US3427491A - Discharge tube - Google Patents

Discharge tube Download PDF

Info

Publication number
US3427491A
US3427491A US631221A US3427491DA US3427491A US 3427491 A US3427491 A US 3427491A US 631221 A US631221 A US 631221A US 3427491D A US3427491D A US 3427491DA US 3427491 A US3427491 A US 3427491A
Authority
US
United States
Prior art keywords
zirconium
cathodes
borides
carbonate
oxides
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US631221A
Other languages
English (en)
Inventor
Hideo Mizuno
Hidezo Akutsu
Eijiro Moriguchi
Katsuyuki Yamashita
Shigeru Kamiya
Koshi Iwata
Yoshio Tawara
Atsushi Iga
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Holdings Corp
Original Assignee
Matsushita Electronics Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electronics Corp filed Critical Matsushita Electronics Corp
Application granted granted Critical
Publication of US3427491A publication Critical patent/US3427491A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/04—Electrodes; Screens; Shields
    • H01J61/06—Main electrodes
    • H01J61/067—Main electrodes for low-pressure discharge lamps
    • H01J61/0675—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode
    • H01J61/0677—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode characterised by the electron emissive material

Definitions

  • the present invention relates to an improvement in discharge lamps, and more particularly to an improvement of low presure mercury discharge tubes such as fluorescent lamps.
  • Oxide cathodes of the prior art utilized as electrodes in low pressure mercury vapor type discharge tubes such as fluorescent lamps were formed by coating double coils or so-called triple coils of tungsten having a fine filament wound around said double coil of tungsten with a compound carbonate consisting of barium carbonate, strontium carbonate and calcium carbonate, enclosing the resulting coated structures in a discharge tube, thereafter subjecting these carbonates to thermal decomposition during the process of exhausting gas from said tube, thereby producing oxides of barium, strontium and calcium.
  • the oxide layers thus produced were of high resistivity and poor thermal conductivity.
  • a discharge tube incorporating cathodes led, when lighted, to the development of cathode spots locally having a high temperature and such cathode spots constituted the centers of thermionic emission.
  • this temperature of the cathode spots did not make any substantial change, due to their thermal inertia, either during the re-ignition or extinction of the arc of the cathodes in all AC cycles, but rather the cathode spots continued to have a high temperature.
  • Japanese patent publication No. 1,581/ 1964 proposes lowering the temperature of the cathode spots by restricting the thickness of the oxide layers to 30p or less to sub stantially enhance the thermal conductivity of cathodes and to thereby enlarge the cathode spots.
  • this prior method is not desirable because it inevitably reduces the absolute volume of the electron-emitting oxides, and this in turn, reduces the life of the discharge tube.
  • Another attempt has been reported in Japanese patent publications N0.
  • a fluorescent lamp for practical use which is substantially noiseless, namely, producing a radio-interfering noise as low as 15 db or less and which is free from the development of blackening of the tube is obtained by the use of a cathode emitter consisting principally of oxides of barium, stronium and calcium, said oxides containing iron-cobalt borides having high melting points and having a markedly superior thermal conductivity as compared to ordinary ionic crystals and having been stabilized by substituting a part of said iron with one or more of the substances selected from the group consisting of titanium, zirconium, hafnium, vanadium, nobium, tantalum, chromium, molybdenum, tungsten, aluminium and silicon, and further, containing powder of a reducing metal selected from the group consisting of zirconium, hafnium, niobium and tantalum.
  • Powders of said reducing metals namely, zirconium, hafnium, niobium and tantalum satisfactorily prevent the metal borides from being oxidized during the thermal decomposition of the carbonates, which is conducted during the process of exhausting gas from the discharge tubes.
  • the discharge tube embodying the present invention with its oxide cathodes being made of a material consisting of oxides of barium, stronium and calcium and containing 1% by weight of metal borides corresponding to the composition formula of and 3% by weight of zirconium, relative to the total weight of said oxides, respectively, is of a remarkably superior noise minimizing effect to conventional discharge tubes wherein the cathodes are made of such oxides.
  • the drawing shows a comparison 'between the magnitudes of noise imparted to a radio-receiver by a fluoroescent lamp embodying the persent invention and by a conventional fluorescent lamp.
  • curve 1 represents the magnitude of the noise, caused by a fluorscent lamp in which a conventional oxide is used.
  • the metal borides used in the present invention point to such poly-element metal borides as are represented by the composition formula of wherein Me represents one or more of the metals selected from the group consisting of titanium, zirconium, hafnium, canadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminium and silicon.
  • Me represents one or more of the metals selected from the group consisting of titanium, zirconium, hafnium, canadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminium and silicon.
  • a mixture of the aforesaid metal borides and carbonates of barium, strontium and calcium is applied to the surfaces of the coils of electrodes.
  • the coated electrodes are heated to the order of 1200 C. during the process of exhausting the gas from the fluorescent lamp, and as a result the aforesaid carbonates are decomposed by the heat to form the so-called
  • the added metal borides have a melting point of 1300 C. or higher and that they do not become oxidized when heated to a temperature of the order of 1200 C. in a carbon dioxide gas atmosphere.
