GB1582645A - Process for the high-speed processing of photographic material - Google Patents

Abstract

In this rapid-processing method for photographic material, the treatment fluid is foamed by injection of air or inert gas to about 2 to 10 times its volume immediately before application, warmed up to about 50 DEG C to 80 DEG C and then passed in a thin layer, as far as possible in laminar flow, several times over the material to be processed. Per treatment, only such a quantity of treatment fluid is used each time as is chemically absolutely necessary, and is then not used again.

Description

(54) PROCESS FOR THE HIGH-SPEED PROCESSING OF PHOTOGRAPHIC MATERIAL (71) We, CIBA-GEIGY AKTIENGESELLSCHAFT, a company organized under the laws of the Confederation of Switzerland, of Klybeckstrasse 141, 4002 Basle, Switzerland, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a process for the high-speed processing of photographic material, in which a heated processing liquid is passed over the emulsion surface of a photographic material in a thin layer, the thickness of which is of the same order of magnitude approximately as that of the photographic material.

Processes of this kind enable very short processing times to be obtained and are therefore particularly useful where it is necessary to produce a finished photographic picture in the minimum amount of time. This is the case, for example, in coinoperated photographic booths, in screen photography, microscopic photography, the production of printing blocks, computer print-out equipment, and so on.

A method of-the above kind is disclosed in U.S. Patent specification 3 886 576. This process operates on the once-through principle, i.e. fresh processing liquid is continually pumped through the processing chamber during any one stage of the process, the partially spent processing liquid is then discharged. The disadvantage of this once-through principle is that the processing liquid is not used under optimum conditions and much more liquid is used than that required to achieve the desired chemical action for the particular process concerned.

In addition to increased material costs, this also leads to unnecessary high effluent discharge. The partially spent processing liquid could be returned to a fresh liquid reservoir and be reused together with fresh liquid, but it is known from experience that spent processing liquid is much less stable and less storable, so that such reuse is frequently impossible. This applies particularly to coin-operated photographic booths in which a processing operation takes place infrequently and only a small amount of processing liquid is used each time. In those cases the total loss process is to be preferred since the processing liquid is used once only.

A disadvantage of a high-speed processing method such as that disclosed in U.S.

Patent specification 3 886 576 is that the liuidiskept at entire stock of processing liquid is kept at the operating temperature. With the tively high operating temperatures conventional in high-speed processing methods, the conventional processing liquids are relatively unstable and can be stored only for a very limited time. In consequence such methods are generally only suitable for processing plants which are continuously in operation and not for those which are used only occasionally such as coin-operated photographic booths.

The object of this invention is to provide a high-speed processing method suitable particularly for intermittent operation whilst using the minimum amount of processing liquid.

In accordance with this invention we provide a method of processing photograph material comprising heating and foaming only the minimum quantity of processing liquid required to produce a desired chemical action on the material to be processed, repeatedly passing the foamed liquid over said material in a thin layer, the thickness of which is of the same order of magnitude as that of the photographic materiaL, and discharding the foamed liquid after the desired chemical action has been achieved.

There is also provided the method as defined, comprising a processing chamber in the form of a slit, means for positioning the photographic material in the chamber, means for repeatedly passing processing liquid through the chamber, means for heating the liquid and means for foaming the liquid prior to its introduction into said chamber wherein the means for passing the liquid into the chamber comprise metering means for supplying a specific volume of liquid into the chamber sufficient to produce the required chemical action on said material.

A preferred embodiment of the invention will now be described with reference to the accompanying drawing which is a section through the processing apparatus showing the liquid conveying means, metering means and foaming means in a simplified form.

Referring to the drawing, the processing chamber comprises a bottom part 1 hinged to a top part 2 with an annular gasket 3 between the two parts for form a processing slit or chamber 5. The photographic material 4 is clamped between the gasket 3 and top part 2 along its edges. The slit width or height H of the processing chamber is of approximately the same order of magnitude as the thickness of the photographic material to be processed, i.e. about 0.1 to about 0.5 mm. The volume of the processing chamber should be approximately equal to the minimum volume of processing liquid required to achieve the desired action for that particular processing operation.

The top part 2 is provided with a slot system 6 connected to a suction source (not shown) via a connection 7 for retaining the photographic material to be processed against the underside of the top part 2.

Slots 8 and 9 extending over the entire chamber width (perpendicularly to the drawing plane) are formed in the bottom part 1, one on either side of the processing chamber 5. These two slots are connected via ducts 10 and 11 to a ring pipe 12 containing a circulating pump 13. Bottom part 1 also contains a duct system 14 forming a heat exchanger, the duct system 14 being connected to a heat exchange liquid reservoir 15 provided with heating and circulating means. By means of this heat exchanger duct system 14, the bottom part 1 and hence the processing liquid which flows through the ducts 10 and 11 and the chamber 5 can be heated to the required temperature.

