Patent Application
20080318033
The invention relates to a method for production of coated substrates with a temporary protective layer, whereby at least one functional layer is deposited on at least one side of the substrate by means of a CVD or PVD process, and a temporary protective layer is applied to at least one coated side of the substrate, also a substrate that is coated with a temporary protective layer.
Temporary protective layers, i.e., removable layers for protecting the surfaces of sensitive substrates, particularly for protection against mechanical damage or chemical attacks, are known from many different branches of industry. These protective layers serve to protect the surfaces during further treatment and/or during transportation and/or during storage of the substrates until the time of their intended use.
Typical protective layers consist of polymers or waxes. Removal of these types of substances takes place by means of organic or inorganic solutions, for example acidic or alkaline solutions, hydrocarbonates or alcohol solutions. These solutions have the shortcoming, however, that they are incompatible with and corrosive to many substrate materials and/or coating materials. Particularly for transparent substrates of glass or plastic with a large variety of functional layers, temporary protective layers of this type are unsuitable.
Patent document WO 01/02496 discloses a protective layer of carbon, which is formed by means of application of a liquid polymeric layer composition to the substrate or coated substrate and subsequent hardening or drying of the layer composition. This protective layer is used particularly as mechanical protection of glass substrates with a multitude of functional layers. The protective layer can be rinsed off by means of a suitable liquid, especially water, or burned off. In many practical applications, the very thin functional layers are deposited on the substrates in a vacuum chamber by means of CVD (chemical vapor deposition) or PVD (physical vapor deposition.) The subsequent application of the protective layer according to WO 01/02496 requires significant time and expenditure, as the substrates must be removed from the vacuum chamber and treated in an additional treatment station. This method is particularly unsuitable if the substrates are already provided with a protective layer on the coated front, for example for purposes of coating the back, and must again be transported into a vacuum chamber for further coating.
This is the case, for example, when coating optical substrates, more particularly lenses. These are provided on both sides with optical functional layers and/or scratch-protection layers and a [sic] final hydrophobic and/or oleophobic clean-coat layers, by means of reactive processes in the vacuum. The clean-coat layer is sensitive, especially to the action of reactive components. In patent document WO 03/057641 A1, the hydrophobic and/or oleophobic coating that already exists on one side of the substrate is coated for protection purposes in the vacuum chamber with a temporary thin protective layer of a metal fluoride, more particularly of MgF2, LaF3 or CeF3, prior to the subsequent treatment of the other side of the substrate. These metal fluorides can be also vapor-deposited in the vacuum chamber. The temporary protective layer can subsequently be wiped off. This, again, involves significant time and expenditure. Moreover, when the protective layer is wiped off, a very sensitive hydrophobic and/or oleophobic clean-coat layer that is located underneath may be damaged in the process.
The invention therefore has as its object to provide a simple and economical method for the production of coated substrates with an easily removable temporary protective layer, also a coated substrate with an easily removable protective layer.
This object can be met with a method according to claim 1 and with a coated substrate according to claim 25. Additional advantageous embodiments are specified in the respective subclaims.
In the inventive method for production of a coated substrate, at least one functional layer is applied to the substrate by means of chemical or physical deposition of a coating material from the vapor phase, and a temporary protective layer is deposited on the functional layer by means of evaporation of a salt that is easily soluble in water or in a polar organic or protic organic solvent, and/or by means of evaporation of a compound that forms a salt-like layer that is easily soluble in water, in a polar organic or protic organic solvent.
Easily soluble in water or in a polar organic or protic organic solvent within the meaning of this invention refers to a solubility of more than 1 g per 100 cm3 of solvent at room temperature.
In a particularly advantageous embodiment of the method, a salt-like alkali metal halide, especially sodium chloride, is evaporated for deposition of the temporary protective layer.
Alkali metal halides are chemical compounds of the halogens, i.e., of the elements of the 7th main group (fluorine, chlorine, bromine, iodine, astatine) with alkali metals, i.e., elements of the 1st main group (lithium, sodium, potassium, rubidium, cesium, francium.)
The protective layer is applied only temporarily, i.e., for a transient period of time during which the layers that are located underneath must be protected, and is easily removed without negatively impacting the surface that is located underneath it. Removal of the salt-like alkali metal halide protective layer is accomplished preferably by means of rinsing with a polar liquid, especially with water.
In an advantageous embodiment of the invention, both the functional layer, or functional layers, as well as the protective layer are deposited by means of evaporation using a thermally heated resistance evaporator or an electron-beam evaporator, so that the coating process can take place in a vacuum chamber.
An optically active layer that is composed of a plurality of individual layers, a so-called multilayer coating, and/or a scratch-protection coating, which comprise metals or metal compounds, more particularly metal oxides, is applied as the first functional layer.
In an additional embodiment, a second, hydrophobic and/or oleophobic functional layer is applied as so-called clean-coat layer with a highly smoothing action to the first functional layer and/or to the substrate. This second functional layer is preferably deposited by means of evaporation of organic silicon compounds or fluorinated hydrocarbon compounds. The organic silicon compounds or fluorinated hydrocarbon compounds preferably comprise at least partially perfluorinated carbon atoms or carbon chains. The organic silicon compounds or fluorinated hydrocarbon compounds may additionally have saturated aliphatic carbon atoms or carbon chains and/or oxygen-containing and nitrogen-containing functional groups.
In order to improve the adhesive property of the functional layers on the substrate, it is advantageous in this context if the substrate is treated with a plasma beam or ion beam prior to the deposition of a functional layer and/or if the first functional layer is deposited by means of a plasma-assisted or ion-assisted process in order to affect layer properties.
In an additional embodiment of the inventive method, the substrate is treated and/or coated on both sides, in such a way that the front of the substrate is treated in a first step with a plasma beam or ion beam and/or coated with at least one functional layer, and subsequently coated with the temporary protective layer. When treating and/or coating the back of the substrate in a second step, the front of the substrate, which was coated first, is then protected by the temporary protective layer. This is advantageous particularly if the treatment and/or coating of the back of the substrate takes place under the action of ions or a plasma.
The thickness of the protective layer is dependent in this context upon the penetration depth of the charge carriers into the layer, and it is preferably selected such that the surfaces or functional layers located underneath cannot be affected
The inventive method may be carried out using any desired vacuum coating apparatus that is equipped with a suitable evaporator for vapor-deposition of the protective layer.
The inventive coated substrate, which preferably has been produced with the inventive method, comprises at least one functional layer, and deposited on the functional layer one temporary protective layer comprising a salt or salt-like compound that are easily soluble in a polar or protic organic solvent.
In a particularly advantageous embodiment, the temporary protective layer comprises an alkali metal halide, preferably sodium chloride. A temporary protective layer of sodium chloride can be easily applied by means of evaporation and easily rinsed off with water without negatively affecting very sensitive functional layers located underneath.
The protective layer preferably has a thickness of 5 nm to 100 nm, more particularly of 10 nm.
The functional layers may preferably be implemented in the form of optically active functional layers, and/or scratch-protection layers, and/or hydrophobic and/or oleophobic functional layers, and may be applied either to one side, or to a front and back of the substrate. Likewise, the temporary protective layer may be applied to one side, or also to a coated front and coated or uncoated back of the substrate.
The invention will be further described below based on an exemplary embodiment, with drawings depicting the following:
In ophthalmics, for example for the production of eyeglass lenses, substrates consisting of glass or plastic must be coated on both sides with anti-reflective layers and clean-coat layers.
For the production of the eyeglass lenses, a plurality of substrates 1 are arranged for coating as shown in
In a first process step the fronts 5 of the substrates 1 are coated in an evacuated vacuum chamber. The substrates 1, which are supported in the substrate holder 7, are pretreated for this purpose by means of an ion beam. As the first functional layer 2, an anti-reflective coating consisting of a plurality of individual layers, for example titanium oxides, zirconium oxides, tantalum oxides, aluminum oxides, silicon oxides, are vapor-deposited by means of an electron-beam evaporator 9. Coating of the substrates 1 with the first functional layer 2 consisting of a plurality of individual layers, takes place with the aid of an ion beam. Switching of the coating materials 11 for generation of the various layers is accomplished by means of a rotating crucible. As the second and last functional layer 3, a hydrophobic clean-coat layer is vapor-deposited on the first functional layer 2 by means of the electron-beam evaporator 9.
If the substrate 1 were already turned over at this time and coated from its back 6 as described above, the very sensitive clean-coat layer would be destroyed by the above-described action of charge carriers, which is shown in
To prevent this from occurring, an additional layer in the form of the protective layer 4 is vapor-deposited in the first process step during coating process of the front 5 of the substrate 1. The temporary protective layer 4 is produced by evaporation of pure sodium chloride by means of the electron-beam evaporator 9.
After venting of the vacuum chamber, the substrates 1 are turned over on the substrate holder 7 for coating the back 6. In a second process step, the backs 6 of the substrates 1 are then coated in the newly evacuated vacuum chamber, as described above, with a first and second functional layer 2, 3.
After coating of the back 6 of the substrate 1, the protective layer 4 is removed. The protective layer 4 of sodium chloride is not stable in the long term and does not have good adhesion to the clean-coat layer underneath and is therefore very easily removable by rinsing with water, without damaging the clean-coat layer. After removal of the protective layer 4, the hydrophobic behavior of the clean-coat layer is fully restored.
The edges of substrates 1 that have been coated with a clean-coat layer must be treated further for the production of eyeglass lenses. Since the clean-coat layer creates a very high degree of surface smoothness, the adhesive pads used for substrate-edge machining no longer adhere properly. The substrate 1 frequently slips about its axis during the process of grinding its periphery, and can then no longer be used.
If, in this case, the substrate 1 is provided during the coating process with a temporary protective layer 4 on both sides, the adhesive pads for substrate-edge machining can again adhere well. After machining of the substrate edges, the temporary protective layer 4 on both sides can again be removed as described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 014 031.9 | Mar 2005 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/002629 | 3/22/2006 | WO | 00 | 5/28/2008 |
