Transfer Decorative Sheet Weld Line Wrinkle Prevention
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Solution Overview
Problem
The decorating injection molding method using transfer decorative sheets often results in wrinkles and unevenness at weld lines due to the inherent properties of the base film, which cannot be effectively prevented without improving the molding apparatus or requiring specialized skills.
Innovation Solution
A transfer decorative sheet with a base film surface roughness controlled to an average of 0.08 to 1 µm, incorporating a release layer, peel layer, picture layer, and adhesive layer, utilizing specific resin compositions and matting agents to prevent wrinkles and enhance glossiness and peeling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transfer decorative sheet with a smooth base film is used in decorating injection molding, then the sheet can be easily laminated on the resin molding surface, but wrinkles are formed at weld lines where molten resin flows join
Solution Approach 1:
The base film is designed with different surface roughness at different locations: the region that contacts weld lines has a roughness of 0.03-0.5 µm to prevent wrinkles, while other regions maintain smoothness for easy lamination and aesthetic appearance. This local differentiation resolves the contradiction between lamination ease and surface uniformity.
Solution Approach 2:
The surface roughness parameter of the base film is precisely controlled within specific ranges (0.03-0.5 µm at weld line regions, 0.01-0.1 µm at other regions) to achieve optimal balance between preventing wrinkles and maintaining lamination ease, resolving the contradiction through quantitative parameter optimization.
2Manufacturing precision
If the base film surface roughness is increased to prevent wrinkles at weld lines, then surface uniformity improves, but the glossiness of the decorated molding surface deteriorates
Solution Approach 1:
Different surface roughness values are applied to different regions: weld line regions have higher roughness (0.03-0.5 µm) for wrinkle prevention, while non-weld regions maintain low roughness (0.01-0.1 µm) for glossiness, thus locally optimizing both surface uniformity and illumination properties.
Solution Approach 2:
Surface roughness is increased only partially and locally at weld line regions rather than uniformly across the entire base film, achieving sufficient wrinkle prevention while minimizing the impact on overall glossiness through controlled, limited application.
3Reliability
If a laminate decorative sheet is used to protect the transferred layers, then protection function is improved, but trimming operations become necessary
Solution Approach 1:
The base film is designed with a specific roughness configuration that enables it to prevent wrinkles at weld lines during the transfer process itself, eliminating the need for an additional protective laminate layer and subsequent trimming operations, thus extracting the protection function from the post-transfer stage to the transfer stage.
4Reliability
If the base film is made transparent to remain on the outermost surface, then protection function is improved, but the peeling property deteriorates
Solution Approach 1:
The base film is optimized with specific surface roughness values that enable effective peeling after transfer, extracting the protection function to the decorative layers rather than requiring the base film to remain as the outermost protective layer, thus resolving the contradiction between protection and peeling ease.
Data Source
Figure 1
AI summary
Provided is a transfer decorative sheet comprising a base film and at least a peel layer provided on one surface thereof, wherein a surface of the base film at a peel layer side is subjected to release treatment, and the other surface of the base film brought into contact with a metal die has an average surface roughness Ra of 0.08 µm or more. A transfer decorative sheet which does not produce wrinkles on an injected molding can be provided.