CA1072741A - Method of manufacturing an electric discharge tube and electric discharge tube manufactured by said method - Google Patents
Method of manufacturing an electric discharge tube and electric discharge tube manufactured by said methodInfo
- Publication number
- CA1072741A CA1072741A CA229,107A CA229107A CA1072741A CA 1072741 A CA1072741 A CA 1072741A CA 229107 A CA229107 A CA 229107A CA 1072741 A CA1072741 A CA 1072741A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- envelope
- gallium
- parts
- vessel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/24—Manufacture or joining of vessels, leading-in conductors or bases
- H01J9/26—Sealing together parts of vessels
- H01J9/263—Sealing together parts of vessels specially adapted for cathode-ray tubes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J5/00—Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
- H01J5/02—Vessels; Containers; Shields associated therewith; Vacuum locks
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/38—Exhausting, degassing, filling, or cleaning vessels
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
- Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
- Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
- Joining Of Glass To Other Materials (AREA)
Abstract
ABSTRACT:
In a method of manufacturing an electric discharge tube at least one of the components of the tube is subjected to a treatment in a vessel sealed from the atmosphere. The envelope of said vessel con-sists of at least two parts which are sealed against each other hermetically with the interposition of a gallium-containing material in the liquid state. At least one of the said parts preferably forms already part of the final envelope of the tube to be manu-factured, while a gallium-containing material is also used for the final seal of the tube. This method is suitable in particular for the manufacture of an electric discharge tube having a radiation-sen-sitive layer vapour-deposited on a part of the envelope, for example, television camera tubes and photomultiplier tubes.
In a method of manufacturing an electric discharge tube at least one of the components of the tube is subjected to a treatment in a vessel sealed from the atmosphere. The envelope of said vessel con-sists of at least two parts which are sealed against each other hermetically with the interposition of a gallium-containing material in the liquid state. At least one of the said parts preferably forms already part of the final envelope of the tube to be manu-factured, while a gallium-containing material is also used for the final seal of the tube. This method is suitable in particular for the manufacture of an electric discharge tube having a radiation-sen-sitive layer vapour-deposited on a part of the envelope, for example, television camera tubes and photomultiplier tubes.
Description
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'~ethod of manufacturing an electric discharge tube and electric discharge tu~e manufactured by said method".
The invention relates to a method o manu-facturing an electric discharge tube in which at least one of the components of the tube is subjected to an operation ln a vessel sealed from the atmosphere, Nhich vessel is composed of at least two parts to be sealed hermetically against each other.
The invention furthermore relates to an electric discharge tube manufactured by said method.
In the manufacture of electric discharge tube3 it frequently occurs that certain componen~s of the tube are to be subjected to operations which have an undesired and frequently detrimental influence on other components of the tube. For that reason it ls desired that the components in question be subjected to the required treatments in separate spaces before they are assembled to form a tube. Moreover, the spe-c~fic problem may occur that the components after t~eir treatment ma~ no longer be exposed to atmos-p~eric influences. A known example hereof is found in the manufacture of electric discharge tubes hav-ing a given radiation-sensitive layer, for example, televlsion camera tubes and photomultiplier tubes.
'~ethod of manufacturing an electric discharge tube and electric discharge tu~e manufactured by said method".
The invention relates to a method o manu-facturing an electric discharge tube in which at least one of the components of the tube is subjected to an operation ln a vessel sealed from the atmosphere, Nhich vessel is composed of at least two parts to be sealed hermetically against each other.
The invention furthermore relates to an electric discharge tube manufactured by said method.
In the manufacture of electric discharge tube3 it frequently occurs that certain componen~s of the tube are to be subjected to operations which have an undesired and frequently detrimental influence on other components of the tube. For that reason it ls desired that the components in question be subjected to the required treatments in separate spaces before they are assembled to form a tube. Moreover, the spe-c~fic problem may occur that the components after t~eir treatment ma~ no longer be exposed to atmos-p~eric influences. A known example hereof is found in the manufacture of electric discharge tubes hav-ing a given radiation-sensitive layer, for example, televlsion camera tubes and photomultiplier tubes.
- 2 -~7Z7~L~
It is kno~n that the properties of the radiation-sensitive material with respect to, for example, the sensikivity or the inertia, can vary unfavourably when they are exposed to the atmosphere.
United States Patent Specification 3,334,955 describes a method of manufacturing a vacuum tu~e in ~hich the components of the tube are assembled in an evacuated space after having been subjected in separate vessels to various treatments. Said vessels are temporarily sealed b~ a metal foil and are opened again in the evacuated space by cutting said foil from an annular frame.
German Patent Specification l,915,710 de-scribes a method of manufacturing a television camera tube in which a photocathode is vapour-deposited on a window in a closed vessel comprising said window.
