Abstract:
A rolled product, especially a rolled product consisting of a metallic material, such as an aluminium sheet, for using in lighting engineering as a reflector surface, the surfaces on both sides of the rolled product displaying essentially the same reflective properties. One such rolled product is especially suitable as a material for constructing a reflector or for the anti-glare shade of a louvered light fitting. The rolled product is produced by first rolling the product and then providing the two optionally differently reflecting surfaces with similar reflective properties by a polishing process following the rolling.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a rolled product, in particular a rolled product made of a metallic material for use as a reflector material in lighting engineering, comprising a first surface and a second surface, in which the surfaces of the two sides exhibit a dispersive reflection behaviour for light. The invention also relates to a method for producing the rolled product, a device for carrying out the production method for the rolled product and the use thereof.  
         [0002]     Metal sheets, such as in particular rolled aluminium sheets, are used in technology for the most varied tasks. Thus, for example, rolled aluminium sheets have been used successfully for a long time as reflectors for lamp housings, in particular for lamp housings of fluorescent lamps (for example neon strip lamps with or without shielding louvres). In order to achieve an adequate gloss level for this application, it is generally still necessary to subsequently polish the rolled metal sheet, which can be achieved, for example, by a mechanical method (for example by glossing) or else by an electrolytic or chemical method (by a treatment in caustic baths), or else as a combination thereof.  
         [0003]     The demands which are to be made of lamp housings of fluorescent lamps are in accordance with the old DIN 5035, UGR DIN 12464 or the newly revised standard DIN 5035, Part 7. These standards aim to prevent people who are in the room lit with the corresponding lamp from being dazzled. This is important, in particular for monitor workstations. In the standard, for example, a light radiation behaviour, which is directed as far as possible downward, is required with different luminances being permissible as a function of the angle of the reflected beam. The standard is currently being revised. According to the old DIN 5035 standard, a luminance of a maximum of 200 cd/m 2  is permissible, for example, at a 50° angle (starting from the vertical). According to the new DIN 5035, Part 7, this value will probably be raised to 1,000 cd/m 2  if the monitors used meet certain minimum requirements.  
         [0004]     The production of the above-described reflector plates—in particular aluminium sheets—by means of a plurality of graduated rolling processes, is known per se.  
         [0005]     In the previously conventional metal sheets, the production of the metal sheet always took place under the premise that only one of the two sides of the metal sheet has to have a defined reflection behaviour for incident light.  
         [0006]     The rolled crude metal sheets, due to manufacturing, have different surface qualities on their upper and lower side. In order to be able to use the crude metal sheets as a reflector plate, polishing methods are required. These polishing methods have only been used on one of the two surfaces of the rolled product up to now. This was based on the assumption that good reflection behaviour on only one surface of the metal sheet is completely sufficient for its use as a reflector plate and therefore costs can be saved.  
         [0007]     However, it has been proven that it is advantageous for many reflector arrangements if the two surfaces of the reflector plate have substantially the same light dispersion behaviour. For certain reflector arrangements, the arrangement can be produced substantially more simply with a metal sheet of this type, as in a number of manufacturing steps, a separation process that would otherwise be necessary and a subsequent connecting process can be replaced by simple punching and bending of the proposed metal sheet. This corresponds to so-called follow-on composite manufacturing. A different reflection behaviour of the front and rear side of the aluminium sheet is also undesirable from the point of view of lighting engineering for use as glare protection plates, as this either spoils the appearance or the glare protection plate has to be implemented in two layers, for example as a V-plate.  
         [0008]     A further problem in known aluminium sheets consists in that the surface of the rolled metal sheet provided for the reflection also generally has an anisotropic light dispersion behaviour. In other words, a light beam shining on the metal sheet surface is conically expanded in the reflection, with, however, the cone in cross-section not having a circle as the base, but a form which differs therefrom, such as generally an ellipse as the base. This reflection behaviour leads to largely random illumination conditions and is therefore undesired.  
         [0009]     Highly diffuse light dispersal is also undesired, as, in this case, a too small directing effect and therefore too little influencing of the illumination conditions results and also the recommendations of DIN 5035, Part 7, would not be met. In particular, regulated light dispersion behaviour can then generally not be achieved. A highly glossy surface is indeed optimally suited per se to achieve the lighting engineering specifications, but the illumination behaviour thus occurring is felt to be unaesthetic by many people and is therefore undesired.  
         [0010]     The object of the invention is therefore to propose a rolled product which is suitable in respect of its properties to a special degree for use as a reflector material in lighting engineering, as well as a production method which is particularly suitable for the production of a rolled product of this type. Moreover, a suitable device is to be provided for carrying out the production method as well as an advantageous use of the proposed rolled product.  
