BACKGROUND

[0001] Electronic devices, such as laptops and mobile phones, include various components located within a housing. The housings can bear images of, for example, logos and decorative print designs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figures 1 is a schematic illustration of a cross-section of part of a housing according to a first example of the present disclosure.

[0003] Figure 2 is a schematic illustration of a cross-section of part of a housing according to a second example of the present disclosure.

[0004] Figure 3 is a schematic illustration of a cross-section of part of a housing according to a third example of the present disclosure.

[0005] Figure 4 is a schematic illustration of a cross-section of part of a housing according to a fourth example of the present disclosure.

[0006] Figure 5 is a schematic illustration of a cross-section of part of a housing according to a fifth example of the present disclosure.

[0007] Figure 6 is a schematic illustration of a cross-section of part of a housing according to a sixth example of the present disclosure.

[0008] Figure 7 is a schematic illustration of a cross-section of part of a housing according to a seventh example of the present disclosure.

[0009] The figures depict several examples of the present disclosure. It should be understood that the present disclosure is not limited to the examples depicted in the figures

DETAILED DESCRIPTION

[0010] As used in the present disclosure, the term“about” is used to provide flexibility to an endpoint of a numerical range. The degree of flexibility of this term can be dictated by the particular variable and is determined based on the associated description herein.

[0011] Amounts and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not just the numerical values explicitly recited as the limits of the range, but also to include individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.

[0012] As used in the present disclosure, the term“comprises” has an open meaning, which allows other, unspecified features to be present. This term embraces, but is not limited to, the semi-closed term“consisting essentially of and the closed term“consisting of”. Unless the context indicates otherwise, the term “comprises” may be replaced with either“consisting essentially of” or“consists of.

[0013] 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 context clearly dictates otherwise.

[0014] The present disclosure relates to a housing for an electronic device. The housing comprises a substrate, a primer layer overlying at least part of the substrate; and a water transfer print layer overlying at least part of the primer layer. The substrate comprises at least one of (i) a metal or metal alloy substrate having an oxide layer and/or passivation layer, (ii) a fibre composite substrate, and (iii) a polymer composite substrate comprising a first polymer region and a second polymer region. Where the substrate comprises the polymer composite, the primer layer overlies at least part of a join between the first polymer region and the second polymer region. In some examples, the primer layer may not only overly the join between the first polymer region and the second polymer region but may also overly at least part of the surface of the first polymer region and the second polymer region.

[0015] The present disclosure also relates to a method of producing a housing for an electronic device. The method comprises applying a primer to a substrate and applying a water transfer print layer to the primed substrate. The substrate comprises at least one of (i) a metal substrate having an oxide layer and/or passivation layer, (ii) a fibre composite substrate, and (iii) a polymer composite substrate comprising a first polymer region and a second polymer region. Where the substrate comprises the polymer composite substrate, the primer is applied to at least part of a join between the first polymer region and the second polymer region. In some examples, the primer layer may not only overly the join between the first polymer region and the second polymer region but may also overly at least part of the surface of the first polymer region and the second polymer region.

[0016] In some examples, the primer layer is applied by spray coating. In some examples, the primer layer is polished prior to application of the water print transfer layer.

[0017] A water transfer print film can be used to apply an image onto a substrate. A water transfer print film may comprise an image printed on a water-soluble film. To transfer the image onto an object, the water transfer print film is placed on the surface of a volume of water. An activator comprising organic solvent may be applied over the water transfer print film to initiate dissolution of the water-soluble film. As the water-soluble film dissolves, the printed image remains on the surface of the water. When an object is immersed into the water, the printed image contacts and adheres to the substrate as a water transfer print layer. The surface tension of the water allows the printed image to form around objects having a variety of shapes including, for example, objects having contoured, curved, raised or recessed surface features.

[0018] Although water transfer printing techniques are suitable for applying images onto objects having contours and other surface features of a macroscopic scale, it has now been found that water transfer print layers may not adhere as effectively to surfaces having smaller surface features that are, for example, on a micro- and/or nanoscale. For example, in the case of (i) a metal substrate having an oxide layer and/or passivation layer, the oxide or passivation layer may introduce a degree of surface roughness to the surface of the substrate. This surface roughness may be due to e.g. micro- or nano-sized surface features, which can affect adhesion.

