PROCEDURE FOR MANUFACTURING THE CATHODE OF AN IMAGE INTENSIFIER DIODE TUBE AND IMAGE INTENSIFIER TUBE PROVIDED WITH A CATHODE OBTAINED BY THE PROCEDURE

Description

TITLE PROCEDURE FOR THE CATHODE OF AN INTENSIFIER INTENSI FIER OF A CATHODE PROCEDURE THE MANUFACTURE OF IMAGE DIODIC TUBE AND IMAGE TUBE PROVVI OBTAINED BY THE INV. DES. LAM3ERTUS KAREL VAN GEEST AND JOHANNES JACOBUS HOUTKAMP PRIORITY NETHERLANDS PATENT DOM.N.7708321 OF 27 JULY 1977 THE DIRECTOR Rome, there C>rt. 042β79 / «1 · (ÌQ.OOOI - Alluma spA · $ Uivi ￎﾗￎﾱￎﾹￎﾗￎﾕￎﾙ- ￢ﾀﾙthe Hl The year of the month of the Company rannrACipnt-at A ￂﾫag.AN.prot.......................£.8586 A / 78 PROVINCIAL OFFICE OF INDUSTRY, COMMERCE AND CRAFTS OF TURIN Minutes of filing of patent application for industrial invention on VL8TI22J LBQLXO at the hours of eleven and minutes of five o'clock nine ι·ν· 0RX3C8U JMiomis otm Barr· You» MUrwwltlMB ?, Bolft (ΛμμΛ MmA) ttM&OTAlXtik QÌmHÈOtt* from JACOBACCI - CASETTA & PERANI Snc with elective domicile in TURIN at Via Alfieri n. 17 at JACOBACCI - CASETTA & PERANI Sn,c. - has presented to me, the undersigned, a stamped application for the granting of a principal industrial invention patent for the invention entitled: •'Proeettwerte >«r U ùfcbfcrieasloM of the cathode of tra «hìn dlodloo iatrawlfle»tor« of Imttela» · «rto latmrtflwlor» by iasw <lAe prawis» di rat cartate etteeuto con 11 yrnamll irato* Designated Inventors « Urtar*» JUrei VA» OjOST · Jokram» Jaoov» BDCTXA^F Priority: The right of priority has been claimed arising from: a) previous patent application No. 7T«ì2l filed in F&oel Batti on 27 U©Uo 1977 b) exhibition at ___ carried out on c) publication on carried out on Various notes; Attached documentation; a) description, in duplicate, of 23 pages of writing; b) drawings, in duplicate, of 3 tables; c) letter of assignment, power of attorney, or reference to a general power of attorney; d) priority document with Italian translation: (••gBe) éf authorization or deed of transfer; f) declaration of inventor's consent to be mentioned in the patent; g) proof of payment (on postal account no. 1 / 11770, made out to the Tax and Concession Registry Office of Rome) of lire issued by the Turin Post Office 2J.7.1WW h) inarca d. stamp of bTW ““ The application, description and drawings listed above have been signed by the * Interested Party * and countersigned by me and stamped with the office seal. A copy of this report was signed by me and delivered to the interested party. / » MINISTRY OF INDUSTRY, TRADE AND ART Pr / RK 7716 3-230 CENTRAL PATENT OFFICE > ROME NV OPTISCHE INDUSTRIE DE OUDE DELFT_______ .Vari Miereveltla&n 9, Delfi (Basel Countries) Dutch nationality by means CASETTA 4 PERANI sjlc. ed_______ electively domiciled for legal purposes in Turin, Via Alfieri 17 ---- presses the agents, requests the -granting- of a PRINCIPAL patent ΟΑΓ rinvonzionA. Hai litalai π,τφηκννΓνφ wer si iviv ·— - — - — — ---------— - — - —. .. — — -----_Procedure for the manufacture of the cathode of a diode tube, with image intensifier and image intensifier tube provided with a cathode obtained with the process_________________ Designated Inventors» Lambertus Karel VAN GEEST and Johannes Jacobus HOU'l'KAMP. Priority — the right is claimed arising from;— __________________________ previous application lift· 7706321 of 27 July 1977___ filed in the Netherlands. ATTACHED DOCUMENTATION Description in duplicate (pages- 'j of writing) Drawings in duplicate copy (number-----1 tables) Letter of appointment Priority document with Italian translation_(continued)____ Designation of inventors Proof of payment (on cxjl M l / 11770) - made out to—ab T-Registry Office and concessions of Rome ofJ_ 84.Q0Q___ issued by the Post Office of Turin on 25.7.1978 N. on behalf of K. TU QPTISCHE INDUSTRIE DE PUPE DELFT TnrfOO οχζ TVrttOr» cIO / / JACOSADGr- CASrflA & PERANl DESCRIPTION of the industrial invention entitled: Process for the manufacture of the cathode of an image intensifier diode tube and image intensifier tube provided with a cathode obtained by the process 77163-230, by: NV OPTISCHE INDUSTRIE DE OUDE DELFT, Dutch nationality, Van Miereveltlaen 9, Delft, Netherlands Filed on July 26, 1978 68786A / 78 XXX Excerpt from the description Process for manufacturing the cathode of an image intensifier diode tube, by evaporation. of certain alkali metals and antimony on the inner surface of a cathode window which is connected, by means of a porous glass layer, to a metal cathode flange, and in which between the cathode and the cathode flange, or as the case may be the cathode casing, an electrical resistance of a predetermined value is provided such that (at illumination levels at which there is danger of the anodos being burned out) the image intensifying diode tube is defocused or disconnected, and in which prior to the evaporation of the metals a reactive layer is applied to the porous glass layer. OTcliP ' alkali-resistant and insulating, and the evaporation of the ι 1\ / monium is carried out in such a way that an area extending around the cathode and the cathode flange is formed between the cathode and the cathode flange. AD / ip in which there is no antimony, and in which at least one galvanic connection is passed through a vacuum-tight a_l. the exterior of the image intensifier diode tube, and one end of said connection is disposed at the site of the cathode to be formed to supply voltages of a predetermined magnitude to the cathode during its manufacture and thereafter during