DE1162001B - Electron discharge device, in particular television pickup tubes - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

LIBRARY DES GERMAN PATENT OFFICE

Boarding school Kl .: HOIj

German class: 21g-13/25

Number:
File number:
Registration date:
Display day:

E 15322 VIII c / 21g
February 6, 1958
January 30, 1964

The invention relates to an electron discharge device, the protective screen of which is made of a layer contains a material which, when bombarded with electrons, has a sufficiently high velocity Property of induced conductivity shows so that on the layer when scanning with electrons A charge image dependent on the respective intensity of the scanning beam is generated at high speed which can be compensated for by scanning the layer with low-speed electrons is. Such electron discharge devices are found, for example, in television or for others Purposes use.

The property of "induced conductivity" is understood to mean that the material of the The catching screen or the catching electrode is normally non-conductive or semiconducting, but becomes conductive, when bombarded with a high speed electron beam. Devices where Collecting electrodes with such properties are used, have already become known. Some examples can be found in German Patent 941545.

All previous devices have in common that the collecting electrodes are built up with solid, tightly packed layers made of the material which has the property of induced conductivity. Such collecting electrodes, however, have an undesirable "lag". For example, in one of the electron discharge devices disclosed in the above-mentioned patent, an electron image is projected onto one side of the target electrode by a beam at a sufficiently high speed so that an induced conductivity is produced. The opposite side of the target electrode is scanned with a slow speed electron beam, the charge distribution generated on the target electrode by the electron image being substantially equalized to an equilibrium potential in order to produce the image signals suitable for television. The above-mentioned lag is manifested in the fact that a noticeable time elapses before the charges on the surface of the target electrode are returned to their equilibrium value. For example, in the case of a solid layer with a thickness of 0.5 μ, the lag can last for several seconds. This is an undesirable factor. For this reason, it has heretofore been considered necessary to keep the material layer thin (for example in the above-mentioned thickness) in order to have the desired effect of the induced conductivity electron discharge device,
especially TV recording tube

Applicant:

Electric & Musical Industries Limited,

Hayes, Middlesex (Great Britain)

Representative:

Dr. K. R. Eikenberg, patent attorney,

Hanover, Am Klagesmarkt 10/11

Named as inventor:

James Alec Lodge, Ealing, London,

Reginald Sidney Webley, Hayes, Middlesex

(Great Britain)

Claimed priority:
Great Britain 7 February 1957
and January 27, 1958 (No. 4225)

shows at a suitable working voltage. The lag mentioned above can be caused by that the lag is a property of the material itself and / or that the layer is so thin that the capacity across the layer is necessarily large.

The lag of the layer possessing the property of induced conductivity is reduced, when according to the invention the layer is composed of loosely packed material particles.

To produce such a layer, the material is expediently applied to the in a gas atmosphere Evaporated catch screen, preferably the mean free path of the evaporated material particles is kept less than the total path that these particles travel in the gas.

The thickness of the loosely packed layer can be 2 to μ. As a material for such a layer red antimony trisulfide has proven to be very suitable. This material, which acts as a photoconductor in television pick-up tubes with photoconductive umbrella, e.g. B. the vidicon tube, is known, was used for catching