[0019] Similarly, with (ii) a fibre composite substrate, any fibres protruding from the surface of the substrate may also introduce a degree of surface imperfection that can sometimes affect adhesion. Finally, with (iii) a polymer composite comprising a first polymer region and a second polymer region, the join between the first polymer region and second polymer region may give rise to an interface that can affect adhesion.

[0020] Without wishing to be bound by any theory, it is believed that the surface tension of the water may be unable to bend the printed image around small surface features and imperfections, thus compromising the adherence of the water transfer print layer to the underlying surface. By applying a primer layer over the substrate, it may be possible to provide a smoother layer overlying at least part of the substrate. When a water transfer print layer is applied over at least part of the primer layer, adhesion may be more effective, as the surface area of contact between the water transfer print layer and underlying surface may be increased.

[0021] In some examples, the substrate comprises (ii) a fibre composite substrate.

[0022] In some examples, the fibre composite substrate comprises a carbon fibre composite substrate.

[0023] In some examples, the fibre composite substrate is a composite structure comprising a first region comprising a carbon fibre composite substrate and a second region comprising a metal substrate or metal alloy substrate.

[0024] In some examples, the substrate comprises (i) a metal or metal alloy substrate having an oxide layer and/or passivation layer.

[0025] In some examples, the metal or metal alloy substrate is a magnesium alloy substrate.

[0026] In some examples, the oxide layer is a microarc oxide layer.

[0027] In some examples, the passivation layer comprises a layer comprising a salt selected from at least one of a molybdate salt, a vanadate salt, a phosphate salt, a chromate salt, a stannate salt and a manganese salt.

[0028] In some examples, the primer comprises a particulate filler.

[0029] In some examples, the filler is selected from carbon black, titanium dioxide, clay, mica, talc, barium sulphate, calcium carbonate, a synthetic pigment, a metallic powder, aluminum oxide, carbon nanotubes (CNTs), graphene, graphite, and an organic powder.

[0030] In some examples, the primer comprises a polyurethane.

[0031] In some examples, the substrate comprises a polymer composite substrate (iii) comprising a first polymer region and a second polymer region, which polymer composite substrate (iii) is a double-shot injection moulded plastic composite substrate. Metal or Metal Alloy Substrate

[0032] In one example, the substrate comprises (i) a metal or metal alloy substrate having an oxide layer and/or passivation layer.

[0033] The metal or metal alloy substrate may have a thickness of about 0.1 to about 5 mm, for example, about 0.2 to about 4 mm or about 0.3 mm to about 2 mm.

[0034] The substrate may comprise a metal selected from aluminum, magnesium, lithium, titanium, zinc and alloy thereof. These metals are light-weight and can provide a durable housing. In one example, the metal or metal alloy substrate may be a magnesium alloy substrate.

[0035] The substrate may be an insert molded metal substrate. For example, the insert molded metal substrate may be formed by insert molding the metal with a plastic, such as a plastic selected from polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyamide (nylon), polyphthalamide (PPA), acrylonitrile butadiene styrene (ABS), polyetheretherketone (PEEK),

polycarbonate (PC), and ABS/PC with 15- 50% glass fiber filler.

[0036] When the substrate is made of a magnesium alloy, the resulting housing may be mechanically durable, is light-weight and can provide an exterior metallic appearance. Magnesium alloys have a specific gravity that is about 70% that of aluminum, a high specific strength, and excellent heat removal characteristics. Electronic devices having a lighter and thinner housing can be manufactured when the substrate is made from a magnesium alloy.

[0037] The magnesium alloy may comprise a content of magnesium of at least about 75 wt.%. For example, the magnesium alloy may comprise at least about 80 wt.% or at least about 90 wt.% of magnesium.

[0038] The magnesium alloy may further comprise aluminum, zinc, manganese, silicon, copper, a rare earth metal or zirconium. The aluminum content may be about 2.5 wt.% to about 13.0 wt.%. When the magnesium alloy comprises aluminum, then at least one of manganese, zirconium or silicon is also present. Examples of magnesium alloys include AZ31 , AZ61 , AZ60, AM60, and AZ91 alloys, according to the American Society for Testing and Materials standards.

[0039] As discussed above, the metal or metal alloy substrate may have an oxide layer and/or passivation layer. In one example, the metal or metal alloy substrate layer has an oxide layer. In another example, the metal or metal alloy substrate is a magnesium alloy substrate having an oxide layer.

