Stamping tool, casting mold and methods for structuring a surface of a work piece

Abstract

A simple, cost-effective stamping or molding in the nanometer range is enabled using a stamping surface or molding face with a surface layer having hollow chambers that have been formed by anodic oxidation.

Claims

.[.1. Method for producing a stamping tool with a structured stamping surface, comprising the steps of: oxidizing a surface or covering layer of the stamping tool for forming the stamping surface at least partially anodally and forming open hollow chambers that are at least essentially uniformly shaped and at least essentially evenly distributed over the surface or surface area of the stamping surface without the use of a model..].

.[.2. Method according to claim 1, wherein the surface or covering layer is oxidized potentiostatically..].

.[.3. Method according to claim 1, wherein the surface layer or covering layer is oxidized with varying voltage..].

.[.4. Method according to claim 3, wherein the surface or covering layer is oxidized galvanostatically..].

.[.5. Method according to claim 1, wherein the surface or covering layer that is oxidized is formed of a material selected from the group consisting of aluminum, silicon, iron, steel and titanium..].

.[.6. Method according to claim 1, comprising the additional step of modifying the stamping surface at least one of before and after said oxidizing step for producing a rough structure..].

.[.7. Method for structuring a surface of a work piece in a nanometer range by means of a stamping tool with a structured stamping surface, comprising at least one of pressing and rolling a stamping surface, formed of an anodally oxidized surface or covering layer with open hollow chambers which have diameters in a nanometer range that have been created model-free by anodic oxidation, onto the surface to be structured..].

.[.8. Method according to claim 7, wherein the surface is first roughly structured in a first step by means of a first stamping tool and then is finely structured by means of a second stamping tool in a second step..].

.[.9. Method according to claim 8, wherein the surface is finely structured by means of said second stamping tool in said second step with a stamping force that is reduced relative to that applied with said first stamping tool..].

.[.10. Method according to claim 8, wherein the surface is finely structured by means of said second stamping tool in said second step after hardening of the surface structured by said first step..].

.[.11. Method for at least partially structuring a surface of a cast work piece, comprising the steps of: casting the work piece using a casting mold with a structured molding face having an anodally oxidized surface or covering layer with open hollow chambers created model-free by anodic oxidation..].

.[.12. Method according to claim 11, wherein the surface or covering layer is formed at least substantially of a material selected from the group consisting of aluminum oxide, silicon oxide, iron oxide, oxidized steel, and titanium oxide..].

.Iadd.13. Method for producing an anti-reflection surface having a moth-eye structure on a workpiece, comprising: pressing or rolling a first tool onto a surface of the workpiece to form a rough structure on the surface of the workpiece, and then pressing or rolling a second tool onto the surface of the workpiece to form the moth-eye structure having a plurality of fine protrusions. .Iaddend.

.Iadd.14. The method of claim 13, wherein the rough structure has projections of an order ranging from 0.1 to 50 micrometers. .Iaddend.

.Iadd.15. The method of claim 13, wherein the diameters of the plurality of fine protrusions is ranging from 10-500 nm. .Iaddend.

.Iadd.16. The method of claim 15, wherein the diameters of the plurality of fine protrusions is ranging from 15-200 nm. .Iaddend.

.Iadd.17. The method of claim 16, wherein the diameters of the plurality of fine protrusions is ranging from 20-100 nm. .Iaddend.

.Iadd.18. The method of claim 13, wherein the first tool is pressed or rolled onto the surface of the workpiece with a first stamping force, and the second tool is pressed or rolled onto the surface of the workpiece with a second stamping force which is reduced relative to the first stamping force. .Iaddend.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a very schematic sectional elevation of a stamping tool and a work piece structured therewith according to a first embodiment; and

(2) FIG. 2 is a very schematic sectional elevation of a proposed casting mold and a work piece structured therewith according to an second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(3) In a highly simplified sectional elevation, FIG. 1 shows a proposed stamping tool 1 with a structured, i.e., profiled or relief-like, stamping surface 2. The stamping surface 2 is formed by a side of a surface layer 3 which is provided with open hollow chambers 4 produced by anodic oxidation or an originally flat surface.

(4) In the illustrative example, the surface layer is applied to a support 5 of the stamping tool 1. For example, the surface layer 3 is applied to the support 5 by plasma coating. However, the surface layer 3 can also be formed directly by the support 5, and thus can be a surface area of the support 5.

