Electrophotographic Photoreceptor Surface Layer Dielectric Control
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Solution Overview
Problem
Electrophotographic photoreceptors face issues with increased residual potential and surface potential differences between image and non-image portions, leading to ghost phenomena and image defects due to polarization of alkyl fluoride group-containing copolymers in the uppermost surface layer, which affects the internal electric field and image quality.
Innovation Solution
The use of a conductive substrate with a photosensitive layer and a surface protective layer composed of a cured film containing reactive charge transporting materials with —OH and —OCH3 groups, fluororesin particles, and an alkyl fluoride group-containing copolymer, adjusting the relative dielectric constant to a range of 3.5 to 4.0 to inhibit polarization and maintain a stable internal electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an alkyl fluoride group-containing copolymer is used in the uppermost surface layer, then the dispersibility of fluororesin particles is improved, but polarization occurs leading to increased residual potential and ghost phenomena
Solution Approach 1:
The patent changes the dielectric constant parameter of the uppermost surface layer by selecting specific charge transporting materials with appropriate dielectric constants to ensure the layer's dielectric constant is 4.0 or less. This parameter adjustment prevents excessive polarization while maintaining the copolymer's dispersibility function, thereby resolving the contradiction between improved dispersibility and reduced ghost phenomena.
Solution Approach 2:
The patent employs a composite material system in the uppermost surface layer that includes fluororesin particles, alkyl fluoride group-containing copolymer, and specifically selected charge transporting materials. This composite structure allows the copolymer to perform its dispersibility function while the carefully chosen charge transporting materials control the overall dielectric properties, preventing polarization-related defects.
2Reliability
If the dielectric constant of the uppermost surface layer is increased to reduce polarization, then ghost phenomena are reduced, but the internal electric field stability deteriorates
Solution Approach 1:
The patent optimizes the dielectric constant parameter to a specific range (≤4.0) that balances two competing requirements: it is low enough to prevent excessive polarization and ghost phenomena, yet high enough to maintain stable internal electric field characteristics. This precise parameter control resolves the contradiction between ghost suppression and electric field stability.
3Duration of action of stationary object
If a resin with high mechanical strength is used to extend photoreceptor life, then durability is improved, but the polarization tendency increases leading to image defects
Solution Approach 1:
The patent creates a composite uppermost surface layer that combines fluororesin particles (providing mechanical strength and durability) with specifically selected charge transporting materials (controlling dielectric properties). This composite structure allows the fluororesin to extend photoreceptor life while the charge transporting materials prevent excessive polarization, thereby resolving the contradiction between durability and image quality.
Solution Approach 2:
The patent applies local quality control by ensuring that the uppermost surface layer has specific dielectric properties (dielectric constant ≤4.0) that differ from other layers. This localized property adjustment prevents polarization in the critical surface region where image formation occurs, while allowing other parts of the photoreceptor to maintain high mechanical strength for durability.
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 reduces residual potential and surface potential differences, preventing ghost phenomena and image defects, thereby improving image quality and extending the life of the electrophotographic photoreceptor.
Implementation Method 1
a cured film of a composition that contains at least two kinds of reactive charge transporting materials selected from a first reactive charge transporting material having an —OH group as a reactive functional group and a second reactive charge transporting material having an —OCH3 group as a reactive functional group
Implementation Method 2
an alkyl fluoride group-containing copolymer having repeating units represented by the following Structural. Formulae A and B, and a relative dielectric constant ∈r of the uppermost surface layer satisfies the following Formula (1): 3.5 ≤ ∈r ≤ 4.0
Data Source
AI summary
Provided is an electrophotographic photoreceptor including a conductive substrate and a photosensitive layer provided on the conductive substrate, wherein an uppermost surface layer thereof is constituted with a cured film of a composition that contains at least two kinds of reactive charge transporting materials selected from a first reactive charge transporting material having an —OH group as a reactive functional group and a second reactive charge transporting material having an —OCH3 group as a reactive functional group, fluororesin particles, and an alkyl fluoride group-containing copolymer having repeating units represented by the following Structural Formulae A and B, and a relative dielectric constant ∈r of the uppermost surface layer satisfies the following Formula (1):