US2861207A - Storage screen for direct-viewing storage tube - Google Patents

Storage screen for direct-viewing storage tube Download PDF

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Publication number
US2861207A
US2861207A US649721A US64972157A US2861207A US 2861207 A US2861207 A US 2861207A US 649721 A US649721 A US 649721A US 64972157 A US64972157 A US 64972157A US 2861207 A US2861207 A US 2861207A
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United States
Prior art keywords
storage
screen
viewing
direct
thickness
Prior art date
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Expired - Lifetime
Application number
US649721A
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English (en)
Inventor
George F Smith
Henry M Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Co
Original Assignee
Hughes Aircraft Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to BE565956D priority Critical patent/BE565956A/xx
Application filed by Hughes Aircraft Co filed Critical Hughes Aircraft Co
Priority to US649721A priority patent/US2861207A/en
Priority to GB31560/57A priority patent/GB845598A/en
Priority to FR1202314D priority patent/FR1202314A/fr
Priority to CH347902D priority patent/CH347902A/fr
Application granted granted Critical
Publication of US2861207A publication Critical patent/US2861207A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens
    • H01J29/395—Charge-storage screens charge-storage grids exhibiting triode effect
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/28—Luminescent screens with protective, conductive or reflective layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
    • H01J31/18—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen with image written by a ray or beam on a grid-like charge-accumulating screen, and with a ray or beam passing through and influenced by this screen before striking the luminescent screen, e.g. direct-view storage tube

