U.S. patent application number 16/119201 was filed with the patent office on 2019-01-17 for heads up display system.
The applicant listed for this patent is Gentex Corporation. Invention is credited to David J. Cammenga, George A. Neuman, Mario F. Saenger Nayver.
Application Number | 20190018242 16/119201 |
Document ID | / |
Family ID | 57546146 |
Filed Date | 2019-01-17 |
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United States Patent
Application |
20190018242 |
Kind Code |
A1 |
Saenger Nayver; Mario F. ;
et al. |
January 17, 2019 |
HEADS UP DISPLAY SYSTEM
Abstract
An electro-optic assembly of a vehicle includes a first
substrate with a first surface and a second surface and a second
substrate with a third surface and a fourth surface. The first
substrate and the second substrate are configured to be held in a
parallel spaced apart relationship. A transflective coating is
positioned on at least one of the first and second surfaces of the
first substrate. An antireflective electrode positioned on at least
one of the second and third surfaces. An antireflection coating is
positioned on at least one of the first surface and the fourth
surface. An electro-optic medium is positioned between the second
surface of the first substrate and the third surface of the second
substrate. The electro-optic assembly is configured to reflect an
image from a projector of the vehicle.
Inventors: |
Saenger Nayver; Mario F.;
(Zeeland, MI) ; Neuman; George A.; (Holland,
MI) ; Cammenga; David J.; (Zeeland, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gentex Corporation |
Zeeland |
MI |
US |
|
|
Family ID: |
57546146 |
Appl. No.: |
16/119201 |
Filed: |
August 31, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15184254 |
Jun 16, 2016 |
10101583 |
|
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16119201 |
|
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62180386 |
Jun 16, 2015 |
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62205376 |
Aug 14, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 27/0101 20130101;
G02F 1/133555 20130101; G02B 1/115 20130101; G02B 5/23 20130101;
G02F 1/13439 20130101; G02B 2027/0118 20130101; G02F 2201/50
20130101; G02F 1/157 20130101 |
International
Class: |
G02B 27/01 20060101
G02B027/01; G02F 1/1335 20060101 G02F001/1335; G02B 5/23 20060101
G02B005/23; G02F 1/1343 20060101 G02F001/1343; G02F 1/157 20060101
G02F001/157 |
Claims
1. An electro-optic assembly of a vehicle, comprising: a first
substrate comprising a first surface and a second surface; a second
substrate comprising a third surface and a fourth surface, wherein
the first substrate and the second substrate are configured to be
held in a parallel spaced apart relationship; a transflective
coating positioned on at least one of the first and second surfaces
of the first substrate; an antireflective electrode positioned on
at least one of the second and third surfaces; an antireflection
coating positioned on at least one of the first surface and the
fourth surface; and an electro-optic medium positioned between the
second surface of the first substrate and the third surface of the
second substrate, wherein the electro-optic assembly is configured
to reflect an image from a projector of the vehicle.
2. The electro-optic assembly of claim 1, wherein the transflective
coating comprises a spectrally selective dielectric multilayer.
3. The electro-optic assembly of claim 1, wherein the transflective
coating comprises a diamond-like carbon coating.
4. The electro-optic assembly of claim 1, wherein the transflective
coating comprises a dielectric layer.
5. The electro-optic assembly of claim 1, wherein the transflective
coating comprises a dielectric-metal multilayer.
6. The electro-optic assembly of claim 1, wherein the projector is
a component of a heads up display system.
7. The electro-optic assembly of claim 1, wherein the refractive
index of the electro-optic material is at least about 1.2.
8. The electro-optic element of claim 1, wherein the antireflection
coating comprises a metal-based antireflection coating.
9. An electro-optic assembly of a vehicle, comprising: a first
substrate comprising a first surface and a second surface; a second
substrate comprising a third surface and a fourth surface, the
first substrate and the second substrate configured to be
positioned in a parallel spaced apart relationship; a transflective
coating positioned on at least one of the first and second
surfaces; and an electro-optic medium positioned between the second
surface of the first substrate and the third surface of the second
substrate, wherein a reflectance across the transflective coating
is substantially non-varying, wherein the electro-optic assembly is
configured to control a transmittance from a clear state to a
darkened state, and wherein the electro-optic assembly is
configured to reflect an image from a projector of the vehicle.
10. The electro-optic assembly of claim 9, wherein the
transflective coating is positioned on the first surface of the
first substrate.
11. The electro-optic assembly of claim 9, wherein the
transflective coating has a reflectance of from about 15% to about
45%.
12. The electro-optic assembly of claim 10, further comprising: a
scratch-resistant coating positioned on the transflective
coating.
13. The electro-optic assembly of claim 12, wherein the
scratch-resistant coating comprises diamond-like carbon.
14. The electro-optic assembly of claim 11, further comprising: an
antireflection coating positioned on at least one of the first and
fourth surfaces of the second substrate.
15. The electro-optic assembly of claim 9, wherein the
antireflection coating is positioned on the fourth surface, the
antireflection coating comprising a metal-based antireflection
coating.
16. An electro-optic assembly, comprising: a substrate defining a
first surface and a second surface; a transflective layer
positioned on the first surface of the first substrate; a second
substrate defining a third surface and a fourth surface; an
antireflective electrode positioned on the second surface of the
first substrate and the third surface of the second substrate; an
antireflection coating positioned on the fourth surface of the
second substrate; and an electro-optic medium positioned between
the second surface of the first substrate and the third surface of
the second substrate and operable between a clear state and a
darkened state, wherein the electro-optic assembly is configured to
reflect an image from a projector.
17. The electro-optic assembly of claim 16, wherein at least one of
a reflected light and a transmitted light has a color rendering
index of at least 85.
18. The electro-optic assembly of claim 16, wherein the
transflective layer comprising a metal-dielectric-metal (MDM)
structure with a reflectance of from about 15% to 35%.
19. The electro-optic assembly of claim 16, wherein a reflectance
from the antireflection coating and antireflective electrode are
each less than 1%.
20. The electro-optic assembly of claim 16, wherein the
antireflection coating a single layer of a metallic material having
a thickness of from about 0.1 nm to about 5 nm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 15/184,254, filed Jun. 16, 2016,
entitled HEADS UP DISPLAY SYSTEM, which claims the benefit of and
priority to U.S. Provisional Patent Application No. 62/180,386,
filed on Jun. 16, 2015, entitled ELECTRO-OPTIC ASSEMBLY, and U.S.
Provisional Patent Application No. 62/205,376, filed on Aug. 14,
2015, entitled ELECTRO-OPTIC ASSEMBLY, the entire disclosures of
which are hereby incorporated herein by reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure generally relates to an electro-optic
assembly, and more particularly, to a heads up display having an
electro-optic assembly.
SUMMARY OF THE DISCLOSURE
[0003] According to a feature of the present disclosure, an
electro-optic assembly of a vehicle includes a first substrate with
a first surface and a second surface and a second substrate with a
third surface and a fourth surface. The first substrate and the
second substrate are configured to be held in a parallel spaced
apart relationship. A transflective coating is positioned on at
least one of the first and second surfaces of the first substrate.
An antireflective electrode positioned on at least one of the
second and third surfaces. An antireflection coating is positioned
on at least one of the first surface and the fourth surface. An
electro-optic medium is positioned between the second surface of
the first substrate and the third surface of the second substrate.
The electro-optic assembly is configured to reflect an image from a
projector of the vehicle.
