Last week Patently Apple posted a patent report titled "An Advanced Force Touch Patent for the iPad Surfaces in Europe." Today the U.S. Patent Office published a patent application from Apple that expands upon the foundation that was laid out last week. Apple's patent reveals that their 2-layer force-sensitive films will apply to a wide range of devices including the iPad, wearables, keyboards, the magic mouse and beyond. While it's a surety that Apple's Force Touch is coming to the iPhone 6s in a few weeks, we know that Apple is likely to bring this feature to the iPad as this invention reveals. The timing of course isn't known at this moment but we can assume it will arrive in the next year or so as Apple expands Force Touch across more products.

Apple's Patent Background

Mobile devices typically include a display screen and one or more components for providing user input to the device. In some cases, it may be advantageous for the user to provide touch input on a surface that overlays the display or other portion of the device. Some traditional touch sensors are configured to detect the presence and location of a touch on a surface using capacitive sensing techniques. However, many traditional touch sensors are not able to determine the magnitude or degree of force associated with a touch.

Apple's Invention: Transparent Force Sensor with Strain Relief

Apple's invention generally relates to force sensing and, in particular, to force sensing using a transparent force-sensitive film having one or more strain-relief features on devices such as an iPad as noted below. The invention may also extend to other devices which Apple lists as "a mobile phone, a wearable electronic device, a health monitoring device, a tablet computing device, a notebook computer and a desktop computer."

One example embodiment includes a transparent force sensor for detecting a force on a surface of a device. The applied force may be due to a touch on an exterior surface of the device. The transparent force sensor may include a transparent force-sensitive film having an array of slit features oriented along a first direction. The transparent force-sensitive film may be formed from a transparent piezoelectric material that exhibits a substantially reduced net charge when strained along a primary direction.

The force sensor may also include a display element disposed relative to one side of the transparent force-sensitive film. The force sensor may also be integrated into a user-input device, including, for example, a touch pad, a track pad, a keyboard, a mouse and the like.

In some embodiments, the piezoelectric material exhibits a strain-direction dependent charge polarity. In some embodiments, the piezoelectric material is a poly-L-lactide (PLLA) or poly-D-lactide (PDLA) polymer film material.

Apple's patent FIG. 1 noted below depicts an example electronic device having a force sensor incorporated with a display element; FIG. 6 depicts components of an example electronic device which includes transparent force-sensitive layers integrated into the tablet's display.

Generally, Apple's patent FIGS. 2A to 2C depict an example of charge characteristics for a transparent force-sensing film having strain-direction dependent charge polarity; FIGS. 3A and 3B depict force-sensitive film layers having an array of strain-relief features substantially oriented along a Y-direction; FIGS. 4A and 4B depict force-sensitive film layers having an array of strain-relief features substantially oriented along an X-direction.

More specifically, the transparent force-sensing film may exhibit a different charge polarity depending on the direction along which the film is strained. FIGS. 2A-C depict an example of charge characteristics for a transparent force-sensing film (film 200) having strain-direction dependent charge polarity. In the following examples, the film 200 is a PLLA piezoelectric film that has been drawn along a primary direction, as indicated by the tensor, primary direction #210 shown in FIGS. 2A-C. In some cases, the orientation of the primary direction is due to a drawing process that substantially aligns the polymer chains of the film along a single (primary) direction.

In Apple's patent FIG. 5A noted above we're able to see a depiction of an example of a force-sensitive film integrated into a display stack #500. In this example, the display stack includes two force-sensitive films #510 and # 520 that are incorporated with a display element #501. The display element may include, for example an LCD display, an LED display, an OLED display, or the like.

Furthermore, one or more other components or layers may be disposed on the top of the display stack 500, including, for example, a cover glass layer, another sensor layer, an optical conditioning layer, or other component layers.

Patent Credits

Apple credits James Pedder and John Smith as the inventors of patent application 20150242037 which was filed in Q4 2014. Considering that this is a patent application, the timing of such a product to market is unknown at this time.

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