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Publication numberUS3464822 A
Publication typeGrant
Publication dateSep 2, 1969
Filing dateSep 13, 1965
Priority dateSep 13, 1965
Publication numberUS 3464822 A, US 3464822A, US-A-3464822, US3464822 A, US3464822A
InventorsBlake Ralph Kingsley
Original AssigneeDu Pont
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for making electrically conductive images
US 3464822 A
Images(11)
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Description  (OCR text may contain errors)

United States Patent Oifice 3,464,822 Patented Sept. 2, 1969 3,464,822 PROCESS FOR MAKING ELECTRICALLY CONDUCTIVE IMAGES Ralph Kingsley Blake, Westfield, N.J., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. a corporation of Delaware No Drawing. Filed Sept. 13, 1965, Ser. No. 487,031 Int. Cl. G03c 5 /54; C23b 5 48 US. Cl. 9638.4 9 Claims ABSTRACT OF THE DISCLOSURE A process which comprises (a) Forming a latent developable silver halide image in a photographic element having a water-permeable, macromolecular organic colloid-silver halide emulsion layer, by imagewise exposure of said layer to actinic radiation,

(b) Forming by silver transfer development by means of a developer solution containing a silver halide developing agent, a silver halide solvent and a silver nucleating agent, an electrically conductive silver surface image having a resistance not more than 5.0 ohms per square in the unexposed areas of an outer water-permeable organic colloid layer of said photograhic film element, and a difference in resistivity of at least 1X10 times between the conductive coating and the exposed regions, and

(c) Passing an electrical current or impulse through the said electrically conductive silver surface image for utilization.

This invention relates to a process for making electrically conductive silver images, or, more specifically, to a photographic method for the preparation of electrically conductive silver surface images. Even more specifically, this invention relates to a new process for the preparation by silver transfer development of elements containing electrically conductive silver surface images from photographic light-sensitive elements. This invention also relates to the product produced by this novel process where said product contains electrically conductive silver surface images.

Normal chemical development of the typical silver halide photographic light-sensitive emulsion gives developed silver images that have almost no electrical conductance. For certain purposes it is desirable to make silver surface images which conduct electricity. Such images can be used as a printed circuit. The prior art has disclosed a method of forming an electrically conductive silver surface image on the surface of a silver halide photographic emulsion. The electrically conductive silver surface images produced by the novel process of this invention are superior to the prior art silver surface images, in that, among other reasons, the silver surface image has far lower electrical resistivity.

It is an object of this invention to produce a new improved product having electrically conductive silver surface images. Another object of this invention is to obtain a product having electrically conductive silver surface images which have essentially nonconductive backgrounds. A further object is to make conductive images rapidly and, where desired, on a flexible support. A further object of this invention is to obtain an electrically conductive silver image on the surface of the photographic element which can be used as a printed circuit board. Still further objects will be apparent from the following description of the invention.

The process for photographically forming the positive electrically conductive elements of this invention in its broader aspects comprises (a) Forming a latent developa-ble silver halide image in a photographic element having a water-permeable, macromolecular organic colloid-silver halide emulsion layer, by imagewise exposure of said layer to actinic radiation.

(b) Forming by silver transfer development an electrically conductive silver surface image having a resistance not more than 5.0 ohms per square in the unexposed areas of an outer water-permeable colloid layer of said photographic film element and a difference in resistivity of at least l 1() times between the conductive coating and the exposed regions, and

(c) Passing an electrical current or impulse through the said electrically conductive silver surface image for utilization of the current or impulse.

The silver halide surface image can be formed in the original silver halide emulsion layer or in a contiguous water-permeable, oleophobic, macromolecular organic colloid layer initially free from the light-sensitive silver salts.

In the process, the imagewise exposure preferably is carried out to form a printed circuit image for a machine, apparatus, instrument, dial or a component thereof, and the current or impulse utilized in the reverse printed circuit image having a resistivity of from about 0.1 to 5.0 ohms per square to control or actuate a part or parts of such an article.

This invention is not restricted to the use of the specific processing solutions and exposure conditions disclosed in the following specific description and in the detailed or working examples.

A surface has adequate electrical conductivity for use in accordance with this invention when the resistance is not greater than 5 .0 ohms per square. Electrically conductive silver surface images having an electrical resistivity of about 0.1 ohm per square are obtained readily in accordance with this invention.

Conventional, low silver halide solvent, photographic developers reduce exposed areas of a silver halide element to a negative silver image. When a silver halide solvent and a nucleating agent are added to low solvent developers, a conventional negative image also forms, but silver transfer, by the diffusion of silver complex ions to the surface of the layer, takes place in the unexposed areas where they reduce to form an electrically conductive positive silver image. Since an inverse or reverse image forms, this type of development is often known as inverse transfer development. If the developer is too slow in its action, an electrically conductive surface silver image having a resistivity not greater than 5.0 ohms per square will not form. Electrically conductive images are Obtained on the surface of exposed film by inverse transfer development using certain monoand dual-bath developing solutions. In general, when a sulfide compound and a thiocyanate compound, or their respective equivalents are added to a high energy developer, electrically conductive silver surface images having a resistance not more than 5.0 ohms per square can be formed. A high energy developer is defined as any developer that develops seventy-five percent of the total developable density in one minute.

