EP0694814A1

EP0694814A1 - Apparatus and method for processing imaging materials

Info

Publication number: EP0694814A1
Application number: EP95401769A
Authority: EP
Inventors: Norman C/O M. M. & M. Co. Newman; Guglielmo C/O M. M. & M. Co. Izzi; Mark T. C/O 3M United Kingdom Plc Leonard; Basavaraj D. C/O Pic.Prod.Ltd.Part. Desai
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1994-07-27
Filing date: 1995-07-26
Publication date: 1996-01-31
Also published as: JPH08171187A

Abstract

An apparatus (10) and method for processing an imaging material (12), such as a silver halide-based imaging material, which allows for a reduced replenishment rate and a reduced volumetric consumption of processing chemistry and which includes the use of a fluid recirculation loop having a reservoir (38).

Description

Field of the invention

The present invention relates to the processing (i.e., development, bleaching, stabilizing, fixing, and/or washing) of silver halide photographic film, radiographic film, diffusion transfer imaging material, proofing plates and proofing materials, and other imaging materials.

Background of the Art

The processing or development of an imaging material, such as photographic film, is a well-known process. Generally, an exposed imaging material is transported through a bath of processing fluid. The term "exposed" is used in the art to mean that an imaging material, e.g., a photographic film, was struck by some form of image-forming (or exposing) radiation, such as light, x-ray, etc. Imaging materials are generally exposed between 30 to 70 per cent in normal use.
The uniformity and reproducibility of development is dependent on a number of factors including temperature, chemical activity and agitation of the developer solution. Automated processors controlling various aspects of these factors are commonly used for developing photographic elements. Processors use well-known technology to carefully control parameters of the development process. Temperature controls permitting limitations in temperature variations to ±0.5°C are routine. In addition, some degree of movement of the processing fluid (a.k.a. agitation) is important and various methods are available for creating this movement within the processing liquids. Among such available methods are roller movement and recirculation of the bath liquid. The chemical activity of the processing bath is maintained through an automated replenishment process.
It is desirable to reduce the amount of materials used in the processing of photographic film from both an economic and ecological point of view. While a square-meter, dry sheet of silver halide imaging material can imbibe up to 40 milliliters of developer fluid, inefficient fluid usage occurs in known developers via deterioration due to oxidation of the developer fluid in a large volume tank. Manufacturers of newer silver halide developers have attempted to optimize the processing of silver halide materials as efficiently as possible using the least amounts of processing chemicals, while assuring no sacrifice in the high quality of performance that is expected of such materials.
Maintenance of the appropriate level of chemical activity is an important aspect of the development process which assures consistent performance for the product. During development, components of the developer are depleted as reactants are consumed and reaction products are formed. Of particular note are the depletion of hydroquinone and hydroxide ion as reactants and the ultimate formation of hydroquinone monosulfonate and bromide ion as reaction products. The depletion of the reactants and formation of the reaction products lead to deterioration of the processing bath's capability to develop further images. The leaching of materials from the photographic element can also lead to a deterioration of development quality. It is the role of agitation to remove the reaction products from the surface of the photographic medium and to provide fresh chemistry to the surface of the medium to assure continued development of the medium by diffusion into the layer where the image-forming reaction is occurring. It is the role of replenishment to provide a continued supply of reactants and dilution of the reaction products to maintain the overall chemical activity for the processing bath.
The replenishment requirements and sustained capacity of a processing bath to develop film are determined by a number of factors including the silver content of the film, the degree to which the silver halide crystals are converted to image silver (i.e., the usage rate) and the formulation of the developer. An overall requirement is to achieve a steady state in which the replenishment maintains the activity of the bath at a constant level to provide consistent and reproducible development results. Under-replenishment, i.e., insufficient replenishment, leads to deterioration of the processing bath with a decreased processing activity. A result of under-development is insufficient image (low density), low contrast and eventually exhaustion where there is little or no development. Over-replenishment, on the other hand, can lead to a condition in which the activity of the bath becomes excessive and results in over-development, excess image (high density), high contrast and excessive fogging (Dmin) of the film. Conventionally, the recommended practice to provide consistency has been to use a very large reservoir of reactants, which is wasteful with respect to the chemicals being used.
A distinction must be made between the developer in the processing bath and the developer in the replenisher, which is added to maintain the activity of the bath. The developer within the bath, also known as the working developer, may be derived from the replenisher. However, the working developer in an automated processor includes reaction byproducts as well as a reduced level of reactants when compared to the replenisher. In a steady state situation, the developer and reaction products remain at a constant level, accumulating reaction products and depleting reactants during development, while replenishment supplies fresh reactants and dilutes the reaction byproducts. At a proper replenishment rate, the system maintains an approximately steady state balance providing consistent development for the photographic film. The use of a replenisher solution for the development of a film in a replenisher would normally result in an over-developed image, as the replenisher solution is a stronger developing bath than the seasoned or working developer bath. It is, however, common in the art to prepare a working developer bath from a replenisher by either diluting the replenisher solution, adding some reaction products, e.g., bromide, running some exposed film through without replenishment, or some combination to suppress the excess activity of the replenisher and bring it to the level of the working developer.
