US3223525A

US3223525A - Method of manufacturing, by photographic means, external, electrically conductive noble-metal patterns on non-metallic, electrically non-conductive, macromolecular supports and products obtained by these methods

Info

Publication number: US3223525A
Application number: US41799A
Authority: US
Inventors: Jonker Hendrik; Dippel Cornelis Johannes
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1959-07-22
Filing date: 1960-07-11
Publication date: 1965-12-14
Anticipated expiration: 1982-12-14
Also published as: NL113853C; SE303074B; NL241541A; ES259764A1; DK107988C; DE1446699A1; CH420853A; DE1446699B2; GB954208A

Description

h nited States itlatn i 3,223,525 ldti'lilfli) F MANUFACEURWG, BY PHUTO- Rr-tPl-lilt? MEANS), EXTERNAL, ELEQTRICALLY CUNDUCTEVE NQBLE-METAL FAETERNS 0N NON-METALLIQ, ELEQTRKCALLY NGNN= DUCZEVE, MACRQIvdULECULAR SUPPGRTS AND PRODUQTS OETAINED BY THESE METHEDS Hendrik ionizer and Corneiis .lehannes Dippel, Eludhoven, Netherlands, assignors to North American Philips Company, llnc., New York, NFL, a corporation of Delaware No Drawing. Filed duly 11, 1969, Ser. No. 41,79 Claims priority, application Netherlands, Study 22, 195?, 241,541 29 Claims. (Cl. 96-35) The invention relates to a method of manufacturing, =by photographic means, external, electrically conductive noble-metal layers on at least superficially non-metallic, electrically non-conductive, slightly hydrophilic or at least superficially hydrophilized macro-molecular supports and to products obtained by this method.

In the method of the invention there is used a lightsensitive layer, which contains at least one light-sensitive compound which is converted by the reaction of light into a light-reaction product and which, as such, can be physically developed or which is capable of forming, in a secondary reaction, physically developable metal germs, the metal forming the erm image being provided, as a compound, in the layer either prior to the exposure or being added to the layer subsequent to exposure, the metal germ image formed being intensified by means of stabilized, purely physical development.

The term noble-metal layers is to be understood to mean herein not only layers having an uninterrupted surface of a noble metal but also the layers having patterns having continuous or discontinuous portions, for example, station-name dials for radio apparatus, ornamental objects, printed wirings, printed circuits and so forth.

The term purely physical development referred to above is to be understood to mean the intensification of a weak, photographic metal germ image into an image of the desired optical density or with the required quantity of image metal by treating said weak germ image with a developing solution containing photographic reducing agents, and reducible compounds of metals nobler than copper, for example, silver, gold, platinum and so forth. A frequently used physical developer is, for example, a solution of silver nitrate in water, to which is added metol, hydroquinone or p-phenylene diamine. To such a developer are furthermore added, as a rule, other substances, in order to improve the preservability or to control the speed of development, for example, organic acids, butler mixtures or substances reacting with the noblemetal compound while forming complex ions. During the physical development free noble metal, formed by reduction from noble-metal salt, is deposited on the photographic metal germ image, which may lead to a considerable intensification of this image.

Purely physical developers, however, in contradistinction to chemical developers, are unstable systems, since between the noble-metal compound and the reducing agent there may occur, apart from the heterogenous reaction at the photographic metal germ image in the solution a further homogeneous reaction which gives rise to the spontaneous formation of noble-metal germs. Thus, these developers, even if not used, rapidly deteriorate while separating out noble metal. During the developing process a noble-metal deposit, a so-called superficial fog may be formed from the developer even on the nonexposed parts of the exposed layer. In the literature it is 323,525 Patented Dec. 1 3-, 1955 therefore recommended to clean the surface of the developed layer with the aid of a plug of cottonwool (J. M. Eder: Rezepte, Tabelle and Arbeitsvorschriften 1415 Aufiage. (1933), page 86, and Eder: Ausfuhrliches Handbuch der P'hotographie Ill, 2, 6, Anti. (1930), page 229).

However, it is possible to manufacture comparatively stable physical developers in accordance with the criteria applied to physical development, the spontaneous decomposition thereof being considerably delayed, so that they may be used for a materially longer time. For this purpose use may be made of the addition of one or more suitable, so-called ionic, surface-active compounds to the physical developer into which there may be added a non-ionic, surface active compound.

A physical development in which use is made of th stabilizing effect of ionic, surface-active substances in conjunction or not in conjunction with a non-ionic, surface-active compound is termed herein a stabilized physical development. If the use of these surface-active compounds in the physical development is dispensed with, reference is made herein to non-stabilized physical development. Such stabilized physical development is shown in copending U.S. application Serial No. 845,098.

