Developing Roller Surface Layer for Bleeding and Toner Fusion Control
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Solution Overview
Problem
Existing electrophotographic developing rollers face challenges in maintaining high-quality image formation across varying environments, particularly due to bleeding under high-temperature, high-humidity conditions and toner fusion under low-temperature, low-humidity conditions, which affect image quality and consistency.
Innovation Solution
A developing roller with a surface layer composed of a polyester-polyurethane resin, optimized with specific chemical structures and carbon black, and a controlled storage modulus to prevent bleeding and toner fusion, ensuring stable performance across different environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the developing roller is stored under high-temperature, high-humidity environment, then the unreacted product migrates to the surface causing bleeding, but using conventional materials cannot suppress this migration
Solution Approach 1:
The patent changes the chemical composition parameters of the elastic layer by incorporating specific substances (polyester polyol, isocyanate compound, and silicone oil) with controlled ratios. This compositional parameter change suppresses the migration of unreacted products to the surface under high-temperature, high-humidity conditions, thereby preventing bleeding while maintaining image quality consistency.
Solution Approach 2:
The patent creates a composite elastic layer material combining polyester polyol, isocyanate compound, and silicone oil in specific proportions. This composite material structure provides both the mechanical properties needed for developing roller function and the chemical stability to prevent unreacted product migration, resolving the contradiction between reliability and compositional stability.
2Strength
If the surface hardness of the developing roller increases, then the structure becomes more stable, but the stress on toner becomes excessively strong causing toner fusion
Solution Approach 1:
The patent optimizes the hardness parameter of the elastic layer by controlling the composition ratios of polyester polyol, isocyanate compound, and silicone oil. This parameter optimization achieves a balanced hardness that provides structural stability while maintaining sufficient softness to prevent excessive stress on toner particles, thereby avoiding toner fusion.
Solution Approach 2:
The patent creates a surface layer with differentiated properties by controlling the curing characteristics of the composite material. The surface region has optimized mechanical properties that differ from the bulk material, providing appropriate hardness at the surface to prevent toner fusion while maintaining overall structural integrity.
Data Source
AI summary
Provided is a developing roller in which: even when the roller is stored under a high-temperature, high-humidity environment over a long period of time, bleeding is suppressed; and the fusion of toner to its surface upon repeated output of images under low temperature and low humidity is suppressed. The developing roller includes: a mandrel; an elastic layer on an outer periphery of the mandrel; and a surface layer on an outer periphery of the elastic layer, in which: the surface layer contains carbon black and a polyester-polyurethane resin containing a specific structure; and the surface layer has a storage modulus E′ as measured at a temperature of 0° C. and a frequency of 10 Hz of 5 MPa or more and 20 MPa or less.