LEP Printing System Maintenance for Ghost Memory
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Solution Overview
Problem
Liquid electro-photographic (LEP) printing systems face issues with 'negative dot gain (NDG) ghost memory' and related printing defects, where repetitive printing of the same image leads to uneven pigment distribution and ghost images due to hidden charged and uncharged spots on the intermediate transfer member (ITM), causing print quality issues.
Innovation Solution
The system switches to maintenance mode by applying a higher voltage difference between the photoconductor (PIP) and the ITM, disabling particle transfer and selective discharge, and increasing the bias voltage on the ITM to mitigate NDG ghost memory effects, which involves disengaging the BID assembly from the PIP, halting the pressure roller, and applying a high voltage to the ITM during a null cycle to reduce or eliminate these defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If repetitive printing of the same image is performed in production mode, then printing productivity is improved, but negative dot gain ghost memory and uneven pigment distribution occur on the intermediate transfer member
Solution Approach 1:
The system alternates between production mode and maintenance mode periodically. During maintenance mode, a higher voltage difference is applied to the photoconductor and ITM to redistribute accumulated pigment and eliminate ghost memory effects, thereby restoring uniform pigment distribution without compromising long-term printing productivity
Solution Approach 2:
The voltage difference parameter between the photoconductor and ITM is dynamically adjusted. In production mode, a lower voltage difference is used for normal printing. In maintenance mode, a higher voltage difference is applied to mitigate NDG ghost memory and restore uniform pigment distribution on the ITM surface
2Manufacturing precision
If higher voltage difference is applied to mitigate NDG ghost memory, then print quality is improved, but energy consumption increases
Solution Approach 1:
The high voltage maintenance operation is performed periodically rather than continuously. The system switches to maintenance mode only when ghost memory or pigment accumulation is detected, applying higher voltage temporarily to restore print quality, then returns to production mode with lower energy consumption
Solution Approach 2:
The system automatically detects print quality degradation through monitoring mechanisms and autonomously initiates maintenance mode with higher voltage application. This self-regulating mechanism ensures high print quality is maintained only when necessary, minimizing unnecessary energy consumption while keeping the system self-correcting
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 approach effectively reduces or eliminates NDG ghost memory and related printing defects, improving print quality by ensuring uniform pigment distribution and preventing ghost images, and can be initiated based on predefined print counts or detected defects, with the option to repeat the maintenance program as needed.
Implementation Method 1
Liquid electro-photographic (LEP) printing, sometimes also referred to as liquid electrostatic printing, uses liquid toner to form images on paper, foil, or another print medium. The liquid toner, which is also referred to as electro-ink, includes charged pigmented particles, and a printing process is controlled on the basis of electrophoresis.
Implementation Method 2
The ITM may comprise a blanket or belt and is to be charged to a bias voltage
Data Source
AI summary
A liquid electro-photographic, LEP, printing system, comprising a photo imaging plate, PIP, an intermediate transfer member, ITM, and a control unit. The control unit causes the system to initiate a maintenance program, wherein the maintenance program comprises driving the PIP and the ITM while disabling particle transfer to the PIP and applying a voltage difference between the PIP and surface portions of the ITM.