Folding Phone Evolution – How it Achieved and durability

The most important sign of the evolution of mobile phones from feature phones to smartphones is the screen. In 2007, the Apple iPhone was born, which enabled the smartphone to start moving toward touch and large screen, and gradually eliminated the physical keyboard.

In the following period, with the development of mobile Internet, the office and entertainment properties of mobile phones became more and more prominent. The size of the screen as the content window also increased. The current mainstream mobile phone screen size has exceeded 6.0 inches.

Of course, the screen of the mobile phone also has a border. In order to obtain a larger screen ratio per unit area, the smartphone opens a full screen upgrade.

In the past 2018, the full-screen mobile phone ushered in explosive development, in addition to Notch Display, water drop screen, dip screen and other special-shaped screens, as well as sliders, lifting and other comprehensive screens created by mechanical structure. The advantage of a full-screen mobile phone is obvious. In terms of user experience, the full screen accommodates a larger mobile phone screen in a limited space, and can present richer content. However, these full-screen mobile phones still have to be limited by the size of the mobile phone. Even if we can achieve 100% screen ratio, it is difficult to put a 7-inch mobile phone into the pocket easily. How can the mobile phone screen boundary break through?

In fact, mobile phone manufacturers have begun to work on the next technology slogan – folding screen.

In November 2018, Samsung officially presented its collapsible screen prototype at the developer conference. The prototype uses a small screen plus a folding screen design that can be used to achieve normal operation of a conventional mobile phone using a small screen, while a fully expanded 7.3-inch large screen can be obtained. At the conference, Samsung announced that it is ready to do mass production work in the next few months, and officially launched the folding screen mobile phone to the market in 2019.

Domestic soft-tech technology launched FlexPai, a folding screen product, before Samsung. This folding screen phone adopts the second generation of 7.7-inch flap flexible screen, which is lighter and thinner than traditional LCD and OLED displays. It can be folded to 4.0 inches in daily use. It is convenient for mobile phones. At the same time, it can fully realize the experience of 7.8-inch tablet in the case of office, video entertainment and other large screen experience.

In addition to the above two manufacturers, Huawei, OPPO, and Xiaomi have also begun preparations for folding screen equipment. It can be seen that the era of folding screens is really coming.

How is the screen folding achieved?

In the normal form, if you want to increase the screen area in the case of the same size of the body, it is obviously impossible, then you need to find another way. The folding screen concept began to be initially formed. In the folded state, the size of the body was sufficient to plug the inlet pocket, and in the unfolded state, it was equal to twice the original folding size.

This opening fold, the mobile phone screen can be enough to achieve 180 degree bending, although the curved OLED screen can be bent, but whether it is a curved TV or a curved screen mobile phone, the angle of the curved screen is not large, the main reason is the screen Component and structural design issues, especially the non-arbitrable bending of the glass as the screen substrate, naturally can not achieve a large angle of the fold.

But if you use plastic instead of glass, it’s not the same. The properties of the plastic make it the most suitable substrate material for the foldable screen, which not only allows the substrate to be folded, but also increases the screen’s resistance to falling, while also making the screen lighter and thinner.

In addition to the substrate, there are a conductive layer and an emission layer composed of an organic substance. Indium tin oxide (ITO) is currently used in the industry as a transparent anode because of its high transparency, low sheet resistance and perfect manufacturing process. However, ITO is expensive and brittle, susceptible to crack-induced crack formation, foldable screens, or graphene materials that are excellent in ductility and conductivity. Not only that, but also optical adhesives, etc., all need to find new materials.

In terms of structural design, Samsung submitted a folding design patent in August 2017. The first design patent increases the bending degree of the OLED screen in order to achieve flatness of the folded body, and the screen forms a large arc shape inside the rotating shaft to protect the screen from being excessively bent and damaged.

The latter patents are more like the hinges on the Microsoft Surface Book. The width of the hinges after folding is higher than other parts, and the gaps at the folds are larger.

It can be seen that the “folding screen” has evolved from “concept” products to consumer products, and in the process, there are still many problems in the folding screen that need further argumentation.

Does the folded screen affect the service life?

If the flexible screen is bent for a long time and used for a long time, even if the plastic material with excellent physical properties will affect the life of the folding screen after being subjected to repeated compression and tensile stress, it will have much influence. unknown.

In addition, the hinge design has many difficulties. Although the notebook computer also uses hinge technology to connect the host computer and the computer screen, the hinged use rate of the foldable mobile phone is much higher than that of the notebook computer, and even the mobile phone will adopt three-screen or multi-screen, multi-layer folding. The problem of the angle of fit between the folding screen and the hinge is still a major difficulty. According to relevant researchers, the folding screen and the hinge are dead and not attached to the dead. If you don’t stick to it, you will always rub it. If you stick it, the neutral surface will run away. Moreover, the existing hinge processing yield is very low and the cost is high.

How to lightly handle the hinge problem is also one of the problems. After folding, the thickness of the mobile phone will increase. At present, the folding screen mobile phone launched by Rouyu has a thickness of 15mm and a weight of 380g, but the current mainstream flagship mobile phone has a thickness of only 7-8mm, which means that today’s folding screen mobile phone The thickness is twice that of a typical mobile phone, and the thinning of the screen is also a consideration in the future.

Folding screens bring more space for interaction, and it also means changes in interaction logic, with the UI and App needing to be redesigned. The current solution is to use the mobile version interface when using a small screen, and automatically switch to the HD tablet version when using a large screen. However, this poses a challenge for the application adaptation of the Android version, and it is not optimistic to meet the application adaptation of the folding screen mobile phone in a short time. For example, Samsung’s One UI based on Android 9.0 for folding screen phones, Samsung is redesigning almost all the apps, so that all UI elements that require finger clicks are concentrated at the bottom of the screen, making it easy for users to click.

Final Words

Based on the user’s natural preference for large screens, folding screen mobile phones are undoubtedly the next technology outlet for mobile phone screen development, but folding screens are not like the evolution of previous generations of screens, but the improvement of simple size and screen ratio, it puts forward to technology and supply chain. Higher requirements. Therefore, the folding screen mobile phone may only be emerging this year, and it will officially usher in an explosion next year. Let us look forward to this product that is expected to change our lives again.

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