Composite liquid application device

Abstract: A curtain-type coating liquid application device having a slide hopper and an application start plate used to prevent an increase in the thickness of the initially applied portion of the liquid on a web to thereby make the initial coating portion flat and smooth. Liquid freely falling the form of a thin curtain from the slide hopper is caused to collide against the web continuously moving around a backup roller so that the liquid is applied to the web. The application start plate has an upper end extending at an oblique angle to the direction of width of the curtain, or it may be provided with a curtain receiving part at the upper end of the plate.

Description: BACKGROUND OF THE INVENTION The present invention relates to a device for applying a composite liquid to a continuously moving web having the form of a belt-like carrier and which is used to manufacture a photographic film, photographic printing paper, a magnetic recording material such as a magnetic recording tape, an adhesive tape, information recording paper such as pressure-sensitive paper and thermosensitive paper, photographic printing plate, or the like. Particularly, the invention relates to a curtain application device employing a slide hopper. A curtain application device employing a hopper is often used for applying a liquid to a moving web. In such a device, a freely falling curtain of a thin film of one or more kinds of liquid is made to collide against the web so that an applied liquid film is formed on the web. Curtain application devices have long been used for application to furniture, iron plating, etc. Recently, however, curtain application devices have begun to be used in accuracy-requiring processes such as the manufacturing of photographic photosensitive materials, as disclosed in US-A-3,508,947 and US-A-3,632,374. It is very important for such a curtain application device to uniformly apply a freely falling curtain of a liquid to a moving web at the start of the liquid applying operation of the device. Since the speed of application by the curtain application device is required to be higher than that of an application device employing a slide hopper, the flow rate of the liquid must be made higher in the curtain application device than in the latter. For this reason, it has generally been considered that it is more difficult for a curtain application device to uniformly apply a liquid to a moving web at the start of the liquid applying operation than for a slide-hopper type device. If the liquid is not uniformly applied to the moving web at the start of the operation, problems such as contamination due to spattering of the applied liquid, contamination of a roller due to non-drying of greater thickness portions of the applied liquid downstream to a drying zone can occur, making the final product unacceptable. In the curtain application device disclosed in US-A-3,632,374, an application start plate, which is a turnable or slidable deflector, is provided which feeds a prescribed quantity of a liquid at the start of the application of the liquid to form a stable thin curtain. The excess liquid may be recovered and reused. The features known from this document are included in the preamble of claim 1. Figure 7 shows a side view of the curtain application device disclosed in US-A-3,632,374. In this device, liquid 13 flows out from the interior of a slide hopper 11 to a slide surface 12 thereof, and then freely falls in the form of a thin film from the downstream end 14 of the slide surface to form thin curtain 15, which collides against a moving web 16 so as to be applied thereto. Before the curtain 15 begins to be applied to the web 16, the application start plate 18, which is a rectangular flat plate, is in such a position as to prevent the curtain from reaching the web. The liquid first flows down onto the application start plate 18 and is gathered into a recovery vessel 21. The application start plate 18 is then turned about a fulcrum 19 so that the liquid curtain is allowed to reach the web 16, thus starting the application of the liquid curtain to the web. Both side edges of the curtain 15 are defined by edge guides 20 extending down from the downstream end 14 of the slide hopper 11 to points which are lower than the place where the curtain reaches the web 16. Although this application device has the advantage that the curtain 15 falling from the slide hopper 11 before the start of the application of the curtain to the web 16 is received by the application start plate 18 and then recovered by the recovery vessel 21 so as to be used again, the device has a first problem in that a large space for turning or sliding the application start plate needs to be provided in the device, a second problem in that the side edge portions of the curtain are always discarded and not applied to the web but have to be recovered for reuse, and a third problem in that, at the instant the application start plate is