Process for coating of a surface made of glass

For coating the glass edge of two wall elements (2, 3) forming interspace (5) for heat insulating structural and/or light element (1), metallic adhesive layer (4) is produced with the use of a physical (PVD) or chemical (CVD) deposition of the coating material from a gas or vapor phase on one side of each wall element (2, 3). On this adhesive layer (4) barrier layer (6) protecting the latter is deposited and the barrier layer is provided with subsequent solder layer (7). These solder layers (7) are bonded with sheet (8) that edges structural and/or light element (1) on the edge in a gastight manner.

The invention relates to a process for the coating of a surface made of 
glass or a glass alloy by physical (PVD) or chemical (CVD) deposition from 
a gas or vapor phase. 
As is known, the coating methods initially mentioned, PVD--short for 
"physical vapor deposition"--and CVD--short for "chemical vapor 
deposition" comprise vapor deposition sputtering, ion plating, the 
reactive variants of these methods, thermal, plasma and photon activated 
as well as laser induced CVD. These coating methods are described in 
detail in the technical book "Oberflaechen- und Duennschicht-Technologie" 
[Surface and Thin-Layer Technology], 1987 edition by Rene A. Haefer. 
In the PVD processes the deposition from the gas phase takes place by vapor 
deposition, sputtering or ion plating. In vapor deposition in a vacuum, 
the coating material vaporizes in a heatable source and the vapor atoms 
that propagate in a straight line can be deposited on the substrate as a 
layer. 
Sputtering or cathode spraying is a vacuum process in which ions meet the 
coating material (target material) and atomize it by pulse transmission. 
In ion plating in a vacuum, a part of the atoms reaching the substrate are 
ionized and accelerated by an electrical field. Through the acceleration 
energy, with which the particles hit the substrate, the properties of the 
layer deposited are enhanced. In this way, thin layers for optical, 
opto-electronic, magnetic and microelectronic components are produced. 
Further fields of application are tribology, protection against corrosion, 
coating for heat insulation as well as decorative layers. 
CVD processes are carried out with chemical deposition from the vapor 
phase. In the thermal CVD process, chemical reactions take place in the 
vapor phase, whereupon the reaction material is deposited as a layer on 
the substrate. 
Further, there are plasma-activated CVD, photon-activated CVD as well as 
laser induced CVD. The CVD processes are used mainly in machine building 
and apparatus engineering as well as in the electronics industry and they 
serve for the production of layers for protection against wear or for 
protection against corrosion. 
By these processes the material and condition properties of the substrate 
can be altered to a specific penetration depth. The properties of the edge 
layer then depend on the substrate material, the process chosen and the 
process parameters. 
The production and use of insulated glass windows is concerned to a large 
extent with the insulation zone between the individual glass panes and 
their sealing in relation to the environment. 
Windows of this kind, formed from two or more glass panes, are provided 
with shaped metal strips glued on the edges with an elastically acting 
paste. In another design the edge sealing of the so-called insulated glass 
windows is produced by a lead strip soldered with the glass panes, and the 
edge of the glass panes is previously provided with a copperplated or a 
tinplated adhesive layer by a flame-spraying process. 
Experience shows that such sealings are not gastight, since, on the one 
hand, the argon introduced as an insulating gas into the hollow space 
provided between the glass panes diffuses by the rubber sealing, or since, 
on the other hand, the adhesive layer between the glass pane and the 
copper layer is porous. This permeability permits the penetration of 
moisture between the glass panes, so that the window is fogged at times. 
Gastight edge seals have remained an unsolved problem for years and thus an 
obstacle in the development of greatly improved heat insulations, 
particularly in the window industry. 
Moreover insulation glazings with high insulation values permit the 
recovery of energy from natural light in an economical manner. 
In particular, because of the unsolved sealing problem, it has not as yet 
been possible to design a light element or window which exhibits an 
extremely high insulation value as a result of an evacuated hollow space. 
A permanently evacuated structural and/or light element would open up new 
possibilities for home and industrial construction, particularly in the 
area of thermal energy significant savings could be achieved, if for 
example, by evacuated transparent walls the heating of homes could be 
achieved by the incident light, and thus a reduction of considerable 
amounts of fossil fuels that are harmful to the environment could be 
realized. 
Consequently, because of an unsatisfactory situation, the object is to 
create a process according to the initially mentioned type, with which 
heat losses in closed spaces are largely eliminated or the heating of 
closed spaces can take place principally by daylight. 
According to the invention this object is attained in that to form a 
gastight structural and/or light element consisting of at least two 
separated wall elements, the edge is connected on the periphery of at 
least one lateral surface of each wall element with a metallic adhesive 
layer. 
This procedure guarantees the production of structural and/or light 
elements consisting of at least two separated wall elements that form an 
insulating interspace with a gastight edge sealing. 
By the use of this process loosened atoms of the coating material strike 
the solid surface of the wall elements (substrate) and are loosely bonded 
as adatoms. As adatoms they diffuse over the surface until they condense 
as a stable nucleus or by attachment to existing nuclei. The mobility of 
the adatoms on the surface depends on their kinetic energy, the 
temperature of the substrate and the strength of the interaction between 
adatom and substrate. If there exists a strong interaction, a high nucleus 
density is obtained, and vice versa. By attachment of adatoms the nuclei 
grow into so-called islands, and the latter coalesce into a coherent film. 
The nucleus density and the nucleus growth determine the contact surfaces 
in the transition zone. When there is great nucleus density the adhesive 
force is correspondingly great because of large contact surfaces. The 
layer material is anchored in pores of the substrate surface or the 
surface of the wall elements. 
The layer connected with the substrate in these processes attains a tensile 
strength that is greater than that exhibited by the glass material of the 
wall elements. In addition the transition zone, also called interface 
zone, is just as gastight as the wall element itself that is made of 
glass. 
The atoms dusted with this procedure are ejected with high energy which 
reaches 10 to 40 electron volts (eV) depending on the target or coating 
material, while vaporized atoms exhibit energies of only 0.2 to 0.3 eV in 
the vaporization process. The higher energies in sputtering is a reason 
for better adhesiveness of the layer applied in contrast to the 
vaporization process. 
The adhesiveness of a sputtered surface on glass depends on the traps on 
which centers of nuclear bonding arise in the first moment of the layer 
formation. These centers are formed by faults in the surface; from faults 
in the crystal lattice, local changes in potential as a result of free 
bonds or electrical charges. 
The cathode atomization or sputtering favor the formation of such traps. 
Of the processes mentioned, the magnetron sputtering system from the PVD 
(physical vapor deposition) group should prove to be the best suitable 
process for the achievement of a gastight bonding between the insulation 
glass and the edge, which thus far had not been achieved. This sputtering 
system allows for relatively high rates of deposition and large deposition 
surfaces with low substrate heating. 
Before sputtering is begun, ion erosion is advantageously produced on the 
glass surface, for example on the width of the adhesive layer to be 
produced by shifting the target potential on the glass surface. Thus the 
glass surface is cleaned and additional faults which act as coupling 
agents are created in the crystal lattice. 
This effect can be strengthened by placing an electrode supplied with high 
frequency over the glass surface, so that the glass comes under electron 
bombardment. 
The first atom layers of the reactive metallic adhesive layer oxidize and 
alloy with the glass. 
To prevent damage to the metallic adhesive layer during the production of 
the airtight bond between the wall elements, advantageously a protective 
barrier layer can be provided, which is suitable as a material that can be 
soldered or welded. This barrier layer consists of nickel, copper or 
similar metals or metal alloys that can be easily soldered and that 
exhibit a similar expansion coefficient as glass. 
By the barrier layer during the melting process the soft solder deposited 
on the barrier layer is prevented from alloying with the adhesive layer 
and from destroying the latter. The soft solder advantageously has an 
expansion coefficient like glass. 
The melting temperature of the soft solder should not be higher than the 
temperature tolerance of a heat shield layer of the window glass. 
As an alternative, with the exception of the adhesive layer, the building 
up of the metallic layer can be carried out by electrodeposition or 
chemical deposition or by thermal spraying, and with the electrodeposition 
method it is advantageous, if for better electrical conductivity the 
adhesive layer is first provided with a copper deposit. 
A structural and/or light element proves to be particularly simple, if two 
separated wall elements are edged in a gastight manner on their respective 
coated edge with a striplike sheet soldered with a soft solder. 
Such edging is suitable for the formation of a hollow space between the 
front edge of the wall elements and the gastight sheet surrounding them. 
This hollow space can be equipped with getter means that favor the 
maintenance of the vacuum between the wall elements. 
For the protection of the wall elements from excessive heating to about 
350.degree. C. when the getter means is activated it is advantageous for 
the front edge of the wall elements to be coated with an air permeable 
insulation layer. 
So that air can flow against the getter means, it is preferable to provide 
a permeable layer or a wire mesh between the insulation and the getter 
means.

With 1 a structural and/or light element of a building is illustrated in a 
cutout. The one edge of this structural and/or light element 1 consisting 
of two wall elements 2, 3 discloses an adhesive layer 4 of a metallic 
material produced by physical (PVD) or chemical (CVD) deposition from the 
gas or vapor phase, a layer which is provided for a gastight connection 
between wall elements 2, 3 consisting of glass and forming, by a distance, 
interspace 5 that can be evacuated. This adhesive layer 4 could also be 
deposited on the edges turned toward each other between wall elements 2, 3 
for the formation of a seal. 
In the present representation on adhesive layer 4, barrier layer 6 
protecting the adhesive layer is deposited, a barrier layer which is 
distinguished as solderable and is produced by electro or chemical process 
or by thermal spraying. Another layer 7 made of solderable material is 
fused with barrier layer 6 and serves for the airtight bonding of 
solderable sheet 8 that edges the edge of structural and/or light element 
1 formed by two wall elements 2, 3. 
As shown, this sheet 8 can be placed so that it forms a hollow space 9 
between the front edge of structural and/or light element 1 with it; this 
hollow space can be provided for the deposit of getter means 10. 
To avoid damage when getter means 10 is activated and to its effectiveness, 
air permeable insulation 11 lies against the front edge of wall elements 
2, 3 as a heat shield, and in front of the insulation is permeable layer 
12 in the form of wire mesh, fiber or similar materials suitable for this 
purpose.