A dual-bath developer as described herein is used in the preferred embodiment of the invention. A major reason for preferring this developer is that is assures high electrical resistivity in the background regions, that is, the exposed regions. By developing the background first, no exposed silver halide remains to dissolve in the second developer containing a high concentration of silver halide solvent, and the difference in resistivity of the exposed and unexposed regions is kept to a maximum.

Electrically conductive silver surface images fonm when a single-agent conventional low solvent developer, containing additional silver halide solvent and a nucleating agent,

is used. Single-agent developer means a developer bath containing a single developing agent; a two-agent developer means a developer bath containing two developing agents, etc. A mono-bath developer means a developer consisting of a single developing bath; a dual-bath developer means a developer consisting of two developing baths, etc.

The preference for a two-agent developer of the type specified is emphasized in the case of a film which is classified in the art as a slow developing film. In developing this type film, a two-agent developer is aided by increasing solution pH to increase developing rate.

In the unexposed areas during development, it is believed that the silver halide migrates to or near the surface of the film as a complex ion. The nucleating agents, having permeated the surface region, catalyze the reduction of the silver halide complex to metallic silver in the presence of the developing agent.

The following examples illustrate this invention but are not intended to limit it in any way.

EXAMPLE I The first developer solution, Solution A, of a dualbath developer was prepared as follows:

Water ml 800 l-phenyl-3-pyrazolidone (reagent grade) gm 0.25 Ascorbic acid (reagent grade) gm 2.5 Potassium carbonate (anhydrous) gm 5 Sodium hydroxide grams dissolved in sufiicient water to make up 100 ml. of solution) ml 5 Water to make up to 1000 ml.

The method developer solution, Solution B, was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm 120 Hydroquinone (anhydrous) gm 4 1-phenyl-3-pyrazolidone (reagent grade) gm 0.25 Boric acid (H BO (crystals) gm 5.5 Sodium hydroxide (10 grams dissolved in sufiicient water to make up to 100 ml. of solution) ml 180 Sodium sulfide (1 gram dissolved in sufficient water to make up 100 ml. of solution) ml 8 S-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved in sufficient ethanol and water, in equal portions, to make up 100 ml. of solution) ml Potassium thiocyanate (anhydrous) gm Water to make up to 1000 ml.

A photographic film of the lithographic type was exposed at a distance of 26 inches for seconds to a high intensity tungsten filament lamp (a No. 2 General Electric Photofiood lamp) operated at 13 volts, A.C. Exposure was to a line pattern having a uniform silver density of 1.4 which is intended to simulate a camera exposure. The film comprised a high contrast silver chlo ride-silver bromide emulsion, in which the silver salt contained mol percent silver bromide and 70 mol percent silver chloride, and which contained grams of gelatin per mole of silver halide, and a polyester base. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution B for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image (that is, a negative image) was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The measurement ohms per square is defined as one one-hundredth of the resistivity, in ohms, of a line 100 times longer than its width. The probes of a Weston Model 785 Industrial Circuit Tester were placed at each end of a line that was 100 squares long. The resistivity of the line was measured as 10 ohms.

This represents a surface resistivity of 0.1 ohm per square, thereby showing that this coating was capable of conducting an electrical current. A measurement of the background, i.e., exposed regions, showed that those regions had an electrical resistivity of greater than 3 10 ohms per square (the upper measurement limit of the meter used). A difference in resistivity of approximately 1 10 times between the conductive coating and the background regions will assure that there is no leakage of the electrical current into the background regions, or current passage between two separate and distinct conductive coatings. This essential difference is greatly exceeded by the final film element in this example.

EXAMPLE II The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution C, of a dual- Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then Washed with water for two minutes. The exposed film was immersed in Solution C for two minutes and then Washed with Water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive, while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE III The first developer solution, Solution A, of a dualbath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution D, of a dualbath developer was prepared as follows:

Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution D for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.5 ohm per square.

EXAMPLE IV The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution E, of a dualbath developer was prepared as follows:

Water ml 500 Sodium sulfite (anhydrous) gm 120 Hydroquinone (anhydrous) gm 48 l-phenyl-3-pyrazolidone gm 3 Boric acid (H BO (crystals) gm 5.5 Potassium thiocyanate (anhydrous) gm 160 S-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved in sufficient ethanol and water, in equal portions, to make up 100 ml. of solution) ml 30 Sodium sulfide (1 gram dissolved in sufficient water to make up 100 ml. of solution) ml 8 Sodium hydroxide (10 grams dissolved in sufiicient water to make up 100 ml. of solution) ml 180 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution E for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive, while in the exposed regions the gray silver image was nonconductive. The silvery electrically conductive surface image had a resistivity of 1 ohm per square.

EXAMPLE V The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution F, of a dualbath developer was prepared as follows:

Sodium sulfide (1 gram dissolved in sutficient water to make up 100 ml. of solution) ml 8 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution F for two minutes, and then washed with water for two minutes. Then film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were an electrically conductive image, While in the exposed regions the gray silver was nonconductive. The electrically conductive surface image had a resistivity of 2.5 ohms per square.

