DE608171C - Process for the preparation of light-sensitive photographic layers - Google Patents

Description

The invention relates to a novel photographic Fositiwerfahren, at the black material can be bleached under the action of light. It is known that cobalt salts under certain conditions for the production of photosensitive. Layers can be used, however, in these cases it is under the action of light causes blackening or darkening of the light-sensitive Layer achieved.

According to the invention it has now been found that certain heavy metal sulphides of brown or black color are oxidized to a white material, presumably with conversion into the corresponding sulphates under the influence of light in the presence of certain salts. These salts are essentially the trivalent cobalt salts. They cause the metal sulfides to oxidize through a photochemical reaction initiated by light. Among the salts that carry out this oxidation, the hexamine-cobalt chloride (Co (NH ₃ ) s Cl ₃ ), the nitrosopentamine-cobalt chloride (Go (NHg) ₅ NO) Cl ₂ and the trinitro-triamine Cobalt chloride (Go (NHj) ₃ (NO ₂ ) ₃ ) found.

As metal sulfides that are used for the new process can be used, come mainly lead, copper, bismuth, nickel., Mercury and silver sulfides in question, all of which are dark in color. The Kahaltsalza are added to the layers containing these sulphides or are placed on top of them in a layer.

The reaction in these cases is, as mentioned, "photochemical in nature. It is after." the method according to the invention possible, on a layer, which one of the mentioned Metal sulphides and one of these cobalt salts contains, on exposure to light, a white pattern versus a black one Background ', with the white areas being the areas with the strongest lighting effect correspond.

This effect was made the subject of a new practical copying method,

The following is an example of the practice of the invention.

Lead sulfide is suspended in gelatin according to the following formula:

Solution a

Lead acetate 10 g,

Gelatin 20 g,

Sodium sulfide 100 ecm.

After this solution of gelatin and lead acetate is made, the following solution becomes added:

Solution b

Sodium sulfide ίο g,

Gelatin, 20 g,

Water 100 ecm.

After the solution B is added to the solution A. the whole solution is allowed to settle. It is then noodled and washed and melted again in exactly the same way as the ordinary ones photographic emulsions is the case. This mixture is then on 'one Base, for example paper, in the usual way in a layer that is as thin as possible applied. After the layer has dried, the following solution is applied to its surface applied:

Solution C

Hexamine ^ cobalt chloride, saturated solution at room temperature, citric acid ... 5 S j ' ^e liter, glycerine 3 g per liter.

When this second coating has dried, the paper is ready to be copied. It will exposed to a photograph, for example a negative under bright light until the image becomes visible. At the places where the light could act on the dark colored lead sulfide, this is faded. If you consider the exposure complete, you can fix the image by washing thoroughly. Washing removes any remaining Cobalt four-bond removed, after which the layer will lose its photosensitivity loses.

Instead of the method given here, the method by mixing solutions A and B the lead sulfide emulsion prepared, the cobalt compound is added directly, and to do this it is only. necessary, the mixed emulsion A and B Add an equal volume of solution C. The finished emulsion, which already contains cobalt salt, is then poured and is then ready to be copied as described.

In order to carry out the procedure, it is of course necessary to have enough Add amount of cobalt so that all lead sulfide can be converted into lead sulfate. Otherwise you wouldn't be pure Achieve whiteness in the copy.

Any of the metal sulfides mentioned herein can be used in place of the lead sulfide will. The amount of sulfide used in the emulsion can be varied will. The limits are determined by practical considerations. The coating should of course have sufficient coverage ", to ensure a suitable copy. Furthermore, of course, the coating must not be like this be thick or contain so much sulfide that the quantity of cobalt salt that is available is not sufficient to bleach or oxidize the sulfide. The described Metal sulfides are precipitated from their appropriate salts of metals, by processes that are sometimes somewhat are different from the one given above, but which are known per se.

The copying process described here requires the presence of very little Amount of moisture to give satisfactory results. For this reason there is a little in solution C. Glycerin indicated. This amount of glycerine can be omitted if the paper is moistened in another way before drying. -You can take the place of the glycerine also, use other hygroscopic substances if they are not harmful to the layer influence. The examples given are to be assessed as such, without being affected by the invention deviate, numerous equivalents are still possible.

Claims (7)

Patent claims: ι. Method of manufacturing photosensitive Photographic layers, characterized in that a a layer containing heavy metal sulfide and a trivalent cobalt salt are applied will. 2. The method according to claim 1, characterized in that on the layer support one is a heavy metal sulfide from the group of lead, copper, bismuth, mercury, nickel and silver sulfides containing layer applied and over this layer, a second, a light-sensitive, layer containing oxidizing trivalent cobalt salt is poured on. 3: The method according to claim 1, characterized in that the trivalent cobalt salt is added to the layer containing the heavy metal sulfide. 4. The method according to claim 1 to 3, characterized by the use of trivalent cobalt salts such as hexamine cobalt chloride, nitrosopentamine cobalt chloride and trinitro triamine cobalt chloride. 5. Process for producing photographic positives by bleaching a dark colored layer using the method of claims 1 to 4, characterized in that, on ■ a suitable layer support with a dark colored. Layer that is a heavy metal sulfide and a photosensitive, oxidizing, trivalent carbon salt contains, copied any transparent picture template and the The layer containing the image is fixed by simply washing. 6. The method according to claim 5, "characterized by the presence of nygroscopic Substances in the splint. 7. The method according to claim S, characterized in that it is ensured that that during the copying process in the dark colored layer moisture in is present to a small extent.