GB1593510A

GB1593510A - Method of metallizing materials

Info

Publication number: GB1593510A
Application number: GB5241877A
Authority: GB
Original assignee: Stauffer Chemical Co
Current assignee: Stauffer Chemical Co
Priority date: 1977-12-16
Filing date: 1977-12-16
Publication date: 1981-07-15

Description

thereof. The mixtures of hydrophilic components tend to provide coatings having enhanced wettability and plateability when compared to a blend having only a single hydrophilic component. It is highly preferred that the hydrophilic component be a water-soluble polymeric component.

The following theoretical hypothesis explains how the foregoing composite material system forms a hydrophilic surface.

Each component of the composite material system has a particular function in forming the hydrophilic composite material coating.

The film-forming component gives the hydrophilic composite material coating strength thus eliminating the possibility of disintegration of the coating during subsequent treatments. This component also provides some adhesion of the coating to the substrate material during the subsequent treatment and plating steps.

The hydrophilic component renders the hydrophilic composite material coating wettable to aqueous electroless metal plating solutions. The preferred water-soluble polymeric component is inherently hydrophilic due to its watersolubility and it has the further effect of producing a microporous surface on the coating. This microporous surface is produced when the water-soluble polymeric component in the surface of the coating is partially dissolved on contacting water or aqueous solutions of organic or inorganic salts. The water-soluble polymeric component is dispersed throughout the coating. Thus, when it dissolves, micropores are left in the surface of the coating.

If a water-soluble polymeric component is not used in the composite material system and only a water-insoluble hydrophilic component is used, the composite material surface will be rendered hydrophilic and thus wettable, but not microporous. Thus, the use of a water-soluble polymeric component enhances the wettability and plateability of the composite material coating.

The solvents serve to dissolve all of the foregoing components into a homogeneous solution. Selection of the solvents is based on conventional knowhow for preparing solvent-based coating.

The components of the composite material system are preferably compatible so that when they are dissolved in a suitable solvent system, there is no phase separation and the composite material system is thus a clear solution. Some deviation from the preferred compatibility can, however, be tolerated. For example, a slightly cloudy solution and a solution wherein phase separation occurs after standing, may give excellent results within the scope of the present invention.

The operability of a given composite material system may be determined by one skilled in the art by testing and by utilizing the literature and manufacturers' tables on compatibility of the various components in various solvents and the compatibility of various solvents in other solvents. Useful literature for selecting solvents includes the following: The Technology of Solvents and Plasticizers A. K.

Doolittle (N.Y. 1954); Solvents Guide, Marsden and Mann (N.Y. 1963); Industrial Solvents I. Mellan (N.Y. 1950); and Properties of Organic Solvents, J. E. Morgan (1962).

Preferred solvents for the preferred hydrophilic composite material used in accordance with the present invention are chlorinated alkyls, e.g. 1,2dichloroethane, ketones, e.g. methyl ethyl ketone and methyl isobutyl ketone, aliphatic alcohols, e.g. ethanol and isopropanol, tetrahydrofuran or mixtures thereof. A particularly preferred solvent system consists of 44.5% 1,2dichloroethane, 44.50/, methyl ethyl ketone and I 11% ethanol (by volume).

Information on selecting film-forming components may be found in various publications including publications on paints. Exemplary literature includes the following: Synthetic Resins and Coatings, Noyes Data Corporation (1965) and Paint Additives Noyes Data Corporation (1970).

Particularly preferred film-forming components are vinyl chloride, vinyl acetate and copolymers thereof; certain cellulose esters, such as cellulose acetate butyrate, and certain polyvinyl acetals, such as polyvinylbutyral.

In addition to the foregoing references, water-insoluble hydrophilic components and water-soluble polymeric components may be selected from references, such as: Modern Plastics Encyclopedia, Vol. 51, No. 10A (McGraw Hill.

October, 1974).

A particularly preferred water-soluble polymeric component is polyvinylpyrrolidone.

A particularly preferred water-insoluble hydrophilic component is cellulose acetate.

The trade literature of manufacturers may also be utilized to select the various components and solvents for use according to the present invention.

The solids content of the components in the composite material system is generally from 1 to 40 percent, by weight, of the system. The weight ratio of the film-forming component to the hydrophilic component is generally from 3:10 to 10:1. When a water-soluble polymer component is utilized, the weight ratio of that component to the film-forming component is preferably from 1:10 to 2:1.

