US 3788892 A
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Description (OCR text may contain errors)
1974 J. A. VAN RAALTE EI'AL 3,788,892
METHOD OF PRODUCING A WINDOW IIEVTCF] 2 Sheets-Sheet 1 Filed May 1. 1970 1 \K [51. H5 Victor Christiano & John A Vim Baa/[e ATTORNEY United States Patent O 3,788,892 METHOD OF PRODUCING A WINDOW DEVICE John A. van Raalte, Princeton, and Victor Christiano, Trenton, N.J., assignors to RCA Corporation Filed May 1, 1970, Ser. No. 33,699 Int. Cl. B29c 13/00, 17/08; H01j 33/04 US. Cl. 117-212 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention relates to a method for producing a window device and particularly to a method for producing an evacuated tube comprising a thin window element, such as a printing tube or particle detector, wherein the window element is permeable to particles, including electrons.
In the prior art, a device that includes a window element having the central region thereof (i.e., of the window element) unsupported, generally has been limited to a relativey narrow window element, particularly in the case where the device is evacuated. This is because the pressure differential between the interior of the device and its environment requires suflicient structural strength to avoid breakage, buckling, etc., of the window element, the relatively narrow dimension of the window element enabling the achievement of sufiicient support at the peripheral regions thereof.
The prior art has disclosed a window structure wherein a reinforcing mesh is used with the window element to provide strength and support thereto, thereby allowing the window element to be made to relatively wide dimensions and relatively small thicknesses, the latter being an important consideration where electron-permeability of the window is desired.
In the prior art, such window devices, including both those that do and those that do not include such a reinforcing structure, are made by producing the window element separately from the envelope that is to be used in the device and subsequently sealing the window element on the envelope. Such sealing is often done by, for example, frit-sealing, soldering, or otherwise thermallybonding the window element to the envelope, or by utilizing a sealant that does not require the application of heat.
Where frit-sealing or other thermal bonding is used, there is often encountered the problem of heat damage to the window element, particularly in those more prevalent cases where the window element is relatively thin and small in area size so that there is a low heat capacity. Where there is used a sealant that does not require the application of heat, there is often encountered the problem of volatile materials in the sealant, the presence of which volatile materials requires special procedures (e.g., baking) for their removal in order to minimize their contaminating the subsequently evacuated device. However, such sealants (and, for that matter, solders) limit the processing temperatures (e.g., bake out) that can :be employed. Also, where such window elements are separately prepared and subsequently mounted on the en- 8,788,892 Patented Jan. 29, 1974 velope, there often arises the problem of damage to the relatively fragile window element arising from the handling thereof.
In another method in the prior art, electron-permeable window elements are provided to an envelope at an opening in the wall of the latter, by means of: a plate that is boltable to the envelope; a gasket; and an apertured disk. The plate receives the gasket and the disk and all of these co-act with the tube to retain a metal foil in place over the opening in the tube and, thereby, provide a mechanical seal. Such an arrangement is not completely satisfactory, however, because of the possibility of air leakage through the mechanical seal.
Also known in the prior art are electrostatic printing tubes wherein the opening in the envelope is closed by an overlying window element of electrically insulating material that is impervious to electrons. An electron beam is caused to scan a surface of the window element to deposit an electron charge pattern thereon. The charge pattern acts on the outside environment of the tube in a well-known manner for the recording of the information embodied in the charge pattern.
SUMMARY OF THE INVENTION The invention is a novel method of producing a window device that includes a housing portion having an opening in the wall thereof, which method comprises substantially closing the opening by means of a rigid temporary support film; producing a layer of solid window material over the temporary film by molecular deposition, the layer having peripheral regions that extend beyond the edges of the temporary film and bond directly to a surface of the housing portion surrounding the temporary film; and removing the temporary film. The layer of window material comprises a window element of the device.
In one embodiment of this invention, the temporary film is produced on a surface of the housing, or envelope portion, such that the temporary film substantially completely closes the opening.
The temporary film can be produced directly on the envelope portion, or produced separate from the envelope portion and disposed thereon. The temporary film preferably is removable by dissolution.
In further embodiments of this invention, the window device can further comprise a foraminous reinforcing member for further supporting the window element. The reinforcing member can be located at either that surface of the window element that faces the interior of the device or that surface that faces the exterior of the device.
Among its advantages, the present invention permits the manufacture of window devices without the need for bonding the window element to the envelope portion thereof by thermal methods or by the use of sealants therewith. Also, the invention substantially eliminates the need for handling the device window (that includes the window element with or without a reinforcing member), and, thereby, eliminates the possibility of damage thereto from such handling. The elimination of handling reduces the necessity that the window element be relatively thick for structural strength, thereby allowing the achievement of thinner window elements.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial sectional view, along line 1-1 of FIG. 2, of a thin window tube of a type producible according to the present invention.
