Apple Invents a new Protective Layer for Foldable Displays that is designed to Resist Cracking at the Fold Mark
Sometimes while searching for new patents in Europe I'll come across a U.S. based patent that I originally missed when it was posted. Today I discovered a patent application that was published by the US Patent & Trademark Office on March 26, 2020. It's an interesting patent filing as it attempts to correct the display cracking issue in foldable devices today which has definitely turned off consumers to the whole idea of foldable smartphones. Apple's patent specifically relates to protective cover layer structures for smartphones, and more particularly for flexible displays that could fold while being crack resistant.
Apple's invention describes display modules and protective cover layer structures that may be implemented in curved, flexible, conformable and foldable display modules, and in particular with curved, flexible, conformable and foldable display panels.
Various embodiments are described in which a hardcoat layer is applied to a transparent support substrate to form a protective cover layer structure. The hardcoat layer may be characterized as possessing a lower elastic modulus, higher elongation-to-break and optionally a lower hardness than the transparent support substrate.
In one aspect, such a hybrid structure may prevent cracks from forming in the transparent support substrate.
In another aspect, such a hybrid structure may move the neutral plane of protective cover layer so that the surfaces of the transparent support substrate see a lower strain upon bending.
Apple's patent FIG. 1 below is a schematic isometric view illustration of a protective cover layer; FIG. 2 is a schematic cross-sectional side view illustration of a bent protective cover layer.
Apple notes that typically, glass fracture initiates from the presence of micro-cracks. The hardcoat layer #104 in accordance with embodiments may fill pre-existing micro-cracks and also make it harder to initiate a crack.
Furthermore, the hardcoat layer may be engineered to have a sufficiently high hardness and tensile strength to function as an exterior protective coating for the electronic device, while being able to withstand more strain before fracture compared to the transparent support substrate #102. Thus, the hardcoat layer is sufficiently durable for high puncture and scratch resistance.
Apple's patent FIG. 4A above is a schematic top view illustration of crack propagation in a scratched transparent support substrate; FIG. 4B is a schematic top view illustration of crack propagation in a scratched transparent support substrate with hardcoat layer
Apple's patent FIGS. 12A-12B above are schematic isometric view illustrations of an electronic device #1200 such as an iPhone. The display panel #150 and protective cover layer #100 may be curved, flexible, conformable and/or foldable. Apple's patent FIG. 12A illustrates an outward bending application, while FIG. 12B illustrates an inward bending application.
Apple states that the display that could be curved, flexible, conformable or bendable could apply to a number of products including an iPhone, Apple Watch, TV, MacBook, iPad, or iMac (an all-in-one desktop).
Apple's patent application that was published in late March by the U.S. Patent Office was filed back in Q3 2019. Considering that this is a patent application, the timing of such a product to market is unknown at this time.
Hoon Kim: Display Investigation, Lead Technologist (Hardware Engineering Manager). Previously worked at Samsung as a Foldable OLED Display Module Architect.
Paul Drzaic: Director, Display Investigations
ChangChia Huang: Senior Emerging Display Engineer
Christopher Jones: Chemist/Materials Scientist
Masato Kuwabara: Sr. Optical Film Engineer
Nikhil Kalyankar: Sr Optical Engineer
Yasmin Afsar: Hardware Engineer, Emerging Display Technology
Terry Shyu: Engineer, Emerging Display