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US3875454A - Low-pressure mercury vapour discharge lamp and method of manufacturing said lamp - Google Patents

Low-pressure mercury vapour discharge lamp and method of manufacturing said lamp Download PDF

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US3875454A
US3875454A US41260673A US3875454A US 3875454 A US3875454 A US 3875454A US 41260673 A US41260673 A US 41260673A US 3875454 A US3875454 A US 3875454A
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Prior art keywords
coating
lamp
glass
oxide
wall
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Der Wolf Rein Willemse Van
Vette Thomas Hendrik De
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North American Philips Lighting Corp
Philips Corp
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Philips Corp
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas- or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/30Vessels; Containers
    • H01J61/35Vessels; Containers provided with coatings on the walls thereof; Selection of materials for the coatings
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas- or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/38Devices for influencing the colour or wavelength of the light
    • H01J61/42Devices for influencing the colour or wavelength of the light by transforming the wavelength of the light by luminescence
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas- or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/38Devices for influencing the colour or wavelength of the light
    • H01J61/42Devices for influencing the colour or wavelength of the light by transforming the wavelength of the light by luminescence
    • H01J61/46Devices characterised by the binder or other non-luminescent constituent of the luminescent material, e.g. for obtaining desired pouring or drying properties

Abstract

In a low-pressure mercury vapour discharge lamp a tin oxide coating having a resistance per square of more than 10,000 Ohm is provided on the wall so as to avoid blackening of the glass. Particularly this coating is used in the aperture of a lamp for photo-copying purposes.

Description

United States Patent Van Der Wolf et a1.

LOW-PRESSURE MERCURY VAPOUR DISCHARGE LAMP AND METHOD OF MANUFACTURING SAID LAMP Inventors: Rein Willemse Van Der Wolf;

Thomas Hendrik De Vette, both of Emmasingel, Eindhoven,

Netherlands Assignee: U.S. Philips Corporation, New

York, NY.

Filed: Nov. 5, 1973 Appl. No.: 412,606

Foreign Application Priority Data Nov. 25, 1972 Netherlands 7216025 US. Cl 313/488, 117/97, 313/220,

313/493, 313/489 Int. Cl [-101] 1/70, HOlj 61/35 Field of Search 313/108 R, 109, 220221, 313/110, 113, I34, 44, 488, 493; 117/97 Primary Examiner.lames W. Lawrence Assistant ExaminerMarvin Nussbaum [57] ABSTRACT In a low-pressure mercury vapour discharge lamp a tin oxide coating having a resistance per square of more than 10,000 Ohm is provided on the wall so as to avoid blackening of the glass. Particularly this coating is used in the aperture of a lamp for photo-copying purposes.

2 Claims, 1 Drawing Figure LOW-PRESSURE MERCURY VAPOUR DISCHARGE LAMP AND METHOD OF MANUFACTURING SAID LAMP ln low-pressure mercury vapour discharge lamps in which the energy in the gas discharge is converted into radiation, particularly into light the phenomenon often occurs that the glass wall gets a grey appearance after a number of operating hours. This grey discoloration which is caused by an interaction of mercury and the glass wall results in radiation absorption and an unesthetic appearance of the lamp.

The number of operating hours after which the radiation absorption becomes inadmissible due to the grey discoloration and the lamp thus has to be replaced is firstly dependent on the current density in the lamp, i.e. the number of mA/sq.cm of the cross-section of the discharge space. Furthermore, as regards the grey discoloration, it is a great difference whether the wall of the lamp is bare or is coated with a luminescent coating. In a bare lamp having a bare wall the grey discoloration, both at high and at low current densities, i.e. above and below a value of 50 mA/sq.cm is already inadmissible after a number of operating hours which in lamps having a luminescent coating on the wall does not result in a disturbing grey discoloration. At a low current density the grey discoloration in lamps having a luminescent coating on the inner side of the glass wall of the lamp is often so little that no special steps are necessary.

In a given type of lamp having a luminescent coating (furthermore denoted by S-lamp) an apertured part of the glass wall extending longitudinally is not coated with a luminescent material. in such lamps which are particularly used for photo-copying equipment the glass in the aperture is directly exposed to the mercury discharge and a very strong grey discoloration occurs after a very short time at that area especially when the current density in the discharge is chosen to be high so as to obtain an intensive radiation.

To inhibit the grey discoloration it has already been proposed to coat the glass with a transparent protective coating of a metal oxide namely titanium dioxide. This titanium dioxide coating is always formed in practice from a solution of tetrabutyltitanate. ln S-lamps the glass in the aperture must then be coated in any case with such a protective coating. Often, however, the entire glass wall is coated prior to the luminescent coating being provided because this is simpler than providing the protective coating alone in the aperture with the aid of special equipment.

