DE3347918C2 - - Google Patents

Description

The invention relates to glass substrates with a thermo-chromatic VO ₂ or V ₂ O ₃ containing coating, which is manufactured in a certain way and doped with metal oxides of metal, which have a larger inner radius than vanadium.

US-PS 43 07 942 describes a thermochromatic Ver bundle material, in which the thermochromatic Eigen layer mediating layer a porous, with the temperature-sensitive substance impregnated material is placed between panes of glass.

US Pat. No. 3,984,591 describes a method for applying metal oxide layers to substrates such as glass. Vanadium is also mentioned in the case of the metals and a V ₂ O ₅ layer is described in one example.

From US-PS 34 10 710 ver provided with metal oxide optical filters are known which have a reflection of at least 25% in the infrared spectral range and a transmittance of at least 30% in the visible range. The oxide layers are generated by pyrolysis of suitable metal compounds. Metal oxide layers containing V ₂ O ₅ can also be involved.

From US-PS 39 51 100 is the application of metal oxide layers on hot glass surfaces by chemical Separation of organometallic compounds from the Vapor phase known.  

In US-PS 34 83 110 a method for producing thin VO ₂ films is described, which show a transition in the semiconductor phase, which is due to the single crystal form. These films do not deteriorate by repeating the transition. In one embodiment of the method for producing such films, a V ₂ O ₅ cathode is sputtered in an inert atmosphere in the presence of the desired substrate to obtain an amorphous film of VO _x , where x is greater than 1.5 or less than 2 is. Then the film is either weakly oxidized to VO ₂ or strongly reduced to V ₂ O ₅ and then the V ₂ O ₅ to V ₂ O ₃ . Alternatively, a vanadium cathode is similarly sputtered in an inert atmosphere to produce a polycrystalline vanadium film that is first oxidized to V ₂ O ₅ and then reduced to V ₂ O ₃ .

The object of the invention is to use thermochromatic To provide coated glass substrates, the Um conversion temperature is reduced.

This task is solved by the glass substrate after Claim 1.

The subclaims describe preferred embodiments of the invention and the use of the coated glass as a pane of a window unit. Vanadium oxide films containing VO ₂ show both an electrical and an optical transition at a nominal transition temperature of around 68 ° C. Glass substrates, which are coated according to the invention with vanadium oxide films containing VO ₂ , are particularly useful for the control of passive solar energy, since they have a significantly lower transmission of infrared in the conductive phase compared to the infrared transmission speed of the semiconductor phase. Vanadium oxide films containing V ₂ O ₃ are electrically conductive at ambient temperature, show a specific surface resistance of less than about 1000 ohms per unit area with a film thickness with a light transmission rate of about 24 to 25% with 6 mm thick clear flat glass. According to the invention, vanadium oxide films containing V ₂ O ₅ can also be produced by chemical deposition. These films are subsequently reduced to form thermochromatic films containing VO ₂ or V ₂ O ₃ .

The thermochromatic films according to the invention, which contain VO ₂ or V ₂ O ₃ , have a lower temperature range for the conversion than the normal transition temperature of about 68 ° C. The reduced conversion temperature is due to the doping of the VO ₂ or V ₂ O ₃ film with metal oxides, preferably with oxides of niobium, molybdenum, iridium, tantalum or tungsten. The suitable metal oxides are those of metals that have a larger inner radius than vanadium. Glass substrates coated with vanadium oxide films according to the invention have a sufficiently low range of transition temperatures to be useful in a wide range of climatic conditions.

The invention will be described with reference to the drawings explained in more detail, which show the following

Fig. 1 explains the optical change of a vanadium oxide (VO ₂ ) film, which was obtained directly by chemical vapor deposition.

Fig. 2 explains the change in electrical resistance of a vanadium oxide (VO ₂ ) film depending on the temperature.

Fig. 3 illustrates the optical change of a doped vanadium oxide film according to the invention by comparing the permeability of the solar energy of a coated glass sample at room temperature with the permeability of the sample heated above its transition temperature.