309 807/314

3 4

shields, which the property of induced conductive on the potential of the layer 3 is kept. The ability to possess, not yet in overall proposal accelerated electrons pass through the layer 3 ^bracIlt · through and enter the layer. 4 In the following, the safety screen can contain several layers of the elementary areas of the layer 4, different loosely packed layers. The 5 conductivities can also be selected, depending on the arrangement, in such a way that the layer has an intensity of 2 to 3 μ with the intensity of the corresponding areas of the electrical power. The tron images, which in turn consist of the solid layers made of the same material, can depend on the exposure of the corresponding elementary areas of the loosely packed layer or on the optical image thereof. This gives a different charge material. io pattern on that surface of the layer 4, which further details are referred to in the embodiment for the electron beam generator, as well as an example with reference to the drawings more detailed current flow through the layer 4, which is greater than the clarifies. The current of the image electrons shows, so that a current amplifier Fig. 1 the application of the stratification described occurs. Said surface of the layer 4 in the case of a television _{pick-up tube, 15} is activated by an electron beam from the electronics. 2 a sampled Modi tronenstrahlerzeuger on an enlarged scale, whereby the erfikation be made of the capture screen of the device according to mentioned elementary regions back to Fig üir DC-1-equilibrium potential. The ray from the in FIG. 1 shown television tube of the cathode 9 scans the surface of the protective screen corresponds in its general structure to Fig. 3 20 in the presence of a longitudinal magnetic field, the already mentioned German patent which is generated by a solenoid coil 15, so 941545, but is within its evacuated that the scanning beam impinges on the target electrode in the w & - shell 1 with a described protective screen substantially perpendicular to the scanning movement, see. This catch screen contains a conductive The equilibrium potential of the catch code network 2, which, for example, has 240 spaces 25 essentially the potential of the Kapro centimeters. On this network is a method 9. In the case of the thinning continuous layer 3 of conductive dimensions described above, the conductive layer 3 is applied to a material, for example aluminum, which has a positive potential of 100 V for example as a carrier for a continuous layer 4 from a held onto the cathode 9, so that a positive material is used, which when bombarded with electrons produces the property of the induced conductivity layer 4 on the scanned surface of the electrons. This positive ii l i Di Shih 3 ki idi bk id d bh

gp g

shows. The layer 3 can then be in any known manner by the scanning beam of low ge

Wise made, for example, that speed unload. The unloading of the elementary

first on the surface of the network 2 a KoI area of the scanned surface generates the image

iodium film is formed and then aluminum on these 35 signals via a resistor 16, which is connected to the conductive

Collodion film is evaporated, whereupon the layer 3 is finally connected. The required po-

the collodion film is removed by heating. potentials for electrodes 9, 10, 11, 12 and 13

At one end of the sheath 1 a photon can be taken from a source 17 over

electrical cathode 5 in contact with a trans- which a potentiometer 18 is placed, on the number of

Parent conductive electrode 6 arranged. With the 40 rich taps the electrodes are connected,

This device is an optical image of a counter- The cathode 9 is kept at ground potential, the

Stand, which is from a (in the drawing only an- cathode shield 10 on a negative po-

interpreted) lens system on the cathode 5 potential with respect to earth, the acceleration

is projected, transmitted. Through the optical image electrode 11 at a positive potential with respect to

5 photoelectrons are released from the cathode, 45 on the cathode 9, the wall anode 12 on one

the high positive potential with respect to the cathode 9 by means of an electrode 7 against the collecting electrode

accelerated and by means of a focusing coil 8 and the deceleration electrode 13 on a something

be focused. In the example in FIG. 1, there are lower positive potentials than the wall anode 12.

which the photoelectrons pass through the network 2 and through The layer 4 is a porous layer made up of

the thin, continuous layer 3 of the conductive male 50 is composed of loosely packed particles. A

terials thrown through onto layer 4. suitable material from which the layer 4 is formed

The surface of layer 4 on which the photo can be taken is red antimony trisulfide. To educate

The cathode remote side is set up so that the antimony trisulfide is underneath the porous layer

from a low speed electron beam low gas pressure onto the conductive layer 3

can be scanned. This electron beam 55 is vaporized. The gas can be air, argon, or xenon

low velocity will be another suitable gas in an electron. The gas pressure can

generated jet generator that has a cathode 9, a Ka- for example 0.3 Torr when using xenon

method shield 10 and an acceleration, but it can also be a higher gas pressure of

electrode 11 includes. The electron beam will be used, for example, 1 Torr or more,

accelerated by a wall anode 12 and then 60 The mean free path of the evaporated partial

delayed by a delay electrode 13. The data in the gas should be noticeably less than that

with the electron beam the surface of the layer 4 removal over which the evaporation process

can scan, scanning coils 14 are provided. takes place. For example, to generate a

The photographic layer area of 1 cm ² emerging from the photocathode 5 is the mean free path

electrons will be at a suitably high velocity 65 0.01 cm while the evaporation source

Speed is accelerated by placing the electrode 6 on one at a distance of 1 cm from the catch screen

suitable negative potential and the electrode 7 is arranged. The porous layer can be a thickness

have a suitable positive potential with respect to more than 0.5 μ. It was found,

that with a thickness of the layer of 2 to 3 μ the lag is about Ve seconds or less.

