DE850383C - Process for the production of a direct positive image in a silver halide emulsion - Google Patents

Description

(WiGBL p. 17S)

ISSUED SEPTEMBER 25, 1952

E 2752 IVa / 57 b

The invention relates to photography and, more particularly, to a method of manufacture direct positive photographs.

Direct positive effects can be achieved by solarizing the developable latent image by means of Overexposure by a second exposure to achieve the Sabattier or Clayden effect or by second developing a developed negative image. Solarizable, sensitized emulsions require a very strong exposure to get the desired direct positive Obtain photography. The application of a second exposure has from the point of view practical technology from obvious disadvantages.

The second development requires at least two additional operations to the usual one and normal development procedures.

It is therefore the object of the present invention to provide a new method of production to develop direct positive photographs, a process that does not involve solarization, still requires a second exposure, still a second development. This is supposed to have the disadvantages the known method can be avoided. Another goal is to create a process Find direct positive photographs that do not have unusually high intensity and exposure also does not require a second exposure. Other

Features emerge from the following description of the invention.

The object is achieved by using a suitable silver halide emulsion layer, preferably an inner grain latent image emulsion, exposed in the usual manner and with a photographic Developer capable of forming an air curtain.

The drawing shows a sensitometric curve that has been obtained according to the invention.

The photographic emulsion used in the method of the present invention is one Gelatin-silver halide emulsion, e.g. B. a SiI berbromid emulsion, a silver bromoiodide emulsion or a silver chloroiodide emulsion. she does not need to contain any optically sensitizing dyes, although you do have certain sensitizing ones Dyes can be added to form air curtains, as detailed below ao is described. The emulsion should be unripened, or if it is ripened, the ripening should be without the use of a sulfur sensitizer. An emulsion of this type is as Burton emulsion known emulsion, described in Wall, "Photographic Emulsions", 1929, p. 52 and 53. The Burton emulsion is prepared as follows:

A. Silver nitrate 100 g

Water 500 ecm

Ammonia to clear

Form solution

B. Potassium bromide 80 g

Potassium iodide 50 g

Soft gelatin 20 g

Water 1000 ecm

C. Dry gelatin 250 g

B is heated to 70 ⁰ C. A is added in the cold state B with constant shaking, digested for 20 Miimiten at 50 ⁰ C and then allowed to slow cool. C is added after the gelatin has been swollen in water for 20 minutes, then drained and melted. The emulsion is then allowed to solidify and then washed.

An internal grain image latent emulsion; H. an emulsion that has the latent image mainly within of the silver halide grains, as on pages 296 and 297 in The Theory of the Photographic Process "described by Mees, 1942, is special for the process according to the invention useful.

Most of the internal grain image latent emulsions are silver bromoiodide emulsions with a high Iodide content, d. H. preferably with at least 10 to 20% iodide. The Burton emulsion is one Emulsion of this type because it has a silver iodide content of approximately 40% of the silver halide content Has. However, it is not absolutely necessary for the emulsion to contain silver iodide.

A latent grain image emulsion made in the manner described by D a ν e y and K η ο 11 can also be used in accordance with the present invention. This emulsion is prepared, irtdem first in the absence of ammonia in one or more sections Silver salt grains are formed, which at least partially consist of a silver salt, the better is water soluble as silver bromide. Then the grains are in silver bromide or silver bromoiodide converted, and if the silver iodide content of the emulsion is less than 6%, calculated on total silver halide content, the grains are treated with an iodine compound to reduce the content to bring silver iodide to at least 6%. Then, ideally in the absence of ammonia, mature, and then either some of the soluble salts are washed out or all of them become soluble Washed out salts, whereupon soluble salts such as soluble chloride or bromide are added will. An example of an emulsion made in this way is the following:

Solution ι

Inert gelatin 20 g

KCl .. ". 20g

Water 560 ecm

Solution 2

KCl 100 g

Water 520 ecm

Solution 3

AgNO ₃ 195g

Water 520 ecm

Solution 4

KBr 160 g

KJ 40 g

Water 500 ecm

40 ⁰ C

45 ° C

45 ⁰ C

45 ° C

The solutions 2 and 3 are poured into a vessel at the same time as the solution, within 90 seconds. The whole is then left to ripen at 45 ° C. for a minute. The solution 4 is then added, and the mixture is then left to ^{ripen at 45 °} C. for 20 minutes. Then 235 g of inert gelatin (dry) are added. It is then left to ^{ripen at 45 °} C. for a further 15 minutes. During this time the gelatin dissolves. The emulsion is then allowed to solidify, cut into strips and washed until it is free of all soluble bromide, and then about 150 ecm of a 10% by weight KCl solution is added, and then enough water until there is a total of 3V21.

