DCT
1:25-cv-01554
Kuraray America Inc v. Sekisui Chemical Ltd
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Kuraray America Inc. (Delaware)
- Defendant: Sekisui Chemical Ltd. (Japan)
- Plaintiff’s Counsel: Hogan Lovells US LLP
- Case Identification: 1:25-cv-01554, E.D. Va., 09/17/2025
- Venue Allegations: Plaintiff alleges venue is proper in the Eastern District of Virginia under 35 U.S.C. § 293, which grants jurisdiction over a foreign patent owner (Sekisui) who has not designated an agent for service of process in the U.S.
- Core Dispute: Plaintiff Kuraray America seeks a declaratory judgment that six U.S. patents owned by Defendant Sekisui, related to interlayer films for laminated glass, are invalid.
- Technical Context: The technology concerns specialized polymer films used in laminated glass, such as automotive windshields, which are designed with a wedge-shaped cross-section to improve Head-Up Display (HUD) performance and incorporate sound-insulating properties.
- Key Procedural History: This U.S. action follows an aggressive international patent enforcement campaign by Sekisui against Kuraray entities. Sekisui has pursued infringement actions in Germany and Korea on foreign counterpart patents, securing a judgment (now on appeal) and an injunction in Germany. Sekisui also successfully petitioned the Korean Trade Commission, which found infringement by certain Kuraray products. In the U.K., Sekisui consented to the revocation of its counterpart patents after Kuraray filed a nullity action.
Case Timeline
| Date | Event |
|---|---|
| 2005-01-01 | Kuraray's predecessor's "Wedge" product known and used in the U.S. |
| 2006-05-12 | Earliest Priority Date for Patent Family A (’871, ’360, ’756, ’386, ’932 Patents) |
| 2011-01-01 | Sales of Kuraray's predecessor's "Wedge" product to customers |
| 2011-02-15 | U.S. Patent No. 7,886,871 Issues |
| 2011-10-11 | U.S. Patent No. 8,033,360 Issues |
| 2014-04-15 | U.S. Patent No. 8,695,756 Issues |
| 2014-09-30 | Sekisui's S-LEC Prior Art Film allegedly sold before this date |
| 2015-06-30 | U.S. Patent No. 9,067,386 Issues |
| 2015-09-30 | Earliest Priority Date for U.S. Patent No. 10,913,244 |
| 2016-08-30 | U.S. Patent No. 9,427,932 Issues |
| 2021-02-09 | U.S. Patent No. 10,913,244 Issues |
| 2024-07-01 | Sekisui sends notice letter to Kuraray's parent company (approximate date) |
| 2024-09-01 | Sekisui files patent actions in Germany and petitions Korean Trade Commission (approximate date) |
| 2025-05-23 | Kuraray Europe files revocation actions in the U.K. |
| 2025-08-28 | Korean Trade Commission announces decision finding infringement |
| 2025-09-17 | Complaint for Declaratory Judgment filed in E.D. Va. |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,886,871 - "Interlayer Film for Laminated Glass and Laminated Glass"
The Invention Explained
- Problem Addressed: The patent describes a problem with laminated glass used in automotive windshields equipped with Head-Up Displays (HUDs). Because the glass consists of two parallel sheets, reflections of the HUD projection from both the inner and outer surfaces can create a "double image" in the driver's field of view. Additionally, conventional laminated glass may have inferior sound-insulating properties (’871 Patent, col. 1:12-48).
- The Patented Solution: The invention is a multi-layer interlayer film designed to be sandwiched between glass sheets. The film has a "wedge shape as a cross-sectional shape," meaning it is thicker at one end than the other. This wedge angle is precisely controlled to converge the reflections from the two glass surfaces, eliminating the double image (’871 Patent, col. 2:1-5). The film also includes a dedicated "sound-insulating layer" between two "protection layers" to improve acoustic performance (’871 Patent, col. 1:65-67, Fig. 2).
- Technical Importance: This structure aims to simultaneously solve two distinct problems—optical distortion in HUDs and acoustic noise transmission—within a single, integrated interlayer film for automotive glass.
Key Claims at a Glance
- The complaint challenges Claims 1-8 (Compl. ¶28). Independent Claim 1 is asserted.
