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(11) | EP 0 081 360 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method of making an electrode assembly |
| (57) This invention is concerned with the making of an electrode assembly which comprises
forming partial slots in the bottom surface of a glass plate, providing anode electrodes
in the slots, applying cathode electrodes on the top surface of the plate oriented
transversely to the anodes, etching out the remainder of the plate material to form
through-slots extending between the top and bottom surfaces of the plate, the anodes
and cathodes being in operative relation with each other through the slots. |
BACKGROUND OF THE INVENTION
[0001] There are many types of electronic devices, such as dot matrix display panels, which include two sets of electrodes spaced apart in operative relation with each other. In one device of this type, the electrodes are separated by a slotted plate of electrical insulating material which is difficult to make and align with the associated electrodes. In other types of devices, the structures composed of insulating materials for supporting the electrodes are relatively complex and include grooved plates or holes which are also expensive and difficult to make. In general, the supporting structures utilized in electronic devices have been fabricated from glasses, glass-ceramics, ceramics, or organic plastic materials.
[0002] Organic plastics have several advantages when being considered for such devices since they are relatively inexpensive, they can be manufactured and drilled, punched, machined, or otherwise shaped into complex geometries with reasonable ease, and they have sufficient mechanical strength for most applications. However, organic plastics cannot be used in vacuum- sealed devices.
[0003] Sintered ceramic materials, e.g., aluminum oxide, have been proposed as supports in electronic devices. Those materials ably withstand exposure to high temperatures but suffer from such disadvantages as being relatively expensive to manufacture, being difficult to machine or otherwise shape into complex configurations, and being relatively fragile.
[0004] Glasses and glass-ceramics have been utilized as supports in electronic devices because of their excellent electrical insulating characteristics, their relative cheapness, their ability to withstand high temperatures, their low vapor pressure, and their high mechanical strength. However, most glasses and glass-ceramics, like sintered ceramics, are difficult to machine and holes cannot be readily drilled or punched therein.
[0005] United States Patents Nos. 2,628, 160 dated February 10, 1953 and 2,684,911 dated July 27, 1954 of Stanley D. Stookey disclose thermally opacifiable glass compositions which exhibit photosensitivity and the capability of being chemically machined to fine tolerances. The glasses described in those patents consist essentially, by weight on the oxide basis, of 9-15% Li20, 0-8% total Na20 and/or K20, 9-23% Li2O + Na2O + K20, 70-$5% SiO2, 0.001-0.020% Ag, computed as AgCl, O-1C% Al2O3, 0-2.4% F, and 0-0.05% Ce02. Exposing portions-of such glass bodies to actinic radiation, commonly ultraviolet radiation, produces a latent image in the glass. A subsequent heat treatment at temperatures generally below the softening point of the glass causes the development of crystallites selected from the group of a lithium silicate and an alkali metal fluoride in the previously-exposed portions of the bodies. Such crystals are many more times soluble in dilute hydrofluoric acid than the surrounding glass. Advantage has been taken of this difference in solubility between the crystals and the residual glass to promote the chemical machining or sculpturing of glass articles into very intricate designs and shapes and to produce holes of complex configurations therein.
[0006] In common with conventional opal glasses, the above-described photosensitive opal glasses are low in actual crystal content. United States Patent No. 2,971,853, dated February 14, 1961, to Stanley D. Stookey, however, describes the production of glass-ceramic articles which demonstrate photosensitivity and the capability of being chemically sculptured. The articles are produced by subjecting portions of glass bodies consisting essentially, by weight on the oxide basis, of 60-85% Si02, 5.5-15% Li20, 2-25% Al2033 the ratio Al2O3:Li2O being less than 1.7:1, and a photosensitive metal in the indicated proportion selected from the group of 0.001-0.03% gold, computed as Au, 0.001-0.3% silver, computed as AgCl, and 0.001-1% copper, computed as CuO, to actinic radiation, again commonly ultraviolet radiation, to produce a latent image in the glass. A subsequent two-step heat treatment, the first step utilizing temperatures between the annealing and softening points of the glass and the second step involving temperatures above the softening point of the glass, effects the generation of crystals in the previously-exposed portions of the bodies. Those portions of the glass-ceramic body are highly crystalline and contain at least one lithium-containing crystal phase which is more readily soluble in dilute hydrofluoric acid than the residual glass and other crystal phases present. These glass-ceramic products are mechanically stronger and are capable of being used at higher temperatures than the above-described photosensitive opal glasses.
