EP1725895A1

EP1725895A1 - Scratch-resistant optical multi-layer system applied to a crystalline substrate

Info

Publication number: EP1725895A1
Application number: EP05716114A
Authority: EP
Inventors: Mohammad Jilavi; Martin Mennig; Peter William Oliveira; Helmut Schmidt
Original assignee: Leibniz Institut fuer Neue Materialien Gemeinnuetzige GmbH
Current assignee: LEIBNIZ-INSTITUT fur NEUE MATERIALIEN GEMEINNUETZ
Priority date: 2004-03-17
Filing date: 2005-03-16
Publication date: 2006-11-29
Also published as: DE102004012977A1; US8133573B2; US20070196640A1; JP2007529769A; WO2005091021A1

Abstract

The invention relates to an optical multi-layer system that is applied to a crystalline substrate. Said system is obtained by a method, according to which: a composition that contains nanoparticles comprising polymerisable and/or polycondensable groups is applied to a crystalline substrate; the groups of nanoparticles are polymerised and/or polycondensed to form an organically cross-linked layer; one or more additional layers are applied in the same manner; the layered composite thus obtained is thermally compressed and the organic components thus obtained are burnt out. In the case of the layer that is applied last, the polymerisation and/or polycondensation of the groups of nanoparticles, which form an organically cross-linked layer, can take place directly in the final stage, or the nanoscalar inorganic solid particles may contain no polymerisable and/or polycondensable organic groups. The optical multi-layer systems produced according to said method are suitable for use as scratch-resistant interference layer systems, such as reflection and anti-reflection coatings on a crystalline substrate. The system is suitable e.g. for sapphire substrates such as sapphire watch-glasses.

Description

SCRATCH-RESISTANT OPTICAL MULTILAYER SYSTEM ON A CRYSTALLINE SUBSTRATE

The invention relates to an optical multilayer system on a crystalline substrate, which is obtainable by a single-stage baking process ("stack baking"), a method for producing the optical multilayer system and its use.

Multi-layer systems with an optical effect can be produced on glass in addition to sputtering and vapor deposition processes using the so-called sol-gel process; see e.g. Dislich et al. DE 1941191. The principle of this production method is that the corresponding glass substrate is coated with a sol by means of a dipping process and the layer is dried and baked at higher temperatures in order to achieve compaction. Predrying at higher temperatures is necessary to give the first layer sufficient chemical stability, otherwise the new coating sol will either dissolve or dissolve it. The process is complex since after each layer application a temperature treatment at temperatures of 400 - 500 ° C is required. This makes the production of multilayer systems, as is required in special optical applications (broadband. Anti-reflective coating, cold light mirrors, etc.), extremely labor intensive and costly.

P. W. Oliveira, H. Krug, A. Frantzen, M. Mennig, H. Schmidt describe in SPIE, Vol. 3136, pages 452-461, a process for the production of optical multilayer systems on plastic substrates using 3-glycidoxypropyltrimethoxysilane surface-modified nanoscale particles in one organically modified inorganic matrix. Photolytic curing takes place. A thermal treatment takes place up to a maximum of 80 ° C. This allows interference layer systems to be produced on plastic substrates.

WO 99/61383 describes a process for the production of optical multilayer systems on glass substrates, in which at least two coating layers tion compositions containing nanoscale inorganic solid particles with polymerizable and / or polycondensable organic surface groups are applied to a glass substrate and baked in one stage.

The wet chemical optical multilayer systems obtained according to the prior art are based on a glass or plastic substrate. The object of the invention was to provide optical multilayer systems on crystalline substrates.

This object is achieved according to the invention by an optical multilayer system on a crystalline substrate comprising the following steps: a) applying a nanoscale inorganic solid particles with polymerizable and / or polycondensable organic groups containing flowable composition to a crystalline substrate; b) polymerization and / or polycondensation of the groups of the solid particles to form an organically crosslinked layer; c) applying a further composition according to a), which gives a different refractive index than the preceding composition, to the organically crosslinked layer; d) polymerization and / or polycondensation of the groups of the solid particles to form a further organically crosslinked layer; e) optionally repeating steps c) and d) one or more times to form further organically crosslinked layers on the already existing organically crosslinked layers and / or other surfaces of the substrate; and f) single-stage thermal compression of the layer composite and burning out of the organic constituents contained, with the last applied layer

1) optionally the polymerization and / or polycondensation of the groups of the solid particles with formation of an organically crosslinked layer can also take place directly in the final stage f) or

2) if appropriate, the nanoscale inorganic solid particles have no polymerizable and / or polycondensable organic groups, so that in this case there is no polymerization and / or polycondensation of groups of solid particles for the uppermost layer with the formation of an organic crosslinking before or in step f).

