Tokyo Shibaura Elec. Co., Ltd. v. Zenith Radio Corp.

404 F. Supp. 547
CourtDistrict Court, D. Delaware
DecidedNovember 7, 1975
DocketCiv. A. 4672
StatusPublished
Cited by15 cases

This text of 404 F. Supp. 547 (Tokyo Shibaura Elec. Co., Ltd. v. Zenith Radio Corp.) is published on Counsel Stack Legal Research, covering District Court, D. Delaware primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Tokyo Shibaura Elec. Co., Ltd. v. Zenith Radio Corp., 404 F. Supp. 547 (D. Del. 1975).

Opinion

OPINION

STAPLETON, District Judge:

I. PARTIES AND JURISDICTION

This is a declaratory judgment action which poses questions regarding the validity, infringement and enforceability of a patent on certain improvements in color television picture tubes. Plaintiffs, Tokyo Shibaura Electric Co., Ltd., Toshiba America, Inc., and Toshiba Hawaii, Inc., (hereinafter collectively referred to as “Toshiba”) are respectively, a Japanese corporation and its wholly-owned New York and Hawaiian subsidiaries which sell color television picture tubes in the United States. Defendant, Zenith Radio Corporation (“Zenith”) is a Delaware corporation whose principal place of business is neither New York nor Hawaii; venue is properly laid in this district under 28 U.S.C. § 1391(e). Toshiba seeks a judgment declaring the invalidity, non-infringement and unenforceability of Zenith’s United States Letters Patent No. 3,146,368 (the “ ’368 patent”), issued August 25, 1964 to J. P. Fiore and S. H. Kaplan. Zenith, as *550 their assignee, has counterclaimed for infringement of the ’368 patent by Toshiba. These issues have been tried, 1 and I find that there exists a substantial and actual controversy between the parties on the issues presented in this action, justifying a declaratory determination of their respective rights.

II.' BACKGROUND FACTS

The story of color television picture tube design begins almost half a century ago (see DX 21, p. 1177), but it is sufficient for present purposes to refer only to the period commencing in 1953, when the Federal Communications Commission determined that television pictures transmitted in color had to be “compatible” with- — that is, able to be received on —conventional black and white television receivers. 2 Several different kinds of television picture tubes were proposed for use in the new “compatible” system and competed for favor in industry laboratories for some years. Although only one type ultimately entered commercial production, three types play a role in the present action and a description of the structure and operation of each is necessary.

, A. Common Features Of Relevant Tubes

In all three types of tubes, the color picture seen by the viewer is created in the same basic manner. On the inside surface of the viewing screen 3 of the picture tube are deposited a very large number of “phosphors” — chemical materials which have the property of emitting visible light when bombarded by electrons (Tr. 47). Different phosphors will emit light of different colors, and by placing phosphors which emit the three “primary” colors of red, blue and green in close conjunction with each other on the viewing screen, any visible col- or can be reproduced by bombarding a suitable combination of these phosphors (Tr. 61; DX 21, p. 1178). For convenience, these phosphors will hereinafter be called red, blue and green, even though they are in reality whitish except when being bombarded (Tr. 62, 448). The emitted colors can be made brighter or dimmer by varying the intensity of the bombardment (Tr. 46, 50).

1 This bombardment is accomplished by means of one or more “beams” of electrons generated by one or more “electron guns” which are mounted in the neck of the tube and which project the beams onto the viewing screen (Tr. 46-47). These beams bombard only a small portion of the screen at any one instant, but the different phosphors are so small and so close together, and the beam “scans” the viewing screen at so rapid a pace, that the human eye can perceive only a single color picture (Tr. 46-51).

The electrons striking the glass viewing screen have a tendency to remain there. Their accumulation can cause the screen to repel the similarly charged electrons aimed at it on the beam’s next scan (Tr. 52), and for this reason a thin layer of aluminum is ordinarily placed on top of the phosphors on the inside surface of the viewing screen (see Fig. 3, infra). This layer not only conducts the electrons away from the screen after they have bombarded the phosphors but also increases the efficiency of the phosphors by reflecting out to the viewer the light initially emitted by the phosphors towards the inside of the tube (Tr. 52-53, 457).

*551 B. The Shadow Mash Tube 4

It is essential for any color picture tube to have means for assuring that the electron beam bombards the proper phosphor at the proper time and with the proper intensity&emdash;otherwise the resulting picture will not be the picture intended. The shadow mask tube, which is the- type of tube used in every commercially available color television set today (DX 20, p. 2), accomplishes this essential function of color selection by utilizing three electron guns and a “shadow mask” from which it takes its name.

A shadow mask is a thin metal membrane which is placed inside the tube, immediately behind and parallel to the screen, as shown in this cross-sectional view : 5

The mask is perforated with a very large number (a third of a million would be a typical number&emdash;DX 20, p. 42) of small apertures, 6 each aperture positioned directly behind the center of a set or “triad” of three adjacent phosphor dots or stripes, one of each primary col- or.

In the shadow mask tube, the electron beams that bombard the phosphors come from a cluster of three electron guns, with each gun emitting the electrons intended to strike only the phosphors of a given color (DX 20, pp. 42-43). The geometrical relationship of the guns, the mask and the screen is designed such *552 that the beams from the three guns converge at the mask, with each beam at a different angle. The result is that only so much of each beam as will strike the correct phosphor is able to pass through the mask:

(see Tr. 63-69; DX 20, pp. 12-14; PX 116 generally). It is in this manner that the color selection is achieved in a shadow mask tube.

Figure 2 is especially exaggerated in showing the shadow mask midway between the electron guns and the viewing screen. In reality, the mask is mounted immediately behind the screen (see PX 172), so that for practical purposes the size of the aperture in the shadow mask and the size of the electron beam landing area will be the same (Tr. 200, 598).

C. The Post-Deflection Focusing Tube

One disadvantage of the simple shadow mask tube, as can be seen in Figure

2, is that the mask intercepts the bulk of the electrons generated by the electron guns, thus considerably reducing the brightness of the picture which can be generated by a gun of a given efficiency (see Tr. 72-74).

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