Patent GB-1304030-A (GB)
IPC: H01Q1/12
Filed: 1970-06-09
Abstract: 1304030 Windscreens; anti-dazzle devices LIBBEY-OWENS-FORD CO 9 June 1970 [16 June 1969] 27731/70 Heading B7J [Also in Divisions C1 H1 and H4] A motor car windscreen comprises a transparent glass sheet and lines of a conductive material applied directly thereupon to form an aerial. At least part of a surface of the conductive material is discoloured, to reduce reflection of light therefrom. As described, a windscreen is made up of two sheets of glass 14, 15 and an interposed layer of plastics material 16, all bonded together under heat and pressure to form a composite unit. An aerial is provided by means of a surface conductive pattern on the inner glass sheet 14. This pattern consists of a broad, substantially crescent-shaped tab 24 located centrally at the bottom of the sheet 14, two thin vertical lines 20, 21 which extend from said tab to near the top of the sheet 14, and two thin horizontal lines which extend outwardly from the ends of the lines 20, 21 (Fig. 5, not shown). A further thin horizontal line may be provided above the said two horizontal lines, and be joined to them at their ends to forn a loop (Fig. 1, not shown). The lower edges of the outer glass sheet 15 and of the plastics layer 16 are provided with notches 17, 17<SP>1</SP> in alignment with the tab 24 so that a connecting wire 30 may be soldered therein to said tab, after which said notches may be filled with a plastics sealing compound. The conductive pattern may be applied to the glass sheet 14 as a paste of, for example, 80-98 parts of powdered silver with 2-20 parts of borosilicate glass frit in an organic vehicle. The vertical and horizontal lines may be painted by means of a suitable too] (25), Fig. 6 (not shown), preferably for widths from 0À005-0À015 inch, or a conventional process, such as silk screen printing, may be used. The paste may be fused into the glass whilst it is being heated either for bending, or for compositing as a laminate. Surface discoloration of the aerial surface is carried out in one of the following ways. In a first example, the surface of the glass sheet carrying the lines is exposed to sulphur in a convenient form until said lines are uniformly tarnished to a desired darkness, after which the compositing process is carried out. In a second example, the lines are sprayed with an acid halogen solution, such as 1% iodine with 1% concentrated hydro - chloric acid and 98% isopropyl alcohol before exposure to the action of sulphur, such as by spraying with a 1-10% aqueous solution of sodium sulphide. In a third example, similar to the second example, from 5-10% of a metal compound, such as lead tetra-acetate, is added to the sodium sulphide solution. In a fourth example, from 3-10% of silver iodide is added to the conductive paste before it is applied to the glass sheet. The fired pattern is sprayed with sodium sulphide solution. In a fifth example, darkening is effected by electrochemical treatment. The conductive paste may include a tarnish accelerator, and the electrolyte may be a 10% solution of sodium sulphide or, for continuous production, a dilute solution of caustic soda in which hydrogen disulphide is bubbled. The fired-on pattern is connected as the anode. Alternatively a press and/or rubbing technique may be employed in which a pad or pads soaked with electrolyte is or are in contact with the pattern. The positive lead may be connected to the pattern and the negative lead to a pad holder, or both leads may be connected to the respective holders of different pads. In a sixth example, the pattern is placed in contact with a fresh concentrated solution of ammonium sulphide (light) until sufficiently tarnished. In a seventh example, use is made of a 10% aqueous solution of sodium sulphide that has been saturated with elemental powdered sulphur at room temperature. In an eighth example, the pattern is sprayed with a stabilized sodium polysulphide solution. A stock solution may be made by dissolving 0À84 lbs. of sodium sulphide in one gallon of water, adding 0À70 lbs. of flowers of sulphur, heating to 170‹ F., and stirring until dissolved. This stock solution is  then diluted to 20 gallons with water at 180‹ F. and 0À84 lbs of stabilizer is stirred in, when it is ready for use. Many neutral or alkaline compounds can be used as stabilizers, but sodium sulphide is preferred. In a ninth example, use is made of a sulphur bearing organic compound. In a tenth example the glass sheet bearing the pattern is pre-heated, and is then introduced into a closed chamber containing heated sulphur. In an eleventh example, tarnishing is effected by exposing the pattern to a mixture of sulphur and carbon. A slurry or a dry mixture of equal parts of the two materials is applied over the pattern, and the glass sheet bearing it is then heated. A twelfth example features tarnishing the pattern by contacting it with a sulphur compound, covering it with another sheet of glass, and then heating the whole.