EXAMlPLE VI The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution G, of a dualbath developer was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm 8 1-phenyl-3-pyrazolidone gm 0.5 Boric acid (H BO (crystals) gm 5.5 Potassium thiocyanate (anhydrous) gm 32 S-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved in sufiicient ethanol and water, in equal portions, to make up 100 ml. of solution) ml 30 Sodium hydroxide (10 grams dissolved in suflicient water to make up 100 ml. of solution) ml Sodium sulfide (1 gram dissolved in sufiicient water to make up 100 ml. of solution) ml 0.4

Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film as immersed in Solution G for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive, while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.25 ohm per square.

EXAMPLE VII The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution H, of a dualbath developer was prepared using the method described in Example VI for preparing Solution G, except that 40 ml. of sodium sulfide solution were used in preparing Solution H.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution H for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 1.5 ohms per square.

EXAMPLE VIII The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution I, of a dualbath developer was prepared as follows:

-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved in sufficient ethanol and water, in equal portions, to make up 100 ml. of solution) ml 30 Sodium hydroxide grams dissolved in suflicient water to make up 100 ml. of solution) ml 180 Sodium sulfide (1 gram dissolved in sutficient water to make up 100 ml. of solution) ml 78 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution I for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.0 ohms per square.

EXAMPLE IX The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution J, of a dualbath developer was prepared using the method described in Example VI for preparing Solution G, except that none of the sodium sulfide solution was used in preparing Solution J.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution J for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive image had a resistivity of 0.8 ohm per square.

The other pieces of photographic film of the type described in Example I were exposed and developed as described above, except that the first piece of film was developed for 1 minute in Solution 1 and the second piece of film was developed for 4 minutes in Solution J. The electrically conductive surface image of the first piece and second piece had a resistivity of 3.5 and 0.25 ohm per square, respectively. In general, those high-energy developers containing a sulfide and a silver halide solvent have an optimum processing time of about two minutes.

Sample N o.

With a processing time of much over two minutes, the electrically conductive image starts to turn to silver sulfide, and, with a processing time much under two minutes, there is not suflicient time for the silver image to properly form. In either case, the result is lower conductivity than could be obtained. However, for a developer which does not have any sulfide as a starting constituent, that is, one using the silver halide solvent, a thiocyanate compound, as the nucleating agent, no such optimum processing time is found. In that case, the image conductivity increases with development time until it reaches some plateau, and any processing beyond this plateau time does not appear to decrease the conductivity.

EXAMPLE X A mono-bath developer, Solution I, was prepared using the method described in Example VI for preparing Solution G, except that no sodium sulfide solution was used in preparing Solution J.

Twelve pieces of photographic film of the lithographic type described in Example I were exposed as described in Example I. These pieces of exposed film were processed as follows:

Time of developm ent in Solution .1 (min) Time of predevelopment wash (min.)

Was a conductive image formed? ewermwrozocncnenoo wreww-zewmzeww-mw 1 Seconds.

These data show that a pro-development water wash for the exposed film will allow the formation of an electrically conductive image in the unexposed regions when a mono-bath developer containing high energy developers, among other constituents, is used.

EXAMPLE XI The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution K, of a dualbath developer was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm 133 Hydroquinone (anhydrous) gm 2.7 1-phenyl-3-pyrazolidone gm 0.17 Boric acid (H BO (crystals) gm 4 Sodium hydroxide (10 grams dissolved in suflicient water to make up ml. of solution) ml 45 Sodium sulfide (1 gram dissolved in sufiicient water to make up 100 ml. of solution) ml 5 Water to make up to 1000 ml. pH 2 11.5.

A photographic film was exposed as described in Example I. The film comprised a silver chloride emulsion, which contains 46.8 grams of gelatine per mole of silver chloride, that is overcoated with a clear, hardened gelatin layer, and a polyester base. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution K for six minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, posi tive coating which latter coating is electrically conductive. The surface areas of the film were measured for 9 electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The silvery electrically conductive surface image had a resistivity of ohms per square.

EXAMPLE XII The first developer solution, Solution A, of a dualbath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution L, of a dualbath developer was prepared as follows:

Water ml" 700 Sodium sulfite (anhydrous) grn 105 Hydroquinone (anhydrous) gm 4.0 1-phenyl-3-pyrazolidone gm 0.25 Potassium carbonate gm 22 Potassium thiocyanate (anhydrous) gm 30 Sodium sulfide 1 gram dissolved in sulficient water to make up 100 ml. of solution) ml 8 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution L for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE XIII The first developer solution, Solution A, of a dualbath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, solution M, of a dualbath developer was prepared as follows:

Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution M for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.15 ohm per square.

1 0 EXAMPLE XIV The first developer solution, Solution A, of a dualbath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution N, of a dualbath developer was prepared as follows:

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution N for two mintues and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 2.6 ohms per square.

EXAMPLE XV The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution 0, of a dualbath developer was prepared as follows:

Water ml 700 Sodium sulfite (anhydrous) gm 60 p-aminophenol gm 5 Glucose gm 20 Tri-sodium phosphate gm 1 Salicylic acid gm 0.5 Monomethylparaminophenol sulfate (reagent grade) gm 4 Potassium thiocyanate (anhydrous) gm 30 Sodium sulfide (1 gram dissolved in sufficient water to make up ml. of solution) ml 8 Sodium hydroxide (10 grams dissolved in suflicient water to make up 100 ml. of solution) ml 60 Water to make up to 1000 ml. pH=12.8.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution 0 for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.25 ohm per square.

