WO2003004253A1

WO2003004253A1 - Casting mould and usage of an anodically oxidized surface layer

Info

Publication number: WO2003004253A1
Application number: PCT/EP2002/007240
Authority: WO
Inventors: Thomas Sawitowski
Original assignee: Alcove Surfaces Gmbh
Priority date: 2001-07-02
Filing date: 2002-07-01
Publication date: 2003-01-16
Also published as: DE10154756C1; EP1401633A1

Abstract

The invention relates to a casting mould (1) and the usage of an anodically oxidized surface layer (3). The aim of the invention is to provide a surface structure in the nanometer range in a simple, cost-effective manner. To achieve this, a surface layer (3) comprising cavities (4), which are formed using anodic oxidation without a model, is moulded by casting.

Description

Casting mold and use of an anodized surface layer

The present invention relates to a casting mold according to the preamble of claim 1 and a use according to the preamble of claim 6.

In the present invention, the nanometer range means profiles or structuring with structure widths <1000 nm, in particular <500 μm, preferably at least 1 or 10 nm. The structure width denotes the extent to which individual structure elements, such as surveys, are repeated regularly, in particular. H. thus for example the center distance of mutually adjacent elevations or depressions which are adjacent to one another.

In the nanometer range, lithographic processes for structuring can only be used to a very limited extent. It should be noted here that the wavelength of visible light alone is already 400 to 750 nm. In any case, the lithographic processes are very complex.

The post-published DE 100 20 877 Cl discloses the use of a surface layer with cavities formed by anodic oxidation as a die during embossing.

From CH 251 451, which forms the starting point of the casting mold according to claim 1, the use of anodically oxidized surface layers made of aluminum or magnesium in casting molds to increase the resistance is known. However, the formation of voids by the oxidation for structuring a casting in the nanometer range is not disclosed.

The formation of cavities in the anodic oxidation of aluminum is described for example in EP 0 931 859 AI, which forms the starting point for use according to claim 6.

The present invention has for its object a casting mold and the use of an open cavity by anodic oxidation

BESTATIGUNGSKOPIE Specify provided surface layer, a structuring of a casting or workpiece in the nanometer range is made possible in a simple, inexpensive manner.

The above object is achieved by a casting mold according to claim 1 or by a use according to claim 6. Advantageous further developments are the subject of the subclaims.

An essential idea of the present invention is to use a porous oxide layer, in particular a surface layer with open cavities, which are formed by anodic oxidation directly or without a template, that is to say independently of a cathode shape, as the mold surface or inner surface of a casting mold. This leads to several advantages.

First, an oxide layer, in particular the aluminum oxide that is preferably provided, is relatively hard. This is advantageous in view of the often very high loads during casting or molding, in order to be able to produce workpieces of a wide variety of materials and to achieve a long service life for the casting mold.

Second, the template-free oxidation is very simple and inexpensive to implement. In particular, the creation of the cavities (quasi) regardless of the shape and arrangement of the cathode used, that is, a template or negative form is not required.

Third, the proposed template-free formation of open cavities by anodic oxidation enables the production of structures in the nanometer range in a very simple, inexpensive manner. In particular, structure widths of 500 nm and less, even of 100 nm and less, are made possible.

Fourthly, depending on the choice of process conditions, the arrangement - regular or irregular - and the surface density of the cavities can be varied as required. Fifth, likewise by simply varying the process conditions - in particular by varying the voltage during anodization - the shape of the cavities and thus the structure of the molding surface can be adjusted and varied.

Sixth, the anodized surface layer can be used directly, that is to say without further molding, as the mold surface of a casting mold.

Further advantages, properties, features and objectives of the present invention emerge from the following description of a preferred exemplary embodiment with reference to the drawing. The only figure shows

a very schematic partial sectional view of a proposed casting mold and a workpiece structured with it.

The figure shows a very schematic partial sectional view of a proposed casting mold 1 with an at least partially structured, that is profiled or relief-like inner surface or molded surface 2. The surface 2 is formed by an upper or flat side of a surface layer 3, which with open, through Anodic generated cavities 4 is provided.

In the example shown, the surface layer 3 is applied to a carrier 5 of the casting mold 1. For example, the surface layer 3 is applied to the carrier 5 by plasma coating. However, the surface layer 3 can also be formed directly by the carrier 5, that is to say be a surface region of the carrier 5.

Of course, the surface layer 3 can also be deposited on the carrier 5 by other methods.