In a copending application a method has been described, which uses a light-sensitive layer which does not contain, during the exposure, a metal compound forming a germ image and in which, by the exposure, a light-reaction product is formed which is capable, in a secondary reaction, of setting free metal from a solution of a mercurous or silver compound. In this method is used a special, so-called mirror exposure, after which the layer is contacted with a solution of the said metal compound (the so-called germ introduction bath), so that an at least partly external metal germ image (lying on the surface of the support) is formed, this external metal germ image, upon intensification by means of non-stabilized, purely physical development, grows into an external, electrically conductive noble-metal layer. The external metal germ image does not grow into an external, electrically conductive noble-metal layer, however, if it is subjected to a treatment with a stabilized, purely physical developer.

The term mirror exposure is to be understood to mean that exposure energy per surface unit of the light-sensitive layer which, at the chosen concentration of metal ions in the germ introduction bath, provides an at least partly external metal germ image, which after intensification by means of a chosen non-stabilized, purely physical developer, provides, under chosen conditions of temperature and developing time, an external noble-metal layer which exhibits an electric resistance not exceeding 18 ohms per square.

in accordance with the invention electrically conductive, noble-metal layers may be manufactured, by photographic means, on at least superficially non-metallic, electrically non-conductive, at least hydrophilized macromolecular supports, which noble-metal layers have an excellent adhesion to the support and a beautiful gloss.

According to the invention applicants have unexpectedly found that when one of said non-conductive supports is treated with a light sensitive compound such as a silver halide or one which produces, upon exposure to light, a light reaction product capable of producing in the presence of water silver or mercury germs from water soluble silver and mercury compounds either present before or after exposure and this layer is exposed to light for a certain critical minimum exposure energy called herein the outgrowth exposure and the layer after the silver or mercury genn image is formed is developed with a stabilized physical developer for a prolonged period of time the internal image which has been formed before physical development is made to grow out beyond the surface of the support and become an external image having a resistance of less than 10 ohms per square.

In contradistinction to the method, in which use is made of a mirror exposure, and an at least partly external metal germ image is obtained and this image is caused to grow by nonstabilized, physical development into an external noble-metal layer, a substantially only internal metal germ image is, in accordance with the invention, intensified by stabilized physical development, or else only the internal portion of a partly external metal germ image, is intensified by stabilized physical development, While initially an internal, neutrally grey to black noble-metal image is formed, which, upon a prolonged stabilized development, grows into an external, electrically conductive noble-metal layer, which exhibits an improved adhesion to the support and, as a rule, a more beautiful gloss than such a layer obtained by the method described in the copending application. In accordance with the method of the invention appreciably longer developing times are, as a rule, required than in the known method.

By electron-microscopic investigation it was determined that under these conditions, in a stabilized physical developer only the internal metal germ image formed grows and that this growth, if the development is not prematurely interrupted, continues until the noble-metal image projects from the support, after which it constitutes an external, electrically conductive noble-metal layer according to the image pattern. Such a prolongation of the physical development not disturbed by spontaneous noble-metal deposition has become possible, in a simple manner, only by using stabilized development.

It was a great surprise to find that while an external metal germ image substantially does not grow in a stabilized physical developer, an internal metal germ image grows in such a developer and upon projecting from the support does not stop growing but grows on undisturbedly for some time.

Consequently, the method according to the invention has the great advantage that now for the manufacture, by photographic means, of external, electrically conductive noble-metal layers use may be made of stabilized, purely physical development.

Since the development of an internal metal germ image into an external, electrically conductive noble-metal layer requires, as a rule, an appreciably longer time than the development of such a germ image into an internal, photographic image for more conventional uses or the nonstabilized development of an at least partly external metal germ image into an external noble-metal layer, the activity of the developer is required to be accelerated in order to reduce the developing time. This may be achieved by using a higher developing temperature, by choosing higher concentrations of the noble-metal compound and/or of the photographic reducing agent in the developer, of a higher pH of the developer, and so on than is common practice for the development of normal internal images. With stabilized physical development this may, as a rule, be achieved without troublesome spontaneous formation of noble-metal germs. Owing to this activation of the developer the development into an external image can be accelerated by a factor 10 to 20.

The exposure energies to be employed to obtain photographic metal germ images which grow, upon a prolonged stabilized purely physical development, into external, electrically conductive noble-metal layers with reproducible properties, are termed herein outgrowth exposures. The term outgrowth exposure is to be understood to mean herein that exposure energy per surface unit of the light-sensitive layer which, with a chosen photographic system and with a chosen composition of the light-sensitive layer, yields a photographic metal germ image, which, upon intensification in a stabilized, physical developer obtained by dissolving, in distilled water,

4.- Metol mol/litre 0.025 Citric acid do 0.100 Silver nitrate do 0.010 Lissapol N percent by weight 0.02 Armac 12D do 0.02

at a developing temperature of 20 C. within 180 min., the developer being refreshed each time after one hour, grows into an external, electrically conductive noble-metal layer which, after washing in water has a resistance not exceeding 10 ohms per square.

