WO2020046324A1

WO2020046324A1 - Coated substrates for electronic devices

Info

Publication number: WO2020046324A1
Application number: PCT/US2018/048779
Authority: WO
Inventors: Kuan-Ting Wu; Chi-Hao Chang; Chalam Kashyap
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2018-08-30
Filing date: 2018-08-30
Publication date: 2020-03-05

Abstract

The present disclosure is drawn to a coated substrate for an electronic device, and can include a substrate for housing or support electronic components, a primer layer on the substrate, and a ceramo-metallic layer on the primer layer. The ceramo-metallic layer can include a composite of ceramic particles in an amount of about 3 wt% to about 15 wt%, reflective metal particles in an amount of about 0.1 wt% to about 2 wt%, and polymer binder in an amount of about 70 wt% to about 97 wt%, with the ceramo-metallic layer weight percentages based on dry weight.

Description

COATED SUBSTRATES FOR ELECTRONIC DEVICES

BACKGROUND

[0001 ] Electronics and other devices often include a substrate, such as a metal substrate, that may act as a housing or support for electronic components. In some cases, that housing includes an outer surface that is visible to the user, and thus, a level of attractiveness can be desirable in many instances. Furthermore, the outer surface of the substrate that is visible to the user can also be selected to avoid interfering with the functionality of the electronic device that it houses or supports. Thus, coatings for substrates, such as metal substrates, that may be attractive to many potential users and which do not interfere with electronic functionality can be useful.

BRIEF DESCRIPTION OF THE DRAWINGS [0002] FIG. 1 graphically illustrates an example substrate coated with a primer layer and a ceramo-metallic layer in accordance with the present disclosure;

[0003] FIG. 2 graphically illustrates an example substrate coated with a micro-arc oxidation (MAO) layer, a primer layer, and a ceramo-metallic layer in accordance with the present disclosure;

[0004] FIG. 3 graphically illustrates an example substrate coated with a primer layer and multiple ceramo-metallic layers in accordance with the present disclosure;

[0005] FIG. 4 graphically illustrates an example substrate coated with a primer layer, a ceramo-metallic layer, and a protective layer in accordance with the present disclosure; [0006] FIG. 5 graphically illustrates an example substrate coated with a powder coat layer, a primer layer, and multiple ceramo-metallic layers in accordance with the present disclosure;

[0007] FIG. 6 graphically illustrates an example substrate coated with a powder coat layer, a primer layer, and a ceramo-metallic layer, and a protective layer in accordance with the present disclosure; and

[0008] FIG. 7 is a flow diagram illustrating a method of coating a substrate for an electronic device. DETAILED DESCRIPTION

[0009] There are many components in electronic devices that interact with wireless signal, such as radio, Wi-Fi, Satellite (GPS), Bluetooth®, and cellular signal. In some instances, coatings for application to housings or other support substrates for electronics that may have an attractive metallic appearance or luster may also interfere with various wireless or other electrical signals. For example, to achieve a highly metallic luster, metal powders of about 10 wt% by dry weight, can be used, but at this level of metal, there may be antennae radiation transportation issues introduced for some types of electronic signal. Still, a coating with a metallic luster can be attractive to a user, and thus may provide some advantages with respect to user interest or marketing. In accordance with this, the present disclosure is drawn to coatings for substrates, such as metal substrates used for electronic device housings, and these coatings may also have a stone-like appearance as well as a metallic luster, e.g., a gray/silver metallic sheet. These coatings can also in many cases avoid some of these antennae radiation transportation diminishment issues, including unwanted antennal radiation shielding, e.g., retaining a higher strength of antennae signal (compared to a highly metallic coating) which is useful particularly for enhanced internet connection speeds, internet-based game play, internet-based video or audio communications, etc.

