METHOD OF MANUFACTURING A CONTROL SUBASSEMBLY FOR FLAT DISPLAY DEVICES

Abstract: For a flat display device, a control subassembly is needed which consists of two control plates (1; 7) each formed by a layer of parallel conductors (2; 8) which are isolated from each other. During the manufacture of the control subassembly, the first control plate is provided with a glass frit in the form of continuous strips (10) perpendicular to the conductors. The glass frit is set, and the application of the strips is repeated. The second control plate is then put on the first control plate in such a way that their conductors are mutually perpendicular. After that, the glass frit is crystallized.

Description: Description Method of Manufacturing a Control Subassembly " for Flat Display Devices The present invention relates to a method of manufacturing a control subassembly for a flat display device, said control subassembly consisting of a fi rst control plate and a second control plate, as set forth in the preamble of cla m 1. Such a method is disclosed in European Patent 0 050 294. In that method, a fi rst glass frit is applied to a fi rst control plate and then heated unti l it crystallizes. Next, a second glass frit is applied to the crystallized glass frit, and the second control plate is placed on t. Further heating causes the second glass .frit to c ry : sta I I i ze , whereby the two control plates are bonded together in a predetermined spaced relationship from each other. This method requires two different glass frits with different crystallization points. Another disadvantage is that two heating processes to about 450 C and 350 C, respectively, are necessary. It is the object of the present invention to provide a simpler method of manufacturing control subassemb Ii es . This object is attained by the steps set forth in claim 1. Further advantageous aspects of the invention are cla med in claims 1 to 5. The novel manufacturing method uses only one glass frit which can be set by irradiation with infrared light for about 1 to 5 minutes. T s irradiation can take place without the control plate having to be removed from the silk-screening apparatus required to apply the glass frit. Immediately after the irradiation, the next layer of glass frit is applied until the des red height of the glass frit and, thus, the desired distance between the two control plates is reached. Through the application of a continuous strip of glass frit perpendicular to the conductors, the latter are fixed in place already after the solidification of the first glass-frit layer, and the control plate is extremely stabil zed. Through the introduction of holding edges with a line- shaped portion of reduced cross section at the transition to the conductors, the control plates are easy to handle before be ng bonded together into the control subassembly. T e holding edges are removed simply by being bent over. T einvention will now be explained in greater detail with the aid of embodiments illustrated in the accompany¬ ing drawings, in which: Fiα. 1 is a toe view of a part of the first control plate with holding edges prior to the application of the glass frit; Fig. 2 is a top view of the fi rst control plate with a simplified holding edge prior to the application of the glass frit; Fig. 3 is a section taken along line 111-111 of Fig. 2; Fig. 4 is a top view of a part of the second con¬ trol plate; Fig. 5 is a top view of the fi rst control plate of Fig. 2 after application of the glass frit; Fig. 6 i s a section taken along line VI - VI of Fig. 5, and Fig. 7 is a top view of a part of the finished contro subassembly. The control subassembly fabricated by the novel method, after being united with a perforated extract anode, * can be used as a control system in the flat evacuated disolay device disclosed in German Patent Application P 37 34 387.4, This display device has a phosphor-dot glass faceplate and a back metal envelope. In the latter, an area cathode consisting of a periodic array of fi laments is disposed in front of a segmented counterelectrode, and the control system, consisting of the Derforated extract anode, which is attached to a frame, and the control subassembly bonded thereto, is disposed in front of the area cathode. The first control plate 1, shown n Fig. 1 n a top view, consists of a plurality of coplanar, parallel conductors 2 which are isolated from each other. The conductors 2 are provided with a regular pattern of holes 3. To be able to handle this unstable structure during the manu¬ facture of the control subassembly, the control plate is surrounded by holding edges 4a and 4b. All ends of the conductors 2 are connected with the holding edges 4a by a line-shaped portion of reduced cross-sectional area 5a, and the two outer conductors are connected with the holding edges 4b by a line-shaped portion of re¬ duced cross sectional area 5b. Fig. 2 shows the control plate 1 with simplified holding edges. In this embodiment, only the ends of the con¬ ductors 2 are linked via the portion of reduced cross- sectional area 5a with the holding edges 4a. The outer conductors have alignment marks 6 near their ends. Fig. 3 shows a section taken along line III - III of Fig. 2. The portion of reduced cross-sectional area.5a is formed by an etching process, for example, which may take place simultaneously with the etching of the control plate to obtain the conductors 2 and the holes 3. The thickness of the portion of reduced cross-sectional area is about one fourth the thickness of the control plate. Fig. 4 shows the second control plate 7, which consists of a plurality of coplanar, parallel conductors 8 that are isolated from each other. To be able to handle this unstable structure during the manufacture of the control subassembly, the ends of the conductors 8 are linked by holding edges 9. The first control plate 1 is provided with a glass frit using silk-screening techniques. Fig. 5 shows part of the fi rst control plate of Fig. -2 after this process. The glass frit is applied in the form of strips 10 which are perpendicular to the conductors 2 and cover the conductors and the spaces between the conductors. Each of the strips 10 lies between two rows of holes, and it is important that the holes remain uncovered. For the sake of clarity, only two strips 10 are shown. In a practical embodiment, strips of glass frit are present beside all rows of holes. The glass frit consists, for example, of the type G 017-918/K4 of Schott, Landshut, a binder of methyl metha c ry lat e, avai lable under the name "Elvacite Type 2041" from DU PONT DEMOURS, Dϋsseldorf, and a solvent consisting of buthyl diglycol acetate and cyclo- hexanone. 200 g of frit powder are mixed with 30 g of binder and solvent in the usual manner to obtain the glass frit. The 30 g of binder and solvent contain Elvacite, buthyl diglycol acetate, and cyc lohex anone in a weight ratio of 0.2 : 1 : 1. This glass frit is set by the action of heat, e.g., by hot ai r or preferably by i rradiation th infrared light for 1 to 5 minutes. In this manner, the first control plate is stabilized and the risk of crosses between the conductors during displacement of the control plate is avo ded. In addition, further glass frit can be de¬ posited on the strips 10 applied first. For the irradiation with infrared light, the first control plate need not be removed from the s lk-screening apparatus, so that further glass frit can be applied immediately thereafter without realignment. This process is repeated until the desired thickness of the glass frit is achieved. Compared with the width of the strips, very great str p th cknesses can be achieved, which may measure several 100 micrometers. In Fig. 6, the first control plate 1, provided with glass frit, is shown in a section taken along line VI - VI of Fig. 5. In this example, three superposed strips of glass frit are present on the conductors 1 of the control plate These strips were applied one after the other and are denoted by 10, 10', and 10". On the first control plate 1, provided with the glass frit, the second control plate 7 is laid, which is shown in Fig. 4. The two control plates 1 and 7 are so aligned relative to each other that the conductors 2 and 8 are mu¬ tually perpendicular and the holes 3 are centrically below the slots between the conductors 8. Then, heat is applied to crystallize the glass frit. The two control plates are thus joined together in a spaced relat onship from each other, the distance between them being determined by the thickness of the strips 10. The temoeratures and duration of this f itting process are given in the data sheet of the manufacturer of the frit powder Next, the holding edges 4a are removed from the fi rst control plate 1 by being bent over. In the second con¬ rol plate 7, isolation grooves 11 are formed in the holding edges 9, e.g., by stamping, such that conductors lying side by side are electrically isolated f om each other. The advantage of the stamping of the isolation grooves lies in the fact that no stress is produced in the conductors. Through the positions of the isolation grooves, an interdigital structure of the conductors 8 is obtained, with the holding edges now serving as electric connecting Lines. A top view of the control subassembly formed from the two control plates is shown in Fig. 7. This control subassembly is stable and can now be frit-bonded to a perforated extract anode to form the control system needed in the flat display device.

