Abstract:
A method for manufacturing of a decorative element, particularly intended to be used as an emblem on a motor vehicle, comprises the steps of forming a body of a transparent plastic material, having a front face and a back face which comprises a base surface and at least a shaped hollow impression defining a tridimensional symbol raised with respect to the base surface, applying a decoration layer usually colored and/or providing an ornamental pattern, on the base surface, and forming a metalized layer on the back face by a paint containing metallic pigments so that also the inner surface of each hollow impression is coated. The pigments of the metalized layer are laminar metallic pigments, and the metalized layer is made by spray applying a plurality of coats of pigmented paint according to mutually crossing directions, in which the pigments are oriented parallel to the surface of the back face.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention refers in general to decorative members to be used for example as emblems in order to represent symbols or marks, particularly intended to be applied on motor vehicles in order to allow the producer to be identified. 
         [0002]    In particular, the invention relates to a method for manufacturing such a decorative member including the steps of:
       forming a body of a transparent plastic material, having a substantially smooth front face and a back face comprising a base surface and at least a shaped hollow impression adapted to define a tridimensional symbol raised with respect to the base surface,   applying a decoration layer, usually colored and/or providing an ornamental pattern, on the base surface, and   forming a metalized layer on the back face by a paint containing metallic pigments, in order to cover also the inner surface of each hollow impression.       
 
         [0006]    This method, known from EP-1 927 480, comprises initially the step to form a body of transparent plastic material, typically made by molding, the back face of which comprises a base surface, which is flat or slightly concave, and at least a hollow shaped impression adapted to define a symbol. Only on the base surface, except for the hollow impressions, a usually colored transparent layer is applied before, and then a metallic layer with reflecting characteristics, in such a manner that these two overlapping layers confer a reflecting aspect to the base surface. Subsequently, on the whole base surface, therefore also inside each hollow impression, a single pigmented paint layer, typically including metallic pigments, is applied, and on the pigmented paint layer a protective layer with a function of outer cover is finally applied. 
         [0007]    Although the decorative member of this document is able to produce a good effect of depth and tridimensionality of the image reproduced by it, it has the drawback that it does not stands out in a full satisfactory manner. In fact, the traditional type of pigmented paint used, that commonly comprises pigments having a generally spherical or globular shape, does not allow a clear and highly defined appearance to be obtained for the symbol, that instead turns out to be rather opaque and dull. 
         [0008]    Therefore, it would be desirable to make a decorative member standing out in a very clear manner, and having an improved aesthetic worth in order to determine a strong attraction for the attention of an observer. 
       SUMMARY OF THE INVENTION 
       [0009]    In view of the attainment of this object, the subject of the invention is a method for manufacturing of a decorative member, particularly intended to be used as an emblem on a motor vehicle, such as claimed. 
         [0010]    By virtue of the method of the invention, a very bright decorative member can be obtained, which is highly clear and defined, and has improved characteristics of visibility by an observer, so that it is able to exercise an effective attraction. Moreover, the decorative member according to the invention can be made by mass production with reduced costs and, for its constitution, it allows to comply with the requirements of duration and resistance to atmospheric agents imposed by motor vehicles manufacturing industries. 
         [0011]    Further characteristics and advantages of the invention will turn out to be clearer from the following detailed description, supplied as a non-limitative example and referred to the appended drawings in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic front perspective view of a first modification of a decorative member made by the method of the invention, 
           [0013]      FIG. 2  is a perspective view of the member of  FIG. 1  sectioned along line II-II of such a figure, 
           [0014]      FIG. 3  is a side elevational view sectioned from arrow III of  FIG. 2 , 
           [0015]      FIG. 4  is a view similar to  FIG. 3  of a second modification of the member of the invention, 
           [0016]      FIG. 5  is a view similar to  FIG. 3  of a third modification of the member of the invention, and 
           [0017]      FIG. 6  is a view similar to  FIG. 4  of a fourth modification of the member of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    With initial reference to  FIGS. 1 to 3 , a decorative member that can be obtained by a first modification of a method according to the invention, is indicated  10 . In spite of the fact that the shape of the member  10  of these figures is circular, it could obviously be any one. 
         [0019]    The emblem  10  comprises a body  12  of transparent plastic material, usually of polymethyl-methacrylate (PMMA), of polycarbonate (PC) or of another material with similar characteristics of transparency, formed by a molding process, typically of the injection type. 
         [0020]    The front face  12   a  of the body  12 , intended to face towards the outside in the use, and therefore towards an observer, is substantially smooth and preferably has a convex shape, while the back face  12   b , opposite to the face  12   a , includes a flat or slightly concave base surface  13 , so that the body  12  has the general appearance of a lens. 
