Patent Publication Number: US-2020283648-A1

Title: Electronic device housings with waterborne metallic paint coatings

Description:
BACKGROUND 
     Electronic devices such as notebook computers, tablet computers, mobile phones, and the like may include housings to house various electronic components. To make the electronic devices fashionably and aesthetically appealing to users, decorative metallic-appearing coatings may be formed on housings of electronic devices. The metallic-appearing coatings may also provide a metallic-appearance. Metallic-appearing coatings may include significant amount of metal powder such as aluminum flakes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples are described in the following detailed description and in reference to the drawings, in which: 
         FIG. 1  illustrates a schematic representation of an example electronic device housing having a waterborne metallic paint coating on a top surface; 
         FIG. 2A  illustrates a schematic representation of an example insulating material encapsulated metal powder that is used in formulation of the waterborne metallic paint coating; 
         FIG. 2B  illustrates a schematic representation of n example surface modified synthetic mica that is used in the formulation of the waterborne metallic paint coating; 
         FIG. 2C  illustrates a schematic representation of an example surface modified glass platelet that is used in the formulation of the waterborne metallic paint coating; 
         FIG. 3  illustrates a cross-sectional side-view of an example electro device; 
         FIG. 4A  illustrates a schematic representation of an example electronic device housing, depicting a 2-layer waterborne metallic paint coating on a metal/plastic substrate; 
         FIG. 4B  illustrates a schematic representation of an example electronic device housing, depicting a waterborne metallic paint coating and a water-based primer coating on the metal/plastic substrate; 
         FIG. 5  illustrates a schematic representation of an example electronic device housing, depicting a 2-layer waterborne metallic paint coating and a waterborne primer coating on a carbon fiber composite substrate; 
         FIG. 6A  illustrates a schematic representation of an example electronic device housing, depicting a 2-layer waterborne metallic paint coating, and a powder coating on a forged/die casted/computer numeric control (CNC) machined metal substrate; 
         FIG. 6B  illustrates a schematic representation of an example electronic device housing, depicting a waterborne clear top coating applied on the waterborne metallic paint coating; 
         FIGS. 7A-7D  illustrate schematic representations of example electronic device housings, depicting at least one waterborne metallic paint coating in combination with a micro-arc oxidation (MAO) layer on the metal substrate; 
         FIGS. 8A-8C  illustrate schematic representations of example electronic device housings, depicting at least one waterborne metallic paint coating in combination with a passive layer on the metal substrate; 
         FIG. 9A  illustrates an example process for manufacturing an electronic device housing; and 
         FIG. 9B  illustrates the example process for manufacturing the electronic device housing of  FIG. 9A , depicting additional features. 
     
    
    
     DETAILED DESCRIPTION 
     Decorative metallic-appearing coatings may be formed on housings of electronic devices. The metallic-appearing coatings may also provide a metallic luster. Metallic-appearing coatings may involve significant amount of metal powder such as aluminum flakes. Such metallic-appearing coatings may shield antenna radiation performance of the electronic devices. Further, the metal powder may not be suitable for water-based paint formulation due to a corrosion risk of the metallic-appearing coatings and poor bonding at an interface of the metal powder and water-based binders. In addition, metallic-appearing coatings may involve solvent-based paint formulation, which can cause volatile organic compound (VOC) emission issues. Solvent-based metallic-appearing coatings on substrates may have the VOC emission issues, which can affect the health of people working in such painting environments. 
     Examples described herein may provide an electronic device housing having a substrate and a waterborne metallic paint coating formed on a surface of the substrate. The waterborne metallic paint coating may include an insulating material (e.g., polymer resin, silicon dioxide, and the like) encapsulated metal powder (e.g., aluminum flakes) in combination with at least one of a surface modified synthetic mica and a surface modified glass platelet. 
     Examples described herein may enhance metallic lustering of the electronic device housing by internal light scattering through high brightness/transmittance glass platelets, high transparent synthetic mica, and/or polymer resin/silicon dioxide encapsulated aluminum flakes. Examples described herein may resolve antenna radiation shielding issues while maintaining metallic luster surface finish on the electronic device housings (e.g., cover surfaces) without corrosion risk of the metallic-appearing coatings and/or poor bonding at the interface of the metal powder and water-based binders. Examples described may eliminate/reduce the VOC emission issues by utilization of waterborne metallic paint coatings on substrates. Furthermore, examples described herein may provide a green product solution and offer an environment friendly process. 
