At present, the more common transparent screens include transparent LCD screens, transparent OLED screens and transparent LED screens.
Liquid crystal screen, also known as LCD screen, is a display device based on liquid crystal electro-optic effect and using liquid crystal material as the basic component. The LCD screen is composed of a certain number of color or black and white pixels. The main principle is to stimulate the liquid crystal molecules through the current to generate dots, lines, and planes, and then cooperate with the backlight to form a picture. Therefore, the general LCD screen needs to be equipped with lighting equipment such as a light source and a reflector on the back, which does not meet the requirements of a transparent screen.
However, for LCD display cabinets, such as the aforementioned transparent screen vending machines and some transparent screen display windows, the situation is somewhat different. They cancel the light source and reflector on the back of the LCD screen, but use the back box (ie, showcase or container) as a backlight unit for lighting, which means that although these screens are indeed “transparent screens”, they are still inseparable from the back the light source. If you turn off the box light of the showcase, it will seriously affect the use effect.
Transparent OLED screens are the mainstay of current transparent screen devices. The OLED screen can emit light by driving an organic thin film through a current, and has the characteristic of “self-luminescence”. Each pixel of it can emit light by itself without relying on an additional backlight.
The basic structure of an OLED is a thin and transparent indium tin oxide (ITO) with semiconducting properties, connected to a power supply anode, plus another metal cathode to form a sandwich-like structure. The whole structure layer includes a hole transport layer (HTL), an emissive layer (EL) and an electron transport layer (ETL). When the power is supplied to an appropriate voltage, the anode holes and cathode electrons will combine in the light-emitting layer to generate photons. Depending on the material properties, the three primary colors of red, green and blue can be generated, which constitute the basic colors we see.
In addition, there are “transparent sub-pixels” in the transparent OLED screen. This kind of pixel itself does not emit light and does not participate in image display, but it is made of transparent materials. Therefore, the transparent OLED screen not only takes into account the display of color images, but also A certain transparency effect is obtained. When the density of “transparent sub-pixels” is large enough to deceive people’s eyes, it is “transparent” in our opinion, and some transparent TVs use transparent OLED screens.
The principles of the transparent LED screen and the transparent OLED screen are somewhat similar, in which the light-emitting units (light beads) are arranged on a transparent background to achieve a transparent effect. It is just limited by the size of the LED lamp beads, and the screen must be made larger to achieve a better transparent effect.
Therefore, the transparent LED screens we see are mostly used in the window or large stage of the outer wall of the shopping mall, and it is difficult to see small transparent LED screens.
The paradox between transparency and privacy
In fact, there are already some transparent screen products appearing in our lives.
In 2009, Sony Ericsson launched the first transparent screen mobile phone Xperia Pureness. Unfortunately, limited by the technical level at that time, the screen transparency of this mobile phone is not very high, and it is still a black and white screen.
In 2011, Lenovo’s S800, the first mobile phone with a color transparent screen, came out. Compared with the Xperia Pureness, the transparency of the S800 has been greatly improved. However, it is a feature phone like the Xperia Pureness, and it is still a long way from the cool smart device in the movie.
In 2020, transparent screen devices have made new progress, and Xiaomi has launched a transparent screen TV. Transparent screen TVs have been greatly improved in terms of effect and transparency, but there are also some problems, such as the inability to guarantee the viewing effect from the back, and the light transmittance and resolution are not high.
At present, the transparent screen technology is still developing. And the transparent screen that looks cool and full of technology is also controversial.
On the one hand, the most important thing is that a completely transparent mobile phone is bound to have problems of privacy and information leakage, and if it becomes opaque during use, it deviates from the original intention of a transparent screen mobile phone.
On the other hand, for a mature transparent device, not only the screen is transparent, but also the battery, processor, camera, microphone, speaker and other components are transparent, which is still relatively difficult. If it is really completely transparent, then the assembly, strength, surface wear resistance and other issues of the mobile phone also need to be considered by manufacturers and users.