It’s all about the ink and where it ends up – By Tim Cabot, President of DCHN
Silkscreen and pad printing are common methods for printing in general and are used regularly for printing on anodized aluminum articles. So what’s the difference between these methods and Sanford Print?
Let’s start with how silkscreen and pad printing work. In both cases, ink is deposited on the surface of the object as a thin film where the ink dries and becomes solid print. Adhesion is achieved mechanically as the ink wets out the surface and through physisorption (van der Waals forces). The commonality in both techniques is that ink is placed on the object’s surface, which dries to form a hard, durable, print. In addition, both techniques typically use pigmented based inks that cover the substrate (and block out the underlying color of the substrate).
In Sanford Print, the ink is physically deposited into the pores of purposely open anodic cells. The pores will later be sealed, locking in the ink below the surface of the anodic coating. Given that the diameter of the pores of anodic cells are measured in angstroms, physical pigments are much too large to enter the pores. To fill the pores with color, Sanford Print uses specialty dye based inks where the dye is soluble and is not physically restricted by pore size.
The different methods of printing are relevant when we start talking about performance. The problem with printing on the surface of an object is that the print can, and likely will, delaminate, chip, and/or abrade off, as he materials are dissimilar. A common mechanism for delamination on printed anodic coated surfaces is the differences in the coefficient of thermal expansion between the ink and the aluminum oxide that causes a loss of adhesion. This mechanism is prevalent when the part is used in a medical procedure, as the part passes through frequent autoclave sterilization cycles.
In Sanford Print, the ink is deposited into the oxide pores before sealing and cannot expand or contract. Further, it is below a surface of sapphire hard aluminum oxide that is typically much harder than other materials, so the ink can not abrade and/or chip.
Sanford Print is unique because of the type of film formed by Sanford Process Corp’s Low Voltage process (QUANTUM®) where a clear, translucent hard coat is formed. This specialized hard coat process produces a coating unlike conventional high voltage hard coat where the coating becomes dark. QUANTUM is not only equally hard to conventional hard coat (and much harder than Type II decorative anodizing), as a dense, thick hard coat it also protects the substrate from scratching, abrading, and other physical damage. Further, the thicker, more porous, Quantum Low Voltage hard coat allows for greater ink volume to be deposited into the pores due to the greater pore volume. This in turn allows for a much deeper, higher optical print density or simply put, easier to read and sharper graphics.
Feel free to contact us if you have questions on this technique using our Contact Us Form.