EP0853328B1 - Frittable evaporable getter device having a high yield of barium - Google Patents

Frittable evaporable getter device having a high yield of barium Download PDF

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Publication number
EP0853328B1
EP0853328B1 EP97830748A EP97830748A EP0853328B1 EP 0853328 B1 EP0853328 B1 EP 0853328B1 EP 97830748 A EP97830748 A EP 97830748A EP 97830748 A EP97830748 A EP 97830748A EP 0853328 B1 EP0853328 B1 EP 0853328B1
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EP
European Patent Office
Prior art keywords
powders
packet
container
barium
metallic
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
EP97830748A
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German (de)
English (en)
French (fr)
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EP0853328A1 (en
Inventor
Daniele Martelli
Stefano Trivellato
Luisa Mantovani
Giuseppe Urso
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SAES Getters SpA
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SAES Getters SpA
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
    • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
    • H01J7/186—Getter supports

Definitions

  • the present invention relates to a "frittable" evaporable getter device with a high yield of barium.
  • the evaporable getter materials are mainly employed for the maintenance of vacuum at the inside of picture tubes for television sets and of computer screens.
  • the use of evaporable getter materials at the inside of flat displays, being at present in a developing stage, is also under study.
  • the getter material being commonly used in picture tubes is the metallic barium which is deposited in the form of a thin film on an inner wall of the tube.
  • metallic barium which is deposited in the form of a thin film on an inner wall of the tube.
  • evaporable getter devices which are introduced in the tube during its manufacturing. These devices comprise an open metallic container innerly comprising powders of a compound of barium and aluminum, BaAl 4 , and powders of nickel, Ni, in a ratio by weight of about 1:1.
  • Barium is caused to evaporate by induction heating the device by means of a coil at the outside of the picture tube itself, in an activation process also defined as "flash"; when the temperature in the powders reaches a value of about 800°C, the following reaction takes place: BaAl 4 + 4 Ni ⁇ Ba + 4 NiAl
  • the processes for the manufacture of picture tubes involve a step of welding to each other two glass portions, that is carried out in a so-called "frit sealing" operation, by causing a glass paste with a melting temperature of about 450°C to be molten or softened between the two portions in the presence of air.
  • a getter device may be introduced after the frit sealing through the neck provided for housing the electronic gun; however in this case the size of the getter device is conditioned by the neck diameter and the precise positioning of the device within the picture tube is difficult.
  • Evaporable getter devices which can withstand frit sealing without alterations, or however without causing the above-described drawbacks, are defined as "frittable".
  • a frittable getter device for example in EP-A-0036681: the powder packet held in a container comprises a source of evaporable gettering metal and a material able to release gas upon heating.
  • the gas so formed acts as a scattering medium for the evaporated metallic getter.
  • the gas-releasing material grains are protected from the influence of moist air and of high temperatures during the frit sealing by means of a layer of metal. This is applicable, however, only in the case in which a gas-releasing material is present in the powder packet.
  • Frittable getter devices are already manufactured and sold by the applicant. These devices can be manufactured with traditional technologies as long as some critical values are not exceeded: in particular it is impossible to go beyond certain given thicknesses of the packet of powders, because with too great thicknesses the quantity of heat generated in the body of the packet of powders is dissipated only slowly, thus giving rise to problems as described above. It has been found empirically that the ratio between the quantity of barium comprised in the device, given in mg, and the device diameter, given in mm, must not be more than about 10. Due to reasons relating to the manufacturing of picture tubes, the maximum possible diameter of the getter devices is of about 20 mm, so that the maximum quantity of barium that can be evaporated from frittable getter devices manufactured with traditional technologies is of about 200 mg.
  • Frittable getter devices capable of evaporating barium quantities of more than 200 mg will be defined, in the following part of description and in the claims, as of the 'high yield type".
  • WO 8910627A describes an evaporable getter device having recesses on the surface of the packet of powder or grooves on the bottom of the container able to retard heat propagation in circumferential and radial direction. The heat, in fact, propagates along preferential paths and can cause the formation of hot points from which chips can be ejected.
