DE884150C - Process for the formation of a direct positive image in a silver halide emulsion - Google Patents

Description

The invention relates to a method for generating a direct positive image with magnified Maximum density in a silver halide emulsion.

Direct positive effects can be achieved by solarization of the developable latent image by overexposure be obtained, namely by a second exposure to the Sabattier or the To achieve the Clayden effect, or by reverse development of a developed negative image. Solarizable, Photosensitive products require extremely intense exposures in order to achieve the desired to achieve direct positive photography. The application of a second exposure has been obvious Disadvantages from the point of view of practical technical application. The regression makes In addition to the usual and normal development process, at least two additional operations necessary.

A method not yet known in the art produces a direct positive image generated in a suitable silver halide emulsion by exposing the emulsion in the usual manner and treated with a developer capable of producing an air curtain. As an emulsion the latent inner grain image type is preferably used as it is e.g. B. in the magazine for scientific photography 44 (year 1949), pp. 44 to 50, is described.

It has now been found that certain compounds previously used as photographic antifoggants or emulsion additives have been used to which developers can be added, those in the process according to the American

Fallesen '2,497,875 and that the air curtain grows. This means that there is a higher maximum density of the reverse image from this application of the compound results.

The compounds to be used according to the invention are heterocyclic nitrogen-containing ring compounds that contain 5 or 6 atoms in the heterocyclic Have a ring and are such that the maximum density of the positive image increases, that is obtained in developer solutions that have the ability to create an air curtain. It was further found that in the development of certain emulsions, such as the latent internal grain image emulsions, the use of certain antifoggants or other compounds in the Developer solutions increase the density in the unexposed layers by intensifying the air curtain in grows in the lower exposure areas. At the same time, the ordinary anti-fogging property comes in the apex part of the inversion curve, d. H. in the area of maximum exposure, expressing. This enlargement of the air curtain in the unexposed areas are likely to be a new phenomenon, which is of considerable value for presents direct positive photographic materials. In the drawing are the two images characteristic curves of photographic emulsions showing the results obtained according to the invention illustrate.

The photographic emulsion used in the process according to the invention is a gelatin-silver halide emulsion, e.g. B. a silver bromide emulsion, a silver bromoiodide emulsion or a chloroiodide emulsion. It does not have to contain spectrally sensitizing dyes, but certain optical sensitizers can be added to it in order to induce an air haze phenomenon, as is explained in more detail in American patent specification 2497875 to Fallesen. A suitable emulsion is known as Burton's emulsion, which is described in the book " Photographic Emulsions" by Wall, 1929, pp. 52 and 53. Burton's emulsion is made as follows:

A. Silver nitrate 100 g

Water. 500 ecm

■ ammonia (to clarify the 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 and A was added in the cold state B with continuous shaking for 20 minutes digested at 50 ⁰ C and then cooled slowly. C is added after the gelatin has been swollen in water for 20 minutes, drained and finally melted. The emulsion is then allowed to solidify and washed off.

An internal grain latent image emulsion, that is, an emulsion which has the latent image essentially within the silver halide grain forms and those in Mees' book λ-The Theory of the Photographic 6g Process * ?, 1942, pp. 296 and 297, is particularly suitable for the method according to the invention.

Most of the grain internal latent image emulsions are silver brom j iodide emulsions with high iodide content, which preferably contain at least 10 ° / ₀ iodide to 20th Burton emulsion is an emulsion of this type, which has a silver iodide content of approximately 40 ° / ₀ of the content of silver halide. However, it is not essential that the emulsion contain silver iodide.

A latent inner grain image emulsion, which was produced according to the information in the magazine for scientific photography 44 (1949), pp. 44 to 50, can also be used according to the invention. This emulsion is prepared by first forming, in the absence of ammonia and in one or more stages, silver salt grains consisting at least partially of a silver salt which is more soluble in water than silver bromide, and then converting the grains into silver bromide or silver bromoiodide. When the content of silver iodide of the emulsion is less than 6 ° / ₀ (based on the total silver halide), those granules are treated with an iodine / to bring the silver iodide content at least 6 ° _0th The ripening is preferably carried out in the absence of ammonia, and this is followed either by washing out some of the soluble salts or all of the soluble salts and finally adding soluble salts, e.g. B. soluble chlorides or bromides. An example of an emulsion made in this way is the following:

Solution no. Ι

Inert gelatin 20 g 1

KCl 20 g [at 40 ^° C

Water 560 ecm J

Solution # 2

KCl ... 100 g "1 _{,. Ö} o _r

Water. 520 ecm J ^{Del 45 U}

Solution No. 3

AgNO ₃ ................ 195g} at ₄ HO _C «0

Water 520 ecm J

Solution # 4

KBr 160 g 1

Kl 40 g [at 45 ^° C

Water. 500 ecm J

Solutions No. 2 and 3 are allowed to run simultaneously into the vial of solution No. 1 over a period of 90 seconds. This is followed by ripening at 45 ° C. for 1 minute. Then the solution no. 4 is added, and it is followed by a ripening for 20 minutes at 45 ⁰ C. Then 235 g of inert gelatin (dry) is added, and it is aged again minutes at 45 ° C, where the gelatin dissolves. The emulsion is allowed to solidify and is divided

strips and then washes them until free of all soluble bromides. That'll be about 150 ecm of an 10 percent (weight) solution of K Cl and then added enough water to make 3.5 liters.