[0010] In one example, the present disclosure is drawn to a coated substrate for an electronic device, the coated substrate including a substrate for housing or supporting electronic components, a primer layer on the substrate, and a ceramo- metallic layer on the primer layer. The ceramo-metallic layer can include (based on dry weight percentages) a composite of ceramic particles in an amount of about 3 wt% to about 15 wt%, reflective metal particles in an amount of about 0.1 wt% to about 2 wt%, and polymer binder in an amount of about 70 wt% to about 97 wt%. In one example, the substrate can be a metal substrate including aluminum, magnesium, lithium, titanium, or an alloy thereof. In another example, the primer layer can include polymer binder and filler. The filler of the primer layer can include carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, synthetic pigment, metallic powder, aluminum oxide, graphene, graphite, or a combination thereof. The ceramic particles of the ceramo-metallic layer can include, for example, alumina, zirconia, aluminum silicate, zirconium silicate, alumina-zirconia ceramic, or a combination thereof. In one example, the reflective metal particles can be shaped to have light reflective properties that are directionally dependent, e.g., aluminum flakes may have a large mirror-like surface and provide a reflective silver finish. The reflective metal particles can include, for example, aluminum, titanium, chromium, nickel, zinc, or a combination thereof. The coated substrate can also include a second ceramo-metallic layer positioned between the primer layer and the ceramo-metallic layer. Thus, the second ceramo-metallic layer also includes ceramic particles, reflective metal particles, and polymer binder that can be the same or different than that present in the ceramo-metallic layer. In another example, the second ceramo-metallic layer further includes a filler not present in the ceramo-metallic layer, and the ceramo-metallic layer includes a UV curable binder. The coated substrate can also include a polymeric top layer positioned on the ceramo-metallic layer. In one example, the ceramo-metallic layer can have a pencil hardness of about 6H to 9H.

[0011 ] In another example, a coated substrate can include a substrate, a surface- treatment layer on the substrate, a primer layer on the treatment layer, and a ceramo- metallic layer on the primer layer. The ceramo-metallic layer can include (based on dry weight percentages) a composite of ceramic particles in an amount of about 3 wt% to about 15 wt%, reflective metal particles in an amount of about 0.1 wt% to about 2 wt%, and polymer binder in an amount of about 70 wt% to about 97 wt%. The substrate can be a metal substrate and surface-treatment layer can be a powder coating layer or a micro-arc oxidation (MAO) layer positioned on the metal substrate. In one example, the coated substrate can be a housing for an electronic device.

[0012] In another example, a method of coating a substrate for an electronic device can include applying a primer coating composition on a substrate or a surface- treated substrate. The primer coating composition can include liquid vehicle, polymer binder, and filler. The method can include heating the primer coating composition after application to drive off solvent from the liquid vehicle and form a primer layer having a thickness from about 5 pm to about 25 pm. In further detail, the method can include applying a ceramo-metallic coating composition to the primer layer. The ceramo-metallic coating composition can include liquid vehicle, ceramic particles, reflective metal particles, and polymer binder. The method can also include heating the ceramo-metallic coating composition after application to drive off solvent from the liquid vehicle and form a ceramo-metallic layer having a thickness from about 8 pm to about 30 pm. The ceramo-metallic layer can include (by dry weight) a composite of ceramic particles in an amount of about 3 wt% to about 15 wt%, reflective metal particles in an amount of about 0.1 wt% to about 2 wt%, and polymer binder in an amount of about 70 wt% to about 97 wt%. The method can further include UV curing the ceramo-metallic layer to at from 500 mJ/cm² to about 1 ,500 mJ/cm²

[0013] It is noted that when discussing either the coated substrates or the methods of coating substrates herein, such discussions can be considered applicable to one another whether or not they are explicitly discussed in the context of that example. Thus, for example, when discussing primer coating in the context of one of the coated substrate examples, such disclosure is also relevant to and directly supported in the context of the method or other coating substrate examples, and vice versa. It is also understood that terms used herein will take on their ordinary meaning in the relevant technical field unless specified otherwise. In some instances, there are terms defined more specifically throughout or included at the end of the present disclosure, and thus, these terms are supplemented as having a meaning described herein.

[0014] In further detail, it is noted that the spatial relationship between layers is often described herein as positioned“on” or applied“on” another layer and does not infer that this layer is positioned directly on the layer to which it refers, but could have intervening layers therebetween. That being stated, a layer described as being positioned on another layer can be positioned directly on that other layer, and thus such a description finds support herein for being positioned directly on the referenced layer. [0015] Substrate

[0016] The substrate that can be coated as described herein can be any substrate that is suitable for application of the coating layers of the present disclosure, including polymer substrates, metal substrates, etc. In one example, the substrate can be rigid with a thickness suitable for use as an electronic device housing or support. For example, the electronics housing or support could be a desktop tower housing, a laptop housing, a keyboard housing, a mouse housing, a monitor housing, tablet housing, smart phone housing, etc., and can be configured or shaped by molding and/or machining, for example. In particular, the substrate can be a metal substrate, such as metal or metal alloy of multiple metals or a metal alloy of metal and non-metal. The metal substrate can, for example, include aluminum, magnesium, lithium, titanium, or an alloy thereof. When used as an electronics housing, the thickness of the substrate can depend on the material chosen, the density of the material (for purposes of controlling weight, for example), the hardness of the material, the malleability of the material, etc.