       FIG. 1  illustrates a schematic representation of an example electronic device housing  100  having a waterborne metallic paint coating  104  on a top surface. Example electronic device housing  100  may be a housing of a mobile phone, personal digital assistant (PDA), notebook computer, tablet computer, MP3, MP4, global positioning system (GPS) navigator, digital camera, convertible device, a personal gaming device, or the like. Electronic device housing  100  may include a substrate  102  having a surface  106 . Example substrate  102  may be made of plastic, metal, carbon fiber composite, or any combination thereof. In other examples, substrate  102  may be made of glass or ceramic. 
     Further, electronic device housing  100  may include at least one waterborne metallic paint coating  104  formed on surface  106  of substrate  102 . For example, waterborne metallic paint coating  104  may have a thickness of about 10-25 μm. In one example, waterborne metallic paint coating  104  may include an insulating material encapsulated metal powder in combination with at least one of a surface modified synthetic mica and a surface modified glass platelet in the formulation. Example formulation of waterborne metallic paint coating  104  is explained in  FIGS. 2A-2C . 
       FIG. 2A  illustrates a schematic representation of an example insulating material encapsulated metal powder  200 A that is used in the formulation of waterborne metallic paint coating  104 , Example metal powder  202  may include aluminum flakes. Example insulating material  204  may include at least one of polymer resin and silicon dioxide. Insulating material  204  may have a thickness of about 20-80 nm. In one example, polymer resin/silicon dioxide  204  encapsulated aluminum flakes  202  may make the surface of aluminum flakes  202  electrically insulated. 
       FIG. 2B  illustrates a schematic representation of an example surface modified synthetic mica  2008  that is used in the formulation of waterborne metallic paint coating  104 . In one example, surface modified synthetic mica  2008  may include a synthetic mica  206  coated with a first metallic-appearing coating  208 . Example synthetic mica  206  may be fluorphlogopite. Example first metallic-appearing coating  208  may be selected from a group consisting of titanium dioxide and iron oxide. 
     Further, surface modified synthetic mica  200 B may have a color appearance selected from a group consisting of silver, gold, red, blue, green, bronze, copper, and russet. The color appearance on synthetic mica  206  may depend on a thickness of first metallic-appearing coating  208 . For example, the thickness of first metallic-appearing coating  208  may be about 10-160 nm, specifically about 10-60 nm. 
       FIG. 2C  illustrates a schernatic representation of an example surface modified glass platelet  200 C that is, used in the formulation of waterborne metallic paint coating  104 . In one example, surface modified glass platelet  200 C may include a fine glass platelet  210  coated with a second metallic-appearing coating  212  having less diffuse scattering effect. Fine glass platelet  210  may be a high brightness and high whiteness glass platelet. Example fine glass platelet  210  may include calcium sodium borosilicate flakes. In one example, second metallic appearing coating  212  may be selected from a group consisting of titanium dioxide, silica, and tin oxide. Second metallic-appearing coating  212  may have a thickness of about 10-160 nm, specifically about 10-60 nm. For example, titanium dioxide coated synthetic mica and glass platelet may enhance whiteness of painting layer and improve blue shade appearance to resolve yellowness issues on the top surface of electronic device housing  100 . 
     Thus, examples described in  FIGS. 1 and 2A-2C  may develop waterborne metallic paint coating  104  using polymer resin or silicon dioxide encapsulated metal powder in combination with high whiteness surface modified synthetic mica, and/or high brightness and high whiteness surface modified fine glass platelets. Waterborne metallic paint coating  104  may resolve the antenna radiation shielding issue and maintain the metallic luster surface finish on surface  106  of electronic device housing  100  without painting layer corrosion risk and poor bonding at the interface of metal powder and water-based binders. 
