GB1587260A

GB1587260A - Production of a printing plate

Info

Publication number: GB1587260A
Application number: GB2665977A
Authority: GB
Original assignee: TACHIHARA M
Current assignee: TACHIHARA M
Priority date: 1976-06-27
Filing date: 1977-06-24
Publication date: 1981-04-01
Also published as: JPS532103A; DE2729391A1; AU2631477A; DE2729391C2; AU509128B2

Description

(54) IMPROVEMENTS IN OR RELATING TO THE PRODUCTION OF A PRINTING PLATE (71) We, MIYAKO TACHIHARA and NORIBUMI TACHIHARA, Japanese citizens, residing at No. 2-37-9, Higashi-Mizumoto, Katsushika-ku, Tokyo, Japan, respectively, 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: The present invention relates to a supporting blank suitable for the preparation of a printing plate, e.g. a planographic printing plate, which may be used in a lithographic printing press.

Printing plates employed for lithographic printing have a surface consisting of inkadhering image areas and hydrophilic nonimage areas which repel ink. Lithographic printing is carried out by transcription of impressions by transferring ink from the inkadhering image areas of the printing plate to a printing sheet. In case of planographic and planoconcavegraphic plates which are employed in ordinary lithographic printing, there is formed a hydrophilic layer on the surface of a supporting metal plate to provide ink-repelling non-image areas so that water is caused to adhere to those nonimage areas of the printing surface of the plate to repel ink thereby. The preparation of such lithographic printing plates may be approached in two ways.One of them is directed mainly to an improvement of adherence of a lacquer or a light-sensitive resin onto the image areas in the surface of the metal supporting plate. The other way is directed mainly to imparting a hydrophilic property to the non-image areas of the printing surface of the supporting plate.

As the supporting plate for use in such lithographic printing, aluminium alloys have been most widely used because of their practicability. There have been proposed and put into practice a number of methods for treating the surface of a printing plate made of an aluminium alloy.

A typical method which has been employed widely is as follows. A metal support plate is subjected first to mechanical graining or electrochemical surface-roughening or chemical etching for producing a supporting blank having a grained or coarse surface.

In some cases, the resulting supporting blank is subjected to anodization or electrolytical oxidation or other treatment to form an oxide film on the above-said processed surface of the supporting blank. The resulting surface of the supporting blank involving the anodic oxidation treatment is generally called an anodic-oxidized film which is a layer having matured into a porous layer.

Some of these supporting blanks having an anodic-oxidized film formed on one surface thereof are effective mainly in enhancing the adherency of a lacquer or a lightsensitive resin to the image areas of the printing surface. Some others are effective in imparting a hydrophilic property to the nonimage areas of the printing surface of the plate. Still others provide a hydrophilic layer.

Yet some others are intended for good durability for storing purposes. In so far as the inventor is aware, however, no one has ever proposed or produced any printing plate of a construction which simultaneously meet substantially all of the above-mentioned conditions which are required of a printing plate, although each of the known printing plates can satisfy a single individual condition among the above-mentioned various requirements.

For example it has previously been proposed to carry out anodic oxidation of an aluminium sheet in an electrolytic solution containing 2W85g, phosphoric acid to form, on top of the aluminium sheet, an aluminium oxide layer having pores of an average diameter of 200-750A scattering in cellular fashion. The resulting printing plate is indeed good in the adherency of the imageforming substances to the image areas. This prior art, however, has the disadvantages that the non-image areas easily tend to be soiled and stained during printing and that, after an active diazo resin has been applied to the image-forming surface, the prevention of the reaction between the image-forming substance and the supporting material when kept in darkness cannot be relied upon.

Also Japanese Patent Specification No.

38-8907 of Kalle Aktiengesellschaft (priority dates of August 5, 1960 and February 25, 1961 claimed from West German applications) discloses a printing plate having a thin layer consisting of phosphonic acid and/or its derivatives formed on top of an aluminium support sheet. This printing plate is easy to manufacture, and it has a better durability during printing than a printing plate comprised of an aluminium support sheet having a mere mechanically grained surface. This printing plate disclosed in the said Japanese Patent Specification, however, is much inferior to a printing plate having an anodic-oxidized film forming on the coarsened surface of the support plate.