       SUMMARY OF THE INVENTION  
       [0011]     In the scope of the invention, a rolled product with a first surface and a second surface, in which the surfaces of the two sides exhibit a dispersive reflection behaviour for light, is proposed, in which the reflection behaviour of the two surfaces is substantially the same. Differing from the previously prevailing paradigms, that, to avoid unnecessary costs, only one surface is processed in such a way that it receives the required reflection behaviour, it is therefore proposed, that the two surfaces of the metal sheet exhibit the desired reflection behaviour, and this should preferably be a regulated light-dispersive behaviour. Although this can lead to an increase in costs in the production process for the rolled product and therefore for the rolled product itself, these disadvantages can be balanced for a large number of applications by improved reflection behaviour and a simpler construction of the lamps, mirror optics and other light-directing components produced therefrom, such as louvered light fittings.  
         [0012]     Thus, for example, glare protection plates of louvered lamps with the proposed rolled product could simply consist of one piece of the proposed metal sheet, without the optics of the lamps or the light emitted thereby exhibiting undesired inhomogeneities. The rolled product can also be advantageously used for certain reflector arrangements, as in the case of a fissure line of the reflector, separation of the metal sheet, a rotation by 180° and a subsequent connection of the two parts is no longer necessary. Instead, substantially the same result can be achieved when using the proposed metal sheet, by means of composite manufacturing by simple punching and bending. In this follow-up composite manufacturing, the mirror optics are produced by punching and bending a single piece of, for example, aluminium sheet, so expensive joining of a plurality of parts, in which, moreover, care always has to be taken that the surfaces do not become scratched during the assembly processes, becomes unnecessary. The previously necessary marking of the preferred direction in the case of direction-dependent surfaces can also be dispensed with.  
         [0013]     It is advantageous if the surfaces exhibit an at least partially diffusely dispersive reflection behaviour. Owing to the diffuse light dispersion, relatively uniform illumination behaviour can be improved in different directions. The surfaces preferably exhibit a diffusely dispersive reflection behaviour which is as regulated as possible. Wishes with respect to an aesthetic appearance of the mirror optics can therefore be fulfilled.  
         [0014]     It is advantageous when the surfaces exhibit substantially isotropic reflection behaviour. A uniform illumination and improved glare protection can also be promoted thereby. It is called isotropic reflection behaviour when the light beam emitted from the reflector surface is rotationally symmetrical to the main beam direction (in other words to the angle of incidence). In a reflection with a certain diffuse beam expansion a light cone with a circle as a base would thus be produced, for example, from an incident laser beam, with a plurality of concentric circular lines in each case standing for lines of the same luminous intensity.  
         [0015]     It has been shown to be adequate if the gloss levels of the surfaces measured in different directions differ by less than 15%, preferably by less than 12%, particularly preferably by less than 9%, preferably by less than 6%. On the one hand, a substantially optimum radiation can be achieved thereby, on the other hand, the production costs are kept within limits, so the cost of producing the rolled product is not excessively increased. Values are to be regarded as gloss levels here, which can be measured, for example, with a reflectometer according to Dr. Lange, to DIN 67530 with a measuring angle of 60°. The measuring apparatus was calibrated with a metal mirror and set at 91%.  
         [0016]     It is also proven to be favourable if the gloss levels of the surfaces are higher than 45%, preferably higher than 50%, particularly preferably higher than 60%, preferably higher than 70%.  
         [0017]     It is also advantageous if the gloss levels of the first and second surface of the rolled product differ by less than 15%, preferably by less than 12%, particularly preferably by less than 9%, preferably by less than 6%.  
         [0018]     It is also to be preferred if the total reflection is greater than 80%, preferably greater than 84%, particularly preferably greater than 86%. This is the total reflection to DIN 5036, Part 3 for visible light. In the case of visible light this may be the standard light type A (artificial light) or the standard light type D65 (daylight).  
         [0019]     The values can be produced particularly advantageously if the surfaces have a polished surface layer, an anodised surface layer or a combination of these.  
         [0020]     To protect the surfaces, at least one transparent scratch protection layer, at least one transparent corrosion protection layer or a combination of layers of this type can be arranged on the surfaces.  
         [0021]     Obviously, a combination of said surface layers with one another is also possible.  
         [0022]     It has also proven to be particularly advantageous if the rolled product consists of aluminium or alloys thereof or contains aluminium and alloys thereof, wherein the aluminium base metal contains a purity of at least 99% by weight, in particular at least 99.5% by weight, preferably at least 99.8% by weight, particularly preferably at least 99.85% by weight, preferably at least 99.9% by weight, particularly preferably at least 99.95% by weight.  
         [0023]     Reference is also made to the fact that in all the intervals mentioned above, all the intermediate values are to be regarded as also disclosed.  
