US 3321657 A
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Description (OCR text may contain errors)
y 1957 G A. GRANITSAS ETAL 3,321,657 UCTING ELECTROSTATIC PRI NTING CATHODE RAY TUBE WITH COND Filed Dec. 18, 1962.
WIRES IN FACE PLATE 3 Sheets-Sheet l INVENTO seams AGPANITSAS 4w; 5 FREDERICK :2. HAYS Tam ATTQRNEY May 23. 1 67 G. A. GRANITS AS ETAL 3,321,657
ELECTROSTATIC PRINTING CATHODE RAY TUBE WITH CONDUCTING WIRES IN FACE PLATE Filed Dec. 18, 1962 .'5 Sheets-Sheet 2 32 70 72 I 4 W l NW & 4 74 I INVENTORS cEoRcE AGRANITSAS y\ \i & meoemcx RHAYS "GRANITSAS ETAL NTING CATHODE RAY TUBE WITH May 23. 1967 3,321,657 CONDUCTING G. FRI
ELECTROSTATIC WI'RES IN FACE PLATE 5 Sheets-Sheet 3 Filed Dec. 18. 1962 h mm Y om E TGQ. m m VEUM ME A 0 Mn @F J 0 age/4 2 2 Y w w 6 w United States Patent 3,321,657 ELECTROSTATIC PRINTING CATHODE RAY TUBE WITH CONDUCTING WIRES IN FACE PLATE George A. Grauitsas, Marlboro, Mass., and Frederick R. Hays, Woodstock, Conn., assignors to American Optical Company, Southbridge, Mass., a voluntary association of Massachusetts Filed Dec. 18, 1962, Ser. No. 245,443 5 Claims. (Cl. 313-73) This invention relates to energy-conducting components and more particularly to plate-like energy-conducting structures for use in or in conjunction with cathode ray tubes or similar electronic devices and to a method of making same.
There is a class of electronic devices which requires a plate-like barrier between component parts or sections thereof capable of hermetically sealing the respective sections, one from the other, and/ or from the external surrounding atmosphere. In this class of electronic devices there are those (i.e. electrostatic printing cathode ray tubes and image energy converters) which must have individual electrical conductors extending through the barrier to electrically connect discrete areas on opposite surfaces thereof. In many instances, there is the further requirement that the electrical conductors lead to or from accurately located spaced zones or areas on one or both sides of .the plate-like barrier.
Since a barrier of the above-mentioned character must be vacuum tight and capable of withstanding high temperature processing during fabrication of the electronic device, a structure formed of spaced electrical conductors fused within a glass matrix has been found to be useful. However, since glass normally experiences plastic flow when heated to fusing temperatures, the achievement of accurate registry of energy-receiving or emitting ends of the conductors in the matrix material ordinarily presents a difiicult problem.
The present invention overcomes this problem and contemplates the provision of an improved energy-conducting plate-like structure wherein electrical energy to be transferred therethrough may be received or emitted at discrete accurately located zones or areas on a side of the structure.
Accordingly, an object of the present invention is to provide for isolation of one internal section of an electronic device from another internal section thereof or from an external atmosphere while providing for conduction of electrical energy from one of said sections to accurately located zones externally of the device or internally of another or adjacent section thereof.
Another object is to hermetically seal one section of an electronic device from another section thereof or from an atmosphere surrounding the device while providing for the transfer of electrical energy to or from prearranged accurately located zones or discrete areas within a respective one of said sections or externally of said device.
A further object is to provide a novel energy-conductive plate-like structure and method of making the same.
To attain the aforesaid objects and otherswhich may appear from the following description, we provide a platelike structure formed of a glass matrix incorporating a multiplicity of electrical conductors fused therein in individually spaced random arrangement. The conductors extend generally parallel to each other from one side of the structure toward the opposite side thereof. Certain selected conductors are terminated within the glass matrix material and electrically insulated from the opposite side of the structure. Other conductors extend completely through the structure to preselected accurately spaced zones on the opposide side thereof. The con- 3 ,321,657 Patented May 23, 1967 doctors in the random arrangement are sufficient in number and close enough together so that at least one conductor will lead to each respective zone on said opposite side of the structure.
