FIELD OF THE INVENTION
The present invention generally relates to optical multilayer coatings. In particular,
some embodiments herein relate to optica! multilayer coatings having region provided
by a physical vapor deposition process and region provided by a chemical vapor
deposition process.
BACKGROUND
Optical interference coatings, sometimes also referred to as thin film optical coatings
or filters, comprise alternating layers of two or more materials of different indices of
refraction. Some such coatings or films have been used to selectively reflect or
transmit light radiation from various portions of the electromagnetic radiation
spectrum, such as ultraviolet, visible ajid infrared radiation. For instance, optical
interference coatings are commonly used in the lamp industry' to coat reflectors and
lamp envelopes. One application in which optical interference coatings are useful is to
improve the illumination efficiency, or efficacy, of lamps by reflecting infrared
energy emitted by a filament, or arc, toward the filament or arc while transmitting
visible light of the electromagnetic spectrum emitted by the light source. This
decreases the amount of electrical energy necessary for the light source to maintain its
operating temperature.
Optical interference coatings generally comprises t\\^ different types of alternating
layers, one having a low retractive index and the other having a high refractive index.
With these two materials having different indices of refraction, an optical interference
coating, which can be deposited on the surl^ace of the lamp envelope, can be designed.
In some cases, the coating or filter transmits the light in the visible spectmm region
(generally from about 380 to about 780 nm wavelength) emitted from the light source
wliile it reflects the intrared light (generally from about 780 to about 2500 nm). The
returned infrared light heats the light source during lamp operation and, as a result, the
lumen output of a coated lan?p is considerably greater than the lumen output of an
uncoated lamp.
With the advent of potential energy regulations for incandescent and halogen lamps, it
has become increasingly important to develop and introduce energy efficient
products. In view of this, improved optical interference multilayer coatings and
methods for their production have been developed, which have shown enhanced gain
or energy etTiciency. in some previous work, a low-pressure chemical vapor
deposition (CVD) process has been employed to prepare optical inteHerence coatings
for lamps (for example, see commonly owned XJS Patent 5,412,274). In some other
previous work, physical vapor deposition (PVD) prwesses have advantageously been
employed, e.g. magnetron sputtering processes.
There remains a need for new and improved methods to develop and introduce energy
efficient products.
B.RJBF SUMMARY OF THE INVENTION
One embodiment of the present invention is directed to an article comprising an
optical interference multilayer coating, the coating having a first region formed by a
physical vapor deposition process and a second region formed by a chemical vapor
deposition process. The first region comprises a first plurality of alternating first and
second layers, the tust layers having relatively low refractive index and the second
layers having relatively higher refractive index than the first layers; and tlte second
region comprises a second plurality' of alternating third and fourth layers, the third
layers having relatively low refractive index and the fourth layers having relatively
higher refractive index than the third layers.
A further embodiment of the present InvetUion is directed to a lamp comprising a
light-transmissive envelope having a surface and a light source, the envelope at least
partially enclosing the light source. At least a portion of the suilace of the lighttransmissive
envelope is provided with an optical interference multilayer coating, the
coating having a first region formed by a physical vapor deposition process and a
second region formed by a chemical vapor deposition process. The first region
comprises a first plurality of alternating first and second layers, the first layers having
relatively low refractive index and the second layers having relatively higher
refractive index than the first layers; and the second region comprises a second
plurality of alternating third and fourth layers, the third layers having relatively low
refractive index and the fourth layers having relatively higher refractive index than the
third layers.
Other features and advantages of this invention will be better appreciated from tlie
following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
ErabodJTnents of the invention vsoll now be described in greater detail with reference
to the accompanying Figures.
Figure 1 is a schematic illustration of an article having a bottom PVD region and atop
CVD region, in accordance with embodiments of the invention.
Figure 2 is a schematic illustration of an article having a bottom CVD region and a
top PVD region, in accordance with embodiments of the invention.
Figure 3 is a schematic depiction of bottom multilayers of tl^e article of Figure 1, in
accordance with embodiments of the invention.
Figure 4 is a schematic depiction of top multilayers of the article of Figure 1, in
accordance with embodiments of the invention.
Figure 5 is a schematic depiction of an exemplar>' lamp, in accordance with
embodiments of the invention.
