CA2172686A1 - Combination of materials for integrated getter and mercury-dispensing devices and devices thus obtained - Google Patents
Combination of materials for integrated getter and mercury-dispensing devices and devices thus obtainedInfo
- Publication number
- CA2172686A1 CA2172686A1 CA002172686A CA2172686A CA2172686A1 CA 2172686 A1 CA2172686 A1 CA 2172686A1 CA 002172686 A CA002172686 A CA 002172686A CA 2172686 A CA2172686 A CA 2172686A CA 2172686 A1 CA2172686 A1 CA 2172686A1
- Authority
- CA
- Canada
- Prior art keywords
- mercury
- dispensing
- materials
- dispensing device
- combination
- 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.)
- Abandoned
Links
- 239000000463 material Substances 0.000 title claims abstract description 75
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims abstract description 78
- 229910052753 mercury Inorganic materials 0.000 claims abstract description 76
- 239000010949 copper Substances 0.000 claims abstract description 39
- 239000000203 mixture Substances 0.000 claims abstract description 37
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 24
- 239000000956 alloy Substances 0.000 claims abstract description 24
- 238000010438 heat treatment Methods 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 13
- 239000002184 metal Substances 0.000 claims abstract description 13
- 238000007789 sealing Methods 0.000 claims abstract description 12
- 229910052802 copper Inorganic materials 0.000 claims abstract description 11
- 229910000765 intermetallic Inorganic materials 0.000 claims abstract description 11
- 230000001737 promoting effect Effects 0.000 claims abstract description 10
- 239000010936 titanium Substances 0.000 claims abstract description 10
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 9
- 230000008569 process Effects 0.000 claims abstract description 8
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 7
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 7
- 150000002739 metals Chemical class 0.000 claims abstract description 7
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 6
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 6
- 229940126062 Compound A Drugs 0.000 claims abstract description 5
- NLDMNSXOCDLTTB-UHFFFAOYSA-N Heterophylliin A Natural products O1C2COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC2C(OC(=O)C=2C=C(O)C(O)=C(O)C=2)C(O)C1OC(=O)C1=CC(O)=C(O)C(O)=C1 NLDMNSXOCDLTTB-UHFFFAOYSA-N 0.000 claims abstract description 5
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000000843 powder Substances 0.000 claims description 22
- 150000001875 compounds Chemical class 0.000 claims description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 10
- 238000010586 diagram Methods 0.000 claims description 9
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 239000010955 niobium Substances 0.000 claims description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 2
- 229910052715 tantalum Inorganic materials 0.000 claims description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 claims description 2
- 229910001122 Mischmetal Inorganic materials 0.000 abstract description 4
- 238000001994 activation Methods 0.000 description 17
- 230000004913 activation Effects 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 12
- 238000002844 melting Methods 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 7
- 239000002775 capsule Substances 0.000 description 7
- 239000007788 liquid Substances 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- 230000008901 benefit Effects 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 239000011521 glass Substances 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 229910000497 Amalgam Inorganic materials 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000006698 induction Effects 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 238000011282 treatment Methods 0.000 description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000012634 fragment Substances 0.000 description 2
- 238000010943 off-gassing Methods 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000002269 spontaneous effect Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910017945 Cu—Ti Inorganic materials 0.000 description 1
- 229910017985 Cu—Zr Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000003926 complexometric titration Methods 0.000 description 1
- 229940125898 compound 5 Drugs 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- KHYBPSFKEHXSLX-UHFFFAOYSA-N iminotitanium Chemical compound [Ti]=N KHYBPSFKEHXSLX-UHFFFAOYSA-N 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 229910001000 nickel titanium Inorganic materials 0.000 description 1
- 230000001473 noxious effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000006187 pill Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
- H01J61/26—Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope
-
- 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
- H01J7/183—Composition or manufacture of getters
-
- 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
- H01J7/20—Means for producing, introducing, or replenishing gas or vapour during operation of the tube or lamp
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Discharge Lamp (AREA)
- Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
- Gas Separation By Absorption (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
Abstract
The mercury-dispensing combination according to the invention consists of a mercury-dispensing intermetallic compound A including mercury and a second metal selected among titanium, zirconium and mixtures thereof, preferably Ti3Hg, and a promoting alloy or intermetallic compound B including copper, tin and one or more metals selected among the rare earths, in particular misch metal (MM). There are also disclosed mercury-dispensing devices containing such a combination and in particular further including a getter material C, as well as a process for introducing mercury into the electron tubes, the process consisting in the introduction into the open tube of one of said devices, and then heating the device to get mercury free at a temperature between 600°C and 900°C
for a time between 10 seconds and one minute after the tube sealing.
for a time between 10 seconds and one minute after the tube sealing.
Description
Z~ 7~686 "A COMBINATION OF MATERIALS FOR INTEGRATED GETTER AND
MERCURY-DISPENSING DEVICES AND DEVICES THUS OBTAINED"
The present invention relates to a combination of materials for the production of devices combining the getter and mercury-dispensing functions, to the devices thus produced and to a process for the introduction of mercury inside electron tubes.
The use of small amounts of mercury in electron tubes such as, for example, mercury-arc rectifiers, lasers, various kinds of alphanumeric displays and, particularly, fluorescent lamps is well known in the art.
A precise dosage of mercury inside these devices is extremely important for the quality of the devices and most of all for ecological reasons. In fact, the high toxicity of this element implies serious problems of environmental pollution upon end-life disposal of the devices containing it, or in case of accidental break-up of the devices. These problems of ecological nature impose the use of amounts of mercury as small as possible, compatibly with the functionality of the tubes. These considerations have been lately included also in the legislative sphere, and the trend of the recent international regulations is to establish top limits for the amount of mercury which can be introduced into the devices:
for example, for standard fluorescent lamps the use of a total amount of Hg not greater than 10 mg per lamp has been suggested.
Mercury can be introduced into the tubes in liquid form. However, the use of liquid mercury first of all poses problems concerning the storing and handling in the plants for the production of tubes, due to its high vapor pressure also at room temperature. Secondly, a common drawback of the techniques for the introduction into the tubes of mercury in liquid form is the difficulty in precisely and reproducibly dosing volumes of mercury in the order of microliters, which difficulty usually takes to the introduction of amounts of the element higher than needed.
These drawbacks have taken to the development of various techniques in alternative to the use of liquid mercury in free form.
The use of liquid mercury contained in capsules is disclosed in several prior art documents. This method is described, for example, in US
patents nos.4.823.047 and 4.754.193, referring to the use of metallic capsules, and in US patents nos.4.182.971 and 4.278.908 wherein the 21 7~6~b mercury container is made of glass. After closing the tube, the mercury is released by means of a heat treatment which causes the breakage of the container. These methods generally have some drawbacks. First of all, the production of the capsules and their mounting inside the tubes may be 5 complicated, especially when they have to be introduced inside small-size tubes. Secondly, the breakage of the capsule, particularly if it is made of glass, may produce fragments of material which can jeopardize the tube quality, so much that US patent no.4.335.326 discloses an assembly wherein the mercury-containing capsule is in turn located inside a capsule 10 acting as a shield for the fragments. Moreover, the release of the mercury is often violent, with possible damages to the inner structure of the tube.
Finally, these systems still have the drawback of employing liquid mercury, and therefore they do not completely solve the problem of the precise and reproducible dosage of few milligrams of mercury.
US patent no.4.808.136 and the European patent application EP-568.317 disclose the use of tablets or small spheres of porous material soaked with mercury which is then released by heating once the lamp is closed. However, also these methods require complicated operations for the loading of mercury into the tablets, and the released amount of 20 mercury is difficult to be reproduced.
The use of amalgams of mercury, for example with indium, bismuth or zinc, is also known. However, these amalgams generally have the drawback of a low melting temperature and a high mercury vapor pressure already at temperatures not very high. For example, the zinc amalgams 25 described in the commercial bulletins of the APL Engineered Materials Inc.
have a vapor pressure at 43C which is about 90% of that of liquid mercury. Consequently, these amalgams badly withstand the thermal treatments for the production of the lamps in which they are introduced.