As the coated surface dries at room temperature, by evaporation of solvent, in a relatively short time, the cleaning and etching processes utilized in the prior art are replaced in the present invention, by, effectively, a one-step coating process.

The thickness of the hydrophilic composite material coating is from 0.05 to 5 mils.

The hydrophilic composite material coating is made conductive by electroless metal plating. Various conventional electroless metal plating methods may be used.

Suitable methods are described in U.S. Patent No. 3,667,972 and Plating on Plastics With Metals, J. McDermott (Noyes Data Corp. 1974).

For example, electroless nickel, copper and silver, may be used.

Once the surface of the hydrophilic composite material coating is rendered conductive by electroless plating various conventional electroplating techniques may be used. Suitable electroplating methods are described in Modern Electroplating F. A. Lowenheim (J. Wiley, 1942); Electroplating Engineering Handbook. A. K. Graham (Rheinhold, 1962) and Handbook Galvanotechnik, Karl Hanser Verlag (Munich 1966).

The type of metal electroplated will generally be selected on the basis of economics and the end use of the metallized material.

If the substrate material is a cellular material, for example, the metallized foam product might be used in a heat regenerator. In this case, an electroplated metal having high heat conductivity and high heat capacity would be selected. Typical metals would then be nickel, copper or chromium.

Metallized foams made in accordance with the present invention may be modified by several subsequent procedures for particular applications. The following two operations exemplify such subsequent procedures and may be performed alone or in combination with others. These operations are as follows: (1) pyrolysis to destroy organic materials; and (2) compression to dimensions required for the desired filling factor.

Pyrolysis may only be carried out when the cellular material is organic.

Methods of pyrolysis are described in, for example, above-mentioned U.S. Patent No. 3,549,505. The need for pyrolysis depends on the end use for the metallized foam. For example, if that use is to be in a hot enivronment that could destroy the cellular organic material, pyrolysis prior to use would be desirable.

Under appropriate conditions, the pyrolysis step may be carried out simultaneously with annealing of the brittle electroplated metal. The parameters under which the electroplated metals may be annealed depend upon the type of metal. These parameters are well-known to those skilled in the art. Once annealing is carried out, the shape of the metallized foam may be changed by, for example, compression, bending or twisting.

The annealed metallized foam may be compressed for applications where a low filling factor is needed. The filling factor is defined as follows: Filling Factor=(V,V2)/V, wherein Vj represents the volume of a solid having the overall dimensions of the metallized foam; and V2 represents the actual volume of the metallized foam, for example, the water displacement volume. Applications requiring a low filling factor are well-known in the art and may include, for example, uses of the metallized foam as a catalyst support or a heat exchanger.

It is advantageous to metallize a cellular material having a high filling factor.

This is because the cells are larger and the screening effect of the cell walls during the electroplating is thereby minimized. Accordingly, more uniform electroplating may be achieved in a foam having a high filling factor.

If the substrate material is a textured material, electoplated metal having sufficient stength to be used as an embossing roller or plate would be selected.

Metals, such as iron, nickel and copper, also alloys thereof, are suitable for this purpose. As in the case of metallized foam, the brittle electroplated metal may be annealed to improve strength. This annealing step may be carried out (54) METHOD OF METALLIZING MATERIALS (71) We, STAUFFER CHEMICAL COMPANY, a corporation organised under the laws of the State of Delaware, United States of America, of Westport, Connecticut 06880, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of metallizing materials; more particularly, it concerns a method of providing a substrate with a coating of a hydrophilic composite material which is then electrolessly plated with a conductive metal, prior to being electrolytically metal plated.

Various applications for metallizing materials are known. Some examples of these applications are as follows: Metallized foams having macroscopic inter-connected cells therein have been prepared according to the prior art. A method of metallizing polyurethane foams, for example, is described in United States Patent No. 3,549,505.

In the above-mentioned reference a reticular, electrically non-conductive cellular structure of polyurethane having a self-supporting three-dimensional network of inter-connected annulets with macroscopic inter-connected cells therein is coated with a conductive material, followed by electroplating. Pyrolysis following the electroplating step is optional.

One method of coating the polyurethane with a conductive material according to the above-mentioned reference is by electroless metal plating. When this method is utilized, the surface of the polyurethane is rendered hydrophilic by cleaning and etching processes. After the surface is rendered hydrophilic, the surface is electrolessly metal plated.

