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Technology | LCD Limit Challenge! Full screen borders in the end can do more narrow?
Jul 07, 2017

To say that this year's mobile phone ring is the most popular topic, must be non-comprehensive screen is none other than. In fact, the concept of a comprehensive screen is not made this year, as early as 2 years ago in Japan, Sharp launched a Crystal class full screen mobile phone, but the brand influence relationship does not cause attention in the mobile phone circle.


Later millet in October 2016 launched the first full screen for the black technology selling point of mobile phone millet Mix, stunning appearance and millet company manufacturing topic ability, and instantly pushed the word full of the word to the mobile phone industry, name. Lei Jun is full of full-screen mobile phone phone is the direction of the next 10 years, this year there will be a comprehensive screen mobile phone war. After that, the launch of Samsung S8 seems to verify the Lei Jun's prediction, the surface of the screen + full screen design concept swept away last year's Note7 decline, the agencies have raised Samsung sales forecast, in the last year the public media port like Pisa like dumping Samsung Building moment is righting.


As the only place on the planet and Samsung mobile phone can be a hard change of the face of the Apple, of course, will not let Samsung alone in the world, so deliberately inadvertently a new generation of iPhone8 rendering map pipa half-like to the public eyes. Fantastic full-screen design suddenly attracted countless marvels, of course, mixed with a little man touched the purse sigh. At this point, the concept of a comprehensive screen has completely detonated mobile phone ring, Mr. Lei Jun proud of their own accuracy in the prediction may also secretly feel the production of millet Mix.

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From a professional point of view, to deconstruct the possibility of a comprehensive screen and the manufacturing process of the difficulties


The full screen of the technical points have five directions, respectively, ① Slim Border ② COF ③ 18: 9AA ④ C / R / L Angle ⑤ U cut .. In fact, in essence, is the three aspects, 18: 9 AA area display specifications, four sides of the narrow frame and shaped structure. This article is mainly about the narrow frame of the solution, shaped structure will be explained in detail below.


18: 9AA area display specification

18: 9 show comparison 16: 9 more fit the size of the phone, you can in the same size of the phone mold put down a larger size screen, significantly enhance the screen share. This design change in theory on the panel design will not have any challenges, but the mobile phone operating system and the APP software needs to cooperate with the new aspect ratio to re-optimize the design to achieve a better experience, to avoid the black edge.

Narrow border

Panel narrow border concept has been going on for many years, to explain the narrow border of the problem First of all we have to first understand the display panel drive principle.

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From the above figure we can see that our display panel is arranged by RGB three-color pixel matrix, and by the horizontal Gate line and the vertical source line (data line) in series. Gate line function is equivalent to the same switch, open on behalf of the line began to charge the line display, Source signal determines the brightness of the pixel display, usually divided into 256 gray. This Gate line in accordance with the order of progressive scan, pixel line by line and use the human eye retention effect of the final formation of the pattern we see.


Early panel has two signal input, that is, Gate terminal and the source terminal, usually the width of the terminal is relatively wide, generally about 5mm, the panel for the design of symmetry, so there was no narrow border concept.


GIA makes three narrow sides become a reality

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Gate drive signal as shown above, only a simple open and close the two states, so with the TFT design improvements, the function of a single Gate IC is integrated into the TFT line, the separate Gate IC is canceled, Gate terminal also Does not exist, this is GIA (Gate in Array) technology. The following figure is a simple GIA equivalent circuit diagram and physical map.

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GIA technology to solve the problem of Gate IC, so the panel only left the bottom of the Source terminal, the remaining three sides have the possibility of designing a narrow frame.


Then the Source IC can do the same design. The answer is temporarily not, we look at the Source drive signal as shown below, usually divided into 256 states corresponding to the display we need 256 gray scale, relative to the gate drive signal to be more complex, so there is no way to integrate into the TFT line.

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Here again to explain the meaning of 256 gray scale. The so-called gray scale, is the brightest (pure white) and the darkest (black) between the brightness changes, divided into several copies, in order to facilitate the signal input corresponding to the screen brightness control. The current display area is mainly used in the 256 gray scale, the following figure can clearly show the gray scale we show the image quality.

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Three sides narrow border

Now we look at the phone's three sides of the border, from the AA area to the outside, to determine the width of the border left our GIA line and bonding TFT / CF glass frame glue.

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Frame glue in the production process is a soft solid glue, was coated on the glass, need to irradiate ultraviolet light can be cured. In the a-Si process, some of the semiconductor devices in the GIA line will be about 100um in size, and this will affect the curing of the frame glue. Therefore, the shell coating needs to be avoided from these areas, only to move out, taking into account the safety of production Sex, usually need to avoid the distance of more than 100um.


Another mobile phone panel stereotypes before the production will generally be through the drop experiment to determine the panel strength enough to withstand the user accidentally dropped the phone to the ground on the impact. This is on the adhesive strength of the box made a request. To the current characteristics of the box material, at least to do more than 350um width is safe. Taking into account the limitations of the current frame coating flexibility, there will generally be about +/- 150um fluctuations, so 500um is more mass production of plastic box design width.


The last is the edge of the computer glass cutting accuracy, the current capacity is usually about 50 to 100um.


In this way, our width of the border came out, it is GIA semiconductor device size + safe avoidance distance + frame width + cutting accuracy, roughly 700 to 800um or so.


Of course, for the LTPS process, because of its electron mobility is a-Si more than 100 times, so the GIA line of semiconductor devices can be controlled within the size of 10um, which has no effect on the block glue curing, so that we You can lose 100um width. If coupled with the frame coating accuracy and cutting accuracy of the challenge, the final LTPS panel border width to 600um or even challenge 500um can be achieved. In recent years the major photoelectric exhibition, Tianma JDI and other advanced panel manufacturers have exhibited a border 600um products.


Terminal section narrow frame

To solve the three sides of the problem, of course, to start the terminal section of course. Similarly, let's take a look at what is the terminal.

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As shown in the figure, there are three additional things, the Source IC, the oblique lines connecting the Source and the IC, and the FPC Bonding area, in addition to the width of the frame. At present, the width of the three are about 1.5mm or so, plus the box of plastic 0.5mm, the terminal part of the border is generally around 5mm, it is too ... wide ... the. Here we talk about how to solve.


COF technology helps to reduce the width of the terminal section

As mentioned above, there is no way to integrate the Source IC into the TFT line just like GIA technology. But the poor is thinking change thinking, no way to cancel how to do, engineers wanted a way, can not take away I removed you, moved from the glass to the FPC. Because the FPC can be bent, so that it can be folded to the back of the glass, it will not affect the panel width, and this is the COF technology.

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Compared to IC on the glass COG technology, COF technology can narrow the border about 1.5mm width.


Oblique wiring

The Source line must be connected to our IC in one root to enter a different Source signal. The current resolution of the flagship machine must be FHD take-off, and even some will reach the degree of QHD. To FHD, for example, his resolution is 1920 * 1080, that is, there are 1080 columns Pixel, consider each Pixel is divided into three sub-Pixel, so a total of 3240 oblique wiring to be designed to a narrow space, As shown below, is absolutely intensive fear of cautious.

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