WO2003050193A1

WO2003050193A1 - Lacquer layer, which reflects infra-red radiation

Info

Publication number: WO2003050193A1
Application number: PCT/DE2002/004490
Authority: WO
Inventors: Detlef Burgard; Rüdiger Nass
Original assignee: Nanogate Technologies Gmbh
Priority date: 2001-12-08
Filing date: 2002-12-09
Publication date: 2003-06-19
Also published as: AU2002358427A1; EP1458823A1; JP2005511292A

Abstract

The invention relates to a method for producing a transparent IR shield. According to said method, a carrier is provided with an active substance and is placed in the radiation path. To achieve this, a lacquer system comprising nanoparticulate particles and solvents that are conventionally contained in lacquers are applied to a substrate in a wet process.

Description

Title: INFRARED RADIATION REFLECTIVE PAINT LAYER

description

The present invention relates to the subject of the preamble and thus deals with infrared radiation shielding layers.

Shielding infrared radiation is becoming increasingly important in various areas. In architectural applications, such as large glass surfaces on high-rise buildings, it is often desirable to keep the radiation of infrared radiation into the building as low as possible in order to prevent the interior from heating up in southern countries, even though a maximum of daylight is let in , The same applies in the field of automotive glazing, where improvements in aerodynamics, with the desired constant visibility, force larger glazing. Here, too, it is desirable to avoid heating the interior. If heat radiation is not adequately shielded, many users in both homes and automobiles require air conditioning by means of strongly cooling air conditioning systems. The excessive heat radiation then causes increased energy consumption.

It may also be necessary to change the behavior of the current to heat in other situations; this is especially true in Nordic countries, for greenhouses etc. It is desirable to have heat radiation in one

Let buildings in, but don't let heat radiation out. The same applies to certain foils such as

l - Greenhouse films, for tarpaulins, clothing, etc. Here is a case that is the reverse of that where excessive heating per se is to be avoided by allowing the internal heat to be radiated and, if possible, radiant heat should be prevented. It should be explicitly mentioned that this particular behavior is only desired in certain cases and is therefore not always sought. There may also be cases in which the overall heat flow is to be suppressed, that is, an exchange from inside to outside or from outside to inside is not permitted. An example is an automobile whose interior is to be protected from the sun in summer, while in winter the heat available from the heating should remain as much as possible in the interior to promote rapid warming but to prevent it from cooling down when stationary.

It has been proposed (EP 0 727 306 A2) to provide a laminated glass in which an interlayer film is interposed between the first and second transparent glass plates, which has dispersed functional ultrafine particles which have a particle diameter of up to 0.2 μm. The intermediate film should consist in particular of plasticized PVB (polyvinyl butyral) or an ethylene-vinyl acetate copolymer (EVA). EP 0 727 306 A2 proposes as functional particles those which are selected from the group consisting of metals, metal-containing compounds and composites which contain metal. The metals are said to consist of Sn, Ti, Si, Zn, Zr, Fe, Al, Cr, Co, Ce, In, Ni, Ag, Cu, Pt, Nn, Ta, W, V and Mo. They are mentioned as metal compounds Oxides, nitrides, oxinitrides and sulfides; the composite should have at least one Be doped substance and the connection with the at least one substance doped. The oxides mentioned are Sn0 ₂ , Ti0 ₂ , Si0 ₂ , Zr0 ₂ , Zn0 ₂ , Fe ₂ 0 ₃ , Al ₂ 0 ₃ , FeO, Cr ₂ 0 ₃ , Co ₂ 0 ₃ , Ce0 ₂ , ln ₂ 0 ₃ , NiO , MnO and CuO. It is discussed what amounts of substance have to be incorporated in the starting resin for the interlayer film and it is discussed that the film obtained may only have a certain maximum conductivity in order to have a satisfactory radio wave transmittance.