Other methods of producing metallized foams are known. Examples of such methods are described in United States Patent Nos. 3,698,929 and 3,679,552.

A method of plating on plastics is described in United States Patent No.

3,501,332. According to this reference, organic polymer substrates are conditioned for electroless metal plating by impregnating the surface layer of the substrates with a metal diffused into the surface layer from a solution of a complex. The complex contains the metal in a zero-valent form dissolved in an organic solvent which has a dissolving or swelling action on the substrate.

Other methods of plating on plastics are known. Examples of such methods are described in United States Patent Nos. 3,597,266; 3,632,388; 3,632,704; 3,661,538; and 3,716,394.

In accordance with the present invention, a method is provided wherein the surface of a substrate material is coated with a non-conductive hydrophilic composite material. The hydrophilic character of the composite material enables it to be electrolessly metal plated with a conductive metal. Accordingly, this coating step eliminates the need for the cleaning and etching operations that are generally employed according to the prior art.

One utility of the present invention is the production of metallized foams. The metallized foams are produced by coating cellular materials, the material generally dimensional network having macroscopic, inter-connected cells therein. The metallized foams are produced by coating cellular materials, the material generally being in the form of a structure having a self-supporting, three-dimensional network of macroscopic inter-connected cells, with a hydrophilic composite material, electrolessly metal plating the hydrophilic composite material to render the surface conductive; followed by electro-plating a metal onto the electrolessly plated metal; and, optionally, pyrolyzing the metallized structure to destroy the cellular material.

The metallized foam product may be compressed to a desired filling factor for use in, for example, heat exchangers, regenerators, catalyst supports, battery plates and electrodes.

Another utility of the present invention is in the reproduction of textured surfaces. The textured surface, for example a leather or another material having a surface grain, is metallized by rendering the surface conductive in accordance with the above-described method; followed by electroplating. The textured surface is then removed from the metal. The side of the metal that was in contact with the conductive textured surface is left having a negative impression of that surface. The metal may thus be used conventionally for an embossing roller or plate to reproduce artifically the textured surface in other materials, for example, plastics.

Other utilities for the present invention include producting decorative metal coatings on substrate materials.

The substrate materials utilized in accordance with the present method, for a particular utility that might be envisioned, may be conductive or non-conductive.

Accordingly, the present invention provides a method for metallizing a substrate which comprises: applying to the substrate a coating comprising a blend of at least one film-forming component and at least one hydrophilic component, the hydrophilic component comprising a water-insoluble hydrophilic component and/or a water-soluble polymeric component; applying to the resulting material a coating of a conductive metal by electroless plating; and applying to the resulting material a coating of a metal by electrolytic metal plating.

The hydrophilic composite material, i.e. the blend, applied preferably comprises a solvent therefor.

Various substrate materials may be used in accordance with the present invention. These materials may be flexible or rigid.

Substrate materials utilized to make metallized foams, for example, may be comprised of various cellular materials. Thermally reticulated polyurethane foam is an excellent material as it is inexpensive and readily available. The composition of the cellular material utilized in accordance with this aspect of the present invention, however, is not critical as it is coated with the hydrophilic composite material prior to electroless plating.

Suitable cellular materials include organic and inorganic open-cell foam materials for example; polyurethane foam, carbon or graphite foams, silicate foams, styrene ceramic foam, aluminium foam and tungsten carbide foam. Also, cellular materials comprised of textiles, for example natural fibres, such as cotton, synthetic fibres, natural and synthetic fibre blends and wood products, including paper and cardboard. In general terms, any material that may be coated with the hydrophilic composite material may be used.

In the reproduction of textured surfaces, the substrate material utilized may be comprised of a selected material having a textured surface. The material may of course, be conductive or non-conductive. When conductive materials are used, the hydrophilic intermediate coating serves as a parting media for making embossing rollers or plates.

Exemplary materials include organic and inorganic materials, such leather, textured polymeric materials, wood, natural or synthetic fibres and blends of natural and synthetic fibres. As mentioned above, in general terms, any material that may be coated with the hydrophilic composite material may also be used.

It is clear from the foregoing that virtually any solid material may be utilized as a substrate and may be metallized in accordance with the present invention.

