US2185439A

US2185439A - Method for optionally altering the after-glow period of phosphorescent screens

Info

Publication number: US2185439A
Application number: US109592A
Authority: US
Inventors: Hinderer Heinrich
Original assignee: FIRM FERNSEH AKTIEN GES
Current assignee: FIRM FERNSEH AKTIEN GES; FIRM FERNSEH AKTIEN-GESELLSCHAFT
Priority date: 1935-11-28
Filing date: 1936-11-06
Publication date: 1940-01-02
Anticipated expiration: 1957-01-02

Description

HI. HINDERER MET HOD FDR OPTIOMLLY ALTERING THE AFTER-GLOW PERIOD OF PHOSPHORESCENT SCREENS Filed NOV. 6, 1936 mwwoflzau aim y grime/14M I 55 In the drawing, whereas the photographically non-active ones UNITED STATES PATENT orrlce METHOD FOR OPTIONALLY ALTERJNG THE AFTER-GLOW PERIOD or rnosrno- RESCENT SCREENS Heinrich Hinderer, Berlin Zehlendorf, Germany,

assignor to the firm Fernseh Aktien-Gescllschatt, Zehlendorf, near Berlin, Germany Application November 6, 1936, Serial No. 109,592

' In Germany November 28, 1935 Claims. (Cl. 250--27.5)

The invention relates to a method for option- Figure 1 illustrates One form of Cathode my ally altering the after-glow period of phosphotube adapted for utilizing the method of the inrescent screens, especially those used in cathode vention; and y u es. Figure 2 illustrates graphically the conditions Such optional control of the after-glow period occurring in the case of a material selected by 5 is of the greatest significance when rapidly varyy Of p ing phenomena are to be rendered visible or de- Referring to Figure 1, the envelope l houses lmeated, whether it be because the after-glow a c t e 2, a control r an anode 18 entirely undesired or, as occurs in television fleeting plates 5 and a phosphorescent Screen 1o practice, because it should have varying optimum The latter comprises conductive supportin l0 duration depending on the delineation method means havi g a phosphorescent Coating- A used' heating current is passed through screen 6 from Attempts have heretofore been made to control source I, and the heating or polarization is conthe after-glow by suitable choice and mixture trolled by rheostat of the luminous substance used. It is, however, In Figure 2, the curves indicate the duratio 15 very dimcult to achieve a. perfect result in thi of the after-glow in relation to the temperature manner. for the various phosphorescence bands of a It is known that each phosphorescence band of Zn-S-Mn material. The bands are designated a phosphorescent substance when energized by as usual as a, b and cbands. The after-glow of the light has an upper instantaneous condition. By a band of this phosphorescent material starts at 20 this is meant the temperature ab v whi h th about +190 0., and the duration of the afterphosphorescence of the band passes into fluoresglow rises very strongly up to +100". From this cence, that Where it no longer shows aftertemperature on the band after-glows up to --1'70 glowin a strong and continuous manner.

In accordance with the present invention the The blue b band is in its upper instantaneous p phorescence is entirely or partially converted condition even at room temperature; at C. into fluorescence by excitation by means of it starts to after-glow and at -150 is still very cathode or Roentgen rays, and this is effected prolonged. by heating the phosphorescent material up to The 0 band after-glows at +20" to a very short 30 near the corresponding upper instantaneous conextent, and at +50 it ceases. It has its longest 30 dition existing for the cathode or Roentgen ray after-glow at -30 and its lower instantaneous excitation. By suitably choosing the temperacondition at 100. If the phosphorescence of ture above or below the upper instantaneous conthe 0 band is to be used, the material must be dition, the after-glow may be either entirely supheated to at least above 50 C., since the upper Dressed or decreased in a desired manner. instantaneous condition for the 0 band is +50 The heating of the phosphorescent material to and is room temperature for the 12 hand. If the the working temperature may be effected by placmaterial is heated still further, theafter-glow ing the screen material for example on a sheet period of the 0 band may be varied since it first of metal, for example of chromium-nickel alloy. passes into the upper instantaneous condition at m which is adapted to be electrically heated. The +190". In this case the upper limit temperature 40 temperature is preferably measured with the aid for the two other bands has already been exceedof a thermo-element attached to the sheet of ed, that is, they glow no longer. It is thus posmetal as by means of spot welding. It is also sible, by plotting the operative temperature possible to attain the temperature of the upper against the temperature of the highest upper ininstantaneous condition by heating the phosstantaneous condition, to suppress all of the un- 45 phorescent material by cathode ray bombarddesired bands present in the phosphorescent mament. Furthermore, the temperature of the upterial used. Furthermore, the operative temperaper instantaneous condition can be attained by ture can be so selected when several bands are preheating with the above-described arrangement present that the phosphorescence of a band is and then first attaining the operative temperatransformed into fluorescence.

ture by the impact of cathode rays. By using the For photographic purposes, and by suitably secenter of the phosphorescence for fluorescent illecting the temperature, the result can be prolumination purposes, an increase in instantaneous duced that only all photographically active bands luminosity may be obtained at the same time. of the material become free from after-glow,

10 tor the phosphorescent material and this screen may be heated electrically or by means of eddy currents in order to bring the phosphorescent material to the necessary working temperature. When an electrically heated screen is used the screen itself is preferably traversed by the current.

Admixing the phosphorescent material withconducting particles has also been found to be advantageous in using the method of the inven- 80 tion.

Having thus described my invention, I claim:

1. The method of operating a cathode ray tube having a luminescent screen which comprises polarizing said screen to a temperature equal to 25 the upper limit at which said screen remains phosphorescent, and bombarding said screen with cathode rays to produce a fluorescent response.

2. The method of operating a cathode ray tube having a luminescent screen which comprises polarizing said screen to a temperature equal to the upper limit at which said screen remains in part phosphorescent, and scanning a modulated cathode ray beam across said screen to produce a partially phosphorescent and partially fluorescent image.

3. The method of operating a cathode ray tube having a luminescent screen which comprises polarizing said screen to a temperature equal to the upper limit at which saidscreen remains phosphorescent by means of unmodulated cathode rays, and directing modulated cathode rays upon said screen to produce a fluorescent image.

4. The method of operating a cathode ray tube having a luminescent screen which comprises polarizing said screen to a temperature equal to the upper limit at which said screen remains phosphorescent by means of heating current passing through said screen, and scanning modulated cathode rays across said screen to produce a fluorescent image.

5. Method of operating a cathode ray tube having a luminescent screen 01' Zn-S-Mn material which comprises polarizing said screen to a temperature at which the response at certain colors becomes fluorescent, and bombarding said screen with cathode rays to produce an image.

HEINRICH HINDERER.