UV Cured Varnish Ink Adhesion on Plastic
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Solution Overview
Problem
Existing ink jet printing technologies face challenges in achieving durable and strong adhesion of pigmented ink on substrates like plastic and metal, especially with heavily pigmented inks such as black or white, which require extensive and expensive equipment for curing and often result in uneven surfaces and defects like 'fish eyes'.
Innovation Solution
A system and method utilizing an x-y gantry-based ink jet printer with a scan assembly including multiple print heads and an ultraviolet (UV) lamp for controlled UV curing, where a clear varnish is applied and cured in stages to improve ink adhesion and durability, allowing the ink to thicken without full drying, and then fully curing the ink and varnish combination for enhanced abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV curing is used to dry pigmented ink on plastic substrates, then the ink can be cured and fixed, but the ink may not adhere properly and durability is reduced
Solution Approach 1:
A clear varnish layer is applied to the substrate before printing the pigmented ink. This preliminary action creates a prepared surface that enhances ink adhesion and durability before the curing process begins, resolving the adhesion problem without requiring complex equipment modifications
Solution Approach 2:
The clear varnish acts as an intermediary layer between the substrate and the pigmented ink. This mediator improves the bonding interface, allowing the ink to adhere more effectively to the substrate while maintaining durability through the UV curing process
2Manufacturing precision
If UV pinning is used to thicken ink and minimize droplet mixing, then ink mixing is reduced, but the ink is not fully dried and durability is compromised
Solution Approach 1:
The clear varnish is applied and cured before the pigmented ink is printed. This preliminary curing creates a stable base layer that allows subsequent ink layers to be properly cured, ensuring both uniformity and durability without requiring the ink to be fully dried during the pinning stage
Solution Approach 2:
The curing process is divided into multiple stages with different UV exposure parameters. The initial varnish curing uses specific UV parameters, followed by ink printing, and then final curing with adjusted parameters to achieve both uniformity and complete durability
3Reliability
If thick pigmented ink layers are applied for durability, then ink durability is improved, but curing becomes extensive and expensive equipment is required
Solution Approach 1:
The curing process is segmented into distinct stages: first curing the clear varnish layer, then printing the pigmented ink, and finally curing the ink layer. This segmentation allows each layer to be cured independently with appropriate UV parameters, making the process simpler and more cost-effective while maintaining durability
Solution Approach 2:
Different UV curing parameters are used for different stages and layers. The clear varnish is cured with specific UV exposure settings, and the pigmented ink is cured with adjusted parameters optimized for pigment-containing materials, enabling effective curing of thick layers without requiring expensive specialized equipment
4Reliability
If clear varnish is applied before curing to improve adhesion, then adhesion and durability are improved, but the process requires multiple steps and time
Solution Approach 1:
The process maintains continuous useful action by applying the clear varnish, curing it, printing the ink, and curing the ink in a sequential flow without unnecessary interruptions. Each step prepares the surface for the next, and the UV curing lamp can be repositioned efficiently between stages, minimizing idle time while ensuring proper adhesion
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 enables efficient and cost-effective printing of thick, durable ink layers on substrates with improved adhesion and reduced defects, allowing for quicker curing and more even surfaces without the need for additional expensive equipment.
Implementation Method 1
The ink and varnish, once applied to the substrate, may be cured using the UV lamp included in the sub-assembly as described above
Implementation Method 2
UV pinning, also known as gelling, can be used to cause the ink to thicken, to minimize the mixing of ink droplets, without fully drying the ink
Data Source
AI summary
Systems and techniques for improving ink jet ink durability and adhesion to a substrate. The techniques may include applying a varnish to the surface of the substrate, curing, in an initial curing step, the varnish with an ultraviolet (UV) lamp, and applying a pigmented ink to at least a portion of the substrate. The initial curing step may comprise pinning the varnish with the UV lamp in a low-power state. The techniques may additionally or alternatively include applying a layer of pigmented ink and varnish at substantially the same time, allowing the pigmented ink and varnish to at least partially mix, then pinning or curing the ink/varnish combination.