Rolling mobiles vs. folding mobiles: what technology do they use

The end of 2019 and 2020 was the beginning of folding mobiles. Samsung, Motorola, Huawei and Royole were the first (and only) manufacturers to bet on this technology, which, all told, has a lot of room for improvement. Folding screens were a trend in 2020, but we are in 2021 and folding mobiles have come up with a competitor: roll-up mobiles. Or rather, it seems that a competitor is going to come out, since there is still not a single roller mobile on the market.

Thus, it seems that the future of smartphones is divided in two ways: in one, the screens fold, either inwards or outwards, to make a mobile something bigger or smaller. In another, the screens roll up like parchment and make it possible to convert a conventional mobile into something larger. What does each brand propose? How is the panorama of what, apparently, are the screens of the future? Let’s see it.

Those who bet on folding mobiles screen

First we are going to focus on the brands that bet on folding screens. Perhaps the most popular is Samsung, which is the only one that, to date, has launched three folding phones: the Samsung Galaxy Fold (and its review ), the Samsung Galaxy Z Flip and the Samsung Galaxy Z Fold 2. Two of them are in book format and only the Galaxy Z Flip, for now, drinks from the old flip phones. Only the Galaxy Z Flip 5G and Z Fold 2 5G are currently officially sold.

On the screen of these two phones we find what Samsung calls “UTG”, short for “Ultra Thing Glass” or ultra thin glass. It’s an interesting leap from the original Fold’s screen, which was made of polymer (aka plastic). It’s a folding glass screen made by Schott and apparently by the Korean company Dowoo, and it does have some plastic in it. Specifically, a top layer that is the one we touch and the one that is scratched.

The physics is simple: any material can be folded if you can make it thin enough. The glass on the Samsung Galaxy Z Flip and Z Fold 2 is 30 microns (0.03 millimeters) thick and is also treated to polish imperfections. And why does it have plastic on it? Because if such a thin glass is scratched the least, it is most likely that when folding it will break, especially if the damage is in the area of ​​the fold. It is a kind of protective shield, so when you touch the screen it feels somewhat more plastic than conventional screens.

Samsung galaxy z flip
Samsung galaxy z flip

On the other hand, it should be remembered that the screen does not fold completely, but has a small radius of curvature. In the case of the Z Fold 2, it is 1.4R. Basically, the fold is not pointed (like when you fold a sheet of paper), but is slightly curved. The idea of ​​this implementation, which is similar to what we see in the Motorola Razr, for example, is to reduce the crease crease, but since the top layer is plastic, it is still visible against the light and is noticeable to the touch.

Then we have Huawei, which in the absence of presenting the Mate X2, currently only sells the Huawei Mate Xs. This device, unlike Samsung’s, does not fold in, but out. That is, when it is folded we have a screen both at the top and at the bottom. Samsung, however, preferred to put a secondary screen on the front of its Z Fold 2 to function as a mobile to use when it is folded.

The folding screen of the Huawei Mate Xs is made of a double layer of aerospace grade polyamide, that is, a polymer, that is, plastic. However, it is a fairly expensive material, three times more than gold, according to Huawei. This layer is “glued” onto the flexible OLED panel using a transparent optical adhesive. By having a double layer, the surface is 80% more resistant, but being plastic it feels like one and, as in the case of Samsung, the area of ​​the fold wrinkles over time.

And so we come to Motorola, whose only foldable launched to date has been the Motorola Razr. There is no news on a second version. The Motorola Razr has a screen that folds inward and vertically, like the Galaxy Z Flip, and its screen is pOLED. These screens have a matrix substrate made of plastic (PET), not glass, and what we touch is plastic, so it feels like one to the touch.

The key to the Motorola Razr is on the hinge. Not only does it have a ratio of curvature, it is also teardrop shaped. Under the screen, in the fold area, there are metal cams that, when unfolding the device, push the screen up and prevent a crease from being created in the fold. The system is not perfect, but when we were able to test it we could notice that the wrinkle was not very noticeable, although it was noticeable to the touch.

And so far the list of manufacturers that have folding mobiles on the market. However, there are other brands that have shown some interest in this technology and that, incidentally, have not yet launched a commercial product. They are Xiaomi, OPPO and TCL, two brands whose folding phones we have heard countless times and that we are still waiting to see with our own eyes.

The first time we saw the foldable Xiaomi, which the Internet has been commissioned to baptize as Xiaomi Mi Flex or Xiaomi Dual Flex , was on January 3, 2019. In the video, courtesy of Evan Blass, we saw a mobile that was folded on two sides, so it had a double fold. Xiaomi confirmed at that time to be working on the device and only mentioned that the flexible screen was being developed by Xiaomi and a supply chain partner, but nothing else. At the moment, it’s little more than a leaked cell phone.

OPPO, for its part, let us see its first folding prototype at MWC 2019. His proposal was similar to Huawei’s with the Mate X, that is, the screen was folded out. There is no information or name about this device, we only know that OPPO said they would consider making it if enough interest was shown. We are February 18, 2021 and of a folding OPPO we have only seen photos of prototypes and patents , each one with their interpretation.

Oppo folding mobiles design
Oppo Folding mobiles

At the end of 2020, OPPO showed another concept of sliding folding mobile, to call it somehow. It has several folds and the screen can be put in various positions until you get a fully unfolded mobile with a fairly elongated 7.2-inch panel. Again, nothing beyond concepts and ideas, but nothing palpable.

We finished with TCL. The company has plans for folding and we have known it since February 2019, when they showed us their first prototypes in the framework of the Mobile World Congress 2019. They told us that the device would arrive in 2020 and at a price lower than 2020 euros, but neither of him nothing is known. According to Peter Lee, General Manager of TCL Communication, “the strategy is not to be the first, we want to launch these products when we are able to offer them to everyone.” We will have to wait.

In Technoeager we had the opportunity to test a TCL prototype with a double fold, but its state of development was in an initial phase. The mobile was folded on two sides, like the Xiaomi concept, so it is literally a phone that becomes a full-fledged table. As we could see, the thickness of the extended device was thin, but greater than that of a Galaxy Fold when folded.

And before moving on to talk about rolling mobiles, from the end of 2020 it is rumored that 2021 will be the year in which we see the folding of OPPO, Vivo, Xiaomi and even Google. The source is Ross Young, founder and analyst of DisplaySearch and DSCC. Young summoned us for the second half of 2021, so perhaps throughout the year we will get out of doubt.

Those who bet on rolling mobiles screen

And now, yes, we start with the brands that are committed to rolling mobiles. First of all, it should be noted that all we have seen so far are prototypes and concepts, but there is not a single mobile for sale currently. That said, we start with one of the brands with the longest history in the world of roller screens: LG.

We know that LG has the LG Rollable in the oven. After countless rumors and leaks, LG confirmed the existence of the device with a small teaser at CES 2020. It is a device with an extendable screen, that is, the panel is rolled up on the lower frame and unfolds upwards or down when we hold it horizontally. The mobile will go from 6.8 inches to 7.4 inches. How will it work? What technology will your screen use? We will have to wait for it to be presented, something that the leaks suggest will happen in March 2021.

LG is a brand that has a track record in rolling screens. In 2019 they presented the LG Signature OLED TV 65R9, the first rollable TV, whose 65-inch OLED screen is hidden in a chassis similar to a sound bar and is displayed in three phases: Zero View (completely hidden), Line View (se displays a third of the screen) and Full View (fully displayed screen).

Then we have TCL, whose roller prototype was apparently scheduled to be unveiled at Mobile World Congress 2020. It was not. However, at the end of 2020 some videos appeared in which they could be seen in operation. One of them unrolled vertically, like a roll of toilet paper, and the other was more like parchment. At Technoeager we have had the opportunity to test a mock-up of a roll-up TCL and the operation, although it was a bit rough, revealed the possibilities of this technology. However, it is still a prototype pending materialization.

On the other hand, at CES 2020 TCL showed two roll-up display technologies. The first was a 17-inch printed rollable OLED screen. This panel is 0.18 millimeters thick and can be adapted to any format. According to TCL, the panel reproduces 100% of the colors and is 20% cheaper to manufacture than traditional display technologies. We may not see it on smartphones, but we can think of a small portable television.

The second is a 6.7-inch AMOLED screen that, this one, is aimed at smartphones. The panel shown stretched to convert a 6.7-inch mobile into a 7.8-inch one. According to TCL, the service life of the mechanism is up to 100,000 cycles. Be that as it may, we don’t know anything about the technology under the hood, so we’ll have to wait for the company to show them off.

And we are done with OPPO. At the end of 2020, the company presented the OPPO X 2021, its first folding mobile concept. To develop it, OPPO used 122 patents, of which 12 are directly related to the screen. This one has an OLED screen that expands to the side and hides at one of the edges. Basically, the mobile goes from 6.7 inches to 7.4 inches.

From its technology we only know that OPPO has implemented a Roll Motor to unfold the screen, a two-in-one plate that moves to the side, and a high-strength screen laminate called Warp Track. How does it work? It is not known. We only know that it is a concept and that, from its name, we can intuit that it will be officially presented throughout this year. Again, patience.

Those that have not yet commented on the matter

Patent for a foldable iPhone.
Patent for a foldable iPhone.

And what about the other brands? Well, little thing. There are companies like Apple, HTC, Realme and Sony that have not yet been animated with either of these two technologies. In May 2019, rumors emerged that Sony was working on a foldable phone codenamed Sony Xperia F, but little else.

About HTC we know that it has a patent related to a folding mobile, but little more than that. Apple, for its part, is rumored to be working on a similar device and, in fact, there are patents related to it , but not a foldable as such, but an iPhone with two screens, something similar to what we can get with an LG G8 ThinQ, for example.

The most recent we know of Apple is the prediction of the Omdia organization, which estimates that a foldable iPhone will arrive by 2023. This, they say from Omdia, will have a 7.3 or 7.6-inch OLED screen and will have support for Apple Pencil. Gurman, for his part, said that Apple already has two folding screen prototypes, but that it has yet to decide whether or not to advance the project.

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