SoftBank Corp. and TOPPAN Holdings Develop Lightweight, Durable Skin for Solar HAPS Aircraft Wings

Skin's compatibility with stratospheric conditions such as extreme UV rays and ultra-low temperatures makes longer HAPS operations possible

TOKYO, April 27, 2026 /PRNewswire/ -- SoftBank Corp. (TYO: 9434) (President & CEO: Junichi Miyakawa, "SoftBank") and TOPPAN Holdings Inc. (TYO: 7911) (President & COO: Satoshi Oya, "TOPPAN Holdings") jointly developed a lightweight, durable skin for use on solar High-Altitude Platform Station (HAPS) aircraft wings and devised a testing method that replicates the stratosphere's environment. Test production will go forward, and the aircraft wing skin is planned for use with HTA-type^[1] HAPS, which SoftBank plans to deploy for commercial services from 2029 onwards.     

This jointly developed HAPS aircraft wing skin and test method that reproduces stratospheric conditions were made possible by combining SoftBank's HAPS expertise and TOPPAN Holdings' know-how accrued over years of creating advanced multi-layered film technology designed for packaging and construction materials. TOPPAN Holdings also leveraged its proprietary technology that evaluates weather resistance. This joint development mitigates film damage (degradation) caused by strong ultraviolet (UV) rays and ultra-low temperatures of almost -100°C. As a result, the aircraft can stay in the stratosphere for longer periods. 

Development Background
HAPS, also referred to as "base stations in the sky," provide communication services from uncrewed aircraft that remain airborne in the stratosphere. Being able to keep an aircraft with a communications payload airborne for extended periods of time would make it possible to provide an alternative means of communications in the aftermath of large-scale natural disasters, as well as provide communication services to under-connected areas, such as mountainous regions and remote islands. As these platforms operate from the stratosphere at an altitude of approximately 20 km above, they offer wider-area coverage than base stations on the ground, while also providing high-quality, high-volume, low-latency communications superior to satellite-based communications. However, at this altitude in the stratosphere, UV ray and ozone exposure is far greater than at ground level, and with exposure to extremely cold temperatures that sometimes drop to almost -100℃, impaired efficacy due to these environmental factors had been a serious issue with conventional all-purpose skins. Responding to this challenge, SoftBank and TOPPAN Holdings jointly developed a new ultra-lightweight, high-durability skin for aircraft wings capable of withstanding the harsh conditions of the stratosphere, along with a specialized methodology for its evaluation.     

Wing Skin & Evaluation Method Characteristics
1. Use of impact-resistant advanced resin and proprietary structure to achieve both lightweighting and safety
Leveraging converting technology^[2] developed for packaging by TOPPAN Holdings, an optimized skin structure was achieved by precisely layering original materials and impact-resistant advanced resin suitable for use at extremely low temperature conditions. The resulting skin weighs the same as or less than average conventional all-purpose skin, and even if damage to the skin were to occur, the break-resistant design keeps damage from spreading, allowing for both a safe and lighter HAPS airframe.    

2. Advanced durability to address harsh stratospheric conditions
SoftBank has contributed real-world data from its stratospheric HAPS flights, including actual temperature measurements and deep ultraviolet (UV-C) ray exposure conditions, and has also defined requirements such as weight reduction and other performance criteria. This has enabled TOPPAN Holdings to design a skin that addresses exposure to the harsh environmental conditions of the stratosphere by applying technology developed for construction materials. These conditions particular to the stratosphere include everything from extremely low temperatures (approximately -50℃ to -95℃) to extreme heat (approximately 100℃) from direct sunlight. The skin is also resistant to short wave UV-C and high-concentration ozone (10-20 ppm, parts per million) exposure that are far stronger than at ground level. This durability will allow for extended HAPS operation periods.      

3. Establishing a testing method that simulates stratospheric conditions to ensure reliability
TOPPAN Holdings leveraged its knowledge of packaging film testing and accelerated durability testing of construction materials, to construct a new test environment that assesses the skin under a simulation of the ultralow temperatures of the stratosphere, while also facilitating the testing of simultaneous exposure from short wave UV rays and the ozone. By using this test environment, it is possible to understand the detailed mechanisms of deterioration particular to the stratosphere and to use that knowledge for improved product design. This understanding and design adjustment makes it possible to carry out a more precise and more reliable evaluation compared to former testing methods.     

Roles of Both Companies
SoftBank
Provide expertise required to evaluate the suitability of the skin as well as expertise on HAPS operations
Supervision of advancing use with HAPS aircraft and transferring advances to practical application

TOPPAN Holdings
Develop and provide skin material suitable for HAPS aircraft
Proposal for evaluation method in stratospheric environment

Future Developments
SoftBank and TOPPAN Holdings will proceed with research to make the skin material developed within the scope of this project even lighter and stronger by fiscal 2027 (the year ending March 31, 2028). Additionally, while evaluating durability in the stratosphere, both companies will also attempt to establish mass production technology capable of ensuring sufficient supply and reliable quality by fiscal 2028. Also, based on testing outcomes, additional functions will be added, and the skin is expected to be used by SoftBank on HTA-type HAPS aircraft that provide commercial services, planned for launch from 2029 onwards. Both companies also plan to apply this skin to other fields that require a high level of durability.

For more information:
https://www.holdings.toppan.com/en/news/04/newsrelease260427_1.html 

About SoftBank Corp.
Guided by the SoftBank Group's corporate philosophy, "Information Revolution – Happiness for everyone," SoftBank Corp. (TOKYO: 9434) operates telecommunications and IT businesses in Japan and globally. Building on its strong business foundation, SoftBank Corp. is expanding into non-telecom fields in line with its "Beyond Carrier" growth strategy while further growing its telecom business by harnessing the power of 5G/6G, IoT, Digital Twin and Non-Terrestrial Network (NTN) solutions, including High Altitude Platform Station (HAPS)-based stratospheric telecommunications. While constructing AI data centers and developing homegrown LLMs specialized for the Japanese language, SoftBank is integrating AI with radio access networks (AI-RAN), with the aim of becoming a provider of next-generation social infrastructure.
https://www.softbank.jp/en/corp/

About the TOPPAN Group
Established in Tokyo in 1900, the TOPPAN Group is a leading and diversified global provider committed to delivering sustainable, integrated solutions in fields including printing, communications, security, packaging, décor materials, electronics, and digital transformation. The TOPPAN Group's global team of more than 50,000 employees offers optimal solutions enabled by industry-leading expertise and technologies to address the diverse challenges of every business sector and society and contribute to the achievement of shared sustainability goals.
https://www.holdings.toppan.com/en/
https://www.linkedin.com/company/toppan/

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SOURCE TOPPAN Holdings