US3694050A

US3694050A - Method of fabricating a scan conversion device

Info

Publication number: US3694050A
Application number: US168996A
Authority: US
Inventors: Harry E Smithgall; Elmer O Stone
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1971-08-04
Filing date: 1971-08-04
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26

Abstract

A method is provided for fabricating an improved scan-conversion device formed as a combination of two separate cathode ray tube sections utilizing a common faceplate portion therebetween. The method of fabrication embodies peripherally sealing an envelope funnel to a first surface of the common faceplate, whereupon a cathodoluminescent screen is formed. Upon positioning and sealing an electron gun in the funnel portion of the first envelope, the envelope is evacuated, sealed and processed to provide a displayforming section. A target electrode is then formed on the outer surface of the common faceplate, and a second envelope funnel, having an electron gun positioned and sealed therein, is peripherally bonded thereto; whereupon the second envelope is evacuated, sealed and processed to provide a display-reading section oriented to directly cooperate with the display-forming section.

Description

United States Patent Smithgall et al.

[54] METHOD OF FABRICATING A SCAN CONVERSION DEVICE [72] Inventors: Harry E. Smithgall; Elmer 0. Stone,

both of Seneca Falls, NY.

[73] Assignee: Sylvania Electric Products Inc.

[22] Filed: Aug. 4, 1971 [21] Appl. No.: 168,996

Related US. Application Data [62] Division of Ser. No. 886,109, Dec. 18, 1969,

Pat. No. 3,624,442.

[52] US. Cl. ..316/19, 29/25.13

[51] Int. Cl ..H0lj 9/18 [58] Field of Search ..316/19, 17, 18; 29/25.l3; 313/2 [56] I References Cited UNITED STATES PATENTS 3,182,223 5/1965 McNaney ..315/l0 3,215,484 11/1965 Burtt ..316/18 1 Sept. 26, 1972 Primary Examiner.lohn F. Campbell Assistant Examiner-D. M. Heist AttorneyNorman J. OMalley et al.

[ 5 7] ABSTRACT A method is provided for fabricating an improved scan-conversion device formed as a combination of two separate cathode ray tube sections utilizing a common faceplate portion therebetween. The method of fabrication embodies peripherally sealing an envelope funnel to a first surface of the common faceplate, whereupon a cathodoluminescent screen is formed. Upon positioning and sealing an electron gun in the funnel portion of the first envelope, the envelope is evacuated, sealed and processed to provide a display-forming section. A target electrode is then formed on the outer surface of the common faceplate, and a second envelope funnel, having an electron gun positioned and sealed therein, is peripherally bonded thereto; whereupon the second envelope is evacuated, sealed and processed to provide a display-reading section oriented to directly cooperate with the displayforming section.

8 Claims, 2 Drawing Figures PATENTED I972 3.694.050

INVENTORS. HARRY E. SMITHGALL 8. ELMER 0. STONE ATTORNEY METHOD OF FABRICATING A SCAN CONVERSION DEVICE CROSS-REFERENCE TO RELATED APPLICATION This application is a divisional application of Ser. No. 886,109, filed Dec. 18, 1969 now US. Pat. No. 3,624,442,, which is assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION This invention relates to a cathode ray tube combination and more particularly to a method of fabricating an integrated scan-conversion device.

Cathode ray tube structural combinations are conventionally used as scan-conversion devices wherein one portion of the device serves to read-in a certain type of information, and another portion functions to read-out a translation of the information in another desired form. Such devices are employed where display information is continuously transformed from one scanning rate or time base to another of a differing value. For instance, by employing suitable components and appropriate deflection signals, the form of in-put scan is readily converted to a different form of out-put scan, i.e., a P.P.I. radar display to a horizontal scan rectangular presentation. Scan-conversion devices also make possible a change in the rate of scan frequency during the respective read-in and read-out operations.

\ defect occurring during the final stages of manufacturing can ruin the complete structure, thereby greatly increasing the costs of fabrication. Attempts have been made to fabricate double-ended cathode ray tubes having a common faceplate, whereof difficulties in glass sealing and screen deterioration resultant of glass sealing temperatures have been encountered.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the afore mentioned disadvantages and to provide a method of fabricating an improved scan-conversion device embodying two individual hermetically sealed and evacuated cathode ray tube enveloped structures having a common faceplate therebetween.

A further object is to provide method of fabricating a scan-conversion device that can be expeditiously and economically executed.

