U.S. patent application number 17/840484 was filed with the patent office on 2022-09-29 for colored coatings for electronic devices.
The applicant listed for this patent is Apple Inc.. Invention is credited to Khadijeh Bayat, Di Fan, Yoshitaka Matsui, Martin Melcher, Daisuke Nozu, Naomi Sugawara, James R. Wilson, Avery P. Yuen, Xianwei Zhao.
Application Number | 20220312614 17/840484 |
Document ID | / |
Family ID | 1000006402878 |
Filed Date | 2022-09-29 |
United States Patent
Application |
20220312614 |
Kind Code |
A1 |
Bayat; Khadijeh ; et
al. |
September 29, 2022 |
Colored Coatings for Electronic Devices
Abstract
An electronic device may have transparent housing structures
such as walls formed of glass or sapphire. Housing structures such
as transparent housing structures may have a colored coating. The
colored coating may include an absorptive layer and a metal layer.
The coating may exhibit a color that can be adjusted by adjusting
the thickness of the thin absorptive layer. A colored layer such as
a layer of colored polymer may be incorporated into the colored
coating to further adjust the color of the coating. The colored
coating may be formed on an inner or outer housing structure
surface. The surface may have a texture to provide the coating with
a matte appearance. When formed on an outer surface, a diamond-like
carbon layer may protect the colored coating. When formed on an
inner surface, a passivation layer may be used to prevent oxidation
of the metal layer.
Inventors: |
Bayat; Khadijeh; (Los Altos,
CA) ; Matsui; Yoshitaka; (Yokohama, JP) ;
Sugawara; Naomi; (Yokohama, JP) ; Nozu; Daisuke;
(Saitama, JP) ; Zhao; Xianwei; (Cupertino, CA)
; Yuen; Avery P.; (Campbell, CA) ; Melcher;
Martin; (Paris, FR) ; Wilson; James R.;
(Saratoga, CA) ; Fan; Di; (Cupertino, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc. |
Cupertino |
CA |
US |
|
|
Family ID: |
1000006402878 |
Appl. No.: |
17/840484 |
Filed: |
June 14, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16403425 |
May 3, 2019 |
11399442 |
|
|
17840484 |
|
|
|
|
62693872 |
Jul 3, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K 5/0243 20130101;
H05K 5/069 20130101; C03C 2217/72 20130101; C03C 17/3684 20130101;
C03C 17/3655 20130101; B32B 1/02 20130101; H05K 9/0009
20130101 |
International
Class: |
H05K 5/06 20060101
H05K005/06; C03C 17/36 20060101 C03C017/36; H05K 5/02 20060101
H05K005/02; H05K 9/00 20060101 H05K009/00; B32B 1/02 20060101
B32B001/02 |
Claims
1. An electronic device having an interior and an exterior,
comprising: a structure that is transparent to visible light,
wherein the structure has an inner surface facing the interior; and
a coating on the inner surface, wherein the coating includes an
amorphous semiconductor layer.
2. The electronic device defined in claim 1, wherein the amorphous
semiconductor layer comprises an amorphous silicon layer.
3. The electronic device defined in claim 1, wherein the coating
further comprises a metal layer, wherein the amorphous
semiconductor layer is interposed between the metal layer and the
inner surface.
4. The electronic device defined in claim 3, wherein the coating
further comprises a passivation layer on the metal layer.
5. The electronic device defined in claim 4, wherein the
passivation layer comprises amorphous silicon.
6. The electronic device defined in claim 1, wherein the structure
comprises glass.
7. The electronic device defined in claim 1, wherein the structure
comprises a housing wall and wherein the inner surface is
textured.
8. The electronic device defined in claim 7, wherein the inner
surface has a surface roughness of 25 nm to 400 nm.
9. The electronic device defined in claim 7, wherein the coating
further comprises a protective layer on the metal layer.
10. The electronic device defined in claim 9, wherein the
protective layer comprises diamond-like carbon.
11. An electronic device, comprising: a structure that is
transparent to visible light; and a colored coating on the
structure, wherein the colored coating includes a metal layer and
an amorphous semiconductor layer between the metal layer and the
structure.