The previously known method may lead to acceptable results under special applications, but is not always completely satisfactory. This applies in particular if, in addition to good IR shielding, layers with improved conductivity are also desired, for example in order to obtain antistatic properties or to provide conductive coatings. In addition, difficulties arise in the production of infrared-shielding, complex-shaped objects, such as particularly strongly curved windshields or the like.

Another method which is known in the prior art is the gas phase coating of flat glass, which can be carried out by sputtering, CVD, PVD etc. Sputtering can be used to apply ultra-thin layers of conductive or semiconductively doped oxides, for example made of ATO (Sn0 ₂ : Sb) FTO (Sn0 ₂ : F) AZO (ZnO.Al) or ITO (In ₂ 0 ₃ : Sn). In an ultra-thin state, these layers are transparent to visible light and reduce the transmission of infrared radiation. Conductive layers can be used as continuous layers. The systems used to apply such dense layers are however, very expensive, which is why they only pay for themselves with high throughput, i.e. the coating of very large quantities of material. In addition, significantly more target material is required than is ultimately deposited on the substrate. The rest of it is deposited in the machine, from where it typically has to be removed, which is extremely undesirable not only because of the poor exploitation of the expensive targets.

Although such sputtering systems are technically very complex, it is still very difficult to coat them with complex shaped objects in small or special series, since each change of geometry requires a considerable redesign of essential parts of the system. The previous attempt to sputter car windows flat and then bend them into the desired aerodynamic shape has so far failed. In addition, coating of polymers or foils, as is often desired, is at best possible to a limited extent.

The aim of the present invention is to provide something new for commercial use.

The goal is achieved with the characteristics of the independent claim. Preferred embodiments can be found in the subclaims.

The present invention thus proposes, according to a first aspect, a method for producing a transparent IR shield, in which a support is provided with active substance in order to be arranged in the beam path, in which it is provided that one is already without nanoparticulate Particle film-forming paint system comprising nanoparticulate particles and customary paint solvents is applied wet on a substrate.

It was surprisingly recognized that the nanoparticulate particles, even if they are equipped for incorporation into a coating system in which they are to be incorporated, give a good infrared shielding effect. This effect is used to enable the paint system with the nanoparticulate particles to be applied wet. The advantage of wet application is that, on the one hand, less technical effort is required for the application itself, which opens up a large number of new applications, even when no large series are to be produced, and on the other hand, more complex geometries can also be formed. In addition, more materials, in particular polymers and / or films, can be coated than is possible in the prior art.

The nanoparticulate particles are preferably dispersed in the coating system. For this purpose, the nanoparticulate particles which are used in the production of the coating system can be appropriately equipped for simple dispersion or redispersion in the coating system. The way to achieve the desired redispersibility is known per se. What is important here, however, is the knowledge that good IR shielding results from application of measures known per se.

It is possible to maintain the infrared shielding effect of the nanoparticulate particles for a large number of solvents customary in lacquers, which broadens the possible uses, because in particular the paint system can be optimized for certain substrates and / or application conditions, such as indoor use, on exterior facades under various typical weather conditions such as high humidity, frequent rainfall, etc., for aircraft, in particular cockpit glazing, automobiles, etc. If a particularly temperature-resistant paint system can also be selected, infrared shielding should be achieved in the area of high-temperature applications in which a high-temperature interior such as an oven or the like should radiate less heat to the outside.

It is possible to use a mixture of different common solvents to optimize different properties at the same time, such as abrasion and scratch resistance, resistance to peeling and peeling, heat resistance, UV resistance, etc.

A binder, in particular in the form of organic components, can be added to the coating system. The organic components can be added in monomeric, oligomeric or polymeric form and it can in particular be at least one from the polymer group polyacrylates, in particular PMMA, polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB), polyvinyl alcohols (PVA), polyethylene glycols, polyurethanes, bisphenol-based Polymers, polyesters, and oligomers and / or monomers of the aforementioned polymers and / or cellulose derivatives, in particular methyl cellulose, hydroxypropyl cellulose and / or nitrocellulose and / or organometallic compounds. It is also possible to use silicones and / or silanes in monomeric, oligomeric and / or to add polymeric form. The nanoparticulate particles are typically in a size range between 1 and 200 nm. This ensures that, on the one hand, the manufacturing processes can be easily managed and, on the other hand, the properties of the coating system are defined with sufficient precision.