Furthermore, a method has been previously prepared which comprises the use of an aluminium sheet having a coarsened surface produced by an AC electrolysis in hydrochloric acid; the formation of a film of the zirconium fluoride type on said coarsened surface, and coating the resulting surface with a diazo resin. The film of the zirconium fluoride type is effective as a hydrophilic layer. However, because the supporting surface does not carry an anodic oxidized film, said known printing plate cannot be termed as being sufficient with respect to its durability in printing and also to the adherency of the image-forming substance to the image areas.

In Japanese Patent Specification No.

36-22063 there is proposed the step of providing a hydrophilic layer on a metal substrate made of aluminium by treating same with an aqueous solution of zirconium hexahalide. However, the method of this surface treatment includes several drying steps after each of the treating steps. Thus, this known technique has the drawback that the process is troublesome and complicated.

Also, the method disclosed in German Patent Specification No. 1,151,818 concerns the formation of a boemite layer on top of an aluminium support plate. In order to carry out these methods, however, there is required the use of a great amount of energy in, for example, placing the metal support plate in a bath having a temperature as high as 95-980C- for a period as long as 1 > 15 minutes. Furthermore, the printing plate thus obtained cannot be termed as being satisfactory as compared with the printing plate utilizing the anodic-oxidation process, with respect to both the image adherency and the duration during printing.

In addition to those prior techniques mentioned above, there is a known process of manufacturing a printing plate by forming a known porous anodic-oxidized film on the surface of the metal support for the purpose of enhancing the durability in printing.

Furthermore, there are other known techniques such as those disclosed in, for example, Japanese Patent Publication No.

48-9007 which claims the priority dates of May 23, 1963 and October 29, 1963 from U.S. Patent Applications Nos. 282,810 and 319,685 which have matured into U.S.

Patents. Neither one of them, however, can be termed as sufficiently satisfying the current high level requirements of - printing techniques.

According to one aspect of the invention there is provided a supporting blank suitable for the preparation of a printing plate, comprising a metal support plate (a), having a hydrophilic water-receptive surface (b) and applied td the water-receptive surface (b) a substantially non-porous barrier or barrierforming anodic oxidic continuous or discontinuous layer (c) formed by anodic electrolysis.

According to a second aspect of the invention there is provided a method of manufacturing the supporting blank of the invention comprising forming a hydrophilic waterreceptive surface (b) on a metal support plate (a) and applying by anodic electrolysis a substantially non-porous barrier or barrierforming anodic continuous or discontinuous oxidic layer (c) on the surface (b).

According to a third aspect of the invention there is provided a printing plate comprising the supporting blank defined by the first aspect of the invention or the supporting blank produced by the method defined by the second aspect of the invention and an image-forming layer (e) applied to layer (c). The image-forming layer (e) may be of the kind suitable for the production of a planographic or planoconcavegraphic printing plate. The layer (e) may be a light-sensitive layer, preferably a light-sensitive resinous layer and especially a diazo resinous layer.

With regard to the first and second aspect of the invention the water-receptive surface (b) may be a grained or roughened surface -such can be achieved by known means.

The plate (a) may be chosen from aluminium, tantalum, niobium, titanium and alloys thereof. In a preferred form of process embodying the second aspect of the invention the formation of the surface (b) is carried out by first forming a roughened grained surface on the metal support plate (a) and then forming on this grained surface a porous anodic oxidized layer by the use of an electrolyte which is an aqueous solution of phosphoric acid or an aqueous solu tion of a mixture of phosphoric and sulphuric acids.

If desired, formation of the surface (b) may be carried out by- applying by anodic electrolysis an anodic oxidic layer (d) to the metal support plate (a) - and subsequently removing the layer (d) by dissolving same.

The barrier or barrier-forming anodic oxidation technique employable to form sub stantially non-porous layer (c) is different from the known ordinary porous anodic oxidation. When the support metal plate (a) is made of an aluminium alloy, an under standing of what is intended by a substan tially non-porous barrier or barrier-forming layer may be found from recourse to "The Surface Treatment of Aluminium and Its Alloys" by S. Wernick & R. Pinner,-page 372, published by Robert Draper Ltd., Ted dington in 1964 which refers to such sub stantially non-porous barrier layers as "barrier-type coatings". A research on the structure of a substantially non-porous barrier or -barrier-forming anodized film is reported in J.Electrochem. Soc; P1645, Dec.