An internal latent grain image type of a silver halide solution can be described as such, of the exposed one of an intensity scale for a certain time between ¹ Z ₁₀₀ and 1 second and then 4 minutes at 20 ⁰ C, in the ordinary surface developer (Example 1) developed a high density shows that is no greater than ¹ ₅ Z, the maximum density, which is achieved when the same emulsion exposed in the same manner and then 3 minutes at 20 ⁰ C with a grain internal latent image developer (example 2) is treated. Usually the maximum density achieved with the surface developer is no greater than ^{1 in} _{10 of} the maximum density achieved when the same emulsion is treated with the internal grain latent image developer. Conversely stated: an inner grain latent image emulsion, when treated with an inner grain latent image 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 used in the same manner exposed and developed in a surface developer (Example 1).

The developer to be used in accordance with the invention should be one which is anti-oxidant or creates air curtains. Such developers were made by Dundon and Crabtree in the book "American Photography", 1924, Vol. 18,

P. 742. An example of such a developer is a hydroquinone developer that has little or contains no sulfite at all and which is given in Example 3.

The air curtain can and can be created in the developer in a number of ways can be accelerated or intensified by making use of various aids. Of the developer used should preferably have a low sulfite content, and preferably none Contain silver halide solvents which (as a silver halide solvent) are more potent than sulfite. The air curtain can also be strengthened by blowing air bubbles forcefully through the developer in this way that the air often comes into contact with the emulsion surface during development Photography is coming. Also, certain chemical agents, such as copper sulfate, can either be in the developer or can be incorporated into the emulsion itself in order to create or form an air curtain to promote. Hydrogen peroxide or certain dyes, such as methylene blue, also enhance the Air curtain. However, obscuring agents containing labile sulfur are unsuitable. The veiling Effect should be surface developable latent images in the undeveloped silver halide grains cause, as in the aforementioned American patent 2497875 of Fallesen was set out.

Compounds which are suitable according to the invention for air curtain reinforcement and their preferred The concentration ranges are as follows:

,,,. , Amount per liter of compound developer

Benzotriazole 0.4 g

Methyl benzotriazole 0.05 to 0.2 g

Ethyl benzotriazole 0.05-0.1 g

i-ethyl oxindole 0.1 g

5-nitroindazole 0.05 to o, i g

6-nitrobenzimidazole 0.05-0.1 g

Histidine 0.1-0.2 g

Ethyl benzoxazole 0.10 g

N-ethyl pyrrole 0.1 to 0.2 g

2,5-dimethylpyrrole 0.05-0.2 g

2,4-Dimethyl-5-carbethoxypyrrole ... 0.05-0.2 g

2,3-Dimethylquinoxaline 0.05-0.40 g

2-thio-2,4 (3, 5) -thiazoldione 0.05-0.20 g

2,4-Tri-isopropylamino-S-triazine .... 0.1-0.2 g

2,4-Dimethylamino-6-chloro-S-triazine. 0.1-0.2 g 2, 4-di - (/? - methoxyethylamino) -

6-chloro-S-triazine 0.2 g

2, 4, 6-tri-n-butylamino-S-triazine .... 0.2 g i-carboxymethyl ^ -phenyl ^ -thio-

hydantoin 0.1-0.5 g

ι, 4-diphenyl-3-aniline-5-phenylimine

i, 2, 4-triazoline 0.05-0.50 g

An ordinary surface developer, i.e. one that only creates an image on the surface of the grains of the latent inner grain image emulsion is the following:

example 1

p-oxyphenylglycine 10 g

Sodium carbonate (crystals) 100 g

Water on 11

Development time: 4 minutes at 20 ^° C.

An internal grain image developer, i.e. one that creates an image within the grains of an internal grain latent image emulsion is the following:

Example 2

Hydroquinone 15 g

Monomethyl p-aminophenol sulfate ... 15 g

Sodium sulfite (anhydrous) 50g

Potassium bromide 10 g

Sodium hydroxide 25 g

Sodium thiosulphate (crystals) 20 g

Water on 11

Development time: 3 minutes at 20 ^° C.

