U.S. patent application number 09/873851 was filed with the patent office on 2001-10-11 for method for producing a laminated glass pane free of optical obstruction caused by warping, use of a particular carrier film for the production of the laminated glass pane and carrier films particularly suitable for the method or the use.
Invention is credited to Costa, Peter.
Application Number | 20010028940 09/873851 |
Document ID | / |
Family ID | 7772375 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010028940 |
Kind Code |
A1 |
Costa, Peter |
October 11, 2001 |
Method for producing a laminated glass pane free of optical
obstruction caused by warping, use of a particular carrier film for
the production of the laminated glass pane and carrier films
particularly suitable for the method or the use
Abstract
The invention relates to a method for producing a laminated
glass pane free of optical obstruction, caused by warping, in
reflected and transmitted light. The laminated glass pane comprises
a first pane of glass, a second pane of glass and a multilayer
spacer layer comprising a first composite film, a
biaxially-stretched, thermoplastic carrier film provided with a
thin layer system, and a second composite film. A carrier film
provided with the thin layer system is mounted on the first
composite film and has a thickness of from 30 to 70 .mu.m and a
degree of heat shringage of from 0.3 to 0.8%, measured after a heat
treatment of 20 seconds at 120.degree. C., in both directions. The
second composite film is mounted on the carrier film. The packet of
films is arranged between the two panes of glass so as to be
wrinkle-free, pressed using pressure and heat and made into a
composite with the panes of glass. A suitable carrier film and the
use thereof for producing the laminated pane of glass are also
disclosed.
Inventors: |
Costa, Peter; (Witten,
DE) |
Correspondence
Address: |
Donald A. Schurr
Marshall & Melhorn, LLC
8th Floor
Four SeaGate
Toledo
OH
43604
US
|
Family ID: |
7772375 |
Appl. No.: |
09/873851 |
Filed: |
June 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09873851 |
Jun 4, 2001 |
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09043366 |
Jul 31, 1998 |
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6242088 |
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Current U.S.
Class: |
428/106 ;
156/102; 428/332; 428/339 |
Current CPC
Class: |
B32B 17/10036 20130101;
B32B 17/10963 20130101; B32B 17/10807 20130101; B32B 27/36
20130101; B32B 17/10761 20130101; Y10T 428/269 20150115; Y10T
428/26 20150115; B32B 17/10788 20130101; Y10T 428/24066 20150115;
G03C 2200/51 20130101; B32B 17/10005 20210101; B32B 2367/00
20130101 |
Class at
Publication: |
428/106 ;
428/339; 428/332; 156/102 |
International
Class: |
B32B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 1995 |
DE |
DE 195 34 420.0 |
Claims
1. A process for the manufacture of a laminated safety glass pane
which in reflected and/or transmitted light is free from
wrinkle-related optical distortions, comprising a first glass pane,
a corresponding second glass pane and a multi-layer intermediate
layer, which intermediate layer in the form of a foil laminate
consists of a first laminating foil, a bi-axially stretched
thermoplastic carrier foil provided with a thin-film system, and a
second laminating foil, with the characteristics: 1.1) Placed on
the first laminating foil is a carrier foil provided with the
thin-film system, which 1.11) has a thickness of 30 to 70 .mu.m and
1.12) in both stretching directions displays a heat shrinkage
degree of 0.3 to 0.8%, measured after a heat treatment of 20
seconds at 120.degree. C., and the second laminating foil is placed
on the carrier foil, 1.2) the foils according to characteristic
1.1) are arranged wrinkle-free between the two glass panes and
pressed, using pressure and heat, as well as joined to the glass
panes, wherein within the framework of the measures according to
1.1) and/or 1.2) at least one deaeration is carried out.
2. A process according to claim 1, wherein on the first glass pane
a pre-laminate consisting of the first laminating foil and the
carrier foil is placed and the second laminating foil is placed on
the pre-laminate.
3. A process according to claim 2, wherein after applying the
pre-laminate, a pre-pressing is carried out using pressure and
heat, and subsequently the second laminating foil is put on and
pressed.
