DE102007043651A1 - Silicon / titanium dioxide layer with improved surface properties - Google Patents

Abstract

The present invention relates to a catalytically active silicon / titania-containing coating having a high porosity and activity.

Description

The The present invention relates to surfaces and / or Coatings which have cleaning properties.

at Surfaces, in particular transparent surfaces Like glass and plastic, there is a need for soiling which ones due to organic substances, to remove. This should possible by "self-cleaning" the surfaces are made, i. H. through heat or Sunlight, the applied organic substances are to be decomposed.

The WO 2004/085701 proposes for this purpose a CVD applied titanium dioxide coating, which should have catalytic properties. However, it has been found that in the WO 2004/085701 often have unsatisfactory activities.

It Therefore, the task is to find a coating that is able, at least in part, the above-mentioned disadvantages overcome and especially in many applications with higher activity catalytically.

These Task is by a silicon / titanium dioxide-containing coating solved according to claim 1. According to the will a catalytically active transparent silicon / titanium dioxide-containing Coating proposed, characterized in that the silicon / titanium dioxide-containing Coating a porosity of ≥ 30% and a Refractive index of ≤ 2.2

The Designation "titanium dioxide-containing coating" in the sense of the present invention means or comprises in particular that the coating titanium dioxide as catalytically active main components contains.

The Designation "catalytically active" in the sense of the present invention Invention means in particular that the coating is capable of is, organic substances in the presence of at least oxygen, Water and light (especially UV light) at least partially in to decompose volatile substances oxidatively.

The Designation "transparent" in the sense of the present invention means or in particular includes a permeability of ≥ 80%, preferably ≥ 85%, and most preferably ≥ 90% in the respectively used wavelength range, in particular in the visible wavelength range.

According to one more preferred embodiment is the porosity the coating ≥ 40% to ≤ 90%, still preferably ≥ 65% up to ≤ 85%.

According to one more preferred embodiment is the refractive index the coating ≤ 2, still preferably ≤ 1.9.

The Task is further by a silicon / titanium dioxide-containing coating solved according to claim 2 of the present invention. Accordingly, a catalytically active transparent Silicon / titanium dioxide-containing coating proposed by characterized in that the silicon / titanium dioxide-containing coating has an active titanium dioxide surface area of ≥ 1%.

there is under "active titanium dioxide surface of X% "understood that the surface of the coating too X% consists of titanium dioxide and / or the "X%" of the surface the coating is covered by titanium oxide. This value lets z. B. determined by TEM measurements.

Prefers the silicon / titania-containing coating has an active titanium dioxide surface area of ≥ 20% the coated substrate surface of the layer, still preferably ≥ 50% of the coated substrate surface the layer on.

• – Die Beschichtung ist aufgrund der verbesserten Oberflächeneigenschaften über einen langen Zeitraum katalytisch mit einer hohen Durchsatzrate aktiv.
• – Die Dicke der hergestellten Silizium/Titandioxidhaltige Beschichtung beträgt bei vielen Anwendungen höchstens wenige Mikrometer. Sie ist daher weitgehend unempfindlich gegenüber thermischem Stress und beeinflusst Bauteilabmessungen und Toleranzen nur unwesentlich.
• – Der Katalysatorträger hat aufgrund seiner hohen Oberfläche hydrophile Eigenschaften und lagert Wasser aus der Luft ein. Dieses ist als Edukt für die Photokatalyse verwendbar; somit werden die katalytischen Aktivitäten der Beschichtung nochmals erhöht.
• – Die Beschichtung weist oftmals sowohl eine erhöhte Transparenz wie auch eine bessere UV-Selbstreinigung auf und kann daher auch sehr gut zur Entspiegelung/Reflektionsminderung verwendet werden.

