DE2058640A1 - Signal window for electron tubes - Google Patents

Description

I- 4439 PHN. 4439 .

Nov 27, 1970

dJo / ¥ JM.

Signal window for electron tubes.

The invention relates to a signal window for electr cathode ray tubes, in particular cathode ray tubes. There are in the first place meant image pickup tubes of the vidicon type and oscilloscope tubes; leaves the signal window in the first case the incoming light "and in the second case the emerging light through.

The windows of such tubes consist of a light-permeable base, on which one is used for image recording serving layer of a radiation-sensitive substance attached? is. The underlay that is transparent to light is at least on the surface of the radiation-sensitive substance electrically conductive, so that they can dissipate electrical Charge and can be used as an electrode «

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Under "radiation-sensitive substance" is meant here a substance can be understood that under the action of electromagnetic or corpuscular radiation changes reversible the electrical properties such as conductivity or the dielectric constant or the light emission. The term therefore includes both photo-conductive as well as luminous fabrics.

For light-permeable, electrically conductive surfaces, as is known, by vapor deposition of metal in particular Precious metal can be obtained on a support. One disadvantage, however, is that thin layers of metal do not have show even light transmission across the entire spectrum. For example, thin gold layers are colored blue to green .

The well-known, colorless, electrically conductive layers of tin oxide are considerably better in this regard and indium oxide. For the present purposes, these oxide layers also have sufficient chemical resistance. It has been found, however, that in contact with the metal compounds that make up radiation-sensitive Layers often exist, e.g. photoconductive compounds such as lead oxide and antimony trisulfide and luminescent compounds like willemite, the chemical inertness of the conductive layers, e.g. of tin oxide and indium oxide, leaves something to be desired - r

It is the object of the invention to provide a signal window for an electron tube which has this disadvantage

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does not have.

According to the invention, the object is achieved by means of silicon carbides, which are already related with particular chemical inertness have proven useful for various uses in the art. It is known that silicon carbide can be absorbed by donors and / or acceptors while maintaining light transmission achieve the required electrical conductivity.

The invention relates to a signal window for a Electron tube, in particular an image pickup tube of the vidicon type, which window of a light permeable Underlay consists of a radiation-sensitive layer on one side with a layer serving for image recording Coated substance and electrically conductive at least on the surface with the radiation-sensitive layer and is characterized in that the substrate is made of compact silicon carbide at least on the mentioned side a content of donors and / or acceptors.

The signal window according to the invention can be a Have a base that is completely made of compact silicon carbide and is electrically conductive on at least one surface.

Compact silicon carbide bodies are known by sublimation, by gas phase reactions such as pyrolysis of a methylchlorosilane in the presence of hydrogen and by converting graphite, silicon or quartz

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body completely or superficially through reaction with To obtain silicon or carbon or compounds thereof in silicon carbide. '

Quartz substrates with a compact layer of silicon carbide are preferred, since quartz bodies have the required Dimensions are available and can easily be superficially converted into silicon carbide.

The electrical conductivity of at least the surface of silicon carbide can be achieved, as agreed, by incorporating donors and / or acceptors. Preferably if additives are selected for this purpose which cause at most a slight discoloration of the silicon carbide, see above that the passage of light over the entire spectrum can take place as unhindered as possible. The incorporation of additives can take place during the formation or the deposition of the silicon carbide in the gas phase or also by diffusion.

The windows according to the invention can be used for

Melt the assembly of the electron tubes to other parts using transition glasses. In the case of window substrates which consist entirely of silicon carbide, j

Purpose borosilicate glasses are used. For melting v

of substrates made of a quartz body, which is superficially in;

Silicon carbide is converted, the usual come to Fusing quartz to glass available intermediate)

glasses into consideration. I.

The electrically conductive silicon carbide of the windows,

j can be achieved by melting metals such as alloys of gold \

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V · PHN. 4439.

i ■

■ ;! and Taft Valley, of nickel and molybdenum, and of platinum and tin locally provided with electrical contacts.

The invention is explained in more detail below for an exemplary embodiment with reference to the accompanying drawing. The figure of the drawing shows, for example, schematically a longitudinal section of an image pickup tube of the vidicon type which is provided with a signal window according to the invention.

I The image pick-up tube shown has a devi- ^

Λ -

'' lifted, elongated, cylindrical flask 1 made of glass, ; that at one end through the substrate 2 of a signal window (and terminated at the other end by the glass base 3.

i This glass stem 3 "of which a central part is formed by a \, fused Entlüftungsrohrchen 4,

■■ { metal grommet 5 mounted in the piston

V with different parts of the electrode system 6 electrically

■, * "are connected.

'The electrode system 6 contains an M through a

ο filament 7 to be heated, thermal cathode 8, a

■■■> neltylinder 9 and a perforated anode 10, the electrically

I is connected to a cylindrical electrode 11. The elec-

^ trode 11 is on the window side with a gauze-shaped

. ^: Electrode 12 provided.

j The signal window consists of a transparent one

Substrate 2 made of silicon carbide or quartz, which is on the Electrode 11 facing side with a transparent sign

^: ':> Nalelectrode 13 is provided, which consists of a compact layer

; electrically conductive silicon carbide. The body with

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the substrate 2 with the electrode 13 is, as mentioned above, if necessary by means of one or more intermediate glasses melted in the cylindrical piston 1. The signal electrode 13 is connected to an outward conductor 1 ^ Mistake.

