US3911315A - Cathode ray tube whose image screen is both cathodochromic and fluorescent and the material for the screen - Google Patents

Cathode ray tube whose image screen is both cathodochromic and fluorescent and the material for the screen Download PDF

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Publication number
US3911315A
US3911315A US456961A US45696174A US3911315A US 3911315 A US3911315 A US 3911315A US 456961 A US456961 A US 456961A US 45696174 A US45696174 A US 45696174A US 3911315 A US3911315 A US 3911315A
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United States
Prior art keywords
cathodochromic
screen
fluorescent
cathode ray
ray tube
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US456961A
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English (en)
Inventor
Jr Lee T Todd
Eugene F Farrell
Arthur Linz
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Massachusetts Institute of Technology
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Massachusetts Institute of Technology
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Priority to US456961A priority Critical patent/US3911315A/en
Priority to JP50039715A priority patent/JPS50141970A/ja
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    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/26—Aluminium-containing silicates, i.e. silico-aluminates
    • C01B33/28—Base exchange silicates, e.g. zeolites
    • C01B33/2807—Zeolitic silicoaluminates with a tridimensional crystalline structure possessing molecular sieve properties; Isomorphous compounds wherein a part of the aluminium ore of the silicon present may be replaced by other elements such as gallium, germanium, phosphorus; Preparation of zeolitic molecular sieves from molecular sieves of another type or from preformed reacting mixtures
    • C01B33/2892—Zeolitic silicoaluminates with a tridimensional crystalline structure possessing molecular sieve properties; Isomorphous compounds wherein a part of the aluminium ore of the silicon present may be replaced by other elements such as gallium, germanium, phosphorus; Preparation of zeolitic molecular sieves from molecular sieves of another type or from preformed reacting mixtures containing an element or a compound occluded in the pores of the network, e.g. an oxide already present in the starting reaction mixture
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K9/00—Tenebrescent materials, i.e. materials for which the range of wavelengths for energy absorption is changed as a result of excitation by some form of energy
    • 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
    • H01J29/14—Screens on or from which an image or pattern is formed, picked up, converted or stored acting by discoloration, e.g. halide screen

