US2177735A - Luminous body - Google Patents

Description

Oct. 31, 1939. w. MEYER 2,177,735

LUMINOUS BODY Filed Aug. 4, 1957 INVENTOR Wilfried Mgyer ATTORNEY Patented Get. 31, 1939 UNITED STATES PATENT OFFICE LUMINOUS BODY Application August 4, 1937, Serial No. 157,424

. In Germany August 12, 1936 dclaima.

My invention relates to improvements in luminous bodies adapted when acted upon by electrons or ultraviolet rays to emit light.

There are a large number of substances which 5 when acted upon by light of short wave length or by electrons are made luminous. Such substances are used for example in the manufacture of luminous screens in Braun tubes. It is known that the radiationcaused by the action of elec- 10 trons is so much the stronger the higher the velocity of the electrons. However, a difficulty is caused by the fact that most of the luminous substances such for example as zinc silicate or cadmium silicate containing oxides of heavy 1| metals such as manganese oxide are non-conductive. When such substances are impinged upon by electrons they are charged thus producing an electric counterfield. Thus the intensity of the radiation is reduced. Where the velocity of the Q electrons is small their energy may not even be suflicient to excite luminescence of the substances, because the action'of the active field on the electrons is nearly compensated by the action of the retarding field. To avoid this the luminous substances are applied to the conductive screen in layers which are as thin as possible, in order to reduce the resistance opposed to the flow of the electrons from the screen. However, the particles of the luminous screen make 30 contact with their carrier only at some po nts,

' and a luminous grain presents a very small crosssection for transmitting the electrons to the metal.

The object of the improvements is to provide a luminous body in which the luminous substance is in large surface contact with the conductive carrier and thus to produce luminous screens which have strong radiation also in case of low velocity of the electrons. ,With this ob- 40 ject in view my invention consists in manufacturing the carrier of the luminous substance from compounds, and preferably from oxides, themetallic components of which simultaneously are parts of the luminous coating, the said luminous 45 coating being produced on the said conductive carrier by chemical transformation of the surface, for example by transformation in a solid state. i

For the purpose of explaining theinvention a 50 discharge lamp having a luminous body'has been illustrated in the accompanying drawing, showing a sectional elevation of the said discharge lamp.

Referring at first to the drawing, in the axis 55 of an evacuated glass receptacle I an indirectly heated glowing cathode 2 in the form of a rod is located, which is surrounded by a screen 3 which is in the form of a funnel opening towards the apex .of the glass receptacle. The said screen consists of zinc oxide and provides a conductive carrier of a surface layer 4 providing the source of light, the said layer 4 being provided on the inner side of the screen and opposite to the g1owing cathode. The said surface layer 4 likewise consists of a zinc compound, and preferably it consists of zinc silicate activated by means of manganese oxide, the said surface layer 4 being made luminous by electrons emitted from the glowing cathode.

' The outside .of the screen 3 of zinc oxide has a metal coating 5 by means of which the current is removed.

Within the press 6 of the receptacle four wires 1, 8, 9 and ill are fused. The metal coating 5 of the screen 3 is connected with the contact ll through the wire I, the cathode 2 is connected with a contact I2 through the wire I0, and the heating body l3 of the glowing cathode is connected with contacts l4, l5 through wires 8, 9. To the metal coating 5 of the screen 3 wires 16 and" are connected which provide a support for the screen. The wire I! is connected to a wire I, and it is used for removing the current from the screen.

The luminous body such as the aforesaid screen is manufactured as follows; A sintered plate of zinc oxide having a resistance of from 10 to 100 ohms per cube of one centimeter length or less and containing a few hundredths, preferably a few thousandths of a percent of manganese oxide in a state of finest distribution has a coating of colloidal silicic acid or fine silicic acid powder applied thereto, and the said plate is baked. By such baking zinc silicate containing traces of the activating manganese oxide contained in the zinc 4o oxide is produced on the surface by transformation in solid state, the said surface emitting gree'n light when it is impinged upon by electrons. It will be understood that in a luminous body thus manufactured the luminous substance is in large surface contact with its carrier, and that it is rigidly fixed thereto, so that the electrons are readily removed. Therefore the screens have a very high luminous density, and they emit light even if they are impinged upon by electron rays of small velocity.

In a similar way a luminous body may be manufactured on the basis of cadmium silicate phosphorus. In this case on a plate of cadmium oxide having a specific resistance of 1 ohm or less silicic acid is spread, and it is baked so as to produce cadmium silicate.

For obtaining a particularly fine distribution of the silicate I proceed as follows: By vaporization or cathode atomization of metallic silicon on a plate of zinc oxide or cadmium oxide containing manganese a layer of silicon is produce which may have a thickness of 1 ,u., preferably of from 0.1 to 0.5 a or less. These zinc oxide plates are baked at the open air and at a temperature of more than 400 0., preferably at a temperature of from 1000 to 1200 C. Thereby at first silicon dioxide is produced, which thereafter forms silicates with the zinc or cadmium oxides containing manganese, so that the luminous body is produced.

The manufacture of sulfldic phosphorus may be carried out in a similar way, for example by glowing a conductive plate consisting of a mixture of cadmium oxide and zinc oxide having an addition of silver, in hydrogen sulfide at a temperature of more than 400 C. Thereby on the conductive carrier a luminous and very thin layer of zinc-cadmium sulfide having an addition of silver is produced which rigidly adheres to the carrier.

Ina modification of the process the layers are produced as follows: To a carrier consisting of platinum or another noble metal a coating of zinc or cadmium is applied, for example by vaporization or electrolysis, or by another method,

which coating is anodically transformed in an electrolyte, or by glowing in the presence of oxygen into zinc oxide or cadmium oxide, the said oxide being treated in the manner described above. As compared to other processes, this process is a little more diificult, but it may be preferable for various purposes.

In another modification mixtures of compounds of several metals, such for example as-zinc and cadmium, are subjected to the process.

I claim:

1. A luminescent body capable of light emission under excitation, comprising a conductive carrier, the surface of said carrier being luminescent and comprising a compound of a metal the sion under excitation comprising a conductive carrier of zinc oxide and cadmium oxide, the surface of said carrier containing zinc, cadmium and sulphur and being luminescent.

W'ILFRIED MEYER.

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