4. A process according to claim 1, wherein onto the first glass
pane the first laminating foil, the carrier foil and the second
laminating foil, a pre-laminate of these foils is applied and
subsequently the pressing is carried out.
5. A process according to claim 1, wherein on the first laminating
foil a carrier foil provided with the thin-film system is placed,
the heat shrinkage degree of which according to characteristic
1.12) and 2.12) respectively lies in the range of 0.3 to 0.6%.
6. A process according to claim 1, wherein on the first laminating
foil a carrier foil is placed, which has a thickness of 40 to 60
.mu.m, preferably approximately 50 .mu.m.
7. A process according to claim 1, wherein on the first laminating
foil a carrier foil provided with the thin-film system is placed,
which on both surfaces has a surface energy of at least 40
mJ/m.sup.2.
8. A process according to claim 1, wherein laminating foils are
used based on polyvinyl butyral or ethylenevinyl acetate and a
carrier foil of polyethylene terephthalate.
9. A process according to claim 1, wherein the pressing according
to characteristic 1.1) is carried out at a temperature in the range
of 115 to 135.degree. C. with a pressure of maximum 13 bar.
10. Use of a carrier foil of stretched thermoplastic plastic
provided with a thin-film system, which carrier foil has a
thickness of 30 to 70 .mu.m as well as a bi-axial stretching, for
the manufacture of laminated safety glass panes, in particular for
the manufacture of laminated safety glass panes which in reflected
and/or transmitted light are free from wrinkle-related optical
distortions, comprising a first glass pane, a corresponding second
glass pane and a multi-layer intermediate layer in the form of a
foil laminate consisting of a first laminating foil, the bi-axially
stretched carrier foil and a second laminating foil, wherein the
carrier foil in both stretching directions displays a heat
shrinkage degree of 0.3 to 0.8%, measured after a heat treatment of
20 seconds at 120.degree. C.
11. Use according to claim 10 wherein the heat shrinkage degree of
the carrier foil lies in the range of 0.3 to 0.6%.
12. Stretched carrier foil of thermoplastic plastic provided with a
thin-film system for carrying out the process according to claim 1,
which has a thickness of 30 to 70 .mu.m and in both stretching
directions a heat shrinkage degree of 0.3 to 0.8%, measured after a
heat treatment of 20 seconds at 120.degree. C.
13. Stretched carrier foil of thermoplastic plastic provided with a
thin-film system for the use according to claim 10, which has a
thickness of 30 to 70 .mu.m and in both stretching directions a
heat shrinkage degree of 0.3 to 0.8%, measured after a heat
treatment of 20 seconds at 120.degree. C.
14. Stretched carrier foil according to claim 10, which has a
thickness of 40 to 60 .mu.m.
15. Stretched carrier foil according to claim 12, which on both
surfaces has a surface energy of at least 40 mJ/m.sup.2.
16. Stretched carrier foil according to claim 12, which comprises
polyethylene terephthalate.
17. Stretched carrier foil according to claim 14, which has a
thickness of approximately 50 .mu.m.
18. Stretched carrier foil of thermoplastic plastic provided with a
thin-film system adapted for use in a laminated safety glass pane,
which has a thickness of 30 to 70 .mu.m and in both stretching
directions a heat shrinkage degree of 0.3 to 0.8%, measured after a
heat treatment of 20 seconds at 120.degree. C.
Description
RELATED APPLICATION
[0001] This application is a continuation of application Ser. No.
09/043,366 filed Jul. 31, 1998, which is hereby incorporated by
reference. This application is claiming the benefit under 35 U.S.C.
.sctn.120 of said Application.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a process for the manufacture of a
laminated safety glass pane which in reflected and transmitted
light is free from wrinkle-related optical distortions, comprising
a first glass pane, a second glass pane and a multi-layer
intermediate layer, which intermediate layer in the form of a foil
laminate consists of a first laminating foil, a bi-axially
stretched thermoplastic carrier foil provided with a thin-film
system, and a second laminating foil. The invention furthermore
relates to the use of a carrier foil for the manufacture of the
laminated safety glass pane as well as to a carrier foil
particularly suitable for the process and the use respectively. The
laminated safety glass panes may be either flat or curved panes.
