PPG Industries v. Guardian Industries Corp.
| Decision Date | 01 October 1998 |
| Docket Number | No. 97-1513,97-1513 |
| Citation | 48 USPQ2d 1351,156 F.3d 1351 |
| Parties | PPG INDUSTRIES, Plaintiff-Appellant, v. GUARDIAN INDUSTRIES CORP., Defendant-Appellee. |
| Court | U.S. Court of Appeals — Federal Circuit |
Ford F. Farabow, Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P., Washington, DC, argued, for plaintiff-appellant. With him on the brief were Donald R. Dunner, and Darrel C. Karl. Of counsel on the brief were Arland T. Stein and Robert A. Matthews, Jr., of Reed Smith Shaw & McClay, Pittsburgh, PA.
Robert G. Krupka, P.C., Kirkland & Ellis, Chicago, IL, argued, for defendant-appellee. With him on the brief were Jeffrey D. Mills, Jay I. Alexander and Gregg F. LoCascio, Washington, DC; and John M. Desmarais, New York City.
Before MICHEL, PLAGER, and BRYSON, Circuit Judges.
Opinion for the court filed by Circuit Judge BRYSON. Dissenting opinion filed by Circuit Judge MICHEL.
This case involves a type of glass composition known as "solar control glass," which is used to produce tinted automobile windows. PPG Industries, Inc., sued Guardian Industries Corp. in the United States District Court for the Western District of Pennsylvania, asserting that Guardian was infringing PPG's U.S. Patent No. 5,240,886 (the '886 patent) by marketing a type of solar control glass known as Solar Management Glass (SMG). After a ten-day trial, a jury concluded that SMG glass did not fall within the scope of the '886 patent claims. The district judge subsequently entered judgment on the verdict. On appeal, PPG argues that the district judge erred in construing the claims of PPG's patent and, alternatively, that substantial evidence did not support the jury's verdict of non-infringement. We affirm.
PPG and Guardian both manufacture green-tinted solar control glass. The glass filters out much of the ultraviolet and infrared radiation from the sun while maximizing the transmission of light in the visible spectrum. Infrared radiation transmits heat energy, and ultraviolet radiation can be damaging to materials. The capacity of solar control glass to block the transmission of sunlight at those wavelengths, while remaining largely transparent to visible light, makes the product particularly well suited for use in automobile windows.
Guardian began selling SMG glass in 1992. PPG's '886 patent issued on August 31, 1993. After licensing negotiations failed, PPG sued Guardian for infringing the patent.
The '886 patent is directed to a green-tinted glass with specific light transmittance characteristics. The patent contains one independent claim, which reads as follows:
1. A green tinted, ultraviolet absorbing glass having a base glass composition
consisting essentially of
SiO sub2 68"75 weight %
Na sub2 O 10"20
CaO 5"15
MgO 0"5
Al sub2 O sub3 0"5
K sub2 O 0"5
and a colorant portion consisting essentially of
CeO sub2 Less than 0.5 weight %
*Total iron Greater than 0.85 weight %
(as Fe sub2 O sub3 )
FeO/total iron Less than 0.275
exhibiting ultraviolet transmittance no greater than 31 percent (300 to 390 nanometers) and luminous transmittance (illuminant A) of at least 70 percent, both at a reference thickness of 3.9 millimeters.
Claim 4, the only claim asserted against Guardian at trial, adds an additional limitation that the glass must exhibit a total solar energy transmittance of less than 45 percent at a reference thickness of 3.9 millimeters.
The '886 patent identifies iron and cerium oxide as colorants. Iron may be present in either the ferrous (Fe2+) or ferric (Fe3+) states. Ferrous iron gives the glass a greenish tint and is an infrared radiation absorber. Ferric iron gives the glass a yellowish tint and acts to absorb ultraviolet radiation.
One of the advantages of the invention described by the '886 patent is that the glass requires only minimal amounts of cerium oxide to achieve the desired light transmittance properties. Cerium oxide is expensive and presents special difficulties in the manufacturing process. PPG's patent teaches that using relatively high concentrations of iron oxides as colorants and maintaining the glass composition at a low redox ratio (the ratio of ferrous iron to total iron) reduces or eliminates the need for cerium oxide in the glass. Guardian's SMG glass uses similarly high levels of iron oxide as a colorant and uses no cerium oxide.
