The rise of full lamination technology
The structure of a screen can be roughly divided into three parts: protective glass, touch screen, and display screen, which are arranged in sequence. To ensure the perfect presentation of the screen, it is usually necessary to perform two bonding operations: one between the protective glass and the touch screen, and the other between the display screen and the touch screen. And the film we are familiar with in daily life is actually the bonding process between the protective glass and the protective film. Although it may seem simple, it also requires exquisite bonding technology.

Screen bonding technology, according to its bonding method, is mainly divided into two categories: full bonding and frame bonding. Frame adhesive, also known as mouth glue bonding, refers to the simple fixation of the four sides of the touch screen and display screen through double-sided tape. This is the bonding method currently used by many display screens, which has the advantages of simple process and low cost. However, due to the presence of an air layer between the display screen and the touch screen, the refraction of light can affect the display effect, which is the main drawback of frame pasting technology.

Full lamination technology uses water-based adhesive or optical adhesive to completely stick the panel and touch screen together without any gaps. Compared to frame stickers, it provides a better display effect. The common full screen solutions in the market mainly come from OGS solutions from touch screen manufacturers, as well as On Cell and In Cell technology solutions led by panel manufacturers. The advantage of full lamination technology is that it eliminates the air layer between the screens, reduces the reflection between the display panel and glass, makes the screen more transparent, and thus improves the display effect of the screen. IMacs using full lamination technology can reduce reflection issues by up to 75%. In addition, full lamination technology can effectively prevent screen dust from entering and enhance the strength of the touch module. More importantly, it can significantly reduce the interference of display panel noise on touch signals.

Although full lamination technology has many advantages, its yield rate is relatively low, mainly due to the possible surface glass and panel loss during the lamination process. Therefore, controlling the defoaming and bonding yield has become the key to reducing costs.

In terms of full lamination technology, there are three main screen technologies: InCell, On Cell, and OGS. If frame pasting technology is used in the production process of mobile phone screens, it will seriously affect the display effect. And full lamination technology can significantly improve the yield rate, thereby reducing costs.

Different screen bonding technologies
In order to reduce the number of bonding cycles and improve the yield rate, several new development directions have emerged. Touch screen manufacturers mainly promote OGS/TOL solutions, while panel manufacturers are more inclined towards On Cell and In Cell technology solutions. These solutions can reduce the number of bonding times, save costs, and achieve the goal of lightweight.

In Cell technology is an innovative technique that embeds touch panel functionality into liquid crystal pixels. By embedding touch sensor functionality inside the display screen, the original three-layer structure (protective glass touch screen+display screen) has been optimized to two layers (protective glass+display screen with touch function), making the screen thinner and lighter. However, the research and development threshold for this technology is relatively high, mainly led by panel manufacturers.

Screen imaging principle
In the past, mobile phones had complex functions and rich details, but now, smartphones seem to be simplified into a single screen. We rely on this screen to operate and obtain information. The mobile phone screen displays colorful images through a combination of red, green, and blue pixels. With the development of technology, mobile phones are no longer limited to call functions, and the importance of screens has also become prominent. Whether watching videos, browsing pictures, or playing games, the screen carries the core content. Therefore, when choosing a smartphone, the screen often becomes an indispensable consideration for us.

However, are we really deep enough in our understanding of screens? When choosing a phone, we often only focus on screen size and resolution, but can these two really comprehensively measure the quality of the screen? In complex screen technology, which letter combinations truly reveal the material and panel technology of the screen? In fact, our misunderstanding of screens may be deeper than we imagine.

Unveiling the Technology and Principles of Mobile Screen

To present the text and images in our eyes, mobile phone screens rely on the three primary colors of red (R), green (G), and blue (B). Each pixel on the screen contains a complete RGB sub-pixel arrangement, and colors are recorded and expressed through RGB values. The RGB components of each pixel are within the intensity range of 0-255. It is through the different proportions of red, green, and blue that we can see a rich and colorful world.

Pixel, the color wizard of mobile phone screens

The colorful colors in our eyes are the clever combination of the three primary colors of red (R), green (G), and blue (B) on the screen. Each pixel contains a complete RGB sub-pixel arrangement, which creates a myriad of colors through different combinations of RGB values. Within the brightness range of 0-255, the proportional changes of the RGB three colors constitute the rich and colorful world in our eyes.

The comparison between 441ppi and 326ppi shows that the display effect of 441ppi on the left is more delicate and smooth.

After upgrading to 2K resolution, the screen's delicacy has reached a level that is difficult for the naked eye to distinguish. We have witnessed the continuous increase in screen resolution, which signifies that with the continuous advancement of technology, screens of the same size can now accommodate more pixels. By using PPI (pixel density) as an indicator, we can understand the number of pixels contained in each inch of the screen.

In the early days of the 1080p era of smartphones, we compared the screens of HTC Butterfly and iPhone 5, the world's first 1080p models. After capturing and zooming in on the screen with a macro lens, we found that the 441ppi HTC Butterfly surpassed the 326ppi iPhone 5 in terms of delicacy. This means that visually, the graininess on the screen is significantly reduced, and the overall display effect is more delicate and smooth. Nowadays, as mobile phone screens enter the 2K era, this level of delicacy has reached new heights, although it is still uncertain whether the naked eye can detect this change.

However, to comprehensively evaluate the quality of a mobile phone screen, relying solely on screen size and resolution is far from enough. These visible red, green, and blue small bright spots, also known as pixels, are undoubtedly the foundation, but they are only a part of screen display technology. The screen material and display technology also have a profound impact on the final visual effect.