In the example shown, the surface layer 3 is preferably made of aluminum, which is applied to the carrier 5 in particular by plasma coating and adheres very well to the carrier 5, which preferably consists of metal, in particular iron or steel. The surface layer 3 is at least partially anodically oxidized to the depth of a cover layer 6 in the illustrated example, as a result of which the cavities 4 are formed directly in the surface layer 3 or cover layer 6. The cavities 4 are formed directly or without templates, ie the arrangement, distribution, shape and the like. The like. The cavities 4 - in contrast to the Elysier - is therefore at least essentially independent of the surface shape and proximity of the cathode used (not shown) during the oxidation. Rather, according to the invention, the "valve effect", namely the independent formation of the cavities 4 that occurs when the surface layer 3 is oxidized or anodized - at least in particular in the case of the so-called valve metals. However, this direct or template-free creation of the cavities 4 does not preclude additional (previous or later) shaping or structuring of the surface 2 or the cavities 4 by a negative shape.

Depending on how completely or how deeply the surface layer 3 is oxidized or whether the surface layer 3 is formed directly by the carrier 5, the surface layer 3 can correspond to the oxidized cover layer 6. In this case, for example, the intermediate layer 7 made of aluminum in the example shown, which provides very good adhesion between the cover layer 6 and the carrier 5, can be omitted.

For example, according to an alternative embodiment, the uncoated carrier 5 can be anodically oxidized on its surface forming the surface 2 to form a porous oxide layer or cavities 4. This is possible, for example, in the case of a support 5 made of iron or steel, in particular stainless steel. In this case, the surface layer 3 corresponds to the cover layer 6, that is to say the oxidized layer.

Aluminum and iron or steel, in particular stainless steel, have already been mentioned as particularly preferred materials which can be used at least essentially to form the anodized surface layer 3 or the cover layer 6. However, silicon and titanium and other valve metals can also be used, for example. In the example shown, the proportions are not shown to scale.

The surface 2 preferably has a structure width S in the nanometer range, in particular from 30 to 600 nm and preferably from 50 to 200 nm.

The cavities 4 or their openings have an average diameter D of essentially 10 to 500 nm, preferably 15 to 200 nm and in particular 20 to 100 nm.

In the example shown, the cavities 4 are essentially elongated, their depth T preferably being at least approximately 0.5 times the aforementioned average diameter D and in particular approximately 1.0 to 10 times the diameter D.

The cavities 4 are at least substantially uniform here. In particular, the cavities 4 are essentially cylindrical. However, the cavities 4 can also have a different shape, for example be essentially conical.

In general, the cavities 4 can also have a cross section that varies in shape and / or diameter over their depth T. In addition, the cavities 4 can each be substantially conical as a rough structure and can be provided with many fine depressions (small cavities) along their walls to form a fine structure.

The cavities 4 are preferably arranged at least substantially regularly distributed over the surface of the surface layer 3 or over the surface 2. However, an irregular distribution can also be considered.

The cavities or their openings are preferably distributed over the surface 2 with a surface density of 10 ⁹ to 10 ^π / cm ² . In the example shown, the areal density is essentially constant over area 2. However, the areal density can also vary in areas on area 2 as required. The area of the openings of the cavities 4 is preferably at most 50% of the expansion area of the area 2. This results in a sufficiently high stability or resilience of the area 2 or the surface layer 3 / cover layer 6 in view of the sometimes high ones occurring during molding or casting Stresses reached.

In general, the shape, arrangement, areal density and the like of the cavities 4 can be controlled by appropriate selection of the process conditions during anodizing. For example, when aluminum is oxidized under potentiostatic conditions - that is to say at least substantially constant voltage - an at least substantially uniform cross section of the cavities 4 is achieved across their depth T, that is to say an at least substantially cylindrical shape. Accordingly, the shape of the cavities 4 can be influenced by varying the voltage. For example, galvanostatic oxidation - i.e. H. with at least substantially constant current - to an approximately conical or hill-like shape of the cavities 4, so that a kind of "moth eye structure" or the like can be formed in this way. Furthermore, the areal density of the cavities 4, i.e. H. the number of cavities 4 per unit area on the surface 2, u. a. on the voltage and current when anodizing.

If necessary, the cavities 4 can vary in their shape, depth and / or area density over the area 2, in particular in certain areas, or can be formed on the area 2 only in areas.

If necessary, the surface 2 can also be modified before and / or after the oxidation - that is to say the creation of the cavities 4 - for example by lithographic processes, etching and / or other, preferably material-removing processes, in order, for example, to have a rough structure in the form of webs, webs, Generate areas with or without cavities 4, large-scale elevations or depressions and the like on the surface 2.

To modify the surface 2 or the cavities 4, mechanical processing and / or chemical expansion can also be carried out, in particular by partially etching away oxide material. In this way the surface ratio of the opening areas of the cavities 4 to the extension area of the area 2 can be varied or enlarged. Of course, this also makes other modifications of the surface 2 or the cavities 4 possible, depending on the exposure time and intensity.

A particular advantage of the proposed solution is that the surface 2 can have virtually any shape.

The figure also shows a cast part or workpiece 8, likewise in a greatly simplified, not to scale sectional view, in the already finished state, that is to say after casting with a surface 9 already structured by the casting mold 1.