Definitions

  • This invention relates to direct-viewing storage tubes of the mono-tone type and particularly to a storage screen for use in this type of tube that has a storage surface on which substantially higher writing speeds may be eifected.
  • an electron beam of elemental cross-sectional area is modulated with an image signal and scanned over a storage screen to produce a corresponding charge replica.
  • the resulting charge replica thus produced is acted upon by flood electrons to decrease all charges less than a critical potential to the potential of the associated flood gun cathode and to charge all potentials greater than the critical potential to the potential at which the collector grid is maintained. Accordingly, the potentials at which the flood gun cathode and the collector grid are maintained are referred to as stable potentials.
  • the resulting mono-tone charge replica thus produced is, in turn, employed to control the flow of other flood electrons to a viewing screen to produce a visual presentation of the charge replica.
  • the storage surface be provided by a dielectric material that is granular in form, e. g., a powder. If the surface were smooth such as the type prepared by vacuum evaporation, there would be no stable range at all. The reason for this phenomenon is that the flood or viewing beam of electrons produce what is known as bombardment induced conductivity which conductivity tends to discharge the sharp boundary between written and unwritten areas and cause the boundary therebetween to move one way or the other so that the image produced by the stored pattern turns all white or all black.
  • the writing of a charge pattern on the storage surface can be shown to be a simple process of charging a capacitor, i. e., the storage dielectric, by means of secondary electron emission produced by a high energy electron beam of elemental Patented Nov. 18, 1958 ice cross-sectional area. Since this writing takes place in a very short interval of time, the bombardment conductivity efiects are relatively unimportant during this phase of operation even though the higher energy beam might be expected to produce more such bombardment conductivity.
  • the writing speed depends upon the inherent capacitance of the storage dielectric, upon the voltage required to be written and upon the secondary electron emission ratio of the storage surface.
  • the dielectric material which provides the storage surface be reasonably thick to decrease the storage capacitance to the extent that the collector capacitance predominates and that the surface of the dielectric material provide good secondary electron emission.
  • the dielectric material for providing the storage surface must be a powder; it must be capable of being sprayed; and to effect a stable range, there are certain powder parameters to be optimized.
  • the powder particle size for example, should be relatively large and uniform to make the bombardment conductivity produced by the flood beam comparatively low thereby effecting a large stable range.
  • the secondary electron emission from the storage surface should be as high as possible for high speed writing.
  • Another object of the invention is to provide a storage screen having a granular storage surface with low bombardment induced conductivity, particularly from granule to granule, and high secondary electron emission.
  • Still another object of the present invention is to provide a process for enhancing the secondary electron emissive characteristics of a storage screen particularly adapted to store or retain mono-tone charge images.
  • a directviewing storage tube incorporating a storage screen with a storage surface having the above-mentioned properties is attained by first assembling a storage screen in the manner described in United States Patent No. 2,788,467, entitled Direct-Viewing Storage Tube, issued April 9, 1957, by Henry M. Smith.
  • talc has been found to be an optimum dielectric material for providing the storage surface because it sprays well and simultaneously has very high secondary electron emission.
  • Magnesium fluoride on the other hand, has a greater secondary electron emission ratio, but can hardly be sprayed at all and will not build up to the required thicknesses because of its physical properties. in powder form.
  • a final thin evaporated layer of dielectric material with a high secondary electron emission ratio such as, for example, magnesium fluoride is then applied over the entire area of the storage screen.
  • This final secondary electron emitting layer can even be applied over the contactingcollector grid of the completed storage screen as a last step before sealing into the tube envelope to maintain easy freedom from contamination.
  • the evaporation may be done over the contacting aluminum collector grid if this type of storage grid assembly is used as no harmful electrical effects result since the layer of magnesium fluoride is sufiiciently thin as to prevent any appreciable voltage from being built up across it and thus interfere with the function of the collector grid.
  • This final evaporated layer of, for example, magnesium fluoride should have the highest possible secondary electron emission and preferably should show low bombardment induced conductivity, particularly from grain to grain.
  • the layer In order to accomplish the intended purposes of the present invention, there are two limits to the thickness of the evaporated layer of magnesium fluor de employed.
  • the layer On the one hand, the layer must be thick enough to give its characteristic secondary electron emission to the storage surface and, on the other hand, it must not be so thick as to produce a continuous smooth film over the entire target and thus result in a complete loss of astable range of operation. It has been found that this range of thickness is from 0.2 to 2 or 3 wavelengths of mercury green light (5461 Angstroms) or sodium yellow light (5890 Angstroms). Thus, in actual practice this range of thickness is from 800 Angstroms to from 10,000 to 20,000 Angstroms.
  • Fig. 1 illustrates a cross-sectional schematic presentation of a direct-viewing storage tube incorporating the storage screen of the present invention
  • Fig. 2 shows a plan 'view of an enlarged portion of the storage screen of the storage tube of Fig. 1;
  • Fig. 3 shows section 3-3 of the plan view of the enlarged portion of the storage screen shown in Fig. 2;
  • Figs. 4 and 5 illustrate greatly enlarged cross-sectional views of the granular characteristic of the storage surface with correct and incorrect thicknesses, respectively, of the secondary electron emissive layer thereon;
  • Fig. 6 is a schematic drawing illustrating an example process for applying the secondary electron emissive coating of the present invention to the storage screen of the storage tube of Fig. 1.
  • FIG. 1 there is shown a direct-viewing mono-tone storage tube of the type which is more fully described in United States Patent No. 2,788,466, entitled Direct-Viewing Storage Tube, issued to Siegfried Hansen on April 9, 1957, and assigned to the assignee of the present application.
  • an embodiment of the storage screen of the invention is described that is particularly adapted for operation in the type of direct-viewing storage tube disclosed in the above Patent No. 2,788,466 issued to Siegfried Hansen.
  • This type of direct-viewing storage tube comprises an evacuated bulbous envelope l0 having a neck portion 11 and a flat end portion 12 at opposite extremities.
  • the neck portion 11 of envelope houses an electron gun 14 which is coupled to a signal source 16 for producing an electron beam that is modulated in accordance with the signal.
  • This modulated electron beam is focused by means of a focusing coil 18 and deflected by means of pairs of deflecting coils 20, 22.
  • a flood gun 30 is disposed about the path of the electron beam adjacent the neck portion 11 which, in conjunction with electrodes 32, 33 and 34 disposed concentrically about the inner surface of envelope 10 intermediate gun 14 and the end portion 12, is adapted to direct flood electrons uniformly over the entire area of the storage screen 26.
