Note: Descriptions are shown in the official language in which they were submitted.
~9~
ME~IIOD FOR THE MANUFACTURE OF A TEMPERED AND/OR BENT GLASS PANE
WITH PLATINUM COATING OR THE LIKE
The invention relates to a method for the manufacture of 8
tempered and/or bent glass pane of soda-lime-silica glass with
reduced transmission for solar radiation, in which to at least
one side of the transparent glass carrier is applied a metal
coating of platinum, iridium or optionally rhodium, alloys of
these metals or metal alloys with a preponderant proportion of
at least one of these metals in a thickness ~uch that the light
permeability of the laminate for~ed from the glass carrier and
the metal coating is between 10 and 90%, particularly between
30 and 90~ of that of the glass carrier alone and a tempering
and/or bending process is performed in air at a temperature of
580 to 680 C, preferably 600 to 650C.
Glass panes having a surface coating of a metal or metal alloy
are used in the building ~ector and in vehicle glazing for
reducing the transmission of the uncoated glass carrier in
certain spectral ranges. This is done e.g. in order to subdue
the light and/or pre~ent glare. Metals or metal alloys from
elements with atomic numbers 22 to 28 of the periodic table are
preferably used for the metal coating, if it is wished to obtain
glass panes in which there is no colour change to the coating in
direction vision and in reflection. Generally standard soda-lime-
silica glass is used as the glass carrier and can be additionally
dyed in th~ mass, as is the case with bronze, grey and green
glass. This dying in the mass already leads to a basic glare
pre~enting action, which is reinforced by the coating. Particularl~-
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in the case of glazing systems for motor vehicles, frequent useis made of green glass dyed in the mass, which has a ~ood glare
preventing action, in conjunction with high light permeability.
In such cases, particular interest is attached to mixed glazing
systems, some of the panes being additionally coated. Thus,
for example, the windscreen and furthest forward side windows,
which are subject to legal requirements regarding the minimum
light transmittance, are made from green glass which has been
dyed in the mass. For the rear part of the vehicle, where lower
light transmittance values are accepted, use is made of panes
which are dyed in the mass and additionally coated in order to
increase the protection against the sun. It is particularly
important in such mixed glazing systems to use a coating without
any colour distortion in reflection and direct ~ision, so that
direct vision from the interior can take place in uniform manner
in all directions, i.e. without any disturbing colour distortion
betweenthe individual panes. The same applies regarding a uniform
colour impression of the vehicle when viewed from the outside.
In many application~, including those described hereinbefore,
it is necessary to thermall~ temper the glass carrier, which e.g.
takes place for increasing the mechanical stability, for preventing
heat jumps and for reducing injury risks in the case of the glass
breaking. Tempering is carried out by heating the almost
exclusively used soda-lime-silica glass panes in air rapidly to
a temperature above the glass transformation point, followed by
rapid cooling. The temperatures required for tempering are in
the range 580 to 680C and prefcrably 600 to 650 C. The same
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temperature range is also required if the glass panes which comeflat from the glass manufacturing process undergo a bending
process so that in certain ca~es, e.g. in the automobile field,
bent glass plates are obtained. Hitherto the application of
said colour-neutral metal coatings has taken place at the end
of the tempering and/or bending process and the cooling of the
pane~, use generally being made of vacuum coating proces~es.
This procedure of carrying out coating following the tempering
and/or bending process has numerous disadvantages compared with
a procedure in which initially the coating is applied and then
the tempering and/or bending process is carried out. Thus, in
the former case only cut sizes can be coated, because tempered
panes cannot be cut. However, with regards to the coating
procedure it is much more advantageous to coat standard sizes,
particularly the lehr end sizes of glass production by the float
process. In the latter case, it is much easier to solve the
problems of a uniform coating thickness in the case of vacuum
coatings than with cut sizes with corresponding gaps between the
individual panes in the coating field. Tn addition, the transfer
of such standard sizes through the coating plants i~ much less
complicated than in the case of having to transfer individual
pieces of different sizes.
Another disadvantage is that as a result of the high temperatures
of the tempering and/or bending process impurities on the glass
surface frequently form such a firm bond therewith that they
cannot be removed during the following surface cleaning and before
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performing the coating process to the extent necessary for said
coating process. They are quasi burned into the glass surface,
which leads to a disturbing deterioration of the coating quality.
In the case of coating bent plates, the problem of obtaining an
adequate coating uni~ormity is naturally particularly serious,
because the angles and distances from the coating sources
additionally change due to the curvature of the panes. In
addition, the costs of vacuum coating plants for coating bent
panes are much higher than for coatirg flat panes, because it is
necessary for the inlet and outlet locks, as well as the locks
between the different coating stations to be much wider than
when coating flat glass.
lS Thus, considerable advantages are associated with a procedure
in which flat glass, particularly having standard sizes, is
coated and then tempered and/or bent, particularly after
separating to cut sizes. However, this procedure has not
hitherto been possible in the case of the metal coatings of
metals or metal alloy* of elements with atomic numbers 22 to 28
preferred for colour neutrality reaeons, because the necessary
temperatures above 580C lead to disturbing coating changes,
part;cularly as a result of the oxidation of the coatings, as
described e.g. in German patent application 17 71 223. The latter
describes a method for producing oxide coatings, according to
which the metal coatings or sub-oxidic coatings of these metals,
particularly coatings from the group of metals cobalt, iron,
manganese, cadmium, bismuth, copper, gold, lead and nickel
, :
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produced by vacuum evaporation undergo a heat treatment stage
at temperatures between 315 and 677.5C and are consequently
converted into the corresponding oxides. However, through the
conversion into the oxides, the transmission of the coatings,
particularly in the near infrared increases. This leads to an
undesirable deterioration of the glare prevention action as
compared with metal coatings.
In addition to the aforementioned metal coatings, combinations
of these coatings with transparent oxide coatings ha~e been
proposed. Thus, to the side of the metal coating remote from
the glass carrier it is possible to provide a transparent oxide
coating as a protective coating for improving the mechanical
characteristics, or when constructed as a quarter-wavelength
coating for the visible range as an antireflection coating for
increasing the selective transmission. Such a coating arrange-
ment is e.g. known from US patent 38 46 152. Tests have shown
that even in the case of such an arrangement an adequate stability
cannot be achieved if said coating arrangements are exposed to
thermal stresses, such as occur during the tempering and~or
bending proce~s.
For eliminatin~ the aforementioned difficulties, namely permitting
the application of the coating prior to the tempering and/or
bending process when using metals or metal alloys of elements
with atomic numbers 22 to 28, it has already been proposed
(German patent application P 35 44 840.7-45), prior to the
tempering and/or bending process, to apply to the substantially
flat glass carrier the metal coating with a preponderant content
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of a metal or metal alloy from the elements ~-ith atomic numbers
22 to 28 of the periodic table and to the side remote from the
glass carrier a protective coating of at least one metal oxide
or mixed metal oxide which, based on a metal atom of the metal
oxide or oxides, has an ox~gen deficit x of O.O5 S x < 0.4 and
a thickness of lO to lOO nm and a co~position such that, during
the tempering and/or bending process, there is no significant
oxygen diffusion to the metal coating.
It is admittedly obvious for permitting this for making it
possible to carry out the tempering and/or bending process
follow~ng the application of the coating to use platinum, iridium
or optionally rhodium as a result of their oxidation stability,
this does not apply to transparent gold and/or silver coatings,
because they are coloured in direct vision and/or in reflection
and therefore do not have the desired neutrality for many
applications. However, the use of the process known from French
patent 12 71 584 of providing glass carriers with platinum or
rhodium coatings prior to a tempering process and then to carry
out the latter has not been successful in a method of the type
on which the present application is based. For explanation
purposes, it is pointed out that French patent 12 71 584 describes
a procedure in which platinum or rhodium coatings, which in
direct vision and reflection have the desired neutrality for
many uses, have their adhesiveness improved by corresponding
aftertreatment in air at elevated temperature, e.g. during a
tempering process and it is also possible to apply to the
precious metal coating a protective coating of an enamel or glaze,
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which can b~ burnt in in the furnace. If this process of
providing the glass carrier with the platinum or rhodiurn coating
and then carrying out a tempering and/or bending process is used
with the coating thicknesses as provided in the method on which
the present application is based, the tempering process leads to
disturbing coating modifications. The coating turns cloudy, which
can be detected as a disturbing stray light level, e.g. when
illuminating with direct sunlight. Therefore such glass panes
are unsuitable for glare prevention purposes in building or
vehicle glazing systems. Moreover, particularly in the case of
coated glass carriers with a light transmittance above approx-
imately 4OX, based on the light transmittance of the uncoated
glass carrier, there is an increase ~ the transmission for the
spectral range of solar radiation and therefore a deterioration
of the,glare preventing action due to the tempering and/or
bending process.
The problem of the present invention is to so further develop the
method on which the application is based that the disadvantages
linked with coating the glass carrier only following the
tempering and/or bending process are avoided and, without any
risk of changes to the metal coating, it is possible to carry out
the necessary coating measures prior to the tempering and/or
bending process, whilst obtaining the relatively high transmission
values.