In this type of construction, it can be seen that a platelike structure of glass, initially having a more or less random arrangement of electrical conductors fused therein, is rendered capable of receiving or transmitting electrical energy only at accurately located positions or zones on a side thereof.
When incorporated as the face plate of a cathode-ray tube such plate-like structures are particularly useful in xerographic printing where, for special purposes, only selected portions or incremental areas of a complete electron image are desired to be recorded.
In a cathode ray tube provided with a face plate of the character of this invention having accurately located electrically conductive zones disposed outwardly of the tube, the electron gun of the tube may be operated to form a complete electron image on the inner surface of the face plate while only selected portions or increments thereof will be transferred through the face plate and become accessible externally of the tube. A special paper such as is used in xerographic printing or other suitable means may be placed against or adjacent the outer surface of the face plate to receive and record its output.
Alternatively, in conjunction with such cathode ray tube face plates, suitable electrical conductors maybe connected to the accurately located zones and lead therefrom to further circuitry for exciting electronic means or the like in remotely located computing and/ or recording mechanisms for purposes of storing, recording or otherwise utilizing the output of the cathode ray tube.
The present invention will be more fully understood by reference to the following detailed description which is accompanied by drawings in which FIG. 1 illustrates, in elevation and partially in section, an embodiment of the present invention.
FIG. 2 illustrates, in front elevation, another embodiment of this invention while FIG. 3 illustrates, in section, still another embodiment of the invention.
4 of another embodiof making the structure of FIG. 5.
In the embodiment of the invention illustrated in FIG. 1, there is shown cathode ray tube 20 having face plate 22 functioning with the remainder of the envelope to hermetically seal internal section 24 of tube 20 from a surrounding atmosphere.
Face plate 22 comprises glass matrix 26 having a number of electrical conductors or wires 28 extending from inner surface 30 thereof toward outer surface 32.
In accordance with the invention, certain wires 28 or portions thereof are terminated internally of matrix 26 and electrically insulated from surface 32 while other wires extend completely through matrix 26'. Wires 28 which extend completely through matrix 26 are only those whose outer ends, or portions of their outer ends, coin cide with specific accurately located zones 34 on surface 32 which are intended to be electrical conductors whereby electrical energy produced internally of tube 20 is accessible at the exterior faces.
Thus, by operation of tube 20 in the conventional manner, a pattern of electrons from beam 35 may be imimage while only selected portions of the image will be electrically conducted through face plate 22 and acces sible at respective zones 34 on surface 32. The ends of wires 28 at respective zones 34 may be provided with electrically conducting heads 36.
In a manner of utilizing the output of tube 20 at zones 34, a recording medium 38 such as paper used in xerographic printing or the like may be placed adjacent surface 32 of face plate 22. In this way, substantially only portions of the medium 38 in registry with energy emissive zones 34 will become sensitized or otherwise affected by the electrical output of tube 20 to produce a recording of said output.
Alternatively, the electrical output of tube 20 at zones 34 may be fed to a recording and/ or computing mechanism 40, as shown diagrammatically in FIG. 2, by the provision of electrical conductors 42 leading from zones 34. Conductors 42 may be formed on side 32 of face plate 22 as a conventional printed circuit or the like each connected directly to the ends of wires 28 at one of the zones 34 or to a head 36 which might be provided at each zone 34.
Electrical conductors or leads 44 might be used to connect conductors 42 to mechanism 40.
