Toagosei Annual R&D Report “TREND” – Issue No. 25

ARONTACK MPT-29 and MPT-69 are solvent-based acrylic pressure-sensitive adhesives developed for decorative film lamination by vacuum pressure forming, also known as Out Mold Decoration (OMD). As an automotive decorative film adhesive, OMD adhesive, vacuum thermoforming adhesive, and 3D decorative film adhesive, the series bonds thermoplastic films carrying color, pattern, or texture to molded 3D parts, curved surfaces, and deep-draw shapes. This paint-replacement and paint-free decoration process can improve automotive design aesthetics while supporting lower-CO2 automotive surface decoration for interior and exterior components.

During thermoforming, a decorative film may be stretched by about 200%, creating shrinkage stress that can cause peeling, delamination, film edge lifting, or adhesive failure after heating. Conventional acrylic PSA can also lose adhesion at elevated temperature or show poor adhesion to low-polarity resins. This tackifier-modified acrylic PSA uses tackifier segregation technology: an appropriate tackifier becomes surface-enriched in the adhesive layer, improving high-temperature adhesion. MPT-29 is designed for ABS and polycarbonate and also showed strong adhesion to PMMA and rigid PVC; MPT-69 is optimized for difficult-to-bond polypropylene. Both grades have low tack for handling during vacuum thermoforming and are available as solution-type MPT products or substrate-free MF adhesive films.

In peel tests, MPT-29 and MPT-69 maintained high adhesion over a broad temperature range, whereas a general PSA lost almost all adhesion at 60°C or higher. At 90°C under a 1 kg shear load, both showed no displacement after 24 hours. They also retained peel strength after up to 1,000 hours of heat, 85°C/85% RH, and hot-water exposure. In a cross-cut vacuum-forming test with 200% film stretch, MPT-29 on ABS at 110°C and MPT-69 on PP at 80°C for 15 hours showed no peeling and less than 1 mm displacement. These results support durable decorative sheet adhesion, 3D surface lamination, and high-temperature automotive decorative film applications.

ARONIX Sheet NIR Series is an infrared-transmitting optical sheet for LiDAR covers, IR/NIR sensor covers, and near-infrared filters. By integrating a LiDAR sensor cover with a visible-light-cut NIR pass filter, it reduces parts count and supports LiDAR miniaturization and weight reduction. As a plastic optical window and glass alternative for automotive LiDAR, it combines high infrared transmittance with visible-light blocking to suppress sensor noise.

At 2 mm thickness, ARONIX Sheet NIR showed transmittance of 90.2% at 950 nm, 90.7% at 1310 nm, and 87.4% at 1550 nm without an anti-reflection coating. The visible-cut wavelength can be adjusted by dye formulation, supporting 905 nm, 940–950 nm, and 1550 nm systems. For FM-CW LiDAR, this low-retardation, low-birefringence optical sheet had an average phase difference of 9 nm and a max–min distribution of 46 nm, demonstrating optical homogeneity.

As a durable LiDAR window material, standard NIR has 4H pencil hardness, while double-sided hard-coated NIR-HC reaches 6H for high hardness and scratch resistance. Drop-weight impact resistance was comparable to chemically strengthened glass, and the deflection temperature under load exceeded 250°C. Its specific gravity of 1.2 supports a lightweight LiDAR cover versus glass. It also resisted methanol, acids, alkalis, tetrahydrofuran, xylene, dichloromethane, acetone, and automotive brake fluid, supporting heat-resistant and chemical-resistant sensor covers. Hardness and NIR transmittance remained stable after 1,000-hour heat, humidity, and weathering tests.

The sheet is processable with laser cutters and NC routers and can be manufactured as a dimensionally stable curved cover. Sputtered anti-reflection films showed good adhesion, including after hot-water immersion. High heat resistance also enables Ag-paste and ACF processing, direct conductive-circuit formation, and heater integration. These capabilities support lightweight, hard-coated LiDAR covers with high NIR transmittance, low retardation, impact resistance, component integration, and processing-cost reduction.

ARONIX UVX and ARON MELT are fuel cell adhesives adopted in Toyota’s second-generation MIRAI. They meet fuel cell stack adhesive requirements for seconds-scale bonding, mass production, hydrolysis resistance, durability, and quality stability. In a stack of hundreds of cells, they support fuel cell bonding and sealing of hydrogen, air, and cooling-water flow channels.

ARONIX UVX is a solvent-free, acrylate-based UV-curable fuel cell adhesive for fuel cell membrane bonding. It bonds the edge of the MEA polymer electrolyte membrane to the hot-melt layer of a frame-shaped plastic sheet separating the anode and cathode spaces. As a fast-curing PEM fuel cell adhesive and membrane electrode assembly adhesive, it cures within seconds after UV irradiation and requires no drying process, supporting short cycle time and high productivity. The formulation maintained adhesion to the electrolyte membrane after immersion in 90°C hot water for 3,000 hours. Thixotropic fine particles improved screen printability and coatability, enabling high-speed frame application with controlled thickness and few bubbles. Monomer and photoinitiator selection also reduced catalyst-poisoning risk.

ARON MELT is a hot melt fuel cell adhesive applied to both sides of a three-layer sheet core. Seconds-scale heat and cold pressing bond it to the metal separator and core. It functions as a fuel cell separator adhesive, metal separator bonding layer, fuel cell sealing adhesive, and fuel cell stack sealing material, maintaining gas sealing for hydrogen and air and leak prevention for cooling water. A specially modified polyolefin composition provides metal adhesion, water resistance, hydrolysis resistance, and high-temperature durability. Its 142°C melting point, 109°C crystallization temperature, and increased crystallization rate support rapid solidification and short-cycle bonding. Antioxidant optimization and metal-impurity control support adhesive reliability. Together, these UV-curable and hot-melt systems enable reliable fuel cell bonding for mass production of hydrogen fuel cells and FCVs.