Polaroid Corp. v. Eastman Kodak Co.

MEMORANDUM OF DECISION

Polaroid Corporation, the assignee of numerous patents in the field of instant photography, brought this action against Eastman Kodak Company for infringement of twelve of its patents relating to the art/technology of both film and camera. Kodak denied infringement and alleged that all of the patents are invalid or unenforceable or both.

One of the film patents, U.S. Patent No. 3,761,269, this Court, on Kodak’s motion for summary judgment, held invalid as obvious within the meaning of 35 U.S.C. § 103. The parties waived their claims of infringement and invalidity with respect to a second patent, U.S. Patent No. 3,757,657, alleged to have been infringed by certain features of Kodak’s EK-4 camera. Trial proceeded with respect to the remaining ten patents 1 on the issues of liability and infringement, on one hand, and invalidity and/or unenforceability on the other. This memorandum shall constitute my findings of fact and conclusions of law as to those issues. 2

I. Background.

In conventional photography, as opposed to instant photography, a picture begins as a sheet of plastic or paper coated with a thin layer of gel which has in it a suspension of microscopic crystals of silver halide. When that coating is exposed through the lens of the camera, the silver halide grains are modified to form an invisible image— the latent image. Exactly how the latent image is formed is apparently still subject to debate, but it involves the transformation of the silver halide into concentrations of minute, reduced silver particles depending upon the intensity of light on various portions of the film.

To make the latent image visible, the film is placed into a developer — a reducing agent. The developer delivers electrons to the concentration of silver halide grains that form the latent image and further transforms them into metallic silver. Because the developer will continue to deliver electrons to the silver halide; ultimately reducing all to silver, the process must be stopped after a period of time when the latent image has become optimally visible. This is accomplished by briefly immersing the film in a dilutable acid bath. Because exposure of the film to light would wipe out the latent image, developing must be accomplished in a dark room.

Following development, the film is put into a solvent for silver halide — hypo— *830 which converts the remaining silver halide crystals into soluble silver salts and removes them by dissolving them. Since all of these chemicals would in time adversely affect the quality of the image, the film finally is thoroughly washed in water and dried, leaving a permanent negative image.

The negative image is formed where light converted the silver halide into metallic silver, which is seen as black. The more light reaches a particular area, the denser the concentration of silver and the darker the image in that area. The brightnesses on the negative are thus totally reversed. To produce a positive, the process just described is repeated. The negative is projected onto sensitive paper carrying a silver halide emulsion either through an enlarger or by pressing the negative directly against the positive. The positive is then processed in essentially the same manner as was the original film.

Edwin H. Land, the founder of Polaroid and the inventor of numerous patents, including several of those in suit, began work on what he came to call “one-step photography” in 1944. In 1947, he first introduced his version of the diffusion-transfer process by which the negative and positive were produced simultaneously. The film which will become the negative was exposed in the same manner as in conventional photography. The steps thereafter differed radically from those described above. The negative is brought into juxtaposition with a positive sheet within the camera and a viscous reagent contained in a sealed pod on one of the sheets is spread between them by means of two rollers. The positive and negative, which are symmetrical, are developed at the same time. After a defined period of time, the sandwich, positive and negative with reagent in-between, is pulled out of the camera and peeled apart. The camera also serves as the darkroom. Later, in the SX-70 system, the sandwich itself becomes the dark room.

One-step photography, as first marketed in December 1948, produced a sepia colored photograph. That was replaced by black and white peel-apart film in the early 1950s. At the same time that these sepia and black and white films and cameras were being developed and improved, Land and his associates addressed the problem of instant color photography.

Color photography requires three negative layers, each sensitive to a different primary color — blue, green or red. Complimentary dye layers — yellow, magenta and cyan, the subtractive colors positioned between the sensitive layers — absorb the primary color to be recorded on each sensitive layer. Thus, the blue sensitive layer controls the yellow dye layer next to it, which absorbs blue light; magenta absorbs green; and cyan, red. The dye layers are therefore sometimes called minus blue, minus green, and minus red. In conventional color photography, each sensitive layer contains a “coupler” and the dye layer a “color developer” which, by a reduction-oxidation process, will join together and form a dye. After exposure, the color developer is oxidized — it gives up electrons to the sensitive layer where the latter has been catalyzed by light. The silver halide layer is reduced — it gains electrons, enabling the col- or developer and silver halide to join. Each color uses a different coupler and the coupling process takes place within each layer. There is no transfer to different layers. Moreover, the reaction time of each coupler is different. Instant photography relies on a diffusion transfer process in which the reagents that form the negative image at the same time operate to form the positive. Coupler chemistry did not easily adapt to diffusion transfer.