Fig. 4 illustrates the range of transition temperature of a doped vanadium oxide film according to the invention, the resistance being represented as a function of temperature.

It is known that coatings made of numerous metals or metal oxides are suitable for controlling solar energy. Such coatings reflect a high proportion of the incident solar energy and thereby reduce the warming inside a building to a minimum, whereas they allow a sufficient proportion of the visible area to illuminate the inside of the building. A particularly suitable window for the passive control of solar energy is a window with a variable permeability which reduces the permeability to a minimum in summer when the outside temperature is high and the solar energy is at its maximum, but the solar energy when the outside temperature is high is low, lets through. You can achieve different permeabilities in a glass window by photochromism, in which a darkening occurs in response to UV solar radiation, with silver halides previously being used for this purpose. However, the absorption of solar energy through the glass over the entire spectral range leads to heating and bleaching of the glass, as a result of which the photochromatic properties of the glass are impaired. With the present invention, variable transmissivity is achieved by a thermo-chromatic reaction, which is the result of an optical change when a VO ₂ or V ₂ O ₃ film is heated by the absorbed solar energy.

Vanadium oxide (VO ₂ ) undergoes a phase change from the monoclinic crystallographic form to a tetragonal form at a nominal temperature of 68 ° C. This phase change is accompanied by a rapid change in electrical resistance, from a semiconductor behavior to that of a metal, with a change in surface resistivity of 10 ³ to 10 ⁵ times in a single crystal. In addition to the change in electrical conductivity, a vanadium oxide VO ₂ film also undergoes a significant optical change in the infrared spectrum.

There is also a slight change in the spectral range of visible light.

VO ₂ films experience both an optical change ( FIG. 1) and an electrical change ( FIG. 2).

Vanadium oxide films are made according to one embodiment of the present invention by chemical deposition of a Organovanadium compound from the vapor phase and its Decomposition produced. Suitable compounds are liquid vanadium isopropylate and vanadium n-propylate. To act as a thermochromatic window for passive control The vanadium should be suitable for solar energy covered a temperature range for the permeability change in the infrared range with temperature range of actual temperatures that the window achieved in sunshine, agrees and sufficient pronounced change properties with a film thickness show where iridescence is avoided. The film thickness is preferably 10 to 150 nm. The vanadium oxide films according to the invention meet these conditions.  

Thin films of vanadium oxide can be made on glass substrates using a variety of Organovanadinverbin manufacture the usual Ambient temperatures and pressures are liquid.

Soda-lime-silicon dioxide is flat as glass suitable for glass and borosilicate glass. The glass substrates are preferred to a temperature of at least 350 ° C in a conventional oven for heating glass preheated. For example, you can use a common tube Use a renofen with the inlet and outlet open. For feeding and discharging the glass substrates into the heating zone an air powered push arm can serve. That he warmed glass substrate can be used in an assembly line Chamber for chemical deposition in vacuum, over which there is a deduction be transported. The coating chamber contains one Organovanadine compound such as vanadium isopropy lat or vanadium-n-propylate, which is sufficient on a high temperature is heated to the vanadium compound to evaporate. The vapors of the organovanadine compound are using a gas flow with the heated sub strat brought into contact with the Organovanadinver bond pyrolyzed and the vanadium oxide is formed.  

To improve an optical response of the vanadium oxide film, it may be useful to prime the glass surface prior to chemical vapor deposition of the vanadium oxide. Optimal primers are tin oxide, typically in a thickness of 70 to 80 nm. Priming with tin oxide is preferably achieved by pyrolytic decomposition of an organotin compound. Films made of silicon dioxide and titanium dioxide are also suitable primers. The use of such primer films, particularly SnO ₂ , appears to promote crystallinity and the formation of VO ₂ over other vanadium oxides, thereby creating a film rich in VO ₂ which shows very good properties with regard to the optical change.

The properties of the optical change are determined of the vanadium oxide coating by scanning with a suitable spectrophotometer.

The scanning takes place over the spectral range from 0.8 to 2.2 micrometers. The glass sample coated with vanadium oxide is then held in an insulated holding device with a radiation opening. Two cylindrical 25 watt heaters, which are in contact with the glass edges just outside the radiation opening, are used to heat the glass sample coated with vanadium oxide above the transfer temperature. Without moving the sample, a spectral scan is performed before and after heating the sample. Typical results for VO ₂ films are given in FIGS . 1 and 3.

The temperature range of the optical change is in a separate experiment. This attempt is also a measure of the change in electrical resistance with the temperature. Known Ge councils are used. So you can use the flat measuring head a commercially available temperature meter flush with a narrow strip of Connect the surface of the vanadium oxide film. In closer The proximity of the measuring head is On end clamps on each side of the measuring head connected to an ohmmeter to measure resistance.  

The resistance is measured as a function of the temperature of the coated sample, the sample being heated by the range of the transition temperature. The measurement results for VO ₂ and doped VO ₂ films are shown in FIGS. 2 and 4.

In general, there is a 10 ³ to 10 ⁵ fold change in the ability of the thermoresistivity of vanadium oxide (VO ₂ ), a thermoresistive change in the order of magnitude of approximately two times being sufficient to control the optical change for the required size of passive solar energy in the spectral range from 0.8 to 2.2. The temperature range for the optical change of nominally 68 ° C for relatively pure single crystals of vanadium oxide (VO ₂ ) is close to the range of approximately 45 to 60 ° C that is actually achieved with windows facing south in summer. In addition, according to the invention, optical properties are achieved with vanadium oxide films, by means of which visible iridescence is avoided.

The VO ₂ films according to the invention have low conversion temperatures. For this purpose, metal oxides, preferably niobium, molybdenum, iridium, tantalum or tungsten oxide, are used as dopants since these metals have a larger ionic radius than vanadium. In another embodiment of the invention, glass substrates are immersed in a solution containing one volume of vanadium isopropylate, three volumes of 2-propanol and 2.5 to 4 g of WOCl ₄ . Immersion can follow at room temperature. Film formation occurs through hydrolysis in the surrounding air. The coated glass is then heated, preferably in a reducing atmosphere and particularly preferably in an atmosphere of nitrogen with proportions of hydrogen which still contains an aromatic hydrocarbon. It is heated to a sufficiently high temperature for a sufficiently long period of time to form the thermochromic VO ₂ film, which shows a change in the properties already indicated in the range above room temperature but below the characteristic temperature of 68 ° C. The VO ₂ film is semiconducting at ambient temperatures and has the total transmission shown in FIG. 3 for infrared rays. Above the transition temperature, the film containing VO ₂ is electrically conductive and has a transmittance for infrared sun rays of less than about 10%, see FIG. 3.

A higher thermoresistive conversion can be obtained by using liquid vanadium isopropoxide in nitrogen gas to form highly oxidized vanadium oxide (V ₂ O ₅ ) on a glass surface which is heated to at least 300 ° C. The vanadium oxide-coated glass travels within an air-rinsed tunnel to a tempering furnace, which is also rinsed with air. In it, the coated glass is cooled to ambient temperature. The vanadium oxide coating obtained mainly consists of V ₂ O ₅ . To maintain the thermochromatic VO ₂ , the vanadium oxide coating is reduced in a reducing atmosphere, preferably with a nitrogen / hydrogen mixture containing a small amount of an aromatic hydrocarbon, at a temperature of 325 to 475 ° C. The thermochromatic VO ₂ film produced in this way is semiconducting at ambient temperatures.

Above the transition temperature, the VO ₂ film is characteristically conductive with an overall solar transmission of less than about 10% as shown in FIG. 1. The thermoresistive change is about 1000 times, as can be seen from FIG. 2.

