Coldset Web Offset Varnish for Rub Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coldset web offset printing faces issues with interpage set off and poor rub resistance, leading to quality limitations, and previous attempts to address these with water-based varnishes have been unsuccessful due to substrate stability problems like fluting and curling.
Innovation Solution
A coldset web offset printing process where a clear varnish is applied to the printed substrate with a film weight no more than 2 gsm on at least one side, drying within 120 seconds, using a varnish comprising a drying resin and solvent, such as styrene-acrylic copolymers, without the need for UV or electron bombardment, and applied using conventional printing equipment with optional heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a water-based varnish is applied to prevent interpage set off and improve rub resistance, then ink migration is prevented, but substrate dimensional stability deteriorates causing fluting and curling
Solution Approach 1:
The patent changes the chemical composition parameters of the overprint varnish by using a solvent-free formulation containing specific resins (acrylic, vinyl, polyester, polyurethane, epoxy, or combinations) instead of water-based varnishes. This parameter change eliminates the harmful effect of substrate fluting and curling while maintaining the protective function against ink migration and improving rub resistance.
2Reliability
If a thick overprint varnish coating is applied to ensure adequate protection, then ink migration prevention is improved, but substrate fluting and curling worsen
Solution Approach 1:
The patent changes the formulation parameters of the overprint varnish to a solvent-free composition with specific resin types and proportions. This allows the use of thinner coatings (reducing the burden on substrate stability) while achieving adequate ink migration prevention through the improved chemical composition and drying characteristics of the solvent-free varnish.
3Object-generated harmful factors
If conventional water-based varnish is used to protect printed matter, then interpage set off is reduced, but blocking and sticking together of the web occurs
Solution Approach 1:
The patent changes the chemical parameters of the varnish by eliminating water and using solvent-free formulations with specific resins. This parameter change prevents the blocking and sticking together of the web during processing while maintaining effective prevention of interpage set off, as the solvent-free composition does not exhibit the adhesive properties that cause blocking.
4Reliability
If both sides of the substrate are coated with varnish to ensure complete protection, then ink migration prevention is improved, but coating material waste increases
Solution Approach 1:
The patent applies local quality by allowing selective coating of only one side of the substrate when the printed side faces outward, rather than requiring coating of both sides. The improved composition of the solvent-free overprint varnish ensures adequate protection with single-sided coating, reducing material waste while maintaining ink migration prevention for the printed surface.
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 solution prevents interpage set off and improves rub resistance without causing substrate fluting or curling, allowing for efficient one-sided or dual-sided coating without timing constraints, enhancing the quality and economic viability of the printing process.
Implementation Method 1
the varnish drying to no adhesion within 120 seconds
Implementation Method 2
a drying resin and a solvent or dispersant therefor
Data Source
AI summary
By appropriate selection of an overprint varnish, so that it dries to no adhesion within 120 seconds, it is possible to coat one side only of newsprint or other similar substrates or to coat both sides of the substrate (without having regard to the relative times at which the sides are coated), without, in almost all cases, causing any fluting or curling of the substrate.