DCT

2:25-cv-00589

Kuraray America Inc v. Sekisui Chemical Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:25-cv-01554, E.D. Va., 09/17/2025
  • Venue Allegations: Plaintiff alleges venue is proper because there is no district in which the action could otherwise be brought and Defendant, a foreign corporation, is subject to personal jurisdiction in the district under 35 U.S.C. § 293.
  • Core Dispute: Plaintiff seeks a declaratory judgment that Defendant’s patents related to interlayer films for laminated glass are invalid, preempting threatened litigation in the United States following Defendant's patent enforcement actions against Plaintiff's affiliates in Europe and Asia.
  • Technical Context: The technology concerns specialized polymer interlayer films used in laminated glass, primarily for automotive windshields, which provide sound insulation and enable features like head-up displays (HUDs).
  • Key Procedural History: The complaint details an aggressive international patent enforcement campaign by Defendant Sekisui against Plaintiff Kuraray's affiliates. This includes infringement actions in Germany, resulting in a finding of infringement now on appeal, and ongoing proceedings in Korea. Kuraray affiliates have filed corresponding nullity (invalidity) actions in Germany and the UK. The complaint alleges that this history, combined with a notice letter from Sekisui, creates an immediate threat of litigation in the U.S. warranting declaratory relief.

Case Timeline

Date Event
2006-05-12 Earliest Priority Date for Patent Family A (’871, ’360, ’756, ’386, ’932 Patents)
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
2015-06-30 U.S. Patent No. 9,067,386 Issues
2015-09-30 Earliest Priority Date for Patent Family B (’244 Patent)
2016-08-30 U.S. Patent No. 9,427,932 Issues
2021-02-09 U.S. Patent No. 10,913,244 Issues
2024-07 Sekisui sends notice letter to Kuraray's parent company
2024-09 Sekisui files patent infringement actions in Germany
2024-09 Sekisui petitions the Korean Trade Commission
2025-05-23 Kuraray Europe files revocation actions in the UK
2025-08-28 Korean Trade Commission announces infringement finding
2025-09-17 Complaint for Declaratory Judgment filed

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 addresses the challenge of creating automotive windshields that provide effective sound insulation while also being suitable for Head-Up Displays (HUDs), which can suffer from double-image distortions if the glass surfaces are perfectly parallel (’871 Patent, col. 4:9-32). Conventional wedge-shaped interlayer films used to correct HUD distortion often have thin portions that compromise sound-dampening performance (’871 Patent, col. 4:13-17).
  • The Patented Solution: The invention is a multi-layer interlayer film with a specific construction to solve both problems simultaneously. It comprises a central "sound-insulating layer" sandwiched between two "protection layers" (’871 Patent, Abstract). The overall film has a wedge shape to correct for HUD double images, achieved by making the outer protection layers themselves wedge-shaped while the central sound-insulating layer can maintain a more uniform, minimum thickness required for acoustic performance (’871 Patent, col. 5:31-36; Fig. 1).
  • Technical Importance: This design allows for the optimization of both acoustic and optical properties independently, which was a significant challenge for single-layer or simpler multi-layer films.

Key Claims at a Glance

  • The complaint asserts that Claims 1-8 are invalid (Compl. ¶28). Claim 1 is the sole independent claim.
  • Essential elements of Claim 1:
    • 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, acetalization degree, and/or acetylation degree.
  • The complaint challenges dependent claims 2-8 as invalid as well (Compl. ¶28).

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 balancing sound insulation and optical requirements for HUD-compatible automotive windshields (’360 Patent, col. 4:9-32).
  • The Patented Solution: The patent describes the same fundamental structure: a sound-insulating layer positioned between two protection layers to form a wedge-shaped composite film (’360 Patent, Abstract). The claims of the ’360 Patent, however, focus on different specific material properties for the layers, particularly the composition of the protection layers, to achieve the desired performance.
  • Technical Importance: This patent further explores the material science aspects of the multi-layer film structure, aiming to refine performance by specifying the chemical composition of the protective layers.