[0040] The oxide layer may be formed on exposure to air. In some examples, the oxide layer may be applied, for example, by an electrochemical method. Examples of electrochemical methods include anodising and micro-arc oxidation. To form an oxide layer by anodising, the substrate is made an anode of an electrochemical cell. The cathode may be an inert cathode, for example, stainless steel, while the electrolyte may be an acid solution. When a direct current is passed through the cell, hydrogen is released at the cathode and oxygen at the surface of the anode, which reacts with the metal (e.g. magnesium or aluminium) at the anode’s surface to form an oxide layer. The potential applied across the cell may be about 1 to about 200 V, for example, about 10 to about 30 V.

[0041] In microarc oxidation (MAO), higher potentials are applied. For example, potentials of greater than about 200V may be applied, for instance, about 200 to about 500 V. these potentials can exceed the dielectric breakdown potential of the growing oxide film and, as a result, discharges can occur. These discharges can result in localised plasma reactions that modify the growing oxide by, for example, melting, re-solidification, sintering and densification of the growing oxide layer. These modifications can enhance the mechanical properties of the resulting oxide layer. The modifications can result in microcracks and micropores in the surface of the oxide layer.

[0042] Micro-arc oxidation (MAO) may involve creating micro-discharges on a surface of the magnesium alloy immersed in an electrolyte to produce a crystalline oxide coating. The resulting micro-arc oxide layer may also be ductile and have a relatively high hardness in comparison to an oxide layer produced by a

deposition process, a micro-arc oxide layer may have a higher adhesion to the underlying magnesium alloy.

[0043] The electrolytic solution for MAO may comprise an electrolyte selected from sodium silicate, sodium phosphate, potassium fluoride, potassium hydroxide, sodium hydroxide, fluorozirconate, sodium hexametaphosphate, sodium fluoride, aluminum oxide, silicon dioxide, ferric ammonium oxalate, a salt of phosphoric acid, polyethylene oxide alkylphenolic ether and a combination thereof. [0044] In one example, the oxide layer may be a micro-arc oxide layer. In one example, the substrate is a magnesium alloy substrate having an oxide layer, for instance, a micro-arc oxide layer.

[0045] The oxide layer of the metal or metal alloy substrate can have a thickness of from about 3 to about 15 pm, for example, from about 5 to about 12 pm. In one example, where the oxide layer is a micro-arc oxide layer, the micro-arc oxide layer may have a thickness of from about 3 to about 15 pm, for example, from about 5 to about 12 pm.

[0046] In some examples, the metal or metal alloy substrate has a passivation layer. In some examples, the metal or metal alloy substrate is a magnesium alloy substrate having a passivation layer.

[0047] The passivation layer may comprise a salt selected from a molybdate salt, a vanadate salt, a phosphate salt, a chromate salt, a stannate salt and a manganese salt. In one example, the passivation layer comprises a phosphate salt. The passivation layer contains oxidic salts that can provide the first surface with a dark grey appearance.

[0048] The passivation layer may be applied by exposing the surface of the substrate to a solution of the relevant salt. For example, the surface of the metal or metal alloy substrate may be exposed to a solution of a salt selected from a molybdate salt, a vanadate salt, a phosphate salt, a chromate salt, a stannate salt and a manganese salt. In one example, the passivation layer comprises a phosphate salt.

[0049] The passivation layer can have a thickness of from about 0.5 to about 5 pm, for example, about 1 to about 4 pm.

[0050] In some examples, the primer layer may overly the oxide layer or passivation layer of the metal or metal alloy substrate. The primer layer may be in contact with the oxide layer or passivation layer of the metal or metal alloy substrate.

[0051] In some examples, the primer layer may be applied directly to the oxide layer or passivation layer of the metal or metal alloy substrate. In other examples, intervening layer(s) may be present. For example, a pigment layer may be applied over the oxide layer or passivation layer of the metal or metal alloy substrate. [0052] In some examples, the metal substrate or metal alloy substrate may form part of a composite structure. The composite structure may comprise a region comprising the metal substrate or metal alloy substrate. In some examples, the composite structure may comprise a region comprising the metal substrate and a region of plastic that may be insert moulded around the metal substrate. In other examples, the composite structure may also comprise a supporting layer. The supporting layer may be used to support the metal substrate or metal alloy substrate, such that the resulting structure has improved e.g. strength or flexibility.

