Water-Based Ink Formulation for High-Speed Inkjet Printing

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Solution Overview

Problem

Water-based inks for inkjet recording face challenges with ejectability and offset issues on non-water absorptive substrates like plastic and metal, and hydrophobic coated or art paper, especially during high-speed printing, due to their slower drying rates and poor fixability.

Innovation Solution

A water-based ink formulation incorporating a urea compound and specific organic solvents such as 3-methoxy-1-butanol, propylene glycol, and glycerin, which helps in maintaining ink ejectability and achieving excellent rubfastness without causing offset when printed sheets are stacked.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If water-based ink is used for inkjet recording, then fire risk and mutagenicity are reduced, but drying rate becomes slower compared to solvent ink

Engineering Contradiction:

Improvefire riskVSAvoiddrying rate

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

The patent changes the chemical parameters of the water-based ink by incorporating specific organic solvents (3-methoxy-1-butanol, propylene glycol, glycerin) and urea compounds to adjust the drying rate and ejectability characteristics while maintaining the water-based formulation's safety advantages

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite ink formulation combining water, multiple organic solvents with different boiling points and vapor pressures, urea compounds, and pigments to achieve both slow drying (for safety) and adequate ejectability (for performance)

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If water-based ink is used on non-water absorptive substrates like plastic or metal, then substrate versatility is improved, but offset occurs in printed portions during high-speed printing

Engineering Contradiction:

Improvesubstrate versatilityVSAvoidoffset resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent adjusts the ink's rheological and drying parameters by selecting organic solvents with specific boiling points (100-200°C) and vapor pressures (0.5 hPa or more at 20°C), along with urea compounds, to optimize drying speed and offset resistance on non-absorptive substrates

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The organic solvents and urea compounds act as intermediaries that facilitate proper drying and adhesion on non-water absorptive substrates, preventing offset while maintaining substrate versatility

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If water-based ink is used on highly hydrophobic coated or art paper, then substrate versatility is improved, but fixability becomes poor

Engineering Contradiction:

Improvesubstrate versatilityVSAvoidfixability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent modifies the ink's surface tension and drying characteristics by incorporating specific organic solvents (3-methoxy-1-butanol, propylene glycol, glycerin) and urea compounds to improve adhesion and fixability on highly hydrophobic surfaces

Inventive Principle:

Principle #35Parameter changes

4Productivity

If ink with excessively high drying rate is used, then productivity is improved, but ink dries and adheres to nozzle forward ends affecting ejectability

Engineering Contradiction:

Improvedrying rateVSAvoidejectability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent carefully balances the drying rate parameters by selecting organic solvents with specific vapor pressures and boiling points, preventing both excessive drying (which causes nozzle adhesion) and insufficient drying (which causes offset), thereby maintaining both productivity and ejectability

Inventive Principle:

Principle #35Parameter changes

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 exhibits improved ejectability and rubfastness on non-water absorptive substrates, preventing offset and ensuring good drying properties, even when printed sheets are stacked immediately after printing.

Implementation Method 1

When an ink with an excessively high drying rate is used, the ink may dry and adhere to the forward ends of the nozzles

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

excellent in ejectability

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 3

capable of providing an image surface with excellent rubfastness even when the substrate is a non-water absorptive substrate

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentEP3235884B1Water-based ink for ink jet recording

Publication Date: 2019.07.03 DIC CORP

Figure 1

AI summary

A water-based ink for inkjet recording contains a pigment, water, organic solvents, at least one compound selected from urea compounds, and a binder resin. The organic solvents include at least (1) a water-soluble organic solvent having a boiling point of from 100°C to 200°C inclusive and a vapor pressure at 20°C of 0.5 hPa or more, (2) propylene glycol, and (3) glycerin, diglycerin, and/or a derivative thereof serving as an organic solvent. Preferably, the water-based ink further contains a polymer (A) serving as a pigment dispersant. The polymer (A) has an anionic group and has a solubility in water of 0.1 g/100 mL or more, a number average molecular weight within the range of 1,000 to 6,000, and an acid value within the range of 40 to 190 mg KOH/g.