The embodiment of the invention shown in FIG. 3 illustrates a structure 22 similar to face plate 22, described above, which is utilized as an energy-conductive barrier between two sections 46 and 48 of an energy converting device 50. By way of example, light indicated by arrows 52 in section 46 might be converted into an electrical signal by a suitable photoreceptor layer 56 such as cadmium sulphide, cadmium selenide or selenium placed upon one side 58 of structure 22'. The layer should preferably be characterized by a high lateral resistance so that a local change of resistance or a local generation of electrical energy is not dissipated by lateral spreading effects. In view of this high lateral resistance, it is necessary to make electrical contact over the entire surface of photoreceptor layer 56 in order to avoid volt- ,age drop toward the center of the device. Therefore, a semitransparent conductor 59 such as a film of stannous oxide is used. The electrical signal is conducted through structure 22' by wires 28 to selected zones 34' on side 60 thereof and re-converted into light by the provision of a layer 62 of electro-luminescent material such as, for example, zinc sulphide activated with copper or manganese applied to side 60. Another semi-transparent film 61 of stannous oxide or the like is provided on the electro-luminescent layer 62 to complete the circuit connection. 'Leads 65 and 67 are provided to connect films 59 and 61 to a power supply '63 of from 200 to 400 volts A.C. which is operated at frequencies within the range of from 60 to 1000 cycles per second.
In FIG. 4, which shows the face plate structure of an embodiment of the invention in greater detail,,it can be seen that both the glass matrix material 26 and wires 28 or portions thereof between zones 34 are recessed and filled with electrical insulating material 64. Thus, only remaining wires or portions thereof which lead from surface 30 to zones 34 on surface 32 will conduct electrical energy through face plate 22 and emit the same at surface 32.
Alternatively, a similar result may be accomplished by recessing only wires 28 substantially without removal .of matrix material 26 as shown in FIG. 5. In the modirecesses formed by removal of filled with electrical insulating fication shown in FIG. 5, portions of wires 28 are material 66.
A typical face plate constructed in accordance with the invention would comprise a matrix 26 of crown or soda lime glass or the like having stainless steel wires 28 therein each of a diameter of approximately 1 mil and spaced approximately 3 mils from each other. Wires 28 or portions thereof which lead toward areas intermediate predetermined zones 34 on surface 32 are recessed approximately from 3 to mils and electrically insulated from surface 32 by fillers 64 or 66 of low melting solder glass or a glass frit known commercially as Pyroceram #95 or its equivalent which is fused to matrix 26. Respective zones 34 may for example each be approximately 4 mils in diameter and spaced approximately 80 mils from each other.
While a selection of materials for matrix 26 and wires 28 has been given hereinabove, it should be understood that other met-a1 and glass combinations may be used. For example, wires 28 formed of tungsten in a matrix of Pyrex glass or Dumet in a soft lime glass matrix might be used.
Since most cathode ray tubes are provided with envelopes formed of glasses having co-efficients of expansion and softening temperatures similar to those of sodalime glass and the face plate 22 is normally intended to be secured thereto by fusion, it should be apparent that the use of glasses having heat-softening and expansion characteristics similar to those of the tube envelopes are preferred in the construction of face plate 22.
By selecting a material for matrix 26 which has softening and expansion characteristics similar to those of the glasses of articles to receive the face plate 22, problems of subsequent assembly are minimized. That is, fused junctions between the face plate and the envelope of an electronic device intended to receive the same can be made without excessively distorting or causing fracturing of one or the other of the parts to be joined.
In constructing the embodiment of the invention illustrated in FIG. 4, the basic structure of face plate 22 is first formed with all of its wires 28 extending completely through matrix 26. This may be accomplished by supporting a number of wires 28 in spaced relation with each other and flowing a molten matrix material around the wires or by laying up an assembly of wires with glass spacer members therebetween and fusing the assembly with applied heat and pressure to accomplish generally the same result.
A preferred manner of forming the basic structure of face plate 22, however, would be to bundle a number of glass clad wires together substantially as fragmentarily shown in FIG. 7. The bundle would then be fused under applied heat and pressure. In this way, the glass claddings form a continuous impervious matrix 26 illustrated in FIG. 8 as a fragmentary portion of face plate 22.
In all cases, wires 28 in the basic structure of face plate 22 are close enough together to permit the end of at least one'wire to coincide with each predetermined zone 34 on surface 32 of the completed face plate 22.
