Patent Publication Number: US-2011064915-A1

Title: Metal workpiece with three-dimensional pattern and production method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority benefits of U.S. Patent Provisional Application No. 61/241,962, filed on Sep. 14, 2009. The entirety of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to a production method of a metal workpiece, and more particularly to a method of producing a three-dimensional pattern on a surface of a metal workpiece. 
     2. Description of Related Art 
     Currently, electronic devices such as notebook computers, mobile phones, or digital cameras mostly adopt metal material for constituting the exterior. In order to advance the overall aesthetic appearance of electronic devices, various patterns are usually formed on the appealing configuration. Patterns are produced on the surface of metal material frequently by etching metal material with a solvent or by paint-spraying and transfer printing. Nonetheless, the surface treatment technique of the former is complicated and difficult, and the production thereof is highly contaminative. The latter is restrained by the chemical property of metal material, such that artistic configuration cannot be produced. 
     If patterns are formed on a plastic casing, IMD (In Mold Decoration), such as IMR (In Mold Roller) or IMF (In Mold Film), is commonly used which bonds a decoration stack having patterns therein to the plastic casing by injection molding. However, the method requires high adhesion for each layer of the decoration stack so that shedding problem often arise in practice. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a production method of a metal workpiece, so that a three-dimensional pattern is formed on the metal workpiece. 
     An embodiment of the invention provides a production method of a metal workpiece. An adhesive layer is applied on a metal workpiece. The adhesive layer is impressed by a mold so as to form a three-dimensional pattern. The adhesive layer is cured by implementing a plurality of heat treatments thereon. 
     In light of the foregoing, in the embodiments of the invention, the three-dimensional pattern is formed by applying the adhesive layer on the metal workpiece and impressing the mold on the adhesive layer. As a consequence, the technical requirements for forming three-dimensional pattern on metal workpiece are lowered effectively. Moreover, the readily production also increases the production efficiency of the metal workpiece. 
     Additionally, the main reasons of applying the invention to metal parts are as follows: 
     1. Post-Processing: the production method of the invention is applied to a flat workpiece to produce three-dimensional patterns thereon, and then a press molding is applied to the flat workpiece. 
     2. Temperature: the temperature of the primer selected in the invention is about 170° C., and the temperature of the common plastic ranges 90 degrees Celsius (polycarbonate, PC) to 160 degrees Celsius (acrylonitrile-butadiene-styrene, ABS). Therefore, the production method of the invention is not suitable for plastic casing. 
     In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIGS. 1-4  are flow diagrams of a production method of a metal workpiece according to an embodiment of the invention. 
         FIG. 5  is a schematic view of a metal workpiece according to another embodiment of the invention. 
         FIG. 6  is a schematic view of a metal workpiece according to another embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIGS. 1-4  are flow diagrams of a production method of a metal workpiece according to an embodiment of the invention. Referring to  FIGS. 1-4 , in the present embodiment, an adhesive layer  200  is applied on a metal workpiece  100 . The adhesive layer  200  is impressed by a mold  300 , where the adhesive layer  200  is cured simultaneously. Upon completion, the mold  300  is removed so as to form a three-dimensional pattern on the metal workpiece  100 . 
     In the present embodiment, the metal workpiece  100  is made of, for example, aluminum alloy (5052), stainless steel (430, 304), cold rolling steel (spcc), magnesium alloy (AZ91D, AZ61) or other metal materials suitable for constituting the exterior. Before the adhesive layer  200  is applied on the metal workpiece  100 , pre-treatment processes such as degreasing and baking are first performed to the metal workpiece  100  to ensure impurities that prevent the adhesive layer  200  from adhering to the metal workpiece  100  are eliminated. 
     After being applied on the metal workpiece  100 , the adhesive layer  200  is suitably baked and heated to reduce the fluidity thereof. The mold  300  having a three-dimensional pattern is provided and the mold  300  is usually made of transparent material so as to be pervious to light. A three-dimensional pattern complementary to the pattern of the mold  300  can be formed on the adhesive layer  200  by impressing the mold  300  on the semi-dry adhesive layer  200 . The adhesive layer  200  is then cured by photo-curing or thermal-curing depending on the type of the adhesive layer  200  used, wherein photo-curing may be applied by UV irradiating, thermal-curing may be applied by heat baking, and the operating parameters may be adjusted based on actual conditions. Generally, thermal-curing may be applied to a batch by baking them in a large oven, and the baking temperature ranges 150 to 200 degrees Celsius. 
     Additionally, the photo-curing process includes two parts as follows. Firstly, when the mold  300  is impressed on the adhesive layer  200 , the adhesive layer  200  is irradiated with UV of lower energy intensity (200 to 300 mj/cm 2 ) to keep the shape of the three-dimensional patterns of the adhesive layer  200 . Secondly, when the mold  300  is moved away from the adhesive layer  200 , the adhesive layer  200  is irradiated with UV of higher energy intensity (1000 to 1200 mj/cm 2 ) to fix the shape of the three-dimensional patterns of the adhesive layer  200 . 
