This application claims priority benefit to European patent ap plication No. EP19209417.5, filed on November 15, 2019, and In ternational patent application No. PCT/CN2020/083446, filed on April 07,32020, the disclosures of which are hereby incorpo rated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a component, in particular a top plate of a gas hob and/or a burner cap of a gas burner for a gas hob, having a non-stick and/or non-wetting coating. Further, the present invention relates to a cooking appliance, in partic ular a gas hob having such a component. Moreover, the present invention relates to a method for manufacturing a component, in particular a top plate of a gas hob and/or a burner cap of a gas burner for a gas hob top plate, wherein the non-stick and/or non-wetting coating is applied to the component.

BACKGROUND One problem for the customer is the cleaning of components of a gas hob, such as a top plate of a gas hob or the burner cap of a gas burner gas hob after usage, especially after food items, such as cheese, sauces, oils, fat or the like, splashing out from a pan or pot and that are burned onto the surface of the component. Therefore, there are different approaches on the mar ket to make cleaning easier, for example top plates that are coated with an enamel that is more easy to clean and less sensi tive to impacts and scratches than stainless steel. One disadvantage of said coatings is that they are usually ap plied in two steps and high burning temperatures are required during its manufacturing process, which causes high costs and effort. In a first step a first layer of an enamel coating, e.g. a granite enamel, for providing good adhesion properties and having a dark colour is applied to the top plate. In a second step, a second layer having a light colour is applied to the first layer. Afterwards, the coating has to fired at high burn ing temperatures of over 800°C. Furthermore, the cleanability of such surfaces needs to be improved.

SUMMARY

It is an object of the present invention to provide component, in particular a top plate of a gas hob and/or a burner cap of a gas burner for a gas hob, a cooking appliance comprising such component and a method for manufacturing such a component, hav ing improved properties, in particular with regard to cleaning behaviour . These and other problems are solved by the subject matter of the attached independent claims.

The first object of the present invention is achieved by a com ponent, in particular a top plate of or for a gas hob and/or a burner cap of a gas burner of or for a gas hob according to claim 1.

A Component, in particular a top plate of a gas hob and/or a burner cap of a gas burner for a gas hob, having a non-stick and/or non-wetting coating on a surface is obtainable by (or: prepared by) a process characterised by the following steps: a) providing the uncoated component, in particular the top plate or the burner cap, in particular a plate-shaped top plate, hav ing an upper surface and a bottom surface, b) preferably, pretreating of at least the upper surface of the component, in particular the top plate or the burner cap, for providing a surface having a roughness being suitable for applying a non-stick and/or non-wetting coating, by mechanical treatment, physical treatment or chemical treatment, in particular by sand blasting and/or laser treatment and/or a surface activation treat ment, particularly a plasma treatment, and/or an enamelling pro cess to form a ground layer (13), thus applying an enamel layer onto the upper surface of the component, in particular the top plate or the burner cap, c) applying the non-stick and/or non-wetting coating, directly or indirectly, to the pretreated upper surface of the component, in particular the top plate or the burner cap,, wherein the non stick and/or non-wetting coating comprises at least one layer that is obtained by a sol-gel process from a first composition comprising a silica sol and a silane.

In other words: The non-stick and/or non-wetting coating is a sol-gel coating. The at least one layer, hereinafter also re- ferred to as base layer, is composed of a matrix comprising the condensation reaction product of a silica sol and a silane. Ob tained by a sol-gel process from a first composition has there fore to be understood in such a way, that the first layer is ob tained by means of hydrolysis and (poly-)condensation of an aqueous mixture comprising at least a silica sol and a silane. Thus, the starting materials of the first composition, namely at least silica sol, silane and water if needed, are mixed together and stirred. The mixture obtained thereof is then applied to the upper surface of the component and dried to obtain the first layer. Such a coating having one layer is known for example from EP 2177 580 B1.

The expression "non-stick" indicates a surface that resists ad herence of food items, such as cheese, sauces, oils, fat or the like, what permits easy cleaning of the component, in particular the top plate or the burner cap. The expression "non-wetting" terms a surface that repels liquids, e.g. water. The property is evidenced by a large contact angle between a drop of water and the surface on which the drop rests, wherein a contact angle of at least 95 degree is desirable.

According to the present invention, however, the "upper surface" of component, in particular the top plate or the burner cap, is the surface directed to the user and/or providing or surrounding the cooking areas of the gas hob. Accordingly, a "bottom sur face" of the component, in particular the top plate or the burner cap, is the surface facing away from the user and said cooking areas. For reasons of clarity, we mainly refer to top plates in the following but the explanations apply in the same way to other components of a gas hob.

