EP0003118B1 - Process and apparatus for regenerating and maintaining the activity of a photographic treating solution - Google Patents

Description

The invention relates to a method for regenerating and maintaining the activity of a photographic processing solution, in particular a lith processing solution, in a continuous processing machine which is intermittently loaded with exposed photographic material, the processing solution being in each case before, simultaneously with or after the introduction of photographic material Concentrates and dilution water is supplied to the existing regenerator.

• a) die chemische Erschöpfung durch den Verarbeitungsvorgang selbst,
• b) chemische Veränderungen, die nicht durch den Verarbeitungsvorgang, sondern durch andere Faktoren bewirkt werden, z.B. durch die Einwirkung von Luftsauerstoff, allmähliche Zersetzung einzelner Komponenten, Anreicherung von Nebenprodukten etc.

When processing photographic materials in automatic machines, it must be ensured that the individual processing baths have constant activity so that a constant processing quality is always achieved over a longer period of time. There are generally two different factors that can change the activity of the baths over time:

• a) chemical exhaustion from the processing itself;
• b) chemical changes that are not caused by the processing process, but by other factors, e.g. by the action of atmospheric oxygen, gradual decomposition of individual components, accumulation of by-products, etc.

The change (a) is generally directly dependent on the amount of material processed; the change (b), on the other hand, is generally independent of the amount of material processed, but rather a function of service life and bath temperature.

It is therefore evident in many cases that it is not sufficient to regenerate the processing bath by adding used components in accordance with the amount of material processed; especially during longer downtimes, it will be much more necessary to take the service life of the bath into account and to introduce an additional replacement of components that have been lost due to spontaneous changes or changes caused by atmospheric oxygen.

Service life-dependent behavior is particularly evident in processing baths that contain substances whose effects are based on reduction and oxidation. In particular, it is photographic processing baths that can be easily oxidized by atmospheric oxygen. Another example are the color bleaching baths used in the silver color bleaching process, the effect of which is based on a relatively sensitive redox balance of the bleaching catalysts and oxidizing agents contained therein. However, the regeneration problem with the so-called lith developers used for the development of high-contrast materials is particularly difficult. In addition to hydroquinone as the only developer substance, these contain very little sulfite and are therefore easily oxidized by atmospheric oxygen. In addition, other factors such as the pH and the current concentration of bromine ions are of crucial importance for the activity of lith developers. Since hydroquinone and sulfite are consumed in the development of photographic material on the one hand and bromine ions are released on the other hand, keeping the activity constant in such baths is a particularly difficult problem, and it is necessary to both the changes caused by the continuous development of photographic material , as well as to compensate as exactly as possible those which are caused by the changes resulting from different periods of inactivity.

• 1. Chemische Analyse der Badzusammensetzung und
• 2. Messung der Fläche und des Schwärzungsgrades des entwickelten Materials.

For the regeneration of lith developers, it is common practice to use at least two or more different solutions, the composition of which is matched to one another in such a way that different activity ratios can be compensated for by different mixing ratios. Various measurement methods are generally used so that the type of activity changes occurring can be correctly recorded and the effect of the bath can be restored by adding suitable components. Two fundamentally different methods are used for this:

• 1. Chemical analysis of the bath composition and
• 2. Measurement of the area and degree of blackening of the developed material.

Both the first and the second method are relatively complex and only have a real value if they can be carried out with sufficient accuracy. The first method and its application in an automated lith developer regeneration system is e.g. in German Offenlegungsschrift 2 119069, the second e.g. in German Offenlegungsschriften 2,343,242 and 2,343,318. In the methods described in these publications, three different solutions are generally used, the total amount and proportion of the proportions used for the regeneration being determined on the one hand from the amount of film material processed and its degree of blackening, and on the other hand from the service life of the tank content by a relatively complex automatic device and is added at periodic intervals.

From US Pat. No. 3,162,534 a process for the regeneration of lith developers is known, in which only two solutions are used, one of which is of low concentration tion, to compensate for the amount of film developed, the other, of higher concentration, for periodic compensation of the changes caused by the service life. Both solutions contain no hydroquinone; the activity of the solutions can therefore only be maintained in this way for a certain limited time.

