PROCESS AND APPARATUS FOR MAKING

A PHOTOGRAPHIC MATERIAL

BACKGROUND OF THE INVENTION The subject of the invention is a process and apparatus for making a photographic material, in which a web-shaped substrate in motion is continuously coated with one or more layers of liquid, and is dried in a drying zone. The substrate constitutes the base for carrying the applied light-sensitive recording layer of the photographic material. In photographic films the recording layer is generally a multi-layer configuration, and consists of silver halide emulsion layers which are usually covered by a protective layer. The silver halide emulsion coatings are applied, usually as a multi-liquid coating, to the substrate by means of a coating apparatus, hereinafter also briefly termed a caster. Facilities for manufacturing photographic films are exclusively operated on a continuous basis. However, the continuous manufacturing process must be interrupted when the coating apparatus is cleaned, or when a change in the various silver halide emulsions, hereinafter briefly termed casting solutions, requires such a stop. In manufacturing a photographic material, minimizing stoppages of production facilities is a basic goal. DE 26 48 574 discloses a production facility for making a photographic material, in which, by means of a changeover apparatus, casting solutions may be changed without interrupting the casting process. A number of casting solutions, ready for use, are fed to the changeover apparatus through a group of lines, but only one casting solution is conducted further to the casting unit. The other casting solutions are conducted into a circulating system. When a change is made to another casting solution, a changeover piston releases the new solution to the casting unit, and conducts the rest into the circulation system.

DE 19 62 089 describes a multiple casting facility for manufacturing webs that are multi-coated with photographic casting emulsions. Along the meandering course in which the web is conducted there are a number of application sites, also for diverse types of coating units; and multiple drying devices are also provided. The purpose of this casting facility is to dry, under varying drying conditions, layers of liquids or layer groups that have been sequentially applied in-line.

A common feature of these production facilities is that the manufacturing process is interrupted when the casting unit fails, or must be repaired or cleaned. Cleaning is always needed after a certain period of operation. And the casting unit must also be cleaned if another casting solution is utilized that is incompatible with the casting solution previously used.

In addition to the production facilities cited above for making photographic film, there are also test facilities which are operated for testing new films and the methods of making them. Unlike production facilities, test facilities are not operated continuously, but on a batch basis. In each instance, they serve to make a small quantity of a new film for testing purposes. The film web width in a test facility is usually about 20 to 30 cm, i.e. about 1/10 the width of the film web in a production facility. The coating apparatus is configured for discontinuous operation of the laboratory facility. The casting solutions are conveyed not continuously, but intermittently. EP 0 003 281 discloses as test facility for single or multiple coating of a test loop that is in a movable drying apparatus. By means of a number of casting units positioned on a stationary casting frame, the loop is coated with casting solution in a timed sequence. Each caster is positioned with respect to the casting roll by means of grippers and stops. A similar test facility, in which a closed loop is coated and the loop is moved circumferentially through a drying unit, is described in EP 0 589 388.

DE 22 46 789 also describes a test facility. In this laboratory facility as well, an endless loop of a paper or film web is coated by a number of casting units, and dried in a jet dryer. Unlike the test facilities described above the casting units are not stationary, but are positioned to be movable on a revolving platform. During operation of the test facility, several test casting units, even those of differing types, may be applied to the casting roll.

SUMMARY OF THE INVENTION The task of the invention is to shorten shutdown times caused by failure of, or need to clean, the coating apparatus and, where relevant, when the casting solution or the casting unit itself is changed.

The task is successfully achieved by means of a process for making a photographic film in which a moving weblike substrate is continuously coated with one or more liquid layers and is dried in a drying zone, whereby the coating includes the following steps: the casting solution, ready for casting, is conveyed to a coating apparatus in a coating zone, and the substrate is coated with a first liquid; the casting solution, ready for casting, is conveyed to at least one coating apparatus kept in readiness in a preparation zone; the coating apparatus units are interchanged by transferring the coating apparatus that is in the coating zone into the preparation zone, and transferring one of the coating apparatus units kept in readiness is the preparation zone, into the coating zone;