       FIG. 3  illustrates a cross-sectional side-view of an example electronic device  300 . Example electronic device  300  may be a computing system, for example, a mobile phone, personal digital assistant (PDA), notebook computer, tablet computer, MP3, MP4, global positioning system (GPS) navigator, digital camera, convertible device, a personal gaming device, or the like. Example convertible device may refer to a device that can be “converted” from a laptop mode to a tablet mode. In some examples, electronic device  300  may include a first housing and a second housing rotatably, detachably or twistably connected to the first housing. Examples described herein can be implemented in the first housing, second housing, or a combination thereof. 
     Example electronic device  300  may include at least one antenna  302  and a housing  304  to house at least one antenna  302 . For example, antenna  302  may include an antenna with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, hybrids of these designs, and the like. Different types of antennas may be used for different bands and combinations of bands. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link antenna. 
     In some examples, housing  304  may house a display (e.g., a touchscreen display). Example display may include liquid crystal display (LCD), light emitting diode (LED), electro-luminescent (EL) display, or the like. Electronic device  300  may be equipped with other components such as a camera, audio/video devices, and the like, depending on the functions of electronic device  300 . 
     Housing  304  may include a substrate  306  and at least one waterborne metallic paint coating  308  formed on a surface of substrate  306  to allow transmission and/or reception of antenna signals. Waterborne metallic paint coating  308  may be applied as a non-impact antenna coating on substrate  306 . For example, waterborne metallic paint coating  308  formed on substrate  306  can be nonconductive to not block electromagnetic waves. For example, substrate  306  may be made of plastic, metal, glass, or carbon fiber composite. Example waterborne metallic paint coating  308  may include an insulating material encapsulated metal powder in combination with at least one of a surface modified synthetic mica and a surface modified glass platelet. 
     In another example, housing  304  may include a waterborne clear top coating formed on a top surface of at least one waterborne metallic paint coating  308 . In one example, waterborne clear top coating may be a glossy and transparent coating that forms the final interface with the environment. Waterborne clear top coating may withstand ultraviolet light. In some examples, waterborne clear top coating can be applied on waterborne metallic paint coating  308  as a spray coat. In yet another example, housing  304  may include at least one intermediate coating formed between substrate  306  and at least one waterborne metallic paint coating  308 . The intermediate coating may be selected from a group consisting of a waterborne primer coat, a powder coat, a micro-arc oxidation (MAO) layer, and a passive layer. Each intermediate coating may have a thickness of about 50 nm-60 μm depending on a type of the intermediate coating. 
     For example, the intermediate coating may have a smooth surface for enhancing bonding between substrate  306  and waterborne metallic paint coating  308  or subsequent coatings. In some examples, intermediate coatings can be omitted, and at least one waterborne metallic paint coating  308  can be directly formed on substrate  306 . Example intermediate coatings and the waterborne dear top coating may be explained in  FIGS. 4-8 . 
       FIG. 4A  illustrates a schematic representation of an example electronic device housing  400 A, depicting a 2-layer waterborne metallic paint coating  404 A and  404 B on a metal/plastic substrate  402 . Waterborne metallic paint coatings  404 A and  404 B may contain a polymer resin encapsulated aluminum powder, silicon dioxide coated metal powder, high whiteness surface modified synthetic mica and/or high brightness and high whiteness surface modified fine glass platelets in the formulation. Further, each waterborne metallic paint coating  404 A and  404 B may have a thickness of about 10-25 μm. 
       FIG. 4B  illustrates a schematic representation of an example electronic device housing  400 B, depicting a waterborne metallic paint coating  404 A and a water-based primer coating  406  on metal/plastic substrate  402 . In this example, water-based primer coating  406  may be an intermediate coating with a thickness of about 5-20 μm and formed between metallic/plastic substrate  402  and waterborne metallic paint coating  404 A. Water-based primer coating  406  may be used as a bonding agent between waterborne metallic paint coating  404 A and metallic/plastic substrate  402 . Alternatively, water-based primer coating  406  may be omitted to directly apply waterborne metallic paint coating  404 A on metallic/plastic substrate  402 . 
       FIG. 5  illustrates a schematic representation of air example electronic device housing  500 , depicting a 2-layer waterborne metallic paint coating  506 A and  506 B and a waterborne primer coating  504  on a carbon fiber composite substrate  502 , In this example, waterborne primer coating  504  may be an intermediate coating with a thickness of about 10-30 μm and formed between carbon fiber composite substrate  502  and waterborne metallic paint coating  506 A. Each waterborne metallic paint coating  506 A and  506 B may have a thickness of about 10-25 μm. 
