Apparatus for simultaneous multilayer application

Abstract: A device for simultaneous multilayer application in which discrete liquid substances are applied as at least two mutually-overlaid layers to a continuously moving web comprises a web, a backup roller around which the web moves and a hopper for simultaneously applying upper and lower layers to the web. The hopper includes first and second guide surfaces along which the liquid substances flow onto the web, and first and second slots for individually supplying the liquid substances to each of the guide surfaces. The slots are designed such that the length of the slot for supplying the lower layer is longer than the length of slot for supplying the upper layer and the width of the slot for supplying the lower layer is smaller than the width of the slot for supplying the upper layer. In this manner, the edges of the applied liquid substances are continuous along the length of the web and streaks are prevented from forming along the applied surfaces.

Description: APPARATUS FOR SIMULTANEOUS MULTILAYER APPLICATION BACKGROUND OF THE INVENTION The present invention relates to an apparatus for applying a liquid composite substance to a continuously moving web in manfacturing a photographic photosensitive material such as a photographic film and printing paper, a photoengraving material or a recording material such as pressure-sensitive recording paper and thermosensitive recording paper. More particularly, the invention relates to an apparatus for simultaneously applying liquid substances as two or more mutually-overlaid layers to a continuously moving web. A method of rapid simultaneous multilayer application in a slide-hopper-type application device or the like was disclosed in the United States Patent No.4,001,024. In order to increase the application speed in the method, a liquid substances having a viscosity as low as 1 cps to 8 cps is applied as the lowermost layer to a web to set the degree of wet application of the liquid substance at 2 cm³ to 12 cm³ per 1 m² of the surface of the web. A meniscoid vortical movement is allowed only to mix the lowermost layer and the second lowermost layer with each other but not allowed to affect the other layers. A method of applying to a web a thin carrier layer of a pseudo-plastic liquid substance of 20 cps to 200 cps in viscosity at the shear rate of 100 sec⁻¹ and 10 cps or less in viscosity at the shear rate of 100,000 sec⁻¹ was disclosed in the United States Patent No.4,113,903. In the method, the pseudo-plastic liquid substance whose viscosity is high at the low shear rate and low at the high shear rate is used as the lowermost layer on the web in order to eliminate the instability of an application bead, as in the method disclosed in the United States Patent No.4,001,024. The liquid substance is characterized in that it performs non-Newtonian flow. The liquid substance needs to be a selected special composite substance and subjected to careful preparation. From FR-A-2310809 there is known a multilayer coating apparatus in which the entirety of slots are enlarged in their downstream side. According to Figures 1 and 4 of said prior art reference, the slot for forming the lower most layer on the web is not made smaller than the slot for forming the second lower most layer. From US-A-4,154,879 there is known a multilayer application device in which the width of the various slots is generally coextensive with the width of the web. In the slide-hopper-type application according to JP-54975/1988 (not prior art), the width of a first slot for supplying a liquid substance for the lowermost layer on a web, the width of a second slot for supplying a liquid substance for the second lowermost layer, and the width of a third slot for supplying a liguid substance for the third lowermost layer are equal to each other. When rapid application is to be performed by the application device, very slight streaks take place as defects in the surface of the assembly of the layers in the direction of the application, randomly along the width of the web. The present invention was made in order to solve the above-mentioned problem. Accordingly, it is an object of the present invention to provide a simultaneous multilayer application device capable of performing stable rapid application without causing a very slight streak as a defect in the direction of the application. The above object is achieved by the subject matter of claim 1. As a result of intensive study on the cause of the occurrence of the streak, it has been discovered that the streak occurs because the applied liquid substance 15 for making the second lowermost layer falls at the outlet opening of the slot 5 through which the applied liquid substance 14 for making the lowermost layer is supplied, as shown in Fig. 3. Therefore, the simultaneous multilayer application device provided in accordance with the present invention applies liquid substances as two or more mutually-overlaid layers to a continuously moving web. The device is characterized in that the width of a slot for supplying the liquid substance for forming the lowermost layer is smaller than that of a slot for supplying the liquid substance for forming the second lowermost layer. Preferably the width of the slot for supplying the liquid substance for forming the lowermost layer is set at 0.05 mm to 0.7 mm, and more preferably 0.1 mm to 0.5 mm. The width of the slot for supplying the liquid substance for forming the second lowermost layer is preferably set at 0.1 mm to 1.5 mm, and more preferably 0.2 mm to 1.0 mm. Furthermore, the bead back pressure may be applied to the simultaneous multilayer application method or device of the present invention, in order to make the bead stable. The application of the back pressure for the bead is described in detail in the United States Patent No.3,220,877. BRIEF DESCRIPTION OF THE DRAWING Fig.1 shows a sectional view of a slide-hopper-type application device for simulaneously applying three layers in a stable rapid simultaneous multilayer application method to which the present invention is to be applied; Fig.2 