Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
  • B05C5/007—Slide-hopper coaters, i.e. apparatus in which the liquid or other fluent material flows freely on an inclined surface before contacting the work
  • B05C5/008—Slide-hopper curtain coaters
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/74—Applying photosensitive compositions to the base; Drying processes therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C9/00—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important
  • B05C9/06—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important for applying two different liquids or other fluent materials, or the same liquid or other fluent material twice, to the same side of the work
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/74—Applying photosensitive compositions to the base; Drying processes therefor
  • G03C2001/7433—Curtain coating
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/74—Applying photosensitive compositions to the base; Drying processes therefor
  • G03C2001/747—Lateral edge guiding means for curtain coating

Definitions

• the present invention relates to a method and apparatus for coating objects or moving supports, advancing continuously past a coating station, by the curtain coating method. More particularly, it relates to an improved curtain coating method and apparatus for the manufacture of photographic materials such as photographic film and paper.
• a moving support is coated by causing a free-falling vertical curtain of coating liquid to impinge onto the moving support to form a layer on said support.
• An apparatus is described in Hughes US Patent 3,508,947 wherein a multilayer composite of a plurality of distinct layers is formed on a slide hopper and caused to impinge onto an object or moving support to form a coated layer thereon.
• US Patent 3,508,947 particularly relates to the manufacture of multilayer photographic materials such as photographic film and paper.
• the quality of coating is largely determined by the properties of the liquid curtain. It is important to insure that a laminar flow of liquid film is formed by the slide hopper and that a laminar—flow liquid curtain is formed from that film. To prevent contraction of the falling curtain under the effect of surface tension, it is known that the curtain width must be guided at its edges by curtain edge guides.
• edge guides are stationary, solid members which are attached to the slide hopper used to supply coating liquid to the curtain and extend downwardly from the initial point of free fall of the curtaih. Wetting contact of the edges of the falling curtain with the edge guides should be maintained the entire length of the edge guide to avoid a break in the curtain. The wetting contact of the edges of the curtain with the edge guides causes nonuniformities in the coating in the edge region of the coating because of viscous drag between the falling curtain fluids and edge guides. By making the curtain wider than the support, a substantially uniform coating can be formed on the support.
• the curtain edge guides can be arranged in such a way that the moving support is coated (a) up to the edge, (b) leaving an uncoated margin on the support edges, or (c) in such a way that the width of the coating liquid extends beyond one or both of the support edges.
• edge band liquids can be advantageous when it is desirable to have the curtain wider than the support to be coated, because it permits the use of a separate edge band liquid which does not include all of the expensive ingredients used for photographic materials.
• the edge band liquid may be collected and recirculated to the edge band-liquid supply for reuse.
• the edge band liquid can be up to 10 centimeters in width. It is also advantageous to supply a sufficient quantity of edge band liquid so that the thickness of the edge—band region of the curtain is somewhat greater than the thickness of the curtain, thereby increasing the stability of the curtain against curtain breaks originating at the edge guides.
• a curtain coating process using such edge band-liquid technique is disclosed in US Patent 4,019,906 issued April 26, 1977, and in Research
• edge band liquid is introduced onto the edges of the slide-hopper surface adjacent the fluids flowing down the slide surface so as to feed the curtain with edge bands of liquid of any desired width and thickness.
• the support is coated edge-to-edge.
• the curtain naturally separates at the edge of the support, and the edge band-liquid portions of the curtain will neck in toward the edge guides and fall into a catch basin.
• the coating roller must be narrower than the support so that the edges of the roller do not become contaminated by the curtain fluids. Consequently, when the width of the support to be coated is substantially changed as is often the case, the coating roller must also be changed, which is a time—consuming and disadvantageous procedure.
• edge portions of the film support embossed by a knurling wheel it is customary to have the edge portions of the film support embossed by a knurling wheel to increase the effective thickness of the support.
• the increased thickness of the edges protects the sensitive photographic materials from higher localized winding pressure occurring as a result of minute variations in support thickness. It is desirable to avoid applying any coating compositions to the knurled areas because inherent tackiness of photographic coatings at high humidity makes it difficult to unwind the support during finishing operations.
• One way of achieving this is to maintain a free-falling curtain having a width less than the width of the support.
• techniques for providing coating—free margins would be highly useful in connection with edge—knurling of the support.
