Charging Roller Surface Composition for Uniform Charging
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Solution Overview
Problem
Conventional charging rollers fail to uniformly charge the surface of an image bearing member, leading to image defects such as uneven discharge, and have high rotational resistance due to the use of thermosetting resins that are environmentally dependent.
Innovation Solution
A charging roller with a surface layer containing a thermoplastic resin and a combination of carbon black and metal oxide conductive particles, optimized by specific water contact angle and surface area ratios, to ensure uniform charge distribution and low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional charging roller with thermosetting resin is used, then the charging roller can provide structural stability, but it causes high rotational resistance and uneven discharge
Solution Approach 1:
The patent changes the material parameter from thermosetting resin to thermoplastic resin, which fundamentally alters the electrical resistance characteristics. This parameter change reduces rotational resistance while maintaining charging functionality, directly resolving the contradiction between charging reliability and rotational resistance.
Solution Approach 2:
The patent creates a composite surface layer combining thermoplastic resin with conductive particles (carbon black and metal oxide). This composite structure achieves both low rotational resistance (through conductive particles) and uniform charging (through the thermoplastic resin matrix), resolving the technical contradiction.
2Reliability
If the surface layer contains only thermosetting resin, then the structure is simple, but it leads to uneven discharge and high rotational resistance
Solution Approach 1:
The patent applies composite materials by combining thermoplastic resin with conductive particles in the surface layer. This composite approach achieves uniform discharge and low rotational resistance while maintaining reasonable structural complexity, resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The patent implements local quality by creating a surface layer with specific composition (thermoplastic resin + conductive particles) distinct from the inner elastic body layer. This localized optimization of material properties achieves uniform charging without requiring complex changes throughout the entire charging roller structure.
3Reliability
If the water contact angle and surface area ratio are not optimized, then the manufacturing process is simpler, but uneven discharge occurs
Solution Approach 1:
The patent optimizes specific parameters (water contact angle within 40°-180°, surface area ratio of carbon black particles within 1%-50%) to achieve uniform charging. These parameter optimizations ensure reliable discharge uniformity while maintaining manufacturability through clearly defined specification ranges.
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 suppresses uneven discharge and reduces rotational resistance, ensuring uniform charging and improved electrical response.
Implementation Method 1
The surface layer contains a binder resin and conductive particles. The binder resin contains only a thermoplastic resin. The conductive particles contain first conductive particles and second conductive particles. The first conductive particles are carbon black particles.
Implementation Method 2
A water contact angle of the thermoplastic resin and a ratio of a surface area of the first conductive particles with respect to a surface area of the entire conductive particles satisfy expressions (1) to (3).
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 conductive particles (102) contain first conductive particles (102a) and second conductive particles (102b). The first conductive particles (102a) are carbon black particles. A particle size distribution of the conductive particles (102) has at least one peak within a range of not less than 0.01 µm but not more than 1 µm. A water contact angle y of the thermoplastic resin and a ratio x of a surface area of the first conductive particles with respect to a surface area of the entire conductive particles satisfy the following expressions: 40≤y<180, y≤(800/13)x+(408/13), and y≤-400x+3440.