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

In recent years, in the automotive field, decorative methods that can replace painting have been studied with the aim of reducing CO₂ emissions and improving design aesthetics. Among these, a film decoration method known as vacuum thermoforming (OMD), in which a thermoplastic film with designs such as colors, patterns, and textures that cannot be reproduced by painting is bonded to three-dimensional parts using an adhesive material, has been attracting attention.

Our company has found that by adding an appropriate tackifier (TF) to an acrylic pressure-sensitive adhesive, the TF segregates at a high concentration on the surface of the adhesive coating, thereby significantly improving adhesion at elevated temperatures. In this paper, we introduce the performance and characteristics of Pressure-Sensitive Adhesive for Decorative Film “ARONTACK MPT-29, MPT-69,” which were developed by applying this tackifier segregation technology.

In recent years, the demand for highly accurate sensing technologies has been increasing with the advancement of autonomous driving, drones, and IoT applications in the automotive field. Infrared sensors are one of the key sensing technologies due to their high positional accuracy; however, further improvements in durability, as well as miniaturization and cost reduction, are essential for broader adoption.

To meet these demands, we have developed an ARONIX sheet equipped with both a sensor cover and a noise-cut filter function. By integrating the cover and filter, which were previously separate components, the number of parts has been reduced and weight has been lowered, while achieving high durability and excellent infrared transmittance.

In this report, we present the results of our study on the developed ARONIX sheet, focusing on its optical properties, durability, and processability for automotive infrared sensor (LiDAR) applications.

In response to the need to reduce CO₂ emissions associated with global warming, there has been a growing movement worldwide to regulate gasoline- and diesel-powered vehicles. Under these circumstances, Toyota has been working on the development of a second-generation fuel cell with excellent mass productivity, aiming for the widespread adoption of fuel cell vehicles. Toyota’s second-generation fuel cell has a structure in which several hundred cells are stacked, and in order to enable low-cost mass production, bonding technology capable of achieving short cycle times on the order of seconds was required. The bonded areas were also required to exhibit durability and quality stability suitable for automotive applications. In response to these needs, development efforts led to the adoption of a UV-curable adhesive and a hot-melt adhesive for two different bonding areas, respectively, and these technologies have been incorporated into the recently released second-generation MIRAI. This report outlines the overview of these developments.