When with a chosen photographic system the outgrowth exposure has once been determined, any other stabilized physical developer is capable of providing an external, electrically conductive noble-metal layer by developing for such a long time that the resistance of the noble-metal layer is at the most 10 ohms per square.

The physical development may be carried out, as stated above, as an alternative with aid of a stabilized, physical developer which has been activated to shorten the developing time.

Many uses of the external noble-metal layers produced in accordance with the invention on non-metallic, electrically non-conductive, macro-molecular supports are found in the electrical and electro-technical fields. In these cases it is frequently important that the electric resistance should not exceed by far that of corresponding layers containing the same quantity of noble metal in compact state and that this resistance should not vary much in the course of time. The noble-metal layers obtained after physical development usually do not fulfill this requirement without the need for further means. By a thermal and/or chemical after-treatment and/or a mechanical polishing treatment the high resistance value can be reduced to a materially lower, reasonably constant and reproducible value.

The thermal after-treatment is carried out by heating the noble-metal layer at a temperature of at least C. The desired effect is attained more rapidly with an increase in temperature but the effect of the temperature on the material of the support must be considered. The chemical after-treatment to reduce the electric resistance of external silver layers consists in bringing these into contact with an aqueous solution containing one or more compounds separating off a hydrogen ion or a potential determining anion with respect to the silver metal, for example (31 BF, J'-3, CNS CN 3, 8 803 S203: 01 OH. Mechanical polishing of the layer reduces, in many cases, the electric resistance of the layer to a sufficient extent. Moreover, such a treatment improves the optical decorative properties of the noble-metal layer.

A great number of uses both in the electrical and in the decoration field require or desire that an external noble-metal layer obtained by the method according to the invention should be subjected to an electro-chemical aftei treatment, after which a superficial chemical conversion or coloration may be carried out. For this purpose use may be made, for example, of electrolytic polishing, electrolytic deposition of metals, while use is made or not made of an external current source, electrolytic coloration of the deposited metal or electrophoretic coating with a protective or insulating or photoand/ or semiconductive surface layer. If desired, a combination of various electro-chemical and/ or chemical after-treatments is possible. For various uses a choice may furthermore be made from a great number of mechanical after-treat ments, which may be combined with the after-treatments described above. A few important suitable after-treatments of this kind are, inter alia: polishing of the surface, application of a lacquer or varnish layer to the layer surface, embedding of the layer, together with the support, in an insulating envelope of thermo-hardening or thermoplastic material, transfer of the layer, if necessary together with the support, to a different, support of high electrical qualities, also of thermo-hardening or thermo-plastic material, application of electrical connections by soldering (for example, dip soldering).

In the electronics field use may be made, for example, of external noble-metal layers manufactured according to the invention, in conjunction with one or more of the aforesaid after-treatments, for the manufacture of printed wirings, circuits, screen grids, switches and other component parts.

The method according to the invention may, consequently, be carried out by means of all those photographic materials in which, by exposure, a physically developable metal germ image can be obtained directly or indirectly. These materials are, in the first place, those which contain a light-sensitive compound of which the light-reaction product behaves, as such, i.e. without previous chemical conversion, as a physically developable photographic metal germ image, for example, the materials containing, as a light-sensitive compound, silver halide. They include furthermore all photographic materials containing a light-sensitive compound of which the light-reaction product, as such, cannot be physically developed, this product being, however conversible, in a secondary reaction, into a physically developable, photographic metal germ image, while the metal forming the germ image is contained in the photographic layer in the form of a compound prior to exposure. This secondary reaction, if the light reaction product is a metal compound, will consist in setting free metal germs therefrom, as is, for example, the case with the photographic process in which use is made of the light-sensitivity of the so-called Eder solution and in which the light-reaction product consists of mercurous chloride. An important group of photographic materials which may be employed in the method according to the invention are the materials containing a light-sensitive compound of which the light-reaction product, in a secondary reaction, is capable of setting free physically developable mercury or silver germs from mercurous or silver compounds respectively.

This secondary reaction may be based on a so-called disproportioning of mercurous ions in accordance with the reaction equation:

Free mercury is formed since the light reaction product reacts with mercuric ions. Or it may be based on the reduction of silver ions in accordance with the equation:

The mercury atoms or silver atoms set free respectively unite to form mercury or silver germs respectively.

In these systems the mercurous compound or the silver compound may be provided prior to exposure in the layer containing the light-sensitive compounds (US. Patents 2,067,690 and 2,738,272) or a solution of such a compound may be brought into contact with the layer after the latter has been exposed. The last-mentioned variant is termed germ introduction method and the solution of the metal compound by which the introduction of the germs is carried out is termed germ introduction bat (US. Patent 2,764,484).

