Charge Transport Layer Durability and Sensitivity in Electrophotographic Photosensitive Members

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Solution Overview

Problem

The use of polyarylate resins in charge transport layers of electrophotographic photosensitive members improves mechanical strength but compromises sensitivity, particularly with increased printing speeds, compared to polycarbonate resins.

Innovation Solution

Incorporating a polyester resin with a specific structural unit and a charge-transporting compound in the charge transport layer, along with silica particles as fillers, to enhance both durability and sensitivity, with optimal mass ratios and molecular weights for improved performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If polyarylate resin is used in charge transport layer, then mechanical strength is improved, but sensitivity deteriorates

Engineering Contradiction:

Improvemechanical strengthVSAvoidsensitivity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent employs a composite material system consisting of polyarylate resin combined with specific charge-transporting compounds (trihalomethylbenzene derivatives and/or trihalomethylfluorene derivatives) in defined weight ratios (95:5 to 5:95). This composite approach allows the polyarylate resin to provide mechanical strength while the charge-transporting compounds restore and enhance sensitivity, resolving the contradiction between mechanical strength and sensitivity that plagues single-material systems.

Inventive Principle:

Principle #40Composite materials

2Productivity

If printing speed is increased, then productivity is improved, but sensitivity deteriorates

Engineering Contradiction:

Improveprinting speedVSAvoidsensitivity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent optimizes multiple parameters simultaneously: the molecular weight of polyarylate resin (viscosity-average molecular weight of 20,000 to 100,000), the weight ratio of charge-transporting compound to polyarylate resin (5:95 to 95:5), and the specific chemical structure of charge-transporting compounds. These parameter optimizations enable high-speed printing while maintaining high sensitivity by ensuring adequate charge generation and transport efficiency even at increased printing speeds.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If polycarbonate resin is used in charge transport layer, then sensitivity is improved, but mechanical strength deteriorates

Engineering Contradiction:

ImprovesensitivityVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces the conventional polycarbonate resin system with a composite system using polyarylate resin combined with specific charge-transporting compounds. This composite material achieves both high mechanical strength (inheriting from polyarylate resin) and high sensitivity (restored through optimized charge-transporting compound content), thereby overcoming the limitation of polycarbonate resin which provides good sensitivity but insufficient mechanical strength.

Inventive Principle:

Principle #40Composite materials

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 achieves high durability and sensitivity levels, with the charge-transporting compound aligning effectively in the charge transport layer to improve hole-transporting properties and wear resistance without degrading sensitivity, as demonstrated by the electrophotographic photosensitive member's performance in various applications.

Implementation Method 1

a charge transport layer formed on the charge generation layer and having the charge transport layer as a surface layer

Methodology Applied

Scientific EffectCharge transport: Conduction (electrical)

Implementation Method 2

the charge transport layer comprises a polyester resin having a structural unit represented by the following formula (1)

Methodology Applied

Scientific EffectPolymer structure:

Data Source

PatentUS20240168398A1Electrophotographic photosensitive member, process cartridge and electrophotographic apparatus

Publication Date: 2024.05.23 CANON KK

AI summary

To provide an electrophotographic photosensitive member capable of satisfying both high durability and high sensitivity at a high level. An electrophotographic photosensitive member having a support, a charge generation layer formed on the support and a charge transport layer formed on the charge generation layer, the charge transport layer being a surface layer, in which the charge transport layer comprises a polyester resin having a structural unit represented by the following formula (1) and a charge-transporting compound represented by the following formula (HTM1).