PPG and Guardian use similar technologies to produce tinted glass. The glass is produced by the "float" process, which refers to the method of cooling the glass after it exits the furnace by floating it on a pool of molten tin. The tin provides an extremely flat surface for cooling the glass, so that sheets of glass can be produced at precise, uniform thicknesses.
Two features of the float process are particularly pertinent to the current dispute. The raw materials for the glass are typically added together in a furnace, where they are mixed and melted. As the various glass constituents melt, they release gas. That is potentially a problem because some of the gas may remain trapped in small bubbles in the glass. If the bubbles remain in the final product, they result in visible imperfections in the glass. To avoid that problem, various melting and fining aids are added to the glass mixture in the furnace. Sodium sulfate (Na sub2 SO sub4 ) is one such additive. In the mixture, much of the sulfate decomposes into sulfur dioxide and oxygen. Those gases cause the trapped gas bubbles to dissipate, leaving few visible imperfections in the glass. Some of the sulfate introduced into the batch remains dissolved in the glass composition, but it is colorless and has no effect on the transmittance properties of the glass.
The second pertinent feature of the process is the interaction between the glass and the pool of molten tin on which it floats after exiting the furnace. Both Guardian's SMG manufacturing process and PPG's patent specification require that the glass be produced at a low redox ratio, which means that the glass is produced under oxidizing conditions. Although the redox ratio is commonly reported for the glass as a whole, oxidation conditions are considerably different at the boundary of the glass and the molten tin. That interface zone experiences strong reducing conditions, resulting in a high redox ratio. Under those conditions, oxygen atoms are stripped away from the sulfate remaining in the glass, reducing it to sulfide ions (S2-). When the sulfide ions combine with ferric iron, the resulting compound (FeS subx ) imparts a yellowish-brown coloration to the glass. Testimony at trial indicated that iron sulfide formation could be observed to a depth of about 20 microns from the glass surface contacting the molten tin. That narrow band is commonly referred to as the "tin layer" of the glass.
At the inception of this suit, the chemistry of the tin layer was not an issue. PPG sought a preliminary injunction and Guardian defended on the ground that SMG glass contained iron sulfide, an ingredient unlisted in PPG's patent, as a colorant. The district judge credited testimony from PPG's experts that iron sulfide could not form in Guardian's glass because of the low redox ratio at which the glass was produced. As a result, the district judge rejected Guardian's "sulfide defense" and granted a preliminary injunction. On appeal, this court affirmed. See PPG Indus., Inc. v. Guardian Indus. Corp., 75 F.3d 1558, 1565, 37 U.S.P.Q.2d 1618, 1624 (Fed.Cir.1996).
By the time of trial, Guardian had refined its non-infringement position. While Guardian still claimed that the presence of iron sulfide differentiated SMG glass from PPG's patent, Guardian now identified the primary source of the iron sulfide as the tin layer of the SMG glass. Witnesses for each side agreed that the iron sulfide in the tin layer of the SMG glass resulted in a 0.5% change in total light transmittance and a small change in color, measured by a 3 nanometer shift in the dominant wavelength of the light transmitted by the glass. PPG argued that the small changes in the properties of the glass attributable to the iron sulfide in the tin layer did not avoid infringement of the claims of the '886 patent. PPG also contended that the iron sulfide in the tin layer was an inherent by-product of the float glass manufacturing process used by both Guardian and PPG. The jury, however, returned a verdict in Guardian's favor, finding that the SMG glass did not infringe the '886 patent. In view of its infringement verdict, the jury did not reach the merits of Guardian's invalidity defense. PPG appealed the denial of its motions for judgment as a matter of law and for a new trial.
PPG contends that the district judge improperly construed the term "consisting essentially of" in the '886 patent and that the jury verdict must be vacated because it was based on an incorrect claim construction. "Consisting essentially of" is a transition phrase commonly used to signal a partially open claim in a patent. Typically, "consisting essentially of" precedes a list of ingredients in a composition claim or a series of steps in a process claim. By using the term "consisting essentially of," the drafter signals that the invention necessarily includes the listed ingredients and is open to unlisted ingredients that do not materially affect the basic and novel properties of the invention. A "consisting essentially of" claim occupies a middle ground between closed claims that are written in a "consisting of" format and fully open claims that are drafted in a "comprising" format. See Ex parte Davis, 80 U.S.P.Q. 448, 449-50, 1949 WL...
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