In some examples, however, the thickness of the substrate when used as a housing or support can be from about 2 mm to about 2 cm, or from about 3 mm to about 1.5 cm, or from about 4 mm to about 1 cm.

[0017] Ceramo-metallic Layer(s)

[0018] The ceramo-metallic layers of the present disclosure can be a composite of three components, including ceramic particles, reflective metal particles, and a polymer binder. The ceramic particles can include, for example, alumina, zirconia, aluminum silicate, zirconium silicate, alumina-zirconia ceramic, chromia, or a

combination thereof. In one specific example, the ceramic particles can be a gray ceramic powder that is a mixture of alumina and alumina-zirconia, e.g., AI₂O₃/AI₂O₃- Zr0_2. The ceramic particles can have a particle size from about 0.1 pm to about 10 pm, from about 0.3 pm to about 7 pm, or from about 0.5 pm to about 5 pm, for example, which is based on the length of the ceramic particles along the longest dimension. In one example, the ceramic particles can have an aspect ratio from about 1 : 1 to about 5:1 (based on longest dimension to shortest dimension), and can have a variety of morphologies, including spherical, rounded, angular, spongy, flakey, cylindrical, acicular, cubic, etc. The ceramic particles can be included in the ceramo-metallic layer at from about 3 wt% to about 15 wt%, from about 4 wt% to about 12 wt%, or from about 5 wt% to about 10 wt%, by dry weight, for example.

[0019] The reflective metal particles can include, for example, aluminum, titanium, chromium, nickel, zinc, or a combination thereof. These metal particles can have a particle size from about 1 pm to about 30 pm, from about 3 pm to about 25 pm, or from about 5 pm to about 20 pm, for example, which is based on the length of the metal particles along the longest dimension. In one example, the reflective metal particles can be shaped to enhance their luster, e.g., they can be shaped to reflect light in a manner that is directionally dependent. For example, aluminum flakes include a large surface (relative to thickness) that is flat or flattened, and thus, depending on the direction of the light that is applied to the flake, the light may reflect more directionally than with more rounded metal particles. Thus, in one example, the metal particles can have a morphology that is something other than a 1 : 1 aspect ratio, e.g., flakes or plate- like, needle-like, etc., with an aspect ratio of from 5:1 to 100:1 , or from 15:1 to 50:1 , for example. That being stated, aspect ratios outside of these ranges, including aspect ratios from about 1 : 1 to about 2:1 , can also be used for the metal particles.

[0020] The ceramo-metallic layer can also include a polymer binder in an amount of about 70 wt% to about 97 wt% (by dry weight in the ceramo-metallic layer). The polymer binder can be, for example, any polymer resin suitable for binding the various particles together, such as acrylate epoxy, acrylate urethane, acrylate polyether, acrylate polyester, or a combination thereof. The polymer can have a weight average molecular weight from about 1 ,000 Mw to about 12,000 Mw, from about 1 ,000 Mw to about 8,000 Mw, from about 2,000 Mw to about 6,000 Mw, or from about 2,500 Mw to about 5,000 Mw.

[0021 ] To apply the ceramo-metallic layer on the primer layer, for example, a ceramo-metallic coating composition can be prepared that includes liquid vehicle, ceramic particles, reflective metal particles, and polymer binder. Upon application, the coating composition (as a coating layer) can be heated to drive off solvent from the liquid vehicle, for example, leaving the ceramo-metallic layer. Example layer thickness can be from about 8 pm to about 30 pm, from about 10 pm to about 25 pm, or from about 12 pm to about 22 pm, for example. Heat can be applied, for example, at from about 50 °C to about 90 °C for about 5 minutes to about 45 minutes or from about 10 minutes to about 45 minutes, or from about 60 °C to about 80 °C for about 15 minutes to about 40 minutes, for example. In one specific example, drying can be by baking at about 50 °C to about 60 °C for about 5 minutes to about 10 minutes. In other examples, drying or baking can include or be followed by UV curing, such as at about 500 mJ/cm² to about 1 ,500 mJ/cm², or from about 800 mJ/cm² to about 1 ,200 mJ/cm²