To assist in maintaining consistent chemical activity, it is common practice that automated processors have a developer bath with a significant volume of liquid, e.g., 20 liters or more. These are generally called "deep tank processors". Deep tank processors have provided the highest throughput rate and have provided a buffering capacity for the developer bath which contributes to the consistency of the process.
Disadvantages of deep tank processors, however, are significant. First and probably foremost, the use and eventual disposal of a large volume of processing fluid is ecologically undesirable. Second, the large volume is economically undesirable to purchasers. Third, a significant period of time is required to heat the large volume to the desired operating temperature.
Shallower tanks or reduced volume tanks have been made commercially available to address the disadvantages of the deep tank processors. However, they have not met with significant acceptance. One of the primary reasons for lack of general acceptance is that low-volume processors traditionally have either not provided the output requirements (productivity for processing imaging material, i.e., throughput rate) or not provided the consistency of performance (development uniformity and consistency) that are provided by deep tank processors.
United States Patent No. 5,168,296 describes a processor tank with an interior chamber which is partitioned into a plurality of serially arranged development compartments. This processor was specifically designed to develop 35 millimeter film and to use approximately one liter of developer. While this may be a reduction over other deep tank processors, this volume of processing fluid is still very large when considering the narrow film being processed therein. In addition, this reference discloses replenishing directly into the most upstream chamber and directing fluid to flow in the same direction as the film. As a result, the concentration of the chemistry will be highest near the entrance of the processor and lowest near the exit of the processor. Plus, requiring a plurality of compartments results in a relatively complex processor to make and to maintain.
WO Patent No. 93-00612 defines an apparatus for photographic processing in a low-volume tank and teaches the importance of agitation. It states that in low-volume processors, the confines of the tank restrict adequate agitation and, therefore, access of fresh processing solution to the film surface. The patent defines means to assure the access of fresh processing solution to the film surface.
In EPO Patent No. 410322, the chemistry is dispensed directly onto the film for processing. Such imbibement processing requires that the chemistry be formulated so there are sufficient reactants in the volume imbibed to assure full development of the image. This embodiment requires a minimum of two dispensings of the developer formulation. However, the material dispensed does not become part of the developer in a processing tank.
As previously noted, chemical activity is maintained by replenishment in which fresh chemistry is added at a rate commensurate with the quantity (area) of film processed, or more properly, the quantity of silver image that is developed. For most processes in the industrial black and white markets, e.g., the medical and graphic arts areas, the prescribed replenishment rate is usually about 450 milliliters of the replenisher fluid per square meter of film processed. This prescribed replenishment rate is based on the assumptions that the development process develops about 50% of the available silver (resulting from a normal exposure level), that the silver coating weight of the materials used is in the range of 3 to 4 grams per square meter of film processed, and that the processing fluid and the replenishment fluid are diluted as prescribed by the supplier for the particular processing and replenisher fluids. This prescribed replenishment rate corresponds to 35 milliliters for a normally exposed 50% imaged, 10-inch by 12-inch film sheet or about 70 milliliters for a 100% or fully exposed, 10-inch by 12-inch film sheet. In processes where the preponderance of film going through the process has a different silver coating weight or the balance of silver converted to image is significantly different than 50%, the recommended replenishment rate is normally adjusted to compensate for the differences.
As an example, for 50% imaged or exposed films, the data sheets for one company's products generally recommend 39 milliliters per square foot for 50% imaged silver halide photographic film (53 milliliters per square foot for 75% imaged film). The 39 milliliters per square foot is equivalent to 420 milliliters per square meter. Usage in some processors as low as 29 milliliters per square foot can be envisaged, which is equivalent to 312 milliliters per square meter. Other uses in the range of 22 to 35 milliliters per square foot for 50% imaged film, which is equivalent to 235 to 375 milliliters per square meter, have been recommended. In this regard, it should be noted that while a number of patents refer to the benefits of low-volume processor tanks and the resultant reduction in chemistry usage, such references are always to the tank volumes and the requirements associated with filling or dumping such tanks. None of the references appear to refer to the requirements of replenishment other than that replenishment conventionally used to maintain the process over an extended period of time and to provide extended usage of developer materials.
One known, commercially available processing chemistry formulation achieves a reduction in the volume of replenishment chemistry used. However, the volume reduction does not translate to an equivalent reduction in the material usage, i.e., the absolute amount of hydroquinone (HQ) used. While using this formulation allows for a reduction of the replenishment volume from 450 to 125 milliliters per square meter of film developed, the concentration of the hydroquinone used in the processing bath is increased by 1.5 to 2 times that of a normal concentration (from 50 to 80, but nominally 65 grams HQ per liter to approximately and nominally 113.8 grams HQ per liter). As a result, the usage of HQ is only reduced from 29.3 grams per square meter (at a 50% image) to about 14.3 grams HQ per square meter. This usage still results in a significant waste of HQ. (Approximately 1 gram of HQ is all that is used per square meter of film developed when the film includes 4 grams Ag/square meter of film developed, and the film is 50% imaged.)
A need remains for a method and apparatus which minimizes the use of the chemicals involved, yet provides adequate development uniformity and productivity (throughput rate). This need is particularly felt for processing imaging materials, such as photographic films, proofing plates, and diffusion transfer-type imaging materials.

