Hydroxygallium Phthalocyanine Pigment Dark Decay Reduction
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Solution Overview
Problem
Existing electrophotographic photosensitive members with thick charge generating layers suffer from increased dark decay, leading to fogging in non-image areas and reduced image quality, despite improvements in phthalocyanine pigment electrical properties.
Innovation Solution
The use of hydroxygallium phthalocyanine and chlorogallium phthalocyanine pigments with specific X-ray diffraction spectra and crystallite correlation lengths, controlled through a two-step milling process and optimized water content, to reduce dark decay and enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the charge generating layer thickness is increased to reduce interference fringes, then image quality is improved, but dark decay increases causing fogging
Solution Approach 1:
The patent changes the crystal form parameter of the phthalocyanine pigment from conventional forms to Form H, which has specific X-ray diffraction characteristics (peaks at 2θ=7.0°±0.3°, 9.8°±0.3°, 12.4°±0.3°, 16.2°±0.3°, 18.5°±0.3°, 25.0°±0.3°, and 28.2°±0.3°). This parameter change in crystal structure reduces dark decay while allowing the charge generating layer to maintain optimal thickness for reducing interference fringes.
Solution Approach 2:
The patent uses a composite charge generating layer containing both the specific phthalocyanine pigment (Form H) and a charge generating polymer. This composite structure combines the advantages of reduced dark decay from the pigment's crystal form with the charge generation capabilities needed for high-quality imaging, resolving the contradiction between image quality and dark decay.
2Reliability
If conventional phthalocyanine pigments are used to improve electrical properties, then charge generation is enhanced, but dark decay increases
Solution Approach 1:
The patent changes the crystal form parameter of the phthalocyanine pigment to Form H, which has specific X-ray diffraction characteristics that distinguish it from conventional forms. This parameter change in crystal structure reduces dark decay while maintaining the charge generation capabilities needed for high reliability electrical properties.
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 solution effectively reduces dark decay and improves image quality by controlling the crystallite correlation lengths and pigment alignment, leading to high-quality images with reduced interference fringes and improved charge carrier migration.
Implementation Method 1
Multilayer photosensitive layers including a charge generating layer containing a charge generating material and a charge transport layer containing a charge transporting material are the mainstream of the photosensitive layer of electrophotographic photosensitive members
Implementation Method 2
The hydroxygallium phthalocyanine pigment exhibits a CuKα X-ray diffraction spectrum having peaks at Bragg angles 2θ of 7.4°±0.3° and 28.2°±0.3°
Data Source
AI summary
An electrophotographic photosensitive member includes, in this order, a support, a charge generating layer having a thickness of more than 200 nm and containing a hydroxygallium phthalocyanine pigment or a chlorogallium phthalocyanine pigment as a charge generating material, and a charge transport layer containing a charge transporting material. The charge generating material satisfies a requirement for a specific parameter.