Conductive vanadium oxide thin films containing V ₂ O ₃ can be prepared by chemical vapor deposition using vanadium n-propylate as the starting material. For this purpose, glass substrates are typically preheated to a temperature of at least about 450 ° C. in a conventional tube furnace that is open at both ends. Liquid vanadium-n-propylate is evaporated and brought up to the heated substrates in a stream of nitrogen gas. The organovanadine compound pyrolyzes and forms the vanadium oxide. The glass coated with vanadium oxide migrates through a nitrogen / hydrogen purged tunnel to a tempering furnace, which is also flushed with the gas mixture, where the coated glass is cooled to ambient temperature. The resulting conductive V ₂ O ₃ film is gray compared to the yellow or brown color of the VO ₂ and typically has a specific surface resistance of 200 to 300 ohms per unit area. Preferred film thicknesses are in the range from 20 to 150 nm. The invention is explained in more detail in the following examples.

example 1

A glass substrate is heated to a temperature of about 635 ° C warmed and brought into contact with a solution that two volumes of dibutyltin diacetate and one volume Contains methanol. It becomes a tin oxide coating with a Thickness of 70 to 80 mm formed on the glass surface. The glass primed with tin oxide is then covered with a doped thermochromatic coating.

Example 2

A plate of clear float gas is immersed in a solution containing one volume of vanadium isopropylate, three volumes of 2-propanol and about 4 g per liter of WOCl ₄ at ambient temperature. The glass is removed and the hydrolysis proceeds at ambient temperature to form a clear yellow film. The coated glass is then heated to 375 ° C in nitrogen / hydrogen. The coated glass is then subjected to hydrocarbon vapors in a stream of nitrogen / hydrogen for a period of one minute. The hydrocarbon vapors are obtained by heating paraffin oil to 160 ° C.

The glass with the resulting vanadium oxide (VO ₂ ) coating shows the optical properties shown in FIG. 3 and has the electrical properties shown in FIG. 4.

Other substrates, such as borosilicate glass, can also be used in the invention. Other vanadium compounds are also suitable as a vanadium source, such as vanadium ethylate, butylate and vanadium oxychloride, VOCl ₃ . Reduction of the V ₂ O ₅ can be avoided by introducing a reducing agent, such as an aromatic hydrocarbon, into the atmosphere of the deposition chamber. For example, niobium, molybdenum, iridium, tantalum and tungsten oxide can be used as dopants. The process described for the chemical deposition of the vanadium oxide from the vapor phase is particularly suitable for covering moving glass strips, such as those obtained with the continuous flat glass process. Suitable processes and facilities for chemical deposition in the vapor phase are described in US Pat. Nos. 38 50 679 and 39 51 100. The deposition of the vanadium oxide can take place in different atmospheres, for example oxidizing atmospheres such as air, inert atmospheres such as nitrogen or argon and reducing atmospheres, a gas mixture containing mainly nitrogen and some hydrogen or mixtures of inert gases and reducing gases. Other deposition methods can also be used, such as vacuum deposition. The thermochromatic VO ₂ films are preferably used in window units with several panes for the control of the solar energy through variable transmission of infrared radiation. A unit with several disks before is described in US Pat. No. 3,919,023.

Claims (4)

1. Glass substrate with a thermochromatic, VO ₂ or V ₂ O ₃ containing coating with variable transmission for sun rays, whereby an optical change takes place within a temperature range of 25-75 ° C and the transmission for all solar energy in the infrared range by a factor decreases from at least two when the coating is heated by its temperature transition range, characterized in that the coating containing VO ₂ or V ₂ O ₃ is a layer produced by decomposition and, if necessary, reduction of a chemically deposited vanadium compound, which is coated with metal oxides of metals which have a larger ionic radius than vanadium is doped. 2. Glass substrate according to claim 1, characterized, that the dopant niobium, molybdenum, iridium, tantalum or is tungsten oxide. 3. Glass substrate according to claim 1 or 2, characterized, that the glass substrate has a primer layer of tin oxide, Titanium dioxide or silicon dioxide. 4. multi-pane window unit, characterized, that one of the panes is a glass substrate according to one of the Claims 1-3 is where the thermochromatic Coating on the inner surface of the glass substrate located.