1975 by Yoon H. Choo and -Owen F.

Devereux. These literature refererices are academic and none of them contains a state ment about the use of such a substantially non-porous barrier or barrier-forming anodic oxidized layer, especially its suitability for use in a printing plate.

Known substantially non-porous barrier or barrier-forming anodic oxidized layers will hereunder be briefly discussed. For instance; a sheet of aluminium, tantalum, niobium, titanium or other metal or an alloy of such metals is subjected to anodic - oxidation by the use of an electrolyte which is an aqueous solution of acid or salt which does not dis solve these metals or which is a non-aqueous solution such as ethylene glycol, and there is formed a thin but dense oxide layer on the surface of such metal sheet. In the instance of, for example, an aluminium alloy, anodic oxidation may be carried out by the use of a weak acid such as boric acid, tartaric acid or other organic acid, or by the use of a salt such as borax or ammonium tetraborate.

Usually, the anode which is employed in the DC electrolysis is the object which is given the surface treatment, i.e. anodic oxidation.

However, there has been proposed also AC electrolysis for the anodic oxidation of a metal. This latter treatment can be equally effectively applied to the present invention.

Aluminium is hardly dissolved in the above-mentioned electrolytes, and therefore the known substantially non-porous barrier or barrier-forming anodic oxidized layer grows as a dense film. The value of density of the electric current in electrolysis is sub stantially smaller than that needed in the formation pf a porous layer. However, the known substantially non-porous barrier pr barrier-forming anodic layer formed accord-.

ing to the known anodic oxidation process is very thin and the resulting pores have very small diameters. Therefore, the layer thus formed lacks such adherency of image-form-ing substance as that exerted by a porous film, and accordingly the known substantially non-porous barrier or barrier-forming anodic layer cannot be utilized forf enhancement of adherency of either a light-sensitive layer or an image substance onto the surface of the supporting plate. Also, in view of the fact that the thickness of the known substantially non-porous barrier-forming anodic layer is thinner than that of a porous film, the said anodic layer cannot have as great a mechanical hardness as a porous layer has.

The said anodic layer per se has hardly any hydrophilic or water-holding ability which is required of a lithographic printing plate.

Because of these- essential differences between the known substantially non-porous barrier or barrier-forming anodic layer and the known porous layer, thi: substantially non-porous barrier or barrier-forming anodic layer has not been used in practice except as a charge-storing layer in an electrolytic capacitor.Needless to say, we have no knowledge that a substantially non-porous barrier or barrier-forming anodic layer has ever been applied to a printing plate As stated above, this substantially - nonporous barrier or barrier-forming anodic layer (c) per se does not exhibit any property suitable for use in a printing plate It has been - found by the inventor, however, that in the event that this substantially nonporous barrier or barrier-forming anodic layer (c) is combined with such a hydrophilic layer as is employed in the present invention, said layer (c) contributes to the production of an unexpectedly effective printing plate. According to the experiments conducted by the inventor, the thickness of the substantially non-porous barrier or barrier-forming anodic-oxidized layer (c) is generally sufficient if it is from 0.1 to 1 micrometre.The voltage needed for the formation of layer (c) by anodic electrolysis using an electrolyte bath is generally le-50 volts. It should be noted that the application of a high voltage such as 300- 500 volts which is needed in the formation of a layer for use in an electrolytic capacitor is not desirable for the formation of the substantially non-porous barrier or barrierforming anodic oxidized layer (c) used in the present invention from an economical point of view, and such a high voltage is unnecessary in the present invention. Furthermore, the conditions of electrolysis for the application of the- substantially non-porous barrier or barrier-forming anodic layer - (c) for use in the present invention can have a broad range of toleranoe.For example, the value of the electric current density applied at the time the layer is formed can be varied over a wide range, e.g. 0.1-2 A/dm2. It is that if the operation is carried out at a high current density the layer-forming operation can be completed in a short period of time, whereas if the layer-forming operation is conducted at a low current density, the treatment time then will naturally be prolonged.

Furthermore, the layer-forming operation can be done performed by the use of a con stant current density or by the use of a constant voltage.

