On June 14th, a patent application filed by Motorola Mobility LLC. (Chicago, IL) was published. It discloses a means to address the issue of semi-permanent screen deformation in foldable displays. The basic idea in Motorola’s disclosure is the use of heat to minimize damage to the flexible display caused by folding and unfolding the display.
The application is entitled “Method to Recover Permanent Set in a Foldable Display.” The publication number is US 2018/0164854 A1. The application number is 15/375,986. A copy of the application is available on-line and can be found here.
While OLEDs and other foldable displays can be very flexible, frequent bending can cause permanent deformations at the crease. This can be true whether the display is folded either inwards or outwards. Motorola notes in its application that foldable displays are particularly susceptible to such deformation when the temperature is low.
The foldable smartphone disclosed by Motorola has a hinge that runs the entire width of the display. It is also disclosed to have a second hinge making it possible to bend the device at several points.
A detection module is used to measure if the display is in the bent position. Then it is calculated how long the display is in a curved position. The timer uses a backup battery so that the time can be measured even when the device is turned off. If the time off is determined to be longer than a predefined duration and / or if the temperature becomes too low, then the system calculates the extent that there is semi-permanent deformation.
Once the screen is completely unfolded and the display is inactive, the automatic recovery process begins. The dynamic heating system is switched on and the temperature is increased, after which the display is restored. Movement can also be used to correct screen bend deformations. In this case, the phone will automatically bend slightly in an opposite direction while the display is heated.
The figure below illustrates the approach disclosed by Motorola to minimize screen deformation in foldable display applications. -Arthur Berman