• a known technique for achieving this object uses curtain interceptors, disposed between the coating hopper and the web for intercepting marginal zones of the curtain, which would otherwise fall on the support margins which are to be left uncoated.
• a second lower curtain edge-severing device is used to remove the heavy curtain edge bead produced by the first upper curtain—severing device.
• a method of coating a support with at least one layer of a liquid coating composition comprising moving the support along a path through a coating zone over a support roller having a length less than or equal to the width of the moving support, and forming, at the coating zone, a free—falling curtain transversely of the path of the moving support and having a width greater than that of the support and impinging on the moving support to deposit a coating thereon.
• Curtain—severing means are positioned proximate to the impingement locus of the falling curtain for intercepting and diverting edge portions of the falling curtain which would otherwise impinge on edge portions of the support, thereby providing uncoated marginal portions of the support. Diverted portions of the falling curtain are collected in a catch basin.
• the free—falling curtain is maintained in wetting contact with edge guides spaced apart by a distance greater than the support to be coated.
• the curtain—severing means is positioned so that the parted edge portion of the curtain is diverted away from the support, and purging liquid is applied to a severing—blade component of said means to assure efficient removal of curtain fluid to the catch pan to obtain the desired uncoated edge portion of the support.
• the invention also includes the embodiment of using tubular edge guides which terminate in their lower extremity at a point just above the curtain—severing means. Flushing fluid is caused to flow through the tubular edge guides and serves to extend wet contact with the edge region of the curtain to a region proximate to the catch basin.
• This embodiment is used to facilitate movement of the slide hopper into a coating position during start—up without interfering with the curtain—severing means.
• This invention also includes an apparatus for carrying out the method for the coating of a layer or layers onto a moving support disclosed herein.
• such apparatus uses a curtain—severing means comprising a severing—blade element positioned proximate to the edge of the support at the curtain impingement locus, which severing— lade element parts the curtain and diverts the falling curtain to both sides of the blade, so that one side of the parted curtain is diverted away from the support toward the edge guide and then to the catch basin and the other side is diverted toward the support to impinge on the support a predetermined distance from the edge of the support.
• the blade element is positioned approximately tangent to the support at the point of impingement and angled outwardly with respect to the direction of travel of the support. Purging liquid is delivered to the surface of the blade to divert curtain fluids impinging on the blade in a direction away from the support and into a catch basin.
• the width of the coating within the edges of the support can be optimized according to the desired product requirement.
• An uncoated margin can be carried out with an e fectiveness which results in significantly reducing the waste resulting from unusable support material.
• Coating within the edges of the support provides a knurl area free from coating material.
• the ability to coat within the edges of the support also eliminates coating on the underside of the support, which occurs with a curtain coating technique wherein the falling curtain impinging on the support is wider than the support to be coated. Undried coating composition on the underside of the support will adversely affect downstream conveying equipment which transports the coated support through the drier.
• FIG. 1 is a simplified perspective view of a curtain coating apparatus of the slide—hopper type in accordance with a preferred embodiment of my invention.
• Fig. 2 is an edge sectional view of a solid edge guide and a falling curtain extending beyond the edge of the moving support in accordance with the prior art.
• Fig. 3 is a simplified perspective view of a curtain—severing device according to the present invention.
• Fig. 4 is a side elevation of section 4—4 of the curtain—severing device shown in Fig. 3.
• Fig. 5 is a top view of section 5—5 of the curtain—severing means arrangement shown in Fig. 1.
• Fig. 6 is a partial elevation view of a curtain—severing device and a falling curtain extending beyond the edge of the moving support in accordance with an embodiment of the invention.
• Fig. 7 is a partial elevation view of a curtain—severing device and a falling curtain extending beyond the edge of the moving support in accordance with another embodiment of the invention.
• the invention will now be described in more detail with reference to the known curtain coater of a slide—hopper type as shown in Fig. 1.
• the coating liquids are delivered laterally to the slide hopper 10, ascend to exit slots 12, and are deposited in a form of a layer on the individual inclined surfaces 14. Under the effect of gravity, the individual layers flow down the surfaces 14, flow over one another, and flow to the coating edge 16 where a -9- free-falling composite curtain 18 is formed.
• the slide hopper can be any desired width, such as a width of from several inches to several feet.
• the support 20 is preferably guided onto and around a coating roller 22.
• the width of the coating roller can be chosen correspondingly smaller than the width of the support guided around it.
• the coating roller 22 is mounted on and preferably driven by a motor which is not shown.
• photographic coating composition can be coated on a variety of supports.