  • the modulated electron beam is scanned over the storage screen 26 by means of the deflecting coils 20, 22 to produce a charge replica of the signal on its storage surface. This charge replica is then acted upon by the flood electrons whereby it is converted into a mono-tone charge replica which controls the flow of other flood electrons from the flood gun 30 to the viewing screen 24 to produce a visual presentation of the charge replica.
  • FIGs. 2 and 3 there is shown plan and sectional views, respectively, of an enlarged portion of the storage screen 26 of the direct-viewing storage tube illustrated in Fig. l.
  • the storage screen 26 comprises a support mesh 40 on one side of which is disposed a uniform layer 42 composed of granules of dielectric material such as, for example, ball-milled talc and a thin aluminum collector grid 44 disposed in contact with the layer 42 of dielectric material whereby the areas of layer 42 within the interstices of grid 44 provide storage surface.
  • the thickness of layer 42 is of the order of from 1 to 2 mils.
  • the meshes of the aluminum collector grid 44 are disposed at an angle with those of support mesh 40 so as to minimize what is known as moire effect on the flood electrons flowing to the viewing screen 24.
  • the above-mentioned storage screen 26 may be manufactured in accordance with the teachings of the aforementioned Henry M. Smith Patent No. 2,788,467.
  • a final thin evaporated film 46 of dielectric material having high secondary electron emissive characteristics such as, for example, magnesium fluoride is applied over the entire area of the storage screen 26.
  • This evaporated film 46 may be applied before or after the aluminum collector grid 44 is disposed in contact with the storage surface. It is preferable, however, to apply the evaporated film 46 iust prior to inserting the storage screen 26 within the tube envelope 10 so as to minimize any possibility of contamination of the storage surface.
  • the evaporation of the high secondary electron emissive dielectric over the metallic parts of the storage screen does not cause any detrimental electrical effects since the film 46 is sufliciently thin as to prevent appreciable voltage build up across it.
  • the penetration power of an electron beam through aluminum is nearly the same as that through magnesium fluoride. It has been shown that a 3 kilovolt electron beam can penetrate a layer of aluminum 800 Angstroms thick. A thickness of 800 Angstroms corresponds to 0.2 wavelength of either mercury green or sodium yellow light.
  • Fig. 4 there is shown a highly magnified section of the conductive support mesh 40 and the layer 42 composed of granules of dielectric material on which is disposed film 46 of magnesium fluoride which film 46 is of the correct relative thickness in accordance with the present invention. It is to be noted that the film 46 of magnesium fluoride does not form a continuous layer over the individual granules of dielectric material constituting layer 42.
  • a film of magnesium fluoride over layer 42 of talc will become a continuous smooth film when thicknesses of the order of from 2 to 3 wavelengths of either mercury green or sodium yellow light are reached.
  • This range corresponds to the thicknesses of the order of from 10,000 to 20,000 Angstroms. It is to be noted that even a thickness of 20,000 Angstroms is only 0.00008 inch whereas the thickness of layer 42 is generally of the order of 0.002 inch. In accordance with the in this figure, it will be too thick to achieve the characteristics desired for the storage screen 26 of the present invention.
  • the maximum range of thickness may be determined by analogy to the characteristics of a film of aluminum evaporated on talc. That is, a film of aluminum having a thickness of from 2 to 3 wavelengths of mercury green or sodium yellow light begins to conduct at this thickness and hence may be considered as being on the verge of becoming continuous.
  • a similar process may be adapted in manufacturing the storage screen 26 in accordance with the present invention.
  • An example of such a process is illustrated in Fig. 6 wherein the storage screen 26 is disposed within an evacuated chamber 52 above a boat 54 filled with magnesium fluoride to be evaporated.
  • a lens 56 is mounted at an adjustable distance from the boat 54 containing the magnesium fluoride and is adapted to be illuminated by a sodium yellow lamp 58 in the manner shown in the drawing.
  • the lens 56 is at same distance from the boat 54 as is the storage screen 26, it will indicate a thickness of one-quarter wavelength at the first minimum of reflection. By moving lens 56 closer or farther from boat 54, one can get less or more on the storage screen 26 than at the A wavelength point of the lens.
  • a lens is preferable to a piece of plane glass for this purpose, since the images of the lamp 52 from the two sides thereof can be separated by the eye.
  • the index of refraction of magnesium fluoride is better suited for giving minimum reflection from a high index (optical) glass of the type used for lenses.
  • a current is caused to flow through the boat 54 to evaporate the magnesium fluoride until the reflected image of the lamp 58 from the side of the lens 56 nearest boat 54 goes to extinction for the first time.
  • the second minimum reflection point corresponds to A wave length thickness. For sodium yellow light these thicknesses would correspond to 1470 and 4400 Angstrom units, respectively, the desired range being from 800 to 10,000 Angstroms.
  • a target element comprising a conductive'member for providing a support surface, a comparatively thick layer composed of individual granules of dielectric material disposed over at least a portion of said support surface to provide storage surface, and a film of magnesium fluoride disposed over said storage surface.
  • the target element as defined in claim 1 wherein said film of high secondary electron emissive dielectric material is constituted of mag nesium fluoride and is from 800 to 20,000 Angstroms thick.
  • a target element comprising a conductive member for providing a support surface, a uniformly thick layer of individual granules of talc disposed over at least a portion of said support surface thereby to provide storage surface, and a film of magnesium fluoride disposed over said storage surface, the thickness of said film being from 800 to 20,000 Angstroms.
  • the target element as defined in claim 3 wherein said uniformly thick layer of individual granules of tale is from 0.001 to 0.002 inch thick.
  • a storage grid assembly comprising a first metallic screen, a comparatively thick layer composed of granules of dielectric material disposed over one side of said first metallic screen coextensive with the meshes thereof, a second metallic screen disposed in contact with said comparatively thick layer composed of granules of dielectric material whereby the areas of said layer within the interstices of said second screen provide storage surface and a thin evaporated film of high secondary electron emissive dielectric material disposed over said second screen and said storage surface.
  • a direct-viewing mono-tone storage tube including a storage grid assembly comprising an electroformed nickel screen of predetermined thickness; a layer composed of ball-milled talc disposed over one side of said nickel screen coextensive with the meshes thereof, the thickness of said layer being comparable to said predetermined thickness; an aluminum screen that is thin compared to said predetermined thicknessdispcsed in contact with said layer whereby the areas thereof within the interstices of said aluminum screen provide storage surface; and a thin evaporated film of magnesium fluoride disposed over said aluminum screen and said storage surface, the thickness of said film being from 800 to 20,000 Angstroms.

