Active Energy Ray-Curable Composition for Crack-Free Coatings
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Solution Overview
Problem
Photocurable resin coatings face issues with insufficient curing around air interfaces due to oxygen inhibition and hydrolysis/condensation polymerization leading to shrinkage, cracks, and warpage, particularly in high-temperature and high-humidity conditions, which affects the hardness and scratch resistance of laminates used in devices like smartphones.
Innovation Solution
A curable composition comprising a condensate with a weight average molecular weight of 20,000 or less, obtained by hydrolysis/condensation of silane compounds containing hydrolyzable silyl groups, along with a photoacid generator and alicyclic epoxy compounds, under basic conditions, to enhance hardness, scratch resistance, and impact resistance while minimizing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hydrolyzable silyl group is used for curing to achieve high hardness and scratch resistance, then the coating achieves sufficient hardness and scratch resistance, but hydrolysis/condensation polymerization causes shrinkage on curing, resulting in cracks and warpage
Solution Approach 1:
The patent changes the molecular weight parameter of the silane compound to 20,000 or less, which fundamentally alters the shrinkage behavior during curing. This parameter change allows the coating to achieve high crosslink density and hardness while minimizing shrinkage-induced cracks and warpage, resolving the contradiction between strength and manufacturing precision
Solution Approach 2:
The patent creates a composite curing system that combines cationic curing (via photoacid generator) with controlled hydrolysis/condensation polymerization. This composite approach allows simultaneous achievement of high crosslink density for hardness and controlled shrinkage to prevent cracks, resolving the technical contradiction
2Productivity
If a photoradical generator is used for UV curing, then the coating can be cured with UV light, but curing is inhibited by oxygen, resulting in insufficient curing around the interface between the coating agent and air
Solution Approach 1:
The patent merges two curing mechanisms: photoradical curing (for bulk curing and speed) and cationic curing via photoacid generator (for oxygen-insensitive curing at the air interface). This combination allows both high productivity and complete curing reliability, resolving the contradiction between curing speed and curing completeness
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 excellent hardness, scratch resistance, and impact resistance while preventing crack formation caused by shrinkage, and effectively suppresses warpage in laminates, even under high-temperature and high-humidity conditions.
Implementation Method 1
a photoacid generator, the condensate (A) being obtained by hydrolysis/condensation of: (I) a silane compound containing a hydrolyzable silyl group
Implementation Method 2
the condensate (A) being obtained by hydrolysis/condensation of: (I) a silane compound containing a hydrolyzable silyl group
Implementation Method 3
When curable compositions mainly including a compound containing a cationic curable functional group such as a hydrolyzable silyl group or epoxy group are photocured
Data Source
AI summary
An active energy ray-curable composition includes (A) a condensate having a weight average molecular weight of 20,000 or less, and (B) a photoacid generator, with the condensate (A) being obtained by hydrolysis/condensation of: (I) a silane compound containing a hydrolyzable silyl group represented by formula (I): R1—(SiR2a(OR3)3-a. A ratio (Y/X) of Y to X is 0.2 or less, where X represents the number of moles of OR3 groups directly bonded to silicon atoms in the silane compound (I) which is a starting material of the condensate (A) and Y represents the number of moles of OR3 groups directly bonded to silicon atoms in the condensate (A).