Abstract:
An anodizing color drawing method includes the steps of providing a metal workpiece; performing an anodic treatment of the metal workpiece to form a coating layer on a surface of the metal workpiece and a plurality of pores on the coating layer; using a plurality of electronic ink-jet nozzles to spray a plurality of dyes by a printing method and the dyes permeate into the pores of the coating layer, and forming a color drawing pattern on the coating layer; and performing a sealing treatment on the coating layer with the color drawing pattern. A color drawing layer processed by the anodic treatment has an enhanced hardness to reduce scratches and damages and maintain the aesthetic look.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention The present invention relates to a color drawing method, and more particularly to the anodizing color drawing method. 
         [0002]    2. Description of the Related Art 
         [0003]    In general, an electronic 3C product such as a mobile phone or a notebook computer usually comes with a light, convenience and low-priced housing made of engineering plastics. For the aesthetic purpose, dyes are sprayed on the surface of the housing to form a color drawing pattern. However, the plastic housing generally has an insufficient hardness and may be scratched or damaged easily. Therefore, some manufacturers provide a service of wrapping invisible shields on an electronic product such as the mobile phone. However, the wrapt products is lack of textures and usually unacceptable by users. To enhance the hardness of the housing while maintaining the lightweight condition, metals including aluminum alloy or aluminum magnesium alloy are used for making the housing of 3C products, and the 3C products of this sort are introduced to the market in a large quantity. 
         [0004]    On the other hand, the aluminum alloy may be oxidized easily. Even though the oxide layer has an inactivation effect, yet the oxide layer may still falls off and loses its protective effect due to its exposure for a long time, and the purpose of the anodic treatment is to use the easy oxidation feature and an electrochemical method to control the formation of the oxide layer, so as to prevent aluminum from being oxidized while enhancing the mechanical properties of the surface. Another purpose is to produce color and luster by different chemical reactions to improve the aesthetic appearance. 
         [0005]    At present, the conventional anodic treatment comprises the procedures of degreasing, etching, neutralization, anodic treatment and sealing Wherein, the degreasing procedure is to place the aluminum alloy workpiece in a heated degreasing solution to wash away oil stains on the surface of the aluminum alloy surface; the etching procedure is to dip the aluminum alloy workpiece into an alkaline solution to remove the naturally existing oxide film on the surface of the aluminum alloy and produce hydroxide to remove any physically attached oil and grease; the neutralization procedure is to dip the aluminum alloy workpiece into a nitric acid solution to neutralize black stain on the alkaline washed surface; the anodic treatment procedure is to place the aluminum alloy workpiece in an electrolytic trough and connect an anode and pass direct current to electrolyze the electrolyte, so that the surface of the aluminum alloy is oxidized gradually to form a porous oxide film with appropriate color and luster; and the sealing procedure is to seal the small holes on the surface of the porous oxide film on the surface of the aluminum alloy after the anodic treatment takes place, so that the workpiece is smooth, wear-resistant, and corrosion-resistant. 
         [0006]    After the anodic treatment, laser engraving or CNC is used for damaging the surface of the oxide film to create a required pattern or text label on the surface of the aluminum alloy workpiece, and thus the pattern and text label are limited to the color and luster of the aluminum alloy and cannot be expressed in other colors. In general, manufacturers will take the texture into consideration by using a colorless or a light color for the oxide film. As a result, the pattern and text label are not obvious. In addition, the pattern and text label are formed by damaging the surface of the oxide film, so that the oxide film at the positions of the pattern and text label will lose its hardening and protective effects. 
         [0007]    To overcome the aforementioned problems, some manufacturers attempted to paint a multiple of colors on the workpiece of the anodic treatment to provide changes to the stylish look of the pattern, and the painting methods are described as follows: 
         [0008]    1: The workpiece is degreased, rinsed and anodically treated to form a single color, and the desired color portions are coated with corrosion resisting ink, and then the workpiece is put into a processing trough containing nitric acid to perform a surface etching and corrosion process of the ink surface without coated with ink, and then an anodic treatment of the workpiece is performed by putting the workpiece into an electrolytic trough containing a second dye solution, and a second color is formed at positions where the aforementioned surface etching process is taken place by nitric acid, and so on. The same procedure is repeated according to the number of colors. When the procedure is repeated to accomplish the desired a plurality of colors, an organic solvent is used to remove the ink, and finally a chemical sealing is performed at the surface to produce a protective film layer. Obviously, such procedure is complicated and time consuming, and requires a large quantity of dyes, not only incurring a higher cost, but also causing environmental pollution. 