At Dr. Land’s direction, Howard G. Rogers, starting in 1947, began work on the problem of instant color film. The solution he evolved discarded couplers and relied instead on dye developers, a combination of preformed dye and developer, and led eventually to one of the patents in suit, U.S. Patent No. 3,245,789. By 1957, Polaroid had made a prototype of the first one-step color photograph, and in 1963 it introduced instant color to the market under the name Polacolor, a peel-apart product.

*831 Further work on both film and camera led to the introduction of the SX-70 system in 1972, described by Dr. Land as “absolute one-step photography.” It is an elegant, highly sophisticated camera and film system. The photographic unit, which is ejected from the camera immediately after exposure, develops into a visible image in daylight and requires no peeling. The camera designed for the particular needs of this film unit contains a motor, gear train, and pick which, working together, operate to eject the film unit. The photographer needs to do nothing but focus the camera and expose the film to obtain a finished print.

Except for the ’789 dye developer patent mentioned above and the 165/262 opacifying layer patents to Rogers, all of the patents in suit pertain to innovations incorporated into the SX-70 system.

From the early 1950s, Kodak had supplied Polaroid’s needs for negative material. After Polaroid’s development of the one-step color photograph, the parties, in December 1957, entered into an agreement pursuant to which Polaroid disclosed to Kodak certain of its color technology, including Rogers’ concept of dye developers, and Kodak cooperated with Polaroid to develop and produce negative material adapted to this technology. Kodak then continued to supply Polaroid’s requirements for negative material and the parties periodically met to discuss their research activities. About 1963, the research meetings terminated, although Polaroid continued to work on refinements and improvements in color and continued to inform Kodak of its progress from time to time. In April 1968, Polaroid advised Kodak of a radically new film, which would ultimately become the SX-70, and in October of that year, Dr. Land showed Henry C. Yutzy, Kodak's vice president of research, photographs made with the new method. The parties discussed a licensing and continuing supply arrangement, without coming to any resolution. In April 1969, Kodak notified Polaroid of its intention to terminate the 1957 agreement.

, In early 1969, Kodak also launched its project PL-976 — an effort to put an instant product on the market by 1976. The object was to produce a high quality color print in the camera which preferably would not require peeling and to do so without the assistance of existing patents. PL-976, then optimistically redesignated PL-974 (moving back to 1974 the projected market date) investigated a variety of photographic chemistries. During 1970, groups at Kodak outside the research laboratory became more interested and the project was once again renamed and restructured. Project P-129 was begun to develop an instant color film similar to Polacolor and compatible with Polaroid cameras. P-130 was to produce an integrated system — Kodak film for a Kodak camera. The former, P-129, was abandoned toward the end of 1972 after an expenditure of 94 million dollars. Although the stated reason was that Kodak had been unable to solve certain problems caused by the particular chemistry used, the cessation of work on P-129 followed shortly upon the introduction by Polaroid of its SX-70. Contemporaneous Kodak memoranda recognized that any product created by P-129 would be obsolete even if it appeared on schedule.

The P-130 effort continued with increasing intensity. Because Kodak sought to attain its objectives — camera and film— simultaneously, not sequentially, the expenditures of manpower and money were enormous. Between 1,300 and 1,400 people were assigned to P-130 at the peak period — late 1973 to mid-1975. Dr. Albert Sieg, Director of Photographic Strategic Planning, described the approach taken by Kodak. The different groups assigned to solve various discrete problems were to explore the existing technology and pursue parallel work on different applicable technologies. When no technology existed to solve a particular problem, invention was called for. That, in turn, required increased funding and increased resources. Despite these efforts, numerous problems defied solution.

*832 By the early part of 1972, Kodak had developed the “Lanyard” camera model, so called because the picture was to be ejected by use of a lanyard. It advanced the film by means of front picks. It did not contain a motor nor a gear train but did include devices to strip the pod from the photograph and to trim its edges. Although, as a consequence, the camera was relatively large, Kodak’s marketing people were content with its size. Following Polaroid’s SX-70 announcement in April 1972, and review by the P-130 committee of its implications, the committee found that the “P-130 program as earlier defined, was no longer desirable.” The Lanyard camera was too large by comparison to that marketed by Polaroid.