FIG. 2 is an elevation end view of the faceplate portion of the tube in FIG. 1.
FIG. 3 is a partial axial sectional view along line 3-3 of FIG. 4, of a thin window tube of the type producible according to one embodiment of this invention, at an intermediate processing step.
FIG. 4 is a partially cut-away elevation end view of the tube in FIG. 3.
FIG. 5 is a partial axial sectional view along line 55 of FIG. 6, of a thin window tube of the type producible according to another embodiment of this invention, at an intermediate processing step, the window tube comprising a reinforcing member.
FIG. 6 is a partially cut-away end view of the tube in FIG. 5.
FIG. 7 is a partial axial sectional elevation view along line 7--7 of FIG. 8, of a thin window tube of the type producible according to another embodiment of this invention, at an intermediate processing step, the window tube comprising a reinforcing member.
FIG. 8 is a partially cut-away elevation end view of the tube in FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate an evacuated thin-window, electron-printing tube 10 that includes: an envelope portion 12 that is made of glass, metal or some other vacuumtight material and includes an opening 14 in the wall thereof in the form of a relatively narrow slit; an electron-permeable window element 16 that completely closes the opening 14 and is bonded to the envelope portion 12; an electron source, such as an electrically heated filament 18; a beam-modulating electrode 20; electron accelerating means and electron beam-shaping means (not shown); and electron beam-deflecting means, such as electrostatic plates 22 or magnets (not shown). No electrical wires are shown for simplicity. The envelope portion 12 usually comprises two parts, a faceplate portion 24 (which contains the opening 14) and a funnel portion 26, that are connected in well-known manner. Such electron-printing tubes and their mode of operation are well known in the art. Briefly, the window element 16 (sometimes referred to, in the prior art, as a Lenard window) has the peripheral regions 28 thereof bonded to the areas of the outer surface 30 of the faceplate portion 24, which areas are adjacent to and surround the opening 14. These areas of the outer surface 30 provide support to the window element 16, the window elements peripheral regions 28 and these areas of the surface 30 provide a vacuum-tight seal.
In the production of the thin-window tube 10 (FIGS. 1 and 2) according to this invention, a temporary support film 32 (FIG. 3) is produced at the exterior surface 30 of the faceplate portion 24 so that the temporary film 32 completely closes the opening 14 in the wall of the faceplate portion 24 and has peripheral areas 34 thereof disposed on those areas of the exterior surface 30 that surround the opening 14. Identical numbers in FIGS. 1 through 4 indicate corresponding parts. The temporary film 32 should comprise a material that is relatively rigid, such as a cellulosic material. The temporary film 32 can be produced by bringing the surface 30 of the faceplate portion 24 in contact with the film material that is in a liquid condition so as to form a solid film on the exterior surface 30, or by producing the temporary film 32 separately from the faceplate portion 24 and thereafter disposing the temporary film on the exterior surface 30 of the faceplate portion 24. Where the temporary film is produced by contacting the faceplate portion to the liquid film material, it is preferred that the film material exhibit a relatively high level of surface tension so as to facilitate the production of the temporary film. Where it is produced separately from the faceplate portion, the temporary film may be attached to the faceplate portion by means of a temporary adhesive, which preferably is removable with the temporary film, as by dissolution.
A layer of a suitable solid window material is then deposited on the temporary film 32, the layer providing the window element 16 having peripheral regions 28 that extend beyond the edges of the temporary film 32 by a substantial amount. The window element material may be a metal or a nonmetal, and can be produced by a molecular deposition process, such as evaporation, electroless deposition, sputtering, electrolytic deposition (including electrophoresis), or some other suitable process. The rigid film 32 thus serves as a temporary support, for part of the window material during deposition thereof. The peripheral regions 28 of the window element 16 extend beyond the temporary film 32 and are bonded directly to a portion of the surface 30 of the faceplate portion 24 surrounding the temporary film so as to provide a vacuum-tight seal. The production of the window element 16 in this way allows the bonding thereof to the surface 30 without necessity for thermal-bonding or for the use of sealants therewith.
After deposition of the window material, the temporary film 32 is removed to leave the window element 16 covering the opening 14 in the faceplate portion. It is preferred that the temporary film material be readily soluble and that the removal thereof be done by dissolution in a suitable solvent (e.g., acetone or water).
The faceplate portion 24 and the funnel portion 26 are then joined and the parts (18 through 22) for producing and controlling the electron beam 29 are provided within the envelope portion 12, which is thereafter evacuated. Where it is desired, the funnel portion 26 and the faceplate portion 24 may be joined before the temporary layer and window element are produced. The electron-permeable window element 16 may comprise, for example, a foil (e.g., about one-half micron thick) of aluminum or nickel, or a layer of insulating material (e.g., glass).
