EMITTER COMPONENT WITH A REFLECTIVE LAYER, AND METHOD FOR PRODUCING SAME

Abstract

In a known method for producing an emitter component with a reflector, a flowable aqueous SiO2 slip is produced using a slip method, and the slip is applied onto a quartz glass main part in the form of a slip layer. The slip layer is then dried and glazed, thereby forming a quartz glass layer which is more or less opaque and diffusely reflective. In order to produce an optical component with a reflective layer made of opaque quartz glass with increased reflective optical power, a method is proposed having the steps of: providing a main part with a surface which is at least partly coated with a reflective layer made of opaque glass, compressing a surface region of the reflective layer made of opaque glass, and applying a mirror-reflective layer on at least one part of the compressed surface region.

Claims

1. A method for producing an emitter component with a reflector, including the method steps: (a) providing a main part with a surface that is at least partly coated with a reflector layer made of opaque glass, (b) compressing a surface region of the reflector layer made of opaque glass, (c) applying a mirror-reflective reflector layer on at least one part of the compressed surface region.

2. The method according to claim 1, wherein the compressing of the surface region takes place by heating to a heating temperature of at least 1,100° C. during a heating period of at least 5 seconds.

3. The method according to claim 1, wherein that the mirror-reflective reflecting reflector layer is produced from a metal.

4. Method according to claim 3, wherein the mirror-reflective reflector layer is produced from a gold-containing metal or from gold, and has a layer thickness in the range of 50 to 300 nm.

5. The method according to claim 1, wherein the reflector layer is made of opaque glass having a thickness in the range of 0.5 mm to 2 mm.

6. The method according to claim 5, wherein, upon compression according to method step (b), a surface region is formed which has less than 50% of the thickness of the reflector layer made of opaque glass.

7. The method according to claim 1, wherein the provision of the main part according to method step (a) includes a measure in which an emitter component that is in use, with a reflector layer made of opaque glass, is dismantled and is reworked using the method steps (b) and (c).

8. An emitter component having a main part whose surface is at least partly coated with a reflector, which reflector comprises an inner reflector layer made of at least partially opaque glass and an outer, mirror-reflective reflector layer, wherein a sealed glass film is arranged between the inner reflector layer and the outer reflector layer.

9. The emitter component according to claim 8, wherein the glass film has a thickness of less than 300 μm, preferably less than 150 μm.

10. The emitter component according to claim 8, wherein the mirror-reflective reflector layer consists of a metal, preferably of a gold-containing metal or of gold; and in that it has a layer thickness in the range of 50 to 300 nm.

11. The emitter component according to claim 8, wherein the reflector layer made from opaque glass is provided with a thickness in the range of 0.5 mm to 2 mm.

12. The emitter component according to claim 8, wherein the main part is designed as an enveloping body for receiving a radiation emitter, wherein the reflector is arranged on the outer side of the enveloping body, facing away from the radiation emitter; or in that the main part is designed as a tile-shaped radiation emitter, wherein the reflector is arranged on a plane side of the tile.

Description

EXEMPLARY EMBODIMENT

[0067] The invention is explained in more detail below using exemplary embodiments and a drawing. Thereby shown in detail are

[0068] FIG. 1 in schematic presentation and in cross section, an embodiment of an emitter component according to the invention in the form of an infrared emitter with a cladding tube, the upper side of which is partially covered with a reflector layer,

[0069] FIG. 2 a photo of a short-wave twin tube infrared emitter with a QRC reflector layer, which has subsequently been coated with a gold reflector (after the infrared emitter has been put into operation) using the method according to the invention, and

[0070] FIG. 3 a diagram with the result of radial measurements of the emission of infrared emitters with and without a mirror-reflective reflector layer, in comparison.

[0071] FIG. 1 schematically shows a horizontal lamp tube 1 made of quartz glass in cross section, the outer lateral surface 2 of which is coated approximately on one half of a side with a reflector 3. The reflector 3 is composed of an inner, diffusely reflecting reflector layer (opaque layer 4), an intermediate layer in the form of a thermally compressed surface region of the opaque layer 4 (glass film 5), and an outer mirror-reflective reflector layer (mirror layer 6). The presentation is not to scale; in particular, the thicknesses of glass film 5 and mirror layer 6 are shown extremely thick to improve recognizability.

[0072] A preferred procedure for producing the reflector 3 is explained in more detail in the following:

[0073] The production of the opaque layer 4 on the outer shell surface 2 of the cladding tube 1 takes place according to the known slip method described in DE 10 2004 051 846 A1. The flowable aqueous SiO.sub.2 slip is applied as a slip layer on the upper side of the cladding tube 1; the slip layer is subsequently dried and glazed to form the opaque layer 4. The opaque layer 4 thus obtained consists of porous, opaque quartz glass. It has a mean layer thickness of 2 mm and a density of approximately 2.15 g/cm 3. Its surface is open-pored, as shown by a dye penetration test.