[0004] According to another feature of the present disclosure, an
electro-optic assembly of a vehicle includes a first substrate with
a first surface and a second surface and a second substrate with a
third surface and a fourth surface. The first substrate and the
second substrate are configured to be positioned in a parallel
spaced apart relationship. A transflective coating is positioned on
at least one of the first and second surfaces. An electro-optic
medium is positioned between the second surface of the first
substrate and the third surface of the second substrate. A
reflectance across the transflective coating is substantially
non-varying. The electro-optic assembly is configured to control a
transmittance from a clear state to a darkened state. The
electro-optic assembly is configured to reflect an image from a
projector of the vehicle.
[0005] According to yet another feature of the present disclosure,
an electro-optic assembly includes a substrate defining a first
surface and a second surface. A transflective layer is positioned
on the first surface of the first substrate. A second substrate
defines a third surface and a fourth surface. An anti reflective
electrode is positioned on the second surface of the first
substrate and the third surface of the second substrate. An
antireflection coating is positioned on the fourth surface of the
second substrate. An electro-optic medium is positioned between the
second surface of the first substrate and the third surface of the
second substrate and operable between a clear state and a darkened
state. The electro-optic assembly is configured to reflect an image
from a projector.
[0006] These and other features, advantages, and objects of the
present disclosure will be further understood and appreciated by
those skilled in the art by reference to the following
specification, claims, and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] In the drawings:
[0008] FIG. 1 is a front perspective view of a heads up display
system incorporating an electro-optic-element, according to one
example;
[0009] FIG. 2 is a front perspective view of a heads up display
system incorporating an electro-optic-element, according to another
example;
[0010] FIG. 3 is a cross-sectional view of the electro-optic
assembly of FIG. 1 across line III;
[0011] FIGS. 4A and 4B illustrate the eye-weighted transmittance
versus reflectance for a single metal layer on the first surface of
the electro-optic assembly;
[0012] FIG. 5 illustrates the transmittance versus reflectance
relationship for a single layer of Cr and a bilayer of ITO/Cr
bilayer on the electro-optic assembly first surface;
[0013] FIG. 6 illustrates the transmittance versus reflectance
relationship for a Cr/ITO/Cr multilayer transflector on the
electro-optic assembly first surface;
[0014] FIG. 7 illustrates the transmittance versus reflectance
relationship for a single layer of a diamond-like-carbon (DLC)
coating on the electro-optic assembly;
[0015] FIG. 8 illustrates the transmittance versus reflectance
relationship for a single layer of ITO and an ITO/TiO2 bilayer on
the electro-optic assembly first surface;
[0016] FIG. 9 illustrates the eye sensitivity weighted reflectance
in dependence of the thickness of a metallic AR coating;
[0017] FIG. 10 illustrates the spectral reflectance of a dielectric
multi-layer transflective coating; and
[0018] FIG. 11 illustrates the reflectance versus wavelength
dependence of a metallic and a dielectric AR coating compared to
raw glass.
DETAILED DESCRIPTION
[0019] The present illustrated embodiments reside primarily in
combinations of method steps and apparatus components related to an
electro-optic assembly, more particularly, a heads up display
system having an electro-optic assembly. Accordingly, the apparatus
components and method steps have been represented, where
appropriate, by conventional symbols in the drawings, showing only
those specific details that are pertinent to understanding the
embodiments of the present disclosure so as not to obscure the
disclosure with details that will be readily apparent to those of
ordinary skill in the art having the benefit of the description
herein. Further, like numerals in the description and drawings
represent like elements.
[0020] For purposes of description herein, the terms "upper,"
"lower," "right," "left," "rear," "front," "vertical,"
"horizontal," and derivatives thereof, shall relate to the
disclosure as oriented in FIG. 1. Unless stated otherwise, the term
"front" shall refer to the surface of the element closer to an
intended viewer of the electro-optic heads up display assembly, and
the term "rear" shall refer to the surface of the element further
from the intended viewer of the electro-optic heads up display
system. However, it is to be understood that the disclosure may
assume various alternative orientations, except where expressly
specified to the contrary. It is also to be understood that the
specific devices and processes illustrated in the attached
drawings, and described in the following specification are simply
exemplary embodiments of the inventive concepts defined in the
appended claims. Hence, specific dimensions and other physical
characteristics relating to the embodiments disclosed herein are
not to be considered as limiting, unless the claims expressly state
otherwise.
[0021] The terms "including," "comprises," "comprising," or any
other variation thereof, are intended to cover a non-exclusive
inclusion, such that a process, method, article, or apparatus that
comprises a list of elements does not include only those elements
but may include other elements not expressly listed or inherent to
such process, method, article, or apparatus. An element preceded by
"comprises a . . . " does not, without more constraints, preclude
the existence of additional identical elements in the process,
method, article, or apparatus that comprises the element.
[0022] In regards to FIGS. 1-3, reference numeral 10 generally
designates an electro-optic assembly. The electro-optic assembly 10
may be utilized in a heads up display system 14 of a vehicle 18.
The electro-optic assembly 10 can have a first partially
reflective, partially transmissive glass substrate 22 and a second
partially reflective, partially transmissive glass substrate 26.
The first substrate 22 can have a first surface 22A and a second
surface 22B. The second substrate 26 can have a third surface 26A
and a fourth surface 26B. The first and second substrates 22, 26
can be positioned in a parallel spaced-apart relationship and can
have a seal 30 substantially around a perimeter of the first and
second substrates 22, 26. The first substrate 22 and the second
substrate 26 define a cavity 34. An electro-optic medium 38 is in
the cavity 34 between the first and second substrates 22, 26. In at
least one example, the electro-optic assembly 10 is configured to
have a non-varying reflectance and a varying transmittance. A
"clear state" of the electro-optic assembly 10 refers to the
condition of maximum transmittance. The activation of the
electro-optic medium 38 may reduce the transmittance of the
electro-optic assembly 10 to a "darkened state". The "low end"
transmittance refers to the minimum transmittance attainable by the
electro-optic assembly 10.
[0023] By way of explanation and not limitation, the electro-optic
assembly 10 can be included in the heads up display (HUD) system 14
of the vehicle 18. In such an example, the electro-optic element 10
may function as a combiner screen to reflect a primary image
projected by a projector 46. The electro-optic assembly 10 can be
controlled to vary the amount of light transmission based on input
from a control circuit. For example, in daylight conditions the
electro-optic assembly 10 may be darkened to improve or increase
the contrast ratio and allow for improved visibility of information
projected on the electro-optic assembly 10 from the projector 46.
The contrast ratio may represent the ratio of a primary reflected
image from the projector 46 and the light transmitted through the
electro-optic assembly 10 (e.g., in either the clear state or the
darkened state).
[0024] The heads up display system 14 is capable of use in a
variety of applications, such as automotive and aerospace
applications, to present information to a driver or pilot while
allowing simultaneous forward vision. In some examples the heads up
display system 14 may be provided vehicle rearward of a windscreen
54 and protruding from an instrument panel 58 (FIG. 1) while in
other examples the electro-optic assembly 10 may be positioned
directly on the windscreen 54 (FIG. 2). The electro-optic assembly
10 may be any size, shape, bend radius, angle or position. The
electro-optic assembly 10 can be used to display many vehicle
related functions or driver assistance systems such as alerts,
warnings or vehicle diagnostics. In the depicted examples, the
speed of the vehicle 18 is being displayed on the electro-optic
assembly 10.