Kodak also encountered numerous difficulties in its attempt to develop the film. Like Polaroid, it had to work out the imaging chemistry of integral film. By the fall of 1971 Kodak researchers had focussed on two dye release chemistries but did not achieve sufficient speed with either one of them until late 1972. By mid-April 1972, Kodak researchers had still not worked out a solution to the problem of dye stability and they had yet to solve problems associated with the mordant and the opacification layers. Although they hoped to achieve a “no-inventions” prototype by January 1973, a host of difficulties remained as late as mid-December 1972.

It is undisputed that Kodak purchased large quantities of SX-70 cameras and film in October 1972, after they became commercially available. It is also undisputed that the several groups and departments involved in P-130 were ordered to familiarize themselves with the Polaroid product and to test it. As a result, Kodak’s marketing coordinators and managers commented in January 1973 that the P-130 program, as it then existed, was only “marginally acceptable.” They recognized that Polaroid had set the standard Kodak would have to meet and that even a “me-too” program would require more than two and one-half years to produce a less than equal design.

Kodak did, in fact, introduce an integral system consisting of its EK-4 and EK-6 cameras and PR-10 film in April 1976. It is those products which, in several particulars, are alleged to infringe the patents in suit. Although, as Kodak correctly points out, this case involves nine 3 different patent disputes and instant photography is not the perpetual domain of Polaroid, the response of Kodak to the SX-70 system has some bearing on the judgment concerning the underlying patents. Also while it is by no means decisive on the question of infringement of any particular patent, so does the suggestion in September 1973 of Kodak’s Development Committee that “[development should not be constrained by what an individual feels is potential patent infringement.”

Kodak denies each allegation of infringement and argues the invalidity of each claim asserted against it. I will deal with the specific allegations of infringement and validity in the discussion pertaining to each patent. Certain broad contentions recur, however, and are properly addressed here.

The parties are in substantial agreement on the standards for judging anticipation and obviousness under 35 U.S.C. §§ 102 and 103. They disagree in one area that bears on several of the patents in suit — the effect of Polaroid’s internal work and whether it constitutes part of the prior art against which the validity of a particular patent is to be judged. Work done within Polaroid which was not published is not prior art and I have not considered it in judging the validity of any patent. Del Mar Engineering Laboratories v. United States, 524 F.2d 1178, 1182, 207 Ct.Cl. 815 (1975).

As to each patent, Polaroid relies on the presumption of validity. Kodak claims that this presumption is in nearly every instance undercut by Polaroid’s failure to disclose pertinent prior art to the *833 Examiner. The parties have genuine disagreements as to what constitutes prior art, but I rule that Polaroid has fulfilled its obligation to the Patent Office where the patent in suit is in the class of patents that was cited. See, e.g., E.I. Du Pont de Nemours v. Berkley & Co., Inc., 620 F.2d 1247, 1267 (8th Cir.1980); International Telephone & Telegraph v. Raychem Corp., 188 U.S.P.Q. 214, 219 (D.Mass.1975), aff'd, 538 F.2d 453 (1st Cir.), cert. denied, 429 U.S. 886, 97 S.Ct. 238, 50 L.Ed.2d 167 (1976). In addition, prior art described in the specifications is expected to be considered by the Examiner. Gould v. General Photonics Corp., 534 F.Supp. 399, 403 (N.D.Cal.1982). Patent Examiners are also presumed to be aware of patents which issued from applications they had earlier examined. Hahn & Clay v. A.O. Smith Corp., 320 F.2d 166, 172 n. 15 (5th Cir.), cert. denied, 375 U.S. 944, 84 S.Ct. 351, 11 L.Ed.2d 274 (1963).

In support of its argument that the patents are valid, Polaroid points to the commercial success of the processor product disclosed. The SX-70 camera and film system has unquestionably been immensely successful, as has Kodak’s product. The evidence presented is, however, inadequate to permit me to assign to any one patent credit for the commercial success of the whole. Accordingly, this factor has played no part in the decision.

Finally, I have for the sake of completeness proceeded to consider the issue of infringement even as to those claims found to be invalid.