[0022] The ceramo-metallic layer can be prepared, in one example, to have a grayish color with metallic silvery luster, with a stone-like appearance. The ceramo- metallic layer can also have a high surface hardness, good strength, and can also provide corrosion resistance when the substrate is a metal substrate, for example. With respect to hardness, the ceramo-metallic layer can have a pencil hardness of about 6H to 9H. Pencil hardness can be tested by ASTM D 3363 (Standard Test Method for Film Hardness). Essentially, the standard test method includes the following details: Pencil type: 6B-5B-4B-2B-B-HB-F-H-2H-3H^lH-5H-6H-7H-8H-9H (brand: Mitsubishi) with 6B being softest and 9H being hardest; Test Protocol: Force loading at 750g; drawing lead sharpened; ceramo-metallic layer placed on a level, firm, horizontal surface; starting with the hardest lead, hold the pencil or lead in holder firmly with the lead against the ceramo-metallic layer at a 45° angle (point away from the operator) and push away from the operator; allow the load weight to apply uniform pressure downward and forward as the pencil is moved to either cut or scratch the film or to crumble the edge of the lead (length of stroke to be 1/4 inch (6.5 mm); repeat process down the hardness scale until a pencil is found that will not scratch or gouge the ceramo-metallic layer; the hardest pencil that does not scratch or gouge the ceramo-metallic layer is then considered the pencil hardness of the ceramo-metallic layer. Thus, a pencil hardness from about 6H to 9H is considered to be at the more durable end of the pencil hardness scale. That being stated, the pencil hardness within this range can be present, or in some instances, pencil hardness below 6H can alternatively characterize some ceramo-metallic layers of the present disclosure.

[0023] In further detail, in some instances, there can be multiple ceramo-metallic layers present on the coated substrates of the present disclosure. For example, a second ceramo-metallic layer can be positioned between the primer layer and the ceramo-metallic layer. The second ceramo-metallic layer can also likewise include the ceramic particles, reflective metal particles, and polymer binder described above.

However in some examples, where there are two (or more) ceramo-metallic layers, ceramo-metallic layer that is positioned more distally with respect to the substrate may include more polymer than the ceramo-metallic layer that is more proximal with respect to substrate. In further detail, the ceramo-metallic layer that is more proximal to the substrate can include fillers, such as barium sulfate, talc, and/or a colorant, for example.

[0024] Primer Layer

[0025] A primer layer can be applied on the substrate to provide adhesion between the underlying layer, e.g., metal substrate or surface-treatment layer if present, and a ceramo-metallic layer that may be applied thereon. The primer layer can be, for example, applied as a coating composition to the substrate or surface-treatment layer or any other suitable layer that may be present therebeneath. The primer coating can be applied as a composition that includes liquid vehicle, e.g., water, organic co-solvent, thickener, surfactant, etc.; polymer binder, such as a binder of polyurethane, polyester, polyacrylic, or a combination thereof; and filler, which can be inorganic or organic powders or particulates. More specifically, the filler can be carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, synthetic pigment, metallic powder, aluminum oxide, graphene, graphite, or a combination thereof. The primer coating can be converted to a primer layer by driving off liquid vehicle, such as by heating the primer coating. Heating can be carried out, for example, at about 50 °C to about 90 °C for about 5 minutes to about 45 minutes, about 10 minutes to about 45 minutes, or from about 60 °C to about 80 °C for about 15 minutes to about 40 minutes, for example. Other heating profiles can be used as well. Once the primer coating is formed, the thickness can be, for example, from about 5 pm to about 25 pm, from about 4 pm to about 20 pm, or from about 5 pm to about 15 pm.