By means of a silicon / titanium dioxide-containing coating according to the invention, one or more of the following advantages can be achieved in many applications within the present invention:

• The coating is catalytically active at a high throughput rate over a long period of time due to the improved surface properties.
• The thickness of the produced silicon / titanium dioxide-containing coating is at most a few micrometers in many applications. It is therefore largely insensitive to thermal stress and affects component dimensions and tolerances only insignificantly.
• - The catalyst support has hydrophilic properties due to its high surface area and stores water from the air. This is useful as a starting material for photocatalysis; Thus, the catalytic activities of the coating are increased again.
• The coating often has both an increased transparency and a better UV self-cleaning and can therefore also be used very well for antireflection / reflection reduction.

A preferred embodiment of the invention is characterized in that that the ratio of silicon / titanium (in mol / mol) of ≥ 0.1: 1 to ≤ 10: 1. This has become for many purposes of the present invention have been found to be favorable.

Prefers this is the ratio of silicon / titanium (in mol / mol) of ≥ 0.2: 1 to ≤ 5: 1, more preferably ≥ 0.5: 1 to ≤ 2: 1.

A preferred embodiment of the invention is characterized in that that the ratio of silicon / titanium (in mol / mol) of ≥ 0.1: 1 to ≤ 5: 1 and the thickness of the coating at ≥ 90 nm to ≤ 120 nm. This has changed For many applications turned out to be particularly favorable. The thickness of the coating is preferably 95 nm up to ≤ 115 nm.

These Embodiment has often then in practice as particularly valuable, especially if the optical Properties of the layer are important and / or at least in partial focus. In this case, a good self-cleaning is usually done at the same time Improvement of the transparency of the coated substrate achieved.

A preferred alternative embodiment of the invention characterized in that the ratio of silicon / titanium (in mol / mol) of ≥ 5: 1 to ≤ 10: 1 and the thickness of the coating at ≥ 150 nm to ≤ 500 nm is located. This has proven to be special for many applications favorably exposed. The thickness of the coating is preferably at ≥ 250 nm to ≤ 400 nm.

These Embodiment has often then in practice as especially valuable when exposed to the self-cleaning effect stands in the foreground.

A preferred embodiment of the invention is characterized in that that the coating is essentially a porous full-formed body, in particular a homogeneous porous shaped body is or forms such a body.

Of the Term "substantially" designates in particular ≥ 90 Vol%, preferably ≥ 95 vol% of the coating.

Thereby can be used in many applications within the present invention an easily manufacturable and even further reflection-reducing coating be achieved.

A preferred embodiment of the invention is characterized in that that the coating has transmission-enhancing properties, especially for light in the visible wavelength range. Preferably, the coating is capable of reducing the transmission of Substrate by ≥ 2%, preferably by ≥ 4% in the respective used wavelength range, especially in the visible Increase wavelength range.

A preferred embodiment of the invention is characterized in that that the average diameter of the pores is ≥ 1 nm to ≤ 50 nm. This has happened with many Applications of the present invention as particularly favorable for the antireflective properties of the coating. Preferably, the average diameter of the Pores of ≥ 2 nm to ≤ 40 nm, more preferably nm to ≤ 20 nm.

A preferred embodiment of the invention is characterized in that that the diameter of ≥ 90% of the pores of ≥ 1 nm to ≤ 50 nm.

A preferred embodiment of the invention is characterized in that that the diameter distribution of the pores of the coating according to the invention essentially a log-normal distribution with a half width of ≦ 20 nm, preferably ≦ 10 nm, more preferably ≦ 8 nm follows.

"In the essential "means that ≥ 90% of the pores, preferably ≥ 95% of the pores, and most preferably ≥98% of the pores thereof Distribution follow.

A Such distribution has become popular for many applications present invention particularly favorable, because of a uniform pore geometry often an improved supply and removal of the reactants can be observed can.

A preferred embodiment of the invention is characterized in that that the coating is produced by means of a sol-gel process.

The The present invention also relates to a method for producing a transparent coating for a transparent substrate material, characterized in that the Procedure based on a sol-gel process.

