Process for making a tempered and/or curved glass plate with a reduced transmission

The invention relates to a method for producing a pre-stressed and / or bent glass plate with reduced transmission according to the preamble of Main claim.

Glass panes, which superficially a coating of a metal or a metal alloy and subsequently thereon a protective layer of a metal oxide or comprise mixed metal oxide are in the construction sector and used in the automotive glazing, around the Transmission of the uncoated glass substrate in certain reduce spectral regions. this happens z. B. to a light attenuation effect and / or a sunscreen effect to obtain, wherein the metal layer preferred metals or metal alloys from the Elements with atomic numbers 22-28 of the Periodic Systems are used when color-neutral glass panes be desired. In many such applications, it is necessary, the glass substrate thermally bias. This happens, for. Example, to increase the mechanical Stability, to avoid thermal breakage and to reduce the risk of injury in wheel breakage.

For the generation of thermal prestressing in the application mentioned almost exclusively Discs used for soda lime silicate glass in Air rapidly to a temperature above the transformation temperature heated the glass and then quenched. The need for the tempering process Temperatures are in the range of 580 ° C to 680 ° C, preferably in the range of 600 ° C to 650 ° C. The same temperature range is also needed if the plan of glassmaking her glass panes be subjected to a bending process in order in particular Applications, eg. As in the automotive sector, curved to obtain glass sheets.

With the generic method previously carried out the Applying the metal layer as well as of course the Depositing the metal oxide after completion Toughening or bending process and cooling of the slices, which end usually vacuum-coating process apply.

This method, the coating subsequent to perform the toughening or bending process, has ver distinct disadvantages compared to a procedure where the first applied coating and then the toughening or bending process would be carried out. So can only cut sizes coated in the former case be as biased wheels not known cut them. For coating technology it is much cheaper contrast, unit dimensions, in particular the tapes of the glass forming the float process, to coat. In the latter case can be at Vacuum coatings the problems of constant much lighter and easier to solve thickness than when cut sizes with respective gaps between the coated individual disks in the coating field will. In addition, the transport unit of such dimensions through the coating systems less costly is as if individual pieces of various dimensions must be transported.

A further disadvantage is that by the high temperatures of the toughening or bending process Impurities on the glass surface frequently with her form a strong bond so that they followed in Surface cleaning prior to performing the Coating process is not that far away can be, as for the subsequent coating process necessary is. They are quasi in the glass surface baked. This leads to a disruptive Deterioration of the coating quality.

In the case of the coating of curved panes are naturally the problems, a sufficient layer DC get temperance, particularly large because Angle and distance to the coating sources by additionally change the curvature of the discs. in addition is that the cost of vacuum coating equipment essential for the coating of bent disks greater than the planner for coating slices is because input and output locks and sluices considerably between different coating stations wider than the coating of flat glass Need to become.

For these reasons, has a procedure in which flat glass, particularly in the form of unit dimensions, coated, and then - in particular after production of the fixed dimensions by cutting - biased or is bent, considerable advantages. However, this procedure is in the generic Method, ie when the metal layers, which for said applications are used, not feasible, because the required temperatures above 480 ° C disturbing layer changes - caused - in particular by the oxidation of the layers will.

The DE-OS 17 71 223 describes a process for preparing oxide layers, after which by vacuum deposition manufactured metal layers or sub-oxidic Layers of these metals, in particular layers from the group of the metals cobalt, iron, manganese, cadmium, Bismuth, copper, gold, lead and nickel a heat treatment step at temperatures between 315 ° C subjected and 677.5 ° C and characterized in the respective Oxides are converted. By converting into but the oxides increases the transmission of Layers, especially in the near infrared. In order to deteriorates undesirably Suns protective action against the metal layers.

Investigations carried out have shown that at Layer arrangements such as those described above, in which a metal layer by an oxide layer on is the glass substrate side remote protected, no sufficient stability can be achieved, if this layer arrangements of temperature stress be exposed as the toughening or bending process occurs.

The US-PS 39 62 488 also relates to the preparation of of electrically conductive coatings with a high Light transmittance, but in which a silver or gold layer embedded in both sides titanium oxide and the titanium oxide is to avoid by agglomeration of the noble metal layer with a be applied oxygen deficit. Finally shows DE-OS 30 27 256, the use of sub-stoichiometric Titanium oxide layers as a component of Cladding for transmission changing Metallschich th with the purpose, in this way, among other Measures the corrosion resistance of the metal layers etc. to improve. However, can be in the latter publications listed combinations of materials, accordance in particular with a procedure DE-OS 30 27 256 is not in a process of the generic Insert type in such a manner, that a modification of the previously known process control coating the glass substrate prior to the tempering process made: Such a procedure leads namely this inevitably leads to a disturbing change in the Metal layer, or by oxidation, either by Agglomeration, so that these documents no can give stimulation to the disadvantages of generic to avoid proceedings.

The invention is therefore based on the object, the generic method to further develop, that with the coating of the glass substrate after the toughening or bending process related procedural avoided disadvantages and without the risk of Layer changes the metal layer required Coating measures before the prestressing and / or bending process can be performed.

According to the invention this object is achieved by the characterizing Part of the specified claim 1. dissolved. The claims 2 to 12 advantageous embodiments the inventively proposed method at.

The invention in the course, for example, when manufactured prestressed Spandrels to be, the light transmittance of the Glass plates can be reduced to zero, based on the startling realization that for biasing or bending required protective effect on a of the glass substrate side facing away from the metal layer applied oxide layer is then achieved when the Oxide in composition from the stoichiometric Composition of the relevant oxide differs. What is needed is an oxygen deficit, which a maximum and minimum value does not exceed or fall below allowed. It is also necessary that, in a Metal layer to a preponderant content a Metal or metal alloy consisting of elements with atomic numbers 22-28 in the Periodic Table having the protective layer of suitable, according to the invention's proposed Material; a combination of materials, as known from DE-OS 30 27 256 known it would be totally useless because when heated the there described slices on bending and prestressing temperature the metal layer is inevitably destroyed.

This result is unexpected. It would in fact assume that the action of oxygen on the Metal layer on heating is lowest then, if for the protective layer the stoichiometric composition present. The diffusion through a layer occurs namely known about flaws in the Layer. Their number, however, is the lowest when the stoichiometric composition of the oxide present. The reasons for the observed protective effect in the range of a certain oxygen deficit is not known.

It is also surprising that the oxygen deficit Protective layer and a predetermined value does not may proceed. Thus, layers with higher Sauer material deficit unsuitable. When using such Layers it comes back to a stronger change the optical data of the protected metal layer, in particular occur after the temperature treatment Spotting and clouding phenomena. It it can be assumed that stoichiometric especially strong in this Area, the protective layer unevenly is oxidized, so that the formation of additional grain boundaries with increased oxygen diffusion or comes to crack formation in the coating. However, again because of the complexity of the processes only guesses possible.

As materials for the metal layer are the elements with atomic numbers 22-28 of the Periodic Sy stems, in particular the metals chromium, iron, nickel, Titanium and vanadium, and alloys of these metals, but compositions having a predominant Content of one of the aforementioned metals or metal alloys suitable.

Have proved z. B. chromium-iron-aluminum alloys.

As protective layers, layers have made or a predominant amount of at least one metal oxide or metal oxide from the group Sn, In, Ta as found suitable. As already stated, this must Oxide or mixed oxide layers in deviation from the stoichiometric composition of oxides specific having oxygen deficit. This deficit is, in each case based on a metal atom of the corresponding Oxides, approximately equal. The required Composition corresponds to the relations InO_1,5-<i>x</i>. SnO_2-<i>x</i>, TaO_2,5-<i>x</i>, in which <i>x</i> in the range 0.05 <i>x</i> 0.4 lies.

It has been found that the thickness of the oxide layer with not fall below a minimum value of oxygen deficit allows for in connection with the temperature cycle the toughening or bending process sufficient is protection available. This minimum thickness is at 10 nm, preferably 13 nm.

Thicker layers can also be used. This is, for. Example, the case when the interference effect over its additional to the metal layer optical Effects, such as an antireflection or a color effect to be achieved. The for needed oxide layers lie generally in The range of 20 nm to 70 nm.

In the existing oxygen deficit of the protective layers , these generally have a hardness and Abrasion resistance as used for further manipulation the coated glass substrate prior to the biasing or bending is required. However, these Values ​​slightly lower than that of stoichiometric oxide layers with Composition are achieved.

To further improve the coating hardness and abrasion resistance a method has been proven, in which First, the protective layer having oxygen deficit in the required minimum thickness and over another Oxide layer is applied. The second oxide layer can an oxide of a stoichiometric composition of the same metal as for the protective layer is used to be. However, it can also be an oxide layer other metal are applied. This method of applying a double layer is particularly advantageous when optical desirable because Effects the required layer thickness over the Minimum value for the protective effect is, since then this Point with an even improved layer hardness can be combined. Within the inventive concept is it in the rest of course quite possible between the glass substrate and the metal layer further Layers, for example, silver or palladium layers, to arrange, according to the desired spectral or generally optical properties companies, as long as in the invention substantially Way remote the metal layer on the glass carrier Side by a substoichiometric applied Protective layer of the composition according to the invention and thickness against the Herandiffundieren of oxygen in the bending and / or toughening processes protected required times and temperatures becomes.

The coating according to the invention is generally effected by vacuum coating. The Layers can by evaporation from resistively heated Evaporator devices or else be deposited by electron beam evaporation. In addition, sputtering are as DC or Niederfrequenzzerstäubung, but especially high frequency and MAGNETRON sputtering. The metal or Metal alloy layers may either direct evaporation or sputtering in neutral atmosphere getting produced. For the preparation of Oxide is the method of reactive Evaporation, especially the method of reactive Atomization. Especially economical is the method of reactive magnetron sputtering, with which corresponding metal or metal alloy targets in an atmosphere containing oxygen, among other things, atomized. This method can be the required oxygen deficit of well layer Setting defined.

Under a metal layer having a predominant content to a metal or metal alloy from the Elements with atomic numbers 22 to 28 of the Periodic System is in connection with the invention understood such a metal layer in the rest of whose Properties substantially by the said elements are determined. As a rule, this is at Layers of the case in which the or at a Gahalt more of these elements in total at least 50 atomic percent is. The same applies to the invention Protective layers having a predominant Containing at least one metal oxide or metal oxide from the group Sn, In, Ta, said even with these Metal protective layers, the layer properties by be determined ones of said metal oxides should. This usually is in such layers The case in which the content of In, Sn and / or Ta, based on the total metal content of the oxide layer, total of at least 50 atomic percent.

In the following description, embodiments the invention using a schematic Drawing in detail explained. In which:

<b>Fig.</b> 1 shows a first embodiment of a by the novel process produced glass in section perpendicular to the disc plane;

<b>Fig.</b> 2 shows a further embodiment of a by the novel process producible glass, also in Section perpendicular to the disc plane;

<b>Fig.</b> 3 shows the spectral transmittance before and after Carrying out the tempering process for the glass sheet prepared according to Example I;

<b>Fig.</b> 4, the spectral transmittance before and after Carrying out the tempering process for Example II;

<b>Fig.</b> 5, the spectral transmission of the sample after III glass produced before and after the opening process; and

<b>Fig.</b> 6 the results of appropriate spectral the procedure of Example IV.

In the in <b>Fig.</b> 1 illustrated embodiment is on a glass slide <b>10</b> a metal layer <b>12</b> of nickel deposited with a thickness of 10 nm, to which a protective layer <b>14</b> connects with a thickness of 20 nm, the front of the tempering process, the composition SnO_1.7 Has.

In the embodiment of <b>Fig.</b> 2 transmits the glass substrate <b>10</b> successively an underlayer <b>16</b> out In₂O₃ having a thickness of 6 nm as an adhesion-improving Layer acts, a metal layer <b>12</b> of cobalt with a thickness of 22 nm, a protective layer <b>14</b>That before the tempering process, the composition SnO_1.7 has with a thickness of 16 nm and a covering layer <b>18</b> out SnO₂ having a thickness of 20 nm.

Slices of in <b>Fig.</b> 1 and 2 are reproduced Art By working analogously to the hereinafter Described examples produced:

example I

In a vacuum coating plant, which with coaters for Magnetron sputtering equipped, were on a float glass pane 10 cm in the following sequence format 10 cm × layers applied: First, a nickel layer having a thickness of 8.5 nm by sputtering of a nickel target in Argon atmosphere at a pressure of 5 × 10^-3 mbar. Then, on the nickel layer, a tin oxide by reactive sputtering of a Zinntargets in an argon-oxygen atmosphere with 40% oxygen at a pressure of 4 × 10^-3 mbar applied. The coating parameters of reactive sputtering were chosen such that the coating composition SnO_1.83 exhibited. The composition was thereby to manufacture the overall coating on a Auger electron analysis determined. The thickness of the layer was 28 nm.

The coated disc had in the review and in Viewed from the glass side of a neutral appearance on. The coated disc was then in a biasing oven heated to 600 ° C and quenched. The tempering process changed the Appearance of the disc practically not.

In <b>Fig.</b> 3 is a curve 1 and curve 2 the spectral Transmission before and after carrying out the tempering process for the wavelength region of 300 to 800 nm reproduced. As from<b>Fig.</b> 3 can be seen, the Change in the transmission, in particular in the visible Spectral, slightly. These minimal changes are likely through further oxidation of outer protective layer during tempering process and thus associated decrease in existing when oxygen deficit Residual absorption caused. Added to this are Tempereffekte by this temperature treatment as generally occur in vacuum layers.

example II

The procedure was as in Example I, with the difference that the tin oxide layer by appropriate Choice of coating parameters without measurable oxygen deficit, ie according to the stoichiometric Composition of SnO₂was applied.

The results of the spectral measurements prior to and after Carrying out the tempering process at 600 ° C is for Curve 1 and 2 in <b>Fig.</b> 4 reproduced. They show that considerably by the tempering process, the transmission increases, that is a significant light attenuation and Sunscreen effect is no longer present.

example III

The procedure was as in Example I, with the difference that the coating parameters for the production of tin oxide were adjusted so that a sub-oxidic layer of the composition SnO revealed.

The spectral transmission of the coated pane is before the tempering process as curve 1 in <b>Fig.</b> 5 reproduced. Due to the high absorption capacity the SnO layer arise substantially lower Transmission values ​​as in Example I and II. After Carrying out the tempering process (curve 2) delivers a significant increase in transmission on. Furthermore the coating has a speckled appearance and is thus not suitable for the applications mentioned.

example IV

In the coating system according to Example I were tested for a float glass plate of 10 cm × 10 cm in succession The following layers are applied:

<ul><li>- A SnO₂Layer of 20 nm thickness by reactive Sputtering of a tin target at a pressure of 4 × 10^-3 mbar in an argon-oxygen atmosphere the composition 50% O₂, 50% Ar;</li><li>- A nickel layer of thickness 2 nm by sputtering from a nickel target in an argon atmosphere at a pressure of 4 × 10^-3 mbar;</li><li>- A silver layer of 8 nm thickness by sputtering from a silver target in an argon atmosphere at a pressure of 3 × 10^-3 mbar;</li><li>- A nickel layer of 3 nm thickness by sputtering from a nickel target in an argon atmosphere at a pressure of 4 × 10^-3 mbar;</li><li>- A tin oxide of the composition SnO_1.70 having a thickness of 30 nm by reactive sputtering of a tin target, at a pressure of 4 × 10^-3 mbar in an argon-oxygen atmosphere, the Composition 35% O₂, 65% Ar.</li></ul>

The coated pane exhibited in transmission a easy umbral on color cast when viewed from the Glass side, the disc was practically neutral. The conducted Spectral (curve 1, <b>Fig.</b> 6) show that the disc in the visible region, a high light transmittance in conjunction with low transmission having in the near infrared, that is, the sunscreen effect is very good.

After carrying out the tempering process resulted reproduced as curve 2 transmission curve. they shows that the optical data for the total radiation area the sun are essentially retained. Only in the short-wave visible spectral range is the transmission bit higher than before. These Transmission increase, probably by the post-oxidation the SnO_1.70Layer is caused reduced the originally present slight color cast and thus improves visibility.

LIST OF REFERENCE NUMBERS

<b>10</b> glass slides<b>12</b> metal layer<b>14</b> protective layer<b>16</b> interlayer<b>18</b> topcoat