EXAMPLE XVI The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution P, of a dualbath developer was prepared as follows:

Water ml 700 1-phenyl-4-methyl-3-pyrazolidone (reagent grade) gm 1 Ascorbic acid gm Potassium carbonate "gm Potassium thiocyanate (anhydrous) gm 50 Sodium sulfide (1 gram dissolved in sufiicient water to make up 100 ml. of solution) ml 8 Sodium hydroxide (10 grams dissolved in suificient water to make up 100 ml. of solution) ml 15 Water to make up to 1000 ml. pH: 10.4.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution P for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.4 ohm per square.

EXAMPLE XVII The first developer solution, Soluton A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developed solution, Solution Q, of a dualbath developer was prepared as follows:

5-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved in sufiicient ethanol and water, in equal portions, to make up 100 ml. of solution) ml Potassium thiocyanate (reagent grade) "gm 18 Thiourea (0.1 molar solution) ml 4 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution Q for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.5 ohms per square.

EXAMPLE XVIII The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution R, of a dualbath developer was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) "gm 40 sMonomethylparaminophenol sulfate (reagent grade) "gm 12 Hydroquinone (anhydrous) gm 20 Potassium carbonate (anhydrous) gm 20 Sodium hydroxide (10 grams dissolved in suflicient water to make up 100 ml. of solution) ml 120 5-nitrobenzimidazole nitrate (1 gram dissolved in sufiicient ethanol and water, in equal portions, to make up 100 ml. of solution) ml 10 Sodium selenide (0.1 molar solution) ml 8 Potassium thiocyanate (reagent grade) gm 10 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution R for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undevelo ed areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.5 ohms per square.

EXAMPLE XIX The first developer solution, Solution A, of a dualbath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution S, of a dualbath developer was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) "gm Monomethylparaminophenol sulfate (reagent grade) 2,4-diaminophenol (reagent grade) "gm 9.4

Boric acid (H BO (crystals) "gm 5.5

Sodium hydroxide (24 grams dissolved in sufiicient water to make up ml. of solution) ml 40 S-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved in sufiicient ethanol and water, in equal portions, to make up 100 ml. of solution) ml 80 Sodium sulfide (0.1 molar solution) ml 10 Potassium thiocyanate gm 30 Water to make up to 1000 ml.

A photographic film of the X-ray type was exposed as described in Example I. The film comprised a highspeed bromoiodide emulsion, in which the silver salt contained approximately 1.5 mole percent silver iodide and 98.5 mole percent silver bromide, and which contained 200 grams of gelatin per mole of silver halide, coated on both sides of a polyester base, and an antiabrasion layer over coated on each emulsion layer. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution S for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally underdeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface of the film was measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.5 ohms per square.

13 EXAMPLE xx The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution T, of a dualbath developer was prepared as follows:

S-nitrobenzimidazole nitrate (1 gram dissolved in suflicient ethanol and water, in equal portions, to

make up 100 ml. of solution) ml 40 Sodium sulfide (0.1 molar solution) ml Potassium thiocyanate (anhydrous) gm 30 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution T for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.5 ohms per square. a

EXAMPLE XXI The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution B, of a dualbath developer was prepared using the method described in Example I for preparing Solution B.

A photographic film of the lithographic type was exposed as described in Example I. The film comprised a high contrast silver chloride-silver bromide ortho chro-' matically sensitized emulsion, in which the silver salt contained 20 mole percent silver bromide and 80 mole percent silver chloride, and which contained 110 grams of gelatin per mole of silver halide, overcoated with a clear hardened gelatin layer, containing silica particles, and a polyester base coated with a dyed gelatin-NH backing. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution B for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 1.0 ohm per square.

EXAMPLE XXII The first developer solution, Solution A, of a dualbath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution B, of a dualbath developer was prepared using the method described in Example I for preparing Solution B.

A photographic film of the lithographic type as described in Example I was exposed in a camera through the base of the film so that there was lateral image reversal. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution B for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE XXIII The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution B, of a dualbath developer was prepared using the method described in Example I for preparing Solution B.

A photographic film of the lithographic type as described in Example I was exposed by the contact exposure method. The contact exposure was made to a negative having a density greater than four. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution B for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray, silver image was nonconductive. The electrically conductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE XXIV The first developer solution, Solution V, of a dual-bath developer was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm 16 Boric acid (H BO (crystals) gm 5.5

The second developer solution, Solution 13, of a dualbath developer was prepared using the method described in Example I for preparing Solution B.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution V for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution B for two minutes and washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a. continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had resistivity of 0.5 ohm per square.

EXAMPLE XXV A mono-bath developer, Solution Y, was prepared using the method described in Example I for preparing 15 Solution B, except that 45 grams of potassium thiocyanate (instead of 30 grams) were used in preparing Solution Y.

Two pieces of photographic film of the X-ray type as described in Example XIX were exposed as described in Example I. The first exposed piece of film was immersed in Solution Y for two minutes and then washed with water for two minutes. The second exposed piece of film was immersed in Solution Y for four minutes and then washed with water for two minutes. Both pieces were dried at room temperature. A developed image was obtained in each piece with the normally undeveloped areas having a continuous, silver metal, positive coating which is electrically conductive. The surface areas of the pieces of film were measured for electrical conductivity. The unexposed regions were electrically conductive, while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image of the first piece of film had a resistivity of ohms per square and the second piece had a resistivity of 4.5 ohms per square.