1 shows the transmission behavior of a crystalline substrate, which according to the example below is provided with an optical multilayer system (curve 2), and that of the uncoated substrate (curve 1).

The invention allows multilayer optical systems to be applied to crystalline, non-metallic, inorganic substrates. The multilayer systems obtained are characterized by high scratch resistance. The crystalline substrate can e.g. are single crystals or polycrystalline materials. Any known crystalline material that is suitable for the respective purpose can be used. Examples of preferred crystalline substrates are substrates made of silicon, lithium niobate, lithium tantalate, quartz, sapphire, other precious or semi-precious stones and other optical crystals, crystalline detectors, e.g. for electromagnetic radiation, such as PbS or selenium, and optical filters (UV, IR, NIR and VIS), with sapphire being particularly preferred among the crystalline substrates. The crystalline substrate is preferably a transparent substrate. The substrate can e.g. also be present as a surface layer on a carrier made of a different material.

The substrate can have any desired shape. It can be flat or curved, for example, concave or convex. The substrate can be provided on one side or on both sides with an optical multilayer system. For example, the substrate may be in the form of a rectangular or round disc or a lens or any other shape. In a preferred embodiment, the substrate is a wafer, a screen, an instrument cover glass, a crystalline detector, an optical filter or in particular a watch glass made of a crystalline material. In some areas of application, the designation "glasses" for the crystalline substrates used is common in the trade or in technology for some embodiments, for example if real glasses can also be used for the application. Particularly preferred special embodiments for the substrates are silicon wafers, sapphire disks, such as can be used, for example, in laser scanner registers, instrument cover glasses made of sapphire and in particular sapphire watch glasses.

The optical multilayer systems are generally suitable as interference multilayer systems, e.g. as reflective or anti-reflective coatings, anti-reflective coatings being a preferred application. Other useful applications are NIR reflection filters, edge filters and bandpass filters. Other uses are listed below.

The process for producing the multilayer optical systems on crystalline substrates is explained in more detail below.

By using nanoscale particles that are coated with polymerizable and / or polycondensable groups, there is the possibility of chemically stable layers even at very low temperatures, e.g. B. via photopolymerization and in this way to apply further layers by the same method. It was surprisingly found that these layers can be compacted on crystalline substrates without crack formation, even in layer systems with up to 10 or more individual layers, and that their optical effect can be calculated precisely in advance. This results from the content of inorganic components in the respective coating system, the application quantity (layer thickness) and the refractive index achieved after the final thermal compaction.

In the present description and the appended claims, “nanoscale inorganic solid particles” are understood to mean those having an average particle size (an average particle diameter) of not more than 200 nm, preferably not more than 100 nm, and in particular not more than 70 nm. A particularly preferred particle size range is 5 to 50 nm. The average particle size is understood here to mean the average particle diameter based on the volume average, and a UPA (Ultrafine Particle Analyzer, Leeds Northrup (laser-optical, dynamic laser light scattering)) can be used for the measurement. For the determination of very small particles (eg less than 3.5 nm), electron microscopic methods (eg via HR-TEM) can also be used.

The nanoscale inorganic solid particles can consist of any materials, but preferably they consist of metals or semi-metals and in particular of semi-metal or metal compounds such as (optionally hydrated) oxides such as ZnO, CdO, SiO ₂ , TiO ₂ , ZrO ₂ , CeO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , La ₂ O ₃ , Fe ₂ O ₃ , Cu ₂ O, Ta ₂ O ₅ , Nb ₂ O ₅ , V ₂ O ₅ , MoO ₃ or WO ₃ ; Chalcogenides such as sulfides (eg CdS, ZnS, PbS and Ag ₂ S), selenides (eg GaSe, CdSe and ZnSe) and tellurides (eg ZnTe or CdTe), halides such as AgCI, AgBr, Agl, CuCI, CuBr, Cdl ₂ and Pbl ₂ ; Carbides such as CdC ₂ or SiC; Arsenides such as AlAs, GaAs and GeAs; Antimonides such as InSb; Nitrides such as BN, AIN, Si ₃ N ₄ and Ti ₃ N ₄ ; Phosphides such as GaP, InP, Zn ₃ P ₂ and Cd ₃ P ₂ ; Phosphates, silicates, zirconates, aluminates, stannates and the corresponding mixed oxides (eg those with a perovskite structure such as BaTiO ₃ and PbTiO ₃ ).

The nanoscale inorganic solid particles used in the process according to the invention are preferably those of oxides, sulfides, selenides and tellurides of metals and mixtures thereof. According to the invention, nanoscale particles of SiO ₂ , TiO ₂ , ZrO ₂ , ZnO, Ta ₂ 0 ₅ , SnO ₂ and Al ₂ O ₃ (in all modifications, in particular as boehmite, AIO (OH)) and mixtures thereof are particularly preferred.