In the electron-permeable thin window printing tube, electrons penetrate the thin window and act directly on a suitable recording medium in a manner known in the art. A thin-window tube such as that in FIG. 1 can be modified to produce a light-printing thin window tube that allows printing on a photosensitive medium. Such a modification includes producing a phosphor layer (not shown) on the interior surface of the window element (or, where the window element is electron permeable, producing the phosphor layer on the exterior surface thereof) production of such phosphor layers being well known. In the case where the phosphor layer is on the interior surface thereof, the window element should comprise a light transmitting material (e.g., glass). In addition to the electron-penetrable, thin-window printing tube, both electrostatic-printing and light-printing thin-window tubes (as well as tubes of all of these types that are used for purposes other than printing or recording) and particle detectors, for example, are producible by and intended to be within the scope of the present invention.
The term window device is defined to include, but not limited to, particle detectors and all of these thinwindow tubes, both with and without a reinforcing member that is discussed below. Also, the figures herein are not drawn to scale or proportion.
In an alternative embodiment shown in FIGS. 5 and 6, a thin-window tube 50 includes a foraminous rigid reinforcing member 52 of a suitable material in contact with the window element 54 thereof, the reinforcing member 52 providing structural support for the window element 54. The reinforcing member 52 may be of a metallic or nonmetallic material (e.g., aluminum or glass) and may be of a matrix or grid configuration, for example. The material comprising the reinforcing member 52 may be the same as or different from that of the window element 54. According to this invention, the reinforcing member 52 and the window element 54 of the thin-window tube 50 are produced on the envelope portion 56 of the tube by steps that include: producing a rigid temporar film 58 on the surface 60 of the faceplate portion 62 of the envelope portion 56 in the manner described above, the temporary film 58 completely closing the opening 64 of the faceplate portion; producing a continuous layer (not shown) of reinforcing material on the temporary film 58, this layer of reinforcing material having peripheral regions that extend beyond the edges of the temporary film 58 and that are located on the surface 60 of the faceplate portion 62; and removing portions of the continuous layer of reinforcing materail to produce a plurality of apertures 66 therein, at least a portion of which apertures 66 coincide with the opening 64 in the faceplate portion. The resulting structure is the reinforcing member 52, having peripheral regions 67 thereof disposed on the surface 60. The continuous layer of reinforcing material may be produced by sputtering, evaporation, or other suitable means. The removal of the portions of the continuous layer of reinforcing material is done, for example, by: providing a resist pattern (not shown) of, photosensitive material (e.g., a positive resist such as Shipley resist) on the continuous layer, which resist pattern is of substantially the same configuration as the desired reinforcing member and includes a plurality of holes, corresponding to the apertures 66 in the reinforcing member 52, that extend through the resist pattern to the continuous layer, and, thereafter, etching away (e.g., with HCl where the layer comprises aluminum) the portions of the continuous layer of reinforcing material which are accessible through the holes of the resist pattern, to form the apertures 66. The provision of such a resist pattern is well known in the art. Subsequently, the resist pattern is removed. The apertures 66 in the reinforcing member 52 are then closed, for example, by temporarily filling them with a removable solid material, such as Shipley photoresist (not shown), or by producing thereover a second temporary film (not shown) in the manner by which the temporary film 58 was previously produced (it is, however, preferred that the exterior major surface 68 of the reinforcing layer 52 not be covered so that the window element can later be produced directly thereon). A continuous layer of solid window material is then deposited (e.g., by sputtering, evaporation, etc.) over the reinforcing member 52 and the material closing the apertures 66, this layer of window material comprising the window element 54. The peripheral regions 70 of the window element extend beyond the reinforcing layer 52 and bond directly to a surface of the faceplate portion 62 surrounding that layer to provide a vacuum-tight seal. Thereafter, the temporary film 58 and the removable material filling the apertures 66 in the reinforcing member 52 are completely removed (e.g., by dissolution in a suitable reagent).
Alternatively, to produce the reinforcing member, a resist pattern (not shown) that is the photographic negative of the desired reinforcing member 52 is produced directly on the temporary film 58, and the reinforcing material is deposited through the open portion of the resist pattern on the accessible area of the temporary film 58 and the surface 60. In this example, the photographic negative would be a pattern of spaced squire dots corresponding to the square apertures 66. It is preferred that the reinforcing material not be deposited on the exposed surface of the resist pattern, this being achievable, for example, by providing an electroless deposition-initiatingmaterial on the areas of the temporary film that are accessible through the resist pattern but not on the resist pattern surface and depositing the reinforcing material by electroless deposition. The continuous layer 54 of solid window material is produced, as above, on the reinforcing member 52 and on the resist pattern, after which the resist pattern and temporary film 58 are removed. It is preferred that the resist pattern material be selected such that it can be removed simultaneously with the temporary film 58. The production of the reinforcing member 52 and the window element 54 in either of these above-mentioned ways allows their bonding to the envelope portion, and with respect to the window element, permits the achievement of a vacuum-tight seal to the envelope portion, without the need for thermal bonding or sealants.
