Opinion for the court by Ciruict Judge DYK. Dissenting opinion filed by Circuit Judge NEWAN.
DYK, Circuit Judge.
Appellant Sinorgchem Co., Shandong (“Sinorgchem”) appeals from a limited exclusion order of the International Trade Commission (“ITC”) based on a finding that Sinorgchem infringed four method claims of U.S. Patents 5,117,063 (“the '063 patent”) and 5,608,111 (“the '111 patent”) owned by intervenor Flexsys America L.P. (“Flexsys”). In re Certain Rubber Antide-gradants, Components Thereof, and Products Containing Same, No. 337-TA-533 (I.T.C. July 13, 2006) (commission opinion). Because the ITC’s determination of infringement was based on an erroneous construction of the term “controlled amount” in the claims at issue, and under the correct construction Sinorgchem does not literally infringe, we vacate and remand.
BACKGROUND
Sinorgchem produces in China and sells for importation to the United States a compound known as 6PPD, a rubber anti-degradant that counters the deteriorative effect of various environmental factors on tires. 6PPD is made from an intermediate compound, 4-aminodiphenylamine, or 4-ADPA, which Sinorgchem also makes in China. In turn, Sinorgchem makes the intermediates of 4-ADPA using a process that reacts aniline and nitrobenzene. In that reaction, aniline is a solvent, tetrame-thylammonium hydroxide (“TMAH”) is a base, and water is a protic material. The term “protic material” refers to proton donors. The amount of water used in the condensation reaction of nitrobenzene with [1134]*1134aniline is at least 10 to 15% water throughout the reaction.
The issue is whether Sinorgehem’s method for producing 6PPD and 4-ADPA infringes the asserted method claims of the '063 and '111 patents, owned by Flex-sys. The '111 patent issued from a continuation-in-part application to the application that led to the '063 patent and is subject to a terminal disclaimer based on the earlier filed '063 patent. The specification of the '111 patent includes additional Examples 13 through 21 but is otherwise substantially identical to the '063 patent specification. The parties agree that the term “controlled amount” in both patents should receive the same construction.
At issue are independent claims 30 and 61 of the '063 patent and claims 7 and 11 of the '111 patent. These claims describe methods for producing 4-ADPA and 6PPD. Claim 61 of the '063 patent is representative:
61. A method of producing alkylated p-phenylenediamines [6PPD] comprising the steps of:
a) bringing aniline and nitrobenzene into reactive contact in a suitable solvent system;
b) reacting the aniline and nitroben-zene in a confined zone at a suitable temperature, and in the presence of a suitable base and controlled amount of protic material to produce one or more 4-ADPA intermediates;
e) reducing the 4-ADPA intermediates to produce 4-ADPA; and
d) reductively alkylating the 4-ADPA of Step c) [which produces 6PPD],
'063 patent col.15 11.34-46. The central question is whether Sinorgehem’s method of producing 4-ADPA intermediates satisfies the claim limitations of step (b). There is no dispute that Sinorgchem utilizes steps (a), (c), and (d). The ITC and the private parties particularly focus on a portion of the specification that states: “A ‘controlled amount’ of protic material is an amount up to that which inhibits the reaction of aniline with nitrobenzene, e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.” Id. at col.4 11.48-52.
On February 23, 2005, Flexsys filed a complaint with the ITC alleging, among other things, that Sinorgchem was infringing claims 30 or 61 of the '063 patent or claims 7 or 11 of the '111 patent, and had violated subsection (a)(1)(B) of section 337 of the Tariff Act of 1930, which makes unlawful the importation of articles that either infringe a valid U.S. patent or are produced by a process covered by the claims of a valid U.S. patent. 19 U.S.C. § 1337(a)(1)(B) (2000). The administrative law judge (“ALJ”) issued a final initial determination (“final ID”) on February 17, 2006, holding that Sinorgchem had infringed the claims and violated section 337. In re Certain Rubber Antidegradants, No. 337-TA-533 (I.T.C. Feb. 17, 2006) (final initial and recommended determinations).
