Formaldehyde-Free Protective Overcoat Layer for Photoreceptors

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Solution Overview

Problem

Conventional electrophotographic imaging members with melamine-formaldehyde overcoat layers generate high levels of free formaldehyde, posing health and environmental hazards, and do not meet the demands for improved imaging performance and longer lifespan in high-speed copiers and printers.

Innovation Solution

A protective overcoat layer is developed without melamine formaldehyde, using a polyol binder and a hole transport material with hydroxymethyl substituents capable of cross-linking with the binder, eliminating the need for melamine-formaldehyde cross-linking agents and reducing free formaldehyde levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If melamine-formaldehyde cross-linking agents are used in the overcoat layer, then the overcoat provides adequate protection and adhesion, but high levels of free formaldehyde are generated posing health and environmental hazards

Engineering Contradiction:

Improveovercoat protection and adhesionVSAvoidfree formaldehyde emissions

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent removes the melamine-formaldehyde cross-linking agent from the overcoat composition, extracting the harmful formaldehyde-generating component while retaining the protective function through alternative cross-linking mechanisms using polyol binders and hydroxymethyl-functionalized hole transport materials

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the chemical composition parameters of the overcoat by substituting melamine-formaldehyde with polyol-based binders and hydroxymethyl-functionalized hole transport materials, fundamentally altering the cross-linking chemistry to eliminate formaldehyde emissions while maintaining protective properties

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional overcoat formulations are used, then manufacturing is simplified, but imaging performance and lifespan do not meet the demands for high-speed copiers and printers

Engineering Contradiction:

Improveovercoat formulation simplicityVSAvoidimaging speed and lifespan

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent employs composite materials by combining polyol binders with hydroxymethyl-functionalized hole transport materials to create an overcoat that simultaneously achieves enhanced durability for high-speed operation and acceptable manufacturing complexity through a single integrated formulation

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If melamine-formaldehyde cross-linking is used, then the overcoat forms adequately, but the cross-linking process generates harmful formaldehyde emissions

Engineering Contradiction:

Improveovercoat cross-linking and structural integrityVSAvoidformaldehyde emissions during cross-linking

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the previously harmful melamine-formaldehyde cross-linking chemistry into a beneficial formaldehyde-free alternative by using polyol binders and hydroxymethyl-functionalized hole transport materials that cross-link without releasing harmful emissions, thereby maintaining structural integrity while eliminating harm

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly reduces free formaldehyde emissions while maintaining electrical and mechanical performance, enhancing the imaging member's lifespan and print quality without the use of melamine-formaldehyde cross-linking agents.

Implementation Method 1

a hole transport material with hydroxymethyl substituents capable of cross-linking with the binder

Methodology Applied

Scientific EffectCross-linking: Chemical Bonding

Data Source

PatentUS8309285B2Protective overcoat layer and photoreceptor including same

Publication Date: 2012.11.13 XEROX CORP

AI summary

Disclosed is an electrophotographic imaging member that includes a substrate; a charge generating layer; a charge transport layer; and a protective overcoat layer having a polyol binder; a hole transport material; an acid catalyst; a leveling agent; and no melamine formaldehyde curing agent or cross-linking additive. Also disclosed is a process for forming a photoreceptor that includes providing a substrate; applying to it a charge generating layer, charge transport layer; and protective over coating layer having a polyol binder; a hole transport material; an acid catalyst; a leveling agent; and no melamine formaldehyde curing agent or cross-linking additive. Additionally provided is a method of forming an image with the disclosed electrophotographic imaging member.