         [0024]     It is advantageous when the rolled product is initially rolled and then polished, in such a way that the desired reflection behaviour results. In this case, the crude product produced by rolling can be processed therefrom by means of any gloss methods known per se, such as mechanical polishing methods, electrolytic or chemical polishing methods etc. or by a combination thereof.  
         [0025]     However, it is possible, for the surfaces to be formed initially with different reflection behaviours, and then for at least one surface to be polished in such a way that the surfaces receive substantially the same reflection behaviour. In this method, already available manufacturing routes can be used, in particular. The different surface composition is then compensated by a polishing process of the rougher or matter surface, so the two surfaces as a result have substantially the same reflection behaviour. Obviously, it is also possible for the two surfaces to be polished, one surface then having to be polished more highly, of course, the other surface less highly.  
         [0026]     It is advantageous when the rolling process has a plurality of rolling steps, such as preferably at least one cleaning step for cleaning surfaces. When the rolling process takes place in a plurality of steps, the respective deformation of the rolled product is less, so the surface faults are also reduced. One or more cleaning steps for cleaning the surfaces can be provided for the individual rolling steps, intermediately, or else finally.  
         [0027]     A highly alkaline bath is preferably used for cleaning the surfaces. A bath of this type has already proven advantageous in the treatment of conventional metal sheets.  
         [0028]     In the case of a device that is particularly suitable for carrying out the described production method, rollers are provided, the rollers processing the rolled product having blasted surfaces, in particular surfaces blasted with round or angular grit. Corundums or carbides have proven successful as grit of this type. The blasting should take place in such a way that a homogeneous and isotropic rolling surface is produced.  
         [0029]     A further surface finishing may consist in the rollers processing the rolled product having surfaces which have been prepared by so-called “laser beam finishing”, “electron beam finishing” or “electron discharge texturing”. A combination of these methods, also with the above-described blasting of the surfaces, is obviously possible.  
         [0030]     It is also sensible for at least one speed synchronisation device to be provided which brings about a substantially similar speed of roller surfaces and the surfaces of the rolled product to be processed. There are thus substantially no relative movements between the roller surfaces and the surfaces of the rolled product to be processed. In particular, longitudinal grooves can thus be avoided which could be problematical with respect to an isotropic reflection behaviour of the corresponding surfaces.  
         [0031]     It is advantageous if the described rolled product is used for the reflector of a lamp, for the glare protection of a lamp, or for both. This is particularly advantageous, in particular for lamps for fluorescent tubes, such as, for example, in the case of so-called neon strip lamps or louvered lamps. Obviously, a use for so-called plug louvres, push-through louvres, projection reflector plates and for other reflectors, in which the active side is used on either side in terms of light engineering, is also conceivable.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]     Further advantages, features and details of the invention emerge from the following description of a preferred embodiment and with the aid of the drawings, in which:  
         [0033]      FIG. 1  shows the schematic structure of the measuring process;  
         [0034]      FIG. 2  shows projection images of various surfaces;  
         [0035]      FIG. 3  shows lines of the same brightness for the projection images shown in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0036]     The rolling method for producing the metal sheets from a blank takes place in a manner which is known per se. For example, a blank of a given thickness is rolled in one or more passages or passes between a pair of rollers or a plurality of pairs of rollers to the desired thickness. The material web can then be moved back and forth in the process between two-rollers, or be moved on in a continuous direction and rolled by a plurality of pairs of rollers. A combination of the two possibilities is also conceivable.  
         [0037]     In the following example, a texturing of the surface of the rolled product then takes place by means of a correspondingly formed pair of rollers. A corresponding texturing on the two surfaces of the material web can then be achieved by a texturing of the pair of rollers, in order to achieve predetermined optical properties of the surfaces.  
         [0038]     Following the rolling process, a further surface finishing can be carried out. In this case, surface processing methods, material deposition methods or material application methods that are known per se, can be used.  
         [0039]     For example, polishing may be carried out by electrolytic or chemical polishing. Moreover, an electrolytic or chemical treatment may not only take place for finishing the surface of the rolled product. A chemical surface treatment, for example, by means of a highly alkaline bath is also conceivable in the course of the production method, in order to clean the surfaces prior to the next rolling step.  
         [0040]     A surface treatment by anodising is also conceivable. This may take place, for example, by means of acid electrolytes from the range of sulphuric acid, phosphoric acid, citric acid, tartaric acid, or chromic acid electrolytes, as well as a combination of these. This may take place both by means of direct current methods or by means of alternating current methods.  
         [0041]     Surface removal by means of vapour or gas deposition from a vacuum is also possible. In the process one or more layers of metals, metalloids or their oxides, nitrides or fluorides or mixtures thereof may be provided.  