The idea of the present invention is to provide a component with an easy to clean effect whereby the contact angle of the surface shows more than 95 degrees. Applying a non-stick and non-wetting coating by a sol-gel process has the advantage that a burning process at high temperatures for applying a non-stick coating on the component is not required what saves energy. Besides a good cleaning behaviour, said coating shows good abrasion-resistant and a great surface hardness what leads to an increased life time.

The adhesion of the non-stick and/or non-wetting coating to the pretreated surface of the component may particularly depend on the surface roughness. The present inventors have surprisingly found that such pretreatment of the surface before applying the non-stick and/or non-wetting coating and particularly a roughen ing of the surface is advantageous for the adhesion properties of the non-stick and/or non-wetting coating. Without such pre treatment, particularly such roughening, the at least one layer, and any subsequent layer, of the non-stick and/or non-wetting coating may peel off. Therefore an advantageous surface struc- ture may reduce the risk of peel off of the non-stick and/or non-wetting coating and at the same time allow to reduce the amount of coating and thus decrease costs. However, a surface roughness, which is too high, may also be disadvantageous, as the adhesion of the coating may be not optimal and/or the amount of coating needed will be higher than necessary.

A pretreatment of the surface by laser may be particularly ad vantages in comparison to known sandblasting methods in that in tegration into other production equipment is possible, for exam- pie related to existing laser welding lines, where sandblasting equipment may need totally new equipment and specific housings, protections, or the like. Furthermore it is also advantageous in having no need of process material, like corundum powder usually applied in sandblasting. Furthermore, it is also advantageous in reducing dirt occurring during the treatment and further surface cleaning after pretreatment steps and/or before coating is ad vantageously reduced compared to standard sandblasting methods. Also reproducibility of surface parameter values are advanta geously increased.

The person skilled in the art will recognize that various laser methods and laser equipment may be applied to achieve the de scribed preferably surface roughness. By way of example, in a pretreatment step according to the present invention a laser of type CL100 can be applied with a focal width of 254 mm, a wave length of 1064 nm, and an optical system STAMP10 with suction removal. Thereby, the surface treatment speed may be adjusted according to the desired results and with methods well known to the person skilled in the art. For example such surface treat ment speed may be approximately 10m ² /sec or higher.

According to the invention, the surface of the component might be roughened and/or protected against corrosion by applying a ground layer by an enamelling process, thus by applying an enamel layer, to the surface. The enamelling process in particu lar comprises applying an enamel powder onto the upper surface of the component and heating the enamel powder for providing a ground layer with a surface having a roughness being suitable for applying the non-stick and/or non-wetting coating and/or be ing corrosion resistant.

Such a ground layer is useful for all base materials in order to prepare the component for subsequent coating, thus for providing a good wettability and clean surface to obtain good adhesion performances on the full surface and no detachment of the non stick and/or non-wetting coating. Furthermore, said ground layer may provide corrosion resistance for the surface of the component so that it also functions as a protective layer, in case of a component made of a non-corrosive material itself. Therefore roughening the upper surface of the component by an enamelling process is advantageous with regard to mechanical treatment like sandblasting or by laser treatment as just one single process step has to be carried out in order to form a surface that has a good roughness and is in particular additionally non-corrosive in comparison to apply a protective layer in a first step and to roughen the surface of the protec- tive layer in a second step.

The component can be made of different materials, the material being suitable for intended use, such as stainless steel or an- other material that is non-corrosive itself, for example alumin ium or an aluminium alloy, or made of glass, in particular a tempered glass, or made of glass ceramics. The disadvantage of components made from stainless steel is, however, that they are expensive. Therefore, in a preferred alternative, the component is made of corrosive steel, particularly so-called low-carbon steel is a preferred material for the component. An example for such commonly used low carbon steel typically contains a small percentage of carbon, approximately about 0.05 to 0.30% carbon.

In case of a component made of corrosive material, the component is preferably provided with (or: comprises) a protective layer (or: non-corrosive layer) that is applied to at least the upper surface of the component and wherein said protective layer is pretreated by sandblasting and/or laser treatment and/or an enamelling process, thus applying an enamel layer for providing a surface having a roughness being suitable for applying the non-stick and/or non-wetting coating and applying the at least one layer of the non-stick and/or non-wetting coating is applied to said protective layer. For example, the surface of the compo nent is coated with such a protective layer by spray-painting.