operation of the tube. 00OO00 The present invention relates to a process for manufacturing the cathode of an image intensifying diode tube by evaporating certain alkali metals and antimony on the inner surface of a cathode window which is connected by a layer of porous glass to a metallic cathode flange, between the cathode and the cathode flange or, as the case may be, the cathode case, an electrical resistor having a predetermined value being provided such that at illumination levels at which there is danger of the anode being burned out the image intensifying diode tube is defocused or disconneted. I don't know. According to generally known methods of manufacturing a cathode for an image intensifying diode tube, a certain number of metals, such as potassium, sodium, caesium and antimony, are evaporated on the inner surface of the cathode window. Furthermore, during the manufacturing of the ( 2 ) cathode the photoelectric current within the tube is continuously measured, since from the variation of this photoelectric current it can be seen whether the evaporation of a metal must be continued or can be terminated. If these prior methods are employed for the manufacture of a cathode of an image intensifying diode tube on the inner surface of a cathode window which is connected, by a layer of porous glass, to a metallic cathode flange, and in which between the cathode and the cathode flange or, as the case may be, the cathode casing, is arranged an electrical resistor having a value such that at illumination levels at which there is danger of the anode being burned out the image intensifying diode tube is defocused or disconnected, a number of problems arise. Thus, the value of the resistance of the layer formed by the evaporated metals on the porous glass layer, i.e. of the;. the layer actually formed between the cathode itself and the cathode flange is considerably less than the predetermined value necessary for the image intensifying diode tube to be defocused or disconnected at illumination levels at which there is a danger of the anode being burned out. To solve this problem, it has been found that it is not sufficient to take measures such as to prevent, for example, the deposition of antimony on the porous glass layer( 3 ). In fact, in such a case only alkali metal vapours could come into contact with the porous glass layer, and, as might be expected, no electrically conducting layer would be formed. However, exceptionally, it turns out that under these conditions an electrically conducting layer is formed as well. It is assumed that this electrically conducting layer is formed by a chemical reaction between the alkali metals and the porous glass. An object of the present invention is to provide a process for manufacturing the cathode of an image intensifier diode tube, by evaporation of; the THE Certain alkali metals and antimony on the inner surface of a cathode window which is connected, by means of a I c porous glass layer, to a metal cathode flange and j £ < in which between the cathode and the. cathode flange or, depending on the ; case, the cathode casing, is provided with an electrical resistance of a predetermined value such that at illu levels. where there is a danger of the anode being burned, the image intensifier dichromate tube is defocused or disconnected, thereby preventing the formation of an electrically conductive layer consisting of evaporated metals, having an undesirably low resistance value, between the cathode and the cathode flange. The process of this type is characterized, according to the invention, by the fact that before the evaporation of the metals ( 4 ), an insulating alkali-resistant layer is applied to the porous glass layer, and that the evaporation of the antimony is carried out in such a way that an area is formed between the cathode and the already cathodic plate which extends around the cathode and in which no antimony is present. According to a different aspect of the present invention, the process of the above-mentioned type is characterized in that the thickness of the alkali-resistant and insulating layer is selected so that an electrically conductive layer is formed by chemical reaction between the alkali metals and the porous glass, the resistance value of said insulating layer being substantially equal to, or greater than, said predetermined resistance value. According to yet another aspect of the invention, the method according to the invention is characterized in that at least one galvanic connection is passed vacuum-tight outside the image intensifying diode tube, and one end of it is disposed at the location of the cathode to be formed, in order to be able to supply voltages of a large magnitude to the cathode. predetermined quality during manufacturing and subsequently me ri te during operation of the tube. It should be noted that providing this galvanic connection offers the possibility, in addition to measuring the photoelectric current during evaporation, of externally connecting a shunt resistor between the cathode and the ( 5 ) jlk'.ii cathode flange or, as the case may be, the cathode casing, in cases where the layer formed between the cathode and the cathode flange has substantially the value of resistei! given, or a much higher value, so that the resistance between the cathode and the cathode flange^ the cathode casing, can be adjusted to the value required for the tube to dio. I say image intensifier is defocused or disconnected at illumination levels at which there is a