(5) It is understood that the surface layer 3 can also be deposited on the support 5 using other methods.

(6) In the illustrative example, the surface layer 3 preferably is made of aluminum which is applied to the support 5, especially via plasma coating, and adheres well to the support 5, which is preferably made of metal, especially iron or steel.

(7) The surface layer 3 is at least partially anodally oxidized in the illustrative example, to the depth of a covering layer 6, whereby the hollow chambers 4 are formed in the surface layer 3. The hollow chambers 4 are formed immediately and/or without any model or pattern, i.e., the arrangement, distribution, form and the like of the hollow chambers 4—as opposed to electrolytic machining—is, thus, at least essentially independent of the surface shape and the proximity of the cathode (not shown) used in oxidation. Moreover, according to the invention, the “valve effect,” namely the occurring, independent formation of hollow chambers 4 during oxidation or anodization of the surface layer 3—at least in particular in the so-called valve metals—is used. This immediate or undefined formation of the hollow chambers 4 does not preclude an additional (before or after) formation or structuring of the stamping surface 2 or the hollow chambers 4 by means of a negative form.

(8) Depending on how completely or how deeply the surface layer 3 is oxidized, or whether the surface layer 3 is formed directly by the support 5, the surface layer 3 can correspond to the oxidized covering layer 6. In this case, for example, the intermediate layer 7, which is comprised of aluminum in the illustrative example, and which promotes very good adhesion between the covering layer 6 and the support 5, can be omitted.

(9) For example, according to an alternative embodiment, the uncoated support 5 can be oxidized anodally on its surface forming the stamping surface 2 by formation of a porous oxide layer or hollow chambers 4. This is possible, for example, for a support 5 made of iron or steel, especially stainless steel. In this case, the surface layer 3 then corresponds to the covering layer 6, i.e., the oxidized layer.

(10) Aluminum and iron or steel, especially stainless steel, have already been named as particularly preferred materials, used at least substantially for forming the anodally oxidized surface layer 3 or the covering layer 6. However, silicon and titanium as well as other valve metals, for example, can also be used.

(11) In the illustrative example, the proportions in size are not presented true to scale. The stamping tool 1 or its stamping surface 2 preferably has a structural width S in the nanometer range, especially from 30 to 600 nm and preferably from 50 to 200 nm.

(12) The hollow chambers 4 or their openings have an average diameter D of essentially 10 to 500 nm, preferably 15 to 200 nm and especially 20 to 100 nm.

(13) In the illustrative example, the hollow chambers 4 are designed essentially lengthwise, wherein their depth T is preferably at least approximately 0.5 times the above-mentioned, average diameter D and especially approximately 1.0 to 10 times the diameter D.

(14) Here, the hollow chambers 4 are designed at least substantially similarly in shape. In particular, the hollow chambers 4 are designed substantially cylindrically. However, the hollow chambers 4 can also present a form deviating therefrom, for example, they can be designed substantially conically.

(15) In general, the hollow chambers 4 can also have a cross-section varying in its depth T, form and/or diameter. In addition to this, the hollow chambers 4 can be designed substantially conically as a rough structure, for example, and can be provided along their walls with many fine depressions (small hollow chambers) to form a fine structure in each case.

(16) The hollow chambers 4 are preferably distributed at least substantially uniformly over the surface of the surface layer 3 or over the stamping surface 2. However, uneven distribution is also feasible.

(17) The hollow chambers or their openings are preferably distributed over the stamping surface 2 with a surface density of 10.sup.9 to 10.sup.11/cm.sup.2. In the illustrative example, the surface density is substantially constant over the stamping surface 2. However, the surface density can also vary partially on the stamping surface 2 as required.

(18) The area of the openings of the hollow chambers 4 is, at the most, preferably 50% of the extension area of the stamping surface 2. A sufficiently high stability or carrying capacity of the stamping surface 2 or the surface layer 3/covering layer 6 is hereby achieved with respect to the high stresses arising during the stamping.

(19) In general, the form, configuration, surface density and the like of the hollow chambers 4 can be controlled by corresponding choice of the procedural conditions during anodic oxidation. For example, with oxidation of aluminium under potentiostatic conditions—with at least substantially constant voltage—an at least substantially even cross-section of the hollow chambers 4 is achieved over their depth T, i.e., an at least substantially cylindrical form. Accordingly, the form of the hollow chambers 4 can be influenced by varying the voltage. For example, galvanostatic oxidation—i.e., at an at least substantially constant current—leads to a somewhat conical or hill-like form of the hollow chambers 4, so that a type of “moth eye structure” or the like can be formed in this way. The surface density of the hollow chambers 4, i.e., the number of hollow chambers 4 per surface unit of the stamping surface 2, depends inter alia on the voltage and the current during anodizing.