Selection of a substrate material is therefore left to those skilled in the art working in accordance with the present invention.

Coating the substrate material is generally effected by contacting it with a composite material system which is a solution containing the components of the hydrophilic composite material by, for example, spraying, brushing or dipping.

The composite system, i.e. the solution, should dry as rapidly as possible, generally in less than fifteen minutes at room temperature.

The composite material system comprises at least one solvent and a suitable hydrophilic composite material. The hydrophilic composite material is comprised of a blend of at least one film-forming component and at least one hydrophilic component.

The hydrophilic component may be water-insoluble hydrophilic component, a water-soluble polymeric component (which is inherently hydrophilic) or mixtures simultaneously with pyrolysis of the textured material. The textured material may also be removed before or after annealing by separating it from the metal. This may be done by conventional means, such as by mechanical or chemical means.

The following Examples illustrate the present invention.

Example 1 A series of experiments was conducted to select composite material systems suitable for plating on glass substrates. Glass slides were utilized and viewed under a microscope to determine the quality of the composite material coating and the platability with electroless nickel. Electroless nickel plating was carried out in accordance with United States Patent No. 3,667,972.

The following stock solutions were made up with 10% solids, by weight, in a cold solvent system: (1.) 860/,--14"/, vinyl chloride-vinyl acetate (film-forming component) (II.) 87%13% vinyl chloride-vinyl acetate (film-forming component) (III.) polyvinylpyrrolidone (water-soluble polymeric component) (IV.) polyvinylbutyral (film-forming component) The solvent system was: Parts, Percent, by volume by volume l,2-dichloroethane 100 44.5 methyl ethyl ketone 100 44.5 ethanol 25 11.0 The components of the composite material system will be designated in the following sub-examples by the Roman numerals used to identify the foregoing stock solutions.

(A) 10 millilitres of (I.) were mixed with 5 millilitres of (III). A clear solution resulted. This composite material system was then brushed onto a glass slide and allowed to dry for 5 minutes at 700 F. The dry film was clear and smooth.

Electroless nickel plating was then carried out. 90 percent coverage with electroless nickel was achieved.

(B) 5 millilitres of cellulose acetate butyrate (film-forming component) were added to the composite material system of (A). The resulting solution had a pearllike appearance and separated into layers on standing. After stirring the solution, the same procedure as in (A) was followed. A dry film that was grainy and cloudy resulted. Plating with electroless nickel gave 90 percent coverage with some blistering.

(C) 20 millilitres of (I) were mixed with 5 millilitres of (III). A clear solution resulted. The same procedure as in (A) was followed. The dry film was clear and smooth. Plating with electroless nickel gave 95 percent coverage.

(D) 5 millilitres of cellulose acetate (water-insoluble hydrophilic component) were added to the composite material system of (A). The resulting solution was opalescent, but did not separate into layers on standing. The same procedure as in (A) was followed. The dry film was cloudy, but smooth. 10 percent coverage with electroless nickel was achieved. (The poor plating results are due to the incompatibility of the solvent with the cellulose acetate and the co-action of the cellulose acetate with the other components).

(E) 5 milliliters of (II) were added to the composite material system of (A). A clear solution resulted. The same procedure as in (A) was followed. The dry film was clear and smooth. 100 percent coverage with electroless nickel was achieved.

(F) 5 millilitres of (IV) were added to the composite material system of (A). The resulting solution was hazy, but did not separate into layers on standing. The same procedure as in (A) was followed. The dry film was clear and smooth. 100 percent coverage with electroless nickel was achieved.

(G) 15 millilitres of (II) and 5 millilitres of (IV) were added to the composite material system of (A). The solution was opalescent. 10 millilitres of methyl isobutyl ketone was added, but no improvement in solution compatibility was observed. 10 millilitres of isopropyl alcohol (solvent) was then added. The solution was still opalescent, probably due to the insolubility of polyvinyl-pyrrolidone in methyl isobutyl ketone. The solution separated into two components on standing. After stirring the solution, the same procedure as in (A) was followed. The dry film was smooth and clear. 100 percent coverage with electroless nickel was achieved.

(H) 10 millilitres of (II) and 1 millilitre of (IV) were added to the composite material system of (A). An additional 20 millilitres of the above-defined solvent system also were added. The resulting solution was clear. The same procedure as in (A) was followed. The dry film was smooth, but cloudy. 100 percent coverage with electroless nickel was achieved.

