Apple Patents Technique for Producing Unique Curved Touch Surfaces

Hot on the heels of earlier rumours of Apple experimenting with curved displays, here comes a patent freshly awarded to the company by the US Patent and Trademark Office on Tuesday, spotted by AppleInsider.

US Patent No. 8,603,574, for a “curved touch sensor”, describes a manufacturing technique producing a curved touch surface for displays, touch pads, touch mice and other devices.

The Apple patent offers a solution for manufacturing curved touch surfaces without deficiencies are caused by substrate deformation. Current touch panel technologies – especially those containing thin-film conductors – require relatively low temperatures when layering, which involves heating thin films over flexible substrates such as plastic.

Apple’s solution to avoid deformation during the heating or annealing process is to deposit a thin conductive film over a flexible substrate while it is in a flat state and join that package to a curved forming substrate, which would be subsequently heated.

To give the appearance of a convex touch surface, the thin film (109) is deposited onto the substrate and capped off by a domed cover glass (104). While the setup may appear curved to a user, touch sensitivity may be degraded due to the distance between the surface of the glass and the drive and sense electrodes in the thin film.

On the right is a constant wall touch sensor panel that can not only reduce thickness (y) compared to the flat-substrate design, but will keep touch sensitivity at high levels since the distance between the cover glass and thin film is unchanged from a completely flat stackup. Apple’s patent allows for this type of process without deformation of the substrate or damage to the drive lines.

The technique can be used to form multiple curvatures, even a wave, by adding a second or third forming substrate.

Apple’s patent credits Lili Huang, Seung Jae Hong and John Z. Zhong as inventors, and was filed for in 2010.