Electro-Conductive Layer Structure for Uniform Low-Bias Charging
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Solution Overview
Problem
Electrophotographic image forming apparatuses face challenges in achieving uniform surface potential and high-quality images due to non-uniformity in the electro-conductive layer of charging members, especially when operating at reduced charging biases, leading to graininess in halftone images.
Innovation Solution
An electrophotographic electro-conductive member with a matrix containing a crosslinked product of a first rubber and domains of a crosslinked product of a second rubber and electro-conductive particles, where the electro-conductive particles are uniformly dispersed to maintain consistent electric resistance and prevent discharge unevenness, even at reduced voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the charging bias voltage is reduced to decrease power source size, then the power source can be made smaller, but graininess appears in halftone images due to non-uniform surface potential
Solution Approach 1:
The electro-conductive layer is designed with non-uniform electro-conductive particle concentration: higher concentration near the surface to enhance surface potential uniformity under low charging bias, and lower concentration in the inner layer to maintain appropriate overall electric resistance. This local quality differentiation resolves the contradiction by optimizing surface charging performance without compromising bulk electrical properties.
Solution Approach 2:
The electro-conductive layer is constructed as a composite material with two distinct regions: an outer layer containing electro-conductive particles and an inner layer with different electro-conductive particle concentration. This composite structure enables simultaneous optimization of surface potential uniformity (for low voltage operation) and bulk electrical resistance, resolving the contradiction between power source size reduction and image quality maintenance.
2Reliability
If electro-conductive particles are added to adjust conductivity, then the electric resistance can be controlled, but the electro-conductive path becomes non-uniform causing discharge unevenness
Solution Approach 1:
The electro-conductive layer is segmented into multiple regions with different electro-conductive particle concentrations: the outer layer has higher concentration to ensure adequate surface conductivity and uniform surface potential, while the inner layer has lower concentration to maintain appropriate bulk electric resistance and prevent discharge unevenness. This segmentation resolves the contradiction by distributing electro-conductive particles non-uniformly to optimize both local and global electrical properties.
Solution Approach 2:
The concentration of electro-conductive particles is changed as a gradient from the surface toward the inner layer. The outer layer maintains higher particle concentration for adequate surface conductivity, while the inner layer has reduced concentration to control bulk electric resistance and ensure uniform electro-conductive path formation. This parameter change resolves the contradiction between controlling electric resistance and maintaining electro-conductive path uniformity.
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 ensures efficient charge transfer and stable electric resistivity, suppressing discharge unevenness and enhancing the formation of high-quality electrophotographic images by maintaining a homogeneous electro-conductive path.
Implementation Method 1
transfer of charge in an electro-conductive path is made extremely efficient
Implementation Method 2
a matrix containing a crosslinked product of a first rubber; and domains dispersed in the matrix, each of the domains containing a crosslinked product of a second rubber
Data Source
AI summary
An electro-conductive layer of an electrophotographic electro-conductive member has a matrix-domain structure. The matrix contains a first rubber. The domain contains a second rubber and electro-conductive particles. Where μ represents an average of ratios of the cross-sectional area of the electro-conductive particles contained in each of the domains to the cross-sectional area of each of the domains appearing on a cross-section of the electro-conductive layer in a thickness direction, and σ represents a standard deviation of the ratios, σ/μ is 0 or more and 0.4 or less, and μ is 20% or more and 40% or less. At least eight of samples with a first cubic shape 9 μm on a side, which are sampled at arbitrary nine positions on the electro-conductive layer, satisfy the specified condition.