Said vessel together with the electrode system of the camera tube uhich is already mounted in an envelope ~fiich is open at one end, is then accommodated in a space communicating with an evacuating device. After evacuating the space, the system of electrodes is de-gassed, after which the window having a radiation-sensit1ve layer is removed from the said vessel by means of a thermo-shock treatment and is then placed on the open end of the envelope of the camera tube with the inter-position of an indium sealing ring, ~7Z74~
The methods which are used in -the known manufacturing techniques to obtain a temporary seal of the vessels are far from ideal. The seals can be used only once and require expensive and precise pre treatment.
The invention starts from the above described methods and has for its object to provide an improved method of manufacturing an electric discharge -tube.
According to the invention, there is provided a method of manufacturing an electric discharge tube wherein at least one of the components of the tube is subjected to a treatment in a vessel sealed from the atmosphere, the tube having an envelope being formed of at least two envelope parts, the vessel being composed of at least two vessel parts including at least one of said envelope parts, said vessel parts being hermetically sealed against each other by bringing together smooth facing surfaces thereof with the interposition of a sealant substantially con-sisting of gallium or a low melting point allo~ of gallium in the liquid state provided on at least one of these surfaces.
According to another aspect of the invention there is provided an electric discharge tube comprising an envelope which consists of at least two parts hermetically sealed against each other by means of a sealant substantially consisting of gallium or a low melting point alloy of gallium.
Gallium has a melting temperature of approximately 29C. In the liquid state, said metal can readily wet glass and other metals. Another property which is important for the use according to the invention is that gallium has a vapour pressure lower than 10-8 mm Hg even at a temperature of 500C.
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It is noted that seals of gallium are known as such from the United States Patent Specification 3,038,731, in particular with respect to liquid seals for valves and parts which are arranged so as to be rotatable relative to each other. As described in said Patent Specification, the seal-ing efect of gallium and low-melting-point alloys of gallium is based on an equilibrium of forces between on the one hand the surface forces of the seal-ing material and on the other hand the force acting on said material as a result of the pressure differential across the seal. This equilibrium may ~xist so long as with a given pressure differential the distance between the surfaces of the parts to be connected does not exceed a given value. In the practical case in which the pressure differential across the seal is approxi-mately one atmosphere, this means that the maximum distance of the parts to be connected may not be larger than approximately 10 ~m with a surface ten-sion of ~he sealing material of approximately 500 dyn/cm.
Seals of gallium or a low-melting-point alloy of gallium can be realized in a particularly simple manner. The facing surfaces of the parts to be connected are first polished so as to ensure that said surfaces join each other within a tolerance of 10 ~m. At least one of the surfaces is then wetted with gallium or a low-melting-point alloy of gallium, after which the parts are provided on each other. According to the invention, the parts ~hich are provided on each other are preferably rotated relative to each other so that a pattern of closed rings is formed in the sealing material. In this manner, the occurrence of radial leakage paths by island forma~ion of the sealing material between the surfaces is prevented. The sealing as such is then completed and the space thus closed can be evacuated. The seal can easily ~ithstand large temperature fluctuations. Temperatures exceeding 200C hardly constitute a drawback, while a hermetic seal is also maintained if the sealing material changes into the solid phase as a result of a de-crease of the temperature.
Not only can the above-described seal be realized in a simple man-ner, but parts o an envelope connected together in this manner can also be separated easily without damage thereto. It is thus these properties which ~C~727~
make the seal ex~remel~ suitable for use as a temporary seal in the manufac-ture of electric discharge tubes in which at least one of the composing parts is sub~ected to a treatment in a vessel which is sealed from the atmosphere.
According to the invention the envelope of said vessel preferably constitutes already wholly or partly the final envelope of the tube to be manufactured.
According to the invention, the gallium or a low-melting-point alloy of gal-lium is also used for the final sealing of the tube.
Examples of low~-melting ~point alloys which satisfy the object underlying the invention are alloys of gallium and at least one of the metals lndium and tin containing at least 50% by weight of Ga, and in particular eutectic alloys of gallium, indium and tin the melting point of which is below room temperature.