(20) As required, the hollow chambers 4 can vary in their form, depth and/or surface density over the stamping surface 2, especially partially, and/or be designed only partly on the stamping surface 2.

(21) If required, the stamping surface 2 can also be modified before and/or after oxidation—creation of the hollow chambers 4—for example, via a lithographic process, etching and/or other, preferably material-stripping methods, for example, to create a rough structure in the form of paths, ridges, areas with or without hollow chambers 4, large-surface bumps or depressions and the like on the stamping surface 2.

(22) Chemical sizing, especially by partial etching of oxide material, can also be carried out to modify the stamping surface 2 or the hollow chambers 4. In this way, the surface ratio of the opening surfaces of the hollow chambers 4 to the extension area of the stamping surface 2 can be varied or increased. It is understood that other modifications of the stamping surface 2 or of the hollow chambers 4 can also be made, depending on reaction time and intensity.

(23) A particular advantage of the proposed solution is that the stamping surface 2 can also be designed in a curved manner, for example, cylindrically, bulged, lenticular, or hemispherical. In particular, the stamping surface 2 can have practically any shape at all. Compared to the prior art, it is thus not necessary that the stamping surface 2 or the surface of the surface layer 3/covering layer 6 is at least substantially even.

(24) The figure also shows a work piece 8, likewise in a highly simplified, not true-to-scale, sectional diagram, in the already stamped state, i.e., with a surface 9 already structured by the stamping tool 1. Stamping takes places especially by the stamping tool 1 being pressed with a corresponding stamping force onto the surface 9 of the work piece 8 to be structured, so that the material of the work piece 8 flows at least partially into the hollow chambers 4. Here, it is not necessary that the work piece 8, as illustrated diagrammatically in the figure, is designed in a monobloc manner. Instead, the work piece 8 can also present another type of surface layer or surface coating or the like, not illustrated here, which forms the surface 9 and is structured or designed in a relief-like manner by means of the stamping tool 1.

(25) Instead of the stamp-like embossing, the stamping tool 1 can be unrolled with corresponding shaping/form of the stamping surface 2 and/or the surface 9 to be structured. By way of example, the stamping surface 2 and/or the surface 9 to be structured can be designed in a curved manner—for example, cylindrically—or in a bulged manner, to enable reciprocal unrolling for structuring the surface 9.

(26) Both a die stamping process and also a rolling stamp process can be realized with the proposed solution.

(27) Furthermore, the proposed solution can be used for embossing as well as closed-die coining or coining. A corresponding abutment for the work piece 8 or a corresponding countertool is not illustrated for clarification purposes.

(28) The proposed stamping tool 1 allows very fine structuring of the work piece 8 or its surface 9. If needed, the work piece 8 or the surface 9 can also be profiled or structured repeatedly, first with a rough structured stamping tool—optionally manufactured also in customary fashion—and then with the finer structured stamping tool 1 proposed here. A lower stamping force is employed, especially during the second stamping procedure using the finer stamping tool 1 and/or, in an intermediate step, the surface 9 is hardened in order not to fully neutralize the rough structure produced at first stamping, but to achieve superposition from the rough structure and the fine structure of both stamping tools. Thus, it is possible, for example, to create on the surface 9 relatively large bumps of the order of 0.1 to 50 μm, each with several, relatively small protrusions, for example, of the order of 10 to 400 nm, on the surface 9 of the work piece 8.

(29) The proposed solution very easily and cost-effectively enables very fine structuring of the surface 9. Accordingly, there is a very broad area of application. For example, such especially very fine structuring can be utilized in anti-reflex layers, for altering radiation emission of structured surfaces, in sensory analysis, in catalysis, in self-cleaning surfaces, in improving surface wettability and the like. In particular, the proposed solution also extends to the use of work pieces 8 with structured surfaces 9 that have been structured by use of the proposed stamping tool 1 for the purposes mentioned hereinabove.

(30) In particular, the proposed solution is suited for stamping synthetic materials—for example, PMMA (polymethyl methacrylates), Teflon or the like, metals—for example, gold, silver, platinum, lead, indium, cadmium, zinc or the like, polymer coatings—for example, paints, dyes or the like, and inorganic coating systems etc.