[0053] The supporting layer may comprise a fibre composite. For example, a layer of fibre composite (e.g. carbon fibre composite) may be applied to one surface of the metal substrate or metal alloy substrate. Alternatively, or

additionally, the composite structure may comprise a layer of plastic. The plastic layer may be thermally bonded to the metal substrate or metal alloy substrate.

The plastic layer may be thermally bonded directly to the metal substrate or metal alloy substrate, or indirectly via an intervening layer e.g. a fibre composite layer (e.g. carbon fibre composite layer).

Fibre Composite

[0054] In some examples, the substrate comprises (ii) a fibre composite substrate. The fibre composite substrate may have a thickness of about 0.1 to about 5 mm, for example, about 0.2 mm to about 4 mm or about 0.5 to about 1.5 mm.

[0055] The fibre composite may comprise fibres dispersed in a resin. For example, the fibre composite may comprise glass fibres dispersed in resin, or carbon fibre dispersed in a resin. In some examples, the fibre composite substrate comprises a carbon fibre substrate.

[0056] In some examples, the fibre composite substrate may have an uneven surface. For example, the presence of fibres in the resin may cause the surface to be uneven. In some examples, at least some of the fibres may protrude from the surface of the fibre composite substrate. These protruding fibres may result in irregularities or imperfections on the surface of the fibre composite substrate.

[0057] Suitable carbon fibre substrates may be available from Toray® or BASF®. [0058] In some examples, the fibre composite substrate forms part of a

composite structure. The composite structure may comprise a first region comprising the carbon fibre substrate and a second region comprising a metal substrate or metal alloy substrate, for example, the metal substrate or metal alloy substrate described above. Additionally, or alternatively, the composite structure may comprise a layer or portion of plastic. The plastic layer or portion may be thermally bonded to the fibre composite substrate (e.g. carbon fibre composite substrate).

[0059] In some examples, the primer layer may be applied directly to the fibre composite substrate. In other examples, intervening layer(s) may be present. For example, a pigment layer may be applied over the fibre composite substrate.

Polymer Composite Substrate

[0060] In some examples, a polymer composite substrate comprising a first polymer region and a second polymer region; wherein, where the substrate comprises the polymer composite, the primer layer overlies a join between the first polymer region and the second polymer region. In some examples, the primer layer may not only overly the join between the first polymer region and the second polymer region but may also overly at least part of the surface of the first polymer region and the second polymer region.

[0061] The polymer composite substrate may have a thickness of about 0.1 to about 10 mm, for example, about 0.2 to about 5mm or about 0.3 mm to about 2mm.

[0062] In some examples, the substrate comprises a polymer composite substrate comprising a first polymer region and a second polymer region, which polymer composite substrate is a double-shot injection moulded plastic composite substrate. A double-shot injection moulded plastic composite substrate may be formed by injection moulding a first polymer composition and a second polymer composition in a mould.

[0063] Double shot moulding, which may be referred to as two-shot moulding, is a manufacturing process used to produce moulded parts from two or more different materials. In the process, one material is injected into a mould in order to make the initial piece of the product, followed by a second injection of another material. The two polymer resins may be bonded together and the multi-resin moulded pari may be cooled and ejected from the mould.

[0064] In the context of the housing for the electronic device, a double-shot moulding process may be used to provide a housing comprising polymer regions having different properties, for example, different colours or appearances.

[0065] In some examples, the first polymer region may be formed of a polymer selected from polyurethane, silicone rubber, polyether, or elastomers.

[0066] In some examples, the second polymer region may be formed of a polymer selected from polyacrylic, polyester, polyamide, polycarbonate, ABS, or PC-ABS.

[0067] The first polymer region may be formed from a polymer that is the same or different from the polymer employed to form the second polymer region.

[0068] The join between the first polymer region and the second polymer region may be present on a face or edge of the substrate in some examples, the join between the first polymer region and the second polymer region may be present on a face of the substrate. Thus, when the substrate is used to form e.g. a lid of a housing for an electronic device, the join may be visible on the top surface of the lid, providing a visual effect (e.g. different colours).

[0069] In some examples, the primer layer may be applied directly to the polymer composite substrate. In other examples, intervening layer(s) may be present. For example, a pigment layer may be applied over the polymer composite substrate. Alternatively or additionally, an antimicrobial layer may be present as an

intervening layer.

Primer

[0070] Any suitable primer may be used.

