EP2459656A1

EP2459656A1 - Method for producing thin films and the application thereof

Info

Publication number: EP2459656A1
Application number: EP10757562A
Authority: EP
Inventors: Peter William De Oliveira; Michael Veith
Original assignee: Leibniz Institut fuer Neue Materialien Gemeinnuetzige GmbH
Current assignee: Leibniz Institut fuer Neue Materialien Gemeinnuetzige GmbH
Priority date: 2009-07-30
Filing date: 2010-07-15
Publication date: 2012-06-06
Also published as: DE102009035673A1; US20120129967A1; WO2011012227A1; US20130046041A2; US9051470B2; DE102009035673B4

Abstract

The invention relates to a method for producing thin films, particularly for coating surfaces, preferably pigments or flakes, particularly interference pigments.

Description

Process for the preparation of thin films and their use

Description Field of the invention

The invention relates to a process for the production of thin films, in particular for the coating of surfaces, preferably of pigments or flakes, in particular interference pigments.

PRIOR ART Pigments (lat. Pigmentum, color, make-up) are understood as meaning colorants which are not soluble in the application medium (binder, diluent) and therefore are present in finely divided solids (pigment particles) in the colored end use. Their color impression arises either through absorption or reflection (remission) of certain frequency components of the visible light.

According to this definition, pigments represent a suspension of pigment particles in a matrix. Since they are present as solids, theirs also plays their part alongside the actual base material

Shape, size, surface and arrangement play a role in the resulting color effect. In conventional pigments, the color effect is based on absorption or reflection of certain wavelengths. For example, by selective excitation of electron transitions in atoms and / or molecules of the pigment material or by selective excitation of electron oscillations within characteristic functional groups of the pigment material. Extensive prior art is known for the preparation, processing and handling of pigments, for example in paints or varnishes or other coloring formulations.

In addition to the conventional pigments play in recent times

Gloss or effect pigments play a major role. In this type of pigments, the color effect is influenced or even completely caused by interference or diffraction (diffraction). This effect occurs when light is diffracted at regular structures that have similar dimensions as the wavelengths of the light. Depending on the wavelength of the light, weakening (destructive interference) or amplification (constructive interference) can occur as a result of differences in propagation time. The structures can be, for example, thin high-index layers, but also regular lines or points, for example diffraction gratings. Because of the color generation by reflection is therefore no longer the intrinsic color of the pigment crucial, but its structure and the angle of incidence of the light, as well as its orientation relative to the viewer. This allows color effects that are not possible with conventional pigments. The effects are all the stronger, the more uniform the pigments are aligned.

Diffractive pigments

The generation of colors by using diffractive elements, such. B. Diffraction grating is described for example in US 3,957,354 or EP 0 632 296. These writings reveal Line patterns that produce certain defined color impressions when exposed to sunlight or another polychromatic light source. Another approach is disclosed in the document DE 199 12 160. In order to produce a color image or a hologram, which are present as a digitally stored image, dots are embossed on a material with a permanently embossable surface, each of which has a pattern of lines running in parallel, one of have the dependent color to be generated in the range of 100 nm to 2000 nm. The dots are imprinted by a dot-matrix or dot-matrix machine, which has a set of needle points for the required primary colors.

The use of diffractive structures on pigments or on flake-form pigments (flakes) is disclosed in DE10252645 A1 or WO2003 / 011980. The problem with these structures is that they have to be provided with additional optical properties by applying thin layers because their structure has to be preserved.

interference pigments

Interference pigments usually consist of platelet-shaped substrates which are thinly coated with refractive layers. Depending on the thickness of the coating, different colors can be produced. Such pigments are also referred to as pearlescent pigments. Mostly, mica of different particle size is used as the substrate. The coating used is usually TiO ₂ , preferably in rutile modification. For example, the published patent application WO9920695 (Merck) Interference pigments based on multiply coated platelet-shaped substrates which have at least one layer sequence of: (A) a coating with a high refractive index (B) of a colorless coating with a low refractive index.

In US Pat. No. 3,438,796 and US Pat. No. 5,135,812, for example, metallic luster pigments are described which have a central opaque aluminum film which alternately alternates with dielectric low-refractive-index films on both sides, such as, for example. As silica or magnesium fluoride, and partially transparent metal films such. As chrome or aluminum coated. Due to the manufacturing process, the central metal film of these pigments is coated only on the wafer top and bottom side, while the side surfaces are broken edges and open towards the medium.

