U.S. patent application number 11/499454 was filed with the patent office on 2008-02-07 for window defroster assembly with light control.
Invention is credited to Wilfried Hedderich, Chengtao Li, Rebecca Northey, Keith D. Weiss.
Application Number | 20080028697 11/499454 |
Document ID | / |
Family ID | 38657226 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080028697 |
Kind Code |
A1 |
Li; Chengtao ; et
al. |
February 7, 2008 |
Window defroster assembly with light control
Abstract
A window defrost assembly having a substrate, a polycarbonate
film adjacent to the substrate, a heater grid located between the
substrate and the polycarbonate film, and a light control layer
located between the polycarbonate film and the heater grid. The
heater grid includes first and second bus bars and a plurality of
grid lines extending between and connecting to the first and second
bus bars.
Inventors: |
Li; Chengtao; (Novi, MI)
; Hedderich; Wilfried; (Hilden, DE) ; Weiss; Keith
D.; (Fenton, MI) ; Northey; Rebecca; (Portage,
MI) |
Correspondence
Address: |
EXATEC;C/O BRINKS HOFER GILSON & LIONE
P. O. BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
38657226 |
Appl. No.: |
11/499454 |
Filed: |
August 4, 2006 |
Current U.S.
Class: |
52/171.2 |
Current CPC
Class: |
B32B 27/08 20130101;
H05B 2214/04 20130101; H05B 2203/013 20130101; H05B 3/86
20130101 |
Class at
Publication: |
52/171.2 |
International
Class: |
A47L 1/16 20060101
A47L001/16 |
Claims
1. A window defroster assembly having defrosting properties, the
window assembly comprising: a transparent substrate having a first
side and a second side; a light control assembly overlying the
first side of the substrate; and a heater grid having first and
second bus bars and a plurality of grid lines extending between and
connected to the first and second bus bars, the heater grid located
between the first side of the substrate and the light control
assembly.
2. The assembly of claim 1, wherein the substrate is made from a
material selected from the group including at least one of
polycarbonate, polymethyl methacrylate, polyester, polyurethane,
thermoplastic polyurethane, polyamide, blends or copolymers, and
combinations thereof.
3. The assembly of claim 1, wherein the light control assembly
comprises a first plastic film, a second plastic film and a light
control layer, the light control layer being located between the
first and second plastic films.
4. The assembly of claim 1, wherein at least on of the first and
second plastic films are made from a material selected from the
group including at least one of polycarbonate, polymethyl
methyacrylate, polyester, polyurethane, thermoplastic polyurethane,
polyamide, blends or copolymers, and combinations thereof.
5. The assembly of claim 1, further comprising a weathering layer
applied over or within the light control assembly.
6. The assembly of claim 5, wherein the weathering layer is made
from at least one of acrylic, polyurethane, siloxane, silicone
coating, lonomer, flouropolymer, ultraviolet absorbers, ultraviolet
stabilizers, and combinations thereof.
7. The assembly of claim 5, further comprising a plasma layer
applied over the weathering layer.
8. The assembly of claim 1, further comprising a plasma layer
overlying the second side of the substrate.
9. The assembly of claim 8, further comprising a weathering layer
located between the second side of the substrate and the plasma
layer.
10. The assembly of claim 9, wherein the weathering layer is made
from at least one material selected from the group of acrylic,
polyurethane, siloxane, silicone coating, lonomer, flouropolymer,
ultraviolet absorbers, ultraviolet stabilizers, and combinations
thereof.
11. The assembly of claim 1, further comprising a light emissive
layer located between the second side of the substrate and the
plasma layer.
12. The assembly of claim 1, wherein the heater grid is made of
conductive material.
13. The assembly of claim 12, wherein the conductive material is at
least one of silver, copper, zinc, aluminum, magnesium, nickel, tin
and combinations thereof.
14. The assembly of claim 1, wherein the heater grid is at least
one of a conductive paste, a conductive ink and a conductive
paint/coating, a conductive wire and combinations thereof.
15. The assembly of claim 1, wherein the light control assembly is
an electrochromic layer.
16. The assembly of claim 15, wherein the electrochromic layer is
at least one of liquid-crystal based, suspended particle device
(SPD) based, inorganic, organic, or hybrid based materials.
