Electrophotographic Photoreceptor Polyester Layer for Humidity-Stable Imaging
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Solution Overview
Problem
Existing electrophotographic photoreceptors face issues with non-uniform potential distribution and increased image defects in high temperature-high humidity environments due to the properties of the polyester resin in the charge transport layer.
Innovation Solution
The use of a polyester resin in the charge transport layer with a molecular weight distribution curve featuring at least two peaks and a specific weight average molecular weight range (50,000 ≤ Mw ≤ 200,000) and a peak separation ratio (0.4 ≤ (Mmax - Mmin)/Mw ≤ 5.0) ensures uniform potential distribution and reduces image defects in high temperature-high humidity conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyester resin is used in the charge transport layer, then the photoreceptor can be manufactured with standard materials, but the potential distribution on the surface becomes non-uniform and image defects increase in high temperature-high humidity environments
Solution Approach 1:
The patent changes the molecular weight parameters of the polyester resin, specifically setting Mw between 50,000-200,000 and controlling the molecular weight distribution curve to have at least two peaks with (Mmax-Mmin)/Mw between 0.4-5.0. This parameter optimization resolves the contradiction by achieving both uniform potential distribution and high reliability in harsh environments.
Solution Approach 2:
The patent uses a composite molecular weight distribution structure with at least two peaks in the polyester resin, combining different molecular weight components. This composite approach allows the material to exhibit both good processing properties (uniform potential distribution) and enhanced environmental stability (reduced image defects in high temperature-high humidity conditions).
2Reliability
If polyester resin with single peak molecular weight distribution is used, then the material structure is simple, but the photoreceptor generates image defects in high temperature-high humidity environments
Solution Approach 1:
The patent optimizes the molecular weight distribution parameters by introducing a multi-peak structure with specific characteristics (at least two peaks, (Mmax-Mmin)/Mw between 0.4-5.0). This controlled complexity in the molecular weight distribution provides both the reliability needed to prevent image defects and manages the complexity through defined parameter ranges.
3Manufacturing precision
If polyester resin with Mw outside the 50,000-200,000 range is used, then the material properties differ, but the photoreceptor shows non-uniform potential distribution and increased image defects
Solution Approach 1:
The patent establishes specific parameter boundaries for the molecular weight (Mw between 50,000-200,000) and molecular weight distribution ((Mmax-Mmin)/Mw between 0.4-5.0 with at least two peaks). This parameter optimization simultaneously achieves uniform potential distribution and appropriate material properties, resolving the contradiction between manufacturing precision and material quantity characteristics.
Data Source
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AI summary
An electrophotographic photoreceptor includes: a conductive substrate; and a multilayer-type photosensitive layer that is disposed on the conductive substrate and has a charge generation layer and a charge transport layer. The charge transport layer contains a charge-transporting material and a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B). The polyester resin (1) contained in the charge transport layer has a molecular weight distribution curve with at least two peaks and satisfies 50,000 ≤ Mw ≤ 200,000, and 0.4 ≤ (Mmax - Mmin)/Mw ≤ 5.0, wherein Mmin is a molecular weight at a top of a peak corresponding to a lowest molecular weight, Mmax is a molecular weight at a top of a peak corresponding to a highest molecular weight, and Mw is a weight average molecular weight of the polyester resin (1) contained in the charge transport layer. In formula (A), ArA1 and ArA2 are each independently an optionally substituted aromatic ring, LA is a single bond or a divalent linking group, and nA1 is 0, 1, or 2. In formula (B), ArB1 and ArB2 are each independently an optionally substituted aromatic ring, LB is a single bond, an oxygen atom, a sulfur atom, or -C(Rb1)(Rb2)-, and nB1 is 0, 1, or 2; and Rb1 and Rb2 are each independently a hydrogen atom, a C1-C20 alkyl group, a C6-C12 aryl group, or a C7-C20 aralkyl group, and Rb1 and Rb2 taken together may form a cyclic alkyl group.