US 2863084 A
Description (OCR text may contain errors)
Dec. 2,` 1958 E.' G. F. ARNoTT ET AL 2,863,084
cATHonE-,RAY DEVICE Filed Jui@ 27, 1955 CHfHaDE R4 Y.
Wam/0k INVENTUM 50h/HBD 6. F.' HBA/0mm! HEM/YY F'. IVE'Y BY United States Patent CATHODE-RAY DEVICE Edward G. F. Aruott, Upper Montclair, and Henry F.
Ivey, Bloomiield, N. J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 27, 1955, Serial No. 518,321
Claims. (Cl. S15-1) This invention relates to cathode-ray devices and, more particularly, to a cathode-ray device which can operate with increased brightness.
In many technical devices employing cathodoluminescence, an increase in the attainable light output with out a corresponding increase for the power required for the bombarding cathode-ray beam is advantageous. Of course, the output of a cathode-ray excited phosphor can be increased by increasing either the current in the electron beam or the accelerating potential for the electrons, but this cannot always be done without undesirable secondary effects. For example, if the beam current is increased too much, the eifects of space charge become more pronounced and the beam diameter will increase so as to impair the resolution. It, on the other hand, the beam potential is increased, it becomes more diilicult to deflect the beam and the power dissipated in the deliecting system increases. In addition, there is also the fact that the maximum potential which may be used is limited by the secondary electron emitting property of the phosphor and many phosphors deteriorate under too intensive a bombardment.
It is the general object of the invention to avoid and overcome the foregoing and other diiculties of and objections to prior art practices bythe provision of a cathoderay device which will have an increased brightness without an increase in either beam current or accelerating potential.
The aforesaid object of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing a cathode-ray device wherein a cathode-ray responsive phosphor is placed within the influence of an electric field while being simultaneously excited to luminescence by cathode rays.
For a better understanding of the invention, reference should be had to the accompanying drawing, wherein:
Fig. l is a plan view, partly in section, of a cathode-ray tube incorporating a phosphor-influencing held-producing means in accordance with this invention;
Fig. 2 is a sectional fragmentary enlargement of the phosphor and electric held-producing window section of the tube as illustrated in Fig. l;
Fig. 3 is an alternative embodiment, corresponding to Fig. 2, wherein the phosphor material is imbedded throughout a dielectric material;
Fig. 4 is a further alternative embodiment, corresponding to Fig. 2, wherein the phosphor and dielectric material are included in separate layers;
Fig. 5 is a sectional fragmentary enlargement, corresponding to Fig. 2, showing still another alternative embodiment wherein the phosphor material is deposited as a thin continuous lm and is separated from one of the field-producing electrodes by means of the transparent window portion of the tube.
Although the principles of the invention are broadly applicable to any cathodoluminescent type of device, the invention is usually employed in conjunction with a cath- CII ode-ray tube such as is commonly used in television receivers and hence it has been so illustrated and will be so described.
With specific reference to the form of the invention illustrated in the drawing, the numeral 10 indicates generally a cathode-ray tube having an envelope which comprises an enlarged bulbous portion 12 and an elongated neck portion 14. The neck portion contains an electron gun 16 for generating a stream of electrons adapted to be projected longitudinally within the envelope. A conductive coating 18 (e. g., an aqueous suspension of graphite) is applied to the inner surface of the envelope and extends to within a short distance of the electron gun 16 to constitute an accelerating electrode by means of which an appropriate axial field may be created within the envelope. The end of the envelope which is remote from the electron gun 16 is in the form of a flattened transparent window 20, which window has provided on its inner surface a layer 22 of phosphor material which is adapted to be excited to visible luminescence by the impingement of electrons thereon and which is characterized by having an increased luminescent output when simultaneously placed within the influence of an alternating eld, as hereinafter explained. Electron deflecting means, illustrated diagrammatically as deflecting coils 24 and 26, may be provided adjacent an intermediate portion of the tube in order to cause the electron beam to scan sequentially the various elemental areas of the phosphor material carried by the window so as to develop a picture, such as a television picture, on the screen.
A thin transparent conductive layer 2.8, such as tin oxide, is preferably carried on the interior surface of the envelope window portion 20 and this thin conducting layer is adapted to be connected to a source of alternating current potential through electrical energy connector 30 which is hermetically sealed through the envelope. Over this thin conducting layer is placed the thin layer of phosphor'material 22 and over the phosphor is placed an electr1cally conductive layer of cathode-ray transparent material 34, such as a thin layer of aluminum, for example. This aluminum layer 34 constitutes `a second electrode and may be connected to the envelope bulbous port1on conductive coating 18, as illustrated, or may be connected to a source of alternating current potential through a separate electrical connection adaptor. second electrode 34 may take the form 1f desired. Preferably the electrodes 28 and 34 are substantially parallel to eliminate variations in field intensity.
As a specific example, the thin-transparent conductive layer 28 may be applied as illustrated in Patent No. 2,522,531 to Mochel or Patent No. 2,667,428 to Young. Other suitable thin-transparent coating layers may also be used. The phosphor material must be for the application and must be characterized by capabilof a wire mesh,
, ity of being energized to luminescence by cathode rays, can be enhanced by which cathode-ray luminescent output the simultaneous inuence of an alternating electric eld. In other words, when the phosphor alternating field and is simultaneously subjected to cathode ray bombardment, the output will be enhanced over that output which is realized when the phosphor is subjected to the same cathode ray bombardment alone, with the alternating eld removed. Suitable phosphors for this application are zinc sulfide-manganese activated,
zinc-'cadmium sulfide-manganese activated, zinc-cadmium sulfide-silver and manganese activated and zinc sulfidesilver and manganese activated. As illustrated in Figs. l through 4, these phosphors are in a finely-divided state, as is usual. 7 mole parts zinc sulfide, l mole part cadmium sulfide and activated by 4X 10H3 mole manganese. Such a phos-` phor may be prepared by ball-milling the aforementioned The especially selected is placed within an' As a specic example, the phosphor may be` 3 ingredients and firing in an oxygen-free atmosphere for aboutone hour at 11.00 C., for example. Following are further specific examples:
Example I Example III ZnS: 4` l03 mole Mn and 0.5)(10'-2 mole Ag per mole Mn Example IV per mole Mn The cathode ray transparent conducting layer which constitutes the second electrode may be of aluminum, as heretofore noted, or other suitable material. Such materials are presently utilized in the sohcalled aluminized television tubes.
The intensification of the cathode ray output appears to be essentially independent of the frequency of the applied electric field and it is preferable to use a frequency of 60 cycles per second as obtained from the A. C. mains, but this is by no means necessary and other frequencies may be used, if desired. The field strength required for the cathode ray intensification is not particularly critical and may be in the order of 104 volts per centimeter, or less. For example, if, in the embodiment as illustrated in Fig. 2, the electrodes 28 and 3d are spaced apart 0.06 mm., an applied voltage of 60 volts will produce a iield of 104 volts per centimeter.
In order to prevent electric iield breakdown across the phosphor material, it may be desirable to imbed the phosphor material in a noneluminescent material having a relatively high dielectric strength, such as a polyamide [--COCH2CONH(CH2')6NH-l or methylmethacrylate. Such an embodiment is illustrated in Fig. 3 wherein the phosphor material 22 is imbedded throughout a separate dielectric material 36, which phosphor-dielectric layer is placed between the electro-des 2S and 34 as in the embodiment of Fig. 2. The phosphor and dielectric may be mixed in the ratio of 1 to 2, for example.
In Fig. 4 is illustrated a still further embodiment wherein the phosphor and dielectric material are incorporated as separate layers 22 and 5S. It 4is preferable that the phosphor material be positioned interiorly with respect to the dielectric material in order that the cathode rays are not impeded, although if a cathode ray transparent dielectric material is utilized, the arrangement of the separate layers does not matter. The dielectric material ofthe embodiment as illustrated in Fig. 4 may be a polyamide, as heretofore noted, or a transparent mica, for example, to mention a few of the acceptable materials. The primary requirement of the dielectric material isthat it have a very low vapor pressure, preferably about 2x10*5 mm. mercury or less, for example, and relatively high dielectric strength.
In Fig. 5 is illustrated a still further alternative embodiment wherein the thin, transparent conductive layer of tin oxide 28a is placed exteriorly of the window portion of the envelope and the phosphor material is placed on the interior side of the envelope. The second electrode 34 is placed over the phosphor, as illustrated in the embodiment of Fig. 2. It is desirable that the electrode 28a be protected by a plastic material, for example, although it may be unprotected and may be connected to the ground side of the A. C. supply to eliminate shock hazard. In either of the embodiments of Fig. 2 or Fig. 5, all that is required is that the layer of phosphor material be carried interiorly `with respect to the window 20, preferably continguous therewith and at most only separated therefrom by the electrode 28, and be positioned between the electrodes in order to be within the iniiuence of the luminescent-enhancing alternating field. The phosphor layer 22a, as illustrated in Fig. 5, may be deposited as a thin continuous iilm, such as is illustrated in Patent No. 2,709,765 to Koller. Alternatively, the construction as illustrated in Fig. 5 may incorporate a finely divided phosphor powder such as is illustrated in Figs. 2 through 4. Also, a thin continuous film of phosphor may be used in place of the phosphor powder in the constructions illustrated in Figs. 2.and 4.
Utilizing constructional details as heretofore illustrated and described, a phosphor screen brightness of arbitrary brightness units has been achieved under only cathode ray bombardment. Upon energizing the electric (7Zn1Cd)S X104 mole Mn and 0.5X10 2 mole Ag 'zii field and continuing the cathode ray bombardment, a
light output of 126 arbitrary brightness units is achieved. Thus a cathode ray enhancement of 26% has been achieved by the simultaneous influence of an alternating field.
It will be recognized that the objects of the invention have been achieved by providing a cathode-ray device wherein the brightness is increased.
While in accordance with the patent statutes, one embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.
We claim: v
l. A cathode-ray device comprising, a screen comprising iinely divided phosphor material of one of the group consisting of zinc sulfide and zinc-cadmium suliide and activated by one of the group consisting of manganese and manganese-silver, means for applying an alternating electric field across said phosphor screen, and means `for simultaneously bombarding said phosphor screen with cathode rays.
2. A cathode ray tube comprising an envelope having an enlarged bulbous portion terminating in a flattened transparent window and a neck portion, an electron gun mounted within said neck portion for generating a stream of electrons adapted to be projected toward said window, a conductive coating applied to the inner surface of said bulbous portion and extending to within a short distance of said electron gun and adapted 'to act as an accelerating electrode for creating an axial field within said envelope, electron deflecting means positioned about said neck portion and between said electron gun and said bulbous portion and adapted to have applied thereto a potential for causing said electron stream to scan sequentially elemental areas of said transparent window, said transparent window carrying a first transparent conducting layer, a layer comprising finely-divided phosphor` material carried interiorly Vof said window and in contiguous relationship therewith, a cathode ray Vtransmissive second electrically conductive layer carried over said phosphor layer, said phosphor exhibiting the property of sustained luminescence under excitation by cathode rays and sustained enhanced luminescence under the simultaneous influence of an alternating electric field, and said first and second electrically conductive layers being adapted to have applied thereto an alternating potential.
3. A cathode-ray tube comprising an envelope having an enlarged bulbous portion terminating in a flattened transparent window and a neck portion, an electron gun mounted within said neck portion for generating a stream of electrons adapted to be projected toward said window, a conductive coating applied to the inner surface .of said bulbous portion and extending to within a short distance of said electron gun and adapted to act as an accelerating electrode for creating an axial field within said envelope, electron defiecting means positioned about said neck portion and between said electron gun and said bulbous por.- tion and adapted to have applied thereto a potential for causing said electron stream to scan sequentially elemental areas of said transparent window, said transpar-` ent window carrying a first transparent conducting layer, a layer comprising finely-divided phosphor material carried interiorly of said window and in contiguous relationship therewith, a cathode ray transmissive second electrically conductive layer carried over said phosphor layer, said phosphor being one of the group consisting of Zinc sulfide and zinc-cadmium sulde and activated by one of the group consisting of manganese and manganese-silver, and said rst and second electrically conductive layers being adapted to have applied thereto an alternating potential.
4. A cathode-ray device comprising, a screen including finely-divided luminescent means which exhibits the property of sustained luminescence under excitation by cathode rays and sustained enhanced luminescence under 15 2,185,439
the simultaneous influence of an alternating electric field, means for applying an alternating electric eld across said luminescent means, and means for simultaneously exciting said luminescent means with cathode rays.
5. A cathode-ray device comprising, a screen of dielectric and finely-divided luminescent means, said luminescent means exhibiting the property of sustained luminescence under excitation by cathode rays and sustained enhanced luminescence under the simultaneous inuence of an alternating electric field, means for applying an alternating electric field across said luminescent means, and means for simultaneously exciting said luminescent means with cathode rays.
References Cited in the tile of this patent UNITED STATES PATENTS Re. 22,734 Rosenthal Mar. 19, 1946 Hinderer Jan. 2, 1940 2,239,887 Ferrant Apr. 29, 1941 2,330,172 Rosenthal Sept. 21, 1943 2,650,310 White Aug. 25, 1953 2,704,783 Sziklai Mar. 22, 1955