  • iron boride there are two different composition ratios, namely, Fe B and FeB.
  • Cobalt boride includes two different composition ratios, namely, C 8 and CoB. Their melting points are 1389 C., 1550 C., 1265 C. and 1350 C., respectively.
  • Fe B and Co B have melting points which are slightly lower than those of FeB and CoB.
  • a metal boride containing boron in a larger proportion as in FeB and CoB markedly reduces the life of the cathode emitter.
  • a fluorescent lamp wherein the cathodes are made of an emitter containing by weight of FeB has a life duration of about 2000 hours.
  • a fluorescent lamp whose cathodes are made of an emitter containing 5% by weight of Fe B has a life duration of the order of 5000 hours.
  • iron-cobalt borides whose composition formula is (Fe-Co) B.
  • the proportion of the volume of boron is smaller than that indicated by the chemical composition, however, this leads to the development of free iron or cobalt, which as has been already described, resulting in the metal boride becoming susceptible to oxidation. For this reason, it is desirable to use a volume of boron somewhat larger in proportion, i.e.
  • the metal boride consists of a simple substance of Fe B
  • this substance becomes oxidized to some extent during the decomposition of the electrodes, resulting in the end-band type blackening after about 1000 hours of lighting.
  • This blackening is caused by the mercury oxide particles formed by the coupling of the residual impure gases, especially, oxygen with mercury, depositing on the inner peripheral face of the tube in the area about 3 cm. in front of the electrodes.
  • the metal borides which are used in the present invention are comprised of poly-element borides which are composed principally of the iron-cobalt borides indicated by the composition formula of wherein a part of the iron has been substituted by one or more of the substances selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminium and silicon.
  • y has a value ranging from 0.01 to 0.3.
  • Borides of titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminium and silicon have very high melting points.
  • the melting point of Mo B is 2000 C.
  • that of Ti B is 2790 C.
  • that of Zr B is 3040 C.
  • that of W 13 is 2770 C.
  • they have melting points which lie in the level of 2000 C. or higher.
  • the discharge lamp employing an emitter containing the aforesaid composition in Which the aforesaid borides are added has the superior features that it develops very little amount of blackening during the course of lighting and also that its effect of minimizing radiointerfering noise is hardly reduced.
  • the metals having melting points such as titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten and aluminium, and silicon can be substituted in the range of amount, i.e.
  • y 0.0l to 0.3, and preferably, in the range of from 0.03 to 0.1.
  • y which indicates the amount to be substituted by these metals having high melting points, takes a value less than 0.01, the effect of improving the stability of the emitter at high temperature is reduced, while on the other hand, when it exceeds 0.3, it is rather difficult to make solidsolution of borides.
  • the effect of minimizing to noise interference is noted when the cathodes contain 0.05% or more by weight of such metal borides.
  • the borides in a proportion of the order of from 0.1 to 2%.
  • the addition of metal borides in a proportion in excess of 10% by weight means a reduction in the proportion of oxides of barium, strontium and calcium and results in a reduced duration of life of the lamp, and therefore, the addition of metal borides in such excess proportion is not desirable.
  • an additive consisting of powder of one or more of the reducing metals having high melting points selected from the group consisting of zirconium, hafnium, niobium and tantalum which is to be contained in a proportion of the order of from 1 to 8% by weight in the oxides of the cathodes of the present invention is mandatory for the prevention of blackening of the lamp during lighting and also for the purpose of obtaining a prolonged duration of life of the lamp.
  • EXAMPLE 1 Grams Barium carbonate 35 Strontium carbonate 35 Calcium carbonate 29 (0.4Fe'O.4Co-0.05Ti-0. 05Al) B l Zirconium 3 EXAMPLE 2 Barium carbonate 35 Strontium carbonate 35 Calcium carbonate 29 (0.5Fe- 0.4Co-0.03Zr-0.02Hf) l3 1 Zirconium 3 EXAMPLE 3 Barium carbonate 35 Strontium carbonate 35 Calcium carbonate 29 Zirconium 2 Hafnium 1 EXAMPLE 4 Barium carbonate 35 Strontium carbonate 35 Calcium carbonate 29 (0.7Fe-0.2Co-O.05W) B 1 Zirconium 2 Hafnium 1 EXAMPLE 5 Barium carbonate 35 Strontium carbonate 35 Calcium carbonate 29 (0.7Fe-0.2Co-0.-03V-0.
  • the fluorescent lamps fabricated in the manner described above were subjected to test by connecting them to commonly utilized parallel condensers of 0.0 0 6 ,uf. All of these lamps showed that the interfering noise in the frequency band of from 535 kc. to 1605 kc. was 15 db or less as is indicated by curve 2 in the drawing, and also that the duration of life was similar to that of ordinary discharge tubes, Thus, the lamps manufactured according to the present invention could be termed as being substantially perfectly noiseless fluorescent lamps.
  • a discharge tube satisfactorily low in radio-interfering noise and equipped with cathodes coated with a cathode emitter consisting of oxides consisting principally of oxides of barium, strontium and calcium, said oxides containing, in a proportion of from 0.05 to 10% by weight relative to said oxides, a substance having the composition formula of and consisting principally of iron-cobalt borides of which a part of said iron having been substituted with one or more metals Me selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum and silicon, the mivture of said oxide and said substance containing, in a proportion of from 1 to 8% by weight relative to said oxides, one or more reducing metals having high melting points and selected from the group consisting of zirconium, hafnium, molybdenum and tantalum.

