UV Curing Fibrous Substrates with Reflected Light
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Solution Overview
Problem
Current printing systems face challenges in ensuring that energy curable inks are fully cured on fibrous substrates, as the ink may penetrate and migrate, leading to uncured ink remaining on the substrate and potentially rubbing off during assembly or use, due to penetration into the substrate and shielding by fibers.
Innovation Solution
A method and apparatus that involves depositing energy curable ink on a substrate and using a combination of direct and reflected ultraviolet light to cure the ink, with a light source directing ultraviolet light onto the surface and a reflective device reflecting light through the substrate to reach ink that has penetrated, ensuring thorough curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If energy curable ink is deposited on fibrous substrate, then the ink may penetrate and migrate through the substrate, but this causes uncured ink to remain on the substrate and potentially rub off during assembly or use
Solution Approach 1:
The patent introduces a second curing direction by placing a reflective device (mirror) behind the substrate. This reflects UV light back through the substrate from the opposite side, creating a dual-directional curing approach that addresses ink migrated to the rear surface without requiring increased penetration depth from the front source alone.
Solution Approach 2:
The reflective device acts as an intermediary element that redirects UV light through the substrate. This mediator enables the curing of ink that has migrated to the opposite surface by bouncing light back through the material, solving the problem of incomplete curing without modifying the ink or substrate properties.
2Illumination intensity
If radiation source intensity is increased to cure penetrated ink, then curing effectiveness improves, but fibers within the substrate may still shield the radiation and prevent complete curing
Solution Approach 1:
By adding the reflective device behind the substrate, the system creates a second illumination path from the opposite direction. This dimensional change in light delivery allows UV radiation to reach ink molecules that are shielded from the front-facing source by substrate fibers, effectively bypassing the shielding problem rather than overcoming it through increased intensity.
3Ease of manufacture
If conventional drying operations are used for solvent or aqueous based inks, then additional processing steps are required, but this makes it difficult to complete drying at relatively high manufacturing speeds
Solution Approach 1:
The patent replaces thermal drying operations with photochemical curing using UV radiation. This substitution eliminates the need for evaporation-based drying processes and external heating systems, enabling rapid curing at high manufacturing speeds without compromising the simplicity of the manufacturing process.
Solution Approach 2:
The invention utilizes the phase transition from liquid ink to solid cured polymer through photochemical reaction. This phase change occurs instantly upon UV exposure rather than requiring gradual evaporation, enabling high-speed manufacturing while maintaining process simplicity.
4Productivity
If wax based inks are used to avoid drying steps, then drying operations are eliminated, but specific printing devices with additional heating and fluid handling systems are required
Solution Approach 1:
The patent replaces the thermal melting and solidification process of wax-based inks with photochemical curing. This substitution eliminates the need for heating zones, fluid handling systems, and temperature control mechanisms required for wax ink operation, thereby reducing device complexity while maintaining high-speed productivity.
Solution Approach 2:
The invention changes the fundamental curing parameter from temperature-based (wax melting point) to light-based (UV wavelength). This parameter change allows the use of standard printing heads without complex thermal management systems, reducing device complexity while achieving rapid curing suitable for high-speed production.
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 ensures that energy curable ink is fully cured, preventing migration and rub-off issues, by utilizing both direct and reflected ultraviolet light to reach and cure ink that has penetrated into the substrate.
Implementation Method 1
curing a first portion of the energy curable ink with ultraviolet light traveling from the light source toward the first surface of the substrate
Implementation Method 2
reflecting ultraviolet light traveling from the second surface of the substrate toward the second surface of the substrate
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Aspects of the present disclosure relate to methods and apparatuses printing and curing energy curable inks printed on substrates. The printing systems may include a printing station, a light source, and a reflective device. During operation, the printing station deposits energy curable ink onto a first surface of the substrate to define a printed region, wherein an amount of the curable ink may penetrate into the substrate from the first surface toward a second surface. The light source directs ultraviolet light onto the first surface of the substrate to define a first illumination zone. The reflective device reflects ultraviolet light traveling from the second surface of the substrate back toward the second surface to define a second illumination zone. The substrate is advanced in a machine direction to advance the energy curable ink through the first illumination zone and the second illumination zone to cure the energy curable ink.