According to the invention this problem is solved in that the
metal coating i,s applied to the substantially flat glass carrier
before the tempering and/or bending process and on the side of
- ~X9~680
the metal coating remote from the glass carrier an oxide
stabilizing coating from or with a preponderant content of at
least one metal oxide or mixed metal oxide, preferably from the
group Bi, In, Ni, Sb, Sn, Ta, Ti and Zn is applied with a
thickness of 2 to 20 nm before the tempering and/or bending
process.
The stabilizing coating can be applied in a thickness of max
15 nm.
According to the invention, the stabilizing coating is also
applied in a thickness o~ max 12 nm.
The invention also proposes that In203, mixed oxides of ind~um
and tin, Sb203 or Bi203 are ~sed for the stabilizing coating~
According to the invention, the general procedure is such that
the coating of the transparent glass carrier takes place by
vacuum coating.
It i9 pr~posed that the stabilizing coating is applied by
reactive cathodic sputtering, particularly reactive magnetron
cathodic sputtering.
The invention is based on the surprising finding that it is
possible by applying the stabilizing coating to prevent the
occurrence of cloudiness in the thin precious metal coating. The
reasons for the action of the stabilizing coating are not kno~n.
It cannot be a protective action in the sense that through the
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oxide coating the diffusion of oxygen from the air to the precious
metal coating is prevented, becau~e in the case of such a
mechanism it would be incomprehensible why thicker "open" precious
metal coatings, as are used in the process of French patent
12 71 584, are not affected by the disturbing coating changes,
so that therein and even without the presence of a stabilizing
coating, as proposed by the invention, there can be a tempering
of the coated glass carrier following the application of the
metal coating.
It is also surpri9ing that for the action of the stabilizing
coating it is merely necessary to have very small coating
thicknesses, the necessary minimum being approximately 2 nm. This
is advantageous, because in this range of limited coating thick-
nesses, the optical data, particularly the neutrality in direct
vision and reflection, of the metal coating are not d;sturbed by
interference interaction with the dielectric stabilizing coating.
As is known, such visually disturbing interference effects only
occur with coating thicknesses above 15 nm, particularly above
20 nm. The fact that even very small oxide coating thicknesses
are sufficient for carrying out the method of the invention also
leads to considerable advantages regarding the performance of
the method, because the coating process can then be performed
with considerable tolerances with respect to the coating
thickness, without coating thickness fluctuations leading to a
change in the technical data and the appearance of the coating.
This is a major advantage for coating large glass panes of the
type almost exclusively used in the applications of interest here,
because coating thickness uniformity problems generally increase
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~ith the pane sizes.
In the invention, it is optionally possible to provide between
the glass carrier and the metal coating an additional oxide
coating, in order to impro~e the coating adhesiveness, such oxide
coatings being known per se e.g. from German application L 13 792
VIII d in the form of adhesive coatings for metal layers for
improving the electrical conductivity of the latter. German
Utility Model 17 34 744 already discloses a glass pane with a
platinum coating and an oxidic protective coating applied thereto
and which serves to protect the platinum coating against mechanical
and chemical actions, without this literature reference disclosing
the action of the inventively proposed stabilizing coating in the
case of relatively thin metal coatings of the type provided in
the inventive method.
In connection with the performance of the inventive method, coatings
of In2O3, mixed oxide coatings of the metals indium and tin,
Sb2O3 coatings and Bi2O3 coatings have proved particularly
suitable for the stabilizing coating, becau~e inter alia this
leads to a particularly hard and abrasion-resistance coating,
such as is especially advantageous for the further handling of the
glass panes after performing the tempering and/or bending process.
~part from platinum, which has proved to ~e particularly suitable
as a msterial for the metal coating, iridium and optionall
rhodium, as well as alloy coatings of platinum, iridium and
optionally rhodiu~ have proved suitable. It is also possible to
use alloy coatings in which less precious metals are added to the
aforementioned metals or their alloys. However, these additions
~?~916f~0
11
must be so small that the precious metal character is largely
retained, so that the maximum less precious metal additions
represen~ approximately 50 atomic per cent according to the rule
drawn up by Tamman (G. Tamman, "Lehrbuch der Metallkunde", Edition
IV, 1932, Leopold Frost, Leipzig, p 428 ff).
According to the method of the invention, the coating is generally
produced by vacuum coating. The coatings can be applied by
evaporating from resistance-heated evaporator means or by
electron beam e~aporation. Cathodic sputtering in the form of
direct current or low frequency sputtering, but in particular
high frequency and magnetron cathodic sputtering are also suitable.
The metal or metal alloy coatings can either be produced by
direct e~aporation or sputtering in neutral atmosphere. The
lS reactive e~aporation method is suitable for producing the
oxide coatings. The reactive cathodic sputtering, particularly
reactive magnetron cathodic sputtering, in which sputtering takes
place of corresponding metal or metal alloy targets in an
atmosphere inter alia containing oxygen is also suitable.
ZO
It is also pointed out that particularly when per~orming the
process slowly, as is frequently the case during bending, the
inventive method can also be advantageously used with light
transmittance values of less than 30%, e.g. 20%, because this
also leads to a favourable influence on the otherwise unavoidable
clouding processes.
Further features and advantages of the invention can be
gathered from the following description, in which inter alia
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embodiments are explained in detail with reference to the drawings,
wherein show:
Fig. 1 An embodiment of a glass pane which can be manufactured
according to the inventive method in section and at
right angles to the pane plane.
Fig. Z The spectral transmission curves of a glass pane
manufactured according to the prior art before and
after performing the tempering process.
As shown in fig. 1, the glass plate shown therein has a transparent
soda-lime-silica glass carrier 10 carrying a platinum metal
coating 12. On the side of metal coating 12 remote from glass
carrier 10 is applied an In203 stabilizing coating 14.
Example 1
In a vacuum coating plant equipped with coating means for
magnetron cathodic sputtering, the following coatings were
successively applied to a 10 cm x 10 cm float glass pane. Firstly
a plat~num coating 3.2 nm thick was applied by sputtering a
platinum target in an argon atmosphere at a pressure of 5.10 3
mbar. To the platinum coating as the stabilizing coating was
then applied an antimony oxide coating by the reactive sputtering
of an antimony target in an argon-oxygen atmosphere with a 50%
oxygen proportion at a pressure of 5.10 3 mbar. The antimony
oxide coating thickness was 6 nm.
The coated pane had a neutral appearance in both direct vision
and reflection. The light transmittance of the coatedpane was
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60%, whereas the uncoated pane had a light transmittance of 60%.
The coated pane was then heated in a tempering furnace to 600C
and cooled. There was substantially no change to the appearance
and the light transmittance of the pane as a result of the
tempering process.
Example 2
The procedure of example 1 was adopted, with the difference that
no antimony oxide stabilizing coating was applied. In direct
vision and in reflection, the coated pane had the ~ame neutral
appearance as in example 1 and the light transmittance was 60X.
As in example 1, the coated pane was then tempered. Following
this process, the coating was cloudy and appeared as a disturbing
stray light level after illumination with a projection lamp. In
addition, the light transmittance had increased to 68%.
Fig. 2 shows the spectral transmission curves prior to carrying
out the tempering process (curve 1) and a~ter said process
(curve 2). They show that the glare preventing action has been
considerably reduced by tempering.
Example 3
In a ~acuum coating plant, as described in example 1, the
following coatings were successively applied to a 10 cm x 10 cm
float glass pane:
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a 5 nm thic~ In203 co~ting by the reactive sputtering of an
indil~ target at a pressure of 5.10 3 mbar in an argon-oxygen
atmosphere of composition 60% Ar and 4~ 2~
a 7 nm platinum coating by sputtering a platinum target in an
argon atmosphere at a pressure of 5.10 3 mbar, and
a 5 nm thick In203 top coating by the reacti~e sputtering of an
In target under the same conditions as for $he first In203 coating.
The coated pane had a light transmittance of 40% and had a neutral
appearance in direct vision and reflection. The coated pane was
then tempered as in example 1.
There was substantially no change to the appearance and light
transmittance of the pane as a result of the tempering process.
ExamPle 4
As in example 3, a platinum coating was applied, but without the
additional In203 coatings. Here again the light tran~mittance of
the coated pane was 40%.
Although after tempering the light transmittance was still 40X,
the coating was cloudy and this was ~isible as disturbing stray
light when illwn~nated with a projecting lamp. Thus, in this
form the coating is unsuitable for the indicated uses.
Example 5
A coating system as describedin example 3 was applied, but the
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pure platinum was replaced by a coating of a platinum-silver
alloy of composition 70 atomic % platinum and 30 atomic % silver
in a thickness of 5 nm. The coated pane had a light transmittance
of 51% and a neutral appearance both in direct ~ision and in
reflection.
As in example 3, the appearance and light transmittance of the
plane were substantially unchanged as a result of the tempering
process.
The features of the invention disclosed in the above description,
the claims and the drawings can be essential to the realization
of the inYentive concept in its different embodiments, either
singly or in random combinations.