danger of the anode being burned. Some embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings, in which FIG. 1 shows an elevational view of a cathode window for an image intensifier tube according to the present invention; Figure 2 shows a cross-sectional view of the cathode window of Figure 1; Figure 3 shows a cathode window provided with an electrical conductor; Figure 4 shows a cathode window connected to a cathode flange by porous glass; Figures 5 and 6 show two other possibilities for mounting an electrical conductor; Figure 7 shows a cathode window attached to a cathode flange, with a shield mounted on the cathode flange; C 6 ) Figure 8 shows a cathode window provided with a groove according to the present invention; Figures 9 and W show alternative forms of the scana. figure 8 layout; Figure 11 shows the cathode side of an image intensifier tube; Figure 12 shows a cathode window alternatively provided with a conductor; Figure 13 shows yet another way of providing a cathode window on a conductor; and Figure 14 shows a practical application of the configuration of Figure 13. Figures 1 and 2 show a cathode window for an image intensifier tube. The window, which may be made of glass or a fiber optic plate, has an entrance face 1 and a curved cathode area 2. On the cathode area, the cathode is to be formed. Furthermore, the window has, around the cathode area, a flat part 3. In this flat part 3, grooves 4 and 5 are formed, which extend into the lateral surface of the cathode window. The grooves 4 and 5 serve to accommodate a conductor which, during the formation of the cathode, serves to measure the photoelectric current. For this purpose, the conductor may be placed in the grooves 4 and 5, and its ends may be knotted together for the time being. Figure 3 shows a cross-sectional view ( 7 ) of a cathode window provided with a conductor 6 mounted in the manner described.Figure 4 shows the cathode window provided with a conductor and fixed, by means of a porous glass layer, to a cathode flange 7. The porous glass layer 8 also contains the conductor 6. The part of the conductor 6 overlapping the cathode area is now cut off, and the remaining ends are fixed to the surface of the porous glass layer. Subsequently, a small piece of electrically conductive paste, e.g. silver paste, is applied to both ends to ensure proper contact with the cathode to be formed. It should be noted that the conductor can also be mounted differently. Thus, the conductor can be arranged so that it extends completely through the porous glass layer, or only through the cathode window, through a perforated passage in the cathode window. In the latter case, the conductor is passed vacuum-tight, via a porous glass junction, through the passage in the cathode window. The two possibilities indicated are illustrated in Figures 5 and 6. The passage 10 can be perforated ultrasonically either before or after the cathode window is attached to the cathode flange. Another possibility of mounting a conductor is to provide the cathode window, before connecting it to the ( 6 ) cathode flange, with an electrically conductive strip, which extends over the flat part 3 and the side, said path being formed for example by evaporation of metals or by application of a conductive emulsion, such as silver paste or silver paint. After the cathode window has been provided, in which. In either of the ways described, at least one conductor is used to measure the photoelectric current during formation, and after the cathode window has been joined with porous glass to the cathode flange, an alkali-resistant and insulating layer, consisting, for example, of chromium oxide and water glass, is applied to the porous glass layer. This can be done by painting a suspension of chromium oxide in potassium water glass solution with a brush. Subsequently, the alkaline materials can be applied by vacuum evaporation. If, after evaporation of the alkaline substances, materials that could form a conductive layer between the photocathode and the cathode flange are to be evaporated, an annular shield is preferably placed on the cathode flange before evaporating the alkaline substances. This shield can be attached to the cathode flange, for example by spot welding. The shield should extend from the cathode flange inward to adjacent to the photocathode, so that in any case the porous glass layer, and preferably * the ' also part of the cathode ray tube is covered. This is illustrated in Figure 7, which shows a cathode window 1, which is connected by a porous glass layer 8 to a cathode flange 7. The conductor 6 is installed in the manner described, and connected by an electrically conductive paste 9j such as silver paste, to a metal film, such as aluminum foil, which serves to ensure proper electrical contact with the cathode to be formed. A layer of chromium oxide 12 is applied to the porous glass layer 8. Furthermore, an annular screen 13 is attached to the cathode flange 7. The screen 13 extends parallel to the flat part of the cathode window, inward, beyond the porous glass layer, and is then preferably bent toward the cathode area, approximately parallel to the edge of the cathode area, to end just short of the cathode area. The porous glass layer is now protected by chromium oxide 12 against the effect of alkaline vapors, while the chromium oxide layer is in turn protected by substances, such as antimony, which could form a conductive layer between the cathode flange and the silver contacts 9, as well as the