Summary of the Invention

The present invention addresses the problems associated with deep tank processors and known small volume processors. In one embodiment, the present invention is directed to an apparatus for processing an imaging material. The apparatus includes a fluid recirculation loop which includes a processing cell having a chamber containing processing fluid and through which the imaging material can be transported. The loop also includes a reservoir having a reservoir chamber containing processing fluid, the reservoir being connected to the chamber by a first fluid line. The loop also includes a pump positioned between the reservoir and the processing cell, the pump being connected to the reservoir by a second fluid line and being connected to the processing cell by a third fluid line. The apparatus also includes a replenisher tank containing replenisher fluid and being functionally coupled to the fluid recirculation loop for supplying replenisher fluid to the fluid recirculation loop.

Brief Description of the Drawings

The foregoing advantages, construction, and operation of the present invention will become more readily apparent from the following description and accompanying drawings in which:

Figure 1 is an isometric schematic sectional view of one embodiment of an apparatus, according to the present invention;
Figure 2 is a top sectional schematic view of a processing cell of the apparatus shown in Figure 1; and
Figure 3 is a side sectional view of the processing cell shown in Figure 2.

Detailed Description of the Preferred Embodiments

As shown in Figures 1-3, an apparatus 10 can be used in the processing of an imaging material 12 or element, such as an exposed photographic film sheet coated on at least one side thereof with a photosensitive emulsion (e.g., silver halide photographic emulsion). The apparatus 10 uses a small volume of processing chemicals. Imaging material, such as conventional photographic film, can be of various sizes and can be of various types, such as film used by individuals for personal use. Other examples of imaging material 12 processable with the apparatus 10 include graphic arts films (including high contrast films, such as EXCELERATE™ film), radiographic films (e.g., 3M film and 3M TRIMAX™ film), silver halide-based diffusion transfer printing plates (e.g., ONYX™ plates), and photosensitive polymeric imaging materials including proofing plates and materials (e.g., MATCHPRINT™ and VIKING™ plates and materials). (All of these brands of imaging material are made by 3M Company, St. Paul, Minnesota.) These imaging materials are usually exposed to some degree before being processed by the apparatus 12, although an unexposed material could be transported through the apparatus, for example, to season the processing fluid 24.
The previously-used term "sheet" can refer to a material having a relatively short length, such as an 8-inch by 10-inch sheet, or to a material having a relatively long length, such as a material rolled up on a core. The terms "processing," "processable," and variations thereof are used to refer to the step of developing (and more generally to refer to the steps of fixing and washing) an imaging material. The terms "processing," "processable," and variations thereof are also used to encompass the step of activating (and more generally to refer to the steps of stabilizing and washing) other imaging materials.
The apparatus 10 can include a top plate 14 and a bottom plate 16 relatively aligned to provide a processing cell 18 or housing having a processing chamber 19 between the top plate 14 and the bottom plate 16. End plates (not shown) join the top and bottom plates 14, 16 to form the remainder of the exterior of the processing cell 18. A material inlet port 20 and a material exit port 22 are shown as being defined by the construction of the top and bottom plates 14, 16. These ports 20, 22 communicate with the processing chamber 19 to allow the imaging material 12 to pass through the processing chamber 19.
The processing cell 18 is shown as being substantially flat and substantially horizontally oriented. By "substantially flat" it is meant that the walls of the top and bottom plates 14, 16 which form the processing chamber 19 are not disposed a significant distance from the imaging material 12. One example of a "substantially flat" processing chamber 19 is shown in Figures 1-3 as being straight, while another example could be a curved chamber having, for example, an arcuate shape. The details of the shape of the chamber are not critical for this aspect of the invention. Other examples of a substantially flat processing chambers are described in US 5,266,994; 5,043,756; 5,136,323; and 5,365,299.
The processing chamber 19 can contain the processing fluid 24 useful for processing the imaging material 12 passing through the chamber 19. Some of the processing fluids which work with the apparatus 10 include graphic arts processing fluids (including EXCELERATE™ developer fluid and rapid access fluids), radiographic processing fluids, and diffusion transfer developer or activator fluids (e.g., ONYX™ processing fluids and other diffusion transfer fluids).
The processing chamber 19 can include a mesh-like material (not shown) like that disclosed and shown in U. S. Patent No. 5,266,994 (Desai et al.). One function of the mesh-like material is to maintain the processing fluid 24 upwardly with capillary action. The processing chamber 19 could also include a plastic component such as the blade disclosed and shown in U. S. Patent No. 5,266,994 (Desai et al.). This blade can hold the imaging material 12 down within the processing chamber 19.