  • the recesses and grooves delay the transfer of heat in these directions, but other hot points can be formed due to a non uniform and homogeneous heating, causing, as already stated above, the raising of the packet of powders, the ejections of chips and a partial melting of the container. Consequently this is not a frittable getter.
  • US-A-3558962 describes a screen being buried in the mass of the packet of powder; the screen can be joined and welded to the bottom of the powder container, or placed over the powder and pressed thereinto or put in an intermediate position between the surface and the bottom.
  • GB-A-1216892 discloses a wire ring to be put in an annular U-shaped receptacle, with the getter material pressed in it.
  • the wire ring has a very small diameter, ranging from 0,015 to 0,02 inches and a minimum contact with the powder in the annular container, whereby its function is that of avoiding material ejection due to heat propagation in circumferential direction, as in the case of US-A-5118988. So a uniform heating is not achieved.
  • US-A-4642516 tries to overcome the detachment of the getter metal vapour releasing material by providing the powder annular container with grooves extending into the channel to lock the getter material, but the problems due to a non uniform heating of the powder packet are still present unsolved.
  • US Patent 4127361 owned by the applicant, discloses getter devices which can be made frittable by means of a protective layer of organo-silanes; in spite of its efficiency, this covering process is too slow and thereby unacceptable for an industrial production.
  • Object of the present invention is that of providing an evaporable getter device which is free of the drawbacks of the prior art.
  • a frittable evaporable getter device with a high yield of barium comprising:
  • a metallic member is immersed in the packet of powders at such a position to be spaced apart from the bottom and not to emerge at the surface.
  • the induction heating of the getter device mainly occurs by virtue of the container and the metal member immersed in the powder, which thereafter transfer heat to the getter material powders. It has been observed that in the areas of contact between the metal member and the container bottom the heat transfer to the powders is scarcely efficient and a local overheating takes place; if these contact areas are too many or excessively extended, the non-dissipated heat causes the packet of powders to raise and in some cases parts of the device to melt.
  • the metallic member emerges at the free surface of the packet, the surface itself is subdivided in areas which are poorly bound one to another and during the flash are subject to be ejected within the picture tube.
  • the metallic member can be made of various metals, such as iron alloys, nickel alloys or aluminum alloys; preferred is the use of steel AISI 304 for its easy cold workability.
  • the metal member can have different shapes, provided it is discontinuous and essentially planar.
  • the metal member may be formed as a metallic cut blank having a rayed shape, like the element 10 in the drawing, showing a central hole for helping the release of barium from the underlying powders; it may be a cut blank showing a multiplicity of holes distributed on the surface either in a random or in an orderly way, as exemplified by the member 12; or it may be a wire net as described in the mentioned US Patent 3.558.962.
  • the member must be essentially flat to be able to be immersed in the packet of powders, which generally has a thickness of few millimeters, without contacting the container bottom and without coming out from the surface of the powders.
  • the condition that the metallic member must not be in contact with the bottom of the container can be obtained in various ways. Some examples not being embodiments are shown in Figures 2 to 4 and some embodiments are shown in figures 5-6, wherein various metallic members are represented in correspondence with various methods employed to keep them at a distance from the bottom, but each of the various types of member (ray-shaped cut blank, holed blank, wire net or others) can be used in each one of the configurations described in the following.
  • a possible getter device not being an embodiment of the invention is shown in cross-section in figure 2; such a device 20 is obtained by pouring onto the bottom of the container 21 a first portion 22 of powders, laying on the upper surface thereof a flat metallic member 23 and covering the latter with the remainder portion 24 of powders. Finally the powders are compressed in the container with a shaped punch so that on the upper surface 25 of the packet radial recesses 26,26'... are formed.
  • the ratio by weight between the quantity of powders placed in the container before and after the positioning of the metallic member 23 determines the level of the same member within said packet and therefore it is chosen in such a way that the member will not emerge on the surface 25 not even where the recesses 26,26'...