Central to the dispute before the ALJ was the claim construction of the term “controlled amount of protic material” found in each of the asserted independent claims. Sinorgchem urged the ALJ to adopt a construction of “controlled amount of protic material” as “up to about 4% water in the reaction mixture when aniline is the solvent.” J.A. at 108-09. Under this construction, Sinorgchem does not infringe because its process uses more than 4% water.
Flexsys argued that “controlled amount” meant “that the amount of protic material should be controlled between an upper limit and a lower limit,” where the upper limit was “that amount beyond which the reaction between nitrobenzene and aniline is inhibited,” and the lower limit was “that [1135]*1135amount below which the desired selectivity for 4-ADPA intermediates is not maintained.” J.A. at 108. Under Flexsys’s claim construction, the Sinorgchem process would infringe.
The ALJ rejected Sinorgchem’s construction and adopted Flexsys’s construction of the term “controlled amount.” Based on this construction, the ALJ concluded that (1) Sinorgchem’s processes for making 4-ADPA and 6PPD literally infringed the asserted claims, (2) the claims as construed were not invalid as indefinite, and (3) the claims were not invalid as obvious in view of the prior art.
On appeal, the ITC rejected the construction of “controlled amount” urged by Flexsys and adopted by the ALJ. It found that the patentee in the specification had acted as his own lexicographer and expressly defined the meaning of “controlled amount” of protic material as “an amount up to that which inhibits the reaction of aniline with nitrobenzene.” J.A. at 227. However, it excluded from that construction the second clause of the sentence, which stated “e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.” The ITC read the 4% water limit as inconsistent with other general language found in the same paragraph (quoted below), which the ITC interpreted as teaching that the amount of protic material can change based on other reaction conditions, even where aniline is used as the solvent. Similarly, the ITC read the 4% limit as inconsistent with the reaction in Example 10, where a calculated 10% water level was utilized.
The ITC construed “controlled amount” as specifying an upper limit determined by when protic material “inhibits the reaction of aniline with nitrobenzene.” J.A. at 227. The ITC found that “inhibits” meant inhibits “to the extent where the reaction is no longer significant,” J.A. at 232, and that “significant” in turn meant that the “minimum acceptable conversion rate would be more than 12% but less than 63%,” J.A. at 233-34. In determining what was “significant,” the ITC looked to Example 8 for the conversion rate of nitrobenzene at which a reaction would be considered significant.
Free access — add to your briefcase to read the full text and ask questions with AI
Opinion for the court by Ciruict Judge DYK. Dissenting opinion filed by Circuit Judge NEWAN.
DYK, Circuit Judge.
Appellant Sinorgchem Co., Shandong (“Sinorgchem”) appeals from a limited exclusion order of the International Trade Commission (“ITC”) based on a finding that Sinorgchem infringed four method claims of U.S. Patents 5,117,063 (“the '063 patent”) and 5,608,111 (“the '111 patent”) owned by intervenor Flexsys America L.P. (“Flexsys”). In re Certain Rubber Antide-gradants, Components Thereof, and Products Containing Same, No. 337-TA-533 (I.T.C. July 13, 2006) (commission opinion). Because the ITC’s determination of infringement was based on an erroneous construction of the term “controlled amount” in the claims at issue, and under the correct construction Sinorgchem does not literally infringe, we vacate and remand.
BACKGROUND
Sinorgchem produces in China and sells for importation to the United States a compound known as 6PPD, a rubber anti-degradant that counters the deteriorative effect of various environmental factors on tires. 6PPD is made from an intermediate compound, 4-aminodiphenylamine, or 4-ADPA, which Sinorgchem also makes in China. In turn, Sinorgchem makes the intermediates of 4-ADPA using a process that reacts aniline and nitrobenzene. In that reaction, aniline is a solvent, tetrame-thylammonium hydroxide (“TMAH”) is a base, and water is a protic material. The term “protic material” refers to proton donors. The amount of water used in the condensation reaction of nitrobenzene with [1134]*1134aniline is at least 10 to 15% water throughout the reaction.