     Either photo-curing or thermal-curing is a heat treatment so that photo-curing and thermal-curing may be used together. In an example, photo-curing is used to keep the shape of the shape of the three-dimensional patterns of the adhesive layer  200 , and thermal-curing is then used to fix the shape thereof. In another example, thermal-curing is used to keep the shape of the shape of the three-dimensional patterns of the adhesive layer  200 , and photo-curing is then used to fix the shape thereof. 
     In the present embodiment, the metal workpiece  100  is, for instance, a metal plate. Thus, in the process of producing this metal workpiece  100 , the production efficiency of the metal workpiece  100  can enhanced by transporting and processing with a roller apparatus. 
     Referring to  FIGS. 3 and 4 , when the adhesive layer  200  is cured and the mold  300  is removed, the appealing configuration of the metal workpiece  100  produced from the roller apparatus is further processed using a punching apparatus so as to punch the metal workpiece  100  from a plate state into a three-dimensional workpiece. Accordingly, the metal workpiece  100  of the present embodiment first forms the three-dimensional pattern in the plate state by using the above technique, and the metal workpiece  100  is then processed by the punching apparatus depending on the configuration required. Consequently, the technical difficulty of forming the three-dimensional pattern on the surface of the three-dimensional workpiece is overcome, and the suitability of the metal workpiece  100  is further increased. 
       FIG. 5  is a schematic view of a metal workpiece according to another embodiment of the invention. Unlike the above embodiment, before the adhesive layer  200  is applied on the metal workpiece  100 , a primer layer  300  is first applied on the metal workpiece  100  and then heated to about 170 degrees Celsius for adhering the adhesive layer  200  and the metal workpiece  100 . In addition, in the present embodiment, a color layer  400  is further disposed on the primer layer  300 , so as to color the metal workpiece  100 . The method of coloring the metal workpiece  100  is not limited in the present embodiment, and the color layer  400  can be disposed on the primer layer  300  by applying, screen printing, offset printing or intaglio printing. The color layer  400  may has two-dimensional patterns  410 , which and the three-dimensional patterns are continuous at bending portions of the metal workpiece  100 . The thickness of portions of the adhesive layer  200  at bending portions of the metal workpiece  100  is less than the thickness of portions of the adhesive layer  200  at flat portions of the metal workpiece  100 . Therefore, the three-dimensional patterns of the adhesive layer  200  and the two-dimensional patterns  410  can generate three-dimensional visual effects of pattern or grating by interference. After the adhesive layer  200  is cured, a passivation layer  500  is disposed thereon to prevent the following punching process from damaging the surface of the metal workpiece  100 . 
       FIG. 6  is a schematic view of a metal workpiece according to another embodiment of the invention. Referring to  FIG. 6 , in the present embodiment, the metal workpiece  100  has a first surface S 1  and a second surface S 2  disposed in a back to back manner. Before the adhesive layer  200  is applied, a first primer layer  600  and a second primer layer  700  are applied on the first surface S 1  and the second surface S 2  respectively. Consequently, the first surface S 1  and the second surface S 2  of the metal workpiece  100  are adhesive. Thereafter, the adhesive layer  200  is applied on the first primer layer  600 . After the adhesive layer  200  is cured, a plurality of three-dimensional components  800  are formed on the second primer layer  700  on the second surface S 2  of the metal workpiece  100  by using the injection molding technique. These three-dimensional components  800  are, for example, a plurality of bosses for assembling other components on the metal workpiece  100  conveniently. 
     On the other hand, referring to  FIGS. 5 and 6  simultaneously, in the embodiment shown in  FIG. 6 , the first primer layer  600  is a color primer layer, where a color dye is added to the primer layer  600 , for example. Thus, the metal workpiece  100  is colored without having additional color layer  400  printed on the primer layer  300  in  FIG. 5 . 
     In summary, in the aforementioned embodiments of the invention, the three-dimensional pattern is formed on the metal workpiece by applying the adhesive layer on the metal workpiece and impressing the adhesive layer with the mold. Accordingly, the technical difficulty of forming the three-dimensional pattern on the metal workpiece is effectively reduced. Moreover, the production of the three-dimensional pattern can be performed when the metal workpiece is in the plate state. After the production is complete, the metal workpiece is punched to form the three-dimensional workpiece, or a plurality of three-dimensional components is injection molded on the other side. The metal workpiece thus has lower production cost and higher suitability. 
     In addition, a three-dimensional workpiece is formed by punching a metal plate. The three-dimensional patterns formed by the adhesive layer are continuous at bending portions of the metal plate, and the thickness of portions of the adhesive layer at bending portions of the metal plate is less than the thickness of portions of the adhesive layer at flat portions of the metal plate. Therefore, the three-dimensional patterns and the two-dimensional patterns of the color layer therebelow can generate three-dimensional visual effect of pattern or grating by interference. 
     Although the invention has been described with reference to the above embodiments, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed descriptions.