US2885591A - Cathode and directed ray tubes - Google Patents

Description

May 5, 1959 GOODMAN 2,885,591

CATi-IODE AND DIRECTED RAY TUBES' Filed June 15, 1955 INVENTOR. FIG I2 v DAV/D M. GOODMAN CATHODE AND DIRECTED RAY TUBES- David M. Gdman, Wantagh, N.Y. Application June 13, 1955, Serial No. 514,973 13 Claims (Cl. 315-1) This invention relates to newandusefulimprovements 1n cathode ray and directed ray tubes. More particularly,

it is directed to new improvements in the screens there-' of; and methods of fabricatingthe-sam'e.

Cathode ray tubes, generally=speaking, are evacuated, glassfaced tubes having a luminescent screen at one end, the screen being bombarded by energy emanating-from a suitable source. The luminescent screens of such tubes when used for development of black and white images are relatively simple, usually consisting of a single layer of luminescent material, or phosphor. However, in the case of such tubes adapted for display in color, the fabrication of the screen is complicated by the need of using aplurality of phosphors, as for example, the red-, the blue-, and the green-emitting phosphors. 'The fabrication of the latter screens is further complicated by the need of depositing the phosphors in intricate patterns or layers.

Methods of manufacture used at present comprisethe deposition of phosphors in a pattern onto a transparent, translucent or perforated rigid screen. The tube envelopes are generally made with narrow necks, and in the above described method, the tube envelope must be cut apart, or made in two sections. The rigid, phosphorbearing screen is afiixed therein, and the two sections are then sealed.

An alternative method of fabricating a color tube nited States Patent" 0 without separating the segments of the tube envelope comprises coating the inside of the tube envelope face.

with'a photosensitive layer, exposing this layer to light in a regular pattern, developing the pattern, and then causing a phosphor powder to adhere to the pattern thus formed. With the powder in place, theentire tube .is

baked, fixing the powder in place. After cooling, the excess phosphor and photosensitive material .is washed away, and the cycle of operations is then repeated for as many times as it is desiredto a'dd .additionalphosphors to the pattern.

It is obvious, therefore, thatthe fabrication of a cathode ray tube, or the like,-is lengthy and complex.

I have devised a method whereby a cathode ray tube envelope may be used for the'manufacture of a tube to display colors without the necessity of coating the inside face thereof successively withza plurality of separate phosphors.

In accordance with my invention, a plurality of phosphors are deposited in accordance with a predetermined pattern onto a flexible base or screen, which may be rolled and inserted into a tube envelope.

The flexible screen is then aflixed to the inner face of the tube envelope. Further manufacturing operations are-then carried out to complete the cathode ray tube by customary techniques.

Accordingly, an important object of this invention is the provision of a new method of fabricating cathode ray and directed ray tubes; including those adapted for displaying colored images.

Another object of this invention is to provide new 2,885,591 Patented May 5, 1959 Other objects andadvantages "will become apparent from the followingdetailed description of the invention taken-in conjunction with" the accompanying drawing; wherein:

Fig.- 1 representsa rolled up radiation-emitting screen carried by suitable" means-to typify a method of insert ing the rolled-up screen in a'tube.

Fig; 2 illustrates the stages, of further insertion and aflixation of the rolled-up tube assembly of Fig. 1.

Fig; 3 illustrates a projection on the inner side of the face of the tube which maybe used to support the screen in a fixed position.

Fig. 4 illustrates 'a' screen secured at two points and being unrolled to be securedat the two bottom points.

Fig.5 illustrates, a rolled-upscreen fixed at its two ends to prevent premature'unrolling.

Fig; 6 illustrates two spring=like*mernbers attached to the screen which maybe used to aid in unrolling the screen.

Fig. 7 il1nstr'ates atyp'ical scree'nassembly, utilizing a woven mesh in which the phosphor" (or radiation emitting) pattern is deposited.

v Fig. 8 illustratesa woven'me'sh akin" to that of Fig. 7 in which the phosphor' "(or*other"radiation emitting) material is deposited on'one side of the mesh.

Fig.8A shows awov'en mesh akin to that of Figs. 7 and 8" in which the phosphorpattern' varies in detail at different points;

Fig. '9 illustratesa' mesh which is secured to the phosphor pattern in a tangential manner.

Fig. 10 illustrates aphosphor' pattern secured'to anotherfor'm of rollable member.

Fig. 11 'illustratesa compositescreen'in which the mesh may also serve as an insulating barrier.

Fig; 12 shows a'front'view of a' screen made in accordance with the general structure of Fig. 11.

In Fig. 1, rod 2 of suitablelength is hinged at 4, to support bar 6, onwhich is attached roller 8, about which rolled screen 10 is wrapped? Depending upon the length and dimensions of enve1op'e'12 ofFig. 2, the rod 2, and screen-carrying roller 8 are inserted into envelope 12 until the roller 8 is positioned at the top of the inside surface of'envelope 12 as at position "14, the surface 16 having been prepared'with a suitable adhesive. Screen 10 is then unrolled from supports; After unrolling, the rod 2 and roller 8 are removed, and the screen 10 may then be pressed (or squeegeed)" against the face 16. Suitable adhesives are-sodium silicate or, potassium sili cate sprayed or otherwise deposited'on face 16 in a thin layer, in the form of aqueous solutions. When surface 16 is flat, or cylindrical, the unrolling of 10 proceeds smoothly from top to bottom of face 16. In the case of a spherical surface, screen 10 is preformed so that when unrolled it fits flush, againstface 16. Screen '10 is secured to 16 as by baking or air drying.

Fig. 3 illustrates a screen catch 18 in the formof a projection on surface '16-which is used as illustrated in Fig. 4 to secure the screen-'10 in a fixed. position-with out'nece'ssarily using cements or adhesives. Appropriate holes-or loops are-provided in screen 10 through which projections 18 pass; 5

In Fig. 5, means 22, as in the form of rubber bands, etc., are used to keep pattern rolled up. When used, means 22 are removed after roller 8, with screen 10 aflixed, is properly located in envelope 12.

In Fig. 6, means 20, keep screen 10 unrolled. Spring wire or strips or other means 20, are aflixed to or made integral with screen 10.

In Fig. 7 a woven mesh shown on an enlarged scale, wh ch comprises strands 24, is filled with radiation emitting material 26. The mesh may consist of glass fibers, or of metal filaments, of simple weave and is flexible and rollable. The radiation emitting material or materials are deposited in the mesh screen in any convenient or conventional manner, such as by spraying, painting, printing, photo-resist, etc. A suitable adhesive, if desired, may be incorporated with the radiation-emitting material to secure the latter to the screen. For example, when a phosphor is to be used as the radiation emitting material, and further by Way of example when a P-4 phosphor is to be deposited, I have found that sodium silicate is an excellent adhesive. The phosphor is usually finely ground to particle sizes of the order of 8 microns. For example, when mixed with sodium silicate solution (40-42 Baum scale), the resultant mixture may be applied readily to a mesh consisting of 14 x 18 strands or 20 x 20 strands to the inch of .020 inch strands. Air drying or baking secures the phosphor in the mesh alinside face 16 of envelope 12, with the mesh 28 located though baking results in a slightly more flexible assembly. The screen of Fig. 7 is adapted to be rolled into shape for assembly at this stage. The thickness of the phosphor screen for ordinary viewing is of the order of .010 inch; the usual rate of phosphor deposition is of the order of 5 milligrams per square centimeter. The thickness may be controlled by appropriate choice of strand thickness in the mesh or it may be controlled as illustrated in Fig. 8 where the phosphor-adhesive mixture occupies a portion of the mesh thickness. The rate of deposition, i.e., the amount of phosphor per unit area at a point, may be controlled by varying the ratio of phosphor to adhesive, or when using a fixed amount of adhesive, by adding an inert medium such as zinc sulphide, finely ground and inactivated. It is to be pointed out that by using a close mesh, i.e., more than 20 strands to the inch, and by using a fine strand for the mesh, a pattern with considerable changes in phosphor detail may be easily prepared. In Fig. 8A the phosphor pattern varies in detail at the points 26 26 and 26 by variation of the amount of phosphor present at said points. Screens without such detail may be deposited from settling out of a liquid suspension .or by spraying the material suspended in a volatile liquid such as acetone to which has been added a small amount of binder. In the settling process, a mild electrolyte such as ammonium carbonate is used to prevent the particles from settling non-uniformly.

When fine detail is required in the phosphor pattern, printing techniques are the methods of choice for the formation thereof. The photo-resist method provides a great deal of flexibility and since it is well known, is not described in detail; also the half-tone process, etc. Fig. 9 illustrates a mesh comprising strands 28 adhered or cemented, as by sodium silicate or other suitable adhesive on one side (tangentially), to a film or sheet or lamina of radiation-emitting material 30. The mesh 28 may comprise metal or otherwise electrically conducting material. When connected to a suitable source of voltage, this conducting screen establishes the electrical potential at the position of the mesh. The mesh thus may collect the secondary electrons emitted in the region of the screen. Therefore, in addition to the utilization of the mesh in the screen fabrication process, and in the tube assembly process, said mesh may also replace the electron transparent aluminum layer often used in conventional cathode ray tubes. In such utilization, the radiation-emitting material 30 is secured to the towards the electron gun.

Fig. 10 shows a composite screen composed of materials 32 and 34 when a decalcomania type support is used. Radiation-emissive material 34 is deposited on and supported by 32, which may be a thin rollable layer of nitrocellulose by way of example. After causing the phosphor side of this decalcomania type of assembly to adhere to the inside face of the tube, the thus temporarily used phosphor-supporting material 32 may be volatilized or otherwise removed. Layer 36 may be utilized when other properties are required. For example, 34 may be a particular phosphor pattern, and 36 may be a different phosphor. It may also be desirable to have 36 consist of a thin metallic layer, such as aluminum.

In Fig. 11 a composite, rollable structure is illustrated in which mesh 38, comprised of insulating strands such as glass, not only supports radiation-emitting materials 40, but which adheres to plate or members or lamina 42 with suflicient spacing between 40 and 42 to permit the application of a potential difference between 40 and 42. 42 may be electrically conducting glass, or a thin, metallic layer, part of the rollable assembly.

Fig. 12 is a front view of a structure akin to that shown in Fig. 11 in which radiation-emitting material 40 is removed at desired positions 44 and 46 so that the radiation from these areas are substantially different from that of the remainder of screen 40. This difference is caused by the absence of material 40 and the resultant acceleration or deceleration of an electron stream which may be directed to 44 and/or 46 and which change in velocity will be influenced by the potential difference between 40 and 42.

It will be apparent from the foregoing description of the invention and the several embodiments thereof set forth, that it is now possible to provide a radiation-emitting article of flexible character which embodies radiation-emitting material (as in the form of suitable phosphors, tungsten, molybdenum, etc.) with a suitable base so that the same may be conveniently rolled. A web of flexible material embodying the radiation-emitting mate rial can thus be manufactured to provide a stockpile thereof. Accordingly, segments thereof, and of desired size, can be cut in accordance with production requirements. It will also be apparent that it is possible, as a result of this invention, to manufacture webs formed of bases of the various characteristics hereinabove described, embodying a wide variety of radiation-emitting phosphors or materials and in a wide variety of patterns and densities so as very substantially to reduce costs of producing cathode ray and/or directed ray tubes. Variations in the patterns may be in the configuration or in the density thereof, i.e., either in two dimensional or three dimensional fashion.

It will be understood that the foregoing description of the invention and the embodiments set forth, are merely illustrative of the principles thereof. Accordingly, the appended claims are to be construed as defining the invention within the full spirit and scope thereof.

I claim:

1. A rollable electron-sensitive radiation emitting article comprising a base of flexible meshed structure having radiation-emitting materials disposed within the volume of the interstices of said meshed structure, said radiationemitting material extending across the interstitial volumes of the mesh and being adhered to said mesh on the inside surfaces thereof that form the boundaries of the said interstitial volumes.

2. A rollable target screen that emits electromagnetic radiation upon bombardment by a beam of energy comprising a flexible base of meshed structure having electromagnetic radiation-emitting materials disposed within the volume of the interstices of said meshed structure, said radiation-emitting material extending across the interstitial volumes of the mesh and being adhered to said mesh on the inside surfaces thereof that form the boundaries of the said interstitial volumes.

3. A cathode ray screen which emits electromagnetic radiation upon excitation by cathode rays, the magnitude of said radiation varying between different areas as a predetermined two-dimensional function of position on the screen, which comprises a varying amount of electron sensitive radiation-emitting material deposited within the interstices of a foraminous base of predetermined thickness, the amount of said radiation emitting material deposited per unit area being related to said predetermined two-dimensional function.

4. A cathode ray screen which emits electromagnetic radiation upon excitation by cathode rays the magnitude of said radiation varying as a predetermined two-dimensional function of position on the screen which comprises a screen having a deposition of controlled proportions of radiation emitting material in an admixture with other material of different cathode ray sensitiveness, said admixture being deposited to provide varying amounts of said radiation emitting material per unit area in relation to said predetermined two-dimensional function.

5. A cathode ray tube comprising: an envelope, an electron gun, and a cathode ray sensitive screen structure that emits electromagnetic radiation upon excita tion by cathode rays from said gun, said structure comprising a foraminous electrically conductive network exposed to and facing the electron gun and with the radiation emitter of the screen in tangential contact with said conductive network and on the side thereof opposite said gun.

6. The method of mounting a screen, that emits electromagnetic radiation upon excitation by a beam of energy, in a housing that comprises; rolling a rollable screen, that emits electromagnetic radiation upon excitation by a "beam of energy on a cylindrical carrying member, inserting the so-carried screen into the housing, unrolling said screen from the cylindrical carrying member, afiixing it to the situs of mounting, and withdrawing the carrying member.

7. The method of mounting an electron sensitive screen, that emits radiation upon excitation by cathode rays, into a cathode ray tube comprising: rolling a rollable screen, that emits radiation upon excitation by cathode rays, on a cylindrical carrying member, inserting the so-carried screen into the cathode ray tube, unrolling said screen from the cylindrical carrying member, afiixing it to the situs of mounting, and withdrawing the carrying member.

8. A rollable screen structure containing phosphors that emit electromagnetic radiation upon bombardment by a beam of energy comprising a cylindrical support member and a rollable screen that emits electromagnetic radiation upon bombardment by a beam of energy, and means to hold said rollable screen on said cylindrical support member.

9. A rollable screen for a cathode ray tube comprising a first electrically conductive member that emits electromagnetic radiation upon excitation by cathode rays, said member also establishing a substantially constant electrical potential adjacent one side of a flexible foraminous electrically insulating member, and a second electrically conductive member adjacent the other side of said insulating member for establishing a second substantially constant electrical potential, said first member having apertures to expose said second member through the foramina of the insulating member.

10. A rollable electron-sensitive radiation emitting article comprising a base of flexible meshed structure having radiation-emitting materials disposed Within the volume of the interstices of said meshed structure, said radiation-emitting material extending across the interstitial volumes of the mesh and being adhered to said mesh on the inside surfaces thereof that form the boundaries of the said interstitial volumes wherein the base of flexible meshed structure is comprised of electrically conductive material and provides two sides to the mesh at least one side thereof being free from electrically insulating material.

11. A cathode ray tube comprising: a rollable target screen as defined in claim 10, an envelope enclosing said target, and an electron gun therein for activating said target, with the meshed structure disposed so that a side free from electrically insulating material faces the electron gun.

12. A rollable screen structure adapted to be mounted on a cylindrical carrying member for assembly onto a cathode ray tube member comprising at least one rollable lamina that contains material that emits electromagnetic radiation upon bombardment by cathode rays, and rollable means that separate layers of said lamina when in a rolled position.

13. A rollable screen structure adapted to be mounted on a cylindrical carrying member for assembly onto a cathode ray tube member comprising at least one rollable lamina that contains material that emits electromagnetic radiation upon bombardment by cathode rays, and another rollable lamina which is sheetlike, electrically conductive, and which is transparent to said cathode rays.

References Cited in the file of this patent UNITED STATES PATENTS 2,185,439 Hinderer Jan. 2, 1940 2,195,444 Brett Apr. 2, 1940 2,215,199 Stendel Sept. 17, 1940 2,289,156 Weinhart July 7, 1942 2,425,980 Baird Aug. 19, 1947

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