[0025] In regards to heads up display systems 14, the image
projected onto the electro-optic assembly 10 should be bright
enough to see in any condition. This is particularly challenging
when the lighting outside the vehicle 18 is bright. The contrast
between the light from the projector 46 and the lighting behind the
electro-optic assembly 10 can be low on a bright sunny day. While a
brighter, more intense lighting source (e.g., the projector 46)
improves the contrast, increasing the display brightness may not be
the most economical solution and a display that is bright enough to
provide reasonable contrast in very bright daylight conditions will
be too bright in other conditions. Although controls may be used to
deal with variations in brightness, the specific background is ever
changing in a moving vehicle, and depends in part on the position
of the driver's eyes. In accordance with one example, the
electro-optic assembly 10 can be configured to lower the
transmission and/or to increase the contrast ratio.
[0026] Depending on the application, there may be a need for a
higher or lower transmittance in the clear state, different
reflectance values for optimal contrast ratios, and/or broader
dynamic range of the transmittance levels. The initial reflectance
and range of transmittance properties is further complicated by the
capabilities of the projector 46 employed with the heads up display
system 14 and the light output capabilities of the projector 46
along with the light transmittance levels for the windscreen 54.
The windscreen 54 will have a direct impact on the contrast ratio
and visibility of the image from the heads up display system 14.
There are a number of factors which affect the transmittance levels
of the windscreen 54. The minimum light transmittance is based on
the rules in the location in which the vehicle 18 is sold but
higher transmittance levels may be present based on how the vehicle
18 is equipped and marketed. This range of factors creates the need
for solutions which can be adapted to different vehicle and
environmental conditions.
[0027] Another aspect that should be considered when utilizing the
heads up display system 14 is a secondary reflection from the first
through fourth surfaces 22A-26B of the first and second substrates
22, 26. Reflection off of the first through fourth surfaces 22A-26B
may create a double image effect from secondary reflections that do
not perfectly align with the primary reflected image (e.g., due to
geometries of the components of the electro-optic assembly 10). The
double image that may be formed from secondary reflections off of
the first through fourth surfaces 22A-26B may cause the primary
image projected by the projector 46 and reflected by the
electro-optic assembly 10 to appear blurry or unclear.
[0028] According to one example, the electro-optic assembly 10 can
be assembled using two approximately 1.6 mm glass substrates (e.g.,
the first and second substrates 22, 26) which are both bent with a
spherical radius of approximately 1250 mm. Other thicknesses for
the first and second substrates 22, 26. In other examples the first
and second substrates 22, 26 may be bent to have a "free-form"
shape. The desired shape is one in which the resultant primary
reflected image "appears" to be forward of the electro-optic
assembly 10 and forward of the vehicle 18. The exact surface
contour needed to attain this characteristic is a function of the
properties of the projector 46, projector 46 and driver location,
as well as the electro-optic assembly 10 location relative to the
other two locations. Having the image projected forward of the
vehicle 18 allows the driver to obtain the desired information
without having to change their focal distance. In a traditional
heads up display located within the vehicle 18, the driver's eyes
often have to refocus to the shorter viewing distance thus
decreasing the time spent viewing the road. Furthermore, the
driver's eyes will also then have to re-focus on the road ahead,
which further decreases the time spent viewing the road and forward
conditions. The shape of the electro-optic assembly 10 should also
be selected so as to preserve the basic characteristics of the
projected image (i.e., straight lines remain straight, aspect
ratios of images are preserved, etc.).
[0029] Referring now to FIG. 3, the first substrate 22 includes the
first surface 22A and the second surface 22B. The second surface
22B can be coated with indium tin oxide with a sheet resistance of
approximately 12 ohms/sq. The first surface 22A can be concave and
can be coated with chromium (Cr). The coated first substrate 22 may
have a transmission of approximately 37.8% and reflectance of
approximately 25.4%. The second substrate 26 defines the third and
fourth surfaces 26A, 26B. The third surface 26A can be coated with
indium tin oxide with a sheet resistance of approximately 12
ohms/sq.
[0030] From the first surface 22A, the electro-optic assembly 10
can have a clear state reflectance of approximately 25% and a
transmittance of approximately 24%. The electro-optic assembly 10
can have a low end, or state, transmittance of approximately 10.5%
and a low end reflectance from the first surface 22A of
approximately 15%. Alternatively, in other examples, the high end,
or state, transmittance of the electro-optic assembly 10 may be
greater than 45% or even 60%. The characteristics of the
electro-optic assembly 10 may also be altered so that the low end
transmittance is less than 7.5% or even less than 5% in the
darkened state. In some examples, transmittance levels down to 2.5%
or less may be desirable. Increasing the high-end transmittance may
be obtained by the use of coatings and materials which have low
absorption, as will be described below. Lower low-end
transmittances may be obtained through the inclusion of materials
which have higher absorption. If a wide dynamic range is desired,
then low absorption materials may be used in combination with
electro-optic materials and cell spacings (e.g., the space between
the first and second substrates 22, 26) which attain higher
absorbance in the activated state. Those skilled in the art will
recognize that there exists a multitude of combinations of coatings
and electro-optic materials, cell spacings and coating conductivity
levels which can be selected to attain particular device
characteristics.
[0031] To provide electric current to the first and second
substrates 22, 26 and electro-optic medium 38, electrical elements
may be provided on opposing sides of the first and second
substrates 22, 26 (e.g., the second and third surfaces 22B, 26A) to
generate an electrical potential therebetween. In one example, a
J-clip may be electrically engaged with each electrical element,
and element wires extend from the J-clips to a primary printed
circuit board. To provide the greatest surface area through the
electro-optic assembly 10, the contacts are located along one side
of the device. In this example, there is a back plate and top plate
offset to allow contact such as a bus clip. Other contact designs
are possible including the use of conductive ink or epoxy.
[0032] According to various examples, the electro-optic medium 38
may be an electrochromic medium. In electrochromic examples, the
electro-optic medium 38 may include at least one solvent, at least
one anodic material, and at least one cathodic material. Typically,
both of the anodic and cathodic materials are electroactive and at
least one of them is electrochromic. It will be understood that
regardless of its ordinary meaning, the term "electroactive" may
mean a material that undergoes a modification in its oxidation
state upon exposure to a particular electrical potential
difference. Additionally, it will be understood that the term
"electrochromic" may mean, regardless of its ordinary meaning, a
material that exhibits a change in its extinction coefficient at
one or more wavelengths upon exposure to a particular electrical
potential difference. Electrochromic components, as described
herein, include materials whose color or opacity are affected by
electric current, such that when an electrical current is applied
to the material, the color or opacity change from a first phase to
a second phase. The electrochromic component may be a single-layer,
single-phase component, multi-layer component, or multi-phase
component, as described in U.S. Pat. No. 5,928,572 entitled
"ELECTROCHROMIC LAYER AND DEVICES COMPRISING SAME," U.S. Pat. No.
5,998,617 entitled "ELECTROCHROMIC COMPOUNDS," U.S. Pat. No.
6,020,987 entitled "ELECTROCHROMIC MEDIUM CAPABLE OF PRODUCING A
PRE-SELECTED COLOR," U.S. Pat. No. 6,037,471 entitled
"ELECTROCHROMIC COMPOUNDS," U.S. Pat. No. 6,141,137 entitled
"ELECTROCHROMIC MEDIA FOR PRODUCING A PRE-SELECTED COLOR," U.S.
Pat. No. 6,241,916 entitled "ELECTROCHROMIC SYSTEM," U.S. Pat. No.