The issue is whether Sinorgehem’s method for producing 6PPD and 4-ADPA infringes the asserted method claims of the '063 and '111 patents, owned by Flex-sys. The '111 patent issued from a continuation-in-part application to the application that led to the '063 patent and is subject to a terminal disclaimer based on the earlier filed '063 patent. The specification of the '111 patent includes additional Examples 13 through 21 but is otherwise substantially identical to the '063 patent specification. The parties agree that the term “controlled amount” in both patents should receive the same construction.
At issue are independent claims 30 and 61 of the '063 patent and claims 7 and 11 of the '111 patent. These claims describe methods for producing 4-ADPA and 6PPD. Claim 61 of the '063 patent is representative:
61. A method of producing alkylated p-phenylenediamines [6PPD] comprising the steps of:
a) bringing aniline and nitrobenzene into reactive contact in a suitable solvent system;
b) reacting the aniline and nitroben-zene in a confined zone at a suitable temperature, and in the presence of a suitable base and controlled amount of protic material to produce one or more 4-ADPA intermediates;
e) reducing the 4-ADPA intermediates to produce 4-ADPA; and
d) reductively alkylating the 4-ADPA of Step c) [which produces 6PPD],
'063 patent col.15 11.34-46. The central question is whether Sinorgehem’s method of producing 4-ADPA intermediates satisfies the claim limitations of step (b). There is no dispute that Sinorgchem utilizes steps (a), (c), and (d). The ITC and the private parties particularly focus on a portion of the specification that states: “A ‘controlled amount’ of protic material is an amount up to that which inhibits the reaction of aniline with nitrobenzene, e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.” Id. at col.4 11.48-52.
On February 23, 2005, Flexsys filed a complaint with the ITC alleging, among other things, that Sinorgchem was infringing claims 30 or 61 of the '063 patent or claims 7 or 11 of the '111 patent, and had violated subsection (a)(1)(B) of section 337 of the Tariff Act of 1930, which makes unlawful the importation of articles that either infringe a valid U.S. patent or are produced by a process covered by the claims of a valid U.S. patent. 19 U.S.C. § 1337(a)(1)(B) (2000). The administrative law judge (“ALJ”) issued a final initial determination (“final ID”) on February 17, 2006, holding that Sinorgchem had infringed the claims and violated section 337. In re Certain Rubber Antidegradants, No. 337-TA-533 (I.T.C. Feb. 17, 2006) (final initial and recommended determinations).
Central to the dispute before the ALJ was the claim construction of the term “controlled amount of protic material” found in each of the asserted independent claims. Sinorgchem urged the ALJ to adopt a construction of “controlled amount of protic material” as “up to about 4% water in the reaction mixture when aniline is the solvent.” J.A. at 108-09. Under this construction, Sinorgchem does not infringe because its process uses more than 4% water.
Flexsys argued that “controlled amount” meant “that the amount of protic material should be controlled between an upper limit and a lower limit,” where the upper limit was “that amount beyond which the reaction between nitrobenzene and aniline is inhibited,” and the lower limit was “that [1135]*1135amount below which the desired selectivity for 4-ADPA intermediates is not maintained.” J.A. at 108. Under Flexsys’s claim construction, the Sinorgchem process would infringe.
The ALJ rejected Sinorgchem’s construction and adopted Flexsys’s construction of the term “controlled amount.” Based on this construction, the ALJ concluded that (1) Sinorgchem’s processes for making 4-ADPA and 6PPD literally infringed the asserted claims, (2) the claims as construed were not invalid as indefinite, and (3) the claims were not invalid as obvious in view of the prior art.
