Process Cartridge Developing Roller Surface Structure for Streak Prevention
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Solution Overview
Problem
Electrophotographic image forming apparatuses face challenges in maintaining high image quality and endurance, especially in severe high-temperature, high-humidity environments, where horizontal streaks can occur due to toner accumulation and cohesion clusters.
Innovation Solution
A process cartridge with a developing roller having a conductive substrate, an elastic layer, and a surface layer composed of a binder resin and specific resin particles, along with a toner containing silica particles as external additives, is used to address the issue of toner accumulation and cohesion clusters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cartridge is left to stand for a long time in high temperature and high humidity environment, then toner accumulation occurs between the developing roller and regulating member, but horizontal streaks are generated due to toner cohesion clusters
Solution Approach 1:
The patent introduces a regulating member with a specific surface structure (protrusions and recesses) that acts as an intermediary between the developing roller and toner. This structure prevents direct contact and reduces toner accumulation, thereby eliminating the cause of horizontal streaks while maintaining reliable image quality even after prolonged standing in harsh environments.
Solution Approach 2:
The patent modifies the surface parameters of the regulating member by creating protrusions with specific dimensions (height of 1-10 μm) and surface roughness values (Ra of 0.1-5 μm). These parameter changes optimize the surface to prevent toner cohesion clusters from forming, thus avoiding horizontal streaks while maintaining image quality stability.
2Quantity of substance
If the toner is crushed by pressure between the regulating member and developing roller during accumulation, then toner cohesion clusters form, but the toner cannot be properly applied in the longitudinal direction
Solution Approach 1:
The patent applies local quality by creating a non-uniform surface structure on the regulating member with specific protrusions and recesses. This local structural variation allows the surface to gently guide and distribute toner particles without applying crushing pressure, ensuring uniform toner application in the longitudinal direction while preventing cohesion cluster formation.
Data Source
AI summary
A process cartridge includes a toner, a regulating member, and a developing roller including a conductive substrate, an elastic layer, and a surface layer which includes a binder resin, a first resin particle having an elastic coefficient of 100 to 10,000 MPa, and a second resin particle having an elastic coefficient of 2 to 50 MPa and in which the outer surface has a first protruded portion and a second protruded portion 5.0 μm or more lower than the first protruded portion and has an average maximum height of 6 to 18 μm. The toner includes a toner particle and an external additive A that is a silica particle having a major diameter of 40 to 400 nm, a surface coverage of the toner particle by the external additive A is 3.0% or more, and a dispersion degree evaluation index D of the external additive A is 2.0 or less.