The proposed casting mold 1 permits a very fine structuring of the workpiece 8 or its surface 9. It is possible, for example, to have relatively large elevations in the range from 0.1 to 50 μm with several relatively small projections, for example in the area, on the surface 9 from 10 to 400 nm, on the surface 9 of the workpiece 8.

The proposed solution enables a very fine structuring of the surface 9 in a very simple, cost-effective manner. Accordingly, there is a very wide range of applications. For example, such, in particular very fine structuring in the case of antireflection layers, can be used or used to change the radiation emission of structured surfaces, in sensors, in catalysis, in the case of self-cleaning surfaces, in improving surface wettability and the like.

In particular, the proposed solution can be used for casting with a quasi-arbitrary material, since aluminum oxide in particular is very resistant mechanically, thermally and / or chemically.

In general terms, an essential aspect of the present invention is to cast or mold a surface layer with cavities formed directly or without a template by anodic oxidation in order to enable surface structuring in the nanometer range. In particular, the present invention is not restricted to a casting mold 1 in the narrower sense. Rather, the surface layer 3 or cover layer 6 is to be understood as a template for a general structuring of a surface, a tool, a workpiece or the like in the nanometer range. In particular, any desired impression of the template can be made. In particular, reshaping is not necessary when molding. For example, the structure can be molded by casting or the like. For example, the workpiece 8 to be produced with the structured surface 9 can then be a cast part, the structuring of the surface 9 being carried out by casting or pouring or other molding of the casting mold 1.

Claims

claims:

1. casting mold (1) with a surface layer oxidized by an anodically

(3) or top layer (6) formed molding surface (2), characterized in that the molding surface (2) is at least partially structured in the nanometer range, the surface layer (3) or top layer (6) open cavities created by the anodic oxidation without templates (4) for structuring the shaped surface (2) in the nanometer range.

2. Casting mold according to claim 1, characterized in that the cavities

(4) opening areas with an average, preferably at least substantially uniform, diameter (D) of 10 to 500 nm, preferably of

15 to 200 nm and in particular from 20 to 100 nm.

3. Casting mold according to claim 1 or 2, characterized in that the structural width (S) of the mold surface (2) is essentially 30 to 600 nm, in particular 50 to 200 nm.

4. Casting mold according to one of the preceding claims, characterized in that the cavities (4) have a depth (T) which is at least 0.5 times the average diameter (D) of the cavities (4) and in particular larger than the average diameter (D) of the cavities (4), and / or that the cavities (4) are at least substantially conical, and / or that the cavities (4) in their shape, depth and / or area density over the Mold surface (2), in particular in some areas, vary and or are formed only in some areas on the molded surface (2).

5. Casting mold according to one of the preceding claims, characterized in that the shaped surface (2) has both a fine and a coarse fracture and or that the shaped surface (2) is curved, preferably curved, and / or that the surface layer (3) Cover layer (6) with the cavities (4) consists at least essentially of aluminum oxide, silicon oxide, iron oxide, oxidized steel and / or titanium oxide.

6. Use of a surface layer (3) or top layer (6), in particular a casting mold (1), provided with open cavities (4) directly by anodic oxidation, for structuring a surface (9) of a casting or workpiece (8), characterized that the surface layer (3) or cover layer (6) with the cavities (4) as a molding surface (2) is molded by casting to structure the surface (9) of the casting or workpiece (8).

7. Use according to claim 6, characterized in that the surface layer (3) or cover layer (6) is formed at least essentially from aluminum oxide, silicon dioxide, iron oxide, oxidized steel and / or titanium dioxide.

8. Use according to claim 6 or 7, characterized in that the surface (9) is structured in the nanometer range and / or that the shaped surface (2) has a structure width (S) of essentially 30 to 600 nm, in particular 50 to 200 nm , having.

9. Use according to one of claims 6 to 8, characterized in that the cavities (4) opening surfaces with an average, preferably at least substantially uniform diameter (D) of 10 to 500 nm, preferably from 15 to 200 nm and in particular from 20 up to 100 nm.

10. Use according to one of claims 6 to 9, characterized in that the cavities (4) have a depth (T) which is at least 0.5 times the average diameter (D) of the cavities (4) and in particular larger than the average diameter (D) of the cavities (4), and / or that the cavities (4) are at least substantially conical, and / or that the cavities (4) in their shape, depth and / or area density over the Mold surface (2), in particular in regions, vary and / or are formed only in regions on the mold surface (2).

11. Use according to one of claims 6 to 10, characterized in that the shaped surface (2) has both a fine and a coarse structure, and / or that the shaped surface (2) is curved, preferably curved, and / or that the Form surface (2) before and / or after the oxidation, in particular to produce a coarse structure, is modified, in particular by lithographic processes, etching and / or other, preferably material-removing processes.

12. Use according to one of claims 6 to 11, characterized in that the surface layer (3) or cover layer (6) is oxidized potentiostatically or with varying voltage, in particular galvanostatically.