II. U.S. Patent No. 3,362,821

Land U.S. Patent No. 3,362,821 concerns stabilization in one-step color photography. All photographic processes, as described earlier, implicate three steps — exposure (formation of the latent image), development (formation of a visible image), and stabilization (cessation of chemical reactions and preservation of the visible image). In conventional photography stabilization is accomplished by subjecting the film to different chemical solutions seriatim. One-step photography, by definition, required telescoping all of the steps, which is not to say that numerous steps did not occur sequentially within film and camera. Thus, chemicals were needed which would, when combined with the processing composition, permit development, then stop it at the optimal point and thereafter remain neutral. Solution of this problem was complicated by the fact that each type of film, sepia, black and white, and color, unexpectedly called for markedly different stabilization techniques.

Polaroid’s first one-step film, introduced in 1948, produced sepia prints in a peel-apart format. For stabilization, Dr. Land used metal salts and water soluble esters. In the presence of the processing composition, the metal salts reacted with the esters to reduce the pH. Because their reaction rate with the alkali of the processing composition was relatively slow, they permitted formation of the image before they broke up to produce alcohol and neutralizing acid. Finally, the reaction of the several components of this system reduced the pH to an ideal level, just above neutral. Too much acidity would cause production of sulfur which, in turn, would attack silver and ultimately destroy the photograph.

This stabilization mechanism was highly successful also because the photographer needed to do nothing but take the picture. Brown pictures were not ideal, however, and there was great pressure to produce black and white film.

Because both sepia and black and white film involved silver transfer, Dr. Land and his associates had thought that the same stabilization process would work with black and white film. They found that it did not. To obtain a black and white print, the aggregation of silver ions was changed. That produced a shield. As a consequence, the metal salt, lead acetate, could not uniformly penetrate the black and white surface and the migration of the esters was also retarded. The ultimate solution was the print coater. The photographer had to swab each positive with a solution of a polymer and acetic acid that both washed the film and gave it a protective coating. *834 This stabilizing system also required redesign of the black and white image and the support.

Color film called for still different techniques. The timing needs of color were different from those of both sepia and black and white. During the 1950s and into the early 1960s, when Polaroid and Kodak still cooperated, scientists from both camps discussed a number of proposals, including a suggestion of Kodak’s Dr. Vittum to use an acid layer of commercially available sulfostearic acid. 4 None worked successfully and as the scheduled date for marketing the new color film, Polacolor, approached, Polaroid expected to offer the film with a print coater. Even that, however, presented difficulties. Because the problems inherent in stabilizing color film differ radically from those pertaining to black and white, the coaters used different materials and required different “skills” from the user. The color print had to be coated within five seconds after removal from the camera. It had to be swabbed 16-18 times and the coating was slow to dry.

The print coater was not only cumbersome and difficult to use, it also lacked elegance. During the summer of 1962, Dr. Land and his associates engaged in intensive investigation of alternative stabilizing techniques. To succeed, the stabilizing system had to meet three requirements. It had to allow the processing emulsion to retain its alkaline characteristics long enough to permit adequate image development and dye transfer. It then had to drop the pH abruptly and permanently to prevent further development and dye transfer, and third, it had to remove from the image-receiving layer the alkali metal ions introduced by the processing emulsion. The alkali metal ions, if not removed, would precipitate as salts in the image receiving layer and in time cause the image to become dull.

In September 1962, Land conceived and indeed suggested to Messrs. Yutzy and Damschroder of Kodak, the use of a nondiffusible polymeric acid and associated timing layer. Unlike the esters which first had to decompose to provide a neutralizing acid, the acid polymer would react instantly upon contact with the alkali. The acid polymer would then abruptly drop the pH in the film structure by removing alkali metal ior.s from the processing solution and attaching them to itself. The layer had to be thick enough to provide adequate polymeric acid to accomplish the task, and a mechanism had to be incorporated to delay the reaction until the completion of development. The idea had two additional advantages. The polymeric acid, by removing the alkali metal ions, prevents the precipitation of metal and attendant dullness of picture. It thus produces more brilliant images. Color diffusion transfer by its very nature requires the disposition of a larger volume of alkali than does sepia or black and white film. The polymeric acid layer disposes of that alkaline environment and thus enables maintenance of a good image indefinitely.