In the germ introduction method the light-sensitive compounds of the class of the aromatic diazosulphonates are particularly useful, more particularly in conjunction with so-called anti-regression agents, i.e. substances which, when added to the layer, prevent diazosulphonate from being reformed from its light-reaction product by binding either the sulphite or the diazoniurn radical or both so that the sulphite remains capable of reacting with the mercurous compound while forming mercury germs With this method the gloss and the reproducibility of the external, electrically conductive noble-metal layers may be further improved by adding to the germ introduction bath, apart from the mercurous compound, one or more organic hydroxy acids selected from the group citric acid, tartaric acid, glycolic acid, glycerol acid and malic acid. Then, at least such a quantity of the acid is to be added that the precipitate initially forming with the mercurous compound redissolves.

Other suitable, light-sensitive compounds, of which the light-reaction product sets free, in a secondary reaction, physically developable mercury germs from a mercurous compound, are, for example, o-hydroxy-benzene-diazo nium compounds, o-hydroxy-naphthalene diazonium compounds, aromatic diazocyanides, oand p-nitro-mandelic acid-nitril, the bisulphite compounds of oand p-nitrobenzaldehyde, a series of inorganic, complex compounds from which, by exposure, one or more of the following ions or molecules are set free:

pyridine and derivatives thereof, thiourea and derivatives thereof, which ions and molecules are bound to at least one central metal ion. The light-reaction product of ohydroxy-benzene-diazonium compounds and of o-hydroxynaphthalene diazonium compounds is also capable of setting free physically developable silver germs from silver compounds.

Also suitable are furthermore certain azines, thiazines and oxazine compounds, salts of monoand disulphonic acids, of naphthoquinone and of anthraquinone and certain diazonium compounds, such as amino-l-diethoxy- 2,5-benzene-diazonium borofluoride-4, of which the lightreaction product, in a secondary reaction, is capable of setting free silver germs from silver compounds.

Suitable materials which may be used for the supports in carrying out the method according to the present invention are, in general, all film-forming high polymer products, which if not yet so, are rendered superficially accessible to a certain extent for the various baths, for example, gelatin, regenerated cellulose paper, wholly or partly saponified cellulose esters, polyvinyl alcohol, and so forth.

The invention will now be described in greater detail with reference to the examples which follow.

Example I A superficially saponified cellulose triacetate foil was sensitized by impregnating it for two minutes in an aqueous solution containing 0.15 mol of o-rnethoxy-benzenediazosulphonic acid sodium and 0.1 mol of cadmium lactate per litre, after which it was wiped off and dried. Strips of this foil were then exposed behind a line negative with the aid of a high-pressure mercury-vapour lamp and a sensitometer, after which they were treated for a few seconds with an aqueous solution containing 0.005 mol of mercurous nitrate and 0.01 mol of nitric acid. Then the strips were washed for a short time in distilled water and developed in a stabilized, physical developer, obtained by dissolving in distilled water:

Metol (0.025 mol/litre) Citric acid (0.1 mol/litre) Silver nitrate (0.01 mol/litre) Lissapol N (0.02% by weight), and Armac 12 D (0.02% by weight) Lissapol N is a condensation product of alkylphenols and ethylene oxide, containing a polyethylene chain; Armac 12 D is a mixture of dodecyl and tetradecylamine acetate. By using a developing temperature. of 20 C., a developing time of 180 min., the developing bath being refreshed after 60 and min., respectively, the minimum outgrowth exposure was determined, i.e., the minimum exposure energy per unit of the light-sensitive layer, having, after this development, an outgrown silver layer with an electric resistance which sufiices the aforesaid criterion.

With a developing time of 15 min. in a developer of the aforesaid composition the tested exposure region (1 to 2 times the minimum outgrowth exposure) yielded only internal silver images. The densities of the images obtained with the maximum exposures were, in this case, however immeasurably high.

With a developing time of 30 min. in the said developer, however, an exposure 2V2 times higher the minimum outgrowth exposure produced an outgrown, electrically conductive silver layer was obtained. Exposures of 2 /22 times the minimum outgrowth exposure produces sliver layers with electric resistances from 1900 to 340 ohms per square, which values, after a thermal treatment of one hour at 150 C., dropped to 1.2 and 0.2 ohms per square surface respectively.

With a developing time of 60 min. an exposure being only /2 times the minimum outgrowth exposure produced an outgrown electrically conductive silver layer. The resistance values measured decreased, with an increasing exposure to 2 times the minimum outgrowth exposure, from 400 to 120 ohms per square. After the thermal treatment these values had dropped to a few tenths ohms per square.