Definitions

  • a cathode ray tube (CRT) having an image screen [52] us Cl 313/391. 252/301 4 313/397. composed of a material that is both cathodochromic 313/398. 515/13 and fluorescent and in which the cathodochromic col 51 1111. C1 1101.] 29/20- 11011 31/12 oration lifetime is at least a
  • the material [58] Field of Search 313 391, 397, 398, 101, PlOYed is Nafi A16(GeuSi1-1/)6 024201) Nax wherein 313/311.
  • 315/85 10 13 346/74 z is the fraction of NaX vacancies
  • X is chosen from 5 5 3675523014 the group consisting essentially of chlorine, bromine, OH and iodine and mixtures thereof, and varies from [56] References Cited 0003 to UNITED STATES PATENTS 23 Claims, 4 Drawing Figures 2,752,521 6/1956 lvey .1 313/465 x 1 X x t K I i x 2 M j i 2 I r I F 4fip US. Patent 0m. 7,1975 Sheet 1 of 2 3,911,315
  • the present invention relates to a cathode ray tube whose image screen is both cathodochromic and fluorescent, to the material of which the image screen is composed, and to the means of excitation of said fluorescence.
  • Photochromic materials have the property that they change color reversibly upon illumination by light while cathodochromic materials change color upon excitation by an electron beam. This is not a clear distinction, however, since most photochromic materials are also cathodochromic. A unique distinction can be made if one considers the bleaching or erasing mode. In photochromic materials the colored state can be completely bleached by light while in the cathodochromic materials light causes only partial bleaching. The remaining coloration, thermal mode coloration, must be erased by heating. The lifetime of this coloration at room temperature is, in some cases, greater than several months even under bright ambient light. The coloration can be erased rapidly by heating the material to about 200C for sodalite. The systems described herein relate to sodalite operating in the thermal erase mode.
  • Cathode ray tube (CRT) image screens for cathodochromic materials exhibit high resolution, long lifetime of coloration, gray scale and high contrast in bright ambient light. However, since their contrast capability depends on reflected or transmitted light, they cannot be viewed satisfactorily under low ambient conditions.
  • the fluorescence which is herein disclosed allows the use of such image screens in both high and low ambient light levels. In bright ambient the screen has its (Medved); 4
  • a cathodochromic display device operated in the fluorescent mode is more visually acceptable than present phosphor displays since the viewer sees a dark display on a light background.
  • the brightness of the background can be easily adjusted by varying the intensity of the ultraviolet illumination. In this circumstance the viewer must be shielded from the ultraviolet light by a special absorbing faceplate. If the faceplate is chosen such that it passes only the green fluorescent light, contrast ratios in excess of 40:1 can easily be achieved in the fluorescent mode.
  • the fluorescent-mode display can be employed in airplane cockpits where low light levels are often necessary. In airplane cockpits where low light levels are often necessary, this display offers high resolution, long storage time and high contrast. Even in brightly illuminated areas, the display remains intact and still has high contrast. The same system exists for displays in patrol ears, helicopters and ships. For any night vision use in which phosphor display devices have been employed these fluorescentmode cathodochromic CRTs offer the advantages of high resolution and long storage time and, possibly, even lower cost.
  • cathode ray tube having an image screen composed of cathodochromic sodalite that displays high contrast in high ambient light and is, as well, fluorescent under ultraviolet radiation, thus offering contrast in low ambient light conditions.
  • a further object is to provide a high resolution cathode ray tube comprising cathodochromic sodalite material.
  • Another object is to provide a material for such image screen, a material that gives high contrast under the conditions noted and one that has a long lifetime of coloration of the order of months or years.
  • Still another object is to provide an image screen material that has a contrast ratio or the order of 10:1 in high ambient light and approximately double that ratio in ultraviolet radiations.
  • a cathode ray tube having an image screen composed of a material that is both cathodochromic and fluorescent and in which the screen material has a coloration lifetime of weeks, months or years.
  • the cathode ray tube comprises any envelope having a faceplate upon which the image screen is formed and means for providing an electron beam to write upon the image screen.
  • the screen material is sodalite with a dopant that alters the electronic structure of the material and thus allows fluorescence to occur under ultraviolet excitation, for example.
  • the cathodochromic and fluorescent image screen material discussed herein is Na Al (Ge,,Si .2( l-z)NaX, wherein z in the fraction of NaX vacancies, X is chosen from the group consisting of chlorine, bromine, OH and iodine and mixtures thereof, and y varies from about 0.003 to 0.30.
  • FIG. 1 is a side view, partially cutaway, of a cathode ray tube (CRT) embodying the present inventive concepts and shows a tube having a transparent conductive coating on the faceplate of the CRT and between said faceplate and the image screen thereof;
  • CRT cathode ray tube
  • FIG. 2 is a partial view, in section, showing a modification of the cathode ray tube of FIG. 1, the image screen in the latter figure being disposed between the conductive coating and the faceplate;
  • FIG. 3A is fluorescence spectrum of Ge doped bromine sodalite at 77K.
  • FIG. 3B is the excitation spectrum of the Ge doped bromine sodalite at 77K.