12. The electronic device defined in claim 11, wherein the colored
coating further comprises a colored polymer layer.
13. The electronic device defined in claim 12, wherein the colored
polymer layer comprises dye.
14. The electronic device defined in claim 12, wherein the colored
polymer layer is interposed between the structure and the amorphous
semiconductor layer.
15. The electronic device defined in claim 12, wherein the colored
polymer layer is formed on the metal layer and wherein the metal
layer is between the colored polymer layer and the amorphous
semiconductor layer.
16. An electronic device, comprising: a visible-light transparent
structure; and a coating on the visible-light transparent structure
that includes an amorphous semiconductor layer and a layer
comprising metal.
17. The electronic device defined in claim 16, wherein the
visible-light transparent structure has inner and outer surfaces,
wherein the coating is on the inner surface.
18. The electronic device defined in claim 16, wherein the
amorphous semiconductor layer is interposed between the inner
surface and the layer comprising metal.
19. The electronic device defined in claim 17, wherein the layer
comprising metal is between the amorphous semiconductor layer and
the inner surface.
20. The electronic device defined in claim 16, wherein the
visible-light transparent structure has inner and outer surfaces
and wherein the coating is on the outer surface.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/403,425, filed May 3, 2019, which claims
the benefit of provisional patent application No. 62/693,872, filed
Jul. 3, 2018, which are hereby incorporated by reference herein in
their entireties.
FIELD
[0002] This relates generally to electronic devices, and, more
particularly, to colored coatings for electronic devices.
BACKGROUND
[0003] Electronic devices such as cellular telephones, computers,
watches, and other devices may contain housing structures formed of
glass and other materials. For example, an electronic device may
have a rear housing wall that is covered with a layer of glass.
[0004] If care is not taken, housing structures may have an
undesired appearance. For example, a coating layer on a housing may
have an unattractive color or may have an appearance that changes
more than desired as a function of viewing angle.
SUMMARY
[0005] An electronic device may include electrical components and
other components mounted within a housing. The housing may have
transparent housing structures such as walls formed of glass or
sapphire.
[0006] Housing structures such as transparent housing structures
may have a colored coating. The colored coating may cover a housing
wall or may be patterned to form a logo or trim.
[0007] The colored coating may include a thin absorptive layer and
a metal layer configured so that the coating exhibits a desired
color. Adjustments to the colored coating such as adjustments to
the thickness of the thin absorptive layer may be used to alter the
color of the coating. If desired, a colored layer such as a layer
of colored polymer may be incorporated into the colored coating to
further adjust the color of the coating.
[0008] The colored coating may be formed on an inner or outer
housing structure surface. The surface may have a texture to
provide the coating with a matte appearance. When formed on an
outer surface, a transparent diamond-like carbon layer may be
included in the colored coating to protect the colored coating from
scratches. When formed on an inner surface, a passivation layer may
be included on the inner side of the colored coating to prevent
oxidation of the metal layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of an illustrative electronic
device of the type that may include a coating in accordance with an
embodiment.
[0010] FIG. 2 is a cross-sectional side view of an illustrative
electronic device in accordance with an embodiment.
[0011] FIG. 3 is a cross-sectional side view of an illustrative
housing structure with a coating in accordance with an
embodiment.
[0012] FIG. 4 is a graph in which light reflection has been plotted
as a function of wavelength for structures associated with the
coating of FIG. 3 in accordance with an embodiment.
[0013] FIG. 5 is a side view of an illustrative housing structure
with a coating in accordance with an embodiment.
[0014] FIG. 6 is a graph in which light reflection has been plotted
as a function of wavelength for structures associated with the
coating of FIG. 5 in accordance with an embodiment.
[0015] FIG. 7 is a diagram of an illustrative housing structure
with a textured surface covered with a coating in accordance with
an embodiment.
[0016] FIG. 8 is a side view of an illustrative housing structure
with a radio-frequency transparent colored coating containing a
metal alloy layer in accordance with an embodiment.