The foregoing objects are achieved in one aspect of the invention by the provision of a method of fabricating a scan-conversion device embodying a combination of two separate cathode ray tube sections utilizing a common faceplate portion. The individual cathode ray tube sections provide display-forming and display-reading sections respectively. A method of fabrication is provided wherein a first envelope funnel is peripherally joined to a first surface of the common faceplate portion to provide a first envelope portion. A cathodoluminescent screen is formed on the faceplate of the first envelope portion. Upon positioning and sealing an electron gun in the neck portion of the first envelope, sequential evacuation, sealing and processing provides a completed first display-forming section. A target electrode or screen is formed on the second or exterior surface of the common faceplate, whereupon a second envelope funnel, having an electron gun positioned and sealed therein, is peripherally joined to the faceplate to provide a second envelope means. The second envelope is then sequential evacuated, sealed, and processed to provide a completed second display-reading section which is oriented to functionally cooperate with the aforementioned display-forming section. Thus, there is provided a cathode ray tube scan-conversion device employing separate evacuated sections wherein opposite surfaces of the common faceplate are scanned by different electron beams respectively.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the scan-conversion device illustrating the aspects of one embodiment of the invention; and

FIG. 2 is an enlarged fragmentary plan view of the common faceplate region of the device illustrating aspects of a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawing.

With reference to the drawing, there is shown in FIGURE 1 a plan view of a scan-conversion device 11, having an axis 12 and incorporating in combination, a cathode ray tube display-forming section 13 and a cooperating cathode ray tube display-reading section 15. In the device embodiment shown, the display-reading section 15 is, for example, a cathode ray tube structure in the form of a photoconductive camera or pickup tube such as a Vidicon camera tube. However, it is not intended that the display-reading section be limited to a camera tube, as other cathode ray tube structures such as a display storage medium can likewise be employed in keeping with the intended scope of the invention. Likewise, the display-forming section 13 is not to be limited to a conventional monochrome screen, but is intended to also include plural phosphor screens, exhibiting multiple decay characteristics, responsive to excitation by electron beams of different velocities.

A substantially planar faceplate portion 17, as illustrated in FIGURES 1 and 2, is common to both

display sections

13 and 15, and is of a thickness a to minimize capacitive coupling between the first 19 and second surface 21 thereof. The common faceplate 17 is substantially transparent being of a material such as a fiber optics array, wherein multitudinous glass rods 23 are arranged in an orderly manner to transmit high resolution display imagery between the

respective faceplate surfaces

19 and 21. It has been found that a fiber optics faceplate 17 having a thickness a, for example within the range of 0.5 to 1.0 inch, is beneficial in minimizing crosstalk between the

surfaces

19 and 21.

The envelope of the display-forming section 13 has a first envelope funnel portion 25 which is hermetically joined to the peripheral region of the first surface 19 of the faceplate by a glass formed frit seal 26 to provide a first envelope means 27. This frit seal is accomplished, for example, within a temperature range of 400 to 450 C., and does not affect the structure of the fiber optics array.

The definition of funnel, in this instance, is intended to include both a tubular portion alone, or a tubular -or conical portion with v a contiguous smaller diametered neck portion attached thereto.

A cathodoluminescent display screen 29, having therein at least one electron responsive phosphor, is disposed on the first faceplate surface 19 to provide the screen for the display-forming section 13.

The inner surface of the first envelope funnel 25 has an electrical conductive coating 30 discretely applied thereto in a manner to extend substantially from the region of the screen 29 to an electron gun or beam generating means 31 positioned in the envelope funnel 25. The electron gun 31 has a plurality of connective leads 33, two of which are shown, extending exteriorly of the tube through a stem closure portion 35. Another electrical connective means 37 extends exteriorly through the envelope 27 from the region of the screen to provide means for supplying a final anode voltage to the display-forming section 13. A thin metallic coating 39, such as aluminum, is suitably disposed over the surface of the screen 29 and a portion of the adjacent conductive coating 30. This metallic coating 39 enhances the display imagery of the screen projected through the faceplate 17 and insures electrical connection of the screen 29 and the conductive coating 30 with the electrical connective means 37.

The cathode ray tube display-reading section 15 is formed of a second envelope funnel portion 41 which is hermetically sealed to the peripheral region of the second surface 21 by a glass-metal seal 42, such as indium, to provide a second envelope means 43.