Because of the great importance of the interference pigments as gloss or effect pigments, there is an extensive state of the art for simple and multiple coating with a wide variety of materials. In this case, not only coatings for influencing the refraction of light but also, for example, protective layers (for example DE 10 2006 009 129 A1, EP 1 727 864 B1) or layers for influencing the orientation of the pigments (EP 1 084 198 Bl) are described.

Suitable substrates for such pigments are usually thin platelets of metal oxides, silicates (for example mica), but also glass or metal platelets or even platelets of polymers.

In addition to individual pigments, it is also possible to coat flake-shaped flakes or entire surfaces with one or more interfering layers. However, that is Production of such thin defined layers, in particular of interference layers difficult, since high demands are placed on the homogeneity of the layer. At the same time, the production by vapor deposition is complicated and expensive and is not very variable with respect to the usable substances. Although the use of sol-gel systems for coating is more versatile, the production of thin films is difficult according to the techniques described.

DE 198 23 732 A1 discloses the use of polymerisable solid particles for the production of optical multi-layer systems, but does not describe the influence on the surface tension for the production of thin layers or films or the production of pigments.

Furthermore, the provision of suitable substrates for interference pigments or flakes or larger areas with a suitable layer thickness is a problem. Thinner substrates can reduce not only the thickness of the coated pigments, but also the thickness of the required lacquer layer of a lacquer of these pigments. It is also important that a substrate manufacturing process be particularly versatile in order to provide a wide range of substrates, for example for different colors or refractive indices.

task

The object of the present invention is to provide a method which enables the production of films, in particular for the coating of surfaces, in particular of Pigments or flakes. Ideally, the process should simultaneously be suitable for the production of pigments, flakes or films. The process should be both versatile with respect to the usable materials or substrates, as well as easy to perform and inexpensive.

Solution This object is solved by the inventions having the features of the independent claims. Advantageous developments of the inventions are characterized in the subclaims. The wording of all claims is hereby incorporated by reference into the content of this specification. The invention also includes all reasonable and in particular all mentioned combinations of independent and / or dependent claims.

In the following, individual process steps are described in more detail. The steps do not necessarily have to be performed in the given order, and the method to be described may also have other steps not mentioned.

To solve the above object, a method for the production of films is proposed, which is characterized by the following method steps. a) addition of surface-active substances to nanoscale inorganic solid particles with polymerizable and / or polycondensable organic surface-containing flowable compositions;

b) formation of one or more thin films stabilized by the attachment of the surface-active substances to the interface (s), wherein the formation of one or more thin films thin films by generating bubbles, foam, by forming minimal surfaces and / or by wetting surfaces;

c) solidification of the films by polymerization and / or polycondensation.

Surprisingly, the process according to the invention gives films which have a thickness in the range from micrometers to a few nanometers. The produced fi lms are also homogeneous and their thickness is easy to control. Due to the wide range of possible variations in both educts, additives and process conditions, the process is very versatile and simple. It therefore allows the fast, easy and inexpensive mass production of such films.

Thin in the context of the invention means a thickness in the range from 10 to 1000 nm, preferably in the range from 50 to 800 nm. By using nanoscale particles which contain polymerizable and / or polycondensable surface groups, it is possible to obtain stable films even under very mild conditions For example, to produce low temperatures and / or via photopolymerization. Preference is given to temperatures below 50 ^° C., more preferably below 30 ^° C. This makes it possible to produce very homogeneous films with a high solids content.

It has been found, completely surprisingly, that the addition of surface-active substances makes it possible to produce thin films both without a substrate and for coating surfaces. In the present description and the appended claims, "nanoscale inorganic solid particles" are understood as those having an average particle size (average particle diameter) of not more than 200 nm, preferably not more than 100 nm, and more preferably not more than 70 nm. A particularly preferred particle size range is 5 to 50 nm.

The nanoscale inorganic solid particles may be composed of any materials, but preferably they are metals and in particular metal compounds such as (optionally hydrated) oxides such as Ce ₂ O ₃ , 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 , ITO or WO ₃ ; Chalcogenides such as, for example, sulfides (eg CdS, ZnS, PbS and Ag ₂ S), selenides (eg GaSe, CdSe and ZnSe) and tellurides (eg ZnTe or CdTe), halides such as AgCl, AgBr, AgI, CuCl, CuBr, CdI ₂ and PbI ₂ , carbides such as CdC ₂ or SiC; Arsenides such as AlAs, GaAs and GeAs; Antimonides such as InSb; Nitrides such as BN, AlN, 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 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. Particularly preferred according to the invention are nanoscale particles of SiO ₂ , TiO ₂ , ZrO ₂ , ZnO, Ta ₂ O ₅ , SnO ₂ and Al ₂ O ₃ (in all modifications, in particular as boehmite, AlO (OH)) and mixtures thereof.