In case of a known printing blank made of an aluminium alloy as the support metal which has been discussed above, the surface having been roughened by any one of known surface coarsening processes, and the surface having an oxidized porous layer formed thereon by relying on either a known electrochemical or chemical film-forming process, both invariably give rise to the socalled blurring and/or surface soiling or staining phenomena. In order to avoid such inconveniences, attempts have been made to form an interlayer on the surface of the supporting blank by various kinds of methods.

As will be dicussed later, the method according to the present invention can be regarded as being reliable as compared with any one of the various known methods stated above.

Moreover, the present invention does not depend on the use of any harmful toxious substances which may cause pollution during the process of manufacture. Furthermore, this method is economical. The surface of the supporting blank is able to satisfy various requirements for printing.

It can be conjectured that a supporting blank produced solely by the known methods contains, inevitably, microscopic active points on the surface as residues, and these points are considered to be the major cause for drawbacks such as the soiling or staining of the surface of the printing plate which is obtained therefrom. By the applicalion of a substantially non-porous barrier or barrier-forming anodic film to the surface of a preferably roughened metal support plate, the microactive points are modified, and accordingly it is considered possible to eliminate the drawbacks of the prior art supporting blank without affecting the desirable individual properties of known supporting blanks.

Figure 1 is an illustration showing the general conception of a printing plate embodying the present invention. The surface of a metal supporting plate 11 is roughened to impart hydrophilic and water-receptive ability. On the resulting surface of the supporting plate is applied a substantially nonporous barrier anodic oxide continuous layer 12 so that the surface is in a chemically perfectly passive state. The resulting surface is coated with a light-sensitive layer 16 and is stored in darkness.

Figure 2 is an illustration showing the general conception of another printing plate embodying the present invention. On the surface of an aluminium alloy sheet 11 is formed a porous anodic oxidized film 15.

Numeral 13 represents an aluminium oxide produced as a result of anodic oxidation.

Numeral 14 represents a fine pore. A substantially non-porous barrier-forming anodic oxidic discontinuous layer 12 is applied to the bottom surface of each pore 14 of the film 15, showing that the micro-active points are in a chemically passive state. Numeral 16 represents a light-sensitive layer which firmly adheres to the surface, due to the anchoring effect exerted by the fine pores.

Next, some examples illustrating the proof the present invention will be described, cess of manufacturing the supportng blank It should be noted, however, that these are mentioned only by way of examples, and that the present invention is not limited thereto. For example, titanium and other metals are not used in general at present.

For economic considerations but in the future they may well prove to be economical to use.

EXAMPLE 1.

An aluminium alloy sheet was subjected to a surface-roughening or graining operation by using a known ordinary technique.

The resulting metal sheet was subjected to anodic electrolysis at 200C, and at a current density of 0.5 A/dm2 for 2 minutes in an aqueous solution containing 10% by weight ammonium tetraborate to apply a substantially non-porous barrier oxidized layer to the roughened or grained surface of the aluminium alloy sheet. The voltage applied initially rose gradually and reached about 40 volts in the final stage. The resulting sheet was washed with water and dried. A light-sensitive positive diazo resin was applied to the surface of the metal sheet to render this surface positive. This surface had a suitable hydrophilic water-receptive property and a suitable adherency of image substances required for a printing plate, and was stable and withstood storage and printing for an extended period of time.

EXAMPLE 2.

An aluminium alloy sheet was subjected to a surface-coarsening step by using a known ordinary technique. Thereafter, the sheet was subjected to anodic electrolysis at 200C, at a current density of 1 A/dm2 for 3 minutes in an aqueous solution containing 30% (wt/vol) of phosphoric acid. The voltage applied gradually rose from an initial several volts up to a final 15 volts. Immediately after being washed with water and dried, the sheet was subjected to another anodic electrolysis in an aqueous solution of 3% by weight ammonium tetraborate at 300C and at 50V. As the cathode, a lead plate was- used in these two-stage electrolyses. The current density rose in an initial period to about 2 A/ dm2, but it rapidly dropped and had a value of about -0.1 A/dm2 at the end of 2 minutes.The anodic oxidized layer which was formed in the first electrolysis using the aqueous - solution of phosphoric acid was quite porous, with the diameter of the pores being 300 A or greater.

