WO2015042982A1

WO2015042982A1 - Coatings of metal surfaces

Info

Publication number: WO2015042982A1
Application number: PCT/CN2013/084787
Authority: WO
Inventors: Chung-Hung Huang; Yu-Chuan KANG; Kuan-Ting Wu
Original assignee: Hewlett-Packard Development Company,L.P.
Priority date: 2013-09-30
Filing date: 2013-09-30
Publication date: 2015-04-02

Abstract

The present disclosure presents a coating of a metal surface. In an example, a patterned ceramic coating is generated on a first area of the metal surface via a powder coating process by use of ceramic materials to form a pattern on the first area. A protective coating is generated on a second area of the metal surface after the patterned ceramic coating is generated.

Description

COATINGS OF METAL SURFACES

BACKGROUND

[0001] In many cases coatings can be applied to improve surface properties of an object (usually referred to as a substrate), such as appearance, adhesion, corrosion resistance, wear resistance, and scratch resistance. During the manufacture of devices such as semiconductor products, a coating can form a part of a finished device on the surface of a metal substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] For a better understanding of the present disclosure, reference should be made to the Detailed Description below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures.

[0003] FIG. 1 is a schematic diagram illustrating an object having a metal surface with a coating formed on the metal surface in accordance with an example of the present disclosure;

[0004] FIG. 2 is a schematic diagram illustrating a process of forming a coating on a metal surface in accordance with an example of the present disclosure;

[0005] FIG. 3 is a schematic diagram illustrating a process of forming a coating on a metal surface in accordance with an example of the present disclosure;

[0006] FIG. 4 is a flow diagram illustrating a method of producing a coating of a metal surface provided in an example of the present disclosure;

[0007] FIGS. 5a-5d are illustrative diagrams showing top views of an object formed in different steps of FIG. 4;

[0008] FIGS. 6a-6d are illustrative diagrams showing cross sections of an object formed in different steps of FIG. 4.

DETAILED DESCRIPTION

[0009] Reference will now be made in detail to examples, which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. Also, the figures are illustrations of an example, in which components or procedures shown in the figures are not necessarily essential for implementing the present disclosure. In other instances, well-known methods, procedures and components have not been described in detail so as not to unnecessarily obscure aspects of the examples.

[0010] A coating process may be introduced in the procedure of device manufacture for presenting a pattern such as a logo of the manufacturer on a metal surface of the device. FIG. 1 is a schematic diagram illustrating an object 101 having a metal surface with a coating formed on the metal surface to present a pattern in accordance with an example of the present disclosure. Specifically, a patterned ceramic coating 102 may be generated on a first area of the metal surface, and a protective coating 103 may be generated on a second area of the metal surface. In FIG. 1, the first area 102 is filled with slash, while the second area 103 is the area remaining white. In an example, the protective coating 103 may be formed on an area without the patterned ceramic coating 102 after the patterned ceramic coating 102 is generated. As such, a process that can produce a pattern with multiple colors on a metal surface is provided.

[0011] In an example, the metal mentioned in the present disclosure may be a conductive metal selected from the group including aluminum, titanium, niobium, zirconium, magnesium, lithium, zinc, iron or the like. Alternatively, the metal may be an alloy including at least one of the aforesaid conductive metals.

[0012] In an example, the protective coating 103 may be formed by micro-arc oxidation, or by precipitating electrophoresis coating materials on the metal surface using an

electrophoretic deposition process.

[0013] In an example, micro-arc oxidation (MAO) is an electrochemical surface treatment process for generating oxide coatings on metals. It is similar to anodizing, but it employs higher potentials, so that discharges occur and the resulting plasma modifies the structure of the oxide layer. This process can be used to grow thick (e.g., tens or hundreds of

micrometers), largely crystalline, oxide coatings on metals such as aluminum, titanium, niobium, zirconium, magnesium, lithium, zinc, iron, and their alloys, etc. Because they can present high hardness and a continuous barrier, these coatings can offer protection against wear, corrosion or heat as well as electrical insulation. Specifically, the micro-arc oxidation process is to immerse a piece of metal into an acidic or alkaline electrolyte, generate sparkling discharge spots on the metal surface using an electrochemical method, and obtain a metal-arc oxidized ceramic coating on the metal surface under combined actions of thermochemistry, plasma chemistry and electrochemistry.