- Claim 1 Elements:
- An interlayer film for a laminated glass,
- which comprises at least a pair of protection layers and a sound-insulating layer sandwiched between the pair of the protection layers,
- and which has a wedge shape as a cross-sectional shape, a wedge angle θ of 0.1 to 0.7 mrad, the maximum thickness of 2000 µm or thinner, and the minimum thickness of 400 µm or thicker,
- the minimum thickness of the sound-insulating layer being 20 µm or thicker,
- and wherein the sound-insulating layer is selected from a group of three specific polyvinyl acetal resin compositions defined by plasticizer content and acetalization/acetylation degrees.
- The complaint does not explicitly reserve the right to assert dependent claims but challenges them as a group with Claim 1.
U.S. Patent No. 8,033,360 - "Interlayer Film for Laminated Glass and Laminated Glass"
The Invention Explained
- Problem Addressed: As a continuation of the '871 Patent, the '360 Patent addresses the same technical problems of double images in HUDs and insufficient sound insulation in laminated glass (’360 Patent, col. 1:14-51).
- The Patented Solution: The '360 Patent claims a similar multi-layer, wedge-shaped interlayer film with a sound-insulating layer between protection layers. The claims of the ’360 Patent focus on defining the properties of the protection layers, specifying their plasticizer content and the chemical composition of their polyvinyl acetal resin (’360 Patent, col. 16:11-20). This approach seeks to solve the core optical and acoustic problems while also ensuring the protective outer layers have specific, desirable properties.
- Technical Importance: The invention provides an alternative way to define the multi-layer film structure by focusing on the chemical and physical properties of the protective layers in addition to the sound-insulating core.
Key Claims at a Glance
- The complaint challenges Claims 1-8 (Compl. ¶39). Independent Claim 1 is asserted.
- Claim 1 Elements:
- An interlayer film for a laminated glass,
- which comprises at least a pair of protection layers and a sound-insulating layer sandwiched between the pair of the protection layers,
- and which has a wedge shape as a cross-sectional shape, a wedge angle θ of 0.1 to 0.7 mrad, the maximum thickness of 2000 µm or thinner, and the minimum thickness of 400 µm or thicker,
- the minimum thickness of the sound-insulating layer being 20 µm or thicker,
- wherein the protection layer contains 25 to 55 parts by weight of a plasticizer to 100 parts by weight of a polyvinyl acetal resin having specific properties (acetylation degree, carbon atoms of acetal group, acetalization degree),
- and wherein the sound-insulating layer contains 40-80 parts by weight of a plasticizer to 100 parts by weight of a polyvinyl acetal resin.
- The complaint challenges dependent claims 2-8 along with Claim 1.
U.S. Patent No. 8,695,756 - "Interlayer Film for Laminated Glass and Laminated Glass"
- Technology Synopsis: This continuation patent is directed to a wedge-shaped interlayer film with sound-insulating and protection layers. The claims introduce a functional property, requiring the film to have an "excellent defoaming property," which prevents the formation of bubbles when the laminated glass is produced (’756 Patent, col. 16:4-13).
- Asserted Claims: Claims 1-9 (Compl. ¶51).
- Accused Features: The complaint alleges the ’756 Patent is invalid and thus not infringed by the Accused Trosifol Products (Compl. ¶25, 50).
U.S. Patent No. 9,067,386 - "Interlayer Film for Laminated Glass and Laminated Glass"
- Technology Synopsis: This continuation patent claims a wedge-shaped interlayer film with a sound-insulating layer, defining the invention by the specific chemical compositions of the polyvinyl acetal resin and plasticizer in the sound-insulating layer (’386 Patent, col. 16:6-18).
- Asserted Claims: Claims 1-9 (Compl. ¶67).
- Accused Features: The complaint alleges the ’386 Patent is invalid and thus not infringed by the Accused Trosifol Products (Compl. ¶25, 66).
U.S. Patent No. 9,427,932 - "Interlayer Film for Laminated Glass and Laminated Glass"
- Technology Synopsis: This continuation patent claims a wedge-shaped interlayer film where both the sound-insulating layer and the protection layers have wedge-shaped cross-sections. The claims also specify the plasticizer content of the sound-insulating layer (’932 Patent, col. 16:32-48).
- Asserted Claims: Claims 1-9 (Compl. ¶78).