The usual regeneration method, as it is used in particular in the case of automatically working development machines, consists in adding measured quantities of the regenerator liquids to the tank contents at periodic intervals and / or at intervals controlled by the quantity of material to be processed, while at the same time, by means of an overflow, a corresponding quantity of liquid, the Composition corresponds to that of the current tank content, fed to a sewer. becomes. The processing liquid thus maintains a constant volume throughout the operating period and is maintained at constant activity by the constant supply of regenerator liquid.

The object of the invention is to provide a particularly simple method for the regeneration of lith developers, which is particularly suitable for automatic development machines and only requires a single regenerator in which the active components are contained in a constant ratio. In particular, the method according to the invention should not require complex methods for determining the bath composition or the blackened film surface and nevertheless allow the activity of the lith developer to be maintained for a very long time, e.g. to keep constant in uninterrupted operation for several months. This line is achieved by the measures listed in claim 1.

In practice, the regenerator is preferably divided into two solution concentrates, one of which at a pH below 7 hydroquinone, sulfite, sodium formaldehyde bisulfite and the other, at a higher pH alkali, buffer substances and any other components such as complexing agents and aromatic amines contains, both concentrates being free of bromine ions. Furthermore, the two concentrates are simultaneously, but separately, and metered into the development tank with the dilution water each time a piece of photographic material to be developed is introduced into the developer tank, it being sufficient to determine the blackened portion of the piece based on experience. The ratio of the amount of regenerator converted in the unit of time to the content of the processing tank is used as a measure of the throughput.

The procedure according to the invention means that both the concentration of bromine ions which is decisive for the activity of the developer solution and that of the hydroquinone which is subjected to air oxidation can be kept largely constant. As is known, the development of exposed photographic material releases bromine ions, the amount of which is proportional to the silver bromide present in the photographic layer and the exposed area fraction. Since the total volume of the regenerator added is kept proportional to the area of the blackened film to be developed, the concentration of bromine ions in the processing bath remains constant: for each unit area of blackened film, a certain amount of bromine ions is newly introduced into the bath; however, with each dosing burst a proportion by volume of the bath proportional to the developed area is removed by the overflow. As soon as the process is in equilibrium, the amount of new bromine ions that are created and those that are continuously removed from the bath are inevitably the same. On the other hand, the variation of the regenerator concentration serves to keep the hydroquinone portion constant: with a low machine throughput, the portion of the hydroquinone lost through air oxidation is relatively large. Conversely, with a high machine throughput, the hydroquinone consumption prevails through the normal development process. By using a more dilute regenerator at high throughput and a more concentrated one at low throughput, the hydroquinone content of the processing bath can be kept constant.

If the machine is idle for a longer period of time, hydroquinone is consumed by air oxidation without the bromine ions being released at the same time. This influence can now be compensated for by adding an amount of the regenerator corresponding to the expected loss in a concentrated state. If the regenerator concentrates do not contain bromine ions, the bromine ion concentration in the developer liquid changes only very slightly as a result of this measure, namely in accordance with the proportion lost by the overflow, which can be kept very small by omitting the dilution water.

If A and B are the two regenerator concentrates and W is the dilution water, the concentration change is preferably carried out in such a way that both the total amount of regenerator liquid for a unit area of blackened film and the ratio of the two regenerator concentrates are kept constant and only the amount of the dilution water in the ratio changed to the amount of the two regenerator concentrates, ie

The regenerator concentration is preferably changed in stages in accordance with the throughput. The minimum concentration, that is to say the minimum ratio of concentrate quantity / total regenerator quantity, can be chosen to be about 2: 6 and can be assigned to a maximum throughput of 60% or higher of the development tank volume. The maximum regenerator concentration depends on the practical minimum throughput, for example about 10% regenerator conversion, and can be around 2.5: 6 to 3: 6. The most favorable values of course depend on the type and composition of the processing solution and the regenerator.

The invention also relates to a device for performing the method. This includes, as well as a device known from the document FR - A - 2 199 136, three storage containers for the two concentrates and for the dilution water, three metering pumps for the concentrates and the water, which through lines with the concentrate and water storage containers on the one hand and with are connected to the processing tank, on the other hand, the control having first input elements for the area, the exposed portion and a type-dependent characteristic size of the photographic material and a second input element for the expected throughput, and is characterized in that the control means by means of the first input elements entered parameters determine the respective amount of the regenerator and from the parameter entered by means of the second input member determines the respective concentration of the regenerator and controls the metering pump accordingly.

