Polyurethane Cleaning Blade Hardness Gradient Against Chipping
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Solution Overview
Problem
Existing electrophotographic cleaning blades experience instability and chipping over time, leading to poor cleaning performance due to increased hardness and brittleness, especially when dealing with small toner particles, which can result in streaked images.
Innovation Solution
A cleaning blade with a polyurethane elastic member having a specific Martens hardness gradient and crystal structure, where the hardness decreases from the surface to the interior, and a supporting member, designed to maintain high abutting pressure while reducing brittleness and chipping, achieved through controlled crystallization and crosslinking of the polyurethane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hardness of the abutting portion is increased to increase abutting pressure on the image-bearing member, then cleaning performance for small particle diameter toner is improved, but the cleaning blade is prone to chipping and instability over long period use
Solution Approach 1:
The patent applies local quality by creating a hardness gradient within the elastic member, where the abutting portion (distal end) has higher hardness to provide sufficient abutting pressure for cleaning small toner particles, while the interior portion has lower hardness to maintain flexibility and resist chipping. This is achieved through controlled crosslinking that creates a gradient structure with different degrees of crystallinity and crosslink density at different depths from the abutting surface.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the crosslinking degree and crystallinity of the polyurethane elastomer to optimize the balance between hardness and chipping resistance. Specifically, the abutting portion is designed with a crosslinking degree of 10-30% and controlled crystallinity to achieve the desired hardness gradient, while the interior maintains lower crosslinking to preserve elasticity and prevent brittle fracture during prolonged use.
2Stress or pressure
If the hardness of the abutting portion is increased to reduce contact width and increase abutting pressure, then cleaning property for small particle diameter toner is improved, but fine chipping occurs in the abutting portion over long period use
Solution Approach 1:
The patent implements local quality by designing the elastic member with spatially varying properties: the distal end (abutting portion) is engineered with higher hardness and increased crosslinking density to generate sufficient abutting pressure for effective toner removal, while the interior regions maintain lower hardness and flexibility. This localized differentiation ensures that high pressure is applied only where needed for cleaning, while the softer interior prevents propagation of cracks and chipping during repeated contact cycles.
Solution Approach 2:
The patent effectively creates a composite structure within the single elastic member by combining regions of different crosslinking densities and crystallinities. The abutting portion functions as a hard, pressure-generating zone with high crosslinking (20-35%), while the interior acts as a flexible, shock-absorbing zone with lower crosslinking (5-20%). This internal composite architecture allows the blade to simultaneously achieve high abutting pressure and resistance to chipping-induced instability.
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 cleaning blade exhibits stable and excellent cleaning performance over a long period without chipping, maintaining high abutting pressure and flexibility, thus preventing streaked images and ensuring consistent image quality.
Implementation Method 1
achieved through controlled crystallization and crosslinking of the polyurethane
Implementation Method 2
achieved through controlled crystallization and crosslinking of the polyurethane
Implementation Method 3
a Martens hardness of the elastic member measured at a position of the point P1 is represented by HM1
Data Source
AI summary
Provided is a cleaning blade including: an elastic member containing a polyurethane; and a supporting member configured to support the elastic member. The polyurethane has a linear moiety represented by —(CH2)m-. The elastic member has a plate shape having a main surface and a distal end surface forming a distal end-side edge with the main surface, at least on a distal end side. Martens hardness at positions on a bisector at intervals of 30 μm from a distal end-side edge to a position furthest away from the distal end-side edge by 100 μm decreases from a distal end-side edge to the position. A Martens hardness HM1 of the elastic member at a position P1 is 1.0 N/mm2 or more. The elastic layer satisfies Kω1>Kω2>Kω3. Further, the cleaning blade has an erosion rate E of 0.6 μm/g or less.