Photocatalytically-activated self-cleaning oven

background the invention

Area of invention

0001The present invention relates to photocatalytically-activated, self-cleaning ovens and methods of making and use of such devices.

description of the Related Art

0002Various major household appliances such as conventional Gas or electric ovens, microwave ovens, toaster ovens, freezers, freezers, dishwashers, washing machines, Textile dryer, to name only a few, require frequent cleaning to remove organic impurities to various inner and outer surfaces of such devices have accumulated. Generally this is done manually by applying of various cleansers and detergents, often accompanied by steps of scrubbing and rubbing.

0003To such a manual cleaning to avoid, are currently some self-cleaning appliances, especially stoves available. Self-cleaning ovens only clean the inner surfaces the cooking and baking chamber of the oven by heating the cooking and baking chamber of the furnace to very high temperatures over extended periods of time and so burn organic food residues on the surfaces of Cooking and baking chamber of the oven.

0004Some disadvantages with such self-cleaning devices connected. One disadvantage is the substantial energy costs, necessary to the apparatus to raise temperatures to the self-cleaning step and to maintain these temperatures. For example, working non-self-cleaning ovens at a maximum temperature of about 260 ° C (500 ° F), whereas a self-cleaning oven while the step of self-cleaning at temperatures above 649 ° C (1200 ° F).

0005Other disadvantages include the increased costs, are associated with it to provide such devices so that they the high cleaning temperatures withstand, and the adverse effect such high temperatures on the appliance itself over time on. A further disadvantage is, that the step of self-cleaning at high temperature usually on inner cooktops or -Backflächen limited is.

0006There are procedures for removing organic contaminants from surfaces available, the high temperatures not require. In particular, titanium dioxide, a photocatalytically-activated self-cleaning surface (Photocatalytically-activated self-cleaning; hereinafter "PASC") on a substrate supply. Publications, on the formation of a PASC coating are directed to titanium dioxide on a glass substrate include the US Pat. No. 5,595,813 and the publication "Photooxidative Self-cleaning Transparent Titanium Dioxide Films on Glass; Paz et al., J. Mater, Res., Volume 10, No. 11 (November 1995), pp 2842-2848 "a. Further, it is a Bibliography of patents and publications which are generally located refer to the photocatalytic oxidation of organic compounds, reported in the publication "Bibliography of Work on The Photocatalytic Removal of Hazardous Compounds from Water and Air; D. Blake, National Renewable Energy Laboratory (Mai 1994) "and in the report on the date of October 1995 and the report on the latest Stand out in October 1996.

0007The US Pat. No. 5,308,458 (Urwin et al.) discloses a method for decomposing a photocatalytically degradable organic material, which comprises irradiating an organic Material in fluid form present on the surface of a disk or disk is present, including ultraviolet light, wherein the disc or disc with an anatase titanium oxide film beschicht is. The disc or disc runs and to move the organic material radially outward across the surface the disc or disc.

0008The US Patent Nos 5,256,616. 5,194,161 and 4,997,576 (Heller et al.) Disclose materials and procedures for the photocatalytic oxidation of organic compounds in water. Heller discloses floating beads, which are coated with titanium dioxide to oxidize organic Compounds floating on water, such as oil spills.

0009Despite the fact that in this technical field are known PASC coatings, there are no Disclosure of the use of such materials for the preparation of a PASC oven that or the disadvantage of manual cleaning of such equipment the disadvantages of currently available Self-cleaning equipment would eliminate.

Summary the invention

0010The present invention is directed a self-cleaning oven and to a method for the preparation of and use of such a device, the device photocatalytically is activated to itself of accumulated organic contaminants Clean fabrics on one or more surfaces of the device to. The self-cleaning device closes a PASC coating (a photocatalytically-activated self-cleaning Coating) on ​​the surfaces that are to be self-cleaning. In one embodiment, closes the device a source actinic radiation for photocatalytic activation of the PASC coating (Which photocatalytically-activated self-cleaning coating) under self-cleaning of the surface the device on. The source of actinic radiation may be separate from the device or in the structure the device be installed.

Short description the figures

0011<figref idrefs="S29">1</figref> is a perspective view of a PASC industry product (a Industrial product with photocatalytically activated, self-cleaning Area), more specifically, a PASC oven.

0012<figref idrefs="S30">2</figref> is a cross section along line 2-2 of <figref idrefs="S29">1</figref> and provides a plan view of PASC coatings on a door the device from <figref idrefs="S29">1</figref> are deposited.

0013<figref idrefs="S30">3</figref> is a view similar to the of <figref idrefs="S30">2</figref>, And it illustrates a sodium ion diffusion barrier layer under the PASC coating.

description Preferred Embodiments

0014In the discussion of the figures Note that similar elements similar Numeral wear. Referring now to<figref idrefs="S29">1</figref> reference taken. In<figref idrefs="S29">1</figref> is a PASC oven <figref>10</figref> shown. The oven<figref>10</figref> was chosen to To illustrate the present invention, and the following Discussion is on an oven <figref>10</figref> addressed. further despite the fact that the following discussion mainly on forming a PASC coating within the cooking or baking-space <figref>14</figref> the furnace <figref>10</figref> directional is understood that the PASC coating on some or all of the outer surfaces furnace <figref>10</figref> can be provided to the outer surfaces of the furnace <figref>10</figref> photocatalytically to make self-cleaning.

