Charging Roller Domain Structure for Streak Prevention

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Solution Overview

Problem

Existing charging rollers for electrophotographic image forming apparatuses experience horizontal streaks in low-temperature and low-humidity environments due to uneven charge distribution, leading to suboptimal image quality.

Innovation Solution

A charging roller with an electroconductive mandrel and a surface layer having a matrix with dispersed domains, where each domain is a cross-linked product of a second rubber and electroconductive particles, controlling the direction of triboelectric charge diffusion to prevent local charge accumulation and ensure even discharge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a charging roller with an electroconductive base and electroconductive layer is used, then the charging function is provided, but horizontal streaks occur in low-temperature and low-humidity environments due to uneven charge distribution

Engineering Contradiction:

Improveimage quality stabilityVSAvoidhorizontal streak formation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating domains with different electroconductive properties within the electroconductive layer. The layer contains a matrix phase and dispersed domain phases, where each domain has controlled electroconductive particle content (0.1-10 parts by mass per 100 parts of rubber). This local variation in electroconductive properties ensures uniform charge distribution across the surface, preventing horizontal streaks while maintaining reliable charging function in low-temperature and low-humidity environments.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by formulating the electroconductive layer as a composite structure consisting of a rubber matrix (first rubber and second rubber) with dispersed electroconductive particles. The domain phase contains cross-linked second rubber and electroconductive particles, creating a composite material system that balances electroconductive performance with mechanical properties. This composite structure prevents charge accumulation and ensures even discharge, eliminating horizontal streaks while maintaining charging reliability.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the electroconductive layer uses a simple polymer structure, then the manufacturing is easier, but charge distribution becomes uneven causing horizontal streaks

Engineering Contradiction:

Improveelectroconductive layer fabricationVSAvoidcharge distribution uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by precisely controlling the electroconductive particle content within domains (0.1-10 parts by mass per 100 parts of rubber) and the cross-linking degree of the domain phase. By adjusting these parameters, the electroconductive properties of the domain phase are optimized to ensure uniform charge distribution. This controlled parameter approach achieves high manufacturing precision in charge distribution while maintaining reasonable ease of manufacture through a systematic formulation approach.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies preliminary action by pre-forming domains with specific electroconductive particle concentrations and cross-linking structures before finalizing the electroconductive layer. The domain phase is prepared with controlled electroconductive particle content and cross-linked structure in advance, ensuring that when the layer is manufactured, the charge distribution uniformity is already built into the structure. This preliminary structuring simplifies the overall manufacturing process while guaranteeing charge distribution precision.

Inventive Principle:

Principle #10Preliminary action

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 stabilizes charge distribution, preventing horizontal streaks and ensuring high-quality electrophotographic images across various environments by effectively transferring charge through the domains, thereby maintaining image quality.

Implementation Method 1

controlling the direction of triboelectric charge diffusion to prevent local charge accumulation and ensure even discharge

Methodology Applied

Scientific EffectTriboelectric charge diffusion: Triboelectric Effect

Implementation Method 2

effectively transferring charge through the domains

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP3995900B1Charging roller, process cartridge, and electrophotographic image forming apparatus

Publication Date: 2024.06.26 CANON KK

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AI summary

A charging roller (100) comprising an electroconductive mandrel (101) and an electroconductive layer (103) as a surface layer, the electroconductive layer including a matrix (201) containing a cross-linked product of a first rubber and domains (203) dispersed in the matrix, each of the domains containing a cross-linked product of a second rubber and an electroconductive particle, the domains each having a volume resistivity lower than a volume resistivity of the matrix, and when sampling a cubic sample of the electroconductive layer having a side of 20.0 µm from a region from an outer surface of the electroconductive layer to a depth of 20.0 µm, 50 number% or more of all the domains in the cubic sample satisfy a specific condition.