This is due to the reason, that the non-stick and/or non-wetting coating itself does not protect the base material or substrate, thus the component, from corrosion. Therefore, an additional corrosion protection layer is advantageous if the component is made of any corrosive material so that the non-stick and/or non wetting coating can also be used with base material or substrate that is corrosive itself. In case the base material is non-cor- rosive itself, thus the component is manufactured from stainless steel or another non-corrosive material, the step of applying a protective layer for corrosion protection may be optional. According to preferred embodiments, said protective layer is an enamel layer and/or an aluminium layer and/or a layer comprising aluminium. Preferably the protective layer has a thickness between 50 and 250pm, in particular between 100 and 200pm.

The protective layer and/or the ground layer might be made of a so-called pyro or vitreous enamel that essentially consists of melted and fused glass powder. For applying said enamel layer to the component, high burning temperatures from about 820 to 840°C are needed.

Another kind of protective layer and/or ground layer might be made of an enamel having a low softening point between 450°C and 560°C, respectively a low glass transition temperature, a so- called "low-temperature enamel". The softening point is defined as a temperature, respectively a temperature range, at which the material, e.g. the enamel turns from its hard and relatively brittle state into a molten or rubber-like state when tempera ture is increased. Therefore, said low-temperature enamel can be applied to the surface of the component at lower burning temper atures. Said enamel is for example an aluminium enamel that com prises aluminium oxide.

Compositions of such conventional enamels are known for example from WO 02/02471 A1 or GB 718,132. WO 02/02471 A1 discloses an enamel composition for use in forming an enamel cover coat com prising a glass component comprising at least a first glass frit, comprising by weight from about 30% to about 45%P20s, from about 20% to about 40% AI2O ₃ from about 15% to about 35% L12O and Na20 and K2O, up to about 15% B2O ₃ , up to about 15% MgO and CaO and SrO and BaO and ZnO, up to about 10% T1O2 and Zr02, and up to about 10% S1O2. The glass component may also comprise a blend of at least a first glass frit and a second glass frit. GB 718,132 discloses alkali metal aluminium phosphate vitreous enamel frits. Another kind of protective layer and/or the ground layer might be made of a catalytic enamel, for example known from EP 0565 941 A1, disclosing a catalytically active coating com position comprising an enamel frit, e.g. containing S1O2, B2O3, T1O2, ZrC> ₂ , P2O5, Fe ₂ C> ₃ , AI2O3, alkali metal oxides and alkaline earth metal oxides. The coating further comprises inert sub stances such as, for example, quartz, feldspar or alumina are used and an oxidation catalyst. Another catalytic enamel is known for example from GB 1418 842 disclosing a catalytically active enamel layer for a cooking appliances, wherein an oxide and/or mixed oxide of natural origin containing iron oxide and/or titanium oxide is added to an enamel frit containing typ ical silicates and oxides.

Furthermore, so-called ground coat compositions comprising gen- erally a glassy component and an additive component might be used for forming the protective layer and/or the ground layer providing the effect of a rough and binding surface. Such ground coats are for example described in US 8,778,455 B2 and comprise a combination of one or more alkali oxides, such as Na20 or Ka20, one or more alkaline earth oxides, such as ZnO or BaO, and one or more various transition metal oxides, such as AI2O3, S1O2,

T1O2, ZrC> ₂ , P2O5 or C02O3, as glassy component, and additive such as fluorine or NO ₂ . According to a preferred embodiment, the ground layer, in par ticular the enamel layer obtainable by the enamelling process, has a layer thickness between 5 and lOOpm, in particular between 10 and 80pm, more particularly between 20 and 50pm. Typical enamel thickness is normally larger than lOOpm. Inventors have surprisingly found, that the enamel compositions mentioned above allow forming of thinner layers that give a favorable rough sur face. For providing good adhesion properties of the non-stick and/or non-wetting coating, the surface is pretreated to provide a sur face of the component that has roughness being suitable for ap plying the non-stick and/or non-wetting coating. In a preferred embodiment a surface roughness of a surface of the component and/or a surface of the ground layer and/or a surface of the protective layer achieved with such pretreatment step is between Ra 0.01 pm to 10.00 pm, more preferably between Ra 0.10 pm to 5.00 pm, still more preferably between Ra 0.20 pm to 5.00 pm, still more preferably between Ra 0.50 pm to 5.00 pm, still more preferably between Ra 2.00 pm to 5.00 pm, still more preferably between Ra 2.50 pm to 5.00 pm.