One embodiment of the processing chamber 19, when designed to process a 10-inch by 12-inch (25.4-centimeter by 30.48-centimeter) sheet of imaging material 12 can have an chamber length (from the material inlet port 20 to the material exit port 22) of approximately 8 inches (approximately 20.3 centimeters). The chamber width could be approximately 16 inches (approximately 40.6 centimeters). And, the chamber height could range from approximately 0.10 to 0.3 inch (approximately 0.254 to 0.635 centimeter). (The chamber height is best shown in Figure 3 as being the distance from the inner surface of the bottom plate 16 to the inner surface of the top plate 14.) The volume of the processing chamber 19 within this embodiment would range from approximately 12.8 to 38.4 cubic inches (approximately 210 to 629 cubic centimeters).
The chamber height could, instead, be slightly less than the previously noted range. However, maintaining desired flow rates can be difficult when the chamber is significantly less than this range. Conversely, the chamber height could be greater than this range, for example, up to approximately 2 to 4 inches (approximately 5 to 10 centimeters), by the changing the shape of the bottom plate 16 to define a deeper trough. However, as the depth of that bottom plate trough increases, the benefits of a small volume processor are diminished.
The chamber height of the processing chamber 19 can be chosen such that the processing fluid 24 has a desired fluid thickness contacting the sensitized surface or surfaces of the imaging material 12. In other words, a desired fluid thickness of processing fluid 24 should contact the sensitized surface of a "single-sided" imaging material, such as a printing plate (e.g., ONYX™ plates), or should contact both sensitized surfaces of a "two-sided" imaging material such as some radiographic films. The desired thickness should be between a thickness which uniformly processes the imaging material 12 and a thickness which minimizes the total volume of the processing fluid 24 and allows for the benefits provided by a smaller volume of processing chemicals. An example of a range of the desired thickness could be from 0.04 to 0.4 inch (approximately 0.1 to 1.0 centimeter). So, when the apparatus 10 is processing a particular "single-sided" imaging material (e.g., transported with the sensitized surface facing the top plate 14), the distance between the inner surface of the bottom plate 16 and the top surface of the processing fluid 23 should be at least equal to 0.04 inch plus the thickness of that particular "single-sided" imaging material 12. Or, when the apparatus 10 is processing a particular "double-sided imaging material 12, the distance between the inner surface of the bottom plate 16 and the top surface of the processing fluid 23 should be at least equal to 0.08 inch (two 0.04 inch fluid layers) plus the thickness of that particular "double-sided" imaging material 12. Furthermore, a greater fluid thickness than 1.0 centimeter would function, such as a thickness of 2.5 centimeters or more. But, as previously noted, as the thickness increases, the benefits of using a smaller volume of processing chemicals are diminished.
With a 0.04-inch fluid thickness on only one surface of the imaging material 12, the volume of processing fluid 24 within the previously noted embodiment of the processing chamber 19 (approximately 8 inches long, 16 inches wide) would be approximately 5.12 cubic inches (approximately 84 milliliters). With a 0.4-inch fluid thickness, the volume of processing fluid 24 would be 51.2 cubic inches (approximately 840 milliliters).
Another embodiment of the processing chamber 19, when designed to process a wider imaging material 12, can have an interior length of approximately 16 inches (approximately 40.6 centimeters), an interior width of approximately 24 inches (approximately 61 centimeters), and an interior height (and fluid thickness range) similar to that previously described.
The processing chamber 19 can have dimensions which are different from those just noted, for example, to affect the throughput rate and/or the fluid volume within the processing chamber 19. In addition, the size of the processing chamber 19 can be made smaller (e.g., 30-centimeter width) or larger to accommodate narrower or wider imaging materials, respectively, and imaging materials of various thickness. Furthermore, the inner surfaces of the top and bottom plates 14, 16 could be irregularly shaped, rather than flat as shown.
The imaging material 12 is shown as traveling in a traveling direction (as shown by the arrow) and creates a traveling plane. The processing fluid 24 is shown flowing substantially transversely across the imaging material 12 due to the orientation of the fluid inlet ports 26 and the fluid outlet ports 28. Other embodiments are recognized which could result in a different flow arrangements than that shown.
In addition to the processing cell 18, the apparatus 10 can include a reservoir tank 38 (having, for example, a volume not significantly larger than the volume of the processing chamber 19), associated tubing or lines 40, a first pump 42, and a replenisher tank 44. (A second pump, not shown, can be included to pump the replenisher fluid from the replenisher tank 44 to the fluid recirculation loop. The choice of replenisher fluid depends on the imaging material 12 being processed.) The working developer is recirculated through this fluid recirculation loop (cell 18, reservoir 38, lines 40, and first pump 42). In this embodiment, fresh replenisher fluid can be added to the reservoir tank 38 from the replenisher tank 44 and the first pump 42 can be placed between the reservoir tank 38 and the processing chamber 19 for pumping the processing fluid 24 from the reservoir tank 38 to the chamber 19 from which it flows back to the reservoir tank 38. The first pump 42 could instead be positioned upstream from the reservoir tank 38. And, less preferably, the fresh replenisher can be added to the chamber 19 or the associated lines 40 rather than to the reservoir tank 38.
