DCT
3:25-cv-08631
Resonac Hard Disk Corp v. Mr Tech GmbH
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Resonac Hard Disk Corporation (Japan) and Resonac America, Inc. (California)
- Defendant: MR Technologies GmbH (Austria)
- Plaintiff’s Counsel: Morgan, Lewis & Bockius LLP
- Case Identification: 5:25-cv-8631, N.D. Cal., 10/09/2025
- Venue Allegations: Plaintiff Resonac asserts that venue is proper because Defendant MR Technologies is a foreign entity not resident in the United States, and thus may be sued in any judicial district. Alternatively, Resonac alleges that its U.S. subsidiary is resident in the district and that a substantial part of the events giving rise to the claim occurred there.
- Core Dispute: Plaintiff seeks a declaratory judgment that its magnetic recording media products do not infringe three patents owned by Defendant related to multilayer structures for high-density hard disk drives.
- Technical Context: The technology concerns advanced magnetic recording media designed to overcome the physical limits of data storage density in hard disk drives (HDDs) by balancing data stability with the ability to write new data.
- Key Procedural History: This declaratory judgment action was filed in the context of ongoing litigation initiated by the patent holder, MR Technologies (MRT). MRT previously sued Resonac’s customers, including Western Digital and Toshiba, in the Central District of California, alleging that HDDs incorporating Resonac’s magnetic media infringe the patents-in-suit. Resonac alleges that Toshiba has requested indemnification, creating a direct legal controversy between Resonac and MRT.
Case Timeline
| Date | Event |
|---|---|
| 2006-06-17 | Earliest Priority Date for ’864, ’997, and ’734 Patents |
| 2018-03-27 | U.S. Patent No. 9,928,864 Issues |
| 2021-10-05 | U.S. Patent No. 11,138,997 Issues |
| 2022-08-26 | MRT files suit vs. Western Digital on ’864 & ’997 Patents |
| 2024-06-25 | U.S. Patent No. 12,020,734 Issues |
| 2024-08-22 | MRT files suit vs. Western Digital on ’734 Patent |
| 2025-04-15 | MRT files suit vs. Toshiba on all three Asserted Patents |
| 2025-10-09 | Resonac files Complaint for Declaratory Judgment |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 9,928,864 - "Multilayer Exchange Spring Recording Media," issued March 27, 2018
The Invention Explained
- Problem Addressed: The patent describes a fundamental conflict in magnetic data storage: increasing data density requires smaller magnetic grains, but smaller grains become thermally unstable, leading to data loss (the "superparamagnetic limit"). Making the grains more magnetically stable (increasing their "anisotropy") solves this but makes them too difficult to write to with existing HDD write heads, a challenge known as the "writeability problem" (’864 Patent, col. 1:13-30).
- The Patented Solution: The invention proposes a multilayer "exchange spring" structure. It pairs a magnetically "hard" storage layer, which provides thermal stability, with a "softer" multilayer structure called a "nucleation host." This nucleation host is composed of several ferromagnetic layers with progressively increasing anisotropy. When writing data, the magnetic reversal begins in the softest layer and propagates through the graded layers to the hard storage layer, reducing the overall magnetic field required to write data without compromising the stability of the stored bit (’864 Patent, Abstract; col. 2:50-65).
- Technical Importance: This approach aims to decouple the competing requirements of thermal stability and writeability, a critical obstacle to achieving higher storage densities in the HDD industry.
Key Claims at a Glance
- The complaint asserts non-infringement of independent claim 1 (Compl. ¶31).
- Essential elements of claim 1 include:
- A magnetic recording medium comprising a substrate, an underlayer, and an "exchange coupled magnetic multilayer structure."
- The structure includes a "hard magnetic storage layer" with a high coercive field (Hs>0.5 T).
- The structure also includes a "nucleation host" with a lower coercive field (Hn<Hs).
- Crucially, the nucleation host is formed on the hard magnetic storage layer, is exchange coupled to it, and "comprises ferromagnetic layers with increasing anisotropy constant K from layer to layer."
U.S. Patent No. 11,138,997 - "Multilayer Exchange Spring Recording Media," issued October 5, 2021
The Invention Explained
- Problem Addressed: The ’997 Patent addresses the same writeability problem versus thermal stability challenge described in the ’864 Patent (’997 Patent, col. 1:13-30).
- The Patented Solution: The patent discloses the same core "exchange spring" architecture, featuring a hard storage layer coupled to a multilayer nucleation host with graded anisotropy. This patent family member claims the invention both as a complete "magnetic recording system" that includes a writing head (claim 1) and as the "magnetic recording medium" itself (claim 7) (’997 Patent, Abstract; col. 2:50-65).
- Technical Importance: The technology provides a potential pathway for HDD manufacturers to continue increasing areal storage density beyond the limits of conventional single-layer media.
Key Claims at a Glance
- The complaint asserts non-infringement of independent claims 1 and 7 (Compl. ¶36).
- Essential elements of claim 1 include:
- A magnetic recording system comprising a "writing head" and a disk.
- The disk includes a magnetic recording medium with a substrate, underlayer, hard magnetic storage layer, and a "nucleation host" that "comprises ferromagnetic layers with increasing anisotropy constant K from layer to layer."
- Essential elements of claim 7 are for a magnetic recording medium with a similar structure, adding the limitation that "at least two of the ferromagnetic layers are coupled with a thin exchange coupling layer."
U.S. Patent No. 12,020,734 - "Multilayer Exchange Spring Recording Media," issued June 25, 2024
Technology Synopsis
The ’734 Patent continues the theme of the asserted patent family, addressing the writeability problem in high-density magnetic media (’734 Patent, col. 1:13-30). It claims a magnetic recording system where the nucleation host comprises at least a first ferromagnetic layer with an anisotropy constant K1 and a second ferromagnetic layer with an increased anisotropy constant K2, with the two layers being exchange coupled (’734 Patent, Abstract).
Asserted Claims
The complaint asserts non-infringement of independent claim 1 (Compl. ¶41).
Accused Features
The complaint states that MRT's infringement allegations against Toshiba, which form the basis of this DJ action, are premised on the magnetic recording media supplied by Resonac (Compl. ¶40).
III. The Accused Instrumentality
Product Identification
The accused instrumentalities are "magnetic recording media" products that are designed, manufactured, and sold by Plaintiff Resonac (Compl. ¶¶18, 27). These media are incorporated as the primary data storage component into hard disk drives (HDDs) manufactured and sold by Resonac's customers, such as Toshiba (Compl. ¶27).
Functionality and Market Context
The accused products are the physical platters within HDDs where data is magnetically encoded. Resonac is identified as a key supplier of this technology to major HDD manufacturers (Compl. ¶¶4, 27). The complaint alleges that MRT's infringement suits against these manufacturers "directly target Resonac's products" (Compl. ¶28). The specific end-products containing the accused media include Toshiba's consumer, enterprise, and specialty HDDs (Compl. ¶26, p. 8).
No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
The complaint seeks a declaratory judgment of non-infringement. Its analysis consists of identifying a key limitation from each asserted patent and stating, in a conclusory fashion, that its products do not meet that limitation.
’928,864 Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a nucleation host... [that] comprises ferromagnetic layers with increasing anisotropy constant K from layer to layer | The complaint alleges that Resonac's products do not contain this feature. | ¶32 | col. 6:5-8 |
’11,138,997 Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a nucleation host... [that] comprises ferromagnetic layers with increasing anisotropy constant K from layer to layer | The complaint alleges that Resonac's products do not contain this feature. | ¶37 | col. 6:4-7 |
Identified Points of Contention
- Scope Questions: The dispute raises a central question about the claim term "nucleation host... compris[ing] ferromagnetic layers with increasing anisotropy constant K from layer to layer." The litigation may focus on what structural and magnetic properties are required to meet this limitation—for example, whether it requires discrete, physically distinct layers versus a more continuous or graded material composition.
- Technical Questions: The complaint's denials are conclusory and lack technical detail. A primary question for the court will be an evidentiary one: what is the actual physical construction and what are the magnetic properties of the layers within Resonac's accused media? The outcome will depend on whether the evidence of the products' actual structure and function falls within the court's interpretation of the claim language.
V. Key Claim Terms for Construction
- The Term: "a nucleation host... compris[ing] ferromagnetic layers with increasing anisotropy constant K from layer to layer"
- Context and Importance: This limitation appears in the independent claims of both the ’864 and ’997 patents and is the sole basis for the non-infringement argument presented in the complaint. The construction of this term will be dispositive for infringement, as it defines the core inventive concept of the graded magnetic structure.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification describes embodiments where the anisotropy "assumes more than one value in a substantial magnetic portion of nucleation host 21" (’997 Patent, col. 6:8-10). It also discusses a "gradually varying anisotropy" and a "continuous change of anisotropy," which could support a construction that does not require strictly defined, separate layers (’997 Patent, col. 8:24-26; col. 12:55-56).
- Evidence for a Narrower Interpretation: The claim language recites "layers" (plural) with an "increasing" constant "from layer to layer," which suggests a discrete, stepwise progression. The abstract reinforces this, stating "the anisotropy increases from layer to layer" (’997 Patent, Abstract). MRT may argue that this language requires a specific architecture of distinct layers with a monotonic increase in anisotropy, which it may contend Resonac's products lack.
VI. Other Allegations
- Indirect Infringement: The complaint seeks a declaratory judgment that Resonac does not "directly or indirectly infringe" the Asserted Patents (Compl., Prayer for Relief ¶A). However, the complaint's factual allegations focus exclusively on denying that its products meet the claim limitations, a direct infringement analysis. The complaint does not provide sufficient detail for analysis of any specific theory of indirect infringement.
VII. Analyst’s Conclusion: Key Questions for the Case
This declaratory judgment action appears poised to center on the interplay between claim construction and the technical reality of the accused products. The key questions for the case will likely be:
- A core issue will be one of definitional scope: How will the court construe the central limitation of "ferromagnetic layers with increasing anisotropy constant K from layer to layer"? Does this phrase require discrete physical layers with a strict, stepwise increase in magnetic stability, or can it be interpreted more broadly to cover materials with continuously graded magnetic properties?
- A key evidentiary question will be one of technical implementation: Based on the court's claim construction, what does the factual evidence show about the physical structure and magnetic characteristics of the layers in Resonac’s accused recording media? The case will likely depend on a detailed, technical comparison of the accused products against the specific requirements of the claims.