EXAMPLE XXVI A mono-bath developer, Solution Z, was prepared as Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solutio Z for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 2.0 ohms per square.

EXAMPLE XXV II A mono-bath developer, Solution Z, was prepared using the method described in Example XXVI for preparing Solution Z.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was washed in water for five minutes, immersed in Solution Z for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the black silver image was nonconductive. The electrically conductive Surface image had a resistivity of 0.4 ohm per square.

l a EXAMPLE xxvrn The first developer solution, Solution AA, of a dualbath developer was prepared as follows:

Water ml 800 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm 16 1-phenyl-4-methyl-3-pyrazolidone gm 1 Boric acid (H BO (crystals) ml 5.5 Sodium hydroxide (24 grams dissolved in sufficient water to make up ml. of solution) ml 100 S-nitrobenzimidazole nitrate (1 gram dissolved in sufficient ethanol and water, in equal portions, to make up 100 ml. of solution) ml 8 Water to make up to 1000 ml.

The second developer solution, Solution Z, of a dualbath developer was prepared using the method described in Example XXVI for preparing Solution Z.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution AA for two minutes, and then washed with water for five minutes. The exposed film was immersed in Solution Z for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating with latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 5 ohms per square.

EXAMPLE XXIX The first developer solution, Solution BB, of a dualbath developer was prepared as follows:

Water ml 600 Hydroquinone (anhydrous) gm 9 Sodium sulfite (anhydrous) gm 50.2 Potassium carbonate gm 50.2 Potassium bromide gm 4.5 Monomethylparaminophenol sulfate gm 3 Water to make up to 1000 ml.

The second developer solution, Solution Z, of a dualbath developer was prepared using the method described in Example XXVI for preparing Solution Z.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution BB for two minutes and then washed with water for five minutes. The exposed film was immersed in Solution Z for two minutes and then washed with water for two min utes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive, while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 1 ohm per square.

EXAMPLE XXX The first developer solution, Solution CC, of a dual-bath developer was prepared as follows:

Water to make up to 1000 ml.

17 The second developer solution, Solution DD, of a dualbath developer was prepared as follows:

Water ml 500 Sodium sulfite (anhydrous) gm 130 Hydroquinone (anhydrous) gm 3.2 3-phenyl-2-pyrazolidone gm 0.2 Sodium hydroxide grams in sufiicient water to make up 100 ml. of solution) ml 95 Boric acid (H BO (crystals) gm 4.4 Sodium sulfide (0.1 molar solution) ml 8 S-nitrobenzimidazole nitrate (1 gram dissolved in sufficient water and ethanol, in equal portions, to

make up 100 ml. of solution) ml 65 Water to make up to 1000 ml.

A photographic film of the lithographic type was exposed as described in Example I. The film comprised a high contrast, silver chloride-silver bromide, orthochromatically sensitized emulsion, in which the silver salt contained 30 mole percent silver bromide and 70 mole percent silver chloride, which contained 67 grams of gelatin and 22 grams of polyethylacrylate latex per mole of silver halide, and which is overcoated with a clear hardened gelatin layer, containing silica particles, and a base coated with a dyed gelatin-NH backing. The exposed film was immersed in Solution CC for one minute and then with water for ten minutes. The exposed film was immersed in Solution DD for four minutes and then washed with water for five minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical con ductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.5 ohms per square.

EXAMPLE XXXI The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution EE, of a dualbath developer was prepared using the method described in Example I for preparing Solution B, except that barium sulfide solution was used in place of sodium sulfide solution in preparing Solution BE.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film Was immersed in Solution EE for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image was nonconductive. The electrically conductive surface image had a resistivity of 4.5 ohm per square.

EXAMPLE XXXII The first developer solution, Solution A, of a dual-bath developer was prepared using the method described in Example I for preparing Solution A.

The second developer solution, Solution FF was prepared as follows:

Water ml 400 Sodium sulfite (anhydrous) gm 120 Hydroquinone (anhydrous) gm 4 1-pheny1-3-pyrazolidone (reagent grade) gm 0.25 Boric acid (H BO (crystals) gm 5.5

Sodium hydroxide (10 grams dissolved in sufiicient Hydrogen sulfide was bubbled through Solution FF for 15 minutes at the rate of 2 liters per minute. Water was added to Solution FF to make up one liter of solution.

A photographic film of the lithographic type as described in Example I was exposed as described in Example I. The exposed film was immersed in Solution A for two minutes and then washed with water for two minutes. The exposed film was immersed in Solution FF for two minutes and then washed with water for two minutes. The film was dried at room temperature. A developed image was obtained with the normally undeveloped areas having a continuous, silver metal, positive coating which latter coating is electrically conductive. The surface areas of the film were measured for electrical conductivity. The unexposed regions of the film were electrically conductive while in the exposed regions the gray silver image Was nonconductive. The silvery electrically conductive surface image had a resistivity of 4.5 ohms per square. This example helps demonstrate the broad principle that any compound (or compounds) that decomposes to the sulfide ion, or is a soluble sulfide, will behave as the necessary nucleating agent in this novel process. It may be said that the same statement applies in the case of selenides.