The present inventors have surprisingly found that such an ad vantageous roughness within the above limits further improves the adhesion of subsequent layers or of a first or any subse quent layers of the non-stick and/or non-wetting coating to the component or the protective layer and/or the ground layer to re duce the risk of peel off of the coating and at the same time reduce costs as the amount of coating is reduced in a favorite manner.

In summary, a surface having such a good roughness can be ob tained in particular by applying a ground layer of known enamels as mentioned before. Even mechanical, physical or chemical treatment, in particular laser treatment of the surface can be carried out to achieve required roughness. A lower surface roughness - within the limits above mentioned - may be advantageous as the amount of non-stick and/or non-wet ting coating can be reduced. Preferably, a surface roughness is less than Ra 10.00 gm, pref erably less than Ra 7.50 gm, more preferably less then Ra 5.00 gm.

A higher surface roughness - within the limits mentioned above - may be advantageous as this would improve adhesive capacity for the non-stick and/or non-wetting coating.

Preferably, a surface roughness is more than Ra 0.01 gm, prefer ably more than Ra 0.10 gm, more preferably more than Ra 0.20 gm, still more preferably more than Ra 0.50 gm, still more prefera bly more than Ra 1.00 gm, still more preferably more than Ra 2.00 gm.

The person skilled in the art knows various standard methods to determine the surface roughness value Ra. Particularly the sur face roughness may be preferably determined in accordance with BS EN ISO 4287:2000 British standard, identical with the ISO 4287:1997 standard. In a preferred embodiment, the ceramic non-stick and/or non-wet ting coating comprises at least a first and a second layer, wherein the first layer is applied to the pretreated upper sur face of the component or the surface of the ground layer or the pretreated surface of the protective layer, and wherein the sec- ond layer is applied to the first layer, so that a component comprising a coating having base layer and top layer is ob tained. Particularly, the second layer is obtained by a sol-gel process from a second composition comprising a silica sol, a silane and a siloxane, in particular a polydimethylsiloxane. Such a coating having at least a second layer is also known from EP 2177 580 B1.

In other words: The second layer, hereinafter also referred to as top layer, is composed of a matrix comprising the condensa tion reaction product of a silica sol, a silane and a siloxane. Obtained by a sol-gel process from a second composition has therefore to be understood in such a way, that the second layer is obtained by means of hydrolysis and (poly-)condensation of an aqueous mixture comprising at least a silica sol, a silane and a siloxane. Thus, the starting materials of the second composi- tion, namely at least silica sol, silane, siloxane and water if needed, are mixed together and stirred. The mixture obtained thereof is then applied to the upper surface of the first layer and dried to obtain the second layer. Preferably, the silica sol is present in an amount of 15 to 70wt%, in particular in an amount of 30 to 70wt% and/or the silane is present in an amount of 2 to 70wt%, in particular in an amount of 10 to 40wt%, both in the first and/or the second composition and/or in the first and/or second layer.

In particular the silane in the first and/or the second composi tion and/or in the first and/or second layer is an organoal- koxysilane, in particular a methyltrimethyoxysilane and/or a fluoralkoxysilane .

The first and/or the second composition and/or in the first and/or second layer may comprise a catalyst, in particular an acidic catalyst, more preferably an organic compound containing one or more carboxyl groups and/or a mineral acid, e.g. hydro chloric acid, sulfuric acid or nitric acid. Different monocar- boxylic or dicarboxylic acids like formic acid, acetic acid or oxalic acid may be mentioned here as an example for suitable catalysts.

It has been shown, that it is advantageous, if the catalyst is present in an amount of 0,1 to 5 wt%, in particular in an amount of 0,1 to 2 wt%, both in the first and the second composition and/or in the first and/or second layer. The catalyst generally acts as a catalyst in the hydrolysis and condensation reaction and prevents too slow crosslinking.

In another preferred embodiment, the first and/or the second composition and/or in the first and/or second layer comprise or comprises a solvent, in particular an organic solvent. Examples for organic solvents are alcoholic solvents, for example metha nol, ethanol or propanol. In particular, the solvent is present in an amount of 10 to 60wt%, in particular in an amount of 10 to 40wt%.

Like the second composition or second layer, the first composi tion or first layer may also comprise a siloxane in a preferred embodiment. Said siloxane is in particular a polydimethylsilox- ane.

An advantageous amount of siloxane in the first composition or first layer as well as in the second composition or second layer is between 0,1 to 2 wt%.

In a preferred embodiment, the first composition or first layer and/or the second composition or second layer comprise or com- prises pigments and/or dyes and/or filling materials and/or fur ther additives. In particular, temperature resistant anorganic pigments are favourable. In addition, water is added to the first composition and/or the second composition, if needed.