0015The oven <figref>10</figref> closes the cooking or back-room <figref>14</figref> a, which is a closable housing, the five integrally interconnected walls and a door has. More specifically, the cooking or baking room <figref>14</figref> defined by the inner surfaces of opposing sidewalls <figref>16</figref> and <figref>18</figref> (shown in dashed lines), a bottom <figref>20</figref>, A top wall <figref>22</figref>. the ground <figref>20</figref> opposite; a rear wall <figref>24</figref> and a hinged door <figref>26</figref>. the said rear wall <figref>24</figref> opposite when the door <figref>26</figref> in the closed position. These walls, the floor and the door of the cooking or Back-space <figref>14</figref> are generally made of metal, that is coated with a layer of paint or enamel. A Layer of a thermally insulating material <figref>27</figref> can on one or more of the outer surfaces of the Walls, the bottom and the door the cooking or baking-space <figref>14</figref> be applied to the yarn or back-room <figref>14</figref> thermally isolate. The layer of a thermally insulating material <figref>27</figref> can turn in a (not shown) housing be included, which - if it is available - typically lacquered or enamel becoming compressed metal is formed, thereby a free-standing stove <figref>10</figref> is formed.

0016The oven <figref>10</figref> includes a front panel <figref>28</figref> a, the, the outer vicinity of the opening in the cooking or baking room <figref>14</figref> leads, surrounds and forms when the door <figref>26</figref> in is an open position, as shown in <figref idrefs="S29">1</figref> is shown. The front panel<figref>28</figref> creates a caulking surface for a poetry <figref>30</figref>; this seal<figref>30</figref> is on the inner surface of door <figref>26</figref> fixed and extends around the outer periphery the inner surface the door <figref>26</figref> and thus forming a seal between the inner surface of the door <figref>26</figref> and the front panel <figref>28</figref>. when the door <figref>26</figref> in is the closed position.

0017The door <figref>26</figref> generally includes a metal outer panel <figref>29</figref> on, the dashed subscribed insulation material <figref>27</figref> surrounds. The plate <figref>29</figref> can a painted or acted with enamel its metal plate. The door<figref>26</figref> is about joints fixed and closes more generally a transparent portion or a window <figref>24</figref> on, in one frame <figref>36</figref> is kept to a Into Look in the cooking or baking room <figref>14</figref> to allow, when the door <figref>26</figref> in is a closed position.

0018As can be seen, includes the furnace <figref>10</figref> some additional components, including equipment for heating, systems for temperature control and the like; these are for recognizing of the present invention is not necessarily required, and are therefore in the figures Not shown.

0019In accordance with the present Invention, the furnace <figref>10</figref> a PASC coating on the or on a more of the inner surfaces and / or Outer surfaces of the furnace <figref>10</figref> is deposited. For example, a or more of the internal surfaces the cooking or cooking space <figref>14</figref>Or the side walls <figref>16</figref> and <figref>18</figref>. the floor <figref>20</figref>, The top wall <figref>22</figref>, The rear wall <figref>24</figref>, the door <figref>26</figref> and the transparent portion or window <figref>34</figref>, A PASC coating (A photocatalytically-activated self-cleaning coating) lock in. The front panel <figref>28</figref> can applied thereto PASC coating exhibit. The left side of<figref idrefs="S30">2</figref>. which is more explained in detail further below, illustrates PASC coatings over the various inner surfaces the door <figref>26</figref>. while the right side of <figref idrefs="S30">2</figref> PASC coatings both the various interior surfaces as well as on the various Outer surfaces of the door <figref>26</figref> illustrated. It can be appreciated, however, that when the PASC coating on other interior surfaces or outer surfaces of the furnace <figref>10</figref> is included that from those of the door <figref>26</figref> different are, the PASC coatings in a similar manner as in the were included, the herein in connection with the door <figref>26</figref> is discussed.

0020Still more particularly, is a cross-sectional through the door <figref>26</figref> along the line 2-2 in <figref idrefs="S29">1</figref> in <figref idrefs="S30">2</figref> shown. This illustrates the door <figref>26</figref>. the transparent portion or a window <figref>34</figref> having, the generally centrally therein within a frame <figref>36</figref> kept becomes. The door<figref>26</figref> includes a outer panel <figref>29</figref> on, generally the inner surface the door <figref>26</figref> opposite and an insulating material <figref>27</figref> having, the intervening is disposed as shown by dashed lines in <figref idrefs="S30">2</figref> is shown. The inner surface<figref>38</figref> can with an enamel layer <figref>40</figref> be coated. PASC coatings on the inner surfaces the door <figref>26</figref> on the left side of <figref idrefs="S30">2</figref> as explained below shown. A PASC coating<figref>24</figref> is above the enamel layer <figref>40</figref> shown deposited, a PASC coating <figref>43</figref> is above the frame <figref>36</figref> deposited shown and a PASC coating <figref>44</figref> is above the palm the window <figref>34</figref> deposited shown.