Since the nanoscale particles which can be used according to the invention cover a wide range of refractive indices, the refractive index of the layer (s) can be conveniently adjusted to the desired value by suitable selection of these nanoscale particles. The nanoscale solid particles used according to the invention can be produced in a customary manner, for example by flame pyrolysis, plasma processes, gas phase condensation processes, colloid techniques, precipitation processes, sol-gel processes, controlled nucleation and growth processes, MOCVD processes and (micro) emulsion processes. These methods are described in detail in the literature. In particular, semimetals or metals (for example after the reduction of the precipitation process), ceramic oxidic systems (by precipitation from solution), but also salt-like or multicomponent systems can be used. The salt-like or multi-component systems also include semiconductor systems. The nanoscale solid particles are preferably produced using the sol-gel process.

The production of the nanoscale inorganic solid particles provided with polymerizable and / or polycondensable organic groups, which are used according to the invention, can in principle be carried out in two different ways, firstly by surface modification of nanoscale inorganic solid particles which have already been produced and secondly by producing these inorganic nanoscale solid particles using one or more compounds which have such polymerizable and / or polycondensable groupings. These two approaches are explained in more detail below and in the examples.

The organic polymerizable and / or polycondensable groups can be any groups known to the person skilled in the art which are capable of radical, cationic or anionic, thermal or photochemical polymerization or thermal or photochemical polycondensation (if appropriate in the presence of a suitable initiator or catalyst) are accessible. Surface groups which have a (meth) acrylic, allyl, vinyl or epoxy group are preferred according to the invention, with (meth) acrylic and epoxy groups being particularly preferred. Among the groups capable of polycondensation, hydroxyl, carboxy and amino groups should be mentioned, with the aid of which ether, ester and amide bonds can be obtained between the nanoscale particles. It is also preferred according to the invention that the organic groups present on the surfaces of the nanoscale particles, which comprise the polymerizable and / or polycondensable groups, have a relatively low molecular weight. In particular, the molecular weight of the (purely organic) groupings should not exceed 500 and preferably 300, particularly preferably 200. Of course, this does not exclude a significantly higher molecular weight of the compounds (molecules) comprising these groupings (for example not more than 2,000 or not more than 1,000).

As already mentioned above, the polymerizable / polycondensable groups can in principle be provided in two ways. If a surface modification of nanoscale particles that have already been produced is carried out, all (preferably low-molecular) compounds are suitable for this purpose, which on the one hand have one or more groups that have functional groups (such as, for example, OH groups on the surface of the nanoscale solid particles) of oxides) can react or at least interact, and on the other hand have at least one polymerizable / polycondensable group. Thus, the corresponding compounds can, for example, form both covalent and ionic (salt-like) or coordinative (complex) bonds to the surface of the nanoscale solid particles, while dipole-dipole interactions, hydrogen bonds and van der Waals interactions should be mentioned as examples of pure interactions , The formation of covalent and / or coordinative bonds is preferred. Specific examples of organic compounds that can be used to modify the surface of the nanoscale inorganic solid particles are, for example, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, β-dicarbonyl compounds (eg β-diketones or β-carbonylcarboxylic acids) with polymerizable double bonds, ethylenically unsaturated alcohols and amines, amino acids, epoxides and like. Particularly preferred as such compounds according to the invention are - in particular in the case of oxidic particles - hydrolytically condensable silanes with at least (and preferably) one non-hydrolyzable radical which has a polymerizable carbon-carbon double bond or an epoxy ring. Such silanes preferably have the general formula (I):

XR ¹ -SiR ² ₃ (I) where X is CH ₂ = CR ³ -COO, CH ₂ = CH or glycidyloxy, R ^{3 is} hydrogen or methyl, R ^{1 is} a divalent hydrocarbon radical having 1 to 10, preferably 1 to 6, carbon atoms is which optionally contains one or more heteroatom groups (for example O, S, NH) which separate adjacent carbon atoms and the radicals R ² , identical or different from one another, from alkoxy, aryloxy, acyloxy and alkylcarbonyl groups and halogen atoms (in particular F, Cl and / or Br) are selected.

The groups R ² are preferably identical and selected from halogen atoms, -CC alkoxy groups (for example methoxy, ethoxy, n-propoxy, i-propoxy and butoxy), C ₆ -IO aryloxy groups (for example phenoxy), -C ₄ -acyloxy groups ( eg acetoxy and propionyloxy) and C ₂ -ι ₀ alkylcarbonyl groups (eg acetyl). Particularly preferred radicals R ² are C- alkoxy groups and in particular methoxy and ethoxy.

