Photoconductor Overcoat with Radical Polymerizable Groups
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Solution Overview
Problem
Organic photoconductor drums in electrophotographic image forming devices face mechanical abrasion issues due to repeated use, leading to electrical property degradation and reduced image quality, necessitating a protective overcoat layer that maintains charge transport efficiency without being too insulating or conducting.
Innovation Solution
A curable overcoat layer composed of a charge transport molecule with four radical polymerizable hydrophilic functional groups containing oxygen atoms, which provides excellent hole mobility and mechanical robustness by crosslinking, thereby extending the life of the photoconductor drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a protective overcoat layer is coated onto the surface of the photoconductor drum, then the durability and abrasion resistance are improved, but the electrical properties (charge transport efficiency) may deteriorate if the overcoat is too insulating or conducting
Solution Approach 1:
The patent applies parameter changes by carefully controlling the functional group content (0.1-10 mmol/g) and molecular weight (1,000-1,000,000) of the polymeric material in the overcoat layer. These parameter optimizations ensure the overcoat provides sufficient mechanical protection while maintaining appropriate electrical conductivity for charge transport, thus resolving the contradiction between durability and electrical property stability.
Solution Approach 2:
The patent uses composite materials by combining the polymeric material with specific functional groups (carboxyl, hydroxyl, or carbonyl) to create an overcoat layer that integrates both mechanical protection and electrical functionality. This composite structure allows the overcoat to simultaneously improve durability while preserving charge transport efficiency through the polar interactions of the functional groups.
2Strength
If the overcoat layer is made too electrically insulating, then mechanical protection is improved, but the photoconductor drum cannot discharge properly resulting in poor latent image
Solution Approach 1:
The patent optimizes the concentration of polar functional groups (0.1-10 mmol/g) to balance mechanical strength and electrical discharge capability. This parameter control ensures the overcoat is sufficiently protective while allowing adequate charge discharge for latent image formation, preventing the overcoat from being too insulating.
3Ease of operation
If the overcoat layer is made too electrically conducting, then charge migration is improved, but the electrostatic latent image spreads resulting in blurred image
Solution Approach 1:
The patent precisely controls the functional group content (0.1-10 mmol/g) and molecular weight parameters to regulate electrical conductivity. This optimization ensures sufficient charge migration capability while preventing excessive conductivity that would cause latent image spreading and blurred images, thus maintaining manufacturing precision.
4Ease of manufacture
If conventional polymeric materials are used in the overcoat layer, then ease of manufacture is improved, but the photoconductor drum surface undergoes mechanical abrasion leading to electrical property degradation
Solution Approach 1:
The patent employs composite materials by incorporating polymeric materials with specific polar functional groups (carboxyl, hydroxyl, or carbonyl) into the overcoat layer. This composite approach enhances abrasion resistance compared to conventional materials while maintaining ease of manufacture through standard coating processes, thus extending photoconductor drum life.
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 enhances the durability and image quality of organic photoconductor drums, allowing for extended use without significant electrical property alteration, achieving ultra-long life and maintaining image quality throughout the print life.
Implementation Method 1
a charge transport molecule with four radical polymerizable hydrophilic functional groups containing oxygen atoms, which provides excellent hole mobility and mechanical robustness by crosslinking
Data Source
AI summary
An improved overcoat layer for an organic photoconductor drum used in an electrophotographic image forming device is provided. The overcoat layer is prepared from a curable composition including a charge transport molecule containing four radical polymerizable hydrophilic 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. This overcoat layer improves wear resistance of the organic photoconductor drum without negatively altering the electrophotographic properties, thus protecting the organic photoconductor drum from damage and extending its service life.