In this invention the silver halide emulsion layer is preferably overcoated with the transparent receptive layer of gelatin which may also act as an antiabrasion layer. It is this layer that the nucleating agents, complex silver ions, and developer interact within to form the electrically conductive silver. This layer must be a hard, nonremovable, water permeable layer which is uncleated after exposure and during development. Any silica, or similar materal, in this layer may improve the process results, but it is not essential. When the nucleating agent is applied prior to exposure over an emulsion layer without an antiabrasion layer, or in, or on the antiabrasion layer, the resultant electrically conductive image is often of poor quality.

The water-soluble nucleating agent must be capable of diffusing through an oleophobic, water-permeable binder. Examples of this type of nucleating agent are sodium and potassium sulfides, sodium and potassium selenides, sodium and potassium thiocyanates, thiourea and barium sulfide. Also, the water-soluble sulfide or selenide can be produced in the developer itself in a variety of ways of which Example XXXV is an illustration. The concentration of the nucleating agent in the developer solution varies with the type of developer and with the type of film used. The operable concentrations are readily determined in each case by relatively simple laboratory techniques; optimum concentrations are determined in the same manner.

The silver halide solvent can be a thiosulfate or a thiocyanate compound.

In general development time is important. If development time is too short, the electrical conductivity of the image will be too low; if development time is too long, the image will lose electrical conductivity. This occurs because too short a development time does not allow enough metallic silver to form, and excessive development time allows the metallic silver to react with sulfide ions to form nonconductive silver sulfide. The optimum time,

agent, silver halide solvent, and developing agent.

Any nonfogging developer can be used to develop the negative image, but ascorbic acid or litho developers are the most desirable because of their low sulfite ion concentration.

A high-energy developer must be used in developing the unexposed regions to obtain the electrically conductive silver surface images.

Monomethylparaminophenol sulfate, 2,4-diaminophenol/hydroquinone, p-aminophenol, p-aminophenol/monomethylparaminophenol sulfate, hydroquinone/monomethylparaminophenol sulfate, and hydroquinone are singleand double-agent high-energy developers which give good results in developing the unexposed regions to obtain the electrically conductive images. If a monomethylparaminophenol sulfate or hydroquinone system is used, the pH should be greater than 11.75.

The following compounds are representative of 3-pyrazolidone silver halide developing agents which are useful in the developer compositions of this invention which are used to obtain electrically conductive silver surface images.

1-phenyl-3-pyrazolidone l-p-tolyl-3-pyrazolidone 5-phenyl-3-pyrazolidone 5-methyl-3-pyrazolidone 1-p-chlorophenyl-3-pyrazolidone l-phenyl-5-phenyl-3-pyrazolidone l-m-tolyl-3-pyrazolidone 1-phenyl-S-methyl-3-pyrazolidone l-p-tolyl-5-phenyl-3-pyrazolidone l-m-tolyl-3-pyrazolidone 1-p-methoxyphenyl-3-pyrazolidone l-acetamidophenyl-3-pyrazolidone 1-phenyl-2-acetyl-4,4-dimethyl-3-pyrazolidone l-phenyl-4,4-dimethyl-3-pyrazolidone 1-m-aminophenyl-4-methyl-4-propyl-3-pyrazolidone 1-o-chlorophenyl-4-methyl-4-ethyl-3-pyrazolidone (17) l-m-acetamidophenyl-4,4-diethyl-3-pyrazolidone 1 8 1- (p-B-hydroxyethylphenyl) -4-dimethyl-3- pyrazolidone (19) 1-p-hydroxyphenyl-4,4-dimethyl-3-pyrazolidone (20) 1-p-methoxyphenyl-4,4-diethyl-3-pyrazolid0ne (21) 1-p-tolyl-4,4-dimethyl-3-pyrazolidone pyrazolidone (23) .l-p-diphenyl-4,4-dimethyl-3-pyrazolidone (24) 1-(p-fi-hydroxyethylphenyl)-3-pyrazolidone (25) l-o-tolyl-3-pyrazolidone (26) 1-o-tolyl-4,4-dimethyl-3-pyrazolidone (27) l-phenyl-4-methyl-3-pyrazolidone Examples of two and three component high-energy developers, containing at least one 3-pyrazolidone agent, which are used in obtaining electrically conductive images, are 1-phenyl-3-pyrazolidone/N-methyl 2 pyrazolidone/ hydroquinone, hydroquinone/ l-phenyl 3 pyrazolidone, ascorbic acid/l-phenyl-3-pyrazolidone, ascorbic acid/lphenyl 4 methyl-3-pyrazolidone, and hydroquinone/ 1- phenyl-4-methyl-3-pyrazolidone.

Normally an electrically conductive silver surface image is obtained when a two-agent developer is used for either the first, second, or both baths of a dual-bath developer, and the second bath contains a nucleating agent and a silver halide solvent. The most preferred embodiment of a two-agent developer is shown in Example I.

In general, three variables, i.e., sulfide concentration, sulfite concentration, and silver halide solvent/developer concentration, must be optimized to obtain the best product.