The flat laminated safety glass panes are used for a great variety
of applications, e.g. in the building industry or as side windows
of motor vehicles. The term curved laminated safety glass panes
denotes, within the framework of the invention, singly curved and,
in particular, double curved (spherically bent) laminated safety
glass panes, and also so-called complex curved laminated safety
glass panes, which at least in some parts have large curvatures,
i.e. small radii of curvature. Complex curved laminated safety
glass panes are used, in particular, as windscreens or rear windows
of motor vehicles.
SUMMARY OF THE INVENTION
[0003] With the described laminated safety glass panes the
thin-film system forms a so-called functional layer. This serves to
produce the laminated safety glass panes in such a way that they
can fulfil other functions. These functions include, among others,
the heatability, the changing of the light and energy transmission
degree and reflectance respectively, and the fitting with antennas
for the most varying uses. The structure of the thin-film systems
and the production thereof are known and proven. Particularly
suitable are thin-film systems based on silver layers or
semi-conductive metal oxide layers. These thin-film systems are
integrated into the laminated safety glass pane with the aid of a
transparent thermoplastic carrier. With regard to the state of the
art reference is made in so far, for example, to the WO 90/08334,
which describes known carrier foils, proven thin-film systems and
also customary laminating foils.
[0004] Laminated safety glass panes of the type described at the
outset often display optical distortions, in particular in
reflected light. These optical distortions are caused by phenomena
that can be attributed to corrugations in the carrier foils. The
optical distortions occur in flat laminated safety glass panes of
the described type as well as in curved, especially complex curved
laminated safety glass panes.
[0005] The known measures from which the invention proceeds (EP 0
077 672) relate to a selectively light-transmitting or electrically
conductive film on a carrier foil, which has a thickness between 12
and 125 .mu.m and after a heat treatment at 120.degree. C. for 30
minutes displays a heat shrinkage which depends in a complicated
manner on the thickness of the carrier foil. This serves to avoid
optical distortions in a laminated safety glass pane, in which the
carrier foil is integrated with the thin-film system. Also here the
laminated safety glass pane may be flat or curved. Tests have shown
that the results that can be obtained according to these teaching
are open to criticism. The problems described at the outset, which
occur with flat as well as with complex curved laminated safety
glass panes, especially in the case of small radii of curvature,
are not dealt with.
[0006] To prevent that a carrier foil provided with a thin-film
system, in particular one of polyethylene terephthalate, which is
integrated in a laminated safety glass pane of the type described
at the outset, during the manufacture of the laminated safety glass
pane changes its properties and as a result thereof causes optical
distortions, it is known (EP 0 457 209 A2) to bi-axially stretch
the carrier foil at temperatures above the so-called glass
temperature, followed by thermo-fixing, and after the thermo-fixing
to carry out a further stretching at temperatures below the glass
temperature. The measures known in this respect are complicated,
the result is unsatisfactory. The problems mentioned at the outset
are not dealt with.
[0007] The invention is based on the technical problem to indicate
simple measures suitable for an industrial series production of the
laminated safety glass pane, with which flat as well as curved
laminated safety glass panes of the type described at the outset
can be manufactured, which do not display optical distortions in
reflected and/or transmitted light.
[0008] To solve this technical problem, the subject of the
invention is the process according to patent claim 1.
[0009] The deaeration which belongs to the teachings of the
invention is customary and necessary to avoid in the laminated
safety glass pane distortions caused by air inclusions. The
deaeration must take place effectively and adequately in respect of
the laminated safety glass pane as a whole as well as in respect of
the foil laminate consisting of laminating foils and carrier foils.
The characteristic 1.2) is to be understood as meaning that the
laminating technology customary in the manufacture of laminated
safety glass is used. The process step according to characteristic
1.1) includes the possibility of producing a pre-laminate of the
first laminating foil and the carrier foil as well as, optionally,
the second laminating foil. The foils that must be pre-laminated
are in this case drawn off, in particular, from stock rolls and
joined together using pressure and heat with a simultaneous or
prior deaeration, before the pre-laminates produced in this manner
are cut to size and placed between the two glass panes.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0010] In detail, there exists within the framework of the
invention several possibilities for carrying out the process
according to the invention. According to a preferred embodiment of
the invention a pre-laminate of the first laminating foil and the
carrier foil is placed on the first glass pane, and then the second
laminating foil is put onto this. This method of operation can be
recommended when a second laminating foil is used which is not
available on rolls, as is known from the use of laminating foils
with anti-glare strip that are stretched according to the shape of
windscreens. When curved laminated safety glass panes must be made,
a pre-laminate will be applied on the concave side of the first
glass pane. After applying the pre-laminate a pre-pressing can be
carried out using pressure and heat and then the second laminating
foil can be put on and pressed. It lies within the framework of the
invention to work with a pre-laminate which comprises a first
laminating foil, the carrier foil provided with the thin-film
system and the second laminating foil. However, it is also possible
to proceed in such a way that the first laminating foil, the
carrier foil and the second laminating foil are put onto the first
glass pane and then the pressing of the complete laminate is
carried out. When curved laminated safety glass panes must be
produced, the first laminating foil will be applied on the concave
side of the first glass pane. Although within the framework of the
measures according to the invention it is recommended to work as
described, when manufacturing curved laminated safety glass panes
it is also possible to proceed the other way around and to apply
the laminating foil or the pre-laminate onto the convex side of the
first glass pane. Care must always be taken that during this
application wrinkles are not already formed in a laminating foil or
in the carrier foil.
[0011] With the process according to the invention distorting
deformations in the carrier foil as well as a destruction of the
thin-film system are avoided or suppressed. The invention proceeds
from the discovery that the described optical distortions in
reflected light can be attributed to wrinkles with amplitudes in
the micrometer range. These wrinkles occur as a result of incorrect
handling and when using unsuitable carrier foils within the
framework of the usual laminating processes, also in particular
during the required deaeration processes and when using pressure
and heat to join the constituents of the laminated safety glass
panes to one another. The risk of the formation of such wrinkles is
particularly great when curved, in particular complex curved glass
panes are made. If in the course of the manufacture of the
laminated safety glass pane the carrier foil has wrinkles, this
will be visible mainly when looking at the reflection.
[0012] Surprisingly, with the process according to the invention
optical distortions in transmitted and, in particular, reflected
light are avoided. The state of the art does not lead one to assume
that the invention would achieve this, and this not only with
regard to the manufacture of flat laminated safety glass panes, but
also with regard to the manufacture of curved and complex curved
laminated safety glass panes. This also applies when the complex
curves are so large that curing the adaption of the carrier foil
with the thin-film system to these curvatures, a considerable
wrinkling could be expected. This applies, in principle, to all
laminating foils that are commonly used for the manufacture of
laminated safety glass panes and to all customary carrier foils
with thin-film systems. As laminating foils, in particular foils
based on polyvinyl butyral, ethylenevinyl acetate, polyurethane and
polyvinyl chloride can be used, whereas suitable carrier foils
consists, in particular, of polyesters and their derivatives, in
particular of polyethylene terephthalates. Other materials for the
carrier foil can be cellulose esters or acryl polymers as well as
polycarbonates and polyvinyl fluorides. The materials must be
selected such that they form a dimensionally stable substrate for
the thin-film system, that they are compatible with the laminating
foils and adhere to these sufficiently. In addition they have to
withstand the laminating process without being damaged, be
compatible with the thin-film system, transparent and
UV-stable.
[0013] The carrier foil can easily be stretched in such a way that
the indicated heat shrinkage properties are ensured prior to
manufacturing the laminated safety glass panes. Suitable processes
are known. For making the carrier foils suitable for the process
according to the invention, the starting foils are stretched
bi-axially by 1% and more at temperatures above the so-called glass
temperature, subsequent to which the stretching is thermo-fixed. It
is important to control the process for the application of the
thin-film system in such a way that the carrier foil at most
shrinks slightly, so that a shrinkage behavior according to the
characteristic 1.12) is also still present after the coating and
before the use within the framework of the process according to the
invention. If need be, an adequate cooling of the carrier foil
during the coating must be ensured, or the foil must be
mechanically clamped in. Surprisingly, the stretching of the
carrier foil in both directions required to ensure the heat
shrinkage according to characteristic 1.12) does not cause double
refraction effects in the completed laminated safety glass panes.
According to a preferred embodiment of the invention, a carrier
foil provided with the thin-film system, the heat shrinkage degree
of which according to characteristic 1.12) lies in the range of 0.3
to 0.6%, is placed on the laminating foil.--The individual glass
panes of the laminated safety glass pane according to the invention
have the usual thicknesses. They may consist of normally cooled or
chemically or thermally pre-stressed glass. Also partially
pre-stressed glass panes can be used.
[0014] The described effects, essential to the invention, are
obtained with normal thicknesses of the laminating foils. These lie
in the range of 0.38 mm or a multiple thereof. Preferably, a
carrier foil with a thickness of 40 to 60 .mu.m, preferably
approximately 50 .mu.m, is placed on the first laminating foil.
Depending on the materials used and the temperatures and pressing
times during the pressing, special measures that ensure the bonding
between the laminating foils and the carrier foil are not
necessary. A particularly thorough bonding in this foil laminate is
obtained, however, when a carrier foil provided with the thin-film
system, which on both surfaces has a surface energy of at least 40
mJ/m.sup.2, is placed on the first laminating foil. To this end the
carrier foil can be subjected on the uncoated side to, for example,
a corona or plasma treatment.
[0015] The indicated value parameters are particularly advantageous
and largely optimal when laminating foils of polyvinyl butyral
(PVB) or ethylenevinyl acetate copolymers (EVA) and with a carrier
foil of polyethylene terephthalate (PET) are used. The pressing
according to characteristic 1.2) will normally be carried out at a
temperature in the range of 120 to 130.degree. C., at a pressure of
up to 13 bar. Attention is drawn once again to the deaeration which
is always required prior to producing a laminate or pre-laminate.
The deaeration can take place with the usual means such as link
rollers, a vacuum bag or vacuum lips.
[0016] According to the invention specially prepared carrier foils
provided with the thin-film system are used for a special purpose,
i.e. for the manufacture of laminated safety glass panes that are
free from wrinkle-related optical distortions, in particular curved
and complex curved laminated safety glass panes. This is possible
because of the measures 1.11), 1.12) which are significant for the
invention. This also applies to the described pre-laminates
(duplet/triplet). The described and claimed use can also take place
in the form of the pre-laminates which consist of a laminating foil
and the carrier foil as well as, optionally, the second laminating
foil. When curved and, in particular, complex curved laminated
safety glass panes are manufactured, the foil systems, in addition
to the influences of pressure and temperature, are subjected to
external forces which ensure the adaptation of the originally flat
foils of the foil system to the single or double curvature of the
laminated safety glass panes that are to be produced. When
manufacturing curved laminated safety glass panes with a double
curvature, these forces produce, so to speak, compression
phenomena. This applies, in particular, when manufacturing complex
curved laminated safety glass panes. In addition there are the
deformations from internal forces which the foils of the foil
systems, so to speak, bring with them. When manufacturing curved
laminated safety glass panes with a single curve, these forces may
cause thrust phenomena, and also here there are the additional
influences of the internal forces. The situation is similar when
manufacturing flat laminated safety glass panes. Surprisingly, the
teachings of the invention in all cases solve the technical problem
that forms the basis of the invention. This also applies when
additional mechanical influences (formation of air flow channels)
occur during the deaeration.
[0017] The invention also covers carrier foils which are
particularly suitable for the described process and the described
use, respectively. These carrier foils form the subject of patent
claims 15 to 19.