Since the nanoscale particles which can be used according to the invention have a Covering a wide range of refractive indices, the refractive index of the films can be conveniently adjusted to the desired value by suitable selection of these nanoscale particles. The production of nanoscale solid particles used in the invention can be carried out in a conventional manner, for. 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, z. As metals (for example, after the reduction of the precipitation method), ceramic oxide systems (by precipitation from solution), but also salt-like or Mehrkomponen- tensysteme be used. The salt-like or multi-component systems also include semiconductor systems.

The preparation of the nanoscale inorganic solid particles which are provided with polymerizable and / or polycondensable organic surface groups and which are used according to the invention can be carried out in two different ways, namely by surface modification of already produced nanoscale inorganic solid particles and by production of these inorganic nanoscale solid particles using one or more compounds having such polymerizable and / or polycondensable groups.

The organic polymerisable and / or polycondensable surface groups may be any groups known to the person skilled in the art which undergo a free-radical, cationic or anionic, thermal or photochemical polymerization or a thermal or photochemical polymer. condensation (optionally 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. Hydroxyl, carboxy and amino groups, which can be used to obtain ether, ester and amide bonds between the nanoscale particles, should be mentioned in particular in the polycondensable groups.

It is also preferred according to the invention for the organic groups present on the surfaces of the nanoscale particles, which comprise the polymerizable and / or polycondensable groups, to have a relatively low molecular weight. In particular, the molecular weight of the (purely organic) groups should not exceed 500 and preferably 300, more preferably 200. Of course, this does not preclude a significantly higher molecular weight of the compounds (molecules) comprising these groups (eg.

1000 and more).

As already mentioned above, the polymerisable / polycondensable surface groups can in principle be provided in two ways. If a surface modification of already produced nanoscale particles is carried out, suitable for this purpose are all (preferably low molecular weight) compounds which on the one hand have one or more groups which are present on the surface of the nanoscale solid particles functional groups (such as OH groups in the case of oxides) or at least can interact, and on the other hand have at least one polymerizable / polycondensable group. Thus, the corresponding compounds z. Both covalent and ionic form (salt-like) or coordinative (complex) bonds to the surface of the nanoscale solid particles, while the pure interactions would exemplify dipole-dipole interactions, hydrogen bonds, and the Waals interactions. Preference is given to the formation of covalent and / or coordinative bonds. Specific examples of organic compounds which can be obtained for surface modification 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) having polymerizable double bonds, ethylenically unsaturated alcohols and amines, amino acids , Epoxides and the like. According to the invention particularly preferred as such compounds are - especially in the case of oxidic solid particles - hydrolytically condensable silanes with at least (and preferably) a nonhydrolyzable radical having a polymerizable carbon-carbon double bond or an epoxide ring, more preferably (meth) acryloyloxyalkyltrialkoxysilanes such as z. For example, 3-methacryloyloxypropyltri (m) ethoxysilane and glycidyloxyalkyltrialkoxysilanes such as 3-glycidyloxypropyltri (m) ethoxysilane.

If the preparation of the nanoscale inorganic particulate solids using one or more compounds having polymerizable / polycondensable groups already occurs, subsequent surface modification may be dispensed with (although, of course, this may be an additional measure).

The flowable composition according to the invention surfactants are added. Surface-active substances are substances that affect the surface tension of a surface Reduce liquid or interfacial tension between two phases. Their effect is based on the preferred attachment to the phase interface. Under ideal conditions, a monolayer of surface-active substances is formed at the interface. The resulting films can be very thin due to the reduced surface tension, down to a few nanometers. The films may be formed on a surface of a substrate or without substrate as bilayers of surfactants, ie, films in which both surfaces have a liquid / gaseous interface stabilized by the surfactants. The best known example of the formation of bilayers of surfactants is the formation of foams or bubbles.

