the surface of the elastic layer are represented by X, Y and Z, respectively, the X, Y and Z satisfy a specific relationship.