Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2000-06-28
2002-08-27
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S192120, C204S192260, C204S298230, C204S298280, C204S298140
Reexamination Certificate
active
06440280
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for sputter coating articles, and especially, for reactive sputter coating of plastic ophthalmic lens elements using a sputter source with multiple anodes. As used herein, lens elements include, according to context, edged lenses, semi-finished lenses and lens blanks. Also included are wafers for forming laminate lenses or wafer blanks therefor. Ophthalmic uses of the lens elements include uses in eyeglasses, goggles and sunglasses.
BACKGROUND AND OBJECTS OF THE INVENTION
Many ophthalmic lenses produced today are made from a single plastic body or laminated plastic wafers. The plastic material may include thermoplastic material such as polycarbonate or thermoset material such as diallyl glycol carbonate types, e.g. CR-39 (PPG Industries). The material may also be a cross linkable polymeric casting composition such as described in U.S. Pat. No. 5,502,139 to Toh et al. and assigned to applicant.
Ophthalmic lens elements are frequently coated to achieve special properties. Anti-reflection coatings improve the transmittance of visible light and the cosmetic appearance of the lenses. Reflective and absorptive coatings may be employed in sun lenses to reduce light transmittance to the eye, to protect the eye from UV radiation and/or to impart cosmetic colorations to the lens. Coatings may also provide other beneficial properties such as increased hardness and scratch resistance and anti-static properties.
Desirable lens coatings may be created by applying single or multiple layers of metal, metal oxides or semi-metal oxides to surfaces of the lens element. Such materials include oxides of silicon, zirconium, titanium, niobium and tantalum. Metal and semi-metal nitrides are also used. Examples of such multilayer coatings are given, for example, in U.S. Pat. No. 5,719,705 to Machol entitled “Anti-static Anti-reflection Coatings”, assigned to applicant. Interference filter coatings for sunglasses are disclosed, for example, in U.S. Pat. No. 2,758,510 to Auwärter. Other lens coatings are disclosed in International Application WO 99/21048 to Yip, et al., which is hereby incorporated by reference.
Various methods are disclosed in the prior art for applying metal and semi-metal oxide coatings to ophthalmic lenses. Such coatings have traditionally been deposited by means of thermal evaporation, and more recently, by electron-beam (e-beam) evaporation and reactive sputtering. Evaporations are typically carried out at vacuums better than 10E-5 Torr. Ritter et al. U.S. Pat. No. 4,172,156, for example, discloses e-beam evaporation in an oxygen atmosphere of Cr and Si to form coating layers on a plastic lens. The use of reactive sputter deposition to form various oxide layers on lens elements is disclosed in the above-mentioned '705 patent to Machol.
Reactive sputtering in general is a conventional technique often used, for example, in providing thin oxide coatings for such items as semiconductor wafers or glass lamp reflectors. Examples of various conventional vacuum deposition systems for the formation of coatings by reactive sputtering are disclosed in the following patents: U.S. Pat. No. 5,616,224 to Boling; U.S. Pat. No. 4,851,095 to Scobey et al.; U.S. Pat. No. 4,591,418 to Snyder; U.S. Pat. No. 4,420,385 to Hartsough; British Patent Application GB 2,180,262 to Wort et al.; Japanese Kokai No. 62-284076 to Ito; and German Patent No. 123,714 to Heisig et al.
The coating of plastic lenses in spinning drum coaters by means of sputtering technology, including DC reactive sputtering, is a relatively recent development. A conventional drum vacuum coating system used for this purpose is shown in FIG.
1
. The system includes a vacuum chamber
11
, which contains a hollow workpiece holder or drum
12
. Lens elements, such as lens
13
are arranged in columns on an external surface of the drum
12
. A coating applicator
14
is located near a wall of the vacuum chamber adjacent the drum
12
. The coating applicator
14
may comprise a combination of magnetron sputtering sources and microwave plasma generators with a reactive gas supply such as disclosed in U.S. Pat. No. 5,616,224 to Boling, which is hereby incorporated by reference. Power is delivered to the coating applicator
14
by one or more power supplies (not shown) via an electrical lead assembly
17
. A reversing power supply for arc suppression such as disclosed in U.S. Pat. No. 5,616,224 to Boling may be included. A sputtering gas is introduced into the vacuum chamber through gas-supply plumbing built into the coating applicator or through a separate port (not shown) on the vacuum chamber
11
. The sputtering gas is controlled by a gas controller (not shown) and may be an inert gas such as argon or a reactive gas mixture such as argon/oxygen or argon
itrogen.
The vacuum chamber
11
is evacuated by vacuum pumps (not shown) attached to a pumping plenum
15
. A cryopumping surface, known as a Meissner trap, is conventionally provided in the form of cryocoils
16
in the plenum
15
. A coolant with a temperature well below the freezing point of water flows through the cryocoils
16
, allowing the Meissner trap to remove water vapor from the vacuum chamber
11
. A Meissner trap may be advantageously configured in the vacuum chamber
11
rather than in the pumping plenum
15
to improve the cryopumping of water vapor. Such a configuration is especially useful when coating plastic lens elements because plastic lens elements have a tendency to outgas substantially more water vapor than conventional glass lenses, as disclosed in U.S. Pat. No. 6,258,218, hereby incorporated by reference.
A drum vacuum coating system with an elongated magnetron sputter source
14
such as that illustrated in
FIG. 1
provides a convenient means of coating numerous lens elements or other articles. However, Applicants have observed that such systems typically do not produce uniformly thick coatings on multiple articles disposed in a given column of the drum
12
due to the variation in sputter rate along the length of the sputter source. In other words, an article or lens element positioned near the top of a given column may not receive a coating of the same thickness as an article or lens element positioned near the center of that column.
Several methods directed toward improving coating uniformity of sputtered films have been disclosed in the prior art. U.S. Pat. No. 5,645,699 issued to Sieck discloses a system comprising two cylindrical magnetron sputter sources, each with an anode substantially spanning the length of the sputter source, wherein the placement of a third anode between the two sputter sources has improved coating uniformity. U.S. Pat. No. 4,849,087 issued to Meyer discloses the use of multiple gas nozzles distributed along the length of a sputter source to deliver varying amounts of an argon/oxygen gas mixture to local regions of the plasma above the sputter target (cathode). Individual resistance probes disposed along the width of the substrate measure the local resistance of the coating and provide feedback signals to adjust the gas flow through the various nozzles to maintain uniform electrical resistance in various regions of the coating. While this approach provides control of the electrical resistance of the coating, it does not necessarily provide control of the coating thickness, a quantity of importance for optical coatings.
U.S. Pat. Nos. 5,487,821 and 5,683,558 to Sieck et al. disclose the use of “wire brush” anodes in conjunction with magnetron sputter sources and indicate that the wire-brush point density of an anode may be adjusted along the length of the sputter source to affect the uniformity of the deposited film. U.S. Pat. No. 5,616,225 issued to Sieck et al. discloses the use of wire brush anodes and the use of multiple anodes in conjunction with a single magnetron sputter cathode for coating substrates (especially large substrates) wherein the anode voltages may be individually controlled. The '225 patent indicates that this control may be u
Burton Clive H.
Pratt Rodney
Samson Frank
Burns Doane Swecker & Mathis L.L.P.
Cantelmo Gregg
McDonald Rodney G.
Sola International Inc.
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