Photoconductor Overcoat with Four-Functional Charge Transport Molecule

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Solution Overview

Problem

Organic photoconductor drums in electrophotographic image forming devices suffer from mechanical abrasion, leading to electrical degradation and reduced image quality, necessitating a protective overcoat that enhances durability without compromising electrophotographic properties.

Innovation Solution

A curable overcoat layer comprising a charge transport molecule with four radical polymerizable hydrophilic functional groups containing an oxygen atom, such as acrylate or methacrylate groups, is applied to the photoconductor drum, providing improved mechanical properties and hole mobility while maintaining charge transport efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If a protective overcoat layer is applied to the photoconductor drum surface, then mechanical durability and service life are improved, but electrical properties such as charge transport efficiency may deteriorate

Engineering Contradiction:

Improveservice lifeVSAvoidelectrical properties

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent changes the chemical parameters of the overcoat layer by incorporating charge transport molecules with specific functional groups (acrylate, methacrylate, glycidyl ether, or epoxy groups) that enable both mechanical protection and electrical functionality. The molecular structure parameters are optimized to balance durability and charge transport efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The overcoat layer is formulated as a composite material containing charge transport molecules combined with polymeric binders and crosslinking agents. This composite structure integrates the mechanical strength of polymers with the electrical charge transport capabilities of the functional molecules, resolving the contradiction between protection and electrical performance

Inventive Principle:

Principle #40Composite materials

2Strength

If the overcoat layer is made more robust for durability, then mechanical strength is improved, but charge migration capability to the photoconductor surface deteriorates

Engineering Contradiction:

Improvemechanical strengthVSAvoidcharge migration capability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The charge transport molecules in the overcoat layer are designed to perform multiple functions simultaneously: providing mechanical strength through polymer network formation and enabling charge migration through their inherent charge transport properties. Molecules with four functional groups serve both structural and electrical roles, eliminating the need to choose between strength and charge migration

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Strength

If crosslinking density is increased to improve mechanical properties, then abrasion resistance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveabrasion resistanceVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The overcoat formulation includes crosslinking agents and initiators that enable the coating to self-crosslink during the curing process. The system automatically forms the crosslinked network structure without requiring complex external processing equipment or multi-step manufacturing procedures, achieving high abrasion resistance through a relatively simple manufacturing process

Inventive Principle:

Principle #25Self-service

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 overcoat layer significantly extends the life of the photoconductor drum, allowing for printing of at least 100,000 pages without replacement, with excellent adhesion, optical transparency, and crack-free performance, while maintaining image quality and electrical properties.

Implementation Method 1

a charge transport molecule with four radical polymerizable hydrophilic functional groups containing an oxygen atom

Methodology Applied

Scientific EffectRadical polymerization: Photopolymerisation

Implementation Method 2

four radical polymerizable hydrophilic functional groups containing an oxygen atom, such as acrylate or methacrylate groups

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Data Source

PatentUS10495991B2Photoconductor having protective overcoat layer with a charge transport molecule with four radical polymerizable hydrophilic functional groups containing an oxygen atom and method of making the same

Publication Date: 2019.12.03 LEXMARK INTERNATIONAL INC

AI summary

A method to make an improved organic photoconductor drum of an electrophotographic image forming device is provided. The improved organic photoconductor drum is prepared using a curable composition including a charge transport molecule containing four radical polymerizable functional groups containing an oxygen atom of the general structure shown below:wherein R1 and R2 contain a spacer group and a radical polymerizable hydrophilic functional group containing an oxygen atom, R3 and R4 are a non-radical polymerizable functional group, and R5 and R6 contain a spacer group and a radical polymerizable hydrophilic functional group containing an oxygen atom. The curable composition may also contain at least one optional curing agent.