On appeal, the ITC rejected the construction of “controlled amount” urged by Flexsys and adopted by the ALJ. It found that the patentee in the specification had acted as his own lexicographer and expressly defined the meaning of “controlled amount” of protic material as “an amount up to that which inhibits the reaction of aniline with nitrobenzene.” J.A. at 227. However, it excluded from that construction the second clause of the sentence, which stated “e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.” The ITC read the 4% water limit as inconsistent with other general language found in the same paragraph (quoted below), which the ITC interpreted as teaching that the amount of protic material can change based on other reaction conditions, even where aniline is used as the solvent. Similarly, the ITC read the 4% limit as inconsistent with the reaction in Example 10, where a calculated 10% water level was utilized.
The ITC construed “controlled amount” as specifying an upper limit determined by when protic material “inhibits the reaction of aniline with nitrobenzene.” J.A. at 227. The ITC found that “inhibits” meant inhibits “to the extent where the reaction is no longer significant,” J.A. at 232, and that “significant” in turn meant that the “minimum acceptable conversion rate would be more than 12% but less than 63%,” J.A. at 233-34. In determining what was “significant,” the ITC looked to Example 8 for the conversion rate of nitrobenzene at which a reaction would be considered significant. It found that when DMSO was the solvent, the conversion rate of nitrobenzene drops from 63 to 12% when the amount of water increases from 6 to 9.75%. Sinorgchem’s process, the ITC determined, yields a conversion rate of around 85%. Under this new construction of the disputed term “controlled amount,” the ITC likewise found infringement.
The ITC next concluded that the claims as construed were not invalid as indefinite. Although the ITC rejected the 4% water limit, it found that “controlled amount” was not indefinite since an upper limit— where the amount of protic material yields an acceptable conversion rate between 12 and 63% — could be found in the specification. Given this definition of “controlled amount,” the ITC rejected Sinorgchem’s argument that the claims were indefinite.
As to obviousness, the ITC held that while the asserted prior art — a 1903 German article published by Wohl (the “Wohl” reference) — disclosed the reaction of aniline with nitrobenzene, the formation of a small amount of intermediate, and the presence of water as a protic material, it failed to disclose or teach “whether or how water or any other protic material affects the conversion of nitrobenzene.” J.A. at 245.
Sinorgchem timely appealed the ITC’s decision to our court. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(6).
DISCUSSION
I
The main issue on appeal is the meaning of the claim term “controlled amount.” [1136]*1136The parties here agree that “controlled amount” does not have any well-accepted meaning in the field of chemistry. Si-norgchem contends that the ITC misconstrued the term “controlled amount” and on that basis erred in finding infringement. Claim construction is a question of law which we review de novo. Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448, 1456 (Fed.Cir.1998) (en banc).
Our opinions have repeatedly encouraged claim drafters who choose to act as their own lexicographers to clearly define terms used in the claims in the specification. See, e.g., CCS Fitness, Inc. v. Brunswick Corp., 288 F.3d 1359, 1366 (Fed.Cir.2002) (“[A] claim term will not receive its ordinary meaning if the patentee acted as his own lexicographer and clearly set forth a definition of the disputed claim term in ... the specification.... ”); Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed.Cir.1996) (“The specification acts as a dictionary when it expressly defines terms used in the claims or when it defines terms by implication.”).
The approach of those cases was endorsed in Phillips v. AWH Corp., 415 F.3d 1303, 1316 (Fed.Cir.2005) (en banc). In Phillips, we described the specification as “the single best guide to the meaning of a disputed term.” Id. at 1315 (citing Vitronics, 90 F.3d at 1582). We confirmed that “our cases recognize that the specification may reveal a special definition given to a claim term by the patentee that differs from the meaning it would otherwise possess. In such cases, the inventor’s lexicography governs.” Id. at 1316.
Here, the drafters have done just that. The specification states:
A “controlled amount” of protic material is an amount up to that which inhibits the reaction of aniline with nitrobenzene, e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.