When forming the face plate structure of glass clad wires, as illustrated in FIGS. 7 and 8, the thickness of glass claddings determines generally the spacing between wires 28 but due to plastic flow during the heating and pressing operations spacings between individual wires may depart from the optimum.
Having provided the basic structure of face plate 22, its surface 32 is treated as follows:
A continuous layer 68 of photosensitive resist is applied substantially uniformly to surface 32 by knife coating, settling or spin coating. Layer 68 should be resistant to acids which are subsequently used to etch matrix 26 and wires 28 and be hardenable when exposed to actinic light (i.e. light within the ultra-violet and blue region of the spectrum or within the range of from approximately 3500 angstroms to 5000 angstroms). Where not appreciably exposed to such light, layer 68 must be readily removable with a solvent. A photosensitive resist which is sensitive to infrared light may be used.
Such photosensitive materials are commercially available and referred to as photoresists. Some photoresists are soluble in water when not hardened by actinic light. Special solvents referred to as developers are also supplied commercially for purposes of washing off or removing unhardened portions of photoresists not readily removable with water. By way of example, a
photoresist known commercially as K.P.R. (Kodak Photoresist) may be used.
With layer 68 applied to surface 32, a partially opaque and partially transparent grill-like master 70 is placed over layer 68 substantially as shown in FIG. 6. Master 70 is provided with transparent areas 72. Each area 72 is of a size and shape and spaced from adjacent areas 72 in accordance with the size, shape and spacings desired of zones 34 ultimately to be provided on surface 32 of face plate 22. Other portions 74 of master 70 are opaque.
Master 70 may be in the form of a photographic film processed conventionally to provide the predetermined transparent and opaque areas. Alternatively, it might be formed of sheet metal, opaque paper, plastic sheeting or cardboard or the like having areas 72 punched, etched or otherwise cut out to provide the grill-like structure illustrated in FIG. 6.
With master 70 in place upon layer 68, actinic light, as represented by arrows 76, is directed through transparent areas 72 for a time period sufiicient to fully harden portions 78 of layer 68 therebeneath. Since exposure takes place on the surface of layer 68, remote from the surface of face plate 22, exposure should continue until layer 68, in the portions to be hardened is affected through its entire thickness.
This having been done, master 70 is removed and unhardened portions of layer 68 (portions not exposed to light 76) are washed away with water or a suitable solvent therefor to produce the photoresist mask 80 illustrated in FIG. 9. Mask 80, thus formed, provides a protective coating over discrete areas of surface 32 which areas are to constitute zones 34 of the finished face plate structure. Areas 82 of surface 32 which are unprotected by mask 80 are then recessed as shownin FIG. 10. This is accomplished by immersing surface 32 of face plate 22 in an acid etch solution 83 as illustrated in FIG. or otherwise applying solution 83 thereto.
A suitable acid etch solution which will recess both matrix 26 and wires 28 to accomplish the result illustrated in FIG. 10 might consist of Ammonium Bifluoride dissolved in 20-30 percent by volume dilute Nitric Acid. It is pointed out, however, that various other known acid etch solutions may be used such as, for example, a solution consisting of 50% hydrofluoric acid and 50% sulfuric acid.
As illustrated in FIG. 10, wires 28 which lead to areas of surface 32 underlying mask 80 will be uneffected by the acid etch solution and provide discrete electrical conducting paths extending from surface 30 to surface 32 of face plate 22. Other wires or portions thereof not protected by mask 80 are recessed along with matrix 26. Following the etching step, surface 32 is rinsed with water to stop the etching action and dried.
In order to electrically insulate wires 28 in the recessed areas 82 from surface 32, these areas are filled with electrical-insulating material 64, see FIG. 11.
