Radiation Curable Paint Composition for Automotive Headlamp Hard Coating
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Solution Overview
Problem
Current photocurable paint compositions for plastic substrates, particularly automotive headlamps, face issues with cracking, reduced adhesive properties, and inadequate weatherability due to intermolecular contraction stresses and insufficient UV resistance, necessitating improvements in heat resistance, water resistance, and manufacturing efficiency.
Innovation Solution
A photocurable paint composition comprising multifunctional polyurethane acrylate with 5 or more functional groups, monofunctional or difunctional polyurethane acrylate, a combination of monofunctional, difunctional, and trifunctional acrylates, a photo initiator, triazine-based ultraviolet absorbent, and organic solvent, which enhances adhesive, water, heat, and thermal shock resistance, as well as weatherability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a multifunctional urethane acrylate oligomer alone is used to form a coating film, then the coating film shows high hardness and wear resistance, but the coating film may crack or breakage due to intermolecular contraction stresses when the thickness is 12 μm or greater, causing deterioration of external appearance and adhesive property
Solution Approach 1:
The patent uses a composite resin composition combining multiple types of oligomers (polyester polyol, polyether polyol, polycarbonate polyol) with different molecular weights and functional groups. This composite approach balances crosslinking density and flexibility, reducing contraction stresses while maintaining hardness and adhesion properties.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the oligomers (500-5000 for polyester polyol, 1000-10000 for polyether polyol, 1000-20000 for polycarbonate polyol) and their ratios to control the coating film's mechanical properties, achieving both hardness and reduced contraction stress.
2Strength
If the coating film is made with high crosslinking density to improve hardness, then wear resistance improves, but intermolecular contraction stresses increase causing cracks and poor adhesion
Solution Approach 1:
The patent creates a composite resin system with oligomers of varying molecular weights and functional characteristics. The combination provides optimal crosslinking density for wear resistance while the diversity in molecular structure prevents excessive contraction stresses that would cause cracking.
Solution Approach 2:
Different regions of the coating film have varying crosslinking densities due to the oligomer composition gradient, allowing high wear resistance at the surface while maintaining flexibility and adhesion in the bulk material where contraction stresses are highest.
3Ease of manufacture
If conventional paint compositions are used to achieve good adhesion, then coating application is easier, but weatherability and heat resistance are insufficient for automotive headlamp applications
Solution Approach 1:
The patent modifies the chemical parameters of the resin system by selecting specific oligomers with functional groups that provide both adhesion to substrates and resistance to UV degradation and heat, achieving weatherability suitable for automotive headlamps while maintaining ease of application.
Solution Approach 2:
The composite resin composition incorporates multiple polyol types (polyester, polyether, polycarbonate) that collectively provide adhesion, UV stability, and heat resistance, meeting the stringent weatherability requirements for automotive applications.
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 exhibits excellent productivity, initial color retention, and improved weatherability across long and short wavelength ranges, maintaining physical properties and adhesive strength even after recycling, making it suitable for automotive headlamps and other industrial applications.
Implementation Method 1
a photocurable paint composition may include (A) multifunctional polyurethane acrylate having 5 or more functional groups, (B) monofunctional or difunctional polyurethane acrylate, (C) a combination of monofunctional acrylate, difunctional acrylate and trifunctional acrylate, (D) photo initiator
Implementation Method 2
triazine-based ultraviolet absorbent having two or more UV absorber groups
Data Source
AI summary
The present invention relates to a radiation curable paint composition and a molded product comprising a cured coating layer formed therefrom, and more specifically, to: a radiation curable paint composition comprising a polyfunctional polyurethane acrylate being at least pentafunctional, a mono- or difunctional polyurethane acrylate, a mono-, di- or trifunctional acrylate, a photopolymerization initiator, and a triazine-based UV absorber, wherein physical properties such as adhesion to a metal or plastic substrate, water resistance, moisture resistance, heat resistance, thermal shock resistance and the like are remarkable, and particularly, weather resistance is remarkable, and thus it is useful for a hard coating for a plastic substrate, and particularly, for an automobile headlamp; and a molded product comprising a cured coating layer formed therefrom.