It is deposited on the signal electrode 13 by vapor deposition in a gas atmosphere containing oxygen and water vapor, an approximately 15 to 20 μm thick photoconductive layer made of lead monoxide (PbO) attached.

The layer 15, which the target 15 in

the tube forms, on the surface facing the anode 10 can be scanned by an electron beam 16 emanating from the cathode 8. By means of the usual, the tube surrounding deflection and focusing coils 17 is the electron beam 16 focused on the target 15 and moved for scanning.

^ t means of a schematic through a simple lens

18, an image to be converted into electrical signals is applied to the target plate during operation of the tube 15 projected. The electrical signals are, as usual, when the target 15 is scanned by the Electron beam 16, via a signal resistor 19 in the conductor 14 received the signal resistance over which the signal electrode 13 receives a positive bias voltage of 20 to 60 volts with respect to the cathode 8.

Some examples of substrates for signal windows according to the invention and the manufacturing

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indicated.
Example ί.

Pure silicon carbide, which was obtained by pyrolysis of a methylehlorsilane, was in a graphite gauge for one hour in argon with less than 1 ppm nitrogen at 2200 ° C. to form a cylindrical body with an outside diameter of 70 mm, an inside diameter of 40 mm and a height of 100 mm sintered. %

The cylinder was then left on for five hours Heated 2500 ° C in a graphite crucible in helium with less than 0.1 ppm nitrogen, making sure that the temperature gradient along the brick wall was small both axially and radially.

Large, clear, plate-shaped crystals of pure silicon carbide grew on the inner wall of the cylinder.

Crystals of 10x10x1 mm ³ were on a

Surface by diffusion of aluminum with a thin, ^

transparent layer with a specific resistance of 0.5 Ohm. cm.

Disks were formed from the crystals, which were provided with contacts by fusing gold strips with 5 ° tantalum on the electrically conductive surface.

The discs were fused into tubes made of borosilicate glass, with the gold alloy contacts through the Tube wall were performed.

' Example II.

In a graphite brick with a plate-shaped

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Cover with a diameter of 70 mm and made of graphite pure silicon carbide powder was heated in an argon atmosphere with 0.01 io nitrogen to 26OO ° C. At a temperature of the lid of 240 ° C., a dense, light green layer of silicon carbide sublimed on it and grew to a thickness of 4 mm in five hours. After the graphite had been burned off in an oxygen atmosphere, disks were formed by grinding and sawing, which can be used as a conductive substrate for signal windows. The specific resistance of the substrates, which were conductive by nitrogen doping, was 1 ohm.cm.

The disks were provided with contacts by melting strips made of an alloy of nickel with 10 ^ molybdenum and melted in a tube made of borosilicate glass, the contacts being led to the outside. Example III .

A graphite plate with a diameter of 40 mm was raised to 1550 ° C in a hydrogen flow of 10 liters / minute heated with 1 volume percent methylchlorosilane. Within an hour a layer of yellowish, clear, pure silicon carbide with a thickness of 1 mm. As a result of the nitrogen present in the gas stream, the was partially absorbed into the silicon carbide, this was electrically conductive. The specific resistance was 200 ohms. cm.

After burning away the graphite plate in an oxygen atmosphere at 1000 ° C and after grinding and

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After polishing, a disk with a diameter of kO mm and a thickness of 0.7 mm was obtained, which can be used as a window substrate and can be further processed in the manner shown in Examples I and II. Example IV.

A quartz disk with a diameter of 20 mm and a thickness of 3 now was made on one side with a thin Layer of a carbon suspension covered. ■

After drying, it was on for eight hours

1100 ° C heated in a hydrogen atmosphere. Consequently the quartz was superficially transformed into a silicon carbide. This was followed by heating for two hours in oxygen with 1 percent by volume of nitrogen. As a result, the The remaining carbon remains burned away and due to the presence of nitrogen in the oxygen atmosphere an electrically conductive surface was obtained.

On this window substrate were on the in the ^ previous examples indicated manner contacts attached. In this case, the usual intermediate glasses are used.

. The window substrates became sensitive to radiation Layers attached. If signal window for image capture Vidicon-type acquisition tubes are to be produced, a photoconductive layer, in particular a vapor-deposited one Lead monoxide layer attached. The usual layers of phosphors are used to manufacture oscilloscope tubes e.g. Willemit attached.

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Claims (5)

PHN. 4439 - 10 PATENT CLAIMS. U J signal window for an electron tube, in particular for an image pickup tube of the vidicon type, which window consists of a substrate permeable to light, the one on one side with one used for image recording Layer of a radiation-sensitive substance is covered and at least on the surface with the radiation-sensitive Layer is electrically conductive, characterized in that the substrate at least on the mentioned Side consists of compact silicon carbide with a content of donors and / or acceptors. 2. Signal window according to claim 1, characterized in that that the substrate consists entirely of compact silicon carbide, which is electrically on at least one surface is conductive. 3. Signal window according to claim 1, characterized in that that the substrate consists of quartz, on which a compact layer of silicon carbide is attached. 4. Signal window according to one of Claims 1 to 3 characterized in that the electrically conductive silicon carbide is provided with one or more metal contacts is. 5. Electron tube, in particular image pickup tube of the vidicon type with a signal window according to one of the Claims 1 to 4. 109826/099 8