'063 patent col.4 11.48-52. The term “controlled amount” is set off by quotation marks — often a strong indication that what follows is a definition. See, e.g., Cultor Corp. v. A.E. Staley Mfg. Co., 224 F.3d 1328, 1331 (Fed.Cir.2000) (finding that the claim term “water-soluble polydextrose” was expressly defined in the specification). Moreover, the word “is,” again a term used here in the specification, may “signify that a patentee is serving as its own lexicographer.” Abbott Labs. v. Andrx Pharms., Inc., 473 F.3d 1196, 1210 (Fed.Cir.2007). As such, the patentee must be bound by the express definition. See Durel Corp. v. Osram Sylvania Inc., 256 F.3d 1298, 1303-04 (Fed.Cir.2001). Here the drafter clearly, deliberately, and precisely defined the term “controlled amount” of protic material as “an amount up to that which inhibits the reaction of aniline with nitrobenzene, e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.” 1 Elsewhere in the same paragraph, the specification again refers to the 4% limit.2
[1137]*1137The ITC agreed that the patentee had expressly defined the term “controlled amount” in the specification but held that the language “e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent” should not be considered part of that definition for two reasons. Neither of these reasons is persuasive. First, the ITC dismissed the 4% limit as merely an example that did not apply to all situations in which aniline was used as the solvent. The ITC relied particularly on the emphasized language in the following passage:
When aniline is utilized as a solvent with the same base [TMAH], the upper limit is 4% H20 based on the volume of the reaction mixture. In addition, the amount of protic material tolerated will vary with type of base, amount of base, and base cation, used in the various solvent systems. However, it is within the skill of one in the art, utilizing the teachings of the present invention, to determine the specific upper limit of the amount of protic material for a specific solvent, type and amount of base, base cation and the like.
'063 patent col.4 11.58-68 (emphasis added). The ITC found that this language made clear that the “e.g., up to about 4% H20” language was used in the specification as an example and not a definition of the amount of water permitted when aniline is the solvent.3
[1138]*1138We disagree. This vague language cannot override the express definitional language. We have frequently found that a definition set forth in the specification governs the meaning of the claims. See, e.g., Cultor Corp., 224 F.3d at 1330. “When the specification explains and defines a term used in the claims, without ambiguity or incompleteness, there is no need to search further for the meaning of the term.” Multiform Desiccants, Inc. v. Medzam, Ltd., 133 F.3d 1473, 1478 (Fed.Cir.1998). When aniline is used as the solvent, the express definition is neither ambiguous nor incomplete — the “controlled amount” is “up to about 4% H20 based on the volume of the reaction mixture” — and we need look no further for its meaning. Nor is the specification passage relied on by the ITC inconsistent with the express definition of “controlled amount,” since the passage refers generally to at least six different solvents while the definition refers specifically to reactions in which aniline is the solvent. Moreover, the specification sets forth a different limit of “about 8% water” for the “controlled amount” of protic material when DMSO is the solvent. Quite tellingly, aniline and DMSO were the only two solvents of the six solvents mentioned in the specification for which an express numerical limit was given for the “controlled amount.” The quoted “will vary” language appears to refer to the four other solvents for which a specific percentage was not provided.
Second, the ITC found that the 4% language was inconsistent with Example 10 (which appears identically in both the '063 and the '111 patents), a “preferred embodiment,” which uses more than 10% water in a reaction where aniline is the solvent. Despite the high level of water used in Example 10, the reaction yields a high percentage (92.8%) of 4-ADPA intermediates. On appeal, both the ITC and Flex-sys support the ITC’s decision by relying on statements in our case law that we do “not normally interpret a claim term to exclude a preferred embodiment,” Primos, Inc., v. Hunter’s Specialties, Inc., 451 F.3d 841, 848 (Fed.Cir.2006), as would be the case if the 4% limit were applied to the claims. This rule has particular force where the claims as construed do not encompass any disclosed embodiments. See Johns Hopkins Univ. v. CellPro, Inc., 152 F.3d 1342, 1355 (Fed.Cir.1998) (“A patent claim should be construed to encompass at least one disclosed embodiment in the written description portion of the patent specification.”) (emphasis added). This is not the case here. Example 10 is merely one of twenty-one distinct examples set out in the two specifications, all of which are described as “preferred embodiments].” 'Ill patent col.8 11.5-8.