The Designation "Sol-gel process or sol-gel process" in Meaning of the present invention means or includes in particular all processes and / or processes involving metal precursor materials, in particular metal halides and / or metal alkoxides in solution subjected to hydrolysis and subsequent condensation become.

A preferred embodiment of the invention is characterized in that that during at least part of the sol-gel process at least one porosity-causing component present is removed after completion of the sol-gel process and / or gets destroyed.

This can according to a preferred embodiment the invention after completion of the coating at least partially by themselves, d. H. that the coating is catalytic the porosity-causing component attacks and thus away.

Prefers the porosity-causing component is at least for Part removed and / or destroyed by means of a plasma treatment.

The Designation "plasma treatment" within the meaning of the present Invention means or includes in particular all processes and / or Processes in which ionized molecules, in particular Radicals of a gas generated by an energy source such as high frequency or microwaves were generated, act on the substrate. Most of time this is associated with a temperature increase.

Surprisingly has been found to be true for coatings and / or substrates Plasma treatment in many applications once again an essential Improvement of surface quality and others Properties can be achieved.

Especially then when using temperature-sensitive substrates such as plastics this embodiment is often particularly advantageous, as usually avoided thermal overloading of the substrate can be.

It It should be noted that under "plasma treatment" in the sense of in particular also a corona treatment falls within the scope of the present invention, even if this is often handled differently in the language. A plasma treatment according to the present invention comprises thus explicitly a corona treatment; this is one particular preferred embodiment of the invention.

According to one preferred embodiment of the invention is the plasma treatment performed as atmospheric pressure plasma. This has been found in many applications of the present invention to be very proved advantageous.

The Designation "atmospheric pressure plasma" in the sense of the present invention means or includes in particular all Processes and / or processes in which a plasma is under atmospheric Ambient conditions is applied to the substrate.

Prefers is the plasma treatment at a process gas pressure of ≥ 2 bar up to ≤ 8 bar performed. This has become apparent many applications of the present invention proved to be advantageous.

Prefers the process gas pressure is ≥ 3 bar to ≤ 6 bar, preferably ≥ 3.5 bar to ≤ 5 bar.

Prefers the plasma treatment is carried out while rotating the nozzle.

A preferred embodiment of the invention is characterized in that that the porosity-causing polymer after completion of the sol-gel process is washed out.

A preferred embodiment of the invention is characterized in that that the porosity-causing polymer after completion of the sol-gel process by tempering, in particular at a temperature of ≥ 80 ° C. to ≤ 100 ° C, preferably washed with water becomes.

A preferred embodiment of the invention is characterized in that that the porosity-causing polymer after completion of the sol-gel process Burned out especially at a temperature of ≥ 250 ° C. is burned out.

A preferred embodiment of the invention is characterized in that that the at least one porosity-causing component is a polymer, wherein the average molecular weight of the polymer preferably ≥ 5,000 Da to ≤ 50,000 Da, more preferably ≥ 10,000 Since up to ≤ 35,000 Da.

A preferred embodiment of the invention is characterized in that the polymer is an organic polymer, preferably selected from the group comprising polyethylene glycol, polypropylene glycol, Copolymers of polyethylene glycol and polypropylene glycol, polyvinylpyrrolidone, Polyethers, alkyl-, cycloalkyl- and / or aryl-substituted polyethers, polyesters, Alkyl-, cycloalkyl- and / or aryl-substituted polyesters, in particular Polyhydroxybutyric acid or mixtures thereof.