These problems are overcome by US patent no.3.657.589 in the 30 name of the Applicant, which discloses the use of intermetallic compounds of mercury having the general formula Ti,,ZryHgz, wherein x and y may vary between 0 and 13, the sum (x+y) may vary between 3 and 13 and z may be 1 or2.
These compounds have a temperature of mercur,v-release start 35 variable according to the specific compound, however they are all stable up to about 500C both in the atmosphere and in evacuated volumes, thus resulting compatible with the operations for the assembly of the electron tubes, during which the mercury-dispensing devices may reach temperatures of about 600C. After closing the tube, the mercury is released from the above-cited compounds by an activation operation, 5 which is usually carried out by heating the material between 750C and 900C for about 30 seconds. This heating may be accomplished by laser radiation, or by induction heating of the metallic support of the Hg-dispensing compound. The use of the Ti3Hg compound, manufactured and sold by the Applicant under the trade name St505, results particularly 10 advantageous; in particular, the St505 compound is sold in the form of compressed powder in a ring-shaped container or of compressed powder in pills or tablets, under the trademark STAHGSORB~, or in the form of powders laminated on a metallic strip, under the trademark GEMEDIS~.
These materials offer various advantages with respect to the prior 1 5 art:
- as mentioned above, they avoid the risks of mercury evaporation during the cycle of production of the tubes, in which temperatures of about 350400C may be reached;
- as described in the cited US patent no.3.657.589, a getter material 20 can be easily added to the mercury-dispensing compound with the purpose of chemisorption of gases such as CO, C2, 2~ H2 and H2O, which would interfere with the tube operation; the getter is activated during the same heat treatment for the release of mercury;
- the released amount of mercury is easily controllable and 25 reproducible.
Despite their good chemical-physical characteristics and their great ease of use, these materials have the drawback that the contained mercury is not completely released during the activation treatment. In fact, the processes for the production of mercury-containing electron tubes 30 include a tube-closing operation performed by glass fusion (e.g. the sealing of fluorescent lamps) or by frit sealing, i.e. welding two pre-shaped glass members by means of a paste of low-melting glass. During these operations, the mercury-dispensing device may undergo an indirect heating up to about 600C. In this step the device is exposed to gases and 35 vapors emitted by the melted glass and, in almost all industrial processes, to air. In these conditions, the mercury-dispensing material undergoes a ~1 72686 surface oxidation, whose final result is a yield lower than about 40% of the total mercury content during the activation process. In the particular case of compact circular lamps, during the lamp sealing and bending steps the mercury-dispensing material undergoes an indirect heating up to about 600C. In this case the mercury yield during the activation process drops as low as about 20% of the total mercury content of the device.
The mercury not released during the activation operation is then slowly released during the life of the electron tube.
This characteristic, together with the fact that the tube must obviously work from the beginning of its life cycle, leads to the necessity of introducing into the device an amount of mercury which is at least double than that which would theoretically be necess~ry.
In order to overcome these problems, patent application EP-A-091.297 suggests the addition of Ni or Cu powders to the Ti3Hg or Zr3Hg compounds. According to this document, the addition of Ni and Cu to the mercury-dispensing compounds c~ ~ses the melting of the combination of materials thus obtained, favouring the release of almost all the mercury in few seconds. The melting takes place at the eutectic temperatures of the systems Ni-Ti, Ni-Zr, Cu-Ti and Cu-Zr, ranging from about 880C for the Cu 66% - Ti 34% composition to 1280C for the Ni 81% - Ti 19% composition (atomic percent), though the document erroneously gives a melting temperature of 770C for the Ni 4% - Ti 96%
composition. The document acknowledges that the mercury-containing compound is altered during the tube working treatments, and it needs a protection. To this purpose, there is suggested to close the powder container by means of a steel, copper or nickel sheet which is broken during the activation by the pressure of the mercury vapor generated inside the container. This solution is not completely satisfactory: in fact, same as it happens in the methods employing capsules, mercury bursts out violently and can cause damages to portions of the tube; the manufacturing of the container is quite complicated, since it requires the welding of small-size metallic members. Furthermore, this document does not contain experimental data to support the stated good mercury-release characteristics of the combinations indicated. Finally, the devices in this application, contrary to those illustrated in the cited US patent no.3.657.589, do not allow to integrate a getter material, whose presence is necessary for the correct working of the lamps, into a same device.
Therefore, the object of the present invention is to provide an improved combination of materials for dispensing mercury in the electron tubes, which allows to overcomes one or more drawbacks of the prior art.
In particular, the object of the present invention is first of all to provide an improved combination of materials for dispensing mercury which is capable of releasing amounts of mercury higher than 60% during the activation step, even after partial oxidation, so as to be able to reduce the total amount of employed mercury.
Another object of the present invention is to provide a combination of materials whose residue, after the activation operation for releasing mercury, has a getter activity.
Another object of the present invention is to provide mercury-dispensing devices containing the combination of materials of the 1 5 invention.
Still another object is to provide a process for introducing mercury by means of the devices of the invention into the electron tubes which require said element.
According to the present invention, these and other objects are achieved by using a mercury-dispensing combination of materials made up of:
- a mercury-dispensing intermetallic compound A including mercury and a second metal selected among titanium, zirconium and mixtures thereof;
- an alloy or an intermetallic compound B including copper, tin and one or more metals selected among the rare earths.
Further objects and advantages of the present invention will be apparent from the following detailed description referring to the annexed drawings wherein:
Fi~.1 is a perspective view of a mercury-dispensing device of the present invention according to a possible embodiment thereof;
Fi~s.2 and 2a are, respectively, a top plan view and a sectional view along ll-ll of a device of the invention according to another possible embodiment;
Fi~s.3, 3a and 3b are, respectively, a top plan view and two sectional views along lll-lll of a device of the invention according to a further embodiment, in two possible variations;
Fi~.4 shows, in a ternary diagram, the alloys of the present invention.
Component A of the combination of the present invention, hereafter also defined mercury dispenser, is an intermetallic compound 5 corresponding to formula TixZryHgz, as disclosed in the cited US patent no.3.657.589, to which reference is made for further details. Among the materials corresponding to said formula, Zr3Hg and, particularly, Ti3Hg are preferred.
Component B of the combination of the present invention has the 10 function of favouring the release of mercury from component A, and hereafter will also be defined promoter. This component is a metallic alloy or an intermetallic compound including copper, tin and a metal selected among the rare earths or a mixture of rare earths. The use of a mixture of rare earths is preferred over the use of single elements in that, since these 15 metals have a similar chemistry, the separation of the single elements is a difficult and expensive operation; on the other hand, by using a mixture of rare earths it is possible to obtain, in this application, essentially the same results obtained with the single elements. The mixtures of rare earths are known in the art by the name Umisch metal"; this denomination, and its short form MM, will be used hereafter in the rest of the specification and in the claims.
The weight ratio between copper, tin and MM can vary within a wide range, but advantageous results have been obtained with compositions which, in a ternary diagram of percentage compositions on a weight basis (fig.4), fall within a polygon defined by points:
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c) Cu 30% - Sn 10 % - MM 60%
d) Cu 3% - Sn 37 % - MM 60%
e) Cu 3% -Sn 96,5% -MM 0,5%
With copper percentages higher than 63% the alloy reaches a high melting point and consequently requires excessive temperatures for its activation, while on the contrary with copper percentages lower than about 3% the alloy has a melting point too low and this implies the risk of having a low-viscosity liquid phase at the temperatures, varying about from 600 to 800C, reached during the production of the lamps. With misch metal concentrations higher than 60% by weight the alloy becomes excessively reactive, and could give rise to violent reactions both during the lamp production step and during the activation step. Finally, with tin contents lower than 10% by weight the alloy reaches again a high melting point.
