Patent Application
20180319061
The claimed invention relates to the art of in mold decorating. More specifically, the claimed invention relates to a molded cup with a hard exterior shell and a method for molding a cup with a hard exterior shell.
Many decorated containers are not molded. Instead, the container is decorated using dry offset or pad printing processes. Those products that are molded use a laminated or coated label. These types of labels are susceptible to damage as will be further discussed below.
Typical in-mold cup labels are made with a coating applied over the ink to prevent the ink from escaping the surface. There are several disadvantages of such coatings. Typically, the coating process produces a film layer that is less than 0.001″. Such a thin layer is often inadequate to create a continuous film that is free from voids. Additionally, the coating layer is susceptible to scratches and abrasion from normal usage. Such voids, scratches and abrasions can create a pathway for contaminates to damage the image. These same pathways can allow for moisture to get under the coating and to further damage the coating layer and the image.
Lamination has also been used to seal the ink under the surface of the laminate. Typically, the laminate is a thin gauge layer of polypropylene. Lamination has been used because the laminated film expands and shrinks at a rate similar to the molded cup, which is critically important when the cups are exposed to multiple cycles of a dishwasher. Laminated films typically range from 0.0005″-0.003″ in the thickness. Although such films typically provide a continuous film seal, they are susceptible to scratches and abrasions. Additionally, the laminate typically has an edge that is close to the top and bottom edges of the cup and is thus susceptible to peeling. Deterioration of either a coating layer or a laminate layer can allow for ink migrations and will cause deterioration to the image and may allow ink and adhesive to be exposed to human contact.
Existing production methods are deficient for other reasons. For example, existing methods do not allow for photographic quality graphics. Additionally, existing production methods are not flexible, that is, they do not allow for personalization and customization of individual products.
A significant obstacle to using existing materials in the molding process is that polypropylene, a typically preferred molding material, shrinks significantly as it cools after the molding process. For example, shrinkage in a relatively thin-walled cup is typically 0.009-0.025 inches/inch. This level of shrinkage creates sheer stress between the label and the molded polypropylene material. Ideally, the in-mold label absorbs the shrinkage or the label itself shrinks as it cools. If the label does not either absorb the shrinkage of the polypropylene or shrink itself, the label could be damaged during the molding process. For this reason, typical IML labels are made with a polypropylene base layer and a coating to protect the inks. Use of this type of base layer molds relatively easily and without shear stress between the molded cup and the layer because the polypropylene label bonds well with the polypropylene molded material, which have similar shrink rates.
What is needed is a decorated in-mold product with a hard exterior shell that prevents ink migration and that maintains a high level of graphic image quality.
The claimed invention teaches a method for producing a molded article with a rigid, digitally printed label. More specifically, the claimed invention is a method for molding a cup wherein the ink is encapsulated by a thin hard shell to prevent ink migration and to protect the integrity of the in-mold decoration. The claimed invention further provides for a digital printing process used to print the label. The claimed invention further provides for a label that thermally bonds to the injection molded article. The label itself is designed to protect the inks used during the injection molding process. The claimed invention further employs an adhesive that bonds to the digital print and the thermally protective layer. A specific aspect of the label, the adhesive and the thermal bond layer is that they are collectively designed to withstand the shear forces of the injection molded article. The claimed article provides a superior product in terms of aesthetics and durability, including through dishwashing cycles.
Now referring to the drawings in detail wherein like reference numerals refer to like elements throughout,
Hard shell material 11 can be one of a number of possible materials including polycarbonate (“PC”) and polyethylene terephthalate (“PETG”). Primary considerations for hard shell 11 materials are price, heat softening and food safety. For these reasons, PETG is the currently preferred material for the hard shell 11. PETG is also preferable because it provides a very glossy appearance in comparison to other materials. PETG can also provide an alternative satin luster finish not currently available with other materials. Using PETG as an external protective layer protects the ink from degradation, making for longer lasting decoration, which is very important in the highly brand conscious souvenir cup industry. PETG is also BPA free, food safe and dishwasher safe.
Referring to
Referring back to
It is critical that the ink layer withstands the molding process and that it withstands the shear forces created between the label and the cup when the molten plastic cools, hardens and shrinks relative to the label. For this reason the PETG is either subsurface printed or surface printed using a fusion layer. Either treatment allows the ink to absorb higher shear forces.
Alternatively, as shown in the process diagram in
The claimed process provides a new and unique method for molding a souvenir cup using a rigid outer shell to protect the ink layer. The claimed process and cup provides a cup structure wherein both the ink and the adhesive are within the wall of the molded cup, thus reducing the potential for exposure to either the ink or the adhesive. The claimed structure is significantly less susceptible to lamination peel than polypropylene laminated parts and ink migration. Additionally, the structure of the claimed invention is significantly less susceptible to deterioration from everyday use, including dishwasher cleaning and abrasion.
The present invention has been described in terms of embodiments. While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the invention.
