WO2004109397A1

WO2004109397A1 - Photographic processing

Info

Publication number: WO2004109397A1
Application number: PCT/GB2004/002194
Authority: WO
Inventors: John Richard Fyson
Original assignee: Eastman Kodak Company
Priority date: 2003-06-10
Filing date: 2004-05-21
Publication date: 2004-12-16
Also published as: GB0313299D0

Abstract

A method of processing photographic material in which a processing chamber is indirectly heated to an aim temperature, the chamber being replenished substantially simultaneously with the passage of the material through the chamber. Either the replenisher is at ambient temperature and the material is heated to a temperature above aim temperature or the material is at ambient temperature and the replenisher is heated to a temperature above aim temperature, the final temperature of the solution being the aim temperature.

Description

Photographic Processing

Field of the Invention

The present invention relates to the field of photographic processing, in particular to processors using low volumes of processing solution.

Background of the Invention

In photographic processing the materials may be processed in web or sheet form by passing the material through a plurality of processing stages, for example, developer, bleach, bleach/fix, wash and stabiliser stages.

The reactions taking place during photographic processing are temperature dependent. Photographic processing machines must be maintained at constant temperature so that the sensitometry of the process remains constant. In colour processes manufacturers often recommend process temperature kept at +0.15°C from the aim temperature.

Small processing machines often have low volumes of liquid in the processing tanks. These tanks may also be heated externally, for example by means of a water bath partially surrounding the tanks or by means of heat mats attached to the tanks. The temperature 'buffering' of these tanks is poor and when paper or film at ambient temperature is passed through the first tank, usually the developer, the tank temperature is decreased with a corresponding decrease in developer activity, causing a change in the sensitometry of the processed material.

To prevent the working characteristics of a bath of photographic developer from changing during development of a quantity of exposed silver halide photographic material, and also to maintain the volume of the developer, it is common practice to add a replenisher. Such a replenisher is usually a more concentrated aqueous solution of principal developer constituents that are consumed during development. The replenisher has a reduced concentration of components released during development so that these compounds are diluted. In this way the developer tank solution can be maintained at a constant composition.

However, if the addition rate of this replenisher is significant compared to the volume of the processing solution in a processor's tank, the temperature of the replenisher will influence the temperature of the tank. For instance, if the replenisher is at ambient temperature and the tank temperature at 40°C, a normal operating temperature for a colour process, the addition of replenisher will tend to cool the tank down. This in turn will affect the sensitometry of processed materials.

US 5631121 discloses a method of improving the temperature stability during the development stage of a photographic process by heating the material to the same temperature as the developer solution. The material is passed through a conditioning chamber prior to entering the development stage of the processor.

Problem to be solved by the Invention

The present invention aims to provide a method of mamtaining the temperature of a low volume photographic process witiiin narrow limits such that the temperature is not significantly affected by the paper or replenisher entering the processor.

Summary of the Invention

The processor temperature, i.e. the temperature of the solution inside the processor, hereinafter referred to as the aim temperature, can be maintained by heating either the paper or replenisher to a temperature above this aim temperature before addition to the processor such that one effectively warms the other as it enters the processing space. The replenishment must be more or less continuous and should be synchronised with the passage of the material through the processor. According to the present invention there is provided a method of processing photographic material in which a processing chamber is heated indirectly to an aim temperature, the chamber being replenished substantially simultaneously with the passage of photographic material through the chamber, wherein either the replenisher is at ambient temperature and the material is heated to a temperature above aim temperature such that the final temperature is aim temperature or the material is at ambient temperature and the replenisher is heated to a temperature above aim temperature such that the final temperature is aim temperature.

Preferably the replenisher is fed into the chamber within plus or minus two seconds of the material being fed into the chamber.

Advantageous Effect of the Invention

By heating either the material to be processed or the replenisher solution to a temperature higher than the temperature required for the process a constant temperature is achieved for the process itself. Thus constant sensitometry is achieved

It is not necessary to heat both the material and the replenisher. This means the number and heaters and sensors can be reduced. This results in less costly and complicated processors.