Polaroid immediately incorporated the concept of a nondiffusible polymeric acid layer into its Polacolor film which was, with that stabilization mechanism, introduced to the market in 1963. Dr. Land considered building the polymeric acid layer described above into two possible locations of the film unit: between the support and the adjacent image-receiving layer; or beyond the far part of the negative, that is, between the support associated with the negative and the innermost layer of dye developer. Two patents issued on this invention, one pertaining to the location of the acid layer near the positive, Land U.S. Patent No. 3,362,819; the other pertaining to an acid layer near the negative, Land U.S. Patent No. 3,362,821, the patent in suit. Polacolor employs the location described in the ’819 patent. Polaroid alleges *835 that Kodak’s PR-10 film, which admittedly contains an acid layer, places the layer in the photosensitive element thereby infringing the ’821 patent.

The ’821 patent discloses a layer of a nondiffusible acid-reacting reagent in the photosensitive element. It describes the preferred embodiment of the invention as a layer containing an acid-reacting polymer, and particularly, a polymer-containing free carboxyl group. The patent uses the shorthand expression — a polymeric acid layer. It includes a list of specific polymeric acids suitable to the purpose. The specifications teach that the polymeric acid layer is preferably 0.5 to 1.5 mils thick; that is, relatively thick as compared, for example, with the dye layers.

The acid layer contains acid groups attached to a polymer so as to be nondiffusible. It reduces the pH in the image-receiving element by attracting alkali ions and then trapping them by precipitating them into the acid layer. The patent accordingly describes the acid layer as “a mordant for alkali.” 5 It further teaches that the action of the polymeric acid must be controlled so that it will not interfere either with the development of the negative or with the image transfer of unoxidized dye developers. In other words, the reduction of pH must be properly timed. The patent suggests three timing mechanisms. A separate spacer layer of inert polymer may be used to delay contact between the alkali ions and their trap, or an inert poisoner may be mixed into the acid polymer to make the acid less accessible to the alkali ions. A third method calls for an acid layer with a relatively lower concentration of acid groups, again to prevent too rapid attraction and precipitation of alkali ions.

The patent states that the polymeric acid layer “is provided in the photosensitive element and is positioned adjacent the support, i.e., between the innermost layer of dye developer and the support.” That positioning is depicted as well in Figure 1 of the patent. The specifications by reference to Figure 1 describe the photosensitive element as comprising “a support bearing, in turn, a layer containing as a nondiffusible acid-reacting reagent, a polymeric carboxylic acid ...” and the dye developer layers. The image-receiving element comprises a “support carrying an image-receiving layer.”

Claim 1 is the only claim asserted against Kodak. In the context of color diffusion transfer processes, it claims the use of a layer of a nondiffusible polymeric acid containing sufficient acid groups to effect a reduction of at least two pH units in the surface of the image-receiving layer, compared with the initial pH of the processing composition, prior to the completion of the imbibition period. The acid layer is claimed to be contained in the photosensitive element and positioned between the support and the innermost negative layer.

Kodak denies infringement and contends that the patent is, in any event, invalid under 35 U.S.C. §§ 102, 103 and 112 and that it is unenforceable. It relies in its post-trial brief on two prior art references listed in the Section 282 Notice: U.S. Patent No. 2,584,030 and Kodak French Patent No. 1,293,709. 6

The ’709 patent is said to disclose the process described in claim 1 of ’821 and thus to render that claim invalid under 35 U.S.C. §§ 102(a) and 102(b). French Patent No. 1,293,709 describes color diffusion transfer processes employing coupler chemistry in which the photosensitive element is exposed, an alkaline-processing solution is applied, and a diffusible colored image is transferred to an image-receiving layer. It acknowledges that in “processes involving the transfer of dye images to mordanted reception layers, small amounts *836 of alkali ...” may also be transferred and may be objectionable. One proposed solution is to wash the reception layer to remove such materials, and one method offered is “to squeegee the dye images into contact with a moist sheet containing ... an acrylic acid polymer ... to neutralize the alkali____” Alternatively, it suggests providing “a hydrophylic [sic] organic colloid layer containing the mentioned acids ... between the mordanted support and ...” reception layer, which layers are later stripped from the mordanted support.

