Why is borderless mobile phone so difficult to achieve?

I recently watched CES 2015 and saw that Nubia seemed to have released a borderless phone, which looked very fashionable. Why is it so rare to see borderless phones from other brands? Is it technically difficult to achieve a borderless phone?

Concepts such as borderless and transparent have actually been hyped for a long time. From a technical point of view, it is indeed difficult to achieve absolute borderless.

At present, there is no absolutely borderless mobile phone. The borderless mobile phones promoted by various manufacturers can only be called ultra-narrow border mobile phones, the difference is only in the narrowness of the border. The ultra-narrow borders of products launched by manufacturers with higher technology and manufacturing levels will have a stronger visual impact. If you don’t look closely at some products, you can hardly see the thickness of the border. For example, the bone conduction mobile phone launched by Sharp previously caused quite a stir with its extremely narrow border.

The same is true for the Nubia borderless mobile phone unveiled at this CES. Judging from the leaked spy photos, this borderless mobile phone adopts a curved design on both sides, and the thickness of the borders on both sides is almost negligible. It can be seen that in the past two years, the craftsmanship and technology level of domestic mobile phones are indeed not inferior to world-class manufacturers.

Simple question, simple answer. Above we have confirmed that borderless mobile phones are indeed difficult to realize. Now we will extend it based on this. Friends who are interested can read on.

Screen Limits

When it comes to the difficulty of achieving borders, the first thing we have to mention is the limitations of screen technology. So why is it that in today's era of increasingly advanced screen technology, we still cannot achieve true borderless display?

This still has to start with the nature of the LCD screen. The "liquid crystal" in the LCD screen, as the name suggests, is "liquid crystal". It has the fluidity of liquid and also has the properties of crystal (fluidity and anisotropy) because it is a substance in between liquid and crystal.

There are also many "liquid crystals" around us. For example, soapy water of a certain concentration will produce the "liquid crystal" phenomenon. When we wash our hands or take a shower with soap, we can see bubbles appearing, and these bubbles will show different colors under the light. In principle, this characteristic of bubbles is similar to the "liquid crystal" in the LCD screen. The "liquid crystal" in the LCD screen can be controlled by the circuit, so its color can also be controlled.

The reason why borderless mobile phones are difficult to make is that "liquid crystal" has the characteristics of liquid and is fluid, so a certain space must be used to limit the flow of liquid crystal, and there must be edges. The screen is made of liquid crystal, and the edges must be sealed with glue or other substances. Technologies such as dispensing are also applied to the screen frame, which can narrow the frame while reducing the risk of screen breakage.

As long as it is an LCD screen, the edges must be there. Even if the border is narrowed to a nearly borderless effect, the border still exists, even if it is only a few tenths of a millimeter.

Technical obstacles: multi-layered design

In addition to process limitations, there are also certain limitations in screen technology. Although existing smartphones of different brands have adopted a series of touch screen technologies, they essentially use built-in capacitors to achieve touch operations through changes in charge.

For example, Samsung's S Pen stylus has a built-in magnetic field on the tip that can affect the capacitor. In addition, operations like "air suspension" are achieved by building in more sensitive capacitors, allowing you to achieve the same operating effect at a greater distance.

Regardless of the capacitive touch technology, two separate capacitive layers are built into the touch screen to achieve accurate finger detection, one on the X axis and one on the Y axis, which is particularly important for multi-touch operations. This technology is dependent on the screen border because it needs to detect current changes and requires additional circuits to be designed around the screen border to achieve accurate operation. This is why "borderless screen" is actually a very difficult technology.

In addition, when it comes to actual mass production, using two separate axes to record data is not ideal because signal crosstalk occurs between the two capacitor layers (X and Y axes), so a layer of insulating material needs to be placed between them, followed by a wiring layer and external protective glass. This design makes it impossible to effectively reduce the thickness of the screen. At the same time, if any layer fails, the capacitive screen will not work properly.

If the entire screen of the mobile phone is made frameless, the frame of the LCD screen will be exposed. The frame glue is used to stick the upper and lower glass substrates, so the glue area cannot be used for display like the LCD. The liquid crystal molecules rotate after being powered on, and the frame glue is solidified, and does not have the same physical and chemical properties as the liquid crystal.

At present, even if the mobile phone screen is made frameless, there will be about 0.3-1mm (the thickness of the frame glue) around the screen that cannot display. In addition, the backlight of the LCD screen will be partially exposed from the position of the frame glue. Even if the fragility and accidental touch are ignored, this part still needs to be covered. Therefore, it is basically impossible to make a truly frameless mobile phone with an LCD screen at present.

Cost Limitation

In addition to the screen, if mobile phone manufacturers want to make a borderless mobile phone, cost is also a priority. If the mobile phone is very expensive, I believe it will not have much market prospects. So what kind of cost restrictions are involved in making a borderless mobile phone?

Human cost: Currently, no manufacturer has made borderless products and there is no precedent to refer to, which poses a huge challenge to R&D personnel with insufficient capabilities.