[0007] Chemically machinable'glasses and glass-ceramics have been used commercially in a number of applications including electronic and fluidic devices where grooves, holes, slots, etc., of high tolerances have been etched therein. For a number of years, Corning Glass Works, Corning, New York, has marketed a chemically machinable glass product under the trademark FOTOFORM and a chemical machinable glass-ceramic under the trademark FOTOCERAM.
DESCRIPTION OF THE DRAWINGS
[0008]
Fig. 1 is a plan view of a plate of electrical insulating material at one stage in the preparation of an assembly according to the inventive method;
Fig. 2 is a sectional view through the plate of Fig. 1 along the lines 2-2 in Fig. 1;
Fig. 3 shows the composite article formed incorporating the plate of Fig. 2 at a later stage in the preparation of an assembly according to the inventive method;
Fig. 4 is a plan view of the assembly at the stage depicted in Fig. 3;
Fig. 5 shows the composite article of Fig. 3 at a still later stage in the preparation of an assembly according to the inventive method;
Fig. 6 shows a completed assembly prepared from the composite article of Fig. 5 according to the inventive method; and
Fig. 7 is a perspective view of a completed assembly.
OBJECTIVES OF THE INVENTION
[0009] The primary objective of the invention is to provide an improved method for fabricating electrode assemblies comprising two sets of electrodes spaced apart in operative relation with each other in which the supporting structure therefor is of such complex geometry that removal of material from the supporting structure is conventionally required, said inventive method obviating the need for machining, drilling, punching, or other mecahnical means for removing material from the supporting structure.
[0010] Another objective of the invention is to fabricate electrode assemblies which can be utilized in gas-filled display panels or in other types of devices that employ crossed electrodes and cell matrices.
SUMMARY OF THE INVENTION
[0011] The method of the invention comprises five general steps:
First, a plate cf photosensitive, electrical insulating material is exposed to actinic radiation to develop a latent image therein in a pattern of parallel strips across a face of said plate;
Second, said plate is heat-treated in a manner to develop a phase in the previously-exposed strip portions which can be selectively chemically removed from said plate material;
Third, one surface of said plate in at least the strip portions thereof is contacted with a solvent to selectively remove the phase in said strip portions part way into said plate to form parallel slots therein;
Fourth, an array of electrodes, e.g., anodes, is disposed along said slots;
Fifth, an array of electrodes, e.g., cathodes, is provided on the continuous surface of said plate opposite to said first array of electrodes oriented transversely to said first array of electrodes; and then
Sixth, said plate in at least the strip portions thereot is again contacted with a solvent to selectively remove the phase of said strip portions completely through said plate. '
DESCRIPTION OF THE INVENTION
[0012] The following description of the invention is directed to photosensitive glasses and glass-ceramics of the types described above in Patents Nos. 2,628,160 and 2,971,853 because of their inherent high mechanical strength and refractoriness and low vapor pressure.
[0013] Referring now to the appended drawings, a plate 10 of a photosensitive glass is exposed to ultraviolet radiation in the form of collimated beams, or through a patterned mask comprised of material opaque to ultraviolet radiation, or in some other manner to produce latent images in the form of parallel, linear exposed regions 20 through the body of plate 10 as seen in Fig. 2. As illustrated in Fig. 1, regions 20 do not extend to the edges of plate 10 so that the edge portions of plate 10 remain in place to maintain the integrity of plate 10 when portions thereof are subsequently removed in exposed regions 20. It will be understood that other arrangements can be devised to hold plate 10 together after exposed regions 20 have been removed.
[0014] Exposed regions 20 are then heated to temperatures generally below the softening point of the glass to develop crystallites therein selected from the group of a lithium silicate and an alkali metal fluoride, following which the crystallized regions are contacted with dilute hydrofluoric acid at surface 12 of plate 10 to remove the crystallized regions part way through the cross-section of plate 10 to form slots 40 seen in Fig. 3.