(31) Expressed in general terms, an essential aspect of the present invention according to the first embodiment is using a surface layer with hollow chambers formed by anodic oxidation as a bottom die or upper die, to enable surface structuring in the nanometer range.

(32) Now, the second embodiment of the present invention is discussed with reference to FIG. 2.

(33) In a highly simplified partial sectional elevation, FIG. 2 shows a proposed casting mold 11 with an at least partially structured, thus profiled or relief-like inner face or molding face 12. The face 12 is formed by a top or flat side of a surface layer 13 that is provided with open hollow chambers 14 produced by anodic oxidation.

(34) In the illustrative example, the surface layer 13 is applied to a support 15 of the casting mold 11. For example, the surface layer 13 is applied to the support 15 by plasma coating. However, the surface layer 13 can also be formed directly by the support 15, and thus can be a surface area of the support 15.

(35) It is understood that the surface layer 13 can also be deposited on the support 15 using other methods.

(36) In the illustrative example, the surface layer 13 preferably comprises aluminum, which is applied to the support 15 especially via plasma coating, and adheres well to the support 15 that is preferably made of metal, especially iron or steel.

(37) The surface layer 13 is at least partially anodally oxidized, in the illustrative example, to the depth of a covering layer 16, by means of which the hollow chambers 14 are formed in the surface layer 13 or covering layer 16. The hollow chambers 14 are formed directly or model-free, that is, the configuration, distribution, form and the like of the hollow chambers 14 is, compared to electrolytic machining, therefore at least substantially dependent on the surface shape and proximity of the cathodes (not illustrated here) used during oxidation. Rather, the ‘valve effect’ is made use of here, as per the invention, namely the automatic development of the hollow chambers 14 occurring during oxidation or anodizing of the surface layer 13, at least especially with so-called valve metals. Such direct and model-free production of the hollow chambers 14 does not exclude additional (prior or subsequent) forming or structuring of the face 12 or of the hollow chambers 14 by a negative form.

(38) Depending on how completely or how deeply the surface layer 13 is oxidized, or whether the surface layer 13 is formed directly by the support 15, the surface layer 13 can correspond to the oxidized covering layer 16. In the illustrative example, in this case, for example, the intermediate layer 17, which is comprised of aluminum and which promotes very good adhesion between the covering layer 16 and the support 15, can be omitted.

(39) For example, according to a design alternative the uncoated support 15 can be oxidized anodally on its surface forming the face 12 by formation of a porous oxide layer or hollow chambers 14. This is possible for example, for a support 15 made of iron or steel, especially stainless steel. In this case the surface layer 13 then corresponds to the covering layer 16, i.e., the oxidized layer.

(40) Aluminum and iron or steel, especially stainless steel, have already been named as particularly preferred materials, used at least substantially for forming the anodally oxidized surface layer 13 or the covering layer 16. However, silicon and titanium as well as other valve metals for example, can also be used.

(41) In the illustrative example, the proportions in size are not presented true to scale. The face 12 preferably has a structural width S in the nanometer range, especially of 130 to 600 nm and preferably of 50 to 200 nm. The hollow chambers 14 or their openings have an average diameter D of essentially 10 to 500 nm, preferably 15 to 200 nm and especially 20 to 100 nm.

(42) In the illustrative example, the hollow chambers 14 are designed essentially lengthwise, wherein their depth T is preferably at least approximately 0.5 times the above-mentioned, average diameter D and especially approximately 1.0 to 10 times the diameter D.

(43) The hollow chambers 14 are designed, here, at least substantially identically. In particular, the hollow chambers 14 are designed substantially cylindrically. However, the hollow chambers 14 can also present a form deviating therefrom, for example, they can be designed substantially conically.

(44) In general the hollow chambers 14 can also have a cross-section varying in its depth T in form and/or diameter. In addition to this, the hollow chambers 14 can be designed substantially conically as a rough structure, for example, and can be provided with many fine depressions (small hollow chambers) along their walls to form a fine structure in each case.

(45) The hollow chambers 14 are preferably distributed at least substantially uniformly over the surface of the surface layer 13 or over the face 12. However, uneven distribution is also feasible.

(46) The hollow chambers or their openings are preferably distributed with a surface density of 10.sup.9 to 10.sup.11/cm. In the illustrative example, the surface density is substantially constant over the face 12. However, the surface density can also vary selectively on the surface 12 as required.