As surface-active substances it is possible to use all substances which reduce the surface tension of the sol used, for example phenol derivatives, modified lecithin, modified siloxanes or modified polysiloxanes, phosphoric acid esters and salts, modified polyurethanes, polyamine-polyester condensates, modified polyacrylates, Polyethyleneimine derivatives or alkylene oxide copolymers or mixtures thereof. Of advantage are those which are stable under the process conditions. Particularly preferred are surface-active substances which consist of polysiloxanes, for example BYK-306, BYK-307, BYK-333, BYK-337, BYK-341 (available from BYK Chemie).

The surface tension of the flowable composition is preferably between 16 and 50 nm / m, more preferably between 20 and 30 nm / m, measured by means of Processor Tensiometer K12 -Krüss. The content of surface-active substances in the flowable composition can be between 0.0001% by weight and 1% by weight, preferably between 0.01% by weight and 0.1% by weight. In a development of the invention, in step b) the formation of one or more thin films is carried out by generating bubbles, foam and / or by forming minimal surfaces, preferably by generating bubbles or foam. In a preferred embodiment of the invention, the thin films by the introduction of gases, for example air, ie by generating bubbles or foam. In this case, for example, hemispherical bubbles are applied to a surface. It is preferred that the diameter of these bubbles is preferably less than 5 cm, preferably between 0.5 and 3 cm. In the case of foam, the diameter of the bubbles in the foam is preferably between 0.1 and 3 cm on average.

Furthermore, flat films can also be produced by forming minimal surfaces between edges of one or more bodies, for example by immersing loops or nets. This allows the production of films and large-area films. Advantageously, the thickness of the resulting films, for example, by the size of the resulting surfaces in combination with the properties of the flowable composition, for example content of surfactants, temperature, viscosity, type of surfactants, type of solvent or be influenced.

The film is preferably not arranged on a surface. However, it is possible that the flowable composition Composition added platelets are arranged within the formed film.

Before the films are produced, the flowable mass can be adjusted to a suitable viscosity, for example by adding solvent or evaporating volatile constituents (in particular already existing solvent).

The produced films would not be stable for a long time due to convection or evaporation. The use of the polymerizable and / or polycondensable surface groups ensures that the films cure without much change in their shape or surface. In step c) 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 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 known 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 appropriate, such polymerization / polycondensation takes place in the presence of a suitable catalyst or initiator (initiator). which is added to the flowable mass at the latest immediately before the formation of the thin films.

Suitable initiator / initiator systems are all known starter / start systems known to the person skilled in the art, including radical photoinitiators, free-radical thermostats, cationic photoinitiator, cationic thermostarter and any combinations thereof.

Concrete examples of usable radical photoinitiators are Irgacure ™ 819 (bis-acylphosphine oxide), Irgacure ™ 819DW, Irgacure ™ 184 (1-hydroxycyclohexylphenyl ketone), Irgacure ™ 500 (1-hydroxycyclohexylphenyl ketone, benzophenone) and others available from Ciba Specialty Chemicals Inc. Irgacure ™ type photoinitiators; Darocur ™ TPO, 4265, MBF, 1173, 1116, 1398, 1174 and 1020 (also available from Ciba Specialty Chemicals Inc.); 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 Thermostarter are u. a. organic peroxides in the form of diacyl peroxides, peroxydicarbonates, alkyl peresters, alkyl peroxides, perketals, ketone peroxides and alkyl hydroperoxides and azo compounds. Particular examples which may be mentioned here are dibenzoyl peroxide, tert-butyl perbenzoate and azobisisobutyronitrile.

An example of a cationic photoinitiator is Cyracure ™ UVI-6974, while a preferred cationic thermostarter is 1-methylimidazole.

These starters are used in the customary amounts known to those 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 Circumstances are completely dispensed with the starter, such as in the case of electron beam or laser hardening). The polymerization / polycondensation of stage c) of the process according to the invention is preferably carried out thermally or by irradiation (in particular with UV light). Particularly preferred is a photochemical polymerization / polycondensation or a combination of thermal and photochemical polymerization / polycondensation. As a result, burdens on the films can be avoided. The exposure is preferably carried out by light sources emitting UV light (eg mercury vapor lamps, xenon lamps, laser light).

The organic crosslinked structure resulting from the polymerization and / or polycondensation simultaneously renders the films elastic and stable.

The polymerization / polycondensation may precede the separation of other volatile, non-polymerizable / non-polycondensable compounds from the layer applied to the substrate. However, this removal of volatile constituents may also or additionally take place at the stage of the polymerization / polycondensation or after.