I find that ’709 does not anticipate claim 1 of '821. The acid layer in ’709 is not located in the photosensitive element, but between the photosensitive layer and its support. Both Dr. Land and Kodak’s expert, Dr. Trautweiler, agreed that the ’709 layer does not reduce the pH of the surface of the mordanted support, the analog of the image-receiving layer of ’821. More fundamentally, the acid layer of ’709 is a scavenging layer designed to prevent alkali from reaching the mordanted support, not a stabilizing system designed to stop the development process and prevent subsequent chemical reactions. The experts agreed, moreover, that they knew of no commercial unit in which dyes diffuse through an acid layer, that is, one in which the acid layer is positioned as in ’709. That patent does not describe the process of '821 and the process it does describe does not solve the problem addressed by '821.

Kodak asserts that ’709, in any event, and U.S. Patent No. 2,584,030 disclose the technique of using an acid layer in the photosensitive element to reduce pH and that ’821 therefore represents no more than the application of routine skill. Kodak’s assertion is premised on a most narrow reading of the patent in suit, namely, that the purpose of the acid layer is to neutralize the processing composition and thereby to prevent stain caused by the oxidation of the developer. I do not, in view of the evidence adduced at trial, treat the invention so severely. The ’821 patent describes a system of stabilization that not only lowers the pH but does so in a specified manner with a timing mechanism. Its purpose is not merely to prevent stain but also to increase the light-stability of the dyes in the image. The specifications and examples teach the use of particular acids and acid layers of particular thicknesses. They teach three different timing mechanisms, which are earlier detailed, and the means of achieving light stability through trapping positive cations in the acid layer so that they cannot go to the image layer and damage it.

For the reasons outlined earlier, I do not find in the '709 patent the teaching of the stabilization system of ’821, even to one of the high level of skill characteristic of those engaged in this field. The single reference on page 52 of a 53-page document 7 to a “hydrophylic [sic] organic colloid layer containing ... acids” to remove “small amounts of alkali” from the mordanted reception layers does not teach the use of an acid layer with a timing mechanism. Nor does the peel-apart film of ’709 teach the location of the acid layer “in the photosensitive element.”

The second prior art reference relied on by Kodak is Land’s ’030 patent, issued ten years before ’821. It teaches stabilization techniques useful for sepia images and describes two processes, one using heavy metal salts and the other, an acid. One of the acids specified is cellulose acetate hydrogen phthalate, which is also a preferred polymeric acid in '821. The ’030 teaches the need to reduce the pH of the liquid composition to 7, 6 or lower, and while it is preferable that “the acidifying substance” be “included on or associated with the image-carrying layer ...” such is not essential and “it might, for example, be positioned between the photosensitive layer and the base carrying this photosensitive layer____” This patent, like ’709, describes a peel-apart film structure. The acid layer *837 is available to the alkaline reagent directly so that neutralization occurs immediately. The amount of acid must be small enough not to interfere with silver development. During processing, the acid is slowly dissolved by the processing composition while simultaneously the pH of the processing composition is slowly lowered.

I credit the testimony of Dr. Land that this mechanism does not teach the system embodied in ’821. To say, as did Dr. Trautweiler, that if one deletes the words “col- or” and “dye” from claim 1, one gets the process described by the ’030 patent does not take sufficient account of the essential differences between the processes for sepia and color. Color diffusion transfer requires more time than the simpler silver transfer of sepia, and color requires the removal of the alkali metal ions from the environment of the image entirely. Neither these unique requirements of color, nor the mechanisms disclosed in ’821 for meeting them are disclosed in ’030.

The evidence is undisputed, moreover, that the art had been full of experiment for several years, but no one had perceived the particular conformation, position and qualities of the ’821 polymeric acid layer for stabilizing color diffusion transfer film units until Dr. Land did in 1962. He was the first despite the fact that the parties in this case include on their staffs, without doubt, the world’s preeminent experts in the field of instant photography.

Kodak further argues that the ’821 patent is invalid because it does not teach how to make the claimed invention as required by 35 U.S.C. § 112. One of the requirements of claim 1 is that the polymeric acid layer contain sufficient acid groups to effect reduction in the pH of the surface of the image-receiving layer of at least 2 pH units compared with the initial pH of the processing composition. Kodak’s expert, Dr. Trautweiler, calculated the drop in pH in several examples cited in ’821. His computations show a substantially smaller reduction and Kodak argues therefrom that the patent does not teach how to make the claimed invention. The calculations are just that — they are not based on experimental data. Moreover, Dr. Trautweiler did not view the system as a whole. Other components effect some reduction of pH before the acid layer begins its work. But the acid layer completes the process and does thereby cause reduction of the pH on the surface of the image-receiving layer by at least two pH units. In this fashion, the invention works precisely as claimed.