A low-pressure mercury vapour discharge lamp according to the invention, having a glass envelope whose inner side has a luminescent coating and a transparent metal oxide coating located between this coating and the wall is characterized in that the metal oxide coating consists of tin oxide and has a resistance per square of at least 10,000 Ohm.

In this connection resistance per square of the tin oxide coating is understood to means the resistance measured between 2 strip-shaped parallel electrodes of 1 cm length pressed on the tin oxide coating and being spaced 1 cm apart.

The resistance per square of the tin oxide coating must be higher than 10,000 Ohm because otherwise the protective coating is conducting in such a manner that it detrimentally interferes with the gas discharge so that black spots and specks are produced after a given number of operating hours.

Likewise as the above-mentioned known protective coating consisting of titanium dioxide the tin oxide coating is very satisfactorily transparent and quite scratch resistant. The tin oxide can also easily be provided during a bulk manufacturing process.

The invention is of special importance for those kinds of lamps (furthermore denoted by F-lamps) in which the lamp wall not only has a luminescent coating but also a reflective coating. Such a reflective coating serves to concentrate the light generated in the luminescent coating in a given direction. To this end the reflective coating is present between the glass wall and the luminescent coating but it is not provided over the entire circumference of the glass envelope. Two differ ent types of lamps can be distinguished in this respect, namely those in which the luminescent coating extends over the entire circumference and those in which the luminescent coating and hence the reflective coating leave a apertured part of the glass wall uncoated. Lamps of the latter type (further denoted by FS-lamps) are thus the same as the S-lamps described above, but have a reflective coating between the luminescent coating and the glass wall. The reflective coating and the luminescent coating may extend or not extend over the same circumferential angle. Granular titanium dioxide is commonly used as a material for the reflective coatmg.

Both in F-lamps and in FS-lamps it is possible to provide the known protective coating of titanium dioxide or the tin oxide coating according to the invention as a first coating on the glass wall likewise as in lamps without a reflective coating, and to subsequently provide the reflective coating on the protective coating and finally provide the luminescent coating. To adhere the coatings to the wall or to a previously provided coating a separate heat treatment, the so-called sintering treatment, is always necessary in order to remove the solvent and binder used for the formation of the coating. Thus the lamp is to be placed three times in a furnace, heated, cooled and removed. These operations make the manufacture of such types of lamps time-consuming and expensive.

Departing from the above-described manufacture the reflective coating may alternatively be firstly provided on the wall, followed by the protective coating and the luminescent coating. It is true that a slightly better adhesion of the reflective coating is then obtained, but when using a protective coating of titanium dioxide three times sintering remains necessary. In addition a large quantity of titanium dioxide is required to form the protective coating because the sintered reflective coating is very porous.

Unlike a protective coating of titanium dioxide, a protective coating of tin oxide according to the invention may be formed in situ from a suitable organic tin compound such as, for example, dibutyltinmaleate on a reflective coating which has not been previously sintered. Thus one of thr three sintering operations is then omitted. Moreover, less material is used for the protective coating because this coating in case of a suitable solvent being chosen is directly provided on the reflective coating which still comprises binder and is thus not porous for the organic tin compound.

When using the method described in the previous paragraph lamps are obtained in which the tin oxide is directly supportted by the glass wall at those areas where there is no reflective coating and is located between the reflective coating and the luminescent coating in the other part of the lamp.

The tin oxide coating of a suitably chosen organic tin compound such as, for example, dibutyltinmaleate may of course alternatively be provided in situ in lamps in which the protective tin oxide coating is directly supported by the glass wall over the entire circumference of the lamp.

Further advantages of the use of organic tin compounds over tetrabutyltitanate are that the solution of the tin compounds from which tin oxide can be forced in situ does not foam, does not hydrolize and does not form a gel. Also the rate of coating of the lamps may be much faster than when using titanium dioxide particularly because foaming does not occur.

The invention will now be described in greater detail with reference to a drawing of an FS-lamp and a description of an example of its manufacture.

The drawing shows in a cross-sectional view an F- lamp in which the protective coating of tin oxide in the aperture is supported by the glass wall and is furthermore located between the reflective coating and the luminescent coating. In this FIG. 1 is the glass wall, 2 is the reflective coating, for example, of titanium dioxide, 3 is the tin oxide coating having a resistance per square of more than 10,000 Ohm and 4 is the luminescent coating, for example, of willemite. The drawing clearly shows that in the aperture which is denoted by 5 the glass wall I is only coated with the protective tin oxide coating 4. There is no reflective coating and no luminescent coating in the aperture.