[0026] Surface-treatment layer

[0027] In some examples, particularly when the substrate is a metal substrate, a surface-treatment layer can be applied to the metal substrate prior to application of the primer layer. The surface treatment layer can be, for example, a micro-arc oxidation (MAO) layer. Micro-arc oxidation is an electrochemical process where the surface of a metal is oxidized using micro-discharges of compounds on the surface of the substrate when immersed in a chemical or electrolytic bath, for example. The electrolytic bath may include predominantly water with about 1 wt% to about 5 wt% electrolytic compound(s), e.g., alkali metal silicates, alkali metal hydroxide, alkali metal fluorides, alkali metal phosphates, alkali metal aluminates, the like, and combinations thereof. The electrolytic compounds may likewise be included at from about 1.5 wt% to about 3.5 wt%, or from about 2 wt% to about 3 wt%, though these ranges are not considered limiting. The MAO layer can be applied using a plasma electrolytic oxidation process at a voltage from about 250 V to about 600 V for about 5 minutes to about 25 minutes, for example. Temperatures can be from about 20 °C to about 40 °C, or from about 25 °C to about 35 °C, for example, though temperatures outside of these ranges can be used. MAO can be carried out on aluminium, titanium, lithium, magnesium, and/or alloys thereof, for example. The process can be used to grow a dense, ductile nano-ceramic oxide layer that can improve mechanical wear and corrosion resistance, as well as modify thermal and dielectric properties. If the surface treatment layer is a MAO layer, then a thickness of about 2 pm to about 15 pm, from about 3 pm to about 10 pm, or from about 4 pm to about 7 pm can be applied.

[0028] The surface-treatment layer can alternatively be a powder coating layer. A powder coating can be applied as a free-flowing, dry powder. It can be applied electrostatically, for example, and can be cured on the substrate. The powder can be a polymer, for example, such as a thermoplastic or a thermoset polymer. If a powder coating is applied, the powder coating can include a polymer such as an acrylic, a polyurethane, an epoxy, or a combination thereof. The powder coating composition used to prepare the layer can further include, in some examples, filler particles, such as from about 1 wt% to about 15 wt%, or from about 2 wt% to about 10 wt%, or from about 3 wt% to about 8 wt% ceramic particles, e.g., titanium dioxide, clay, talc, calcium carbonate, pigment, metallic powder, aluminum oxide, graphene, graphite, etc. The powder coating can be applied at a thickness of about 20 pm to about 100 pm, from about 30 pm to about 80 pm, or from about 40 pm to about 60 pm. In one example, the powder coating composition can be applied using electrostatic spray deposition (ESD) at a thickness and then baked at about 150 °C to about 200 °C for about 10 minutes to about 45 minutes, or at about 170 °C to about 180 °C for about 30 minutes to about 40 minutes.

[0029] Clear Protection Layer

[0030] In some examples, the ceramo-metallic layer can be overcoated with a clear protection layer. The clear protection layer can be a polymeric layer that protects the outer surface of the ceramo-metallic layer, but which allows the look of the layer to be seen by the user. The polymer layer can thus include, for example, any polymer resin or lacquer that is clear, dry to the touch after applied and dried, etc. Polymers such as urethane-acrylate, polyester, polyurethane, or a combination thereof, can be used. The polymer can have a weight average molecular weight from about 1 ,000 Mw to about 10,000 Mw, from about 1 ,000 Mw to about 6,000 Mw, from about 1 ,500 Mw to about 5,000 Mw, or from about 2,000 Mw to about 3,500 Mw. In some examples, the clear protective layer can be prepared from a clear protective coating composition that is applied to a previously applied ceramo-metallic layer. Heat can be applied, for example, at from about 50 °C to about 90 °C for about 5 minutes to about 45 minutes or from about 10 minutes to about 45 minutes, or from about 60 °C to about 80 °C for about 15 minutes to about 40 minutes, for example. In one specific example, drying can be by baking at about 50 °C to about 60 °C for about 5 minutes to about 10 minutes. In other examples, drying or baking can include or be followed by UV curing, such as at about 500 mJ/cm² to about 1 ,500 mJ/cm², or from about 800 mJ/cm² to about 1 ,200 mJ/cm² [0031 ] Coated Substrates

[0032] Example coated substrates prepared in accordance with the present disclosure are shown in FIGS. 1-6, all of which include a substrate, a primer layer, and a ceramo-metallic layer. Some of the examples shown in the FIGS further include various arrangements of surface-treatment layers (MAO layer or powder coat layer), second ceramo-metallic layers, and/or clear protection layers. The layers applied to one another can be bound together as a composited layered structure.