0021In an alternative embodiment, as described by on the right side <figref idrefs="S30">2</figref> shown is, can additionally the PASC coatings <figref>42</figref>. <figref>43</figref> and <figref>44</figref> on the inner surfaces the door <figref>26</figref> the Outer surfaces of the door <figref>26</figref> PASC coatings include as follows: the outer panel <figref>29</figref> of furnace <figref>10</figref> can also with a PASC coating <figref>46</figref> overdrawn be. Similarly Example, the outer surface of the transparent part and the window <figref>34</figref> with a PASC coating <figref>48</figref> overdrawn be, and the outer surface of the frame <figref>36</figref> also boasts of a PASC coating <figref>50</figref> overdrawn be. The on the right side of<figref idrefs="S30">2</figref> shown embodiment provides PASC coatings both on the inner surface and on the outer surface of the furnace <figref>10</figref> before, but can - as recognized is in alternative embodiments the PASC- coatings only the inner surface or only on the outer surface of the furnace <figref>10</figref> be included, eg. as wherever a self-cleaning he wishes is or is required.

0022Many substrates, particularly glass substrates, conclude Sodium ions derived from such surfaces deposited over such substrates in can hike coatings, particularly when such substrates maintained at elevated temperatures (such. as at least above about 400 ° C (752 ° F)). When sodium ions in the PASC coatings hiking, the photocatalytic self-cleaning activity of such Coatings is reduced if not eliminated. This process is generally as "sodium poisoning" or "sodium ion poisoning" of the PASC coatings designated. Poisoning by sodium ions can be prevented either by reacting the PASC coating thick enough makes to prevent migration through the coating, or characterized in that a sodium ion diffusion barrier layer (sodium ion diffusion barrier layer; SIDB layer) between the substrate and the subsequent deposited PASC coating arranges. The document WO 98/41480 (Charles B. Greenberg et al) entitled "Photocatalytic activated self-cleaning article and method for its production "(hereinafter the" application called by Greenberg et al. ") contains a detailed discussion of reducing or eliminating the sodium ion poisoning of PASC coatings by these methods.

0023In <figref idrefs="S30">3</figref> are PASC coatings over the various internal and external surfaces of the door <figref>52</figref> shown. The door <figref>52</figref> differs from the door <figref>26</figref> just in that the door <figref>52</figref> SIDB layers between each of the PASC coatings and the surfaces of the door <figref>52</figref> includes, on the PASC coatings have been deposited as set forth below becomes.

0024Referring now to the embodiment Referring, of on the left side <figref idrefs="S30">3</figref> is shown. There is a door<figref>52</figref> shown, the SIDB layers and PASC- coatings on their inner surfaces defining a SIDB layer <figref>54</figref> between an enamel layer <figref>40</figref> and a PASC coating <figref>42</figref> arranged lock in, a SIDB layer <figref>55</figref> in between the frame <figref>36</figref> and the PASC coating <figref>43</figref> arranged include and a SIDB layer <figref>56</figref> between the inner surface of the transparent portion or window <figref>34</figref> and the PASC coating <figref>44</figref> arranged lock in.

0025In an alternative embodiment of the present invention as of on the right side <figref idrefs="S30">3</figref> is shown, the door <figref>52</figref> In addition to the described PASC coatings and SIDB layers over the inner surfaces the door <figref>52</figref> a SIDB layer <figref>58</figref>That between the PASC coating <figref>46</figref> and the outer panel <figref>29</figref> is arranged, and a SIDB layer <figref>60</figref>, Between the frame <figref>36</figref> and the PASC coating <figref>50</figref> is arranged, and / or SIDB layer <figref>62</figref>That between the outer surface and the transparent part or window <figref>34</figref> and the PASC coating <figref>48</figref> arranged is involving.

0026Although the <figref idrefs="S30">2</figref> and <figref idrefs="S30">3</figref> and the related discussions on the doors <figref>26</figref> and <figref>52</figref> addressed; However as of professionals with skill in the art Area is detected, the same arrangement of sodium ion diffusion barrier layers and PASC coatings as above the doors <figref>26</figref> and <figref>52</figref> shown is, also be applied, when such layers and coatings on the sidewalls <figref>16</figref> and <figref>18</figref>. the floor <figref>20</figref>, Top wall <figref>22</figref>, The rear wall <figref>24</figref> the cooking or baking-space <figref>14</figref> or any of the Outer surfaces of the furnace <figref>10</figref> are applied.

0027PASC coatings, the present invention with the compatible are close photocatalytically-activated self-cleaning oxides in general a and can chosen more particularly be made, but are not limited to titanium oxides, iron oxides, Silver oxides, copper oxides, tungsten oxides, aluminum oxides, silicon oxides, Zinkstannate, molybdenum oxides, Zinc oxides, strontium titanate and mixtures thereof. As of professionals is recognized with expertise in the art, can include the metal oxides or suboxides of the metal.

0028A preferred PASC coating is titanium dioxide. Titanium dioxide exists in an amorphous form and three crystalline forms, namely in the Forms anatase, rutile and brookite. Titanium oxides, in particular Titanium oxide of the anatase phase is preferred because it exhibits the strongest PASC activity, that is, it shows a suitable band gap (ie, about 360 nm), as for a photocatalytically-activated self-cleaning is required, and has excellent chemical and physical resistance on. Further, it has permeability in the visible region of the spectrum on which it is useful to Use on a transparent portion or window makes. The rutile form also shows PASC activity. Combinations of the anatase and / or rutile phase with the brookite and / or amorphous phases are acceptable for the present invention provided the combination exhibits PASC activity. A discussion of inducing and measuring the photocatalytic activated self-cleaning activity and a discussion about what represents a sufficient level of PASC to denote a surface with "self-cleaning", are discussed below.