         [0042]     Thermal evaporation, electron beam evaporation, sputtering, (in particular magnetron sputtering) with and without ion support may be provided as evaporation methods, in particular. Apart from these or other physical vapour deposition methods (physical vapour deposition, PVD), chemical gas phase depositions (chemical vapour deposition, CVD) can obviously be used with and without ion support.  
         [0043]     A transparent scratch protection layer or corrosion protection layer may also be provided. A layer of this type may also be provided, in particular, on a surface which has already been provided with a metal layer by vapour deposition.  
         [0044]     The surface finishing steps described are carried out in such a way here that substantially similar surfaces of the rolled product subsequently result. If the surfaces of the crude metal sheet thus have an initially different surface quality, different surface finishing steps are accordingly applied to the two surfaces, or the finishing steps used are carried out with a different intensity.  
         [0045]      FIG. 2  shows projection images  29  of different surfaces.  FIG. 2   c  shows a particularly suitable surface, the two surface sides of the rolled product substantially exhibiting the same reflection behaviour in the present case.  
         [0046]      FIG. 1  schematically shows the measuring arrangement for producing the projection images  29  shown in  FIG. 2 . A laser beam  22  generated by a laser  21  falls on a first side  15  of the material web  14 . Only one section of the material web  14  is shown in the present case for reasons of clarity.  
         [0047]     The incident laser beam  22  is partially diffusely dispersed from the first side  15  of the material web  14 . An expanded reflection beam  24  forms around a preferred direction  25  (this is determined according to the conventional reflection law). This generates a projection image  29  in a measuring region  27  of the monitor  26 . The projection image  29  is recorded by a camera  31 , the angle distortion in the present embodiment, which occurred owing to the recording of the projection image  29  at an angle, was corrected by an electronic computer (not shown here).  
         [0048]     In a partial reflection, the projection image has a bright central point  33 , the position of which coincides with the impact point of the preferred direction  25  of the reflection beam  24  on the monitor  26 . Around this central point  33 , the luminous intensity decreases radially outwardly.  
         [0049]      FIG. 2  shows projection images  29  of different surfaces. In this case, the surface shown in  FIG. 2   c  corresponds very substantially to the ideal of an isotropic expansion in a limited angle space of, for example, 2°. The luminous intensity has dropped to a relatively large degree after the first circle of the graticule and has substantially dropped completely after the second circle of the graticule. A circle of the graticule corresponds to an angle range of  20 . It can also clearly be seen in  FIG. 2   c  that the light dispersion is substantially isotropic, and consequently the projection image  29  is radially symmetrical to the centre of the central point  33 .  
         [0050]     The surface in  FIG. 2   b  is too glossy in comparison. In other words, the beam expansion of the reflection beam  24  is too small. The luminous intensity has already dropped substantially completely after an angle range of about 0.50. Moreover, the light distribution is too anisotropic, i.e. the light drop in the x- and y-direction of the coordinate system takes place at different rates.  
         [0051]     In  FIG. 2   e  and  2   d , the light expansion is relatively marked in each case; moreover, these surfaces have an isotropy. This reflection behaviour lies within a still just usable limit range.  
         [0052]      FIG. 2   e  finally shows a very diffusely dispersive surface which moreover exhibits too high an isotropy. The associated surface, similarly to the surface associated with  FIG. 2   b , can no longer be used for the provided purpose.  
         [0053]      FIG. 3  finally shows a further manner of application for the projection diagrams of  FIG. 2 . The drawn-in lines are lines with the same brightness. The respective numbering below corresponds to that of  FIG. 2 . A surface is therefore desirable which exhibits the diagram of  FIG. 3   c  in the case of a measurement, so the lines with the same brightness lie substantially in a circular manner around the central point  33  and lie at a defined spacing from one another—the spacing of the lines being a measure for the angle expansion of the reflection beam  24 .  
         [0054]     The surfaces should preferably be the same on the two sides of the rolled product and, in the ideal case, have the reflection behaviour according to  FIG. 2   c  or  3   c.    
         [0055]     Slight deviations between the two sides are tolerable, however. Thus, for example, a rolled product with a first side which has a dispersion behaviour according to  FIG. 2   c  or  FIG. 3   c  and the second side of which has a dispersion behaviour according to  FIG. 2   b  or  2   d  or  FIG. 3   b  or  3   d  can still be used advantageously to form a lamp reflector.  
         [0056]     The rolled products preferably consist of a metal, such as, in particular, aluminium. In the use of aluminium, the mass fraction of the aluminium in base metal should fulfil certain minimum requirements, such as for example have a weight fraction of more than 99% by weight, 99.5% by weight, 99.8% by weight, 99.85% by weight, 99.9% by weight or 99.95% by weight.