Charge Transporting Layer Gradient for Wear Resistance
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Solution Overview
Problem
Existing methods for producing electrophotographic photosensitive members with a charge transporting layer that simultaneously achieve high wear resistance and potential stability are costly and complex, often requiring multiple lamination steps and annealing processes, which can lead to insufficient wear resistance and increased production costs.
Innovation Solution
A method involving a charge-transporting-layer coating liquid containing a charge transporting substance, a polycarbonate or polyester resin, an aromatic hydrocarbon solvent, and a compound with a higher boiling point, where the solubility of the charge transporting substance in the solvent creates a concentration gradient in the charge transporting layer, enhancing wear resistance and potential stability without the need for multiple lamination or annealing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple lamination steps are used to create charge transporting layers with different concentrations, then potential stability is improved, but device complexity and production cost increase
Solution Approach 1:
The patent combines multiple charge transporting layers with different concentrations into a single layer by using a concentration gradient structure. Instead of laminating separate layers, the invention creates a continuous gradient of charge transporting substance concentration within one layer, thereby reducing the number of manufacturing steps while maintaining potential stability.
Solution Approach 2:
The patent applies local quality by creating a concentration gradient of the charge transporting substance within the charge transporting layer. The concentration varies continuously from the surface toward the charge generating layer, with higher concentrations near the charge generating layer and lower concentrations at the surface. This local variation in concentration provides different functional characteristics at different depths of the same layer.
2Ease of manufacture
If charge transporting substance is contained in the vicinity of the surface of the charge transporting layer, then ease of manufacture is improved, but wear resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of the charge transporting substance within the charge transporting layer. The concentration varies continuously from the surface toward the charge generating layer, with higher concentrations near the charge generating layer and lower concentrations at the surface. This local variation in concentration provides different functional characteristics at different depths of the same layer.
3Reliability
If annealing or solvent vapor holding steps are added to create concentration gradient, then potential stability is improved, but production time increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the concentration gradient structure during the coating process itself, rather than requiring subsequent annealing or solvent vapor holding steps. The coating liquid is designed with specific components that automatically form the gradient structure as the coating dries, eliminating the need for additional time-consuming post-processing steps.
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 method simplifies the production process while achieving high wear resistance and potential stability, ensuring stable image quality even after repeated use, by forming a charge transporting layer with a graded structure that optimizes the distribution of charge transporting substances and binder resins.
Implementation Method 1
the charge-transporting-layer coating liquid contains: (α) a charge transporting substance, (β) at least one resin selected from the group consisting of a polycarbonate resin having a structural unit represented by the following formula (1A), and a polyester resin having a structural unit represented by the following formula (1B), (γ) an aromatic hydrocarbon solvent, and (δ) a compound having a boiling point under 1 atmosphere higher than that of the (γ); the charge-transporting-layer coating liquid is free of any polyester resins having a siloxane structure at the end thereof and any polycarbonate resins having a siloxane structure at the end thereof; and the (α), the (γ) and the (δ) satisfy the following expression. X(g)>Y(g) In the expression, X(g) represents the solubility of the (α) in 100 g of the (γ) in an environment at 23° C. under 1 atmosphere, and Y(g) represents the solubility of the (α) in 100 g of the (δ) in an environment at 23° C. under 1 atmosphere.
Implementation Method 2
forming a coat for the charge transporting layer using a charge-transporting-layer coating liquid, and drying the coat to form the charge transporting layer
Data Source
AI summary
A method for producing an electrophotographic photosensitive member having a charge transporting layer, the charge transporting layer being a surface layer, the method including drying a coat of a charge-transporting-layer coating liquid to form the charge transporting layer, wherein the charge-transporting-layer coating liquid contains components (α), (β), (γ) and (δ), and when the solubility of the component (α) in 100 g of the component (γ) is defined as X(g) and the solubility of the component (α) in 100 g of the component (δ) is defined as Y(g), solubility X and solubility Y satisfy a relationship of X>Y.