[0033] More specifically, with respect to FIG. 1 , a coated substrate 100 is shown that includes a substrate 110, such as a metal substrate, a primer layer 120, and a ceramo-metallic layer 130. In FIG. 2, a coated substrate 200 is shown that includes a coated substrate 110, such as a metal substrate, a micro-arc oxidation (MAO) layer 240, a primer layer 220, and a ceramo-metallic layer 230. In FIG. 3, a coated substrate 300 is shown that includes a substrate 310, such as a metal substrate, a primer layer 320, a second ceramo-metallic layer 350, and a ceramo-metallic layer 330. In FIG. 4, a coated substrate 400 is shown that includes a substrate 410, such as a metal substrate, a primer layer 420, a ceramo-metallic layer 430, and a clear protective layer 460. In FIG. 5, a coated substrate 500 is shown that includes a substrate 510, such as a metal substrate, a powder coat layer 570, a primer layer 520, a second ceramo-metallic layer 550, and a ceramo-metallic layer 530. In FIG. 6, a coated substrate 600 is shown that includes a substrate 610, such as a metal substrate, a powder coat layer 670, a primer layer 620, a ceramo-metallic layer 630, and a clear protective layer 660.

[0034] Methods of Coating Substrates

[0035] Turning now to FIG. 7, a method 700 of coating a substrate for an electronic device can include applying 710 a primer coating composition on a substrate or a surface-treated substrate. The primer coating composition can include liquid vehicle, polymer binder, and filler. The method can include heating 720 the primer coating composition after application to drive off solvent from the liquid vehicle and form a primer layer having a thickness from about 5 pm to about 25 pm. In further detail, the method can include applying 730 a ceramo-metallic coating composition to the primer layer. The ceramo-metallic coating composition can include liquid vehicle, ceramic particles, reflective metal particles, and polymer binder. The method can also include heating 740 the ceramo-metallic coating composition after application to drive off solvent from the liquid vehicle and form a ceramo-metallic layer having a thickness from about 8 pm to about 30 pm. The ceramo-metallic layer can include (by dry weight) a composite of ceramic particles in an amount of about 3 wt% to about 15 wt%, reflective metal particles in an amount of about 0.1 wt% to about 2 wt%, and polymer binder in an amount of about 70 wt% to about 97 wt%. In this example, heating one or both of the primer coating composition or heating the ceramo-metallic coating composition can be carried out at about 50 °C to about 90 °C for about 10 minutes to about 45 minutes. In further detail, the method can include applying any of the layers shown or described in FIGS. 1 -6 to a substrate, such as a metal substrate. These layers can include, but are not limited to, the primer layer and the ceramo-metallic layer described above, but can also include various arrangements of these layers with a surface-treatment layers (MAO layer or powder coat layer), a second ceramo-metallic layer, and/or clear protection layer.

[0036] Definitions

[0037] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise.

[0038] The term "about" as used herein, when referring to a numerical value or range, allows for a degree of variability in the value or range, for example, within 5% or other reasonable added range breadth of a stated value or of a stated limit of a range. The term“about” when modifying a numerical range is also understood to include the exact numerical value indicated, e.g., the range of about 0.1 wt% to about 2 wt% includes 0.1 wt% to 2 wt%, as an explicitly supported sub-range.

[0039] As used herein, the term“composite” refers to the act of combining individual elements into a single unified element, including with components combined together as a single composited layer, or as two or more layers that are physically and/or chemically bound together along one or more interface. For example, a ceramo- metallic layer can be said to be a layer of multiple components composited together in layer. In further detail, multiple layers bound together as applied to one another can be considered to be a composited layered structure. Thus, context can be used to determine how the term is applied.

[0040] The term“electronic component(s)” refers to the individual parts or elements that, when combined, make up an electronic device. Such components may have an electrical, mechanical, or electromechanical function, and can include structural components, operational components, aesthetic components, etc. The coated

substrates of the present disclosure can be used to house individual components or component assemblies on an interior of an electronic device housing, or as a sub- housing of a larger electronic device, or can act as an outermost housing of an electronic device.

[0041 ] The term“composition” herein typically refers to the formulation that is used to form a“layer” after application and drying (and in some instances, photo curing). Thus, the composition typically includes solvent or other carrier that may be driven off by drying to leave behind a dry layer.

[0042] Numerical values are typically provided and refer to the average of the numerical value given. For example, a thickness range for a layer of from about 5 pm to about 25 pm indicates the range as it relates to the average thickness of the layer.

[0043] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience.

However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list based on their presentation in a common group without indications to the contrary.

