US3919584A - Cathode ray tube screen having both short and long persistence phosphors - Google Patents

Cathode ray tube screen having both short and long persistence phosphors Download PDF

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Publication number
US3919584A
US3919584A US453336A US45333674A US3919584A US 3919584 A US3919584 A US 3919584A US 453336 A US453336 A US 453336A US 45333674 A US45333674 A US 45333674A US 3919584 A US3919584 A US 3919584A
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phosphor
phosphors
kinds
persistent
trace
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Expired - Lifetime
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US453336A
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English (en)
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Jean-Pierre Galves
Pierre Merloz
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Thales SA
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Thomson CSF SA
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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
    • H01J29/18—Luminescent screens
    • H01J29/187—Luminescent screens screens with more than one luminescent material (as mixtures for the treatment of the screens)

Definitions

  • the present invention relates to cathode-ray tubes. It relates more particularly to tubes of that kind which are designed for the simultaneous display of two pieces of information in different colours and with different persistences.
  • cathode-ray tubes which comprise a screen the luminescent layer of which is made up of kinds of phosphors having different remanences and different spectra, that is to say kinds of phosphors whose light traces at the location of electron impact have different colours and different decay times, and, among these kinds of phosphors, in particular those whose decay time can be controlled by means of the acceleration voltage applied to the electrons.
  • Screens of this kind are known from the prior art, in particular from the UK. Patent Specification No. 1,303,749.
  • the luminescent layer of the screen of a mixture of two kinds of phosphors one having virtually no remanence at all and the other having a not insubstantial degree of remanence, several seconds for example, and protected by a barrier layer (that is to say a layer which does not luminesce under the effect of electron bombardment), it is possible, by a mere variation of the accelerating voltage applied to the electrons, to achieve degrees of persistence on the part of the light trace produced on the screen, which are variable from a value of virtually zero. If, moreover, the two kinds of phosphors have different spectra, the colours of the two traces will differ from one another.
  • the screen of the cathode-ray tube is supplied with two pieces of information, that coming from the radar, or in other words the real video information, and that coming from an outside source, which we shall refer to as the synthetic video information and which consists for example of various symbols, beacons, vectors, etc. These two kinds of information are recorded on the tube in the form of light traces produced by the impact upon the screen of electrons forming part of the beam issuing from the electron-gun of the cathode-ray tube.
  • the radar screen in its turn, operates in the PPl mode for example (plan position indicator mode) with the following characteristics:
  • the radar emits pulses of l microsecond duration, every millisecond.
  • this is displayed upon the screen of the tube in accordance with another scanning function, known random scanning, in respect of which it is sufficient to say that it takes place at a frequency of 50 Hz for example, that is to say at a rate of one complete scan of the screen every 20 milliseconds.
  • This frequency is sufficiently high to give the impression of a signal in which there is no flicker.
  • low voltage pulses at the preceding low voltage of 10 kv, for example, are applied to the beam during a small fraction of the aforesaid time of 20 miliseconds.
  • This voltage is nothing more than the potential on the anode of the tube or the conductive layer of the luminescent screen, the potential of the gun cathode being taken as the reference.
  • the screen is fully scanned in accordance with the random scanning function, the latter being repeated, as already mentioned, every fiftieth of a second and there being recorded upon the screen, in the form of a light trace, synthetic video information.
  • the light trace on a screen having two kinds of phosphors such as the screens of the prior art disclosed in the said Patent, has the colour of the non-remanent kind of phosphor, this being the only one excited at the voltage in question.
  • the precise duration of these pulses will not be specified since it has no real bearing upon the invention.
  • the pulses in accordance with what has been stated earlier, are spaced at around 20 millisecond intervals, the duration of each pulse, as already mentioned, being only a small fraction of the 20 millisecond interval.
  • the aforementioned high voltage, 18 kv for example is applied to the beam, during said time only the PH radar scan being operative; it is during this time that there are produced upon the screen real video data from the radar, these persisting upon the screen following electron impact, for several seconds for example, as specified earlier on.
  • the high voltage, the two kinds of phosphors compounds, the non-remanent one and the remanent one equipped with its barrier, are both excited, each in accordance with the colour of its own spectrum, green for instance for the non-remanent one and orange, for example, for the remanent one.
  • the true video information (PPI) and the synthetic video information can be effectively displayed, using a screen with two different kinds of phosphors as described in the prior art referred to hereinbefore, the said kinds of phosphors producing different colours, by a suitable choice of the spectra of the two kinds of phosphors; although the trace corresponding to the true video information will, at the instant of its appearance on the screen and for a short time thereafter, have a colour identical to that of the synthetic video information; thus, each orange trace corresponding to the PPI scan function, will be preceded by a kind of green flash. This is more generally referred to as a flash phenomenon. The presence of this kind of flash is extremely undesirable from the observers point of view not because of the confusion which it might produce between the traces corresponding to the two scanning functions, but because of the rapid alternation between the perceptions of the two different colours with which the observer is confronted.
  • the object of the invention relates to cathode-ray tubes in which this drawback is avoided.
  • the invention provides for the luminescent layer of the screens of cathode-ray tubes to consist of three kinds of phosphors having different spectra, two of which possess barriers in the sense intended in accordance with the earlier description, this under the conditions specified hereinafter, with the help of the attached figures in which:
  • FIGS. 1 and 2 illustrate two variant embodiments of the luminescent layer used in the screens in accordance with the invention.
  • FIGS. 3 and 4 are diagrams corresponding to two cases of operation of screens in accordance with the invention.
  • FIGS. 1 and 2 respectively illustrate the kind of phosphor which has virtually no remanence, and the remanent phosphor, whilst B signifies the barrier associated with the remanent phosphor and defined in the aforementioned patent, in respect of which barrier it is known, from said patent, that it plays the essential part in the creation of the variable remanence effect. This part will be recapitulated here:
  • V rises beyond V remanence whose duration varies in accordance with V is obtained by reason of the relative disposition of the straight lines r and nr which respectively,- as a function of V, represent the luminances L of the beam traces on the remanent phosphor 2 and on the non-remanent phosphor 1, this disposition being such that the fraction of the overall luminance of the trace appearing on the screen, at the point of impact of the beam, which is due to the remanent phosphor, varies in accordance with said voltage.
  • the luminescent layer comprises, as FIGS. 1 and 2 show, a third component 3 consisting of a kind of phosphor which likewise has virtually no remanence, associated with a barrier B as in the case of the phosphor 2
  • the straight line nr represents, in the diagrams of FIGS. 3 and 4, the luminance of said third phosphor equipped with its barrier.
  • the spectrum of the phosphor 3 should be chosen so that superimposition of the spectra of the kinds of phosphors 1 and 3 yields substantially the same colour as that produced in accordance with the spectrum of the phosphor 2.
  • the value of the high operating voltage V (FIG. 3) also has an effect, this voltage corresponding with the luminances L L L, of the traces produced by the three kinds of phosphors, as indicated in the diagram of FIG. 3.
  • the thicknesses of the barriers associated with each of the kinds of phosphors 2 and 3 have a part to play, these barriers, generally made of the same material, having been uniformly illustrated in the drawings by the letter B and by the cross-hatched areas. A wide variety of these materials are known in the art of luminescent screens.
  • V and V are the values of the voltage V beyond which excitation of the phosphor 3 and the phosphor 2, respectively, takes place.
  • V is the operating high voltage.
  • FIG. 2 pertains to another example of the invention in which the non-remanent phosphor 1 covers the nonremanent phosphor 3 and the barrier B associated with the latter.
  • the non-remanent phosphor 1 to some extent plays the part of a barrier vis-avis the phosphor.
  • the two non-remanent kinds of phosphors were used in proportions of between 20 and 30% by weight, in the mixture.
  • the green phosphor had no such barrier.
  • the screens were operated at 10 and I8 kilovolts and at beam currents which could be in excess of 500 microamps.
  • a cathode-ray tube with an electron gun a screen whose luminescent coating comprises two kinds of phosphors; one having no persistence, on which an electron beam, at the location of its impact, produces a light trace of given spectrum which disappears virtually as soon as said impact appears; and the other having a certain persistence, upon which said trace, having a spectrum differing from that of the preceding one, remains visible for a certain time after said impact, and being equipped with an inert barrier producing no light trace under the effect of such an impact; said screen producing a persistent trace if a voltage accelerating the electrons of the beam is higher than the value necessary for said excite to cross said barrier and exicte luminescence in the persistent phosphor, and a nonpersistent trace in respect of any voltage lower than said value, characterized in that said coating further comprises a third non-persistent kind of phosphor equipped with a barrier, the latter being such that said third phosphor is also excited when the voltage exceeds said value, its spectrum, superimposed upon that of the other non

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Luminescent Compositions (AREA)
US453336A 1973-03-27 1974-03-21 Cathode ray tube screen having both short and long persistence phosphors Expired - Lifetime US3919584A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7310944A FR2223830B1 (enrdf_load_stackoverflow) 1973-03-27 1973-03-27

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US3919584A true US3919584A (en) 1975-11-11

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US (1) US3919584A (enrdf_load_stackoverflow)
JP (1) JPS5842581B2 (enrdf_load_stackoverflow)
DE (1) DE2414842C3 (enrdf_load_stackoverflow)
FR (1) FR2223830B1 (enrdf_load_stackoverflow)
GB (1) GB1465187A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4424467A (en) 1979-07-04 1984-01-03 Matsushita Electronics Corporation Cathode-ray tube having a mixture of long and short persistence phosphors

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2924176C2 (de) * 1979-06-15 1982-11-18 Fried. Krupp Gmbh, 4300 Essen Verfahren zur Darstellung von Rückstrahlortungssignalen zur Ausübung des Verfahrens

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2446764A (en) * 1944-04-21 1948-08-10 Emi Ltd Cathode-ray tube
US3651362A (en) * 1968-07-23 1972-03-21 Iwatsu Electric Co Ltd Screens for cathode ray tubes with discrete phosphor layers
US3780371A (en) * 1969-07-28 1973-12-18 Us Navy Electronic counter-countermeasures system

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3552989A (en) * 1967-11-21 1971-01-05 Sylvania Electric Prod Cathode ray tube screen forming process
US3522463A (en) * 1968-07-15 1970-08-04 Rca Corp Electron tube multicolor dual persistence screen comprising phosphorcoated phosphor particles
FR2068015A5 (enrdf_load_stackoverflow) * 1969-11-25 1971-08-20 Thomson Csf

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2446764A (en) * 1944-04-21 1948-08-10 Emi Ltd Cathode-ray tube
US3651362A (en) * 1968-07-23 1972-03-21 Iwatsu Electric Co Ltd Screens for cathode ray tubes with discrete phosphor layers
US3780371A (en) * 1969-07-28 1973-12-18 Us Navy Electronic counter-countermeasures system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4424467A (en) 1979-07-04 1984-01-03 Matsushita Electronics Corporation Cathode-ray tube having a mixture of long and short persistence phosphors

Also Published As

Publication number Publication date
JPS5010066A (enrdf_load_stackoverflow) 1975-02-01
DE2414842A1 (de) 1974-10-10
GB1465187A (en) 1977-02-23
FR2223830A1 (enrdf_load_stackoverflow) 1974-10-25
FR2223830B1 (enrdf_load_stackoverflow) 1976-11-05
DE2414842B2 (de) 1981-04-30
DE2414842C3 (de) 1982-03-04
JPS5842581B2 (ja) 1983-09-20

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