Development Roll Coating for Electrophotography
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Solution Overview
Problem
Development rolls for electrophotographic equipment often experience breakage of convex portions on the rubber elastic layer, leading to contamination of the photosensitive member and image defects due to friction with opposing members.
Innovation Solution
A development roll with a rubber elastic layer and a coating layer composed of a thermoplastic urethane, polyol, and curing agent, where the mass percentages of these components satisfy specific ratios, enhancing thixotropy and adhesion to prevent breakage and maintain an irregular shape for high toner-conveying capability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If convex portions are formed by transfer molding on the rubber elastic layer to enhance toner-conveying capability, then image quality is improved, but the convex portions are prone to breakage due to friction with opposing members
Solution Approach 1:
A coating layer is applied in advance onto the rubber elastic layer before the convex portions undergo friction with opposing members. This coating layer acts as a protective cushion that prevents direct contact and friction between the convex portions and the opposing member, thereby preventing breakage while maintaining the surface irregularity structure
Solution Approach 2:
The development roll employs a composite structure consisting of a rubber elastic layer with transfer-molded convex portions and an additional coating layer formed thereon. This composite material structure combines the toner-conveying benefits of the irregular surface with the protective properties of the coating layer, resolving the contradiction between surface structure effectiveness and durability
2Reliability
If the coating layer thickness is increased to protect convex portions from breakage, then reliability is improved, but the toner-conveying capability may be reduced due to excessive coverage
Solution Approach 1:
The thickness of the coating layer is precisely controlled within a specific range (0.1 μm to 10 μm, preferably 0.5 μm to 5 μm). By optimizing this parameter, the coating layer provides sufficient protection to prevent convex portion breakage while maintaining enough exposure of the irregular surface structure to preserve high toner-conveying capability
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 breakage of convex portions and maintains a high toner-conveying capability by ensuring sufficient coating layer thickness and adhesion, reducing image defects and extending the equipment's operational lifespan.
Implementation Method 1
a coating layer which is composed of a cured body of a coating material containing (A) a thermoplastic urethane, (B) a polyol, and (C) a curing agent
Implementation Method 2
the coating material has high thixotropy, and when the coating material is applied onto the outer circumference of the rubber elastic layer
Implementation Method 3
adhesion between the rubber elastic layer and the coating layer can be improved
Data Source
AI summary
A development roll for electrophotographic equipment includes a shaft body, a rubber elastic layer formed by molding on an outer circumference of the shaft body and having many convex portions formed by transfer molding on the outer circumferential surface thereof, and a coating layer disposed on an outer circumference of the rubber elastic layer. The coating layer is composed of a cured body of a coating material containing (A) a thermoplastic urethane having a number-average molecular weight in the range of 50,000 to 200,000, (B) a polyol having a number-average molecular weight in the range of 500 to 4,000, and (C) a curing agent. The mass percentages a, b, and c of the components (A), (B), and (C) satisfy the following expressions: a+b+c=100, 40≦a≦75, 5≦b≦20, and 20≦c.