Gradient Charge Transporting Layer for Photoconductor Durability

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current electrophotographic photoconductors face issues with durability and reliability, leading to abnormal images such as background smear and toner filming, especially when used for extended periods, and there is a need for a method to reduce environmental burdens associated with halogen solvents.

Innovation Solution

A latent electrostatic image bearing member with a charge generating layer and a charge transporting layer, where the charge transporting layer contains a charge transporting material and a binder resin, has a thickness of 30 μm to 50 μm, and undergoes surface treatments like heat, UV, or corona discharge, using a non-halogen solvent to enhance durability and reduce environmental impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the thickness of charge transporting layer is increased to 30 μm or more to improve durability and prevent background smear, then the photoconductor can be used repeatedly with reduced background smear, but the electric field intensity is reduced causing resin and toner adhesion leading to abnormal images

Engineering Contradiction:

Improvedurability and background smear preventionVSAvoidresin and toner adhesion causing abnormal images

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a charge transporting layer with non-uniform composition - specifically, a gradient structure where the binder resin content varies through the thickness. The surface region has lower binder resin content (5-20 mass%) to prevent toner adhesion, while the inner region has higher binder resin content (20-40 mass%) to ensure durability and prevent background smear. This compositional gradient resolves the contradiction by providing different local properties at different depths of the same layer.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of binder resin content distribution within the charge transporting layer. Instead of uniform composition, it establishes a gradient where binder resin content decreases from the inner region toward the surface. This parameter change allows the layer to simultaneously achieve high durability (through sufficient overall thickness and inner region resin content) and low toner adhesion (through reduced surface resin content), resolving the technical contradiction.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If halogen solvents are used to achieve good solubility and coating properties of resins, then the charge transporting layer can be formed with excellent coating quality, but environmental burdens increase

Engineering Contradiction:

Improvecoating quality and solubilityVSAvoidenvironmental burdens

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical parameter of the solvent from halogen-containing to non-halogen-containing. Specifically, it uses esters (e.g., ethyl acetate, butyl acetate) or ethers (e.g., ethyl methyl carbonate, ethyl lactate) as coating solvents. This parameter change eliminates the environmental burden of halogen solvents while maintaining adequate solubility and coating properties through proper selection of ester or ether solvents with appropriate polarity and boiling points.

Inventive Principle:

Principle #35Parameter changes

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 provides improved durability and stability, preventing abnormal images and reducing environmental burdens, while maintaining high-quality image formation over long periods.

Implementation Method 1

subjecting the charge transporting layer to at least one of surface treatment selected from heat treatment, UV irradiation treatment, electron beam irradiation treatment, and corona discharge treatment

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Implementation Method 2

Methodology Applied

Scientific EffectUV irradiation: Photopolymerisation

Implementation Method 3

Methodology Applied

Scientific EffectCorona discharge: Corona Discharge

Data Source

PatentUS7560204B2Latent electrostatic image bearing member, and the method for producing the same, image forming method, image forming apparatus, and process cartridge

Publication Date: 2009.07.14 RICOH CO LTD

AI summary

The present invention provides a latent electrostatic image bearing member which includes a support, a charge generating layer, and a charge transporting layer, the charge generating layer and the charge transporting layer being arranged in this order on or above the support, wherein the charge transporting layer comprises at least a charge transporting material and a binder resin and has a thickness of 30 μm to 50 μm; and the distribution representing the relation between the absorbance ratio of the charge transporting material and the binder resin measured by infrared spectroscopy and the distance from the surface of the charge transporting layer toward the thickness direction thereof represents a generally linear shape without having inflection points within 20 μm from the surface of the charge transporting layer toward the thickness thereof.