COMPARATIVE EXAMPLE

[0074] In first experiments, the open-pore surface was impregnated with a gold-containing emulsion (gold resinate). The emulsion thereby penetrated into the open pores of the surface and was subsequently fired via heating. Upon firing, the gold resinate decomposes into metallic gold and resin acid which, for their part, along with the other components of the paste, are volatilized by the high firing temperature. However, contrary to expectation, a sealed, reflective metal layer, for example a noble metal layer, did not result; rather, the mass discolored black upon firing.

Example

[0075] In further experiments, the surface of the opaque layer 4 was thermally compressed beforehand before the mirror layer 6 is applied thereon. The thermal compression takes place by heating the opaque layer 4 with an oxyhydrogen burner. Very high temperatures of around 1800° C. are thereby produced locally, which enables the production of an optimally thin compression region (glass film 5) within a few seconds. The glass film 5 has only the function of sealing the surface of the opaque layer 4, and is kept as thin as possible and only as thick as necessary to fulfill this function. The thickness is approximately 200 μm, but at most 500 μm. Its surface is then dense and has no open porosity, as a dye penetration test shows. To reduce mechanical stresses, the cladding tube 1 is subsequently tempered in an oven. The tempering program includes heating to a temperature of around 1050° C. for a period of at least 3 hours.

[0076] The mirror layer 6 is subsequently applied onto the glass film 5 in the usual manner by printing, spraying, dipping, or coating technology. In the exemplary embodiment, an approximately 5 μm thick layer of a paste is applied onto the glass film 5 with a brush, which layer consists of a solution of gold resinate in a thick oil with low additives (˜1%) of resinates of glass formers for adhesion promotion. The cladding tube 1 with the deposited resinate layer is brought to a temperature of around 800° C. in an oven. In this heat treatment, the gold resinate decomposes into metallic gold and resin acid which, for their part, along with the other components of the paste, are volatilized by the high firing temperature. A thin, metallic mirror layer 6 of approximately 0.1 μm remains on the glass film. The mirror layer 6 thus produced (gold layer) exhibits no defects and a good adhesion to the thermally compressed glass layer 5.

[0077] The subsequent gold plating of an emitter that is already in use with a mirror layer 26 is explained using FIG. 2. The photo shows a short-wave infrared emitter in the form of what is known as a “twin tube emitter” 21, the upper side of which was provided with a reflector, in the form of an opaque layer with an open-pore surface, upon being put into operation. To produce the mirror layer 26, the twin tube emitter was dismantled and the surface of the opaque layer was subsequently thermally compressed, as explained above, and finally provided with a gold layer. The gold layer shows no defects and a good adhesion to the thermally compressed opaque layer.

[0078] In order to determine the effect of the additional mirror layer, the emitted optical power density (irradiance) was measured at infrared emitters with and without mirror layer. The radial measurement takes place in the usual manner using an infrared emitter mounted on a rotatable mounting, which rotates by 360 degrees in 5 degree increments. A thermopile sensor mounted at a distance of 20 cm thereby detects the radiation emitted by the infrared emitter. In the diagram of FIG. 3, the normalized irradiance (rel. unit) on the circle radius is plotted against the circumferential angle position (in degrees) of the measuring points. The measurement curve A, marked with diamonds, shows the result of the radial measurement given a commercially available short-wave infrared emitter with a diffusely reflecting reflector layer (“QRC emitter”), and the measurement curve B, marked with rectangles, shows the result of the radial measurement given retrofit coating of the QRC emitter with a gold layer using the method according to the invention.

[0079] In the rear emitter chamber 30, the measurement curve A shows a certain proportion of irradiation intensity. This is composed of transmitted primary radiation and of secondary radiation, which is to be ascribed to the heating of the opaque layer and the secondary radiation of the QRC emitter that is therefore diffusely emitted. In the measurement curve B, this portion is not present, or is at least markedly smaller than in measurement curve A.

[0080] In contrast, in the actual irradiation field 31, the measurement curve B shows a higher irradiance than the measurement curve A. This is to be ascribed to the fact that the secondary radiation radiated backwards is reduced by the gold reflector and instead is directed forward, and the power radiated forward is increased accordingly.

[0081] Via the additional gold reflector, the effective reflectivity of the infrared emitter increases from 82% (measurement curve A) to 91% (measurement curve B), and the power that can be used for the heating process increases by approximately 11%. These values result via integration of the areas enclosed by the measurement curves A or B in the rear space 30 or in the irradiation field 31.