Finally, Kodak contends that the patent in suit is unenforceable because Polaroid’s attorney and Dr. Land allegedly misrepresented the content of ’030 to the examiner and failed to inform the Patent Office of the existence of the ’709 patent. To prevail in this defense Kodak must show that Dr. Land and his attorney made misrepresentations with knowledge of their falsity or in an atmosphere of gross negligence as to their truth. It must further show that any information withheld was material. Materiality means facts known to the applicant which but for nondisclosure would have prevented the patent from issuing or would have restricted the claims. Digital Equipment Corp. v. Diamond, 653 F.2d 701, 715 (1st Cir.1981) (citing Union Carbide Corp. v. Filtrol Corp., 170 U.S.P.Q. 482 (C.D.Cal.1971), aff'd, 179 U.S.P.Q. 209 (9th Cir.1973)). The First Circuit does point out that the questions of culpability and materiality are interrelated such that an intentional scheme to defraud may require a lesser showing of materiality; a negligent misstatement, a greater one. Digital Equipment Corp. v. Diamond, 653 F.2d at 716.

The ’030 patent was unquestionably cited to the examiner. Given my finding above on the relevance of its contents to the invention of the patent in suit, I find that Dr. Land and his attorney did not in any way misrepresent its significance. French Patent No. ’709 was not cited at all, but I credit the testimony of the attorney, Mr. Mervis, that he was unaware of it until many years later. I find, therefore, that the ’821 patent is valid against all of the defenses raised by Kodak.

*838 The issue of infringement hinges on the definition of the location of the acid layer in Kodak’s PR-10 film. Specifically, the question is whether the acid layer is “in the photosensitive element.” The parties do not disagree that the PR-10 acid and timing layers are positioned between a support and the photosensitive silver halide and associated dye layers. But Kodak points out first that in the manufacture of PR-10 the acid layer is coated on one support, the negative layers on another support, and that they are manufactured as separate elements and then assembled into one film unit. Because the negative and acid layers are coated on different supports, it argues, the acid layer is not positioned “in the photosensitive element.” The difficulty with that argument is that claim 1 is admittedly a process, not a product claim, and in defining the process it describes the position of the acid layer in the photosensitive element precisely where it is located in PR-10, “between the support and the innermost layer containing ... dye image-forming substance.” The photosensitive element is described in the specifications as including, in order, a support, a polymeric acid layer, a spacer or timing layer, and the layers containing the silver halide emulsions and dye developer. Regardless of the manner of manufacture, the sequence of layers in PR-10 is that described in the patent, and during processing, PR-10 is comprised of the same layers depicted in Figure 1 of the patent and has the same structure described in claim 1.

Conflicting definitions of “photosensitive element” in other Polaroid patents do not save PR-10 from the claim of infringement. The term clearly has various possible meanings, as is shown by Kodak’s recital of other references. ’821, however, provides its own clear definition. 8 A patentee is entitled to choose his own terms and to insist on them so long as he is consistent and does not contravene any single established or accepted meaning. Mooney v. Brunswick Corp., 663 F.2d 724 (7th Cir.1981); Harrington Manufacturing Co. v. White, 475 F.2d 788, (5th Cir.), cert. denied, 414 U.S. 1040, 94 S.Ct. 542, 38 L.Ed.2d 331 (1973).

For the reasons stated, Land U.S. Patent No. 3,362,821 is valid and infringed by Kodak’s PR-10 film.