Using the reservoir tank 38 provides advantageous mixing of the fresh replenisher fluid with the working processing fluid before it contacts the imaging material 12 in the processing chamber 19. Mixing can be particularly important when the replenisher and processing fluids are diluted to other than the prescribed dilutions. Similarly, because the reservoir tank 38 can be heated, the processing fluid temperature can be made more consistent through out the recirculation loop, and particularly within the processing chamber 19. Plus, because the reservoir tank 38 has a relatively small volume when compared to the large bath or deep tank processors, the processing fluid 24 can be quickly heated to the desired operating temperature (and quickly mixed to a desired homogeneity). Mixing can be accomplished by including one of many known mixing mechanisms, such as a magnetic mixing mechanism (not shown). And, temperature control can be accomplished by including one of many known means for controlling fluid temperature, such as the combination of a thermocouple, heating blanket or sleeve, and a programmable controller (not shown).
Furthermore, the reservoir tank 38 allows the processing chamber 19 to remain at a relatively consistent fluid level by compensating for normal fluid loss from the processing chamber 19 or even an unexpectedly large fluid loss. The apparatus 10 could include means for monitoring and controlling the fluid volume in the processing chamber 19, such as a fluid level sensor and programmable controller (not shown) connected to the first pump 42. If an unexpected loss of fluid occurs, a momentarily increased flow of processing fluid from the reservoir 38 to the processing chamber 19 could be achieved by momentarily increasing the output of the first pump 42. In addition, this can be advantageous for minimizing the volume of air introduced into the fluid recirculation lines 40 and for preventing the first pump 42 from being starved.
As noted, one embodiment of the reservoir tank 38 can have a volume not significantly larger than the chamber volume, for example, ranging from, for example, 25% to 150% of the chamber volume. In another embodiment, the reservoir volume can be even larger than the chamber volume, for example, 150% to 200% of the processing chamber 19 (or more). A sufficiently large reservoir volume, which can be heated, assists in the maintenance of processing fluid temperature. And, even with this larger reservoir 38, the apparatus 10 can be constructed such that the total volume of working developer (within the chamber 19, the reservoir 38, the associated lines 40, and the pump 42) can still be significantly less than the deep tank processors.
Recirculation rate is commonly referred to in terms of turnovers per unit time. The term "turnover" means the ratio of the volume of processing fluid 24 replaced to the volume of the processing fluid 24 contained within the processing chamber 19 and the remainder of the recirculation loop (reservoir 38, associated lines 40, pump 42). The recirculation rate of the processing fluid 24 should maintain a minimum flow of 0.2 turnovers of the processing liquid every minute (turnover rate) in a direction which is substantially transverse to the movement of the imaging material 12 through the processing chamber 19. More preferably, the recirculation rate is greater than 0.4 turnovers/minute and, most preferably, greater than 0.6 turnovers/minute. An example of the range of the recirculation rate for a working processing fluid volume (within the loop) of approximately 500 milliliters is from approximately 100 to 1000 milliliters of processing fluid per minute, or more specifically from approximately 150 to 750 milliliters of processing fluid per minute. For a volume of 300 milliliters, the recirculation flow rate could be from approximately 60 to 600 milliliters per minute. For a volume of 800 milliliters, such as when the processing chamber 19 is larger, the recirculation flow rate could be from approximately 160 to 1600 milliliters per minute.
Recirculating at a turnover rate less than 0.2 turnovers per minute can lead to a deterioration of the development uniformity. Recirculating much beyond a turnover rate of 2 turnovers per minute can result in the loss of processing fluid through the material inlet and outlet ports 20, 22.
In addition to benefits of using a small volume of processing fluid 24 within the fluid recirculation loop and the benefits of the in-line reservoir 38, the apparatus 10 minimizes the replenisher liquid added to the recirculating flow of processing chemistry. The R/C ratio of replenisher fluid added per square meter of imaging material surface area processed (R) to the volume of processing fluid within the recirculating processing chemistry loop per square meter of imaging material surface area (C) is preferably greater than 0.12 (or 12%), more preferably greater than 0.15 (or 15%), even more preferably greater than 0.20 (or 20%), and most preferably greater than 0.25 (or 25%). Even though these R/C ratios are higher than the R/C ratio for commercial large bath processors (R/C ratio of approximately 2-3%), the apparatus 10 adds an actual volume of replenishment fluid which is significantly less than commercial processors. The volume of the recirculating processing composition within the apparatus 10 is much smaller than the total volume in a large bath processor that the apparatus 10 still uses significantly less processing fluid per unit of film than the large bath processor. Therefore, the apparatus 10 involves a relatively high R/C ratio is relatively high and allows for a reduced volumetric replenishment rate.