Oubgrown silver layers having electric resistances as stated above could be intensified with copper by electrolytic means, while use was made of an aqueous copperdeposition bath of the following composition:

Copper sulphate 5 aq. (200 g./litre) Concentrated sulphuric acid (50 g./litre), and Phenolsulphonic acid sodium (0.5 g./litre) Use was made, for example, of a copper-deposition time of 2 min. with a current density of 5 A./dm. Copper layers thus obtained could then be electrophoretically coated superficially, for example, with a layer of alumina, by using a suspension of of Alundum in methanol with a field intensity of 37.5 v./cm. for 6 sec. and 3. current of 70 ma. Electrolytic intensification with nickel could take place, for example, by means of an aqueous nickel-coating bath containing, per litre, 240 g. of nickel sulphate, 45 g. of nickel chloride and 30 g. of boric acid. The operational temperature of this bath was 40 C. and the current density amounted to 2 to 4 A./dm.

Many other compositions of stabilized, physical developers, yielded corresponding results. Two very suitable compositions are mentioned here, in particular:

(a) 2 g. of hydroquinone, 0.1 g. of citric acid, 0.2 g. of silver nitrate and 0.2 g. of Aresklene 400 (dibutyl- 'orthophenyl-phenol-sodium disulphonate) per 100 g. of

distilled water,

(b) 0.5 g. of metol, 2 g. of citric acid, 0.2 g. of silver nitrate, 0.02 g. of Sapamine KW and 0.03 g. of Alamac 26 D in 100 g. of distilled water. Sapamine K is the methyl sulphate of monostearylamido-ethylene-trimethylamine; Alamac 26 D is a mixture of oleyl stearyl and palmetyl-amine-acetate.

The activity of the said developers can be kept substantially constant for a satisfactory time by refreshing the silver nitrate used for the image formation from time to time in the form of small quantities of a 10% by weight of an aqueous solution of silver nitrate. By reducing the quantity of citric acid in the developer (b) to 0.067 g. and by increasing the quantity of silver nitrate to 0.4 g., a developer was obtained which yielded, within a few minutes an outgrown, electrically-conductive silver layer.

Sensitizing solutions containing other light-sensitive diazo-sulphates, for example, p-methoxy-benzene-diazosulphonic acid sodium or dimethoxy-Z.S-benzene-diazosulphonic acid sodium-1 and/ or other anti-regression means, such as resorcinol, yielded corresponding results.

Example 11 Unilaterally white, woodfree litho-paper was sensitized by impregnation, on one side, in the solution of a light-sensitive compound as described in Example I and by drying it. The exposure, the treatment with the mercurous nitrate solution and the stabilized physical development at a temperature of 20 C. of strips of this material took place in the manner described in the preceding example. In order to determine the minimum mirror exposure, moreover, a few strips were developed for 10 minutes at 20 C. in a non-stabilized physical developer obtained by dissolving, in distilled water, metol, citric acid and silver nitrate with concentrations as indicated in the first developer of Example I. With a developing time of 20 min. in a stabilized physical developer and with an exposure of 8 times the minimum mirror exposure no outgrown, electrically conductive silver layer was obtained. \Vith a developing time of 30 min. in the said stabilized developer, however, an exposure of even 8 times lower the minimum mirror exposure yielded an outgrown, silver layer with an electrical resistance of 2100 ohms per square. When using an exposure equal to the minimum mirror exposure, the electric resistance of the silver layer obtained amounted to only 180 ohms per square, which value, after a treatment at 150 C. for one hour, dropped to about 1.5 ohms per square.

Such a silver layer, which had been manufactured in the pattern of a screen grid, was intensified for 15 min. with a current density of 4 A./dm. electrolytically with copper by means of an acidic copper-deposition bath containing 20% by weight of copper sulphate (SH O) and 6% by weight of sulphuric acid in distilled water. After washing and drying and soldering to a mounting strip, the copper-coated grid was dipped in a polyvinyl-chlorideacetate lacquer and again dried. Then a polyvinylchloride foil of about 25 was applied to the image side and the assembly was compressed for one minute at C. under a pressure of 10 kgs./cm. The insulated, flexible grid thus obtained could be readily bent into the form of a cylinder and be thus used as a screen grid for electric coils.

Example Ill The support material of Example I was sensitized by impregnating it for two minutes in an aqueous solution containing 2% by weight of anthraquinone-disulphonic acid sodium-2,7, after which it was wiped off and dried. Strips of this light-sensitive material were exposed with the aid of a high-pressure mercury-vapour lamp behind a line negative and then treated, for 15 sec., with an aqueous solution containing 0.01 mol of silver nitrate and 0.2 mol of acetic acid acetate buffer.

The pH of this solution was 6. Then the strips were washed, for three minutes, in distilled water and. developed in a stabilized physical developer as described in Example I. For developing time longer than 60 or 120 minutes respectively, the developing bath was refreshed after 60 min. or after 60 and 120 min. respectively.

