Apple's first foldable device related patent application published today by the US Patent & Trademark Office covered the hinge mechanism of the foldable device. In Apple's second patent application published today, Apple delves into the bendable aspects of the display that could provide a double fold configuration and the processes to the glass to allow it to be flexible.

Apple's second folding patent application of the day relates to techniques for forming flexible cover sheets. In particular, cover sheets may be formed to facilitate localized bending or flexing without producing unacceptable levels of internal stress.

The electronic devices may further include a flexible display layer. An example electronic device comprises a display layer and a cover layer coupled to the display layer and defining a foldable region, wherein the display layer and the cover layer are configured to be moved between a folded configuration and an unfolded configuration by bending the cover layer along the foldable region.

In some embodiments, the cover layer comprises a continuous layer of a ceramic material. An exterior surface of the continuous layer of ceramic material can define an exterior surface of the electronic device. Such an arrangement can present an impact and/or scratch resistant surface to a user. An opposing interior surface of the continuous layer of ceramic material can face the display layer.

Apple's patent FIGS. 1A and 1B below respectively illustrate a device in open and closed configurations.

Apple's patent FIGS. 2A, 2B, and 2C above respectively show cross-sectional views of a device in folded, partially unfolded, and unfolded configurations.

Apple's patent FIG. 2A is the most complex device configuration with a double fold illustrated that is considered in a "closed configuration." In the fully folded or closed configuration, roughly a third of the display layer (#220) is viewable along a first region (#281) of the foldable device #200. The display layer is also viewable along a first foldable region #201 of the device located along the right edge, as shown in FIG. 2A. The cover layer #210 is on the exterior of the device on first region #281 and first foldable region #201. In the fully folded or closed configuration, the display layer isn't viewable along the second region #282 and third region #283 because those regions are folded over themselves with the display layer facing inward. Also for the second region and the third regions, the cover layer is generally protected.

Apple's patent application drills down in how it will treat the flexible glass to be bendable using chemicals and heat treatments. For instance, Apple notes that in glass compositions suitable for ion exchange or field assisted chemical strengthening include, but are not limited to, alumina silicate glass (aluminosilicate glass), soda lime glass, borosilicate glass or lithium containing glass.

For an ion exchange process conducted primarily at temperatures below the strain point of the glass, ions in the glass are exchanged with larger ions to set up compressive stresses in an outer layer of the glass.

For example, the ion exchange process may involve the exchange of alkali metal ions, such as the exchange of sodium ions for potassium ions or the exchange of lithium ions for sodium ions. In an example, the chemical strengthening process involves exposing the glass to a medium containing the larger ion, such as by immersing the glass in a bath containing the larger ion or by spraying or coating the glass with a source of the ions.

For example, a salt bath comprising the ion of interest (e.g., a potassium nitrate bath) may be used for ion exchange. Suitable temperatures for ion exchange are above room temperature and are selected depending on process requirements. In embodiments, the chemical strengthening process includes one or more ion exchange steps. A multi-step ion exchange chemical strengthening process may comprise a step of exchanging ions in the glass for larger ions, followed by a step of exchanging some of the larger ions introduced in the previous step for smaller ions.

For engineers wanting to delve further into the finer details, check out patent application US 20220342450 A1.