Inkjet Ink Curing at Low Temperatures

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Solution Overview

Problem

Heat-curing solvent type inks for ink-jet printing face challenges in achieving rapid curing at low temperatures without thermal deformation of plastic articles, and existing solutions either require high temperatures or generate offensive odors.

Innovation Solution

A heat-curing solvent type ink composed of polyesterpolyol and blocked polyisocyanate, dissolved in a volatile organic solvent, with specific molecular weight and hydroxyl value ranges, and containing pigments, which quickly reacts to form a cured polyurethane film that adheres well to plastics and metals upon heating between 70°C to 130°C for a short period.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If heat-curing solvent type ink is heated at high temperature for short time to achieve rapid curing, then curing speed is improved, but plastic formed articles are thermally deformed

Engineering Contradiction:

Improvecuring speedVSAvoidshape accuracy of plastic articles

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the chemical parameters of the ink composition by using polyesterpolyol with specific molecular weight (≤8000) and hydroxyl value (17-50), combined with blocked polyisocyanate in controlled ratios. These parameter changes enable the curing reaction to proceed at lower temperatures (70-130°C) while maintaining rapid curing speed, thus resolving the contradiction between curing speed and shape accuracy.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If heat-curing solvent type ink is heated at low temperature for short time to prevent thermal deformation, then shape accuracy is improved, but curing is insufficient and ink blurs

Engineering Contradiction:

Improveshape accuracy of plastic articlesVSAvoidcuring completeness and adhesion

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent employs a composite material system consisting of polyesterpolyol and blocked polyisocyanate in specific combinations. This composite formulation creates a chemical reaction system that is highly sensitive to temperature changes within the 70-130°C range, enabling complete curing at low temperatures without blur, thus resolving the contradiction between shape accuracy and curing completeness.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes the dynamic characteristics of the blocked polyisocyanate system, where the blocking groups prevent premature reaction at low temperatures but allow rapid curing when heated. This dynamic behavior enables the ink to remain stable during storage and application, then cure completely at low temperatures, resolving the contradiction between shape accuracy and curing reliability.

Inventive Principle:

Principle #15Dynamics

3Productivity

If ultraviolet ray-curing ink is used to achieve rapid curing without heating, then curing speed and shape accuracy are improved, but cost increases and offensive odor is generated

Engineering Contradiction:

Improvecuring speedVSAvoidoffensive odor from polymerization byproducts

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the ultraviolet light-based curing mechanism with a thermally-initiated chemical reaction system. Instead of using UV photons to trigger polymerization, the system uses controlled thermal energy to activate the blocked polyisocyanate-polyesterpolyol reaction. This substitution eliminates the need for UV lamps and the generation of offensive byproducts, while maintaining rapid curing speed and avoiding thermal deformation through optimized temperature control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 effectively cures at low temperatures, preventing thermal deformation and ensuring strong adhesion to plastic and inorganic surfaces, while avoiding odor issues, thus enabling efficient ink-jet printing on plastic formed articles without blurring.

Implementation Method 1

the ink is a liquid obtained by dissolving or dispersing polyesterpolyol and blocked polyisocyanate... which quickly reacts to form a cured polyurethane film

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Implementation Method 2

dissolving or dispersing polyesterpolyol and blocked polyisocyanate in a volatile organic solvent

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentEP2995660B1Inkjet ink and inkjet printing method

Publication Date: 2020.03.04 NIPPON CLOSURES

AI summary

A solvent type curable ink for ink-jet printing obtained by dissolving or dispersing, in a volatile organic solvent, polyesterpolyol having a molecular weight of not more than 8000, a hydroxyl value (KOH mg/g) of 17 to 50 and a glass transition point (Tg) of not higher than 70°C, and blocked polyisocyanate. The ink is capable of forming ink-jet-printed image on the surfaces of various kinds of formed articles without burring and maintaining close adhesion upon being heated at a low temperature for a short period of time.