The radical R ¹ is preferably an alkylene group, in particular one having 1 to 6 carbon atoms, such as ethylene, propylene, butylene and hexylene. If X is CH ₂ = CH, R ¹ preferably denotes methylene and in this case can also mean a mere bond:

X preferably represents CH ₂ = CR ³ -COO (where R ^{3 is} preferably CH ₃ ) or glycidyloxy. Accordingly, particularly preferred silanes of the general formula (I) are (meth) acryloyloxyalkyltrialkoxysilanes such as 3-methacryloyloxypropyltri- (m) ethoxysilane and glycidyloxyalkyltrialkoxysilanes such as 3-glycidyloxypropyltri (m) ethoxysilane.

If the nanoscale inorganic solid particles are already produced using one or more compounds which have polymerizable / polycondensable groups, it can be surface modification are disregarded (although this is of course possible as an additional measure).

The in situ production of nanoscale inorganic solid particles with polymerizable / polycondensable surface groups is explained below using the example of SiO ₂ particles. For this purpose, the SiO ₂ particles can be produced, for example, by the sol-gel process using at least one hydrolytically polycondensable silane with at least one polymerizable / polycondensable group. Suitable silanes of this type are, for example, the silanes of the general formula (I) already described above. These silanes are preferably used either alone or in combination with a suitable silane of the general formula (II)

SiR ² ₄ (II) in which R ^{2 has} the meaning given above, is used. Preferred silanes of the general formula (II) above are tetramethoxysilane and tetraethoxysilane.

Of course, it is also possible to use other silanes in addition or as an alternative to the silanes of the general formula (II), e.g. those which have a (non-hydrolyzable) hydrocarbon group without any functional group, such as, for example, methyl- or phenyltrialkoxysilanes.

The composition used in the process according to the invention is in the form of a still free-flowing mass (suspension). The liquid constituent of this mass consists, for example, of water and / or (preferably water-miscible) organic solvents and / or compounds which were used or produced in the course of the production of the nanoscale particles or their surface modification (for example alcohols in the case of alkoxysilanes) , together. Suitable organic solvents optionally used are, for example, alcohols, ethers, ketones, esters, amides and the like. However, an (additional) constituent of the flowable mass can also be, for example, at least one monomeric or oligomeric species which has at least one group which is associated with the surface of the nanoscale particles. which polymerizable / polycondensable groups can react (polymerize or polycondense). Examples of such species are monomers with a polymerizable double bond, such as, for example, acrylic acid esters, methacrylic acid esters, styrene, vinyl acetate and vinyl chloride. Preferred monomeric compounds with more than one polymerizable bond are in particular those of the general formula (III):

(CH ₂ = CR ³ -COZ-) _n -A (III) where n = 2, 3 or 4, preferably 2 or 3 and in particular 2; Z = O or NH, preferably O; R ³ = H, CH ₃ ;

A = n-valent hydrocarbon radical having 2 to 30, in particular 2 to 20, carbon atoms, which may have one or more heteroatom groups which are each located between two adjacent carbon atoms (examples of such heteroatom groups are O, S, NH, NR (R = hydrocarbon radical ), preferably O).

The hydrocarbon radical A can also carry one or more substituents which are preferably selected from halogen (in particular F, Cl and / or Br), alkoxy (in particular C ₄ alkoxy), hydroxy, optionally substituted amino, NO ₂ , OCOR ⁵ , COR ⁵ (R ⁵ = C ^ alkyl or phenyl). However, the radical A is preferably unsubstituted or substituted with halogen and / or hydroxy.

In one embodiment of the present invention, A is derived from an aliphatic diol, an alkylene glycol, a polyalkylene glycol or an optionally alkoxylated (e.g. ethoxylated) bisphenol (e.g. bisphenol A).

Further usable compounds with more than one double bond are, for example, allyl (meth) acrylate, divinylbenzene and diallyl phthalate. It is also possible, for example, to use a compound having 2 or more epoxy groups (in the case of using epoxy-containing surface groups), for example bisphenol A diglyci- dyl ether or an (oligomeric) precondensate of a hydrolyzable silane containing epoxy groups (eg glycidoxypropyltrimethoxysilane).

The proportion of organic components in the coating compositions used according to the invention is preferably not more than 20% by weight, based on the solids content. For layers with a high refractive index, it can e.g. 5% by weight, for layers with a low refractive index, e.g. 15% by weight.

The coating composition used according to the invention preferably has a pH> 3, particularly preferably> 4. In general, the pH is in the neutral range up to about 8, preferably up to about 7.5.

In step a) of the process according to the invention, the coating composition is applied to the crystalline substrate in order to coat it in whole or in part. The coating methods suitable for this purpose are the conventional ones known to the person skilled in the art. Examples include dipping, spraying, knife coating, brushing, brushing or spinning.

Before being applied to the crystalline substrate, the flowable mass can be adjusted to a suitable viscosity, for example by adding solvent or evaporating volatile constituents (in particular solvent already present). The substrate can optionally be subjected to a pretreatment (e.g. cleaning, degreasing, etc.) before the flowable mass is applied.