The adhesiveness of the image-forming substances onto the first-formed oxide surface was noted to be strong, but when used on the printing machine, stains of the printing surface tended to develop easily. By the formation of the substantially non-porous barrier-forming barrier anodic oxidized layer in the second electrolysis, stains of the printing surface during printing were prevented without adversely affecting the adherency of the image-forming substance onto the image areas. The diazo resin coated on the surface was stable after a long period of storage.

EXAMPLE 3.

An aluminium alloy sheet was surfaceroughened by brushing. Thereafter, the sheet was subjected to an anodic electrolysis at a current density of 1 A/dm2 for minutes in an aqueous solution containing 15% (vol/ vol) of sulphuric acid and 15% (vol/vol)- of phosphoric acid to form a porous anodic oxidized film thereon. Thereafter, the.resulting sheet was again subjected to another anodic electrolysis at 800C and at a cur- rent density of 0.2 A/dm2 for 2 minutes in an aqueous solution containing 8% iby weight of boric acid and 0.2% by weight of borax to apply a substantially non-porous barrier-forming anodic oxidized film to the surface. The sheet was then washed with water and dried.Thereafter, the surface was provided with image areas by the application of an image-forming substance in a known way of planographic printing technique. On a cylinder press machine, the - ad- hesion of ink was found to be extraordinarily good, and both the water-receptivity and the hydrophilic property of non-image areas were noted to be excellent. No staining of the printing surface was found Prints amounted to 500,000 sheets by this single printing plate. The supporting blank obtained according to the above-said -method was especially hard, and it was found that the preparation of the final printing plate was accomplished with ease and also that the prints obtained by this printing plate were all quite satisfactory.

EXAMPLE 4.

A non-surface-roughened aluminium sheet was subjected to an anodic electrolysis at 200C and at 35V for 1 minute in an aqueous solution containing 10% by weight ammonium tetraborate. Thereafter, the resulting sheet was subjected to an etching step in an aqueous solution containing 1,0% by weight sodium hydroxide to remove the anodic oxidized layer. The sheet was then washed with water to provide a coarsened surface. The resulting sheet was again placed in said electrolyte of the aqueous solution of 10% by weight ammonium tetraborate to perform anodic oxidation at 0.5 A/dm2 for 1 minute, followed by washing with water and drying. The voltage applied in the final stage was 40V. Onto the resulting surface was applied, by relying on the wipe-on technique, a diazo - resin, to provide a printing plate.This printing plate was found to be satisfactory - in its printing characteristic.

EXAMPLE 5.

A sheet of aluminium was subjected to a surface roughened step by relying \ on the ordinary ball-abrading technique. Thereafter, the sheet was given anodic oxidation at 0.3 A/dm2 for 1 minute in an aqueous solution of 10% by weight potassium tetraborate. Onto the resulting surface was applied, by 9 known method, a PVA (pplyvinyl alcohol) sensitizing solution containing ammonium bichromate to provide a planographic printing plate.

Another sheet without being coated with the sensitizing solution was stored for an extended period of time, and thereafter it was coated with a sensitizer solution. Each of these sheets showed a satisfactory printing characteristic. No trace of corrosion or pit was found after the end of a prolonged storage. No difficulty was encountered at the time the final printing plate was pro-' duced.

EXAMPLE 6.

A brush-grained aluminium sheet was subjected to anodic oxidation at 200C and at 0.5 A/dm2 for 1 minute in an aqueous solution of 5% by weight-of sodium metaborate.

Thereafter, the sheet was etched in an aqueous solution of 10% by weight sodium hydroxide to remove the oxide ]ayer formed on the surface, thus providing a surface of fine grains. This sheet was again subjected to an anodic oxidation in the aforesaidaqueous solution of 5% by weight sodium metaborate- at a current density of 0.2 A/dm2 for 2 minutes. After being washed with water and dried, the sheet was noted to have a specially satisfactory water-receptivity and to be suitable for printing.

EXAMPLE 7.

An aluminium alloy sheet was subjected to surface roughening or graining and to anodic electrolysis in the same way as described in Example 1, with the exception that the electrolyte employed consisted of an aqueous solution of 3% by weight ammonium tartrate. The electrolyzing and printing conditions were substantially the same as those for Example 1, and a similar result was obtained. Stains found in the prints were much less than those found from the printing plate applied with a boemite film which was carried out conventionally. Also, the energy consumed for the preparation of the supporting blank was small.