  • the metallic member 33 can be deformed locally thus obtaining thereon some "feet" 34; as shown in figure 3b representing in cross-section a getter device 30 not being an embodiment according to the invention, when the member 33 is placed in the container 31 wherein the powders 32 are present, the feet 34 keep it at a pre-set distance from the bottom 35 of the container. Also in this case on the upper surface 36 of the packet of powders there are the radial recesses 37,37',....
  • the container of the device according to the invention as claimed may be anyone among the containers of the prior art.
  • This is generally made of steel, preferably of the type AISI 304 or 305, for its easy cold workability by pressing and good resistance to the oxidizing conditions during the operation of frit sealing of the picture tube.
  • the shape of said container is essentially that of a short cylinder, closed in the bottom and open at the top, although various modifications of this basic shape are possible, such as e.g. the deformations of the bottom or of the side walls as previously described.
  • the packet of powders is comprised of a mixture of powdered BaAl 4 and of powdered nickel.
  • the particle size of the powders of BaAl 4 is generally lower than about 250 ⁇ m; the particle size of the powders of nickel is generally lower than about 60 ⁇ m.
  • the ratio by weight between the two materials is generally between about 1.2:1 and 1:1.2; preferably this ratio by weight is of about 1:1.
  • the packet of powders is formed locally by pouring a mixture of loose powders in the container and pressing the same by suitable punches. At the upper surface of the packet some recesses are formed in radial direction, in a varying number from 2 to 8, as described in the mentioned US Patent no. 5.118.988.
  • the devices of the invention may also be produced in a nitrogen-containing version: it is known in the field the use of getter devices containing small quantities of nitrogen compounds, such as iron nitride, Fe 4 N, germanium nitride, Ge 3 N 4 or intermediate nitrides of iron and germanium.
  • getter devices containing small quantities of nitrogen compounds, such as iron nitride, Fe 4 N, germanium nitride, Ge 3 N 4 or intermediate nitrides of iron and germanium.
  • the purpose of these components is that of generating small pressures of nitrogen in the picture tube during the step of barium flash, thus allowing to obtain more extended and uniform deposits of barium.
  • a getter device is prepared by using a container of steel AISI 304 having diameter of 20 mm and height of 4 mm with the bottom shaped with elevations 1 mm high like those shown in fig.5. Within the container there is positioned a net of steel AISI 304 with meshes of 1,5 mm width, resting on the bottom elevations. A homogeneous mixture is poured into the container, being comprised of 775 mg of powdered BaAl 4 , for a total content of 403 mg of barium, and 875 mg of powdered nickel. The mixture of powders is then compressed at the inside of the container with a punch so shaped as to form at the surface of packet 4 radial recesses.
  • the sample thus obtained is treated at 450°C during 1 hour in air to simulate the frit sealing conditions.
  • the sample is then placed in a glass flask being connected to a pump system, the flask is evacuated and a barium evaporation test is carried out by following the method described in the standard ASTM F 111-72 while heating the device by means of radio frequencies for 35 s with such a power that the evaporation starts 15 s after the heating begins.
  • the result of the test is reported in Table 1, in which there are indicated notes on the evaporation details, the aspect of the remainder and the quantity of evaporated barium.
  • test of example 1 is repeated with a mixture including a nitrogen dispenser, formed of 785 mg of powdered nickel, 825 mg of powdered BaAl 4 and 40 mg of Fe 4 N. The results of the test are reported in Table 1.
  • test of example 1 is repeated, but by using for compressing the powders in the container a flat punch, so that the surface of the packet does not show radial recesses.
  • results of the test are reported in Table 1.
  • test of example 1 is repeated, but using a container with flat bottom and causing the wirenet to rest on the bottom thereof.
  • the results of the test are reported in Table 1.
  • Example 1 The test of example 1 is repeated, but using a sample in which the net emerges at the surface of the packet of powders: this sample has been obtained by pouring the mixture of powders into the container, laying the net upon the powders and compressing the whole by means of a flat punch. The results of the test are reported in Table 1.
  • EXAMPLE NOTES 1 Intact packet; intact container; evaporated barium: 300 mg. 2 Intact packet; intact container; evaporated barium: 330 mg. 3 Ejection of the packet of powders; evaporated barium: non detectable. 4 Remarkable central swelling of the packet of powders; evaporated barium: 300mg. 5 Melting of the container; evaporated barium: non detectable. 6 Ejection of chips from the surface of the packet of powders; evaporated barium: non detectable.

Landscapes

  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
  • Powder Metallurgy (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Farming Of Fish And Shellfish (AREA)
EP97830748A 1997-01-10 1997-12-31 Frittable evaporable getter device having a high yield of barium Expired - Lifetime EP0853328B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT97MI000037A IT1289875B1 (it) 1997-01-10 1997-01-10 Dispositivo getter evaporabile frittabile ad alta resa di bario
ITMI970037 1997-01-10

Publications (2)

Publication Number Publication Date
EP0853328A1 EP0853328A1 (en) 1998-07-15
EP0853328B1 true EP0853328B1 (en) 2003-08-13

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ID=11375572

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97830748A Expired - Lifetime EP0853328B1 (en) 1997-01-10 1997-12-31 Frittable evaporable getter device having a high yield of barium

Country Status (12)

Country Link
EP (1) EP0853328B1 (cs)
JP (1) JP2849084B2 (cs)
KR (1) KR100304604B1 (cs)
CN (1) CN1113376C (cs)
BR (1) BR9800279A (cs)
CZ (1) CZ287498B6 (cs)
DE (1) DE69724090T2 (cs)
ID (1) ID18337A (cs)
IT (1) IT1289875B1 (cs)
MY (1) MY119622A (cs)
RU (1) RU2137243C1 (cs)
TW (1) TW359845B (cs)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1298106B1 (it) * 1998-01-13 1999-12-20 Getters Spa Dispositivi getter evaporabili azotati ad elevata resistenza al frittaggio e processo per la loro produzione
IT1303731B1 (it) * 1998-11-10 2001-02-23 Getters Spa Dispositivo getter evaporabile con ridotta perdita di particelle eprocesso per la sua produzione.
IT1312511B1 (it) 1999-06-24 2002-04-17 Getters Spa Dispositivi getter per l'evaporazione del calcio
ITMI20011341A1 (it) 2001-06-26 2002-12-26 Getters Spa Dispositivo getter evaporabile per tubi a raggi catodici
ITMI20012273A1 (it) * 2001-10-29 2003-04-29 Getters Spa Leghe e dispositivi getter per l'evaporazione del calcio
CN106457121B (zh) * 2014-06-24 2020-02-21 松下知识产权经营株式会社 气体吸附器件和使用该气体吸附器件的真空隔热件

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1216892A (en) * 1967-02-02 1970-12-23 Union Carbide Corp Improvements in or relating to getter construction
US4128782A (en) * 1974-09-26 1978-12-05 U.S. Philips Corporation Getter holder and electric discharge tube comprising such a holder
US4642516A (en) * 1983-10-07 1987-02-10 Union Carbide Corporation Getter assembly providing increased getter yield
JPH0378928A (ja) * 1989-08-22 1991-04-04 Toshiba Corp 大型電子管用ゲッタ装置

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3560788A (en) * 1968-12-11 1971-02-02 Union Carbide Corp R-f energizable, pan-shaped getter for television tube
US3558962A (en) * 1968-12-11 1971-01-26 Union Carbide Corp High yield getter device
US3669567A (en) * 1969-06-14 1972-06-13 Getters Spa Gettering
NL7016726A (cs) * 1970-11-14 1972-05-16
IT1065291B (it) * 1976-12-06 1985-02-25 Getters Spa Dispositivo getter e metodo per il suo impiego
NL8001759A (nl) * 1980-03-26 1981-10-16 Philips Nv Getterinrichting; werkwijze voor het vervaardigen van een kleurentelevisiebeeldbuis onder toepassing van deze getterinrichting en aldus vervaardigde kleurentelevisiebeeldbuis.
US4717500A (en) * 1985-11-27 1988-01-05 Union Carbide Corporation Getter device for frit sealed picture tubes
IT1216605B (it) * 1988-04-20 1990-03-08 Getters Spa Dispositivo getter a forma di tegame, avente una resa elevata.

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1216892A (en) * 1967-02-02 1970-12-23 Union Carbide Corp Improvements in or relating to getter construction
US4128782A (en) * 1974-09-26 1978-12-05 U.S. Philips Corporation Getter holder and electric discharge tube comprising such a holder
US4642516A (en) * 1983-10-07 1987-02-10 Union Carbide Corporation Getter assembly providing increased getter yield
JPH0378928A (ja) * 1989-08-22 1991-04-04 Toshiba Corp 大型電子管用ゲッタ装置

Also Published As

Publication number Publication date
CN1113376C (zh) 2003-07-02
DE69724090T2 (de) 2004-06-09
TW359845B (en) 1999-06-01
IT1289875B1 (it) 1998-10-19
BR9800279A (pt) 2000-03-28
JPH10208674A (ja) 1998-08-07
ITMI970037A1 (it) 1998-07-10
RU2137243C1 (ru) 1999-09-10
CZ7298A3 (cs) 1998-07-15
JP2849084B2 (ja) 1999-01-20
MY119622A (en) 2005-06-30
KR100304604B1 (ko) 2001-11-02
ID18337A (id) 1998-03-26
EP0853328A1 (en) 1998-07-15
KR19980070412A (ko) 1998-10-26
CZ287498B6 (en) 2000-12-13
DE69724090D1 (de) 2003-09-18
CN1187685A (zh) 1998-07-15

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