separated from the curtain at the start of the application thereof, the curtain is applied to the web over the entire width thereof at the same time, making the thickness of the initially applied portion of the liquid on the web larger than in other portions. The large space, which causes the first problem, needs to be provided so as to make it possible to dispose the slide hopper 11 over the path of the moving web 16 and to make the height of the curtain 15 sufficient. If the liquid is such that the height of the curtain 15 cannot be as high as desired and it can only be made significantly less than that of the slide hopper, the hopper cannot be located over the path of the web and must be located opposite the path across the edge guides 20, making it difficult to turn the application start plate 18 as mentioned above. The second problem is caused by the fact that the width of the application start plate 18 and the web 16 must be smaller than the distance between the two edge guides 20 so as to be able to turn the plate. If the liquid is made of a single constituent and can therefore be recovered for reuse, or if the liquid is made of plural but less expensive constituents, the application device can be economically operated. If, on the other hand, the liquid is made of a large number of constituents and therefore cannot be recovered or the liquid is more expensive, the width of the curtain 15 must be decreased. In that case, the distance between the two edge guides 20 is made smaller than the width of the web 16 or a backup roller 17 so as to place the lower ends of the edge guides in positions which are higher than the line where the curtain 15 collides against the web. If the distance between the web 16 and the edge guides 20 is much increased, the width of the stream of the curtain is decreased, making the applied curtain on the web nonuniform. In that case, the application device, whose application start plate 18 is placed between the web and the edge guides, cannot be used for the desired applications. The third problem is caused by liquid accummulation over the point of collision of the curtain 15 against the application start plate 18 receiving the falling curtain before the start of the application to the web 16, which tends to transfer from the plate 18 to the web 16 at the start of application to the web 16. (See Figure 8). SUMMARY OF THE INVENTION It is the object of the present invention, to provide a liquid application device which allows to use an application start plate, which prevents an increase in the thickness of the initially applied portion of the liquid on a moving web. According to the present invention this object has been performed by a liquid application device as specified in claim 1 and claim 3, respectively. In the curtain application device provided in accordance with the present invention, liquid freely falling in the form of a thin curtain from a slide hopper is caused to collide against a web continuously moving around a backup roller so that the liquid is applied to the web. The device is characterised by the provision of an application start plate which is turnable or slideable, and which has an upper end extending at an oblique angle to the direction of width of the curtain, and which may have a curtain receiving part at the upper end of the plate. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a side view of an application device of an embodiment of the present application having an application start plate whose upper end is arranged at an oblique angle to the direction of width of the thin curtain of liquid to be applied; Figure 2 shows a front view of the application device shown in Figure 1; Figures 3A-3C show examples of the oblique upper end of the application start plate shown in Figure 1; Figure 4 shows a side view of an application device of an embodiment which is in compliance with the present invention, and which has an application start plate having a curtain receiving part at the upper end of the plate; Figure 5 shows a front view of the application device shown in Figure 4. Figures 6A-6C are cross-sectional side views showing how to use the curtain receiving part to begin application of liquid to the web; Figure 7 shows a side view of a conventional application device; and Figure 8 shows liquid accumulation on the application start plate of the conventional application device. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows a side view of an application device constructed according to an embodiment of the present invention. Figure 2 shows a front view of the application device of Figure 1. The application plate 8' of the device is a flat plate, but the upper end of the plate extends at the oblique angle to the direction of width of a thin curtain 5 of liquid. Before the curtain 5 begins to be applied to the moving web 6, the upper end of the application start plate 8' is placed in a position A' so as to prevent the curtain from reaching the web. When the ccurtain 5 begins to be applied to the moving web, the application start plate 8' is turned so that the upper end thereof is moved away from the position A' into another position B' and the plate is completely separated from the curtain. At that time, the curtain 5 gradually moves from the application start plate 8' to the moving web 6 along the width of the plate due to the oblique angle of the upper end thereof to the direction of width of the curtain. As a result, the thickness of the intially applied portion of the liquid on the web is much less likely to become larger than that of other portions. The oblique angle of the upper end of the application start plate 8' relative to the direction of width of the curtain 5 is 1°, to 30° preferably 2° to 10°. Although the upper end of the application start plate 8' is straight as shown in Figure 3A, the upper end is not confined to such a shape, and it may have a sawtooth shape as shown in Figure 3B or a zigzag shape as shown in Figure 3C, and the constituent lines of the sawtooth-shaped or zigzag-shaped upper end may be either straight or curved. The application start plate 8' may be translated instead of being turned to move the upper end thereof out of the position A' into the other position B'. Figure 4 shows a side view of an application device of an embodiment of the present invention, which is in compliance with the present invention. Figure 5 shows a front view of the application device of Figure 4. The application start plate 8'' of the device is bent in an L-shape so that the plate has a curtain receiving part at the upper end of the plate. When a thin curtain 5 of a liquid begins to be applied to a moving web 6 by the application device, the application start plate 8'' is turned so that the upper end thereof is moved away from such a position A'' so as to prevent the curtain from reaching the web, and is then moved into such a position B'' so as to allow the curtain to reach the web. At that time, the curtain 5 changes from a state of colliding against the application start plate 8'' under the curtain receiving part thereof, as shown in Figure 6A, into a state of colliding against the curtain receiving part and falling onto the moving web 6, as shown in Figure 6B. Subsequently, the plate 8 is turned further so that the plate is separated from the curtain 5 to allow it to directly reach the moving web 6, as shown in Figure 6C. Since the curtain 5 is received by the curtain receiving part and then reaches the moving web 6 at the start of the application of the curtain thereto, liquid accumulation is prevented from affecting the thickness of the applied liquid on the web as in the conventional application device described above. The thickness of the initially applied portion of the liquid on the web 6 is thus made much less likely to become larger than that of other portions. The width of the curtain receiving part is 2 mm to 10 mm, preferably 3 mm to 5 mm. The angle 0 of the part to the horizontal plane is 20° to 90°, preferably 40° to 60°. The construction of the application device shown in Figures 4 and 5 may be combined with that of the application device shown in Figures 1 and 2 to apply a thin curtain of liquid to a moving web. The liquid to be applied in the form of the thin curtain 5 to the moving web 6 by each of the application devices described above may contain various substances, such as those for a photosensitive emulsion layer, an undercoating layer, a protective layer or a back layer of a photographic photosensitive material, those for a magnetic layer, an undercoating layer, a lubricant layer, a protective layer or a backing layer of a magnetic recording material, those for a microcapsule layer or a color developer layer on an information recording layer of a photographic printing plate. The web 6 to which the curtain 5 is applied by each of the above application devices may be paper, a plastic film, a metal sheet, resin-coated paper, synthetic paper or the like. For example, the plastic film may be made of a polyolefin such as polyethylene or polystyrene, a vinyl polymer, a polyamide such as 6,6-nylon or 6-nylon, a polyester such as polyethylene terephothalate or polyethylene 2,6-naphthalate, polycarbonate, or a cellulose acetate such as cellulose triacetate or cellulose diacetate. The resin for the resin-coated paper may be a polyolefin such as a polyethylene. The surface of the resin-coated paper may be embossed or not. Embossment is not confined to any particular form. The metal sheet may be an aluminum sheet, for example. Actual examples of embodiments of the present invention are hereafter described to clarify the effects of the invention. Example 1: A thin curtain of liquid was applied to a moving web by the application device shown in Figures 1 and 2. The liquid was prepared by adding 1.5 g/l of an anionic surface active agent together with a blue dye to an aqueous solution of 10.0% by weight of an alkali-treated gelatin of a type typically used in photographic applications. The viscosity of the liquid was 0.48 poise of a temperature of 40° C. The liquid was 0.48 poise at a temperature of 40° C. The liquid of the curtain flowed at a rate of 4.0 ml/cm-sec over the width of the web, which moved at a speed of 200 m/min in the longitudinal direction thereof and was coated with gelatin in advance. The height of the curtain was 100 mm. The distance between the web and the lower ends of the edge guides 10 was 10 mm. The oblique angle of the upper end of the application start plate 8' to the direction of width of the curtain was 5°. As a result, the thickness of the initially applied portion of the liquid on the web was scarcely larger than that of the other portions of the liquid coated thereon. Therefore, the quality of the applied liquid on the web was good. For a comparison, the curtain was applied to the moving web using an application start plate whose upper end extended parallel to the direction of width of the curtain as shown in Figure 7. In that case, the thickness of the initially applied portion of the liquid on the web became larger than that of the other portions. Example 2 A thin curtain of liquid was applied to a moving web by an application device constructed as shown in Figures 4 and 5. The liquid and the conditions of the application were the same as those in Example 1. Before the curtain began to be applied to the moving web, the upper end of the application start plate 8'' was located in the position A'' and the angle of the curtain receiving part of the application start plate to the horizontal plane was 60°. The width of the curtain receiving part was 5 mm. As a result, the thickness of the initially applied portion of the liquid on the web was equal to that of the other portions of the applied liquid. Therefore, the quality of the applied liquid on the web was good. For comparison with Example 1, the curtain was applied to the moving web using an application start plate which was flat as shown in Figure 7. In that case, the thickness of the initially applied portion of the liquid on the web was larger than that of other portions. According to the present invention, an application device is provided in which a liquid freely falling in the form of a thin curtain from a hopper is caused to collide against a continuously moving web so as to be applied to the web, the device having an application start plate which is turnable or slidable. The upper end of the plate extends at an oblique angle to the direction of the width of the curtain of liquid. The plate may be bent in an L-shape so as to have a liquid receiving part at the upper end of the plate. This results in producing effects as follows: 1. Even if if it is difficult due to the properties of the liquid to generate a thin curtain of the liquid, or a large space as is necessary for the application start plate of a conventional application device is not available, the application start plate can nevertheless be effectively operated to stably apply a curtain of the liquid to the moving web. 2. The thickness of the initially applied portion of the liquid on the web is equal to that of other portions. As a result, the energy and time required for drying the liquid applied to the web are reduced, and the applied liquid is prevented from remaining partially undried, which would lead to contamination of other members.

Claims: A liquid application device for applying liquid freely falling in the form of a thin curtain (5) from a hopper against a web (6), continuously moving around a backup roller (7), so that said liquid is applied to said web, said device having a turnable or slidable application start plate (8'), characterized in that an upper end of said application start plate (8') extends with one or more oblique angle lines to a direction of width of said curtain. A liquid application device according to claim 1, characterized in that the upper end of said plate extends in one oblique angle line to the direction of width of said curtain (5). A liquid application device for applying liquid freely falling in the form of a thin curtain (5) from a hopper against a web (6), continuously moving around a backup roller (7), so that said liquid is applied to said web, said device having a turnable or slidable application start plate (8'), characterized in that said application start plate (8') has an L-shaped curtain receiving part formed at an upper end thereof. A liquid application device according to claim 3, characterized in that the width of said curtain receiving part is in a range of 2 mm to 10 mm.

Inventors: KOBAYASHI KIYOSHI, MIYAMOTO KIMIAKI, MORIKAWA MASHIRO, KOBAYASHI, KIYOSHI, MIYAMOTO, KIMIAKI, MORIKAWA, MASHIRO, KOBAYASHI, KIYOSHI, C/O FUJI PHOTO FILM CO., LTD., MIYAMOTO, KIMIAKI, C/O FUJI PHOTO FILM CO., LTD., MORIKAWA, MASHIRO, C/O FUJI PHOTO FILM CO., LTD.
Applicants: FUJI PHOTO FILM CO LTD, FUJI PHOTO FILM CO., LTD.
Application year: 1989
Main classification: G03C1
IPC codes: B05C9, B05C5, G03C1