The invention preferably relates to the manufacture of an electric device having a vapour-deposited layer of radiation-sensitive material sealed from the atmosphere. The part of the tube envelope to be provided with the radiation-sensitive material is for that purpose arranged on a vapour-deposition device with the interposition of a layer of gallium-containing material for the hermetic seal of a first vessel thus formed. The complemen-tary part of the tube envelope comprising the electrode system of the tube is hermetically sealed in an analogous manner by means of a sealing member and thus constitutes a second vessel. The said first vessel and second vessel are then evacuated, after which the radiation-sensitive material is vapour-deposited in the first vessel and the electrode system is degassed in the second vessel. After vapour-depositing the radiation-sensitive material, the first vessel is filled with a gas which does not influence the radiation-sensitive material. When the pressures inside and outside the vessel are substantially equal to each other, the relevant part of the tube envelope may be removed from the vapour deposition device. In the second vessel the de-gassed electrode system is surrounded by an inert gas, after which the seal-3Q ing member of the said complementary part of the tube envelope may be re-moved. Finally the part of the tube enve~lope having a radiation-sensitive layer ~s transferred to the complementary part of the ~ube envelope having - 6 ~
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the said electrode system. The gallium-containing material which is already present on the surfaces to be connected ancl which in the first instance en-sured a temporary seal of the vessels, now produces the final seal of the tu~e.
During the transfer of the part of the tube envelope having a radiation-sensitive layer to the complementary part of the tube envelope, the radiation-sensitive material should be shielded from atmospheric influences.
Said shielding can be obtained in known manner by surrounding the relevant part during the transport with an inert gas, or causing the transport to take place in a vacuum space.
As is already known from the above-mentioned United States Patent Specification 3,038,731, measures are furthermore taken preferably to hold surfaces connected together hermetically with the use of a seal as described above in position relative to each other.
The invention will be described in greater detail with reference to the drawing, in which:
Figure 1 is a diagrammatic sectional view of a device for vapour-depositing a layer of radiation-sensitive material on a part of the envelope of a television camera tube to be manufactured according to the invention, 2~ Figure 2 is a perspective view of a centring holder f~r the part of t~e said envelope shown in Figure 1, Pigure 3 is a diagrammatic sectional view of the complementary part of the part of the tube envelope shown in Figure 1 and having a system of electrodes ready for degassing, ~igures ~ and 5 are sectional views of two embodiments of a final seal of a television camera tube manufactured according to the invention, and Figure 6 is a diagrammatic sectional view of a further embodiment of a television camera tube manufactured according to the invention.
Pigures 1 and 3 show two stages of the manufacture of a television camera tu~e. The envelope of the tube consists of two complementary parts, namely~ a glass window 1 and a glass envelope 20 which is open at one end.
~n t~e stage sho~n in ~i~ure 1J a radiation-sensitive la~er 3 of lead monoxide ~L~7Z74~L
is vapour-deposited on the ulndow 1.
Preparatory to said treatment, a layer of liquid gallium 2 is pro-vided on a smoo~h polished edge 4 of a hollo~ cylinder 5. For that purpose, the edge 4 to be wetted is moved in a rotating manner on a heated flat plate on which a layer of liquid gallium of a few microns thickness is present, a layer of gallium 2 remaining on said edge 4. At its non-wetted end the c~linder 5 is t~en connected hermetically to a vacuum line 6 of an evacuating device not shown. The window l on which a transparent conductive layer 7 of tin oxide or indium oxide has already been vapour-deposited, is placed on the edge 4 by means of a centring holder 8 and rotated a fe~ times so as to wet the surface of the window destined for the sealing~ Moreover, due to the rotary movement, closed concentric rings are formed in the gallium so that possible radial leakage paths are closed. In order to have a good grip on the windou during said rotary movement two apertures 9 are recessed in the centring holder 8 a perspective vie~ of which is shown in Figure 2~ By the arrangement of the window on the edge 4 with the interposition of a layer of gallium 2, a space is obtained which is sealed hermetically from the at-mosphere and which is evacuated via the vacuum line 6. An electric current is now conveyed through the wires 10 and 11 so that a tray 12 filled with lead monoxide 13 is heated. The lead monoxide i5 vapour-deposited on the conductive layer 7 ~hile forming the radiation-sensitive layer 3.
W~en the layer 3 has reached a thickness of approximately 8 microns, the vapour-deposition process is discontinued and the space bounded by the ~ndo~ l and the cylinder 5 is filled, via a closable supply line 14, with a gas, for example helium or nitrogen, which does not influence the radiation-sensitive material. ~eanwhile, a pouch 15 manufactured from a synthetic material, for example, polythene, is slid on the cylinder S and is also filled with an inert gas, for example, helium or nitrogen, via a supply line 16, the air present in said pouch being driven out. After a pressure equal to or 3a slightly larger than the ambient pressure has built up in the space communi-cating with the supply line 1~, the window 1 may be removed from the cylinder 5 and be transported uhile protected by the inert gas present in the pouch, Z74~
the opening of the pouch remaining directed downwards if the gas present therein is lighter than air.
Before placing the window 1 on the complementary part 20 of the ellvelope of the tube, the elec~rode system 21 already mounted in said part is degassed. This phase of the manufacturing process will be explained with reference to Pigure 3.