• photographic supports include polymeric film, wood fiber, e.g., paper, metallic sheet and foil, glass and ceramic supporting elements provided with one or more subbing layers to enhance the adhesive, antistatic, dimensional, abrasive, hardness, functional, antihalation and/or other properties of the support. It may be coated in the form of discrete sheets or, as is more usually the case, in the form of a continuous support.
• Fig. 1 illustrates one type of lateral curtain guiding system, wherein the edge guides 24 and 24' are arranged outside the edges of the moving support 20 to be coated so that the curtain 18 is wider than the support to be coated. In this case, the support is completely coated over its entire width; thereby any peripheral irregularities are situated in the area of the edge guides and therefore outside the useful width of the support.
• the coating fluids which drop past the edges of the support are collected in catch basins 28,28' for reuse, if practical.
• FIG. 2 is an edge-section view of a typical free-falling curtain IB-.,, showing a solid edge guide 24 flushed with a flushing liquid 30 adjacent the edge guide and an edging band liquid 32 adjacent the flushing liquid 30 which are shown being dispensed into the catch basin 28, leading to a drain (not shown).
• the liquid curtain can be seen to wet the backside of the support 20 at the edges of the support at 34 and also over the knurled area 26.
• the liquids which coat the backside of the support will transfer to subsequent conveyance rollers and eventually require termination of the coating process in order to clean downstream conveyance rollers.
• the coating applied on the knurled area 26 results in problems in the finishing operation due to the tacky nature of the gelatin and the high winding pressures associated with knurls.
• severing devices 40,40' comprising a blade 42, respectively disposed outward from the plane of the curtain.
• the blades 42 make an acute angle with the edge of the moving support and are approximately tangentially disposed to the coating roller 22.
• the curtain starts its free fall by falling off the lip 16 of the slide hopper 10 and is severed just above the impingement locus on the support.
• the curtain is parted by the blade 42 so that the center portion of the severed curtain impinges on the support, leaving an uncoated margin of support 48.
• the outer portion of the severed curtain is drawn toward edge guides 24-24* so that all of the edging fluid flows into the catch basins 28,28'.
• Figs. 3 and 4 are a perspective and side elevation view of the curtain-severing device 40.
• the curtain—severing device as mentioned above, comprises a protruding blade 42, a mounting bracket 44 and alternative purging liquid—supply connections 46. Either liquid—supply connection 46 can be used depending upon the mounting arrangement of the curtain—severing device.
• At least the top surface and preferably both surfaces of the blade 42 are purged with a liquid, preferably water, through slots 50 located adjacent the blade and preferably extending the entire width of the blade leaving housing 44.
• the curtain fluids which impinge on the surface of the blade 42 will be diverted to catch basin 28 by the force of purging liquid supplied to the top of the blade 42.
• the bottom surface of the blade is also purged with a liquid because this will minimize any tendency for dried solids in the curtain fluids from forming on the edges of the blade, because the tendency of the bottom purge is to surround the edges of the blade.
• the height of the slot 50 is preferably in the range from 0.006 to 0.025 centimeter.
• Fig. 5 is a top view of the preferred curtain—severing device showing in greater detail the location of the blade 42 used to sever the falling curtain.
• the liquid—supply connections are shown relative to the position of edge guide 24—24' and the edge of the support 20.
• the width of the surface of the. blade 42 protruding from the slot 50 is preferably slightly wider than the remaining portion of the blade, with the width gradually narrowing up to the point of impingement of the curtain with the blade. After the impingement locus on the blade, the width of the blade is essentially uniform until its termination point. This slight variance in the width of the surface of the blade helps to insure that the purging liquid envelops the edges of the blade.
• Curtain movement normally can occur because of disturbances to the curtain by ambient air currents and boundary air moving with the support.
• the blade 42 is disposed at an angle ⁇ with respect to the direction of travel of the support and tangentially disposed to the coating roller 22 so as to divert the edge portion of the falling curtain which impinges on the blade. Purging liquid is projected along the surfaces of the blade 42 to flush the falling curtain away from the edge of the support into the catch basin 28. It can be appreciated that the length and width of the blade and its angle with respect to the direction of support travel are interrelated variables which also depend on the velocity and volume of purging liquid supplied to the blade surface.
• the blade 42 should be as wide as needed to provide the desired width of the uncoated margin 48 on the support and to allow for lateral weave of the support as it is transported around the coating roller 22.
• the width of the blade preferably is in a range of 0.3 to 3.0 centimeters and the angle ⁇ of the axis of the blade with respect to the direction of the moving support can be in the range from 5° to 60°, and preferably 20° to 40°.
• the length "L" of the blade should be of a length sufficient to permit collection of the curtain fluid and purging liquid, and has been found to be satisfactory when in the range of 2 to 5 centimeters, and preferably should be 4 centimeters.