LCD and OLED technology
In the current smartphone market, mainstream screen technologies can be divided into two categories: LCD and OLED.

LCD screens rely on backlighting during display, and light needs to pass through two layers of glass, a substrate, and various optical films, alignment films, color filters, and other components to produce polarization, which inevitably results in a loss of brightness and color. TFT, also known as thin-film transistor technology, is a key technology in LCD screens. It improves image quality by depositing a thin film as a channel area on a glass substrate.

In the TFT-LCD structure, the upper glass substrate is closely adjacent to the color filter, while the lower glass substrate is embedded with transistors. When current passes through a transistor, an electric field change is generated, causing liquid crystal molecules to deflect, thereby changing the polarization of light. Polarizers determine the brightness and darkness of pixels based on this polarity change. At the same time, the color filter attached to the upper layer of glass forms what we call RGB tri color pixels, which together constitute the colors and images displayed on the screen.

Subsequently, we will explore the types or panel technologies of LCD panels. LCD panels can be divided into two categories: simple matrix drive and active matrix drive. Among them, simple matrix driving mainly includes TN and STN technologies, while active matrix driving covers technologies such as TN, IPS, VA, and OCB. In the current smartphone market, TN and IPS technologies are more common, while VA technology is more commonly used in TV products.

TN screen, also known as Twisted Nematic (twisted nematic liquid crystal) screen, has been widely used since the emergence of liquid crystal technology and once dominated the field of electronic devices. However, nowadays many users mistakenly confuse TN screens with TFT screens, which is actually a misunderstanding of the two concepts. However, due to the mature production technology and affordable price of TN screens, they are still favored by some low-cost mobile phone brands. In addition, the high aperture ratio of TN screens makes them more energy-efficient compared to other technologies at the same brightness, and the response speed of 8-15ms is also quite fast. Therefore, although TN screens have shortcomings such as narrow viewing angles and color distortion, these advantages still make them occupy a place in the smartphone market.

IPS screen, also known as In Plane Switching (transverse electric field effect display technology), has significantly improved the color difference and narrow field of view problems of TN screens in poor viewing angles since its introduction in 1996 with its wide viewing angle technology. The electrodes of IPS liquid crystal are located in the same plane as the liquid crystal, thus achieving a wide viewing angle of 178 degrees up, down, left, and right. This breakthrough effectively overcomes the inherent defects of TN screens. However, IPS screens are not flawless. Despite its excellent viewing angle, it consumes relatively high power and has a slightly insufficient response speed, so it is necessary to weigh its pros and cons when using it.

Subsequently, in 1998, Hitachi launched an upgraded version of S-IPS (Super IPS), which not only inherited the original technological advantages of IPS, but also further optimized the response speed. In 1999, LG Philips joined the IPS camp as a joint venture, and after the bankruptcy of the joint venture in 2006, the IPS business was mainly taken over by LG Display and has continued to develop ever since.

Now, let's turn to OLED technology. OLED， The abbreviation for Organic Light Emitting Diode is different from TFT-LCD in that it has self luminescence and does not require backlight support. OLED technology has many advantages such as wide viewing angle, high contrast, low energy consumption, high reaction speed, full-color and simple process.

According to different driving methods, OLEDs can be divided into passive OLEDs (PMOLEDs) and active OLEDs (AMOLEDs). PMOLED and AMOLED are two different types. If OLED is compared to an upgraded version of LCD, then PMOLED is more similar to STN LCD, which has gradually withdrawn from the market. PMOLED performs poorly in displaying dynamic images and has a relatively slow response speed. Despite its power-saving features, it is limited in size. For smartphone users who pursue large screens and high-definition effects, PMOLED's 5-inch low resolution display is clearly not attractive enough to meet their needs. In addition, expanding the size of PMOLED will lead to an increase in pixel brightness and operating current, thereby shortening its lifespan.

Therefore, the vast majority of OLED screens we come into contact with today are AMOLED screens. AMOLED， Active matrix organic light-emitting diode, meaning active matrix organic light-emitting diode or active matrix organic light-emitting diode. The term 'AM' represents the pixel addressing technology behind it. This technology enables AMOLED to achieve low energy consumption and wide viewing angle display while maintaining high resolution and fast response, becoming one of the mainstream display technologies today. Not only smartphones, but also Samsung and LG's TV products use AMOLED screens, further proving their broad application prospects.

The core of AMOLED technology lies in its OLED matrix molecules, which can emit and store or integrate light into TFTs after electrical excitation. By precisely controlling the direction of current flowing to each pixel, AMOLED achieves high resolution and fast response. Each pixel is equipped with at least two TFTs to ensure stable control of continuous current. TFT backplane technology is crucial for AMOLED, and currently this technology has adopted two solutions: polycrystalline silicon and amorphous silicon.

The significant advantages of AMOLED include its self luminescence, wide viewing angle display, high contrast, and fast response time. In addition, compared to PMOLED, AMOLED also has a higher refresh rate, significantly reducing energy consumption. However, under direct sunlight, the reading effect of AMOLED may be affected to some extent. To improve this issue, Samsung has launched Super AMOLED technology, which enhances the display effect under strong light by reducing the screen spacing.

With the advancement of technology, Super AMOLED technology, as an upgraded version of MOLED, has the core improvement of reducing the screen spacing, which significantly improves the display effect in strong light environments. This technological innovation has significantly improved the outdoor reading experience of Super AMOLED, bringing consumers a more comfortable visual enjoyment.