Developer for processing black and white photographs and method of manufacturing of a working solution thereof

Description

Technical field

[0001] The present invention relates to silver halide photography, in particular to developers for black and white film and photographic materials.

Background Art

[0002] The emergence in the global market of the films with variable sensitivity caused the need for a developer for high quality processing of these photo materials. For these needs concentrated solution of the developer is needed having: superadditivity, leveling properties, specificity of an activity, raising or lowering the light sensitivity of the photo material during the exposure depending on the light, being fine grained, noticeably increasing the resolution power of photographic layers, with good storage ability (long expiry term) regardless of the amount of it in the vessel and having minimal adverse effects on the environment.

[0003] This issue was the subject of many studies, the aim of which was to find a developer that reduces graininess and increases the resolution of the light-sensitive layers. The overall conclusion is that the grain is significantly reduced only in case of few fine-grained developers, in particular of parafenilen-diamine ones. The decrease in grain developer such as D-76 (Kodak) is in doubt. So far, no developer is also found that would significantly increase the resolution of photographic layers.

[0004] There is known Levenson's concentrated developer, which is a modification of the developer "Rodinal" by the addition of hydroquinone and phenidone. Its composition is as follows: potassium disulphite 250 g; hydroquinone 20 g; n-Aminophenol hydrogen sulfate 100 g; potassium hydroxide 204 g; potassium bromide 6 g; phenidon 5 g; water 1000 ml (Fotografiya. Encyclopedicheskyj spravochntk. p. 266, Minsk. Belaruskaya entsyklapedya imya Petrusya Brouki 1992). The known developer really has leveling properties, as the use of caustic alkali and potassium bromide of low concentration leads to a sharp decrease in pH in solution in the areas of the emulsion layer, which received greater levels of exposure. This decrease in pH is due to the low buffer capacity of alkali and results in slowdown of the developing process. This case corresponds to the leveled developing. In turn, the slowdown of the developing process in the developer with alkali carbonates is not observed, as hydrobromic acid formed in the emulsion layer is titrated with alkali having a high buffering capacity during the entire process of developing, while the pH remains almost unchanged. However developers containing caustic alkali have a limited shelf life and use. Besides that the use of bisulfites as preserving substances limits the temperature threshold of the developer's use and storage. This also applies to concentrated developers "Rodinal" (R 09), "Kodak T - MAX" and others. The expiry term of the known concentrated solutions of developers in the original packaging is 2 years; in case of opened packaging - a few months only. This significantly limits their applicability. In addition, with increasing sensitivity of the photographic material, the granularity and fogging the image increases when processing in the developer.

[0005] There is also known a developer (patent RU2028651) comprising: hydroquinone - from 5 to 9 g/l; phenidone - from 0.6 to 3.0 g/l; salt cake - from 30 to 50 g/l; sodium sulphite - from 15 to 55 g/l; benzotriazole - from 0.05 to 0.3 g/l; potassium phosphate - from 30 to 45 g/l; boric acid - from 30 to 50 g/l; potassium hydroxide - from 20 to 90 g/l; lower saturated alcohol from 0.79 to 15.8; water - up to 11. With the lapse of time sodium sulphite and lower saturated alcohol crystallize (these crystals are not being soluble in water). Also lower saturated alcohol is quite expensive component, which makes the known developer more expensive. Furthermore potassium phosphate and potassium hydroxide form gel, which decreases quality of development of photographic materials.

Disclosure of Invention

[0006] According to the invention the offered photographic developer for black and white photographs comprises: disodium salt of ethylenediaminetetraacetic acid, diatomic phenol, phenidon or 4-Methyl-1-phenyl-3-pyrazolidinone (Phenidone B), sodium sulfite, alkali metal hydroxide, potassium bromide, water, boric acid salt or boric acid, benzotriazole. As an additional antioxidant and plasticizer a polyatomic alcohol or derivative thereof of general formula R1 (CH₂CH₂)-Z-A-R2, where Z=O or is absent, A=(CH₂CH₂)n, R2, R1-OH, CH₃ or R1-OH, R2-, OCH₃, n=0,1 is introduced into the composition of the developer having the following % ratio of the components:

disodium salt of ethylenediaminetetraacetic acid	from 0.2 to 1;
sodium sulfite	from 2 to 10;
diatomic phenol	from 1 to 8;
benzotriazole	from 0.01 to 0.4;
polyatomic alcohol or its derivatives	from 0.1 to 4;
sodium or potassium hydroxide	from 1 to 8;
phenidon or 4-Methyl-1-phenyl-3-pyrazolidinone	from 0.1 to 1;
boric acid salt and an alkali metal or boric acid	from 1 to 6;
potassium bromide	from 0.01 to 1;
water	the rest.

[0007] Introduction of disodium salt of ethylenediaminetetraacetic acid into the developer softens the water and allows using the developer with distilled and boiled water. Sodium sulfite prevents oxidation of the developer, as well as its decomposition. Benzotriazole allows controlling the speed of the process of development and prevents fogging. Its action in the developer solution is associated with formation of insoluble compounds with silver ions, which are harder to recover than AgBr. Diatomic phenol is a developing agent; being an antioxidant and stabilizer it increases storage length of the developer. In the presence of SO3 products of oxidation are tanning gelatin; this allows processing the photographic materials at a wide range of temperatures. Phenidon or 4-Methyl-1-phenyl-3-pyrazolidinone (Phenidone B) being the second developing agent creates superadditive effect. Use of sodium or potassium hydroxide increases the activity of the developer due to the high pH of the solution and provides the leveling effect on the processed photographic material. Borates or boric acid introduced into the developer increase buffer value of the solution and stabilized pH without compromising the leveling effect of the developer. Since borates soften water, the use of distilled water is no longer obligatory; this facilitates preparation of the developer. Interaction of borates or boric acid with sodium or potassium hydroxide synergistically improves final effect of development without increase of graininess.

[0008] Polyatomic alcohol or its derivatives (ethylene glycol, ethylene glycol monomethyl ether, diethylene glycol, ethylene glycol dimethyl ether, diethyleneglycol monomethyl ether, diethylene glycol dimethyl ether), being plasticizers of gelatin layer, activate the process of developing, increase film's light sensitivity and speed of development. Besides, they act as antioxidants.

[0009] The use of several substances, which are antioxidants, has led to the appearance of synergy, thereby creating a more effective protection against autooxidation of a concentrated solution and increasing the period of the developer's storage term for more than 3 years without deterioration of its properties, regardless of the residual volume in the container.

[0010] Potassium bromide used has a brightening effect and prevents fogging appearing on the photographic material during storage.

[0011] The working solution of developer can be prepared as follows. 300-350 ml of tap water, or water from other sources (filtered) is being heated to a desired temperature (20-40°C). 10 ml of concentrated developer solution is being poured into the water.

[0012] For preparing 1 liter of the working solution for processing photo paper 100-150 ml of concentrated developer solution is being poured into about 750 ml of water having temperature t=18-20°C. Then the volume of the solution obtained is being brought to 1 liter by adding the necessary amount of water.

[0013] Although separate components of the offered developer are known from the prior art, their combination and proportions used allow achieving the unexpected technical effect - increase of light sensitivity of photographic materials for 7-10 ISO sensitivity steps. The offered developer provides leveling effect and increased light sensitivity without increasing graininess. Moreover the developer (concentrated solution) has long shelf life - more than 3 years without deterioration of its properties, regardless of residual volume in the container.

[0014] Processing of a negative in the offered developer allows for exposition of 400 ISO film at night at a diaphragm 4 and exposure 1/60 second and getting a good quality image on the photographic material.

[0015] Processing in the offered developer allows for exposition of a black and white negative film having variable sensitivity (ISO) from nominal up to 10 sensitivity steps, depending on the illumination (Table 1).

Table 1.

Time for film development (in minutes) at variable sensitivity at the developer solution having t=25°C.
Film's nominal ISO:	ISO set on camera when making photographs:
	50	100	200	400	800	1600	3200	6400	12800	25600	51200	102400	204800
	Time for development, min., at 25° C:
50	5	10	15	20	25	30	35	40	50	55	60
100	-	5	10	15	20	25	30	35	45	50	55	60
200	-	-	5	10	15	20	25	30	40	45	50	55	60
400	-	-	-	5	10	15	20	25	35	40	45	50	55
800	-	-	-	-	5	10	15	20	30	35	40	45	50
1600	-	-	-	-	-	5	10	15	25	30	35	40	45

[0016] When photographing with changing light sensitivity of the film from nominal to higher, film development should be made according to the highest light sensitivity set according to Table 1. For example, when using 50 ISO film for photographing at 50, 100, 200, 400, 800, 1600 and 3200 ISO set, the time for the film development (at solution t=25°C) should be set as for 3200 ISO according to Table 1 (35 min). The development at a different solution's temperature (from 20° to 40°C) can be performed. In this case time for film development is to be calculated by applying the correction factor according to Table 2.

Table 2.

Correction factor for calculation film development time depending on a temperature of solution of the developer.
t°C	18°	20°	25°	30°	35°	40°
Correction factor	*2.2	*1.75	-	:3.3	:2.9	:10

[0017] To calculate time for film development using solution of the developer having temperature higher than 25° C the time set forth in the Table 1 should be divided by the appropriate correction factor of Table 2. In turn, to calculate time for film development using solution of the developer having temperature lower than 25°C the time set forth in the Table 1 should be multiplied by the appropriate correction factor of Table 2.

Description of Embodiments

[0018] The offered photographic developer can be prepared using the components and their % ratio set forth above. Some examples with the preferred percentage ratio of the components are set forth below.

Example 1

[0019] 

Components:	ratio (%):
disodium salt of ethylenediaminetetraacetic acid	0.5
sodium sulfite	8
diatomic phenol	6
benzotriazole	0.3
polyatomic alcohol	2
potassium hydroxide	5
phenidon	0.7
boric acid	5
potassium bromide	0.5
water	72

Example 2

[0020] 

Components:	ratio (%):
disodium salt of ethylenediaminetetraacetic acid	0.4
sodium sulfite	6
diatomic phenol	7
benzotriazole	0.2
ethylene glycol	1
potassium hydroxide	6
4-Methyl-1-phenyl-3-pyrazolidinone	0.3
boric acid	2
potassium bromide	0.4
water	76.7

Example 3

[0021] 

Components:	ratio (%):
disodium salt of ethylenediaminetetraacetic acid	0.8
sodium sulfite	4
diatomic phenol	6
benzotriazole	0.1
diethylene glycol	2
potassium hydroxide	4
phenidon	0.4
boric acid salt and lithium	4
potassium bromide	0.2
water	78.5

Example 4

[0022] 

Components:	ratio (%):
disodium salt of ethylenediaminetetraacetic acid	0.3
sodium sulfite	5
diatomic phenol	4
benzotriazole	0.05
polyatomic alcohol	3
sodium hydroxide	2
phenidon	0.8
boric acid salt and potassium	3
potassium bromide	0.3
water	81.55

Example 5

[0023] 

Components:	ratio (%):
disodium salt of ethylenediaminetetraacetic acid	0.6
sodium sulfite	8
diatomic phenol	5
benzotriazole	0.2
polyatomic alcohol	1
sodium hydroxide	3
Phenidone B	0.2
boric acid salt and sodium	1
potassium bromide	0.1
water	80.9

Claims

1. Photographic developer for black and white photographs comprising: disodium salt of ethylenediaminetetraacetic acid, diatomic phenol, phenidon or 4-Methyl-1-phenyl-3-pyrazolidinone, sodium sulfite, alkali metal hydroxide, potassium bromide, water, boric acid salt or boric acid, benzotriazole, polyatomic alcohol or derivative thereof of general formula R1 - (CH₂CH₂)-Z-A-R2, where Z=O or is absent, A=(CH₂CH₂)n, R2, R1-OH, CH₃ or R1-OH, R2-, OCH₃, n=0,1, having the following % ratio of the components:

disodium salt of ethylenediaminetetraacetic acid -	from 0.2 to 1;
sodium sulfite -	from 2 to 10;
diatomic phenol -	from 1 to 8;
benzotriazole -	from 0.01 to 0.4;
polyatomic alcohol or its derivatives -	from 0.1 to 4;
sodium or potassium hydroxide -	from 1 to 8;
phenidon or 4-Methyl-1-phenyl-3-pyrazolidinone -	from 0.1 to 1;
boric acid salt and an alkali metal or boric acid -	from 1 to 6;
potassium bromide -	from 0.01 to 1;
water -	the rest.

2. A working solution for developing black and white films and/or for treating photographic paper, comprising the developer according to claim 1.

3. Use of the developer according to claim 1 for developing black and white film and/or for treating photographic paper.