As already mentioned above, the preparation of the nanoscale inorganic solid particles can be carried out, for example, by the sol-gel process using at least one hydrolytically polycondensable compound having at least one polymerizable / polycondensable group. For example, it is possible to use hydrolyzable alkyl, alkoxy compounds or halides which, in accordance with the above condition, contain at least one polymerisable and / or polycondensable compound

For example, compounds (halides, alkoxides, carboxylates, chelates, etc.) of boron, aluminum, titanium, zirconium, silicon, bismuth, tin, zinc or vanadium may be used. especially preferably containing Cχ- ₆ alkoxides, such as, for example, methoxy, ethoxy, n-propoxy, i-propoxy and butoxy groups. Alternatively, it is of course also possible to use one or more polycondensable compounds in combination with a hydrolytically polycondensable compound having at least one polymerizable and / or polycondensable group.

The hydrolysis and polycondensation are carried out either in the absence of a solvent or preferably in an aqueous or aqueous / organic reaction medium, optionally in the presence of an acidic or basic condensation catalyst such as HCl, HNO ₃ or NH ₃ . When using a liquid reaction medium, the starting components are soluble in the reaction medium. Suitable organic solvents are, in particular, water-miscible solvents, for example monohydric or polyhydric aliphatic alcohols, ethers, esters, ketones, amides, sulfoxides and sulfones.

Advantageously, the hydrolysis and polycondensation of the above-mentioned components is carried out in the presence of one or more complexing agents, which may optionally contain one or more polymerisable groups, e.g. in the presence of nitrates, S-dicarbonyl compounds (e.g., acetylacetonates or acetoacetic acid esters), carboxylic acids (e.g., methacrylic acid) or carboxylates (e.g., acetate, citrate, or glycolate), betaines, diols, diamines (e.g., DIAMO), or crown ethers.

Particular preference is given to alkoxy titanates with addition of surface-modifying polymerizable compounds, particularly preferably alkoxy titanates with the addition of

Dicarbonyl compounds, particularly preferably tetrabutyl orthotitanate with the addition of acetylacetone. In a preferred variant of the process according to the invention, the films are subjected to pyrolysis after drying in order to densify the films and / or to remove the organic constituents. As a result, it is possible, for example, to produce homogeneous oxide layers when oxidic inorganic solid particles are used. The pyrolysis is preferably carried out at temperatures between 400 ⁰ C and 1500 ⁰ C degrees, more preferably between 400 ⁰ C and 600 ⁰ C degrees. The conditions can be selected according to the composition of the film. Those skilled in the art are familiar with such adaptations.

Due to the organically crosslinked structure of the films, there is no crack formation or defect during pyrolysis. Pyrolysis can reduce the thickness of the film. Finished films preferably have a thickness between 10 and 800 nm, preferably between 50 and 700 nm.

After solidification of the films it may be necessary to comminute the films, for example if pigments or flakes have been produced or coated. This can be done with techniques known to those skilled in the art, for example with a ball mill,

Pin mill or air jet mill. The resulting pigments or flakes can subsequently be classified, for example by size. The invention also relates to a thin film, in particular producible by the addition of surface-active substances to a nanoscale inorganic solid particles with polymerizable and / or polycondensable flowable composition containing organic surface groups, forming one or more thin films stabilized by the

Attachment of the surface-active substances to the interface (s), wherein the formation of one or more thin films by the generation of bubbles, foam and / or by BiI- Minimal surfaces and / or by wetting of surfaces and solidification of the films by polymerization and / or polycondensation. Preferably, the thin film contains nanoscale particles selected from the metal compounds, especially oxides, sulfides, selenides and tellurides, or mixtures thereof. SiO ₂ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , SnO ₂ , B ₂ O ₃ or Al ₂ O ₃ or mixtures thereof are particularly preferred.

In an advantageous development of the film was cured by pyrolysis and compacted. In such a pyrolysis, the organic groups are burned out and the film consists only of its inorganic constituents, preferably SiO ₂ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , SnO ₂ , B ₂ O ₃ or Al ₂ O ₃ or mixtures thereof ,

Furthermore, the invention relates to the use of a film or a composition according to the invention for coating surfaces, preferably consisting of metal, an alloy, a ceramic, one or a mixture of metal oxides, in particular iron oxide, Al ₂ O ₃ or SiO ₂ , quartz, graphite, mica, glass or glass-like. These are preferably pigments or flakes.

Furthermore, the high flexibility of the formed films also allows the coating of complicated structures, such as diffractive surface elements, which would not be preserved in conventional processes. Thus, for example, regression pigments or holographic pigments can be coated. In a further advantageous development, the interfering layers can be applied to diffractive surface elements in this way. In a further advantageous development, films can be applied to pigments or flakes or similar substrates by the process according to the invention. These can be easily coated with a thin film. As substrates, substrates known to the person skilled in the art for luster pigments can therefore be used. These are usually platelet-shaped pigments or flakes, which may be of organic or inorganic materials. Platelet-shaped means that they have a length of 3 to 150 μm, preferably of 5 to 70 μm and a width of 3 to 150 μm, preferably 5 to 50 μm and a thickness of 0.1 to 2 μm. Examples of platelets are mica flakes or iron oxide flakes. In a further development of the method, the films obtained can be provided with further coatings, both by repeating the method according to the invention and by using other coating methods which are known to the person skilled in the art. Preferably, several layers of different films will be applied, in particular films with different optical properties. Particularly preferred are further layers with different refractive indices, as well as protective layers, coloring layers or for influencing the hydrophobicity or hydrophilicity of the surface.

In a further development of the method, it is possible to add to the flowable composition further coloring agents, for example, metal colloids, dyes, in order to influence the color of the films.

In a further development of the process, the films obtained can additionally be provided on both sides with different chen coatings are provided, for example, only on the outside of the bubbles or bottom of the films.

In a further development of the method, diffractive surface elements are applied to the films, for example by embossing or lithography.

In a further advantageous development, the films produced according to the invention, which have been produced without a substrate, can be processed, for example, as bubbles or foam, to pigments or flakes or to substrates of effect pigments or flakes.

Furthermore, the invention relates to the use of one or more films for the production of coatings, films, pigments or flakes, in particular for the production of interference effects, such as pearlescent pigments.

This includes, for example, effect or pearlescent pigments, pigments for printing inks, lacquers, paints, security applications, optical systems such as interference filters, anti-reflection systems, color filters.

Further details and features will become apparent from the following description of preferred embodiments

Connection with the subclaims. In this case, the respective features can be implemented on their own or in combination with one another. The possibilities to solve the problem are not limited to the embodiments. For example, area information always includes all - not mentioned - intermediate values and all imaginable subintervals.

Embodiments; Used lacquer composition

20 g of tetrabutyl orthotitanate [Ti (OC ₄ Hg) ₄ ] are placed in a 250 ml three-necked flask and cooled in an ice bath. Is added dropwise slowly (15 min) with stirring 5 g of acetylacetone (AcAc) added. After complete addition, the reaction mixture is removed after 20 min from the ice bath and then stirred at 25 ° C. In a second vessel, 20 g Diethyleneglycoldiethylether (DEGDE) is presented, to 30 mg BYK 307 are added and stirred at 25 ° C for 15 min.

Slowly add the sol prepared in the first step to the second mixture while stirring. After stirring (30 min) at 25 ° C, 0.2 g of the photoinitiator Irgacure ™ 819 is added. The surface tension is 26.2 mN / m (measurement by means of the Processor Tensiometer K12 -Krüss). For the production of effect pigments, mica platelets can still be added.

The composition was processed to blow or foam.

The embodiments are shown schematically in the figures. The same reference numerals in the individual figures designate the same or functionally identical or with respect to their functions corresponding elements. In detail shows:

Fig. 1 a) large bubbles of organically crosslinked TiO ₂ b) small bubbles of crosslinked TiO ₂ ;

Fig. 2 oven treated organically crosslinked TiO ₂ ;

Fig. 3 TEM image of a bubble wall after pyrolysis;

Fig. 4 TEM image of a bubble wall after pyrolysis;

Fig. 5 electron diffraction image;

Fig. 6 elemental analysis; Fig. 7 REM of the cross sections of the interference pigment.

Fig. 1 shows a) large and b) small bubbles of crosslinked TiO ₂ - particles of the coating composition according to the invention after drying at 25 ⁰ C. The dropped paper clip showing the stability of the solidified film.

Figure 2 a) and b) are pyrolyzed films of crosslinked TiO ₂ - particles of the coating composition according to the invention (2 hours at 550 ⁰ C to 600 ° C-1500 ⁰ C). The organic components are burned and TiO _{2 is formed} , the interfering properties of the material are clearly visible. FIG. 3 and FIG. 4 show TEM images of a film after pyrolysis. The structure of the cross-linked nanoparticles is clearly recognizable.