Particularly advantageous results are obtained, within said range of compositions, by means of compositions which, in a ternary diagram of percentage compositions on a weight basis (fig.4), fall within a polygon defined by points:
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c)Cu50%-Sn10 %-MM40%
d) Cu 30% - Sn 30 % - MM 40%
e) Cu 30% - Sn 69,5% - MM 0,5%
A particularly preferred alloy has the percentage composition Cu 40% - Sn 30% - MM 30%, corresponding to point i) in the composition - ternary diagram of fig.4.
The weight ratio between components A and B of the combination of the invention may vary within a wide range, but it is generally included between 20:1 and 1 :20, and preferably between 10:1 and 1 :5.
Components A and B of the combination of the invention may be employed in various physical forms, not necess~rily the same for the two components. For example, component B may be present in the form of a coating of the metallic support, and component A as a powder adhered to component B by rolling. However, the best results are obtained when both components are in the form of a fine powder, having a particle size lower than 250 ,um and preferably between 10 and 125 ,um.
The present invention, in a second aspect thereof, relates to the mercury-dispensing devices which use the above-described combinations of A and B materials.
As previously mentioned, one of the advantages of the combination of materials of the invention with respect to prior art systems is that they do not need a mechanical protection from the environment, thus not posing the limit of a closed container. Consequently, the mercury-dispensing devices of the present invention can be manufactured with the most different geometric shapes, and materials A and B of the combination can be employed without support or on a support, usually metallic.
~1 72686 Some classes of electron tubes for which the mercury dispensers are intended further require, for their correct operation, the presence of a getter material which removes traces of gases such as CO, CO2, H2, 2 or water vapor: it is the case, for example, of fluorescent lamps. An important advantage offered by the combinations of the present invention is that the residue remaining after the evaporation of mercury has a getter activity.
The amount of gas which can be absorbed by said residue, and the absorption velocity, are sufficient to assure an adequate degree of vacuum for many applications. In order to increase the total gas absorption velocity and capacity of this device, it is obviously possible to add thereto another getter material C, according to the manners described in the cited US
patent no.3.657.589. Obviously, in this case the amount of getter material C is lower than that required in prior art devices used in the same application. Examples of getter materials include, among the others, metals such as titanium, zirconium, tantalum, niobium, vanadium and mixtures thereof, or alloys thereof with other metals such as nickel, iron, aluminum, like the alloy having a weight percentage composition Zr 84% -Al 16%, manufactured and sold by the Applicant under the name St101, or the intermetallic compounds Zr2Fe and Zr2Ni, manufactured and sold by the Applicant respectively under the name St198 and St199. The getter material is activated during the same heat treatment by which mercury is released inside the tube.
The getter material C may be present in various physical forms, but it is preferably employed in the form of a fine powder, having a particle size lower than 250 ~m and preferably between 10 and 125 ~m.
The ratio between the overail weight of the A and B materials and that of the getter material C may generally range from about 10:1 to 1:10, and preferably between 5:1 and 1:2.
Some possible embodiments of the devices of the invention are illustrated hereunder with reference to the drawings.
In a first possible embodiment, the devices of the invention can simply consist of a tablet 10 made up of compressed and unsupported powders of the A and B (and possibly C) materials, which for ease of production generally has a cylindrical or parallelepipedal shape; this latter possibility is shown in fig.1.
In the case of supported materials, the device may have the shape of 21 126~6 a ring 20 as shown in fig.2, which represents a top plan view of the device, and in fig.2a which represents a cross-section along ll-ll of device 20. In this case, the device is made up of a support 21 having the shape of a toroidal channel containing the A and B (and possibly C) materials. The 5 support is generally metallic, and preferably of nickel-plated steel.
Alternatively, the device may be made in the shape of a strip 30 as shown in fig.3, which represents a top plan view of the device, and in figs.3a and 3b wherein a section along lll-lll of device 30 is depicted. In this case, support 31 consists of a strip, preferably made of nickel-plated 10 steel, onto which the A and B (and possibly C) materials are adhered by cold compression (rolling). In this case, whenever the presence of the getter material C is required, materials A, B and C may be mixed together and rolled on one or both faces of the strip (fig.3a), or materials A and B
are rolled on one surface of the strip and material C on the opposite 15 surface, as shown in fig.3b.
The invention, in a further aspect thereof, relates to a method for introducing mercury into the electron tubes by using the above-described devices.
The method includes the step of introducing inside the tube the 20 above-described mercury~ispensing combination of materials and preferably in one of the above-described devices 10, 20 or 30, and then the combination heating step to get mercury free. The heating step may be carried out with any suitable means such as, for example, by radiation, by high-frequency induction heating or by having a current flow through the 25 support when the latter is made of a material having a high electric resistivity. The heating is effected at a temperature which ~lses the release of mercury from the mercury-dispensing combination, comprised between 600 and 900C for a time of about 10 seconds to one minute. At temperatures lower than 600C mercury is almost not dispensed at all, 30 whereas at temperatures higher than 900C there is the danger of the development of noxious gases by outgassing from the portions of the electron tube adjacent to the device or of the formation of metal vapors.
The invention will be further illustrated by the following examples.
These non-limiting examples illustrate some embodiments intended to 35 teach to those skilled in the art how to put in practice the invention and to show the accomplishment of the invention which is considered the best.
Examples 1 and 9 concern the preparation of the mercury-dispensing and promoting materials, while examples 3 to 6 concern the tests for the mercury release after the heat treatment simulating the sealing operation.
All the metals used for the preparation of alloys and compounds for the following tests have a minimum pureness of 99,5%. In the compositions of the examples all percentages are on a weight basis if not differently specified.
This example illustrates the synthesis of the mercury-dispensing material Ti3Hg.
143,7 9 of titanium are placed in a steel cradle and degassed by a furnace treatment at a temperature of about 700C and a pressure of 10~
mbar for 30 minutes. After cooling the titanium powder in an inert atmosphere, 200,6 9 of mercury are introduced in the cradle by means of a quartz tube. The cradle is then closed and heated at about 750C for 3 hours. After cooling, the product is ground until a powder passing through a 120,um mesh-size standard sieve is obtained.
The resulting material essentially consists of Ti3Hg, as confirmed by a diffractometric test carried out on the powder.
This example concerns the preparation of a promoting alloy which makes part of the combinations of the invention.
40 9 of Cu, 30 9 of Sn and 30 9 of MM in powder form, are placed into an alumina cradle and then introduced in a vacuum induction furnace.
The misch metal used contains about 50% by weight of cerium, 30% of lanthanum, 15% of neodymium and the rest are other rare earths.
The mixture is heated at a temperature of about 900C, kept at that temperature for 5 minutes to encourage the homogeneity thereof, and finally cast into a steel ingot-mould. Each ingot is ground in a blade mill and the powder is sieved like in example 1. The composition of the obtained alloy is Cu 40% - Sn 30% - MM 30%, and corresponds to point i) in the diagram of fig.4.
This example concerns the preparation of a promoting alloy which makes part of the combinations of the invention. The procedure of example 2 is repeated using 60 9 of Cu, 30 9 of Sn and 10 9 of MM in 21 726~6 powder form. The composition of the obtained alloy is Cu 60% - Sn 30% -MM 10%, and corresponds to point 1) in the diagram of fig.4.
Examples 4 to 9 concem the tests for the mercury release after a 5 heat treatment in air which simulates the frit conditions to which the device is subjected during the tube closing (hereafter generally referred to as sealing). Examples 4 to 7 are comparative examples which show the release after frit sealing respectively by the dispensing component alone (ex.4) and by the same mixed only with copper, tin and the above-cited getter alloy St101 (ex.5-7); a similar comparative test on a mixture of Ti3Hg and MM powders was not possible due to the excessive reactivity of this mixture.
For the simulation of the sealing, 150 mg of each powder mixture have been loaded in a ring-shaped container like in fig.1 or on a strip like 15 in fig.3, and have been subjected to the following thermal cycle in air:
- - heating from room temperature to 450C in about 5 seconds;
- isotherm at 450C for 60 seconds;
- cooling from 450C to 350C, requiring about 2 seconds;
- isotherm at 350C for 30 seconds;
20 - spontaneous cooling to room temperature, requiring about 2 minutes.