Besides mechanical functionality and easy-to-clean behaviour, components of a gas hob, in particular a top plate may also be provided with specific printing for applying product name and/or symbols for a user interface that are touched by a user. Is is desirable to apply such printings without need of removal of the coating in the areas of the printing and without worsen the cleanability of the component. According to a preferred embodi- ment, the component comprises such a printing, wherein at least a part of an upper surface of the coating provides an activated surface area, in particular being activated by an activation process that increases the surface tension within the activated surface area compared to the remaining surface of the coating before the activation process or parts of the surface that are not activated. Said activation process is in particular acti vated by an activation process using plasma technology. The printing (or printing material) is then applied to the activated surface area, thus on those parts of the surface of the coating for or on which the activation process has been carried out. Ap plication of the printing is in particular carried out by means of ink technology, such as serigraphy or tampography.

Thereby the component comprises a printing, but still shows good cleaning behaviour. Performing the preliminary activation pro cess on the coating increases locally the surface tension so that the coating shows good adhesion properties in said acti vated areas for subsequent applying of the printing. Said acti vation lasts for some days, allowing a convenient application of symbols or the like, in particular by using traditional ink technologies. As the printing is applied to the coating without need of removing parts of said coating, e.g. by laser treatment before, additionally corrosion issues are avoided.

A preferred embodiment is characterized by an activation process which is performed using plasma technology. Particularly, a plasma technology gun or pin is used, moving on or above the part of the exposed surface of the coating to be treated and performing the activation process passing over said area. The coating is essentially non polar and shows non-wetting proper ties. Due to the activation process within the plasma, polar groups are formed at the exposed surface of the coating that in crease the wettability of its surface. Subsequently, the print- ing can adhere to the surface.

In order to perform a quick and cost-efficient treatment, the activation process may be performed by limiting to the area or areas receiving a printing. Hence, areas without any printing may be excluded from such treatment. In order to reach this tar get, the exposed surface of the coating is covered at least par tially, thus blank or non-printed areas are covered before per forming the activation process in order to limit the part of the exposed surface on which the activation process is performed, in particular by covering parts of the exposed surface by means of respective cover elements or cover means. Alternatively, the plasma technology gun or pin may be deactivated when passing over the blank or non-printed areas. The second object of the present invention is achieved by a cooking appliance, in particular a gas hob, according to claim 18. Such a cooking appliance comprises a top plate comprising at least one cooking area and at least one gas burner for heating the at least one cooking area. The cooking appliance further comprises a top plate and/or a burner cap according to the pre- sent invention.

A cooking appliance or gas hob, respectively, according to in vention may be embodied as different types gas hobs, including classic burners in a stainless steel or enameled steel hob, gas burners on a glass or glass ceramics as well as gas-glass-ce- ramic cooking hobs with gas-infrared radiators underneath a glass-ceramic .

The gas burner may have various designs that are well known for person skilled in the art, in general including a burner cap, a burner crown, a spark plug and a thermocouple.

The cooking appliance may comprise further components that are provided to be attached to the cooking appliance and/or the top plate, for example grate or pot carriers or a control panel.

The third object of the present invention is achieved by a method for manufacturing a component, in particular a top plate or a burner cap according to claim 19.

Such a method for manufacturing a component, in particular a top plate or a burner cap having a non-stick and/or non-wetting coating on an upper surface comprises at least the following steps:

Firstly, an uncoated component, in particular a top plate, being in particular planar-shaped, and/or a burner cap each having an upper surface and a bottom surface is or are provided. Secondly, at least the upper surface of the component, in par ticular a top plate or a burner cap is pretreated by mechanical treatment, physical treatment or chemical treatment, in particu lar by sandblasting and/or laser treatment and/or an enamelling process to form a ground layer to provide a surface having a roughness being suitable for applying a non-stick and/or non wetting coating.

In other words: Before applying the non-stick and/or non-wetting coating or - if useful - a protective layer to the component, in particular a top plate or a burner cap, the surface of the un coated component, in particular a top plate or a burner cap is prepared, e.g. by cleaning and/or drying the upper surface and/or activating the upper surface, preferably by roughening the surface by sandblasting and/or laser treatment and/or an enamelling process to form a ground layer on the upper surface, in order to achieve better adhesion of the protective layer or the non-stick and/or non-wetting coating. Regarding the pretreatment and roughening of the surface, we ex plicitly refer to the explanations and examples described with regard to the different methods and materials used for the dif ferent layers, in particular the different enamel compositions, described in the context of the protective and/or ground layer as well as composition of the non-stick and/or non-wetting coat ing described in the context of the component, in particular a top plate or a burner cap.

