Substrate with antimicrobial properties

The present invention relates to a substrate of any type: metal, glass, glass ceramic, wherein at least one of its surfaces has antimicrobial, in particular antibacterial or antifungal properties. The present invention also relates to methods for producing such a substrate.

In the field of ceramic substrates, for example in European Patent EP 653 161 describes the possibility of covering coating consisting of a composition of silver, in order to give them antimicrobial properties.

In the preparation of glass substrates are known sol-gel methods for producing surfaces with antimicrobial properties. These methods require curing step sol-gel layer is conducting at high temperatures of about 500-600 ° C (sintering temperature). Methods are also known that require the substrate is immersed in a mixture containing a silver salt. In this case, a silver layer is not deposited, but an exchange of ions in solution at high temperature.

From EP A 1449816 it is known a method for producing a glass substrate having antimicrobial properties. This method requires a drying step at a temperature of from 20 to 105 ° C and heat treatment at 600-650 ° C. This thermal treatment has some disadvantages particularly with respect to cost and uniformity of the product. Furthermore, this method makes it poorly reproducible, since it has been found that diffusion of silver at these temperatures is very fast and small changes in the duration of the thermal treatment lead to significant changes in the depth of diffusion of silver, which changes the antibacterial properties of the substrate. It may also be noted that such a thermal treatment causes an undesirable yellow colouration of a substrate of soda-lime glass. Furthermore, after processing in this way the product can no longer be cut into pieces of a certain size because of the necessary heat treatment.

Therefore, a need exists for the substrate, either glass or metallic, with antimicrobial properties, which is easy to manufacture and use which is inexpensive.

The present invention relates to a substrate coated with at least one inorganic layer, particularly selected from metal oxides, oxynitrides, oxycarbides, carbides, DLC or nitrides, said layer comprising at least one antimicrobial agent. Specifically, as such a mineral layer can be selected oxides of silicon, tin, zinc, titanium, niobium, aluminum, zirconium or mixture thereof, for example ZnSnOx. Particularly preferred nitrides are silicon nitride, titanium, and aluminum, as well as mixtures thereof.

As the antimicrobial agent can be selected various inorganic agents known for their antimicrobial properties, in particular silver, copper and zinc. The antimicrobial agent is preferably used in the form of metal.

The substrate may be a metal, such as steel or stainless steel, or ceramics, or be made of plastic or thermoplastic material or glass-like, in particular flat glass, particularly soda-lime glass which may be float glass. The substrate may be colorless or colored glass. It may have a reflective layer (to produce a mirror) or a layer of enamel or painting layer (for wall covering), generally at a side opposite to the antimicrobial surface.

The substrate may have a thickness ranging from 2.5 to 12 mm.

The substrate may have a surface area greater than 0.8 m to 0.8 m; it may be suitable for cutting to a predetermined size in the subsequent cutting process.

In some embodiments, the substrate having antimicrobial agents present at at least one exposed surface may be an annealed sheet of glass. The term "annealed glass sheet" means that the glass can be cut to size without breaking, while a sheet of tempered glass is broken or compressed during cutting. Such an annealed sheet of glass preferably has a surface compression of less than 5 MPa.

It has been found that it is possible to achieve diffusion of the antimicrobial agents in mineral coating formed by one or more layers of metal oxides, oxynitrides, oxycarbides or nitrides in the case where the coating has been previously applied to any type of substrate. The diffusion of the antimicrobial agent can also occur in a topcoat deposited above the layer containing the antimicrobial agent.

For example, the substrate may be coated with a first layer that blocks or slows down the diffusion of antimicrobial agents and, optionally, a second layer serving as a reservoir of antimicrobial agents. These functions can be found in an article made according to the invention by comparing the antimicrobial effect of similar products with and without undercoating and / or by analyzing diffusion profiles.

Each of the layers of the backsheet may have a thickness of 1 to 1000 nm, preferably between 1.5 and 800 nm, most preferably between 2 and 600 nm.

In particular, the blocking underlayer is chosen from pyrolitic and sputtered layers, in particular layers comprising metal oxide, metal or metal alloy such as Pd, Ni-Cr, TiOx, NiCrOx, Nb, Ta, Al, Zr, ZnAl, or mixture thereof .

In the case of using a substrate made of glass, it is possible that the thus obtained antimicrobial glass substrate passes through the stage of heat treatment, such as tempering, bending or hardening, while retaining thereafter their antimicrobial properties.

In the case of metal substrates, most preferred undercoat and / or mixed layers are chosen from titanium oxide, titanium nitride or zirconium oxide.

The substrate of the invention preferably has an antibacterial effect the relatively large number of bacteria both gram-positive Gram negative bacteria, in particular, at least one of the following bacterial species: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus hirae. Antibacterial action in particular, at least one of these bacteria, as measured in accordance with standard JIS Z 2801, higher than log 1, preferably higher than log 2 and particularly preferred higher than log 2,5. The substrate can be considered bactericidal according to the standard JIS Z 2810 if it has an effect higher than log 2. However, the present invention also relates to substrates having a weaker activity (for example bacteriostatic effect, which means that the bacteria are not necessarily killed but can no longer grow).

The substrate according to the invention advantageously has an antifungal (fungicidal or fungistatic) effect on at least one type of fungus, in particular Candida albicans or Aspergillus niger.

It has been found that it is possible to deposit the mineral layer and the antimicrobial agent in one step on the entire substrate, whether it is made of metal such as steel, or a glass-substrate. In particular, in the classic method of magnetron sputtering is possible to create a layer, such as a metal oxide doped with an antimicrobial agent such as silver, using two metal targets in the same deposition chamber (co-sputtering) or using a target with a mixture of metals. This method does not require additional or subsequent diffusion of the antimicrobial agent. Antimicrobial substrate prepared in one step, without any thermal treatment, which reduces production costs.

It was also found that if required to receive the tempered and antimicrobial glass, it is possible to use the same method and, optionally, can be added backsheet. Antimicrobial (in particular bactericidal but also bacteriostatic) properties may be maintained even after quenching (assuming treatment at a high temperature for 5-10 min).

With a simple method, which does not require any heat treatment, were obtained having antimicrobial metal oxide layers with additive Ag, deposited in a single step by co-sputtering, in which the concentration of Ag can vary from 0.1 to 5%.

If the substrate used is a clear glass, it can advantageously have antimicrobial properties and a neutral color in reflection. In particular, the colorimetric indexes by reflection (colorimetric system CIELAB) a * and b * (Illuminant C, an observer angle 10 °) may be in the range of between -10 and 6, preferably between - 5 and 3, and most preferably between - 2 and 0, and the purity may be less than 15%, preferably less than 10% and most preferably less than 5%.

If the substrate is a colored glass, it is possible to give it antimicrobial properties without significantly changing the original color of the substrate. The color change is usually expressed by the colorimetric index DeltaE *; DeltaE * = [(l * l-1 * 2) 2+ (a * 1-a * 2) 2+ (b * 1-b * 2) 2] 1/2. For antimicrobial substrate according to the invention can be prepared DeltaE * lower than 3, preferably less than 2.

When the glass substrate used is a clear glass, it can advantageously have both antimicrobial properties and a visible light absorption of less than 1.5%, preferably less than 1.4% and most preferably less than 1.3%. It may have a visible light transmittance in the range 80-91%, preferably 84 -90%. Visible light reflection may be less than 15%, preferably less than 12%, most preferably less than 10%.

The substrate according to the invention preferably has in particular an antimicrobial effect after at least one of the following accelerated aging tests: test sprinkler (test over 20 days in a chamber with a humidity higher than 95% at 40 ° C), after 500 hours of UV irradiation (4 ATLAS lamps 340 A camera with a temperature of 60 ° C), after 24 hours of immersion in a solution of H2SO4 (0.1 N), after 24 hours of immersion in a solution of NaOH (0.1 N).

It may be advantageous to use an undercoat comprising an oxide of zirconium. This may be particularly useful when the mixed layer comprises an antibacterial agent, and titanium oxide, in particular when it comprises substantially comprises titanium dioxide anatase-crystal form.

Additional or alternative embodiments of the present invention are described in the dependent claims.

Without leaving the scope of this application, the present invention is illustrated below:

EXAMPLE 1

Two samples of clear soda-lime glass coated with a layer of SiO2 (Al): Ag by co-sputtering. We are using two metal targets in an atmosphere of mixture of argon and oxygen: one was composed of silicon with the addition of 8% Al, and the second target was a metallic silver. The current supply to the layers was regulated in order to obtain 0.5 atomic% Ag in the layer for the first sample and 1 atomic% Ag in the layer for the second sample. The layer thickness was 80 nm for the first and 150 nm - for the second sample.

The bactericidal and fungicidal properties (in particular against E. coli) samples were analyzed in accordance with standard JIS Z 2801. Level 1 log shows that for 24 hours under standard conditions of killing 90% of bacteria seeded on the surface of the glass; Log 2 indicates that 99% of the bacteria were killed; Log 3 indicates that 99.9% of the bacteria were killed, etc.

For both samples of example 1, the value obtained 4,2 log.

EXAMPLE 2

Two samples of clear soda-lime glass coated with SnO2-Ag by co-sputtering using two metallic targets (tin (Sn) and silver (Ag)). The layer thickness was 80 and 40 nm and the amount of Ag deposited was 2 and 30 mg / m2, respectively. The antibacterial effect was measured in the same manner as in the previous example. It was obtained values ​​of 4.4 and 4,5 log.

EXAMPLE 3

Two samples of clear soda-lime glass coated with a layer of ZrO2-Ag by co-sputtering using two metallic targets (Zr and Ag). The current supply to the layers was regulated in order to obtain 1.2 atomic% Ag for the first sample and 3.4 atomic% Ag for the second. The antibacterial effect was measured in the same manner as in the previous examples. For both samples, the value obtained 4 log.

EXAMPLE 4

SnO2-Ag was precipitated by co-sputtering two different substrates. The amount of Ag deposited was 46 mg / m2 of surface and the thickness of the mixed layer was 17 nm.

The first substrate is a transparent silica glass with two sublayers SiOx (70 nm) and SnO2: F (320 nm) deposited by chemical vapor deposition. The second substrate is a clear soda lime glass coated with SiO2 layer 50 nm thick deposited by vacuum deposition. Both samples were subjected to conventional quenching (at 670 ° C for 10 min., Followed by rapid cooling).

Antibacterial action against E. coli, measured as in the preceding examples, had values ​​of 1.76 and 1.38 log. This means that as a result of bactericidal action are killed by 90 to 99% seeded bacteria.

EXAMPLE 5

SnO2-Ag was precipitated by co-sputtering onto a substrate from two different metal. The amount of Ag deposited was 46 mg / m2 of surface and the thickness of the mixed layer was 17 nm.

The first substrate was a galvanized steel of ST37 1.5 mm thick. The second substrate was a sample of steel 0.2 mm thick laminated in cold condition and without oil.

Both samples antibacterial activity against E. coli, measured as in the previous examples, the value was 3.53 log.