[0044] Concentrations, dimensions, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include the numerical values explicitly recited as the limits of the range, as well as to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a weight percentage range of a layer (by dry weight) of about 0.1 wt% to about 2 wt% should be interpreted to include the explicitly recited limits of 0.1 wt% and 2 wt%, as well as include individual weights therebetween, such as about 0.5 wt%, 1 wt%, 1.5 wt%, and sub-ranges such as about 0.2 wt% to about 1.5 wt%, 0.5 wt% to about 1 wt%, etc. EXAMPLES

[0045] The following illustrates an example of the present disclosure. However, it is to be understood that the following is illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative compositions, methods, and systems may be devised without departing from the spirit and scope of the present disclosure. The appended claims are intended to cover such modifications and arrangements.

Example 1 - Preparation of Primer Coating Composition

[0046] A primer coating composition is prepared in accordance with Table 1 , as follows:

Table 1 - Primer Coating Composition

Example 2 - Preparation of First Ceramo-metallic Coating Composition

[0047] A first ceramo-metallic coating composition is prepared in accordance with Table 2, as follows: Table 2 - First Ceramo-metallic Coating Composition (UV Curable)

Example 3 - Preparation of Second Ceramo-metallic Coating Composition

[0048] A second ceramo-metallic coating composition is prepared in accordance with Table 3, as follows:

Table 3 - Second Ceramo-metallic Coating Composition

Example 4 - Preparation of Clear Protective Coating Composition

[0049] A clear protective coating composition is prepared in accordance with Table 4, as follows: Table 4 -Clear Protective Coating Composition (UV Curable)

Example 5 - Powder Coating Composition

[0050] A powder coating composition is prepared in accordance with Table 5, as follows:

Table 5 - Powder Coating Composition

Example 6 - Micro-arc Oxidation (MAO) Surface-treatment

[0051 ] A micro-arc oxidation surface-treatment electrolytic bath is prepared that includes from 2 wt% to about 4 wt% of electrolytic compound dissolved in water, including sodium silicate and in some instances, other electrolytic components. Sodium silicate is sparingly soluble in cold water, but starts to go into solution as the

temperature is raised, e.g., 30 °C. More generally, other components that may be included in the electrolytic bath, depending on the metal substrate to be treated, can include alkali metal silicates, alkali metal hyroxides, alkali metal fluorides, alkali metal phosphates, alkali metal aluminates, the like, and combinations thereof.

[0052] Example 7 - Coated Substrates for Electronic Devices

[0053] Various metal and metal alloy substrates are prepared in accordance with Table 6, as follows: [0054] Table 6 - Coated Substrates for Electronic Devices

[0055] Ten coated substrates (1 -10) are prepared in accordance with Table 6. The substrate identities (Substrate IDs) are set forth in Table 6, and the various layer thickness for the applied layers are identified in the subsequent columns. A dash indicates that a particular type of layer is not present. As a note, the first ceramo- metallic layer of Example 2 (Ex2) is positioned more distally with respect to the substrate than the second ceramo-metallic layer of Example 3 (Ex3), when the second ceramo-metallic layer is indeed present. However, this can be reversed, where the second ceramo-metallic layer is positioned more distally with respect to the substrate than the first ceramo-metallic layer.

[0056] The various coating and surface-treatment compositions identified in Examples 1 -6 are used to prepare various layers that are applied serially in these examples (from left to right in Table 6), by example, as follows:

i) To form one type of surface-treatment layer, the powder coating

composition of Table 5 is applied to a metal substrate using electrostatic spray deposition (ESD) at a thickness from about 40 pm to about 60 pm, and then baked at about 170 °C to about 180 °C for about 30 minutes to about 40 minutes.

ii) To form another type of surface-treatment layer, a micro-arc oxidation surface-treatment is carried out on a substrate using a plasma electrolytic oxidation process at a voltage from about 250 V to about 600 V for about 5 minutes to about 25 minutes to generate a thickness of about 4 pm to about 7 pm. The electrolytic bath includes predominantly water with about 2 wt% to about 3 wt% electrolytic compounds, e.g., sodium silicate, potassium hydroxide, and postassium fluoride, though other elelctrolytic bath formulations can be used.

iii) To form a primer layer, the primer coating composition of Table 1 is applied to a substrate or a surface-treatment layer at a thickness from about 5 pm to about 25 pm, and then baked at about 60 °C to about 80 °C for about 15 minutes to about 40 minutes.