• the velocity of the purging liquid across the blade surface can be in the range of 200 to 800 centimeters per second with a volume of purging liquid of about 2 to 10 cubic centimeters per second per centimeter of slot width 50, and preferably 6 to 7 cubic centimeters per second per centimeter of slot width 50.
• low-viscosity flushing liquid 30 is delivered to the top of the solid edge guide 24 and distributed over the entire height of the edge guide from the coating edge to the point where the edge guide terminates below the level of the blade 42.
• An edging band liquid 32 is also supplied to the edge regions of the curtain to increase the stability of the curtain and reduce waste.
• edging band liquid When using an edging band liquid, it may be advantageous to supply a sufficient quantity of edging band liquid to the edges of the slide hopper so that the thickness of the curtain and thus the flow rate of edging band liquid are somewhat greater than the thickness and flow rate of the center curtain, thereby greatly increasing the stability of the curtain at the edge guides and thus avoiding curtain breaks.
• the width and thickness of the curtain edge band liquid are such that a relatively large quantity of edging band liquid may be required, typically 1 liter per minute or more.
• the process provides good results when the edging band—liquid viscosity approximates the viscosity of central curtain coating liquids. Gelatin solutions of appropriate concentration with added wetting agents are suitable.
• the height of the severing blade 42 above the support at the impingement locus be as small as is practical from an operating point of view. It was found that this height should be less than about 0.4 centimeter and preferably about 0.15 centimeter. Because the blade of the curtain—severing device is closely spaced to the support, it will of necessity be approximately tangentially disposed to the axis of the moving support 20 on the coating roller 22 at the impingement locus of the curtain.
• FIG. 7 illustrates another embodiment of my invention, combining the functions of a flushing liquid 30 and the edging band liquid 32 supplied to the edge regions of the curtain.
• the edge guide 56 is fabricated from a hollow tube to which a flushing fluid is supplied at the top of the edge guide from a source not shown. The edge guide 56 terminates a short distance above severing blade 42.
• the fluid edge—guide extension flowing out of the edge guide creates a fluid extension which acts to combine with flushing fluid 30 to extend and stabilize the edge region of the falling curtain, the use of a shorter edge guide 56 allows for the slide hopper to be moved into a coating position and avoid mechanical interference with a fixed severing device 40. It was found that fluid flowing from the end of the edge guide was an effective extension of the edge guide when the hollow tubes had inside diameters of about 0.035 to 0.240 centimeter, an outside diameter of about 0.075 to 0.300 centimeter and a fluid flow rate of from 10 to 200 cc per minute.
• the water jet tends to break up before the edge band of the fluid has completed its necking in toward the edge guide, resulting in an uneven and pulsating breakup of the edge band of the curtain and the possibility of contaminating the apparatus in its immediate vicinity with curtain fluids, including the coating roller and also the edge of the support.
• the curtain—severing blade is used to part the curtain according to the preferred embodiment described above, then all of the curtain fluids impinging on the blade are directed by the purging liquid to the catch basin.
• the width of that part of the severed curtain deposited on the support can be reduced by changing the width of the blade and the position of the blade with respect to the edge of the support.
• the preferred position of the blade is to have its center along the line of impingement of the curtain on its surface be located just above the edge of the support on the coating roller.
• the width of the uncoated edge margin of support will be equal to half the width of the blade at the curtain impingement line, varying from this width more or less depending on the amount the support weaves as it travels around the coating roller. It has been found that, if the blade is approximately tangentially disposed to the coating roller at the impingement locus and spaced above the coating roller by no more than .15 centimeter, then any edge bead of coating which may form on the support will not exceed 20 percent of the thickness of the remaining coating and is easily dried before the film is wound at the end of the coating machine.
• flushing liquid 30, edge band liquid 32, fluid edge guide extension 57 and the purging liquid emitted from slot 50 of the curtain—severing device are all preferably a low-viscosity liquid having a viscosity of 0.5 to 10 centipoise.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Coating Apparatus (AREA)
• Road Signs Or Road Markings (AREA)
• Materials For Medical Uses (AREA)
• Paints Or Removers (AREA)

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Cited By (5)

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Citations (5)

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• 1988
  • 1988-07-20 WO PCT/US1988/002458 patent/WO1990000939A1/en unknown
• 1989
  • 1989-07-18 WO PCT/US1989/003113 patent/WO1990001179A1/en active IP Right Grant
  • 1989-07-18 KR KR1019900700570A patent/KR920004629B1/ko not_active IP Right Cessation
  • 1989-07-18 BR BR898907561A patent/BR8907561A/pt not_active IP Right Cessation
  • 1989-07-18 DE DE68919699T patent/DE68919699T2/de not_active Expired - Fee Related
  • 1989-07-18 EP EP89908604A patent/EP0425562B1/de not_active Expired - Lifetime
  • 1989-07-18 AU AU40324/89A patent/AU626316B2/en not_active Ceased
  • 1989-07-18 AT AT89908604T patent/ATE114514T1/de not_active IP Right Cessation

Patent Citations (5)

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