In stage b) of the process according to the invention, a polymerization and / or polycondensation of the polymerizable / polycondensable surface groups of the nanoscale inorganic solid particles (and optionally of the polymerizable / polycondensable groups of the additionally used monomeric or oligomeric species) is carried out. This polymerization / polycondensation can be carried out in the manner familiar to the person skilled in the art. Examples of suitable processes are thermal, photochemical (for example with UV radiation ), electron beam curing, laser curing, room temperature curing, etc. If necessary, such a polymerization / polycondensation takes place in the presence of a suitable catalyst or starter (initiator), which is added to the flowable composition at least immediately before it is applied to the substrate.

Suitable initiator / initiator systems are all common starters / starter systems known to those skilled in the art, including radical photo starters, radical thermal starters, cationic photo starters, cationic thermal starters and any combination thereof.

Specific examples of radical photo starters that can be used are Irgacure ^® 184 (1-hydroxycyclohexylphenyl ketone), Irgacure ^® 500 (1-hydroxycyclohexylphenyl ketone, benzophenone) and other photo initiators of the Irgacure ^® type available from Ciba-Geigy; Darocur ^® 1173, 1116, 1398, 1174 and 1020 (available from Merck); Benzophenone, 2-chlorothioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, benzoin, 4,4'-dimethoxybenzoin, benzoin ethyl ether, benzoin isopropyl ether, benzil dimethyl ketal, 1, 1, 1-trichloroacetophenone, diethoxyacetophenone and dibenzosuberone.

Examples of radical thermal starters include organic peroxides in the form of diacyl peroxides, peroxydicarbonates, alkyl peresters, alkyl peroxides, perketals, ketone peroxides and alkyl hydroperoxides and azo compounds. Dibenzoyl peroxide, tert-butyl perbenzoate and azobisisobutyronitrile should be mentioned as specific examples. An example of a cationic photoinitiator is Cyracure ^® UVI-6974, while a preferred cationic thermal initiators, 1-methyl imidazole.

These starters are used in the customary amounts known to the person skilled in the art (preferably 0.01-5% by weight, in particular 0.1-2% by weight, based on the total solids content of the coating composition. Of course, in certain circumstances, entirely the starter can be dispensed with, such as in the case of electron beam or laser curing. The polymerization / polycondensation of stage b) of the process according to the invention is preferably carried out thermally or by irradiation (in particular with UV light). Photochemical polymerization / polycondensation or a combination of thermal and photochemical polymerization / polycondensation is particularly preferred.

The polymerization / polycondensation can be preceded by the removal of further volatile, non-polymerizable / non-polycondensable compounds from the layer applied to the substrate. However, this separation of volatile constituents can also or additionally take place at the polymerization / polycondensation stage or thereafter.

In the following, a typical method according to the invention is to be outlined by way of example, the value ranges and procedures given being of general validity irrespective of the materials actually used.

Nanoscale particles of, for example, SiO ₂ , TiO ₂ , ZrO ₂ or other oxidic or sulfidic materials (particle size 30 to 100 nm, preferably 40 to 70 nm) are in a solvent (for example in a lower alcohol such as methanol, ethanol, propanol) in one Concentration of 1 to 20 wt .-%, preferably 5 to 15 wt .-%, dispersed and with a surface modifier with polymerizable / polycondensable groups in an amount of preferably 2 to 25 wt .-%, in particular 4 to 15 wt .-% (based on the total solids content). If, for example, silanes are used, the surface modification can be carried out by stirring for several hours at room temperature. If appropriate, a monomeric or oligomeric material with polymerizable / polycondensable groups, which is compatible with the surface modifier or the surface groups, can then be added in an amount of, for example, up to 20% by weight, preferably 4 to 15% by weight, (based on the total solids content) are added.

After adjusting the viscosity by adding or removing solvent, one or more suitable starters (each in an amount of, for example 0.01 to 5 wt .-%, based on the total solids content) and optionally other conventional additives.

The coating composition is then applied to the substrate, the application amount depending on the desired refractive index and the field of application being generally chosen so that layer thicknesses in the range from 50 to 200 nm, preferably 100 to 150 nm, are achieved.

The subsequent polymerization / polycondensation (crosslinking) takes place at a relatively low temperature, preferably in the temperature range from 10 to 50 ° C., in particular 10 to 30 ° C., and particularly preferably at room temperature. In another embodiment, for example in the case of thermal crosslinking, the formation of the organically crosslinked layer (s) preferably takes place at temperatures of 150 ° C. or less and more preferably 130 ° C. or less.

If a reduction in the reaction times is desired, photopolymerization is preferably used; any light sources, in particular UV light emitting sources, can be used (e.g. mercury vapor lamps, xenon lamps, laser light).

