US3858080A

US3858080A - Target assemblies especially for single chamber deformographic storage display tubes

Info

Publication number: US3858080A
Application number: US00398288A
Authority: US
Inventors: R Wohl
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1973-09-17
Filing date: 1973-09-17
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31

Abstract

Higher resolution and increased recording speeds are attained in a Deformographic Storage Display Tube (DSDT) having a layered target assembly with at least one layer providing higher conductivity and greater optical transmissivity or reflectivity as required. A simple structure of a DSDT comprises compatible target and electron gun assemblies arranged in a common envelope affording longer life by permitting a higher temperature bakeout process. In one embodiment, the target assembly comprises but a transparent, conductive coating of stannous oxide, for example, on the inner surface of the faceplate and a deformographic member laid down over the coating. The film preferably is one of silicone rubber, a gel, liquid crystal, or the like. With a low vapor pressure and a reasonably high resistance, the material will not deteriorate under electron beam bombardment from a compatible electron gun assembly having a cathode of lanthanum hexaboride or like material. In another embodiment, a more conventional electron gun assembly such as one having an oxidecoated cathode, is used with barrier layer comprising a protecting film over the deformographic member. The protecting film is one which is capable of deforming with the deformographic member and transmit or reflect light as required in the overall system. In such arrangements, the tube is baked out under vacuum with the faceplate of the tube immersed in a chilling bath. Another barrier layer is alternatively interposed between the deformographic member and another layer for preventing migration of metallic ions through the target assembly and thereby increasing the effective life of the DSDT.

Description

United States Patent [191 Wohl [451 Dec. 31, 1974 TARGET ASSEMBLIES ESPECIALLY FOR SINGLE CHAMBER DEF ORMOGRAPHIC STORAGE DISPLAY TUBES [75] Inventor: Robert James Wohl, San Jose, Calif.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

22 Filed: Sept. 17, 1973 21 Appl. No: 398,288

Primary Examiner-Paul L. Gensler Attorney, Agent, or Firm-George E. Rousch [57] ABSTRACT Higher resolution and increased recording speeds are attained in a Deformographic Storage Display Tube (DSDT) having a layered target assembly with at least one layer providing higher conductivity and greater optical transmissivity or reflectivity as required. A simple structure of a DSDT comprises compatible target and electron gun assemblies arranged in a common envelope affording longer life by permitting a higher temperature bakeout process. In one embodiment, the target assembly comprises but a transparent, conductive coating of stannous oxide, for example, on the inner surface of the faceplate and a deformographic member laid down over the coating. The film preferably is one of silicone rubber, a gel, liquid crysta], or the like. With a low vapor pressure and a reasonably high resistance, the material will not deteriorate under electron beam bombardment from a compatible electron gun assembly having a cathode of lanthanum hexaboride or like material. 1n another embodiment, a more conventional electron gun assembly such as one having an oxide-coated cathode, is used with barrier layer comprising a protecting film over the deformographic member. The protecting film is one which is capable of deforming with the deformographic member and transmit or reflect light as required in the overall system. In such arrangements, the tube is baked out under vacuum with the faceplate of the tube immersed in a chilling bath. Another barrier layer is alternatively interposed between the deformographic member and another layer for preventing migration of metallic ions through the target assembly and thereby increasing the effective life of the DSDT.

TARGET ASSEMBLIES ESPECIALLY FOR SINGLE CHAMBER DEFORMOGRAPHIC STORAGE DISPLAY TUBES DESCRIPTION OF THE INVENTION The invention relates to deformographic storage display tubes and target assemblies therefor, intended for use in deformographic display systems and the like.

Heretofore, in prior art deformographic display systems, the display tube comprised two separately evacuated chambers with a target assembly in one chamber apart from an electron gun assembly arranged in the other chamber. Embodiments of such systems are found in U.S. Pat. Nos. 3,626,084, issued on the 7th day of Dec., 1971, to Robert J. Wohl et al. for Deformographic Storage Display Tube and 3,676,588 issued on the 11th day of July 1972, to Eugene T. Kozol and Robert J. Wohl for Deformographie Target Assembly with Integral Conductive Member.

To date, a single envelope deformographic storage display tube (DSDT) has not been practicable despite the fact that a single envelope tube would greatly simplify construction and result in a tube having longer life time because high temperature vacuum baking processes can be employed in the fabrication. Additionally, the electron charges can be laid down essentially on the surface where the deformation is required, which object would lead to higher resolution and to a faster recording speed.

