Recently, Apple’s stock price fluctuated, falling below $100 for the first time since 2014, causing concern for the company. Apple’s performance heavily relies on the iPhone, and the next generation iPhone is crucial for Apple’s future. Recent reports suggest that Apple will adopt a new screen for the iPhone 7S, set to release in 2017.
1. Evaluation Criteria for Mobile Screens
Mobile screens are also display screens, and their evaluation criteria are similar to those of flat-screen TVs and monitors, including PPI, brightness, contrast, color, and response time.
The higher the PPI, the more delicate the mobile screen appears. However, since Apple introduced the Retina display, most smartphones now exceed 300 PPI; at normal viewing distances, 300 PPI essentially eliminates the perception of pixelation, making this metric less significant.
Brightness is better when higher, and it is adjustable. A higher maximum brightness is beneficial for visibility in sunlight, as human eyes automatically adjust their sensitivity to light; if the screen brightness is too low, it becomes unreadable.
Contrast refers to the ratio of brightness between black and white on the screen. The higher the contrast, the deeper the black and the brighter the white, making all colors appear more vivid.
Color has several metrics, one being the color gamut, which indicates the range of colors a screen can display compared to the real-world color spectrum (the entire visible light spectrum is vast, and display devices generally cannot reproduce all real-world colors).
Another metric is the number of colors displayed, such as 8-bit or 10-bit color; the more colors available, the more nuanced the color gradation. Typically, the human eye cannot distinguish color gradation in 8-bit color, hence it is also called true color.
Additionally, there is the concept of color accuracy. Images and videos are produced under certain color standards, and to achieve the original production effect, the screen’s colors should also conform to these standards, which is the concept of color accuracy.
A screen with a large color gamut, many color displays, and good color accuracy is considered a screen with good color quality.
Furthermore, another important metric is response time, which refers to the speed at which the screen can switch images. A faster image switch means less motion blur.
2. Advantages and Disadvantages of OLED
Although traditional LCD and OLED are both display technologies, their display principles are entirely different. LCD uses a backlight panel, where a liquid crystal layer blocks the backlight to form a matrix of varying brightness, combined with color filters to achieve color display; whereas OLED consists of small light-emitting materials that emit light when stimulated by electrical current.
LCD needs to block the backlight, but it cannot block all the light; when displaying black images, some light will leak through, resulting in a lower true contrast ratio for LCD displays. OLED, being self-emissive, can turn off the light-emitting points when displaying black, thus achieving much higher contrast, making OLED screens appear more vivid than LCD.
In terms of color gamut, LCD generates colors through color filters, leading to a limited color gamut; hence, common LCD smartphone screens tend to have weaker colors, usually achieving only 70% to 80% of the NTSC color gamut. OLED, on the other hand, can easily exceed 100%, displaying more vibrant colors.
In terms of response time, OLED switches faster, providing better performance.
However, OLED also has its drawbacks. Firstly, OLED’s light-emitting materials are organic, and their lifespan is related to brightness, so OLED screens typically fall short of LCD screens in maximum brightness; otherwise, it would affect their lifespan.
Secondly, OLED requires red, blue, and green light-emitting materials, which age at different rates. As a result, after some time, the materials that degrade faster will lose brightness quicker, leading to color shifts on the screen. To extend OLED’s lifespan, manufacturers often adjust the preset screen colors slightly, which can cause some issues with color accuracy.
Additionally, due to the extremely thin organic films in OLED devices—about one-hundredth the diameter of a human hair—the thickness of the electron injection layer is even less than 20 angstroms (1 angstrom = 0.1 nm), and the subpixel films are extremely fine, measuring just a few tens of microns. To uniformly produce such thin, fine organic films without pinholes requires advanced precision manufacturing technology, making costs difficult to reduce.
Moreover, because organic materials undergo irreversible photochemical oxidation reactions in the presence of moisture and oxygen, and water and oxygen have strong corrosive effects on electrode materials like aluminum or magnesium-silver; therefore, OLED device packaging requires very high impermeability to water and oxygen, which raises the standards for packaging technology and increases costs further.
3. Why iPhone is Switching to OLED
In fact, as early as the iPhone 5 era, there were rumors that Apple would switch to OLED screens; however, at that time, OLED screens were almost monopolized by Samsung, and Apple was in fierce competition with Samsung, striving to reduce reliance on them, so this rumor did not materialize.
Years have passed, and OLED technology has made significant progress, with improvements addressing its previous weaknesses of low brightness, short lifespan, and color shifting. From the perspective of display quality, OLED has far surpassed LCD. For Apple, the high cost of OLED is not an issue, as the high price of the iPhone can absorb this cost.
With the technology becoming more widespread, OLED is no longer solely monopolized by Samsung; LG and AUO’s OLED screens have also emerged. Apple has consistently avoided exclusive monopolies in procurement, and the diversification of OLED suppliers has given Apple more options.
With clear advantages in performance, minimal cost pressure, and multiple suppliers available for procurement, Apple will not be at the mercy of competitor Samsung. Coupled with the pressure for performance improvements, it is only logical for Apple to switch to OLED screens for the iPhone 7S.
Due to the technological advantages of OLED, the display quality of the iPhone 7S will see a significant enhancement. For consumers, the iPhone 7S will be the most beautiful iPhone screen ever, and Apple fans can start saving money now.