(I) An additional 100 millilitres of (I) were added to the composite material system of (H). The same procedures as in (H) were followed and yielded the same results, except that the dry film was clear.

(J) 5 millilitres of (II) and 5 millilitres of (IV) were added to the composite material system of (C). An additional 20 millilitres of the above-defined solvent system also were added. The resulting solution was clear. The same procedure as in (A) was followed. The dry film was clear and smooth. 100 percent coverage with electroless nickel was achieved.

(K) 10 millilitres of (I) 10 millilitres of (II) 2 millilitres of (11), 2 millilitres of (IV) and 20 millilitres of the above-described solvent system were mixed. The resulting solution was clear. The same procedure as in (A) was followed. The dry film was clear and smooth. 100 percent coverage with electroless nickel was achieved.

The procedure of (K) was repeated, except that the coating was peeled off prior to electroless plating. The thickness of the coating was 0.3 mil.

The procedure was again repeated except that two and three coatings were applied to the glass slide. These coatings had thicknesses of 0.6 mil and 0.9 mil, respectively. Plating on the double and triple coated slides gave 100 percent coverage with electroless nickel.

EXAMPLE 11 A thermally reticulated polyurethane foam was coated with about 0.3 mil thickness of hydrophilic composite material.

The hydrophilic composite material contained 4 grams polyvinylpyrrolidone (water-soluble polymeric component), 8 grams of a 9W10 /" mixture of vinyl chloride-vinyl acetate copolymer (film-forming component), 8 grams of a 8713 /" mixture of vinyl chloride-vinyl acetate copolymer (film-forming component) and 5 grams of cellulose acetate butyrate (film-forming component), dissolved in 50 millilitres of ethylene dichloride, 125 millilitres tetrahydrofuran and 50 millilitres of methyl ethyl ketone. This formulation is suitable for dipping or brushing, but is adapted for spraying by diluting it in 1:2 or 1:3 ratio using a solvent mixture of the following composition: ethylene dichloride-22%; tetrahydrofuran-56%; and methyl ethyl ketone-22%.In this Example, the polyurethane foam was sprayed with the composite material system to effect coating.

The polymer coating was allowed to dry for 5 minutes at room temperature (22"C) and this was followed by electroless nickel plating as described in United States Patent No. 3,667,972. This step was followed by conventional electroplating of copper to a thickness of about 10 mils.

A layer of nickel was then electroplated to a thickness of about 4 mils on the copper, followed by pyrolysis at 7600C. under a hydrogen atmosphere for one hour.

The resulting metallized foam was ductile.

EXAMPLE III A swatch of leather was sprayed to a thickness of about 0.4 mils with the following composite material system: 4 grams polyvinylpyrrolidone (water-soluble polymeric component) 8 grams 9010% vinyl chloride-vinyl acetate copolymer (film-forming component) 5 grams cellulose acetate butyrate (film-forming component) 100 millilitres ethylene dichloride (solvent) 250 millilitres tetrahydrofuran (solvent) 100 millilitres methyl ethyl ketone (solvent) The coated leather was dried at about 23"C, for 10 minutes. The coating was then plated with electroless nickel as described in United States Patent No.

3,667,972. This step was followed by conventional electroplating of copper to a thickness of about 15 mils. The leather and the hydrophilic composite material layer were then peeled off leaving a high resolution copper negative of the textured leather surface.

Various modifications of the copper negative may be carried out. For example, a backing material, such as a metal or rubber pad, may be fastened to the back of the negative for added strength. Also, a thin coating of a harder metal, such as chromium or nickel, may be plated on the negative side for improved hardness without impairing the resolution of the negative.

WHAT WE CLAIM IS: 1. A method for metallizing a substrate which comprises: applying to the substrate a coating comprising a blend of at least one film-forming component and at least one hydrophilic component, the hydrophilic component comprising a water-insoluble hydrophilic component and/or a water-soluble polymeric component; applying to the resulting material a coating of a conductiye metal by electroless plating; and applying to the resulting material a coating of a metal by electrolytic metal plating.

2. A process as claimed in claim 1 further comprising in the case of an organic substrate, pyrolyzing the metallized substrate.

3. A method as claimed in claim 1 or claim 2 in which the hydrophilic component and the film-forming component are used in a weight ratio of from 1:10 to 3.33:1.