         [0021]    In the body  12 , a series of shaped hollow impressions  14   a  and  14   b  are formed during the molding thereof, which impressions have walls transverse to the base surface  13  and define the outline of an image to be seen by means of the emblem  10 . Therefore, the image defined by the impressions  14   a  and  14   b  is tridimensional since it projects from the base surface  13  towards the front face  12   a , and it is mostly visible thanks to the lens configuration of the body  12 . 
         [0022]    In the more general case, the image defined by the impressions  14   a  and  14   b  includes a commercial trade name or a word  16   a  consisting of letters, and/or a graphical member  16   b  such as a drawing or a logo. 
         [0023]    The plastic material used for making the body  12  preferably contains an agent adapted to filter UV rays, so that the body  12  carries out a protective action for the underlying layers, the latters being described in detail in the following. The filtering agent may consist of a substance belonging to the benzotriazole family. In particular, by adding about 2.5% in weight of a masterbatch concentrated containing 2-(2H-benzotriazole-2-yl)-p-cresol to the plastic material of the body  12 , an effective filtering action against UV rays can be obtained. 
         [0024]    Before the molding step, the plastic material of the body  12  is prepared by subjecting it to a dehumidification process, in order to remove any possible humidity from the material. 
         [0025]    The molding step of the body  12  is performed by using molds with a mirror finished surface, and having therefore a surface roughness usually smaller than 1 μm, in such a manner that the back surface of the body  12 , at least at the hollow impressions  14   a  and  14   b , is mirror finished. 
         [0026]    After the molding step, the body  12  preferably undergoes again a dehumidification process, in order to remove any possible remaining humidity trace. 
         [0027]    Then, the back surface of the body  12 , at least at its impressions  14   a  and  14   b , is subjected to a crown effect cleaning process by means of electric discharges or cold plasma or liquid CO 2 , in order to eliminate possible dusts, impurities and traces of fat. 
         [0028]    A decoration bottom layer  18  including a pigmented ink, for example transparent and preferably acrylic-vinylic based, is applied only on the base surface  13  of the back face  12   b , with a thickness of some micron. The pigments of the ink of the layer  18 , which are usually colored and are conveniently of the type resistant to the action of UV rays, serve to give a color to the base surface  13 , or to define an ornamental pattern on it. In particular, the ink layer  18  can be monochromatic if the background of the emblem  10  must be colored in an even manner, or define several colored zones when a polychrome effect is desired to be obtained. 
         [0029]    The layer  18  is preferably applied by stamping out or molding by a pad (pad-printing), by using a pad or a roll soaked by the pigmented ink, or by means of a serigraphic process. 
         [0030]    After application of the layer  18 , a metalized layer  20  is made on the whole back face  12   b  by using a paint containing metallic pigments, typically aluminum pigments. Differently from the metallic pigments of the traditional metalized paints, which have a spherical or globular shape with diameter in the range between about 5 and 30 μm, the metallic pigments of the paint used in the method of the invention for making the metalized layer  20 , are laminar pigments having a thickness usually in the range between about 1 and 15 Å, with a substantially circular shape the diameter of which is in the range between about 10 and 15 μm. 
         [0031]    The layer  20  is made by spray applying a plurality of coats of the aforesaid metalized paint on the whole back face  12   b  of the emblem  10 , and therefore on the inner surface of the impressions  14   a  and  14   b , and also on the back surface of the layer  18  and on the outer surface of a perimetrale edge  22  of the member  10 . In particular, the direction of application of each coat is tilted, or crossed, with respect to that of the adjacent coats. 
         [0032]    Thus, a metalized layer  20  is obtained that constitutes in practice a continuous metallic film with characteristics of almost perfect reflection and clearness, since the laminar shape and the very small size of the metallic pigments of the paint allow very thin and compact layers to be obtained, in which the pigments are oriented parallel to the surface of the back face  12   b , in particular to the inner surface of the impressions  14   a  and  14   b . This parallel orientation of the pigments, caused by the electrostatic linkage between the material of the body  12  and the metallic pigments of the first pigmented paint coat, as well as between the metallic pigments of the different further coats, allows hiding power and reflectance of the surface to be increased, so that the layer  20  becomes just analogous to a continuous metallic layer. A metalized layer with these characteristics, in the past, could only be obtained by using other processes such as vacuum metalization or ionic vaporization (sputtering), which are remarkably more expensive and intrinsically little resistant to atmospheric agents. 