A latent type of inner grain image of a silver halide emulsion can be described as one which, when a test _{portion is exposed under an intensity scale for a set time between V 10} and ι seconds, and then developed at 20 ⁰ C for 4 minutes in the usual surface developer (Example 1) is, gives a maximum density which is not greater than ₅ V, the maximum density is obtained when the same emulsion exposed in the same manner and corresponds long in an internal grain developers (example 2) at 20 ⁰ C and 3 minutes

is wrapped. Preferably, the maximum density achieved with the surface developer is no greater than V ₁₀ the maximum density achieved when the same emulsion is developed in the internal grain developer. Conversely, an internal grain image latent emulsion, when developed in an internal grain developer (Example 2), exhibits a maximum density of at least five times and preferably at least ten times the maximum density achieved when the same emulsion is exposed in the same way and in a surface developer (Example 1).

The developer used in accordance with the invention should be one which produces an oxidation haze or an air haze. Such Developers were by D u η d ο η and Crab tree in "American Photography" 1924, Vol. 18, p. 742. An example of such a developer is a hydroquinone developer, which contains little or no Sulnt and is described in Example 3.

The new method is based on producing a haze in the unexposed areas the emulsion and the inhibition of development in the exposed areas. With the before described emulsions and happens with the developers mentioned in the previous section this in the following way: The emulsion is exposed in the usual way and in the dei Developed so that an air curtain is formed. The unexposed silver halide grains are thereby perfect and veiled; at the same time, the development in the areas that the contain latent images, so dammed that a very low density in the areas of greatest exposure is achieved. The inhibition of obfuscation in the areas containing a latent image is exactly proportional to the exposure. The lowest density is achieved in the area of greatest exposure. This gave a reflection density of 0.02 on paper in the area of greatest exposure and a fog density of more than 1.5 was measured in the unexposed areas. The air curtain according to the invention is achieved in various ways and can be through use be accelerated or strengthened by various means. Applied developer should preferably have a low sulfite content and contain no silver halide solvent, the (as a silver halide solvent) is stronger than sulfite. As said above, a hydroquinone developer is which has a low sulphite concentration, particularly suitable for creating air curtains. A developer of this type is described in more detail in Example 3. The air curtain can be reinforced by blowing air forcefully through the developer in such a way that the air often in contact with the emulsion surface of the photograph during development comes. Certain chemical agents, such as copper sulfate, either in the developer or in the emulsion self-injected can be used to create air curtains or to enhance formation. Hydrogen peroxide or certain dyes, such as methylene blue, also increase the Air curtain.

In addition to using a developer solution that creates an air curtain, the emulsion can be made more receptive to the air curtain by adding certain dyes. Some Sensitizers such as 3,3'-diethyl-c) -methyl-4, 5-4 ', S'-dibenzthiocarbocyanine chloride (Brooker, American Patents 1,846,301 and 2058405) can be added to the emulsion for this purpose. Other compounds, such as the tetravalent salt benzothiazole iodomethylate, also increase the Sensitivity of the emulsion to the air curtain, as do silver iodide and potassium iodide.

Fog forming agents containing labile sulfur are generally unsuitable for the use according to the invention. The obfuscation process should be a developable latent Bring out the surface image in the unexposed silver halide grains.

An ordinary surface developer, i. H. one of those who have a picture only on the surface of the Grains of a latent inner grain image emulsion developed is as follows:

B e 1 s ρ 1 e 1 ι

p-Hydroxyphenylglycine 10 g, "Sodium carbonate (crystals) 100 g, water on 1 1, development time 4 minutes at 20 ^° C.

An internal grain developer, d. H. one that forms an image within the grains of an internal grain latent image emulsion developed is the following:

Example 2

■ Hydroquinone 15 g, monomethyl-p-aminophenol sulfate 15 g, sodium sulfite (anhydrous) 50 g, potassium bromide 10 g, sodium hydroxide 25 g, sodium thiosulfate (crystals) 20 g, water on 1 1, development time 3 minutes at 20 ^° C.