When an exposure of 16 times that of an exposure energy E, which had yielded an internal density of about 2 after a developing time of 15 min. was used, even in a developing time of 15 min., no external, electrically conductive silver layer was formed, but a very high internal density. After 60 min. of development the strip exposed to 16E exhibited an outgrown silver layer having an electric resistance of about 400 ohms per square, which value, after a thermal treatment (at C. for one hour) dropped to about 2 ohms per square. After 105 min. of development the outgrown silver layer had an electric resistance of about 350 ohms per square which value dropped, after rubbing with a plug of cottonwool, to about 100 ohms per square. After min. of development the resistance of the silver layer obtained amounted to about 300 ohms per square. The last-mentioned value dropped, after a treatment, for one minute, with a 0.1 N solution of potassium chloride in water to about 2.7 ohms per square.

The use of the exposure of the time E yielded, after 60 min. of development, a silver layer with a resistance of about 2250 ohms per square. After the said thermal treatment this value dropped to 5.3 ohms per square. After 165 min. of development a silver layer with a resistance of about 750 ohms per square was obtained. After the aforesaid chemical treatment, this value was 13 ohms per square.

Similar resistance-reducing effects could be achieved by replacing the treatment with the potassium chloride solution by one of the solutions of the following compounds: sodium bromide, Sodium iodide, sodium thiosuphate, sodium sulphite, sulphuric acid, potassium hydroxide, potassium thiocyanide and sodium sulphide.

Example IV The support material of Example I was sensitized by impregnating it for two minutes in an aqueous solution containing 0.4 mol of hydroxy-l-diazo-Z-methyl-G-benzene-sulphonic acid-4, 0.05 mol of mercurous nitrate and 0.1 mol of nitric acid per litre, after which it was wiped off and dried. Strips of this material were exposed with the aid of a high-pressure mercury-vapour lamp and then treated, for a few seconds, with distilled water. Then the strips were developed in the stabilized physical developer of the composition referred to in the preamble of Example I. Eventually the developing bath was refreshed after 60 and 120 min. respectively. Finally the developed strips were washed for about 10 min. in distilled water and dried in air.

When using an exposure of about twice the minimum outgrowth exposure, after a developing time of 30 min., an outgrown, electrically conductive silver layer was obtained. The electric resistance of the external silver layer obtained could be reduced by thermal or chemical aftertreatment or a mechanical polishing treatment to a considerable extent. When using an exposure of about 4 times the minimum outgrowth exposure, after a developing time of 7.5 min., an internal density of about 2 was obtained. When using an exposure of about 64 times the minimum outgrowth exposure, after a developing time of 7.5 min., a very high internal density was obtained.

Example V The support material of Example I was sensitized by impregnation for 2 min. in an aqueous solution containing 3% by weight of hydroxy-l-diazo-2-naphthalenesulphonic acid-4, 2% by weight of citric acid and 4% by weight of silver nitrate, after which it was wiped off and dried. Strips of this material were exposed behind a line negative with the aid of a water-cooled high-pressure mercury-vapour lamp and then washed for two minutes in distilled water. Then the strips were developed in a stabilized physical developer of the comparison indicated in the first recipe of Example I. The developing bath was refreshed after 60 and 120 min. respectively. Finally the strips were washed again and dried in air. With an exposure yielding, after a developing time of 7.5 min. an internal density of about 2, an outgrown silver layer was obtained after 30 min. of development, the electric resistance thereof being 980 ohms per square, which value dropped, after a thermal treatment at 150 C. for one hour, to 0.5 ohm per square and, after a chemical treatment in an aqueous solution containing 0.1% by weight of potassium chloride, to 1.1 ohms per square. After a developing time of 60 min., by using the same exposure, a silver layer was obtained, of which the electric resistance amounted to 340 ohms per square. After the thermal treatment, this value dropped to 0.25 ohm per square. The minimum outgrowth exposure (developing time 180 min.) was about 32 times lower than the exposure used above.

Example VI A superficially saponified cellulose tri-acetate foil was sensitized by impregnating it for two minutes in an aqueous solution of 5% by weight of mercuric chloride, 5% by weight of ferric ammonium oxalate and 2.5% by weight of ammonium oxalate, after which it is wiped off and dried. Strips of this foil were exposed to the light of a high-pressure mercury-vapor lamp and then treated for 10 sec. with a 10% by weight solution of sodium sulphite in water and for 1 min. with distilled water. Then the strips were developed in the stabilized physical developer of Example I. The developing bath was refreshed after 60 and min. respectively. Finally the strips were washed for 10 min. in distilled water and dried in air.

When using an exposure of 32 times E (that exposure which yielded, after a developing time of 7.5 min. an internal density of about 2), also with a developing time of 7.5 min., no external, electrically conductive silver layer was obtained, but a very high internal density.

