Decorative Sheet Cracking Prevention via Ionizing Radiation Curing
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Solution Overview
Problem
Decorative resin molded articles with convex area portions often crack during molding due to heat and stress, and existing methods to prevent cracking limit the design and scratch resistance of the irregularity shape.
Innovation Solution
A decorative sheet with convex area portions formed from a cured product of an ionizing radiation curable resin composition, having a Martens hardness of 10 to 120 N/mm² under 25°C and 50% relative humidity, which provides moderate flexibility and elasticity to prevent cracking and enhance scratch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If an irregularity shape is formed on the surface by embossing to provide design property, then the aesthetic appeal is improved, but the irregularity shape may be restored to a flat surface under heat and stress during molding, causing loss of design property
Solution Approach 1:
The patent changes the material parameter from conventional thermoplastic resin to ionizing radiation curable resin composition, which undergoes chemical crosslinking upon irradiation. This transforms the irregularity shape from a physically embossed feature that can be restored by heat to a chemically fixed structure that maintains its shape stability under molding conditions.
Solution Approach 2:
The patent uses a composite material system consisting of ionizing radiation curable resin composition that combines the benefits of resin flexibility with crosslinked structure stability. The cured resin forms a composite structure where the irregularity shape is locked in place through chemical bonds, preventing restoration to flat surface during subsequent molding processes.
2Shape
If an irregularity shape is formed by embossing to provide design property, then the aesthetic appeal is improved, but the irregularity shape is easily lost or damaged due to abrasion, reducing durability
Solution Approach 1:
The patent changes the material parameter from thermoplastic resin to ionizing radiation curable resin composition with crosslinked structure. This chemical crosslinking dramatically improves abrasion resistance, preventing the irregularity shape from being easily damaged or worn away during use, thereby enhancing durability while maintaining design property.
3Reliability
If the convex area portions are arranged and sized to constitute 45% or less of the surface area to prevent cracking, then the reliability is improved, but the design property and scratch resistance are limited
Solution Approach 1:
The patent changes the material parameter to ionizing radiation curable resin composition, which fundamentally alters the cracking behavior. The crosslinked structure provides superior crack resistance that doesn't depend on limiting the area ratio of convex portions to 45% or less. This allows much higher area ratios and more aggressive irregularity patterns without cracking, greatly expanding design possibilities.
4Ease of manufacture
If a thermoplastic resin is used to form an irregularity shape, then the ease of manufacture is improved, but the irregularity shape is easily lost or damaged due to abrasion, reducing durability
Solution Approach 1:
The patent replaces the mechanical embossing process on thermoplastic resin with a chemical crosslinking process using ionizing radiation. The irregularity shape is first formed by embossing, then the resin is irradiated to create crosslinks that permanently lock the shape. This substitution of mechanical bonding with chemical bonding maintains ease of manufacture while dramatically improving abrasion resistance.
Solution Approach 2:
The patent changes the material parameter from thermoplastic resin to ionizing radiation curable resin composition. This chemical transformation allows the material to be easily formed by embossing like thermoplastics, then cured to achieve superior abrasion resistance, combining the advantages of both material types.
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 decorative sheet effectively inhibits cracking during molding and exhibits excellent scratch resistance and design properties in the irregularity shape of the convex area portions after molding, allowing for improved durability and aesthetic appeal.
Implementation Method 1
convex area portions formed of a cured product of an ionizing radiation curable resin composition
Data Source
Figure 1~4
Figure 5A~5B
Figure 6A~7B
AI summary
The purpose of the present invention is to provide a decorative sheet having a bulging section on the surface thereof, wherein the bulging section is effectively inhibited from cracking during molding, and the decorative sheet is imparted with exceptional scratch resistance and quality of design in the convex/concave features on the bulging section after molding. The present invention pertains to a decorative sheet having a bulging section formed by a cured product of an ionizing-radiation-curable resin composition on a substrate sheet, the cured product of the ionizing-radiation-curable resin composition having a Martens hardness in a range of 10-120 N/mm2 at a temperature of 25°C and a relative humidity of 50%.