[0071] In some examples, the primer may comprise a polymer. The polymer may be a hydrophilic polymer. For example, the polymer may include hydrophilic functional groups. Examples of suitable functional groups include -COOH, -SO ₃ , - SO ₄ , -PO3, -PO ₄ , -OH, and -NH ₂ groups. By including hydrophilic functional groups in the polymer binder, bonding between the primer and the water transfer print layer may be enhanced. [0072] In some examples, the primer may comprise a polymer, for example, polyurethane, polyester, copolymers of acrylic and methacrylic acid, polyvinyl alcohol, poly(carboxylic acids), polyamides, carboxymethyl cellulose,

hydroxymethyl cellulose, hydroxypropylcellulose, and the combinations thereof.

[0073] In some examples, the primer comprises polyurethane.

[0074] In some examples, the primer comprises a particulate filler.

[0075] The filler may comprise at least one of carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, a synthetic pigment, a metallic powder, aluminum oxide, carbon nanotubes (CNTs), graphene, graphite, and an organic powder. The organic powder may, for example, be an acrylic, a

polyurethane, a polyamide, a polyester or an epoxide.

[0076] The primer may include filler in an amount of about 1 to about 30 weight %, for example, about 3 to about 25 weight % or about 5 to about 20 weight % of the total weight of solids in the primer.

[0077] The primer layer may, for example, comprise a polyurethane and at least one filler as described above in some examples, the primer may comprise a polymer and talc. In some examples, the primer may comprise polyurethane and talc. In some examples, the primer may comprise polyurethane and about 5 to about 20 weight %, for instance, about 15 weight % talc based on the total weight of solids in the primer.

[0078] In some examples, the primer may include a pigment (e.g. titanium dioxide).

[0079] In some examples, the filler may help to smooth any imperfections on the surface of the substrate, thereby creating a smoother surface over which the water transfer print film may be applied.

[0080] In some examples, the primer may be coated onto the substrate. In some examples, the primer may be spray-coated onto the substrate. The primer may be applied as a solution or dispersion. For example, the solution or dispersion may comprise a polymer (e.g. polyurethane) dispersed or dissolved in a solvent.

Suitable solvents include ethyl acetate, butyl acetate, propylene glycol

monomethyl ether, isobutyl alcohol, 1 ,4-butanediol, and xylene.

[0081] The primer may be applied at a thickness of about 5 to about 20 pm, for example, about 7 to about 18 pm or about 10 to about 15 pm. [0082] In some examples, the primer layer may be polished prior to application of the overlying water transfer print film.

[0083] In some examples, the primer may be applied to the substrate so that the primer is in contact (e.g. direct contact) with at least part of the substrate.

[0084] In some examples, the water transfer print layer may be applied to the primer so that the water transfer print layer is in contact (e.g. direct contact) with at least part of the primer layer.

Water transfer print layer

[0085] As described above, a water transfer print layer overlies at least part of the primer layer. The water transfer print layer is applied using a water transfer print film. The water transfer print film may comprise a film formed of a water-soluble polymer. For example, the water transfer print film may be formed of polyvinyl alcohol (PVA). The water transfer print film may bear a printed image. The printed image may be printed, for example, gravure printed with an image. This image may be transferred as a water transfer print layer over the primed substrate.

[0086] To transfer the image onto the primed substrate, the water transfer print film is placed on the surface of a body of water. An activator solution may be applied to the water transfer print film to initiate dissolution of the water-soluble film. This leaves the printed ink on the surface of the water. When the primed substrate is dipped into the water, the surface tension of the water allows the ink to conform and adhere to the surface of the substrate. Thus, the printed ink may be transferred onto the primed substrate as a water transfer print layer.

[0087] Any suitable activator solution may be employed. For example, the activator solution may comprise an organic solvent. In one example, the activator solution comprises xylene, for instance, in an amount of about 10 to about 80 weight % or about 20 to about 50 weight %.

[0088] The water transfer print layer may be in contact with at least part of the primer layer. For example, the water transfer print layer may be in direct contact with at least part of the primer layer.

[0089] The water transfer print layer may bear any graphic image.