shows a sectional view of an extrusion-type application device for simultaneously applying three layers in a stable rapid simultaneous multilayer application method to which the present invention is to be applied; Fig. 3 shows an enlarged sectional partial view for describing the occurrence of a streak; Fig. 4 shows a sectional view of a slide-hopper-type application device for simultaneously applying three layers in a stable rapid simultaneous multilayer application method to which the present invention is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows a sectional view of a slide-hopper-type application device to which the present invention is to be applied. Shown in Fig. 1 are a backup roller 1, a web 2, a bead 3(b), slide surfaces 4, 7, 10 and 13, slots 5(b), 8 and 11, manifold spaces 6, 9 and 12, a water film 14 constituting the lowermost layer on the web, liquid substance film 15 constituting the second lowermost layer, and a liquid substance film 16 constituting the third lowermost layer. The web 2 is continuously moved in a direction shown by an arrow in Fig. 1, on the peripheral surface of the backup roller 1 by a conveyance means not shown in the drawing. The water 14 for making the lowermost layer is supplied by a pump P₁ so that the water is spread to the entire width of the slot 5(b) by the manifold space 6. The water then flows from the slot 5(b) to the slide surface 4, gravitates thereon and forms the bead 3(b) so that the water is applied to the web 2. The other liquid substances 15 and 16 for making the second and the third lowermost layers, which become the first and second layers of a final product, respectively, are similarly applied to the web 2 through the manifold spaces 9 and 12 and the slots 8 and 11 along the slide surfaces 7 and 10 while being overlaid on the water film 14 and forming the bead 3(b) together therewith. Fig. 2 shows a sectional view of an extrusion-type application device for simultaneously applying three layers in a rapid stable simultaneous multilayer application method to which the present invention is to be applied. Shown in Fig.2 are a backup roller 21, a web 22, slots 24, 25 and 26, manifold spaces 27, 28 and 29, a water film 30 constituting the lowermost layer on the web, a liquid substance film 31 constituting the second lowermost layer, which becomes the first layer of a final product, and a liquid substance film 32 constituting the third lowermost layer, which becomes the second layer of the final product. The web 22 is continuously moved in a direction shown by an arrow in Fig.2, on the peripheral surface of the backup roller 21 by a conveyance means, not shown in the drawing. The water 30 for making the lowermost layer is supplied by a pump P₁ so that the water is spread to the entire width of the slot 24 by the manifold space 27. The water is then pumped through the slot 24 and applied to the web 22. The other liquid substances 31 and 32 for making the second and the third lowermost layers are similarly pumped through the manifold spaces 28 and 29 and the slots 25 and 26, repectively, and applied to the web 22 together with the water 30. The following embodiment to be applied to the device of Fig. 2 is described below. Here, the length of the slot 24 for the lowermost layer is set to be larger than those of the slots 25 and 26. Therefore, the liquid substance 30 is applied to the web, with the length of the substance 30 being larger than the length of the liquid substances 31 and 32. There is not a figure showing the relationship between the lengths of the liquid substance supply slots of the device. Since the length of the slot through which water for forming the lowermost layer on the web is supplied to a slide surface is made larger than that of each of the slots through which water-soluble composite substances for making the second and the third lowermost layers, respectively, are supplied to other slide surfaces, the quantity of the applied water is larger for the side edges of an application bead controlled by application width control plates than for the central portion of the bead, so that the side edges of the bead are continuous. For that reason, the liquid substances can be stably and rapidly applied to the web. An actual example of this embodiment is hereafter described to make the effect of the embodiment understood more clearly. An experiment was conducted on an application device which is the actual example of this embodiment. The device was of the slide-hopper-type as shown in Fig.1. In the experiment, liquid substances, whose compositions and physical properties are shown in Table 1, were applied to a web under conditions described below. The web was made of cellulose triacetate and had a width of 18 cm. Actual Example of Embodiment The liquid substances were applied as three layers under conditions shown in Table 2. The liquid substances could be applied as the three layers under the above conditions without making the side edges of an application bead unstable at an application speed of 400 m/min. or less for the web. Comparative Example The liquid substances were applied as three layers under conditions shown in Table 3. The side edges of an application bead became unstable at an application speed of 250 m/min. or more for the web so as to make the surface of the assembly of the layer nonuniform. According to the above embodiment, the length of a slot through which water for making the lowermost layer on a web is supplied to a slide surface is larger than those of slots through which water-soluble composite substances for making the second and the third lowermost layers are supplied to slide surfaces, so that the water sufficiently wets the side edges of an application bead to strengthen it against disturbances. For that reason, the layers can be stably and rapidly applied to the web to enhance the productivity. The simultaneous multilayers application device of the present invention will be described hereinafter. The simultaneous multilayer application device provided in accordance with the present invention applies liquid substances as two or more mutually-overlaid layers to a continuously moving web. The device is characterized in that the width of a slot for supplying the liquid substance for making the lowermost layer is made smaller than that of a slot for supplying the liquid substance for making the second lowermost layer. The width of the slot for supplying the liquid substance for making the lowermost layer is set at 0.05 mm to 0.7 mm, preferably 0.1. mm to 0.5 mm. The width of the slot for supplying the liquid substance for making the second lowermost layer is set at 0.1 mm to 1.5 mm, preferably 0,2 mm to 1.0 mm. In the case where the invention is applied to the device of Fig.1, the width of slot 5 for supplying a liquid substance for forming the lowermost layer on a web is made smaller than that of a slot 8 for supplying a liquid substance for forming the second lowermost layer, as shown in Fig. 4. As a result, a streak is not occurred as a defect in the surface of the assembly of the layers as done in the device of the publication No. JP-54975/1988. In the case where the invention is applied to the device of Fig. 2, width of a slot 24 for supplying a liquid substance for forming the lowermost layer on a web is made smaller than that of a slot 25 for supplying a liquid substance for forming the second lowermost layer. Since the width of the slot for forming the lowermost layer on the web is made smaller than that of the slot for forming the second lowermost layer, in the simultaneous multilayer application device provided in accordance with the present invention, the liquid substance supplied to make the second lowermost layer is prevented from falling into the slot through which the liquid substance is supplied for making the lowermost layer. As a result, a streak is not caused in the surface of the assembly of the layers, so that the surface is made uniform. An actual example of the invention is hereafter described to make the effect of the present invention understood more clearly. An experiment was conducted on an application device which was of the slide-hopper-type as shown in Fig.4. In the experiment, liquid substances whose compositions and physical properties are the same as shown in Table 1 were applied to a web under conditions described below. The web was made of cellulose triacetate and had a width of 18 cm. Comparative Example Liquid substances were applied by conventional slide-hopper-type application device in which slots for supplying the liquid substances are equal to each other in width. The conditions of the application are shown in Table 4. After a film made of the liquid substances applied at a speed of 150 m/min. was caused to gel by cold air, the film was dried in a conventional procedure and the surface of the film was inspected by eyesight. It turned out that very-slight longitudinal streaks had been caused in the surface of the film over the total width thereof. Actual Example of Embodiment Liquid substances were applied by a slide-hopper-type application device which was an actual example of the embodiment of the present invention and in which the widths of slots for supplying the liquid substances were set along with other conditions as shown in Table 5. After a film made of the liquid substances applied at a speed of 150 m/min. was caused to gel by cold air, the film was dried in a conventional procedure and the surface of the film was inspected by eyesight. It turned out that no streak had been caused in the surface of the film. Therefore, the surface of the film was uniform. In a simultaneous multilayer application device for applying liquid substances as two or more mutually-overlaid layers to a continuously moving web, the width of a slot for supplying the liquid substance for making the lowermost layer the web is made smaller than that of a slot for supplying the liquid substance for making the second lowermost layer, in accordance with the third embodiment. As a result, stable rapid simultaneous multilayer application can be performed without causing a streak as a defect in the direction of the application. The above-described embodiments can be combined as follows. 1 A preferred combination provides a simultaneous multilayer application device for applying discrete liquid substances as at least two mutually-overlaid layers to a continuously moving web that comprises a continusouly moving web, a backup roller around which the web moves, and a hopper for simultaneously applying upper and lower layers to the web, the hopper comprising first and second guide surfaces along which the liquid substances flow onto the web and first and second slots, whose lengths extend in a width-wise direction of the web, for individually supplying the liquid substances to each of the guide surfaces, wherein the length of the slot for supplying the lower layer is longer than the length of the slot for supplying the upper layer such that the edges of the applied liquid substances are continuous along the length of the web, and wherein the width of the slot for supplying the lower layer is smaller than the width of the slot for supplying the upper layer so as to prevent streaks from forming along the applied layers. In particular, the length of the lowermost slot has been increased to permit coating of the full width of a substrate at high coating velocities. 2 Another combination provides such the simultaneous multilayer application device for applying discrete liquid substances as at least two mutually-overlaid layers to a continuously moving web that comprises a continusouly moving web, a backup roller around which the web moves, and a hopper for simultaneously applying upper and lower layers to the web, the hopper comprising first and second guide surfaces along which the liquid substances flow onto the web and first and second slots, whose lengths extend in a width-wise direction of the web, for individually supplying the liquid substances to each of the guide surfaces, wherein the length of the slot for supplying the lower layer is longer than the length of the slot for supplying the upper layer such that the edges of the applied liquid substances are continuous along the length of the web, the width of the slot for supplying the lower layer is smaller than the width of the slot for supplying the upper layer so as to prevent streaks from forming along the applied layers and wherein the lower layer is water and the upper layer is water-soluble substance having a viscosity not less than 40 cps at a shear rate of 100 sec⁻¹. The above viscosity requirement for the second layer when water is used to form the first coating layer, alleviates transverse non-uniformity of coating layers at relatively low coating speeds under certain coating conditions. An actual example of the combination (2) is hereinafter described, in order to make the effect of the combination of the embodiments of the present invention understood more clearly. Liquid substances were applied by a slide-hopper type application device which was an actual example to which the first and the third embodiments of the present invention were applied. The lengths and the widths of the slots for supplying the liquid substances were set along with the conditions as shown in the Table 6. In the experiment, liquid substances as described below were applied to the web made of cellulose triacetate (TAC) and having a width of 18 cm. Water of 0.65 cps in viscosity at a temperature of 40 °C, an antihalation liquid containing an anion active agent of 60 cps in viscosity at a temperature of 40 °C and a gelatin liquid containing an anion active agent of 20 cps in viscosity at a temperature of 40 °C were simultaneously applied to the web, at flow rates of 2 cc/cm-min, 60 cc/cm-min and 15 cc/cm-min, as the lowermost layer on the web, the second lowermost layer and the third lowermost layer, respectively. The bead clearance was selected to 0.25 mm, and the bead back pressure was selected to -40 mmAq. The experiment was conducted with changing the application speed. As a result, it turned out that the uppermost limitting application speed with which the side edges of an application bead can be made stable was 450 m/min. Furthermore, in order to examine the occurrence of the very-slight longitudinal streaks, the following experiment wag conducted: After a film made of the liqui substances applied at a speed of 200 m/min was caused to gel by cold air, the film was dried in a conventional procedure and the surface of the film was inspected by eyesight, It turned out that no streak had been caused in the surface of the film due to the falling of the second lowermost layer into the slot for the water. Comparative Example A comparative experiment was conducted with the conditions the same with those for the actual example of the present invention described above without the conditions of the width and the length of the slot for the lowermost layer. That is, the length of the slot for the lowermost layer was changed to 15.0 cm, and the width of the slot for the lowermost layer was changed to 0.8 mm. Therefore, the widths of the slots for the three layers were made equal to one another and the lengths of the slots for the three layers were made equal to one another. As a result, it was turned out that the uppermost limitting application speed with which the side edges of an application bead can be made stable was 250 m/min, which was lower than the uppermost limitting application speed of the above-described example of the present invention. Furthermore, in order to examine the occurrence of the very-slight longitudinal streaks, after a film made of the liquid substances applied at a speed of 200 m/min was subjected to the experiment conducted for the actual example described above. As a result of the inspection by eyesight of the surface of the obtained film, it turned out that very-slight longitudinal streaks had been caused in the surface of the film over the total width thereof. As described above according to the simultaneous multilayer application apparatus of the present invention, rapid simultaneous multilayer application can be perforemed.

Claims: An apparatus for rapid, stable, simultaneous multilayer application, in which discrete liquid substances are applied as at least two mutually-overlaid layers to a continuously moving web (2,22), comprising: a continuously moving web; a backup roller (1,21) around which said web moves; a hopper for simultaneously applying said layers to said web, said hopper comprising guide surfaces along which said liquid substances flow onto said web and first and second slots (5b,8,11);(24,25,26) for individually supplying said discrete liquid substances to each of the guide surfaces, characterized in that the width of the slot (5b,24) for supplying the lowermost layer (14,30) to the web (2,22) is smaller than that of the slot for forming the second lowermost layer, so as to prevent streaks from forming along the applied layers. Apparatus according to claim 1, wherein first and second guide surfaces (4,7) are coplanar and separated from one another by said slot (5b) for supplying the lowermost layer, said first guide surface (4) terminating at a liquid substance application point adjacent said web (2,22). Apparatus according to claim 1, wherein said guide surfaces are angularly displaced and converged to a liquid substance application point adjacent said web. Apparatus according to claim 1, wherein the width of the slot (5b;24) for supplying the lowermost layer (14;30) is between 0.05 mm and 0.7 mm and the width of the slot for supplying the second lowermost layer is between 0.1 mm and 1.5 mm. Apparatus according to claim 1, wherein said first and second slots extend in a width-wise direction of said web (2,22) for individually supplying said liquid substances to each of said guide surface, wherein the length of the slot (5b,24) for supplying the lowermost layer is longer than the length of the slot for supplying the second lowermost layer, such that the edges of the applied liquid substances are continuous along the length of said web.

Inventors: ISHIZUKA SEIJI, ISHIZUKA, SEIJI
Applicants: FUJI PHOTO FILM CO LTD, FUJI PHOTO FILM CO., LTD.
Application year: 1988
Main classification: G03C1
IPC codes: B05C9, B05C5, G03C1, B05D1