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  • Surface Treatment Of Glass (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US649721A 1957-04-01 1957-04-01 Storage screen for direct-viewing storage tube Expired - Lifetime US2861207A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
BE565956D BE565956A (fr) 1957-04-01
US649721A US2861207A (en) 1957-04-01 1957-04-01 Storage screen for direct-viewing storage tube
GB31560/57A GB845598A (en) 1957-04-01 1957-10-09 Storage screen for direct-viewing storage tube
FR1202314D FR1202314A (fr) 1957-04-01 1958-03-15 écran pour tube d'emmagasinage à vision directe
CH347902D CH347902A (fr) 1957-04-01 1958-03-20 Ecran pour tube d'emmagasinage à vision directe

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US649721A US2861207A (en) 1957-04-01 1957-04-01 Storage screen for direct-viewing storage tube

Publications (1)

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US2861207A true US2861207A (en) 1958-11-18

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US649721A Expired - Lifetime US2861207A (en) 1957-04-01 1957-04-01 Storage screen for direct-viewing storage tube

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US (1) US2861207A (fr)
BE (1) BE565956A (fr)
CH (1) CH347902A (fr)
FR (1) FR1202314A (fr)
GB (1) GB845598A (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2967255A (en) * 1958-08-05 1961-01-03 Rca Corp Image pickup device
US3051861A (en) * 1957-04-24 1962-08-28 Pye Ltd Colour television apparatus
US3179833A (en) * 1960-03-15 1965-04-20 English Electric Valve Co Ltd Signal storage tubes
DE1639448A1 (de) * 1967-02-23 1971-03-25 Tektronix Inc Bistabil speichernde Elektronenstrahl-Bildroehre
US4556818A (en) * 1981-12-29 1985-12-03 Matsushita Electric Industrial Co., Ltd. Insulating crystals for coating on a metal mesh of a storage tube

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2259507A (en) * 1936-12-19 1941-10-21 Rca Corp Electronic relay device
US2711289A (en) * 1951-02-01 1955-06-21 Rca Corp Electronic simulator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2259507A (en) * 1936-12-19 1941-10-21 Rca Corp Electronic relay device
US2711289A (en) * 1951-02-01 1955-06-21 Rca Corp Electronic simulator

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3051861A (en) * 1957-04-24 1962-08-28 Pye Ltd Colour television apparatus
US2967255A (en) * 1958-08-05 1961-01-03 Rca Corp Image pickup device
US3179833A (en) * 1960-03-15 1965-04-20 English Electric Valve Co Ltd Signal storage tubes
DE1198940B (de) * 1960-03-15 1965-08-19 English Electric Valve Co Ltd Signalspeicherroehre
DE1639448A1 (de) * 1967-02-23 1971-03-25 Tektronix Inc Bistabil speichernde Elektronenstrahl-Bildroehre
US4556818A (en) * 1981-12-29 1985-12-03 Matsushita Electric Industrial Co., Ltd. Insulating crystals for coating on a metal mesh of a storage tube

Also Published As

Publication number Publication date
BE565956A (fr)
FR1202314A (fr) 1960-01-08
GB845598A (en) 1960-08-24
CH347902A (fr) 1960-07-31

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