Invisible fingerprint coatings and process for forming same

#The present disclosure relates, in exemplary embodiments, to coating compositions for coating a substrate to render fingerprints invisible or nearly invisible.

#A person naturally produces sebum (from the sebaceous gland) and other oils from the face and fingertips. A person deposits such oils on cell phone (or other article) display screens, such as glass (or a screen protector, typically a polymeric plastic), glass ceramic, metal oxide, Plexiglas or the like materials or surfaces. Often. Such oils are visible and can reduce the quality of the images seen on the device, as well as contribute (with dirt, dust, etc.) to a reduced aesthetic appearance of the screen. Invisible fingerprint (“IFP”) coatings are generally oleophilic coatings that cause oils to be invisible, or nearly invisible, by causing the oils, e.g., from fingerprints, to spread along the screen surface. The oils will match the index of refraction of the screen material, e.g., glass, so that light passes through making it appear that there are no fingerprints. The fingerprints are still present, one just cannot see them (at least not without scrutinizing the surface). Coatings and coating materials displaying IFP properties need to be hydrophobic enough that the oils bead up and evaporate. If the coating is too hydrophilic, then one can see the fingerprint. Also, if the coating is too hydrophobic (e.g., contact angles greater than about 85 degrees), it does not exhibit adequate properties.

#In contrast, “anti-fingerprint” (“AFP”) coatings are oleophobic coatings that resist wetting and can make fingerprints which do form more easily cleaned, but do not prevent formation of fingerprints or reduce the conspicuousness of fingerprints that do form. IFP coatings function in a different manner than AFP coatings.

#The drawings disclose exemplary embodiments or test results in which:

#FIG. 1A is a photograph of a fingerprint placed between two pieces of Gorilla Tempered Glass showing two substrates: the substrate on the left is coated according to Example 1 and the substrate on the right is uncoated.

#FIG. 1B is a detailed view of the photograph of FIG. 1A.

#In exemplary embodiments, the substrate may be glass screens, for example as used in electronic displays, such as, but not limited to, cell phone screens, computer monitors, television screens, touch screens, appliances, heads-up displays, glasses (e.g., eyeglasses and sunglasses), masks (e.g., welding masks), interior wall paints, and the like. In exemplary embodiments, the substrate may also be used in appliance equipment and cosmetic finishes fields, for example decorative panels for appliances such as domestic electrical equipment (refrigerator doors, oven doors, display cases, etc.). The substrate may be made of glass (or a screen protector, typically a polymeric plastic), glass ceramic, metal oxide, Plexiglas or other material.

#It is to be understood that in the present disclosure, the term “invisible” means invisible, nearly invisible or inconspicuous (e.g., not visible unless the surface is scrutinized). It is to be understood that “invisibility” also depends, to an extent, on the refraction of the light and on the way one views the surface. from some angles a fingerprint may be invisible, while at other angles it may be discernable. The term “wettability” means the property whereby polar or non-polar liquids adhere to a substrate, forming an undesirable film, and also the tendency of a substrate to retain dust or dirt of all kinds, fingerprints, insects, etc.

#The presence of liquids, often laden with oil, is critical in electronic display particularly for reducing the visibility of fingerprints on the surface. The wetting properties of a substrate can be categorized into hydro/oleophobic and hydro/oleophilic. A hydrophobic/oleophobic substrate means an oil (including organic liquids) and water repellent substrate. Usually, the contact angle of omniphobic surface is higher than about 60 degrees for hexadecane and about 90 degrees in the case of water in case of flat surface. Hydrophilic/oleophilic substrates mean oil and water are attracted to the surface. As such, the liquid will easily spread across the surface and have a low contact angle (less than about 50 degrees).