The invention, in and of itself, centers about the structural arrangements of target and electron gun assemblies for preventing contamination of the cathode, for minimizing further polymerization of the deformo graphic member, and for ultimately enhancing the overall operation of the DSDT.

Display tubes and subassemblies thereof are well known. Examples of this prior art pertinent to the invention are to be found in the following US. Pat. Nos:

2,661,437 12/1953 Beckers 313-71 2,755,404 7/1956 Levy 313-91 2,843,798 7/1958 Hook 315-12 2,943,147 6/1960 Glenn 173-75 3,001,447 9/1961 Ploke 88-6] 3,125,634 3/1964 Murray et a1 l78-7.5 3,125,635 3/1964 Murray et 211 178-75 3,125,636 3/1964 Klebe l78-7.5 3,125,637 3/1964 Klebe l78-7.5 3 148,281 9/1964 Fyler 250-217 3,233,040 2/1966 Crane 178-75 3,238,296 3/1966 Nelson et a1 178-75 3,240,987 3/1966 Hicks 315-86 3.270.133 3/1966 Holub 178-187 3,284,661 11/1966 Rosendahl 315- 3 385,927 5/1968 Hamann 178-7.5 3 429,996 2/1967 Graser et a1 l787.5 3,449,112 3/1970 l'leilmeier et a1 178-7.7 3,517,126 6/1970 Yamada et 211 178-75 3,538,251 11/1970 Gear 178-7.87 3,539,862 11/1970 Kazan 315-169 3,667,830 6/1972 Rottmiller 350-161 and in a published Japanese Patent Application No. 17818/70.

The above-listed patents to Beckers, Levy, Hook, Fyler and Yamada are directed to constructional details of display tubes similar only in some respects to those of the display tube of the invention. Those patents to Hicks, Rosendahl, Graser, I-Ieilmeier, Kazan and the Japanese patent application are likewise directed to construction details but more specifically to what might be termed the target assemblies of display tubes similar in construction but different from that of the display tube according to the invention. More particularly, the patents to Glenn, Ploke, Crane, Nelson et a1, Gear, and Rottmiller are directed to deformographic or similar types of projection systems and represent the closest art of which the applicant is aware. The remaining patents to Holub, Murray et a1, Klebe, and Hamann are directed to the composition of a deformable medium for such display tubes but the media do not comprise the cooperating layers of materials to be described hereinafter.

According to the invention, the objects hereinbefore indirectly mentioned and those that will appear as the specification progresses are attained in deformographic storage display tubes having envelopes enclosing target and electron gun assemblies arranged in various ways for preventing contamination of the cathode, further polymerization of the deformographic member of the target assembly and enhancing the overall operation of the systems. In one embodiment of the DSDT, the target assembly comprises a conducting layer of stannous oxide applied to the inner surface of the faceplate of the tube and a deformographic member laid down over the coating. The deformographic member preferably is one of silicone rubber, a suitable gel, a liquid crystal or the like. The material is chosen from those having low vapor pressure, low modulus of elasticity, low damping, reasonably high resistance, and high stability so that the material will not deteriorate under electron beam bombardment. A silicone rubber deformographic member is made in a cross-linking process (or a process completed) by means of high-density, high-energy radiation. The elastomer, after this treatment, is fairly resistant to the low-energy exposure received from electron beams. Preferably relatively low voltage beams are used in the tube operation for this reason. A thousand volt beam is sufficient for most applications. An electron gun having a cathode element compatible with the deformographic member completes one embodiment of the invention. Lanthanum hexaboride, matrix, and impregnated cathodes are satisfactorily compatible with the materials hereinbefore mentioned. In other embodiments, the more conventional oxide-coated cathode elements may be used in electron-gun assem blies, and the deformographic member is protected with a thin polymer or like sealing film laid over the deformographic member. The protective film is one which is capable of compatibly deforming with the deformographic member. The layered structures of target assemblies according to the invention are further improved in some embodiments by the interposition of a barrier layer in the form ofa film of VAC SEAL (registered trademark of the General Electric Company) or polyvinyl formal interposed between those structural layers between which the migration of metallic ions and the like would prove deleterious. This barrier layer also protects the cathode from poisoning and increases the conductivity, optical quality and strength of films which are to be evaporated on (or adjacent to) the deformographic member, as well as reducing the deterioration of the deformographic member from electron bombardment.