General Groups / Molecule Definition: Within the specification and claims, general groups or molecules, such as e.g. As alkyl, alkoxy, aryl, etc. claimed and described. Unless otherwise described, the following groups within the generally described groups / molecules are preferably used in the context of the present invention:
Alkyl: linear and branched C1-C8-alkyls,
long-chain alkyls: linear and branched C5-C20 alkyls
Alkenyl: C2-C6-alkenyl,
Cycloalkyl: C3-C8-cycloalkyl,
Alkoxide / alkoxy: C 1 -C 6 alkoxy, linear and branched
long-chain alkoxide / alkoxy: linear and branched C5-C20 alkoxy
Aryl: selected from aromatics with a molecular weight below 300 Da.

Polyether: selected from the group containing H- (O-CH ₂ -CH (R)) _n -OH and H- (O-CH ₂ -CH (R)) _n -H where R is independently selected from: hydrogen, alkyl , Aryl, halogen and n from 1 to 250

Substituted polyethers: selected from the group consisting of R ₂ - (O-CH ₂ -CH (R ₁ )) _n -OR ₃ and R ₂ - (O-CH ₂ -CH (R ₂ )) _n -R ₃ where R ₁ R ₂ , R _{3 is} independently selected from hydrogen, alkyl, long chain alkyl, aryl, halogen and n is from 1 to 250

Ether: The compound R ₁ -OR ₂ wherein each of R ₁ and R _{2 is} independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, aryl, long chain alkyl. Unless otherwise stated, the following groups / molecules are more preferred groups / Molecules within the general groups / molecular definition:
Alkyl: linear and branched C1-C6-alkyl,
Alkenyl: C3-C6 alkenyl,
Cycloalkyl: C6-C8-cycloalkyl,
Alkoxy, alkoxide: C 1 -C 4 -alkoxy, in particular isopropyl oxide
long-chain alkoxy: linear and branched C5-C10 alkoxy, preferably linear C6-C8 alkoxy

A polyether selected from the group consisting of H- (O-CH ₂ -CH (R)) _n -OH and H- (O-CH ₂ -CH (R)) _n -H where R is independently selected from: hydrogen, alkyl , aryl, halogen and n is from 10 to 250.

Substituted polyethers: selected from the group consisting of R ₂ - (O-CH ₂ -CH (R ₁ )) _n -OR ₃ and R ₂ - (O-CH ₂ -CH (R ₂ )) _n -R ₃ where R ₁ R ₂ , R _{3 is} independently selected from hydrogen, alkyl, long chain alkyl, aryl, halogen and n is from 10 to 250.

A preferred embodiment of the invention is characterized in that that the silicon oxide in the form of a silicon-alkoxide precursor solution is added.

A preferred embodiment of the invention is characterized in that that the pH of the silicon-containing precursor solution from ≥ 1 to ≤ 6.

A preferred embodiment of the invention is characterized in that that the process is carried out using aged silicon sols.

The Designation "aged silicon brine" means in particular a sol, which by time action at least part of the parallel has undergone ongoing hydrolysis and condensation reactions.

Surprisingly has been proven by this simple procedure at For many applications of the present invention, the coating activity again can be significantly increased. Without being bound to a theory The inventors believe that this is due to the larger number attributed to Si-O-Si bonds in aged sols could be due to the fewer bonds to the titanium dioxide arise.

The The invention also relates to a transparent coating for a substrate prepared according to the invention Method.

The The invention also relates to an optical component comprising a transparent substrate and one on the substrate applied and / or arranged coating according to the present invention.

A preferred embodiment of the invention is characterized in that the substrate is selected from the group comprising Glass, transparent plastics, preferably selected from Group containing polycarbonate, polyacryl, PET, PEN, COC, PES, PSU, transparent thermosetting compounds, especially epoxies and acrylates and mixtures thereof, metals, and mixtures thereof.

The The present invention also relates to a method for producing an optical according to the invention Component, characterized in that the coating on the Substrate is applied by dipping and / or spin-coating.

• – optische Instrumente
• – Brillen
• – Scheinwerfergehäuse in der Automobiltechnik
• – Scheiben, besonders in der Automobiltechnik
• – Cockpitverglasungen
• – Schilder
• – Autospiegel
• – Solarzellen, insbesondere flexible Solarzellen

The present invention also relates to the use of a coating according to the invention and / or an optical component according to the invention for

• - optical instruments
• - glasses
• - Headlight housing in automotive engineering
• - Washers, especially in the automotive industry
• - Cockpit glazings
• - signs
• - Car mirror
• - Solar cells, in particular flexible solar cells

The the aforementioned and the claimed and in the application examples described to be used according to the invention Components are subject in size, shape design, Material selection and technical conception no special exceptions, so that the selection criteria known in the field of application unrestricted Application can be found.

More details, features and benefits The subject of the invention will become apparent from the subclaims and from the following description of the accompanying drawings and examples, in which - by way of example - several embodiments of a silicon / titanium dioxide-containing coating according to the invention is shown. In the figures shows:

1 a transmission measurement of a glass substrate with and without applied inventive coating

Degradation of stearic acid on one Glass substrate coated according to the invention:

Of the Degradation of stearic acid was based on several glass substrates examined.

Basically, the following pattern was used: First, two solutions were provided:
Solution 1: 4.5 g of polyethylene glycol (molar mass 35,000 Da) were prepared in 40 g of ethanol and, while stirring, 1.4 g of water were slowly added. If no solution occurred, additional water (if necessary with heating to 40 ° C in an ultrasonic bath) was added. Then, 0.1 g of 1N HCl was added.
Solution 2: 4 g tetraethoxysilane in 10 ml EtOH.

solution 2 was then mixed with solution 1 and stirred for 2 h.

The The resulting mixture was allowed to stand for 14 days to age to effect sol. If there was a cloudiness, While stirring, slowly add enough water until the turbidity disappeared.

Solution 3:

In 30 ml of ethanol, 5 g of a titanium component (Fa. Sachtleben Hombikat XXS 100) and stirred (if necessary under ultrasound), until complete solution occurred.

Subsequently, to the aged sol, much of the solution 3 was added, which resulted in a molar ratio of silicon to titanium of 9: 1 (hereinafter defined as "10% TiO ₂ ".) Optionally, aftertreatment was carried out in the ultrasound (at room temperature).

The Glass substrate was then mixed with the solution dip-coated; it resulted in a 340 nm thick layer. After that was dried in air and at 400 ° C for 1 h in the oven.

The Porosity of the coating was about 50%, the refractive index 1.3.

The active TiO ₂ surface was about 80%.

In addition to a glass substrate coated with a "10%" TiO ₂ coating, four further coatings of 20%, 30%, 40% and 50% were prepared, with the mixing ratios in solution 2 changed accordingly, otherwise the production was the same.

All Glass substrates were coated with an approx. 2 μm thick layer covered by stearic acid and in "Sun-Tester" (Fa. Atlas) in order to simulate the irradiation with sunlight.

Already after 18 h exposure, almost complete degradation was observed in the samples with ≥ 30% TiO ₂ and more.

To 24 h exposure time was stearic acid in all samples completely decomposed except for the "10%" sample; after 40 hours of exposure time, all samples were complete Determine degradation.

Transmission improvement by application a coating according to the invention

1 refers to further example according to the invention and shows a transmission measurement of a glass substrate with and without applied coating according to the invention.

The coating was produced as described above with "10%" TiO ₂ , but applied in a thickness of about 100 nm.

Degradation of stearic acid on one coated plastic substrate

Of the Degradation of stearic acid was additionally demonstrated a coating according to the invention on a Plastic substrate examined.

To was half on a ca. 3 mm thick polycarbonate substrate applied a coating.

First the substrate was cleaned (IPA with ultrasound, then Rinsing with deionized water) and even with atmospheric pressure plasma pretreated to wetting the coating solution improve. For this purpose, a device of the company. Plasmatreat with a high-frequency generator FG 3001 and a rotary nozzle RD 1004 equipped with a nozzle head type AGR123 was, used.