A preferred volumetric replenishment rate of the apparatus 10 can be expressed as an average value and as being the addition of less than 100 milliliters of replenisher into the recirculating loop per square meter of silver halide imaging material developed. A more preferred rate would be less than 85 milliliters per square meter of silver halide imaging material developed, an even more preferred rate would be less than 75 milliliters per square meter of silver halide imaging material developed, and an even more preferred rate would be less than 65 milliliters per square meter of silver halide imaging material developed. These preferred rates are predicated on the use of the prescribed dilution of the processing and replenishment fluids.
An example in which the apparatus 10 was used is described within the following: A high-contrast, hybrid-type, silver halide-based graphic arts material (EXCELERATE™) with its corresponding chemistry was used for this experiment. Film sheets were exposed using sensitometric exposures and 50% dot exposures and these were interspaced with sheets of fully exposed film sheets. Normal usage exposures of such graphic arts films usually use about one-half of the silver to form the image. Fully exposing the film and converting substantially all the silver in the film sheet to image is equivalent to consuming twice the developer per sheet of film and simulating a larger quantity of processed film. The number of sheets of the fully exposed film used between sensitometrically and 50% dot exposed film sets corresponded to an area of between 1 to 2 square meters and equivalent to 2 to 4 square meters of normally exposed film. Several experimental series were run at different replenishment rates. These rates was based on the area of film processed and on prescribed dilutions of the replenisher fluid (approximately one part water, one part concentrated replenisher fluid) and the processing fluid (approximately one part water, one part concentrated processing fluid). The replenisher fluid was added automatically at the set rate on a per sheet basis. The process was run in a series of sets which were normally an 8-hour day of operation. Different sets within a replenishment level were not necessarily run on consecutive days. Normally, the starting point for the process was the processing chemistry left from the previous set's operation, which may or may not have been at the same level.
This procedure and the data shown in the following tables were based on prescribed dilution of the processing and replenisher fluids. This was done to show the advantages provided by the apparatus 10. However, a lesser diluted replenisher fluid or an undiluted replenisher fluid can be used within the apparatus 10 which deliver the required developing chemistry to sustain the activity of the process. When the apparatus 10 uses a less diluted or an undiluted replenisher fluid, the volume of processing fluid 24 discarded can be reduced. For example, when the dilution of the EXCELERATE™ fluids is reduced from the prescribed dilution of one part water, one part concentrated fluid to an undiluted concentrated fluid, the replenishment rate can be reduced by at least 50 percent. This higher concentration also allows for an even greater percentage reduction in the volume of processing fluid 24 discarded to sustain the activity of the process (because the volume of processing fluid imbided by a given imaging material is virtually constant). The dilution, the replenishment rate, the fluid temperature, and other processing conditions can be adjusted to an extent to optimize the processing of particular imaging materials with particular processing fluids.
Tables 1-4 show the sensitometric speed performance for various development series under the conditions of reduced replenishment rate. The process was shown to be sustainable; i.e., consistent sensitometric performance was maintained, even under the conditions of the significantly reduced replenishment rate. Replenishment rate could be reduced to less than 90 milliliters per square meter for 100% exposed film equivalent to less than 45 milliliters per square meter for normally exposed film. And, replenishment rate could be reduced to less than 70 milliliters per square meter for 100% exposed film equivalent to less than 35 milliliters per square meter for normally exposed film. This corresponds to more than a 90% reduction in developer usage with concomitant sustainability of the process. At about 50 milliliters per square meter for fully exposed film or 25 milliliters per square meter for normally exposed film there was a continued deterioration in sensitometric performance and the process could not be sustained at such low replenishment for this film.
The results of the experiments in terms of the cumulative processed area in square meters. Set numbers indicate (usually) one day's run. "SPD" indicates the photographic speed of each cumulative processed area. As is well known, photographic speed is a parameter which is particularly sensitive to the stability of the process and is a basic measurement for performance.