(47) The area of the openings of the hollow chambers 14 is at the most preferably 50% of the extension area of the face 12. A sufficiently high stability or carrying capacity of the face 12 or the surface layer 13/covering layer 16 is thereby achieved with respect to the high stresses arising partially from molding or casting.

(48) In general, the form, configuration, surface density and the like of the hollow chambers 14 can be controlled by corresponding choice of the procedural conditions during anodic oxidation. For example, with oxidation of aluminium under potentiostatic conditions—i.e., at least at substantially constant voltage—an at least substantially uniform cross-section of the hollow chambers 14 is achieved over their depth T, i.e., an at least substantially cylindrical form. Accordingly, the form of the hollow chambers 14 can be influenced by varying the voltage. For example, galvanostatic oxidation, i.e., at an at least substantially constant current, leads to a somewhat conical or hill-like form of the hollow chambers 14, so that a type of “moth eye structure” or the like can be formed in this way. The area density of the hollow chambers 14, i.e., the number of hollow chambers 14 per area unit on the face 2, depends inter alia on the voltage and the current during anodizing.

(49) As required, the hollow chambers 14 can vary in their form, depth and/or surface density over the face 2, especially partially, and/or be designed only partially on the face 12.

(50) And, if required, the face 12 can also be modified before and/or after oxidation—thus, creation of the hollow chambers 14—for example, via a lithographic process, etching and/or other, preferably material-stripping methods, for example, to create a rough structure in the form of paths, ridges, areas with or without hollow chambers 14, large-surface bumps or depressions and the like on the face 12.

(51) Mechanical processing and/or chemical sizing, especially by partial etching of oxide material, can also be carried out to modify the face 12 or the hollow chambers 14. In this way, the area ratio of the opening areas of the hollow chambers 14 to the extension area of the face 12 can be varied or increased. It is understood that other modifications of the face 12 or of the hollow chambers 14 can also be made, depending on reaction time and intensity.

(52) A particular advantage of the proposed solution is that the face 12 can also be designed in practically any shape at all.

(53) The figure also shows a molded article or work piece 18, likewise in a highly simplified, not true-to-scale, sectional diagram, in the already finished state, i.e., with a surface 19 already structured by the casting mold 11 after casting.

(54) The proposed casting mold 11 allows very fine structuring of the work piece 18 or its surface 19. It is possible, for example, to create relatively large bumps of the order of 0.1 to 50 μm each with several, relatively small projections on the surface 19, for example, of the order of 10 to 400 nm, on the surface 19 of the work piece 18.

(55) The proposed solution very easily and cost-effectively enables very fine structuring of the surface 19. Accordingly, there is a very broad area of application. For example, such especially very fine structuring can be utilized in anti-reflex layers, for altering radiation emission of structured surfaces, in sensory analysis, in catalysis, in self-cleaning surfaces, in improving surface wettability and the like.

(56) Expressed in general terms, an essential aspect of the present invention is casting or molding a surface layer with hollow chambers formed directly or model-free by anodic oxidation, to enable surface structuring in the nanometer range.

(57) The present invention is especially not limited to a casting mold 11 in the narrower sense. Rather, the surface layer 13 or covering layer 16 is to be understood as model for a general structuring of a surface, a tool, a work piece or the like in the nanometer range. In particular, the model may be molded in any way at all. In particular, no reshaping is required when molding. For example, with the work piece 18 to be manufactured having a structured surface 19, this can be a cast article, wherein the surface 19 is structured by casting or decanting or any molding of the mold 11.

(58) In general, the present invention enables a simple, cost-effective stamping or molding in the nanometer range by a surface layer with hollow chambers formed by anodic oxidation being used as matrix or as casting mold.

TECHNICAL APPLICABILITY

(59) The proposed solution very easily and cost-effectively enables very fine structuring of the surface. Accordingly, there is a very broad area of application. For example, such especially very fine structuring can be utilized in anti-reflex layers, for altering radiation emission of structured surfaces, in sensory analysis, in catalysis, in self-cleaning surfaces, in improving surface wettability and the like. In particular, the proposed solution also extends to the use of work pieces with structured surfaces that have been structured by use of the proposed stamping tool for the purposes mentioned hereinabove. Further, the proposed solution can be used for casting with practically any material, since aluminum oxide especially is highly resistant mechanically, thermally and/or chemically.