The glass part 20 of the envelope has a smooth polished edge 22 which is wetted wi*h the gallium in the above described manner. Via an ex-haust tube 23, the part 20 of the envelope is hermetically connected to a vacuum line 25 with the interposition of a sealing ring 24. An auxiliary ~indow 28 is placed on the edge 22 in the above-described manner with the interposition of the layer of gallium 26 and by means of a centring holder 27. The space in which the electrode sys~em 21 shown diagrammatically in the drawing is mounted on a number of pins 29 in the cap of the tube is hermetical-ly sealed from the atmosphere. After evacuating said space, the assembly is heated in a furnace to a temperature of 250C and the electrode system is then degassed at a temperature of 700C by means of a high-frequency coil 30.
After degassing, nitrogen is admitted to the said space through the duct 31 until the pressure in the space is equal to that of the surrounding atmos-phere, after which the auxiliary window 28 may be removed from the part 20 of the envelope. The window 1 having a layer of lead monoxide is now placed on the edge 22 of the part 20 of the envelope. The nitrogen supply through the line 31 is discontinued and ~he gallium present on the surfaces of the w~ndo~r and envelope to be connected now serves for the final seal of the tube.
The final envelope of the tube thus formed is finally evacuated via the line 25 after which the tube is completed.
In the case of large temperature Eluctuations as they occur upon degassing the tube, no large temperature differences should arise between the ~rindow and the envelope of the tube since differences in expansion result-3a ing therefrom may stimulate the formation of radial leakage paths in the seal.
An improvement in this respect is obtained by replacing the centring holder 27 in this phase of t~e manufacturing process by a holder in ~rhich the aper-_ g , ~.
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tures 9 are not provided. It ls also po~sible, as is shown in broken lines in Pigure 3, to provide a temporary envelope 32 around the device to be de-gassed during firing, which envelope is pumped to a rough vacuum via a line 33, that ls to say, a pressure of a few mm Hg. If desired, the firing tem-perature may then be increased from 250C to 450C without any objection, while in addition the leadthrough pins 29 are protected against possible oxidation.
In Figures 4 and 5 two embodiments of a completed gallium seal are shown in an enlarged scale. A window 41 is hermetically sealed against a c~linder 43 while using a gallium seal 42. Window and cylinder both have ground edges 44 and 45, respectively, which together constitute a V-shaped groove. A layer 46 of lead monoxide ls vapour-deposlted on a transparent signal electrode 47. The signal electrode 47 is led through to the exterior via a strip-shaped extension 48. In order to prevent a radial movement of the window 41, the groove formed by the ground edges 44 and 45 is filled with a hardening synthetlc material 49.
The embodlment shown in Figure 5 dlffers from that shown in Figure 4 in that a metal ring is provlded which covers the gallium seal and makes an electric contact with the extension 48 of the signal electrode 47. Since said ring locks the window against a radlal movement, the filllng of the V-s~aped groove with a cement or hardenlng synthetic material 49 may be omitted.
The invention is not restrlcted to the above-described examples in which one of the complementary parts of the en~elope of the tube is formed b~ a ~ndow. In the television camera tube shown diagrammatically in Figure 6 the window 60 forms one assembly with the cylindrical envelope 61 while said cylindrical envelope is sealed hermetically on its open end against a closing plate 62 while using a gallium seal 63. The method of manufacturing said tube is analogous to that described with reference to Figures 1 and 3.
Tnstead of an auxiliary windo~ an auxiliary envelope is used during the de-3Q gassing of the electrode system 64 shown diagrammatically, while during trans-port the lead mon~ de layer 65 formed on the window is protected against atmospherlc influence by an lnert gas, for example helium, admitted insida ~7;~7~
the envelope 61.
The closing plate 62 has a raisecl edged 66 to lock it against a radial movement. If desired, the gallium seal 63 may be protected against atmospheric influences and dust by means of a synthetic material 67 or by means of a ring as described with reference to Figure 5. Conductive pins 68 via which the various electrodes of the electrode system 6~ can be brought at the desired potential are' sealed in the closing plate. A transparent sig-nal electrode 69 vapour-deposited on the window 60 is electrically led through the wall of the envelope 61 br means of a current supply conductor 70.
Photoelectric devices manufactured according to the above-described method have highly reproducible properties. The individual phases in the manufacturing process of the device can be carried out in conditions optimum for each phase. A further advantage is that no high temperatures are required either for producing or for disrupting the seals. As a result of this, not only the manufacturing process of the tube is simplified, but it is also pre-vented that temperature-sensitive co~ponents, for example, a radiation-sensitive la~er, are detrimentally influenced.
It is kno~n that the properties of the radiation-sensitive material with respect to, for example, the sensikivity or the inertia, can vary unfavourably when they are exposed to the atmosphere.