Key Claims at a Glance

  • The complaint asserts that Claims 1-8 are invalid (Compl. ¶39). Claim 1 is the sole independent claim.
  • Essential elements of Claim 1:
    • An interlayer film for a laminated glass, comprising at least a pair of protection layers and a sound-insulating layer sandwiched between them,
    • having a wedge shape as a cross-sectional shape, a wedge angle of 0.1 to 0.7 mrad,
    • a maximum thickness of 2000 μm or thinner, and a minimum thickness of 400 μm or thicker,
    • a minimum thickness of the sound-insulating layer of 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 with specific properties (acetylation degree, acetal group carbons, 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 as invalid as well (Compl. ¶39).

U.S. Patent No. 8,695,756 - “Interlayer Film for Laminated Glass and Laminated Glass”

  • Patent Identification: U.S. Patent No. 8,695,756, issued April 15, 2014.
  • Technology Synopsis: As a continuation in the same family as the ’871 and ’360 patents, the ’756 Patent is also directed to a multi-layer, wedge-shaped interlayer film for laminated glass. It adds a functional limitation requiring the film to have an "excellent defoaming property" to prevent bubble formation during the glass lamination process, linking this property to the specific wedge-shaped construction of both the sound-insulating and protection layers (Compl. ¶59).
  • Asserted Claims: The complaint seeks a declaratory judgment that Claims 1-9 are invalid (Compl. ¶51).
  • Accused Features: The technology is embodied in Plaintiff's Trosifol® Wedge Acoustic and Wedge Acoustic Shadeband products (Compl. ¶17).

U.S. Patent No. 9,067,386 - “Interlayer Film for Laminated Glass and Laminated Glass”

  • Patent Identification: U.S. Patent No. 9,067,386, issued June 30, 2015.
  • Technology Synopsis: This continuation patent continues to claim the multi-layer, wedge-shaped interlayer film. The claims further refine the chemical composition of the sound-insulating layer, requiring it to contain a specific polyvinyl acetal resin and a plasticizer content of 50 parts by weight or more (Compl. ¶69).
  • Asserted Claims: The complaint seeks a declaratory judgment that Claims 1-9 are invalid (Compl. ¶67).
  • Accused Features: The technology is embodied in Plaintiff's Trosifol® Wedge Acoustic and Wedge Acoustic Shadeband products (Compl. ¶17).

U.S. Patent No. 9,427,932 - “Interlayer Film for Laminated Glass and Laminated Glass”

  • Patent Identification: U.S. Patent No. 9,427,932, issued August 30, 2016.
  • Technology Synopsis: This continuation patent further refines the claims around the multi-layer, wedge-shaped interlayer film. The claims specify that both the sound-insulating layer and the protection layers have wedge shapes as their cross-sections, a configuration alleged in other patents in the family.
  • Asserted Claims: The complaint seeks a declaratory judgment that Claims 1-9 are invalid (Compl. ¶78).
  • Accused Features: The technology is embodied in Plaintiff's Trosifol® Wedge Acoustic and Wedge Acoustic Shadeband products (Compl. ¶17).

U.S. Patent No. 10,913,244 - “Interlayer for Laminated Glass and Laminated Glass”

  • Patent Identification: U.S. Patent No. 10,913,244, issued February 9, 2021.
  • Technology Synopsis: This patent, from a separate family, addresses problems that arise during the manufacturing and storage of wedge-shaped interlayer films, such as the formation of wrinkles (’244 Patent, col. 2:5-12). The invention claims an interlayer film defined by specific thermal shrinkage characteristics when tested at different points along its length, which allegedly prevents wrinkling and poor appearance in the final laminated glass product (’244 Patent, col. 2:20-27).
  • Asserted Claims: The complaint seeks a declaratory judgment that Claims 1-17 are invalid (Compl. ¶89).
  • Accused Features: The technology is embodied in Plaintiff's Trosifol® Wedge Acoustic and Wedge Acoustic Shadeband products (Compl. ¶17).