         [0009]    2: The workpiece is painted by performing a first anodic treatment, wherein a first color is formed on the surface of the workpiece, and then a manufacturing cutting removal method is applied to cut and remove the portion wherein a second color is desired. After the portion is removed, the anodizing coloring process of the second color takes place. Besides the manufacturing cutting removal method, laser can be used to sinter a portion of the surface in order to remove the portion of the first color. The same process can be applied and repeated according to the numbers of required colors. Finally, chemicals are used for sealing to form a surface protective film layer, and this method also has the drawbacks of consuming more time, labor and dyes, and thus incurring a higher cost and environmental pollution, and the process of applying the dyes for many times may contaminate with each other during the coloring process to result in a color difference and a high defective rate. 
         [0010]    3: The anodic treatment method is used for applying a first color, and then a discoloring agent such as hydrogen peroxide is used to remove a portion of the color, and the anodic treatment is performed to apply a second color on the color removed portion, and so forth. Finally, chemicals are used for sealing to form a surface protective film layer. However, such manufacturing process also consumes much time, labor and dyes to increase the cost and cause environmental pollutions, and the process of applying the dyes for many times may contaminate with each other during the coloring process to result in a color difference and a high defective rate. 
       SUMMARY OF THE INVENTION 
       [0011]    In view of the problems of the prior art, it is a primary objective of the present invention to provide an anodizing color drawing method capable of enhancing the hardness of a color drawing layer and preventing the color drawing layer from being scratched or damaged, so as to reduce the occurrence of patterns peeling off 
         [0012]    To achieve the aforementioned objective, the present invention provides an anodizing color drawing method, comprising the steps of: providing a metal workpiece; performing an anodic treatment of the metal workpiece to form a coating layer on a surface of the metal workpiece and a plurality of pores on the coating layer; using a plurality of electronic ink-jet nozzles to spray a plurality of dyes on the coating layer by a printing method and the dyes permeate into the pores of the coating layer, and forming a color drawing pattern on the coating layer; and performing a sealing treatment on the coating layer with the color drawing pattern. 
         [0013]    Wherein, the dye comprises a black oil-based solvent ink, a green oil-based solvent ink, a red oil-based solvent ink and a yellow oil-based solvent ink. 
         [0014]    Wherein, the anodic treatment is a decorative anodic treatment, a semi-hard coating anodic treatment, a hard coating anodic treatment, a super hard coating anodic treatment or a lubricated anodic treatment. 
         [0015]    Wherein, the metal workpiece is made of aluminum, aluminum alloy, magnesium, magnesium alloy, titanium, titanium alloy, tantalum or tantalum alloy. Wherein, the electronic ink-jet nozzle is a piezoelectric ink-jet nozzle, such that when power is turned on, a piezoelectric transistor of the piezoelectric nozzle produces a deformation to squeeze out the dyes. 
         [0016]    Wherein, the electronic ink-jet nozzle is a thermal sensing ink-jet nozzle, such that when power is turned on, the thermal sensing ink-jet nozzle forms bubbles of the dyes, so as to produce a pressure to squeeze out the dyes. 