III. U.S. Patent No. 3,245,788

As noted earlier, Howard G. Rogers began in 1947 to explore the possibility of importing color into one-step photography. Conventional color photography relied on coupler chemistry to produce color. A col- or developer became oxidized, and as a result combined with a coupler compound to form a dye. Different couplers were needed to produce different colors and each had a different reaction rate, making this process unsuitable for diffusion transfer which required a synchronization of reactions that coupler chemistry simply did not permit. Rogers sought to solve that problem by his coupling dye process disclosed in U.S. Patent No. 3,087,817, a patent not directly involved in this litigation. It used preformed dyes with coupling groups attached. In that process, the oxidized color developer joined with the coupler and its attached dye and thereby controlled not the formation of dye but the transfer of the preformed dye to the positive layer. That is, when the processing composition is introduced, the color developer is oxidized where silver halide was exposed and, as described before, it then joins with the coupler. The junction of color developer and coupler forms an insoluble compound which remains in the negative layer and is ultimately discarded as the negative is peeled. Where silver halide was not exposed no oxidation-reduction and no coupling takes place; the coupler with dye attached re *839 mains soluble in the processing solution and can transfer to the positive layer. The coupling dye process eliminated the problems attendant on different reaction times as the same coupling groups could be used for all dyes. But all color developer compounds used in the coupling process, paraphenylenediamines, themselves presented other difficulties. They were unstable when stored in the negative and had a tendency to desensitize the silver halide emulsion; they sometimes stained the picture; they could cause dermatitis; and they gave relatively slow reaction time and film speeds.

In the early 1950s, Mr. Rogers proposed an entirely new approach, the use of dye developers. A single molecule of such compounds contains both dye to form the image and developer to develop the latent image in exposed silver halide and to control diffusion. 9 The idea was to change the solubility and therefore mobility of the dye through oxidation by the developing silver. Mr. Rogers, in fact, hypothesized two possibilities, a “positive” dye developer which as a consequence of oxidation would produce a less soluble product, and a “negative” dye developer which would create a more mobile dye product. These concepts were ultimately embodied in two patents, respectively, U.S. Patent No. 2,983,606 and No. 3,245,789, the patent in suit. The positive dye developer process disclosed in the ’606 patent is the one which Polaroid has used commercially in all of its color films since the introduction of Polacolor. Polaroid alleges that the negative dye developer process was incorporated into Kodak’s PR-10 film.

The positive dye developer process works as follows. After exposure and the introduction of the processing compound, an auxiliary developer, which may be included in the processing compound or built into the negative layer, will in the exposed portions of silver halide, give its electrons to the silver halide. It, in turn, takes electrons from the dye developer, which thereby becomes oxidized. Oxidation precipitates the dye, thereby fixing it in the negative layer. Where silver halide was not exposed, the dye developer is not oxidized; the dye is not precipitated, and the dye therefore is able to transfer to the positive layer to form the colored image. In both the developed and undeveloped portions, the silver halide stays in the negative. Where the scene is light, the dye is held back in the negative by its precipitation there, while in the darker portions of the picture where silver halide remains undeveloped, and the dye developer unoxidized, the dye is free to move to the positive, the image-receiving layer.

As described in Rogers U.S. Patent No. 3,245,789, issued to Polaroid Corporation on April 12, 1966, on Application Serial No. 107,889, filed on May 5, 1961, in the negative dye developer process the dye is transferred to the positive layer in the exposed — the developed — region of silver halide. In general terms, the dye developer, which has relatively low mobility to begin with, is, as is true for the positive dye developer process, oxidized. In the negative dye developer process, however, the dye developer splits off a dye molecule as a result of oxidation. This molecule then has a lower molecular weight and greater solubility, so it becomes more mobile. It is then able to transfer to the positive layer. Where silver halide is not exposed, the dye developer is not oxidized and not split. Being relatively immobile, the unoxidized dye developer remains in the negative.

Specifically, the patent discloses a color diffusion transfer process for forming col- or photographs or transparencies using compounds referred to as “negative transferring developing agents.” If colored, these compounds are described as being dye developers in the reduced state, “i.e., *840 they are compounds which are both dye and a silver halide developing agent.” They are characterized as being “relatively nontransferable to the image-receiving layer” but they form a substantially more mobile, diffusible oxidation product. That is, the colored oxidation product is more diffusible than the unoxidized negative transferring developing agent.

The patent suggests that the photosensitive element of the film unit, the negative, contains in the silver halide emulsion a layer of the dye developer. 10 When, after exposure, the liquid processing composition is introduced, it permeates the emulsion to provide a solution of dye developer. Then, as the exposed silver halide is developed, the oxidation-reduction reactions previously described and the attendant transfers of dye molecules take place.

Polaroid charges infringement of claims 5 through 9. Claims 6 through 9 are dependent on claim 5.

Claim 5 describes the process outlined above. Claim 6 adds the requirement that the