metal film. Under the conditions prevailing during evaporation, the vapor pressure of the antimony is so low that antimony atoms cannot penetrate the space between the porous glass layer and the screen 13α ( 1 ). As a result of the measures described, the cathode flange remains effectively electrically isolated from the cathode. An alternative way of maintaining an electrically insulating area between the cathode flange and the cathode is, in accordance with the present invention, to provide a groove in the cathode window, surrounding the cathode area, or an elevation on the cathode window, surrounding the cathode area. In all cases, the aim is to produce a configuration that provides a shielded or leeward area. In the shielded area, the conductive substance is then prevented from depositing; tarsi, so that an insulating area surrounding 1' is maintained THE I cathode area. ' '{ Figure 8 shows an embodiment of a cathode window ί provided with a groove 14· While the antimony ; ( ì; ί c is evaporated from a source disposed approximately at the center of curvature of the inner surface of the cathode window, the inner wall of the groove remains free of antimony. In the embodiment illustrated, the conductor 6 is passed through a channel 10 in the cathode window and is connected at the end of the channel 10 to the cathode area by a silver spot 9. The conductor 9 is fixed within the channel 10, for example by a porous glass layer 17. The end of the channel 10 lies within the area enclosed by the groove 14. Due to this arrangement, it is generally not necessary to deposit silver dioxide ( 11 ) on the porous glass layer, since the groove ensures that both the conductor 6 and the cathode remain insulated from the porous glass layer and the cathode flange. It should be noted that the groove can have various configurations. Two alternative possibilities are illustrated in figures 8 and 10. It is further noted that when a screen 13 is used, it is not generally necessary to deposit chromium oxide on the porous glass layer, provided that the conductor 6 does not contact the porous glass layer, and provided that a sufficiently large insulating area is maintained between the porous glass layer and the edge of the photocathode 15. The latter depends on the dimensions of the screen. Figure 11 shows a cathode window 1 which is connected by a porous glass layer δ to a cathode flange 7. The photocathode is to be formed on the curved inner surface 2 of the cathode window. In the illustrated configuration, two conductors δ are connected to the inner surface 2. For this purpose, the ends of the conductors are interrupted at the surface of the porous glass layer, and fixed with a spot of silver paste 9. The conductors 9 are allowed to rest against the surface of the cathode window θ and are then fixed by the porous glass layer 8. Figure 12 shows another possibility of providing a conductor connected to the carotid area. In this case, an ( 12 ) electrically conductive strip 16 is formed at one or more locations on the cathode window, for example by evaporating metals or by applying a conductive emulsion, such as silver paste or silver paint. The strip may follow (for example) the configuration of the conductor illustrated in Figure 11. The conductive emulsion should be resistant to the further treatment to which the cathode window is subjected during the manufacture of the image intensifier tube. The conductor formed in this way can be connected in a known way, for example by welding, to a self-supporting conductor n Figure 13 shows yet another possibility for providing a cathode window for a conductor connected to the cathode area. A passage 10 has been drilled in the cathode window, taking into account that this should not interfere with the incidence of light on the cathode through the fi. window. The passage ends at one end at the edge of the cathode area and at the other end in the side wall of the cathode window above the porous glass layer 8. A conductor 6 is passed through the passage 10. The end. The conductor surface adjacent to the cathode area is again ground flat and provided with a patch 9 of conductive material, such as a silver patch, to ensure proper electrical contact with the photocathode to be formed. The conductor 6 is housed, for example (vacuum-tight), by a porous glass junction 17, in the passage 10. This embodiment is particularly advantageous if a groove is formed in the cathode window at the edge of the cathode area to electrically isolate the cathode flange from the cathode area. This is illustrated in Figure 14, which shows a cathode window 1 provided with a circumferential groove 18. The passage 10 terminates within the area enclosed by the groove 18. In all embodiments described, there may be one or more conductors mounted in the manner described. Additionally, a metal ring, such as an aluminum ring, may be evaporatively deposited around the circumference of the cathode area, the ring covering the silver spot or spots and further improving the electrical contact between the conductor or conductors and the cathode to be formed, or already formed. An aluminum ring, which entirely surrounds the cathode, is illustrated in Figure 7 at 19, and an open ring (which partially surrounds the cathode) is illustrated in Figure 20 at 12. It should be noted that various modifications of the methods and image intensifier tubes described will be readily apparent to those skilled in the art without departing from the scope of the present invention.