DETAILED DESCRIPTION
In accordance with embodiments, new types of coatings and methods of making are
disclosed herein, which can have increased effectiveness for forming relatively thick
(e.g., greater than 10 micron) optical inteiference coatings. These methods typically
may utilize both CVD process and PVD process. In accordance with embodiments of
this disclosure, the favorable aspects of each coating process may be employed, with
minimization of the problematic aspects of each process.
As noted, an embodiment of the invention is direaed to an aaticle comprising an
optical interference muitiiayer coating, the coating having a first region fonned by a
physical vapor deposition process and a second region foitned by a chemical vapor
deposition process. The first region comprises a first plui^lity of alternating first and
second layers, the first layers having relatively low refractive index and the second
layers having relatively higher refractive index than the first layers; and the second
region comprises a second pluralit>' of alternating third and fourth layers, the third
layers having relatively low refractive index and the fourth layers having relatively
higher refractive index dian the third layers. Typically, the alternating firsii and second
layers in the first plurality of layers tiiay be spectrally adjacent to at least each otlier,
and may also be physically adjacent to each other. Furthennore, it is typical for the
alternating third and fourth layers in the second plurality of layers to be spectrally
adjacettl to at least each other; these may also be physically adjacent to each other.
In general, the first layers and third layers may be referred to the "low index" layers,
and may have a refractive index of from about 1.35 to about 1.7 at 550 nm. Typically,
these low index layers may include a material independently selected from ceramic
materials, refractoiy materials, silicon, oxides of metals or metalloids, and nitrides of
metals or metalloids; fluorides of metals or metalloids; or the like. Fluorides of metals
may include compounds such as MgFs. Often, these low index layers may include a
silicon oxide, such as glass or quartz or other form of ainoiphous or crj'stalline silica.
The most commonly employed low index material is one or more form of Si02, due to
its low refractive indices, low cost, and favorable thermal property. Tlie first layer
material can be the same as the third layer material, or the first layer material can be
ditTerent from the third layer material.
In general, the second layers and said fourth layers may be referred to a the "high
index" materials, and may have a refractive index of from about 1,7 to about 2,8 at
550 nm. Typically, such high index materials may comprise aiw material having a
refractive index relatively higher than that of the first and third layers. N4any
refractory materials are suitable for high index materials. Often, such high index
materials may be independently selected from one or more oxides (or mixed oxides)
of one or more metal selected from the group consisting of Ti, Zr, lif, Nb, W, Mo, In,
5
and Ta; or the like. The second layer material caii be the same as the fourth layer
material, or the second layer material can be different from the fourth layer material.
The composition of the second and fourth layers may include (for example): (l)
physical mixtures of two or more of such metal oxides; or (2) may include physical
mixtures of a mixed metal oxide and another metal oxide; or (3) may include a mixed
metal oxide of at least two metals in the group; among other possibilities Specific
po.ssibie examples may include NbTaX oxide where X is selected from the group
consisting of Hf, Al and Zr; or NbTiY oxide where Y is selected from the group
consisting of Ta, Iff, Al and Zr; or Ti.AlZ oxide where Z is selected from the group
consisting of Ta, Hf and Zr. In general, then, the second and fourth layers may
comprise any material heretofore typically employed as a higli refractive index
material in optical interference multilayer coatings, as well as other high refractive
index materials.
In accordance with embodintetils of the invetition, the first region is formed by a
physical vapor deposition process (PVD), and the second region is formed by a
chemical vapor deposition process (CVD). Other regions may also be present in the
coating, formed via either of these methods or other methods. In general, PVD
processes employed may be selected from the group consisting of: thermal
evaporation; RF evaporation; electron beam evaporation; reactive evaporation; DC
sputtering; RF sputtering; microwave sputtering; magnetron sputtering; microwaveenhanced
DC magnetron sputtering; arc plasma deposition; reactive sputtering; laser
ablation; and combinations thereof; or the like. Typically, CVD process employed
may be selected from the group consisting of. atmospheric pressure CVD; lowpressure
CVD; high-vacuum CVD; ultrahigh-vacuum CVD; aerosol-assisted CVD;
direct liquid-injection CVD; microwave plasma-assisted CVD; plasma-enhanced
('VD, remote plasma-enhanced CVD; atomic layer ('VD; hot wire CVD; metalorganic
CVD; hybrid physical-chemical vapor deposition; rapid thermal CVD; vapor
phase epitaxy; and combinations thereof; or the like.
