Japanese LED maker Nichia has initiated another patent infringement suit, this time against a Washington state hand tool company called Wilmar Corporation (Wilmar).
The complaint (nichia-wilmar-complaint.pdf), filed in the Eastern District of Texas in Marshall, accuses Wilmar of infringing U.S. Patent Nos. 5,998,925 (’925 Patent), 7,531,960 (’960 Patent), 5,652,434 (’434 Patent) and 6,093,965 (’965 Patent).
The ‘925 and ‘960 Patents are members of the same patent family. The two related patents describe a light emitting diode (100) that minimizes deterioration in emission light intensity by including a phosphor in the coating resin (101) that covers the light emitting component (102).
According to the ‘925 Patent, incorporating a phosphor in the LED reduces deterioration:
the phosphor used in the light emitting device has excellent resistance against light so that the fluorescent properties thereof experience less change even when used over an extended period of time while being exposed to light of high intensity. This makes it possible to reduce the degradation of characteristics during long period of use and reduce deterioration due to light of high intensity emitted by the light emitting component . . . to provide a light emitting device which experiences less color shift and less luminance decrease.
The ‘434 and ‘965 Patents, entitled “Gallium nitride-based III-V group compound semiconductor,” are related patents in a different family.
The “III-V” in the title refers to those columns of the periodic table, and the full title means a nitride semiconductor of a Group III element containing gallium, such as GaN, GaAlN, InGaN or InAlGaN.
These patents are directed to an LED (10) having an electrically insulating substrate (11) and a layer (12) of an n-type gallium nitride-based III-V Group compound semiconductor on a surface (11a) of the substrate.
A layer (13) of a p-type gallium nitride-based III-V Group compound semiconductor is formed on the surface of the n-type semiconductor layer (12) (the “p” means that extra positive charge is added to the semiconductor; the “n” means extra negative charge is added).
A p-type electrode (15) covers the surface of the p-type semiconducting layer (13), which is partially etched away to partially expose the surface of the n-type semiconductor layer (12). An n-type electrode (14) is formed on the exposed surface portion of the n-type semiconductor layer (12).
The p-type electrode (15) is connected with a bonding wire (21) at a bonding pad (17) formed on a portion of the surface of the p-type electrode (15).
According to the ’434 and ‘965 Patents, prior gallium nitride-based III-V semiconductors suffered from conductivity problems.
They also required that light be observed on the side of the substrate, opposite the side of the semiconductor layers, which led to large chip sizes.
According to the ’434 and ‘965 patents, the patented structure is a major improvement for this type of LED and alleviates these problems.
Nichia’s complaint doesn’t name any specific accused products, but Wilmar makes headlamps and flashlights that incorporate LED lighting.
Nichia has aggressively asserted its LED patents in recent years, including in a global patent war against Korean rival Seoul Semiconductor that the parties settled last year.
Eric Lane is a patent attorney at Luce, Forward, Hamilton & Scripps in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at elane@luce.com.