[0015] Thereafter, as represented in Figs. 3 and 4, an array of elongated cathode electrodes 50 is applied by any suitable method to the obverse surface 14 of plate 10 in transverse orientation to exposed regions 20. It will be appreciated that this cathode array may be formed upon plate 10 before slots 40 are produced.
[0016] Subsequently, plate 10 is secured through any convenient means to the surface of a support plate 60 of an electrical insulating material, e.g., glass, which carries elongated parallel anode electrodes 70 which have been applied to support plate 60 by any suitable method. As depicted in Fig. 5, plate 60 is oriented in such relation to plate 10 that anodes 70 are aligned with and positioned within slots 40.
[0017] Finally, crystallized regions 20 are again contacted with dilute hydrofluoric acid to remove the remainder thereof such that slots 40 penetrate totally through the cross-section of plate 10 providing the completed assembly shown in Figs. 6 and 7. The resulting assembly, after the attachment of leads thereof, can be incorporated into a gas-filled display panel or into any other type of device which utilizes crossed electrodes and cell matrices.
[0018] It will be recognized that the anodes and cathodes can be formed from any suitable material which is highly electrically conducting and has a coefficient of thermal expansion relatively closely matching that of the plate material. Commonly, the electrodes will be metallic, fabricated from stainless steel, nickel, or an alloy having the necessary expansion characteristic. They can be applied through'any suitable process including, but not limited to, silk screening, evaporation, RF sputtering, electroless metal plating, and vapor deposition. Galvanic plating may be used.
[0019] It will be apparent that configurations other than rectilinear slots, such as V-shaped grooves or arc-shaped channels, will be equally operative in the final assembly.
[0020] The securing of support plate 60 to plate 10 can be accomplished through any suitable technique. Customarily, a sealing glass frit having a fusing temperature lower than those of plates 10 and 60 will be applied to support plate 60 to contact areas of plate 10 between slots 40. The assemblage is then fired at a temperature sufficiently high to fuse the sealing glass frit and thereby bond together plates 10 and 60.
[0021] Further, a multi-unit assembly can be produced by laying up two or more individual units and securing them together via frit-sealing or other means.
[0022] Finally, where a glass-ceramic body is desired, the heat treatment will consist of first exposing the glass to temperatures above the annealing point of the glass but below the softening point thereof, and thereafter subjecting the glass to temperatures above the softening point of the glass to cause the generation of crystals therein in the manner described in Patent No. 2,971,853, supra.
forming a plurality of parallel slots extending partially into a plate of insulating material of a type which can be chemically etched,
said plate having top and bottom surfaces,
providing an array of electrodes disposed along said slots, and
etching said slots to form through-slots which extend fully through said plate from said top surface to said bottom surface.
providing a first insulating plate of a photosensitive material and having a top surface and a bottom surface,
exposing and developing a pattern of parallel strips through said first plate from the top surface to the bottom surface,
providing an array of first electrodes on said top surface of said plate and oriented across said strips,
removing some of the material of said strips to form partial slots in said first plate and extending inwardly from said bottom surface,
providing second electrodes aligned with and disposed in said partial slots in said first plate and oriented generally transverse to said first electrodes, and
etching out the remainder of said strips to form through-slots extending fully through said plate from the top surface to the bottom surface, said first and second electrodes being in operative relation through said through-slots.
exposing a plate of photosensitive, electrical insulating material to actinic radiation to develop a latent image therein in a pattern of parallel strips across a face of said plate,
heat treating said plate in a manner to develop a phase in the previously-exposed strip portions which can be selectively chemically removed from said plate material,
contacting one surface of said plate in at least the strip portions thereof with a solvent to selectively remove said phase in said strip portions part way into said plate to form parallel slots therein,
disposing a first array of electrodes along said slots,
applying a second array of electrodes upon the other surface of said plate opposite to said first array of electrodes oriented transversely to said first array of electrodes, and
again contacting said plate in at least said strip portions with a solvent to selectively remove said phase in said strip portions completely through said plate.