Brief Description of the Drawings

For a better understanding of the present invention, reference will now be made, by way of example only, to the accompanying drawings in which;

Figure 1 is a schematic side view of a processor which can be used with the method of the invention; Figure 2 is a schematic end view of an embodiment of a processor which can be used with the method of the invention;

Figure 3 is a graph illustrating temperature of liquid exiting the processor against time with respect to example 1 ;

Figure 4 is a schematic end view of a second embodiment of a processor which can be used with the method of the invention; and

Figure 5 is a graph illustrating temperature of liquid exiting the processor against time with respect to example 2.

Detailed Description of the Invention Figure 1 is a schematic side view of a processor for use with the method of the invention. Example 1

The processor is provided by a stainless steel shallow tray 1 provided within a water bath 7. The tray holds a volume of solution of less than 100 ml, preferably less than 50 ml. At the bottom of the tray there is a channel 10. This channel extends along the length of the tray and across a substantial part of the width thereof. A pair of input rollers 3 are provided at one end of the tray 1. The other end of the tray is provided with a pair of output rollers 4. A temperature controlled plate or ramp 20 is provided before the pair of input rollers 3. The tray 1 is 350 mm long and is raised by 35 mm at the ends, with a constant curvature in between. Sides 6 form a watertight chamber. A block 13 rests on top of the sides 6. Arms 14 are movably attached to the block 13. These arms 14 guide a reciprocating roller 2. The roller 2 is long enough to cover the width of the tray 1. The roller rests on the sides of the channel 10 under its own weight. The arms 14 can move freely within holes in the block 13. This can be seen in figure 2 of the drawings. The block 13 is attached to a belt 15. The belt 15 is driven by rollers 16 and 17 and reciprocates to move the roller 2 between positions 2a and 2b. In figure 1 positions 2a and 2b represent the extreme positions of the roller 2, there being only one roller in the apparatus illustrated. It is of course possible to have two or more rollers which reciprocate. It is also possible to have some rollers which reciprocate and some which do not. A delivery pipe 8 is carried on the block 13 for supplying replenisher from a flexible supply pipe 18 onto the roller 2. A discharge pipe 19 is provided at the bottom of the tray 1. There may be more than one pipe 19.

The photographic paper 5 is fed through a guide, not shown, along the temperature controlled ramp 20 into the input rollers 3 while the reciprocating roller 2 is already moving from position 2a to 2b at a rate of approximately 1 Hz. Preferably the replenisher is fed into the chamber within one or two seconds of the material being fed into the chamber. The paper 5 passes through the shallow tray, under the reciprocating roller 2 and out through the output rollers 4. The arms 14 rise up witl in the block 13 as the roller moves towards the limit of its travel. If the processor is running in continuous mode then replenisher solution is added continuously through the delivery pipe 8 from the flexible supply pipe 18 onto the roller 2. Processing solution can also be added and removed through pipe 19 at the bottom of the tray itself at the same rate as the replenisher is added to the tray, thus mamtaining constant volume of liquid in the tray. Processing solution can also be added at any other point within the shallow tray. Processing solution can be added or removed from underneath the paper 5 or above the paper.

For the purposes of example 1 two trays 1 were fixed together with a suitable turn around such that paper travelled from one tray to another allowing two processing stages to be carried out in succession. In this example one tray was used for developer and one for bleach/fix. Paper exited the bleach /fix and was taken away to be washed and then hung up to dry.

The solutions used in the process were as follows

Developer and Replenisher

To make one litre

875g water (deinineralised)

33g potassium carbonate

5g DEHA

7.5g CD3 (used part b of a kit as had run out ) lOdrops Tween 80

1ml Dequest 2010

2g Blankophor REU pH adjusted with 10% nitric acid to 10.5

Bleach-fix and Replenisher To make 1 litre

200 ml 1.56M ferric ammonium EDTA solution

140g ammonium thiosulphate

20g sodium hydrogen sulphite lOg glacial acetic acid pH adjusted to 6.0 with either ammonia solution or sulphuric acid.

The temperature of the developer tray, or tank, was monitored by measuring the temperature of the liquid exiting the tray through the pipe 19. A thermocouple was inserted into the tube until it reached the end, almost going into tray 1 . The thermocouple was connected up through a sensing module, made by Pico, which in turn was suitably connected to a computer with suitable software for logging the temperature The process was run under three conditions:

1) The temperature ramp 20 was unheated

2) The temperature ramp was set at the shallow tray temperature

3) The temperature ramp was set a temperature in excess of that of the shallow tray by an amount estimated that is needed to heat the replenished liquid

The temperature against time profiles are shown Figure 3.