The present invention will now be explained with the following specific examples.

Example 3

An emulsion as described above was poured onto a support, dried and using a Eastman IIB Sensitometers (Journal of the Society of Motion Picture Engineers, 17, 1931, p. 536)

exposed. The exposed emulsion was then 12 minutes developed at 20 ° C in the following solution:

Hydroquinone 22.5 g

Sodium sulfite 30.0 g

p-formaldehyde 7.5 g

Potassium metabisulphite 2.6 g

Boric acid crystals 7.5 g

Potassium bromide 1.6 g

Water on 11

The developer was agitated during development by forcing air through a sintered, porous glass tube and immersing it completely in the developer vessel. An emulsion exposed in the same way was developed for the same time in the same solution which contained 0.4 g of benzotriazole per liter of the developer solution. In each case, direct positive images were obtained as shown in Figure 1 of the drawings. Curve A was generated from the developer containing no benzotriazole and curve B from the developer containing benzotriazole. The curves show that a higher maximum density is achieved with a developer containing benzotriazole.

Example 4

The same emulsion that was used for Example 3 was exposed in the same way, and Parts of the same were developed in a solution of the following composition:

Hydroquinone ....-.- 10 g

Sodium sulfite 16 g

Paraformaldehyde 4 g

Sodium carbonate 25 g

Water on 11

which contained no, or 0.05, or 0.1, or 0.4 g of methylbenzotriazole per liter of the developer solution. Sensitometric curves were obtained from these development processes as shown in FIG. 2, and these show the effect of the concentration ranges of the antifoggant. Curve A was obtained when developing without anti-fogging agent, curve B when developing with an addition of 0.05 g of methylbenzotriazole per liter, curve C when developing with an addition of 0.1 g of methylbenzotriazole per liter and curve D when developing with an addition of 0.4 g of methylbenzotriazole per liter. These curves show that at concentrations of 0.05 to 0.1 g methylbenzotriazole per liter of developer, the maximum density and the gamma value increase, but at higher concentrations the maximum density and gamma value decrease; and at a concentration of 0.04 g per liter they are lower than with a developer which does not contain methylbenzotriazole.

Example 5

Further strips of the film used in Example 3 were exposed in the same manner and in one Solution developed according to Example 4, namely with different concentrations of 6-nitrobenzimidazole nitrate, that was added to the developer. It took 5 minutes to develop, and so did the developer was enriched with air as in Examples 3 and 4. The concentration in the order of 0.05 g of 6-nitrobenziniidazole nitrate per liter of des The developer was found to be effective in increasing the maximum density and decreasing the minimum density allow. At higher concentrations the maximum density decreases, although at a concentration of 0.1 g per liter of developer, the maximum density was higher and the minimum density was lower than in the case in which the developer did not contain antifoggant. Table 1 shows the maximum and minimum densities, obtained in this treatment.

Table 1

Concentration of the maximum-minimum

6-nitrobenzimidazole nitrate density

without addition 0.56 0.48

0.05 g per liter of developer. 1.12 0.16

ο, ΐο g - - -. 0.90 0.16

0.20 g - - - 0.40 0.12

0.40 g - - - 0.12 0.12

The following examples illustrate developer solutions that have been used to increase the Achieve maximum density beyond that achieved with the same developer but no anti-fog agent was achieved.

Example 6

Hydroquinone 10 g

Sodium sulfite .. 16 g

p-formaldehyde 4 g

Sodium carbonate 25 g

Benzotriazole 0.1 g

■ water on 11

Example 7

Hydroquinone 20 g

Sodium sulfite 32 g

p-formaldehyde 8 g

Sodium carbonate 50 g

Benzotriazole, 0.8 g

Water on 11

Example 8

Hydroquinone 30 g

Sodium chloride 48 g

p-formaldehyde 12 g

Sodium carbonate 75 g

Benzotriazole 1.2 g

Water on 11

Example 9

Hydroquinone 30 g

Sodium sulfite 48 g

p-formaldehyde 12 g

Benzotriazole 2.4 g

Water on 11

Example ίο

Hydroquinone 30 g

Sodium sulfite 24 g

p-formaldehyde 6 g

Benzotriazole 2.5 g

Water on 11

Example 11

Hydroquinone 30 g

Monomethyl p-aminophenol sulfate .. 0.25 g

Sodium sulfite 50 g

p-formaldehyde 12.5 g

Sodium hydroxide 6 g

Benzotriazole 2.5 g

¹ ^ water on 11

When alkalis, such as sodium hydroxide or sodium carbonate, use these developers in large quantities Increasing the pH can be added and to decrease the development time, show the developer the tendency to produce a lower maximum density and a higher minimum density. This tendency can be overcome by adding small amounts of agents to the developers, such as p-phenylenediamine or N-methyl-p-aminophenol sulfate, Oxy-hydroquinone or oxy-hydroquinone acetate. Example 11 provides a developing solution of this Kind of, the sodium hydroxide and N-methylp-aminophenol sulfate has been added. It is a disadvantage of developer compounds with small amounts of phenylenediamines or aminophenols, that the amino groups of these compounds apparently slowly with the formaldehyde of the developer react and form the Schiff bases. This is why these developers are most effective when used within can be used a few hours after their creation.

The amounts of phenylenediamines and aminophenols considered highly satisfactory for incorporation Tried to the developers are in the order of 0.12 to 0.5 g per liter of developer solution. When oxyhydroquinone and oxyhydroquinone triacetate are used, the amounts which have been found to be most effective are in of the order of 0.12 to 0.4 g per liter of developer solution.

Not all compounds that may exhibit anti-fogging properties are suitable for the Increase the maximum density of the reverse image achieved with latent internal grain image emulsions. For example put / J-phenylindole, 1,3-dimethylindole, Phenyl - mercapto - tetrazole, 2 - methylbenzoxazole iodethylate, 2-methylbenzothiazole, methyl p-toluidsulfonate, Thiobarbituric acid, 2,6-dimethyl-quinoline, 2,6-dimethyl-quinolinium iodoethylate and 5-sulfonamido-benzotriazole decreased the maximum density compared to the developers who did not contain these agents. Other compounds, such as 3,5-dimethylpyrazole, Barbituric acid and 2 - /? - acetanilido-vinyl-benzoxazole methylate, did not produce any effect beyond the maximum or minimum densities achieved.

From the above examples and from the description

It appears that the new and useful features of the invention are in its discovery and application certain anti-fog agents or heterocyclic nitrogen compounds in developers for the production of direct positive photographic images with improved contrast and expansiveness Blackening scale (increased maximum density) through development in developer types with low Sulphite or formaldehyde bisulphite content. It is to be understood that the scope of the invention does not is limited to the specific concentrations or mixtures given by the above examples are.

Observation of a developing solution containing benzotriazole before and after developing revealed the fact that it was greatly discolored during development. This is likely to point out be due to the fact that intermediate oxidation products of the hydroquinone cause the formation of air veils reinforced. With regard to the developer containing benzotriazole, this observation shows that that the level of production of intermediate oxidation products of hydroquinone is increased, and that this results in an increase in the formation of air curtains. This property of the compounds described above appears to be quite independent of their normal anti-fog properties, the at the same time as the accelerating effect on the air curtain, like the top features of the examples given above.

Claims (5)

PATENT CLAIMS: 1. A process for producing a direct positive image, characterized in that a silver halide emulsion which, when developed in a surface developer, reaches a maximum density which is not greater than ¹ Z _{5 of} the maximum density which is achieved when the emulsion is in a developer is developed with internal grain development, exposed to light, and that it is treated with a silver halide developer capable of producing air curtains and containing a heterocyclic nitrogen-containing ring compound having at least 5 but not more than 6 atoms in the heterocyclic ring which is so composed that it has the highest density of the positive image obtained in the developing solution suitable for creating air curtains. 2. A method for generating a direct positive image in a silver halide emulsion layer, characterized in that a silver halide emulsion layer, of which a sample after exposure under an intensity scale for a certain time between ¹ Z ₁₀₀ and 1 second and development for 3 minutes at 20 ⁰ C in the following internal grain developer solution: 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 when the silver halide emulsion exposed in the same way is developed for 4 minutes at 20 ^° C. in the following surface developer: p-oxyphenylglycine 10 g Sodium carbonate 100 g Water on il that this emulsion is exposed and treated with a developer solution, the air curtains that blackens the unexposed parts and a heterocyclic nitrogen-containing ring compound containing at least 5, but not has more than 6 atoms in the heterocyclic ring and is so composed that it has the The maximum density of the positive image obtained in the air curtain developing solution is increased. 3. Method of forming a direct positive image in a silver halide emulsion layer according to claim 2, characterized in that the emulsion is treated with a developer solution which contains so much benzotriazole that the highest density of that producing in the air curtain The image obtained in the developing solution is increased. 4. A method of forming a direct positive image in a silver halide emulsion layer according to claim 2, characterized in that the emulsion is treated with a developer solution which contains so much 5-nitroindazole that the highest density of that generating in the air curtain. Image obtained from developing solution is increased. 5. Method of forming a direct positive image in a silver halide emulsion layer according to claim 2, characterized in that the emulsion is treated with a developer solution which contains so much 6-nitrobenzimidazole that the highest density of the in the air curtain producing developing solution is increased. 1 sheet of drawings 1 5275 7.53