Transparent Displays for Vehicles: How Far Can They Go? – Analysis of Regulations, Technology, and Market Applicability

The application areas of transparent displays applicable to automobiles are diversifying along with technological advancements, and currently, the feasibility of four major areas is being discussed. First, a windshield transparent display that directly integrates the display into the windshield of a vehicle; second, a front combiner-type transparent display installed within the driver’s field of vision; third, a rear-seat side transparent display applied to the rear-seat side window; and fourth, a transparent partition display that separates the driver’s seat and the rear seat. Each display has different transmittance and technical requirements depending on the characteristics of the application area and legal standards. A windshield transparent display is a technology that projects vehicle driving information directly onto the windshield, allowing the driver to recognize various information without taking their eyes off the road. However, the windshield is legally required to have a visible light transmittance (VLT) of 70% or higher, and the current transparent OLED (approximately 45%) and Micro LED (approximately 55%) technologies do not meet this requirement. Therefore, directly inserting a display into the windshield is still realistically difficult not only due to technical limitations but also from a regulatory perspective.

The front combiner type transparent display is a method of installing a separate transparent display panel on the instrument panel or near the windshield, and requires a transmittance of VLT 70% or higher. Therefore, even in this area, OLED or Micro LED technology currently has limitations in meeting regulations in terms of transmittance, and some pilot products are being developed in a way that circumvents regulatory standards by limiting the size and installation location.

The rear seat side transparent display can be used for entertainment, information provision, advertising, etc., and most countries have no or relaxed regulations on transmittance for rear seat side windows, so commercialization is highly likely. OLED and Micro LED technologies with transmittances of 45-55% can also be sufficiently applied, and there have been cases where they have been used as advertising-type transparent displays because visibility is secured from outside the vehicle. In particular, Micro LED is evaluated more favorably than OLED in terms of commercialization due to its high brightness, durability, and strong resistance to external temperature changes.

The transparent partition display is a new area that can separate the driver’s seat and the rear seat space in a vehicle as autonomous driving becomes more advanced, while simultaneously performing privacy protection and information transmission functions. Since the relevant area is located in the interior of the vehicle, legal regulations on transmittance do not apply, and both OLED and Micro LED can be freely used.

The biggest limitation of current automotive transparent display technology is low transmittance. Transparent OLED has a VLT of about 45%, and Micro LED has a VLT of about 55%, so a transmittance of at least 70%, and ideally 75% or more, is essential for application to the windshield or front combiner area. To achieve this, various technological advances are necessary, such as improving the pixel transparency, minimizing the light-emitting area, developing high-transparency electrodes, and optimizing the optical structure. In particular, Micro LED is a structure that can theoretically increase transmittance by expanding the non-occupied area between pixels, so it is attracting attention as a technology with a higher possibility of meeting future regulations.

In conclusion, the applicability and required transmittance of vehicle transparent displays differ depending on the area, and with the current level of technology, it can be applied primarily to areas such as the rear seat side and interior partition. In order to apply it to the windshield and direct view area, two tasks must be solved simultaneously: improving technical transmittance and meeting legal standards. The transmittance required at this time should be at least 70%, and ideally 75% or more for actual use. When technology that satisfies these conditions is developed, a truly transparent display-based smart car environment can be realized.