Decorative Sheet Surface Roughness Control for Injection Molding
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Solution Overview
Problem
Existing decorative sheet production processes for molded articles often result in surface irregularities and differences in smoothness and gloss between the decorative sheet and the final molded article, leading to inconsistent design feelings and issues with dents, scratches, and wrinkles during handling and molding.
Innovation Solution
A production process involving a primer layer, design layer, and surface protective layer formed on a base material using an ionizing radiation curable resin, with a roughening treatment on the rear face to control the ten point average roughness RzJIS and arithmetic average roughness Ra to specific equations, ensuring a smooth and glossy surface while preventing foreign matter-induced damage and surface contact issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a design layer is formed on a base material and a surface protective layer is laminated thereon, then the decorative sheet provides design functionality and protection, but irregularities are produced on the surface and smoothness is damaged
Solution Approach 1:
The patent applies preliminary smoothing treatment to the design layer before laminating the surface protective layer. This prevents irregularities from being transferred to the protective layer surface, thereby maintaining both protection function and surface smoothness.
Solution Approach 2:
The patent separates the smoothing treatment as a distinct preliminary step before lamination. By treating the design layer surface independently before combining it with the protective layer, the process ensures that irregularities are eliminated without compromising the protective function.
2Manufacturing precision
If smoothing treatment is applied to the decorative sheet surface, then high gloss and smoothness are achieved, but irregularities of the design layer remain and resurface after heating in molding
Solution Approach 1:
The patent applies smoothing treatment to the design layer before laminating the surface protective layer. This preliminary action ensures that the design layer irregularities are eliminated and prevented from resurfacing during subsequent molding processes, while maintaining the achieved smoothness.
3Manufacturing precision
If both surfaces of the decorative sheet are smoothed, then high gloss is achieved, but small dusts and rubbishes are wrapped in the roll to generate dents and wounds
Solution Approach 1:
The patent applies smoothing treatment selectively only to the design layer surface that will be visible on the front of the decorative sheet, rather than smoothing both surfaces. This local approach maintains high gloss where needed while reducing the risk of foreign matter entrapment during rolling.
4Manufacturing precision
If the decorative sheet is made smooth, then high gloss is achieved, but the smoothness and gloss differ notably from the molded article after injection molding
Solution Approach 1:
The patent applies smoothing treatment to the design layer before lamination, creating a surface that is pre-conditioned to match the smoothness and gloss characteristics of the final molded article. This preliminary preparation ensures design feeling consistency between the decorative sheet and the finished molded product.
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 process produces a decorative sheet with maintained high gloss and smoothness after three-dimensional molding, reducing the likelihood of dents, scratches, and wrinkles, and ensuring consistent design feelings between the sheet and molded article.
Implementation Method 1
an ionizing radiation curable resin composition is laminated on the primer layer formed on the base material and the ionizing radiation curable resin composition is cross-linked and cured to form a surface protective layer
Data Source
AI summary
A decorative sheet includes a design layer, a primer layer and a surface protective layer formed by cross-linking and curing an ionizing radiation curable resin composition in this order on a base material. A surface of the surface protective layer is smooth. A ten point average roughness RzJIS on a rear face of the decorative sheet and a thickness T of the base material satisfies the following equation (I); and an arithmetic average roughness Ra on the rear face and a thickness T of the base material satisfies the following equation (II):T×0.30≥RzJIS (I)T×0.20≥Ra≥T×0.005 (II)Or an arithmetic average roughness Ra on a rear face of the decorative sheet is 1.0 to 10.0 μm. A decorated resin molded article is produced by integrating the decorative sheet with an outer surface of a resin molded article at the same time as injection molding.