[0014] In an example, an electrophoretic deposition (EPD) process may include a broad range of industrial processes such as electrocoating, e-coating, cathodic electrodeposition, anodic electrodeposition, electrophoretic coating, or electrophoretic painting. Colloidal particles may be used to form stable suspensions and carry a charge applied by

electrophoretic deposition. A feature of this process is that the colloidal particles suspended in a liquid medium migrate under the influence of an electric field (electrophoresis) are deposited onto an electrode. The EPD process is useful for applying materials to an

electrically conductive surface. The materials which are being deposited are the major factor in determining the actual processing conditions and equipment which may be used. The materials may include such as polymers, pigments, dyes, ceramics and metals. Specifically, the electrophoretic deposition process may include several sub-processes. A coating sub- process normally involves submerging an object having a metal surface into a container or vessel which holds the coating bath or solution and applying direct current electricity through the EPD bath using electrodes. After deposition, the object is normally rinsed to remove the undeposited bath. A baking or curing sub-process is normally used following the rinse. This will crosslink the polymer and allows the coating, which will be porous due to the evolution of gas during the deposition process, to flow out and become smooth and continuous.

[0015] In an example, the patterned ceramic coating on the metal surface may present a pattern which may be a decorative design such as a logo of a manufacturer. In an example, the patterned ceramic coating 102 on the metal surface is formed by a powder coating process. In an example, dyed ceramics may be used during the forming of the patterned ceramic coating. In this way, the multi-color performance can be achieved through the original color of ceramics and dyed ceramics. Specifically, the colorant with multiple colors as required is applied to designated locations of an intermediate ceramic film half formed on the metal surface during the powder coating process. Then, the dyed ceramic film is fired to obtain a final ceramic film with a designed pattern. As such, the patterned ceramic coating may be of multicolor, which is relatively bright for presenting such as a logo of a semiconductor product. Compared with adopting a polymer layer as the logo (which is obtained by an acidic or alkaline lithography), the patterned ceramic coating may closely bond to the metal surface and cannot easily fall off. In view of the above, there are less operations to form the coating including the patterned ceramic coating 102 and the protective coating 103.

[0016] As shown in FIG. 2, a coating is produced on a metal surface according to an example of the present disclosure. The coating of the metal surface includes a patterned ceramic coating 201 and a micro-arc oxidized ceramic coating 202. In an example, the patterned ceramic coating 201 is used for presenting a pattern as required such as a logo, a symbol, a sign, etc. Specifically, logos of a manufacturer may be presented on the metal surface in FIG. 2 via the patterned ceramic coating 201. Apart from a first area of the metal surface to which the patterned ceramic coating 201 is adhered, a second area of the metal surface are treated with micro-arc oxidation to obtain the micro-arc oxidized ceramic coating 202 thereon. In an example, the micro-arc oxidized ceramic coating can be a metal micro-arc oxidation layer 202.

[0017] Further, a topcoat is formed upon the patterned ceramic coating 201 and/or the micro- arc oxidized ceramic coating 202, to prevent the patterned ceramic coating and/or the micro- arc oxidized ceramic coating from deterioration. In an example, the topcoat may be used to provide the characteristics of anti-finger print and hydrophobic surface.

[0018] In an example, a specific process may be employed to form the topcoat mentioned in the present disclosure. The specific process may, for example, be a process selected from the group including but not limited to: a spray coating process, a spin coating process, an in mold decoration process, a nano-imprint lithography process, an ink transfer process, a continuous inkjet printing process or the like. In an example, the material used to form the topcoat mentioned in the present disclosure may be: nanoparticles, polymer, ceramic particles, metal particles, glass particles, fiber substance, and the combination thereof or the like.