FIG. 5 shows an electron diffraction pattern of a pyrolyzed TiO ₂ -FiImS. The electron diffraction shows crystalline TiO ₂ .

FIG. 6 Elemental analysis of a pyrolyzed TiO ₂ -FiImS.

Fig. 7 SEM (Scanning Electron Microscope) Cross section through a prepared interference pigment. The picture shows a uniform and homogeneous coating. List of quoted literature:

US 3,957,354

EP 0 632 296

DE 199 12 160

DE 102 52 645

WO 2003/011980

WO9920695

US 3,438,796

US 5,135,812

DE 10 2006 009 129 Al

EP 1 727 864 Bl

EP 1 084 198 Bl

DE 198 23 732 Al

Claims

claims

1. A process for the preparation of thin films characterized by the following process steps: a) addition of surface-active substances to nanoscale inorganic solid particles with polymerizable and / or polycondensable organic surface-containing flowable compositions;

b) formation of one or more thin films stabilized by the attachment of the surfactants to the interface (s), wherein the formation of one or more thin films by the generation of bubbles, foam, by the formation of minimal surfaces and / or by wetting from

Surfaces done;

c) solidification of the films by polymerization and / or polycondensation.

2. The method according to claim 1, characterized in that the solidification in step c) is carried out by photochemical polymerization and / or polycondensation.

3. The method according to any one of claims 1 or 2, characterized in that the preparation of the nanoscale inorganic solid particles by the SoI gel method.

4. The method according to any one of claims 1 to 3, characterized in that in step b) the formation of one or more thin films by generating bubbles, foam

and / or by formation of minimal surfaces.

5. The method according to any one of the preceding claims, characterized in that the nanoscale solid particles of metal compounds, in particular oxides, sulfides, selenides and tellurides or mixtures thereof, are selected.

6. The method according to claim 5, characterized in that the nanoscale solid particles are selected from those of SiO ₂ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , SnO ₂ , B ₂ O ₃ or Al ₂ O ₃ or mixtures thereof.

7. The method according to any one of the preceding claims, characterized in that the polymerizable and / or polycondensable surface groups are selected from organic radicals having a (meth) acrylic, vinyl, AlIyI-, ß-dicarbonyl or epoxy group ,

8. The method according to any one of the preceding claims, characterized in that the films are subjected to a pyrolysis, preferably at temperatures in the range of about 400 ⁰ C to about 1500 ⁰ C, in particular in the range of about 400 ⁰ C to about 650 ⁰ C.

9. A thin film, in particular producible by a method according to any one of claims 1 to 8, comprising the addition of surface-active substances to a nanoscale inorganic particulate solids with polymerizable and / or polycondensable organic surface-containing flowable composition, forming one or more thin films stabilized by the attachment of the surface-active substances to the interface (s), wherein the formation of one or more thin films by the generation of bubbles, foam, by formation of minimal surfaces and / or by Benet- zen of surfaces, and solidification of the films by polymerization and / or polycondensation.

10. A thin film according to claim 9, characterized in that the film has been subjected to pyrolysis.

11. A thin film according to any one of claims 9 or 10, characterized in that it contains nanoscale particles selected from the metal compounds, in particular oxides, sulfides, selenides and tellurides or mixtures thereof.

12. A thin film according to claim 11, characterized in that it consists of SiO ₂ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , SnO ₂ , B ₂ O ₃ or Al ₂ O ₃ or mixtures thereof.

13. Use of one or more films according to any one of claims 9 to 12, characterized in that the film on one or more surfaces, preferably consisting of metal, an alloy, a ceramic, quartz, mica, graphite, glass or glass-like, a or a mixture of metal oxides, in particular Al ₂ O ₃ or SiO ₂ , is applied.

14. Use of one or more films according to claims 13, characterized in that the film is applied to diffractive surface elements.

15. Use of one or more films according to any one of claims 13 or 14, characterized in that the film is applied to pigments or flakes.

16. Use of one or more films according to any one of claims 13 to 15, characterized in that a plurality of layers the same or different films are applied, in particular films with different optical properties.

17. Use of one or more films according to any one of claims 13 to 16, characterized in that the film is processed into pigments or flakes.

18. Use of one or more films according to any one of claims 13 to 17, characterized in that they are used for the production of films, pigments or flakes, in particular for the production of interference effects.