The present invention relates to a method for producing a reflector on a reflector base made of glass having a curved surface, provided in the area of a coating surface with a metal-containing reflective layer, in particular a noble metal-containing reflective layer, in which a metal-containing coating fluid is deposited on the coating surface and is subjected to a burning-in treatment at a temperature below a softening temperature of the glass.
Functional layers made from reflective metals are deposited on lamps, light sources, or separate reflector components. Here, reflector components are elements which are used in light sources or other devices that reflect optical radiation. Suitable reflector materials are, for example, gold, silver, copper and aluminum, based on their reflectivity according to the respective spectral range.
From DE 35 30 873 A1, a method of this generic class is known for producing a headlamp reflector. Here, an approximately 5 μm thick layer made from a metal-containing paste is deposited by a pad printing method on the concave inner side of a reflector body made of glass. The reflector body comprises high-temperature glass having a softening point Tg of approximately 550° C. The paste comprises a solution of platinum or gold resinate in a fat oil having low additives (˜1%) of resinates from glass formers for adhesion. The reflector body having the deposited resinate layer is brought to a temperature of around 500° C. in a furnace. During this heat treatment, the gold resinate decomposes into metallic gold and resin acid, which in turn is volatilized, just like the other components of the paste, by the high burning-in temperature. A thin, metallic reflective layer having a thickness of approximately 0.1 μm remains on the reflector body. This is resistant to corrosion, so that a coating layer is not required for protection from corrosion.
In the pad printing method, the printing paste is transferred from the printing block to the printing object by an elastic pad made of silicone rubber.
Instead of this method, for depositing noble metal resinate layers that can be burned-in for the purpose of producing reflectors, template or screen-printing methods are also common. For screen printing, the printing paste is deposited with a rubber squeegee through a fine-mesh fabric onto the printing object, wherein the mesh openings of the fabric are impermeable at positions at which no paste should pass through the template.
The above-described printing methods require the previously complicated production of a printing block or template for the exact transfer of printing paste. This disadvantage is avoided by deposition methods in which the paste is spread on or sprayed on. These procedures for the production of infrared-reflective linings of IR emitters, as well as for suitable gold and other noble metal resinate compositions, are described, for example, in German Patent No. 1 540 740.
In these methods, however, it is difficult to reproducibly maintain a specified layer thickness of the noble metal-containing paste, as well as defined contours and edges, and to produce small structures of less than 2 mm. Frequently, beads, non-straight profiles, spray and droplet artifacts are observed, which require complicated rework processing. Losses of usually expensive pastes due to overdosing, dripping, overspraying, waste, and rework lead to high material costs.
The use of noble metals, in particular, exacerbates the combination of inexact dosing, variation of consumption, high losses, as well as monitoring the remaining material. Thus, allocating the exact consumption to certain products or orders is possible only in an unsatisfactory way. Also, monitoring and preventing theft is only possible in an unsatisfactory way.
Therefore, an objective of the present invention is to provide a method for producing a reflector on a lamp, a light source, or a separate reflector component, which makes it possible to deposit a reflector layer having a specified layer thickness in a reproducible way with tight tolerances, as well as to generate clean edges without a printing block or the like. In particular, losses of noble metals should be minimized, and a close monitoring and order-related tracking of the material flow and allocation of consumption to individual orders or workpieces should be made simpler.