If the particles are smaller than 200 nm, this ensures that there is no impairment of the transparency in the visible range, in addition high proportions of particle sizes around or below 100 nm lead to a particularly good homogeneity by increasing the total number of particles. Particularly suitable nanoparticles are those mentioned above in the discussion of EP 0 727 306.

In addition to inorganic glasses, such as silicate glasses, which are typically used for flat glasses, in particular PMMA, PVB and the like can be used as substrates. This makes it possible to use the coating system according to the invention with polymers, which is advantageous in order to produce glazings with reduced weight, open up new areas of application, etc. For example, beverage bottles can easily be provided with an infrared radiation-shielding coating, which has advantages if drinks are in the bottle should stay cool. The coatings presented here guarantee this.

The present invention enables the application by a variety of different techniques, all of which are inexpensive to implement. While techniques such as diving provide complete coverage, a pattern can also be created on the object, for example by printing, which in particular in connection with the improved conductivity is advantageous. For example, conductive, transparent and at the same time IR-shielding antenna areas for radio reception and / or transmission and reception of mobile radio signals can be printed on automobile windows. This arrangement can also be designed to be very large.

If an application on a very complex shaped structure is desired or individual patterns are to be printed on, which do not repeat from object to object, or which are only identical for a small number of products, as is the case with serial numbers, batch numbers or the like if so, an application can be made using an inkjet process. Since the layers generated are invisible, it is in particular possible to carry out hidden coding. Either in the case of coatings lying on the surface of the coated object, the different conductivity of areas can be scanned, for example by placing electrodes at predetermined locations, and / or the hidden information can be scanned by irradiating infrared radiation, either the heating on the substrate is detected or the transmission behind the coated substrate. In such a case, the coating can also be enclosed between two surfaces, for example on the inside of thermal glazing or the like. The combination of predetermined conductivities and IR shielding also enables particularly reliable authenticity verification.

Drying is typically very gentle, for example at temperatures below 100 ° C. A first option is to dry at room temperature; alternatively it is possible to at a slightly elevated temperature such as Heat 50 ° to 70 ° C without losing the positive properties of the coating.

It should be mentioned that it is particularly advantageous to also obtain at least antistatic properties with the coating, or, if the layer has an even further improved conductivity, to provide a discharge through it or an overall conductive layer. This is particularly possible if nanoparticulate particles with a high conductivity are used. It is particularly preferred to use ITO, in particular ITO with a comparatively high conductivity, as doped ITO. It should be pointed out that the expensive ITO material has high conductivity in comparatively small amounts and in particular below the percolation limit can already have the desired effect.

As mentioned at the outset, it is particularly preferred for various applications if a type of heat radiation trap or a diode-like behavior for heat radiation is provided, ie radiated heat radiation only passes in one direction, but heat cannot be radiated in the reverse direction. In a particularly preferred variant, the present invention proposes to choose an absorption edge in such a way that the coating is transparent at the maximum of the solar energy radiation. This solar energy radiation has its maximum in the range between about 800nm and llOOnm. This area is therefore particularly relevant for warming. It was recognized that the radiation of thermal solar radiation can be largely allowed by the choice of the absorption edge position, while the radiation of the thermal radiation from the inside is largely possible can be reduced. This is due to the fact that the heat radiation to be emitted, if possible not here, is typically significantly longer wavelength than the radiated radiation. In a particularly preferred variant, therefore, the absorption edge lies between the near infrared (NIR) of the radiation and the far infrared of the radiation (FIR), which is therefore reflected and / or absorbed rather than transmitted. The position of the absorption edge beyond, but close to 11OOnm, in particular in the range between 1120 to 1350, is therefore particularly preferred. Absorption edges lying at shorter wavelengths result in more of the thermal solar radiation desired here being shielded. It was found that the coatings found were completely or at least almost completely transparent in the visible, regardless of a yellowness index of the underlying material.

In a further variant which is preferred for other purposes, it is provided to use an ITO which has an absorption edge at approximately 100 nm and then additionally to introduce a further absorber into the coating which absorbs in regions below 900 nm. The use of UV-resistant absorbers is particularly preferred. At the same time, it is desirable to use an organic absorber that can be applied without problems in common coating systems. Phthalocyanine dyes that are transparent in the visible and also UV-resistant have proven to be particularly suitable. A particularly suitable absorber is the phthalocyanine dye available from Yamamoto Chemicals under the name YKR 50/10. It was found that 10% by weight of the

Dye based on the amount by weight of ITO sufficient to get a broadband absorbent coating.

The invention is described below only by way of example with reference to the drawing. In this shows:

Fig. La the transmission through an uncoated glass substrate; Fig. Lb the transmission through a coated glass substrate; 2a shows the transmission through an uncoated PC substrate; Fig. 2b, the transmission through a coated

PC (polycarbonate) substrate; 3a as before for an uncoated PMMA substrate;

3b as before for the coated PMMA

substrate; 4a as before for an uncoated borosilicate glass substrate; 4b as before for the borosilicate glass with coating; 5 as before for the borosilicate glass; Fig. 6 Transmission curves for coatings in which ITO produced by different process controls is used.

Indium tin oxide powder is produced in nanocrystalline form. A size analysis shows that the nanopowder obtained has a maximum in the size spectrum at 100 nm and this maximum has dropped to almost 0% at 200 nm, while below 1 nm there are also no ITO particles available. Then the conductivity of the ITO powder is determined by filling a round weighing glass with a volume of 45 ml, a diameter of 35 mm and a height of 70 mm half with the powder, placing a suitable press ram on the loose powder filling and for 30 Seconds with a weight of 1 kg. The press ram is removed and pin-shaped measuring electrodes with a diameter of 1.5 mm are pressed 0.7 mm deep into the compressed powder bed at a distance of 1 cm. The electrical DC resistance between the electrodes is determined. A powder is selected that has a very good conductivity with 30-50 Ohm powder filling resistance.

The powder is used for the examples as follows:

example 1

50 grams of a dispersion of the nanocrystalline ITO in n-

Butanol with a solids content of 25% by weight are mixed with 25 grams of a 15% by weight polymer solution Paraloid B 72 in

Ethyl acetate mixed. Glass is coated with this coating solution by spraying and the resulting coating is dried at 70 ° C. The layer thickness is determined to be 1. The layer is clearly transparent. It is included in a transmission curve. This is shown in Fig. La. The conductivity of the layer is determined to be 8 × 10 ⁴ Ω ² .

Example 2 50 grams of an ethanolic dispersion of the nanocrystalline ITO powder with a solids content of 25% by weight are mixed with 50 grams of a 15% by weight polymer solution Paraloid B 72 in Ethyl acetate mixed. This coating solution is applied to a glass plate by spin coating. The glass is then dried. The layer thickness is determined to be 1 μm. The transmission curves result from Fig. 2a. The conductivity of the layer is determined to be 10 ⁵ Ω ² .

Example 3

The coating system from Example 2 is used and sprayed onto PMMA plates. Again a thickness of 1 μm is set and dried at 70 ° C. The transmission is shown in Fig. 3. The conductivity is determined to be 8xl0 ⁴ Ω ² .

Example 4

50 grams of an ethanolic dispersion of the nanocrystalline ITO with a solids content of 25 wt

Gram of a 10 Ges.% Polymer solution polyvinyl butyral (PVB) mixed in isopropanol. This coating solution is scraped onto glass plates and dried at 50 ° C. The layer obtained has a thickness of 3 μm and is highly transparent. A transmission curve is determined as can be seen in FIG. 4. The conductivity is determined to be 8xl0 ³ Ω ² .

The figures each show that the transmission in the infrared range is significantly reduced compared to uncoated substrates.

Conductivity measurements are then carried out on the layers obtained. For example 2 there is a conductivity of 2 x 10 ⁵ Ω ² '. For examples 1 and 3 there is a conductivity of 8 x 10 ⁴ Ω ² '. For example 4 there is a conductivity of 8 x 10 ³ Ω ^2nd The comparison of Examples 2 and 4 shows that the sheet resistance is which is dependent. An examination of the quantities of nanocrystalline ITOs contained in the applied layers shows that the concentration is below the percolation limit.

In another example, the transmission is pure

ITO of a layer thickness of 1 μm, as obtained by spraying on an aqueous dispersion and then heating to 500 °, compared with a coating according to the invention according to Example 1. The coating which is particularly preferred according to the invention, which is shown as a solid line in FIG. 5, shows a falling transmission at already considerably shorter wavelengths, and thus results in better infrared shielding.

Another example shows how the absorption edge can be shifted:

Nanocrystalline in ₂ 0 ₃ / Sn0 ₂ (ITO) powders are produced from an aqueous solution using a co-precipitation process in which soluble In or Sn components are precipitated by increasing the pH. In this example, the concentrations of these compounds are chosen such that the Sn concentration is 5 at.% Based on In; in principle, however, the Sn concentration can be set as desired.

This constant choice was made because it is known that different concentrations of Sn strongly influence the absorption behavior of ITO; In this example, the concentration of Sn is kept constant in order to show that the process properties alone specifically target the absorption properties of an ITO material with a fixed composition. can be put. After the reaction product has been separated off, it is dried and tempered for 1 h at 300 ° C. under a normal air atmosphere in order to adjust the crystalline phase.

Then the crystalline In ₂ 0 ₃ / Sn0 _{2 is divided} into different samples and the individual samples are post-annealed under forming gas at 300 ° C for different times (see Table 1)

The respective powders (60 g) are then dispersed in 100 g of isopropoxyethanol (IPE) and 39 g of nitrocellulose are added to the dispersions. The dispersions are then used to produce layers on glass using a 50 μm doctor blade. After heating for one hour at 120 ° C, the layer thicknesses are 4 μm.

The color values and the transmission curves of coatings obtained with the powders are then determined. The yellowness index of both layers is measured with a color pen (Dr. Lange), according to DIN 6167 and ASTM D 1925 evaluated (standard illuminant C; normal viewer 2 °). Powders with color values between the maximum values listed in Table 1 (IT-05 HCB and IT-05-HCG) and layers with yellow values between the corresponding values from Table 1 can also be obtained by mixing the different powders.

The corresponding x, y color values of the powders and the yellowness values of the layers are listed in Table 1; transmission curves can be found in FIG. 6. Table 1

There is a correlation between the yellow value and the absorption edge position. Based on this, it is recognized that ITO powders with a yellowness index greater than 0.15, in particular greater than 0.5, have absorption edges lying far in the IR. Depending on the application, this is preferable.

In a further variant, the powder IT-05 HCG obtained is mixed with 10% YKR-50/10-phthalocynanine dye from Ya amoto Chemicals. The coating obtained in this way proves to be particularly suitable for applications in which complete IR shielding is desired.

Claims

claims

1. A method for producing a transparent IR shield, in which a carrier is provided with active substance in order to be arranged in the beam path, characterized in that a coating system comprising nanoparticulate particles and customary coating solvents is applied wet to a substrate.

2. The method according to the preceding claim, characterized in that the coating system is formed by dispersing nanoparticulate particles.