[0019] FIG. 3 is a schematic diagram illustrating a process of forming a coating on a metal surface according to an example of the present disclosure. The metal surface is coated with a patterned ceramic coating 301 on a first area, and coated with an electrophoretic deposition layer 302 on a second area. In an example, the patterned ceramic coating 301 is used as a logo. As shown in FIG. 3, the logo attached on one part of the metal surface may be a graphic mark, an emblem, a symbol, an icon, or composed of a name, a brand or a trademark of a manufacturer, etc. The other part of the metal surface has an electrophoretic deposition layer coated on it by use of an electrophoretic deposition process. Further, a topcoat is formed on the patterned ceramic coating 301 and/or the electrophoretic deposition layer 302 to protect them from deterioration. In an example, the patterned ceramic coating and the electrophoretic deposition layer on the metal surface are not overlapped with each other.

[0020] FIG. 4 is a flow diagram illustrating a method of manufacturing a coating of a metal surface provided by an example of the present disclosure.

[0021] At block 401, a patterned ceramic coating is generated on a first area of the metal surface. The patterned ceramic coating forms a first part of the coating. In an example, the patterned ceramic coating may be used to show a logo, and the first area may be considered as a logo area of the metal surface.

[0022] In an example, the patterned ceramic coating at block 401 may be achieved by use of a powder coating process. Specifically, ceramic materials are used for powder coating. Also, the powder coating process may require the temperature to reach a ceramic firing temperature.

[0023] In an example, powder coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The powder coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin". It is usually used to create a hard finish that is tougher than a liquid paint. In an example, the powder coating can be used for coating of metals, such as household appliances, aluminium extrusions, drum hardware, and automobile and bicycle parts. Specifically, the powder coating process may include the following operations. First, perform pre-cleaning and washing on a surface of a metal substrate, and perform surface treatment on the metal surface via a phosphating process to remove impurity of the surface of the metal substrate. Then, re-wash the metal surface in order to remove phosphating substances on the metal surface. Later, dry the logo area on the metal surface. Thereafter, apply the powder coating on the logo area of the metal surface to form a patterned ceramic coating, and dye the patterned ceramic coating during the powder coating to provide required colors to the patterned ceramic coating. In an example, the powder coating is applied to the metal surface by spraying the powder using an electrostatic gun, or by using specifically adapted electrostatic discs.

[0024] At block 402, a protective coating is generated on a second area of the metal surface for protecting the metal surface in the second area. In an example, the second area is a non- logo area which may not embody a logo. Specifically, the protective coating at block 402 may be a metal micro-arc oxidation layer. In an example, micro-arc oxidation is performed on the non-logo area of the metal surface to form the metal micro-arc oxidation layer.

Alternatively, the protective coating may be an electrophoretic deposition layer. In an example, electrophoretic treatment is performed on the non-logo area of the metal surface to form the electrophoretic deposition layer.

[0025] At block 403, a topcoat is formed above the patterned ceramic coating and/or the protective coating for providing further protection for respective areas. In an example, block 403 may not be performed, then the patterned ceramic coating and/or the protective coating may be exposed to environmental elements without the topcoat.

[0026] During the procedure shown in FIG. 4, a patterned ceramic coating which is non- electrically conductive is firstly formed on the metal surface at block 401 to present a logo. Thereafter, the micro-arc oxidation process or the electrophoretic deposition process may be applied on the metal surface at block 402, and form the metal micro-arc oxidation layer or the electrophoretic deposition layer, respectively, on the non-logo area of the metal surface which is electrically conductive, without affecting the patterned ceramic coating obtained at block 401. It can be seen that the method described in FIG. 4 is not so complicated and may have low cost.

[0027] In an example, FIGS. 5a-5d and FIGS. 6a-6d are provided as illustrative drawings showing top views and cross sections of an object formed in different steps of FIG. 4.