Where, as here, multiple embodiments are disclosed, we have previously interpreted claims to exclude embodiments where those embodiments are inconsistent with unambiguous language in the patent’s specification or prosecution history. Telemac Cellular Corp. v. Topp Telecom, Inc., 247 F.3d 1316, 1326 (Fed.Cir.2001); see also N. Am. Container, Inc. v. Plastipak Packaging, Inc., 415 F.3d 1335 (Fed.Cir.2005). In Telemac, the district court looked to the specification to determine the meaning of the claim term “communication means,” since that term was written in the claim in “means-plus-function” form. 247 F.3d at 1324. Telemac challenged the district court’s construction on the basis that it left certain embodiments inoperable. Id. at 1326. We held that the description of those embodiments did not call for a different construction. Id. Instead, we held that those embodiments “could not provide the structure or equivalent structure for performing the claimed function” and were therefore outside of the scope of the claims. Id. See also Rheox, Inc. v. [1139]*1139Entact, Inc., 276 F.3d 1319, 1327 (Fed.Cir.2002) (“where the prosecution history requires a claim construction that excludes some but not all of the preferred embodiments, such a construction is permissible”) (emphasis added).
It is moreover significant that Example 10 does not specifically disclose the amount of water used in the reaction. Instead, the amount of water used in that reaction can only be determined by a complex calculation.4 In stark contrast, the patentees in Tables 2 and 6, accompanying Examples 3 and 8 respectively, specifically disclose the amount of water used in those reactions. '063 patent col.9 11.32^18, col.ll 11.25-33. In Example 3, for example, the amount of water added to the reaction where aniline is the solvent ranges from 2.2 to 4.7%, and illustrates the effect of water on the yield of 4-NDPA and p-NDPA. Table 2 shows that the yield dropped from 0.18 mmole to 0.05 mmole, an unacceptably low level, as the amount of water added was increased from 3.45 to 4.7%. Similarly, Example 8 illustrates the effect of the amount of water added to a reaction where DMSO is the solvent. Water added there ranged from 2.3 to 14.7%, and again shows that the yield dropped to an unacceptably low level when more than 8% water is added. Significantly, Example 10 is not even directed toward illustrating the control of the amount of protic material to be used in the reaction. Rather, its stated purpose is to illustrate “the reaction of aniline, nitrobenzene and tet-ramethylammonium hydroxide dihydrate under anaerobic conditions at 50°C.” '063 patent col. 11 11.61-63. Examples 3 and 8, on the other hand, are explicitly directed toward the control of the amount of protic material:
“[Example 3] illustrates that control of the amount of protic material present in the reaction is important.”
“[Example 8] illustrates the effect that the amount of protic material present in or added to the reaction has on the extent of conversion and yields of 4-NDPA and p-NDPA.”
Id. at col.9 11.20-21, col.ll 11.10-13. Under these circumstances, the fact that the calculated amount of water in Example 10 exceeds 4% where aniline is used as the solvent is entitled to little weight, and cannot override the clear definitional language set forth in the specification.5
Flexsys further argues that the doctrine of claim differentiation supports the ITC’s refusal to read into the claims the 4% water limit. We have characterized the doctrine of claim differentiation generally as the “presumption that each claim in a patent has a different scope.” Curtiss-Wright Flow Control Corp. v. Velan, Inc., 438 F.3d 1374, 1380 (Fed.Cir.2006) (internal citation omitted). Flexsys points out [1140]*1140that independent claim 30 of the '063 patent does not specify a numerical limit for “controlled amount of protic material,” while dependent claim 41 recites “up to about 4 v/v % water.”6 Claim 30 states:
30. A method of producing 4-aminodi-phenylamine (4-ADPA) comprising the steps of:
a) bringing aniline and nitrobenzene into reactive contact in a suitable solvent system;
b) reacting the aniline and nitroben-zene in a confined zone at a suitable temperature, and in the presence of a suitable base and controlled amount of protic material to produce one or more 4-ADPA intermediates; and
c) reducing the 4-ADPA intermediates under conditions which produce 4-ADPA.