Claims

1. CLAIMS 1. - A method of manufacturing the cathode of an image intensifying diode tube by evaporation( 14 ) of certain alkali metals and antimony on the internal surface of a cathode window which is connected by a porous glass layer to a metallic cathode flange, and in which between the cathode and the cathode flange or, as the case may be, the cathode casing, there is provided an electrical resistance having a predetermined value (such that at illumination levels at which there is a danger of the anode being burned out the image intensifying diode tube is defocused or disconnected), characterised in that before evaporation of the metals an alkali-resistant and insulating layer is applied to the porous glass layer, and that the evaporation of the antimony is carried out in such a way that an area extending in. fc around the cathode and where there is no antimony. ; cc2. - Process for manufacturing the cathode of an image intensifying diode tube, by evaporation.of certain alkali metals and antimony on the inner surface of a cathode window which is connected, by a layer of porous glass, to a metallic cathode flange, and in which between the cathode and the cathode flange or, as the case may be, the cathode casing, there is provided an electrical resistance having a predetermined value (such that at illumination levels at which there is a danger of the anode being burned out the image intensifying diode tube is defocused or disconnected), characterised in that at least one galvanic connection( 15 ) is passed vacuum-tight outside the image intensifying diode tube, and one end of said connection is disposed at the location of the cathode to be formed, for supplying voltages of a predetermined magnitude to the cathode during its manufacture and subsequently during operation of the tube.