This may be accomplished by removing mask 80 from the face plate structure and placing a commercially available glass frit such as Pyroceram #95 in recessed areas 82. Mask 80 may be removed with a solvent such as acetone or by scraping or grinding it away from surface 32 whereupon the glass frit would be knife coated into recessed areas 82. Alternatively, an aqueous suspension of the glass frit might be provided and the frit then al lowed to settle into recessed areas 82 by placing the face plate structure in the suspension medium before or after removal of mask 80. Once the recessed areas 82 are substantially filled with the glass frit, the face plate is heated to a temperature of approximately 440 C. for about 60 minutes or approximately 455 C. for about 30 minutes to fuse the frit to matrix 26 and burn off mask 80 if mask 80 had not been previously removed. Surface 32 is preferably ground and/or polished to remove excess frit and to produce the result illustrated in FIG. 11.
If desired, an epoxy resin or other electrical-insulating resins or plastics may be used to fill recessed areas 82.
In another aspect of the invention, a procedure which is especially applicable to the making of a face plate 22 having electrically conducting heads 36 on the ends of wires 28 at zones 34 is illustrated in FIGS. 12 and 13.
As shown in FIG. 12 a photoresist mask is formed over areas of surface 32 which are to be subsequently recessed rather than over zones 34 as described above. This is accomplished by using a grill-like master similar to master 70 but having areas 72 opaque and remaining portions 74 transparent.
A coating 74 of electrically conducting material such as gold or silver which is resistant to the above-mentioned acid etch solutions is next electroplated or otherwise formed to a desired thickness (1 to 5 mils, for example) over mask 80' and areas of surface 32 which are unprotected by mask 80' (see FIG. 12). Coating 84 and a portion of mask 80' is then removed by abrading or cutting the same down to the level indicated by dot-dash line 86 in FIG. 12. This leaves coating 84 only on areas unprotected by mask 80 and provides heads 36 on zones 34. Heads 36 are thus attached to the ends of respective wires 28 which are intended to conduct energy through face plate 22.
Remaining portions of mask 80 are removed with a solvent such as acetone to expose the areas of surface 32 which are between heads 36. These areas are next etched and substantially filled with electrical insulating material 64' to produce the result illustrated in FIG. 13. The etching and filling operations are performed in the manner described hereinabove with relation to FIGS. 10 and 11. I
Heads 36, being formed of material resistant to acid etch solutions will protect underlying portions of surface 32 and the structure illustrated in FIGS. 4 and 13, complete with electrically conducting heads 36, is formed.
In forming the face plate structure illustrated in FIG. 5 wherein only the wires 28 are recessed in matrix 26 sub stantially without removal of matrix material therearound, the procedure outlined hereinabove with relation to FIGS. 6-9 is followed to provide a photoresist mask 80' (FIG. 14) on surface 32 similar to mask 80 (FIG. 9).
Surface 32 of structure 22 having mask 80' thereon is then immersed in an acid etch solution 87 (see FIG. 14) adapted to etch wires 28 which are exposed between portions 80" of mask 80' substantially without removal of the material of matrix 26. An acid etch solution for accomplishing this result might consist of one part nitric acid with three parts hydrochloric acid. Such a solution is known as aqua regia which does not appreciably affect glass but will dissolve metals such as stainless steel or others used as electrical conductors 28.
After having recessed wires 28 which are unprotected by mask 80" to a desired depth such as from 3 to 5 mils in matrix 26 as shown in FIG. 14, structure 22 is rinsed with water to stop the etching action and dried.
Recesses 88 resulting from the etching of wires 28 are next filled with an electrical insulating material 66 or 92 as shown in FIGS. 5 and 16. This may be accomplished by electrophoretical-ly depositing a glass frit into recesses 88 in the manner illustrated in FIG. 15.
Surface 32 of structure 22 is immersed in an ionized electrolyte 90 having a pulverized glass frit 92 suspended therein. Electrolyte 90 is preferably thorium nitrate in a supporting medium of alcohol or a similar agent which, in itself, is substantially non-conductive to electricity and capable of dissolving the thorium nitrate.