Upper Coating Layer [0090] In some examples, an upper coating layer is applied over the water transfer print layer. The upper coating layer may comprise a polymer selected from a polyurethane, a polycarbonate, a urethane acrylate, a polyacrylate, a polystyrene, a polyetheretherketone, a polyester, a fluoropolymer and a mixture thereof. Examples of fluoropolymers include fluoroacrylates,

fluorosiliconeacrylates, fluorourethanes, perfluoropolyethers,

perfluoropolyoxetanes, fluorotelomers, polytetrafluoroethylene (PTFE),

polyvinylidenefluoride (PVDF), fluorosiloxane, fluoro UV polymers and

hydrophobic polymers.

[0091] The upper coating layer may be transparent.

[0092] The upper coating layer may have hydrophobic, anti-bacterial, anti smudge, and anti-fingerprint properties. By using an anti-smudging upper coating layer, the surface of the housing may be smudge free.

[0093] The upper coating layer can have a total thickness of from about 10 pm to about 25 pm, such as about 15 pm to about 20 pm.

[0094] In some examples, the upper coating layer may be the uppermost layer of on the substrate.

Housing

[0095] As mentioned above, the present disclosure relates to a housing for an electronic device.

[0096] The housing may provide an exterior part of the electronic device, such as a cover or a casing of the electronic device. The housing may include a support structure for an electronic component of the electronic device.

[0097] The housing may include a battery cover area, a battery door or a vent.

[0098] The housing may provide a substantial part of the cover or the casing of the electronic device. The term“substantial part” in this context refers to at least about 50 %, such as at least about 60 %, at least about 70 %, at least about 80 % or at least about 90 %, of the total weight of the cover or the casing. The housing may provide the entire cover or casing of the electronic device.

[0099] The housing can be a cover, such as a lid, the casing or both the cover and the casing of the electronic device. The casing may form a bottom or lower part of the cover of the electronic device. In one example, the housing is the casing of a laptop, a tablet or a cell phone. In some examples, the housing in the casing of a laptop, tablet or electronic notebook. For example, the substrate may form at least part of the lid or base of the casing of a laptop or electronic notebook.

Method of manufacture

[0100] The present disclosure also relates to a method of manufacturing a housing for an electronic device.

[0101] As explained above, the method comprises applying a primer to a substrate and applying a water transfer print layer to the primed substrate. The substrate comprises at least one of (i) a metal substrate having an oxide layer and/or passivation layer, (ii) a fibre composite substrate, and (iii) a polymer composite substrate comprising a first polymer region and a second polymer region. Where the substrate comprises the polymer composite substrate, the primer is applied to a join between the first polymer region and the second polymer region. In some examples, the primer layer may not only overly the join between the first polymer region and the second polymer region but may also overly the surface of the first polymer region and the second polymer region.

[0102] In some examples, the primer layer may overly at least about 10%, for example, at least about 30%, at least about 50%, at least about 80% of the surface of the first polymer region and the second polymer region. In some examples, the primer layer may overly up to 100% of the surface of the first polymer region and the second polymer region.

[0103] In some examples, the primer layer is applied by spray coating. In some examples, the primer layer is polished prior to application of the water print transfer layer.

[0104] As discussed above, the water transfer print layer may be applied by applying a water transfer print film bearing a printed image onto the surface of a body of water. An activator solution may be applied to the water transfer print film to initiate dissolution of the water-soluble film. This leaves the printed ink on the surface of the water. When the primed substrate is dipped into the water, the surface tension of the water allows the ink to conform and adhere to the surface of the substrate. Thus, the printed ink may be transferred onto the primed substrate as a water transfer print layer. Drawings

[0105] Various examples of the present disclosure are now described with reference to the drawings.

[0106] Figure 1 is a schematic illustration of a cross-section of part of a housing according to a first example of the present disclosure. The housing 10 comprises a substrate 12, a primer layer 14 overlying the substrate 12, and a water transfer print layer 16 overlying the primer layer 14.

[0107] The substrate 12 may comprise a metal substrate. The substrate 12 may be a composite structure comprising one region formed of a metal substrate, and another region formed from a different material, for example, a plastic material. In one example, the substrate 12 may comprise a metal substrate that is over moulded with plastic to form a composite structure (i.e. by insert moulding).

[0108] The surface of the metal substrate may be treated by micro-arc oxidation (MAO) to provide an oxide layer. Both the upper and lower surfaces of the substrate may be treated. Thus, a micro-arc oxidation layer 18 is present on the upper and lower surfaces of the substrate.

[0109] A primer layer 14 is applied over the upper micro-arc oxidation layer 18. The primer may comprise a polyurethane polymer. The primer may be applied by spray-coating. The primer layer 14 may provide a smooth surface over the micro cracks or micro-pores introduced as a result of the micro-arc oxidation treatment.