DETAILED DESCRIPTION
[0017] Electronic devices and other items may be provided with
structures that have coatings. The structures may be formed from
glass, polymer, crystalline material such as sapphire, metal,
and/or other materials. In some arrangements, the structures may
form a rear housing wall, sidewall, or other housing structures.
The housing structures may, if desired, be transparent housing
structures such as layers of glass or sapphire. Coatings can be
formed on the inner or outer surfaces of housing structures. For
example, an inner surface of a transparent rear housing wall may be
provided with a logo-shaped coating or a blanket coating that
covers the entire wall. In some configurations, edge portions of a
protective display cover layer that overlaps a layer of pixels in a
display may be provided with a coating.
[0018] A coating may be colored to impart a desired color to a
portion of a device. The color that is provided by the coating may
be a non-neutral color such as red, yellow, blue, green, rose gold,
champagne, or other non-neutral color. The coating may, if desired,
exhibit desirable properties such as color invariance over a wide
range of viewing angles (e.g., exhibiting less than 5% or less than
10% change in color coordinate values over viewing angles ranging
+/-40.degree. from the surface normal of a coated surface), the
ability to form the coating from a relatively small number of
layers of material (e.g., 2 or 3 layers, 2-4 layers, etc.), the
ability to cover a wide range of different color options, high
reliability, good manufacturability, and/or low cost.
[0019] An illustrative electronic device of the type that may
include a structure that is coated with a colored coating layer is
shown in FIG. 1. Electronic device 10 may be a computing device
such as a laptop computer, a computer monitor containing an
embedded computer, a tablet computer, a cellular telephone, a media
player, or other handheld or portable electronic device, a smaller
device such as a wristwatch device (e.g., a watch with a wrist
strap), a pendant device, a headphone or earpiece device, a device
embedded in eyeglasses, goggles, a helmet or other equipment worn
on a user's head (e.g., a head-mounted display), or other wearable
or miniature device, a television, a computer display that does not
contain an embedded computer, a gaming device, a navigation device,
an embedded system such as a system in which electronic equipment
with a display is mounted in a kiosk or automobile, equipment that
implements the functionality of two or more of these devices, or
other electronic equipment. In the illustrative configuration of
FIG. 1, device 10 is a portable device such as a cellular
telephone, media player, tablet computer, wrist device, or other
portable computing device. Other configurations may be used for
device 10 if desired. The example of FIG. 1 is merely
illustrative.
[0020] In the example of FIG. 1, device 10 includes a display such
as display 14 mounted in a housing. The housing may include housing
structures such as housing sidewalls 12 and other structures for
supporting display 14.
[0021] Display 14 may be a touch screen display that incorporates a
layer of conductive capacitive touch sensor electrodes or other
touch sensor components (e.g., resistive touch sensor components,
acoustic touch sensor components, force-based touch sensor
components, light-based touch sensor components, etc.) or may be a
display that is not touch-sensitive. Capacitive touch screen
electrodes may be formed from an array of indium tin oxide pads or
other transparent conductive structures.
[0022] Display 14 may include an array of pixels formed from liquid
crystal display (LCD) components, an array of electrophoretic
pixels, an array of plasma pixels, an array of organic
light-emitting diode pixels or other light-emitting diodes, an
array of electrowetting pixels, or pixels based on other display
technologies. If desired, display 14 may use a
microelectromechanical systems pixel array.
[0023] Display 14 may include one or more layers of transparent
material. For example, the outermost layer of display 14, which may
sometimes be referred to as a display cover layer, may be formed
from rigid polymer or a hard transparent material such as glass or
sapphire to help protect more sensitive portions of display 14 from
damage. Other portions of device 10 such as housing structures on
the sidewall or rear wall of device 10 may also be formed from
transparent material (e.g., glass, sapphire, polymer, etc.).
[0024] FIG. 2 is a cross-sectional side view of an illustrative
device such as device 10 of FIG. 1. As shown in FIG. 2, the housing
for device 10 may include housing structures such as housing
sidewalls 12 on the sides of device 10 and rear housing wall 24 on
a rear face of device 10 (as an example). Sidewalls 12 and/or rear
housing wall 24 may be formed from metal, glass, sapphire or other
crystalline material, polymer, fiber composite materials, and/or
other materials.