When Process gas was selected compressed air; the sample distance to the Nozzle was 8 mm. It became a traversing speed set from 2 cm / sec.

The coating itself was prepared as described above with "10%" TiO _2. The application was carried out again by dip coating, which also resulted in an approximately 330 nm thick layer.

Subsequently was dried for 20 min at 100 ° C and a like Plasma treatment described above, whereby the polyethylene glycol was removed.

The Porosity of the coating was about 55%, the refractive index 1.35.

The active TiO ₂ surface was about 80%.

The substrate was then covered with an approximately 2 μm thick layer of stearic acid and stored in the "Sun Tester" (Atlas), power X watt / m ^{2 in} order to simulate the irradiation with sunlight.

there was after 18 h exposure already a large area Dismantling occurred.

To 24 h exposure time was the stearic acid except for a few Percent dismantled; after 40 h exposure time were more complete Determine degradation.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - WO 2004/085701 [0003, 0003]

Claims (15)

Catalytically active transparent silicon / titanium dioxide-containing coating, characterized in that the silicon / titanium dioxide-containing coating has a porosity of ≥ 30% and a refractive index of ≤ 2.2. Catalytically active transparent silicon / titanium dioxide-containing Coating, characterized in that silicon / titanium dioxide-containing Coating an active titanium dioxide surface of ≥ 1% the coated substrate surface of the layer. Silicon / titanium dioxide-containing coating according to claim 1 or 2, characterized in that the ratio of Silicon / titanium (in mol / mol) of ≥ 0.1: 1 to ≤ 10: 1 is. Silicon / titanium dioxide-containing coating after a of claims 1 to 3, characterized in that the Ratio of silicon / titanium (in mol / mol) of ≥ 0.1: 1 to ≤ 5: 1 and the thickness of the coating at ≥ 90 nm to ≤ 120 nm. Titanium dioxide coating according to one of the claims 1 to 3, characterized in that the ratio of Silicon / titanium (in mol / mol) of ≥ 5: 1 to ≤ 10: 1 and the thickness of the coating is ≥ 150 nm to ≤ 500 nm. Silicon / titanium dioxide-containing coating according to one of claims 1 to 5, characterized in that, characterized in that the SiO ₂ - coating is produced by means of a sol-gel process. Process for the preparation of a transparent coating for a transparent substrate material, characterized that the process is based on a sol-gel process. Method according to claim 7, characterized in that that during at least part of the sol-gel process at least one porosity-causing component present is removed and / or destroyed after completion of the sol-gel process becomes. Method according to one of claims 6 to 8, characterized in that the at least one porositätsverursachende Component is a polymer, where the average molecular weight of the polymer is preferably ≥ 5,000 Da to ≤ 50,000 There is. Method according to one of claims 6 to 9, characterized in that the polymer is an organic polymer, preferably selected from the group comprising polyethylene glycol, Polypropylene glycol, copolymers of polyethylene glycol and polypropylene glycol, Polyvinylpyrrolidone, polyether, alkyl, cycloalkyl and / or aryl-substituted Polyether, polyester, alkyl, cycloalkyl and / or aryl-substituted Polyester or mixtures thereof. Method according to one of claims 6 to 10, characterized in that the silicon in the form of a silicon-alkoxide precursor solution is added. Method according to one of claims 6 to 11, characterized in that the pH of the silicon-containing Precursor solution of ≥ 1 to ≤ 6. Method according to one of claims 7 to 12, characterized in that the method using aged Silicon brine is done. Transparent coating for a transparent Substrate, produced according to one of claims 6 to 13. Use of a silicon / titanium dioxide-containing coating according to one or more of the claims 1 to 6 and 14 for - optical instruments - glasses - Headlight housing in automotive engineering - Slices, especially in the Automotive engineering - Cockpit glazings - signs - Car mirror - solar cells, in particular flexible solar cells