Electrophotographic Photosensitive Layer with Silica for Pattern Memory

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Solution Overview

Problem

Pattern memory occurs in electrophotographic images under high-temperature and high-humidity environments due to sensitivity changes in electrophotographic photosensitive members containing metal-free phthalocyanine or oxytitanium phthalocyanine as charge-generating substances and toners with polyester resins having polyethylene terephthalate segments, leading to density differences in halftone images.

Innovation Solution

Incorporating silicon atom-containing particles, such as silica or silicone resin particles, into the surface layer of the electrophotographic photosensitive member to reduce moisture influence on the charge-generating substance, thereby suppressing pattern memory.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If metal-free phthalocyanine or oxytitanium phthalocyanine is used as charge-generating substance and polyester resin with polyethylene terephthalate segment is used in toner, then image formation capability is improved, but pattern memory occurs under high-temperature and high-humidity environment

Engineering Contradiction:

Improveimage formation capabilityVSAvoidpattern memory

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Silicon atom-containing particles are introduced as an intermediary substance between the charge-generating substance and moisture in the environment. These particles form a protective interface that prevents moisture from directly interacting with the metal-free phthalocyanine or oxytitanium phthalocyanine, thereby eliminating the pattern memory effect while preserving the excellent image formation capability provided by these charge-generating substances

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the physical and chemical parameters of the surface layer by incorporating silicon atom-containing particles with specific properties (silica particles with 5-20 nm diameter or silicone resin particles). This parameter change modifies the surface characteristics to reduce moisture affinity, preventing the sensitivity changes that cause pattern memory under high-temperature and high-humidity conditions

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If silica particles or silicone resin particles are added to the surface layer, then pattern memory is suppressed, but device complexity increases

Engineering Contradiction:

Improvepattern memory suppressionVSAvoidphotosensitive member structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The surface layer is segmented into distinct functional components: binder resin, charge-generating substance, hole-transporting substance, electron-transporting substance, and silicon atom-containing particles. This segmentation allows each component to perform its specific function independently, with the silicon particles specifically targeting moisture interaction to suppress pattern memory without interfering with other functions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The surface layer is formulated as a composite material containing multiple substances in specific proportions. The silicon atom-containing particles are integrated into the composite structure at 0.1-10 mass% concentration, creating a multi-functional material that maintains charge generation, charge transport, and moisture resistance properties simultaneously

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

The solution effectively suppresses pattern memory in electrophotographic images by minimizing sensitivity changes caused by moisture, ensuring stable image formation even in high-temperature and high-humidity conditions.

Implementation Method 1

Methodology Applied

Scientific EffectMoisture barrier effect: Adsorption

Implementation Method 2

an image exposing unit configured to irradiate the charged surface of the electrophotographic photosensitive member with image exposure light to form an electrostatic latent image

Methodology Applied

Scientific EffectPhotoexcitation: Photoelectric Effect

Data Source

PatentUS20250231521A1Electrophotographic apparatus

Publication Date: 2025.07.17 CANON KK

AI summary

Provided is an electrophotographic apparatus that suppresses the occurrence of a pattern memory and enables stable image formation under a high-temperature and high-humidity environment. The electrophotographic apparatus includes: an electrophotographic photosensitive member; a charging unit; an image exposing unit; a developing unit including a toner; a transfer unit; a cleaning unit; and a fixing unit. The electrophotographic photosensitive member includes a monolayer-type photosensitive layer containing a binder resin, a charge-generating substance, a hole-transporting substance, an electron-transporting substance, and silicon atom-containing particles. The monolayer-type photosensitive layer is a surface layer of the electrophotographic photosensitive member. The charge-generating substance is one of metal-free phthalocyanine or oxytitanium phthalocyanine. The silicon atom-containing particles are one of silica particles or silicone resin particles. The toner includes toner particles each containing a polyester resin having a polyethylene terephthalate segment.