Despite the care taken during the manufacture of these devices (work in clean rooms, pulsed supply for the film-deposition cathodes, vertical deposition line, high-quality substrates), it may happen that surface defects usually called “pinholes” do appear. These pinholes can arise in many ways. They may arise from environmental dust particles that have not been retained and/or removed by the means for filtering the atmosphere of the treatment chambers or from residues emanating from the devices that have to deposit the various layers according to the active (electrochromic, photovoltaic, electroluminescent, etc.) systems, especially at the targets, or else poor quality of the substrate. These defects are unacceptable as they may cause, by coming into contact with the electrodes, permanent deterioration of the functionality of these glazing assemblies.
Because of the financial loss that may be engendered by scrapping a device containing a few defects, it has been endeavored to eliminate these defects, especially at an advanced stage in the manufacturing process.
A first technique aiming to eliminate surface defects consists, after having visually detected defects present in the form of an aureole, in ablating the constituent material of the layer at the aureole using a scratching device of the cutter or equivalent type.
This first technique does allow effective elimination of the defects, but they can be ablated only when the layers of the active system are still accessible, that is to say, in the case of a laminated windshield, before the step of laying down the sheet interlayer and before joining the substrates together, which further reduces the field of application of this technique (it is inoperable when the substrate and the active system have been fully assembled, the layers of the active system being inaccessible).
A second technique is known for ablating the layers of an active system that uses laser radiation. This second technique is conventional in the field of marginating layers and makes it possible, by laser radiation, to remove around the periphery of a glass substrate, for example, layers with silver in order to prevent corrosion phenomena occurring throughout the active system, or to limit leakage current phenomena in the case of an active system of the electrochromic or photovoltaic type.
This second technique is very effective for eliminating part or all of the layers forming an active system (the material of the layers being completely or partially destroyed by the laser).
In addition, the margination technique is a method limited to ablating just the layers around the periphery of the substrate, that is to say in a place where removal of the destroyed material is easy. It will be readily understood that it is impossible to operate through a laminated substrate, since the material destroyed by the laser radiation must not remain trapped between the two substrates forming the laminate.
The inventors have quite unexpectedly discovered that, by adapting the laser radiation operating conditions, it is possible to use this type of radiation to destroy layers of an active system even when they are not located around the periphery of a laminated substrate.
The method forming the subject of the invention is particularly intended for what is called “smart” glazing, which is capable of adapting to the user requirements.
As regards smart glazing, this may be used to control the amount of sunlight passing through the windows mounted on the outside of buildings or of vehicles of the automobile, train or plane type. The aim is to be able to limit excessive heating inside passenger compartments/rooms, but only when there is strong sunlight.
It may also involve controlling the degree of vision through windows, especially so as to darken them, make them scattering or even completely prevent vision when this is desirable. This may relate to the windows mounted as interior partitions, in rooms, trains or planes, or mounted as side windows in automobiles. This also relates to mirrors used as rear-view mirrors, to prevent the driver from being dazzled, or indicating panels, so that messages appear when necessary, or intermittently in order to better attract attention. Glazing that may be rendered diffusing at will can be used, when so desired, as projection screens.
Various electrically controllable systems allowing this kind of modification in appearance or in thermal properties are in existence.
To modulate the light transmission or light absorption of glazing, there are so-called viologen based systems, such as those described in patents U.S. Pat. No. 5,239,406 and EP-612 826.
To modulate the light transmission and/or heat transmission of glazing, there are also systems called electrochromic systems. As is known, these generally comprise two layers of electrochromic material separated by an electrolyte layer and flanked by two electrically conducting layers. Each of the layers of electrochromic material can reversibly inject cations and electrons, the change in their oxidation state as a result of these injections/ejections resulting in a change in its optical and/or thermal properties.
There are also systems called “optical valves”. These are films comprising a generally crosslinked polymer matrix in which there is dispersed microdroplets containing particles that are capable of lining themselves in a preferential direction under the action of a magnetic or electric field. Thus, patent WO93/09460 discloses an optical valve comprising a polyorganosilane matrix and polyiodide-type particles that intercept light much less when the film is under voltage.
Mention may also be made of what are called electroluminescent systems, which, as is known, generally comprise at least one thin layer of an organic or inorganic electroluminescent material sandwiched between two appropriate electrodes.
It is usual to classify electroluminescent systems into several categories according to whether they are of the organic type, commonly called OLED (Organic Light-Emitting Diode) systems or PLED (Polymer Light-Emitting Diode) systems, or of the inorganic type, and in this case usually called TFEL (Thin Film Electroluminescent) systems.