  • a cathode ray tube embodying the present concepts comprising an envelope 1 having a faceplate 2.
  • a cathodochromic image screen 3 disposed upon a transparent conductive coating 4 of SnO for example, that serves as the anode of the electron beam producing means later discussed.
  • SnO transparent conductive coating
  • the image screen here is shown as part of a composite structure adhered to the inside surface of the faceplate 2 and this particular type arrangement has advantages, particularly in terms of cost of manufacture and structural stability, but the present concepts have use in cathode ray tubes wherein the image screen is physically displaced from the faceplate of the tube and deposited on another substrate.
  • the image screen is made of the cathodochromic and fluorescent material Na Al (Ge,,Si 0 .2( l-z)NaX, wherein X is chosen from the group consisting essentially of chlorine, bromine, OH and iodine and mixtures thereof, y varies from about 0.003 to 0.30 and z is the fraction of NaX vacancies created during hydrogen annealing. A value of y of the order of 0.01 (i.e., l percent) has been found to give optimum fluorescent characteristics. Annealing of the material in hydrogen is necessary to create negative ion vacanies which are essential for color center formation, in this case, F centers. This process is also required for the occurrence of fluorescence.
  • the fluorescent and excitation spectrum of an annealed germanium doped bromine sodalite power are shown in FIGS. 3A and 3B, respectively.
  • the emission band peaks at 5250A when excited by 2750A or 3400A radiation.
  • the material colors and acquires an F absorption band at approximately 5500A. Since the absorption band occurs very close to the emission band, much of the fluorescence created within the colored portions of the image screen is re-absorbed. Additional atomic quenching also occurs leading to a very high contrast between the colored and uncolored areas.
  • the coloration lifetime of this material is of the order of months and even years.
  • Writing on the image screen is effected by an electron beam provided by an electron gun 5 and the anode in combination.
  • the anode configuration depends on the means of ultraviolet excitation of the fluorescence and is discussed in detail below. It is not believed that any further discussion of electron beam producting, focusing and deflection need be pursued since these are matters well within the scope of workers in the art.
  • Erasing the image is effected by raising the temperature of the cathodochromic sodalite screen material. This can be accomplished by resistive heating with the image screen deposited on a thin substrate within the envelope, (see US. Pat. No.
  • the fluorescent and cathodochromic CRT can be operated in either of two modes rear or front illumination.
  • One form of CRT fabrication used for rear illumination is that shown in FIG. 1.
  • the anode comprises a transparent conductive coating 4 on the inside surface of the faceplate 2 between the faceplate and the image screen 3 and extending at 6 along the side walls labeled 7 of the envelope toward the electron gun 5; an aluminum or Aquadag coating 8 which overlaps the transparent conductive layer 4 extends further along the sidewalls 7; and an Aquadag coating 9 which overlaps the coating 8 and extends along the tube neck 10 to the electron gun 5.
  • the image In high ambient light, the image is read in a transmission mode using a lamp 1] which directs visible radiation (white light) through the screen 3 toward the viewer. The uncolored portions of the screen transmit the viewing light while the colored areas absorb it thus creating a high contrast image.
  • the image In low ambient conditions, where white light is not allowed, the image is read in the fluorescent mode with the fluorescence being excited by one or more ultraviolet lamps 12 which direct radiation upon the surface designated 13 of the screen facing the electron gun.
  • the excitation source 14 may be located outside of the envelope, as shown in FIG. 1 with the exciting radiation entering through a rear port 15 and striking the screen surface designated 13.
  • the port cover 16 must be a material, such as quartz, which transmits the exciting light.
  • the faceplate 2, or an auxilliary filter must absorb the ultraviolet radiation to protect the viewer.
  • the screen construction is as shown in FIG. 2.
  • the image screen 3 is deposited directly on the faceplate 2 and the anode consists of an opaque conductive coating 17, usually aluminum, on the back surface 18 of the screen and extending along the sidewalls 7 of the envelope to the tube neck where the anode circuit is completed with an Aquadag coating 9, as before.
  • the image is written by the electron beam and read, in high ambient conditions, with light incident on the front surface 19 of the image screen.
  • the uncolored areas of the screen reflect the incident light while the colored areas partially absorb the reading light and reflect the remainder thus causing a colored image.
  • the screen fluorescence is excited by one or more ultraviolet lights 20 outside the envelope which direct radiation upon the front surface 19 of the image screen.
  • the aluminum layer 17 serves several purposes in this configuration: 1) it is part of the anode; (2) in high ambient conditions, it reflects the incident viewing light back through the image screen thus increasing its whiteness and hence its contrast capability; (3) in the fluorescent mode, it reflects the incident ultraviolet radiation back through the screen and thus increases the ultraviolet exposure; and (4) in this latter mode, it also reflects the green fluorescent light which is directed away from the viewer back toward the viewer thus increasing the fluorescent light output.
  • the product is a slurry of crystalline powder in a concentrated NaOH solution.
  • the NaOH is removed by washing the powder repeatedly with distilled water.
  • the powder is dried for one hour in an oven at about 130C and then crushed to a fine particle size.
  • the X-ray powder pattern consists of diffraction peaks representing single phase germanium doped sodalite. (Electron microprobe measurements made in work done revealed that the powder contained only one atomic percent germanium substituted for silicon rather than the intended three atomic percent due to the incomplete substitution of the larger germanium ions for the smaller silicon ions.)
  • the powder is annealed in hydrogen to create lattice vacancies which are necessary for the formation of color centers, in this case F centers.
  • the hydrogen annealing treatment is also essential for the occurrence of fluorescence.
  • the above powder has an absorption band at 5400A and an emission band at 5250A.
  • Germanium doped sodalite bromine is also produced by a combination of sintering and hydrothermal methods. Chemicals are combined according to the equa tion:
  • bromine sodalite containing 10 atomic percent germanium substituted for silicon 4.12 grams NaBr, 6.12 grams A1 0 6.49 grams SiO 1.26 grams GeO and 4.80 grams NaOH are thoroughly mixed and then sintered in a furnace at 750C for 2 hours. The resulting product, in the form of a hard calcined mass, is next ball milled for several hours to reduce it to a fine-grain powder.
  • the sintered powder is next reacted in a hydrothermal vessel at low temperature. 3.14 grams of sintered powder are placed in a teflon'lined acid digestion vessel with an internal capacity of 30 ml. An 18 ml solution of 7.20 grams NaOH and H 0 are added to the charge in the vessel and the vessel sealed. The base of the vessel is maintained at 130C for about hours and then cooled to room temperature. The resultant is a slurry of crystalline powder in a concentrated NaOl-l solution. The product is then processed as in Example 1. After annealing for 15 minutes at about 650C, the material exhibits an absorption band at 5500A and an emission band at 5250A.
  • a cathode ray tube that comprises an envelope having a faceplate, a cathodochromic image screen in said envelope, said cathodochromic image screen comprising a material that has a coloration or F-center as well as a luminescent or fluorescent center so that said material is cathodochromic and is also fluorescent, the coloration or F-center absorption band of said material occurring very close to the emission band of the luminescent of fluorescent center; and means for producing an electron beam to write on the image screen.
  • a cathode ray tube as claimed in claim 1 in which the electron beam producing means includes an electron gun and an anode, in which the anode is a transparent conductive coating on the faceplate, and which includes aluminum on the inside surface of the envelope side walls and connected to the transparent conductive coating such that the anode circuit is complete.
  • a cathode ray tube as claimed in claim 1 that further includes ultraviolet light means positioned to direct radiation upon said screen.
  • a cathode ray tube as claimed in claim 7 in which the means to produce the electron beam is an electron gun and an anode, in which the anode is a thin aluminum layer on the major surface of the screen and between the screen and the electron gun, and in which the ultraviolet radiation is directed upon the other major surface of the screen.
  • a cathode ray tube as claimed in claim 7 in which the means to produce the electron beam includes an electron gun and an anode, and in which the anode is a transparent conductive coating on the inside surface of the faceplate between the envelope and the screen and extending along the side walls of the envelope toward the electron gun.
  • a cathode ray tube as claimed in claim 7 in which the means to produce the electron beam is an electron gun and an anode, in which the anode is a transparent conductive coating on the inside surface of the faceplate between the envelope and the screen and extends along the side walls of the envelope toward the electron gun and in which the ultraviolet light means directs ultraviolet radiation upon the surface of the screen facing the electron gun.
  • a cathode ray tube as claimed in claim 10 in which the ultraviolet light means is outside the envelope and in which the envelope transmits ultraviolet radiation to the screen.
  • a fluorescent and cathodochromic material that comprises Na Al -(Ge Si O 2(l-z)NaX, wherein z is the fraction of NaX vacancies, X is chosen from the group consisting essentially of chlorine, bromine, OH and iodine and mixtures thereof and y varies from about 0.003 to 0.30.
  • a fluorescent and cathodochromic material that consists essentially of l la Al (Ge,,Si O, 2(1- z)NaX, wherein X is bromine y varies from 0.003 to 0.30 and z is greater than zero but less than 1.
  • a cathode ray tube that comprises an envelope having a faceplate, image screen means that has a coloration or F-center as well as a luminescent of fluorescent center so that the image screen means is both cathodochromic and fluorescent, the coloration or F- center absorption band of the image screen means occurring very close to the emission band of the luminescent or fluorescent center, the cathodochromic coloration lifetime being at least the order of hours, means producing an electron beam to write on the image screen, and means effecting luminescence of the image screen.
  • Apparatus as claimed in claim 20 in which the image screen comprises a cathodochromic and fluorescent sodalite material that contains a dopant that alters the electronic structure of the material such that fluorescence occurs.
  • Apparatus as claimed in claim 20 that further includes means illuminating the image screen in the visible range of the electromagnetic spectrum.

