Process Cartridge Hardness and Elasticity for Smear Control
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses face challenges in achieving both suppression of image smearing and suppression of drum scratches while maintaining high image quality, durability, and printing speed.
Innovation Solution
A process cartridge comprising an electrophotographic photosensitive member with a Martens hardness of 245 to 300 N/mm², a developing roller with a specific elastic modulus distribution, and a toner containing silica particles as an external additive, which provides a spacer effect and improves nitrogen oxide removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hard surface layer is formed on the photosensitive member to suppress image smearing, then image quality is improved, but drum scratches occur due to increased friction and stress
Solution Approach 1:
The invention applies local quality by creating a surface layer with specific hardness characteristics (Martens hardness 245-300 N/mm²) only on the photosensitive member surface, while the bulk material maintains different properties. This localized hardness control suppresses image smearing without causing excessive drum scratches, as the hardness is optimized for the specific surface function rather than throughout the entire component.
Solution Approach 2:
The invention utilizes parameter changes by precisely controlling the Martens hardness within the range of 245-300 N/mm². This specific parameter range was determined to be the optimal balance point where image smearing is suppressed but drum scratches are minimized. The parameter optimization extends to the developing roller elastic modulus distribution as well.
2Productivity
If repeated circumferential rubbing occurs during operation, then printing speed and productivity are improved, but member deterioration and toner damage occur
Solution Approach 1:
The invention applies beforehand cushioning by designing the developing roller with a specific elastic modulus distribution (higher at the surface, lower at deeper layers) that anticipates and cushions against the stresses of repeated circumferential rubbing. This pre-engineered elastic structure absorbs and distributes rubbing stresses before they can cause significant member deterioration or toner damage, enabling sustained high-speed printing.
Solution Approach 2:
The invention utilizes composite materials by combining the photosensitive member with specific surface layer properties and the developing roller with its layered elastic modulus structure. This composite approach creates a system where different materials and structures work together to withstand repeated rubbing - the hard surface layer prevents smearing while the elastic developing roller structure cushions against damage, achieving both high productivity and reliability.
3Duration of action of stationary object
If silica particles are added to toner to reduce stress and prevent damage, then member life is extended, but image smearing may occur due to particle detachment
Solution Approach 1:
The invention applies parameter changes by optimizing the silica particle characteristics including particle size distribution, surface treatment, and concentration within the toner. These parameter optimizations ensure that silica particles provide stress reduction and damage prevention while maintaining sufficient adhesion to prevent detachment and image smearing. The particle parameters are precisely controlled to balance protection and stability.
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 suppresses image smearing and drum scratches, enhances the life and speed of the electrophotographic apparatus, and maintains high image quality and durability.
Implementation Method 1
the large-diameter silica particle produce a spacer effect, the toner is suppressed from being in direct contact with the developing roller, the regulating member, and the like, and the stress on the toner is reduced
Implementation Method 2
a surface layer of the electrophotographic photosensitive member has a Martens hardness of 245 to 300 N/mm² as measured with an indentation force of 7 mN
Implementation Method 3
when an elastic modulus of the binder resin in a first region is E1, the first region being a region from an outer surface of the single-layered surface layer to a depth of 0.1 μm, and an elastic modulus of the binder resin in a second region is E2, the second region being a region from a depth of 1.0 μm to a depth of 1.1 μm from the outer surface, the following formulas (1) and (2) are satisfied: E1≥200 MPa; 10 MPa≤E2≤150 MPa
Data Source
AI summary
A process cartridge includes a photosensitive member, a toner, and a developing roller, a surface layer of the photosensitive member has a Martens hardness of 245 to 300 N/mm2, the developing roller has a single-layered surface layer containing a substrate and a binder resin; when an elastic modulus of the binder resin in a first region is E1, and an elastic modulus of the binder resin in a second region is E2, E1≥200 MPa and 10 MPa≤E2≤150 MPa are satisfied; the elastic modulus in the second region continuously decreases from that in the first region; the toner comprises a toner particle and an external additive A; the external additive A is a silica particle having a major diameter of 40 to 400 nm; and a coverage of the external additive A with respect to surface of the toner particle is 5.0% or more.