Ring pipe 12 is connected via valves 16 and 17 to a compressed air supply 18 and to unheated tanks 19, 20, and 21 for a developer solution, a fixer solution and water respectively. The fluid in the circuit formed by the ring pipe 12, ducts 10 and 11 and the processing chamber 5 can be discharged via another valve 22. Valves 16, 17 and 22, pump 13 and reservoir 15 are controlled by a central control system 23.

To process the photographic material it is introduced manually or automatically into the chamber 12 and is retained against the underside of the top part 2 with the emulsion side downwards by the suction applied via connection 7 to the slot system 6. A specific quantity of develoPer solution is then introduced from tank 19 into the ring pipe 12 by valve unit 17 responding to an appropriate command given by the control system 23. The amount of liquid corresponds to the minimum quantity of developer required to develop that size of photographic material. Since this quantity is much less than the entire circulation volume, compressed air or inert gas, e.g. nitrogen, is injected into the ring pipe 12 via valve 16 so that the developer is made to foam to about twice to 10 times and occupy the entire circulation volume.Since the volume of the foam is restricted at a maximum to about ten times the volume of liquid, the ring pipe 12 with all the ducts, conduits and cavities communicating therewith, is so constructed that the entire circulation volume is not more than a maximum of approximately ten times the volume of the processing chamber. To assist the foaming operation, the developer solution may preferably also contain foam-active and foam-stabilizing additives.

The foamed developer solution is then repeatedly pumped through the processing chamber by the pump 13. In view of the small volume in circulation, the solution is heated practically instantaneously to the required temperature of about 50"C to 80 C, preferably 80"C or more on entering the bottom part 1 and flowing through the processing chamber 5. The speed of circulation is selected so that the now in the processing chamber is as far as possible laminar (Reynolds numbers between approximately 20 and 2300).

In a practical example, the liquid throughput was 1 ml/sec corresponding to a linear speed of flow of about 5 cm/sec. (Processing chamber cross-section 100 mm x 0,2 mm), This speed of flow, which is relatively high as compared with the prior art, in conjunction with the small height of the processing chamber (0.2 mm) gives a very intensive and hence very rapid processing.

When development is complete, the valve 22 is opened and the circuit is flushed with water from tank 21. Practically all the used developer solution is discharged and is not re-used. The flushing water is then removed from the circuit by means of compressed air.

All these operations are again carried out automatically by the control system 23. The minimum quantity of fixer solution to fix the photograph is then introduced into the circuit from tank 20 and, like the developer solution, is made to foam by means of com pressed air and is pumped through the processing chamber a number of times. When fixing is complete, water is again admitted and the processed photographic material is finally dried with compressed air.

If the temperatures used are at least 60 C, processing times of about 5 to 7 sec. per processing stage or final wash can be achieved in this way. Intermediate washes require about 1 second. For a four-stage process (inclusive of final wash), the total processing time is about 30 seconds.

In the above-described apparatus the processing liquids are circulated but they could be pumped to and fro across the emulsion side of the photographic material.

One of the main differences between the invention and the prior art is that the processing liquid is made to foam. In most prior art processes every attempt is made to prevent foaming by using additives for the processing liquids since such foaming has created problems. Despite all such experience, it has now quite surprisingly been found that foaming in conjunction with a small volume processing chamber not only does not cause such problems but even brings about a more intensive effect and enables the quantity of processing liquid required to be reduced to practically the theoretical minimum, thereby enabling the total loss process with its known advantages to be used. The volume of the parts required for passing the processing liquid through the chamber (i.e.

ducts, conduits, cavities, pumps etc.,) is much larger than the volume of the minimum amount of processing liquid required to achieve the desired chemical action. If the volume of liquid were not increased by foaming, it would be practically impossible to circulate such a small quantity of liquid so that more liquid than that required to achieve the same chemical result would have to be used. The very smallest volumes of liquid can be reliably circulated as a result of the foaming operation and can be heated up more easily, quickly and economically. In particular, it is possible to store the processing liquid in a cool state and to bring to the required operating temperature immediately upstream of, or in, the processing chamber, only the amount of liquid required for that particular processing operation.This is of great importance in intermittently operating processing plants since the stocks of processing liquid will remain stable and storable for much longer periods.

In the embodiment illustrated, the heat exchanger is incorporated in the chamber base. A suitable heat exchanger could be disposed outside the processing chamber but this would increase the circuit volume.

Instead of a heat exchanger any other heating means may be used, e.g. an electrical resistance heater.

Control system 23 may be electronic or pneumatic.

WHAT WE CLAIM IS:- 1. A method of processing photograph material comprising heating and foaming only the minimum quantity of processing liquid required to produce a desired chemical action on the material to be processed, repeatedly passing the foamed liquid over said material in a thin layer, the thickness of which is of the same order of magnitude as that of the photographic material, and discarding the foamed liquid after the desired chemical action has been achieved.