R&D costs: Innovating an unprecedented process and product requires a lot of experiments. However, based on current technical means, the investment in this area is unknown, and companies with weak foundations dare not try it easily.

Manufacturing cost: Currently, the various basic components of the mobile phone supply chain are relatively homogeneous, but the cost of the screen accounts for a large proportion of the entire mobile phone cost (from the cost of iPhone 5, we can see that the cost of the screen + touch screen + glass exceeds 15% of the overall cost). Therefore, even if a new solution is developed, without sufficient materials, it will only greatly increase the production cost, and even face sales pressure when it is questioned by the market.

Can simulate borderless through the principle of refraction

Having mentioned so many limiting factors, is it really impossible to achieve borderless display?

The inability to achieve absolute borderless does not mean that there are no other solutions. As we know, traditional LCD panels are all rectangular in design, and there is always a black area around the panel that cannot display. In fact, this is because traditional LCD panels need to place the gate driver circuit in the border area, so even if the width of the non-display area is reduced as much as possible, it cannot be eliminated in the end, otherwise the LCD panel will not work.

To overcome this limitation, this part of the circuit must be "disappeared". Sharp's "free form display" technology integrates these circuits into each pixel of the LCD panel, so that the circuit part at the edge of the panel can be completely eliminated.

In addition, since the gate driver circuits are integrated into the panel pixels, there are no restrictions on the shape of the panel, and panels of various shapes can be produced according to product requirements.

However, the "free form display" LCD panel has not yet been mass-produced, and it may take some time before it can be applied to mobile phones. So Sharp came up with an easier way to achieve it. Although it cannot be completely borderless, it can be "almost borderless."

Its own AQUOS CRYSTAL borderless mobile phone adopts this method, which is similar to optical magic. It uses the principle of refraction to make special bevel cuts on the edges of the mobile phone's screen panel, creating a "lens" effect. The black edge of the panel below the glass is "hidden" through the refraction of light.

In this way, the edge of the glass can completely cover the front of the phone, giving people a "borderless" feeling visually. And obviously, the nubia borderless phone mentioned by this netizen should also adopt this method, which can be seen from its curved side.

The current shortcomings of borderless phones

Mobile phones with borderless designs do look very cool, but this coolness comes at a price. The exposed edge of the screen means that when people hold the phone, their palms can easily touch the screen, which may cause misoperation of the touch screen. This problem may require manufacturers who provide touch solutions to solve it through algorithm judgment.

In addition, current borderless mobile phones cannot be extremely thin. The curvature radius of 1mm is still too high for a body less than 6mm thick. Sharp's CRYSTAL Display technology also requires the glass to have a certain thickness so that it can be cut at an angle to produce protective glass with a lens effect.

The most important point is that the screen glass without the frame protection is very easy to break in the bump, which is a big problem for many mobile phones with frame. In fact, many mobile phones with 2.5D protrusion design on the edge of the screen have also verified this problem, that is, the protruding screen glass is much more likely to break when the phone falls to the ground than the screen glass protected by the frame.

Unless mobile phone manufacturers abandon glass materials and use plastic materials with high light transmittance, this will reduce the screen's ability to resist scratches. In short, from the perspective of manufacturing conditions alone, borderless mobile phones can be born now, but it will take some time to solve many problems in actual use.

When will the era of perfect borderless mobile phones come?

So, how long do we have to wait? As we mentioned earlier, no matter how cool the borderless design looks, it has a most direct disadvantage, which is that it cannot provide sufficient protection for the screen.

As a tool for daily use, mobile phones are prone to accidents. Once they happen, the screen is the most vulnerable part. What's more frightening is that the price of a mobile phone screen often accounts for more than one-third of the price of the entire device. Once the screen that uses full lamination technology is broken, its price is not divided into the inner and outer screen as before.

Although the strength of glass is constantly improving with the growth of technology, and Corning Gorilla Glass is becoming more and more scratch-resistant, the toughness of glass has not yet reached a level of being very drop-resistant. In addition to strengthening the overall strength, the most important point of the frame is to prevent bumps on the edge of the screen. Nubia has been working towards a narrow frame in order to ensure overall strength and protection of the screen while trying to get closer to a frameless screen.

The narrower the border is, the better the visual experience will be. If a mobile phone is borderless, its overall structure will not be the same as that of current mobile phones. Either the screen as a whole is outside the support system, or the screen itself is used as a guarantee of the strength of the whole machine. Therefore, if flexible screen materials are really popularized one day, perhaps the perfect borderless era will really come.

At present, what manufacturers can do is probably just to make industrial innovations based on ultra-narrow bezels. Finally, back to the question, from the spy photos of Nubia, in order to avoid some known defects of borderless mobile phones, the glass cover of Nubia's mobile phone is likely to be covered on the frame as a dome, and then the ultra-thin glass cover is refracted through the principle of perspective mirror to achieve a borderless visual effect.

In terms of bonding, Nubia is likely to use LCD frameless glue bonding to improve stability. The fusion of new glass + touch layer + display panel realizes simulated borderless. If this is true, then this phone is really worth looking forward to.

As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity.