DE102007009785A1 - Glass production process for reinforced coated glass involves chemically pre-stressing glass after tempering in medium containing potassium - Google Patents

Abstract

The invention relates to a method for producing a coated sodium-containing glass, as well as a producible with the process glass in which the glass is provided with a sol-gel coating and the glass with the sol-gel coating for curing the coating in a Temperature of more than 200 ° C is annealed. The thus-coated glass is chemically tempered after annealing the sol-gel coating by storing the coated glass in a potassium-containing medium such that sodium ions of the glass at the surface and in near-surface regions are at least partially supported by potassium ions be replaced, wherein the ion exchange through the annealed sol-gel coating is carried out.

Description

The This invention relates generally to coated glasses, especially sol-gel coated Glasses.

The coating of glass sheets by sol-gel methods is known to the person skilled in the art. In this coating, a sol is applied to a glass substrate to be coated. From this sol, or the forming gel is then produced by annealing an oxide layer. For example, SiO ₂ layers can be produced by means of a sol which contains TEOS (tetraethoxysilane) as precursor. For high-index layers, titanium oxide layers can be produced by the sol-gel method. A common precursor for such layers is titanium tetraisopropoxide. Such coatings are used inter alia as interference layers, for example for the antireflection of glasses.

It would be here desirable, such coated glasses to confer further advantageous properties. An important property is the strength of the glass. To increase the strength is Commonly known is the chemical and thermal tempering of glasses. The thermal preload, or thermal curing based that the to be hardened Glass is quenched. It cools first the surface of the Glass off while still liquid inside or soft glass. The temperature difference to the environment is bigger then in Outside. The Inside of the glass would to contract more in the following, which, however, by the already solid surface is prevented. This causes internal tension, while on the surface forms a compressive stress. Chemical hardening is based on the fact that an im Glass available smaller ion at the surface replaced by a larger one becomes. Due to the higher space requirement These ions create a compressive stress on the surface.

thermal Although biasing is a relatively inexpensive method for increasing the Strength, but also to the chemical toughening with some disadvantages. Thus, thin glasses can not or at best only inadequate thermally to be biased, since when cooling the glass no adequate Temperature gradient can be reached in the glass. Furthermore, thermally tempered glasses no longer be cut. For chemically toughened glasses comes on the other hand, in a subsequent heating of the glass to a relaxation the built-up voltages. So be for the tempering of sol-gel layers Temperatures over 200 ° C used.

Of the The invention is therefore in view of the above-mentioned problems Object to provide coated glasses with increased strength. This task is already in the most surprising simple manner solved by the subject of the independent claims. advantageous Refinements and developments of the invention are specified in the dependent claims.

Accordingly, see the invention a method for producing a coated Sodium-containing glass in which the glass with a sol-gel coating and the glass with the sol-gel coating to cure the Coating annealed at a temperature of more than 200 ° C becomes. Ddabei is the coated glass after annealing the Sol-gel coating chemically toughened by the coated Glass is stored in a potassium-containing medium, so that sodium ions of the glass at the surface and near the surface Areas are at least partially replaced by potassium ions. As a medium is in particular a potassium-containing melt, such as a suitable molten salt suitable. Also other media, like about potassium-containing solutions is being brought up for consideration. At the preferred bias in a molten salt In general, high temperatures above 350 ° C are used. At these temperatures increases the ion mobility accordingly, so that the Ion exchange accelerates.

Of the Ion exchange accordingly takes place according to the invention the tempered sol-gel coating through. The thing with this procedure manufacturable coated sodium-containing glass is accordingly provided with a sol-gel coating and chemically tempered, wherein the chemical bias after coating with the sol-gel coating in one Potassium-containing medium is, so that sodium ions of the glass in near-surface Areas are at least partially replaced by potassium ions, wherein the ion exchange through the tempered sol-gel coating through, wherein the sol-gel layer due to the chemical biasing Potassium from the for contains the bias used medium. The potassium ions in the Sol-gel coating is a characteristic of this manufacturing process.

It is an unexpected effect that a chemical biasing of the glass is still possible through the cured sol-gel coating. It has further been found that the chemical bias can be done both by a silicon oxide-containing sol-gel coating produced on the glass, as well as by a titanium oxide-containing sol-gel coating. This is generally true for many metal oxide containing Coatings, as they can be produced by the sol-gel process, in particular also for such metal oxides, as they are used for optical, in particular also interference-optical coatings.

Generally may be the coating composition for preparing the sol-gel coating hydrolyzable compounds or salts of at least one of the elements main groups III to V, for example Al, In and / or subgroups II to V, for example Sn, Zn, Zr, Nb, Ta, V and / or hydrolyzable Compounds of lanthanides, such as Ce included. Others too hydrolyzable compounds be used, such as those of elements of main groups I and II of the Periodic Table, z. B. Na, Ca, Mg and subgroups VI to VIII of the Periodic Table, such as Mn, Cr, Ni. The finished tempered and hardened sol-gel coating contains then according to oxides of the aforementioned elements. As especially important for optical, In particular, optical interference coatings are oxides of the metals Ti, Si, Nb, Ta, Al, Zr.

Also can even use a multi-layered sol-gel coating, especially with the above-mentioned metal oxides and after annealing the chemical bias can be performed. In particular, you can do this the individual layers of the multilayer coating different Having compositions with oxides of the above elements. The aforementioned elements can in particular also for producing desired layer properties, such as a certain refractive index, so that corresponding ones Mixed oxide layers are obtained.

Such single- or multi-layer coatings can be designed in particular as interference layers become. For example, you can by means of the invention in this way glass panes with anti-reflection layers and then chemically hardened become.

In preferred embodiment of the invention, the ion exchange takes place for the chemical hardening in a potassium nitrate-containing medium, in particular a potassium nitrate-containing Melt. Preferably, the glass is for several hours in the potassium-containing Medium stored. Independently of the type of potassium-containing medium, the glass should last longer than 30 minutes, preferably at least 2 hours, more preferably stored in the medium for at least 3 hours to get a good tempering effect to reach. Depending on the case you can even much longer Biasing times, approximately up to 16 hours can be selected. Typical preload times are often in the range of 4 to 16 hours. These preload procedures can be found in same degree too for the coated according to the invention Used glasses become.

Around to apply the sol-gel coating is further preferred dip coating used. In the dip coating, the to be coated Dipped glass in the sol and then slowly pulled out. In this method, the desired layer thickness, for example a Interference optical acting λ / 4-layer set very precisely by adjusting the pulling speed become. But there are also other contracting considered. In particular, the spray coating should be mentioned here. Also This coating process is still pretty accurate Adjustment of the applied amount of coating material possible, wherein At the same time, this process is much faster allows.

The Invention is particularly suitable for coating soda-lime glasses. The high sodium content of such glasses predestines them for the chemical Toughening. In addition, the sol-gel layers adhere very well to one such glass.

With the invention can be an increase in breaking strength by at least a factor of 2.5 over one achieve similar, not inventively tempered glass.

The Invention will be described below by means of embodiments and below Reference to the accompanying drawings explained in more detail. It demonstrate:

1 a cross section through an inventively coated and chemically toughened glass,

2 a bar graph with strengths of uncoated, coated and additionally chemically toughened glass,

1 shows a product produced according to the invention 1 which is a glass pane 3 with pages 5 . 7 includes. On the glass 3 is both sides on the sides 5 . 7 a three-layer coating 9 with layers 11 . 12 . 13 applied by sol-gel coating. The coating can be designed in particular as a three-layer antireflection coating. For this purpose, the layers 11 . 12 . 13 different refractive indices and have an optical thickness of preferably each an integer multiple of a quarter wavelength. According to one exemplary embodiment of a three-layer antireflection coating, a mixed oxide layer is the first 11 with silica and titania 11 , then a high refractive titanium oxide layer 12 and then a silicono oxide layer 13 applied by sol-gel coating in a dipping process. The refractive index of the situation 11 lies between the refractive indices of the layers 12 and 13 , Preferably, for an effective anti-reflection the optical thickness of the layers 11 and 13 each quarter wavelength and the optical thickness of the layer 12 a half wavelength for one wavelength of the optical spectral range. The layer system thus obtained is then tempered at a temperature above 200 ° C and cured.

One Sol-gel method, as it is used according to the invention, is a wet-chemical coating process, using the inorganic oxide layers can be produced. The production of the coating is always from a liquid sol from which is converted by a sol-gel transformation in a solid gel state. The sol represents a dispersion of particles, which typically Sizes in the range well below 1 micron. In many cases organometallic Compounds used as precursor substances for the coating, where the term "metal" also includes semiconductors, especially including silicon. In the transformation of the sol in a gel results in a crosslinking of the dispersed particles in the solvent. When the sol has been applied and converted into a gel, the so obtained Coating still - preferably tempered under air or in another oxidizing environment, so that organic Pyrolyze residual components of the coating and a compacted inorganic oxide layer is obtained. The implementation of organometallic Precursors typically occur through hydrolysis and condensation reactions.

The starting compound (the precursor) for preparing a coating solution contains a metal or transition metal, for example silicon. The most commonly used precursor compounds are metal alkoxides and salts. To prepare the sol, one or more starting compounds, if appropriate with acidic or basic catalysis, are hydrolyzed in aqueous or organic solvents and optionally at least partially condensed. The coating compositions may generally, without limitation to the embodiment of the 1 be varied. Inter alia, mixed oxide layers can also be produced. For the preparation of silicon oxide layers, suitable precursors include TEOS (tetraethoxysilane). Titanium oxide layers can be prepared, for example, with titanium tetraisopropoxide as precursor. It then forms by hydrolysis and condensation, a colloidal solution of metal alkoxides, which is applied to the glass to be coated. Subsequently, the glass is tempered. In the temperature range between 200 ° C and 550 ° C, in which the heat treatment is preferably carried out, the residual organics pyrolyzed from the coating and the coating densifies.

Following the sol-gel coating with curing is the coated glass sheet 3 chemically toughened.

This is the glass 3 stored in a potassium nitrate-containing melt, preferably a potassium nitrate melt for several hours. The potassium ions of the solution diffuse through the sol-gel coating 9 into the glass of the glass pane 3 into it. Conversely, sodium ions of the glass diffuse through the coating 9 through into the solution. It forms accordingly on the sides 5 . 7 near-surface areas 15 in which sodium is at least partially replaced by potassium. These ranges are generally much deeper than the layer thicknesses of the individual layers of an interference-optical sol-gel coating, which typically have thicknesses smaller than the optical wavelengths of the optical spectral range. In contrast, typical exchange depths are in the range of 10 to 100 μ.

2 shows a bar graph with strengths of different glasses with a thickness of 6 mm. Strength measurement was performed by placing the glass panes on a 100 millimeter inner diameter ring and then applying pressure to the glass sheet on the point of the surface above the center of the ring until the glass broke. In the 2 given values are given relative to an untreated, uncoated float glass, used as a reference (reading A) for measurements on other glass panes. Measurement B is the measurement on a similar glass pane, which was provided with a three-layer anti-reflection coating by sol-gel coating. The sol-gel coating has little effect on the strength. The slight deviations of the strength with respect to the untreated glass are within the scope of the measurement uncertainty. Measured value C is the measured strength on a glass sheet treated according to the invention, which was first provided with a three-layer antireflection coating and then chemically tempered. This was the glass 4 Hours stored in the potassium nitrate-containing bath. The comparison with measured value A shows that the strength is higher by a factor of 3 than in the case of the untreated float glass pane. Also, the strength is surprisingly comparable to that of uncoated, chemically tempered glasses (measured value D). Although the strength measured to measure D Density is sometimes even higher, but also a much longer biasing time, 16 hours in the potassium salt-containing molten salt, was used. It turns out that too surprisingly, a three-layered sol-gel coating hardly has any influence on the achievable strength, although here the potassium ions must diffuse through the coating into the glass and conversely sodium ions have to diffuse through the coating into the melt.

Claims (17)

A method for producing a coated sodium-containing glass, wherein the glass is provided with a sol-gel coating and the glass is annealed with the sol-gel coating for curing the coating at a temperature of more than 200 ° C, characterized in that the glass thus coated is chemically tempered after annealing of the sol-gel coating by storing the coated glass in a potassium-containing medium so that sodium ions of the glass at the surface and in near-surface regions are at least partially replaced by potassium Ions are exchanged, whereby the ion exchange takes place through the tempered sol-gel coating. Method according to claim 1, characterized in that a Sol-gel coating is produced, which is an oxide at least one of the elements of main groups III to V, in particular Al, In and / or the subgroups II to V, in particular Sn, Zn, Zr, Nb, Ta, V and / or the lanthanides, in particular Ce, and / or a Elements of main groups I and II of the periodic table, especially Na, Ca, Mg, and / or subgroups VI to VIII of the periodic table, in particular Mn, Cr, Ni. Method according to the above Claim, characterized in that a sol-gel coating which at least one of the elements Si, Ti, Al, Ta, Nb, Zr contains as oxide. Method according to one the two preceding claims, characterized in that a sol-gel coating with a mixed oxide of at least two of the above two claims mentioned elements is produced. Method according to one the preceding claims, characterized in that the Ion exchange in a potassium nitrate-containing medium, preferably a potassium nitrate-containing melt takes place. Method according to one the preceding claims, characterized in that the Glass is coated with a multilayer sol-gel coating, their layers have different compositions of one or more Oxides of in the claims 2 and / or 3 mentioned elements. Method according to one the preceding claims, characterized in that the Glass with an on or multilayer interference layer, in particular a multilayer interference layer, preferably an antireflection coating in the sol-gel process coated becomes. Method according to one the preceding claims, characterized in that the sol-gel coating by dip coating or spray coating is applied. Method according to one the preceding claims, characterized in that the Glass for that chemical tempering longer than 30 minutes, preferably at least 3 hours in a potassium-containing solution is stored. Coated sodium-containing glass, in particular preparable with a method according to any one of the preceding claims, which with a sol-gel coating provided and chemically prestressed, characterized in that the chemical Preload after preparing the sol-gel coating in one Potassium-containing solution carried out is, so that sodium ions of the glass in near-surface Areas are at least partially replaced by potassium ions, wherein the ion exchange through the tempered sol-gel coating through, wherein the sol-gel layer due to the chemical Biasing potassium out of the solution contains. Coated sodium-containing glass according to claim 10, characterized in that the Coating a sol-gel coating which comprises an oxide of at least one of the elements of the main groups III to V, in particular Al, In and / or subgroups II to V, in particular Sn, Zn, Zr, Nb, Ta, V and / or the lanthanides, in particular Ce, and / or an element of main groups I and II of the Periodic Table, in particular Na, Ca, Mg, and / or the subgroups VI to VIII of the Periodic Table, in particular Mn, Cr, Ni. Coated sodium-containing glass according to claim 11, characterized in that the Coating of at least one of the elements Si, Ti, Al, Ta, Nb, Zr contains as oxide. Coated sodium-containing glass according to claim 11 or 12, characterized in that the sol-gel coating a Mixed oxide at least two of those mentioned in the two preceding claims Contains elements. Coated sodium-containing glass according to one of the preceding claims, characterized in that the glass is coated with a multilayer sol-gel coating. Coated sodium-containing glass according to a the preceding claims, characterized in that the Glass with a single or multilayer interference layer, in particular a multilayer interference layer, preferably an anti-reflection layer coated in the sol-gel process. Coated sodium-containing glass according to a the preceding claims, characterized in that the Glass opposite a similar, unbiased glass one at least a factor of 2.5 higher Having breaking strength. Coated sodium-containing glass according to a the preceding claims, characterized in that the Glass is a soda-lime glass.