In order that full advantage of the invention may obtain in practice, preferred embodiments thereof, given by way of example only, are described in detail hereinafter with reference to the accompanying drawing, forming a part of this specification and in which:

FIG. 1 is a schematic cross-sectional diagram of one embodiment of deformographic storage display tube according to the invention; and

FIG. 2 is a schematic cross-sectional diagram of another embodiment of a DSDT according to the invention.

One embodiment of a deformographic storage display tube (DSDT) according to the invention is illustrated schematically by a cross-section diagram in FIG. 1. The tube comprises an envelope 10, shown here as one completely closed glass structure capable of being evacuated to a high degree, having a planar face plate portion 12, an optical window portion 14, and two neck portions in which electron gun assemblies 16 and 18 are arranged. A structure 20, referred to hereinafter as a target assembly 20, is mounted within the envelope to divide the tube into two vacuum-tight chambers. Part of the target assembly comprises a nonconducting substrate 22, frequently made of mica. Electrons from the

electron guns

16 and 18 impinge on the substrate 22 establishing electron charges thereon. The electron gun 16 is generally arranged to flood the substrate 22 with a uniform electron charge, which in effect erases any distinction between adjacent charges, that is, erases any electron charge pattern previously established. The electron gun assembly 18 is arranged to produce a narrow beam of electrons of intensity dependent upon an information signal applied in conventional form whereby an electron charge pattern is established on the substrate 22; Conventional electron beam deflection systems are applicable.

Full information for the understanding of the construction and operation of this dual chamber tube as thus far described will be found in US. Pat. Nos. 3,626,084 and Wohl, Hawn, and Medley and 3,676,588 of Wohl and Kozol, to a paper on A New Storage and Display Tube Employing Schlieren Optics presented at the 13th Annual Technical Symposium of the S.P.I.E. in 1968 by Robert J. Wohl and Robert M. Ross as recorded in the Proceedings at pages 95-l0l, and to an article entitled A Practical Display Projection Tube by Arthur Sansom and Eugene T. Kozol published in Data Communications Design magazine for May and June of 1972, pages 20, 21, and 25.

A target assembly 20 according to the invention comprises a dielectric substrate 22, such as a mica-disk or a KAPTON (registered trademark of E. I. Dupont de Nemours and Company) membrane onto which electron beams impinge on one side thereof. On the other side of the substrate 22 remote from the electron beam, there is an electrostatically deformable solid deformographic (DFG) member 24, of a silicone polymer material, for example. This deformable member 24 remains substantially flat at the side which is in contact with the substrate 22. The other side of the deformable member 24 will be increased or decreased in thickness in accordance with the relative strength of the electrostatic field resulting from the electron charge pattern established on the substrate 22 by the electron beam modulated in accordance with the information to be displayed. A thin barrier layer 26, of VAC SEAL or polyvinyl formal, such as FORMVAR (registered trademark of Shawinigan Products Corp.) SIS-95, or other compatibly deformable material is laid over the'deformable solid member 24 between the latter and a conductive film 28, forming a ground plane for the DSDT. The film 28 preferably is gold, silver or aluminum, but may be any other suitable conductor readily deposited by an evaporative or sputtering process, or the like. The inner surface of the faceplate portion 12 of the envelope 10 is coated with a transparent conducting film 30, such as a thin layer of aluminum or stannous oxide, for example, of the type known NESA (registered trademark of Pittsburgh Plate Glass Co.) coating which is optically transparent. The conducting film 28 and the conducting coating 30 are electrically connected to a connector pin 32. A conductive fillet 34 of a conventional conducting paste or epoxy establishes a low impedance connection to the conducting

films

28 and 30. In this embodiment, the film 30 can be omitted as the better performance is obtained with the conducting film 28 laid down as an integral part of the target assembly 20. However, the film 30 on the faceplate reduces potential electrostatic charging that may adversely affect the display.

This target assembly 20 provides higher conductivity and greater optical transmissivity for transmission type DSDT systems and better reflectivity for reflective type DSDT systems. The over-write protection (that is, the ability to withstand higher charge densities without cracking and/or crazing) is better by a factor of five to ten. The conductivity of the conducting film 28 is increased over that of a conductor of the same thickness. The barrier layer 26 improves the uniformity, reflectivity, and optical features of reflecting systems, for example, employing aluminum of sufficient thickness as to be highly reflective. Used in transmissive tubes, thinner aluminum films are of higher transmission and greater uniformity than those prepared without the barrier layer. The barrier layer 26 also prevents the migration of metallic ions through the deformable member 24 and thereby intends to increase the effective life of the target assembly 20.

