Inkjet Printer UV Lamp Segmentation for Clear Ink Yellowing
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Solution Overview
Problem
Inkjet printers using ultraviolet light to harden clear ink often result in yellowing due to the long absorption wavelength of photoinitiators, leading to suboptimal coating quality when printing on print media with color ink.
Innovation Solution
An inkjet printer configuration that uses separate inkjet heads and lamps for color and clear inks, with specific wavelength ranges for hardening, allowing the use of photoinitiators sensitive to shorter wavelengths for clear ink, reducing yellowing and improving coating glossiness, and incorporating a moving mechanism to enhance leveling and prevent bleeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultraviolet light with long wavelength (385 nm) is used to harden clear ink, then the inner curing property of color ink is secured, but the clear ink coating is likely to yellow
Solution Approach 1:
The patent divides the single UV light source into two separate lamps with different wavelength characteristics: a first UV lamp (365-405 nm) for hardening color ink and a second UV lamp (200-365 nm) for hardening clear ink. This segmentation allows each lamp to be optimized for its specific function, preventing yellowing while maintaining curing effectiveness.
Solution Approach 2:
The patent applies different UV wavelength characteristics to different locations in the processing system. The first UV lamp with longer wavelength is positioned for color ink hardening, while the second UV lamp with shorter wavelength is positioned for clear ink hardening. This local differentiation of UV wavelength quality prevents yellowing in the clear ink region while maintaining effective curing.
2Device complexity
If a single UV lamp is used for both color and clear ink hardening, then the device structure is simple, but the clear ink coating quality deteriorates due to yellowing
Solution Approach 1:
The patent segments the UV hardening function into two separate systems with different wavelength characteristics. This segmentation, while increasing device complexity, is necessary to achieve the manufacturing precision required for yellowing-free clear ink coatings.
Solution Approach 2:
The patent changes the wavelength parameter of the UV light source from a single long-wavelength source to two sources with different wavelength ranges. This parameter change enables selective hardening of clear ink without yellowing, improving coating quality despite increased structural complexity.
3Object-affected harmful factors
If separate UV lamps with different wavelengths are used for color and clear ink hardening, then yellowing is reduced, but the device size and weight increase
Solution Approach 1:
The patent segments the UV hardening function into two specialized lamps, which reduces yellowing but increases device weight. This segmentation is necessary to achieve the desired coating quality.
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 yellowing of clear ink coatings and enhances the glossiness and print quality by using appropriate wavelength ranges for ink hardening and optimizing the positioning of inkjet heads and lamps, while also reducing the size and weight of the printer.
Implementation Method 1
a color ink hardening process of hardening the color ink by ultraviolet light with a wavelength equal to or longer than 365 nm radiated toward the color ink by the lamp for color ink
Implementation Method 2
a clear-ink hardening process of hardening the clear ink by ultraviolet light with a wavelength equal to or shorter than 365 nm radiated toward the clear ink by the lamp for clear ink
Data Source
AI summary
The disclosure provides an inkjet printer capable of reducing yellowing of a coating attributable to clear ink with respect to printing on a print medium with color ink. An inkjet printer (10) having LED lamps (26) for hardening color ink and an ultraviolet lamp (27) for hardening clear ink ejects ultraviolet curing type color ink toward a print medium (90) by inkjet heads (24) for color ink, and radiates ultraviolet light with a wavelength equal to or longer than 365 nm toward the color ink having adhered to the print medium (90) by the LED lamps (26), and ejects ultraviolet curing type clear ink toward the hardened color ink by inkjet heads (25) for clear ink, and radiates ultraviolet light with a wavelength equal to or shorter than 365 nm toward the clear ink having adhered to the color ink by the ultraviolet lamp (27).