US3536946A - Temperature-resistant reflective coating for quartz envelope - Google Patents

Temperature-resistant reflective coating for quartz envelope Download PDF

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Publication number
US3536946A
US3536946A US688821A US3536946DA US3536946A US 3536946 A US3536946 A US 3536946A US 688821 A US688821 A US 688821A US 3536946D A US3536946D A US 3536946DA US 3536946 A US3536946 A US 3536946A
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United States
Prior art keywords
coating
quartz
envelope
filament
temperature
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Expired - Lifetime
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US688821A
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English (en)
Inventor
Bernard Kopelman
Marshall E Kulberg
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GTE Sylvania Inc
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Sylvania Electric Products Inc
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Publication date
Application filed by Sylvania Electric Products Inc filed Critical Sylvania Electric Products Inc
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Publication of US3536946A publication Critical patent/US3536946A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J5/00—Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
    • H01J5/02—Vessels; Containers; Shields associated therewith; Vacuum locks
    • H01J5/08—Vessels; Containers; Shields associated therewith; Vacuum locks provided with coatings on the walls thereof; Selection of materials for the coatings

Definitions

  • a diffusely-reflecting coating on quartz is made of a silico-phosphate. It can be used on a tubular quartz envelope to increase the effective size of an incandescent filament coil for optical purposes.
  • the coating can be applied as a mixture of phosphoric and silicic acids with some ammonium bifluoride added, and then heated to a temperature of about 1125 C.
  • a porous and adhesive white-coating is formed on the glass. Heating to 1150 C. will fuse the mixture to the quartz as a clear coating and cause cracking due to unequal coeflicients of expansion.
  • the coating can also be used on the quartz envelope of an electric discharge tube such as a high pressure mercury vapor lamp, and the coating can be used for other purposes.
  • the coating can be made thin for diffusion or heavy for reflection.
  • This invention relates to a diffusing coating suitable for use on quartz and high silica glasses.
  • it relates to a lamp in a quartz envelope having such a coating over at least part of its surface.
  • Lamps having extended area planar type filaments such as the so-called C13 and C13D filaments, have found wide use in slide projector equipment and in fixtures used in television and motion picture studios.
  • planar filaments often called monoplane or biplane filaments, depending on whether the multiplicity of parallel filament coils of which they are composed is arranged in a single plane or in two slightly-spaced parallel planes, are usually made in soft or hard glass envelopes.
  • the quartz envelope of the tungsten-halogen almp operates at very high temperatures, often well above 600 C., and ordinary coatings are unsatisfactory, because they will either crack the quartz, because of its much lower expansion coeificient, or they will burn off.
  • the application of the mixture to the enevlope is quite critical. After being applied to the quartz as a paste, it is heated slowly; at about 300 C., the liquids having 3,536,946 Patented Oct. 27, 1970 mostly evaporated, it has the appearance of a grey frozen slush. At about 1000 C. it begins to sinter to a porous but cohesive mix, and shows the beginning of adhesion to the quartz at about 1125 C. However, the mixture will fuse to a clear glass coating at about 1150 C. and the quartz envelope will eventually crack. Accordingly, the final temperature of the coating during manufacture must be below 1150 C., and about 1125 C. being effective, and the temperature during subsequent operation must be less than 1150 C. The latter limitation is not a disadavntage, however, since the tungsten halogen lamp generally operates well below that temperature.
  • the silico-phosphate is the only coating we have found that can be made to adhere to quartz throughout the thermal cycling and recycling normal to the operation of the lamp. It appears to do this by a combination of relatively low thermal expansion coeflicient, only two or three times that of quartz itself, and a porous structure which takes up any stresses involved.
  • silico-phosphate should contain an addition such as ammonium bifluoride, which appears to etch the quartz surface so that a better bond is achieved between the quartz and the silico-phosphate. Without such an additive, the coating will flake ofli.
  • Other fluorides can :be used.
  • ammonium bifluoride When ammonium bifluoride is used, it breaks down on heating to become ammonium fluoride and hydrofluoric acid, the latter apparently etching the glass at the same time the coating is sintered, thereby forming a good bond.
  • the coating In order to prevent cracking, the coating must not be heated to the point of complete fusion, but should be heated only to sintering or semi-fusion.
  • FIG. 1 is a perspective view of a lamp according to the invention.
  • FIG. 2 is a cross-sectional view, showing the filament coils.
  • the tubular quartz envelope 1 has the pressed seal 2 at one end and the sealed exhaust tube 3 at the other end.
  • the external lead-in wires 4, 5' extend into the press seal 1, where each is attached in the usual manner to the thin molybdenum ribbons 6, 7 and act also as support wires for the coiled-coil filament 10 shown in FIG. 2, but obscured in FIG. 1 by the coating 11 on the outside of envelope 1.
  • the coiled-coil tungsten wire filament 10 is mounted axially in the tubular envelope 1, the longitudinal axis of the coil being substantially on the longitudinal axis of the tubular envelope 1, the coil 10 being supported by the lead-in wires 8, 9, which are joined together a short distance above the seal 1 by the corrugated quartz bead 12.
  • An additional support wire 13 extends to hold the middle portion of the filament coil 10, as shown more fully in FIG. 2
  • the lead-in and support wire 8 extends into the exhaust tube 3 to aid in centering and supporting the filament coil 10.
  • Support wire 14 is wrapped around the upwardly-extending end 15 of wire 8 and extends from there in a bight 16 having an upwardly-extending end 17, which engages the singly-coiled end of the coiledcoil filament 10.
  • the lead-in wire 9 extends upwardly and laterally, terminating in the downwardly-extending portion 18 to which an end 19 of filament coil '10 is affixed.
  • the coating 11 can be applied to the quartz as a mixture of 20 grams of syrupy phosphoric acid, grams of silicic acid having a bulk-density of about 6.0 grams per cubic centimeter, and 2 grams of ammonium bifiuoride, results in a paste which can be applied in a layer.
  • the coating is then slowly heated to 300 C., cooled, a second layer applied and heated similarly and then a third. A bubbly white coating results. It is then heated to 1125 C. If heated for minutes, the coating remains a bubbly white with excellent adhesion and good reflectance. If heated for A of an hour, the material sinteres to an advanced sintered state, 'which could be called semi-fused. Adhesion is excellent and no cracking of the quartz occurs.
  • the resultant lamp should not be operated at a temperature of 1100 C. or above, because at such temperatures the silico-phosphate coating will eventually change to a clear glaze and lose its reflecting power.
  • An electric lamp comprising a tubular quartz envelope, a light source inside said envelope, and a porous semi-fused silico-phosphate coating on said quartz envelope, said light source is a compact incandescent filament and said coating is on a portion of the circumference of said envelope in register with said filament and covers an area substantially greater than the area correspending to the product of the length-and outside diameter of said filament, whereby the effective size of the light source is increased by reflection from the coating.