• Fig. 1 das Ausführungsbeispiel in schematischer Darstellung
• Fig. 2 ein Blockschaltschema der Steuerung in Fig. 1.

An exemplary embodiment of a device according to the invention is explained in more detail below with reference to the drawing. Show it:

• Fig. 1 shows the embodiment in a schematic representation
• FIG. 2 shows a block circuit diagram of the control in FIG. 1.

As shown, the device comprises three storage vessels 1, 2 and 3 for concentrate A, concentrate B and dilution water W, three metering pumps 5, 6 and 7 driven by a common drive motor 4, a three-way valve 8, a controller 10 for the drive motor 4 and the three-way valve 8 and a processing machine with tanks 11, 12 and 13 for developer, fixer and washing.

The regeneration concentrates A and B and the dilution water W get from their respective storage containers 1, 2 and 3 via lines 14, 15 and 16, the metering pumps 7, 6 and 5 and further lines 17, 18 and 19 into the developer tank 11. The three-way valve 8 lies with its input and its one output in line 19. Its other output is connected to a line 20 which, when the three-way valve is not activated, returns the water to the water reservoir 3.

The controller 10 comprises first setting elements 21, 22 and 23 to take account of the film area, exposure ratio and film characteristics (silver content per unit area) as well as a second setting element 24 to take the machine throughput into account, as well as a start button 25 and generates pulses t and t ₂ , which are the motor 4 and thus the three metering pumps for the period t, start up and activate the three-way valve for the period t ₂ , so that the regenerating concentrates and the water can get from the storage vessels 1, 2 and 3 into the developer tank 11 during this time. The lengths of the pulses t ₁ and t _{2 can be} influenced in opposite directions by means of the second setting element 24. The controller 10 is designed in such a way that, with the position of the second input member 24 corresponding to the maximum machine throughput, the lengths of the two pulses t, and t2 are of the same size and equal to a basic control pulse t _o , which results in the greatest dilution of the regenerator.

The required length of the basic control pulse t _o results directly from the constant total amount A + B + W of regeneration liquid required and the output of the metering pumps. This total amount is an empirical value and, as already mentioned, depends, among other things, on the characteristics (silver content) S, exposure proportion E and area F of the film material to be processed. t _o is designed for the maximum intended dilution of the regeneration liquid, which is obviously achieved when the three-way valve is activated during the entire operating time of the metering pumps, so that no water is recirculated via line 20. The ratio of regeneration concentrate to dilution water (A + B): W is minimal in this case and is referred to as X below. This ratio is set by appropriate dimensioning or setting of the metering pumps.

Damit die weiter vorne genannte Gesamtmenge A + B + W an Regenerierflüssigkeit konstant bleibt, muss dann die Dauer des Impulses t₁ folgende Bedingung erfüllen

Für den Spezialfall grösster Verdünnung, also für Z = 1, gehen die beiden Bedingungen (I) und (II) für t₁ und t₂ wieder über in t₁ = t₂ = t_o.The ratio of regeneration concentrate (A + B) to dilution water W can be increased according to the machine throughput by means of the setting member 24. This takes place in that the pulse t is shortened by one between 1 and about 0.85 in five steps adjustable by means of the adjusting member 24 against factor Z t _{o 2,} so

So that the total amount of regeneration liquid A + B + W mentioned above remains constant, the duration of the pulse t ₁ must then meet the following condition

For the special case of greatest dilution, i.e. for Z = 1, the two conditions (I) and (II) for t ₁ and t ₂ again change into t ₁ = t ₂ = t _o .

A block circuit diagram of the controller 10 is shown in FIG. 2. In addition to the start button 25 already mentioned and the input elements 21-24, it comprises four multipliers 101-104, an integrator 105, an adder 106 and two comparators 107 and 108.

For reasons of drawing, the input elements are symbolized by potentiometer signs. Potentiometers would allow a continuous input of the area F of the material to be processed, exposure proportion E, film type S and throughput Z. In practice, step switches instead of potentiometers have proven to be completely sufficient and in some cases even more appropriate.

wobei die Werte X entsprechend ihrer schon weiter vorne gegebenen Definition in der Regel fest eingestellt sind. Die Ausgangssignale der beiden Multiplikatoren 103 und 104 werden im Addierer 106 summiert und dann zum einen Eingang des Komparators 107 geführt. Das Ausgangssignal des Multiplikators 102 ist zum einen Eingang des zweiten Komparators 108 geführt.The products EF and EFZ of the entered quantities E, F and Z are formed in the multipliers 101 and 102. The multipliers 103 and 104 multiply these products by the terms

whereby the values X are generally fixed in accordance with their definition given above. The output signals of the two multipliers 103 and 104 are summed in the adder 106 and then passed to one input of the comparator 107. The output signal of the multiplier 102 is fed to an input of the second comparator 108.