'063 patent col.14 11.16-26 (emphases added). Claim 41 states:
Method of claim 30 wherein said solvent system includes aniline and up to about Ip v/v % water based on the total volume of the reaction mixture.
Id. at col. 14 11.50-52 (emphasis added).
Thus, according to Flexsys, interpreting “controlled amount” in claim 30 to have an upper limit of “e.g., up to about 4% H20 ... when aniline is utilized as the solvent” would render the scope of the independent claim and the dependent claim identical. Flexsys’s argument might have some merit if claim 30 referred only to aniline solvents. But it does not. Claim 30 refers generally to “a suitable solvent system,” which, as the specification indicates, can include “dimethylformamide, aniline, pyridine, nitrobenzene, nonpolar hydrocarbon solvents such as toluene and hexane, ethy-leneglycol dimethyl ether, diisopropyl ethylamine, and the like, as well as mixtures thereof.” 'Ill patent col.4 11.24-27. Because claim 41 refers merely to a subset of the solvent systems described in claim 30, and is significantly narrower in scope, the claims are not rendered identical and present no claim differentiation problem. Therefore, Flexsys’s claim differentiation argument is without merit.
For these reasons, we hold that the correct claim construction of the term “controlled amount” is that defined expressly in the specification, namely: “an amount up to that which inhibits the reaction of aniline with nitrobenzene, e.g., up to about 4% H20 based on the volume of the reaction mixture when aniline is utilized as the solvent.”
II
In light of the correct claim construction of “controlled amount” it is clear that there is no literal infringement. Based on the specification’s express definition of “controlled amount,” each asserted claim can only encompass processes that utilize at most 4% water when aniline is the solvent. There is no dispute that Sinorgchem always uses more than 4% water when it reacts aniline with nitrobenzene, and thus there can be no literal infringement of any
[1141]*1141of the asserted claims. Because the ITC found that Sinorgchem literally infringed Flexsys’s patents, it did not reach the question whether Sinorgchem’s process would infringe under the doctrine of equivalents. Although Flexsys argued below that under Sinorgchem’s construction of “controlled amount,” the Sinorgchem process would infringe under the doctrine of equivalents, J.A. at 236, neither Flexsys nor the ITC contends here that Sinorgch-em infringes under the doctrine of equivalents when the claims are construed to limit the controlled amount to 4% water when aniline is used as the solvent. On remand, the ITC should address the claim of doctrine of equivalents infringement in light of our holding that there was no literal infringement. See Exxon Chem. Patents, Inc. v. Lubrizol Corp., 137 F.3d 1475, 1479 (Fed.Cir.1998).
Ill
Sinorgchem also argues that the asserted claims are invalid as indefinite and obvious. Under Cardinal Chemical, in an appeal from a district court action, once we have addressed infringement we generally must nonetheless address counterclaims of invalidity. See Cardinal Chem. Co. v. Morton Int’l, Inc., 508 U.S. 83, 113 S.Ct. 1967, 124 L.Ed.2d 1 (1993). Since the invalidity issues before the ITC were raised only as affirmative defenses, decisions on these issues would be necessary only if on remand there was a determination of doctrine of equivalents infringement. See MEMC Elec. Materials, Inc. v. Mitsubishi Materials Silicon Corp., 248 Fed.Appx. 199, 205, 2007 WL 2728376 at *5 (Fed.Cir.2007). Under these circumstances, we do not address the invalidity issues in this appeal.
CONCLUSION
For the foregoing reasons, the decision below is VACATED and REMANDED. No costs.