         [0033]    The treatments performed on the plastic material of the body  12  before and after the molding thereof, as well as the mirror finish of the back face surface  12   b , allow the service life and the clearness of the image of the decorative member  10  to be remarkably increased. In fact, by virtue of the mirror finish of the surfaces on which the layer  20  is applied, the pigments of the metalized paint are applied on a surface lacking in any discontinuity, which allows an optimal specular effect to be obtained. Moreover, by virtue of the fact that any trace of humidity has been removed from the material of the body  12 , that otherwise could oppose adhesion of the metallic pigments and promote its oxidation, the weatherability of the image of the member  10  turns out to be improved in the time. 
         [0034]    In spite of the fact the layer  20  requires a series of paint coats to be applied, the method turns out to be simpler and cost saving in its whole, with respect to those used in the prior art for obtaining images with a specular reflection. In particular, the whole time required for drying of the various coats of the layer  20  is substantially smaller than that required for drying a single thicker layer of metalized paint used in the prior art, containing spherical or globular metallic pigments of a much greater size. 
         [0035]    On the whole back surface of the layer  20 , including the outer surface of the edge  22 , a protective covering layer  26  is then applied by spray painting. The layer  26  is preferably made by a dark colored, for example black, polymeric polyurethane or acrylic based paint, with a low content of colored pigments. 
         [0036]    Conveniently, the protective layer  26  includes at least 10% in weight of zinc powder. The zinc contained in the layer  26  carries out a function of anodic protection of the aluminum metallic pigments of the layer  20  towards the corrosive atmospheric agents, both acid or basic based. This protection is particularly useful when the member  10 , as often happens, is subsequently fixed to a support frame shaped member (not shown), usually made of plastic material with chromium plated surface, since the presence of chromium may make worse galvanic corrosion phenomena of the aluminum pigments contained in the layer  20 . 
         [0037]      FIG. 4 , that is similar to  FIG. 3 , shows a second modification of the decorative member of the invention, here indicated by reference  10   a . The numeral references used in this figure for indicating elements equal or similar to those of the previous modification, are the same of the previous figures, and the elements already described will not be considered again. 
         [0038]    The decorative member  10   a  is made with a decoration layer  18  containing transparent colored pigments, and moreover includes a metallic laminar layer  22  having characteristics of specular reflection, preferably of bright chromium, applied directly on the back surface of the layer  18 . In this manner, the layers  18  and  22  applied on the flat surface of the face  12   b  constitute a reflecting and colored bottom surface. 
         [0039]    Preferably, the laminar metallic layer  22  is applied by using the known hot-stamping technology, consisting of a dry stamping process by means of which colored pigments or a thin metallic layer are permanently transferred on a component starting from a continuous support film, for example of a plastic material, as a result of the application of pressure and/or heat. Commonly, in the hot-stamping process, a silicone rubber pad or roll, the shape of which corresponds to the shaped surface to be stamped, is commonly used. As an alternative, the pigmented ink layer  18  may be directly applied on a metallic sheet or on a metalized sheet constituting the layer  22 , and then the layers  18  and  22  are transferred together on the base surface  13  of the body  12  by a single step, for example of hot-stamping. 
         [0040]      FIG. 5 , that is similar to  FIG. 3 , shows a third modification of the decorative member of the invention, indicated here by reference  10   b . The numeral references used in this figure for indicating equal or similar elements, are the same of  FIGS. 1 to 3 , and the elements already described with reference to the first modification will not be considered again. 
         [0041]    The decorative member  10   b  includes moreover a layer  24  of transparent colored paint, applied by a spray application process on all the back surface  12   b  of the body  12 , including therefore also the impressions  14   a  and  14   b.    
         [0042]    The layer  24 , that is therefore interposed between the impressions  14  and  14   b  of the body  12  and the layer  20 , allows a color of a desired tonality to be given to the layer  20 , and possibly to the layer  18 . In particular, if the layer  20  contains aluminum pigments and therefore constitutes a metallic film having an appearance similar to bright steel or silver, a layer  24  yellow or red colored allows an appearance of the image of the decorative member  10   b  similar to the gold or copper to be obtained, respectively. 
         [0043]      FIG. 6 , that is similar to  FIG. 5 , shows a fourth modification of the decorative member of the invention, here indicated by reference  10   c . The numeral references used in this figure for indicating equal or similar elements, are the same of  FIGS. 1 to 5 , and the elements already described with reference to the previous modifications will not be considered again. 
         [0044]    The decorative member  10   c , comprises both the layer  22  at the back of the layer  18 , described with reference to the second modification, and the colored layer  24  described with reference to the third modification, which layers are applied on the back face  12   b  before the metalized layer  20  is made on it