United States Patent Specification 3,334,955 describes a method of manufacturing a vacuum tu~e in ~hich the components of the tube are assembled in an evacuated space after having been subjected in separate vessels to various treatments. Said vessels are temporarily sealed b~ a metal foil and are opened again in the evacuated space by cutting said foil from an annular frame.
German Patent Specification l,915,710 de-scribes a method of manufacturing a television camera tube in which a photocathode is vapour-deposited on a window in a closed vessel comprising said window.
Said vessel together with the electrode system of the camera tube uhich is already mounted in an envelope ~fiich is open at one end, is then accommodated in a space communicating with an evacuating device. After evacuating the space, the system of electrodes is de-gassed, after which the window having a radiation-sensit1ve layer is removed from the said vessel by means of a thermo-shock treatment and is then placed on the open end of the envelope of the camera tube with the inter-position of an indium sealing ring, ~7Z74~
The methods which are used in -the known manufacturing techniques to obtain a temporary seal of the vessels are far from ideal. The seals can be used only once and require expensive and precise pre treatment.
The invention starts from the above described methods and has for its object to provide an improved method of manufacturing an electric discharge -tube.
According to the invention, there is provided a method of manufacturing an electric discharge tube wherein at least one of the components of the tube is subjected to a treatment in a vessel sealed from the atmosphere, the tube having an envelope being formed of at least two envelope parts, the vessel being composed of at least two vessel parts including at least one of said envelope parts, said vessel parts being hermetically sealed against each other by bringing together smooth facing surfaces thereof with the interposition of a sealant substantially con-sisting of gallium or a low melting point allo~ of gallium in the liquid state provided on at least one of these surfaces.
According to another aspect of the invention there is provided an electric discharge tube comprising an envelope which consists of at least two parts hermetically sealed against each other by means of a sealant substantially consisting of gallium or a low melting point alloy of gallium.
Gallium has a melting temperature of approximately 29C. In the liquid state, said metal can readily wet glass and other metals. Another property which is important for the use according to the invention is that gallium has a vapour pressure lower than 10-8 mm Hg even at a temperature of 500C.
7Z~4~L
It is noted that seals of gallium are known as such from the United States Patent Specification 3,038,731, in particular with respect to liquid seals for valves and parts which are arranged so as to be rotatable relative to each other. As described in said Patent Specification, the seal-ing efect of gallium and low-melting-point alloys of gallium is based on an equilibrium of forces between on the one hand the surface forces of the seal-ing material and on the other hand the force acting on said material as a result of the pressure differential across the seal. This equilibrium may ~xist so long as with a given pressure differential the distance between the surfaces of the parts to be connected does not exceed a given value. In the practical case in which the pressure differential across the seal is approxi-mately one atmosphere, this means that the maximum distance of the parts to be connected may not be larger than approximately 10 ~m with a surface ten-sion of ~he sealing material of approximately 500 dyn/cm.
Seals of gallium or a low-melting-point alloy of gallium can be realized in a particularly simple manner. The facing surfaces of the parts to be connected are first polished so as to ensure that said surfaces join each other within a tolerance of 10 ~m. At least one of the surfaces is then wetted with gallium or a low-melting-point alloy of gallium, after which the parts are provided on each other. According to the invention, the parts ~hich are provided on each other are preferably rotated relative to each other so that a pattern of closed rings is formed in the sealing material. In this manner, the occurrence of radial leakage paths by island forma~ion of the sealing material between the surfaces is prevented. The sealing as such is then completed and the space thus closed can be evacuated. The seal can easily ~ithstand large temperature fluctuations. Temperatures exceeding 200C hardly constitute a drawback, while a hermetic seal is also maintained if the sealing material changes into the solid phase as a result of a de-crease of the temperature.
Not only can the above-described seal be realized in a simple man-ner, but parts o an envelope connected together in this manner can also be separated easily without damage thereto. It is thus these properties which ~C~727~
make the seal ex~remel~ suitable for use as a temporary seal in the manufac-ture of electric discharge tubes in which at least one of the composing parts is sub~ected to a treatment in a vessel which is sealed from the atmosphere.
According to the invention the envelope of said vessel preferably constitutes already wholly or partly the final envelope of the tube to be manufactured.
According to the invention, the gallium or a low-melting-point alloy of gal-lium is also used for the final sealing of the tube.
Examples of low~-melting ~point alloys which satisfy the object underlying the invention are alloys of gallium and at least one of the metals lndium and tin containing at least 50% by weight of Ga, and in particular eutectic alloys of gallium, indium and tin the melting point of which is below room temperature.