Thereafter, the mercury release tests have been carried out on the thus treated samples by induction heating thereof at 850C for 30 seconds inside a vacuum chamber and by measuring the mercury remained in the dispensing device through the method of the complexometric titration 25 according to Volhart.
The results of the tests are summarized in Table 1, which shows the mercury-dispensing compound A, the promoting material B (letters (i) or (I) in examples 8 and 9 refer to the composition of the Cu-Sn-MM alloy as shown in the diagram of fig.4), the weight ratio between components A and 30 B and the mercury yield as a percentage of released mercury on the total content of the device.
The comparative examples are marked by a star.
Table 1 EXAMPLEN. A B A/B Hgyield (%) 4 Ti3Hg ~ - 35,2 5* Ti3Hg Cu 7/3 34,0 6* Ti3Hg Sn 5/1 25,0 7* Ti3Hg St 101 1/1 22,4 8 Ti3HgCu-Sn-MM (i) 2/1 80,0 9 Ti3HgCu-Sn-MM (I) 2/1 87,0 Examples 10 to 14 concern the tests for the functionality as getter materials of the residues remaining after the mercury release by the combinations of the invention and by some comparative combinations.
These tests have been carried out by simulating the frit conditions to which the materials are subjected during the bending and sealing operations of the compact fluorescent circular lamps, which conditions, as mentioned above, are harder that those reached for straight lamps. In particular, the combinations of the examples have been subjected to the following thermal cycle in air:
- heating from room temperature to 600C in about 10 seconds;
- isotherm at 600C for 15 seconds;
- spontaneous cooling to room temperature, requiring about 2 minutes.
The mercury release tests (activation) have been carried out after simulation of the frit sealing on the samples. The fritted samples have been introduced inside a vacuum chamber having a volume of 1 liter, and heated under vacuum at 850C for 10 seconds and kept at said temperature for 20 seconds.
The capacity of the residue to work as a getter is measured after the activation; this measurement is performed by introducing in the chamber an amount of hydrogen such as to bring the pressure to 0.1 mbar at a temperature of 30C, and by measuring the time required for the pressure in the chamber to decrease to 0.01 mbar. The measure of the pressure is taken by means of a capacitive manometer. The results of these tests are summarized in Table 2, which shows the composition of the sample and the hydrogen absorption velocity at 30C. The USAMPLE COMPOSITION"
column gives the weight percentages of the component materials. The comparative combinations are marked by a star.
21 726~6 Table 2 EXAMPLE N. SAMPLE COMPOSITIONH2 absorption velocity (cc/s) 10* Ti3Hg notmeasurable 11* Ti3Hg: 50% 7,2 St 101: 50%
12 Ti3Hg: 60% 6,9 Cu-Sn-MM (i): 40%
13 Ti3Hg: 60% 3,5 Cu-Sn-MM (I): 40%
14 Ti3Hg: 30% 15,3 Cu-Sn-MM (i): 20%
St 101: 50%
It may be noted from the data of Table 1 that the combinations with 5 promoter of the invention allow mercury yields higher than 80% during the activation step even after frit sealing in air at 450C, thus permitting the reduction of the overall mercury amount introduced in the electron tubes.
Furthermore, as shown by the data in Table 2, the residue remaining after the mercury release has a getter activity: in fact, while the residue 10 remaining after the mercury release by the Ti3Hg compound alone has no getter activity, the sample of example 13 to which no getter has been added exhibits a significant hydrogen absorption velocity. Moreover, sample 12 has a hydrogen absorption velocity comparable to that of the sample of example 11, which is a combination of a mercury dispenser with 15 a getter, widely used by lamp manufacturers.
When a getter material is added to the combination of example 12, the hydrogen absorption velocity becomes nearly twice that of example 11, with the same percentage of getter. These properties of the combination of the invention make it possible to use very small amounts of additional 20 getter material or even none, while retaining the functionality of the devices in which it is used.
The combinations with promoter of the present invention offer another important advantage, consisting in the possibility of carrying out the activation operation at temperatures or with times lower than those 21 726~6 allowed by prior art materials. In fact, in order to have industrially acceptable activation times, Ti3Hg alone requires an activation temperature of about 900C, whereas the present combinations allow the reduction of the operation time and of the size of the lines for the 5 production of the lamps; in both cases a double advantage is achieved of causing less pollution inside the tube due to the outgassing of all the materials present therein and of reducing the amount of energy required for the activation.
MERCURY-DISPENSING DEVICES AND DEVICES THUS OBTAINED"
The present invention relates to a combination of materials for the production of devices combining the getter and mercury-dispensing functions, to the devices thus produced and to a process for the introduction of mercury inside electron tubes.
The use of small amounts of mercury in electron tubes such as, for example, mercury-arc rectifiers, lasers, various kinds of alphanumeric displays and, particularly, fluorescent lamps is well known in the art.
A precise dosage of mercury inside these devices is extremely important for the quality of the devices and most of all for ecological reasons. In fact, the high toxicity of this element implies serious problems of environmental pollution upon end-life disposal of the devices containing it, or in case of accidental break-up of the devices. These problems of ecological nature impose the use of amounts of mercury as small as possible, compatibly with the functionality of the tubes. These considerations have been lately included also in the legislative sphere, and the trend of the recent international regulations is to establish top limits for the amount of mercury which can be introduced into the devices:
for example, for standard fluorescent lamps the use of a total amount of Hg not greater than 10 mg per lamp has been suggested.
Mercury can be introduced into the tubes in liquid form. However, the use of liquid mercury first of all poses problems concerning the storing and handling in the plants for the production of tubes, due to its high vapor pressure also at room temperature. Secondly, a common drawback of the techniques for the introduction into the tubes of mercury in liquid form is the difficulty in precisely and reproducibly dosing volumes of mercury in the order of microliters, which difficulty usually takes to the introduction of amounts of the element higher than needed.
These drawbacks have taken to the development of various techniques in alternative to the use of liquid mercury in free form.
The use of liquid mercury contained in capsules is disclosed in several prior art documents. This method is described, for example, in US
patents nos.4.823.047 and 4.754.193, referring to the use of metallic capsules, and in US patents nos.4.182.971 and 4.278.908 wherein the 21 7~6~b mercury container is made of glass. After closing the tube, the mercury is released by means of a heat treatment which causes the breakage of the container. These methods generally have some drawbacks. First of all, the production of the capsules and their mounting inside the tubes may be 5 complicated, especially when they have to be introduced inside small-size tubes. Secondly, the breakage of the capsule, particularly if it is made of glass, may produce fragments of material which can jeopardize the tube quality, so much that US patent no.4.335.326 discloses an assembly wherein the mercury-containing capsule is in turn located inside a capsule 10 acting as a shield for the fragments. Moreover, the release of the mercury is often violent, with possible damages to the inner structure of the tube.
Finally, these systems still have the drawback of employing liquid mercury, and therefore they do not completely solve the problem of the precise and reproducible dosage of few milligrams of mercury.
US patent no.4.808.136 and the European patent application EP-568.317 disclose the use of tablets or small spheres of porous material soaked with mercury which is then released by heating once the lamp is closed. However, also these methods require complicated operations for the loading of mercury into the tablets, and the released amount of 20 mercury is difficult to be reproduced.
The use of amalgams of mercury, for example with indium, bismuth or zinc, is also known. However, these amalgams generally have the drawback of a low melting temperature and a high mercury vapor pressure already at temperatures not very high. For example, the zinc amalgams 25 described in the commercial bulletins of the APL Engineered Materials Inc.
have a vapor pressure at 43C which is about 90% of that of liquid mercury. Consequently, these amalgams badly withstand the thermal treatments for the production of the lamps in which they are introduced.
These problems are overcome by US patent no.3.657.589 in the 30 name of the Applicant, which discloses the use of intermetallic compounds of mercury having the general formula Ti,,ZryHgz, wherein x and y may vary between 0 and 13, the sum (x+y) may vary between 3 and 13 and z may be 1 or2.