A principle reason for the dual chamber DSDT structure is that it represents a simple arrangement for preventing poisoning of the cathodes of the electron guns 16 and/or 18 by vapors that would be released from the deformographic member 24. This emanation is even more contaminating if the electron beams impinge directly onto the DFG member 24.

According to the invention, a single chamber DSDT may be realized in a form which will afford increased resolution and writing speed, as compared to the prior art DSDT. This tube comprises an envelope 10, shown in FIG. 2 as being entirely of glass, although any conventional high vacuum tube envelope construction will be readily employed by those skilled in the art. A substantially planar faceplate portion 12' is formed at one end of the tube and a neck portion at the other end of the tube contains an electron gun assembly 38. The electron gun assembly 38 is chosen from the many conventional electron guns available; those skilled in the art will select an electron gun for the purpose at hand and, of course, may use separate discharging and charging electron guns as the application indicates. A conducting (NESA glass) coating 30' is electrically connected to an electric wire connector 32' shown here more or less as a snap type connector which is conventional in all respects. An electrostatically deformable solid member 24' is arranged in the forepart of the tube against the conducting coating 30. The latter coating 30' acts as the ground plane electrode against which the charge pattern on the deformed surface of the deformable member 24 reacts. This tube has the desirable configuration of that tube of FIG. 1 wherein the charge deposited by an electron beam is attracted to the electrostatic image in the conductive coating just a few thousandths of an inch away. Thus, the force causing the elastomer to deform is the simple coulomb force which yields larger deformations and higher resolution than in the original DSDT configuration of U.S. Pat. No. 3,626,084. This tube, according to the invention, is fully operative with only the conducting film 30 (on a suitable substrate such as the glass faceplate 12') and the deformable solid member 24'. In order to yield any life, however, the oxidecoated cathode of the electron gun 38 must be protected against vapors from the material in the deformable member 24. The deformable member 24 may be a silicone rubber, a gel, a liquid crystal or the like as in the earlier described arrangements. However, comparatively non-poisonable cathode materials are known. One such material is the previously mentioned lanthanum hexaboride. Matrix and impregnated type cathodes of this material have been tried and found satisfactory as have filaments coated with tungsten thorium zirconium. The latter have been operated in high vacuum tubes for 3,000 hours at l,550 Centigrade without the slightest sign of deterioration while yielding an electron emission exceeding 2 amperes per square centimeter, a figure which is better than that normally expected from an oxide-coated cathode.

By adding a barrier layer 26' (as the uppermost layer) over the deformographic member 24, an oxidecoated cathode can also be used. The barrier layer 26 may be composed of one of many available polymer films such as PARYLENE (registered trademark of the Bakelite Company, a subsidiary of the Union Carbide Company), Formvar, or inorganic films such as silicon dioxide. Such a sealing coating or barrier layer is readily evaporated in place or formed elsewhere and floated into place by conventional methods used in electron microscopy, for example. The barrier layer is used primarily for preventing poisoning of the oxidecoated cathode or a cathode that shares the evacuated envelope. The normal vapor from the elastomer and/or the vapor produced by electron bombardment of the elastomer can be expected to poison oxide-coated cathodes.

Electron bombardment affects elastomers in several ways. The bombardment is expected to further crosslink the constituents of the elastomer and stiffen it with the passage of time until it loses the desired elasticity and/or the desired optical transparency. Thus, the protection of the elastomer from such bombardment is another advantage of the barrier layer.

If the tube is meant to be used in the transmissive mode, the foregoing description is sufficient. However,

terference phenomenon. ln the event that the resistivity of the uppermost layer is undesirable, a final layer 40 is added. For maximum storage time the resistivity should be of the order of 10 10 ohm centimeters. For rapidly varying displays, such as motion pictures, a value of the order of 10 ohm centimeters is desirable.

DSDT according to the invention, are contemplated with deformographic material having equilibrium vapor pressure of the order of 10 or 10 Torr. Cer tainly, if the vapor pressure exceeds 10 Torr, the tube would probably break down under high voltage. Other than using a barrier film (or even in conjunction with one), the following techniques are of value: crustal curing of the deformographic material by chemical means, by electron bombardment, or by other actinic radiation should seal the surface to prevent loss of lower molecular-weight fractions. It is contemplated that in some instances the dielectric mirror 42 itself may provide the scaling function. A prolonged bakeout of the deformographic material, perhaps at relatively elevated temperature may be used to drive off the high vapor-pressure components prior to final processing of the vacuum tube.