The present invention will now be described with reference to the following specific example:

An emulsion as described above as Davey and Knott emulsion was applied to a support, dried and tested in an Eastno man II-b sensitometer (J. Soc. Mot. Pict. Eng., 17 [ 1931], p. 536) exposed. The exposed emulsion was then ^{treated for 5 minutes at 20 °} C. in the following developer solution:

115 Example 3

Hydroquinone 22.5 g, sodium sulfite 30 g, paraformaldehyde 7.5 g, potassium metabisulphite 2.6 g, boric acid (crystals) 7.5 g, potassium bromide 1.6 g, water, to fill up to 1 1.

The developer was agitated during development by blowing air into it in the way became that it came into contact with the emulsion. The emulsion was then in hyposulfuric acid Sodium fixed and washed. The resulting sensitometric curve was measured and recorded

drawn, as done in the drawing, in the increasing exposures as ordinates and the Density is shown as the abscissa. It is obvious that a positive image with suitable characteristics as indicated by the slope and location of the curve.

It is obvious to those skilled in the art that the method according to the invention means for obtaining a direct positive photograph by simple exposure and processing technique and hence the need for very strong exposures or a second exposure or a second development, to get positive images straight away, avoids.

Claims (7)

PATENT CLAIMS: i. Process for the production of a direct positive image in a silver halide emulsion layer, characterized in that a silver halide emulsion layer, from which a sample is exposed after exposure under an intensity scale for a certain time between V ₁₀₀ and ^ 1 second and development for 3 minutes at 20 ^° C In the following internal grain developer: hydroquinone 15 g, monomethyl-p-aminophenol sulfate 15 g, anhydrous sodium sulfite 50 g, potassium bromide 10 g, sodium hydroxide 25 g, sodium thiosulfate 20 g, water on 11 results in at least five times the maximum density compared to that which is achieved if the silver halide emulsion exposed in the same way is developed for 4 minutes at 20 ^° C. in the following surface developer: p-hydroxyphenylglycine 10 g, sodium carbonate 100 g, water on il is irradiated with a type of light to which it is sensitive, and that only the unexposed part of said emulsion layer in an air-fogging developer ler is developed with the addition of air or oxygen. 2. Method of making a direct positive image in a silver halide emulsion layer according to claim 1, characterized in that only in the unexposed parts of the Emulsion layer creates a latent image on the silver halide grains in a single bath and this latent image is developed into metallic silver. 3. Method of making a direct positive image in a silver halide emulsion layer according to claims 1 and 2, characterized in that the silver halide grains only the unexposed part of the layer in an air curtain developer upon access made developable by air or oxygen and while staying in it Developer to be developed into metallic silver. 4. Process for producing a direct positive image in a silver halide emulsion Sion layer according to Claims 1 to 3, characterized in that only the unexposed silver halide grains the layer can be made developable in the following developing solution: hydroquinone 22.5 g, sodium sulfite 30 g, p-formaldehyde 7.5 g, potassium metabisulphite 2.6 g, Boric acid (crystals) 7.5 g, potassium bromide 1.6 g, water up to 1 1 and in the same solution in which they were made evolvable, evolved into metallic silver. 5. Method of making a direct positive image in a silver halide emulsion layer according to claims 1 to 4, characterized in that the layer is immediately in a only developer solution is introduced which makes the unexposed silver halide grains developable makes and develops it into a silver picture. 6. Process for producing a direct positive image in a silver halide emulsion Sion layer according to Claims 1 to 5, characterized in that the layer is immediately converted into a Developer solution is introduced which makes silver halide grains developable and develops, which have been made developable in the following developer: hydroquinone 22.5 g, Sodium sulfite 30 g, p-formaldehyde 7.5 g, potassium metabisulfite 2.6 g, boric acid (crystals) 7.5 g, potassium bromide 1.6 g, water to 1 1. 7. A method of making a direct positive image in a silver halide emulsion layer according to claims 1 to 6, characterized in that the layer is immediately in a Introduced developer solution of essentially the following composition: Hydroquinone 22.5 g, sodium sulfite 30 g, p-formaldehyde 7.5 g, potassium metabisulfite 2.6 g, boric acid (Crystals) 7.5 g, potassium bromide 1.6 g, water to 1 1 and that on contact with the Emulsion Air blown through and metallic silver in the unexposed parts of the emulsion is being developed. 1 sheet of drawings © 5368 9.