[0018] In the following the invention will be explained in greater
detail with reference to an exemplified embodiment. The exemplified
embodiment relates, without limitation, to the manufacture of
complex curved laminated safety glass panes.
[0019] An 0.38 mm thick PVB laminating foil of the firm Monsanto,
grained on both sides, a PET carrier foil with a highly
light-permeable sun protection film with a double silver layer
(product designation XIR 75) of the firm Southwall, as well as a
second 0.38 mm thick laminating foil of the firm Monsanto, grained
on both sides, were drawn off from rolls and joined together at
about 60 to 70.degree. C. between a pair of rollers, to form a
deaerated and partially glued pre-laminate, which next was cut to
the required dimensions.
[0020] Prior to the coating, the PET carrier foil had been
bi-axially stretched and thermo-fixed. The stretching and coating
had taken place under such conditions that the PET carrier foil,
after the coating and prior to the manufacture of the pre-laminate,
displayed the folowing heat shrinkage behaviour.--During a 20
second immersion in a liquid bath of polyethylene glycol (molecular
weight about 400), heated to 120.degree. C., the coated PET carrier
foil shrunk by about 0.4% in the foil plane parallel and
perpendicular to the longitudinal stretching. The measuring took
place by clamping both ends of a foil strip with a length of 150 mm
and a width of 15 mm between the jaws of a length measuring device.
The length of the foil strip is measured prior to the immersion in
the temperature bath and on completion of the heat treatment, at
the same starting temperature. From this the percentage of the
change in length is calculated as the shrinkage value at a given
shrinking temperature and dwell time.
[0021] The coated PET carrier foil, to ensure an adequate adhering
to the laminating foil, had a surface energy on both sides of more
than 40 mJ/m.sup.2.
[0022] The pre-laminate produced as described was placed free from
wrinkles on the concave side of a complex curved glass pane with a
thickness of 2.1 mm. The glass pane was curved in the longitudinal
as well as in the transverse direction and had sharply curved side
parts. Along its edge it was provided with a printed on and burned
in opaque anti-glare strip. Then a second complex curved glass
pane, with a thickness of 1.5 mm, the curving of which corresponded
to that of the first glass pane, was placed on the pre-laminate.
The edges of the pre-laminate sticking out over the edges of the
glass panes were cut off. Around the edge of the pane, as generally
known from the manufacture of curved laminated safety glass, a lip
profile was provided connected to a vacuum system for the purpose
of the deaeration.
[0023] During the subsequent deaeration process, a vacuum was
applied to the lip profile for about 20 minutes, and by doing so
the glass-foil pack was deaerated. Next, whilst maintaining the
vacuum, it was pre-laminated in an autoclave with the aid of a heat
treatment of about half an hour at a maximum temperature of
approximately 100.degree. C. This was followed, after an interim
cooling, by the actual laminating process in an autoclave with a
heating of the pre-laminated glass-foil pack to about 125.degree.
C. and a pressure treatment at up to 13 bar.
[0024] After removing it from the autoclave, the reflection and
transmission optics of the completed laminated safety glass were
checked. Also in the area of the more sharply curved side parts of
the glass pane, the coated PET carrier foil was practically
wrinkle-free and the glass pane met the stringent requirements on
windscreens or rear windows of motor vehicles in respect of safety
properties and reflection/transmission optics.
[0025] Comparison tests with coated carrier foils, the heat
shrinkage behaviour of which was clearly outside the range claimed
by the invention, which therefore during a heat treatment at
120.degree. C. for 20 seconds shrunk by less than 0.3%, did not
result in laminated safety glass which was free from optical
distortions, which in particular became noticeable by a bothersome
wash-board effect in the reflection optics of the glass panes. When
using carrier foils which clearly shrank by more than 0.8%, the
so-called orange peel skin effect was observed, which occurs as a
result of the formation of irregular elevations and depressions in
the carrier foil. Also tests with carrier foils outside the claimed
thickness range did not, on the whole, lead to satisfactory
results.
* * * * *