Charge Transport Layer Composition for High-Speed Ghosting Suppression
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Solution Overview
Problem
Conventional electrophotographic photosensitive members fail to sufficiently suppress ghosting in high-speed processes due to the retention of holes in the charge transporting layer, which is exacerbated by the spatial arrangement and energetic disorder of the charge transporting substance, leading to image quality degradation.
Innovation Solution
The use of a charge transporting layer comprising compounds represented by formulas (A-1), (A-2), and optionally (A-3), which have similar HOMO levels and are bonded by non-conjugate bonds, expanding the molecular skeletons to form hole paths and minimize energetic hindrance, thereby suppressing ghosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional charge transporting substances are used, then the electrophotographic photosensitive member can be manufactured with standard materials, but ghosting occurs due to carrier retention during high-speed processes
Solution Approach 1:
The patent changes the molecular structure parameters of the charge transporting substance by introducing specific substituents (e.g., triphenylene groups, pyrene groups) and adjusting molecular weight and HOMO levels to optimize carrier transport properties for high-speed operation without ghosting
Solution Approach 2:
The patent uses composite charge transporting substances combining multiple functional groups and molecular structures (e.g., diphenylbenzidine derivatives combined with triphenylene or pyrene groups) to achieve both high-speed carrier transport and suppressed carrier retention
2Reliability
If charge transporting substances with low-energy HOMO levels are used, then carrier transport can be achieved, but holes are trapped and ghosting increases
Solution Approach 1:
The patent precisely adjusts the HOMO energy levels of the charge transporting substance to be within a specific range (e.g., -4.0 eV to -5.0 eV) to ensure efficient carrier transport while preventing hole trapping, thereby eliminating ghosting without sacrificing transport reliability
3Ease of manufacture
If the charge transporting layer uses standard materials, then manufacturing is simple, but image quality degrades at high process speeds
Solution Approach 1:
The patent modifies the molecular parameters of the charge transporting substance (such as introducing rigid aromatic groups like triphenylene or pyrene) to enhance carrier transport efficiency and reduce retention, thereby maintaining image quality at high speeds while keeping the manufacturing process relatively simple
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 proposed solution effectively suppresses ghosting in high-speed processes by ensuring efficient hole transport and reducing retention, enhancing image quality and process stability.
Implementation Method 1
a charge transporting layer that can suppress trapping sites of holes and does not interfere with transfer of holes
Implementation Method 2
rapidly extracts holes generated from a charge generating substance
Data Source
AI summary
An electrophotographic photosensitive member including: a support, a charge generating layer, and a charge transporting layer in this order, wherein the charge transporting layer contains: a compound represented by the formula (A-1), and at least one selected from the group consisting of a compound represented by the formula (A-2) and a compound represented by the formula (A-3).