These compounds have a temperature of mercur,v-release start 35 variable according to the specific compound, however they are all stable up to about 500C both in the atmosphere and in evacuated volumes, thus resulting compatible with the operations for the assembly of the electron tubes, during which the mercury-dispensing devices may reach temperatures of about 600C. After closing the tube, the mercury is released from the above-cited compounds by an activation operation, 5 which is usually carried out by heating the material between 750C and 900C for about 30 seconds. This heating may be accomplished by laser radiation, or by induction heating of the metallic support of the Hg-dispensing compound. The use of the Ti3Hg compound, manufactured and sold by the Applicant under the trade name St505, results particularly 10 advantageous; in particular, the St505 compound is sold in the form of compressed powder in a ring-shaped container or of compressed powder in pills or tablets, under the trademark STAHGSORB~, or in the form of powders laminated on a metallic strip, under the trademark GEMEDIS~.
These materials offer various advantages with respect to the prior 1 5 art:
- as mentioned above, they avoid the risks of mercury evaporation during the cycle of production of the tubes, in which temperatures of about 350400C may be reached;
- as described in the cited US patent no.3.657.589, a getter material 20 can be easily added to the mercury-dispensing compound with the purpose of chemisorption of gases such as CO, C2, 2~ H2 and H2O, which would interfere with the tube operation; the getter is activated during the same heat treatment for the release of mercury;
- the released amount of mercury is easily controllable and 25 reproducible.
Despite their good chemical-physical characteristics and their great ease of use, these materials have the drawback that the contained mercury is not completely released during the activation treatment. In fact, the processes for the production of mercury-containing electron tubes 30 include a tube-closing operation performed by glass fusion (e.g. the sealing of fluorescent lamps) or by frit sealing, i.e. welding two pre-shaped glass members by means of a paste of low-melting glass. During these operations, the mercury-dispensing device may undergo an indirect heating up to about 600C. In this step the device is exposed to gases and 35 vapors emitted by the melted glass and, in almost all industrial processes, to air. In these conditions, the mercury-dispensing material undergoes a ~1 72686 surface oxidation, whose final result is a yield lower than about 40% of the total mercury content during the activation process. In the particular case of compact circular lamps, during the lamp sealing and bending steps the mercury-dispensing material undergoes an indirect heating up to about 600C. In this case the mercury yield during the activation process drops as low as about 20% of the total mercury content of the device.
The mercury not released during the activation operation is then slowly released during the life of the electron tube.
This characteristic, together with the fact that the tube must obviously work from the beginning of its life cycle, leads to the necessity of introducing into the device an amount of mercury which is at least double than that which would theoretically be necess~ry.
In order to overcome these problems, patent application EP-A-091.297 suggests the addition of Ni or Cu powders to the Ti3Hg or Zr3Hg compounds. According to this document, the addition of Ni and Cu to the mercury-dispensing compounds c~ ~ses the melting of the combination of materials thus obtained, favouring the release of almost all the mercury in few seconds. The melting takes place at the eutectic temperatures of the systems Ni-Ti, Ni-Zr, Cu-Ti and Cu-Zr, ranging from about 880C for the Cu 66% - Ti 34% composition to 1280C for the Ni 81% - Ti 19% composition (atomic percent), though the document erroneously gives a melting temperature of 770C for the Ni 4% - Ti 96%
composition. The document acknowledges that the mercury-containing compound is altered during the tube working treatments, and it needs a protection. To this purpose, there is suggested to close the powder container by means of a steel, copper or nickel sheet which is broken during the activation by the pressure of the mercury vapor generated inside the container. This solution is not completely satisfactory: in fact, same as it happens in the methods employing capsules, mercury bursts out violently and can cause damages to portions of the tube; the manufacturing of the container is quite complicated, since it requires the welding of small-size metallic members. Furthermore, this document does not contain experimental data to support the stated good mercury-release characteristics of the combinations indicated. Finally, the devices in this application, contrary to those illustrated in the cited US patent no.3.657.589, do not allow to integrate a getter material, whose presence is necessary for the correct working of the lamps, into a same device.
Therefore, the object of the present invention is to provide an improved combination of materials for dispensing mercury in the electron tubes, which allows to overcomes one or more drawbacks of the prior art.
In particular, the object of the present invention is first of all to provide an improved combination of materials for dispensing mercury which is capable of releasing amounts of mercury higher than 60% during the activation step, even after partial oxidation, so as to be able to reduce the total amount of employed mercury.
Another object of the present invention is to provide a combination of materials whose residue, after the activation operation for releasing mercury, has a getter activity.
Another object of the present invention is to provide mercury-dispensing devices containing the combination of materials of the 1 5 invention.
Still another object is to provide a process for introducing mercury by means of the devices of the invention into the electron tubes which require said element.
According to the present invention, these and other objects are achieved by using a mercury-dispensing combination of materials made up of:
- a mercury-dispensing intermetallic compound A including mercury and a second metal selected among titanium, zirconium and mixtures thereof;
- an alloy or an intermetallic compound B including copper, tin and one or more metals selected among the rare earths.
Further objects and advantages of the present invention will be apparent from the following detailed description referring to the annexed drawings wherein:
Fi~.1 is a perspective view of a mercury-dispensing device of the present invention according to a possible embodiment thereof;
Fi~s.2 and 2a are, respectively, a top plan view and a sectional view along ll-ll of a device of the invention according to another possible embodiment;
Fi~s.3, 3a and 3b are, respectively, a top plan view and two sectional views along lll-lll of a device of the invention according to a further embodiment, in two possible variations;
Fi~.4 shows, in a ternary diagram, the alloys of the present invention.
Component A of the combination of the present invention, hereafter also defined mercury dispenser, is an intermetallic compound 5 corresponding to formula TixZryHgz, as disclosed in the cited US patent no.3.657.589, to which reference is made for further details. Among the materials corresponding to said formula, Zr3Hg and, particularly, Ti3Hg are preferred.
Component B of the combination of the present invention has the 10 function of favouring the release of mercury from component A, and hereafter will also be defined promoter. This component is a metallic alloy or an intermetallic compound including copper, tin and a metal selected among the rare earths or a mixture of rare earths. The use of a mixture of rare earths is preferred over the use of single elements in that, since these 15 metals have a similar chemistry, the separation of the single elements is a difficult and expensive operation; on the other hand, by using a mixture of rare earths it is possible to obtain, in this application, essentially the same results obtained with the single elements. The mixtures of rare earths are known in the art by the name Umisch metal"; this denomination, and its short form MM, will be used hereafter in the rest of the specification and in the claims.
The weight ratio between copper, tin and MM can vary within a wide range, but advantageous results have been obtained with compositions which, in a ternary diagram of percentage compositions on a weight basis (fig.4), fall within a polygon defined by points:
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c) Cu 30% - Sn 10 % - MM 60%
d) Cu 3% - Sn 37 % - MM 60%
e) Cu 3% -Sn 96,5% -MM 0,5%
With copper percentages higher than 63% the alloy reaches a high melting point and consequently requires excessive temperatures for its activation, while on the contrary with copper percentages lower than about 3% the alloy has a melting point too low and this implies the risk of having a low-viscosity liquid phase at the temperatures, varying about from 600 to 800C, reached during the production of the lamps. With misch metal concentrations higher than 60% by weight the alloy becomes excessively reactive, and could give rise to violent reactions both during the lamp production step and during the activation step. Finally, with tin contents lower than 10% by weight the alloy reaches again a high melting point.
Particularly advantageous results are obtained, within said range of compositions, by means of compositions which, in a ternary diagram of percentage compositions on a weight basis (fig.4), fall within a polygon defined by points:
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c)Cu50%-Sn10 %-MM40%
d) Cu 30% - Sn 30 % - MM 40%
e) Cu 30% - Sn 69,5% - MM 0,5%
A particularly preferred alloy has the percentage composition Cu 40% - Sn 30% - MM 30%, corresponding to point i) in the composition - ternary diagram of fig.4.