0029SIDB layers present with the Invention are compatible, include amorphous or crystalline Metal oxides including Metal oxides such as cobalt oxides, chromium oxides and iron oxides, Tin oxides, silicon oxides, titanium oxides, zirconium oxides, fluorine-doped Tin oxides, aluminum oxides, magnesium oxides, zinc oxides and mixtures thereof. include mixtures , but are not limited to magnesium / aluminum oxides and zinc / tin oxides. As of professionals in this technical field is detected, the metal oxides can Include or suboxides of the metal.

0030about speculations concerning the poisoning with sodium ions , the PASC coating must be sufficiently be thick in order to provide an acceptable level of PASC activity. There is no absolute value, the "acceptable" or "non-acceptable" makes the PASC coating, since the question whether a PASC coating having an acceptable level of PASC activity is determined by the purpose and conditions under which the PASC coating is provided with a Article is used and the performance standards, in conjunction selected with this purpose will. General provide thicker PASC coatings higher PASC activity. however can other considerations for speak to provide a thinner coating, such as an increased Transparency of the article for aesthetic or optical reasons; the expectation that the surface contaminating Substances on the surface accumulate the object, the more easily removed, for example, so are thinner the PASC coating is; the duration and intensity of the ultraviolet light from which it is expected that it irradiates the PASC coating, where, for example, expected that exposed the subject of strong UV light radiation is, can the PASC coating thinner be and still provide sufficient PASC activity. Still other factors such as the nature of the substrate, can considerations the thickness of the PASC coating influence, for. example, if the substrate the PASC coating of a sodium ion poisoning suspends or not. for a big Variety of applications, it is preferred that the PASC coating has a thickness of at least about 200 Angstroms (hereinafter expressed as Å) which preferably has a thickness of at least about 400 Å, and more more preferably a thickness of at least about 500 Å. It was found that, if the substrate is a piece is made of float glass, a PASC coating of an anatase titanium dioxide PASC coating directly on the float-glass piece without SIDB layer is formed, having a thickness of at least about 500 Å, a PASC reaction rate in the range of about 2 to 5 × 10³ reciprocal centimeters, reciprocal × Minutes (hereinafter "cm^-1 min^-1") Returns. A PASC reaction rate in the above-indicated range is acceptable for a great Range of applications.

0031Although varies the thickness of the SIDB layer is necessary to prevent sodium ion poisoning of the PASC coating, with various factors including the chemistry of the SIDB layer, the time period and temperature at which a substrate is held, the nature of the substrate and rate of sodium ion migration from the substrate, the thickness of the PASC coating and the degree of photocatalytic activity, the for a given application is required; but should typically for the most applications, the thickness of the SIDB layer are in the range of about 100 Å, preferably at least about 250Å and more preferably at at least about 500 Å, to a poisoning of the PASC coating layer to prevent with sodium ions.

0032PASC coatings and / or SIDB layers, which are compatible with the present invention, can on the various surfaces the furnace <figref>10</figref> by the sol-gel process, by the spray-pyrolysis method, by the method of chemical deposition from the vapor phase (Hereinafter referred to as "CVD") or by the Magnetron Vakuumabscheide procedure referred to (hereinafter are formed as "MSVD"). The PASC coatings and / or SIDB layers may be on the surfaces the components of the furnace <figref>10</figref> will be made after the Components have been manufactured and before or after the components to the furnace <figref>10</figref> were assembled. Alternatively, the PASC coatings and / or SIDB layers on the flat sheets are formed, which then to the components of the furnace <figref>10</figref> educated , provided that the process of Forming the flat sheet to the components of the furnace <figref>10</figref> or the process of Assembling the component to form the furnace <figref>10</figref> not noticeably the PASC coatings and / or SIDB layers damaged, the at the various surface the components were formed.

0033Generally, in a sol-gel process a colloidal Suspension (the sol) is formed and on a surface about applied at room temperature, and this layer is then Applying heat converted into a gel. More specifically, in cases where which the PASC coating a titanium dioxide PASC coating and is formed by the sol-gel process is a titanium-containing precursor metal to be coated surface applied. The titanium metal-containing precursor may be in the form of a non-crystallized sol solution based on an alcohol solvent present. The sol solution Titan may include a titanium alkoxide in the alcohol solvent, which this surfaces the furnace <figref>10</figref> is applied, is desired of which, that they self-cleaning are. This can be done by spraying, spinning or dip coating. The sol solution is then heated generally at a rate of about 50 ° C per Minute, to a temperature in the range of about 100 to 400 ° C (212 ° F to 752 ° F), preferably at least about a temperature of 500 ° C (932 ° F), and it is then generally at the temperature for about 1 h maintained to the sol solution to a crystalline titanium dioxide PASC coating to calcine (the gel).