17. The assembly of claim 1, wherein the light control assembly is
a photochromic layer.
18. The assembly of claim 17, wherein the photochromic layer is at
least one of TPU, PC, PMMA, polyester or other transparent
thermoplastic or thermosetting material/component further
comprising photochromic dyes or pigments or additives.
19. The assembly of claim 1, wherein the light control assembly is
a thermochromic layer.
20. The assembly of claim 19, wherein the thermochromic material
layer is at least one of semi-conductor compounds, metal compounds
and organic pigments.
21. The assembly of claim 1, wherein the light control assembly is
a solar control layer, which may comprise of IR absorbers/layers or
IR reflective coating/ink/pigments.
22. The assembly of claim 1, further comprising an ink layer
located between the heater grind and the light control
assembly.
23. A method of producing a window assembly, the method comprising
the steps of: forming a light control assembly; trimming the light
control assembly; positioning the light control assembly in a mold
cavity; back molding the mold cavity with a plastic substrate
material; melt bonding the light control assembly to the plastic
substrate material to form the window assembly; removing the window
assembly from the mold cavity; and applying a plasma coating on at
least one side of the window assembly.
24. The method of claim 23, further comprising the step of printing
a stylized ink on the light control assembly.
25. The method of claim 23, further comprising the step of
thermoforming the light control assembly.
26. The method of claim 23, further comprising the step applying a
weathering layer to the window assembly.
27. The method of claim 23, wherein the light control assembly
further comprising a heater grid.
28. The method of claim 23, further comprising the steps of:
forming a light emissive assembly; trimming the light emissive
assembly; position the light emissive assembly in the mold cavity;
back molding the light emissive assembly to the plastic substrate
material; melt bonding the light emissive assembly to form the
window assembly; removing the window assembly from the mold cavity;
and applying a plasma coating on at least one side of the window
assembly.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] This invention relates to a conductive heater grid design
that provides performance characteristics making it amenable for
use in defrosting plastic and glass panels, such as windows in
vehicles.
[0003] 2. Related Technology
[0004] Plastic materials, such as polycarbonate (PC) and
polymethylmethyacrylate (PMMA), are currently being used in the
manufacturing of numerous automotive parts and components, such as
B-pillars, headlamps, and sunroofs. Automotive rear window
(backlight) systems represent an application for these plastic
materials due to their many identified advantages, particularly in
the areas of styling/design, weight savings, and safety/security.
More specifically, plastic materials offer the automotive
manufacturer the ability to reduce the complexity of the rear
window assembly through the integration of functional components
into the molded plastic system, as well as the ability to
distinguish their vehicles by increasing overall design and shape
complexity. Being lighter in weight than conventional glass
backlight systems, their incorporation into the vehicle may
facilitate both a lower center of gravity for the vehicle (and
therefore better vehicle handling & safety) and improved fuel
economy. Further, enhanced safety is realized, particularly in a
roll-over accident because of a greater probability of the occupant
or passenger being retained in a vehicle.
[0005] Although there are many advantages associated with
implementing plastic windows, these windows are not without
technical hurdles that must be addressed prior to wide-scale
commercial utilization. Limitations relating to material properties
include the stability of plastics during prolonged exposure to
elevated temperatures and the limited ability of plastics to
conduct heat. Regarding the latter, in order to be used as a rear
window or backlight on a vehicle, the plastic material must be
compatible with the use of a defroster or defogging system. For
commercial acceptance, a plastic backlight must meet the
performance criteria established for the defrosting or defogging of
glass backlights.
[0006] The difference in material properties between glass and
plastics becomes quite apparent when considering heat conduction.
The thermal conductivity of glass (T.sub.c=22.39
cal/cm-sec-.degree. C.) is approximately 4-5 times greater than
that exhibited by a typical plastic (e.g., T.sub.c for
polycarbonate=4.78 cal/cm-sec-.degree. C.). Thus a defroster or
defogger (hereafter just "defroster") designed to work effectively
on a glass window may not necessarily be efficient at defrosting,
defogging or deicing (hereafter just "defrosting" or "defrost") a
plastic window. The lower thermal conductivity of the plastic may
limit the dissipation of heat from the heater grid lines across the
surface of the plastic window. Thus, at a similar power output, a
heater grid on a glass window may defrost the entire viewing area,
while the same heater grid on a plastic window may only defrost
those portions of the viewing area that are close to the grid
lines.
[0007] A second difference between glass and plastics that must be
overcome is related to the electrical conductivity exhibited by a
printed heater grid. The thermal stability of glass, as
demonstrated by a relatively high softening temperature (e.g.,
T.sub.soften>>1000.degree. C.), allows for the sintering of a
metallic paste on the surface of the glass window to yield a
substantially inorganic frit or metallic wire. Since the softening
temperature of glass is significantly greater than the glass
transition temperature of a typical plastic resin (e.g.,
polycarbonate T.sub.g=145.degree. C.), a metallic paste cannot be
sintered onto a plastic panel. Rather, it must be cured on the
panel at a temperature lower than the T.sub.g of the plastic
resin.
[0008] From the above, it is seen that there is a need in the
industry for a system that will effectively defrost a plastic
window with performance characteristics similar to that of a
conventional glass window.
SUMMARY
[0009] In overcoming the drawbacks and limitations of the known
art, the present invention provides a window assembly having
defrosting capabilities. The window assembly includes a substrate,
a plastic film adjacent to one side of the substrate, a heater grid
located between the substrate and the plastic film and a light
control layer located between the plastic film and the heater grid.
The light control layer may be an electrochromic layer or a
photochromic layer, or a thermochromic layer, or solar control
layer.
[0010] The heater grid or conductive elements includes two
generally opposed bus bars having a plurality of lines extending
between the bus bars. Upon the application of a voltage to the
heater grid, a current will flow through the grid lines from one
bus bar to the other. As a result, the grid lines will heat up via
resistive heating.
[0011] Further objects, features and advantages of this invention
will become readily apparent to persons skilled in the art after a
review of the following description, with reference to the drawings
and claims that are appended to and form a part of this
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of an automobile having a
window panel assembly embodying the principles of the present
invention;
[0013] FIG. 2 is a diagrammatic representation of a heater grid
incorporated into a window panel assembly embodying the principles
of the present invention;
[0014] FIG. 3A is a diagrammatic sectional view of a portion of the
window assembly generally taken along lines 3-3 in FIG. 2;
[0015] FIG. 3B is a cross sectional view similar to FIG. 3A of the
window assembly and further having a coating layer on both sides of
the window assembly;
[0016] FIG. 3C is a diagrammatic sectional view similar to FIG. 3A
of the window assembly and further having a light emissive
layer;
[0017] FIG. 3D is a diagrammatic sectional view of similar to FIG.
3A of the window assembly and further having a light emissive layer
and a weathering layer; and
[0018] FIG. 4 illustrates a method of making the window assembly
embodying the principles of the present invention.
DETAILED DESCRIPTION
[0019] Referring to FIG. 1, an automobile 10 incorporating the
present invention is shown therein. The automobile 10 has an
occupant compartment 11 located within. The automobile 10 includes
a window defroster assembly 12 mounted via a frame 14 to the
automobile 10.
[0020] Although this description describes using the window
defroster assembly 12 as a rear window, the invention is equally
applicable to other areas of the automobile 10. For example, the
window defroster assembly 12 may be appropriately located and
dimensioned to be used as a driver side window, a passenger side
window, rear windows, a front windshield and/or any other windows
the automobile 10 may have.
[0021] Referring to FIG. 2, a more detailed view of the window
defroster assembly 12 is shown. The window defroster assembly 12
includes a heater grid 16 having a series of grid lines 18
extending between generally opposed bus bars 20, 22. As further
discussed below, the heater grid 16 is embedded within the window
defroster assembly 12.
[0022] The bus bars 20, 22 are respectively designated as positive
and negative bus bars. The bus bars 20, 22 each are accordingly
coupled in one or more places to leads 24, 26. Lead 24 is coupled
to a positive terminal 30 of a voltage source 28, while lead 26 is
coupled to a negative (ground) terminal 32 of the a voltage source
28, thereby establishing an electric circuit. The voltage source 28
may be the electrical system of the automobile 10. Such an
electrical system is typically a 12 volt system. Upon the
application of voltage to the heater grid 16, a current will flow
through the grid lines 18 from the positive bus bar 20 to the
negative bus bar 22 and, as a result, the grid lines 18 will heat
up via resistive heating.
[0023] Referring to FIG. 3A, a cross section of a portion of the
window defroster assembly 12, generally taken along lines 3-3 in
FIG. 2, is shown therein. The window defroster assembly 12 includes
a substrate 34 having a first side 36 and a bottom side 38.
Generally, the second side 38 of the substrate 34 faces towards the
occupant compartment 11 of the automobile 10 while the first side
36 of the substrate 34 faces away from the occupant compartment 11
of the automobile 10. The substrate 34 may be made of polycarbonate
(PC), polymethylmethyacrylate (PMMA), polyester, thermoplastic
polyurethane (TPU), PX/polyester blends, PC/ABS or PC/ASA blend
with/without glass fibers, and any combination thereof. Preferably,
the substrate 34 is transparent.
[0024] Located above the first side 36 of the substrate 34 is a
light control assembly 39. In this embodiment, the light control
assembly 39 includes a light control layer 42, a first plastic film
40 and/or a second plastic film plastic film 41. In one embodiment,
the light control assembly 42 is sandwiched between the first
plastic film 40 and the second plastic film plastic film 42.
Generally, the first and second plastic films 40, 41 are made of at
least PC, PMMA polyester, TPU, and combinations thereof.
[0025] The light control layer 42 may be made of a photochromic, an
electrochromic or a thermochromic device, or a solar control
device. The photochromic material is a material that changes from
being transparent to less transparent or even opaque when the
photochromic material is exposed to light and reverts to
transparency when the light is dimmed or blocked. The
electrochromic layer may be multi-layer system, is at least one of
liquid-crystal based, suspended particle device (SPD) based,
inorganic, organic, or hybrid based materials.
[0026] The electrochromic device consists of a sandwich of
materials. One embodiment of this sandwich but not limited to this,
comprises two electrode layers sandwiching an ion storage layer, an
ion conductor/electrolyte layer and an electrochromic material
layer. The photochromic can be single or multi-layer, it is at
least one of TPU, PC, PMMA, polyester or other transparent
thermoplastic or thermosetting material/component further
comprising photochromic dyes or pigments or additives. When a
voltage is applied to the electrochromic device a small electric
charge consisting of ions flows from the ion storage layer into the
electrochromic material layer via the ion conductor/electrolyte
layer thus causing a chemical reaction in the electrochromic
material layer which results in a change from transparent to less
transparent or even opaque. When the voltage direction is reversed
the ions flow back to the ion storage layer so that the
electrochromic device reverts to transparency.
[0027] The thermochromic device contains materials change
reversibly color with changes in temperature, or allow for a visual
response to changes in temperature. When the temperature is raised
to a specified temperature the pigment goes from colorless or light
color to colored or dark color. The pigment returns to the original
color as it cools down. The thermochromic material can be made as
semi-conductor compounds, from liquid crystals or using metal
compounds, or organic pigments which are composed of micro
capsules.
[0028] The solar control device may utilize solar absorbing
pigment/additive or solar reflective coating/ink/pigment to control
the amount of infrared light into the occupant compartment of the
vehicle. A solar control layer suitable for incorporation in the
present invention is described in U.S. application Ser. No.
11/450,732, which is herein incorporated by reference and is
commonly owned.
[0029] Located between the light control assembly 39 and the first
side 36 of the substrate 34 is the heater grid 16. The heater grid
16 may include all or a portion of the grid lines 18 and the bus
bars 20, 22 as best shown in FIG. 2. The heater grid 16 may be
printed directly onto the first plastic film 40 and/or the light
control layer 42. Printing may be affected using a conductive ink
or paste and any method known to those skilled in the art
including, but not limited to, screen-printing, pad printing, ink
jet, or automatic dispensing. Automatic dispensing includes
techniques known to those skilled in the art of adhesive
application, such as drip & drag, streaming, and simple flow
dispensing. Additionally or alternatively, an antenna trace similar
to the heater grid 16, may be printed directly on the plastic film
40 and/or the light control layer 42.
[0030] The heater grid 16 may be formed from any conductive
material including conductive pastes, inks, paints, coatings,
wires/thin wires, or films known to those skilled in the art. If
the conductive element is a paste, ink, or paint, it is preferred
that they include conductive particles (and nano-particles),
flakes, or powders dispersed in a polymeric matrix. This polymeric
matrix is preferably an epoxy resin, a polyester resin, a polyvinyl
acetate resin, a polyvinylchloride resin, a polyurethane resin or
mixtures, blends, and copolymers of the like.
[0031] The conductive particles, flakes or powders may be of a
metal including, but not limited to, silver, copper, zinc,
aluminum, magnesium, nickel, tin, or mixtures and alloys of the
like, as well as any metallic compound, such as a metallic
dichalcongenide. These conductive particles, flakes, or powders may
also be any conductive organic material known to those skilled in
the art, such as polyaniline, amorphous carbon, carbon-graphite and
carbon nanotubes. Although the particle size of any particles,
flakes, or powders may vary, a diameter of less than about 40 .mu.m
is preferred with a diameter of less than about 1 .mu.m being
specifically preferred. Any solvents, which act as the carrier
medium in the conductive pastes, inks, or paints, may be a mixture
of any organic that provides solubility for the organic resin.
Examples of metallic pastes, inks, or paints include silver-filled
compositions commercially available from DuPont Electronic
Materials, Research Triangle Park, N.C. (5000 Membrane Switch, 5029
Conductor Composition, 5021 Silver Conductor, and 5096 Silver
Conductor), Acheson Colloids, Port Huron, Mich. (PF-007 and
Electrodag SP-405), Methode Engineering, Chicago, Ill. (31-1A
Silver Composition, 31-3A Silver Composition), Creative Materials
Inc., Tyngsboro, Mass. (118-029 2k Silver), and Advanced Conductive
Materials, Atascadero, Calif. (PTF-12).
[0032] An ink layer 44 may be disposed between the heater gird 16
and the first plastic film 40 and/or the light control layer 42.
The ink layer 44 may be disposed such that to cover areas of the
heater grid 16, such as the bus bars 20, 22 from view.
Additionally, the ink layer 44 may be stylized in such a way to
provide for manufacturers to differentiate their window defroster
assembly 12 from competitors. As such, the ink layer 44 may be
stylized in any one of a number of patterns.
[0033] Placed above the light control assembly 39 are an optional
first weathering layer 46 and a first plasma layer 48 respectively.
The first weathering layer 46 may be a material that includes the
basic chemistry of acrylic, polyurethane, siloxane, or a
combination of these materials to provide high weatherablity and
long term ultraviolet. Further, the first weathering layer 46 may
also include a material having lonomer or flouropolymer chemistry
or similar material. Moreover, in another embodiment of the present
invention silicon/nanoparticles may be blended into the material of
the first weathering layer 46 or a silioxyane copolymer is formed
into the weathering layer 46 by polymerization. The weathering
layer 46 may be applied by one method selected from the group of
flow coating, dip coating, spray coating, in-mold coating, curtain
coating, and the like. If it's a weathering film, the weathering
layer 46 is produced by extrusion, co-extrusion, lamination,
extrusion-lamination, extrusion-coating, roller-coating, and the
like. The weathering layer 46 may include ultraviolet
absorbers.
[0034] The first plasma layer 48 is a "glass-like" coating
deposited on the weathering layer 46 by plasma enhanced chemical
vapor deposition (PECVD) process, expanding thermal plasma PECVD,
plasma polymerization, photochemical vapor deposition, ion beam
deposition, ion plating deposition, cathodic arc deposition,
sputtering, evaporation, hollow-cathode activated deposition,
magnetron activated deposition, activated reactive evaporation,
thermal chemical vapor deposition, and a sol-gel coating process or
the like. An optional second weathering layer 46' and a second
plasma layer 48' may be deposited on the second side 38 of the
substrate 34. The plasma layers 48, 48' may be multiple layers and
may contain an ultraviolet absorber.
[0035] The plasma layers 48, 48' may be made of aluminum oxide,
barium fluoride, boron nitride, hafnium oxide, lanthanum fluoride,
magnesium oxide, scandium oxide, silicon monoxide, silicon dioxide,
silicon nitride, silicon oxy-nitride, silicon oxy-carbide,
hydrogenated silicon oxy-carbide, silicon carbide, tantalum oxide,
titanium oxide, tin oxide, yttrium oxide, zinc oxide, zinc
selenide, zinc sulphide, zirconium oxide, and zirconium titanate.
Furthermore, the plasma layers 58, 60 may comprise multiple
sub-layers differing in composition or structure.
[0036] Referring to FIG. 3B, an alternative embodiment of the
window defroster assembly 12 is shown. This embodiment is similar
to the embodiment shown in FIG. 3A. The difference is that this the
light control assembly 39 does not include the first and second
plastic film 40, 41.
[0037] Referring to FIG. 3C, another alternative construction for
the window defroster assembly 12 is shown. While this embodiment is
similar to the embodiment shown in FIG. 3A, it varies in that it
includes a light emissive layer 50 and a plastic film layer 51
located between the second side 38 of the substrate 34 and the
second plasma layer 48'. The light emissive layer 50 may emit light
through the plastic film layer 51 to the second plasma layer 48'
and into the occupant compartment 11 of the automobile 10 as best
shown in FIG. 1. A light emissive layer 50 suitable for
incorporation in the present invention is described in U.S.
application Ser. No. 11/317,587 which is herein incorporated by
reference and is commonly owned.
[0038] Referring to FIG. 3D, another alternative construction for
the window defroster assembly 12 is shown. While this embodiment is
similar to the embodiment shown in FIG. 3B, it varies in that it
includes a light emissive layer 50 and a plastic film layer 51
located between the second side 38 of the substrate 34 and the
second plasma layer 48'. The light emissive layer 50 may emit light
through and the plastic film layer 51 to the second plasma layer
48' and into the occupant compartment 11 of the automobile 10 as
best shown in FIG. 1.
[0039] Referring to FIG. 4, a method 60 of producing the window
assembly 12 is shown. First, as indicated by block 62, the light
control assembly is formed. The light control assembly may be
formed by extrusion, co-extrusion, lamination,
extrusion-lamination, printing, coating, solvent casting,
sputtering, electrochemical deposition, or similar process.
[0040] As shown in block 64, an ink layer and heater grid may be
applied to the light control assembly. The stylized ink layer and
the heater grid may be applied by screen printing, pad printing,
membrane image transfer printing, transfer printing, ink jet
printing, digital printing, robotic dispensing, or mask and spray.
Optionally, as indicated by block 66, the light control assembly
may be thermoformed. This thermoforming process may be done by
vacuum thermoforming, pressure assisted thermoforming, drape
forming or cold forming.
[0041] Thereafter, as shown in blocks 68 and 70, the light control
assembly is then trimmed and positioned to fit in a mold cavity.
Once in the mold cavity, as shown in block 72, the light control
assembly is back molded with a substrate material. This may be
accomplished by utilizing injection molding, compression molding,
injection-compression molding, multi-component molding, multi-color
molding or multi-material molding process. The same method may
apply when incorporating a light emissive layer.
[0042] Afterwards, as indicated by blocks 74 and 76, the light
control assembly and substrate material are hot melted, thereby
forming the window panel, which is then removed from the mold
cavity. As shown in block 78, an optional weathering layer may be
applied to the window assembly. Thereafter, a plasma coating is
applied to the window assembly via a PECVD process as shown in
block 80.
[0043] The method 60 may also be executed when incorporating a
light emissive layer. This act would include the steps of the
forming a light emissive assembly, trimming the light emissive
assembly, position the light emissive assembly in the mold cavity,
back molding the light emissive assembly to the plastic substrate
material, melt bonding the light emissive assembly to form the
window assembly, removing the window assembly from the mold cavity,
and applying a plasma coating on at least one side of the window
assembly.
[0044] As a person skilled in the art will readily appreciate, the
above description is meant as an illustration of implementation of
the principles of this invention. This description is not intended
to limit the scope or application of this invention in that the
invention is susceptible to modification, variation and change,
without departing from spirit of this invention, as defined in the
following claims.
* * * * *