An electrically conductive silver surface image can be formed without an added sulfide, thiourea or similar compound. To accomplish this, monoor dual-bath development is carried out using a high-energy developer containing a thiocyanate compound which can act both as a nucleating agent and silver halide solvent. Other silver halide solvents, eg. sodium thio u fi and/or nucleating agents may be used with the thiocyanate compound.

Another mode of this invention involves a mono-bath developer with a silver halide solvent, e.g., thiocyanate, but no sulfide or selenide compound. Not all high-energy developers or films are operable using this mode, which comprises a pre-development water soak followed by a mono-bath development to form the electrically conductive silver surface image. This mode is represented by Example X. All developers, having thiocyanate as a component, also have 8 present because of aerial oxidation of the thiocyanate.

Still another mode of this invention is represented by Examples XXVI and XXVII. A nucleating agent and silver halide solvent were present in the mono-bath developer used in both of the above examples. In Example XXVII a pre-development water soak was used, and the resistance of the positive image was reduced by a factor of five over the positive image of Example XXVI.

The same or different developing agents may be used in each bath of a dual-bath developer. When a dual-bath developer is used, the nucleating agent and the silver halide solvent are normally placed in the second bath. The above restriction also applies when a single-agent developer is used in the first bath, and a two-agent developer in the second bath. A two-agent developer, which gives a conventional negative silver image, when used as the first bath for a two-bath developer, may also be used for sec- 0nd bath by adding a nucleating agent and silver halide solvent. If a single-agent developer is used first, it also may 'be used in the second bath with another appropriate developing agent, silver halide solvent and nucleating agent. The foregoing discussion of mono-bath and dualbath developers is in no way an all inclusive listing of possible developer combinations and was not meant to exclude operative combinations which were not specifically mentioned.

The film preferably, should be sufficiently transparent so that it can be exposed with radiant energy from the front or back. But a film does not have to be transparent, since it can be exposed from the front and developed to give good electrically conductive, surface silver images. A preferred method of film exposure is in a camera through the base so that there is lateral image reversal.

The oleophobic organic colloid of the silver halide emulsion layer used in this invention may be gelatin, or, in place of gelatin, other natural or synthetic oleophobic colloidal binding agents. Such agents include water-permeable or water-soluble polyvinyl alcohol and its derivatives, e.g., partially hydrolyzed polyvinyl acetates, polyvinyl ethers, and acetals containing a large number of extralinear CH CHOH groups; hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compounds such as maleic anhydride, acrylic and methacrylic acid ethyl esters and styrene. Suitable colloids of the last mentioned type are disclosed in U.S. Patents Nos. 2,276,322, 2,276,323 and 2,347,811. The useful polyvinyl acetals include polyvinyl acetal aldehyde acetal, polyvinyl butyraldehyde acetal and polyvinyl sodium 0- sulfobenzaldehyde acetal. Other useful colloidal binding agents include poly-n-vinyllactams of Bolton, U.S. Patent No. 2,495,918, the olephobic copolymers of N- acrylamido alkyl betaines described in Shacklett, U.S. Patent No. 2,833,050, oleophobic cellulose ethers and esters, colloidal albumin, zein and polyacrylamide.

Similarly, silver halide emulsion may be selected from well-known emulsions containing silver chloride, silver bromide and silver iodide, or mixtures thereof, as well as containing optical and chemical sensitizing agents, fogstabilizing compounds, emulsion hardeners, plasticizing compounds, wetting agents, toners and matting agents.

The film support for the emulsion layers used in the novel process may be any suitable transparent plastic. For example, the cellulosic supports, e.g., cellulose acetate, cellulose triacetate, cellulose mixed esters, etc. may

21 be used. Polymerized vinyl compounds, e.g., copolymerized vinyl acetate and vinyl chloride, polystyrene and polymerized acrylates may also be mentioned. The film formed from the polyesterification product of a dicarboxylic acid and a dihydric alcohol made according to the teachings of Alles, U.S. Patent No. 2,779,684, and the patents referred to in the specification of that patent. Other suitable supports are the polyethylene terephthalate/isophthalates of British Patent No. 766,290 and Canadian Patent No. 562,672 and those obtainable by condensing terephthalic acid and dimethyl terephthalate with propylene glycol, diethylene glycol, tetramethylene glycol or cyclohexane 1,4-dirnethanol (hexahydro-p-xylene alcohol). The films of Bauer et al., U.S. Patent No. 3,052,543, may also be used. The above polyester films are particularly suitable because of their dimensional stability.

Paper is another example of a suitable support if the paper is coated with a water resisting and oleopho'bic layer, for example, with a hardened gelatin layer or superficially saponified cellulose acetate. Matting agents,-such as, titanium dioxide, silicon dioxide, barium sulfate, in varying quantities, may be incorporated into such layers. It is also possible to use plates consisting of metals, alloys or metal oxides coated metal as the support.

Besides immersing the film in the developer solution, other methods of applying the solutions can be used such as dip roll, hopper, spray and the like so that a sufficient amount of solution is applied to the surface. It is probable that a highly viscous developer could be placed on the emulsion to provide semi-dry processing.

After development, the film may be dried by any convenient method. If an oven, hot air, or some similar mode is used for drying, care should be taken not to allow the film to reach an excessive temperature that will damage the film, cause the silver image to peel off, etc.

Inverse transfer development is also called silver transfer development and solution physical development.