Landscapes

  • Discharge Lamp (AREA)
US631221A 1966-04-20 1967-04-17 Discharge tube Expired - Lifetime US3427491A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2563066 1966-04-20

Publications (1)

Publication Number Publication Date
US3427491A true US3427491A (en) 1969-02-11

Family

ID=12171171

Family Applications (1)

Application Number Title Priority Date Filing Date
US631221A Expired - Lifetime US3427491A (en) 1966-04-20 1967-04-17 Discharge tube

Country Status (5)

Country Link
US (1) US3427491A (en:Method)
BE (1) BE697243A (en:Method)
DE (1) DE1589230B2 (en:Method)
GB (1) GB1178051A (en:Method)
NL (1) NL146636B (en:Method)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3505553A (en) * 1966-05-12 1970-04-07 Philips Corp Radio-interference-free low-pressure mercury-vapor lamp
US3684401A (en) * 1970-11-17 1972-08-15 Westinghouse Electric Corp Cathode-getter materials for sputter-ion pumps
NL9400731A (nl) * 1994-05-04 1995-12-01 Matsushita Electric Works Ltd Elektrode voor toepassing in een fluorescerende lamp en werkwijze ter vervaardiging daarvan.

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2473358A (en) * 1946-08-23 1949-06-14 Raytheon Mfg Co Cathode coating for electron discharge devices
US2724070A (en) * 1953-02-09 1955-11-15 Westinghouse Electric Corp Cathode coating for electrical discharge devices and method for making the same
US2820920A (en) * 1952-09-17 1958-01-21 Claude Ets Manufacture of coated electrodes
US2849637A (en) * 1956-02-02 1958-08-26 Weiss Harry Electrode for fluorescent lamp
US3312856A (en) * 1963-03-26 1967-04-04 Gen Electric Rhenium supported metallic boride cathode emitters

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2473358A (en) * 1946-08-23 1949-06-14 Raytheon Mfg Co Cathode coating for electron discharge devices
US2820920A (en) * 1952-09-17 1958-01-21 Claude Ets Manufacture of coated electrodes
US2724070A (en) * 1953-02-09 1955-11-15 Westinghouse Electric Corp Cathode coating for electrical discharge devices and method for making the same
US2849637A (en) * 1956-02-02 1958-08-26 Weiss Harry Electrode for fluorescent lamp
US3312856A (en) * 1963-03-26 1967-04-04 Gen Electric Rhenium supported metallic boride cathode emitters

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3505553A (en) * 1966-05-12 1970-04-07 Philips Corp Radio-interference-free low-pressure mercury-vapor lamp
US3684401A (en) * 1970-11-17 1972-08-15 Westinghouse Electric Corp Cathode-getter materials for sputter-ion pumps
NL9400731A (nl) * 1994-05-04 1995-12-01 Matsushita Electric Works Ltd Elektrode voor toepassing in een fluorescerende lamp en werkwijze ter vervaardiging daarvan.

Also Published As

Publication number Publication date
GB1178051A (en) 1970-01-14
DE1589230B2 (de) 1972-01-13
NL146636B (nl) 1975-07-15
NL6705289A (en:Method) 1967-10-23
BE697243A (en:Method) 1967-10-02
DE1589230A1 (de) 1970-12-03

Similar Documents

Publication Publication Date Title
US3389288A (en) Gettering device including a getter metal and a gas releasing material
JPH01115047A (ja) 熱陰極形低圧希ガス放電蛍光ランプ
US2806970A (en) Electron emission coatings and method of preparing air stabilized barium oxide
US3563797A (en) Method of making air stable cathode for discharge device
US3427491A (en) Discharge tube
US3544829A (en) Low pressure mercury vapour discharge lamp
US2686274A (en) Thermionic cathode
JPH1050252A (ja) 放電ランプ用電極
US3427492A (en) Discharge tube satisfactorily low in radio-interfering noise
US2159774A (en) Secondary electron emitter and method of making it
US2175696A (en) Electron emitter
US2840751A (en) Electrode coating composition and electrode for cold cathode gas discharge lamp
US3513349A (en) Discharge tube
US1965587A (en) Gaseous electric discharge device and method of making the same
US3388955A (en) Process for producing within electron tubes,in particular television picture tubes,a thin metallic film capable of sorbing their residual gases
US1981620A (en) Electrode for electron discharge devices
US3313974A (en) High pressure electric discharge device having electrodes with thorium on the exposed surface thereof
US3951874A (en) Method for preparing electron emissive coatings
US2740914A (en) Thermionic cathodes
US2208692A (en) Active metal compound for vacuum tubes
US3911312A (en) Oxide cathode for an electric discharge tube
US2930872A (en) Glow switch
US2232780A (en) Light source and method of producing the same
US2831137A (en) Cathode coating
US1644712A (en) Electric lamp