After 30 min. of development, an outgrown, electrically conductive silver layer was obtained on the strips subjected to exposure E. The minimum outgrowth exposure was 3 to 4 times lower than the exposure E.

The electric resistance of the external silver layers obtained could be reduced also in this case to a considerable extent by a thermal or a chemical after-treatment or mechanical polishing.

Example VII Strips of an optically not-sensitized silver halide film of the firm of Gevaert, known under the trademark of Scientia 14 B 50, were exposed preferably with the aid of a mercury-vapour lamp, behind a line negative.

After the exposure the strips were fixed for 5 min. in an aqueous solution containing 5% by weight of anhydrous sodium sulphite and carefully washed in distilled water. Then the strips were developed in the stabilized physical developer used in the preceding example. When the developing time was longer than 60 and 120 min. respectively, the developing bath was refreshed after 60 and 120 min. Finally the strips were again washed and dried in air. After 45 min. of development an outgrown, electrically conductive silver layer was obtained, when using an exposure of 225 times the minimum outgrowth exposure (developing time min.) the exposure intensity being approximately half that of the exposure yielding, after 15 min. of development, a density of about 2. After 60 min. of development an outgrown, electrically conductive silver layer was formed when using an exposure of 28 times the minimum outgrowth exposure. After 75 min. of development, already with an exposure of 23 times the minimum outgrowth exposure, an electrically conductive layer was obtained.

With a similar film of the firm of Ilford, i.e., 5 B 11, similar results could be obtained, be it in this case that the latent image grew out slightly more rapidly, so that shorter developing times could sufiice.

With the diapositive contrast plate of the firm of Gevaert only after a developing time of 100 min. in the aforesaid, stabilized physical developer, an outgrown, electrically conductive silver layer could be obtained, when the exposure was carried out with the aid of a mercury-vapour lamp. The anti-halo layer was removed, in this case prior to fixation, by treating it with an ammonia solution.

Also on a photographic enlarging paper of the firm of Agfa trademark Brovira, a similar method, using a developing time of at least 30 min. could provide an outgrown, electrically conductive silver layer. The developer had, in the latter case, the following composition: 1.6% by weight of metol, 3.2% by weight of citric acid, 0.4% by weight of silver nitrate, 0.02% by weight of Lissapol N and 0.02% by weight of Armac 12 D in distilled Water.

The electric resistances of all these silver layers could be reduced, by thermal or chemical after-treatment or by mechanical polishing, to a considerable extent.

While we have described our invention in connection with specific embodiments and applications, other modifications thereof will be apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A method of producing by photographic means an external electrically conductive noble-metal pattern on an at least superficially non-metallic, electrically nonconductive, at least slightly hydrophilic macro-molecular support comprising the steps of sensitizing said support With at least one light-sensitive compound selected from the group consisting of the silver halides and those organic compounds the light reaction products of which are capable of reacting in the presence of water with a water soluble metallic compound selected from the group consisting of water soluble silver and mercurous compounds to form free silver and mercury metal at the exposed portions, said water soluble metallic compound being present prior to development, selectively exposing said support for a time at least equivalent to an outgrowth exposure, treating said selectively exposed support with said water soluble metallic compound in the presence of moisture, thereby forming an internal latent image containing free metal selected from the group consisting of silver and mercury at the exposed areas and physically developing said latent image by treatment with a developing solution comprising an aqueous solution of a water soluble reducible salt of a noble metal selected from the group consisting of silver, gold and platinum, said developing stabilized solution being stabilized with an ionic surface active compound for a time at least sufiicient to cause said internal image to grow into an external electrically conductive pattern of said noble-metal.

2. The method of claim 1, wherein the external electrically conductive pattern of the noble-metal is heated at a temperature of at least 80 C.

3. The method of claim 1, wherein the resultant noblemetal pattern is a silver layer and is treated with an aqueous solution of at least one compound having a potential determining anion with respect to the silver metal.

4. The method of claim 1, wherein the resultant noblemetal pattern is treated with an aqueous solution of a member selected from the group consisting of non-oxidizing acids and acid salts.

5. The method of claim 1, wherein the resultant noblemetal pattern is subjected to mechanical polishing.

6. The method of claim 1, wherein the noble-metal pattern is electrolytically intensified.

7. The method of claim 1, wherein electrophoretically a colloidal material is applied to the metal layer.

8. The method of claim 6, wherein the resultant metal layer is subjected to polishing.

9. The method of claim 1, wherein the light-sensitive compound is a light-sensitive silver halide.

10. The method of claim 1, wherein the light-sensitive compound is an organic compound.

11. The method of claim 10, wherein the water-soluble compound is provided prior to exposure in the layer.

12. The method of claim 10, wherein the water-soluble compound is added to the layer after the exposure.

13. The method of claim 10, wherein the light-sensitive organic compound produces a light-reaction product capable of setting free metallic mercury from a watersoluble mercurous compound, in the presence of water.