0034In the cases where the PASC coating by the spray pyrolysis method is formed, it can as a suspension of relatively water-insoluble organometallic coating reactants in an aqueous medium are formed. An aqueous suspension, by spray pyrolysis is applied, includes a metal acetylacetonate compound which aqueous medium in a is suspended with a chemical wetting agent. Aqueous suspensions for a pyrolytic deposition of metal-containing films are described in U.S. Patent No. 4,719,127, in particular column 2, line 16 to column 4, line 48. The metal acetylacetonate may be milled by a process, is well-known in the art as a "jet milling" and / or "wet-milling", and Although a particle size of less than about 10 microns. The metal acetylacetonate (z. B. titanyl (TiO (C₅H₇O₂)₂) For a titanium dioxide PASC coating) is then stirring an aqueous medium added, which contains the wetting agent, whereupon an aqueous suspension is formed. The relative concentration of the metal acetylacetonate in the aqueous suspension is generally in the range of about 5 to 40 wt .-% of the aqueous suspension. The aqueous medium of the aqueous suspension is preferably distilled or deionized water. Suitable include humectants any relatively low foaming surfactant Agent or surfactant is a. The humectant, an anionic, be non-ionic or cationic composition, but is a nonionic preferred. The wetting agent is typically added in an amount from about 0.24 wt .-%, but the amount may Range of about 0.01 wt .-% to 1 wt .-% or more.

0035The aqueous suspension is Pyrolysespray a plant for the surface of the substrate conveyed while the Substrate at a temperature to pyrolytically decompose the metal acetylacetonate is maintained to form a crystalline metal oxide PASC coating, z. B. in at least about 400 ° C (752 ° F), even more preferably at least about 500 ° C (932 ° F). As will be appreciated, the Composition and concentration of under pyrolysis sprayed aqueous suspension, the running speed of the substrate passing under the spray pyrolysis equipment, or Conversely, if the speed of the strike of the spray pyrolysis assembly on a stationary surface Number of pyrolysis spray guns, the surface to be coated, the spray or volume, the spray pattern and the temperature of the surface of the substrate at the time of deposition of the under pyrolysis sprayed aqueous suspension all parameters which will affect the final thickness and morphology of the metal oxide PASC coatings at the various surfaces the furnace <figref>10</figref> be formed by this method. PASC coatings by spray pyrolysis are formed, are described in WO 98/41480.

0036A PASC coating of titanium dioxide can be prepared by applied the CVD method as a titanium metal-containing precursor be that of a carrier gas is worn, the above a surface the furnace <figref>10</figref> is directed, while the surface at a Temperature is maintained, the pyrolytic decomposition of the titanium metal-containing Precursor and the formation of the crystalline titanium dioxide PASC coating to the surface facilitated. The surface temperature to facilitate the decomposition is preferably at least about 400 ° C (752 ° F} and even more preferably at least about 500 ° C (932 ° F). Metal-containing precursors, which are compatible with the CVD method include: Titanium tetraisopropoxide (Ti (OC₃H₇)₄) (Hereinafter "TTIP", titanium tetraethoxide (Ti (OC₂H₅)₄) (Hereinafter referred to as "kills"), titanium tetrachloride (TiCl₄) Or mixtures thereof. A preferred carrier gas the carrier gas is nitrogen (N₂). The concentration of the metal-containing precursor in the carrier gas, the velocity of the flow the carrier gas, the throughput speed of the substrate which passes beneath the CVD coating unit, or Conversely, if the speed of the strike of the CVD coater over a stationary Substrate, the surface to be coated, the nature of the chosen metal-containing Precursor and the required or desired PASC activity are all Factors affecting the final thickness and morphology of the different to the surfaces the furnace <figref>10</figref> formed by this process metal oxide PASC coatings influence. PASC coatings by the CVD method are formed, are described in the document WO 98/41480.

0037If the PASC coating is a titanium dioxide PASC coating, by the MSVD process is formed, a target consisting of titanium metal, in an argon / O₂Atmosphere are sputtered, the approximately 5 to 50% oxygen includes, preferably about 20% oxygen includes. This is done at a pressure of about 5 to 10 millitorr (mTorr) to form a titanium dioxide coating of desired Thickness, generally at least about 500 Å. While it is possible that surface to heat the substrate, and so during the sputtering process form a crystalline titanium dioxide PASC coating; general however, it is preferred to heat the substrate after the substrate from the MSVD coater was removed. The cooled Substrate is heated to a temperature in the range of about 450 ° C to 600 ° C (842 ° F to 1112 ° F) for a time period heated sufficiently to allow the formation of the crystalline anatase form promote titanium dioxide and so the PASC coating provide. Generally, a time at a temperature of at least about one hour preferred. Alternatively, the titanium oxide PASC coating in crystalline form on the surface a substrate in the MSVD coater directly and without subsequent Heating treatment to be applied by growing when a plasma high energy uses.

0038SIDB layers present with the invention compatible are able similarly Manner on the various surfaces of oven <figref>10</figref> by the sol-gel process, by the spray pyrolysis process, be formed by the CVD method or by the MSVD process.

0039In cases in which the tin oxide SIDB layer includes and by the spray pyrolysis method is formed, an aqueous suspension of dibutyl tin [(C₄H₉)₂SnF₂] and water to a substrate via Spray pyrolysis be applied. The aqueous suspension contains typically between 100 and 400 g of dibutyltin difluoride per liter Water; as recognized, however, this ratio may be modified to a thicker or thinner provide the SIDB layer, if this is necessary or desired. humectants can be used as agents for improving the suspension. During the Preparation of the aqueous suspension can the dibutyltin difluoride particles to an average particle size of 1 are milled to 10 microns. The aqueous suspension is preferably vigorous moved so a uniform distribution of particles in the suspension ensure. The aqueous suspension is by spray pyrolysis to the surface applied of the substrate at a temperature in the range of about 600 ° C to 700 ° C is (1112F to 1292 ° F). Thereafter, the aqueous suspension pyrolyzes to form a tin oxide SIDB layer. SIDB layers formed by the spray pyrolysis are formed, are described in WO 98/41480.

0040In cases in which the tin oxide layer SIBD includes and formed by the CVD method is, it may consist of a metal-containing precursor from a steam from monobutyltin trichloride (hereinafter "MBTTCL") in an air comprising carrier gas be deposited, which is mixed with water vapor, which also in air as a carrier is transported. As will be appreciated, the concentration of MBTTCL and water vapor in the carrier gas comprehensive air depends on several factors including the thickness of the desired SIDB layer, the potential of the CVD system application rate, the size of the coated surface, the flow rate the gas, the tendency of the substrate, a migration of sodium ions allow, among other factors. A detailed discussion of SIDB layers formed by the CVD method, can be found in the document WO 98/41480.

0041In cases in which the SIDB layer by the MSVD method is formed, an SIDB layer of tin oxide or silicon oxide by sputtering a tin or silicon-containing cathode target each in an atmosphere from about 5 to 80% oxygen at a pressure of about 5 to 10 formed millitorr (mTorr). If desired, the tin oxide or Silica SIDB layer either simultaneously with the sputtering or thereafter to crystallize the surface of the substrate may, on the the SIDB layer was sputtered, are heated. A temperature of at least about 400 ° C (752 ° F) and preferably of at least about 500 ° C (932 ° F) for at least about one hour is preferred. The document<patcit><text>EP 0787696</text></patcit> entitled "alkali metal diffusion barrier layer" discloses the formation of alkali metal diffusion barriers by magnetron sputtering. It is taught that the Barrier layer is generally effective in a thickness of about 20 Å to about 180 Å, wherein the efficiency increases as the density of the barrier layer increases. The formation of an SIDB layer by the MSVD process is also described in the document WO 98/41480.

0042In cases in which the above-described PASC coatings on surfaces the furnace <figref>10</figref> are present, regardless of whether they have a SIDB layer lock in or not, these areas are made self-cleaning upon exposure to radiation of the appropriate wavelength and the matching intensity for one sufficient period of time. In cases where a PASC activity is induced by ultraviolet radiation, the source of ultraviolet radiation is a natural source (eg. as solar radiation) or an artificial its source. An artificial Source is preferred as its intensity and intervals of irradiation be more easily controlled.

0043In cases in which the PASC coating a titanium dioxide PASC coating, the radiation which on photocatalytic way the self-cleaning type activated ultraviolet radiation having a wavelength in the range of 300 to 400 abbreviated nanometers (hereinafter as "nm").

0044Artificial Ultraviolet radiation sources include a black-light-source on. An alternative light source is available from Q-Panel Company Cleveland (Ohio) under the model designation "UVA-340". The intensity of the ultraviolet Radiation on the PASC coating impinges is selected so that characterized obtain a desired self-cleaning activity becomes. intensities within the range of 5 to 100 watts per square meter (hereinafter abbreviated as "W / m²") preferably intensity of at least about 10 W / m² and even more preferably at least about 20 W / m²measured at the PASC coating surface are desired. The intensity for example, can be measured with an ultraviolet meter such as with that which branded BLACK-RAY^® from Company Ultraviolet Products, Inc., of San Gabriel, CA, under the model designation J-221 is marketed.

0045As in <figref idrefs="S29">1</figref> shown is, an ultraviolet radiation source <figref>70</figref> internally the furnace <figref>10</figref> within the cooking or baking-space <figref>14</figref> as integral component of the oven <figref>10</figref> be included. In this embodiment, , the internal integral ultraviolet radiation source <figref>70</figref> in any visual manner activated / deactivated, including, but not limited is a switch for turning on and off by hand, a remote control and switching mechanism, the integral of the ultraviolet radiation source <figref>70</figref> activated when the doors <figref>26</figref> or <figref>52</figref> opened or be closed or a mechanical or electrical timer. The oven <figref>10</figref> either a single internal integral Ultraviolet radiation source <figref>70</figref> Include, or it may have a plurality of internal integral ultraviolet radiation sources <figref>70</figref>. <figref>72</figref>. <figref>74</figref>. <figref>76</figref> Include in order uniform ultraviolet irradiation all surfaces the cooking or baking-space <figref>14</figref> the furnace <figref>10</figref> ensure. Still more particularly, in the cases, where the cooking or baking room <figref>14</figref> a furnace <figref>10</figref> some having surfaces, which the incident angle of the ultraviolet radiation on the PASC coatings) affected more than one intregrale ultraviolet radiation source is preferred be in the range of cooking or baking-space <figref>14</figref> arranged spatially is to ensure that all surfaces absorb a sufficient amount of ultraviolet radiation.

0046In the cases in which external surfaces of the furnace <figref>10</figref> PASC coatings having applied thereon, either natural ultraviolet radiation (Ie, solar radiation) and / or one or more external artificial Ultraviolet radiation source (s) <figref>78</figref> used in order to activate the PASC coatings photocatalytically. The extreme artificial Ultraviolet radiation source may be an integral component of furnace <figref>10</figref> be, or may be a non-integral source be, the hollow of the inner and outer surfaces of the oven <figref>10</figref> emotional can be. Such external ultraviolet radiation sources, indifferent whether integral or non-integral, may manually or automatically, with remote control switches, electrical or mechanical timers and the like are activated.

0047The duration and intensity for which the Ultraviolet radiation source must be activated depends on a number of from factors, including the type of surface on the PASC coating is applied, the thickness of the PASC coating, the thickness, rate of formation and the structure of the organic contaminants, which on the PASC coating have accumulated, the incident angle of the ultraviolet radiation the PASC coating, the intensity the ultraviolet radiation source on the surface of PASC coating, the nature of the function of the device itself, the requested or required PASC reaction rate, the degree, according to which the ultraviolet radiation through the substrate and / or any of the on existing coatings or can be reflected or absorbed layers to a few to call. Therefore, it is not possible generally prescribe a set period of time or intensity, for the the ultraviolet radiation source must be activated to a obtain process of self-purification. However, for many Applications the ultraviolet radiation source is preferably activated for at least about 1 to 15 hours each day at an intensity of at least about 20 W / m² on the surface of PASC coating to ensure that the total accumulated amount is mineralized organic contaminants on the PASC coating.

0048It is useful, the effectiveness of the photocatalytic self-cleaning activity of the PASC or the coating or the PASC coatings on the various surfaces the furnace <figref>10</figref> are formed, to measure and to compare. Around the PASC activity to assess, A known, readily available organic contaminant may be applied to the PASC coating, followed by a photocatalytic activation of the PASC coating. Thereafter, the assets the PASC coating to remove the organic contaminant observed substance and measured. Stearic acid, CH₃(CH₂)₁₆COOH, is a Model organic "contaminant" to test the PASC activity of PASC coatings, because stearic a carboxylic acid is a long hydrocarbon chain and is therefore a good "model molecule" for those Substances is as usual contaminants such as household oils and dirt are present. The stearic acid can on the PASC coating in Form of a thin applied test film by any convenient procedure be, including Dipping, spraying or spin coating over the PASC coating. General provide stearic acid test films, whose thickness is in the range from 10 nanometers to about 20 nanometers, a matching test film. The stearic acid test film may be applied be in the form of stearic acid / methanol solution. It has been found that a solution with a ratio Stearic acid / methanol of 6 × 10^-3 m / l is satisfactory.

0049The PASC activity on a on a surface of furnace <figref>10</figref> formed PASC coating can be estimated qualitatively by coating the PASC coating with a stearic acid test film in accordance with the above information, irradiating the coated with stearic acid PASC coating with ultraviolet radiation from an ultraviolet radiation source a desired intensity for one desired Period and examining the stearic acid coated PASC coating the naked Eye either on the full Disappearance of the stearic acid test film (This film generally appears as a light brown coat, if, on the PASC coating is applied) or on a return to the darkness of Stearic acid test film in Comparison with a portion of the stearic acid test film formed on the PASC coating was deposited but not exposed to ultraviolet radiation has been.

0050The PASC activity of a PASC coating that on a surface a furnace <figref>10</figref> was formed, can also be measured quantitatively be determined by measuring the integrated intensity of the carbon-hydrogen stretching vibration absorption bands (Hereinafter "CH" -Banden) of on the PASC coating existing stearic acid. The integrated intensity is equal to the amount of stearic acid test film, on the surface the PASC coating has remained, and removal of the stearic acid test film by photocatalytically-activated Self cleaning results - as is to be expected - in a decrease the intensity the CH stretching vibration band. The CH bonds that exist in the stearic acid are infrared radiation absorbing (which - in contrast to ultraviolet Radiation - the PASC coating not photocatalytically activated). This absorption generally occurs at Wave numbers 2800 and 3000 cm between^-1 and can be measured with a device such as a Fourier transform infrared spectrometer (Hereinafter referred to as "FTIR"). The FTIR spectrophotometer can with a detector such as a deuterated triglycine detector (hereinafter abbreviated as "DTGS") or a mercury cadmium telluride detector (hereinafter abbreviated be equipped as "MCT"). The MCT detector is preferred as it provides a much higher signal-to-background ratio than the DTGS detector. This can be important in those cases in which the substrate and / or other coatings over the PASC coating are also present, act in such a way that they absorb infrared radiation, of the spectrophotometer to generate the absorption spectrum is used. In cases in which absorbed infra-red radiation from the substrate and / or other existing coatings is the intensity of is Beam of infrared radiation to the through the stearic acid Detector passes, dramatically reduced. Come this with the low Concentration of stearic acid together, on the surface the PASC coating is present, which produces a very weak infrared radiation absorption signal is the resultant infrared radiation signal is not particularly intense. Therefore provides an instrument equipped with the MCT detector is a spectrum in which the signal-to-background ratio is about an order of magnitude higher as in instruments that are equipped with DTGS detectors. at Measuring the PASC activity of transparent films and substrates, the infrared radiation can be obtained by the composite of the stearic acid test film, PASC coating and the substrate and / or any other existing transparent films and coatings in the Detector pass. In cases in which the films or Substrates do not allow the passage of infrared radiation can the beam of infrared radiation on the surface in a certain angle are directed, can travel through the stearic acid test film pass through and can be reflected off of the sample to be tested will instead pass through the sample to a detector. This latter method is known as reflection IR spectroscopy.