III. The Accused Instrumentality

Product Identification

  • Trosifol® The Wedge Acoustic and Trosifol® The Wedge Acoustic Shadeband products (collectively, the “Accused Trosifol Products”) (Compl. ¶17).

Functionality and Market Context

  • The complaint describes these products as polyvinyl butyral (PVB) interlayer films developed for the automotive industry (Compl. ¶15). These films are imported by Kuraray America and sold throughout North America for use in vehicle manufacturing (Compl. ¶16, ¶25). The complaint notes that Sekisui has targeted these specific products in its international litigation campaign, alleging they infringe foreign counterparts to the Patents-in-Suit (Compl. ¶17-19).

No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

This is a complaint for declaratory judgment of invalidity; it does not contain infringement allegations made by the Plaintiff. Therefore, this section is not applicable.

V. Key Claim Terms for Construction

  • The Term: "sound-insulating layer" (from Claim 1 of the ’871 Patent)

  • Context and Importance: The definition of this term is central to both infringement and validity. The patentability of the invention hinges on the structure where this specific layer is sandwiched between protection layers. Practitioners may focus on whether this term implies only a functional outcome (any layer that insulates sound) or requires a specific chemical composition as described in the specification's embodiments.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The claim language itself defines the layer functionally by its name and by requiring a minimum thickness of 20 μm, without explicitly importing compositional limits from the specification into the claim body itself (’871 Patent, col. 16:34-36).
    • Evidence for a Narrower Interpretation: The specification repeatedly describes the sound-insulating layer in terms of specific compositions, such as a polyvinyl acetal resin with a high plasticizer content (e.g., 40 to 80 parts by weight) (’871 Patent, col. 5:1-4). The patent also distinguishes this layer from the "protection layers" based on these compositional differences, suggesting the term carries implicit structural and compositional meaning beyond just function.

  • The Term: "excellent defoaming property" (from Claim 1 of the ’756 Patent)

  • Context and Importance: This term is a functional limitation that Plaintiff directly challenges as lacking adequate written description under 35 U.S.C. § 112 (Compl. ¶58-60). Its construction will be critical to the validity analysis. Practitioners may focus on whether this term is sufficiently defined by the patent to inform a person of ordinary skill in the art of its scope, or if it is merely a subjective, result-oriented phrase.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The claim itself provides context, stating the property results in "no foam is generated at the time of producing a laminated glass" (’756 Patent, col. 16:1-3). A party could argue this provides an objective, albeit broad, standard for measurement.
    • Evidence for a Narrower Interpretation: The complaint alleges the specification's examples are insufficient to demonstrate possession of the full scope of this claimed property across all configurations (Compl. ¶60). A party may argue that without a clear, objective metric or test defined in the specification to measure what constitutes "excellent," the term is indefinite.

VI. Other Allegations

This is a complaint for declaratory judgment of invalidity; it does not contain allegations of indirect or willful infringement. Therefore, this section is not applicable.

VII. Analyst’s Conclusion: Key Questions for the Case

  • A central issue will be one of validity over prior art: The complaint asserts that the core invention of a wedge-shaped, multi-layer film with a sound-insulating core was anticipated or rendered obvious by prior art that allegedly taught these same elements. The case will likely require a detailed factual analysis of whether the specific combination of features and material properties recited in the claims, particularly for Patent Family A, was disclosed or suggested by references such as Lee, Toyama, and Lu.
  • A second core issue will be one of adequate disclosure under § 112: For patents like the ’756 and ’244, which rely on functional language (e.g., "excellent defoaming property," specific thermal shrinkage ratios), a key legal question will be whether the patent specifications provide sufficient written description and enablement. The court will need to determine if the patents adequately teach a person of ordinary skill how to make and use the full scope of the claimed invention and demonstrate that the inventors were in possession of it.