6,193,912 entitled "NEAR INFRARED-ABSORBING ELECTROCHROMIC
COMPOUNDS AND DEVICES COMPRISING SAME," U.S. Pat. No. 6,249,369
entitled "COUPLED ELECTROCHROMIC COMPOUNDS WITH PHOTOSTABLE
DICATION OXIDATION STATES," and U.S. Pat. No. 6,137,620 entitled
"ELECTROCHROMIC MEDIA WITH CONCENTRATION ENHANCED STABILITY,
PROCESS FOR THE PREPARATION THEREOF AND USE IN ELECTROCHROMIC
DEVICES"; U.S. Patent Application Publication No. 2002/0015214 A1
entitled "ELECTROCHROMIC DEVICE"; and International Patent
Application Serial Nos. PCT/US98/05570 entitled "ELECTROCHROMIC
POLYMERIC SOLID FILMS, MANUFACTURING ELECTROCHROMIC DEVICES USING
SUCH SOLID FILMS, AND PROCESSES FOR MAKING SUCH SOLID FILMS AND
DEVICES," PCT/EP98/03862 entitled "ELECTROCHROMIC POLYMER SYSTEM,"
and PCT/US98/05570 entitled "ELECTROCHROMIC POLYMERIC SOLID FILMS,
MANUFACTURING ELECTROCHROMIC DEVICES USING SUCH SOLID FILMS, AND
PROCESSES FOR MAKING SUCH SOLID FILMS AND DEVICES," which are
herein incorporated by reference in their entirety. The first and
second substrates 22, 26 are not limited to glass elements but may
also be any other element having partially reflective, partially
transmissive properties.
[0033] According to various examples, a perimeter band of the
electro-optic assembly 10 can be modified by adding or removing
material to block or obscure the view of the seal 30 and contact
materials. In a first example, an outside perimeter of the first
and fourth surfaces 22A, 26B can be etched to provide substrates
with a frosted perimeter. In frosted perimeter examples, the
perimeter band is formed by damaging both the first and fourth
surfaces 22A, 26B using a CO.sub.2 laser to form a frosted band
approximately 4 mm wide. Additionally or alternatively, edges of
the first and fourth surfaces 22A, 26B can be ground and/or
polished. Further, a spectral filter material (e.g., a chrome or
metal ring) or light scattering material may be added to the
perimeter of the first and/or second substrates 22, 26 (e.g., any
of the first through fourth surfaces 22A-26B) to aid in concealing
the seal 30. The spectral filter can block the view of the seal 30
and also provides UV protection for the seal 30. In another example
of the spectral filter, chromium oxynitride, or another dark
coating, may be deposited on the perimeter of the electro-optic
assembly 10 to create a dark ring which acts as the spectral
filter. The spectral filter material may be selectively deposited,
or may be deposited over the entire surface and then selectively
removed, to create the perimeter band, such as with selective laser
ablation. Additionally or alternatively, the seal 30 may be
generally clear, colorless or configured to scatter light. In such
examples, the frosted band can extend slightly inboard of the seal
30. It will be understood that any of the above described
techniques of concealing the seal 30 may be used alone, or in
conjunction with, any of the other disclosed concealment techniques
for the seal 30.
[0034] In the depicted example, each of the first and second
substrates 22, 26 include a rounded edge 62 and a contact edge 66
that is not rounded. The non-rounded contact edge 66 may be
desirable for ease of contact, and if the device is supported by
that edge, there would be no need to round the first and second
substrates 22, 26 along the contact edge 66. Any exposed edge on
the electro-optic assembly 10 may be generally rounded. The radius
of curvature of the rounded edges 62 may be greater than
approximately 2.5 mm.
[0035] Still referring to FIG. 3, the electro-optic assembly 10 may
include a transflective coating 70, an antireflection coating 80,
and a scratch-resistant coating 90. In the depicted example, the
transflective coating 70 is positioned proximate the first surface
22A, but may additionally or alternatively be positioned on the
second surface 22B without departing from the teachings provided
herein. In the depicted example, the antireflection coating 80 is
on the first, third and fourth surfaces 22A, 26A, 26B, but it will
be understood that the antireflection coating 80 may additionally
or alternatively be positioned on the second surface 22B without
departing from the teachings provided herein. In some examples, the
antireflection coating 80 is positioned on at least one of the
first and second surfaces 22A, 22B, and may be positioned on
whichever of the first and second surfaces 22A, 22B is opposite the
surface onto which the transflective coating 70 is positioned. The
antireflection coatings on the first and third surfaces 22A, 26A,
in certain examples, function as electrodes (e.g., an
antireflective electrode) to enable darkening of electrochromic
medium 38. It will be understood, that when transflective coating
70 is located on the second surface 22B, in certain examples, it
may also serve a dual purpose and also act as an electrode. In the
depicted example, the scratch-resistant coating 90 is positioned
proximate the first and fourth surfaces 22A, 26B. It will be
understood that although described as separate layers, the
transflective coating 70, the antireflection coating 80 and/or the
scratch-resistant coating 90 may share properties which function as
the other coatings, as described in greater detail below.
[0036] In a first example, the transflective coating 70 may be a
thin metal layer (e.g., a metal-based coating 70) such as Cr or
another metal. A potential downside of using a single metal coating
layer as the transflective coating 70 is that there is a defined
relationship between the reflectance and transmittance which is
derived from the thickness of the metal. For example, combinations
of reflectance and transmittance are shown in FIGS. 4A and 4B. From
the aforementioned FIGS., it can be seen that a single-metal layer
does not generally allow for reflectance and transmittance to be
independently controlled. In another example of the transflective
coating 70, a low absorption layer including a material of lower
absorption than the metal, such as indium tin oxide (ITO) or a
dielectric material, is located in between the substrate (e.g., the
first substrate 22) and the metal coating layer. FIG. 5 depicts
attainable transmittance values in dependence of the reflectance
for an electro-optic assembly 10 with a single Cr layer and a
bilayer of ITO/Cr (e.g., the transflective coating 70) for
different values of the Cr layer thickness. This layer increases
the range of attainable reflectance and transmittance values for
the transflective coating 70 by making it possible to tune the
reflectance and reflected color in dependence of the thickness and
the refractive index. In order to maximize the reflected intensity,
the thickness is chosen to satisfy a condition of constructive
interference as given by the following equation:
2 dn = ( m + 1 2 ) .lamda. , ##EQU00001##
where d is the layer thickness, m is the interference order, n is
the layer refractive index and .lamda. is the light wavelength. For
the bilayer case in FIG. 5, the thickness of the ITO (e.g., the low
absorption layer) is about 70 nm, which corresponds to m=0 and
.lamda..sup..about.575 nm. The refractive index of the low
absorption layer may be greater than about 1.3. In this case, the
deposition conditions for the ITO were chosen to increase the
refractive index of the ITO from a typical 1.8 to about 2.07 at 550
nm and therefore increase the reflectance according to the Fresnel
equation at normal angle of incidence:
R = n 1 - n 2 n 1 + n 2 2 , ##EQU00002##
where n.sub.1 and n.sub.2 correspond to the refractive indices for
the two media of an optical interface. The reflected color can also
be tuned slightly by increasing or decreasing the thickness of the
low absorption layer. The metal layer may be selected from the
metal list provided below and the material of the low absorption
layer may be selected from the list of dielectric materials
provided below which meet the refractive index properties for this
example.
[0037] Even though the example of the transflective coating 70
having a dielectric-metal bilayer provides a higher range of
attainable values for reflectance and transmission than a single
metallic layer, it still may be a challenge to tune the refractive
index and absorption of the materials to achieve a particular
reflectance and transmission level. Therefore, it may be
advantageous to have a transflective coating 70 that allows more
flexibility in terms of reflectance and transmittance values,
especially when lower transmittance values are sought. Accordingly,
in another example of the transflective coating 70, such
characteristics can be obtained with a multi-layer coating such as
a metal/dielectric/metal structure (MDM). Generally, an M-layer of
the MDM coating includes one or more of chromium, molybdenum,
nickel, Inconel, indium, palladium, osmium, tungsten, rhenium,
iridium, rhodium, ruthenium, stainless steel, tantalum, titanium,
copper, gold, platinum, any other platinum group metals, zirconium,
vanadium AlSi alloys, and alloys and/or combinations thereof. It
will be understood that any of the aforementioned metals may be
utilized for the single or bilayer examples of the transflective
coating 70. In some examples, combinations of metals and dielectric
materials may depend on whether the transflective coating 70 is
configured on the first surface 22A or the second surface 22B for
durability or electrode properties. The dielectric material may be
selected from one or more of the following: ITO, SnO.sub.2, SiN,
MgF.sub.2, SiO.sub.2, TiO.sub.2, F:SnO.sub.2, NbO.sub.x, TaO.sub.x,
indium zinc oxide, aluminum zinc oxide, zinc oxide, electrically
conductive TiO.sub.2, CeO.sub.x, ZnS, chromium oxide, ZrO.sub.x,
WO.sub.3, nickel oxide, IrO.sub.2, NiO.sub.x, CrO.sub.x, NbO.sub.x,
and ZrO.sub.x, or other material with a refractive index between
about 1.37 and about 4. It will be understood that any of the
aforementioned dielectrics may be utilized for the bilayer example
of the transflective coating 70. FIG. 6 depicts the reflectance and
transmittance values for a multi-layer transflective structure
(e.g., the transflective coating 70) with a Cr/ITO/Cr structure,
where the ITO thickness is 74.7 nm. Each point denotes a particular
reflectance/transmittance (R/T) value for a combination of 1.sup.st
and 2.sup.nd Cr layer thicknesses. It is possible to see that these
two parameters span a range of transmittance values for a
particular reflectance and it is possible to control reflectance
and transmission separately in this range. The relationship between
the metal layers will change as the thickness and index of the
middle low absorption layer changes. The selection of metal will
also shift the relationships shown in FIG. 6. In certain
embodiments, two different metals may be selected for the top and
bottom M-layers and the D-layer may be further subdivided into
sub-layers and include materials of different refractive indices.
Additional D- and/or M-layers may be added without deviating from
the teachings provided herein. The additional layers may be added
to improve durability, adhesion or alter the color and/or
reflectance and transmittance ranges or robustness.
[0038] Alternate materials that provide different R/T values, as
found in metals, may be used as the transflective coating 70.
Transparent conducting oxides (TCOs) and dielectric layers, along
with materials such as TiO.sub.2 or diamond-like carbon (DLC), are
other options, examples of which are shown in FIGS. 7 and 8 and
Table 1.
TABLE-US-00001 TABLE 1 Transmittance and reflectance parameters for
various transflective coatings on a glass substrate. 1.sup.st layer
2.sup.nd layer 3.sup.rd layer Thickness Thickness Thickness
Material (nm) Material (nm) Material (nm) Yr a*r b*r C*r CRIr Yt
a*t b*t Absorption Cr 4.7 -- 0 -- 0 25.01 -1.07 0.92 1.4 98.8 37.8
1.03 -2.92 37.19 ITO 59.54 -- 0 -- 0 24.26 -2.48 0.05 2.5 95.8 66
1.55 4.49 9.74 DLC 41.45 -- 0 -- 0 26.34 -1.34 -0.29 1.4 97.6 51.71
1.82 8.02 21.95 ITO 35.72 Ti02 34.53 -- 0 26.27 -1.24 6.62 6.7 97.0
66.99 0.73 0.23 6.74 ITO 69.46 Cr 0.77 -- 0 26.39 -2.12 4.89 5.3
96.7 57.79 1.36 3.18 15.82 Cr 0.9 ITO 74.4 Cr 1.8 24.9 -1.12 2.83
3.0 98.3 45.95 0.93 2.42 29.15
TABLE-US-00002 TABLE 2 Integrated eye-weighted reflectance minima
and corresponding transmittance of single layer metallic
antireflection coatings on glass. Metal layer Material thickness
(nm) Yr a*r b*r Yt a*t b*t Absorption Raw Glass 0 8.43 -0.23 -0.95
90.71 -0.33 0.27 0.86 Chromium 1.48 4.74 -0.23 -3.66 63.57 0.45
-3.26 31.69 Cobalt 2.02 5.59 -0.08 -1.37 68.88 -0.27 -1.36 25.54
Iridium 1.62 5.63 -0.59 -1.68 69.14 -0.52 -1.8 25.23 Molybdenum
1.78 4.47 -0.04 -1.11 61.98 -0.04 -1.11 33.55 MoRe-5 1.25 4.46
-0.04 -0.82 61.89 -0.16 1.75 33.65 MoTa-5 2.18 4.58 -0.04 -1 62.61
-0.03 0.81 32.81 MoW-5 1.6 4.44 -0.03 -0.89 61.8 -0.1 1.98 33.76
Niobium 2.77 4.48 0.18 -1.17 62.03 1.62 2.24 33.49 Platinum 2.13
5.42 -0.1 -1.04 67.75 -0.62 -1.4 26.83 Rhenium 1.68 4.63 -0.09
-0.76 62.94 0.76 4.22 32.43 Tantalum 1.89 4.45 -0.06 -0.98 61.83
-0.17 -0.14 33.73 Titanium 3.93 4.99 -0.22 -1.13 65.07 -1.31 -0.85
29.94 Tungsten 1.71 4.45 -0.04 -1.01 61.87 -0.33 0.8 33.67 Vanadium
2.08 4.5 0.38 -1.24 61.16 2.01 3.11 33.34
[0039] The examples in Table 1 demonstrate the eye-weighted
reflectance Yr, transmittance Yt, and absorption of various
transflector coatings (e.g., the transflective coating 70) on a
glass substrate (e.g., the first surface 22a of the first substrate
22), where the reflectance is understood as the reflectance
measured from the coated side of the substrate. The reflectance
from the reflecting surface (e.g., the first surface 22A) is
greater than about 15%, may be greater than about 20%, may be
greater than about 25%, may be greater than about 30%, may be
greater than about 35%, may be greater than about 40% and may be
greater than about 45%. For instance, the transflective coating 70
with a single layer TCO, such as cold ITO, with a refractive index
of about 2.07 at a wavelength of 550 nm, will have a reflectance of
about 23% at a quarter wave optical thickness, while the
transflective coating 70 with TiO.sub.2 with a refractive index of
about 2.34 at a wavelength of 550 nm will have a reflectance of
about 31.2% at a quarter wave optical thickness. The material
and/or refractive index may be selected so that the net reflectance
is at the appropriate level. For most materials, the absorption
will be relatively low with these materials compared to metals.
FIG. 8 depicts modeled values of reflectance and transmittance
dependence for the electro-optic element 10 with a single layer ITO
and with an ITO/TiO.sub.2 bilayer transflective coating 70 in
dependence of the ITO thickness. The TiO.sub.2 and ITO refractive
indices used for the calculations were 2.32 and 2.11 and the
thickness for the TiO.sub.2 layer was kept constant at 34.5 nm.
These layers enable higher reflectance due to their high inherent
refractive indices or constructive interference effects. FIG. 8
depicts modeled values of reflectance and transmission dependence
for the electro-optic element 38 having a single layer of
diamond-like carbon.
[0040] In another example with high contrast, the transflective
coating 70 is based on a spectrally selective dielectric multilayer
able to reflect specific wavelengths from the projector 46. FIG. 9
illustrates a graph with the spectral dependence of the reflectance
for such a transflective coating 70. In this example, the
reflectance is between about 90% and about 100% for wavelengths
near 455, 550 and 630 nm. Other reflectance levels are possible and
within the scope of this disclosure and the reflectance bands may
be centered at different wavelengths as necessary to be compatible
with the HUD display output. In some examples, the reflectance at
the reflectance bands for the spectrally selective dielectric
multilayer is greater than about 35%, greater than about 55% or
greater than about 75%. This example of the transflective coating
70 can be manufactured as a sequence of multiple stacks of high H
and low L index refractive index layers such as Nb.sub.2O.sub.5 and
TiO.sub.2 for H and SiO.sub.2 or MgF.sub.2 for L.
[0041] When reflecting an image, it is important that the color
rendering of the electro-optic assembly 10 is correct. The output
intensities of the different colors from the projector 46 can be
adjusted to compensate for any variations in the reflectance of the
transflective coating 70. In some examples, the transflective
coating 70 will have relatively consistent reflectance across the
visible spectrum. The reflected and transmitted color rendering of
the electro-optic assembly 10 can be controlled by varying the
thicknesses, layer sequence, and adequate selection of materials of
the coatings on each or in some of the first through fourth
surfaces 22A-26B. The color rendering can be quantified in a number
of ways. The color rendering index, or CRI, of the electro-optic
assembly 10 may be greater than about 85, greater than about 90 or
greater than about 95. Alternatively, in units of c*=
(a.sup.*2+b.sup.*2), where a* and b* are color parameters of the
CIELAB color system, the color of the electro-optic assembly 10 may
have a value less than about 20, less than about 10 or less than
about 5. Either of these metrics will describe a surface wherein
the reflected image's colors will be true or approximately match
those of the projector 46. In other examples, the transflective
coating 70 can be tuned to match the output of the projector 46 to
enhance or compensate to achieve the desired colors.
[0042] According to other examples, the transflective coating 70
may include any of the transflective coatings and layers disclosed
in U.S. Provisional Patent Application No. 62/205,376, filed on
Aug. 14, 2015, entitled "ELECTRO-OPTIC ASSEMBLY," the entire
disclosure of which is hereby incorporated herein by reference.
[0043] Since the primary reflectance of the heads up display system
14 comes from the transflective coating 70 located on either the
first surface 22A or second surface 22B of the electro-optic
assembly 10, it is generally important to minimize secondary
reflections from the other surfaces (e.g., the first though fourth
surfaces 22A-26B where the transflective coating 70 is not present)
which may result in a blurry image (i.e., double imaging).
Accordingly, use of the antireflection coatings 80 may be
advantageous. An example of the antireflection coating 80 may be a
transparent conductive oxide. With respect to the examples
described herein, the second and third surfaces 22B, 26A may
include transparent electrodes. Transparent conducting oxides (TCO)
such as ITO, F:SnO.sub.2, doped-ZnO, IZO or other layers are
commonly used in electro-optic devices, such as electrochromic
systems. As noted above, the reflectance of these materials is a
function of the thickness of the coatings due to interference
effects. A minimum reflectance can be obtained by tailoring the
thickness of the conductive oxide coating (e.g., the antireflection
coating 80). The minimum reflectance is at a half wave optical
thickness. Depending on the wavelengths of the projector 46 of the
heads up display system 14, the wavelength for the half wave
condition can be adjusted to get the net lowest reflectance value.
For example, a reflectance of an ITO coating can be as low as, or
lower than, 0.5% from the second and third surfaces 22B, 26A with a
layer about 145 nm thick of antireflection coating 80.
[0044] As noted above, the half wave thickness of an ITO nets a
sheet resistance of about approximately 12 ohms/sq. In some
examples, this is not a low enough sheet resistance to get fast and
uniform darkening of the electro-optic assembly 10. As such,
thicker coating layers (e.g., antireflection coating 80) may be
used to attain lower sheet resistance values. In order to maintain
minimum reflectance values for the antireflection layer 80, the TCO
or ITO needs to be at a multiple of the half wave thickness. For
example, the thickness of the antireflection coating 80 can be a
full wave, 3 half waves, etc. As the thickness of the
antireflection coating 80 moves to higher multiples of half wave
coatings, the reflectance is still at a local minimum but is higher
than the half wave reflectance. The reflectance off of the second
or third surfaces 22B, 26A, with the electro-optic medium 38 having
a refractive index of 1.45 and an ITO refractive index of 1.85 is
about 0.5%. For an antireflection coating 80 two times a half wave
thickness, the reflectance is about 1.25%, and for a coating that
is three times a half wave thickness, the reflectance is about
1.7%. As noted above, the reflectance will drop as the refractive
index of the ITO is lowered, which can be obtained by making it
more conductive. Alternatively, or in combination with the ITO
refractive index, the reflectance can also be decreased by
increasing the refractive index of the electro-optic medium 38 or
the substrate (e.g., the first and/or second substrates 22, 26)
medium or the electro-optic medium 38 and the substrate medium. The
refractive index of the TCO or ITO examples of the antireflection
coating 80 on the second surface 22B and third surface 26A may be
less than about 2.0, less than about 1.92, or less than about 1.88.
The refractive index of the electro-optic medium 38 may be greater
than about 1.2, greater than about 1.4, or greater than about 1.5.
The refractive index of the substrate medium may be greater than
about 1.4, greater than about 1.6, or greater than about 1.8. The
reflectance off of the second and third surfaces 22B, 26A may be
less than about 2%.
[0045] The tailoring of the reflectance off of the surfaces not
having transflective coating 70, such as the first through fourth
surface 22A-26B is important for minimizing double images depending
on whether the transflective coating 70 is on the first or second
surface 22A, 22B. Due to the refractive index of the first and/or
second substrates 22, 26 (glass or plastic at about 1.5) and the
refractive index of the incident media (air at 1.0), the first and
fourth surfaces 22A, 26B have a high reflectance at about 4% and
have the highest likelihood of generating objectionable double
images. The acceptable reflectance off of the first and fourth
surfaces 22A, 26B, as well as the second and third surfaces 22B,
26A, is a function of the materials and their properties which
reside between the surface in question and the observer (e.g., the
driver). The acceptable absolute reflectance levels may be higher
when absorbing materials are present between the surface and the
viewer. Therefore the overall absorption is varied in components
between the viewer and surfaces in question, the absolute
reflectance limits from the first, second, third, and fourth
surfaces 22A, 22B, 26A, 26B may be lower when less light is
attenuated between the surfaces and the observer, such as when
higher dynamic ranges are desired and/or when low reflectance of
the first surface 22A is the design goal. The exact allowable
reflectance threshold will depend on the details of the heads up
display system 14. The reflectance off of the second, third, and
fourth surfaces 22B, 26A, 26B may be less than about 2%.
[0046] In another example, the antireflection coating 80 may be
dielectric antireflection coating such as a S/H/L stack where S is
the first or second substrate 22, 26 and H/L may be a stack of
multiple layers of alternating materials with high and low
refractive indices. Alternatively, the antireflection coating 80
can be a graded coating obtained with a nanostructured, textured
surface or other type of graded coating. In such examples, the
antireflection coating 80 can be tuned to provide the desired
reflectance level along with the desired color reflected from the
surface. However, such an example of the antireflection coating 80
can be fragile, and improved antireflection coatings are needed
which reduce the reflectance of light observed by the driver but
have better durability characteristics.
[0047] In another example, the antireflection coating 80 may be
added to the fourth surface 26B to minimize the intensity of
multiple reflections when viewing the electro-optic assembly 10
from the first surface 22A. The reflectance of the fourth surface
26B can be less than 1%. The heads up display system 14 may operate
optimally when the reflectance of the fourth surface 26B is below
about 0.5%. For instance, the antireflection coating 80 may include
a dielectric antireflection stack having four layers of alternating
high and low refractive index materials, where the sequence of the
stack is SHLHL, where S stands for the substrate, H stands for the
high index material, and L stands for the low index material. The
thicknesses of the layers starting from the first layer adjacent to
the fourth surface 26B are about 0.0617, 0.0796, 0.4758 and 0.2279
FWOT. Examples of high index dielectric materials are
Nb.sub.2O.sub.5, Ta.sub.2O.sub.5, TiO.sub.2 and examples of low
index dielectric materials are SiO.sub.2 and MgF.sub.2. An example
of a metallic containing antireflection coating 80 would be a
single layer of a metallic material such as Cr, Co, Ir, Mo, Pt, Ta,
Zr, W, Re, or Va, with typical thickness between 0.1 and 5 nm.
Also, it is important to minimize reflectance from the second and
third surfaces 22B, 26A. The reflectance at these surfaces is a
function of the refractive indices of the first and second
substrates 22, 26, the coating stack on the substrates 22, 26, and
the electro-optic medium 38 in contact with the coating stack. The
reflectance can also be a function of the coating thicknesses. In
the case of a solution phase electrochromic device, using a fluid
with a refractive index more closely matching that of the coatings
will reduce the reflectance. When using ITO as the electrode for
the electro-optic assembly 10, and assuming an ITO refractive index
of approximately 1.8, the reflectance normal to the surface of each
coating/fluid interface is given by the Fresnel equation provided
above. If the fluid has a refractive index of approximately 1.2,
the reflectance off of each coating/fluid interface can be
approximately 4%. With a fluid having a refractive index of 1.4,
the reflectance off of each coating/fluid surface can be
approximately 1.6%. The intensity of some of the multiple
reflections can be reduced by darkening the electro-optic assembly
10. Although this also reduces forward visibility, there may be
times that there is significant advantage to have the electro-optic
assembly 10 darken thereby improving contrast and reducing the
double imaging. One other consideration is the transmittance of the
coatings of the first surface 22A. Lower transmittance reduces the
forward visibility, but also reduces the double image off of the
second, third and fourth surfaces 22B, 26A, 26B.
[0048] Unlike other antireflective applications, it is important to
note that the problem being solved is not the reflectance, as
viewed from the fourth surface 26B, but rather from the reverse
direction (e.g., from first surface 22A). Thus, the reflectance as
viewed from the fourth surface 26B actually does not have any
reflectance constraints. This unique set of requirements can be
solved with new antireflection coatings designed based on thin
metal layers. Accordingly, in another example, the antireflection
coating 80 may include one or more thin metal coatings. It has been
discovered that the reflectance of a thin metal coating will vary
by the direction viewed. For example, when a Cr coating is applied
to a glass substrate (or material with a comparable refractive
index), the reflectance from the coating side will steadily
increase. This is the normal expected behavior for a metal coating.
Conversely, the reflectance, when viewed through the glass, will
have an alternate behavior. As the metal coating layer increases
thickness, the reflectance drops initially and goes through a
minimum before it steadily increases in reflectance, as expected
for metal layers. This effect occurs for very thin coating layers.
An example of the reflectance in dependence of wavelength in the
visible range is illustrated in FIG. 11 for a glass/air interface
in the uncoated state, a glass/air interface with a four layer HL
antireflection coating, and a glass/air interface with a thin Cr
example of the antireflection coating 80. From this, it is possible
to observe that the thin metal layer examples of the antireflection
coating 80 reduce a dramatic amount of reflectance from the glass,
as viewed from the observer perspective. Examples of metallic AR
coating would be a single, or multi-layer, of a metallic material
such as Cr, Co, Ir, Mo, Pt, Ta, Zr, W, Re, or Va, or alloys
containing these elements. The total thickness of the metals layers
should be between about 0.1 nm and about 5 nm.
[0049] The eye-weighted reflectance (Yr) versus thickness for
several metals (e.g., antireflection coatings 80) when viewed
through a substrate (e.g., the first and/or second substrates 22,
26) is illustrated in FIG. 10. In this example the reflectance is
presented for the substrate which includes an uncoated surface and
an antireflection coated surface. Therefore, the reported
reflectance values are relatively high and the net reflectance from
the coated surface may be obtained by subtracting about 4.2% from
the reported values. From FIG. 10, it is possible to observe that
the metals show a characteristic minimum in the reflectance at a
thickness between 0.5 and 4.0 nm. Table 2 exemplarily illustrates
the normal-incidence integrated eye-weighted reflectance of a glass
substrate with a metal example of the antireflection coating 80, as
seen from the uncoated glass side. The reflectance from an uncoated
glass substrate is also shown in Table 2 for reference.
[0050] The examples in Table 3 demonstrate the eye-weighted
reflectance Yr, transmittance Yt, and absorption of various
electro-optic elements with different transflective coatings 70,
TCO coatings and antireflection coatings 80, where the reflectance
is measured normally and towards the first surface 22A. The
examples illustrate a wide range of transmittance values that are
attainable while retaining a similar reflectance of about 25% and
neutral reflected color with absolute reflected a* and b* values
lower than 3 and C* values less than 3.
TABLE-US-00003 TABLE 3 Transmittance and reflectance parameters for
various transflective coatings on electro-optic assemblies:
4.sup.th 2.sup.nd and 3.sup.rd ITO surface 1.sup.st surface
thickness (FWOT) AR Yr a*r b*r Yt a*t b*t G/1stCr/ITO/2ndCr 0.574
Cr 25.09 -0.48 0.07 28.91 -1 4.51 G/1stCr/ITO/2ndCr 1.07 Cr 25.16
0.42 0.14 28.8 -2.42 3.2 G/ITO/Cr 1.07 Cr 24.91 0.69 0.12 34.47
-2.27 4.2 G/1stCr/ITO/2ndCr 2.81 Cr 24.72 -1.85 0 28.7 -1.38 -0.29
G/cold-ITO/Tio2 0.574 Cr 24.93 0.62 -0.22 43.32 -1.25 3.6 G/DLC
0.574 Cr 26.93 -0.56 -0.47 31.59 -0.06 10.01 G/DLC 0.88 Cr 24.51
-1.65 0.13 33.71 0.51 4.05 G/1stCr/ITO/2ndCr 0.574 HLHL 24.28 -0.3
-0.22 43.44 -1.48 6.28 G/1stCr/ITO/2ndCr 1.07 HLHL 25.18 0.49 0.18
43.38 -3.12 4.79 G/ITO/Cr 1.07 HLHL 24.95 0.8 0.18 52.28 -2.95 6.01
G/1stCr/ITO/2ndCr 2.81 HLHL 25.56 -1.37 2.53 36.98 -1.86 -0.11
G/cold-ITO/TiO2 0.574 HLHL 24.99 0.75 -0.24 63.03 -1.89 4.04 G/DLC
0.574 HLHL 26.97 -0.5 -0.46 45.94 -0.5 11.29 G/DLC 0.88 HLHL 24.95
-1.64 0.32 48.46 0.25 4.55
[0051] As shown in Table 2, some of the thin metal examples of the
antireflection coating 80 may have reflectance values greater than
zero for their optimal antireflection situation. This is not
uncommon for antireflection coatings 80 as it can be challenging to
antireflect over a broad wavelength range. The thin metal
antireflection coatings 80 described above can be further improved
by the addition of a thin dielectric layer positioned between the
substrate (e.g., first substrate 22) and the metal coating layer.
Table 4, below, shows the values attainable for chromium metal
coating examples of the antireflection coating 80 using thin film
models. The reflectance is reduced substantially with the addition
of the dielectric layer. The desired thickness and refractive index
of this dielectric layer will vary with the metal being used and
the requirements of the application. The refractive index of the
dielectric layer may be less than about 2.4 or less than about 2.0.
The thickness of the dielectric layer may be less than about 50 nm
or less than about 35 nm.
TABLE-US-00004 TABLE 4 Dielectric Dielectric Cr Reflectance
Transmittance Sample RI Thickness Thickness Y a* b* Y a* b* 1 -- --
1.56 4.66 -0.33 -3.71 65.50 0.61 -3.45 2 1.6 32.73 1.63 4.59 -0.23
-3.81 64.69 0.62 -3.55 3 1.7 31.51 1.87 4.40 0.16 -3.83 61.92 0.69
-3.94 4 1.8 22.42 2.04 4.28 0.51 -3.55 60.12 0.72 -4.22 5 1.9 22.90
2.13 4.23 0.73 -3.07 59.25 0.73 -4.40
[0052] The reflectance of the metal or dielectric metal stack
examples of the antireflection coating 80 may be further reduced by
the modification of the refractive indices of the metal layers.
This can be accomplished by the addition of small dopants or
additives to the metals such as nitrogen, oxygen, both or other
elements. For example, a chromium layer was sputtered with 5%
oxygen and 5% nitrogen and the reflectance was 4.24% and 4.25%,
respectively. Other levels of gasses may be used in the sputtering
atmosphere to change the optical properties of the metals. The
percentages of the dopant gas sources can be varied experimentally
to optimize the reflectance, as needed. The refractive index
relationship described above can be used to guide the optimization
of the materials for the desired antireflection properties.
[0053] The exposed coatings (e.g., the transflective coating 70 and
the antireflection coating 80) on the first and fourth surfaces
22A, 26B may get a buildup of environmental contaminants, or dirt,
which is common in an automotive interior. The coatings will
therefore be subjected to regular cleaning to have the best images
possible. If the coatings are not durable then they may be
scratched or otherwise damaged by the cleaning solvents or methods.
It therefore may be advantageous for these materials to be durable
or a scratch-resistant coating 90 be added. In one example, the
transflective coating 70 may be formed by a diamond-like carbon
(DLC) material. The DLC materials are reflective, somewhat
absorbing and highly durable (e.g., anti-scratch). Examples of the
transflective coating 70, including this material, would be stable
in an automotive environment. FIG. 7 illustrates the reflectance
and transmittance relationship for a single layer DLC on the first
surface 22A in dependence of the thickness and of the
antireflection coating on the fourth surface 26B. Further, the DLC
material may be utilized in the scratch-resistant coating 90. For
example, if additional durability is desired for either the thin
metal or the other types of antireflection coatings 80 described
above, a top DLC layer may be added to the stack as the
scratch-resistant coating 90. Since the DLC typically has a
relatively high refractive index, the other layers may need to be
optimized or adjusted to attain the desired balance between
reflectance and durability.
[0054] One of the functions of a variable transmittance
electro-optic assembly 10 for the heads up display system 14 is to
be able to see through the assembly 10 at different transmittance
levels to see the environment outside the vehicle 18. In one
example, it may be important for the color of the light passing
through the electro-optic assembly 10 in the clear and/or darkened
states to match light not passing through the assembly 10. In other
words, the color rendering index of the transmitted light should be
relatively high similar to the reflected CRI discussed herein. The
color rendering index of the transmitted light should be greater
than about 75, more desirably greater than about 85, even more
desirably greater than 90, and most desirably greater than about
95. These values may pertain to the high transmittance state, the
low transmittance state and/or intermediate transmittance states of
the electro-optic assembly 10. The reflected and transmitted color
of the coatings (e.g., the transflective coating 70, antireflection
coating 80, and/or scratch-resistant coating 90) along with any
absorption present in the materials will play a role in the final
CRI values. Similarly, the absorption of the electro-optic medium
38 in the clear and darkened states will factor into the CRI
calculation. In some embodiments, the characteristics of the
coatings and electro-optic medium 38 may be tuned or adjusted so
that the net color has the appropriate CRI. For example, if one or
more of the coatings has a blue absorption, then the electro-optic
medium 38 may include a yellow absorbing component so that the net
transmittance through the electro-optic assembly 10 meets the CRI
requirements for a given application.
[0055] It will be understood by one having ordinary skill in the
art that construction of the described disclosure and other
components is not limited to any specific material. Other exemplary
embodiments of the disclosure disclosed herein may be formed from a
wide variety of materials, unless described otherwise herein.
[0056] For purposes of this disclosure, the term "coupled" (in all
of its forms, couple, coupling, coupled, etc.) generally means the
joining of two components (electrical or mechanical) directly or
indirectly to one another. Such joining may be stationary in nature
or movable in nature. Such joining may be achieved with the two
components (electrical or mechanical) and any additional
intermediate members being integrally formed as a single unitary
body with one another or with the two components. Such joining may
be permanent in nature or may be removable or releasable in nature
unless otherwise stated.
[0057] It is also important to note that the construction and
arrangement of the elements of the disclosure, as shown in the
exemplary embodiments, is illustrative only. Although only a few
embodiments of the present innovations have been described in
detail in this disclosure, those skilled in the art who review this
disclosure will readily appreciate that many modifications are
possible (e.g., variations in sizes, dimensions, structures, shapes
and proportions of the various elements, values of parameters,
mounting arrangements, use of materials, colors, orientations,
etc.) without materially departing from the novel teachings and
advantages of the subject matter recited. For example, elements
shown as integrally formed may be constructed of multiple parts, or
elements shown as multiple parts may be integrally formed, the
operation of the interfaces may be reversed or otherwise varied,
the length or width of the structures and/or members or connector
or other elements of the system may be varied, the nature or number
of adjustment positions provided between the elements may be
varied. It should be noted that the elements and/or assemblies of
the system may be constructed from any of a wide variety of
materials that provide sufficient strength or durability, in any of
a wide variety of colors, textures, and combinations. Accordingly,
all such modifications are intended to be included within the scope
of the present innovations. Other substitutions, modifications,
changes, and omissions may be made in the design, operating
conditions, and arrangement of the desired and other exemplary
embodiments without departing from the spirit of the present
innovations.
[0058] It will be understood that any described processes or steps
within described processes may be combined with other disclosed
processes or steps to form structures within the scope of the
present disclosure. The exemplary structures and processes
disclosed herein are for illustrative purposes and are not to be
construed as limiting.
[0059] It is also to be understood that variations and
modifications can be made on the aforementioned structures and
methods without departing from the concepts of the present
disclosure, and further it is to be understood that such concepts
are intended to be covered by the following claims unless these
claims by their language expressly state otherwise.
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