[0028] Initially, the object has a metal substrate. FIG. 5a is a top view of the object including the metal substrate 501, and FIG. 6a is a cross section of the object cut from a dotted line 56. The top view and the cross section of the object after block 401 are as shown in FIG. 5b and FIG. 6b, respectively. In FIG. 5b and FIG. 6b, the area filled with slash is the patterned ceramic coating 502 generated at block 401. In an example, the area filled with slash may be a logo, while the blank area around the logo may be the metal area. In an example, the logo layer may have a thickness less than 100 micrometer (um). FIG. 5c and FIG. 6c illustrate the top view and the cross section of the object after block 402, respectively. In FIG. 5c and FIG. 6c, the area filled with dot is the protective coating 503 generated at block 402. The top view and the cross section of the object after block 403 are as shown in FIG. 5d and FIG. 6d, respectively. In FIG. 5d and FIG. 6d, the area filled with vertical line is the topcoat 504 generated at block 403.

[0029] In an example, a metal coated with a patterned ceramic coating as a logo may be used for a shell or housing of various devices, e.g. an electronic device. In an example, the electronic device may be a terminal including a tablet, a laptop, a mobile phone, a

smartphone, etc. Specifically, the housing of the electronic device may include: a metal substrate, a patterned ceramic coating located at a first area of a surface of the metal substrate, and a protective coating located at a second area of the surface. In an example, the second area may be different from the first area, i.e., the first area may not overlay the second area, and vice versa. The housing may further include a topcoat formed on the patterned ceramic coating and/or the protective coating.

[0030] The foregoing description, for the purposes of explanation, has been described with the reference to specific examples. However, the illustrative discussions above are not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The examples were chosen and described in order to best explain the principles of the present disclosure and its practical applications, to thereby enable others skilled in the art to best utilize the present disclosure and various examples with various modifications which are suited to the particular use contemplated.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. A method of producing a coating on a metal surface, comprising:

generating a patterned ceramic coating on a first area of the metal surface via a powder coating process by use of ceramic materials to form a pattern on the first area; and

generating a protective coating on a second area of the metal surface after the patterned ceramic coating is generated.

2. The method according to claim 1, wherein generating the patterned ceramic coating comprises:

using ceramic materials with multiple colors during the powder coating process to form the patterned ceramic coating.

3. The method according to claim 1, wherein generating the protective coating comprises:

performing micro-arc oxidation on the metal surface to form a metal micro-arc oxidation layer on the second area.

4. The method according to claim 1, wherein generating the protective coating comprises:

performing electrophoretic deposition on the metal surface to form an electrophoretic deposition layer on the second area.

5. The method according to claim 1, further comprising:

forming a topcoat on the patterned ceramic coating and/or the protective coating.

6. The method according to claim 5, wherein the topcoat is formed via a process selected from the group comprising: a spray coating process, a spin coating process, an in mold decoration process, a nano-imprint lithography process, an ink transfer process and a continuous inkjet printing process.

7. The method according to claim 5, wherein the topcoat is made of a material selected from the group comprising: nanoparticles, polymer, ceramic particles, metal particles, glass particles, fiber substances and a combination thereof.

8. The method according to claim 1, wherein the metal comprises: a conductive metal selected from the group comprising aluminum, titanium, niobium, zirconium, magnesium, lithium, zinc and iron; or, an alloy including at least one of the conductive metal.

9. An object having a metal surface comprising a coating, the coating comprising:

a patterned ceramic coating located at a first area of the metal surface generated via a powder coating process by use of ceramic materials; and

a protective coating located at a second area of the metal surface, wherein the first area is different from the second area.

10. The object according to claim 9, wherein the protective coating comprises a metal micro-arc oxidation layer or an electrophoretic deposition layer.

11. The object according to claim 9, further comprising:

a topcoat formed on the patterned ceramic coating and/or the protective coating.

12. A housing of an electronic device, comprising:

a metal substrate;

a patterned ceramic coating located at a first area of a surface of the metal substrate generated via a powder coating process by use of ceramic materials; and

a protective coating located at a second area of the surface, wherein the second area is different from the first area.

13. The housing according to claim 12, wherein the protective coating is a metal micro- arc oxidation layer or an electrophoretic deposition layer.

14. The housing according to claim 12, further comprising: