US2112854A - Luminescent device - Google Patents

Description

April 5, 1938 A. N.Luc|AN LUMINESCENT DEVICE 2 Sheets-sheet 1 Filed Dec. 3l, 1954 Aprils, 193s. A. N. LUCIAN y 2,112,854

l LUMINESCENT DEVICE Fired Dec. '31, 1954 2 sheets-sheet 2 HE/mggg INVENTOR .Arum N. Lamar;A

AT ToRN EY.; y

Patented Apr. l5,1938

UNITEDv STATES PATENT Aorlucr;

, LUMINESCENT DEVICE Application December 31, 1934, Serial No. 759,836

13 Claims.

This invention involves the use of cathde ray I or electron devices having luminescent screens for the purpose of providing commercially useful lighting devices designed and constructed in accordance with the principles of luminescence phenomena, which term as employed in this case, includes phosphorescence, fluorescence, and allied phenomena which may be caused by the excitation of certain natural or synthetic compounds by heat, light, cathode rays, X-rays, ra-

dium rays, and the like.

An object o f this invention is to provide commercially new and useful combinations based particularly upon cathode ray or electron excitation of luminescent compounds arranged to form display or advertising devices and light sources.

A specific object of this invention is to provide constructions of' cathode, anode and a plurality of extended surfaces in such geometrical relation to each other, so that the Surfaces to be illuminated will be uniformly irradiated by the action of a` uniforml;r disposed beam of electrons or cathode rays.

Another object of this invention is to provide in combination with devices of this type, and as parts thereof, alternating current rectifiers which directly supply the rectied current for the operation of the device.

Another object is to provide adequate and reliable pressure regulating means in combination with devices of this type, and as parts thereof in order to give to such devices long and uniform life of operation.

Other objects of this invention are- To provide a luminous device for advertising purposes in which the areas to be impressed upon or brought to the observers attention are completely luminous in themselves, and these areas supply all the lightl used in illuminating the sign or other advertising device. l

To provide a source of illumination more emcient as regards the ratio of current consumption to quantity of light produced than any other illuminating device of which I amaware.

To provide a source of illumination which emits light of practically any desired color being generated on a luminous areaof such extent that These and many other objects, as will4 appear from the following detailed disclosure, are successfully secured'by meansof this invention.

In the drawings, l

Fig. 1 illustrates a cathode ray excited luminescent device of a form now generally known and illustrating the basic features of devices ofA this nature;

Fig. 2 is one form of the device in accordance with this invention employing a cold cathode;

llig. 3 is a detailed cross-sectional view of an element of the invention;

Fig. 4 is a view illustrating the application of the principles of this invention to the hot cathode' type of tube; Y

Flg.5 is a top plan view of l a commercially practical form of advertising or display device in accordance with this invention and embodying as a part thereof a halfway rectifier;

Fig. 6 is a front elevational-view of this device;

. Fig. 7 is a top plan view of a modified form of device in which a full-way rectier is incorporated;

Fig. 8 is a front elevational View of a still further modification in accordance with this invention; A

` Fig. 9 is a central vertical cross-sectional view 4of the device of Fig. 8;

Fig. 10 is a plan view of a modified form of device in accordance with this invention particularly adapted as a light source; y

Fig. 11 is a still further modified form employing a. dome-shaped vessel.

Cathode' vray devices employing luminescent materials .have-been known scientifically and in the laboratory for at least half a century. Very little practical and commercial use has been made of this device. The well known X-ray screen which has been highly developed, is in no sense in the samecategory and is not governed by the same considerations and physical and chemical laws as the cathode ray device. lIn the AX-ray device a luminescent screen is frequently employed wherein this screen is external to the tube in which the X-rays are generated and which, of course,-is excited by X-rays. Furthermore, many `substances which respond to X-rays will not re spond to cathode rays and vice versa.

The only .commercially useful forms of cathode ray tubes 'are the cathode ray oscillograph and a modification thereof as employed in television. The cathode ray `oscillograph may or may not employ a luminescent screen. For example, through thel use of a Lenard window the cathode ray beam may be projected upon a photographic and purpose of this invention is to accomplish plate or upon a screen for use, for example, in

visually displaying the voltage and current characteristics of electric currents. As employed in television apparatus the cathode ray tube employs a luminescent screen over which a concentrated beam oi' electrons is caused tov travel by and in accordance with electric currents or impulses representative of a scene whereby those currents are transformed into visible displays of the scene. v Y

The distinctive object of the present invention is to disclose a new type of vacuum tube, for the purpose of uniformly exciting, without icker and fluctuation, large areas of luminescent materials which have been arranged in 4accordance with predetermined color and shape combinations to provide advertising and display devices or to provide these objects;

In furtherance of these objects the present invention provides a device having a life comparable with filament types of light sources and gas discharge types of light sources.

A luminescent light source is one which emits light of practically any desired color by the conversion of cathode ray or other radiations of shorter wave length than red iight into visible light while generating very little heat; that heat which is generated not being usedas a source of light.

While the cathode ray luminescent device is well known scientifically, it may be of hei'p" to briey described in connection with Fig. 1, the fundamental principles involved. The device employs usually a glass envelope I having a hot or cold cathode 2, and an anode 3 mounted therein. Such devices usually contain a. residual of rareed gas, in the use of cold cathodes, such as air or other desirable gas in which the discharge takes place between the electrodes. The application of potentials across the electrodes sets the gas molecules in motion, causing collisions'which break the molecules up into positive and negative ions. The passage of current through the device is accomplished by fthe movement of the positive ions toward the cathode and of the negative ions toward the anode. ions upon the cathode surface causes the ejection of electrons or cathode particles, which in turn travel at high velocities in straight lines at right angles to the surface of the cathode. If any one ofl a large number of known chemical comcompound will become luminescent.

'mostly by scientists have always been characterized by the fact that the area of th layer 5 has been extremely limited, thus generally keeping the device out of the field of commercial utility. Furthermore, uniformity of illumination of the The impact of the positive.

surface has ybeen'entirely lacking, which, added to the fact that such devices have had an extremely short life, 'has prevented them entering useful fields aside from the cathode ray oscillograph, and even in this case the life of the device is unduly short. In accordance with this invention, in adapting the device for the intended purposes, certain definite combinations and control factors have been discovered which must be employed in the device.

The nature of ,the cathode and anode materials and the areas of the cooperating electrodes are important factors in developing a commercially useful lightingor display source. 'I'he electro-l positive elements are the most suitable and eficientv materials of which to make the electrodes and of which sodium, potassium, barium, strontium, calcium, magnesium and aluminum are examples. 'I'hese elements may be used individually or in any suitable combination. A preferred-combination is an alloy of aluminum, magnesium and calcium with traces of barium and strontium.

An important feature of the present invention lresides in the form, shape, size and position of the cathode to secure uniformity of irradiation of the luminescent surface. jected area of the cathode should coincide with the area of said surface. Y

Furthermore, it has been discovered that the electrode area (referring to anode) in relation to the current density is important. In accordance with this invention it has been found that a current density of l milliampere for an-electrode area of 0.2 to 0.5 square centimeter is satisfactory. The minimum value holds particularly where the electrodes are not artificially cooled and where one electrode must act as an element of the rectifier. Larger current densities may be employed in cases where the device is-artiiiciall-y cooled, depending somewhat upc-n the design of the cooling system.

Other important factors in the correct Yoperation of a device of this type involve the nature of the rareed atmosphere within the vessel as well as the pressure thereof. In addition to residual air, and preferably the so-called noble gases, such as argon, neon'and helium, may be employed, either singly or in combination.I Likewise', hydrogen, nitrogen and carbon dioxide, either alone or in combination,` may. be employed sometimes.

'The pressure range is, of course, variable, de-

pending upon the nature of the gas, the dimen.

sions of the device, and the potentials at which it is desired to operate the device. Asv a working range, the pressure within the vessel would be from approximately 0.1 millimeter of mercury down to as low a pressure as is permissible with a particular operating potential. For example, a pressure of 0.001 millimeter of mercury representsl a practical minimum value for the range of potentials to be preferably employed. With cold cathode tubes potentials ranging from 1000 volts upwards to 25,000 -volts are suitable. The above pressure range is not used vin any cathode ray orelectron device now in commercial use.

'I'hese devices may be operatedvfrom energy sources having a rather wide frequency range of the order of from a direct Vcurrent of zeroy vices of this type must be energized by high potential directcurrent, special provision for the supply of such current must be made as the available commercial current sources do not have the.

sur

' cathode ray device referred to above as used by the scientist. This problem is solved by the invention by combining in a single device a cathode ray irradiated luminescent surface and a half or full wave rectifier by a novel arrangement and circuit interconnection of electrodes. Where high frequency currents are used a high .intensity of luminescence may be secured with a high frequency source connected to electrodes external to the vessel. Likewise, eilicient excitation may be obtained through a combinationof electrodes external and internal to the vessel. It is understood that in case of high frequency excitation proper safeguard must be used to eliminate loss of power by leakage.'

There is, of course, a very wide range of luminescent materials or compounds that may 'be employed. By way of example only, kunzites,

calcites, sulphides 'of zinc, cadmium, barium, strontium and calcium, willemite, cadmium tungstate, calcium tungstate, uranyl salts, metallic salicylates, calcium larsenite, and the like, arey available.

A feature of the invention insuring constancy and uniformity of operation is illustrated in Fig. 2. wherein at E is shown the vessel having a rare-h fied atmosphere within which is mounted ,the

cold cathode 'l and an anode 8. Intermediate to uctuate with the age of the device and par- Y ticularly at the beginning of its useful, life. The

' tendency is for the tube to. become "hard", that is, a .decrease in the pressure within the tube which may be restored by means of a suitable pressure regulating device indicated generally by the reference numeral Il. Such a devicemay be, although not necessarily, of the form disclosed in Patent No. 1,603,707, to Lucian, dated October 1'9, 1926. For the purposes of the present disclosure the regulating device consists of a porous thimble l2 within an extension i 5 of the vesseltcontaining a suitable chemical compound i3 a'nd a spark generating apparatus, 'designated generally by the numeral i4 and energized from the cathode circuit through a resistance 36 and a switch 3,5. When the regulator is in operation a small amount of suitable, and preferablyfinert gas is released into thea.l tube to return it to a soft condition, that is, raise the pressure therein.

An important feature of the invention by means of which uniformityv 'and constancy pf excitation of the luminescent material and hence ,a corresponding uniformity and constancy of luminescence is obtained resides in the use of the conducting surfaces i8* and 1 6 on the exterior andl interior walls of the -vessels over an area at least co-extensivewithV the internal extension of the cathode '1. In addition to the above advantages,

the. use' of thesey conducting surfaces which are either grounded or may be electrically connected to the cathode circuitgas illustrated, serve to materially increase the brilliancy andy uniformity of.

facesmay be either internal or external to the' vessel or both, and if desired, may be employed -at both ends of the' vessel, as will be illustrated later. These coatings may, vfor example, vtake the form of actual metallic deposits upon the vessel walls as has been illustrated diagrammatically in the drawings.rr It might be noted at this point that the current density relationship to the electrode areas is in no way affected and does not include the areas of, these coatings, except when the device is energized by strictly high frequency current.

L In order to prevent the accumulation of charges on the luminescent coating, the container or support Ii therefor is ypreferably grounded or connected-to some part of the circuit or to a special circuit combination such as .illustrated in Fig.y 2 as involving the Wire id and the resistance 20 shunted by capacitance 2i. Tofurther aid in the removal of these charges should they accumulate, the coating itself may have mixed therewith conductive material, such as a metal powder, as illustrated4 at Dlil in Figure 2. 'I'he drain circuit if not grounded is preferably connected into the anode circuit and includes the impedances 2 2i to impart the proper impedance to this drain circuit. At this point it may' be noted that the construction of Fig. 3 merely illustrates another way of increasing the conductivity of the luminescent material and of A mounting it upon and holding it on `a support. At 24 is illustrated a ne metallic screen or wire mesh into which the coating material .23 is pressed.

In order to take advantage of the fact that atelevated temperatures the luminescent material is often more active, a heating coil 25 is imbedded in the insulating support 26 upon which the container ii is mounted. This heating coil may be energized through the external circuit 30 and the control switch 28. 'Ihe temperature ,variation-is dependent upon the nature of the materials and the limits in either direction are likewise dictated. by the results secured.

It has also been discovered that the application of an intensel electric field for a short period of time to the luminescent materlalin some cases enhances its intensity of luminescence. In other cases continued application of this eld results electric field f a desired frequency` v In the arrangement of Fig. 2 the various features as emphasized are shown in combination, but it will 'be apparent that in any particular devices these various features Ymay `be used independentlyof each tions.

In Fig. 4 has been illustratedA a hot cathode type of device inaccordance with this invention. 'I'he vessel 3i with a suitable atmospheric cntent Yhas mounted therein a. cathode 32 in the other or tin desired combina- 'l form, for example, ofxa filament or indirectly heated cathode of suitable shape, which may be energized fron'iany suitable current source. This cathode is surrounded with a metallic -shield 31 having a function similar to the coatings I 6* and Iiib of Fig. 2. The luminescent coating assembly is substantially as previpusly described, and need not be further discussed. In this case the metallic member I1 carrying the luminescent coating I functions as anode in the usual circuit.

In the operation of a device of this type the adapted to be connected by wire 38 to a suitable potential source in' order to neutralize the space charge effect. An advantage of 'a structure of this type resides in the fact that it may be operated with a relatively low potential on the anode of the order of a few hundred volts, or even as low as the usual house lighting circuit voltage. In some cases the introduction of a suitable gas, preferably inert, into the hot cathode type of tube, increases the intensity of luminescence of the layer I0, which action may be further intensified by increasing the applied voltage withinmaximum limits that are not too high to cause disintegration of the hot cathode.

It is, of course, apparently within the scope of this invention to make the coating I0 of any one of a number of suitable materials or a combination of them, either in juxtaposition upon the support or in mixture, to give any desired design and color effects. By means of this invention, as will be further illustrated, the areas of the designs may be greatly increased beyond anything herefore practical, becauseY of the features of construction employed. It is likewise clear' that under the term luminescent material it is intended to include both fluorescent and phosphorescent substances. Likewise, as lis well known; there are many liquids which are'either fluorescent or phosphorescent under the excitation of cathode rays, and hence may be employed as luminescent media in connection with devices of this type.

' A practical form of device in accordance with this invention, and which has been successfully operated for a considerable period oi' time is illustrated in Figs. 5 and 6. It comprises a closed vessel 4I| having a rarefled atmosphere of suitable gases and provided with an extension 4i forming a smaller chamber and connected with the vessel45 by means of a restricted neck 42..

The. chamber 4| is provided with a re-entrant.

which is sealed at its inner end and open at its A outer end to the anode chamber.

non-conducting material such as glass, and is further supported within the larger vessel by,

means of the pinches 55. At the other end of the vessel is the cold cathode 5I which may be eithercircular or rectangular in form and is preferably made of a thin sheet of suitable metal such tas previously set forth. 'I'he cathode is provided with a central crease or bend so-that its projected area will coincide with both sides of the screen. ByV this construction the cathode rays which depart from the cathode along lines perpendicular thereto will 'be directed over the display and full wave rectifying device.

Supported on the stem 45 is a metallic entire surface of' the screen. The luminescent material 54' on one or bothsides of the screen is thus subjected to direct impact by' the cathode rays uniformly over its entiresurface.

The cathode end of the tbe is likewise provided with the external and internal coatings 55 and 55 which are at least co-extensive with the cathode. As illustrated in Fig. 5 all coatings are connected to the respective electrode circuits. The terminals of the secondary 52 of a high voltage transformer are connected to the anode and the cathode. vThe primary of the transformer is illustrated at 53. This device is a combined halfway rectier and display device. When the anode is positive and the cathode is negative cathode rays will be generated and projected over the entire area ofthe screen. When the anode becomes negative and the cathode positive, current flow is interrupted. Actual-experience has shown the device after initial ageing capable of the generation of high intensity luminescence of great uniformity and without flickering orvfiuctuation. A device` of this type will not operate satisfactorily on ordinary cycle current. For this reason a rectifier is essential, and in accordance withl this form of structure the rectifier is embodied as a partof the device. If necessary', in order to maintain uniform pressure conditions within the vessel I0, a side chamber 54 is provided containing a vapor or gas generating substance 55 which may be heatedby means of the heating coil 55. To make this structure automatic a thermostatic device 51 isconnected in the heater circuit and subjected to temperature or current fluctuations of the main device so that the heating coil will be switched on and off as necessary to maintain the pressure in the main device.

The structure of Fig. 7 involves a combined In this case the vessel 50 is provided withthe screen 5I which supports the luminescent material. At each endof the vessel are the cathodes 54 shaped to project the cathode rays onto the screen. The anode 53 is mounted in a sidechamber and is connected to the electrical midpoint of the secondary 55, the terminals ofwhich are connected to the cathodes. At 51 is the energizing primary; No discussion is necessary to illustrate the operation of the device as a full wave rectifier.

Another structure for accomplishing similar results is illustrated in Figs. 8 and 9. In this case the vessel 68 is of oval cross-section, illustrating that the transverse dimensions of the tube may ,be reduced where desired. Within the vessel is the screen 55 for supporting the ,luminescent material. At I0 is the cathode, which lin this case may be termed a sort of roof, which extends.

along the top of the screen and is bent so as to direct the cathode rays over the entire surface of both sides'ofjthe screen. In this case a pair of l anodes 1I, 12 are provided which would be connected to the secondary ofthe transformerv while t'he cathode 15 would be connected to the midpoint thereof. Here again'the side tube 13 is supplied to hold a gas generating substance vwhich may be heated asdesired by the heating coil 14 'through the thermostatically controlled circuit by discussed above. The dimensions of said anode 75x are proportioned in accordance with current density variations previously described.

The form of the invention as illustrated in Fig.

. is that of a long tube of relatively small diameter somewhat likethat of the luminescent gas discharge devices now employed for advertising purposes in the form of designs, letters, devices, and the like. As shown it comprises a long glass tube 80 formed'into an airtight vessel and having a rareed atmosphere in accordance with the principles previously described. The vessel has a re-entrant stem 8l in which one end of the cathode B2 is supported. The other end of this cathode passes through a seal in the opposite end of the vessel and to which electrical connections can be made. .The cathode inthis case is in the form of a longv rod of suitable proportion. At 83 is an anode sealed into the vessel and exposed to the interior thereof through the openings 8f3 in the re-entrant stem 8l. At 85 is shown the luminescent coating which in this case is deposited upon the. interiorV wall of the vessel 80 so as to sur-` round the cathode 82 and to form, so to speak, a thin coating. The coating in this case, which may be of any one of the known luminescent materials or desired mixtures thereof, is preferably very thin or else made in the form of a discontinuous surface so that when the material isexcited by the cathode rays the light generated may be transmitted therethrough so as to be observed from the exterior of the vessel.

This tube, although illustrated as a straight cylinder in the drawings, may, of course, assume any desired shapes andv sizes and may be formed up into letters, symbols, devices, or other display forms.

The structure of Fig. l1 comprises a domeshaped vessel 86 having a re-entrant stem 8l! in which is supported the curved cathode 88. At 89 are a pair of anodes mounted in smail chambers open to the interior of the main vessel. The pper dome-shaped portion of the vessel 86 is provided with a coating 90 of luminescent material which mayVas stated before, beelther extremely thin or in the form of a discontinuous surface so that iight may be transmitted to the exterior of the vessel.'

In all of these modifications it will be apparent that the -general principles above described in detail, as well as the materials employed and the various circuit connections, may be used therewith to attain the important objects of uniform excitation of the luminescent coating. Furi thermore, the current conditions of operation and the features of rectification previously described may likewise be employed in connection therewith.

It will be apparent to `those-skilled in the art that this invention resides in certain principles of construction and operation which may be emplayedy in other physical forms. I do not, therefore, desire to be strictly limited to the disclosure as given for purposes of illustration, but rather to the scope of the appended claims.

What I seek to secure by United States Letters Patentis- Y 1. In a luminescent device, a sealed vessel having a rareed atmosphere, a luminescent substance supported within the vessel, means for exciting said substance, comprising any anode and a cathode, and conductive surfaces surrounding the anode andthe cathode and in electrical contact therewith.

2. The combination described comprising a closed vessel having a rareed atmosphere, a

comprising a closed vessel having a rarefied atmosphere therein, a lm of luminescent material lsupported within said vessel, a cathode and an anode within said vessel positioned so as to project cathode rays uniformly over the surface of said film, and conductive shields surrounding the cathode and the anode and connected thereto for `increasing the uniformity of excitation of said film.

4. The combination as described comprising a closed vessel having a rareed atmosphere, a cathode and an anode for said vessel, a. luminescent substance supported within the vessel so as to be between the electrodes and in the dark space region of the discharge, and means controlled by the current for operatingthe device for controlling the pressure lin the vessel to render the operation ofithe device more stable.

5. A luminescent light s ource of the type described comprising a closed vessel having a rarefled atmos'phere, a cathode and an anode supluminescent substance. supported between thev cathode and the anode, and conducting shields surrounding the cathode and anode and extending in an axial direction a distance suflicient to substantially surround the cathode and the anode and connected thereto respectively whereby the electron discharge between the electrodes is uniformly distributed over said coating to effect uniform excitation thereof.

6. A luminescent light source of the type described comprising a closed vessel having a rarefied atmosphere, said vessel having a sealed reentrant stem forming an anode chamber and having an aperture in the wall ,thereof establishing communication between the chamber and vessel, an anode supported in said chamber, a cathode mounted in said vessel and spaced from said anode, a body of luminescent material supported between the cathode and the anode, and means comprising conducting shields connected respectively to the anode and the cathode for causing uniform distribution ofthe discharge between the electrodes over the surface of the.

comprising a closed vessel having rareed at mosphere, an anode and a cathode supported in said vessel, means forming a layer of luminescent material supported between the anode and the cathode, means forming with a portion of said vessel a restricted chamber inl which said anode is supported, and a source of alternating current connected to the cathode and the anode whereby the cathode and anode cooperate to produce a rectifier for producing a rectified current which is applied to the cathode and anode to excite the cathode to produce an electron discharge vwhich is projected over the surface of said luminescent layer to excite it.

8. A device of the type described comprising a closed vessel having a rareed atmosphere,a cathode, an anode of small area-compared with that of the cathode positioned in an adjoining chamber of the main vessel of restricted volume, a screensupported between the electrodes and in the dark space region of the discharge, and

l an alternating current supply source connected to said cathode and anode whereby the alternating current is rectified and applied to the electrodes so that said coating is excited to luminescence.

9. A device of the type described comprising a closed vessel having a rareiled atmosphere, cathodes in said vessel, a plate supported therein substantially between the electrodes and in the free electron region of the discharge having a luminescent coating on both faces, said cathodes having such a geometric shape as to *project Y in adjoining extensions of the main vessel, said coating lying substantially between the electrodes and in the dark space region of the discharge.

11. The combination described comprising a closed vessel having a rai'eiled atmosphere, a

cathode and an anode for saidvessel, a luminescent substance supported within the vessel, substantially between the electrodes and inthe free electron region, so as to be excited by the rays generated by the cathode, and means for maintaining the pressure of the rareed atmosphere to render the excitation of the luminescent substance substantially constant.

12. In a luminescent device the' combination comprising a closed vessel having a rareiied atmosphere therein, a surface of luminescent ma^ terial supportedsubstantially between the electrodes and in the free electron region of the discharge within said vessel, an anode placed in an adjoining extension of the main vessel, and a cathode having such a geometric shape as to project cathode rays uniformly over the entire area of the surface covered with luminescent material.

13. A luminescent light source comprising a closed vessel having a rareed atmosphere, an anode and a cathode supported in said vessel in spaced relation, and means having a luminescent coating `supported substantially between the anode and the cathode and in the free electronl region of the vessel, the cathode being shaped and lpositioned with respect to the luminescent coating whereby electrons projected therefrom are uniformly distributed over the entire surface of the coating.

ARSENE N. LUCIAN.

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