Thirdly, at least one layer of the non-stick and/or non-wetting coating is applied to the pretreated upper surface of the compo nent, in particular a top plate or a burner cap or the surface of the ground layer. According to a preferred embodiment, during the enameling pro cess of the pretreatment, an enamel powder is applied onto the upper surface of the component, in particular a top plate or a burner cap and the enamel powder is heated for providing a ground layer with an upper surface having a roughness being suitable for applying the non-stick and/or non-wetting coating.

According to a preferred embodiment, a protective layer, in par ticular an enamel layer and/or an aluminium layer and/or a layer comprising aluminium, is applied to at least the upper surface of the component, in particular a top plate or a burner cap and the surface of the protective layer is pretreated by sandblast ing and/or laser treatment and/or an enamelling process to form a ground layer.

In other words: Before applying the non-stick and/or non-wetting coating to the surface of the protective layer, the surface of the protective layer is prepared, e.g. by cleaning and/or drying the upper surface and/or activating the upper surface, prefera- bly by roughening the surface for example by mechanical treat ment, in particular sandblasting, laser treatment or chemical treatment of the upper surface of the component, in particular a top plate or a burner cap, in order to achieve better adhesion of the non-stick and/or non-wetting coating. Also preferred is even here, that the surface of the protective layer is made and/or roughened by an enameling process, in particular by ap plying a ground layer.

Thus the ground layer is applied to the upper surface of the component, in particular a top plate or a burner cap, by an enamelling process having a surface roughness between Ra 0.01 pm to 10.00 pm, more preferably between Ra 0.10 pm to 5.00 pm, still more preferably between Ra 0.20 pm to 5.00 pm, still more preferably between Ra 0.50 pm to 5.00 pm, still more preferably between Ra 2.00 mpi to 5.00 mpi, still more preferably between Ra 2.50 mpi to 5.00 mpi and/or a layer thickness between 5 and IOOmpi, in particular between 10 and 80mpi, more particularly between 20 and 50pm. Said properties can be achieved by using enamel compo- sitions described before, thus conventional enamels, catalytic enamels or so-called ground compositions. We refer explicitely to the explanations and examples described in the context of the protective and ground layer of the component, in particular a top plate or a burner cap.

In a preferred embodiment, the non-stick and/or non-wetting coating comprises a first and a second layer, wherein the first layer is applied to the upper surface of the component, in par ticular a top plate or a burner cap or the surface of the ground layer or the pretreated surface of the protective layer, and wherein the second layer is applied to the first layer, so that a top plate comprising a coating having base layer and top layer is obtained. In order to apply a printing on the coated surface, according to a preferred embodiment, the method may comprise additionally the steps performing an activation process on at least a part of the surface of the coating in order to provide an activated surface area, wherein the activation process in particular increases the surface tension within the activated surface area, in particular performing an activation process by using plasma technology, and applying a printing to the activated surface area, in particular by means of ink technology. Novel and inventive features of the present invention are set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in further detail with reference to the drawings, in which FIG 1 illustrates a top view of a gas hob having a top plate according to an embodiment of the present invention,

FIG 2A illustrates a first embodiment of a gas burner having a burner cap,

FIG 2B illustrates a second embodiment of a gas burner having a burner cap,

FIG 3 illustrates a cross-sectional view of the top plate ac cording to a first embodiment of the invention in detail,

FIG 4 illustrates a cross-sectional view of the top plate ac cording to a second embodiment of the invention in de tail,

FIG 5 illustrates a cross-sectional view of the coating accord ing to an embodiment of the invention in detail.

DETAILED DESCRIPTION FIG 1 illustrates a top view of an embodiment of a gas hob 1. The gas hob 1 comprises a component, in fact a top plate 2 ac cording to the present invention being plate-shaped and having exemplary four cooking areas 3 of different sizes on which pans or pots are to be placed for cooking foodstuff.

The gas hob 1 further comprises a control panel 4 with several operating and display elements, e.g. cooking level display or setting knobs. Furthermore, the gas hob may comprise grate or pot carriers (not shown) that can be placed on the top plate 2. The gas hob 1 further comprises gas burners 5a, 5b for heating the cooking areas. Two embodiments of such gas burners 5a, 5b are exemplarily shown in FIG 2A and FIG 2B. The gas burner 5a according to a first embodiment comprises a disc-shaped burner cap 6a being prepared and having a non-stick and/or non-wetting coating according to the present invention, a burner crown 7a, a spark plug 8a and a thermocouple 9a. The gas burner 5b according to a second embodiment comprises a ring-shaped burner cap 6b be- ing prepared and having a non-stick and/or non-wetting coating according to the present invention, a burner crown 7b, a spark plug 8b and a thermocouple 9b.

