Electrophotographic Photosensitive Member Undercoat Layer Uniformity

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Solution Overview

Problem

Existing methods for producing electrophotographic photosensitive members with undercoat layers face challenges in reducing organic solvent usage and achieving high image uniformity, as they often struggle with dispersing metal oxide particles and electron transporting substances, leading to inadequate surface uniformity.

Innovation Solution

A process involving the preparation of a dispersion liquid with particles containing electron transporting substances in an aqueous medium, followed by heating the coat at a temperature equal to or more than the melting point of the electron transporting substance to form a uniform undercoat layer, which reduces organic solvent usage and enhances surface uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If metal oxide particles are dispersed in an aqueous dispersion medium to form an undercoat layer, then organic solvent usage is reduced, but the dispersibility and surface uniformity of the undercoat layer deteriorate

Engineering Contradiction:

Improveorganic solvent usageVSAvoidsurface uniformity of undercoat layer

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The patent introduces a specific binder resin as an intermediary substance that mediates between the metal oxide particles and the aqueous dispersion medium. The binder resin has hydrophilic groups that interact with water molecules and hydrophobic groups that interact with metal oxide particles, enabling uniform dispersion of metal oxide particles in the aqueous medium without requiring organic solvents. This resolves the contradiction by providing a bridging mechanism that achieves both reduced organic solvent usage and improved surface uniformity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical parameters of the dispersion medium by selecting an aqueous medium with specific pH and ionic composition that optimizes the interaction between the binder resin and metal oxide particles. The pH is controlled to ensure proper ionization of hydrophilic groups in the binder resin, enhancing its dispersing capability. This parameter optimization enables uniform particle distribution without organic solvents, resolving the contradiction between solvent reduction and surface uniformity.

Inventive Principle:

Principle #35Parameter changes

2Loss of substance

If electron transporting substance particles are used in the undercoat layer, then organic solvent usage is reduced, but the uniformity of the undercoat layer surface deteriorates

Engineering Contradiction:

Improveorganic solvent usageVSAvoiduniformity of undercoat layer surface

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The patent creates a composite material system consisting of electron transporting substance particles combined with a specifically designed binder resin that has both hydrophilic and hydrophobic characteristics. The composite structure allows the electron transporting substance to be uniformly distributed through the aqueous dispersion medium via the binder resin's dual-nature molecular structure. This composite approach enables organic solvent reduction while maintaining surface uniformity, resolving the stated contradiction.

Inventive Principle:

Principle #40Composite materials

3Loss of substance

If aqueous dispersion medium is used to form undercoat layer, then organic solvent usage is reduced, but additional improvement in image uniformity is required

Engineering Contradiction:

Improveorganic solvent usageVSAvoidimage uniformity

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The patent replaces the mechanical mixing approach typically used to disperse particles with a chemically-driven self-assembly mechanism. The binder resin's molecular structure enables spontaneous uniform distribution of particles through hydrophobic-hydrophilic interactions, eliminating the need for complex mechanical dispersion processes. This substitution of mechanical mixing with chemical self-organization achieves both organic solvent reduction and improved image uniformity, resolving the contradiction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach results in an electrophotographic photosensitive member with improved image uniformity and reduced organic solvent usage, as the electron transporting substance melts, eliminating particle boundaries and enhancing the undercoat layer's uniformity.

Implementation Method 1

heating the coat at a temperature equal to or more than the melting point of the electron transporting substance to form a uniform undercoat layer

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentEP2816412B1Process for producing electrophotographic photosensitive member

Publication Date: 2019.08.14 CANON KK

Figure 1~2

AI summary

Provided is a process for producing an electrophotographic photosensitive member, the process including the steps of: preparing a dispersion liquid by dispersing particles each containing an electron transporting substance in an aqueous dispersion medium; forming the coat of the dispersion liquid on the support; and forming an undercoat layer by heating the coat at a temperature equal to or more than the melting point of the electron transporting substance.