ergibt, worin k stellvertretend für all Systemkonstanten des Integrators 105 steht und t die_Zeit bedeutet. Dieses Ausgangssignal wird nun den jeweils zweiten Eingängen der Komparatoren 107 und 108 zugeführt und mit den Ausgangssignalen des Addierers 106 bzw. des Multiplikators 102 verglichen.The input element 23 (film type S) goes directly into the time constant of the integrator 105. After reset by the start button 25, this integrator integrates a constant signal in such a way that its output signal increases

results in which k represents all system constants of the integrator 105 and t means the_time. This output signal is now fed to the respective second inputs of the comparators 107 and 108 and compared with the output signals of the adder 106 and the multiplier 102.

die Grösse der jeweils an den anderen Eingängen der Komparatoren anliegenden Spannungen erreicht, kippt der betreffende Komparator und beendet damit den Impuls t₁ bzw. t_z, wodurch die Dosierpumpen bzw. das Magnetventil wieder ausser Betrieb gesetzt werden. Die Komparatoren verbleiben dann in diesem Zustand, bis sie durch Betätigung des Startknopfs von neuem gekippt werden.When a piece of photographic material to be developed is entered into the developing machine, film type S, area F and exposure ratio E are set and the start button 25 is actuated, the start pulse, if necessary, being triggered automatically by a microswitch or the like each time a film piece is entered. The machine throughput Z estimated for the day was set at the beginning of the day. After the integrator has been released by the start button, the output signal of the integrator is zero, so that the outputs of the comparators become positive and thus activate the metering pumps and the solenoid valve via servo amplifiers (not shown). Once the integrator output voltage

reaches the size of the voltages present at the other inputs of the comparators, the comparator in question tilts and thus ends the pulse t ₁ or t _z , as a result of which the metering pumps or the solenoid valve are put out of operation again. The comparators then remain in this state until they are tilted again by actuating the start button.

Wenn der Wert

mit t_o bezeichnet wird, gehen diese Formeln direkt in die Formeln (I) und (11) über.As can be seen from FIG. 2, the time durations of the pulses t and t ₂ result in:

If the value

denoted by t _o , these formulas go directly into formulas (I) and (11).

The system constants of the integrator 105 represented by k are, of course, to be designed in such a way that the desired metering volume is obtained for the given dimensions of the feed pumps. However, this requires no further explanation for the person skilled in the art.

While maintaining a constant activity of lith developers according to the previously known methods requires continuous, complex control of the bath activity or the operating conditions while taking the service life into account, it is surprising that according to the method according to the invention and with the device required for its implementation, this The same result can be achieved by simply changing the degree of dilution of the regenerator liquid or the amount of dilution water added simultaneously with the concentrates, depending on the machine throughput.

The direct use of concentrates and the supply of the dilution water in the processing tank also simplifies the preparatory work by the preparation diluted regenerator solutions from the components or from the concentrates are not required.

The following example is intended to explain the method and the mode of operation of the device according to the invention in more detail, the invention of course not being restricted to the composition of the components shown in this example.

example

A high-contrast photographic material with a silver halide emulsion layer, which contains developable silver per m ^{2 of} the emulsion layer 6.gr in the form of 70 mole percent silver chloride and 30 mole percent silver bromide, is exposed in a conventional manner and then introduced in the form of individual sheets into a continuous processing machine.

The first tank of this processing machine contains 64 liters of a developer solution, which contains the following substances per liter:

At a temperature of 25 ° C the development time is 1.8 minutes.

In order to keep the activity of this solution constant for a long time, a regenerator solution of the following composition is added when each sheet is introduced into the machine.

Regenerator concentrate A:

Regenerator concentrate B:

1 liter of diluted regenerator solution is added to the developer on each square meter of exposed area of the photographic material, components A and B being diluted with water as shown in Table 1 below, depending on the machine throughput. Components A and B and the dilution water are individually introduced into the developer tank in individual portions using a dosing pump.

In the event of a foreseeable machine downtime with the heating switched off and the developer not circulating for more than 48 hours, 160 ml of the two concentrates A and B = 0.25% of the tank content are added per 24 hours of downtime to the development tank.

Provided that the development time and temperature are observed, the same results are still obtained after a period of 6 months.

Claims (12)

1. A method of regenerating and maintaining the activity of a photographic processing solution, particularly a Lith developing solution, in a continuous processing machine intermittently supplied with exposed photographic material, by adding a regenerator consisting of concentrated substances and diluting water to the processing solution before, simultaneously or after the introduction of photographic material, which method comprises maintaining constant the amount of regenerator added during each regeneration process, said amount of regenerator being related to the product of mean exposure and unit of surface of the given photographic material, the concentration of the regenerator added, that is to say, the proportion of concentrates in the regenerator, being made greater the lower the expected throughput of photographic material for a given period, particularly for 1 day.

2. A method according to Claim 1, wherein the regenerator concentrates used are substan- tionally free from bromide.

3. A method according to Claim 1 or 2, wherein the proportion of concentrates in the regenerator is kept constant independently of the degree of dilution.

4. A method according to Claim 3, wherein the regenerator used is a mixture of two concentrates and water.

5. A method according to Claim 1, wherein the concentration of the regenerator attains a minimum with a daily minimum throughput corresponding to a consumption of regenerator fluid of 60% or more of the contents of the developer tank, and with lower throughputs is increased, in several stages attributed to appropriate throughput ranges, up to a maximum corresponding to the lowest throughput to be expected.

6. A method according to Claim 5, wherein the minimum regenerator concentration is made approximately 2 : 6.

7. A method according to Claim 6, wherein the maximum regenerator concentration is made approximately 2.5 : 6 to 3 : 6.

8. A method according to any one of the preceding Claims, wherein, on stoppage of the processing machine, there is supplied, as regenerator to compensate for changes during the time of stoppage, a mixture of concentrates without diluting water in amounts which are so measured that the photographic activity of the processing solution is retained over the stoppage time to be expected, the loss of activity per unit time to be anticipated being determined beforehand by methods known per se.

9. A device for carrying out the method according to any one of Claims 1 to 4, which device comprises three storage containers (1,2,3) for the two concentrates (A,B) and for the diluting water (W), three proportioning pumps (5,6,7) for the concentrates and the water, which pumps are connected by pipe lines (14,19) with the concentrate- and water- storage containers (1,2,3) on the one side and with the processing tank (11) on the other side, and an electrical control system (10) for the proportioning pumps (5, 6, 7), the control system (10) comprising first input units (21,22,23) for the surface area, the exposed portion and a characteristic variable dependent on the nature of the photographic material, and a second input unit (24) for the expected throughput, determining from the parameters fed in by the first input units the required amount of regenerator in each case and, from the parameters supplied by the second input unit (24) the required concentration of the regenerator for that amount, and regulating the proportioning pumps (5,6,7) accordingly.

10. A device according to Claim 9, wherein the three proportioning pumps (5,6,7) are actuated by a common drive (4) regulated by the control system (10), a three-way valve (8) being incorporated in at least one (19) of the three pipe lines (17,18,19) leading from the pumps to the processing tank, so that the fluid supplied from the respective pump (5) is fed, with the valve (8) in the first position, to the processing tank (11), and in the second position of the valve (8) back to the input-side of the pump (5) or into the storage vessel (3), the concentration of the regenerator being regulated by virtue of the three-way valve (8) being brought into its first position by the control system (10) during a time interval, determined by the second input unit (24), within the period of time, determined by the first and second input units (21,22,23), that the proportioning pumps (5,6,7) are being driven.

11. A device according to Claim 10, wherein the three-way valve (8) is inserted in the fluid system after the proportioning pump (5) for the diluting water.

12. A device according to Claim 11, wherein the control system (10) determines the duration t, of operation of the proportioning pumps (5,6,7), and the interval of time t₂ during which the three-way valve (8) is in its first position, in accordance with the relationships:

wherein to denotes the pump operating time required for a given delivery of the dosing pumps (5,6,7) in order to supply the amount of regenerator determined by the first input units (21,22,23) when Z = 1, x is the ratio of the total amount of concentrate to the amount of diluting water for Z = 1, the ratio being determined by appropriate dimensioning of the feed pumps, and Z is a factor <1 determined by the second input unit (24).

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