         [0017]    Wherein, the electronic ink-jet nozzle is a static charge type ink-jet nozzle, such that when power is turned on, the static charge type ink-jet nozzle drives the dye to carry electric charges, and an electric field is controlled to guide a traveling direction of the dye. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a flow chart an anodizing color drawing method in accordance with a preferred embodiment of the present invention; 
           [0019]      FIG. 2  is a schematic view of an anodizing color drawing method in accordance with a preferred embodiment of the present invention; 
           [0020]      FIG. 3  is a schematic view of a first electronic ink-jet nozzle used by an anodizing color drawing method in accordance with a preferred embodiment of the present invention; 
           [0021]      FIG. 4  is a schematic view of a second electronic ink-jet nozzle used by an anodizing color drawing method in accordance with a preferred embodiment of the present invention; 
           [0022]      FIG. 5  is a schematic view of a third electronic ink-jet nozzle used by an anodizing color drawing method in accordance with a preferred embodiment of the present invention; and 
           [0023]      FIG. 6  is a schematic view of a printer used by an anodizing color drawing method in accordance with a preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The technical contents of the present invention will become apparent with the detailed description of preferred embodiments and the illustration of related drawings as follows. 
         [0025]    With reference to  FIGS. 1 and 2  for a flow chart and a schematic view of an anodizing color drawing method in accordance with a preferred embodiment of the present invention respectively, the anodizing color drawing method comprises the following steps: 
         [0026]    S 11 : Provide a metal workpiece  11 . 
         [0027]    S 12 : Perform an anodic treatment of the metal workpiece  11  to form a coating layer  12  on a surface of the metal workpiece  11  and a plurality of pores  13  on the coating layer  12 . 
         [0028]    S 13 : Use a plurality of electronic ink-jet nozzles  14  to spray a plurality of dyes  15  on the coating layer  12  by a printing method, and permeate the dyes  15  into the pores  13  of the coating layer  12 , and form a color drawing pattern  16  on the coating layer  12 . 
         [0029]    S 14 : Perform a sealing treatment on the coating layer  12  with the color drawing pattern  16 . 
         [0030]    Wherein, the metal workpiece  11  is one that the anodic treatment can be applied easily, and the metal workpiece can be made of aluminum, aluminum alloy, magnesium, magnesium alloy, titanium, titanium alloy, tantalum or tantalum alloy. 
         [0031]    Wherein, the dye  15  comprises a black oil-based solvent ink, a green oil-based solvent ink, a red oil-based solvent ink and a yellow oil-based solvent ink. 
         [0032]    Before the anodic treatment takes place, the metal workpiece  11  is degreased, rinsed, chemically polished (by acids or alkalis such as phosphoric acid, nitric acid, and strong alkali to corrode the surface of the workpiece and remove impurities on the surface to expose the original color of aluminum), and de-stained. Since the aforementioned procedures are prior art, they will not be described in details. 
         [0033]    In the anodic treatment, the electrolytes and formulas include but not limited to the following: 
         [0034]    1: Sulfuric acid solution: In an Alumilite manufacturing process, 15˜20% sulfuric acid is used, the voltage is controlled within 14˜22 volts, the current density is controlled within 1˜2A/dm2, the operating temperature is controlled within 18˜25 degrees Celsius, and the processing time is approximately equal to 10˜60 minutes. 
         [0035]    The coating thickness falls within a range of 3˜35 μm, and the coating is colorless and transparent. 
         [0036]    2: Chromic acid solution: 5˜10% chromic acid is used, the voltage is controlled to approximately 40 volts, the current density is controlled within 0.15˜0.30A/dm2, the operating temperature is approximately equal to 35 degrees Celsius, and the processing time is approximately equal to 30 minutes. The coating thickness is approximately equal to 2˜3 μm, and the coating is in a gray or grayish green color and has a good corrosion resistance. 
         [0037]    3: Oxalic acid solution: In an Eloxal GX manufacturing process, 3˜5% oxalic acid is used, the voltage is 40˜60 volts, the current density is 1˜2A/dm2, the operating temperature is 18˜20 degrees Celsius, and the processing time is approximately equal to 40˜60 minutes. The coating thickness is approximately equal to 10˜65 μm, and the coating is in a yellow color. 
         [0038]    4: Phosphoric acid solution: 10% phosphoric acid is used, the voltage is 10˜12 volts, the current density is not specified, the operating temperature is 23˜25 degrees Celsius, and the processing time is approximately equal to 20˜30 minutes. The coating thickness is 1˜2 μm and the coating is colorless. 
