DCT
8:19-cv-01792
Document Security Systems Inc v. Seoul Semiconductor Co Ltd
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Document Security Systems, Inc. (New York)
- Defendant: Seoul Semiconductor Co., Ltd. (Republic of Korea) and Seoul Semiconductor, Inc. (California)
- Plaintiff’s Counsel: Russ August & Kabat
- Case Identification: 8:19-cv-01792, C.D. Cal., 09/18/2019
- Venue Allegations: Venue is based on Defendants allegedly having a regular and established place of business within the Central District of California and committing acts of patent infringement in the district.
- Core Dispute: Plaintiff alleges that Defendant’s light-emitting diode (LED) products infringe a patent related to the structure of the phosphor layer used to convert light color.
- Technical Context: The technology concerns the manufacturing of white LEDs, where a phosphor layer converts light from a blue LED die to create a white-light emission, a foundational technology for modern solid-state lighting.
- Key Procedural History: Plaintiff acquired the patent-in-suit as part of a larger portfolio from the original assignee, Agilent Technologies, Inc., or its successors, in 2016. Subsequent to the filing of this complaint, an Inter Partes Review (IPR) proceeding was initiated against the patent-in-suit (IPR2020-00938), which ultimately resulted in a certificate, issued in 2024, cancelling all asserted claims.
Case Timeline
| Date | Event |
|---|---|
| 2004-05-07 | '119 Patent Priority Date |
| 2008-01-01 | '119 Patent Issue Date |
| 2016-11-XX | Plaintiff DSS acquires patent portfolio |
| 2019-09-18 | Complaint Filing Date |
| 2020-05-18 | IPR filed against '119 Patent |
| 2024-08-19 | IPR Certificate issues cancelling claims 1-7 of '119 Patent |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,315,119 - “Light-emitting device having a phosphor particle layer with specific thickness,” Issued January 1, 2008
The Invention Explained
- Problem Addressed: The patent's background describes issues with prior art white LEDs where phosphor particles are mixed into a resin material (e.g., epoxy) that covers the LED chip. This method can lead to a non-uniform distribution of phosphor particles as they settle before the resin cures, resulting in inconsistent color output. It also creates a relatively large, three-dimensional light source, which complicates the design of secondary optics intended to focus or shape the light. (’119 Patent, col. 1:36-55).
- The Patented Solution: The invention proposes creating a thin, uniform layer of phosphor particles directly over the LED die, rather than suspending them in a bulk material. This is achieved by applying a mixture of phosphor particles and a volatile carrier material over the die and then evaporating the carrier, which leaves a compact layer of phosphor. (’119 Patent, col. 3:13-25). This method is described as creating a smaller and more uniform light source. (’119 Patent, col. 3:60-65).
- Technical Importance: This approach aimed to improve the color consistency and optical performance of white LEDs, which were becoming critical components in general lighting and display backlighting applications. (’119 Patent, col. 1:45-55).
Key Claims at a Glance
- The complaint asserts "various claims" of the '119 Patent, with a specific focus on infringement of independent Claim 1. (Compl. ¶¶11, 15).
- The essential elements of independent Claim 1 are:
- A light source comprising a die that emits light of a first wavelength.
- A conformal layer of phosphor particles that covers the die, is in direct contact with the die, and converts a portion of the light to a second wavelength.
- The layer has a substantially uniform thickness of less than 100 µm over the die.
- A reflecting cup with reflective sidewalls, where the die is located in the cup and the phosphor layer covers a portion of the reflective sidewalls.
- The complaint does not explicitly reserve the right to assert dependent claims, but the prayer for relief requests a judgment of infringement of "one or more claims." (Compl. p. 8, ¶A).
III. The Accused Instrumentality
Product Identification
The accused instrumentalities are Defendants' 5630 Series, 3030 Series, 3528 Series, 3020 Series, 5050 Series, and 801 Series LEDs, as well as downstream products (e.g., light bulbs, displays) that contain them. (Compl. ¶11).
Functionality and Market Context
The complaint focuses on the 5630 Series LEDs as an illustrative example. These products are described as LED packages that function by generating blue light from an LED die and using a phosphor layer to convert a portion of that blue light into other wavelengths to produce a combined white light output. (Compl. ¶¶12-13). The complaint alleges these products are sold nationwide and are used in a variety of lighting and display applications. (Compl. ¶¶4, 11).