The weight ratio between components A and B of the combination of the invention may vary within a wide range, but it is generally included between 20:1 and 1 :20, and preferably between 10:1 and 1 :5.
Components A and B of the combination of the invention may be employed in various physical forms, not necess~rily the same for the two components. For example, component B may be present in the form of a coating of the metallic support, and component A as a powder adhered to component B by rolling. However, the best results are obtained when both components are in the form of a fine powder, having a particle size lower than 250 ,um and preferably between 10 and 125 ,um.
The present invention, in a second aspect thereof, relates to the mercury-dispensing devices which use the above-described combinations of A and B materials.
As previously mentioned, one of the advantages of the combination of materials of the invention with respect to prior art systems is that they do not need a mechanical protection from the environment, thus not posing the limit of a closed container. Consequently, the mercury-dispensing devices of the present invention can be manufactured with the most different geometric shapes, and materials A and B of the combination can be employed without support or on a support, usually metallic.
~1 72686 Some classes of electron tubes for which the mercury dispensers are intended further require, for their correct operation, the presence of a getter material which removes traces of gases such as CO, CO2, H2, 2 or water vapor: it is the case, for example, of fluorescent lamps. An important advantage offered by the combinations of the present invention is that the residue remaining after the evaporation of mercury has a getter activity.
The amount of gas which can be absorbed by said residue, and the absorption velocity, are sufficient to assure an adequate degree of vacuum for many applications. In order to increase the total gas absorption velocity and capacity of this device, it is obviously possible to add thereto another getter material C, according to the manners described in the cited US
patent no.3.657.589. Obviously, in this case the amount of getter material C is lower than that required in prior art devices used in the same application. Examples of getter materials include, among the others, metals such as titanium, zirconium, tantalum, niobium, vanadium and mixtures thereof, or alloys thereof with other metals such as nickel, iron, aluminum, like the alloy having a weight percentage composition Zr 84% -Al 16%, manufactured and sold by the Applicant under the name St101, or the intermetallic compounds Zr2Fe and Zr2Ni, manufactured and sold by the Applicant respectively under the name St198 and St199. The getter material is activated during the same heat treatment by which mercury is released inside the tube.
The getter material C may be present in various physical forms, but it is preferably employed in the form of a fine powder, having a particle size lower than 250 ~m and preferably between 10 and 125 ~m.
The ratio between the overail weight of the A and B materials and that of the getter material C may generally range from about 10:1 to 1:10, and preferably between 5:1 and 1:2.
Some possible embodiments of the devices of the invention are illustrated hereunder with reference to the drawings.
In a first possible embodiment, the devices of the invention can simply consist of a tablet 10 made up of compressed and unsupported powders of the A and B (and possibly C) materials, which for ease of production generally has a cylindrical or parallelepipedal shape; this latter possibility is shown in fig.1.
In the case of supported materials, the device may have the shape of 21 126~6 a ring 20 as shown in fig.2, which represents a top plan view of the device, and in fig.2a which represents a cross-section along ll-ll of device 20. In this case, the device is made up of a support 21 having the shape of a toroidal channel containing the A and B (and possibly C) materials. The 5 support is generally metallic, and preferably of nickel-plated steel.
Alternatively, the device may be made in the shape of a strip 30 as shown in fig.3, which represents a top plan view of the device, and in figs.3a and 3b wherein a section along lll-lll of device 30 is depicted. In this case, support 31 consists of a strip, preferably made of nickel-plated 10 steel, onto which the A and B (and possibly C) materials are adhered by cold compression (rolling). In this case, whenever the presence of the getter material C is required, materials A, B and C may be mixed together and rolled on one or both faces of the strip (fig.3a), or materials A and B
are rolled on one surface of the strip and material C on the opposite 15 surface, as shown in fig.3b.
The invention, in a further aspect thereof, relates to a method for introducing mercury into the electron tubes by using the above-described devices.
The method includes the step of introducing inside the tube the 20 above-described mercury~ispensing combination of materials and preferably in one of the above-described devices 10, 20 or 30, and then the combination heating step to get mercury free. The heating step may be carried out with any suitable means such as, for example, by radiation, by high-frequency induction heating or by having a current flow through the 25 support when the latter is made of a material having a high electric resistivity. The heating is effected at a temperature which ~lses the release of mercury from the mercury-dispensing combination, comprised between 600 and 900C for a time of about 10 seconds to one minute. At temperatures lower than 600C mercury is almost not dispensed at all, 30 whereas at temperatures higher than 900C there is the danger of the development of noxious gases by outgassing from the portions of the electron tube adjacent to the device or of the formation of metal vapors.
The invention will be further illustrated by the following examples.
These non-limiting examples illustrate some embodiments intended to 35 teach to those skilled in the art how to put in practice the invention and to show the accomplishment of the invention which is considered the best.
Examples 1 and 9 concern the preparation of the mercury-dispensing and promoting materials, while examples 3 to 6 concern the tests for the mercury release after the heat treatment simulating the sealing operation.
All the metals used for the preparation of alloys and compounds for the following tests have a minimum pureness of 99,5%. In the compositions of the examples all percentages are on a weight basis if not differently specified.
This example illustrates the synthesis of the mercury-dispensing material Ti3Hg.
143,7 9 of titanium are placed in a steel cradle and degassed by a furnace treatment at a temperature of about 700C and a pressure of 10~
mbar for 30 minutes. After cooling the titanium powder in an inert atmosphere, 200,6 9 of mercury are introduced in the cradle by means of a quartz tube. The cradle is then closed and heated at about 750C for 3 hours. After cooling, the product is ground until a powder passing through a 120,um mesh-size standard sieve is obtained.
The resulting material essentially consists of Ti3Hg, as confirmed by a diffractometric test carried out on the powder.
This example concerns the preparation of a promoting alloy which makes part of the combinations of the invention.
40 9 of Cu, 30 9 of Sn and 30 9 of MM in powder form, are placed into an alumina cradle and then introduced in a vacuum induction furnace.
The misch metal used contains about 50% by weight of cerium, 30% of lanthanum, 15% of neodymium and the rest are other rare earths.
The mixture is heated at a temperature of about 900C, kept at that temperature for 5 minutes to encourage the homogeneity thereof, and finally cast into a steel ingot-mould. Each ingot is ground in a blade mill and the powder is sieved like in example 1. The composition of the obtained alloy is Cu 40% - Sn 30% - MM 30%, and corresponds to point i) in the diagram of fig.4.
This example concerns the preparation of a promoting alloy which makes part of the combinations of the invention. The procedure of example 2 is repeated using 60 9 of Cu, 30 9 of Sn and 10 9 of MM in 21 726~6 powder form. The composition of the obtained alloy is Cu 60% - Sn 30% -MM 10%, and corresponds to point 1) in the diagram of fig.4.
Examples 4 to 9 concem the tests for the mercury release after a 5 heat treatment in air which simulates the frit conditions to which the device is subjected during the tube closing (hereafter generally referred to as sealing). Examples 4 to 7 are comparative examples which show the release after frit sealing respectively by the dispensing component alone (ex.4) and by the same mixed only with copper, tin and the above-cited getter alloy St101 (ex.5-7); a similar comparative test on a mixture of Ti3Hg and MM powders was not possible due to the excessive reactivity of this mixture.
For the simulation of the sealing, 150 mg of each powder mixture have been loaded in a ring-shaped container like in fig.1 or on a strip like 15 in fig.3, and have been subjected to the following thermal cycle in air:
- - heating from room temperature to 450C in about 5 seconds;
- isotherm at 450C for 60 seconds;
- cooling from 450C to 350C, requiring about 2 seconds;
- isotherm at 350C for 30 seconds;
20 - spontaneous cooling to room temperature, requiring about 2 minutes.
Thereafter, the mercury release tests have been carried out on the thus treated samples by induction heating thereof at 850C for 30 seconds inside a vacuum chamber and by measuring the mercury remained in the dispensing device through the method of the complexometric titration 25 according to Volhart.