Without the ramp heater on the temperature of the solution reaches 39°C, a degree less than the aim temperature, and gradually falls. With the ramp heater on, but set at 40°C, the temperature of the solution reaches about 39.5°C but again falls slowly as replenisher is added. With the ramp temperature set at 41 °C the aim temperature of the solution is achieved and remains constant.

Example 2

Example 2 was a repeat of example 1 with the exception that the replenisher was heated rather than the paper. The apparatus used is illustrated in Figure 4.

The apparatus shown in Figure 4 is similar to Figure 2. However in this embodiment the delivery pipe 8 is supplied by a tube 21. This tube is a fine bore stainless steel tube and is provided with a heating coil 22. The heating coil is connected to a conventional control unit. It will be understood by those skilled in the art that any other appropriate method of heating may be used to heat the replenisher. These include, but are not limited to, induction, a hot water jacket, by microwave etc. The replenisher is heated to a temperature above the aim temperature prior to delivery to the processor. For the purposes of example 2 the replenisher was heated to a temperature of42.3°C. The temperature against time profile is shown Figure 5.

It can be seen from the experiments that heating either the material to be processed or the replenisher to a temperature above the aim temperature prior to entry into the processor allows the processing to take place at substantially constant temperature.

The temperatures to be used may be determined based on the area of material to be processed, the specific heat capacity of the material per unit area, the volume of replenisher to be used and the specific heat capacity of the replenisher per unit volume.

The calculations may be as follows:

The sum of the product of the individual heat capacities and input temperatures of the replenisher and material, the material being paper for the purposes of the examples, divided by the sum of the heat capacities is equal to the aim temperature,

paper paper paper / - rep rep rep _ n

A paper S paper +^~V rep S rep ^{~ ώn}

where A_pap__r is the area of material processed in unit time S_paper is the specific heat capacity of the material per unit area

V_rep is the volume of the replenisher pumped in unit time S_rep is the specific heat capacity of the replenisher per unit volume θpap_er, is the input temperature of the material θ_rep, is the input temperature of the replenisher and (9_ai_m is the temperature of the tank.

Alternatively the temperature of the replenisher and material can be determined empirically to maintain constant temperature.

It will be understood that although the examples described use paper as the material the invention is equally applicable to film. The invention has been described in detail with reference to preferred embodiments thereof. It will be understood by those skilled in the art that variations and modifications can be effected within the scope of the invention.

Claims

Claims:

1. A method of processing photographic material in which a processing chamber is heated indirectly to an aim temperature, the chamber being replenished substantially simultaneously with the passage of photographic material through the chamber, wherein either the replenisher is at ambient temperature and the material is heated to a temperature above aim temperature such that the final temperature is aim temperature or the material is at ambient temperature and the replenisher is heated to a temperature above aim temperature such that the final temperature is aim temperature.

2. A method as claimed in claim 1 wherein the replenisher is fed into the chamber within plus or minus two seconds of the material being fed into the chamber.

3. A method as claimed in claim 2 wherein the replenisher is fed into the chamber within plus or minus one second of the material being fed into the chamber.

4. A method as claimed in claim 1, 2 or 3 wherein the volume of solution held in the processing chamber is less than 100 ml.

5. A method as claimed in claim 5 wherein the volume of solution held in the processing chamber is less than 50 ml.

6. A method as claimed in any preceding claim wherein the replenisher is heated to a temperature above the aim temperature by means of a heating coil.

7. A method as claimed in any preceding claim wherein the material is heated to a temperature above aim temperature by means of a heated plate.

8. A method as claimed in any preceding claim wherein the temperatures to which the replenisher or the material are to be heated are determined using the following equation:

A paper S paper fi paper + ~^, ιV rep S rep " fl^σ rep _Q

Δ paper paper +V rep S rep ^{~ aim}

where A_paper is the area of material processed in unit time Spa _er is the specific heat capacity of the material per unit area V_rep is the volume of the replenisher pumped in unit time

S_rep is the specific heat capacity of the replenisher per unit volume θ_Pap_er, is the input temperature of the material θ_rep, is the input temperature of the replenisher and rS_ai_m is the temperature of the tank.