Hydrogenated Amorphous Carbon Surface Layer for Electrophotographic Photosensitive Member
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Solution Overview
Problem
The electrophotographic photosensitive members with hydrogenated amorphous carbon (a-C:H) surface layers face challenges in achieving both high barrier properties to prevent oxidation and good image resolving power, as the characteristics required for these properties tend to be mutually exclusive due to the effects of negative ions and discharge products during the charging process.
Innovation Solution
The solution involves an electrophotographic photosensitive member configuration with a hydrogenated amorphous carbon surface layer having a hydrogen content ratio of 0.40 or less and an sp2 bonding ratio of 0.50 or less in the outermost surface region, along with an intermediate layer for improved charge injection blocking and image formation, optimized through specific plasma CVD conditions and surface treatments to balance barrier properties and image resolving power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the a-C:H surface layer is made with high hydrogen content to improve barrier property, then oxidation resistance is improved, but image resolving power deteriorates
Solution Approach 1:
The surface layer is designed with non-uniform hydrogen content distribution: the inner portion has high hydrogen content (0.55-0.70) for oxidation resistance, while the outermost surface region has low hydrogen content (0.05-0.35) for maintaining image resolving power. This local differentiation resolves the contradiction between barrier property and image quality.
Solution Approach 2:
The surface layer is constructed as a composite structure with two distinct regions having different compositions: an inner high-hydrogen a-C:H layer for barrier properties and an outer low-hydrogen a-C:H layer for surface performance. This composite approach allows simultaneous achievement of oxidation resistance and good image resolving power.
2Duration of action of stationary object
If the a-C:H surface layer hardness is increased to improve wear resistance, then durability is improved, but surface resistance decreases making it difficult to maintain latent image
Solution Approach 1:
The surface layer exhibits local quality differentiation where the inner portion has high hardness for wear resistance while the outermost surface region has appropriate surface resistance for latent image maintenance. This spatial variation in properties resolves the contradiction between durability and image maintenance capability.
3Reliability
If negative ions and discharge products reach the layer under the surface layer, then charge injection blocking is improved, but oxidation of underlying layers occurs
Solution Approach 1:
The high-hydrogen inner portion of the surface layer acts as an intermediary that allows negative ions to pass through for charge injection blocking while preventing oxygen permeation that would cause oxidation. This selective permeability mediated by the inner layer resolves the contradiction between charge blocking and oxidation prevention.
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 configuration effectively prevents oxidation of underlying layers while maintaining excellent image resolving power, allowing for both enhanced durability and image quality in electrophotographic applications.
Implementation Method 1
the ability (hereinafter, referred to as a 'barrier property') to prevent the negative ions or the discharge products reaching the a-C:H surface layer from permeating through the layer under the surface layer
Implementation Method 2
a method for forming a hydrogenated amorphous carbon film on a photoconductive layer
Implementation Method 3
The charging step is often performed by atmospheric discharge, and ions generated by the atmospheric discharge reach the surface of the electrophotographic photosensitive member to apply electric charges to the surface of the photosensitive member
Data Source
AI summary
An average value of a hydrogen content ratio of a surface layer made of hydrogenated amorphous carbon is set to be 0.40 or less and a maximum value of an sp2 bonding ratio in an outermost surface region of the surface layer made of the hydrogenated amorphous carbon is set to be 0.50 or less.