Photoinitiator Composition for UV LED Curing

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Solution Overview

Problem

UV LED curing of inks and coatings faces challenges in achieving rapid and effective surface curing due to the limited UV output and specific wavelength emission, which restricts the use of photoinitiators that can absorb the light, making it difficult to formulate effective curing compositions.

Innovation Solution

A photoinitiator system comprising a combination of aminoalkyl phenone and thioxanthone, along with a multifunctional amino benzoate synergist, is used to enhance cure speed and effectiveness, particularly suitable for UV LED light sources, as the thioxanthone acts as a sensitizer and the aminoalkyl phenone improves surface curing, while the synergist aids in chain initiation and cross-linking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If UV LED lamps with single emission band (365-420 nm) are used for curing, then low temperature operation and long life are achieved, but surface cure becomes more difficult and the number of suitable photoinitiators is very small

Engineering Contradiction:

Improvelamp lifeVSAvoidsurface cure quality

Core Design Contradiction:

Duration of action of stationary objectVSManufacturing precision

Solution Approach 1:

The patent uses a composite photoinitiator system combining thioxanthone (absorbs LED emission at 365-420 nm) with aminoalkyl phenone and multifunctional amino benzoate synergist. This composite approach allows the system to absorb the specific LED wavelength while generating sufficient radicals for both surface cure and through curing, resolving the contradiction between lamp durability and surface cure quality.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Thioxanthone acts as an intermediary sensitizer that absorbs UV LED radiation and transfers energy to the aminoalkyl phenone photoinitiator, which then generates radicals for curing. This intermediary mechanism enables effective curing with LED's limited wavelength output, particularly improving surface cure while maintaining the benefits of long-lived LED lamps.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If photoinitiators tuned to LED wavelength (365-420 nm) are used, then curing with LED lamps is achieved, but surface cure is more difficult due to reduced total UV output

Engineering Contradiction:

Improvecompatibility with LED light sourceVSAvoidcure speed

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent changes the chemical parameters of the photoinitiator system by selecting thioxanthone with specific absorption characteristics for LED wavelengths, combined with aminoalkyl phenone and multifunctional amino benzoate. This parameter optimization ensures high absorption efficiency at LED emission wavelengths while maintaining rapid cure kinetics, thus improving both LED compatibility and cure productivity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The photoinitiator system provides different functions at different depths: thioxanthone absorbs LED light and transfers energy, aminoalkyl phenone generates radicals for surface curing, and the multifunctional amino benzoate synergist enhances both surface and through curing. This localized functional distribution optimizes cure speed while maintaining LED source compatibility.

Inventive Principle:

Principle #3Local quality

3Productivity

If conventional medium pressure mercury arc lamps are used, then high total UV output is achieved, but temperature operation is high and lamp life is short

Engineering Contradiction:

Improvetotal UV outputVSAvoidoperating temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent changes the absorption parameters of the photoinitiator system to match LED emission characteristics (365-420 nm single band) rather than the broad spectrum of mercury lamps. The thioxanthone-aminoalkyl phenone-multifunctional amino benzoate combination is specifically selected for high absorption efficiency at LED wavelengths, enabling effective curing with lower power, cooler-running LED lamps while maintaining productivity.

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 photoinitiator system significantly improves cure speed and surface curing performance compared to existing systems, allowing for rapid and effective curing of inks and coatings under air conditions using UV LED light sources, without the need for an inert environment.

Implementation Method 1

a photoinitiator system comprising a combination of an aminoalkyl phenone and a thioxanthone... capable of initiating free-radical curing reactions on exposure to UV radiation from an LED light source

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Implementation Method 2

the thioxanthone acts as a sensitizer... the number of photoinitiators that absorb light in the region of LED emission is very small

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS9321853B2Photoinitiator composition

Publication Date: 2016.04.26 SUN CHEMICAL BV

AI summary

A photoinitiator composition comprising a combination of aminoalkyl phenone, thioxanthone and multifunctional amino benzoate synergist for use in printing inks and coatings that are curable using UV radiation, particularly from LED lamps.