One or more further layers are applied to the resulting organically crosslinked layer in the manner described until the desired layer composite is obtained. The last (outermost) layer no longer requires a separate crosslinking stage, but can be done directly in the final compression and burnout stage f).

For the last or outermost layer, instead of a nanoscale inorganic solid particle with a flowable composition containing polymerizable and / or polycondensable organic groups, which gives a different refractive index than the previous composition, a flowable composition which gives a different refractive index than the previous composition , applied, the nanoscale inorganic solid particles without polymerizable and / or polycondensable organic groups contains. In this case, naturally no organic crosslinking takes place in the outermost layer before or in step f).

It has been shown that organic crosslinking is necessary so that further layers can be applied without damage to layers in which the organic components contained have not yet been compressed and burned out. Since no further layer is applied for the last or outermost layer, the organic crosslinking is also not necessary, so that, as mentioned above, the nanoscale inorganic solid particles in the composition for the outermost layer need not have any polymerizable and / or polycondensable organic groups. Of course, flowable compositions containing nanoscale inorganic solid particles with polymerizable and / or polycondensable organic groups can also be used just as well for the last layer.

For example, in a multi-layer system consisting of two layers, the second layer can alternatively be applied instead of by applying a flowable composition that contains nanoscale inorganic solid particles with polymerizable and / or polycondensable groups, or by applying a flowable composition that contains nanoscale inorganic solid particles without polymerizable and / or polycondensable groups , are formed. The layer composite obtained is then further treated in accordance with step f) explained below.

For the optional composition for the outermost sol-gel layer, which contains nanoscale inorganic solid particles without polymerizable and / or polycondensable groups, the same applies as for the compositions already described, apart from the absence of the polymerizable and / or polycondensable groups. In particular, all of the above information applies to the nanoscale inorganic solid particles, for example with regard to material, size, production, etc. The nanoscale inorganic solid particles can be unmodified; but they can also be surface modified. For surface-modified nanoscale inorganic solid particles, the same applies to surface modification as explained above, except that the surface modification surface applied groups do not include polymerizable and / or polycondensable groups.

Further examples of compounds which can be used for surface modification without polymerizable and / or polycondensable groups are optionally substituted carboxylic acids having 1 to 24 carbon atoms, which can also contain ether bonds, and their anhydrides, esters (preferably CrC ₄ alkyl esters) and amides "Quaternary ammonium salts of the formula NR ⁶ R ⁷ R ⁸ R ⁹⁺ X ^" , in which R ⁶ to R ^{9 are} optionally different aliphatic, aromatic or cycloaliphatic groups with preferably 1 to 12, in particular 1 to 8, carbon atoms, such as, for example, alkyl groups with 1 to 12, in particular 1 to 8 and particularly preferably 1 to 6 carbon atoms (for example methyl, ethyl, n- and i-propyl, butyl or hexyl), and X ^"represents an inorganic or organic anion, for example acetate, OH ^" , CI ^" , Br ^" or I ^" ; Mono- and polyamines, in particular those of the general formula R ₃ - _n NH _n , in which n = 0, 1 or 2 and the radicals R independently of one another are alkyl groups with 1 to 12, in particular 1 to 8 and particularly preferably 1 to 6 carbon atoms ( eg methyl, ethyl, n- and i-propyl, butyl or hexyl) and ethylene polyamines (eg ethylenediamine, diethylenetriamine etc.); Amino acids; imines; β-dicarbonyl compounds with 4 to 12, in particular 5 to 8 carbon atoms, such as, for example, acetylacetone, 2,4-hexanedione, 3,5-heptanedione, acetoacetic acid and acetoacetic acid -CC ₄ -alkyl esters, such as ethyl acetoacetate; and silanes.

Suitable hydrolyzable silanes for modification are, for example, silanes of the general formula: Rt _n SiR ² ₍₄ -n) (IV) in which the radicals R ^{2 are} identical or different and mean hydrolyzable groups or hydroxyl groups and are as defined in formula (I), Rt radicals are the same or different and represent non-hydrolyzable groups and n is 1, 2 or 3, or an oligomer derived therefrom.

The non-hydrolyzable radical Rt without a functional group is, for example, alkyl (preferably C ₂₄ alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl, pentyl, hexyl, octyl or cyclohexyl), alkenyl (preferably C _2, ₂₄ -alkenyl, such as vinyl, 1-propenyl, 2-propenyl and butenyl), alkynyl (preferably C ₂ -24-alkynyl, such as acetylenyl and propargyl), aryl (preferably C ₆ -o-aryl, such as phenyl and naphthyl) and alkyl aryls and aryl alkyls derived therefrom. The radicals R and X may optionally have one or more customary substituents, such as halogen or alkoxy.