14. The method of claim 13, wherein the light-sensitive compound is an o-hydroxy-benzene diazonium compound.

15. The method of claim 13, wherein the light-sensitive compound is an aromatic diazo-sulphonate and the lightsensitive layer contains a material which prevents the diazo-sulphonate from being reformed from the light-reaction products so that the sulphite remains capable of reacting with the mercurous compound to form a mercury nucleus.

16. The method of claim 13, wherein the aqueous solution of the mercurous compound the germ-introduction both there is added an acid selected from the group consisting of citric acid, tartaric acid, glycolic acid, glycerol acid and malic acid, in such a concentration that the precipitate formed initially with the mercurous compound is dissolved.

17. The method of claim 10, wherein the light-sensitive organic compound produces a light-reaction product capable of setting free metallic silver from a water-soluble silver compound in the presence of water.

18. The method of claim 1, wherein the light-sensitive compound is applied to a paper layer.

19. The method of claim 1, wherein the light-sensitive compound is provided in a cellulose ester layer which is rendered superficially hydrophilic by saponification.

20. The method of claim 13, wherein the light-sensitive organic compound is an o-hydroxy-naphthalene diazonium compound.

References Cited by the Examiner UNITED STATES PATENTS 2,067,690 1/1937 Alink et al. 9649 2,317,591 4/1943 Cramwinckel et al. 9663 2,738,272 3/1956 Jonker et al. 9649 2,750,292 6/1956 Dippel et al. 9688 X 2,854,386 9/1958 Lyman.

FOREIGN PATENTS 157,182 6/1954 Australia. 167,781 6/ 1954 Australia.

OTHER REFERENCES Alink et al.: Journal of the SMPTE, volume 54, March 1950, pages 345-366.

Eastman Kodak Abstracts 0177, abstract of P. Lazenby, Outline of Physical Development, Miniature Camera World, vol. 1, pages 457458, 460 and 462, August 1937.

Eastman Kodak Abstracts 0177-65, abstract of R. Namias, Physical Development, 11 Progreso Foto grafico, vol. 41, pages -169, June 1934.

NORMAN G. TORCHIN, Primary Examiner.

MILTON STERMAN, PHILIP E. MANGAN,

Examiners.

Claims

1. A METHOD OF PRODUCING BY PHOTOGRAPHIC MEANS AN EXTERNAL ELECTRICALLY CONDUCTIVE NOBEL-METAL PATTERN ON AN AT LEAST SUPERFICIALLY NON-METALLIC,ELECTRICALLY, NONCONDUCTIVE, AT LEAST SLIGHTLY HYDROPHILIC MACRO-MOLECULAR SUPPORT COMPRISING THE STEPS OF SENSITIZING SAID SUPPORT WITH AT LEAST ONE LIGHT-SENSITIVE COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE SILVER HALIDES AND THOSE OGANIC COMPOUNDS THE LIGHT REACTION PRODUCTS OF WHICH ARE CAPABLE OF REACTING IN THE PRESENCE OF WATER WITH A WATER SOLUBLE METALLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF WATER SOLUBLE SILVER AND MERCUROUS COMPOUNDS TO FORM FREE SILVER AND MERCURY METAL AT THE EXPOSED PROTIONS, SAID WATER SOLUBLE METALLIC COMPOUND BEING PRESENT PRIOR TO DEVELOPMENT, SELECTIVELY EXPOSING SAID SUPPORT FOR A TIME AT LEAST EQUIVALENT TO AN OUTGROWTH EXPOSURE, TREATING SAID SELECTIVELY EXPOSED SUPPORT WITH SAID WATER SOLUBLE METALLIC COMPOUND IN THE PRESENCE OF MOISTURE, THEREBY FORMING AN INTERNAL LATENT IMAGE CONTAINING FREE METAL SELECTED FROM THE GROUP CONSISTING OF SILVER AND MERCURY AT THE EXPOSED AREAS AND PHYSICALLY DEVELOPING SAID LATENT IMAGE BY TREATMENT WITH A DEVELOPING SOLUTION COMPRISING AN AQUEOUS SOLUTION OF A WATER SOLUBLE REDUCIBLE SALT OF A NOBLE METAL SELECTED FROM THE GROUP CONSISTING OF SILVER, GOLD AND PLATINUM, SAID DEVELOPING STABILIZED SOLUTION BEING STABILIZED WITH AN IONIC SURFACE ACTIVE COMPOUND FOR A TIME AT LEAST SUFFICIENT TO CAUSE SAID INTERNAL IMAGE TO GROW INTO AN EXTERNAL ELECTRICALLY CONDUCTIVE PATTERN OF SAID NOBLE-METAL.