Layered Photosensitive Member for EV Curve Linearity and Gradation

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Solution Overview

Problem

Existing electrophotographic photosensitive members face challenges in achieving high character quality and digital gradation characteristics in low-line-number halftones while maintaining analog gradation characteristics, particularly due to high residual potential and poor linearity in the EV curve, which are exacerbated by the demands for size reduction and cost reduction in electrophotographic apparatus.

Innovation Solution

The photosensitive member is designed with specific parameters satisfying I1/2≤0.170 μJ/cm2, AR≤0.370, and LRi≤780 V·cm2/μJ, optimizing the EV curve to balance high sensitivity, low residual potential, and high linearity, ensuring optimal performance in high-speed processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a layered organic photosensitive member is used with conventional EV curve characteristics, then manufacturing cost and productivity are improved, but residual potential becomes high and linearity of EV curve becomes poor

Engineering Contradiction:

Improvemanufacturing cost and productivityVSAvoidlinearity of EV curve and residual potential

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by optimizing the EV curve characteristics through specific design parameters (I1/2≤0.170 μJ/cm2, AR≤0.370, LRi≤780 V·cm2/μJ). This involves adjusting the photosensitive member's material composition and layer structure to achieve the desired sensitivity, residual potential, and linearity parameters, thereby resolving the contradiction between ease of manufacture and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials in the layered organic photosensitive member structure, combining charge generation layer and charge transfer layer with specific materials that exhibit complementary properties. This composite approach allows achieving both low residual potential and high linearity while maintaining manufacturing efficiency through established layering techniques.

Inventive Principle:

Principle #40Composite materials

2Volume of moving object

If the spot diameter of semiconductor laser is reduced for digital gradation, then device size is reduced, but analog gradation characteristics deteriorate due to increased image frequency

Engineering Contradiction:

Improvedevice sizeVSAvoidgradation characteristics

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent changes the parameter relationship between exposure amount and surface potential by optimizing the EV curve linearity. This allows the system to maintain good gradation characteristics across different spot diameters and image frequencies, enabling both small device size and high-quality image formation to coexist.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a photosensitive member with universal performance that works well across different operating conditions (different spot diameters, line numbers, and image frequencies). The optimized EV curve characteristics make the system adaptable to both digital and analog gradation requirements, providing multi-functional performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If exposure light amount is increased to reduce residual potential, then sensitivity is improved, but linearity of EV curve near half-value exposure amount deteriorates

Engineering Contradiction:

ImprovesensitivityVSAvoidlinearity near half-value exposure amount

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by establishing specific relationships between exposure amount and surface potential through the optimized EV curve parameters (I1/2, AR, LRi). This creates a balanced response characteristic that maintains both high sensitivity and excellent linearity across the entire exposure range, including near the half-value exposure amount.

Inventive Principle:

Principle #35Parameter changes

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 enables both analog and digital gradations to be achieved in good balance, improving character quality and digital gradation characteristics in low-line-number halftones, while maintaining analog gradation characteristics, thus enhancing the overall performance of the electrophotographic apparatus.

Implementation Method 1

a charge generation layer containing a charge generation substance such as a photoconductive dye or a photoconductive pigment

Methodology Applied

Scientific EffectPhotoconductivity: Photoconductivity

Implementation Method 2

a charge transfer layer containing a charge transfer substance such as a photoconductive macromolecule or a photoconductive small molecule

Methodology Applied

Scientific EffectPhotoconductivity: Photoconductivity

Data Source

PatentUS12422760B2Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

Publication Date: 2025.09.23 CANON KK

AI summary

Provided is an electrophotographic photosensitive member that includes a support, a charge generation layer on the support, and a charge transfer layer on the charge generation layer and that satisfies specifications on an EV curve based on a measurement method of NESA-EV curve. The electrophotographic photosensitive member can exhibit high character quality and a digital gradation characteristic in a low-line-number halftone while maintaining an analog gradation characteristic in a high-speed process.