The invention preferably relates to the manufacture of an electric device having a vapour-deposited layer of radiation-sensitive material sealed from the atmosphere. The part of the tube envelope to be provided with the radiation-sensitive material is for that purpose arranged on a vapour-deposition device with the interposition of a layer of gallium-containing material for the hermetic seal of a first vessel thus formed. The complemen-tary part of the tube envelope comprising the electrode system of the tube is hermetically sealed in an analogous manner by means of a sealing member and thus constitutes a second vessel. The said first vessel and second vessel are then evacuated, after which the radiation-sensitive material is vapour-deposited in the first vessel and the electrode system is degassed in the second vessel. After vapour-depositing the radiation-sensitive material, the first vessel is filled with a gas which does not influence the radiation-sensitive material. When the pressures inside and outside the vessel are substantially equal to each other, the relevant part of the tube envelope may be removed from the vapour deposition device. In the second vessel the de-gassed electrode system is surrounded by an inert gas, after which the seal-3Q ing member of the said complementary part of the tube envelope may be re-moved. Finally the part of the tube enve~lope having a radiation-sensitive layer ~s transferred to the complementary part of the ~ube envelope having - 6 ~
~L~7z7a~
the said electrode system. The gallium-containing material which is already present on the surfaces to be connected ancl which in the first instance en-sured a temporary seal of the vessels, now produces the final seal of the tu~e.
During the transfer of the part of the tube envelope having a radiation-sensitive layer to the complementary part of the tube envelope, the radiation-sensitive material should be shielded from atmospheric influences.
Said shielding can be obtained in known manner by surrounding the relevant part during the transport with an inert gas, or causing the transport to take place in a vacuum space.
As is already known from the above-mentioned United States Patent Specification 3,038,731, measures are furthermore taken preferably to hold surfaces connected together hermetically with the use of a seal as described above in position relative to each other.
The invention will be described in greater detail with reference to the drawing, in which:
Figure 1 is a diagrammatic sectional view of a device for vapour-depositing a layer of radiation-sensitive material on a part of the envelope of a television camera tube to be manufactured according to the invention, 2~ Figure 2 is a perspective view of a centring holder f~r the part of t~e said envelope shown in Figure 1, Pigure 3 is a diagrammatic sectional view of the complementary part of the part of the tube envelope shown in Figure 1 and having a system of electrodes ready for degassing, ~igures ~ and 5 are sectional views of two embodiments of a final seal of a television camera tube manufactured according to the invention, and Figure 6 is a diagrammatic sectional view of a further embodiment of a television camera tube manufactured according to the invention.
Pigures 1 and 3 show two stages of the manufacture of a television camera tu~e. The envelope of the tube consists of two complementary parts, namely~ a glass window 1 and a glass envelope 20 which is open at one end.
~n t~e stage sho~n in ~i~ure 1J a radiation-sensitive la~er 3 of lead monoxide ~L~7Z74~L
is vapour-deposited on the ulndow 1.
Preparatory to said treatment, a layer of liquid gallium 2 is pro-vided on a smoo~h polished edge 4 of a hollo~ cylinder 5. For that purpose, the edge 4 to be wetted is moved in a rotating manner on a heated flat plate on which a layer of liquid gallium of a few microns thickness is present, a layer of gallium 2 remaining on said edge 4. At its non-wetted end the c~linder 5 is t~en connected hermetically to a vacuum line 6 of an evacuating device not shown. The window l on which a transparent conductive layer 7 of tin oxide or indium oxide has already been vapour-deposited, is placed on the edge 4 by means of a centring holder 8 and rotated a fe~ times so as to wet the surface of the window destined for the sealing~ Moreover, due to the rotary movement, closed concentric rings are formed in the gallium so that possible radial leakage paths are closed. In order to have a good grip on the windou during said rotary movement two apertures 9 are recessed in the centring holder 8 a perspective vie~ of which is shown in Figure 2~ By the arrangement of the window on the edge 4 with the interposition of a layer of gallium 2, a space is obtained which is sealed hermetically from the at-mosphere and which is evacuated via the vacuum line 6. An electric current is now conveyed through the wires 10 and 11 so that a tray 12 filled with lead monoxide 13 is heated. The lead monoxide i5 vapour-deposited on the conductive layer 7 ~hile forming the radiation-sensitive layer 3.
W~en the layer 3 has reached a thickness of approximately 8 microns, the vapour-deposition process is discontinued and the space bounded by the ~ndo~ l and the cylinder 5 is filled, via a closable supply line 14, with a gas, for example helium or nitrogen, which does not influence the radiation-sensitive material. ~eanwhile, a pouch 15 manufactured from a synthetic material, for example, polythene, is slid on the cylinder S and is also filled with an inert gas, for example, helium or nitrogen, via a supply line 16, the air present in said pouch being driven out. After a pressure equal to or 3a slightly larger than the ambient pressure has built up in the space communi-cating with the supply line 1~, the window 1 may be removed from the cylinder 5 and be transported uhile protected by the inert gas present in the pouch, Z74~
the opening of the pouch remaining directed downwards if the gas present therein is lighter than air.