In another thin-window tube 80, shown in FIGS. 7 and 8, a reinforcing layer 82 is located on the surface 84 of the window element 86, which surface 84 is located outside of the tube envelope. Such a tube is producible according to this invention by a method which includes the steps of: producing a rigid temporary film on the surface 92 of faceplate portion 94 of the envelope portion 88 so as to completely close the opening 96 in the wall thereof, the peripheral areas 95 of the temporary film 90 being disposed on the parts of the surface 92 that are adjacent to the opening 96; and producing a layer of solid window material on the temporary film 90, which layer comprises the window element 86 (as in FIG. 3). The peripheral regions 97 of the window element 86 extend beyond the edge of the temporary film 90 and bond directly to a portion of the surface 92 of the envelope portion 88 surrounding the temporary film to provide a vacuum-tight seal. The reinforcing layer 82 is then produced on the exterior surface 84 of the window layer 86 by producing a continuous layer (not shown) of reinforcing material on this surface 84 and subsequently selectively removing portions of this layer of reinforcing material (by, for example, the photoresist-etch methods referred to above, using a resist pattern having the same configuration as the desired reinforcing member) to produce the apertures 98 therein. The resulting reinforcing member 82 has the peripheral regions 99 thereof extending beyond the edges of the window element 86 and bonded to the surface 92 of the envelope portion 88. Alternatively, the reinforcing member 82 can be made by producing on the exterior surface 84 of the window layer 86 an apertured resist pattern (not shown) having a configuration that is the photographic negative of the desired reinforcing members configuration (i.e., the dots in the resist pattern have substantially the configuration and location as the aperture 98 of the desired reinforcing member), and deposition the reinforcing material on those areas of the window layer surface 84 which are accessible through the open portion in the resist pattern, as well as on the surface 92 of the envelope portion 94.
What is claimed is:
1. A method of producing a window device that includes an envelope portion having an opening in a wall area thereof, said method comprising:
(a) providing a rigid soluble temporary support film and attaching it to the surface of said envelope portion such that said opening is completely closed thereby;
(b) molecurlarly depositing a rigid reinforcing metal or glass layer on said temporary film with peripheral regions thereof extending beyond said film and uniting with said envelope, forming a plurality of apertures through the reinforcing layer without disturbing the temporary film and which coincide with said opening in said wall of said envelope portion; and filling said apertures with solid material removable by dissolution.
(c) depositing a metal or glass layer on said reinforcing layer by molecular deposition to form a solid window member, said layer having peripheral regions thereof extending beyond the edges of said reinforcing layer, said peripheral regions being bonded directly to a portion of said envelope surface surrounding said reinforcing layer, at least a portion of said window member coinciding with said filled apertures; and
(d) then removing said temporary film and solid material in said apertures by dissolution.
2. The method defined in claim 1, wherein the apertures in said reinforcing layer are produced by the steps comprising:
(a) selectively applying to the upper surface of said reinforcing layer a positive resist in the form of a pattern having a plurality of holes extending through said resist pattern to said reinforcing layer, said holes being coincident with said opening in said wall of said envelope portion;
(b) then removing by dissolution through said holes parts of said reinforcing layer so as to produce said apertures therein; and
(c) then removing said remaining positive resist pattern.
3. A method of producing a window device that in cludes an envelope portion having an opening in a wall area thereof, said method comprising:
(a) providing a rigid soluble temporary support film and attaching it to the surface of said envelope portion such that said opening is completely closed thereby;
(b) depositing a metal or glass layer on said temporary film by molecular deposition to form a solid window member, the peripheral regions of said layer extending beyond the edges of said film and bonded to a portion of said envelope portion surrounding said temporary film;
(c) molecularly depositing a rigid metal or glass reinforcing layer on said window member, and forming a plurality of apertures extending therethrough and coincident with said opening in said wall of said envelope portion; and
(d) removing said temporary film by dissolution.
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FOREIGN PATENTS 103,071 1/ 1938 Australia 2643 17 OTHER REFERENCES Smith, Emerson C.: Glossary of Communications, Chicago, 1 11., Telephony Publishing Co., 1971, p. 379.
PHHsIP ANDERSON, Primary Examiner US. Cl. X.R.