       FIG. 6A  illustrates a schematic representation of an example electronic device housing  600 A, depicting a 2-layer waterborne metallic paint coating  606 A and  6068  and a powder coating  604  on a forged/die casted/computer numeric control (CNC) machined metal substrate  602 . In one example, metal substrate  602  may be formed into a desired shape by forging, die casting or CNC machining. In this example, powder coating  604  may be an intermediate coating with a thickness of about 20-60 μm. 
     Powder coating  604  may refer to a process of coating metal substrate  602  with a plastic finish applied in powder form and baked to, a fluid state to bond powder coating  604  to a surface of metal substrate  602 . Powder coating  604  contain no solvents and release little or no amount of VOC into the atmosphere. Further, powder coating  604  may produce significantly thicker coatings than liquid coatings. 
       FIG. 6B  illustrates a schematic representation of an example electronic device housing  600 B, depicting a waterborne clear top coating  608  applied on a top surface of waterborne metallic paint coating  606 A. Particularly,  FIG. 6B  illustrates powder coating  604  formed on a forged/die casted/CNC machined metal substrate  602 , waterborne metallic paint coating  606 A formed on powder coating  604 , and waterborne clear top coating  608  applied on waterborne metallic paint coating  606 A. In other examples, waterborne clear top coating  608  can also be applied on a top surface of a 2-layer waterborne metallic paint coating. For example, waterborne clear top coating  608  may have a thickness of about 10-25 μm. 
       FIGS. 7A-7D  illustrate schematic representations of example electronic device housings  700 A- 700 D, depicting at least one waterborne metallic paint coating  706  in combination with an MAO layer  704  on metal substrate  702 . Example metal substrate  702  may be a forged/die casted/CNC machined magnesium alloy. As shown in  FIGS. 7A-7C , MAO layer  704  may be formed on opposite surfaces of metal substrate  702 . For example, MAO layer  704  may be formed on metal substrate  702  using an MAO process, which may be an electrochemical surface treatment process for generating oxide coatings on metals. Micro-arc oxidized metal substrate  702  may include properties such as wearing resistance, corrosion resistance, high hardness and electrical insulation. 
       FIG. 7A  depicts MAO layer  704  formed on metal substrate  702  and a layer of waterborne metallic paint coating  706  formed on MAO layer  704 . In the example shown in  FIG. 7A , MAO layer  704  may have a thickness of about 2-15 μm and waterborne metallic paint coating  706  may have a thickness of about 10-25 μm.  FIG. 7B  depicts MAO layer  704  formed on metal substrate  702  and 2-layers of waterborne metallic paint coatings  706 A and  706 B formed on MAO layer  704 . In the example shown in  FIG. 7B , MAO layer  704  may have a thickness of about 2-10 μm and each waterborne metallic paint coating  706 A and  706 B may have a thickness of about 10-25 μm. 
       FIG. 7C  depicts MAO layer  704  formed on metal substrate  702 , waterborne primer coating  708  formed on MAO layer  704 , and a layer of waterborne metallic paint coating  706 A formed on waterborne primer coating  708 . In the example shown in  FIG. 7C , MAO layer  704  may have a thickness of about 2-15 μm, waterborne primer coating  708  may have a thickness of about 5-20 μm, and waterborne metallic paint coating  706 A may have a thickness of about 10-25 μm. 
       FIG. 70  depicts MAO layer  704  formed on metal substrate  702 , waterborne metallic paint coating  706 A formed on MAO layer  704 , and waterborne clear top coating  710  formed on waterborne metallic paint coating  706 A. In the example shown in  FIG. 7D , MAO layer  704  may have a thickness of about 2-15 μm, waterborne metallic paint coating  706 A may have a thickness of about 10-25 μm, and waterborne clear top coating  710  may have a thickness of about 10-25 μm. 