Before placing the window 1 on the complementary part 20 of the ellvelope of the tube, the elec~rode system 21 already mounted in said part is degassed. This phase of the manufacturing process will be explained with reference to Pigure 3.
The glass part 20 of the envelope has a smooth polished edge 22 which is wetted wi*h the gallium in the above described manner. Via an ex-haust tube 23, the part 20 of the envelope is hermetically connected to a vacuum line 25 with the interposition of a sealing ring 24. An auxiliary ~indow 28 is placed on the edge 22 in the above-described manner with the interposition of the layer of gallium 26 and by means of a centring holder 27. The space in which the electrode sys~em 21 shown diagrammatically in the drawing is mounted on a number of pins 29 in the cap of the tube is hermetical-ly sealed from the atmosphere. After evacuating said space, the assembly is heated in a furnace to a temperature of 250C and the electrode system is then degassed at a temperature of 700C by means of a high-frequency coil 30.
After degassing, nitrogen is admitted to the said space through the duct 31 until the pressure in the space is equal to that of the surrounding atmos-phere, after which the auxiliary window 28 may be removed from the part 20 of the envelope. The window 1 having a layer of lead monoxide is now placed on the edge 22 of the part 20 of the envelope. The nitrogen supply through the line 31 is discontinued and ~he gallium present on the surfaces of the w~ndo~r and envelope to be connected now serves for the final seal of the tube.
The final envelope of the tube thus formed is finally evacuated via the line 25 after which the tube is completed.
In the case of large temperature Eluctuations as they occur upon degassing the tube, no large temperature differences should arise between the ~rindow and the envelope of the tube since differences in expansion result-3a ing therefrom may stimulate the formation of radial leakage paths in the seal.
An improvement in this respect is obtained by replacing the centring holder 27 in this phase of t~e manufacturing process by a holder in ~rhich the aper-_ g , ~.
~7;~7~L
tures 9 are not provided. It ls also po~sible, as is shown in broken lines in Pigure 3, to provide a temporary envelope 32 around the device to be de-gassed during firing, which envelope is pumped to a rough vacuum via a line 33, that ls to say, a pressure of a few mm Hg. If desired, the firing tem-perature may then be increased from 250C to 450C without any objection, while in addition the leadthrough pins 29 are protected against possible oxidation.
In Figures 4 and 5 two embodiments of a completed gallium seal are shown in an enlarged scale. A window 41 is hermetically sealed against a c~linder 43 while using a gallium seal 42. Window and cylinder both have ground edges 44 and 45, respectively, which together constitute a V-shaped groove. A layer 46 of lead monoxide ls vapour-deposlted on a transparent signal electrode 47. The signal electrode 47 is led through to the exterior via a strip-shaped extension 48. In order to prevent a radial movement of the window 41, the groove formed by the ground edges 44 and 45 is filled with a hardening synthetlc material 49.
The embodlment shown in Figure 5 dlffers from that shown in Figure 4 in that a metal ring is provlded which covers the gallium seal and makes an electric contact with the extension 48 of the signal electrode 47. Since said ring locks the window against a radlal movement, the filllng of the V-s~aped groove with a cement or hardenlng synthetic material 49 may be omitted.
The invention is not restrlcted to the above-described examples in which one of the complementary parts of the en~elope of the tube is formed b~ a ~ndow. In the television camera tube shown diagrammatically in Figure 6 the window 60 forms one assembly with the cylindrical envelope 61 while said cylindrical envelope is sealed hermetically on its open end against a closing plate 62 while using a gallium seal 63. The method of manufacturing said tube is analogous to that described with reference to Figures 1 and 3.
Tnstead of an auxiliary windo~ an auxiliary envelope is used during the de-3Q gassing of the electrode system 64 shown diagrammatically, while during trans-port the lead mon~ de layer 65 formed on the window is protected against atmospherlc influence by an lnert gas, for example helium, admitted insida ~7;~7~
the envelope 61.
The closing plate 62 has a raisecl edged 66 to lock it against a radial movement. If desired, the gallium seal 63 may be protected against atmospheric influences and dust by means of a synthetic material 67 or by means of a ring as described with reference to Figure 5. Conductive pins 68 via which the various electrodes of the electrode system 6~ can be brought at the desired potential are' sealed in the closing plate. A transparent sig-nal electrode 69 vapour-deposited on the window 60 is electrically led through the wall of the envelope 61 br means of a current supply conductor 70.
