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.
Innovation Solution
A charging roller with a surface layer containing a thermoplastic resin and a specific combination of carbon black and metal oxide conductive particles, optimized by a water contact angle and particle size distribution, to enhance electrical conductivity and reduce rotational resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional charging roller is used, then the structure is simple, but the charging uniformity is poor and image defects occur
Solution Approach 1:
The surface layer is constructed as a composite material containing thermoplastic resin binder, carbon black particles, and metal oxide particles. This composite structure provides both electrical conductivity and mechanical properties, achieving uniform charging without requiring complex multi-layer constructions or additional functional layers.
Solution Approach 2:
The patent optimizes specific parameters including the water contact angle of the thermoplastic resin (40°-180°) and the content of carbon black particles (0.1%-20.0%) to achieve the desired electrical conductivity and charging uniformity. These parameter optimizations allow the simple composite structure to perform effectively.
2Speed
If the electrical conductivity is increased to reduce rotational resistance, then the charging speed improves, but the risk of short circuit increases
Solution Approach 1:
The patent carefully controls the content of conductive particles (carbon black and metal oxide) within specific ranges to achieve optimal electrical conductivity for fast charging while preventing excessive conductivity that would cause short circuits. The water contact angle parameter of the resin is also optimized to control the overall electrical properties.
Solution Approach 2:
The combination of carbon black particles and metal oxide particles in the thermoplastic resin binder creates a composite material with balanced electrical conductivity. This composite structure provides sufficient conductivity for rapid charging while maintaining insulation properties to prevent short circuits, achieving both speed and reliability.
3Reliability
If the particle size of conductive particles is reduced to improve conductivity, then the electrical response improves, but the manufacturing precision requirement increases
Solution Approach 1:
The patent specifies that the conductive particles have a number average diameter of 0.01 μm to 1 μm, with at least one peak in the particle size distribution within this range. This parameter specification achieves good electrical response while avoiding the need for ultra-fine particles that would require extremely precise manufacturing control.
Solution Approach 2:
The patent allows different regions of the surface layer to have different particle size distributions, with at least one peak within the specified range. This local optimization approach achieves good electrical conductivity without requiring uniform control of all particle sizes, reducing manufacturing precision requirements.
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.
Implementation Method 1
The surface layer contains a binder resin and conductive particles. The conductive particles contain first conductive particles and second conductive particles. The first conductive particles are carbon black particles.
Implementation Method 2
The surface layer contains a binder resin and conductive particles. The binder resin contains only a thermoplastic resin.
Data Source
AI summary
A charging roller includes a conductive shaft, an elastic body layer formed on an outer periphery of the conductive shaft, and a surface layer formed on an outer periphery of the elastic body layer. 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. A particle size distribution of the conductive particles 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 x of the thermoplastic resin and a content y of the first conductive particles in the conductive particles satisfy the following expressions: 40≤y, y≤(800/27)x+(280/9), and y≤−8x+200.