WHAT WE CLAIM IS:- 1. A supporting blank suitable for the preparation of a printing plate, comprising a metal support plate (a), having a hydrophilic water-receptive surface (b) and applied to the water-receptive surface (b) a substantially non-porous barrier or barrier-forming anodic oxidic continuous or discontinuous layer (c) formed by anodic electrolysis.

2. A supporting blank according to Claim 1, in which the water-receptive surface (b) is a grained or roughened surface.

3. A supporting blank according to Claim 1, in which the water-receptive surface (b) is a porous anodic oxidized layer formed on a grained or roughened surface of the metal support plate (a).

4. A supporting blank according to any preceding claim wherein the layer (c) has a thickness of 0.1-1.0 ,lem.

5. A supporting blank according to any preceding claim, wherein the plate (a) is chosen from aluminium, tantalum, niobium, titanium and alloys thereof.

6. A supporting blank according to Claim 1 substantially as herein described and exemplified.

7. A method of manufacturing the supporting blank claimed in Claim 1, comprising forming a hydrophilic water-receptive surface (b) on a metal support plate (a) and applying by anodic electrolysis a substantially non-porous barrier or barrier-forming anodic continuous or discontinuous oxidic layer (c) on the surface (b).

8. A method according to Claim 7, wherein formation of the surface (b) is carried out by graining or roughening the surface of the metal support plate (a).

9. A method according to Claim 8, wherein the formation of the surface (b) is carried out by first forming a roughened grained surface on the metal support plate (a) and then forming on this grained surface a porous anodic oxidized layer by the use of an electrolyte which is an aqueous solution of phosphoric acid or an aqueous solution of a mixture of phosphoric and sulphuric acids.

10. A method according to - Claim 7, wherein formation of the surface (b) is carried out by applying by anodic electrolysis an anodic oxidic layer (d) to the metal support plate (a) and subsequently removing the layer (d) by dissolving same.

11. A method according to any one of Claims 7 to 10, wherein the layer (c) has a thickness of 0.1-1.0 sm.

12. A method according to any one of Claims 7 to 11, wherein the application of layer (c) to the surface (b) by anodic electrolysis is achieved using an electrolyte bath voltage of 1W50 volts.

13. A method according to any one of Claims 7 to 12, wherein the application of layer (c) to the surface (b) by anodic electrolysis is achieved using a current density of 0.1-2 A/dm2.

14. A method according to any one of Claims 7 to 13, wherein the metal support plate (a) is chosen from aluminium, tantalum, niobium, titanium and alloys thereof.

15. A method according to Claim 7 substantially as herein described and exemplified.

16. A supporting blank suitable for the preparation of a printing plate which has been produced by the method claimed in any one of Claims 7 to 15.

17. A printing plate comprising a supporting blank as claimed in any one of Claims 1 to 6 or Claim 16 and an imageforming layer (e) applied to layer (c).

18. A printing plate according to Claim 17, wherein the image-forming layer (e) applied to layer (c) is of the kind suitable for the production of a planographic or planoconcavegraphic printing plate.

19. A printing plate according to Claim 17, wherein the image-forming layer (e) applied to layer (c) is a light-sensitive layer.

20. A printing plate according to Claim 19, wherein the image-forming layer (e) applied to layer (c) is a light-sensitive resinous layer.

21. A printing plate according to Claim 20, wherein the layer (e) is a diazo resinous layer.

22. A printing plate according to Claim 17 substantially as herein described and exemplified.

23. A printing plate substantially as herein described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. to surface roughening or graining and to anodic electrolysis in the same way as described in Example 1, with the exception that the electrolyte employed consisted of an aqueous solution of 3% by weight ammonium tartrate. The electrolyzing and printing conditions were substantially the same as those for Example 1, and a similar result was obtained. Stains found in the prints were much less than those found from the printing plate applied with a boemite film which was carried out conventionally. Also, the energy consumed for the preparation of the supporting blank was small. WHAT WE CLAIM IS:-

1. A supporting blank suitable for the preparation of a printing plate, comprising a metal support plate (a), having a hydrophilic water-receptive surface (b) and applied to the water-receptive surface (b) a substantially non-porous barrier or barrier-forming anodic oxidic continuous or discontinuous layer (c) formed by anodic electrolysis.