Photoelectric devices manufactured according to the above-described method have highly reproducible properties. The individual phases in the manufacturing process of the device can be carried out in conditions optimum for each phase. A further advantage is that no high temperatures are required either for producing or for disrupting the seals. As a result of this, not only the manufacturing process of the tube is simplified, but it is also pre-vented that temperature-sensitive co~ponents, for example, a radiation-sensitive la~er, are detrimentally influenced.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of manufacturing an electric discharge tube wherein at least one of the components of the tube is subjected to a treatment in a vessel sealed from the atmosphere, the tube having an envelope being formed of at least two envelope parts, the vessel being composed of at least two vessel parts including at least one of said envelope parts, said vessel parts being hermetically sealed against each other by bringing together smooth facing surfaces thereof with the interposition of a sealant sub-stantially consisting of gallium or a low melting point alloy of gallium in the liquid state provided on at least one of these surfaces.
2. A method as claimed in Claim 1, wherein after bringing together the parts to be hermetically sealed against each other, these parts are rotated relative to each other.
3. A method as claimed in Claim 1, wherein said low melting point alloy of gallium is chosen from the group consisting of alloys of gallium and at least one of the metals indium and tin containing at least 50% by weight of gallium; and eutectic alloys of gallium, indium and tin the melting point of which is below room temperature.
4. A method as claimed in Claim 1, wherein said treatment includes vapour-depositing a layer of radiation-sensitive material on the inside of at least one of the envelope parts of the tube.
5. A method as claimed in Claim 4, wherein the radiation-sensitive material is vapour-deposited on a part of a first envelope part of the tube in a first vessel which is formed by at least two vessel parts including the first envelope part, which vessel parts are temporarily sealed against each other, and wherein an electrode system of the tube is degassed in a second vessel also formed by at least two vessel parts including a second envelope part of the tube which vessel parts are also temporarily sealed against each other, after which the temporary seals are interrupted and the first envelope part of the tube having the radiation-sensitive layer is hermetically sealed against the second envelope part of the tube adjoining same by a final seal, both the temporary seals and the final seal being obtained with a sealant substantially consisting of gallium or a low melting point alloy of gallium.
6. A method as claimed in Claim 5, wherein the final seal of the two envelope parts of the tube is reinforced mechanically by means of a cover consisting of metal and/or by a hardening synthetic material.
7. An electric discharge tube comprising an envelope which consists of at least two parts hermetically sealed against each other by means of a sealant substantially consisting of gallium or a low melting point alloy of gallium.
8. An electric discharge tube as claimed in Claim 7, wherein at least one of said parts of the envelope has a radiation-sensitive layer.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7407952A NL7407952A (en) | 1974-06-14 | 1974-06-14 | METHOD OF MANUFACTURING AN ELECTRICAL DISCHARGE TUBE AND ELECTRICAL DISCHARGE TUBE THEREFORE MANUFACTURED. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1072741A true CA1072741A (en) | 1980-03-04 |
Family
ID=19821543
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA229,107A Expired CA1072741A (en) | 1974-06-14 | 1975-06-11 | Method of manufacturing an electric discharge tube and electric discharge tube manufactured by said method |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5111685A (en) |
| AU (1) | AU503938B2 (en) |
| CA (1) | CA1072741A (en) |
| DE (1) | DE2524690A1 (en) |
| FR (1) | FR2289046A1 (en) |
| GB (1) | GB1506463A (en) |
| NL (1) | NL7407952A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2022142530A (en) | 2021-03-16 | 2022-09-30 | 富士フイルムビジネスイノベーション株式会社 | Information processing apparatus and information processing program |
-
1974
- 1974-06-14 NL NL7407952A patent/NL7407952A/en not_active Application Discontinuation
-
1975
- 1975-05-20 GB GB2147075A patent/GB1506463A/en not_active Expired
- 1975-06-04 DE DE19752524690 patent/DE2524690A1/en active Pending
- 1975-06-11 JP JP7072375A patent/JPS5111685A/en active Granted
- 1975-06-11 AU AU82010/75A patent/AU503938B2/en not_active Expired
- 1975-06-11 CA CA229,107A patent/CA1072741A/en not_active Expired
- 1975-06-12 FR FR7518367A patent/FR2289046A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB1506463A (en) | 1978-04-05 |
| AU503938B2 (en) | 1979-09-27 |
| DE2524690A1 (en) | 1976-01-02 |
| JPS5111685A (en) | 1976-01-29 |
| AU8201075A (en) | 1976-12-16 |
| NL7407952A (en) | 1975-12-16 |
| FR2289046A1 (en) | 1976-05-21 |
| JPS5338571B2 (en) | 1978-10-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |