DCT

3:25-cv-01430

Samsung Display Co Ltd v. Wuhan China Star Optoelectronics Semiconductor Display Technology Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: Samsung Display Co., Ltd. v. Wuhan China Star Optoelectronics Semiconductor Display Technology Co., Ltd., et al., 3:25-cv-01430, N.D. Tex., 07/11/2025
  • Venue Allegations: Venue is alleged based on Defendants' distribution and sale of accused products within the district. For foreign-domiciled defendants, venue is also asserted under 28 U.S.C. § 1391(c)(3), which permits suit in any judicial district.
  • Core Dispute: Plaintiff alleges that Defendants’ Organic Light Emitting Diode (OLED) displays, incorporated into smartphones and sold as replacement parts, infringe patents related to pixel arrangement structures, pixel driving circuits, and scan driver circuits.
  • Technical Context: OLED display technology is a foundational component of the modern high-end consumer electronics market, particularly for smartphones, where its image quality, power efficiency, and thin form factor are highly valued.
  • Key Procedural History: The complaint alleges a history of disputes between the parties, including a pre-suit notice letter sent in July 2022, and a U.S. International Trade Commission (ITC) investigation (Inv. No. 337-TA-1351) where the asserted patents were found to be valid and infringed. The complaint also notes that Defendant Wuhan China Star filed petitions for inter partes review (IPR) against the asserted patents, and that the Patent Trial and Appeal Board (PTAB) issued Final Written Decisions upholding the validity of the challenged claims of the '578 and '599 patents.

Case Timeline

Date Event
2003-07-07 ’599 Patent Priority Date
2008-08-19 ’599 Patent Issue Date
2012-03-06 ’578 Patent Priority Date
2012-09-20 ’593 Patent Priority Date
2016-05-03 ’593 Patent Issue Date
2020-10-15 TCL CSOT publishes post on "TCL Huaxing Pearl Arrangement"
2022-07-06 Plaintiff sends notice letter to Defendant TCL CSOT regarding ’599 and ’593 patents
2023-02-28 ’578 Patent Issue Date
2023-02-28 TCL CSOT communicates intent to intervene in ITC-1351 Proceeding
2023-03-10 Plaintiff moves to amend ITC complaint to add ’578 Patent
2023-06-09 Defendant Wuhan China Star files IPR petition against ’599 Patent
2023-06-21 Defendant Wuhan China Star files IPR petition against ’578 Patent
2024-03-06 Defendant Wuhan China Star files second IPR petition against ’593 Patent
2024-12-06 PTAB issues Final Written Decision upholding validity of challenged ’599 Patent claims
2025-01-06 PTAB issues Final Written Decision upholding validity of challenged ’578 Patent claims
2025-07-11 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 11,594,578 - "Pixel Arrangement Structure for Organic Light Emitting Display Device"

The Invention Explained

  • Problem Addressed: The patent addresses a fundamental trade-off in OLED manufacturing. To achieve a high "aperture ratio" (the proportion of a pixel that emits light), the gaps between pixels must be small. However, reducing these gaps can degrade the reliability of depositing the distinct organic light-emitting layers for each pixel, a process often done using a fine metal mask (FMM). (’578 Patent, col. 1:46-53).
  • The Patented Solution: The invention proposes a specific geometric layout of pixels to resolve this tension. It describes an arrangement based on a "virtual square," where a first pixel (e.g., green) is located at the center, and second (e.g., blue) and third (e.g., red) pixels are located at the vertices. (’578 Patent, Abstract; col. 3:24-32). This structure is intended to optimize the pixel gaps to improve both aperture ratio and deposition reliability. (’578 Patent, col. 3:1-5).
  • Technical Importance: Advanced pixel layouts are critical for increasing the resolution, brightness, and lifespan of OLED displays used in demanding applications like smartphones.

Key Claims at a Glance

  • The complaint asserts independent claim 1. (Compl. ¶44).
  • Essential elements of claim 1 include:
    • A pixel arrangement structure for an OLED display with pluralities of first, second, and third pixels configured to emit different colors.
    • The first pixels are arranged in "first sets" forming "first lines" along a first direction.
    • The second and third pixels are "alternately arranged" in "second sets" forming "second lines" parallel to the first lines.
    • A key spatial relationship where a region overlapping a row of first pixels is "entirely offset" in a second direction from the adjacent second or third pixels.
    • A requirement that the shortest distance between two nearest first pixels is greater than the shortest distance between a nearest second and third pixel.
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 7,414,599 - "Organic Light Emitting Device Pixel Circuit and Driving Method Therefor"

The Invention Explained

  • Problem Addressed: The thin film transistors (TFTs) that drive individual pixels in an AMOLED display can have inconsistent threshold voltages due to manufacturing variations. This inconsistency causes different pixels to draw different amounts of current for the same data signal, resulting in non-uniform brightness across the screen. (’599 Patent, col. 1:40-50).
  • The Patented Solution: The patent discloses a pixel circuit that "self-compensates" for the threshold voltage of the driving transistor. The circuit includes a specific arrangement of transistors where one transistor is used to temporarily connect the driving transistor "in the form of a diode," allowing the circuit to detect and cancel out its own threshold voltage variation during the data programming phase. (’599 Patent, Abstract; col. 4:24-40).
  • Technical Importance: Threshold voltage compensation circuits are essential for achieving high image quality and manufacturing yields in modern AMOLED displays.

Key Claims at a Glance

  • The complaint asserts independent claim 15. (Compl. ¶54).
  • Essential elements of claim 15 include:
    • A pixel circuit with a first transistor for receiving a data signal.
    • A second (driving) transistor whose source is coupled to the drain of the first transistor.
    • A third transistor "whose drain and source are connected between a gate and a drain of the second transistor."
    • A fourth transistor for supplying power to the second transistor.
    • A fifth transistor coupled between the drain of the second transistor and an electroluminescent element.
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 9,330,593 - "Stage Circuit and Organic Light Emitting Display Using the Same"

Technology Synopsis

  • The patent addresses the design of "stage circuits" used within a scan driver to sequentially activate the rows of pixels in a display. The invention discloses a stage circuit with a reduced number of transistors that operates using only two clock signals, which is intended to improve stability and reduce complexity compared to conventional designs that may require more components and initializing signals. (’593 Patent, Abstract; col. 9:11-25).

Asserted Claims

  • Independent claim 1. (Compl. ¶64).

Accused Features

  • The complaint alleges that the scan driver circuitry integrated into the Accused Products infringes the ’593 Patent. (Compl. ¶63).

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities are OLED displays manufactured by Defendants Wuhan CSOT and CSOT America. (Compl. ¶37). Specific examples cited include the "TCL 20 Pro 5G LCD Screen Digitizer Assembly" and the "Platinum Soft OLED Screen Assembly," which are sold as replacement parts. (Compl. ¶37). These displays are also alleged to be incorporated into smartphones sold in the U.S., such as the TCL 10 Pro, TCL 20 Pro 5G, and TCL 30 5G. (Compl. ¶39).

Functionality and Market Context

  • The accused products function as the primary display screens for smartphones. The complaint alleges that Defendant Wuhan CSOT manufactures and sells these displays using a specific pixel layout it calls the "TCL Huaxing Pearl Arrangement." (Compl. ¶45). The complaint provides a chart from an October 15, 2020 social media post by Defendant TCL CSOT that illustrates this pixel arrangement. (Compl. ¶45, p. 14). The complaint further provides microscope photographs allegedly showing this same "Pearl Arrangement" in the commercial accused products. (Compl. ¶45, p. 15). These displays are supplied to U.S. businesses for resale as replacement parts and to companies like TCL for incorporation into consumer products sold in the U.S. market. (Compl. ¶38).

IV. Analysis of Infringement Allegations

The complaint references claim chart exhibits that were not provided. The infringement theories are summarized below based on the narrative allegations in the complaint.

’578 Patent Infringement Allegations

  • The complaint alleges that the accused OLED displays, which utilize the "TCL Huaxing Pearl Arrangement," infringe at least claim 1 of the ’578 Patent. (Compl. ¶44-45). The infringement theory centers on the specific geometric layout of the red, green, and blue sub-pixels in the accused displays. The complaint asserts that this layout directly maps onto the structural limitations of claim 1, which defines a pixel arrangement in terms of "sets," "lines," and specific directional and spatial relationships, including an "entirely offset" requirement between rows of different colored pixels. (Compl. ¶44; ’578 Patent, cl. 1). To support this, the complaint provides visual evidence from a TCL CSOT publication depicting the "Pearl Arrangement" and microscope images of the accused products allegedly showing the same structure. (Compl. ¶45, pp. 14-15).

Identified Points of Contention

  • Scope Questions: The infringement analysis may turn on the construction of the claim's geometric terms, such as "first sets," "second lines," and "alternately arranged." The central dispute may be whether the accused "Pearl Arrangement" can be accurately characterized by this specific terminology.
  • Technical Questions: A key question will be whether the accused pixel layout satisfies every limitation of claim 1, particularly the negative limitation requiring that a region defined by the first pixels is "entirely offset" from the adjacent second or third pixels. The precise measurement and definition of this offset will be critical.

’599 Patent Infringement Allegations

  • The complaint alleges that the accused OLED displays infringe at least independent claim 15 of the ’599 Patent. (Compl. ¶54). The infringement theory posits that the underlying pixel driver circuitry within the accused displays contains the specific combination of transistors and a capacitor recited in claim 15. (Compl. ¶22). This claimed circuit is designed to self-compensate for the threshold voltage of the driving transistor to ensure uniform brightness. The complaint does not provide a reverse-engineered schematic of the accused circuitry, suggesting this theory will rely on evidence produced during discovery.

Identified Points of Contention

  • Scope Questions: A potential dispute may arise over the meaning of the phrase "a third transistor whose drain and source are connected between a gate and a drain of the second transistor." The scope of "connected between" could be at issue if the accused circuit includes intervening components.
  • Technical Questions: The primary question is evidentiary: does the pixel circuitry in the accused displays actually implement the five-transistor-plus-capacitor structure of claim 15? Specifically, does it contain a transistor that performs the claimed function of creating a temporary diode connection for the driving transistor to enable self-compensation?

V. Key Claim Terms for Construction

’578 Patent

  • The Term: "a region... is entirely offset in the second direction from at least one of the second pixels or the third pixels" (from claim 1).
  • Context and Importance: This negative limitation defines a specific spatial relationship that is central to the claimed pixel geometry. Infringement will depend on whether the accused "Pearl Arrangement" meets this "entirely offset" condition. Practitioners may focus on this term because its interpretation will determine whether the accused layout, which appears to have pixels in distinct rows, falls within the claim scope.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The claim language itself does not specify a minimum distance for the offset, which may support an interpretation that any amount of non-overlap in the second direction satisfies the limitation.
    • Evidence for a Narrower Interpretation: The figures, such as FIG. 1, depict a clear and complete separation between the horizontal line of the first pixels (100) and the horizontal line of the second and third pixels (200, 300). (’578 Patent, FIG. 1). A defendant may argue that "entirely offset" should be construed to require the degree of separation shown in the patent's embodiments.

’599 Patent

  • The Term: "a third transistor whose drain and source are connected between a gate and a drain of the second transistor" (from claim 15).
  • Context and Importance: This element describes the diode-connection that enables the circuit's core self-compensation function. The dispute will likely focus on whether the accused circuit has a component that meets this structural and functional requirement.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specification describes the function as connecting the second transistor "in the form of a diode." (’599 Patent, col. 4:36-40). This functional language could support a broader interpretation where any configuration that achieves this diode-like behavior for self-compensation is covered.
    • Evidence for a Narrower Interpretation: The embodiment in FIG. 3 shows a direct connection, where transistor T33 is placed directly between the gate and drain of the driving transistor T31. (’599 Patent, FIG. 3; col. 6:29-37). A defendant could argue the claim requires this direct connection without any intervening components.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for all asserted patents. The factual basis is that Defendants supply the accused OLED displays to third parties (e.g., smartphone manufacturers, repair businesses) with knowledge of the patents and with the specific intent that those third parties will incorporate them into products or use them in a manner that directly infringes. The complaint also alleges the displays are specially designed to infringe and have no substantial non-infringing uses. (Compl. ¶¶46, 48, 56, 58, 66, 68).
  • Willful Infringement: Willfulness is alleged for all asserted patents. The complaint bases this on multiple grounds, including Defendants' alleged receipt of a notice letter in July 2022, their participation in the ITC investigation that found infringement of the patents, their unsuccessful IPR challenges that resulted in PTAB decisions upholding patent validity, and alleged copying of Plaintiff's patented technologies. (Compl. ¶¶26, 31, 33-35, 47, 49).

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

  • A core issue will be one of structural mapping: Can the specific geometry of the accused "TCL Huaxing Pearl Arrangement," as depicted in the complaint, be shown to meet every spatial, directional, and relational limitation recited in claim 1 of the '578 patent?
  • A key evidentiary question will be one of circuit identity: Can discovery produce evidence, such as circuit schematics from the accused displays, that demonstrates the presence of the specific multi-transistor pixel driving and scan driver circuits required by the claims of the '599 and '593 patents?
  • A significant legal question will be the persuasive impact of prior proceedings: How will the prior ITC final determination of infringement and the PTAB's Final Written Decisions upholding the validity of two of the asserted patents influence the course of the litigation, including claim construction, summary judgment motions, and potential settlement postures?