As is generally understocxJ, in a typical chemical vapor deposition process, a substrate
is exposed to one or more volatile or gas-like precursors (usually molecular
precursors), which precursors react and/or decompose on the substrate surface to
produce the desired deposit. There are a variety of different types of CVD processes,
which may be classified by the features of their operating pressure, characteristics of
the vapor, t>'pes of energy input, or other features. Ail of the following are to be
included within tlie scope of "CVD" processes, as that term is used herein. For
instance, some CVD processes include; atmospheric pressure CVD; low-pressure
CVD (I.PCVD) (wherein chemical vapor deposition typically occurs at subatmospheric
pressures), and high- or ultraliigli-vacuura CVD, which is usually
conducted at below about iO'^ Pa. In other forms of CVD, the precursor is not strictly
in the gaseous state; aerosol-assivSled CVD employs precursors as a liquid-gas aerosol,
while direct liquid-injection CVD (DLICVD) uses liqueform precursors which are
injected and trail spoiled to a substrate.
Some CVD metluKls are assisted by energetic means, such as microwave plasmaassisted
CVD (MPC^VD), plasma-enhanced (or plasma-assisted) CVD (PECVD), and
remote plasma-enhanced CVD (RPECVD). Other types of CVD may include atomic
layer CVD (ALCVD), hot wire CVD (HWCVD), metal-organic CVD (MOCVD);
hybrid physical-chemical vapor deposition (HPCVD), rapid tliennal CVD (RTCVD),
vapor phase epitaxy (VPE); and the like. Iliese respective types of CVD are not
always intended to be mutually exclusive; therefore, combinations employing more
than one of the foregoing C'VD processes are also contemplated. For example, any
person skilled in the field would clearly understand that plasma-assisted CVD may be
inclusive of remote plasma-enhajiced CVD. Similarly, a hot wire CVD process
employing organometallic precursors can also be considered an MOCVD process, as
would be readily understood by those skilled in the art.
Where LPCVD is used to deposit multilayer coatings, it may typically employ the
process as set tbrth in U.S. Pat. No. 5,143,445. Additionally, any of the conditions and
precursors shown in commonly owned US Patent 5,412,274 may be suitable for use in
the present disclosure. .Additionally exemplary' chemical vapor deposition and lowpressure
chemical vapor deposition processes, are described, for example, in U.S. Pat.
Nos, 4,949,005, 5,143,445, 5,569,970, 6,441,541, and 6,710,520, All of these noted
patents are hereby incorporated by reference in pertinent part
7
As would be generally understood by persons skilled in the art, in a typical physical
vapor deposition (PVD) process, a material is vaporized by a physical process and
thereafter condensed at a substrate to form a deposit. Sometimes, the vaporized
material can undergo a reaction such as oxidation (by reaction with oxygen). Often, a
deposit is made on a substrate by the steps of converting the material to be deposited
into vapor by a physical means, transporting the vapor from its source to the substrate,
and condensing the vapor on the substrate. Generally, in PYD processes, the
vaporized material (usually in atomic form, such as metal atoms) does not itself have
to undergo decomposition in order to be deposited. This is the typical distinguishing
factor from CVD, where a precursor (usuially molecular) must decompose or react
before fbiming a deposit. PVD processes are often characterized by the type of
energetic input needed to form the vapor. As used herein, PVD processes may include
thermal evaporation, RF evaporation, electron beam evaporation, reactive
evaporation, DC sputtering, RF sputtering, microwave sputtering, magnetron
sputtering, microwave-enhanced DC magnetron sputtering, arc plasma deposition,
reactive sputtering, laser ablation; and the like.
These respective t>'pes of PVD are not always intended to be mutually exclusive;
therefore, combinations employing more than one of the foregoing PVD processes aje
also contemplated, for example, it would be understood that "tiiagnetron sputtering"
may be inclusive of both DC and RF magnetron sputtering. Similarly, it would be
understood that "DC magnetron sputtering" may be inclusive of "microwaveenhanced
DC magnetron sputtering". However, regardless of whether alternative
methods with overlapping scope is recited, any person skilled in the field would
cleariy understand the nature of the method.
Where RF magnetron sputtering is used to deposit multilayer coatings, one may
suitably employ processes shown in US Pat. No. 6,494,997, hereby incorporated by
reference in pertinent part. Magnetron sputtering is where a higli-energy inert gas
plasma is used to bombard a target. The sputtered atoms condense on the cold glass or
quart?, housing. DC (direct current), pulsed DC (40-400 Kllsr.), or RF (radio
frequency, 13.65 MHz) processes may be used.
2
In accordaiice with embodiments, the article having the first and second regions as
described above, may further comprise at least one supplemetrtal multilayer region
comprising alternating relatively lower refractive index layers and relatively higher
refractive index layers. When such supplemental region (if present) is physically
adjacent to the first region, such supplemental region may be deposited by CVD.
When such supplemental region (if present) is physically adjacent the second region,
such supplemental region may be deposited by PVD.
In accordance with embodiments, the article may further comprise at least one
substrate. In some embodiments, the first region is closer to the at least one substrate
than the second region. In some other embodiments, the second region is closer to the
at least one substrate than the first region.
Schematic illustrations of embodiments are shown in Figures 1 through 4, In Figure 1
is depicted article 10 comprising a substrate II, first region 12 deposited by PVD, and
second region B deposited by CVD. Regions are depicted as physically adjacent in
this illustration, but the invention is not limited to the manner depicted in these
figures. In Figure 2 is depicted an alternatively arranged aiHcle 20 having substrate
21, a second (i.e., CVD) region 22 as a bottom layer, and a first (i.e., PVD) region 23
as a top layer. Figures 3 and 4 illustrate greater detail for regions of article 10. In
Figure 3, the first region is composed of alternating layers 121, 122, 123, 124 having
low and high refractive indices, respectively. In Figure 4, the second region of article
10 is sliown having alternating layers 131, 132, 133, 134 having low and high
retractive indices, respectively. Although only four layers per region are shown, the
invention is not limited to these embodiments.
In some embodiments of the present invention, the article comprises a first region
having a first average interface roughness among the first plurality of alternating first
and second layers; and the article comprises a second region having a second average
interface roughness among the second plurality of alternating third and fourth layers;
vvherein the first average interface roughness is greater than the second average
interface roughness. Generally, any two adjacent layers in a region (for example, first
and second layers) do not have a perfectly atomically smooth interface between them.
There is typically some kind of interface rougluiess between layers, which can be
detected. Interface roughness can be measured by any method known to a person
skilied in the field, including svjch methods as TEM, HRTEM, SIM, SEM, and the
like. "Interface roughness", sometimes also referred to as "interfacial roughness", is
generally measured in units of length such as nra or Angstrojns. As used herein, the
term "interlace roughness" is generally a root-mean-square (mis) roughness for a
given interface.
As noted above, a first region may sometimes be characterized by a "first average
interface roughness", which is the typically the mean of the rms interface roughness
taken over all (or substantially all) the layers of the first portion. Generally, the
interface roughness between substantially all the layers in the first region is quantified
and averaged, l-ikewise, a "second average interface roughness" is the typically the
mean of the mis interface roughness taken over all (or substantially all) the layers of
the second portion. In the case of a hybrid coating having a first portion deposited by
a PVD method, and having a second portion depo.'iited by a CVD method, each
respective portion may have a ditYerent average interface roughness. In typical
embodiments, the first average interface roughness is at least about \(f/o greater than
the second as^erage interface roughness. In other embodiments, tlie first average
interface roughness is at least about 20% greater (e.g., at least about 50% greater) than
the second average interface roughness. In certain embodiments, the first average
interface roughness may be greater than about 10 nm, more particularly greater than
about 20 nm. In certain embodiments, the second average interface roughness may be
less than about 10 nm, more particularly less than about 5 nm.
In some embodiments of the invention, the first and/or second layers of the first
region may be characterized by comprising metal oxide grains having a substantially
columnar or acicular structure, In still other embodiments, the first and/or second
layers of the first region may be further characterized by comprising metal oxide
grains wherein voids are present between at least some of these grains. Either or both
of these can sometimes be a characteristic feature of metal oxides deposited by a PVD
method. However, under certain conditions, especially when deposited at
temperatures exceeding about 500°C, the first region may instead sometimes be
substarUiaiiy amorphous.
fn accordance witii some embodiments is provided an article comprising an optical
interference multilayer coating, wherein the coating has a total geometrical thickness
of from about 0.2 to about 30 microns, or even sometimes even higher. By "total
geometrical thickness" of the coating is included the first and the second regions, but
not the substrate. In other embodiments, the total geometrical thickness of the coating
may be greater than around 10 microns. Other ranges for total geometrical thickness
may include from about 2 to about 22 microns, or from about 8 to about 15 microns.
The endpoints of these ranges are independently combinable to form new ranges, such
as from about 2 to about 15 microns. A relatively thicker total coating can lead to
higher efficiency for applications where the optical interference multilayer coating is
configured to act as a bandpass filter which reflects infrared radiation and transmhs
visible radiation.
Typically, the first region may comprise a geometrical thickness of from about 2% to
about 98% of the total geometrical thickness of the coating In some embodiments,
the first region comprises a geometrical thickness of from about 50*/o to about 90% of
the total geometrical thickness of the coating, and the second region comprises a
geometrical thickness of from about 10% to about 50% of the total geometrical
thickness of the coating. In some contigurations, the first region may include a
geometrical thickness of from about 0.1 to about 20 microns (e.g., greater than about
4 microns), or more narrowly, from about I to about 15 microns. In some
configurations, the second region may include a geometrical thickness of from about
0.1 to about 10 microns, or more narrowly, from about i to about 7 microns.
According to embodiments of the invention, the coating may independently have a
total number of layers in each region of from 4 to 250. All integral values there
between are specifically contemplated. The total number of layers in a region is not
particularly critical. Stated more narrowly, the total number of layers in a region may
range from any integer from 30 to 150 layers. In some cases, the region deposited by
CVD may have 46 layers, while the region deposited by PVD may have 60 layers. In
II
some embodiments of this disclosure, each of said first, second, third, and fourth
layers individually have an average thickness of from about 20 nm to about 500 nm,
or sometimes from about 10 nm to about 200 nm.
In accordaiwe with certain embodiments, the optical interference multilayer coating is
configured to act as a "hot mirror", i.e., a coating which substantially transmits light in
the visible spectrum region (generally from about 380 to about 780 nm waveiength)
emitted from a light source while it substantially reflects infrared light (generally from
about 780 to about 2500 tun). In such embodiments, the optical interference
multilayer coating may have an average transmittance in visible light of greater than
about 60% (more preferably, greater than about 80%) and have an average reflectance
of at least about 30% (and more usually, greater than about 70%) in the infrared
region of the electromagnetic spectrum.
According to embodiments of this disclosure is provided a method tbr making an
article having an optical inteiference multilayer coating as described above. Such
method comprises providing a substrate; and depositing a first regiojt and a second
region, in any order. The first region is deposited by a physical vapor deposition to
form a plurality of alternating first and second layers, the first layers having relatively
low refractive index and said second layers having relatively higher refractive index
than the first layers. The second region is deposited by a chemical vapor deposition
process to form a plurality of alternating third and fourth layers, the third layers
having relatively low refractive index and the fourth layers having relatively higher
refractive index than the third layers. Either one of the first and second region is
adjacent to die substrate. The method may also comprise one or supplemental region
intermediate lo the first and second regions, or one or more supplemental region
between the substrate and the first or second region. After deposition of the first and
the second regions, one may generally employ an annealing step, conducted at a
temperature such as from about ;)00'^C to about 500"C' (e.g., about 400°C) for a time
period such as of from about 12 h to about 60 h (e.g., about 48 h). In some
embodiments, the substrate may comprise a lamp envelope. Such lamp envelope may
be made of any transparent or translucent material, such as quartz or glass or the like,
12.
The shape of the substrate is not particularly limited, but may include shapes such as
cylindrical or elliptical or the like, for example.
Coatings according to embodiments of the invention, usually employed upon
substrates in articles, can be utilized for any of a wide variety of applications where
optical interference coatings are desiral or typically used. These include, for example,
lighting applications (e.g., lamps), optical waveguides, reflectors, decorative
materials, security printing; or the like. In some embodiments the coatings are used to
selectively reflect one portion of the electromagnetic speclnnn while transmitting
another portion of the electromagnetic spectrum. For instance, the coatings can be
used as a "cold mirror" or a "hot mirror", A "cold mirror" is an optical filter that
reflects visible light while at the same time permitting longer wavelength infrared
energy to pass through the fther, A "hot mirror" is an optical filter that reflects
infrared radiation while at the same time permitting shorter wavelength visible light to
pass through the filter. One nonlimiting application of hot mirrors herein is to return
infrared heat to the filament of a lamp in order to increase lamp efficiency'.
hi accordance with embodiments of the invention, there ajte also provided a lamp or
lamps including the optical interference multilayer coatings of the present disclosure.
Such lamps generally comprise a light-transmissive envelope having a surface, and a
light source, with the envelope at least partially enclosing the light source. At least a
portion of the surface of the light-transmissive envelope is provided vvith the optical
interference multilayer coating. As is generally known, such light-transmissive
envelopes may be composed of any material which is light transmissive to an
appreciable extent and is capable of withstanding relatively hot temperature (e.g.,
about SOOT- or even above); for example, it tnay be composed of quartz, ceramic, or
glass; or the like. The light source may be an incandescent source (for example, one
which provides light tlirough resistive heating of a filament); and/or it may be an
electric arc discharge source, such as a high-intensity discharge (E:IJD) source; and.''or
it may be another type of light source.
lisually, where a filament is employed, it is composed of a refractory metal, generally
in coiled form, such as tungsten or the like, as is well known. To energize the lamp,
13
there is typically provided at least one electric element arranged in the envelope and
connected to current supply conductors (or electrical leads) extending through the
envelope. Usually, the envelope encloses a fill gas. A preferable fill gas includes any
gas or gaseous mixture which is selected to promote lamp Vii'ess of at least about 10 micrometers in order to
achieve a high (e.g., > 100%) "gain" for halogen lamps. However, applicants have
found that a CVD process alone cannot produce such a thick coating due to stress
related issues. Although PVD can deposit thick coatings, it is often difficult to control
roughness when coatings approach high thickness. By dividing a coating (for
example) into the present two regions, then the region deposited by CVD can readily
achieve a smooth interface, and the remaining region can be deposited by a PVD
process, with greater control of the interfacial roughness relative to having the whole
\5
coating be made by PVD. The hybrid coating may also achieve cost efficiencies
relative to one made by PVD alone. Moreover, the compressive stress in the PVD
coatings may cancel the tensile stress in the CYD portion, making the coating less
prone to cracking and delamination. This may be especially advantageous where a
CVD-deposited region is adjacent a substrate but is deposited to a thickness which
would othenvise delaminate or crack in the absence of a PVT) overiayer
in order to promote a further understanding of the invention, the following examples
are provided. These examples are illustrative, and should not be construed to be any
sort of limitation on the scope of the claimed invention.
EXAMPLES
Example I.
Two DEQ lamps were coated on the outer envelope surface with an optical
interference multilayer coating via a I.,PCVD process, and denoted lamps A and B,
respectively. Lamp A was coated witli a 46 layer stack of alternating silica and
tantalum oxide, while l.^mp B was coated with a 46 layer stack of alternating layers
of silica and a niobium-tantalum oxide. All stacks deposited by I.-PCVD had a
geometrical thickness of about 4 microns. Each of lamps A and B were further coated
with a second optical interference multilayer slack, via sputtering. The second optical
interference multilayer stack in each case was composed of 36 layers of alternating
silica and Nb~Ti-Al oxide layers, in a hot mirror design. F'or sputter deposition of the
silica layers, cathode power was set to 3 kW, argon flow was 80 seem (standard cubic
centimeters per minute), and O2 pressure was 2.5 x 10"''' torr (0.0033 Pa). For sputter
deposition of tlte Nb-Ti-Al oxide layers, cathode power was set to 4 kW, argon flow
was 80 seem (standard cubic centimeters per minute), and O2 pressure was 3.2 x 10 "*
torr (0.043 Pa). All stacks deposited by sputtering has a geometrical thickness of
about 4 microns. The combined hybrid coatings on each lamp were then annealed at
400°Ctc>r48h.
Example 2.
The methodology of Example 1 was employed to provide a DEQ halogen lamp
having a bottom coating, external to the quartz envelope, of 46 L (layers) deposited to
a thickness of 4.5 microns by LPCVD of alternating silicu/NbTa oxide. .For the top
coating, 60 L of alternating silica/NbTiAl oxide was deposited to 4.5 microns by PVD
(sputtering). Surprisingly, even though the total coating was nearly 10 microns, the
transmittance spectrum showed almost no haze. Furthermore, it was unexpectedly
found that the PVD layer provided a protective effect on the bottom coating, whereby
the CVD-provided coating was observed to not peel when the lajtip is in operation,
despite its thickness Finally, the cdculated LPW gain was about 10% relative to the
same CVD coating without the PVT) layer.
As used herein, approximating language may be applied to modify any quantitative
representation that may vary without resulting in a change in the basic function to
which it is related. Accordingly, a value modified by a term or terms, such as "about"
and "substantially," may not be limited to the precise value specified, in some cases.
The modifier "about" used in connection with a quantity' is inclusive of the stated
value and has tlte meaning dictated by the context (for example, includes the degree
of error associated with the measurement of the particular quantity). "Optional or
"optionally" means that the subsequently described event or circumstance may or may
not occur, or that the subsequently identified material may or may not be present, and
that the description includes instances where the event or circumstance occurs or
where the material is present, and instances where the event or circumstance does not
occur or the material is not present. The singular forms "a", "an" and "the" include
plural referents unless the context clearly dictates otherwise. .All ranges disclosed
herein are inclusive of the recited endpoint and independently combinable.
As used herein, the phrases "adapted to," "configured to," and the like refer to
elements drat are sized, arranged or manufactured to form a specified stnicture or to
achieve a specified result. While the invention has been described in detail in
connection with only a limited number of embodiments, it should be readily
understood that the invention is not limited to such disclosed embodiments. Rather,
the invention can be modified to incorporate aiw number of variations, alterations,
substitutions or equivalent arrangements not heretofore described, but which are
17
commensurate with the spirit and scope of the invention. Additionally, while various
embodimetits of the invention have been described, it is to be understood that aspects
of the invention may include only some of the described embodiments. Accordingly,
the invention is not to be seen as limited by the foregoing description, but is only
limited by the scope of the appended claims.

WE CLAIM :
1. An article comprising an optical interference multilayer coating, said coating
comprising,
a first region comprising a first plurality of alternating first and second layers, said
first layers having relatively low refractive index and said second layers having
relatively higher refractive index than the first layers; and
a second region comprising a second plurality of alternating third and fourtli layers,
said third layers having relatively low retractive index and said fourth layers having
relatively higher refractive index than the tliird layers;
wherein said first region is formed by a physical vapor deposition process, and said
second region is formed by a chemical vapor deposition process.
2. The article of claim 1, wherein said PVD process is selected from the group
consisting of; thermal evaporation; RF evaporation; electron beam evaporation;
reactive evaporarion; DC sputtering; RF sputtering; microwave sputtering; magnetron
sputtering; microwave-enhanced DC magnetron sputtering; arc plasma deposition;
reactive sputtering; laser ablation; and combinations tliereof.
3. The article of claim 1, wherein said CVD process is selected from the group
consisting of, atmospheric pressure CVD; low-pressure CVD; high-vacuum CVD;
ultrahigh-vacuum CVD; aerosol-assisted CVD; direct liquid-injection CVD;
microwave plasma-assisted CVD; plasma-enhanced CVD; remote plasma-enhanced
C'VD; atomic layer CVD; hot wire CVD; metal-organic CVD; hybrid physicalchemical
vapor deposition; rapid thermal CVD; vapor phase epitaxy; and
combinations thereof
4. The article according to claim 1,
wherein said first region has a first average interface roughness among said first
plurality of alternating first and second layers, and said second region has a second
average inteiface roughness among said second plurality of alternating third and
fourth layers, and
wherein said first average interface roughness is greater than said second average
interface jx>ughness.
5. The aiticle of claim 4, wherein said first average inteiface roughness is at least
about 10% greater than said second average interface roughness.
6 The article of claim 1, wherein said first layers and said third layers comprise
a material independently selected trom ceramic materials, retractor)' materials, oxides
of metals or metalloids, fluorides of metals or metalloids, and nitrides of metals or
metalloids.
7. The article of claim 1, wherein said second and said fourth layers comprise a
material independently selected from one or more oxides or mixed oxides of one or
more metal selected from Ti, Zr, Hf, Nb, W, Mo, In, and Ta.
8 The article according to claim 1, wherein said first region comprises a
geometrical thickness of from about 50% to about 90% of the total geometrical
thickness of tlie coa^ng, and said second region comprises a geometrical thickness of
from about iO% to about 50% of the total geometrical thickness of the coating.
9. The article according to claim 1, wherein said coating has an average
transmittance in visible light of greater than 60% and has an average reflectance of at
least about 30% in the infrared region of the electromagnetic spectrum.
10, A lamp comprising:
a light-transmissive envelope having a surface; and a light source, said envelope at
least partially enclosing said light source;
wherein at least a portion of the surface of the IJght-transmissive envelope is provided
with an optical interference multilayer coating comprising,
%0
(a) a first region comprising a first plurality of alternating first and second layers, said
first layers having relatively low refractive index and said second layers having
relatively higher refractive index tlian the first layers; and
(b) a second region comprising a second plurality of alteraating third and fourth
layers, said third layers having relatively low refractive index and said fourth layers
having relatively higher refractive index than the third layers;
wherein said first region is formed by a chemical vapor deposition process, and said
second region is formed by a physical vapor deposition process.
11. The lamp according to claim 10, wherein said optical inteiference multilayer
coating is provided on one or both of an inner surface and an outer surface of said
envelope.
12. The lamp according to claim 10, wherein said light source comprises a
filament and wherein said lamp, when energized to a hot filament temperature,
exhibits an LPW gain of from about 20% to about 150% as compai-ed to the same
lamp eneipzed to the same hot filament temperature without said coating.
13. The lamp according to claim 10, further comprising at least one electric
element arranged in the envelope and connected to current supply conductors
extending through the envelope.
14 The lamp according to cl^m 10, wherein the light source comprises one or
ntore of filament or electric arc.
15 The lamp according to claim 10, wherein the envelope encloses a fill gas
selected to promote iainp life, quality, and/or performance.
16 The lamp according to claim 10,
wherein said first region has a first average interface roughness among said first
plurality of alternating first and second layers, and said second region has a second
average interface roughness among said second plurality of alternating third and
fourth layers, and
^1
wherein said first average interface roughness is greater than said second average
interface roughness-
17. I'he !amp according to claim 10, wherein said coating has an average
transmittance in visibie light of greater than 60% and has an average reflectance of at
ieast about 30% in the infrared region of tlie electromagnetic spectrum.
18 A method for making an article having an optical interference multilayer
coating, said method comprising,
providing a substrate,
depositing by a physical vapor deposition process a first region comprising a first
plurality of alternating first and second layers, said first layers having relatively low
refractive index and said second layers having relatively higher refractive index than
the first layers;
depositing by a chemical vapor deposition process a second region comprising a
second plurality of alternating third and fourth layers, said third layers having
relatively low refractive index and said fourth layers having relatively higher
refractive index than the third layers;
wherein one of said first and second region is adjacent to the substrate.
19. The method of claim 18, wherein said PVD process is selected from the group
consisting of. thennal evaporation; R.F evaporation; electron beam evaporation;
reactive evaporation; DC sputtering; RF sputtering; microwave sputtering; magnetron
sputtering; microwave-enhanced DC magnetron sputtering; arc plasma deposition;
reactive sputtering; laser ablation; and combinations thereof.
20. The method of claim 18, wherein said CYD process is selected from the group
consisting of. atmospheric pressure CVD; low-pressure CVD; high-vacuum CVD;
ultrahigli-vacuum CVD; aerosol-assisted CVD; direct liquid-injection CVD;
microwave plasma-assisted CVD, plasma-enhanced CVD; remote plasma-enhanced
CVD; alojnic layer CV;D; hot wire CVD; metal-organic CVD; hybrid physicai-
22-
chemical vapor deposition; rapid thermai CVD; vapor phase epitaxy; and
combinations thereof.