The top plate 2 can be made of a corrosive material, in particu- lar low-carbon steel, or glass or glass ceramics. The top plate 2 comprises an upper surface 11a, a bottom surface lib and open ings for inserting a gas burner 4a, 4b. Of course, the top plate

2 can have other shapes or openings of different design than shown in FIG 1.

The layers, coating and manufacturing process of the component according to the invention is described in the following FIG 3 to 5 with regard to the top plate 2. The burner caps 6a, 6b shown in FIG 2, may also have such a layers, coating and manu- facturing process.

FIG 3 shows a cross-sectional view of the top plate 2 according to a first embodiment in which the layer structure can be seen. The top plate 2 is obtained by a process wherein the upper sur- face 11a of the top plate 2 is pretreated by an enamelling pro cess to form a ground layer 13 formed by a ground coat composi tion that has burned to the top plate 2 at temperatures of about 820°C on said surface 7a. In general, the temperature for enam elling a ground enamel may be between 680 and 820°C, depending of the specific formulation of the ground enamel. Said ground layer 13 or, respectively, enamel layer, has an upper surface 14a and a bottom surface 14b and shows a surface roughness Ra of about 2 to 3.5pm at its upper surface 14a. The thickness of the ground layer 13 is about 20pm. Ground layer 13 also shows corro sion resistant properties so that the top plate 2 is protected against corrosion, what is in particular useful and necessary if said top plate 2 is made of a corrosive material, for example a low carbon steel to save costs. Inventors have surprisingly found that such a small thickness and small roughness shows good adhesion properties that are sufficient for applying a non-stick and/or non-wetting coating 12 comprising at least one layer 17 that is obtained by a sol-gel process from a first composition comprising a silica sol and a silane and according to embodi- ments of the invention further components like solvents or addi tives in useful amounts as described before.

FIG 4 shows a cross-sectional view of the top plate 2 according to a second embodiment in which the layer structure can be seen. The top plate 2 is presently made from a corrosive material so that a protective layer 15 is applied to the upper surface 11a of the top plate 2 before the pretreatment step for preventing the top plate 2 from corrosion, the protective layer 15 having an upper surface 16a and a bottom surface 16b. Afterwards, for obtaining a top plate 2 with a non-stick and/or non-wetting coating 12, said protective layer 15 is pretreated by sandblast ing or laser treatment to achieve a surface roughness of the surface 16a of the protective layer between about 2 and 3.5pm by sandblasting or a surface roughness smaller than lpm by laser treatment. Inventors have surprisingly found out that even though the surface roughness achieved by laser treatment is smaller, good adhesion behaviour can be achieved, probably due to more fine-grained structure in comparison with a sandblasted surface. The protection layer 15 has a layer thickness of about 150mpi. In particular in case that the protection layer 15 is an aluminium layer or a layer comprising aluminium, it might be useful to carry out an enamelling process to form a ground coat 13 on the surface 16a of the protective layer 15 (shown in dashed lines) to benefit from the good adhesive properties of an enamel layer made from a ground composition having a surface roughness between 2 to 3.5pm.

FIG 5 shows a cross-sectional view of the top plate 2 according to a third embodiment, that differs from the first embodiment according to FIG 3 in that the non-stick and/or non-wetting coating 12 comprises a first and a second layer 17, 18, wherein the first layer 17 is applied to the surface 14a of the ground layer 13 and wherein the second layer 18 is applied to the first layer 17. The second layer 18 is obtained by a sol-gel process from a second composition comprising a silica sol, a silane and a siloxane.

As a matter of course, even a top plate 2 according to the sec- ond embodiment shown in FIG 4 might have a non-stick and/or non wetting coating 12 comprising a first and a second layer 17, 18, wherein the first layer 17 is applied to the surface 16a of the protective layer 15 and wherein the second layer 18 is applied to the first layer 17.