[0025] As an example, some or all of sidewalls 12 may be formed
from metal and some or all of rear housing wall 24 may be formed
from transparent material such as glass or sapphire. Other
configurations may be used, if desired.
[0026] As shown in FIG. 2, display 14 may include display cover
layer 16 (e.g., a layer of glass, sapphire, or clear polymer) and
display layer 18 (e.g., a display layer that includes an array of
pixels to present images for a user on the front face of device
10). Display layer 18, which may sometimes be referred to as a
pixel array layer, may be a liquid crystal display structure, an
organic light-emitting diode display structure (e.g., a flexible
organic light-emitting diode display layer), or other suitable
display. During operation, display layer 18 may present images that
are viewable through transparent portions of display cover layer
16. In some arrangements, edge portions of display cover layer 16
may bend downwards to form portions of sidewall 12 and/or edge
portions of rear wall 24 may bend upwards to form portions of
sidewall 12.
[0027] Internal components in device 10 such as components 22
(e.g., electrical components such as integrated circuits, sensors,
etc.) may be mounted on one or more substrates such as printed
circuit 20 in the interior of device 10.
[0028] To hide internal components such as components 22 from view,
inactive border areas in layer 16 and portions of other transparent
structures (e.g., a transparent rear housing layer such as rear
housing wall 24 on the rear face of device 10 and/or transparent
housing sidewall structures) may be covered with coatings (e.g.,
opaque coatings). Coating layers may be formed on the inner and/or
outer surfaces of these housing structures. For example, a coating
may be formed on some or all of the inner surface of sidewall 12,
the inner surface of rear housing wall 24, and/or the inner surface
of border portions of display cover layer 16. Arrangements in which
the coating is formed on some or all of the outer surfaces of these
structures may also be used.
[0029] In some arrangements, a coating may be used primarily to
block light (e.g., to hide internal device structures from view).
In other arrangements, a patterned coating may be used to form
text, logos, trim, and/or other decorative patterns. Black coatings
may sometimes be used to form opaque masking layers. Coatings for
structures in device 10 may also have non-neutral colors (e.g.,
blue, red, yellow, gold, rose gold, red-violet, pink, etc.).
[0030] A colored coating for device 10 may from metal (e.g.,
aluminum, gold, and/or other highly reflective metals), absorptive
materials (e.g., amorphous semiconductor layers such as layers of
amorphous silicon or amorphous germanium), colored polymers and/or
other dielectrics, and/or other materials. Materials for the
coatings may include organic materials such as polymer layers
and/or inorganic materials such as oxide layers, nitride layers,
and/or other inorganic dielectric materials. Polymer may include
dye, pigment, or other colorants to impart a desired color to the
polymer. In some arrangements, a coating may include a transparent
(optical) diamond-like carbon layer (e.g., a hard amorphous carbon
layer). A transparent diamond-like carbon layer may, for example,
be used as a protective outer layer in a coating. The visible light
transmission of the diamond-like carbon layer in this type of
arrangement may be at least 90%, at least 95%, at least 99%, at
least 99.8%, or less than 99.99% (as examples). The relative
amounts of sp3 bonds, sp2 bonds, and hydrogen content in the
diamond-like carbon layer may be adjusted during deposition to
ensure that the diamond-like carbon layer has a desired hardness
for resisting scratches while maintaining a desired optical
transparency so that underlying color coating layers are visible to
the user.
[0031] FIG. 3 is a cross-sectional side view of an illustrative
coating layer. In the example of FIG. 3, coating 32 has been formed
on an inner surface of layer 30. Layer 30, which may sometimes be
referred to as a substrate layer, may be a transparent layer of
glass, sapphire, or polymer (as examples). In device 10, layer 30
may serve as a housing structure (e.g., some or all of sidewall 12
and/or rear housing wall 24) and/or may be a peripheral border
portion of display cover layer 16 (a housing structure of glass,
polymer, sapphire, or other suitable material that is formed near
the edge of the array of pixels displaying images for a user of
device 10).