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  • Vessels And Coating Films For Discharge Lamps (AREA)
  • Surface Treatment Of Glass (AREA)
US688821A 1967-12-07 1967-12-07 Temperature-resistant reflective coating for quartz envelope Expired - Lifetime US3536946A (en)

Applications Claiming Priority (1)

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US68882167A 1967-12-07 1967-12-07

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US3536946A true US3536946A (en) 1970-10-27

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US (1) US3536946A (enrdf_load_stackoverflow)
GB (1) GB1257476A (enrdf_load_stackoverflow)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3727525A (en) * 1968-06-29 1973-04-17 O Takeuchi Device for making phosphor screen for color picture tubes
US3851200A (en) * 1972-12-11 1974-11-26 Gen Electric Heat and light reflective coating on quartz lamp
US3885149A (en) * 1972-04-14 1975-05-20 Thorn Electrical Ind Ltd Lamp pinch seals
US3932780A (en) * 1974-03-20 1976-01-13 Westinghouse Electric Corporation Electric lamp having an envelope with a specular light-reflective coating of oriented aluminum particles
US3983513A (en) * 1973-10-18 1976-09-28 Westinghouse Electric Corporation Incandescent lamp having a halogen-containing atmosphere and an integral reflector of non-reactive specular metal
US4710677A (en) * 1983-07-30 1987-12-01 Thorn Emi Plc Incandescent lamps
US4816974A (en) * 1986-05-19 1989-03-28 Mycro Group Co. Glare control lamp and reflector assembly and method for glare control
US4947303A (en) * 1986-05-19 1990-08-07 Musco Corporation Glare control lamp and reflector assembly and method for glare control
US5016150A (en) * 1989-10-19 1991-05-14 Musco Corporation Means and method for increasing output, efficiency, and flexibility of use of an arc lamp
US5075828A (en) * 1986-05-19 1991-12-24 Musco Corporation Glare control lamp and reflector assembly and method for glare control
US5134557A (en) * 1989-10-19 1992-07-28 Musco Corporation Means and method for increasing output, efficiency, and flexibility of use of an arc lamp
US5161883A (en) * 1989-10-19 1992-11-10 Musco Corporation Means and method for increasing output, efficiency, and flexibility of use of an arc lamp
US5211473A (en) * 1984-12-31 1993-05-18 Musco Corporation Glare control lamp and reflector assembly and method for glare control
US6825615B2 (en) * 2000-10-24 2004-11-30 Tokyo Electron Limited Lamp having a high-reflectance film for improving directivity of light and heat treatment apparatus having such a lamp
US20090027907A1 (en) * 2004-08-26 2009-01-29 Koninklijke Philips Electronics, N.V. Lamp with reflective coating