         [0039]    In addition, the aforementioned anodic treatments can be a regular anodic treatment, a semi-hard coating anodic treatment, a hard coating anodic treatment, a super hard coating anodic treatment or a lubricated anodic treatment according to the coating thickness and hardness. The regular anodic treatment has a coating thickness approximately equal to 6 μm˜15 μm. The semi-hard coating anodic treatment has a coating thickness approximately equal to 20 μm˜30 μm with excellent friction resistance and corrosion resistance. The hard coating anodic treatment has a coating thickness approximately equal to 30 μm˜50 μm and a hardness above the Vickers hardness HV500. The super hard coating anodic treatment has a coating thickness exceeding 50 μm and a hardness exceeding HV500. In the lubricated anodic treatment, an electrolysis is performed to fill molybdenum disulphide into the pores of the coating layer, and form a composite layer filled with molybdenum disulphide which has the feature of the anodic treatment coated characteristics. 
         [0040]    With reference to  FIGS. 3 ,  4  and  5  for schematic views of the first, second and third electronic ink-jet nozzles used in an anodizing color drawing method in accordance with a preferred embodiment of the present invention respectively, the electronic ink-jet nozzles  14  can be divided into the following types: 
         [0041]    1: Piezoelectric ink-jet nozzle  141 : A piezo head ink-jet technology is adopted, wherein a pushing force similar to that of a piston of an automobile engine is provided for pushing ink out from an ink tank, and an electrically conductive piezoelectric crystal  1411  (or quartz crystal) produce a constant vibration frequency after the piezoelectric crystal  1411  is electrically conducted, so as to push the ink out from the nozzle. 
         [0042]    2: Thermal sensing ink-jet nozzle  142 : Heat energy is used to heat up the ink on a film of a print head  1421  (or nozzle) until the ink is boiled to produce bubbles, so that the pressure of the bubbles can push out the ink. 
         [0043]    3: Static charge type ink-jet nozzle  143 : The flow formed by the ink is passed through a nozzle  1431 , pressurized and sprayed. After the ink is vibrated and divided into ink droplets an electric field plate  1432  is provided, such that after the ink droplets with or without electric charges pass through the electric field will fly straightly forward due to the static charge effect. When the ink droplets pass through an electromagnetic field deviation plate,  1433 , the ink droplets with a large number of electric charges will be attracted strongly to deviate with a greater extent. On the other hand, the ink droplets with a small number of electric charges will be deviated less. The ink droplets without any electric charges will be collected in the ink collection tank for recycle. 
         [0044]    During the sealing treatment, the pores  13  of the coating layer  12  are sealed, so that the coating layer  12  has a non-adhesive surface or chemicals are permeated into the pores  13  to change or modify the properties of the coating layer  12 . The sealing process includes dissolving an oxide or hydroxide reprecipitation in the pores or depositing other substances into the pores to form a dense surface. The sealing operation can be conducted in a dichromic acid solution instead of water to enhance the corrosion resistance. 
         [0045]    Since the color drawing pattern  16  formed by the dye  15  is sealed into the coating layer  12  by the sealing treatment, so that the color drawing pattern  16  has the features of scratch resistance and wear resistance, and such products can be operated and used by users for a long time, and the external look of the housing can be maintained to a high level of quality. 
         [0046]    With reference to  FIG. 6  for a schematic view of a printer used in anodizing color drawing method in accordance with a preferred embodiment of the present invention, the anodizing color drawing method can use any type of ink-jet printer  2  for the printing, and the metal workpiece  11  processed by the anodic treatment is put on a workpiece carrying platform  21  of the ink-jet printer  2 , and then workpiece carrying platform  21  is driven to feed the metal workpiece  11  into a printing operation area of the ink-jet printer  2  to complete the color drawing process. 
         [0047]    In summation of the description above, the anodizing color drawing method of the present invention can overcome the problems of the conventional color drawing layer formed on a plastic object that may be scratched or damaged easily, or the workpiece of the conventional anodic treatment fails to have a multiple of colors.