[0032] Coating layer 32 may include layers 34 and 36. Layer 36 may
be a reflective layer formed from a material such as metal. For
example, layer 36 may be an aluminum layer. The thickness of layer
36 may be at least 30 nm, 30-50 nm, at least 50 nm, at least 20 nm,
less than 70 nm, or other suitable thickness.
[0033] Layer 34 may be an absorptive layer (e.g., a layer that
absorbs at least some of the light passing through layer 34).
Absorptive layer 34 may be interposed between viewer 26 and layer
36. For example, in arrangements in which coating 32 is formed on
the inner surface of a layer such as layer 30, layer 34 may be
interposed between layer 30 and layer 36. Layer 34 may, if desired,
be formed directly on the inner surface of layer 30. Absorptive
layer 34 may be formed form an absorptive material such as
amorphous silicon that absorbs visible light. The index of
refraction of amorphous silicon is relatively high (e.g., the
refractive index of amorphous silicon in the visible light range is
4-4.5), which tends to refract off-axis light towards the surface
normal of layer 34. As a result, coating 32 will tend to have an
appearance that is relatively invariant to changes in viewing
angle. Layer 34 may have a thickness h of at least 15 nm, at least
20 nm, 20-80 nm, at least 40 nm, less than 70 nm, less than 80 nm,
less than 100 nm, less than 120 nm, or other suitable thickness.
The thickness h of layer 34 is preferably much less (e.g., at least
5 times less, at least 15 times less, at least 25 times less, or
more) than the wavelength of visible light (e.g., about 500 nm)
divided by 4*n, where n is the refractive index of amorphous
silicon.
[0034] As shown in FIG. 3, optional passivation layer 38 may be
formed on the innermost surface of layer 36 (e.g., in scenarios in
which layer 30' is not present). Passivation layer 38 may be formed
from any suitable material that helps protect layer 34. For
example, passivation layer 38 may be formed from amorphous silicon
and may help prevent aluminum or other metal in layer 36 from
oxidizing when contacted by the atmosphere.
[0035] As illustrated by optional substrate layer 30', coating 32
may, if desired, be formed on an outer surface of device 10 (e.g.,
in an arrangement in which substrate layer 30 is not present and
coating 32 covers the outer surface of a housing structure or other
layer 30'). In this type of arrangement, a diamond-like carbon
layer may be formed on the outer surface of coating 32 in the
position shown by layer 30 of FIG. 3. The diamond-like carbon layer
may help prevent damage to coating 32 from scratches.
[0036] FIG. 4 is a graph in which light reflectivity R has been
plotted as a function of wavelength .lamda. for layer 36 and
coating 32. Layer 36 may be, for example, a metal layer such as an
aluminum layer and may be characterized by a relatively broadband
reflection spectrum (see, e.g., flat reflectivity curve 40 of FIG.
4). In the presence of silicon layer 34 on layer 36, coating 32 may
exhibit thin-film interference effects (e.g., constructive
interference at some wavelengths .lamda. of visible light) so that
the absorption of visible light by coating 32 may peak and the
reflectivity of visible light may exhibit a valley at a wavelength
such as wavelength .lamda.c. This is illustrated by curve 42 of
FIG. 4, which represents the reflectivity spectrum of coating 32 at
visible light wavelengths. The position of wavelength .lamda.c
within the visible spectrum (390 to 700 nm) may be adjusted by
selecting the value of thickness h of layer 34. The color of
coating 32 can be tuned in this way (e.g., coatings 32 in which the
thickness h of layer 34 is different will have different
non-neutral colors).
[0037] Another illustrative configuration for coating 32 is shown
in FIG. 5. In the example of FIG. 5, coating 32 has been formed on
the inner surface of substrate layer 30. Layer 34 may be an
amorphous silicon layer with a thickness h and layer 36 may be a
metal layer such as an aluminum layer, as described in connection
with FIG. 3. Adjustment of coating 32 (e.g., adjustment of
thickness h) can be used to adjust the color of coating 32. Further
adjustment of the color of coating 32 can be obtained by
incorporating one or more colored dielectric layers into coating
32. For example, colored layer 44 may be interposed between layer
34 and substrate 30 and/or colored layer 46 may be formed on the
innermost surface of layer 36.