[0110] The water-transfer print layer 16 may be applied over the primer layer. The water transfer print layer 16 may bear a graphic design.

[0111] The primer 16 may also be applied over the insert moulded plastic portion of the substrate such that the primer overlies the join between the insert moulded plastic portion and the metal substrate.

[0112] A transparent upper layer 20 is applied over the water transfer print layer 16. The upper layer 20 may be a urethane acrylate containing fluoropolymer as anti-fingerprint top coat.

[0113] Figure 2 is a schematic illustration of a cross-section of part of a housing according to a second example of the present disclosure. The housing 10 is similar to the housing shown in Figure 1 and like numerals have been used to illustrate like parts. The substrate 112 of this example, however, comprises a composite structure comprising iayer(s) of metal substrate and a layer of thermal bonded plastic (e.g. between the layers of metal substrate as a supporting layer, not shown). The metal may be magnesium alloy.

[0114] The surface of the metal may be treated by micro-arc oxidation (MAO) to provide an oxide layer. Both the upper and lower surfaces of the substrate 112 may be treated. Thus, a micro-arc oxidation layer 18 is present on the upper and lower surfaces of the substrate 112.

[0115] Figure 3 is a schematic illustration of a cross-section of part of a housing according to a third example of the present disclosure. The housing 10 is similar to the housing shown in Figure 1 and like numerals have been used to illustrate like parts. However, the metal substrate 212 of this example differs from the metal substrate 12 of Figure 1 in that the metal substrate consists essentially of a metal layer 212. The metal layer 212 may be a magnesium alloy layer. The surface of the metal layer may be treated by micro-arc oxidation (MAO) to provide an oxide layer. Both the upper and lower surfaces of the substrate 212 may be treated. Thus, a micro-arc oxidation layer 18 is present on the upper and lower surfaces of the substrate 212.

[0116] Figure 4 is a schematic illustration of a cross-section of part of a housing according to a fourth example of the present disclosure. The housing 10 is similar to the housing shown in Figure 1 and like numerals have been used to illustrate like parts. However, instead of micro-arc oxidation layers 18, the substrate 12 is passivated with passivation layers 318. The passivation layers 318 comprise salts, for example, salts of at least one of a molybdate salt, a vanadate salt, a phosphate salt, a chromate salt, a stannate salt and a manganese salt.

[0117] Figure 5 is a schematic illustration of a cross-section of part of a housing according to a fifth example of the present disclosure. The housing 10 is similar to the housing shown in Figure 2 and like numerals have been used to illustrate like parts. However, instead of micro-arc oxidation layers 18, the substrate 112 is passivated with passivation layers 318. The passivation layers 318 comprise salts, for example, salts of at least one of a molybdate salt, a vanadate salt, a phosphate salt, a chromate salt, a stannate salt and a manganese salt.

[0118] Figure 6 is a schematic illustration of a cross-section of part of a housing according to a sixth example of the present disclosure. The housing 400 comprises a substrate 412, a primer layer 414 overlying the substrate 412, and a water transfer print layer 416 overlying the primer layer 414.

[0119] The substrate 412 may be a carbon fibre substrate. The carbon fibre substrate may comprise a compression moulded carbon fibre composite.

[0120] A primer layer 414 is applied over the carbon fibre substrate. The primer may comprise a polyurethane polymer. The primer may be applied by spray coating. The primer may provide a smooth layer over the carbon fibre substrate. For example, the primer may provide a smoother surface over any surface imperfections arising, for example, from fibres extending from the surface of the resin matrix of the carbon fibre substrate.

[0121] The water-transfer print layer 416 may be applied over the primer layer. The water transfer print layer 416 may bear a graphic design.

[0122] A transparent upper layer 420 is applied over the water transfer print layer 416. The upper layer 420 may be a urethane acrylate containing fluoropolymer as anti-fingerprint top coat.

[0123] Figure 7 is a schematic illustration of a cross-section of part of a housing according to a seventh example of the present disclosure. The housing 10 is similar to the housing shown in Figure 6 and like numerals have been used to illustrate like parts. However, the carbon fibre substrate 512 of Figure 7 comprises carbon fibre that is thermally bonded to plastic. The primer layer 4141 is applied over the carbon fibre composite surface and smooths the surface as described above.