Sekisui and Bird & Bird deal another blow to competitor Kuraray
Sekisui Chemicals has once again been successful in the dispute over special films for the manufacture of glass for car windows. The Federal Patent Court upheld the validity of one of four patents. Sekisui had previously enforced an injunction issued by the Regional Court Munich against its opponent for this patent. Nevertheless, the two Japanese manufacturers will continue their intense global dispute.
22 April 2026 by Mathieu Klos
Two Japanese companies are fighting it out in German courts. This is rare, but the dispute between Sekisui Chemicals and Kuraray is particularly intense. Sekisui Chemicals has filed four lawsuits based on four patents against its Japanese competitor Kuraray in Germany. The two opponents are also facing off in Korea and the US.
Both speciality chemicals companies produce PVB interlayers. These are installed between layers of glass and are primarily used for sound and heat insulation, and for head-up displays. This glass is mainly used for windscreens in cars.
Sekisui sued Kuraray in 2024 over EP 2 017 237, EP 3 208 247 and EP 3 357 888 at the Regional Court Munich. The court ruled quickly last year, finding Kuraray had infringed all three patents.
Sekisui filed a fourth lawsuit based on EP 3 392 222 at the Regional Court Mannheim. However, the court stayed the proceedings to await the Federal Patent Court’s judgment on the validity of the patent.
Key dispute over EP 237
But the dispute over EP 237 plays a key role. The patent relates to a wedge-shaped multilayer film of PVB interlayer. In April 2025, the Regional Court Munich’s 7th Civil Chamber under presiding judge Oliver Schön issued an injunction ordering Kuraray Europe to cease manufacturing, offering, using, placing on the market, importing or possessing its products (case ID: 7 O 12401/24). According to a press release from Sekisui, this affects Kuraray’s ‘Trosifol The Wedge Acoustic’ and ‘Trosifol The Wedge Acoustic Shadeband’ products.
Nevertheless, it took another six months for Sekisui to enforce the injunction. The step followed in November 2025, after the Federal Patent Court published its preliminary opinion that EP 237 is probably valid. Kuraray currently does not sell its products in Germany.
The final judgment followed last week. The Federal Patent Court upheld EP 237 in full (case ID: 3 Ni 2/25 (EP)). It is considered certain that Kuraray will appeal.
Kuraray defence
In 2025 Kuraray appealed the injunctions regarding EP 237 to the Munich Higher Regional Court (case ID: U 1589/25 e). Kuraray also appealed against the two other injunctions of the Regional Court Munich. However, Sekisui has not yet enforced these.
Kuraray has filed revocation actions against all four patents-in-suit. The Federal Patent Court will hear the revocation action against EP 888 and EP 222 in June. The court upheld EP 247 with restrictions.
Kuraray had also filed revocation actions against the patents in the UK. However, These proceedings were quickly brought to an end by the parties. Kuraray is also challenging Sekisui’s patents in Korea and the US. In the Korean proceedings Kuraray has had better results than in Germany. The US proceedings are still at an early stage.
New client for Bird & Bird
According to JUVE Patent research, this is the first time Sekisui is suing in Germany for this dispute. The company is relying on a mixed team from Bird & Bird led by lawyer Boris Kreye and patent attorney Daniela Kinkeldey. Both are partners at the firm. The client came to the German practice via recommendations from Japan.
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- Boris Kreye
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- Daniela Kinkeldey
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- Stefan Gross
The team also includes patent attorney and counsel Stefan Gross as well as lawyers Lars Hessmann, David Wanner, and Aileen Altschäffl. London-based Bird & Bird partners also lead the UK proceedings.
Hoffmann Eitle and Ter Meer Steinmeister & Partner filed the patents.
Abitz and Hogan Lovells
Kuraray has retained lawyers from Hogan Lovells and patent attorneys from Abitz & Partner.
The patent attorneys of Abitz & Partner have a long-standing relationship with Kuraray’s German subsidiary through their prosecution work. This had grown considerably in 2001 with the takeover of Clariant’s PVA/PVB business. Clariant is also currently one of the Munich law firm’s prosecution clients.
According to the EPO register, Kuraray Europe GmbH files its European patent applications mainly via the head of the patent department, Christian Oliver Janßen. In the dispute with Sekisui, Abitz partners Monica Heinemann and Thomas Kratzmüller are responsible for the revocation actions.
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- Clemens Plassmann
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- Erhard Keller
In the past, the patent attorneys of Abitz & Partner and the lawyers from Hogan Lovells have often worked together litigation, for example for MSD.
The two Düsseldorf partners Clemens Plassmann and Erhard Keller lead the Hogan Lovells team. They also have long-standing ties to Kuraray in Germany. Counsel Felix Banholzer and Marcus Schönknecht as well as senior associate Lisa Bresler are also involved. Washington partner Joe Raffetto is involved in the US proceedings.