4. A method as claimed in any of claims 1 to 3 in which the hydrophilic component used is a water-soluble polymeric component.

5. A method as claimed in claim 4 in which the water-soluble polymeric component and the film-forming component are used in a weight ratio of from 1:10 to 2:1.

6. A method as claimed in any of claims 1 to 5 in which the blend applied comprises a solvent therefor.

7. A method as claimed in claim 6 in which a blend having a solids content of from 1 to 40%, by weight is used.

8. A method as claimed in claim 6 or claim 7 in which a solution without phase separation is used.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

adapted for spraying by diluting it in 1:2 or 1:3 ratio using a solvent mixture of the following composition: ethylene dichloride-22%; tetrahydrofuran-56%; and methyl ethyl ketone-22%. In this Example, the polyurethane foam was sprayed with the composite material system to effect coating.

The polymer coating was allowed to dry for 5 minutes at room temperature (22"C) and this was followed by electroless nickel plating as described in United States Patent No. 3,667,972. This step was followed by conventional electroplating of copper to a thickness of about 10 mils.

A layer of nickel was then electroplated to a thickness of about 4 mils on the copper, followed by pyrolysis at 7600C. under a hydrogen atmosphere for one hour.

The resulting metallized foam was ductile.

EXAMPLE III A swatch of leather was sprayed to a thickness of about 0.4 mils with the following composite material system:

4 grams polyvinylpyrrolidone (water-soluble polymeric component)

8 grams 9010% vinyl chloride-vinyl acetate copolymer (film-forming component)

5 grams cellulose acetate butyrate (film-forming component)

100 millilitres ethylene dichloride (solvent)

250 millilitres tetrahydrofuran (solvent)

100 millilitres methyl ethyl ketone (solvent) The coated leather was dried at about 23"C, for 10 minutes. The coating was then plated with electroless nickel as described in United States Patent No.

3,667,972. This step was followed by conventional electroplating of copper to a thickness of about 15 mils. The leather and the hydrophilic composite material layer were then peeled off leaving a high resolution copper negative of the textured leather surface.

Various modifications of the copper negative may be carried out. For example, a backing material, such as a metal or rubber pad, may be fastened to the back of the negative for added strength. Also, a thin coating of a harder metal, such as chromium or nickel, may be plated on the negative side for improved hardness without impairing the resolution of the negative.

WHAT WE CLAIM IS: 1. A method for metallizing a substrate which comprises: applying to the substrate a coating comprising a blend of at least one film-forming component and at least one hydrophilic component, the hydrophilic component comprising a water-insoluble hydrophilic component and/or a water-soluble polymeric component; applying to the resulting material a coating of a conductiye metal by electroless plating; and applying to the resulting material a coating of a metal by electrolytic metal plating.
2. A process as claimed in claim 1 further comprising in the case of an organic substrate, pyrolyzing the metallized substrate.
3. A method as claimed in claim 1 or claim 2 in which the hydrophilic component and the film-forming component are used in a weight ratio of from 1:10 to 3.33:1.
4. A method as claimed in any of claims 1 to 3 in which the hydrophilic component used is a water-soluble polymeric component.
5. A method as claimed in claim 4 in which the water-soluble polymeric component and the film-forming component are used in a weight ratio of from 1:10 to 2:1.
6. A method as claimed in any of claims 1 to 5 in which the blend applied comprises a solvent therefor.
7. A method as claimed in claim 6 in which a blend having a solids content of from 1 to 40%, by weight is used.
8. A method as claimed in claim 6 or claim 7 in which a solution without phase separation is used.
9. A method as claimed in any of claims I to 8 in which the substrate is a solid

organic material.
10. A method as claimed in any of claims 1 to 8 in which the substrate is a cellular material.
11. A method as claimed in claim 10 in which the substrate is a cellular material having a three-dimensional network having macroscopic interconnected cells.
12. A method as claimed in any of claims 1 to 11 in which the substrate has a textured surface.
13. A method as claimed in claim 1 substantially as herein described.
14. A method as claimed in claim 1 substantially as herein described with references to any one of the Examples.
15. A substrate when metallized by a method as claimed in any of claims I to 14.
16. A substrate as claimed in claim 15 which is subsequently converted into an embossing plate by removal of a textured substrate.