In stage f), the layer composite is heated to temperatures of 400 to 800 ° C., preferably 400 to 600 ° C. and in particular 400 to 500 ° C., and kept at this temperature for 1 minute to 1 hour, for example. The organic (carbonaceous) components are completely burned out without cracking or other defects.

For this purpose, it is preferred to carry out the compression and burnout in stage f) in such a way that the layer composite is heated from the outside inwards in the direction of the crystalline substrate. This enables the organic components contained in the interior of the composite to escape through the already heated outer layers. For the same reason, the layers are preferably heated at a heating rate of at least 100 ° K / min.

The optical multilayer systems produced according to the invention are e.g. As interference systems, such as reflective and anti-reflective coatings, in addition to the applications explained above, they are also suitable for the following applications:

Optical filters: anti-reflection and reflex filters in the field of the glasses industry, displays, screens, semiconductor lasers, microlens coatings, solar cells, "damage-resistant" laser layers, bandpass filters, anti-reflection filters, absorption filters and beam splitters.

Holographic layers: light control systems, information storage, laser couplers, waveguides, decoration and architecture. Embossable layers: anti-reflective systems, focusing in detector fields, lighting of flat screens, imaging in photocopiers, fiber optics (light coupling).

Lithography: Manufacture of micro-optical elements such as waveguides, gratings, pinholes, diffraction gratings (point gratings) as well as in the field of display technology, fiber chip coupling and imaging optics.

The following example serves to further explain the invention and is not restrictive in nature.

Example - AR coating on sapphire watch glass

A. Sol synthesis 1. Basic brine

1.1. TiO ₂ base sol 28.43 g (0.1 mol) of tetraisopropyl orthotitanate are dissolved in 205.83 g of isopropanol and 10.00 g (0.1 mol) of acetylacetone are added with stirring. After stirring for 15 minutes at room temperature, a solution of 6.65 g of concentrated hydrochloric acid (HCl, 37%) in 2.78 g of water is added with stirring. The mixture is stirred at room temperature for 24 h.

1.2. GPTS hydrolyzate 23.63 g (0.1 mol) of 3-glycidyloxypropyltrimethoxysilane (GPTS) and 2.70 g of hydrochloric acid (0.1 N) are placed in a one-neck flask equipped with a reflux condenser, magnetic stirrer and oil bath and 24 hours at 40 ° C stirred. The reaction mixture is concentrated on a rotary evaporator (45 ° C., 50 mbar, 1 h) and a clear, colorless, slightly viscous liquid results.

1.3. TEOS hydrolyzate 20.83 g (0.1 mol) of tetraethoxysilane (TEOS) are mixed with 15.28 g of water and 0.29 g of concentrated hydrochloric acid (HCl, 37%) are added with stirring. After clarification of the reaction mixture (after approx. 5 min) 26.90 g of ethanol are added and the mixture is stirred for a further 2 h at room temperature.

2. Coating brine

2.1. H-Sol To prepare 100 g of H-sol, 63.66 g of the basic TiO ₂ sol are dissolved in 26.37 g of isopropanol and 6.59 g of 1-butanol, while stirring 0.07 g of the GPTS hydrolyzate and 3. 31 g of the TEOS hydrolyzate were added and the mixture was stirred at room temperature for 5 min.

2.2. L-Sol 6.41 g of the basic TiO ₂ sol are dissolved in 52.19 g of isopropanol and 13.05 g of 1-butanol, 28.34 g of the TEOS hydrolyzate are added with stirring and 5 min stirred at room temperature.

B. Production of the multilayer system on sapphire substrate. The brine is applied to a sapphire watch glass by means of a centrifugal technique (spin coater). The substrates are cleaned with ethanol. 2 AR layers (H and L sol) are applied to each side of the sapphire watch glasses (2,000 - 2,500 rpm). After each coating, the substrates are pre-dried at 120 ° C for 1-2 minutes. After the complete coating, the stack is burned in at 450 ° C for 30 min.

C. Results The transmission measurement (GARY 5E spectrophotometer, Varian, Australia pty, Ltd.) shows that the transmission of the sapphire watch glass (curve 2) coated on both sides according to the invention is significantly improved in the entire visible spectral range compared to the uncoated substrate (curve 1) and that it is even better than 99% in the range 510-570 nm (Fig. 1).