The stability of the process is further emphasized by the results in Table 1 for the start of Set 2, in which the speed was higher than normal at startup but soon returned to the normal operational range.

Table 1:

Sensitometric Performance for Replenishment at 95 milliliters per square meter
Area	Set	SPD	Area	Set	SPD	Area	SET	SPD	Area	Set	SPD
0.0	1	1.307	20.1	1	1.328	40.3	2	1.301	60.4	3	1.370
1.5	1	1.288	21.7	1	1.322	41.8	2	1.323	61.9	3	1.380
3.1	1	1.304	23.2	1	1.335	43.4	2	1.324	63.5	3	1.374
4.6	1	1.313	24.8	1	1.309	44.9	2	1.339	65.0	3	1.356
6.2	1	1.347	26.3	1	1.316	46.5	2	1.305	66.6	3	1.353
7.7	1	1.339	27.9	2	1.401	48.0	2	1.326	68.1	3	1.363
9.3	1	1.361	29.4	2	1.414	49.5	2	1.314	69.7	3	1.378
10.8	1	1.341	31.0	2	1.307	51.1	2	1.296	71.2	3	1.323
12.4	1	1.327	32.5	2	1.303	52.6	2	1.307	72.8	3	1.338
13.9	1	1.331	34.1	2	1.316	54.2	2	1.333	74.3	3	1.312
15.5	1	1.348	35.6	2	1.338	55.7	3	1.348	75.9	3	1.301
17.0	1	1.328	37.2	2	1.273	57.3	3	1.329
18.6	1	1.326	38.7	2	1.295	58.8	3	1.339

Table 2:

Sensitometric Performance for Replenishment at 65 ml/m
Area	Set	SPD	Area	Set	SPD	Area	Set	SPD	Area	Set	SPD
0.0	1	1.283	21.7	2	1.287	43.4	3	1.271	65.0	4	1.308
1.5	1	1.301	23.2	2	1.316	44.9	4	1.304	66.6	4	1.280
3.1	1	1.287	24.8	2	1.301	46.5	4	1.300	68.1	4	1.300
4.6	1	1.307	26.3	2	1.306	48.0	4	1.264	69.7	4	1.293
6.2	1	1.291	27.9	2	1.304	49.5	4	1.291	71.2	5	1.294
7.7	1	1.297	29.4	2	1.324	51.1	4	1.263	72.8	5	1.298
9.3	1	1.302	31.0	2	1.316	52.6	4	1.271	74.3	5	1.306
10.8	1	1.284	32.5	3	1.234	54.2	4	1.346	75.9	5	1.348
12.4	2	1.310	34.1	3	1.235	55.7	4	1.339	77.4	5	1.350
13.9	2	1.281	35.6	3	1.254	57.3	4	1.272	79.0	5	1.298
15.5	2	1.239	37.2	3	1.252	58.8	4	1.280	80.5	5	1.296
17.0	2	1.233	38.7	3	1.238	60.4	4	1.274	82.1	5	1.299
18.6	2	2.283	40.3	3	1.261	61.9	4	1.285	83.6	5	1.301
20.1	2	1.286	41.8	3	1.270	63.5	4	1.335

Table 3:

Sensitometric Performance for Replenishment at 45 ml/m
Area	Set	SPD	Area	Set	SPD
0.0	1	1.277	10.8	1	1.320
1.5	1	1.320	12.4	1	1.301
3.1	1	1.322	13.9	1	1.308
4.6	1	1.343	15.5	1	1.337
6.2	1	1.298	17.0	1	1.351
7.7	1	1.298	18.6	1	1.304
9.3	1	1.303	20.1	1	1.308

Table 4:

Sensitometric Performance for Replenishment at 32 ml/m
Area	Set	SPD	Area	Set	SPD	Area	Set	SPD
0.0	1	1.229	12.4	1	1.251	23.2	2	1.339
1.5	1	1.283	13.9	1	1.241	24.8	2	1.279
3.1	1	1.263	15.5	1	1.235	26.3	2	1.273
4.6	1	1.255	17.0	1	1.257	27.9	2	1.239
6.2	1	1.235	18.6	2	1.242	29.4	2	1.239
7.7	1	1.257	20.1	2	1.231	31.0	2	1.238
9.3	1	1.224	21.7	2	1.355	32.5	2	1.251
10.8	1	1.226

When the apparatus 10 was used to process silver halide-based printing plates (e.g., ONYX™ printing plates), similar benefits were achieved. Uniform development can be maintained at, again, a significantly reduced replenishment rate. Normally, this type of silver halide-based imaging material 12 is processed at a replenishment rate of between 100 and 125 milliliters of replenisher per square meter of plate area processed. Using the apparatus 10, a uniform development could be maintained with a minimum replenishment rate varying between 20 and 45 milliliters per square meter of plate area developed. As a result, a particularly desirable rate could be approximately 25 milliliters per square meter of plate area processed.
The apparatus 10 can provide similar benefits to photosensitive polymeric imaging materials, such as proofing materials and proofing plates. By reducing the consumption of processing fluid 24 per square meter of imaging material processed and maintain uniform development, less processing fluid 24 is wasted.
Furthermore, the apparatus 10 can be particularly applicable to the processing of thin photographic film. By 'thin' photographic media, it is meant that the photographic silver halide media (e.g., color photographic, radiographic, graphics art media) is on a film base no thicker than approximately 0.003 inch (approximately 0.076 mm) and that the coating layers (emulsion, barrier, antistatic, antihalation, protective, and filter layers) on the base are also made thinner. Preferably the film base is at least 0.02 mm and no thicker than 0.07 mm, more preferably equal to or less than 0.06 mm, and most preferably between 0.025 mm and 0.055 mm. The total thickness of the layers on the base may be as low as 8 micrometers for some photographic constructions, and for the most complex constructions such as color photographic media which can have as many as 16 or 20 layers, the total thickness of the layers may be 160 micrometers. The total thickness of the photographic media, therefore, including the base and both the emulsion layer and the auxiliary layers may be as thick as 0.12 mm and still be considered a thin photographic element (as long as it is on 0.76 mm base or less) within the practice of the present invention. Replenishment rates lower than those just noted with respect to the EXCELERATE™ example are expected with imaging material having a thinner emulsion layer.
In addition, the apparatus 10 could further include a second processing cell (not shown) and a third processing cell (not show) similar to and positioned adjacent to the processing cell 18. For processing a developable imaging material 12, the processing cell 18 could contain with developer fluid, the second processing cell could contain a fixer fluid, and the third processing cell could contain a wash fluid. For processing an activatible imaging material 12, the processing cell 18 could contain with an activator fluid, the second processing cell could contain a stabilizer fluid, and the third processing cell could contain a wash fluid. With some activatible imaging materials, only two cells may be necessary. Other similar arrangements would also benefit by the use of the apparatus 10 and previously described methods of using the apparatus 10.

Claims

An apparatus for processing an imaging material, comprising: a fluid recirculation loop which includes:
a processing cell having a chamber containing processing fluid and through which the imaging material can be transported;
a reservoir having a reservoir chamber containing processing fluid, the reservoir being connected to the chamber by a first fluid line; and
a pump positioned between the reservoir and the processing cell, the pump being connected to the reservoir by a second fluid line and being connected to the processing cell by a third fluid line; and
a replenisher tank containing replenisher fluid and being functionally coupled to the fluid recirculation loop for supplying replenisher fluid to the fluid recirculation loop.
The apparatus of claim 1, wherein the chamber has a chamber volume and the reservoir has a reservoir volume, and wherein the reservoir volume is not significantly greater than the chamber volume.
The apparatus of claim 1, wherein the replenisher tank is functionally coupled to the reservoir for supplying replenisher fluid to the reservoir.
The apparatus of claim 1, further comprising means for heating and mixing the processing fluid within the reservoir.
A method for using the apparatus of claim 1 for processing an imaging material, comprising the steps of:
transporting the imaging material through said chamber;
pumping processing fluid through the fluid recirculation loop; and
supplying replenisher fluid to the fluid recirculation loop.
The method of claim 5 wherein the imaging material is a silver halide-based imaging material, and wherein the replenisher fluid is supplied at a replenishment rate ranging from 25 to 90 milliliters per square meter of said silver halide-based imaging material being processed in said chamber.
The method of claim 5 wherein the imaging material is a photosensitive polymeric imaging material.
The method of claim 5, wherein the processing cell has a width of approximately 30 to 50 centimeters, wherein the fluid recirculation loop has a loop volume ranging from approximately 300 to 800 milliliters, and wherein the processing fluid is recirculated through the fluid recirculation loop at rate ranging from 60 to 1600 milliliters per minute.
The method of claim 1, wherein the processing cell has a width of approximately 30 to 50 centimeters, wherein the fluid recirculation loop has a loop volume ranging from approximately 300 to 800 milliliters, and wherein the processing fluid is recirculated through the fluid recirculation loop at rate ranging from 150 to 750 milliliters per minute.