Developing Roller Surface Layer Composition for Image Quality
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Solution Overview
Problem
Developing rollers with polyurethane resin surfaces face issues with developer adhesion under high-temperature, high-humidity environments and fog formation under low-temperature, low-humidity conditions, leading to image defects like banding and fog in electrophotographic images.
Innovation Solution
A developing roller with a surface layer formed by curing a mixture containing carbon black, polytetramethylene glycol (PTMG) and polypropylene glycol (PPG) reacted with 4,4′-diphenylmethane diisocyanate, optimizing molecular weights and functional groups to create a polyurethane resin that reduces adhesion and fog formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of the developing roller is made hard to prevent shaving, then toughness is improved, but the developer is squashed excessively causing melt adhesion and fog
Solution Approach 1:
The patent changes the chemical composition parameters of the polyurethane resin by specifying particular polyol compounds (polytetramethylene glycol with Mn≥650 and Mw≥8000, polypropylene glycol with Mn≥700 and Mw≥8000) and isocyanate compounds (4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate with average functional groups≥3.0 and Mw≥25000). This compositional parameter optimization achieves the desired balance between toughness and softness, preventing both surface shaving and excessive developer squashing that causes fog.
Solution Approach 2:
The patent creates a composite polyurethane resin system by combining specific polyol compounds with specific isocyanate compounds in defined proportions. This composite material approach allows the surface layer to exhibit both the toughness needed to resist shaving and the softness needed to prevent developer melt adhesion, resolving the contradiction between these opposing requirements.
2Object-generated harmful factors
If the surface of the developing roller is made soft to prevent developer squashing, then fog is reduced, but the surface lacks toughness and gets shaved upon long-term use
Solution Approach 1:
The patent optimizes the molecular weight parameters and functional group counts of the polyurethane resin components. By setting specific ranges for Mn and Mw of polyol compounds and average functional groups and Mw of isocyanate compounds, the invention achieves the precise balance between softness (to prevent fog) and toughness (to prevent shaving) that cannot be achieved by adjusting a single parameter.
Solution Approach 2:
The patent employs a composite polyurethane resin formulation combining multiple polyol and isocyanate compounds with specifically controlled ratios. This composite material strategy enables the surface to simultaneously possess the softness required to prevent developer squashing and fog formation, and the toughness required to resist surface shaving during long-term operation.
3Duration of action of stationary object
If a polyurethane resin surface layer is used to achieve high toughness and softness, then surface durability is improved, but developer adhesion occurs under high-temperature, high-humidity conditions causing banding
Solution Approach 1:
The patent addresses environmental stability by optimizing the chemical structure parameters of the polyurethane resin. The specific selection of polyol compounds (polytetramethylene glycol, polypropylene glycol) and isocyanate compounds (4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate) with controlled molecular weights and functional groups creates a resin composition that resists developer adhesion even under high-temperature, high-humidity storage conditions, preventing banding while maintaining surface durability.
Solution Approach 2:
The patent uses a composite polyurethane resin system with specifically formulated components and ratios that provide enhanced environmental stability. This composite material approach ensures that the surface layer maintains its properties and prevents developer adhesion under varying environmental conditions, resolving the contradiction between durability and resistance to banding.
4Ease of manufacture
If conventional polyurethane resin is used without specific molecular weight control, then manufacturing is simplified, but fog occurs under low-temperature, low-humidity conditions
Solution Approach 1:
The patent implements specific molecular weight control parameters for the polyol and isocyanate compounds used in manufacturing. By specifying Mn≥650 and Mw≥8000 for polytetramethylene glycol, Mn≥700 and Mw≥8000 for polypropylene glycol, and average functional groups≥3.0 and Mw≥25000 for polymeric diphenylmethane diisocyanate, the invention prevents fog formation under low-temperature, low-humidity conditions while maintaining reasonable manufacturing feasibility through standardized material specifications.
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 prevents developer adhesion and fog formation across varying environmental conditions, ensuring stable and high-quality electrophotographic image production.
Implementation Method 1
a surface layer formed by curing a mixture containing a carbon black, a polyol compound, and an isocyanate compound
Data Source
AI summary
The present invention intends to provide a method of producing a developing roller capable of providing high-quality electrophotographic images under a variety of environments. The method of producing a developing roller according to the present invention is a method of producing a developing roller having a mandrel, a resin layer on the outer periphery of the mandrel, and a surface layer on the outer periphery of the resin layer, the method including the step of curing a mixture containing a carbon black, a specific diol, and a specific isocyanate compound to form the surface layer.