In the manufacture ofa lamp as shown in the drawing the glass tube 1 is brought to a vertical position before the stems with the electrodes and the exhaust tube are provided and is coated with the desired reflective coating by injection or raising a titanium dioxide suspension. The suspension used for this purpose is prepared by suspending 800 gms of granular TiO in 400 ml of butylacetate to which 25 ml of dibutylphtalate have been added. After this suspension has been ground for 7 hours in a ball mill, 280 ml of a 1% solution of nitrocellulose in butylacetate is added and grinding takes place for another hour.

After the TiO -coating is provided it is dried with the aid of hot air of l 8-25C for approximately 10 minutes and butylacetate evaporates but nitrocellulose and dibutylphtalate remain. Subsequently a strip-shaped part of the TiO, coating is wiped off over the entire tube length with the aid of a vulcalon plate.

The partly coated tube wall thus obtained is then coated, by means of injection or raising in the tube, with a thin coating of a solution having the following composition:

750 ml ethanol 250 ml isobutanol l% by volume of ethylcellulose by volume of dibutyltinmaleate. At this manufacturing stage the tin coating of the solution adheres both to the TiO, coating and to the glass in the wiped-out aperture. The binder of the TiO, coating does not dissolve in this solution and the TiO: coating thus remains intact.

After drying at room temperature for approximately 2 minutes the tube having the two coatings is introduced into a furnace and heated for 50 to 150 seconds at a temperature of approximately 580C. Dibutylphtalate, nitrocellulose and ethylcellulose thereby evaporate and burn out and dibutyltinmaleate is converted into a tin oxide layer having a resistance per square of at least 10,000 Ohm.

After the tube has been removed from the furnace and has cooled, the luminescent coating is provided by injecting or raising a suspension of willemite in the vertically placed tube. The suspension used for this purpose is manufactured by grinding gms of willemite for 2 hours in a ball mill in 400 mls of a 1% solution of nitrocellulose in a mixture of 95% butylacetate and 5% rnonoethylglycolaether to which V2% by volume of dibutylphthalate, 2 gms of Sb O and 6 gms of Sr,P O, have been added. After drying (at 20 25C for approximately 10 minutes) of the suspension coating thus provided an aperture is wiped out with the aid of a vulcalon plate in the dried suspension coating at the same area where the aperture has been wiped out of the TiO, coating. Subsequently the tube is again introduced into a furnace and heated for 50 to seconds at approximately 530C during which nitrocellulose completely evaporated and burns out.

The tube having three coatings obtained after this operation is finished in known manner to a fluorescent lamp particularly intended for photo-copying purposes by providing steps with electrodes, exhausting, filling, operating etc.

What is claimed is 1. A low-pressure mercury vapour discharge lamp which comprises a glass envelope whose inner side has a luminescent coating and a transparent metal oxide coating, said metal oxide coating consists of tin oxide and has a resistance per square of at least 10,000 Ohm.

2. A low-pressure mercury vapour discharge lamp as claimed in claim 1 in which a light reflective coating is provided between the glass wall and part of the luminescent coating, wherein the tin oxide coating is directly provided on the glass wall at the area where there' is no light reflective coating and is located between the light reflective coating and the luminescent coating in the other part of the lamp.

l i l l

Claims (2)

1. A LOW-PRESSURE MERCURY VAPOUR DISCHARGE LAMP WHICH COMPRISES A GLASS ENVELOPE WHOSE INNER SIDE HAS A LUMINESCENT COATING AND A TRANSPARENT METAL OXIDE COATING, SAID METAL OXIDE COATING CONSISTS OF TIN OXIDE AND HAS A RESISTANCE PER SQUARE OF AT LEAST 10,000 OHM.
2. A low-pressure mercury vapour discharge lamp as claimed in claim 1 in which a light reflective coating is provided between the glass wall and part of the luminescent coating, wherein the tin oxide coating is directly provided on the glass wall at the area where there is no light reflective coating and is located between the light reflective coating and the luminescent coating in the other part of the lamp.
US3875454A 1972-11-25 1973-11-05 Low-pressure mercury vapour discharge lamp and method of manufacturing said lamp Expired - Lifetime US3875454A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
NL7216025A NL171756C (en) 1972-11-25 1972-11-25 A low-pressure mercury vapor discharge lamp and a method for the production thereof.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US05516633 US3984589A (en) 1972-11-25 1974-10-21 Method of manufacturing a low pressure mercury vapor discharge lamp

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US3875454A true US3875454A (en) 1975-04-01