       FIGS. 8A-8C  illustrate schematic representations of example electronic device housings  800 A- 800 C, depicting at least one waterborne metallic paint coating  806  in combination with a passive layer  804  on opposite surfaces of metal substrate  802 . Example metal substrate  802  may be a forged/die casted/CNC machined magnesium alloy. Passive layer  804  may involve creation of an outer layer of shield material around metal substrate  802  to make metal substrate  802  “passive”, i.e., less affected or corroded by the environment 
       FIG. 8A  depicts passive layer  804  formed on metal substrate  802  and 2-layers of waterborne metallic paint coatings  806 A and  8068  formed on passive layer  804 . In the example shown in  FIG. 8A , passive layer  804  may have a thickness of about 50 nm-1 μm and each waterborne metallic paint coating  806 A and  8068  may have a thickness of about 10-25 μm. 
       FIG. 8B  depicts passive layer  804  formed on metal substrate  802 , waterborne primer coating  808  formed on passive layer  804 , and a layer of waterborne metallic paint coating  806 A formed on waterborne primer coating  808 . In the example shown in  FIG. 8B , passive layer  804  may have a thickness of about 50 nm-1 μm, waterborne primer coating  808  may have a thickness of about 5-20 μm, and waterborne metallic paint coating  806 A may have a thickness of about 10-25 μm. 
       FIG. 8C  depicts passive layer  804  formed on metal substrate  802 , waterborne metallic paint coating  806 A formed on passive layer  804 , and waterborne clear top coating  810  formed on waterborne metallic paint coating  806 A. In the example shown in  FIG. 8C , passive layer  804  may have a thickness of about 50 nm-1 μm, waterborne metallic paint coating  806 A may have a thickness of about 10-25 μm, and waterborne clear top coating  810  may have a thickness of about 10-25 μm. Waterborne paints described in  FIGS. 1-8  can reduce 69% to 93% VOC emission on waterborne topcoat, basecoat, or primer in comparison with solvent-borne liquid paints. 
       FIG. 9A  illustrates an example process  900 A for manufacturing an electronic device housing. At  902 , a substrate may be provided. In one example, the substrate may be formed into a desired shape by forging, die casting or CNC machining. In another example, the substrate may be formed into the desired shape using a superplastic forming process. At  904 , at least one waterborne metallic paint may be coated on a surface of the substrate. In one example, the waterborne metallic paint may be formed of an insulating material encapsulated metal powder in combination with at least one of a surface modified synthetic mica and a surface modified glass platelet. 
       FIG. 9B  illustrates the example process for manufacturing the electronic device housing of  FIG. 9A , depicting additional processes At  952 , a substrate may be provided. At  954 , at least one intermediate coating may be formed on a surface of the substrate. Example intermediate coating may be selected from a group consisting of a waterborne primer coat, a powder coat, an MAO layer, and a passive layer. At  956 , at least one waterborne metallic paint may be coated on the at least one intermediate coating. 
     In one example, prior to coating the at least one waterborne metallic paint on the surface of the substrate, the surface of the substrate may be coated with one of a waterborne primer coat, a powder coat, an MAO layer, and a passive layer. 
     In another example, prior to coating the at least one waterborne metallic paint on the surface of the substrate, an MAO layer may be formed on the surface of the substrate and a waterborne primer may be coated on the formed MAO layer of the substrate. 
     In yet another example, prior to coating the at least one waterborne metallic paint on the surface of the substrate, a passive layer may be formed on the surface of the substrate and a waterborne primer may be coated on the formed passive layer of the substrate. Alternatively, at least one waterborne metallic paint coating can be directly coated on the substrate without any intermediate coatings. In addition, a waterborne clear top coat can be directly coated on waterborne metallic paint coating, at  958 . 
     It may be noted that the above-described examples of the present solution are for the purpose of illustration only. Although the solution has been described in conjunction with a specific implementation thereof, numerous modifications may be possible without materially departing from the teachings and advantages of the subject matter described herein. Other substitutions, modifications and changes may be made without departing from the spirit of the present solution. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
     The terms “include,” “have,” and variations thereof, as used herein, have the same meaning as the term “comprise” or appropriate variation thereof. Furthermore, the term “based on”, as used herein, means “based at least in part on.” Thus, a feature that is described as based on some stimulus can be based on the stimulus or a combination of stimuli including the stimulus. 
     The present description has been shown and described with reference to the foregoing examples. It is understood, however, that other forms, details, and examples can be made without departing from the spirit and scope of the present subject matter that is defined in the following claims.