NIR-Sensitized Adhesive and Sealant Composition for Thermal-Free Curing

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Solution Overview

Problem

Existing adhesive and sealant compositions for optoelectronic devices require thermal curing steps after actinic radiation, leading to potential corrosion and undesirable effects on internal light paths due to incomplete shadow curing, and often compromise thermal criteria like glass transition temperature (Tg) at the cost of tensile strength and adhesive bond strength.

Innovation Solution

A photo-curable adhesive or sealant composition comprising oxetane and cycloaliphatic epoxide monomers, with near-infrared (nIR) absorbing dye, allowing complete curing without thermal steps, achieving high monomer conversion and advantageous cure depths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermal curing is used to complete shadow curing, then curing completeness is improved, but device temperature control and potential corrosion increase

Engineering Contradiction:

Improvecuring completenessVSAvoiddevice temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the curing mechanism from thermal to photopolymerization using UV light. The composition includes photopolymerizable monomers (oxetane and cycloaliphatic epoxide) and a photopolymerization catalyst that activates upon UV exposure, enabling complete curing without thermal heating and thus avoiding temperature-related corrosion risks.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal curing mechanism with a photopolymerization mechanism. Instead of using heat to drive the curing reaction, the invention uses UV light activation of a photopolymerization catalyst to initiate and complete the curing process, eliminating the need for thermal energy and associated temperature control issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If high Tg is achieved through formulation, then thermal stability is improved, but tensile strength and adhesive bond strength compromise

Engineering Contradiction:

Improveglass transition temperatureVSAvoidtensile strength and adhesive bond strength

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent uses a composite curing system combining oxetane monomers, cycloaliphatic epoxide monomers, and a photopolymerization catalyst. This composite approach allows the formulation to achieve both high Tg for thermal stability and adequate tensile strength and adhesive bond strength through the synergistic interaction of multiple components, avoiding the need to compromise between properties.

Inventive Principle:

Principle #40Composite materials

3Speed

If actinic radiation curing is used, then curing speed is improved, but shadow curing completeness deteriorates

Engineering Contradiction:

Improvecuring speedVSAvoidshadow curing completeness

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent ensures continuous and complete curing throughout the entire adhesive layer by using UV light penetration combined with photopolymerization catalysts. The UV radiation penetrates deep into the material, and the photopolymerization catalyst ensures that the curing reaction proceeds to completion in all areas, including shadowed regions, maintaining both speed and completeness.

Inventive Principle:

Principle #20Continuity of useful action

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 composition achieves rapid and complete curing with nIR radiation, maintaining high Tg and ensuring effective adhesion and barrier properties without thermal curing, thus protecting optoelectronic devices from moisture and corrosion.

Implementation Method 1

near-infrared (nIR) sensitized adhesive and sealant compositions

Methodology Applied

Scientific EffectNear-infrared radiation absorption: Absorption (EM radiation)

Implementation Method 2

radiation curable materials have found utility as coatings, adhesives and sealants... through either radical or cationic mechanisms

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentEP4050061B1Near-infrared (NIR) sensitized adhesive and sealant compositions

Publication Date: 2025.10.15 HENKEL KGAA

AI summary

The present invention is directed to a photo-curable adhesive or sealant composition comprising, based on the weight of the composition: from 1 to 10 wt.% of a) at least one oxetane compound according to Formula (I) below: wherein: R1 and R2 are H, C1-C6 alkyl, C6-C18 aryl or C7-C18 aralkyl; each R3 is independently a C1-C12 alkylene group, C6-C18 arylene group, C2-C12 alkenylene group or a poly(C1-C6 alkyleneoxy) group; and, n is an integer of from 1 to 3; from 5 to 20 wt.% of b) at least one epoxide compound, wherein part b) is characterized in that at least 50 wt.% of the total weight of epoxide compounds is constituted by b1) at one cycloaliphatic epoxide; from 0.1 to 5 wt.% of c) at least one ionic photoacid generator; from 0 to 10 wt.% of d) at least one free radical photoinitiator; from 0.01 to 5 wt.% of e) at least one near-infrared absorbing dye; and, from 50 to 90 wt.% of f) particulate filler.