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987002494A1 (en) * 1985-10-18 1987-04-23 Hilliard-Lyons Patent Management, Inc. Programmable interlace with skip and contrast enhancement in long persistence display systems
US6056421A (en) * 1995-08-25 2000-05-02 Michael Brian Johnson Architectural lighting devices with photosensitive lens
US7250723B1 (en) 2004-12-21 2007-07-31 The United States Of America As Represented By The Administrator Of Nasa Cathode luminescence light source for broadband applications in the visible spectrum

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2752521A (en) * 1953-04-09 1956-06-26 Henry F Ivey Screen material
US3253497A (en) * 1961-10-30 1966-05-31 Polacoat Inc Information storage device
US3339099A (en) * 1966-05-31 1967-08-29 Tektronix Inc Combined direct viewing storage target and fluorescent screen display structure
US3452332A (en) * 1965-01-05 1969-06-24 Ibm Memory device and method of information handling utilizing charge transfer between rare earth ions
US3631295A (en) * 1968-06-21 1971-12-28 Atomic Energy Authority Uk Method and apparatus for storing information
US3650975A (en) * 1969-10-31 1972-03-21 Sylvania Electric Prod Rare earth oxide phosphors containing alkali metal silicates and germanates

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2752521A (en) * 1953-04-09 1956-06-26 Henry F Ivey Screen material
US3253497A (en) * 1961-10-30 1966-05-31 Polacoat Inc Information storage device
US3452332A (en) * 1965-01-05 1969-06-24 Ibm Memory device and method of information handling utilizing charge transfer between rare earth ions
US3339099A (en) * 1966-05-31 1967-08-29 Tektronix Inc Combined direct viewing storage target and fluorescent screen display structure
US3631295A (en) * 1968-06-21 1971-12-28 Atomic Energy Authority Uk Method and apparatus for storing information
US3650975A (en) * 1969-10-31 1972-03-21 Sylvania Electric Prod Rare earth oxide phosphors containing alkali metal silicates and germanates

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1987002494A1 (en) * 1985-10-18 1987-04-23 Hilliard-Lyons Patent Management, Inc. Programmable interlace with skip and contrast enhancement in long persistence display systems
US6056421A (en) * 1995-08-25 2000-05-02 Michael Brian Johnson Architectural lighting devices with photosensitive lens
US7250723B1 (en) 2004-12-21 2007-07-31 The United States Of America As Represented By The Administrator Of Nasa Cathode luminescence light source for broadband applications in the visible spectrum

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