[0038] Colored layers 44 and 46 may be formed from polymer or other
dielectric that includes dye, pigment, or other colorant that
provides layers 44 and 46 with desired color casts. The graph of
FIG. 6 in which reflectivity R has been plotted as a function of
wavelength .lamda. illustrates a possible reflection spectrum for
coating 32. Silicon layer 34 on metal layer 36 may be characterized
by a reflection spectrum such as curve 48 (e.g., a reflection
spectrum with a valley at wavelength .lamda.1, corresponding to an
absorption spectrum peak). Colored coating layer 44 (or colored
coating layer 46, or both colored coating layers 44 and 46) may be
characterized by a reflection spectrum such as curve 50 (e.g., a
reflection spectrum with a valley at wavelength .lamda.3,
corresponding to an absorption spectrum peak due to the presence of
dye, pigment, or other colorant). At wavelengths away from the
reflectivity spectrum valleys at .lamda.1 and .lamda.3 (e.g., at
wavelengths such as wavelength .lamda.2, which may correspond to
green light, for example), coating 32 will reflect light. As a
result, coating 32 may have a color determined by the spectral
responses of 1) layers 34 and 36) and 2) the colored coating
material (e.g., layer 44 and/or layer 46). In arrangements in which
the colored polymer material is formed on the inner surface of
metal layer 36 (as shown by illustrative layer 46), ambient light
passes through metal layer 36 before reaching layer 46. Layer 46
can adjust the color of coating 32, provided that layer 36 is
sufficiently thin (e.g., 30-50 nm or less or other suitable
thickness) to allow a non-negligible amount of light to pass to and
from layer 46.
[0039] As illustrated by optional substrate layer 30', coating 32
of FIG. 5 may, if desired, be formed on an outer surface of device
10 (e.g., in an arrangement in which substrate layer 30 is not
present). In this type of arrangement, a transparent diamond-like
carbon layer may be formed on the outer surface of coating 32 in
the position shown by layer 30 of FIG. 5 to help protect coating 32
from scratches.
[0040] In some arrangements, it may be desirable for some or all of
the coated structures in device 10 to exhibit a matte appearance.
As shown in FIG. 7, coating layer 32 may be provided with a matte
appearance by texturing the inner surface of substrate 30 (e.g., so
that this surface has a root-mean-square surface roughness of at
least 25 nm, at least 50 nm, at least 100 nm, less than 400 nm,
less than 1600 nm, or other suitable surface roughness. This rough
surface texture helps scatter ambient light that is reflecting off
of coating 32 and thereby provides coating 32 with a matte
appearance. As illustrated by optional substrate layer 30', coating
32 of FIG. 7 may, if desired, be formed on a textured outer surface
of device 10 (e.g., a textured surface of layer 30') in an
arrangement in which substrate layer 30 is not present. To help
protect coating 32 in this type of arrangement, a protective
coating such as a transparent diamond-like carbon layer may be
formed on the outer surface of coating 32 (e.g., in the position of
layer 30 of FIG. 7).