This method of making electrically conductive silver surface images has several advantages which include (i) high electrical conductivity in the silver image regions, (ii) high electrical resistivity in the background regions, (iii) few circuit breaks in the silver image, even in very narrow circuit-type lines, (iv) rapid and easy processing, and (v) readily available developer components. An advantage of this system is that an electrical circuit pattern for testing may be obtained with the speed of a photographic system. This invention may be used to make a circuit board or may be used to allow the rapid check of the electrical continuity of a circuit board design. The resultant elements of this process can be used whenever electrical conductive images are desired. Additional advantages of the invention reside in the fact that the elements containing electrically conductive surface images of high conductivity can be made in simple, rapid and effective manners that are convenient and versatile.

I claim: 1. A process which comprises (a) forming a latent developable silver halide image in a photographic element having a single developable, water-permeable, macromolecular organic colloid-silver halide emulsion layer, by irnagewise exposure of said layer to actinic radiation, washing the emulsion layer with water, and (b) forming by silver transfer development an electrically conductive silver surface image having a resistance not more than 5.0 ohms per square in the unexposed areas of an outer water-permeable organic colloid layer of said photographic film element, and a difference in resistivity of at least 1X10 times between the conductive coating and the exposed regions by immersion in developing solution containing a silver halide reducing agent, a nucleating agent, and a silver halide solvent, and (c) passingan electrical current or impulse through 22 the said electrically conductive silver surface image for utilization.

2. A process according to claim 1 wherein the outer water-permeable organic colloid layer is the said silver halide emulsion layer.

3. A process according to claim 2 wherein the organic colloid of the outer water permeable organic colloid is gelatin.

4. A process according to the claim 3 wherein the silver halide of the silver halide emulsion layer is silver chlorobromide.

5. A process according to claim 1 wherein the outer water-permeable organic colloid layer is a thin waterpermeable organic colloid layer free from radiation-sensitive silver salts that is contiguous with the silver halide emulsion layer.

6. A process according to claim 1 wherein the outer water-permeable organic colloid layer is a thin gelatin layer contiguous with the silver halide emulsion layer which comprises gelatin.

7. A process according to claim 1 wherein said transfer development is carried out in a single high-energy, silver halide aqueous developer solution containing a 1-aryl-3-pyrazolidone developing agent, sodium or potassium thiosulfate or thiocyanate and sodium or potassium sulfide.

8. A process according to claim 1 wherein said surface image constitutes a printed electrical surface image.

9. A process which comprises (a) forming a latent developable silver halide image in a photographic element having a single developable, water-permeable, macromolecular organic colloidsilver halide emulsion layer, by imagewise exposure of said layer by actinic radiation, and

(b) forming by silver transfer development an electrically conductive silver surface image having a resistance not more than 5.0 ohms per square in the unexposed areas of an outer water-permeable organic colloid layer of said photographic film element, and a difference in resistivity of at least 1 l0 times between the conductive coating and the exposed regions by (l) immersion in a first developer solution containing a silver halide reducing agent, (2) washing the emulsion layer with Water, and (3) immersion in a second developer solution containing a nucleating agent and a silver halide solvent,

(c) passing an electrical current or impulse through the said electrically conductive silver surface image for utilization.

References Cited UNITED STATES PATENTS 2,533,463 12/1950 Ives 96-64 2,612,450 9/1952 Land 96-76 XR 2,751,300 6/1956 James et 31.

2,843,485 7/1958 YutZy et a1 96-76 2,854,386 9/1958 Lyman et al 204-15 3,021,212 2/1962 King 96-64 XR 3,033,765 5/1962 King et a1.

3,155,507 11/1964 Blake 96-64 3,223,525 12/1965 Jonker et a1 96-36.2

OTHER REFERENCES Haist, G. M., et al., Organic Silver-Complexing Agents for Photographic Monobaths, Photographic Science and Engineering, vol. 5, No. 4, July-August 1961, pp. 198203.

Sasai, A., et al., Studies on Photographic Monobaths Containing Potassium Thiocyanate, Photo. Sci. and Eng, vol. 8, No. 5, September-October 1964, pp. 270-275.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner U.S. Cl. X.R.

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Referenced by
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US3649270 *May 21, 1969Mar 14, 1972Du PontNegative image silver transfer development
US3720515 *Oct 20, 1971Mar 13, 1973Trw IncMicroelectronic circuit production
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US3929483 *Jan 18, 1974Dec 30, 1975Horizons IncMetal-plated images formed by bleaching silver images with alkali metal hypochlorite prior to metal plating
US4192640 *Aug 17, 1977Mar 11, 1980Winter Park AssociatesMultiple transfer process and article resulting therefrom
US4269917 *Jul 14, 1980May 26, 1981Drexler Technology CorporationSupported colloid matrix having depth-wise gradient of silver particle concentration; laser recording; direct reading after write
US4278756 *Jul 6, 1979Jul 14, 1981Drexler Technology CorporationReflective data storage medium made by silver diffusion transfer
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US4312938 *Oct 17, 1980Jan 26, 1982Drexler Technology CorporationLayer of reflective, non-filamentary silver particles over silver filaments; photography
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Classifications
U.S. Classification430/311
International ClassificationG03C8/02, G03C8/06, H05K3/10
Cooperative ClassificationG03C8/06, H05K3/106
European ClassificationH05K3/10D2, G03C8/06