0051The PASC reaction rate can for a PASC coating be determined by measuring the rate at which the PASC coating in is capable of a stearic acid test film remove the present on the PASC coating , when the PASC coating ultraviolet radiation. More specifically provides the rate of decrease of the integrated intensity of the CH stretching vibration band (directly proportional to the coverage of the surface) on an accumulated time the exposure to ultraviolet radiation, the PASC reaction rate. For example, an initial PASC activity with the FTIR spectrophotometer a stearic acid test film measured, the present on the PASC coating is. The stearic acid test film may at theinitial ser PASC activity measurement be ultraviolet radiation has been exposed or not. The stearic acid coated PASC coating is then ultraviolet radiation for a measured interval of time exposed, in the end a second PASC activity measurement is carried out with the FTIR spectrophotometer. The integrated intensity of the CH stretching vibrations in the second measurement is expected to be lower than the first measurement, and due to the fact that a subset the stearic acid test film was removed in the exposure to ultraviolet radiation. From these two measurements, a curve of integrated intensity of C-H stretching vibrations are plotted versus time, the slope of the PASC reaction rate supplies. Although rich of two points to provide a curve; however, it is preferred that some FTIR measurements during the Course of PASC activity measurement are included to provide a more accurate curve. It is true that the duration of exposure to ultraviolet radiation between the Measurements are held constant or varied, as it accumulated the Time of exposure to ultraviolet radiation is used, the is to create a plot of the curve, but should the intensity and orientation, ie, the coating side or substrate side the exposure to ultraviolet radiation on the sample constant for all PASC measurements be held to be included when the PASC reaction rate is determined.

0052The PASC reaction rate can be expressed in the unit reciprocal centimeters by reciprocal Minutes ( "cm^-1 min^-1"), Wherein a to displayed so greater PASC activity is, the higher the value is. There is no absolute rate which a PASC coating "acceptable" or "non-acceptable" makes, since the question whether the PASC coating having an acceptable level of PASC activity is largely determined by the Purpose, for which the device is used and the performance standards, the related selected with the purpose will. General is desirable that the PASC reaction rate is as high as possible. the PASC reaction rate is preferably at least about 2 × 10^-3 cm^-1 min^-1 for one Stearic acid test film, the on a PASC coating was formed, when this ultraviolet radiation of about 20 W / m² exposed to intensity of the coating surface is when irradiated from the side of the coating of the substrate is measured with an FTIR spectrophotometer having an MCT detector, what kind of most applications is applicable. Even more preferred is the PASC reaction rate is at least about 5 x 10^-3 cm^-1 min^-1. measured under these same parameters.

0053It is also useful, the thickness of the PASC coatings measure to the PASC activity of PASC coatings meaningful to determine and compare, since the thickness of the PASC coating may affect the photocatalytic activity (eg. B. tend thicker PASC coatings to provide higher PASC reaction rates). The thicknesses of the PASC coating (and / or the SIDB layer, if one is present) can be measured either by spectroscopic ellipsometry with variable angle (Variable Angle Spectroscopic Ellipsometry; hereinafter as "VASE") or from profilometer measurements destruction edge known in the measured film as shown in this technical field is, or can be estimated be of interference color measurements, as is the case also in this technical field.

0054Experts in the art recognize that the PASC coating according to the present Invention and - if available - a SIDB layer must be able to the operating parameters of the device withstand, in which the PASC coating and / or SIDB layer is / are provided. Therefore, they must normal wiping and abrasive forces can withstand and must also can withstand the temperatures at which the unit operates, such as a stove, oven or frozen freezer. You must, too contact with water and detergents can withstand, for example, in those cases in which the device a washing machine or a dishwasher.

0055It is of professionals with expertise recognized in the art that in cases in which the device is a furnace is, the present invention provides a particular advantage over presently available, self-cleaning ovens provides that uncommon high temperatures required (ie, about 1200 ° F (648.9 ° C)) to clean the oven, as described above. A self-cleaning oven of the present Invention of the PASC coating on those surfaces the furnace includes, desirable of which is that they self-cleaning are, requires no such high temperatures to clean such surfaces. Therefore, a self-cleaning oven of the present invention need not to be so designed and constructed that it can withstand the excessive temperatures can that available with present High temperature Selbstreinigungsöfen are connected, resulting in significantly reduced manufacturing costs and significantly longer Uptime leads. Next is no need to "burnt" organic wastes to remove, as it is necessary for the high-temperature Selbstreinigungsöfen currently available, since the organic waste the present invention mainly into carbon dioxide and water vapor are mineralized.

0056As will be appreciated, is the above Revelation described not be as the inventionrestrictive to view and was given to allow a recognition of the invention. The scope of the present invention is defined by the following claims.