- Accused Features: The complaint alleges the ’932 Patent is invalid and thus not infringed by the Accused Trosifol Products (Compl. ¶25, 77).
U.S. Patent No. 10,913,244 - "Interlayer for Laminated Glass and Laminated Glass"
- Technology Synopsis: This patent, from a different family, addresses the problem of wrinkles forming in wedge-shaped interlayer films, especially when rolled for storage or heated during lamination (’244 Patent, col. 2:5-20). The solution is an interlayer film defined by specific thermal shrinkage characteristics when tested according to a detailed procedure set forth in the claims (’244 Patent, col. 33:31-55).
- Asserted Claims: Claims 1-17 (Compl. ¶89).
- Accused Features: The complaint alleges the ’244 Patent is invalid and thus not infringed by the Accused Trosifol Products (Compl. ¶25, 88).
III. The Accused Instrumentality
Product Identification
- The complaint identifies the "Trosifol® Wedge Acoustic and Trosifol® Wedge Acoustic Shadeband products" (collectively, the "Accused Trosifol Products") (Compl. ¶17).
Functionality and Market Context
- The complaint describes these products as interlayer films for the automotive industry, tailored to meet vehicle manufacturer needs (Compl. ¶15). Kuraray America does not manufacture the products but imports them from affiliated entities in Europe and Korea to market and sell throughout North America (Compl. ¶16). The complaint frames these products as being central to a "substantial controversy" between the parties, precipitated by Sekisui's worldwide enforcement actions targeting them (Compl. ¶4, 25). No probative visual evidence provided in complaint.
IV. Key Claim Terms for Construction
The complaint’s invalidity arguments against U.S. Patent No. 10,913,244 raise questions about the scope and support for its functionally-defined claim limitations.
- The Term: "exhibits...thermal shrinkage characteristics when tested according to the procedure set out in the claim" (from Claim 1 of the '244 Patent)
- Context and Importance: This term defines the core of the invention claimed in the ’244 Patent. The patentability of the claim hinges on whether this specific, numerically-defined thermal shrinkage behavior was novel and non-obvious. Plaintiff Kuraray directly challenges the validity of this limitation under 35 U.S.C. § 112, arguing that the specification lacks adequate written description and enablement for the full scope of the claimed shrinkage ranges (Compl. ¶101-106). The construction of this term—specifically, how much descriptive support is required to substantiate the claimed numerical ranges—will be central to the validity dispute.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: A party arguing for a broader interpretation (or arguing that the patentee is entitled to the full scope of the numbers recited) might point to the detailed, multi-step testing procedure defined directly within the claim language itself. They may argue this procedure provides a clear, objective standard for determining if a film meets the limitation, thus defining the invention with sufficient precision (’244 Patent, col. 33:31-55). The specification also states that a purpose of the invention is to provide a film where "wrinkles are hardly generated" and that this is achieved by controlling the shrinkage ratio (’244 Patent, col. 2:21-25; col. 5:56-62).
- Evidence for a Narrower Interpretation: A party arguing for a narrower interpretation (or that the claimed range lacks support) may cite the complaint's allegation that the specification fails to disclose or provide examples of films that meet the specific claimed ranges, particularly "the largest thermal shrinkage ratio among the first, second and third thermal shrinkage ratios being 14% or more and 56% or less" (Compl. ¶103; ’244 Patent, col. 33:49-51). They may argue that the working examples in the patent's tables do not demonstrate possession of the full claimed range, suggesting the inventors did not actually invent or enable a film meeting the entire scope of this limitation (’244 Patent, Table 1, col. 31-32).
V. Analyst’s Conclusion: Key Questions for the Case
This declaratory judgment action appears to present two primary questions for the court regarding the validity of Sekisui’s patents:
- A central issue will be one of obviousness over prior art: Did the combination of prior art references cited by Kuraray—disclosing wedge-shaped profiles, sound-insulating layers, and specific polymer compositions—render the claimed inventions in Sekisui's Patent Family A obvious to a person of ordinary skill in the art at the time of the invention?
- A second key question will be one of adequacy of disclosure under § 112: Does the patent specification for the ’756 and ’244 Patents provide sufficient written description and enablement to support the full scope of the functionally-defined claims reciting an "excellent defoaming property" and specific "thermal shrinkage characteristics," or are these claims invalid for claiming subject matter broader than what the inventors described and enabled?