The results of the tests are summarized in Table 1, which shows the mercury-dispensing compound A, the promoting material B (letters (i) or (I) in examples 8 and 9 refer to the composition of the Cu-Sn-MM alloy as shown in the diagram of fig.4), the weight ratio between components A and 30 B and the mercury yield as a percentage of released mercury on the total content of the device.
The comparative examples are marked by a star.
Table 1 EXAMPLEN. A B A/B Hgyield (%) 4 Ti3Hg ~ - 35,2 5* Ti3Hg Cu 7/3 34,0 6* Ti3Hg Sn 5/1 25,0 7* Ti3Hg St 101 1/1 22,4 8 Ti3HgCu-Sn-MM (i) 2/1 80,0 9 Ti3HgCu-Sn-MM (I) 2/1 87,0 Examples 10 to 14 concern the tests for the functionality as getter materials of the residues remaining after the mercury release by the combinations of the invention and by some comparative combinations.
These tests have been carried out by simulating the frit conditions to which the materials are subjected during the bending and sealing operations of the compact fluorescent circular lamps, which conditions, as mentioned above, are harder that those reached for straight lamps. In particular, the combinations of the examples have been subjected to the following thermal cycle in air:
- heating from room temperature to 600C in about 10 seconds;
- isotherm at 600C for 15 seconds;
- spontaneous cooling to room temperature, requiring about 2 minutes.
The mercury release tests (activation) have been carried out after simulation of the frit sealing on the samples. The fritted samples have been introduced inside a vacuum chamber having a volume of 1 liter, and heated under vacuum at 850C for 10 seconds and kept at said temperature for 20 seconds.
The capacity of the residue to work as a getter is measured after the activation; this measurement is performed by introducing in the chamber an amount of hydrogen such as to bring the pressure to 0.1 mbar at a temperature of 30C, and by measuring the time required for the pressure in the chamber to decrease to 0.01 mbar. The measure of the pressure is taken by means of a capacitive manometer. The results of these tests are summarized in Table 2, which shows the composition of the sample and the hydrogen absorption velocity at 30C. The USAMPLE COMPOSITION"
column gives the weight percentages of the component materials. The comparative combinations are marked by a star.
21 726~6 Table 2 EXAMPLE N. SAMPLE COMPOSITIONH2 absorption velocity (cc/s) 10* Ti3Hg notmeasurable 11* Ti3Hg: 50% 7,2 St 101: 50%
12 Ti3Hg: 60% 6,9 Cu-Sn-MM (i): 40%
13 Ti3Hg: 60% 3,5 Cu-Sn-MM (I): 40%
14 Ti3Hg: 30% 15,3 Cu-Sn-MM (i): 20%
St 101: 50%
It may be noted from the data of Table 1 that the combinations with 5 promoter of the invention allow mercury yields higher than 80% during the activation step even after frit sealing in air at 450C, thus permitting the reduction of the overall mercury amount introduced in the electron tubes.
Furthermore, as shown by the data in Table 2, the residue remaining after the mercury release has a getter activity: in fact, while the residue 10 remaining after the mercury release by the Ti3Hg compound alone has no getter activity, the sample of example 13 to which no getter has been added exhibits a significant hydrogen absorption velocity. Moreover, sample 12 has a hydrogen absorption velocity comparable to that of the sample of example 11, which is a combination of a mercury dispenser with 15 a getter, widely used by lamp manufacturers.
When a getter material is added to the combination of example 12, the hydrogen absorption velocity becomes nearly twice that of example 11, with the same percentage of getter. These properties of the combination of the invention make it possible to use very small amounts of additional 20 getter material or even none, while retaining the functionality of the devices in which it is used.
The combinations with promoter of the present invention offer another important advantage, consisting in the possibility of carrying out the activation operation at temperatures or with times lower than those 21 726~6 allowed by prior art materials. In fact, in order to have industrially acceptable activation times, Ti3Hg alone requires an activation temperature of about 900C, whereas the present combinations allow the reduction of the operation time and of the size of the lines for the 5 production of the lamps; in both cases a double advantage is achieved of causing less pollution inside the tube due to the outgassing of all the materials present therein and of reducing the amount of energy required for the activation.
Claims (30)
1. A mercury-dispensing combination consisting of:
- a mercury-dispensing intermetallic compound A including mercury and a second metal selected among titanium, zirconium and mixtures thereof;
a promoting alloy or intermetallic compound B including copper, tin and one or more metals selected among the rare earths.
- a mercury-dispensing intermetallic compound A including mercury and a second metal selected among titanium, zirconium and mixtures thereof;
a promoting alloy or intermetallic compound B including copper, tin and one or more metals selected among the rare earths.
2. A mercury-dispensing combination according to claim 1, wherein the intermetallic compound A is Ti3Hg.
3. A mercury-dispensing combination according to claim 1, wherein the promoting compound B is an alloy having a composition such that, in a ternary diagram of percentage compositions on a weight basis, it falls within a polygon defined by points:
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c) Cu 30% - Sn 10 % - MM 60%
d) Cu 3% - Sn 37 % - MM 60%
e) Cu 3% - Sn 96,5% - MM 0,5%
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c) Cu 30% - Sn 10 % - MM 60%
d) Cu 3% - Sn 37 % - MM 60%
e) Cu 3% - Sn 96,5% - MM 0,5%
4. A mercury-dispensing combination according to claim 3, wherein the promoting compound B is an alloy having a composition such that, in a ternary diagram of percentage compositions on a weight basis, it falls within a polygon defined by points:
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c) Cu 50% - Sn 10 % - MM 40%
d) Cu 30% - Sn 30 % - MM 40%
e) Cu 30% - Sn 69,5% - MM 0,5%
a) Cu 63% - Sn 36,5% - MM 0,5%
b) Cu 63% - Sn 10 % - MM 27%
c) Cu 50% - Sn 10 % - MM 40%
d) Cu 30% - Sn 30 % - MM 40%
e) Cu 30% - Sn 69,5% - MM 0,5%
5. A mercury-dispensing combination according to claim 4, wherein the promoting compound is an alloy having a percentage composition Cu 40% - Sn 30% - MM 30%.
6. A mercury-dispensing combination according to claim 4, wherein the promoting compound is an alloy having a percentage composition Cu 60% - Sn 30% - MM 10%.
7. A mercury-dispensing combination according to claim 1, wherein the weight ratio between components A and B ranges from 20:1 to 1:20.
8. A mercury-dispensing combination according to claim 7, wherein the weight ratio between components A and B ranges from 10:1 to 1:5.
9. A mercury-dispensing device containing a combination of materials A and B of claim 1.
10. A mercury-dispensing device according to claim 9, wherein the materials A and B are in the form of powder.
11. A mercury-dispensing device according to claim 10, consisting of a tablet (10) of compressed powders of materials A and B.
12. A mercury-dispensing device according to claim 10, wherein the materials A and B are contained in a metallic support (21) having the shape of a toroidal channel.
13. A mercury-dispensing device according to claim 10, wherein the combination of materials A and B is rolled on the surface of a support having the shape of a strip (31).
14. A mercury-dispensing device according to claim 9, further containing a getter material C.
15. A mercury-dispensing device according to claim 14, wherein the getter material C is selected among titanium, zirconium, tantalum, niobium, vanadium and mixtures thereof, or alloys of these materials with nickel, iron or aluminum.
16. A mercury-dispensing device according to claim 15, wherein the getter material C is an alloy having the composition Zr 84% - Al 16% on a weight basis.
17. A mercury-dispensing device according to claim 15, wherein the getter material C is Zr2Fe.
18. A mercury-dispensing device according to claim 15, wherein the getter material C is Zr2Ni.
19. A mercury-dispensing device according to claim 14, wherein the mercury dispenser A, the promoter B and the getter material C are in the form of powder.
20. A mercury-dispensing device according to claim 19, consisting of a tablet (10) of compressed powders of materials A, B and C.
21. A mercury-dispensing device according to claim 19, wherein materials A, B and C are contained in a metallic support (21) having the shape of a toroidal channel.