2. A method according to Claim 1, wherein the processing liquid is made to foam to about twice to ten times the liquid volume.

3. A method according to Claim 1 or 2, wherein the liquid is heated to about 50 to 80"C.

4. Photographic material processed according to any one of Claims 1 to 3.

5. Apparatus for performing the method according to Claim 1, comprising a processing chamber in the form of a slit, means for positioning the photographic material in the chamber, means for repeatedly passing processing liquid through the chamber, means for heating the liquid and means for foaming the liquid prior to its introduction into said chamber wherein the means for passing the liquid into the chamber comprise metering means for supplying a specific volume of liquid into the chamber sufficient to produce the required chemical action on said material.

6. Apparatus according to Claim 5, wherein the means for passing the processing liquid through the chamber are so constructed that their total volume required for passing the liquid through the chamber is not more than approximately ten times the chamber volume.

7. Apparatus according to Claim 5, wherein the height of the slit-like chamber measured perpendicularly to its surface is about 0.1 to 0.5 mm.

8. Apparatus according to any one of Claims 5 to 7 wherein the means for heating the liquid are adapted to heat at any time only the volume of liquid passed through the chamber.

9. Apparatus according to Claim 8, wherein the heating means comprise a heat exchanger in the treatment chamber.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. pressed air and is pumped through the processing chamber a number of times. When fixing is complete, water is again admitted and the processed photographic material is finally dried with compressed air. If the temperatures used are at least 60 C, processing times of about 5 to 7 sec. per processing stage or final wash can be achieved in this way. Intermediate washes require about 1 second. For a four-stage process (inclusive of final wash), the total processing time is about 30 seconds. In the above-described apparatus the processing liquids are circulated but they could be pumped to and fro across the emulsion side of the photographic material. One of the main differences between the invention and the prior art is that the processing liquid is made to foam. In most prior art processes every attempt is made to prevent foaming by using additives for the processing liquids since such foaming has created problems. Despite all such experience, it has now quite surprisingly been found that foaming in conjunction with a small volume processing chamber not only does not cause such problems but even brings about a more intensive effect and enables the quantity of processing liquid required to be reduced to practically the theoretical minimum, thereby enabling the total loss process with its known advantages to be used. The volume of the parts required for passing the processing liquid through the chamber (i.e. ducts, conduits, cavities, pumps etc.,) is much larger than the volume of the minimum amount of processing liquid required to achieve the desired chemical action. If the volume of liquid were not increased by foaming, it would be practically impossible to circulate such a small quantity of liquid so that more liquid than that required to achieve the same chemical result would have to be used. The very smallest volumes of liquid can be reliably circulated as a result of the foaming operation and can be heated up more easily, quickly and economically. In particular, it is possible to store the processing liquid in a cool state and to bring to the required operating temperature immediately upstream of, or in, the processing chamber, only the amount of liquid required for that particular processing operation.This is of great importance in intermittently operating processing plants since the stocks of processing liquid will remain stable and storable for much longer periods. In the embodiment illustrated, the heat exchanger is incorporated in the chamber base. A suitable heat exchanger could be disposed outside the processing chamber but this would increase the circuit volume. Instead of a heat exchanger any other heating means may be used, e.g. an electrical resistance heater. Control system 23 may be electronic or pneumatic. WHAT WE CLAIM IS:-

1. A method of processing photograph material comprising heating and foaming only the minimum quantity of processing liquid required to produce a desired chemical action on the material to be processed, repeatedly passing the foamed liquid over said material in a thin layer, the thickness of which is of the same order of magnitude as that of the photographic material, and discarding the foamed liquid after the desired chemical action has been achieved.

2. A method according to Claim 1, wherein the processing liquid is made to foam to about twice to ten times the liquid volume.

3. A method according to Claim 1 or 2, wherein the liquid is heated to about 50 to 80"C.

4. Photographic material processed according to any one of Claims 1 to 3.

5. Apparatus for performing the method according to Claim 1, comprising a processing chamber in the form of a slit, means for positioning the photographic material in the chamber, means for repeatedly passing processing liquid through the chamber, means for heating the liquid and means for foaming the liquid prior to its introduction into said chamber wherein the means for passing the liquid into the chamber comprise metering means for supplying a specific volume of liquid into the chamber sufficient to produce the required chemical action on said material.

6. Apparatus according to Claim 5, wherein the means for passing the processing liquid through the chamber are so constructed that their total volume required for passing the liquid through the chamber is not more than approximately ten times the chamber volume.

7. Apparatus according to Claim 5, wherein the height of the slit-like chamber measured perpendicularly to its surface is about 0.1 to 0.5 mm.

8. Apparatus according to any one of Claims 5 to 7 wherein the means for heating the liquid are adapted to heat at any time only the volume of liquid passed through the chamber.

9. Apparatus according to Claim 8, wherein the heating means comprise a heat exchanger in the treatment chamber.