3. The method according to any one of the preceding claims, characterized in that at least one of water, alcohols, in particular ethanol, propanol, isopropanol, butanol and / or other alkyl or isoalkyl alcohols, ketones, in particular acetone and / or is provided as the customary solvent MEK, diketones, diols, carbitols, glycols, diglycols, triglycols, glycol ethers, in particular ethoxy, propoxy, isopropoxy, butoxyethanol acetate, esters, in particular glycol esters, in particular ethyl acetate, butyl acetate, butoxyethyl acetate, butoxyethoxyethyl acetate, alkanes and / or alkane-containing mixtures, aromatics, in particular toluene, xylene.

4. The method according to the preceding claim, characterized in that a mixture of more than one of the substances listed is used as the customary solvent.

5. The method according to any one of the preceding claims, characterized in that the coating system comprises a binder.

6. The method according to the preceding claim, characterized in that the binder system comprises at least one organic component.

7. The method according to the preceding claim, characterized in that at least one from the polymer group polyacrylates, in particular PMMA, polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB), polyvinyl alcohols (PVA), polyethylene glycols is provided as the organic component , Polyurethanes, bisphenol-based polymers, polyesters, and oligomers and / or monomers of the aforementioned polymers and / or cellulose derivatives, in particular methyl cellulose, hydroxypropyl cellulose and / or nitrocellulose and / or organometallic compounds.

8. The method according to any one of claims 5 to 7, characterized in that at least one silicone and / or silane in monomeric, oligomeric and / or polymeric form belongs to the coating system.

9. The method according to any one of the preceding claims, characterized in that nanoparticles of size> 1 nm are used.

10. The method according to the preceding claim, characterized in that only nanoparticles of size> 1 nm are used.

11. The method according to any one of the preceding claims, characterized in that nanoparticles of size <200 nm are used.

12. The method according to any one of the preceding claims, characterized in that only nanoparticles of size <200 nm are used.

13. The method according to any one of the preceding claims, characterized in that a proportion of> 70%, in particular> 90% of the nanoparticulate particles has a particle size below 100 nm.

14. The method according to any one of the preceding claims, characterized in that as substrate PVC (polyvinyl chloride), PE (polyethylene), PU (polyurethane), PC (polycarbonate), PET (polyethylene terephthalate), PMMA, PVB and / or a transparent polymeric material and / or composite materials and / or inorganic glass, in particular silicate glass such as flat glass is selected.

15. The method according to any one of the preceding claims, characterized in that the wet application is carried out by printing, spin dip coating, knife coating, dipping and / or spraying, in particular using an inkjet method.

16. The method according to the preceding claim, wherein the wet application is carried out by an inkjet method, characterized in that rheology-changing substances which are per se and which enable inkjet applications are added to the coating system.

17. The method according to any one of the preceding claims, characterized in that after application, drying takes place at temperatures below 100 ° C.

18. The method according to the preceding claim, characterized in that the drying takes place at below 70 ° C.

19. The method according to any one of the preceding claims, characterized in that the drying takes place at over 50 ° C.

20. The method according to any one of the preceding claims, characterized in that the layer is formed with at least antistatic properties, preferably as an at least dissipative layer.

21. The method according to any one of the preceding claims, characterized in that the nanoparticulate particles are at least partially formed by ITO.

22. The method according to any one of the preceding claims, characterized in that an amount of ITO is added below the percolation limit.

23. Coating according to one of the preceding claims, characterized in that it has an absorption edge in the range between 11OOnm and 1350nm.

24. Coating according to one of the preceding claims, characterized in that in addition to an inorganic absorber with long-wave absorption, in particular ITO, a further absorber is provided which is used in areas Chen absorbed around and / or below 900nm, especially in the near infrared.

25. Coating according to the preceding claim, characterized in that an organic absorber is provided as a further absorber, in particular a phta-locyanin dye and / or in particular in a weight amount of less than 10% based on ITO.

26. Coating according to one of the preceding coating claims, characterized in that an ITO with a yellowness index of at least 0.15, preferably at least 0.5, is used.

27. ITO powder with a yellowness index of at least 0.5.