Decorative Sheet Surface Protective Layer Crack Prevention
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Solution Overview
Problem
Existing decorative molding techniques face challenges with surface protective layers, including cracks in curved parts, inadequate abrasion and scratch resistance, and increased production costs due to the use of ionizing radiation curable resins, particularly in three-dimensional forms.
Innovation Solution
A decorative sheet with a specific structure comprising a support layer, a low glossy picture layer, and a surface protective layer made from an ionizing radiation curable resin, where the static frictional coefficient is controlled, and the thickness of the surface protective layer is optimized to prevent cracking and enhance moldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermosetting resin is used for the surface protective layer to enhance moldability, then cracks are less liable to be produced, but abrasion resistance and scratch resistance are not satisfactory
Solution Approach 1:
The invention changes the key parameter of the surface protective layer from thermosetting resin to ionizing radiation curable resin, which allows for controlled curing. By adjusting the curing degree parameter (partially cured state), the invention achieves both good moldability during processing and high abrasion/scratch resistance in the final product, resolving the contradiction between moldability and surface durability.
Solution Approach 2:
The invention creates a composite structure where the surface protective layer is formed by ionizing radiation curable resin that combines the moldability characteristics of thermosetting resins with the superior abrasion and scratch resistance of radiation-curable materials. This composite approach allows optimization of both properties simultaneously.
2Strength
If an ionizing radiation curable resin is used to enhance cross-linking density for abrasion and scratch resistance, then surface durability improves, but cracks are caused in curved parts during molding
Solution Approach 1:
The invention applies preliminary action by controlling the curing process to occur in stages: first allowing the resin to remain in a partially cured, flexible state during the molding process to prevent cracks in curved parts, and then completing the curing process afterward to achieve the desired high cross-linking density and surface durability. This staged approach resolves the contradiction between moldability and surface hardness.
Solution Approach 2:
The invention introduces dynamics into the surface protective layer by using a resin that can change its properties from flexible (during molding) to rigid (after complete curing). The ionizing radiation curable resin allows dynamic adjustment of the curing degree, enabling the material to adapt its characteristics to different process stages and resolve the contradiction between moldability and surface durability.
3Strength
If ionizing radiation curable resin is used and allowed to stay in semi-cured state, then abrasion and scratch resistance improve, but die contamination occurs due to adhesion of uncured resin
Solution Approach 1:
The invention extracts the harmful uncured resin component from the molding process by completing the curing process before the insert molding step. The surface protective layer is fully cured during the decorative sheet production stage, so no uncured resin remains to cause die contamination during subsequent molding operations, while still maintaining the high abrasion and scratch resistance properties.
Solution Approach 2:
The invention applies preliminary action by completing the curing process of the ionizing radiation curable resin during the decorative sheet production stage, before the insert molding process begins. This preliminary curing eliminates the presence of uncured resin that would otherwise cause die contamination, while still achieving the desired high surface durability.
4Object-generated harmful factors
If a protective film is provided on the surface protective layer in semi-cured state, then die contamination is prevented, but production becomes complicated and cost increases
Solution Approach 1:
The invention extracts the need for an additional protective film by completely curing the surface protective layer during decorative sheet production. This eliminates the source of die contamination (uncured resin) without requiring any additional protective layers or complex handling procedures, thereby simplifying production and reducing costs.
Solution Approach 2:
The invention creates a copy of the final cured state during the decorative sheet production stage, eliminating the need for subsequent protective measures. By pre-curing the surface protective layer to its final state, the invention avoids the complexity of managing semi-cured materials and associated protective films throughout the production process.
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 solution provides a decorative sheet with excellent abrasion resistance, scratch resistance, and moldability, eliminating cracks on the surface protective layer and allowing for high design properties, while maintaining a low production cost and enabling the creation of high-grade, textured patterns.
Implementation Method 1
an ionizing radiation curable resin such as a UV ray curable resin and the like for a surface protective layer to enhance a cross-linking density of a resin forming a surface protective layer of a decorative sheet
Data Source
Figure 1~2
AI summary
The present invention relates to a decorative sheet for insert molding prepared by laminating at least a surface protective layer on a support comprising an ABS resin, wherein the above support has a flexural modulus of 1500 to 3000 MPa; the above support has a thickness of 100 to 500 µm; the above surface protective layer is obtained by cross-linking and curing an ionizing radiation curable resin composition; and the above ionizing radiation curable resin composition has a tensile modulus of more than 100 MPa to less than 1000 MPa which is measured by the following method and a static frictional coefficient of 1.0 or less on a surface and a decorative sheet for insert molding comprising at least a picture layer, a low glossy picture ink layer provided partially and a surface protective layer in this order on a support, wherein the above surface protective layer is present on the low glossy picture ink layer and brought into contact therewith, and it is coated over a whole surface including an area where the above low glossy picture ink layer is formed and an area where the low glossy picture ink layer is not formed; the surface protective layer is obtained by cross-linking and curing an ionizing radiation curable resin composition; and the surface protective layer has a thickness of 1 to 30 µm. Capable of being provided are a decorative sheet which has a high abrasion resistance and a high scratch resistance and is provided with a good moldability and which has a surface protective layer causing no cracks and is provided with a high design property and used for molding a decorated molding, a production process for a decorated resin molding by using the above decorative sheet and a decorated resin molding produced by the above production process.