Both, the first layer 17 and, if present, the second layer 18 are obtained by a sol-gel process. For production of the first layer 17, a colloidal silica sol, which is pure S1O2, an or- ganoalkoxysilane, which is an organic-inorganic hybrid material and presently methyltrimethyoxysilane, and an acid catalyst, presently acetic acid are mixed and stirred for about 2 hours at room temperature in order to effect a condensation reaction. The weight proportion of organoalkoxysilane is about 10 to 40wt%, silica sol is present in an amount of 30 to 70wt%. Adding acetic acid in an amount of 0,1 to 2 wt% is sufficient for accelerating the condensation reaction.

Then, a solvent, presently propanol, is added in an amount of 10 to 40wt%. Pigments are added and further additives can be addi tionally added at this step.

For production of the second layer 18, colloidal silica sol, si- loxane and a solvent, even here propanol, are mixed. Organoal- koxysilane and an acid catalyst, presently acetic acid are then added. Even said mixture is mixed and stirred for about 2 hours at room temperature. The weight proportion of organoalkoxysilane is about 10 to 40wt%, silica sol is present in an amount of 30 to 70wt%, acetic acid is present in an amount of 0,1 to 2wt%. Siloxane, presently polydimethylsiloxane, is added in an amount of 0,1 to 2 wt%.

Then, a solvent, presently even here propanol, is added in an amount of 10 to 40wt%. Pigments are added and further additives can be additionally added at this step.

For manufacturing a top plate 2 having a non-stick and/or non wetting coating 12 on its upper surface 11a, a top plate 2 hav ing an upper surface 11a and a bottom surface lib. In a further step, the upper surface 11a of the top plate 2 is pretreated in order to provide good adhesion properties and surface roughness for subsequent apply of the non-stick and/or non-wetting coating 12 (FIG 3). Additionally or in an alternative, a protective layer 15 is applied to the upper surface 11a of the top plate 2 and said protective layer 15 is pretreated (FIG 4). Pretreatment of the surface 7a of the top plate 2 or, if present, the surface 16a of the protective layer 15 is carried out in particular by sandblasting, laser treatment or an enamelling process for form ing a ground layer 13. The enamelling process is in particular carried out by applying an enamel powder onto the upper surface 11a of the top plate 2 and/or onto the surface 16a of the protective layer 15, and heating the enamel powder for providing a ground layer 13 with a surface 14a having a roughness being suitable for applying the non-stick and/or non-wetting coating 12.

Afterwards, at least one layer of the non-stick and/or non-wet- ting coating 12 is applied to the upper surface 11a of the top plate 2 or, if present, to the upper surface 16a of the protec tive layer 15 or the surface 14a of the ground layer 13.

In case of applying a non-stick and/or non-wetting coating 12 comprising at least two layers 17, 18 (FIG 5), the first layer 17 is applied to the upper surface 11a of the top plate 2 or the surface 14a of the ground layer 13 or the surface 16a of the protective layer 15, and the second layer 18 is applied to the first layer 17. Both layers 17, 18 have a bottom surface 17a, 18a facing away from the top plate 2 and an upper surface 17b,

18b facing towards the top plate 2.

The present invention, thus a component, in particular top plate 2 having a non-stick and/or non-wetting coating 12 and a cooking appliance 1 having such a top plate 2 shows an improved cleaning behaviour. The coating 12 is abrasion-resistant and shows a greater surface hardness what leads to an increased lifetime. Furthermore, the coating 12 has shown a good adhesion properties on the top plate 2, in particular on the surface 14a of the ground layer 13 or the surface 16a of the protective layer 15.

As the coating 12 is produced by a sol-gel process, a (second) burning step at high temperatures is not necessary. The top plate 2 may further comprise a printing (not shown) that is applied, in particular by ink technology, to the surface of the coating 12, in particular to a surface area that has been activated by using plasma technology in order to increase the surface tension.

Although illustrative embodiments of the present invention have been described herein with reference to the accompanying draw ings, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the in vention. All such changes and modifications are intended to be included within the scope of the invention as defined by the ap- pended claims.

LIST OF REFERENCE NUMERALS

1 gas hob

2 top plate

3 cooking area

4 control panel

5a, 5b gas burner

6a, 6b burner cap

7a, 7b burner crown

8a, 8b spark plug

9a, 9b thermocouple

10 control panel

11a upper surface of the top plate lib bottom surface of the top plate

12 non-stick and/or non-wetting coating

13 ground layer

14a upper surface of the ground layer 14b bottom surface of the ground layer 15 protective layer

16a upper surface of the protective layer 16b bottom surface of the protective layer

17 first layer of the non-stick and/or non-wetting coating 17a upper surface of the first layer

17b bottom surface of the first layer

18 second layer of the non-stick and/or non-wetting coating 18a upper surface of the second layer

18b bottom surface of the second layer