iv) To form a“first” (UV curable) ceramo-metallic layer, the UV curable

ceramo-metallic coating composition of Table 2 is applied to a previously applied primer layer or another previously applied ceramo-metallic layer at a thickness from about 10 pm to about 25 pm, and then baked at about 50 °C to about 60 °C for about 5 minutes to about 10 minutes, and UV cured using about 800 mJ/cm² to about 1 ,200 mJ/cm²

v) To form a“second” ceramo-metallic layer, the ceramo-metallic coating composition of Table 3 is applied to a previously applied primer layer or another previously applied ceramo-metallic layer at a thickness from about 10 pm to about 25 pm, and then baked at about 60 °C to about 80 °C for about 15 minutes to about 40 minutes.

vi) To form a clear protective layer, the UV curable clear protective coating composition of Table 4 is applied to a previously applied ceramo-metallic layer at a thickness from about 10 pm to about 25 pm, and then baked at about 50 °C to about 60 °C for about 5 minutes to about 10 minutes, and UV cured using about 800 mJ/cm² to about 1 ,200 mJ/cm² [0057] What has been described and illustrated herein include examples of the disclosure along with some of its variations. The terms, descriptions, examples, and figures used herein are set forth by way of illustration and are not meant as limitations. Many variations are possible within the scope of the disclosure, which is intended to be defined by the following claims -- and their equivalents -- in which all terms are meant in their broadest reasonable sense unless otherwise indicated.

Claims

What Is Claimed Is: 1. A coated substrate for an electronic device comprising:

a substrate for housing or supporting electronic components;

a primer layer on the substrate; and

a ceramo-metallic layer on the primer layer, the ceramo-metallic layer including a composite of:

ceramic particles in an amount of about 3 wt% to about 15 wt%, reflective metal particles in an amount of about 0.1 wt% to about 2 wt%, and

polymer binder in an amount of about 70 wt% to about 97 wt%, wherein the ceramo-metallic layer weight percentages are based on dry weight.

2. The coated substrate of claim 1 , wherein the substrate is a metal substrate including aluminum, magnesium, lithium, titanium, or an alloy thereof.

3. The coated substrate of claim 1 , wherein primer layer includes polymer binder and filler, and wherein the filler includes carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, synthetic pigment, metallic powder, aluminum oxide, graphene, graphite, or a combination thereof.

4. The coated substrate of claim 1 , wherein the ceramic particles of the ceramo- metallic layer include alumina, zirconia, aluminum silicate, zirconium silicate, alumina- zirconia ceramic, or a combination thereof.

5. The coated substrate of claim 1 , wherein the reflective metal particles of the ceramo-metallic layer are shaped to reflect light in a directionally dependent manner.

6. The coated substrate of claim 1 , wherein the reflective metal particles include aluminum, titanium, chromium, nickel, zinc, or a combination thereof.

7. The coated substrate of claim 1 , further comprising a second ceramo-metallic layer positioned between the primer layer and the ceramo-metallic layer, wherein the second ceramo-metallic layer also includes ceramic particles, reflective metal particles, and polymer binder.

8. The coated substrate of claim 7, wherein the second ceramo-metallic layer further includes a filler not present in the ceramo-metallic layer, and the ceramo-metallic layer includes a UV curable binder.

9. The coated substrate of claim 1 , further comprising a clear protective layer positioned on the ceramo-metallic layer.

10. The coated substrate of claim 1 , wherein the ceramo-metallic layer has a high pencil hardness of about 6H to 9H.

11. A coated substrate for an electronic device, comprising:

a substrate;

a surface-treatment layer on the substrate;

a primer layer on the treatment layer; and

12. The coated substrate of claim 11 , wherein the substrate is a metal substrate and surface treatment is a powder coating layer or a micro-arc oxidation (MAO) layer positioned on the metal substrate.

13. A housing for an electronic device comprising the coated substrate of claim

1 1 .

14. A method of coating a substrate for an electronic device comprising:

applying a primer coating composition on a substrate or a surface-treated substrate, the primer coating composition including liquid vehicle, polymer binder, and filler;

heating the primer coating composition after application to drive off solvent from the liquid vehicle and form a primer layer having a thickness from about 5 pm to about 25 pm;

applying a ceramo-metallic coating composition to the primer layer, the ceramo- metallic coating composition including liquid vehicle, ceramic particles, reflective metal particles, and polymer binder; and

heating the ceramo-metallic coating composition after application to drive off solvent from the liquid vehicle and form a ceramo-metallic layer having a thickness from about 8 pm to about 30 pm, the ceramo-metallic layer including:

15. The method of claim 14, further comprising UV curing the ceramo-metallic layer to at from 500 mJ/cm² to about 1 ,500 mJ/cm²