Classifications

• • 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
  • 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
• • 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

Definitions

• the present invention concerns coating multiple layers of material onto a moving substrate. More specifically, the present invention teaches a method and apparatus for coating multiple layers of photographic materials onto a photographic support.
• a number of individual layers are coated onto the support by means of a coating hopper.
• One type of coating hopper is known as the multiple slide hopper, which is composed of individual slide elements separated by slots and cavities. By introducing the individual coating liquids into separate cavities, the liquids are distributed to the desired width in a uniform fashion by flowing through the separate narrow slots. Upon exiting the slots, the layers flow down the slide surface by gravity. Layers of different coating liquids become superimposed on one another as layers from upstream slots flow over layers from the downstream slots. It is often advantageous to have steps between adjacent slide elements. These steps or slide offsets generally range from 0.005-0.100 inches. At the end of the slide surface at a lip, the superimposed layers of liquid coating flow off of the slide surface and are coated onto the moving web.
• the width of the coating layers can be less than the width of the hopper slide or web to be coated. It is generally necessary to provide some means of lateral confinement of the coating liquids on the hopper slide in order to achieve the desired width of coating layers on the web. Confining the liquid layers on the hopper slide is achieved by devices known in the art as edge guides. Preferably, edge guides should be designed such that surface tension or inertial effects do not create non- uniformities in the thickness of the layers of the coating composition in the longitudinal (parallel to direction of web travel) edge portions. Such non- uniformities in the coated layers can be a cause of coated waste or problems in drying the longitudinal edge portions of the coating as well as problems in conveying or winding the coated support.
• edge guides described by these patents do not comprise a method for achieving widthwise adjustability of the edge guides on the hopper surface, which is important in minimizing coated waste in an operation where a variety of products are coated that have different finished dimensions.
• the current technology also lacks a method for insuring that the edge guides are held down on the hopper face in such a way as to prevent excessive leakage under the edge guides, which can cause manufacturing or product quality problems.
• the edge guides described in the aforementioned prior art are not capable of accommodating differences in height between the different slide elements, known as slide offsets, in a continuous, integral manner.
• a hopper edge guide system for use in a slide hopper having a plurality of hopper elements forming a slide surface terminating at a lip.
• the hopper edge guide system includes an edger arm extending along the length of the slide surface and having a contact side facing the slide surface. An edge pad is abutted to the contact side of the edger arm and mates with the slide surface to form an effective seal against leakage under the edge pad.
• the edger arm is adjustably positionable across the width of the slide surface. In one embodiment of the edge guide the edger arms are relieved at a point over the second hopper element from the lip.
• a plurality of biasing means are positioned along the edger arm which exert compressive force on the edge pad to provide a leak proof seal between the slide surface and the edge pad.
• the edge pad comprises a slot above the first or second hopper element from the lip which provides proper mating with the slide surface by accommodating various steps in the slide surface.
• the edge pad of the present invention forms a vertical wall perpendicular to the slide surface. This wall is the restraining surface for the lateral edge of the composition flowing on the slide. Above the vertical wall is a surface inclined at an angle of about 10° to about 20° above the horizontal. The edge pad forms an angle of between about 15° to about 30° from the slide surface at the lip of the hopper.
• FIG. 1 shows a cross-sectional view of a multiple layer hopper system used for bead coating a support.
• FIG. 2 shows a top view of the adjustable edge guide of the present invention.
• FIG. 3 shows a side view of the adjustable edge guide of the present invention.
• FIG. 4 shows a side view of the continuous edge pad used in the present invention.
• FIG. 5 shows a top view of the continuous edge pad used in the present invention.
• FIG. 6 shows a side view of the edger arm used in the present invention.
• FIG. 7 shows a top view of the edger arm used in the present invention.
• FIG. 8 shows a side view of an alternative embodiment of the continuous edge pad of the present invention.
• FIG. 9 shows a cross-sectional view of the continuous edge guide and coating composition on a hopper slide.
• FIG. 10 shows the optical density versus widthwise distance for a coating composition whose thickness is 1.17 times the height of the vertical wall of the edge pad on the hopper slide.
• FIG. 11 shows the optical density versus widthwise distance for a coating composition whose thickness is 0.43 times the height of the vertical wall of the edge pad on the hopper slide.
• FIG. 12 shows the optical density versus widthwise distance for a coating composition whose thickness is 1.75 times the height of the vertical wall of the edge pad on the hopper slide.
• FIG. 1 shows a multilayer coating hopper 10 having three hopper slide elements 11 separated by hopper slots 12 which provide coating liquid from cavities 13. The coating liquids flow through slots 12 and down the slide surfaces 23 superimposed on each other.
• a bead coater is shown although the present invention works equally well for curtain coating hoppers.
• FIGS. 2 and 3 show an assembly of the continuous edge guide system for a coating hopper that has eight slots 12.
• the system comprises a pair of stainless steel edger arms 20 and each having a continuous edge pad 22.
• the stainless steel edger arm 20 mates with the continuous edge pad 22 and holds the continuous edge pad 22 securely to the slide surfaces 23.
• Edger arms 20 each comprise a downwardly extended crank portion 20(a) through which a thrust screw 24 contacts the back of the hopper 26 to apply a biasing force to edge pad 22.
• the cylindrical bar or gib 27 acts as a pivot point so that as screw 24 is tightened, the edger arm 20 pivots toward the surface of the hopper forcing the edge pad 22 into contact with the slide surface.
• the edger arm 20 and edge pad 22 are positioned on the hopper by mounting the edger arm 22 on the gib as shown in FIG. 3.
• a mounting opening 28 in the edger arm 20 is slightly more than half round such that the edger arm is captured by the gib 27.
• the edge pad 22 is not attached or fastened to the slide surface directly. It is held in position through the force of edger arm 20.
• the edge pad 22 is positioned under the edger arm 20 by adjoining the top rib of the edge pad to the outboard face of the edger arm which is perpendicular to the slide surface. This is shown in FIG 9.
• the arm 20 is free to move across the width of the hopper when the screw 24 is loosened which enables the continuous edge pad to define virtually any coating width that is desired. This widthwise adjustability is important in minimizing coated waste in an operation where a variety of products are coated that have different finished dimensions.
• the continuous edge pad 22 mates precisely with the hopper slide surface.
• the edge pad can be fabricated by a machining process.
• the edge pad material can be a mica-filled fluoropolymer (trade name FLUOROSINT®, available from Polymer Corporation) selected for its machining, stability, and wetting properties.
• FLUOROSINT® trade name FLUOROSINT®, available from Polymer Corporation
• other polymeric materials or metals such as stainless steel could be used, and it is envisioned that other fabrication techniques, such as moulding or casting could also be employed.
• the continuous edge pad provides a continuous, integral, lateral confinement of the coating liquids on the hopper slide. This is an improvement over systems in which individual edge pads or guides are used for each hopper element because it avoids discontinuities in the confining surface that could introduce flow disturbances that may cause layer thickness variations in the coated film. Discontinuities in the confining surface can also be a source of leakage of coating liquids outboard of the coating width. Such leakage can cause manufacturing problems especially if the leakage contacts the coated support or coating roll or congeals on the hopper slide and edge pad surfaces and causes flow disturbances.
• the continuous edge pad is capable of providing continuous confinement of the coating liquid even when the various slide elements are at different heights. These slide element offsets, as they are known in the art, are often employed to achieve the proper flow field in the vicinity of the hopper slot exit in order to avoid layer thickness non- uniformities. These offsets are shown more clearly in FIG. 8.
• edge pad Two preferred embodiments will now be discussed that improve the mating of the continuous edge pad to the hopper slide surface as well as improve the manufacturing process for the continuous edge pad.
• the fabrication of the edge pad requires great precision.
• the edge pad must be machined to precisely mate with the hopper slide surface and edger arm. If the edge pad is not machined properly, it is possible for coating liquids to leak underneath the edge pad. Such leakage represents a serious manufacturing problem since the leakage can readily contaminate the coating roll and cause coating imperfections or even contaminate the coated web itself. Without the preferred embodiments, it is generally necessary to custom fit a particular edge pad to a particular hopper. It is, therefore, generally not possible to fabricate an edge pad directly from a blueprint.
• the hopper must be sent to the machine shop so the edge pad can be custom fitted to the hopper. This results in the hopper not being available for production, significant costs involved in transporting the hopper to the machine shop, and the risk of possible damage to the hopper in transport or during fitting of the edge pads.
• the edger arm is relieved or undercut beginning at the point where the edger arm would meet the edge pad over the second hopper element from the lip and extending toward gib 27 along the length of the arm where it would contact the edge pad.
• FIGS. 6 and 7, which is a detailed drawing of the edger arm.
• the edger arm is relieved at 40 by 0.010" to 0.100".
• holes 50 for the ball spring plungers are installed in the arm at locations roughly corresponding to the center of each hopper element when the arm is in place. This is shown ' in FIG. 2.
• the ball spring plungers 51 insure contact between the edger arm and pad and provide maximum force to hold the edge pad down on the hopper surface.
• the relief 40 allows the ball spring plungers to compress or relax to compensate for any deviation in the thickness of the edge pad.
• the fabrication tolerances on the edge pad are increased significantly, allowing for the pad to be fabricated without custom fitting it to the hopper.
• the top rib 22(a) of the edge pad 22 is slotted at the point at which the pad is over the first two slide elements 12 when the pad is placed on the hopper. This is shown in FIG. 8.
• This thin slot 80 allows the edge pad 22 to flex under the pressure of the edger arm 20 to allow good contact between the edge pad 22 and hopper slide surface even when there is variability in the position of the first hopper slide element from the lip with respect to the rest of the hopper elements, which sometimes occurs as the hopper is disassembled and reassembled.
• This embodiment insures a good contact between the edge pad and the most downstream hopper slide element.
• FIG. 9 shows a cross-sectional view of the continuous edge pad 22 and the coating liquids 60 as they flow down the hopper slide 61 taken along line 9-9 of FIG. 8.
• the coating liquids 60 are actually confined by the continuous edge pad 22 at a vertical wall 63 that is perpendicular to the slide surface 61.
• a land surface 64 that is inclined at an angle, B, from a horizontal in a plane parallel to the slide surface.
• the angle B is preferably in the range of 10 to 20 degrees in order to discourage significant capillary wicking and provide a controlled wetting line of the coating liquids at the top of the vertical wall should the thickness of the coating liquids on the slide exceed the vertical wall height.
• the front of the edge pad near the hopper lip is fabricated to an angle, A, of preferably 15 to 30 degrees from the hopper slide surface. This range of angles prevents significant capillary wicking on the angled front of the pad that may cause an excess of coating thickness in the extreme longitudinal edge portions.
• the edge pad 22 is held in place by the edger arm 20 as shown in FIG. 8.
• the height of the vertical wall 63 relative to the thickness of the coating liquids on the hopper slide is an important parameter in determining the uniformity of the thickness of the coated layers in the two longitudinal edge portions. While it is recognized that exactly matching the vertical wall height to the thickness of the coating solution is ideal, this is not generally possible in practical situations. It has been found, surprisingly, that good uniformity in the thickness of the coated layers is obtained when the vertical wall height is in the range of being about 30% higher to about 20% lower than the thickness of the coating liquids on each hopper slide element. Thus, one pad can be used for a range of different coating conditions or products. However, if the vertical wall is too high, the coating liquids will flow by surface tension forces up along the vertical wall.
• a three layer bead coating was made at a speed of 300 feet per minute.
• the coating liquids consisted of aqueous gelatin solutions at the following flow rates and viscosities:
• the bottom layer contained a carbon slurry to add optical density, which allowed coated layer thickness measurements to be made by a microdensitometer. An appropriate surfactant was added to the top layer.
• FIG. 10 shows a densitometric trace of the coated film taken in the widthwise direction. Since the upper two layers contained only clear gelatin, the density trace closely approximates the widthwise film thickness profile of the bottom layer. The general shape of the densitometric profile shows the so-called "edge bead" on the longitudinal edge portion of this 9 inch wide coating. It can be seen from this trace that the bottom layer thickness is quite uniform in the longitudinal edge portion of the coating. The bottom layer thickness non-uniformity extends only about 0.28 inches from the absolute longitudinal edge of the coating.
• Example 2 all conditions were the same as Example 1 except the vertical edge pad height on the bottom slide element was changed to a height that was about 130% greater than the thickness of the coating liquids on that slide element.
• the corresponding densito etric trace is shown in FIG. 11.
• the thickness of the bottom layer in the extreme longitudinal experimental edge portion is nearly twice that of the center portion of the coating.
• Significant layer non- uniformity exists up to 1.0 inches from the absolute longitudinal edge of the coating.
• Example 2 all conditions were the same as Example 1 except the vertical edge pad height on the bottom slide element was changed to a height that was about 60% of the thickness of the liquid layers on that slide element.
• the corresponding densitometric trace is shown in FIG. 12.
• the bottom layer non-uniformity extends 0.5 inches from the absolute longitudinal edge of the coating. It was observed that the coating liquids overflowed the vertical wall on the bottom slide element.
• the edger arm and continuous edge pad of the present invention can be used in a curtain coating operation.
• U.S. Patent 3,632,403 describes the curtain coating apparatus and process. Since the hoppers used in a curtain coating operation are similar to those used in a bead coating operation, the edger arm and continuous edge pad of the present invention work just as well in either situation.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Coating Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Magnetic Bearings And Hydrostatic Bearings (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
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• 1992
  • 1992-10-05 EP EP92921499A patent/EP0615632B1/de not_active Expired - Lifetime
  • 1992-10-05 AU AU27725/92A patent/AU658018B2/en not_active Ceased
  • 1992-10-05 JP JP6508978A patent/JPH07502685A/ja active Pending
  • 1992-10-05 WO PCT/US1992/008487 patent/WO1994008272A1/en active IP Right Grant
  • 1992-10-05 DE DE1992627841 patent/DE69227841T2/de not_active Expired - Fee Related

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