[0041] In some arrangements, it may be desirable for the colored
coating to exhibit radio-frequency transparency. For example, in
systems in which layer 30 forms an electronic device housing wall,
it may be desirable to allow wireless power signals and/or
radio-frequency antenna signals to be transmitted and/or received
through layer 30 and the colored coating on layer 30. To enhance
radio-frequency transparency for wireless communications and/or to
support inductive wireless charging, conductive materials (e.g.,
metal layer 36) may be patterned to form isolated islands (e.g.,
rectangular pads or pads of other shapes such as triangles,
hexagons, etc.) on layer 30. The pads may be tiled in an array with
rows and columns or other suitable patterns. A mesh of gaps (e.g.,
intersecting lines extending horizontally and vertically between
rows and columns of pads or other thin elongated gap structures
such as illustrative gaps G in FIG. 7) may be present in the
patterned layer. These gaps are free of metal or other conductive
material in layer 36 and therefore block current flow (e.g., the
gaps block eddy currents and prevent electromagnetic signal
resonances from occurring). Each pad may have lateral dimensions
equal to a fraction of a wavelength for radio-frequency signals of
interest (e.g., less than 1/10 of a wavelength, less than 1/5 of a
wavelength, at least 1/100 of a wavelength, at least 1/20 of a
wavelength, etc.) or may have other suitable shapes and sizes for
reducing or eliminating radio-frequency signal interactions as
radio-frequency antenna signals and/or wireless power signals pass
through layer 30.
[0042] In addition to or instead of patterning conductive layer(s)
of material to form pads, layer conductivity can be reduced by
using low-conductivity alloys. For example, layer 36 may be formed
from a reflective alloy such as a metal-silicon alloy (e.g.,
aluminum silicon), or other metal which has a lower conductivity
than pure aluminum. Lower conductivity metals that may be used in
forming layer 36 include titanium and tin. The use of a lower
conductivity material for forming layer 36 (in alloy form or pure
form) may enhance radio-frequency transparency for layer 36 when
compared to arrangements in which pure aluminum is used in forming
layer 36.
[0043] An illustrative configuration in which layer 30 has a
coating that is radio-frequency transparent is shown in FIG. 8. In
the example of FIG. 8, radio-frequency transparent coating layers
have been formed on the inner surface of substrate layer 30. In
particular, coating 32 has been formed on the inner surface of
substrate layer 30. Layer 36 of coating 32 may be a highly
resistive metal alloy layer containing titanium, aluminum, and
nitrogen such as a TiAlN layer. Layer 34 may be an amorphous
silicon layer. Layer 32 serves as a lossy antireflection coating.
The color of layer 32 and therefore the appearance of the
structures of FIG. 8 when viewed in direction 28 by viewer 26 may
be tuned by adjusting the thickness of layers 34 and 36. The color
of layer 32 may, if desired, be yellow, blue, red, or other
non-neutral color. In general, the thicknesses of layers 34 and 36
may be 10-200 nm, at least 20 nm, at least 50 nm, less than 150 nm,
less than 100 nm, or other suitable thickness. As an example, layer
36 may have a thickness of 75 nm and layer 34 may have a thickness
of 24 nm. Color shifts due to variations in viewing angle may be
negligible.
[0044] To ensure that coating 32 of FIG. 8 has sufficient
radio-frequency transparency, the sheet resistance of the TiAlN
layer may be adjusted (e.g., by adjusting the flow rate of N2 gas
that is present during the deposition process). Increases in N2
flow rates have been observed to increase sheet resistance.
[0045] If desired, one or more coating layers may be formed on the
inner surface of layer 32 to change the appearance of layer 32. In
the example of FIG. 8, a thin-film interference filter that serves
as a mirror (mirror coating) has been formed from thin-film stack
64. Thin-film stack 64 may contain a stack of two or more thin-film
layers with different refractive index values (e.g., alternating
higher and lower refractive index values). In the example of FIG.
8, stack 64 includes a first layer 60 and a second layer 62 with
different respective refractive indices. Layer 60 may be, as an
example, a silicon oxide layer with a thickness of 85 nm and layer
70 may be, as an example, an amorphous silicon layer with a
thickness of 75 nm. Other materials and/or other thicknesses (e.g.,
thin-film thicknesses of at least 5 nm, at least 20 nm, at least 50
nm, less than 400 nm, less than 200 nm, or less than 100 nm) may be
selected for the thin-film layers in stack 64. The thicknesses of
the layers may be selected based on the materials used (and their
refractive indices), the number of layers present, and the desired
optical properties of the mirror coating (e.g., a desired target
reflectivity).
[0046] The foregoing is merely illustrative and various
modifications can be made to the described embodiments. The
foregoing embodiments may be implemented individually or in any
combination.
* * * * *