the substrate is coated with a second liquid., and by means of an - apparatus for making a photographic material in which a moving, web-shaped substrate (4) is coated with one or more liquid layers and is subsequently dried in a drying zone, and which includes: means for continuously moving the substrate (4) through a coating zone (30); at least two feed devices (10) that continuously move the casting solution in each case through feed lines (16) to a coating apparatus (5) in the coating zone (30) that continuously coats the substrate, and to at least one additional coating apparatus (5) that is/are maintained, ready to operate, in a preparation zone (31); at least one transfer device (40) for exchanging the coating apparatus units by transferring the coating apparatus (5) that is situated in the coating zone (30) into the preparation zone (31), and transferring a coating apparatus (5) that is being held in readiness in the preparation zone (31) into the coating zone (30).p

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention is described, utilizing preferred versions, together with the drawings. These are:

Figure 1. a perspective layout of a preferred version of the invention with two rotary arms;

Figure 2. a perspective detail representation of a rotary arm; Figure 3. a section along line III-III in Figure 2 with casting frame, before applying a bead casting unit;

Figure 4. a section along line III-III in Figure 2 with casting frame, in operating position;

Figure 5. a plan projection of a coating and a preparation zone; Figure 6. a preferred version of the invention with a rotary table; Figure 7. a perspective representation, with curtain casting unit. DETAILED DESCRIPTION OF THE INVENTION This invention is based on the use of multiple coating units in a production facility for making a photographic material, whereby in addition to a coating unit that is in operation, at least one other coating unit is maintained in operational readiness, and is quickly put into service when needed. In the context of the invention, operational readiness means that a coating unit is maintained, ready for operation, in a preparation zone, i.e. the said coating unit: i) is connected to all input, supply, auxiliary, metering and tempering facilities, is continuously fed and supplied by them, and is at operating temperature;

ii) is supplied with casting solution in such a manner that the casting solution, tempered and free of bubbles, exits in the relevant casting aperture of the casting unit; iii) is mechanically so adjusted that after transfer to the casting roll, it essentially takes up the specified clearance.

A basic concept of the invention is that, in addition to a production caster in operation, at least one additional caster is held, so to speak, in a waiting position; this latter caster is essentially operated in the same manner as the caster in operation, with the sole exception that its casting solution does not impact on a web in motion, but instead is collected and diverted.

Consequently, in the invention a quick exchange of coating units is achieved by transfer of casting units. In the first step of this exchange, the coating unit operating in a coating zone is transferred into a preparation zone. In a second step, a casting unit held in readiness in a preparation zone is brought into the coating zone. This exchange is quickly accomplished, because the replacement casting unit is immediately available for use. As a consequence, interruptions of the production process caused by cleaning the casting unit can be kept brief. Typical exchange times range from a few minutes to 20 minutes. In contrast, a conventional casting unit change in which the casting unit is first mechanically regulated on the spot, then connected to the supply system and restarted, usually takes more than an hour.

In principle, several casting units of the same or differing types may be held in readiness in the preparation zone. In such event, a selection must be made before implementing the exchange. For example, the same or differing coatings may be successively applied without a long stoppage of the production facility. Even if a narrower substrate is to be coated, after the rapid casting unit exchange the production facility is immediately available for use.

In a production facility, the coating zone is the so-called casting area. Light-sensitive casting solutions are processed under darkroom conditions.

Preparatory work on the casting unit, such as maintenance, cleaning and small repair tasks is conducted in a so-called preparatory zone under light room conditions. It is recommended that these zones be situated in adjacent spaces, and that coating units are exchanged by transferring the coating unit that is in the coating zone into the preparation zone, and moving a coating unit that is being held in readiness in the preparation zone, into the coating zone.

Exchange of coating units is preferably accomplished by a transfer movement that at least sectionally follows an arc of a circle. The transfer movement is then basically a rotational movement. Such a rotational movement is

technically simple to effect. The apparatus for displacing the casting unit, which weighs about a ton, can then be a simple swinging or rotary arm. or a turntable. If the coating apparatus is a curtain-type casting unit, the rotary movement also ensures the substrate coating clearance. In such case, precision positioning is not needed. If the coating apparatus is a bead-type unit, however, after the rotary movement a positioning step is needed to set up the coating clearance of a few micrometers versus the substrate. Depending on the configuration of the caster and the transfer device, after the movement along the arc of a circle, it may thus be necessary to adjust the position of the casting unit perpendicular to the axis of the casting roll. Such a change in position may, for example, be made by means of a sliding carriage on which the casting unit is secured. The coating clearance may, however, also be set up by means of a casting roil positioning device.

It is especially preferable if the casting solutions are conducted in feed lines that extend upward to the coating apparatus near the midpoint of the circular arc of the transfer movement. In such a configuration, no air pockets can be developed in the lines that may cause bubbles in the casting solution and thus give rise to coating malfunctions.

Following transfer of a coating apparatus into the coating zone, it is advantageous to separate the transfer device from the coating apparatus. The transfer device is then mechanically decoupled from the coating apparatus, and no dysfunctional oscillations can be transmitted from the transfer device to the coating apparatus.

The coating zone and the preparation zone are preferably situated in adjoining spaces that are separated by a movable, light-impermeable partition. Illumination in the two zones can then be adapted to requirements.

The adjacent spaces and the movable partition make brief exchange times possible. The movable partition near the transfer movement is opened, lighting conditions are adjusted, and the casting unit is moved. The movable partition may for example be configured as a light-impermeable folding or roller-type partition. Naturally, movement of the casting unit, opening of the movable partition and adaptation of light conditions may be brought together in an electrically controlled program.

The invention presents an apparatus for making a photographic material, so configured that coating units are exchanged by means of a transfer device, thereby providing an available, ready-to-operate coating unit for use. Such an exchange of coating units interrupts the continuous production sequence for only a brief period of time.

It is especially advantageous if the transfer device has two rotary arms, whereby each arm carries a coating unit, and the transfer procedure takes place

along an arc of a circle. In such case, a casting unit can relatively quickly be moved from or into an operating position.

In another advantageous configuration of the invention, the transfer device has a rotary table that carries at least two coating units; and the coating units are transferred at least in sectors along an arc of a circle. If the casting unit is a bead- type caster, after rotation the coating clearance relative to the substrate must be set. This may be done my means of a graduated carriage positioned between the casting unit and the rotary table. The coating clearance may also, however, be established by displacing the casting roll. On the rotary table there may be more than two casting units, of which at least one is maintained in operating readiness. If, for example, there are three casting units at an interval of about 120 degrees on the rotary table, before making the exchange a selection must be made. In this case, the transfer movement consists of a rotation of about 120 degrees. The axis of movement is the axis of the rotary table. Input of the casting solutions also advantageously takes place along this axis.

It is very highly advantageous when the feed lines for the coating unit extend upwards and in the vicinity of a midpoint of the circular arc. This prevents the formation of air pockets in the feed lines - the previously degassed emulsion - with renewed air bubbles, resulting in coating defects. In this context, it is very useful to configure the feed line near the midpoint of the circular arc as a flexible tube line. Such a flexible line absorbs the torsion stress imposed by rotation of the rotary arm or rotary table. Surprisingly, the well known problem of rotary flange air leakage was thereby solved in a simple manner; the feed lines are free of bubbles and easy to clean, because there are no interfering sealing surfaces to get in the way. For example, the flexible line may be an elastomeric plastic tube 1.5 meters in length.

Especially advantageous is the arrangement in which each rotary arm has a device for raising and lowering the coating unit; and in the operating position, the casting unit is positioned on a casting frame and is disengaged from the rotary arm. Such a raising and lowering device makes pickup and deposit of the casting unit very simple. The transfer device is mechanically disengaged from the casting unit in a simple manner. When the casting unit is positioned on a vibration-free casting frame and the transfer device cannot transmit disturbing oscillations, the casting process proceeds free of malfunctions. It is highly favorable to conduct the transfer by means of a drive device that is operationally connected with the rotary arm or rotary table, and which stops if a limiting moment is exceeded. With a motorized drive the casting unit exchange can be automated and reliably controlled. Especially under darkroom conditions, the risk of accident is significantly reduced if the drive shuts off when

a limiting moment is reached. A limiting moment of less than 300 Nm is most especially preferred. This means that with a 3 meter-long rotary arm, the drive unit stops the transfer movement at an opposing force of less than 100N. The motor of the drive unit may, for example, be an electric motor. The transmission between the rotary arm column and drive may, as an example, be a cylindrical worm drive or a tapered spur gear drive. Naturally, in principle the casting unit exchange may also be effected by hand, i.e., by manual operation of the rotary arm or rotary table.

Each coating unit is advantageously connected to a tempering device, which maintains the coating unit at an operating temperature of about 38°C. Energy is fed in through a tempering line which, depending on the source of energy, may be a line with a tempering liquid or an electrical conductor. However, the casting unit may be also be tempered by the casting solutions themselves; in such event, the tempering device for heating the casting solutions functions simultaneously as a tempering device for the casting unit.

The coating apparatus is advantageously a bead-type casting unit with a low-pressure chamber that is connected through a siphon with a discharge line. It is recommended that the low-pressure chamber be connected with the discharge line by means of a siphon. This makes the low-pressure chamber doubly effective. In addition to its major function of maintaining the liquid bridge between casting lip and substrate during the coating operation, the low-pressure chamber is utilized as a vessel for collecting casting solutions, as long as the casting unit is in the standby position. As soon as the casting unit, in the operating position, begins to coat the substrate, the low-pressure chamber again assumes the major function cited above. The siphon therefore blocks the discharge line and, during the coating operation, prevents infiltrated air from being aspirated from the discharge line into the low-pressure chamber.

Moreover, an exchange involving diverse types of casting units, such as curtain, extrusion or bead-type units, is advantageous. In the context of a product change, the casting unit type can be adapted to differing flow properties of the casting solutions.

As noted earlier, it is favorable if the coating zone and the preparation zone are situated in adjacent spaces, with a movable, light-impermeable partition between them. During the exchange operation, the casting units have only a short distance to travel. Light- or darkroom conditions may be independently specified in the zones.

Each rotary arm is advantageously secured to a vertical column and is mounted on a column support so as to be rotatable. From a structural point of

view, this is a simple configuration of a transfer device that moves a heavy - production-type casting unit between the coating zone and the preparation zone.

In particular, this arrangement makes it possible to establish the clearance between casting lip and substrate in a simple manner, by means of stops positioned on the casting frame.

Special advantages result when the supply unit has attached to it a commutator device that assigns a casting solution to a distributing chamber of a coating unit. This makes it possible to assign emulsions, as desired, to individual casting slits of the coating units. Such assignment is optional, and can be automated. The composition of layers on the substrate may thereby consist of diverse photosensitive silver halide emulsions, and may even contain non- photosensitive emulsions. The casting solutions may also contain polymers such as, for example, polyvinyl alcohols or polyvinyl pyrrolidone. As directed by the invention, therefore, the substrate may be coated with various multi-liquid layers, and a quick change between differing photographic materials can be effected.

Long periods of production facility shutdown due to a change in casting solutions or because of necessary repairs to the casting apparatus do not occur.

Figure 1 shows a perspective layout of one preferred version of the invention. The transfer device 40 has two rotary arms 12, each of which has a casting unit 5. In this diagram, both casting units 5 are shown in a position swung away from the casting roll 2. The casting units 5 are shown as bead-type casters. A low-pressure chamber 6 is fixed on each casting unit. The casting unit 5 and low-pressure chamber 6 are secured on the bottom component 29. Each rotar arm 12 is fastened on a vertical column 11. Each column 1 1 is rotatable in a column mount 20. By means of the drive unit 43, each column 1 1 and rotary arm 12 can be swung around an axis 21 (shown in Figure 2) in the direction of the arrow 15 and back. With the transfer device 40, each casting unit 5 can be transferred between a preparation zone 31 and a coating zone 30 (shown in Figure 5). Transferring a casting unit out of the preparation zone 31 into the coating zone 30 thus consists of rotating the rotary arm 12 in the direction of the arrow 15. In the coating zone, the casting unit 5 that has been brought into an operating position coats the web-shaped substrate 4. The substrate 4 is moved continuously in the direction of the arrow 7, and is supported by the casting roll 2. When a casting unit 5 is transferred, the lower component 29 is positioned with respect to the stops 3; and the casting unit 5, including the low-pressure chamber 6 and lower component 29, is lowered onto the casting frame 1. Each low-pressure chamber 6 is connected by low-pressure lines 47 with a partial vacuum generator 46. The columns 1 1 are, at least in their lower sections, configured as hollow columns, within which are situated the feed lines 16 and discharge lines 44 for the

casting solutions. By means of pumps 13, the casting solutions are conducted from the containers 14 through the feed lines 16 to the casting units 5. For the sake of clarity, Figure 1 schematically represents one of such feed devices 10 up to entry of the lines into the column. In Figure 1, one of the casting units is shown with two casting apertures, while the other has three. A degassing and filtration unit 25 ensures bubble-free and purified supply of casting solution. A damping device 26 suppresses dysfunctional pulsations in moving the casting solution. Each low-pressure chamber has a discharge line 44 for emulsions, by means of which emulsion, in the preparation position and during transfer of the casting unit, is diverted and conducted to a collecting vessel 19. While Figure 1 represent bead-type casting units, it is obvious that the transfer device shown is also suitable for handling differing types of casting units, for example curtain or extrusion-type casters.

Figure 2 illustrates a perspective detailed view of a rotary arm. The column 1 1 is rotatable and is positioned in the mount 20. The rotary arm 12 is joined with the column 11 , and can be swung around the axis 21. When the arm 12 makes a swinging movement, the casting unit 5 executes a circular movement. As can be seen in Figure 2, the feed lines 16, which carry the casting solution to the two casting apertures 8 of the casting unit 5 that is shown, are positioned near the center of such a circular movement. When the arm 12 rotates, these lines undergo torsional stress. For structural purposes, it is advantageous to configure a segment of such feed lines 16 as a flexible tubular line 23, such a flexible tubular line may, for example, consist of an elastic plastic tubing about 1.5 meters in length. This flexible tube elastically absorbs the torsional stress. Gaskets - such as for example are always present in a rotary flange type of connection - are avoided. The feed lines 16 can be more easily cleaned with cleaning solutions. Entry of air into the feed line 16 is prevented. Incoming emulsion is free of bubbles. The discharge line 44 for the casting solution and the low-pressure line 47 in this segment may also be configured as flexible tubing. As shown in Figure 2, the flexible tube 23 and feed line 16 extend upward to the casting unit. This prevents formation of bubbles in the feed lines that can be generated by internal air pockets in the feed lines. During the coating operation, the siphon 45 seals the low-pressure chamber 6 from the discharge line 44.

Figure 3 represents a section along the line III-III in Figure 2, before imposition of a bead-type caster, i.e., just before completing movement of a casting unit into the operating position. The bead-type casting unit 5, which is ready to function, is situated on the rotary arm 12, by which it is moved in the direction of the arrow 15 to the casting frame 1. In this phase, the casting unit 5 is ready to operate; it is connected with all feed, supply, discharge and tempering

devices, and it is being fed and supplied by them. The coating clearance versus the substrate 4 is adjusted by means of the positioning unit 28, which shifts the axis of the casting roll 2. The positioning unit 28, which is mounted in the frame 38, is shown in a disengaged position. The tempering unit 9, which is connected by the line 17 with an energy source that is not shown, ensures that the coating unit is at operating temperature. Through the feed lines 16 and the distribution chambers 22, the emulsion arrives at the casting apertures 8, from which it issues, free of bubbles. In this phase of the transfer, i.e., up to engagement of the casting unit, the low-pressure chamber 6 acts as a collecting tank for the casting solutions that are being discharged through the casting lip 37. Line 44 is connected by a siphon with the low-pressure chamber 6, and carries the collected casting solution away. The hoisting unit 42 holds the casting unit 5 above the level of the casting frame 1. The connector terminals on the lower side of the casting unit mate with recesses in the table surface of the casting frame 1. In Figure 4. the operating position of the casting unit along a section of line III-III in Figure 2 is shown. After the casting unit 5 contacts the stop 3. the device 42 lowers the casting unit on to the surface of the casting frame 1. As soon as this is accomplished, the rotary arm 12 is completely dissociated from the casting unit, and is rotated back into the preparation zone. Thus during the coating operation the casting unit is mechanically separated from the transfer device, which cannot transmit dysfunctional oscillations to the coating unit. At this point, the casting unit is in its operating position, i.e., the casting solution is no longer being collected by the low-pressure chamber 6, but instead moves across an interval from the casting lip 37 on to the web 4. The casting clearance is set by means of a positioning device 28 that adjusts the axis 27 of the casting roll 2. The continuously moving web 4 is coated with one or more liquid layers 18.

Figure 5 is a plan view of an arrangement of the coating and the preparation zones. On either side of a coating zone 30 there is a preparation zone 31 , within each of which there is a transfer device 40. These are configured as rotary arms 12, each of which is joined with a column 1 1. By means of each rotary arm 12, a casting unit 5 can be transferred between a preparation zone 31 and a coating zone 30. If, for example, a casting unit is to be brought out of the preparation zone into the operating position, a movable partition 32 separating the two zones is opened. A coating unit is then transferred through the opening thus created into the coating zone. In this transfer, the casting unit is moved along an arc of a circle 41. At the end of this transfer movement, the casting unit is lowered at the casting frame 1 , by means of the device 42. It is now in the operating position. The rotary arm 12, which in this position is shown in the diagram by dotted lines, is now separated from the casting unit, and is swung back

into the preparation zone. The movable partition is closed. Lighting in the ^• coating zone is adapted to the casting solutions being processed, and the coating procedure continues. The partition 32 separating the zones is impermeable to light; hence, during coating with photo-sensitive casting solutions, cleaning or maintenance activities can be conducted on the casting unit under normal lighting conditions in the adjacent preparation zone.

One preferred version of the invention with a rotary table is shown in Figure 6. On the rotary table 39 there are three casting units 5 that are moved between a coating zone 30 and a preparation zone 31 by rotation around the axis 24 of the rotary table. The rotary table is driven by a drive unit (not shown). In this version also, the two zones are separated by a partition 32 that is opened before the casting unit is changed. Figure 6 illustrates a transfer movement in a clockwise direction along the circular arc 41. In this example, a casting unit with four casting apertures replaces one with two apertures. Naturally, either of the two casting units can be displaced from the preparation zone into the coating zone; if the direction of rotation is reversed, the casting unit with three apertures will be engaged. Figure 3 shows bead-type casting units. With this type of casting unit, in order to set coating clearance versus the web the rotary movement must be followed by a positioning movement towards the substrate. A drive unit for such a positioning movement is not shown in Figure 6.

Figure 7 is a perspective of a configuration with curtain-type casting units. The coating zone 30 and the preparation zone 31 are separated by a partition 32 that is movable in the direction of the arrow 35. The two curtain casting units are connected with feed lines 16 that carry the casting emulsion into distribution chambers 22 of the casting units 5. In the preparation zone, a collecting tank 34 collects the casting emulsion and discharges it. The two curtain-type casting units 5 are supplied with emulsions El, E2, E3, E4 through a commutator device 33. By means of this device 33, individual containers 14 in which emulsions are being held in storage are linked with differing casting apertures 8 of the coating units 5. In the version shown as an example, four emulsions El to E4 are conducted by means of pumps 13 to the entries el, e2, e3, e4 of the commutator device 33, and may be assigned, as desired, to the exits al, a2, a3, a4. In the configuration selected, the substrate 4 is being coated with emulsions El and E3. Emulsions E2 and E4 are conducted to the curtain-type casting unit being held in readiness in the preparation zone, and are collected in a collector tank 34. In a change of coating units, schematically indicated by the arrow 36 (the transfer device is not shown here), the apparatus held in readiness is transferred into the coating zone 30. After the change is complete, the substrate is coated with emulsions E4 and E2. By means of the commutator device 33, exits al and a2 may, if desired, be linked

with other emulsions, for example emulsions EN and EM. In a subsequent change by which the former casting unit is again moved into the coating zone, the substrate would then be coated with liquid layers constituted by the emulsions EN and EM, (not shown).