Process Cartridge Toner Composition for Fast Charge Rise
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses with increased speed face challenges in maintaining stable toner charging immediately after startup and density uniformity over long periods, due to insufficient charge rising performance and embedding of external additives in toner particles.
Innovation Solution
A process cartridge with toner containing external additives of specific size, aspect ratio, and resistance, and an electrophotographic photosensitive member with a surface protective layer containing conductive particles within a defined resistivity range, enabling efficient charge injection and uniformity through triboelectric charging and injection charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the process speed of the electrophotographic image forming apparatus is increased, then productivity is improved, but charge rising performance immediately after startup deteriorates
Solution Approach 1:
The invention changes the physical parameters of the external additive particles, specifically setting the long diameter to 100 nm or more and 3,000 nm or less, and the aspect ratio to 5.0 or more. These parameter changes enable the particles to provide sufficient triboelectric charging even at high process speeds, resolving the contradiction between increased productivity and maintained charge rising performance.
Solution Approach 2:
The invention uses composite toner particles comprising toner base particles and external additive particles with specific characteristics. This composite structure ensures that the external additives remain on the toner surface rather than embedding, providing consistent charging performance both immediately after startup and after extended use, thus maintaining reliability while enabling high-speed operation.
2Reliability
If external additive particles are made small to reduce embedding, then charge stability is improved, but charge rising performance immediately after startup deteriorates
Solution Approach 1:
The invention optimizes the size parameters of external additive particles by specifying a long diameter of 100 nm or more and 3,000 nm or less, and an aspect ratio of 5.0 or more. This parameter optimization ensures that particles are large enough to remain on the toner surface for effective charging, yet small enough to maintain stability, resolving the contradiction between charge stability and charge rising performance.
3Productivity
If the electrophotographic apparatus operates at high speed for extended period, then productivity is improved, but density uniformity of halftone image deteriorates
Solution Approach 1:
The invention employs composite toner particles with externally added particles having specific size and shape characteristics that prevent embedding during extended high-speed operation. This composite structure maintains consistent charging performance over time, ensuring density uniformity in halftone images is preserved even during prolonged high-productivity operation.
Solution Approach 2:
The invention ensures continuous effective charging by designing external additives that remain on the toner surface throughout extended operation. The specific particle characteristics (long diameter 100-3000 nm, aspect ratio ≥5.0) enable sustained triboelectric charging action, maintaining density uniformity continuously during high-speed operation without degradation.
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 provides excellent charge rising performance and density uniformity both immediately after startup and throughout extended use, ensuring high-quality imaging.
Implementation Method 1
The toner having externally added thereto the external additive having a certain resistance value is regulated and triboelectrically charged with a blade or the like before a nip where the toner is developed from a developer carrying member onto an electrophotographic photosensitive member.
Implementation Method 2
the electrophotographic photosensitive member includes a electroconductive support, a photosensitive layer formed on the electroconductive support, and a surface protective layer formed on the surface of the electrophotographic photosensitive member, wherein the surface protective layer contains electroconductive particles
Data Source
AI summary
Provided is a process cartridge that is excellent in initial charge rising performance, and in charge uniformity of a halftone image throughout a long period of time from the start of use until after endurance. Specifically, provided is a process cartridge including: an electrophotographic photosensitive member; a toner; and a developing unit, wherein the toner contains toner particles and an external additive A, the external additive A, and wherein the electrophotographic photosensitive member includes an electroconductive support, a photosensitive layer, and a surface protective layer, wherein the surface protective layer contains electroconductive particles.