Risho Kogyo Co., Ltd.
Japanese pioneer in electrical insulating materials and laminated/casting technologies, founded in 1921.
Last updated September 27, 2026
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Overview
Risho Kogyo Co., Ltd. is a Japanese manufacturer of electrical insulating materials, industrial laminates, and electronic materials, headquartered in Osaka. Founded in 1921 by Komajiro Risho as Risho Yoko, the company began by manufacturing and selling electrical insulating materials. It was reorganized as a stock company in 1937 and renamed Risho Kogyo Co., Ltd. in 1941. Over its century-long history, Risho Kogyo has developed foundational technologies in lamination and casting, producing epoxy-molded electrical equipment, instrument transformers, insulators and bushings, molded transformers, phase-advancing capacitors, and a wide range of electronic materials including heat-resistant printed wiring board materials, LED white printed wiring board materials, low-transmission-loss materials, and high-thermal-conductivity materials. The company also supplies thermosetting resin laminates, laminated rods and tubes, entry and backup boards, and other industrial materials. Risho Kogyo has been a pioneer in several areas: it developed Japan's first resin-molded instrument transformer in 1953, began production of epoxy resin molded instrument transformers in 1962, and was the first to domesticate epoxy resin molded distribution transformers in 1973. It also developed the world's first epoxy resin molded high-voltage phase-advancing capacitor in 1985. In recent years, the company has pursued advanced materials such as cellulose nanofiber (CNF), developing a 100% CNF bonnet outer exhibited at the Tokyo Motor Show in 2019, and showcasing CNF pipes and a bicycle at Expo 2025 in Osaka. Risho Kogyo operates manufacturing bases in Japan (Amagasaki, Shiga, Konan) and China (Wuxi), and continues to support global key industries with its insulating and electronic materials technologies.
History
Risho Kogyo Co., Ltd. was founded in 1921 when Komajiro Risho established Risho Yoko and began manufacturing and selling electrical insulating materials. In 1935, the company started production of phenolic resin laminates, rods, and tubes. It was reorganized as a stock company in 1937 and changed its name to Risho Kogyo Co., Ltd. in 1941. In 1942, the Tsukaguchi Plant (now Amagasaki Plant) was completed and began operations. In 1953, the company developed Japan's first resin-molded instrument transformer. In 1962, it began production of epoxy resin molded instrument transformers. The corporate philosophy was established in 1963. In 1964, full-scale production of copper-clad laminates for printed wiring began. In 1967, production and sales of rubber-lined laminates for capacitor sealing started, and production and sales of epoxy resin insulators using the pressurized gelation method began. The Shiga Plant started operations in 1968. In 1971, the company published its 50-year history. In 1973, it became the first in Japan to domesticate epoxy resin molded distribution transformers. In 1979, it developed high heat-resistant glass epoxy tape for semiconductor packaging (now used for IC cards). The 60-year history was published in 1982. The Koga Plant (now Konan Plant) began operations in 1984. In 1985, production of multilayer copper-clad laminates with inner layer circuits began, and the company developed the world's first epoxy resin molded high-voltage phase-advancing capacitor. In 1992, it published a 70th anniversary history and a collection of quotes by Koichi Risho. In 1997, it established a system to recycle used drill entry boards into high-performance activated carbon materials. In 1998, Risho Kogyo (Wuxi) Electric Co., Ltd. was established in China. In 1999, ISO9001 certification was completed for all three domestic plants. In 2001, all three domestic plants simultaneously obtained ISO14001 certification, and the 80th anniversary history was published. In 2003, Risho Kogyo (Wuxi) Chemical Co., Ltd. was established. In 2004, it developed amorphous molded transformers compliant with 2007 energy-saving standards and reactors for solar power conditioners. In 2006, it developed RLP cylinders for transformer insulating tubes, multiple transformers for high-voltage inverters, and high heat-resistant/high light-resistant white copper-clad laminates for chip LEDs. In 2007, it developed high heat-resistant adhesive sheets for heat dissipation boards and metal-base copper-clad laminates. In 2008, it developed pulse transformers for X-ray free electron lasers. In 2009, it developed silicone resin-based white printed wiring board materials for surface-mount LEDs. In 2011, Mikio Risho became Representative Director and President, and the 90th anniversary history was published. In 2012, it developed high thermal conductivity printed wiring board materials (3 W/mK) and adhesive sheets (5 W/mK). In 2014, it developed the MOLCON high-voltage phase-advancing capacitor with 25% weight reduction. In 2015, it registered the trademark RISHOCAST for molded electrical equipment. In 2016, it established a code of conduct for employees. In 2019, it developed a 100% cellulose nanofiber bonnet outer, exhibited at the Tokyo Motor Show. In 2020, its low transmission loss printed wiring board material CS-3379A was adopted for 5G communication antenna boards. In 2021, the company celebrated its 100th anniversary and published a 100-year history. In 2022, it added brown treatment to multilayer printed wiring board materials. In 2023, it launched cellulose nanofiber molded koto picks as an ivory substitute. In 2025, it exhibited 100% CNF pipes and a bicycle (reference) at Expo 2025 Osaka-Kansai, and glass epoxy tape in the Hyogo Zone.
- 2004
Develops amorphous molded transformers compliant with 2007 energy-saving standards and reactors for solar power conditioners.
- 2003
Establishes Risho Kogyo (Wuxi) Chemical Co., Ltd.
- 2001
All three domestic plants obtain ISO14001 certification; publishes 80th anniversary history.
- 1999
Completes ISO9001 certification for all three domestic plants.
- 1998
Establishes Risho Kogyo (Wuxi) Electric Co., Ltd. in China.
- 1997
Establishes system to recycle used drill entry boards into high-performance activated carbon materials.
- 1992
Publishes 70th anniversary history and collection of quotes by Koichi Risho.
- 1985
Begins production of multilayer copper-clad laminates with inner layer circuits; develops world's first epoxy resin molded high-voltage phase-advancing capacitor.
- 1984
Koga Plant (now Konan Plant) begins operation.
- 1982
Publishes 60-year company history.
Products and positioning
Pioneer in electrical insulating materials and advanced electronic materials, supporting global key industries with lamination and casting technologies.
Instrument transformers
Over 100 models from low voltage to extra-high voltage.
Insulators and bushings
Epoxy resin post insulators up to 70kV using pressurized gelation method.
Molded transformers
Special transformers for wind power, power storage, UPS, direct inverter, etc.
Phase-advancing capacitors and accessories
Recommended for use with series reactors and discharge coils.
Reactors
Air-core type reactors without magnetic saturation from large currents.
High heat-resistant printed wiring board materials
High Tg materials with excellent heat resistance.
LED white printed wiring board materials
Materials for LED boards with excellent whiteness and heat discoloration resistance.
Low transmission loss printed wiring board materials
Low dielectric constant/low dielectric loss tangent materials with low signal attenuation.
High thermal conductivity printed wiring board materials
Printed wiring board materials with heat dissipation effect by reducing thermal resistance.
Thermosetting resin laminates
Thermosetting plastics for insulating spacers, heat insulators, jigs, etc.
Laminated rods
Rod-type industrial materials based on thermosetting resin with excellent mechanical strength.
Laminated tubes
Tube-type industrial materials formed by heating and pressing prepreg impregnated with thermosetting resin.
Entry and backup boards
Auxiliary materials used for drilling printed wiring boards.
Rubber-lined laminates
Electronic materials used for sealing plates of aluminum electrolytic capacitors.
Rikocell
Material for solder pallets used when mounting electronic components on printed wiring boards with automatic soldering equipment.
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