Aqueous Ink Composition for Offset Media Smear Reduction
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Solution Overview
Problem
High-speed digital printing on coated offset media often results in ink smearing due to the hydrophobic surface of the media, which prevents adequate ink absorption, leading to ink buildup on rollers and subsequent image damage.
Innovation Solution
An aqueous ink composition comprising 2-5 wt% pigment, 70-95 wt% water, 1-10 wt% binder, 0.1-3 wt% non-ionic surfactant, 1-15 wt% humectant solvent, and 0.3-4.5 wt% non-volatile glycol ether co-solvent with a boiling point of 220° C or greater, which penetrates the media and dries quickly when passed through a heated roller, reducing smear issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If aqueous ink is used on coated offset media, then printing can be performed on coated surfaces, but the ink does not absorb adequately due to hydrophobic surface, causing smearing
Solution Approach 1:
The patent introduces a hydrophilic group-containing compound as an intermediary substance that bridges the hydrophilic aqueous ink and the hydrophobic coated offset media. This compound contains both hydrophilic groups (for affinity with water-based ink) and hydrophobic groups (for affinity with coated media), enabling adequate ink absorption and preventing smearing while maintaining printing capability on coated surfaces.
2Productivity
If high-speed printing is performed (100-800 fpm), then productivity increases, but ink does not dry fast enough, causing ink buildup on rollers and image damage
Solution Approach 1:
The patent modifies the chemical composition parameters of the aqueous ink by incorporating compounds with specific hydrophilic groups and controlled volatility. This changes the evaporation rate and drying characteristics of the ink, enabling it to dry sufficiently fast even at high printing speeds of 100-800 fpm, thus preventing ink buildup and image damage while maintaining high productivity.
3Stability of the object's composition
If ink remains wet on the surface, then penetration into media can occur, but the surface stays sticky causing smearing and image lift-off
Solution Approach 1:
The patent employs a compound that simultaneously provides continuous dual action: facilitating ink penetration into the media while concurrently preventing surface stickiness. The hydrophilic group promotes absorption and penetration, while the hydrophobic group reduces surface tension and prevents sticking, allowing the ink to transition smoothly from wet to dry state without causing smearing or image lift-off.
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 ink composition achieves accelerated penetration and drying, minimizing ink transfer to rollers and ensuring smear-free prints at high speeds from 100 to 800 feet per minute, with images drying within 1-15 seconds, thus preventing image damage.
Implementation Method 1
penetrating the non-volatile glycol ether co-solvent into the offset coated print medium to assist with drawing other liquid vehicle components into the offset coated print medium
Implementation Method 2
The heat that can be transferred from the dryer to the media is often times not sufficient to evaporate and dry the ink before the media is taken up by the wet turn rollers
Implementation Method 3
from 0.1 wt % to 3 wt % non-ionic surfactant
Data Source
AI summary
The present disclosure is drawn to aqueous ink compositions, methods of printing on offset coated print media, and printing systems. In one example, the aqueous ink compositions can include from 2 wt % to 5 wt % pigment, from 70 wt % to 95 wt % water, from 1 wt % to 10 wt % binder, from 0.1 wt % to 3 wt % non-ionic surfactant, from 1 wt % to 15 wt % humectant solvent including a hydrophilic group, and from 0.3 wt % to 4.5 wt % non-volatile glycol ether co-solvent having a boiling point of 220 C or greater.