Claims

1. Optical multilayer system on a crystalline substrate, which is obtainable by a) applying a nanoscale inorganic solid particles with polymerizable and / or polycondensable organic groups containing flowable composition to a crystalline substrate; b) polymerization and / or polycondensation of the groups of the solid particles to form an organically crosslinked layer; c) applying a further composition according to a), which gives a different refractive index than the preceding composition, to the organically crosslinked layer; d) polymerization and / or polycondensation of the groups of the solid particles to form a further organically crosslinked layer; e) optionally repeating steps c) and d) one or more times to form further organically crosslinked layers on the already existing organically crosslinked layers and / or other surfaces of the substrate; and f) single-stage thermal compression of the layer composite and burning out of the organic constituents contained, it being possible for the last applied layer 1), if appropriate, for the polymerization and / or polycondensation of the groups of solid particles to also form an organically crosslinked layer directly in the final stage f) or 2) optionally, alternatively, the nanoscale inorganic solid particles have no polymerizable and / or polycondensable organic groups, so that in this case no polymerization and / or polycondensation of groups of the solid particles for the top layer. takes place with the formation of an organic crosslinking before or in step f).

2. Optical multilayer system according to claim 1, characterized in that the crystalline substrate made of silicon, lithium niobate, lithium tantalate, quartz, sapphire, other gemstones or semi-precious stones, PbS or selenium.

3. Optical multilayer system according to claim 1 or claim 2, characterized in that the crystalline substrate is flat or curved.

4. Optical multilayer system according to one of claims 1 to 3, characterized in that the substrate is transparent.

5. Optical multilayer system according to one of claims 1 to 4, characterized in that the substrate is provided on both sides with an optical multilayer system.

6. Optical multilayer system according to one of claims 1 to 5, characterized in that the crystalline substrate is a disc, in particular made of sapphire, a watch glass, in particular made of sapphire, an instrument cover glass, a wafer, in particular made of silicon, a crystalline detector or a is optical filter.

7. A process for producing an optical multilayer system on a crystalline substrate, characterized by the following steps: a) applying a nanoscale inorganic solid particles with a flowable composition containing polymerizable and / or polycondensable organic groups to a crystalline substrate; b) polymerization and / or polycondensation of the groups of the solid particles to form an organically crosslinked layer; c) applying a further composition according to a), which gives a different refractive index than the preceding composition, to the organically crosslinked layer; d) polymerization and / or polycondensation of the groups of the solid particles to form a further organically crosslinked layer; e) optionally repeating steps c) and d) one or more times to form further organically crosslinked layers on the already existing organically crosslinked layers and / or other surfaces of the substrate; and f) single-stage thermal compression of the layer composite and burning out of the organic constituents contained, it being possible for the last applied layer 1), if appropriate, for the polymerization and / or polycondensation of the groups of solid particles to form an organically crosslinked layer, also directly in the final stage f) or 2) optionally, alternatively, the nanoscale inorganic solid particles have no polymerizable and / or polycondensable organic groups, so that in this case there is no polymerization and / or polycondensation of groups of the solid particles with the formation of an organic crosslinking before or in step f) for the top layer.

8. The method according to claim 7, characterized in that the formation of the organically crosslinked layer (s) is carried out at temperatures up to about 150 ° C, preferably up to about 130 ° C.

9. The method according to any one of claims 7 and 8, characterized in that the formation of the organically crosslinked layer (s) is carried out by photochemical polymerization and / or polycondensation.

10. The method according to any one of claims 7 to 9, characterized in that the single-stage compression and burnout takes place at temperatures in the range of 400-800 ° C, preferably 400-600 ° C.

11. The method according to any one of claims 7 to 10, characterized in that the one-step compression and burn-out is carried out in such a way that the layer composite is heated from the outside inwards in the direction of the substrate.

12. The method according to claim 11, characterized in that the heating rate of the layer (s) is at least 100 ° K / min.

13. The method according to any one of claims 7 to 12, characterized in that the nanoscale particles are selected from semimetal or metal compounds, in particular oxides, sulfides, selenides and tellurides of semimetals or metals and mixtures thereof.

14. The method according to any one of claims 7 to 13, characterized in that the nanoscale particles are selected from those of Si0 ₂ , Ti0 ₂ , Zr0 ₂ , ZnO, Ta ₂ 0 ₅ , Sn0 ₂ and Al ₂ 0 ₃ and mixtures thereof.

15. The method according to any one of claims 7 to 14, characterized in that the polymerizable and / or polycondensable surface groups are selected from organic radicals which have a (meth) acrylic, vinyl, allyl or epoxy group.

16. The method according to any one of claims 7 to 15, characterized in that the solid particles used were prepared by surface modification of nanoscale solid particles with the corresponding surface groups.

17. The method according to any one of claims 7 to 16, characterized in that the solid particles used have been prepared using at least one compound with corresponding polymerizable / polycondensable groups.

18. The method according to any one of claims 7 to 17, characterized in that the production of the inorganic solid particles is carried out by the sol-gel method.

19. The method according to any one of claims 7 to 18, characterized in that the coating composition has a pH in the range of 3 to 8.

0. Use of the optical multilayer system according to one of claims 1 to 6 as an interference layer system and in particular as an anti-reflective layer system.