IV. Analysis of Infringement Allegations
’119 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a light source that generates light of a first wavelength, said light source comprising a die that emits light at said first wavelength | The accused 5630 Series products contain an LED die that emits light of a blue wavelength, such as 475nm. | ¶12 | col. 5:26-29 |
| a conformal layer of phosphor particles covering said die and in direct contact therewith, said phosphor particles converting at least a portion of said light of said first wavelength to light of a second wavelength, said layer having a substantially uniform thickness of less than 100 µm over said die | The 5630 Series includes a conformal layer of phosphor particles in direct contact with the die, which converts the blue light to other wavelengths and has a thickness of less than 0.1 mm (100 µm). A color spectrum graph provided in the complaint shows the conversion of blue light. (Compl. p. 5, Fig. 1). | ¶13 | col. 5:30-35 |
| a reflecting cup comprising reflective sidewalls, said die being located in said cup such that a portion of said light generated by said die is reflected from said cup, said layer of phosphor particles covering a portion of said reflective sidewalls | The 5630 Series includes a reflecting cup where the die is located, and the phosphor layer is alleged to partially cover the reflective sidewalls of the cup. A micrograph of an accused device cross-section is provided to illustrate this structure. (Compl. p. 6). | ¶14 | col. 5:35-39 |
- Identified Points of Contention:
- Scope Questions: A potential dispute may arise over the term "substantially uniform thickness". The complaint alleges a thickness of "less than 0.1 mm" but does not provide evidence demonstrating the degree of uniformity across the die, raising the question of what level of variation is permissible under the claim. (Compl. ¶13). A related question is whether the phosphor layer "cover[s] a portion of said reflective sidewalls" to the extent required by the claim.
- Technical Questions: The complaint alleges the phosphor layer is in "direct contact" with the die. (’119 Patent, col. 5:31; Compl. ¶13). A technical question is whether there is any intervening material, such as a binder residue (which the patent itself contemplates using), between the phosphor particles and the die surface that would defeat a finding of "direct contact."
V. Key Claim Terms for Construction
The Term: "substantially uniform thickness"
- Context and Importance: This term is central to the patent's purported improvement over the prior art, which it criticizes for non-uniform phosphor distribution. The outcome of the infringement analysis could depend on how much thickness variation is permitted by the term "substantially."
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The use of the word "substantially" itself suggests that absolute or perfect uniformity is not required.
- Evidence for a Narrower Interpretation: The patent’s background section frames the problem as phosphor particles settling in a resin, creating a "non-uniform distribution." (’119 Patent, col. 1:39-43). A party could argue that "substantially uniform" must be interpreted to mean a level of uniformity sufficient to solve this specific settling problem.
The Term: "in direct contact therewith"
- Context and Importance: This limitation distinguishes the claimed invention from methods where phosphor particles are suspended throughout a bulk epoxy and may not touch the die. Infringement requires physical contact between the phosphor particles and the die. Practitioners may focus on this term because the patent's own disclosure mentions using a "binder material" that can be added to the carrier to "bind the phosphor particles to one another" after evaporation, which may leave a residue. (’119 Patent, col. 4:46-53).
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: A party might argue that microscopic amounts of binder residue between particles and the die do not constitute an intervening layer, and thus the particles remain in "direct contact."
- Evidence for a Narrower Interpretation: An opposing party could argue that any binder material remaining between the die surface and the phosphor particles, however thin, breaks "direct contact" as required by the plain language of the claim.
VI. Other Allegations
- Indirect Infringement: The complaint alleges induced infringement, stating that Defendants provide "technical guides, product data sheets, demonstrations... and other forms of support" that instruct and encourage customers and end users to use the accused products in an infringing manner. (Compl. ¶17).
- Willful Infringement: The complaint does not use the term "willful infringement." It does, however, allege that Defendants have "actual knowledge of the '119 Patent at least as of service of this Complaint" and requests a finding that the case is "exceptional" to recover attorneys' fees under 35 U.S.C. § 285. (Compl. ¶17; p. 8, ¶D). These allegations could form a basis for seeking enhanced damages for post-suit conduct but do not allege pre-suit knowledge.
VII. Analyst’s Conclusion: Key Questions for the Case
Given the complaint and the patent, the dispute, as originally filed, would have centered on claim interpretation and factual evidence. However, subsequent procedural events have overtaken the initial dispute.
- A primary question would have been one of definitional scope: how much deviation is permitted by the term "substantially uniform thickness," and would the accused products' alleged "less than 0.1 mm" thickness meet the construed definition?
- A key evidentiary question would have been one of physical fact: is the accused phosphor layer truly "in direct contact" with the LED die, or does a binder or other material form an intervening layer that negates this claim element?
- The most significant issue, however, is one of patent viability: following the filing of the complaint, an Inter Partes Review proceeding resulted in the cancellation of all asserted claims of the '119 Patent. The dispositive question for the case, therefore, became what legal effect this cancellation has on the pending infringement action.