Polysiloxane Resin Stabilizes Charge Transporting Layer
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Solution Overview
Problem
Electrophotographic photosensitive members with thick charge transporting layers are prone to coating defects and potential fluctuations, leading to image failures and reduced longevity in electrophotographic apparatuses.
Innovation Solution
Incorporating a polysiloxane resin with a siloxane structure at the end, combined with a polycarbonate resin A or polyarylate resin B, and a charge transporting substance in the charge transporting layer, with a siloxane content between 0.5% to 10% by mass, to stabilize the layer and prevent segregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the thickness of the charge transporting layer is increased to extend the life of the electrophotographic photosensitive member, then the durability is improved, but coating defects such as cissing, orange peel, streaking, or unevenness occur
Solution Approach 1:
The patent changes the chemical composition parameters of the binder resin by introducing a siloxane-modified polyester resin with specific structural characteristics (formula (1) with controlled a value and specific groups). This parameter change allows the resin to maintain proper coating flow and uniformity even when the layer thickness is increased, resolving the contradiction between durability and coating precision.
Solution Approach 2:
The patent uses a composite binder resin system combining siloxane-modified polyester resin with specific structural units (formulas (A) and (B)). This composite material approach provides both the mechanical strength needed for thick layers and the flow properties required for uniform coating, eliminating coating defects while extending component life.
2Manufacturing precision
If a polysiloxane resin is added to improve leveling and reduce coating defects, then the coating uniformity is improved, but the polysiloxane resin segregates on the lower side (charge generating layer side) resulting in poor potential characteristics
Solution Approach 1:
The patent applies local quality by positioning the siloxane structure specifically at the end of the polyester resin chain rather than throughout the entire molecule. This localized siloxane placement provides the necessary leveling effect during coating while preventing bulk segregation to the charge generating layer, maintaining stable potential characteristics.
Solution Approach 2:
The patent precisely controls the parameter 'a' (average number of repetitions of the bracketed structure) to be within 1 to 500, and limits the siloxane content to 0.5-10% by mass. These parameter changes optimize the balance between coating uniformity and potential stability, preventing segregation while maintaining coating quality.
Data Source
AI summary
A charge transporting layer of an electrophotographic photosensitive member contains a polysiloxane resin having a terminal structure represented by the formula (1), at least one selected from the group consisting of a polycarbonate resin A having a structural unit represented by the formula (A) and a polyarylate resin B having a structural unit represented by the formula (B), and a charge transporting substance, wherein the content of the siloxane structure in the polysiloxane resin is not less than 0.5% by mass and not more than 10% by mass based on the total mass of whole resin in the charge transporting layer.