While Apple remains coy about plans to incorporate sapphire into its product lineup, a new patent application published on Thursday suggests the company is at the least experimenting with the hard material for use in touch-capable displays.
Apple’s “Oleophobic coating on sapphire” patent application represents some of the first hard evidence that the Cupertino, Calif. company is looking to include sapphire in its iPhone lineup.
Aside from the illustration of an iPhone on the filing’s cover page, Apple’s document makes repeated mention of sapphire displays in phones, tablets and other portable devices.
Specifically, the filing describes in detail the methods by which an oleophobic, or oil-repelling, coating can be applied to a sapphire slab prior to installation in a mobile device. Oleophobic coatings were first used by Apple with the iPhone 3GS in an attempt to counter the buildup of oil and other detritus inevitable with a touchscreen display.
Since then, iPhone and iPad models have all come with the repellent coating, though methods of application used for Gorilla Glass do not necessarily apply to a material like sapphire. For example, Apple points out that normal bonding techniques may not work with sapphire or sapphire glass because of its crystal structure.
The document also notes certain coatings and oleophobic treatments do not fair well when applied directly to sapphire glass. Abrasion tests have shown some coatings and treatments last for a “lower number of abrasive cycles when applied to sapphire glass and other alumina-based base layers (e.g., less than 300 cycles), as compared to silica glass, where the coatings may not exhibit wear until a higher number of abrasive cycles (e.g., 300 cycles or more).” Additionally, the same surface treatments applied to a silica substrate may exhibit wear at an even lower number of cycles when a transition layer is not present.
To address this issue, Apple proposes a transitional layer be disposed between the base substrate and the oleophobic coating. Further, a surface layer may be composed of alumina, silica or a combination of the two.
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