In the 3a explosion-proof film technology system, TAC (cellulose triacetate) and PET (polyethylene terephthalate) are the two core substrates. Their differences in light transmittance directly affect the application effect of the explosion-proof film in scenarios such as automotive displays and building curtain walls. Light transmittance, as a core indicator of optical performance, not only determines the clarity of screen content but is also deeply linked to key requirements such as driving safety and visual comfort. From material characteristics to process optimization, the difference in light transmittance between the two substrates stems from multiple factors, including molecular structure, surface treatment, and coating synergy.
The light transmittance advantage of the TAC substrate originates from its unique molecular arrangement structure. The triacetate molecular chains are arranged in a regular linear pattern. This structure makes the refraction path of light relatively singular during transmission, reducing light loss due to molecular scattering. Simultaneously, TAC material itself has low birefringence characteristics, which can effectively avoid phase delay caused by light passing through molecular layers in different directions, thereby maintaining the stable polarization state of the transmitted light. This characteristic is particularly important in automotive display scenarios—when drivers wear polarized sunglasses, the explosion-proof film on the TAC substrate will not cause rainbow patterns or dark spots on the screen display due to birefringence, ensuring visual clarity under extreme lighting conditions.
The light transmittance of the PET substrate is closely related to its surface curing process. During the curing and coating process of ordinary PET films, if the process is not properly controlled, micron-level uneven structures can easily form on the surface. While these structures can improve the abrasion resistance of the film layer, they can cause diffuse reflection of light, leading to a decrease in light transmittance. To solve this problem, high-end PET substrates use nanoscale curing coating technology, controlling the coating particle size to be less than 1/10 of the wavelength of visible light, allowing light to pass through almost unimpeded. Some manufacturers also coat the PET surface with an AR (anti-reflective) anti-reflective film, using the principle of optical interference to counteract surface reflected light, further increasing the light transmittance to over 92%, approaching the theoretical limit of the TAC substrate.
In the practical application of 3a explosion-proof film, the difference in light transmittance between TAC and PET substrates will dynamically change due to the superposition of functional coatings. For example, when laminating an AG (anti-glare) coating onto a TAC substrate, the surface roughness needs to be controlled within the range of 0.5-1.0 μm. This ensures that ambient light is scattered to reduce glare while avoiding excessive scattering that would significantly reduce transmittance. However, when laminating an AG coating onto a PET substrate, the hardened layer itself already possesses a certain degree of roughness. Therefore, the proportion of silica particles in the coating formulation must be adjusted to achieve a balance between anti-glare effect and transmittance. This difference in process results in TAC substrate 3a explosion-proof film offering superior visual comfort in strong light environments, while PET substrate products have advantages in cost control and large-scale production.
Environmental adaptability also significantly affects the transmittance of both substrates. While TAC materials possess excellent optical properties, they are highly hygroscopic and prone to hydrolysis in high-temperature and high-humidity environments, leading to molecular structure damage and decreased transmittance. To address this issue, high-end TAC substrates undergo acetylation treatment to seal the hydroxyl groups on the material surface, controlling the water absorption rate to below 0.2%. In contrast, PET substrates exhibit superior chemical stability; the ester group structure in its molecular chain is insensitive to moisture, but it is prone to yellowing under long-term UV exposure. Therefore, 3a explosion-proof films based on PET substrates require an additional UV (ultraviolet) absorption layer, using organic UV absorbers to control the transmittance decay rate to within 0.5% per year.
From an industry application perspective, the transmittance difference between TAC and PET substrates is gradually narrowing through technological innovation. For example, depositing a nano-ceramic coating on the PET surface using vacuum sputtering can simultaneously achieve AR anti-reflection, AG anti-glare, and AF (anti-fingerprint) functions, increasing the transmittance of PET substrates to 94%, approaching the level of TAC substrates. Meanwhile, TAC substrates, through composite with SRF (specially modified PET), maintain high transmittance while enhancing mechanical strength, addressing the weakness of traditional TAC materials being prone to brittleness. This trend of material integration enriches the 3a explosion-proof film product line, meeting the dual demands of high-end fields such as new energy vehicles and aerospace for both optical performance and reliability.
In the end-consumer market, the difference in light transmittance between TAC and PET substrates directly impacts user experience and product pricing. Taking automotive displays as an example, 3a explosion-proof films using TAC substrates, due to their higher light transmittance and superior glare suppression, are widely used in the center console screens and dashboards of luxury vehicles, with a unit price 30%-50% higher than PET substrate products. Meanwhile, PET substrate products, with their cost-effectiveness, occupy the mainstream market share in the low-to-mid-range segment. As consumers' demands for visual quality increase, some manufacturers have begun to launch "dual-substrate hybrid solutions"—using TAC substrates in the critical area directly in front of the driver and PET substrates in other areas, achieving optimal optical performance while controlling costs.
The difference in light transmittance between TAC and PET substrates in 3a explosion-proof films is essentially a comprehensive interplay between materials science, optical engineering, and industry needs. TAC substrates dominate the high-end market with their molecular-level optical purity, while PET substrates achieve cost-effectiveness breakthroughs through process innovation and functional integration. In the future, with the continuous advancement of nanotechnology and coating processes, the boundary between the light transmittance of the two substrates will become even more blurred, and the performance competition of 3a explosion-proof film will shift from a single indicator to the comprehensive optimization of system solutions.