Frit 92, which might a commercially available type known as Pyroceram #95 or its equivalent, takes on a positive surface charge when suspended in electrolyte 90. Wires 28 in recesses 88 must then be rendered negatively charged to attract frit 92 and cause the same to deposit in recess 88.
As shown in FIG. 15, a technique for rendering wires 28 negatively charged while simultaneously exposing surface 32 to electrolyte 90 would be to provide a holder 94 for structure 22. Holder 94 has a compartment 96 in which an electrically conductive fluid medium 98 such as a solution of copper sulphate is placed so as to make contact with respective ends of wires 28 at surface 30.
Fluid medium 98 is connected as a cathode to a 200 to 300 volt source of current 100 and surface 32 is immersed in electrolyte 90 adjacent an anode 102 positioned therein. Anode 102 is also connected to current source 100 as illustrated in FIG. 15. With the above-mentioned voltage at source 100, a space of from 1 to 2 cm. between surface 32 and anode 102 should be provided.
In this manner of directing electrical energy through electrolyte 90, frit 92 is attracted to negatively charged wires 28 and drawn into recesses 88.
When recesses 88 are substantially filled with frit 92, structure 22 is removed from electrolyte 90 and from holder 94. With frit 92 now in recesses 88 as shown in FIG. 16, structure 22 is heated to a temperature of approximately 440 C. for about 60 minutes or 455 C. for about 30 minutes to fuse frit 92 in place and thereby form the electrical insulating material 66 shown in FIG. 5. During this fusing operation, mask 80 will burn off to expose the ends of wires 28 at zones 34. Any excess of frit 92 which might deposit on surface 32 adjacent recesses 88 may be wiped away or otherwise removed before fusing or it may be ground away after fusing.
1. An energy-conducting plate formed of electricalinsulating matrix material having a multiplicity of wires each extending longitudinally from one face of said plate substantially right angularly toward an opposite face thereof wherein the improvement comprises said wires being in closely individually spaced random side-by-side relationship with each other and at least one face of said plate having corresponding ends of said wires exposed within the boundaries of at least one special area of prescribed geometrical configuration, the boundaries of said area discretely excluding similar ends of others of said wires, said excluded ends of said other wires being recessed relatively deeply in said matrix material and an electricalinsulating filler extending between said face and said recessed ends of said other wires whereby electrical energy appliedto a face of said plate andcaused to propagate through said wires will be emitted at the opposite face only by particular wires included within the boundaries of said special area and, accordingly, produce an electric 8 field thereat of a shape corresponding to the shape of said area.
2. An energy-conducting plate as recited in claim 1 including means for electrically interconnecting at least the major portion of all of said exposed ends of said wires within said special area.
3. An energy-conducting plate as recited in claim 2 further including at least one electrical conductor extending from said interconnecting means to a location remote therefrom.
4. An energy-conducting plate as recited in claim 1 wherein portions of both said electrical-insulating matrix material and wires therein which surround said area of prescribed configuration are recessed relatively deeply and replaced by said electrically insulating filler.
5. In an electron tube including a glass envelope having as one wall thereof an energy-conducting plate formed of electrical-insulating matrix material in which a multiplicity of wires extend longitudinally and generally right angularly from one face toward the other thereof, the improvement comprising said wires being arranged in closely spaced random side-by-side relationship with each other and at least one face of said plate having corresponding ends of said wires exposed within the boundaries of at least one special area of prescribed geometrical configuration, the boundaries of said area discretely excluding similar ends of others of said wires, said excluded ends of said other wires being recessed relatively deeply in said matrix material and an electrical-insulating filler extending between said face and said recessed ends of said other wires whereby electrical energy applied to a face of said plate and caused to propagate through said wires will be emitted at the opposite face only by particular wires included within the boundaries of said special area and, accordingly, produce an electric field thereat of a shape corresponding to the shape of said area.
References Cited by the Examiner UNITED STATES PATENTS JAMES w. LAWRENCE, Primary Examiner.
. V. LAFRANCHI, Assistant Examiner.