Charging Roller Surface Layer for Uniform Charging and Low Resistance
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Solution Overview
Problem
Conventional charging rollers fail to uniformly charge the surface of an image bearing member, leading to uneven discharge issues such as spotted unevenness and lateral streaked unevenness, and have high rotational resistance.
Innovation Solution
A charging roller with a conductive shaft, an elastic body layer, and a surface layer containing a thermoplastic resin binder and a combination of metal oxide and other conductive particles, with specific particle size distribution and content ratios, to enhance electrical conductivity and reduce rotational resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional charging roller with insulating particles and resin film is used, then charging defects are prevented to some extent, but uneven discharge cannot be sufficiently suppressed and rotational resistance remains high
Solution Approach 1:
The patent changes the electrical resistance parameter of the surface layer by using a thermoplastic resin with high volume resistivity (≥1×10^12 Ω·cm) instead of conventional resins, and by controlling the conductive particle content and size distribution, achieving both uniform charging and suppression of uneven discharge
Solution Approach 2:
The patent creates a composite surface layer combining a thermoplastic resin binder with conductive particles (carbon black, metal oxides, or metal particles), where the resin provides high volume resistivity and the particles provide controlled conductivity to prevent uneven discharge while maintaining low rotational resistance
2Reliability
If the charging roller has high electrical resistance to prevent discharge, then charging stability improves, but rotational resistance increases
Solution Approach 1:
The patent applies local quality by creating a surface layer with specific localized properties: high volume resistivity (≥1×10^12 Ω·cm) for charging stability, combined with controlled conductive particle distribution to maintain low rotational resistance, distinguishing it from the underlying elastic body layer
3Use of energy by moving object
If conductive particles are added to reduce rotational resistance, then electrical response improves, but charging uniformity deteriorates due to uneven discharge
Solution Approach 1:
The patent carefully controls the parameters of conductive particles including content (0.1-10 parts by mass per 100 parts resin), particle size (0.003-10 μm with specific surface area 10-2000 m²/g), and type (carbon black, metal oxides, or metal particles) to achieve both low rotational resistance and uniform charging without uneven discharge
Solution Approach 2:
The patent creates different local properties within the surface layer by controlling particle size distribution and content, where finer particles provide conductivity for low rotational resistance while the overall distribution and resin matrix maintain uniformity and prevent uneven discharge
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 charging roller effectively suppresses uneven discharge and reduces rotational resistance, ensuring uniform charging and improved electrical response, even under varying environmental conditions.
Implementation Method 1
The thermoplastic resin has a water contact angle of not less than 40° but less than 180°
Implementation Method 2
The conductive particles contain first conductive particles and second conductive particles. The first conductive particles are metal oxide particles
Data Source
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AI summary
A charging roller (51) includes a conductive shaft (51a), an elastic body layer (51b) formed on an outer periphery of the conductive shaft, and a surface layer (51c) formed on an outer periphery of the elastic body layer. The surface layer (51c) contains a binder resin (101) and conductive particles (102). The binder resin (101) contains only a thermoplastic resin. The thermoplastic resin has a water contact angle of not less than 40° but less than 180°. The conductive particles (102) contain first conductive particles (102a) and second conductive particles (102b). The first conductive particles (102a) are metal oxide particles. A content of the first conductive particles (102a) in the surface layer (51c) is not less than 15.0 parts by mass but not more than 200.0 parts by mass with respect to 100.0 parts by mass of the binder resin (101). A particle size distribution of the conductive particles (102) has a peak within a range of not less than 0.01 µm but not more than 1.00 µm.