Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2002-05-24
2004-09-28
Jones, Deoborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S469000, C428S472000, C428S699000, C428S701000, C428S702000, C427S163100, C427S165000
Reexamination Certificate
active
06797389
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to glazing panels and particularly to glazing panels which are intended to undergo heat treatment following application of a solar control filter.
EP 233003A describes a glazing panel carrying a sputter coated optical filter having the structure: glass substrate/SnO2 base dielectric/first metallic barrier of Al, Ti, Zn, Zr or Ta/Ag/second metallic barrier of Al, Ti, Zn, Zr or Ta/SnO2 top dielectric. The optical filter is designed to block a significant portion of the incident radiation in the infra red portion of the spectrum whilst allowing passage of a significant portion of the incident radiation in the visible portion of the spectrum. In this way, the filter acts to reduce the heating effect of incident sunlight whilst allowing good visibility through the glazing and is particularly suitable for car windscreens.
In this type of structure, the Ag layer acts to reflect incident infra red radiation; in order to fulfil this role must be maintained as silver metal rather than silver oxide and must not be significantly contaminated by adjacent layers. The dielectric layers which sandwich the Ag layer serve to reduce the reflection of the visible portion of the spectrum which the Ag layer would otherwise provoke. The second barrier serves to prevent oxidation of the Ag layer during sputtering of the overlying SnO2 dielectric layer in an oxidising atmosphere; this barrier is at least partially oxidised during this process. The main role of the fast barrier is to prevent oxidation of the silver layer during heat treatment of the coating (e.g. during bending and/or tempering) of the glazing panel by being oxidised itself rather than allowing passage of oxygen to the Ag layer. This oxidation of the barrier during heat treatment provokes an increase in TL of the glazing panel.
EP 792847A discloses a heat treatable solar control glazing panel which is based on the same principle and has the structure: glass substrate/ZnO dielectric/Zn barrier/Ag/Zn barrier/ZnO dielectric/Zn barrier/Ag/Zn barrier/ZnO dielectric. The Zn barriers positioned below each of the Ag layers are intended to be oxidised completely during heat treatment and serve to protect the Ag layers from oxidation. As well known in the art, the structure of having two, spaced Ag layers rather than a single Ag layer increases the selectivity of the filter.
EP 275474 A discloses a heat treatable solar control panel having the structure: glass substrate/zinc stannate dielectric/Ti barrier/Ag/Ti barrier/zinc stannate dielectric. Ti barriers are generally favoured in this type of heat treatable structure due to their high affinity for oxygen and relative ease with which they can be oxidised to form titanium oxide.
SUMMARY OF THE INVENTION
According to one aspect, the present invention provides a glazing panel as defined in claim
1
.
The coating layers are preferably deposited by sputtering, preferably magnetron sputtering but other deposition techniques may be used. Different layers of the coating stack may be deposited using different techniques.
The upper layers in the base and central antireflective layers may have the same or substantially the same composition. This may facilitate the use of substantially similar targets to deposit these layers and/or substantially similar deposition conditions.
The combination of the defined upper layers in the base and central antireflective layers as part of the defined coating stack may facilitate the production of glazing panels (and particularly of laminated windscreens) having TL greater than 75% once subjected to heat treatment whilst still providing an advantageous combination of repeatable thermal stability during heat. treatment, low haze, mechanical and chemical resistance and desired colour in reflection and/or transmission.
One or preferably both of the additional materials X and Y is preferably Sn and/or Al. This may give a particularly advantageous combination of properties.
The proportion of Zn in the mixed oxide that forms the base antireflective upper layer and/or that which forms the central antireflective upper layer may be such that ratio X/Zn and/or the ratio Y/Zn is between about 0.03 and 0.3 by weight.
Arranging one or each of the upper layers of the base and/or central antireflective layers in direct contact with its overlying infra-red reflecting layer may also facilitate achieving high levels of TL during heat treatment. Alternatively, an addition layer, for example, a barrier layer, may be interposed between one or each of the upper layers of the base and central antireflective layers and its overlying infra red reflecting layer. Such an additional barrier may be a layer comprising Ti and/or comprising an oxide of Ti. The additional barrier layer may have a geometrical thickness of between about 5 Å and 60 Å.
The base antireflective upper layer and/or the central antireflective upper layer may have a geometrical thickness of less than about 200 Å, less than about 150 Å, less than about 130 Å or less than about 110 Å. This may provide advantageous mechanical properties to the coating stack, particularly with respect to resistance to peel tests.
The base antireflective upper layer and/or the central antireflective upper layer may have a geometrical thickness of greater than about 30 Å, greater than about 50 Å greater than about 100 Å. This may provide a sufficient thickness to enhance the properties of the coating stack, particularly with respect to TL obtainable after heat treatment.
The central antireflective lower layer may comprises at least one layer which provides a sufficient block to the migration of oxygen and/or sodium and/or other materials to prevent significant contamination of and/or diffusion of the layers of the coating stack. Preferably, the central antireflective lower layer is in direct contact with the first barrier layer and comprises a material which resists diffusion of the first barrier layer during heat treatment. The combination of a central antireflective lower layer as defined in claim
5
with a first barrier which is deposited at least partially in metallic or substantially metallic form and subsequently oxidised during heat treatment (and particularly a barrier that comprises or consists essentially of metallic Ti when deposited) may permit particularly high thermal stability of the coating stack during heat treatment. It is believed that diffusion of material from the first barrier layer into the central antireflective lower layer during heat treatment and particularly during severe heat treatment may, in some coating stack arrangements be a critical factor in determining thermal stability of the coating stack; the composition of central antireflective lower layer defined in claim
5
may significantly mitigate against such diffusion.
The base antireflective lower layer may comprise at least one layer which provides a sufficient block to the migration of oxygen and/or sodium and/or other materials to prevent significant contamination of and/or diffusion of the layers of the coating stack. The use of a base antireflective lower layer as defined in claim
6
may be used to facilitate this whilst, in addition, facilitating the arrangement and control of the deposition conditions.
The use of a top antireflective layer as defined in claim
9
may facilitate the arrangement and control of the deposition conditions for the overall coating stack. In addition, this layer may be arranged to provide a block to migration of oxygen during heat treatment and/or diffusion of the second barrier layer.
The top antireflective layer may comprise at least one layer which comprises a mixed oxide of Zn and at least one additional material W, in which the ratio W/Zn in that layer is between 0.02 and 0.5 by weight and in which W is one or more of the materials selected from the group comprising Sn, Al, Ga, In, Zr, Sb, Bi, Mg, Nb, Ta and Ti. This may improve the thermal stability of the coating stack during heat treatment and/or its mechanical or chemical
Glaverbel
Jones Deoborah
Piziali Andrew T
Rudnick LLP Piper
Schneider Jerold I.
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