A photoconductive screen or target electrode 45 is disposed on the second surface 21 of the common faceplate 17. This target electrode 45 comprises a layer of photoconductive material 47 such as antimony trisulfide deposited over a thin substantially transparent electrical conductive film 49 comprised of at least one metallic material selected from the group consisting of tin oxide, gold, and chromium. The aforementioned glass-metal seal 42 provides internal to external electrical connective means for the target electrode 45. Attached to the glassmetal seal 42 is a metallic ring or band 51 of a material such as stainless steel, which provides external terminal means for the target electrode 45.

Positioned adjacent the target electrode 45 is a conventional planar mesh grid 53 which is supported by an insulative ring 55 mounted on the forward open end of the G-3 electrode 57 of the electron gun 59. A plurality of external connective leads 61, two of which are shown, extend from the electron gun 59 through the stem closure portion 61.

Focusing and

deflection systems

63 and 65 are auxiliary operational means oriented relative to the exterior of the respective display-forming section 13 and the display-reading section 15. Although magnetic systems are shown in FIG. 1, electrostatic systems or any combination of the two can be equally employed for either or both display sections.

A second embodiment of the scan conversion device 11 is illustrated in FIGURE 2, wherein the electrical connection from the region of the cathodoluminescent display screen 29 to the exterior of the first envelope means 27 is in the form of a plurality of conductive leads 67 embedded in and extending through the frit seal jointure 26. These conductive leads 67 are of a metallic composition, such as a nickel-chromium-iron alloy, having expansion characteristics substantially matching those of the material of the glass frit seal 26. An example of such a material is No. 4 Alloy as manufactured by Sylvania Electric Products Inc., New York, New York. The conductive leads 67 extend exteriorly of the seal 26 and are of a sufficient length to facilitate a bonded jointure 69 with a conductive terminal ring, or band 71. Exterior support for the terminal band 71 is provided by a supportive adhesive material 73 exhibiting sufficient resilience to accommodate the differential of expansion characteristics of the contiguous associated materials. An example of a suitable supportive material 73 is a room-temperature-setting silicone rubber adhesive/sealant material such as Silastic RTV silicone rubber as manufactured by the Dow Corning Corporation, Midland, Michigan.

One method for fabricating a scan-conversion device of an aforedescribed type comprises a definite sequence of related steps. It has been found expedient to first construct the display-forming section 13 wherein the first envelope funnel portion 25 is joined to the peripheral region of the first surface 19 of the faceplate 21 by a glass frit seal 26 to provide a first envelope means 27 Next, a cathodoluminescent display screen 29, of at least one electron responsive phosphor, is formed by conventional means on the first faceplate surface 19. An electrical conductive coating 30, of a material such as colloidal graphited water, for example, Aquadag, is applied to a discrete area of the inner surface of the first envelope means 27 in a manner to extend from the region of the screen 29 to the location of the electron gun 31. It is preferable to aluminize the region of the screen 19 which is accomplished in a conventional manner by applying a lacquer substrate, not shown, upon which a thin film of aluminum 39 is vaporized. An electrical connection from the electrical conductive coating 30 in the region of the screen 29 is made, for example, by electrical connective means 37 which traverses the wall of the first envelope means 27. The screened and coated first envelope is then heated, for example, at approximately 400 C. for about onehalf hour, to remove volatile substances from the screen and coatings contained within the tube envelope. The electron gun 31, supported by the stem closure portion 35, is then positioned within the first envelope means 27, whereupon the stem closure 35 is peripherally and hermetically joined to the envelope as by seal 74. The first envelope means 27 is then evacuated or exhausted through a suitable opening therein, for example, a tubulation in the stem closure portion 35 which is subsequently closed by seal 75. Conventional processing is thence completed to provide the first display-forming section 13.

A substantially transparent electrically conductive film 49 is applied to the second surface 21 of the faceplate 17 as by, for example, the vaporization of a thin film of at least one metal, selected from the group consisting of gold and chromium. Upon this conductive film 49, a photoconductive coating 47, of a material such as antimony tri-sulfide, is applied by vapor depositing several thin superjacent layers to provide the desired photoconductive deposition. The transparent electrically conductive film 49 and the overlaid photoconductive coating 47 provide the target electrode 45 for the display-reading section 15 under construction.

An indium sealing ring, interiorly adhered to a metallic backing band 51, is positioned to effect cold-sealing of the second envelope funnel portion 41 to the peripheral region of the second surface 21 of said faceplate portion 17 containing the target electrode 45. In this instance, the second envelope means 43 has an electron .gun 59 priorly positioned and sealed therein; the electron gun being supported by stem closure portion 61. The second envelope funnel 41 with the electron gun 59 therein is carefully pressured in an axial manner against the indium sealing ring positioned on the faceplate 17, by means not shown, whereby the indium ring is plastically deformed to provide the glassmetal seal 42. No heat is required for this type of seal which makes it appropriate for this jointure as the adjacent antimony tri-sulfide would not withstand the temperature normally required to effect a glass frit type of seal. Since the indium is electrically conductive, the seal 42 provides an electrical connection from the target electrode 45 to the exterior of the second envelope 43. The metallic backing band 51 provides the exterior connective element for the target electrode 45. The second envelope'43 is then evacuated or exhausted through a suitable opening therein, such as for example, a tubulation in the stern closure portion 61 which is subsequently closed by seal 77. Although conventional processing is employed to provide the second display-reading section 15 of the scan-conversion device 11, care is exercised to protect the indium seal from temperatures exceeding 120 C.

Another embodiment for consummating the electrical connection from the region of the screen 29 to the exterior of the first envelope portion 25 is accomplished by inserting and embedding a plurality of electrically conductive leads 67 in the frit seal jointure 26 at the time that jointure is made.

It has been found that by another method of fabrication, the substantially transparent electrically conductive film 49, that comprises part of the target electrode 45 of the display-reading section 15, is applied as a first step. By this technique, the faceplate portion 17 is discretely heated at a differential of about 2 C. per minute to a temperature of approximately 600 C., whereupon the second surface 21 of the faceplate has stannic chloride evenly applied thereto to provide a conductive tin oxide coating thereover. When the transparent conductive film 49 is applied at this stage of fabrication, care must be exercised to protect this film during the subsequent fabrication of the displayforming section 13.

Thus, there is provided a method of fabricating an improved scan-conversion device embodying two individual hermetically sealed and evacuated cathode ray tube enveloped structures having a common faceplate therebetween. The device, so fabricated, exhibits high sensitivity since light from the phosphor screen of the display-forming section is coupled directly to the target electrode of the display-reading section. In addition, the method of fabricating the combination structure of the device is a procedure that is economically and expeditiously executed.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is: l. A method for fabricating a scan-conversion device having first and second individual cathode ray tube envelope sections with a common faceplate portion therebetween having first and second surfaces with related screen means thereon to provide a first display forming section and a second display reading section each having individual funnel portions with separate electron guns therein, said method comprising the steps of:

joining said first envelope funnel portion to the peripheral region of said first surface of said faceplate by frit seal means to provide a first envelope means;

forming a cathodoluminescent display screen comprising at least one electron responsive phosphor on said first faceplate surface to provide a screen for said display forming section;

applying an electrical conductive coating to a discrete area of the inner surface of the first envelope means;

establishing an electrical connection from the region of said screen to the exterior of said first envelope; heating said first envelope to remove volatile substances from said screen;

positioning and sealing an electron gun in said first envelope means;

exhausting, sealing and processing said first envelope to provide a first display-forming section; applying a substantially transparent electrically conductive film on said second faceplate surface;

depositing a photoconductive coating over said transparent electrically conductive film on said second faceplate surface to form a target electrode; sealing said second envelope funnel portion to the peripheral region of said second surface of said faceplate, containing said target electrode to provide a second envelope means, and establishing an electrical connection from said target electrode to the exterior of said second envelope, said second envelope funnel portion having an electron gun priorly positioned and sealed therein; and

exhausting, sealing and processing said second envelope to provide a second display-reading section.

2. A method for fabricating a scan conversion device according to claim 1 wherein said substantially transparent electrically conductive film applied to said second faceplate surface is formed by the vaporization of a thin film of at least one metal selected from the group consisting of gold and chromium.

3. A method for fabricating a scan conversion device according to claim 1 wherein said electrical connection from the region of said screen to the exterior of said first envelope is established by inserting and embedding I lated screen means thereon to provide a first displayforming section and a second display-reading section each having individual funnel portions and separate electron guns therein, said method comprising the steps of:

applying a substantially transparent electrically conductive film on said second faceplate surface;

I joining said first envelope funnel to the peripheral region of said first surface of said faceplate by frit seal means to provide a first envelope means;

forming a cathodoluminescent display screen comprising at least one electron responsive phosphor on said first faceplate surface to provide a screen for said display-forming section; applying an electrical conductive coating to a discrete area of the inner surface vof the first envelope means; establishing an electrical connection from the region of said screen to the exterior of said first envelope; heating said first envelope to remove volatile substances from said screen;

positioning and sealing an electron gun in said first envelope means; exhausting, sealing and processing said first envelope to provide a first display-forming section;

depositing a photoconductive coating over said transparent electrically conductive film on said second faceplate surface to form a target electrode;

sealing said second envelope funnel to the peripheral region of said second surface to said faceplate to provide a second envelope means, and establishing an electrical connection from said target electrode to the exterior of said second envelope, said second envelope funnel portion having an electron gun priorlyv positioned and sealed therein; and

exhausting, sealing and processing said second envelope to provide a second display-reading sec tion.

6. A method for fabricating a scan conversion device according to claim 5 wherein said electrical connection from the region of said screen to the exterior of said first envelope is established by inserting and embedding a plurality of electrically conductive leads through said frit seal jointure.

7. A method for fabricating a scan conversion device according to claim 5 wherein said substantially transparent electrically conductive film is tin oxide formed by heating said faceplate and applying stannic chloride to said second surface thereof.

8. A method for fabricating a scan conversion device according to claim 5 wherein the deposition of said photoconductive coating over said transparent electrically conductive film on said second faceplate surface is formed by applying a plurality of superjacent layers of antimony tri-sulfide.

Claims

1. A method for fabricating a scan-conversion device having first and second individual cathode ray tube envelope sections with a common faceplate portion therebetween having first and second surfaces with related screen means thereon to provide a first display forming section and a second display reading section each having individual funnel portions with separate electron guns therein, said method comprising the steps of: joining said first envelope funnel portion to the peripheral region of said first surface of said faceplate by frit seal means to provide a first envelope means; forming a cathodoluminescent display screen comprising at least one electron responsive phosphor on said first faceplate surface to provide a screen for said display forming section; applying an electrical conductive coating to a discrete area of the inner surface of the first envelope means; establishing an electrical connection from the region of said screen to the exterior of said first envelope; heating said first envelope to remove volatile substAnces from said screen; positioning and sealing an electron gun in said first envelope means; exhausting, sealing and processing said first envelope to provide a first display-forming section; applying a substantially transparent electrically conductive film on said second faceplate surface; depositing a photoconductive coating over said transparent electrically conductive film on said second faceplate surface to form a target electrode; sealing said second envelope funnel portion to the peripheral region of said second surface of said faceplate, containing said target electrode to provide a second envelope means, and establishing an electrical connection from said target electrode to the exterior of said second envelope, said second envelope funnel portion having an electron gun priorly positioned and sealed therein; and exhausting, sealing and processing said second envelope to provide a second display-reading section.

3. A method for fabricating a scan conversion device according to claim 1 wherein said electrical connection from the region of said screen to the exterior of said first envelope is established by inserting and embedding a plurality of electrically conductive leads through said frit seal jointure.

4. A method for fabricating a scan conversion device according to Claim 1 wherein the deposition of said photoconductive coating over said transparent electrically conductive film on said second faceplate surface is formed by applying a plurality of superjacent layers of antimony tri-sulfide.

5. A method for fabricating a scan-conversion device having first and second individual cathode ray tube envelope sections with a common faceplate portion therebetween having first and second surfaces with related screen means thereon to provide a first display-forming section and a second display-reading section each having individual funnel portions and separate electron guns therein, said method comprising the steps of: applying a substantially transparent electrically conductive film on said second faceplate surface; joining said first envelope funnel to the peripheral region of said first surface of said faceplate by frit seal means to provide a first envelope means; forming a cathodoluminescent display screen comprising at least one electron responsive phosphor on said first faceplate surface to provide a screen for said display-forming section; applying an electrical conductive coating to a discrete area of the inner surface of the first envelope means; establishing an electrical connection from the region of said screen to the exterior of said first envelope; heating said first envelope to remove volatile substances from said screen; positioning and sealing an electron gun in said first envelope means; exhausting, sealing and processing said first envelope to provide a first display-forming section; depositing a photoconductive coating over said transparent electrically conductive film on said second faceplate surface to form a target electrode; sealing said second envelope funnel to the peripheral region of said second surface to said faceplate to provide a second envelope means, and establishing an electrical connection from said target electrode to the exterior of said second envelope, said second envelope funnel portion having an electron gun priorly positioned and sealed therein; and exhausting, sealing and processing said second envelope to provide a second display-reading section.