Foldable phones got off to a rocky start, but TCL's new rollable phone concept offers many of the same advantages as the foldable with fewer trade-offs. In fact, flip phones like Samsung's Galaxy Z Flip look almost conventional.

Imagine a phone with a 6.75-inch display that stretches to 7.8 inches (the size of an iPad mini) at the push of a button. This is the idea behind the TCL concept.

The concept behind the world's first rollable telescoping smartphone utilizing flexible AMOLED display technology is 9 mm thick; the Galaxy Z Flip is a slim 7 mm when open, but thickens to 17.2 mm when closed.

TCL also states that the rollable phone has no creases or folds that could detract from the aesthetic appeal of a foldable phone.

How does it work? There is a motor-driven sliding panel that hides the flexible display, similar to how LG's OLED TV R9 works. Unfortunately, TCL did not have a sample available for demonstration, only a dummy unit. However, at least we were able to get a sense of how the display slides back and forth.

In this concept phone, the camera array is located on the right side of the back, which is essentially the spine of the device. This means that the camera can be used in both phone mode and tablet mode.

Since it is in the early stages of development, if TCL were to commercialize this phone, the display might be extended and retracted by gestures rather than buttons.

I also got to play with TCL's tri-fold concept phone, which is a very nice, but not very practical, device.

This was a practical prototype that transformed from a 6.7" phone to a 10" tablet with 3K display resolution using two different hinges, DragonHinge and ButterflyHinge.

While it was pretty cool to unfold and fold this device, it was very thick and quite heavy when the tri-fold design was closed. Still, it would be of use to power users who are serious about multitasking and running multiple apps on the screen at the same time.

TCL had a demo video showing the possibilities of the three-fold concept, such as video conferencing with multiple people at the same time, or editing a video in one window while running another app in another window.

I'm still not sold on the dual-hinge concept. I would like to see something smarter. But this is just a concept.

Of TCL's two concept phones, I prefer the rollable concept. It has none of the wrinkles of a foldable phone and allows for a larger screen when needed; TCL says it is still figuring out the proper speed for extending and retracting the display.

Overall, TCL is a company better known for its TVs than its cell phones and has relied on other brand names it owns, notably Alcatel, Palm, and Blackberry (RIP). However, such a concept could put TCL on the map as it seeks to gain a foothold with other cell phones bearing the TCL name.