Photoreceptor Protective Layer for Initial Image Deletion

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Solution Overview

Problem

Existing electrophotographic photoreceptors experience image deletion due to charge transfer from non-exposure to exposure parts during the initial stages of printing, which blurs images, despite the use of protective layers with polyfunctional acrylates and metal oxide particles for mechanical strength and electrical properties.

Innovation Solution

Incorporating conductive particles with a band gap of 2.0 eV to 3.6 eV and particles with a band gap of 8.0 eV or more into the protective layer, formed with a curable resin like polyfunctional methacrylate, to enhance charge transport properties and suppress charge flow in the surface direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a protective layer is formed using polyfunctional acrylate or polyfunctional methacrylate as curable resin and incorporating metal oxide particles for enhancing electrical properties, then mechanical strength and abrasion resistance are improved, but image deletion occurs at the initial stage of start of printing due to charge transfer from non-exposure part to exposure part

Engineering Contradiction:

Improvemechanical strengthVSAvoidimage quality

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent uses a composite protective layer containing both conductive particles (metal oxide with band gap 2.0-3.6 eV) and insulating particles (with band gap 8.0 eV or more) in combination with curable resin. This composite structure balances charge transport properties (preventing image deletion) while maintaining mechanical strength and abrasion resistance. The specific combination ratio and particle selection resolve the contradiction between electrical properties and image quality.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conductive particles with band gap of 2.0 eV to 3.6 eV are incorporated into the protective layer to enhance charge transport properties, then image deletion is suppressed, but surface resistivity becomes too low causing charge flow in surface direction

Engineering Contradiction:

Improveimage qualityVSAvoidcharge transfer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by using two types of particles with different electrical properties: conductive particles (metal oxide, band gap 2.0-3.6 eV) for vertical charge transport and insulating particles (band gap 8.0 eV or more) for blocking surface charge flow. This spatial and functional differentiation within the protective layer resolves the contradiction between preventing image deletion and avoiding surface charge transfer.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent controls the band gap parameter of particles incorporated in the protective layer. By selecting conductive particles with band gap 2.0-3.6 eV and insulating particles with band gap 8.0 eV or more, and controlling their content ratios, the protective layer achieves optimal surface resistivity that prevents both image deletion and surface charge flow.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If particles with band gap of 8.0 eV or more are incorporated into the protective layer to suppress charge flow in surface direction, then surface resistivity increases preventing charge transfer, but mechanical strength and abrasion resistance decrease

Engineering Contradiction:

Improvecharge transferVSAvoidmechanical strength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent creates a composite protective layer combining curable resin, conductive particles (metal oxide, band gap 2.0-3.6 eV), and insulating particles (band gap 8.0 eV or more). The curable resin matrix provides mechanical strength and abrasion resistance, while the dual-particle system controls electrical properties. This composite approach resolves the contradiction between suppressing charge transfer and maintaining 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

This combination effectively prevents image deletion at the start of printing by reducing surface resistivity and charge transfer, maintaining image quality and extending photoreceptor life.

Implementation Method 1

a layer that contains a compound having a chain-polymerizable functional group as a binder resin and applying an energy, such as heat, light, or radiation, thereto to cause polymerization

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

conductive particles having a band gap of 2.0 eV or more and 3.6 eV or less... effectively prevents image deletion at the start of printing by reducing surface resistivity and charge transfer

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 3

particles having a band gap of 8.0 eV or more... suppress charge flow in the surface direction

Methodology Applied

Scientific EffectElectrical resistance: Electrical Resistance

Data Source

PatentUS12372889B2Electrophotographic photoreceptor, electrophotographic photoreceptor cartridge, and image forming apparatus

Publication Date: 2025.07.29 MITSUBISHI CHEM CORP

AI summary

The present disclosure relates to an electrophotographic photoreceptor including at least a photosensitive layer and a protective layer in sequence on a conductive support, and the protective layer contains a cured product of a curable compound, conductive particles having a band gap of 2.0 eV or more and 3.6 eV or less, and particles having a band gap of 8.0 eV or more.