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2144438A (en) * 1937-10-06 1939-01-17 Birdseye Electric Company Tubular incandescent electric lamp
US2568459A (en) * 1948-10-29 1951-09-18 Gen Electric Electric discharge device
US2806968A (en) * 1953-12-03 1957-09-17 Westinghouse Electric Corp Color-corrected light source and phosphor mixture therefor
US2877139A (en) * 1953-02-05 1959-03-10 Corning Glass Works Coated illuminating glassware and method of manufacture thereof
US3325662A (en) * 1963-09-19 1967-06-13 Gen Electric Metal vapor lamp having a heat reflecting coating of calcium pyrophosphate

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2144438A (en) * 1937-10-06 1939-01-17 Birdseye Electric Company Tubular incandescent electric lamp
US2568459A (en) * 1948-10-29 1951-09-18 Gen Electric Electric discharge device
US2877139A (en) * 1953-02-05 1959-03-10 Corning Glass Works Coated illuminating glassware and method of manufacture thereof
US2806968A (en) * 1953-12-03 1957-09-17 Westinghouse Electric Corp Color-corrected light source and phosphor mixture therefor
US3325662A (en) * 1963-09-19 1967-06-13 Gen Electric Metal vapor lamp having a heat reflecting coating of calcium pyrophosphate

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3727525A (en) * 1968-06-29 1973-04-17 O Takeuchi Device for making phosphor screen for color picture tubes
US3885149A (en) * 1972-04-14 1975-05-20 Thorn Electrical Ind Ltd Lamp pinch seals
US3851200A (en) * 1972-12-11 1974-11-26 Gen Electric Heat and light reflective coating on quartz lamp
US3983513A (en) * 1973-10-18 1976-09-28 Westinghouse Electric Corporation Incandescent lamp having a halogen-containing atmosphere and an integral reflector of non-reactive specular metal
US3932780A (en) * 1974-03-20 1976-01-13 Westinghouse Electric Corporation Electric lamp having an envelope with a specular light-reflective coating of oriented aluminum particles
US4710677A (en) * 1983-07-30 1987-12-01 Thorn Emi Plc Incandescent lamps
US5211473A (en) * 1984-12-31 1993-05-18 Musco Corporation Glare control lamp and reflector assembly and method for glare control
US4816974A (en) * 1986-05-19 1989-03-28 Mycro Group Co. Glare control lamp and reflector assembly and method for glare control
US5075828A (en) * 1986-05-19 1991-12-24 Musco Corporation Glare control lamp and reflector assembly and method for glare control
US4947303A (en) * 1986-05-19 1990-08-07 Musco Corporation Glare control lamp and reflector assembly and method for glare control
US5016150A (en) * 1989-10-19 1991-05-14 Musco Corporation Means and method for increasing output, efficiency, and flexibility of use of an arc lamp
US5134557A (en) * 1989-10-19 1992-07-28 Musco Corporation Means and method for increasing output, efficiency, and flexibility of use of an arc lamp
US5161883A (en) * 1989-10-19 1992-11-10 Musco Corporation Means and method for increasing output, efficiency, and flexibility of use of an arc lamp
US6825615B2 (en) * 2000-10-24 2004-11-30 Tokyo Electron Limited Lamp having a high-reflectance film for improving directivity of light and heat treatment apparatus having such a lamp
US20090027907A1 (en) * 2004-08-26 2009-01-29 Koninklijke Philips Electronics, N.V. Lamp with reflective coating

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Publication number Publication date
GB1257476A (enrdf_load_stackoverflow) 1971-12-22

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