Sometimes the degree of reinforcement of a porous layer can be less than the degree of reinforcement of a solid layer of the same thickness. However, with a solid layer of, for example, 0.5 μ, the speed of the electron current that is required to generate an induced conductivity with maximum amplification is of the order of about 12 kV and, with a thickness of 2 μ, even of the order of about 24 kV. In contrast, with a porous layer 0.5μ thick, the maximum gain occurs at an electron speed of 3 kV, although the gain is still very low. It has been found, however, that with a porous antimony trisulfide layer 2μ thick, an electron velocity of 7 kV causes about a ten-fold gain.

In the case of a porous layer, the dielectric constant of the layer is reduced with the result: that for the same layer thickness the capacitance across the layer compared to the one solid layer is reduced. In this way it is only possible to replace the solid layer with a porous one Layer of the same thickness also reduces the lag caused by the capacitance. It was found that with a porous layer of antimony trisulfide about 2 μ thick, the overall lag does not exceed the capacitive lag.

Instead of antimony trisulfide, other substances are also suitable for building up the layer, for example Arsenic trisulfide, silicon monoxide, silicon dioxide, magnesium fluoride, calcium fluoride and zinc sulfide. These substances can also be applied in porous form.

If so desired, after the application of the layer 4, in the manner shown in FIG a thinner solid layer 20 made of a material which, when bombarded, has the property of being induced Conductivity shows, can be arranged on the layer 4. This solid layer 20 is attached so that that it points in the direction of the scanning beam. It can be made by evaporating the material in the Vacuum can be generated. If desired, it can also be used before depositing the porous Layer 4 first a solid layer is deposited on the conductive mesh 3. Furthermore can also in place of or in addition to one or several of the additional solid layers such a layer can be used which has the porous layer on both sides. The solid layer or the solid layers can be very thin, for example 0.1 μ thick, they can also be formed from the same material as the porous layer or from a different material.

Claims (7)

Patent claims: 1. Electron discharge device, in particular television pick-up tube, its catch screen contains a layer of a material that is sufficiently high when bombarded with electrons Speed shows the property of induced conductivity, so that on the layer at Scanning with high speed electrons depends on the intensity of the scanning beam dependent charge image is generated, which by scanning the layer with electrons low speed can be compensated for, characterized in that the layer (4) consists of loosely packed material particles is composed. 2. Method of manufacturing an electron discharge device with a layer composed of loosely packed material particles according to claim 1, characterized in that that the material of the layer is vapor-deposited onto the protective screen in a gas atmosphere will. 3. The method according to claim 2, characterized by a gas pressure at which the mean free Path length of the evaporated material particles is less than the total path that these particles put back in the gas. 4. Electron discharge device according to one of claims 1 to 3, characterized in that that the layer is built up from red antimonium trisulfide. 5. Electron discharge device according to one of claims 1 to 4, characterized in that that the layer has a thickness of 2 to 3 μ. 6. Electron discharge device according to a of claims 1 to 5, characterized in that the catch screen is several loosely packed Layers contains a material that is sufficiently high when bombarded with electrons Speed shows the property of induced conductivity. 7. Electron discharge device according to one of claims 1 to 6, characterized in that that the protective screen contains one or more solid, vacuum-deposited layers (20) made of a material that, when bombarded with electrons, has a sufficiently high speed shows the property of induced conductivity (Fig. 2). Considered publications:
German Patent No. 941545;
German patent application ρ 48131 Villa / 21a ¹ (published on 15.3.1951); RCA Reviem, September 1951, pp. 335 to 349. 1 sheet of drawings 309 807/31 + 1.64 © Bundesdruckerei Berlin