22. A mercury-dispensing device according to claim 19, wherein the combination of materials A and B is rolled on the surface of a support having the shape of a strip (31), and material C is rolled on the opposite surface of the same strip (31).
23. A mercury-dispensing device according to claim 19, wherein the combination of materials A, B and C is rolled on a single surface of a support having the shape of a strip (31).
24. A mercury-dispensing device according to claim 14, wherein the ratio between the overall weight of materials A and B and the weight of the getter material C is between 10:1 and 1:10.
25. A mercury-dispensing device according to claim 24, wherein the ratio between the overall weight of materials A and B and the weight of the getter material C is between 5:1 and 1:2.
26. A mercury-dispensing device according to claim 19, wherein the mercury-dispensing material, the promoter and the getter are in the form of powders having a particle size lower than 250 µm.
27. A mercury-dispensing device according to claim 26, wherein the mercury-dispensing material, the promoter and the getter are in the form of powders having a particle size between 10 and 125 µm.
28. A process for introducing mercury inside electron tubes, consisting in the introduction into the open tube of one of the devices of claims 9 to 27, and heating the device to get mercury free at a temperature between 600°C and 900°C for a time between 10 seconds and one minute after the tube sealing.
29. A process according to claim 28, wherein the electron tube consists of a straight fluorescent lamp.
30. A process according to claim 28, wherein the electron tube consists of a compact circular fluorescent lamp.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ITMI950734A IT1273531B (en) | 1995-04-10 | 1995-04-10 | COMBINATIONS OF MATERIALS FOR INTEGRATED DEVICES GETTERS AND MERCURY DISPENSERS AND DEVICES SO OBTAINED |
| ITMI95A000734 | 1995-04-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2172686A1 true CA2172686A1 (en) | 1996-10-11 |
Family
ID=11371284
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002172686A Abandoned CA2172686A1 (en) | 1995-04-10 | 1996-03-26 | Combination of materials for integrated getter and mercury-dispensing devices and devices thus obtained |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0737995B1 (en) |
| JP (1) | JP2858646B2 (en) |
| KR (1) | KR100239823B1 (en) |
| CN (1) | CN1086504C (en) |
| CA (1) | CA2172686A1 (en) |
| DE (1) | DE69608996T2 (en) |
| HU (1) | HU221281B1 (en) |
| IT (1) | IT1273531B (en) |
| RU (1) | RU2113031C1 (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1291974B1 (en) | 1997-05-22 | 1999-01-25 | Getters Spa | DEVICE AND METHOD FOR THE INTRODUCTION OF SMALL QUANTITIES OF MERCURY IN FLUORESCENT LAMPS |
| IT1317117B1 (en) | 2000-03-06 | 2003-05-27 | Getters Spa | METHOD FOR THE PREPARATION OF MERCURY DISPENSING DEVICES FOR USE IN FLUORESCENT LAMPS |
| DE10117365A1 (en) * | 2001-04-06 | 2002-10-10 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | Low-pressure discharge lamp |
| ITMI20041494A1 (en) | 2004-07-23 | 2004-10-23 | Getters Spa | COMPOSITIONS FOR THE RELEASE OF MERCURY AND PROCESS FOR THEIR PRODUCTION |
| KR100641301B1 (en) * | 2004-09-15 | 2006-11-02 | 주식회사 세종소재 | Combination getter and hydrargyrum supplement material |
| ITMI20050044A1 (en) * | 2005-01-17 | 2006-07-18 | Getters Spa | COMPOSITIONS FOR RELEASING MERCURY |
| ITMI20050569A1 (en) * | 2005-04-06 | 2006-10-07 | Getters Spa | MERCURY DISPENSER FOR FLUORESCENT LAMPS |
| ITMI20050570A1 (en) * | 2005-04-06 | 2006-10-07 | Getters Spa | MERCURY DISPENSER FOR FLUORESCENT LAMPS |
| KR100870990B1 (en) * | 2007-11-13 | 2008-12-01 | 희성소재 (주) | Getter composition and device for introducing of mercury into fluorescence lamp for blu |
| ITMI20072424A1 (en) * | 2007-12-21 | 2009-06-22 | Getters Spa | DEVICES FOR RELEASING MERCURY WITH REDUCED LOSS OF PARTICLES |
| ITMI20082187A1 (en) * | 2008-12-11 | 2010-06-12 | Getters Spa | MERCURY DISPENSER SYSTEM FOR FLUORESCENT LAMPS |
| KR100899601B1 (en) * | 2009-02-06 | 2009-05-27 | 희성소재 (주) | Mercury emission getter composition of high-efficiency for lamp |
| US8427051B2 (en) | 2009-07-15 | 2013-04-23 | Saes Getters S.P.A. | Support for filiform elements containing an active material |
| ITMI20100285A1 (en) | 2010-02-23 | 2011-08-24 | Getters Spa | METHOD AND SYSTEM FOR CONTROLLED DISTRIBUTION OF MERCURY AND DEVICES PRODUCED WITH THIS METHOD |
| US8253331B2 (en) | 2010-04-28 | 2012-08-28 | General Electric Company | Mercury dosing method for fluorescent lamps |
| CN102664133A (en) * | 2012-05-10 | 2012-09-12 | 张文知 | Electrodeless lamp tube for enhancing photosynthesis |
| ITMI20131658A1 (en) * | 2013-10-08 | 2015-04-09 | Getters Spa | COMBINATION OF MATERIALS FOR MERCURY RELEASE DEVICES AND DEVICES CONTAINING THIS MATERIAL COMBINATION |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3657589A (en) * | 1969-10-20 | 1972-04-18 | Getters Spa | Mercury generation |
| JPS526071A (en) * | 1975-07-04 | 1977-01-18 | Japan Radio Co Ltd | Mercury emission getter material |
| US4464133A (en) * | 1982-04-05 | 1984-08-07 | Gte Laboratories Incorporated | Method of charging a vessel with mercury |
| IT1273338B (en) * | 1994-02-24 | 1997-07-08 | Getters Spa | COMBINATION OF MATERIALS FOR MERCURY DISPENSING DEVICES PREPARATION METHOD AND DEVICES SO OBTAINED |
-
1995
- 1995-04-10 IT ITMI950734A patent/IT1273531B/en active IP Right Grant
-
1996
- 1996-03-26 CA CA002172686A patent/CA2172686A1/en not_active Abandoned
- 1996-03-29 HU HU9600835A patent/HU221281B1/en not_active IP Right Cessation
- 1996-04-08 CN CN96104609A patent/CN1086504C/en not_active Expired - Fee Related
- 1996-04-09 EP EP96830202A patent/EP0737995B1/en not_active Expired - Lifetime
- 1996-04-09 RU RU96106816A patent/RU2113031C1/en active
- 1996-04-09 DE DE69608996T patent/DE69608996T2/en not_active Expired - Fee Related
- 1996-04-09 JP JP11111496A patent/JP2858646B2/en not_active Expired - Fee Related
- 1996-04-10 KR KR1019960010711A patent/KR100239823B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| JP2858646B2 (en) | 1999-02-17 |
| ITMI950734A1 (en) | 1996-10-10 |
| DE69608996T2 (en) | 2000-11-02 |
| JPH08287822A (en) | 1996-11-01 |
| IT1273531B (en) | 1997-07-08 |
| CN1138209A (en) | 1996-12-18 |
| ITMI950734A0 (en) | 1995-04-10 |
| RU2113031C1 (en) | 1998-06-10 |
| HU221281B1 (en) | 2002-09-28 |
| CN1086504C (en) | 2002-06-19 |
| EP0737995B1 (en) | 2000-06-28 |
| KR960039099A (en) | 1996-11-21 |
| HU9600835D0 (en) | 1996-05-28 |
| HUP9600835A3 (en) | 1999-09-28 |
| KR100239823B1 (en) | 2000-01-15 |
| DE69608996D1 (en) | 2000-08-03 |
| EP0737995A2 (en) | 1996-10-16 |
| HUP9600835A2 (en) | 1997-05-28 |
| EP0737995A3 (en) | 1998-07-01 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |