U.S. patent number 5,122,403 [Application Number 07/332,840] was granted by the patent office on 1992-06-16 for windshield edge seal.
This patent grant is currently assigned to PPG Industries, Inc.. Invention is credited to George H. Bowser, Bruce A. Connelly, Amy M. Roginski.
United States Patent |
5,122,403 |
Roginski , et al. |
June 16, 1992 |
**Please see images for:
( Certificate of Correction ) ** |
Windshield edge seal
Abstract
A laminated transparency with an electroconductive coating
positioned within the laminate. An edge coating composition is
applied about the periphery of the laminate to seal the edge of the
coating and prevent coating degradation.
Inventors: |
Roginski; Amy M. (New
Kensington, PA), Connelly; Bruce A. (Gibsonia, PA),
Bowser; George H. (New Kensington, PA) |
Assignee: |
PPG Industries, Inc.
(Pittsburgh, PA)
|
Family
ID: |
23300083 |
Appl.
No.: |
07/332,840 |
Filed: |
April 3, 1989 |
Current U.S.
Class: |
428/38;
52/786.12; 219/203; 427/165; 156/107; 219/522 |
Current CPC
Class: |
B32B
17/10036 (20130101); B32B 17/10302 (20130101); B32B
17/10174 (20130101) |
Current International
Class: |
B32B
17/10 (20060101); B32B 17/06 (20060101); B32B
017/10 (); B32B 031/12 () |
Field of
Search: |
;52/788-790
;156/99,100,107,109 ;219/203,522 ;427/163-165 ;428/34,38 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Jack Yamaguchi "Insulating rear glass lowers interior temperature",
Automotive Engineering, Apr. 1985..
|
Primary Examiner: Dawson; Robert A.
Attorney, Agent or Firm: Siminerio; Andrew C. Lepiane;
Donald C.
Claims
We claim:
1. In a laminated vehicular transparency of the type having a pair
of glass plies laminated together, a conductive coating between the
plies with portion of the coating extending to a peripheral edge of
the transparency, and external conductive means providing external
electrical access to the coating, the improvement comprising:
a weather resistant sealant completely around the peripheral edge
of the transparency to seal the edge of the glass plies to protect
the coating against degradation caused by exposure to the
environment, said sealant is non-reactive with the coating, the
plies and materials between the plies and is selected from a group
consisting of a polybutene copolymer based coating composition and
a butyl based composition.
2. A laminated assembly comprising:
first and second plies;
a coating positioned between the plies with portions of the coating
extending to a peripheral edge of the assembly; and
a sealant on selected portions of the peripheral edge to isolate
the coating at the edge from the environment, wherein the sealant
is a weather resistant, non-reactive material selected from a group
consisting of a polyvinylidene flouride based coating composition
and a butane octane based coating composition to protect the
coating against degradation caused by exposure to the
environment.
3. The assembly as in claim 2 wherein said plies are glass plies
with said coating positioned therebetween.
4. The assembly as in claim 2 wherein said coating is an
electroconductive coating.
5. The assembly as in claim 3 wherein said coating is disposed
between first and second interlayer plies positioned between said
first and second glass plies.
6. The assembly as in claim 3 further including means to direct an
electric current through said coating to heat said coating and said
assembly.
7. The assembly as in claim 6 wherein said sealant is a
non-electroconductive material.
8. The assembly as in claim 7 wherein said directing means includes
first and second bus bars positioned along opposite sides of and
interconnected by said coating.
9. The assembly as in claim 8 wherein said coating and said bus
bars are on a major surface of said first glass ply.
10. The assembly as in claim 8 wherein said coating is disposed
between first and second interlayer plies positioned between said
first and second glass plies.
11. The assembly as in claim 2 wherein said sealant material is a
polyvinylidene fluoride based coating composition.
12. The assembly as in claim 2 wherein the coating composition
comprises a, a thermoplastic acrylic resin and an epoxy silane.
13. A laminated assembly comprising:
first and second plies;
a coating positioned between the plies with portions of the coating
extending to a peripheral edge of the assembly; and
a sealant on selected portions of the peripheral edge to isolate
the coating at the edge from the environment, wherein the sealant
comprises an isotatic thermoplastic polyolefin, a high molecular
weight polyisobutylene resin, and a saturated hydrocarbon resin to
protect the coating against degradation caused by exposure to the
environment.
14. A laminated assembly comprising:
first and second plies;
a coating positioned between the plies with portions of the coating
extending to a peripheral edge of the assembly; and
a sealant on selected portions of the peripheral edge to isolate
the coating at the edge from the environment, wherein the sealant
comprises an isobutylene based elastomer, a high molecular weight
polyisobutylene resin, and a saturated hydrocarbon resin to protect
the coating against degradation caused by the environment.
15. In a method of fabricating a coated laminate including the
steps of applying a coating between a pair of opposing plies and
securing said plies to each other such that the coating is
positioned therebetween, wherein portions of the coating extend to
the peripheral edge of the laminate and are exposed to the
environment, the improvement comprising:
applying a weather resistant, non-reactive sealant selected from a
group consisting of a polyvinylidene flouride based coating
composition and a butane octane based coating composition to the
exposed edge of the coating to prevent degradation of the coating
caused by exposure to the environment.
16. The method as in claim 15 wherein said sealant applying step
includes applying said sealant to said exposed coating edge and to
a marginal edge portion of said coating adjacent said exposed
coating edge, prior to said securing step.
17. The method as in claim 15 wherein said plies are glass plies
and said sealant applying step includes applying said sealant to a
marginal portion of one of said glass plies.
18. In a method of fabricating a coated laminate including the
steps of applying a coating between a pair of opposing plies and
securing said plies to each other such that the coating is
positioned therebetween, wherein portions of the coating extend to
the peripheral edge of the laminate and are exposed to the
environment, the improvement comprising:
applying a weather resistant, non-reactive, isotatic thermoplastic
polyolefin, a high molecular weight polyisobutylene resin and a
saturated hydrocarbon resin sealant to the exposed edge of the
coating to prevent degradation of the coating caused by exposure to
the environment.
19. The method as in claim 18 wherein said sealant applying step
includes applying the sealant to the exposed coating edge and to a
marginal edge portion of the coating adjacent the exposed coating
edge, and said sealant applying step is practiced prior to said
securing step.
20. The method as in claim 18 wherein the plies are glass plies and
said sealant applying step includes applying the sealant to a
marginal portion of one of the glass plies.
21. In a method of fabricating a coated laminate including the
steps of applying a coating between a pair of opposing plies and
securing the plies to each other such that the coating is
positioned therebetween, wherein portions of the coating extend to
the peripheral edge of the laminate and are exposed to the
environment, the improvement comprising:
applying a weather resistant, non-reactive isobutylene based
elastomer, a high molecular weight polyisobutylene resin, and a
saturated hydrocarbon resin sealant to the exposed edge of said
coating to prevent degradation of the coating caused by exposure to
the environment.
22. The method as in claim 21 wherein said sealant applying step
includes applying the sealant to the exposed coating edge and to a
marginal edge portion of said coating adjacent said exposed coating
edge, said sealant applying step is practiced prior to said
securing step.
23. The method as in claim 21 wherein the plies are glass plies and
said sealant applying step includes applying the sealant to a
marginal portion of one of the glass plies.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a laminated transparency having an edge
seal and in particular to an edge seal for a laminated windshield
having an electroconductive coating between the outer plies of the
windshield.
2a. Technical Considerations
It is well known to coat a major surface of a transparency, e.g. a
glass sheet, with a transparent film to enhance the spectral
properties of the transparency. For example, the film may be used
to reduce the amount of infrared (IR) radiation transmitted through
the transparency by reflecting a predetermined bandwidth of
radiation. This reduction is especially useful where the
transparency is installed in a vehicle, such as an automotive
windshield, since the IR radiation is a major cause of heat
build-up in a vehicle. The resulting reduction in heat build-up
reduces the burden on the vehicle's air conditioning system to
maintain a comfortable temperature within the vehicle for its
occupants. In addition, if the film is electroconductive, a current
may be passed through the film to raise the temperature of the
transparency. The elevated temperature of the windshield will melt
any ice or snow that accumulates on an exposed surface of the
windshield.
In fabricating a laminated transparency such as a windshield with a
film positioned between the glass plies, the film can be applied to
a flat glass sheet which is subsequently shaped and laminated to a
matching glass ply or the film may be applied to a bent glass ply
which is then laminated to a matching ply. It has been found that
when the film extends to the edge of the laminate, it may degrade
due to exposure to the environment. In particular, where the film
contains a silver layer, it has observed that sodium chloride from
salts will react with the silver forming silver chloride. In
addition, high humidity conditions have been found to cause the
silver in the silver layer to form aggregates. The results of
either or both of these conditions is discoloration of the film,
reduced effectiveness of the film as a IR radiation reflecting or
heating film, and/or possible delamination of the windshield. The
marginal edge of the coated glass ply may be masked, for example
with tape prior to coating the glass so that after the coating
operation, the tape is removed, leaving an uncoated marginal edge.
However, this type of processing requires precise positioning of
the tape prior to coating and removal of the tape after coating as
well as introducing the possibility of contaminating the film
during a coating operation.
It would be advantageous to provide a material to seal the
periphery of a coated laminate to prevent degradation of its film
coating.
2b. Patents of Interest
U.S. Pat. Nos. 3,752,348 to Dickason et al.; 4,543,466, 4,668,270,
and 4,743,741 to Ramus; 4,654,067 and 4,725,710 to Ramus et al.;
4,718,932 to Pharms; 4,744,844 to Hurst; 4,778,732 to Hasegawa et
al. and 4,786,784 to Nikodem et al. teach a heatable windshield
with opposing bus bars interconnected by an electroconductive
coating on an interior glass surface of the windshield.
U.S. Pat. No. 3,790,752 to Boaz et al. teaches a heatable laminated
windshield wherein the electrical connection to the electrically
conductive coating of the windshield is made within a notch in the
windshield interlayer material.
U.S. Pat. Nos. 3,794,809 to Beck et al.; 4,368,945 Fujimori et al.
and 4,782,216 to Woodward teach a vehicle windshield with an
electroconductive coating disposed between first and second
laminating interlayers. In Beck et al., the coating is spaced
inwardly from the edge of the glass plies of the windshield a
sufficient amount to seal the coating within the interlayer.
U.S. Pat. No. 4,278,875 to Bain teaches an electrically heated
window with a tin oxide coating extending to the edge of the
window. The edge of the window is seal by an elastomeric sealant
and a peripheral channel.
U.S. Pat. No. 4,284,677 to Herliczek teaches an electrically heated
laminated aircraft glazing with an electroconductive coating. A
layer of polyisobutylene resin is provided between the interlayer
material and selected glass areas to prevent delamination and cold
chipping of the glazing with subsequent moisture ingress and bus
bar failure.
SUMMARY OF THE INVENTION
The present invention covers a laminated transparency having a
coating between the outer plies of the transparency. The coating is
of the type that will degrade when exposed to prolonged adverse
weather conditions, such as high salt and/or humidity. A sealant is
applied about the periphery of the coating to protect any exposed
edge portion of the coating from degradation. The sealant is a
weather resistant material that will adhere to glass and interlayer
material and will not react with the glass, interlayer material, or
coating of the transparency or any adhesives used to secure the
transparency in place.
In one particular embodiment of the invention, the coating includes
at least one silver containing film layer and the sealant may be a
polybutene copolymer based coating composition, a fluoropolymer
based coating composition, or a butyl based composition. The
coating may be used to reduce the level of infrared radiation that
can pass through the laminate and/or an electric current carried by
the coating can heat the transparency.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a laminated transparency incorporating
features of the present invention, with portions removed for
clarity.
FIG. 2 is a view taken along line 2--2 of FIG. 1 with the view
inverted to show a sealant along the edge of the transparency.
FIG. 3 is a view similar to FIG. 2 showing an alternate embodiment
of the invention.
FIG. 4 is a plan view of a heatable laminated transparency
incorporating features of the present invention, with portions
removed for clarity.
FIG. 5 is a view taken along line 5--5 of FIG. 4 with the view
inverted to show a sealant along the edge of the transparency.
FIG. 6 is a view similar to FIG. 2 showing an alternate embodiment
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The description of the invention is taught in connection with a
laminated transparency comprised of two glass plies bonded together
by an interlayer of plastic, which represents a typical windshield
construction, but it is understood that the invention can apply to
transparencies having two plastic plies or any combination
involving numerous glass and/or plastic plies. The invention is not
limited to an automotive windshield but may be used in any
transparency where there is a problem of coating degradation along
an exposed edge.
FIGS. 1 and 2 show a transparency 20 which includes an outboard
glass sheet 22, a plastic interlayer 24 (shown only in FIG. 2)
which may be polyvinyl butyral as is commonly used for laminated
windshields or other suitable interlayer material, and an inboard
glass sheet 26 (shown only in FIG. 2). A coating 28 is preferably
placed on a surface of the transparency 20 that is not exposed,
most preferably on the inboard surface 30 of the outboard glass
sheet 22. Various coating configurations may be applied to the
surface 30, depending on the desired properties to be added to the
transparency 20. For example, although not limiting in the present
invention, coatings similar to those disclosed in U.S. Pat. No.
4,610,771 to Gillery, which teachings are hereby incorporated by
reference, have been used to reflect IR radiation and/or provide an
electroconductive film for a heatable windshield. These coatings
generally include one or more silver films between pairs of zinc
stannate films, each of which may be applied sequentially by
magnetron sputtering. An optional opaque border 32 (shown only in
FIG. 2), such as a ceramic enamel, may be applied about the
marginal edge of the transparency 20 in any well known manner, e.g.
screen printing, and heated to bond the border 32 to surface 30.
After coating, the interlayer 24 is positioned between the bent
glass sheets 22 and 26 and the entire assembly is laminated in any
convenient manner well known in the art to form a unitary
structure. As an alternative, the coating 28 may be applied to a
flat glass ply 22 which is subsequently bent to a desired
configuration.
With continued reference to FIGS. 1 and 2, edge sealant 34 is
applied about the peripheral edge 36 of the laminated transparency
20 to hermetically seal exposed edge 38 of the coating 28 and
isolate it from the environment. In particular, the sealant 34
should be a weather resistant material that provides good adhesion
to the glass plies 22 and 26 and interlayer 24 and prevents
moisture penetration through or under the sealant 34. The sealant
34 must also be non-reactive with the interlayer 24 and coating 28
and prevent penetration of any material that will react with the
interlayer 24 or coating 28. In particular, if the coating 28 is of
the type that includes a layer of silver, the sealant 34 must not
include and must seal against chlorine and/or sulfur containing
compounds, both of which will react with the silver and adversely
affect the coating's IR radiation and/or surface resistivity.
Furthermore, the sealant 34 is preferably a material that can be
easily applied to form a tack free, hermetic seal. The sealant must
also not affect or react with the adhesive system used to secure
the laminated transparency in position.
The following are working examples of preferred edge sealant
formulations.
EXAMPLE 1
Polybutene copolymer based coating compositions exhibit good
durability and weathering resistance. In particular, the butane
octane based coating composition described hereinbelow in Table 1
have been used as sealant to edge seal the periphery of
transparency 20.
TABLE 1 ______________________________________ Amount (Parts by
Weight) Materials A B Est. Min./Max
______________________________________ 1. DURAFLEX polybutene 8910
33.00 32.20 100 2. STATEX N-550 30.40 1.60 0-110 3. MOLECULAR SIEVE
13X -- 29.90 0-110 4. DOW CORNING Z-6030 0.13 -- 0.1-2.0 5. DOW
CORNING Z-6040 0.13 0.13 0.1-2.0 6. NUCREL 925 3.30 3.30 2-30 7.
VISTANEX LM, MS 16.50 16.30 20-70 8. ESCOREZ 1315 16.50 16.30 20-70
______________________________________ (1) DURAFLEX polybutene 8910
is the registered trademark of Shell Chemica Co. for a isotatic
thermoplastic polyolefin which contains 6% ethylene. (2) STATEX
N550 is the registered trademark of Columbian Chemical Co. for a
general purpose amorphous furnace black. (3) MOLECULAR SIEVE 13X is
the registered trademark of Union Carbide Corp for an aluminum
silicate, zeolitetype desiccant. (4), (5) DOW CORNING Z6030 and
Z6040 are the registered trademarks of Dow Corning Corp. for a
silane coupling agent; gamma methacryloxypropyltrimethoxysilane and
gama glycidoxypropyltrimethoxysilan, respectively. (6) NUCREL 925
is the registered trademark of E. I. DuPont deNemours & Co.,
Inc. for an ethylene carboxylic copolymer. (7) VISTANEX LM, MS is a
registered trademark of Exxon Chemical Co. for the high molecular
weight polyisobutylene resin. (8) ESCOREZ 1315 is the registered
trademark of Exxon Chemical Co. for a saturated hydrocarbon
resin.
These polybutene copolymer based coating compositions are
thermoplastic compositions that when heated to about 350.degree. F.
to 400.degree. F. (177.degree. C. to 204.degree. C.) have a
putty-like consistency which can then be applied to the peripheral
edge 36 of the transparency 20 in any convenient manner known in
the art, e.g. using a hot gun extruder. These compositions are 100%
solids so that no venting is required during mixing, application,
or curing and there are no noxious fumes from solvents. The
compositions cool to room temperature and will be tack-free within
5 minutes of application. However, since these materials are a
thermoplastic, it is expected that they will become soft if exposed
to temperatures exceeding about 200.degree. F. (93.degree. C.). The
thickness and shape of the sealant can be controlled to give the
required seal and, if required, protect the periphery of the
transparency 20 against impact.
EXAMPLE 2
Fluoropolymer based coating compositions such as those disclosed in
U.S. patent application Ser. No. 224,837 to Connelly et al., filed
on Jul. 27, 1988, provide excellent durability, resistance to
weather and good adhesion to glass surfaces. In particular, a
polyvinylidene fluoride (PVDF) based coating composition as
described hereinbelow in Table 2 has been used to edge seal the
periphery of the transparency 20.
TABLE 2 ______________________________________ Material Amount
(Parts by Weight) ______________________________________ Pigment
1.05 1. SHEPARD BLACK pigment Binder 2. thermoplastic acrylic resin
12.84 3. bentonite flow additive 0.09 4. UNION CARBIDE A-187 silane
1.94 5. TINUVIN 292 1.21 6. TINUVIN-P 0.39 7. 2-mercapto +
hiazoline 0.76 8. polyvinylidene fluoride 12.84 Solvent 9. toluene
29.15 10. ethanol 0.09 11. ethyl acetate 3.02 12. methal isobutyl
keytone 0.54 13. glycol ether PM acetate 36.08
______________________________________ (1) SHEPARD BLACK pigment is
a registered trademark fo Shepard Pigments for an iron oxide
pigment. (2) The thermoplastic acrylic resin is a copolymer of
ethyl acrylate and methyl methacrylate commercially available from
Rohm and Haas as ACRYLOID B44. (4) UNION CARBIDE A187 is a
registered trademark of Union Carbide Co. for an epoxy silane;
gamma glycidoxypropyltrimethoxy silane. (5) TINUVIN 292 is a
registered trademark of Ciba Geigy Corp. for a hinde amine light
stabilizer. (6) TINUVINP is a registered trademark of Ciba Geigy
Corp. for a UV light absorber.
Due to the volatile nature of the solvent system for this PVDF
based coating composition, venting is required to remove any
noxious fumes that are released during its application and curing.
The PVDF based coating may be applied at room temperature, will dry
tack-free in approximately 15 minutes, and will fully cure in about
120 hours. Drying and curing times can be reduced by increasing the
drying or curing temperature and/or decreasing the relative amount
of solids. The PVDF based coating composition will not flow when
exposed to temperatures of up to about 225.degree. F. (107.degree.
C.) which is the expected upper limit to which the transparency
will be exposed. The coating may be applied in any convenient
manner known in the art, e.g. a roller, dauber, or brush. Although
not limiting in the invention, the thickness of the coating on the
transparency should be about 1 mil (0.025 mm).
EXAMPLE 3
Butyl based coating compositions similar to that disclosed in U.S.
Pat. No. 4,593,175 to Bowser et al., which teachings are
incorporated by reference, have been used as vapor barriers. In
particular, the butyl based composition as described hereinbelow in
Table 3 may be used to seal the exposed coating edge in
transparency 20.
TABLE 3 ______________________________________ Amount (Parts by
Weight) Materials A B C D ______________________________________ 1.
BUTYL 165 100 100 100 100 2. VISTANEX LM, MS 30 30 30 30 3. STATEX
N-550 50 50 50 60 4. ZnO xx4 5 5 5 5 5. MOLECULAR SIEVE 13X -- --
-- 20 6. HI SIL EP -- -- -- 5 7. DOW CORNING Z-6040 -- -- -- 0.4 8.
ESCOREZ 1315 60 70 70 70 9. SP-1055 10 -- -- 70 10. VM&P
NAPHTHA 595 595 474 669 ______________________________________ (1)
BUTYL 165 is the registered trademark of Exxon Chemical Co. for an
isobutyleneisoprene elastomer (11R). (2) VISTANEX LM, MS is the
registered trademark of Exxon Chemical Company for a high molecular
weight polyisobutylene resin. (3) STATEX N550 is the registered
trademark of Columbian Chemical Co. for a general purpose amorphous
furnace black. (4) Zinc oxide xx4 grade is manufactured by New
Jersey Zinc Co. (5) MOLECULAR SIEVE 13X is the registered trademark
of Union Carbide Corp for an aluminum silicate, zeolitetype
desiccant. (6) HI SIL EP is the registered trademark of PPG
Industries, Inc. for a hydrated amorphous silica. (7) DOW CORNING
Z6040 is the registered trademark of Dow Corning Corp. fo a silane
coupling agent; gamma glycidoxypropyltrimethoxysilan. (8) ESCOREZ
1315 is the registered trademark of Exxon Chemical Co. for a
saturated hydrocarbon resin. (9) SP1055 is a registered trademark
of Schenectady Chemicals, Inc. for a bromomethylated alkyl phenol
formaldehyde resin. (10) VM&P NAPHTHA is varnish makers'
naphtha; a solvent with a narrow boiling point.
In testing these butyl based compositions, formulations A, B, and C
exhibited only marginal adhesion to a glass surface. The addition
of the Z-6040 silane to the formulation enhances adhesion. The
formulations will dry in approximately 5 minutes but still remain
tacky. Additional carbon black and/or filler material, such as e.g.
hydrated silica, can be added to the formulation to reduce tack.
The coating may be applied in any convenient manner known in the
art, e.g. brush, dauber, or rollers. Although not limiting in the
invention, the thickness of the coating on the transparency should
be about 1 mil (0.025 mm).
In operation, it is expected that the sealant 34 would be applied
to the laminated windshield 20 after the edge 36 has been trimmed
to remove any excess interlayer 24 that has been extruded about the
periphery of the transparency 20 during the laminating process.
As an alternative to applying the edge sealant 34 after lamination,
it may be applied about the peripheral edge of outer glass ply 22
before lamination. In particular, as shown in FIG. 3, after coating
28 has been applied to glass ply 22, edge sealant 40 may be applied
to the marginal area 42 and peripheral edge 44 of glass ply 22 to
seal the edge of the coating 28 and protect it from the environment
and chemical attack after lamination.
The sealant 34 may also be used to edge seal the periphery of a
heated laminated transparency. Referring to FIGS. 4 and 5,
laminated transparency 46 is a heatable windshield including an
outer glass ply 48, interlayer 50, inner glass ply 52, and
electroconductive coating 54 on inner surface 56 of outer ply 48.
The electroconductive coating 54 is powered by a bus bar and lead
arrangement which, although not limiting in the present invention,
is similar to the double feed bus bar arrangement disclosed in U.S.
patent application Ser. No. 138,008 to Gillery filed on Dec. 28,
1987, which teachings are incorporated by reference. In particular,
a bottom bus bar 58 and top bus bar 60 (shown only in FIG. 4) are
positioned on surface 56 along opposing edges of outer glass ply 48
and are electrically interconnected by electroconductive coating
54. Electrical power from a power source 62 to bottom bus bar 58
and top bus bar 60 is made at terminal 64 through lead 66 and leads
68 and 70, respectively. Although not limiting in the present
invention, the bus bars and leads are preferably a silver
containing ceramic material that is applied to glass ply 48 or a
ceramic border 72 (shown only in FIG. 5) in any convenient manner,
e.g. screen printing, and heated to bond them to the underlying
glass or border.
The leads 68 and 70 are electrically insulated from the coating 54
and bottom bus bar 58 by a mask 74 (shown only in FIG. 5), such as
e.g. a ceramic paint. Referring to FIG. 5, the coating 54 extends
over the mask 74 to the edge 76 of the transparency 46 while
remaining electrically insulated from the leads 68 and 70 (lead 70
is not shown in FIG. 5). Sealant 78 is applied about the peripheral
edge 76 of transparency 46 to seal exposed edge 80 of coating
54.
Because an electrical current is passed through coating 54 in the
heated windshield, it is obvious that the sealant 78 must also be
non-electroconductive so as to electrically insulate the exposed
edge 80 and prevent shorting of the heated coating 54.
The present invention has been presented with a laminated
transparency having a coating on an inner glass surface of the
transparency but based on the teachings of this disclosure, it
would be obvious to one skilled in the art to use the sealant in
combination with any assembly with an exposed coating edge. In
particular, referring to FIG. 6, transparency 82 includes glass
plies 84 and 86 and interlayers 88 and 90. Coating 92 is disposed
between interlayers 88 and 90 of the laminate 82 as disclosed in
U.S. Pat. Nos. 4,368,945 to Fujimori et al. and 4,782,216 to
Woodard, which teachings are incorporated by reference. Sealant 94
is applied to the exposed edge 96 of a coating 92 to seal it
against environmental conditions that could adversely affect the
coating.
The present invention provides a laminated transparency having a
coating therein that is protected against moisture and chemical
attack about its perimeter so as to maintain the integrity of the
coating and the transparency. The form of the invention shown and
described in this specification represents illustrative preferred
embodiments and it is understood that various changes may be made
without departing from the spirit of the invention as defined in
the following claimed subject matter.
* * * * *