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JP (1) JPS5139955B2 (en)
BE (1) BE807769A (en)
CA (1) CA984891A (en)
DE (1) DE2355268C2 (en)
FR (1) FR2208189B3 (en)
GB (1) GB1450785A (en)
NL (1) NL171756C (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2644821A1 (en) * 1975-10-06 1977-04-14 Gte Sylvania Inc Fluorescent lamp with reflector layer
US4058639A (en) * 1975-12-09 1977-11-15 Gte Sylvania Incorporated Method of making fluorescent lamp
US4500810A (en) * 1980-11-25 1985-02-19 North American Philips Lighting Corporation Fluorescent lamp having integral light-filtering means and starting aid
EP0402878A1 (en) * 1989-06-13 1990-12-19 Mitsubishi Denki Kabushiki Kaisha Low pressure rare gas discharge lamp
US5557170A (en) * 1993-12-24 1996-09-17 U.S. Philips Corporation Low-pressure discharge lamp and method of manufacturing a low-pressure discharge lamp
US20030234611A1 (en) * 2002-06-19 2003-12-25 Klinedinst Keith A. Control of leachable mercury in fluorescent lamps

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3205394A (en) * 1960-04-06 1965-09-07 Sylvania Electric Prod Fluorescent lamp having a sio2 coating on the inner surface of the envelope
US3225241A (en) * 1959-07-09 1965-12-21 Sylvania Electric Prod Aperture fluorescent lamp
US3350598A (en) * 1965-12-29 1967-10-31 Sylvania Electric Prod High pressure electric discharge device containing a fill of mercury, halogen and an alkali metal and barrier refractory oxide layers
US3624444A (en) * 1969-07-05 1971-11-30 Philips Corp Low-pressure mercury vapor discharge lamp
US3676729A (en) * 1969-06-23 1972-07-11 Sylvania Electric Prod Arc discharge lamp having a thin continuous film of indium oxide on the inner surface thereof

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL111360C (en) * 1957-01-12
US3141990A (en) * 1960-04-06 1964-07-21 Sylvania Electric Prod Fluorescent lamp having a tio2 coating on the inner surface of the bulb

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3225241A (en) * 1959-07-09 1965-12-21 Sylvania Electric Prod Aperture fluorescent lamp
US3205394A (en) * 1960-04-06 1965-09-07 Sylvania Electric Prod Fluorescent lamp having a sio2 coating on the inner surface of the envelope
US3350598A (en) * 1965-12-29 1967-10-31 Sylvania Electric Prod High pressure electric discharge device containing a fill of mercury, halogen and an alkali metal and barrier refractory oxide layers
US3676729A (en) * 1969-06-23 1972-07-11 Sylvania Electric Prod Arc discharge lamp having a thin continuous film of indium oxide on the inner surface thereof
US3624444A (en) * 1969-07-05 1971-11-30 Philips Corp Low-pressure mercury vapor discharge lamp

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2644821A1 (en) * 1975-10-06 1977-04-14 Gte Sylvania Inc Fluorescent lamp with reflector layer
US4058639A (en) * 1975-12-09 1977-11-15 Gte Sylvania Incorporated Method of making fluorescent lamp
US4500810A (en) * 1980-11-25 1985-02-19 North American Philips Lighting Corporation Fluorescent lamp having integral light-filtering means and starting aid
EP0402878A1 (en) * 1989-06-13 1990-12-19 Mitsubishi Denki Kabushiki Kaisha Low pressure rare gas discharge lamp
US5187415A (en) * 1989-06-13 1993-02-16 Mitsubishi Denki Kabushiki Kaisha Low-pressure rare gas discharge lamp and method for lighting same
US5557170A (en) * 1993-12-24 1996-09-17 U.S. Philips Corporation Low-pressure discharge lamp and method of manufacturing a low-pressure discharge lamp
US20030234611A1 (en) * 2002-06-19 2003-12-25 Klinedinst Keith A. Control of leachable mercury in fluorescent lamps
US6741030B2 (en) * 2002-06-19 2004-05-25 Osram Sylvania Inc. Control of leachable mercury in fluorescent lamps

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Publication number Publication date Type
DE2355268C2 (en) 1983-07-28 grant
NL7216025A (en) 1974-05-28 application
JPS5139955B2 (en) 1976-10-30 grant
FR2208189A1 (en) 1974-06-21 application
BE807769A1 (en) grant
DE2355268A1 (en) 1974-06-06 application
NL171756B (en) 1982-12-01 application
CA984891A (en) 1976-03-02 grant
CA984891A1 (en) grant
NL171756C (en) 1983-05-02 grant
BE807769A (en) 1974-05-24 grant
GB1450785A (en) 1976-09-29 application
JP1087496C (en) grant
FR2208189B3 (en) 1976-10-08 grant
JPS4983277A (en) 1974-08-10 application

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