Claims: Claims 1. Method of manufacturing a control subassembly for a flat display device, said control subassembly consisting of a first control plate and a second control plate each formed by a layer of parallel conductors isolated from one another, comprising the following steps: - forming control plates with holding members inter¬ connecting all conductors; - applying several superposed layers of glass frit to the first control plate; - laying the second control plate on the glass frit; - aligning the control plates so that the conductors are mutually perpendicular; - heating until the glass frit crystallizes, and then - removing the holding elements, c h a r a c t e r i z e d i n that the glass frit, consisting of a frit powder, a binder of methyl metha- crylate, and a solvent of buthyl diglycol acetate and eye lohexanone, is applied to the first control plate as continuous strips perpendicular to the conductors, and that after each application, the glass frit is set by heat. 2. A method as claimed in claim 1, characterized in that the heat is in the form of infrared radiation. 3. A method as claimed in claim 1, character zed in that the holding members of at least the first control plate are constituted by holding edges which surround the con¬ trol plate and between which and the conductors there is a line-shaped portion of reduced cross-sectional area, and which are removed by being bent over. 4. A method as claimed in claim 3, characterized in that the holding edges are present only at the sides perpen¬ dicular to the conductors. 5. A method as claimed in claim 1, characterized in that the holding members of at least the second control plate are constituted by holding edges at the sides perpen¬ dicular to the conductors, and are removed by cutting.

Inventors: REICHELT MICHAEL, TISCHER KURT-MANFRED, REICHELT, MICHAEL, TISCHER, KURT-MANFRED
Applicants: NOKIA UNTERHALTUNGSELEKTRONIK, NOKIA UNTERHALTUNGSELEKTRONIK (DEUTSCHLAND) GMBH
Application year: 1989
Main classification: H01J9
IPC codes: C03C27, H01J9, H01J31