3. - Process for manufacturing the cathode of an image-intensifying diode tube by evaporation of certain alkali metals and antimony on the internal surface of a cathode window which is connected, by means of a layer of porous glass, to a metallic cathode flange, and in which between the cathode and the cathode flange or, as the case may be, the cathode casing, an electrical resistance of a predetermined value is provided such that at illumination levels at which there is a danger of the anode being burned out, the image-intensifying diode tube is deactivated or disconnected, characterised in that before evaporation of the metals, an alkali-resistant and insulating layer is applied to the porous glass layer, and that the evaporation of the antimony is carried out in such a way that between the cathode and the flange approx.iodine is formed which extends around the cathode and where no antimony is present, and that at least one galvanic connection is passed vacuum-tight outside the image intensifying diode tube, and one end of said connection is disposed at the site of the cathode to be formed, to ( 16 ) supply voltages of predetermined magnitude to the cathode during its manufacture and subsequently during operation of the tube,.

4. - A process according to claim 1 or 3, wherein the thickness of the alkali-resistant and insulating layer is chosen such that an electrically conductive layer, having a resistance value substantially equal to said predetermined resistance value, or greater than it, is formed by chemical reaction between the alkali metals and the porous glass.

5. - Process according to claims 1, 3 or 4, wherein the alkali-resistant and insulating layer contains water glass and chromium oxide.

6. - A method according to claims 1, 3, 4 or 5 wherein a screen is provided around the cathode area within the image intensifying diode tube to form the antimony-free area.

7. - Process according to claims 1, 3, 4 or 5, wherein the cathode window is provided with an annular groove formed in such a way that during evaporation at least a portion of the internal wall remains free of antimony.

8. - Method according to claims 2, 3, 4, 5», 6 or 7, wherein the galvanic connection is formed as an electrical conductor.

9. - Process according to claim 8, wherein the conductor is retained by the porous glass layer. ( 17 ) 10. - Method according to claim θ or 9) wherein a groove is formed in the sidewall and edge of the cathode window, and the conductor is seated in said groove.

11. - A method according to claim 8, wherein at least one continuous strip of an electrically conductive material is formed on the lateral surface of the cathode window and between the lateral surface and the cathode area.

12. - Process according to claim 11, wherein the continuous strip is formed by evaporation of metals.

13. - Process according to claim 11, wherein the continuous strip is formed by applying a conductive emulsion. 14· - Process according to claim 13, wherein said conductive emulsion is a silver-containing paste.

15. - The method of claim 8, wherein a passage is drilled in the cathode window for mounting the conductor, said passage terminating at one end at the edge of the cathode and at the other end at the surface of the cathode window located outside the image intensifying diode tube, and the conductor is secured in said vacuum-tight passage.

16. - The method of claim 15, wherein ( 18 ) the conductor is secured in the vacuum-tight passage by a layer of porous glass, 17» - The apparatus of claims 8, 9, 10, 13, 14, 15 or 16, wherein the conductor is mounted so that its end is co-planar with the surface of the cathode window at that point.

18. - A method according to any of claims 8-17, wherein the end of each conductor located adjacent to the cathode is provided with a spot of electrically conductive material to facilitate electrical contact. 19· - Process according to claim 18, wherein silver is used as an electrically conductive material.

20. - A method according to any of claims 8-19, wherein a portion of a metal ring or a complete metal ring is provided around the cathode area, and the end of the conductor located adjacent to the cathode is brought into electrical contact with the ring or portion of the ring, 21 » - Process according to claim 20, wherein an aluminium ring is used as the metal ring.

22. - Image intensifier tube having a cathode manufactured by the process according to any one of the preceding claims. ( 19 ) 68786A / 78 commissioned by NV OPTISCNE INDUSTRIE D^ OUDE DELPT jÌACCMC, rfo 4 68786A / 78 8 10 1 / ,17 9 15 1 FIG.1O u 10 17