It is highly desirable to vacuum-bake electron tubes at elevated temperatures for several hours before seal-' ing. Temperatures of the order of 400 Centigrade are common for high vacuum tubes such as cathode ray tubes and the like. Because the configuration of the envelope 10' is that of standard cathode ray tubes, it is contemplated that this configuration of DSDT be fabricated on essentially standard cathode-ray tube production lines. During final processing, the faceplate portion 12 and the target assembly 20 can be maintained at temperatures of to Centigrade by immersing the faceplate of the tube in a chilling bath, being careful to keep the stresses in the glass envelope below the critical value, while the remainder of the tube is vacuum-baked at a conventional temperature of 400 Centigrade.

While the invention has been shown and described, particularly with reference to preferred embodiments thereof, and various alternative structures have been suggested, it should be clearly undersood that those skilled in the art will effect further changes without departing from the spirit and the scope of the invention as defined hereinafter.

The invention claimed is:

l. A deformographic storage display tube having:

an evacuated electron tube envelope having a trans parent faceplate portion, and an electron gun arranged within said envelope at a location permitting the beam of electrons emanating from the electron gun to impinge on said faceplate portion, and comprising a target assembly arranged at the inner surface of said faceplate portion of said envelope and including:

a transparent conductive film deposited on the inner surface of said faceplate portion of said envelope;

an electrostatically deformable solid member arranged over said conductive film; and

a compatibly deformable photoreactive layer arranged on said deformable member.

2. A deformographic storage display tube as defined in claim 1, and wherein said conducting film comprises a transparent conductive coating of stannous oxide. 3. A deformographic storage display tube as defined in claim 1, and wherein said electron gun assembly comprises an electron emitting cathode of a metal oxide. 4. A deformographic storage display tube as defined in claim 1, and wherein said target assembly is made of materials which render the vaporization from the deformographic member into said envelope substantially noncontaminating to the cathode of said electron gun assembly. 5. A deformographic storage display tube as defined in claim 1, and wherein said electron gun assembly comprises an electron emitting cathode of lanthanum hexaboride. 6. A deformographic storage display tube as defined in claim 1, and wherein said electron gun assembly comprises an electron emitting cathode of tungsten thorium zirconium. 7. A deformographic storage display tube as defined in claim 1, and incorporating a compatibly deformable barrier layer laid over said deformable solid member on the side nearest said electron gun assembly.

8. A deformographic storage display tube as defined in claim 7, and wherein said compatibly deformable barrier layer is a silicone polymer film.

9. A deformographic storage display tube as defined in claim 7, and wherein said barrier layer comprises polyvinyl formal.

10. A deformographic storage display tube as defined in claim 1, and wherein said photoreactive layer is phototransmissive.

11. A deformographic storage display tube as defined in claim 1, wherein said photoreactive layer is photoreflective.

12. A deformographic storage display tube as defined in claim 11, and wherein said envelope comprises a single chamber in which said target assembly and said electron gun assembly are arranged in common.

Claims

1. A deformographic storage display tube having: an evacuated electron tube envelope having a transparent faceplate portion, and an electron gun arranged within said envelope at a location permitting the beam of electrons emanating from the electron gun to impinge on said faceplate portion, and comprising a target assembly arranged at the inner surface of said faceplate portion of said envelope and including: a transparent conductive film deposited on the inner surface of said faceplate portion of said envelope; an electrostatically deformable solid member arranged over said conductive film; and a compatibly deformable photoreactive layer arranged on said deformable member.

2. A deformographic storage display tube as defined in claim 1, and wherein said conducting film comprises a transparent conductive coating of stannous oxide.

3. A deformographic storage display tube as defined in claim 1, and wherein said electron gun assembly comprises an electron emitting cathode of a metal oxide.

4. A deformographic storage display tube as defined in claim 1, and wherein said target assembly is made of materials which render the vaporization from the deformographic member into said envelope substantially non-contaminating to the cathode of said electron gun assembly.

5. A deformographic storage display tube as defined in claim 1, and wherein said electron gun assembly comprises an electron emitting cathode of lanthanum hexaboride.

6. A deformographic storage display tube as defined in claim 1, and wherein said electron gun assembly comprises an electron emitting cathode of tungsten thorium zirconium.

7. A deformographic storage display tube as defIned in claim 1, and incorporating a compatibly deformable barrier layer laid over said deformable solid member on the side nearest said electron gun assembly.