JPH05208159A - Method and device of curtain coating - Google Patents

Abstract

PURPOSE: To prohibit or lessen the formation of perturbations or standing waves at the point where the edge of a curtain leaves a hopper lip. CONSTITUTION: Photographic film webs or other moving supports continuously advancing through a coating station are coated with a free falling liquid curtain 9. An edging means having edge walls 17' extending rearwardly and downwardly from the hopper lip 7 is provided. The free falling curtain 9 is allowed to bend back and its edges follow natural paths on the edge walls 17' to narrow edge guides 19, 19' that precisely guide the free falling curtain 9 from the edge walls 17' to the moving support 11 without including perturbations in the free falling curtain, allowing the free falling curtain 9 to impinge transversely on the moving support 11.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for coating an object or moving support continuously traveling through a coating station with a free-fall coating liquid curtain. More specifically, the present invention provides
The present invention relates to a curtain coating method and apparatus for producing photographic film and paper.

[0002]

Curtain coating is a method of applying a coating liquid to an article or substrate. Curtain coating is characterized by the formation of a free-fall coating liquid curtain that falls from the hopper lip and strikes the article moving through the curtain under the action of gravity to coat. For example, various curtain coating methods and devices are conventionally used for coating furniture or iron sheets. In particular, in recent years, high precision curtain coatings for producing multilayer photographic materials, as disclosed in U.S. Pat. Nos. 3,508,947 to Hughes and 3,632,374 to Greiller. Methods and devices have been developed.

When producing multilayer photographic materials by curtain coating technology, the coating quality is greatly influenced by the quality of the free-fall curtain. The curtain is required to form a stable laminar flow from where it is formed to the line that strikes the moving support. In the absence of suitable equipment, surface tension results in the curtain contracting inward, impairing the desired curtain laminar flow. To prevent this, conventional curtain coating methods use edge guides that engage the free-fall curtain at their edges and prevent them from contracting inward due to surface tension.

Generally, these edge guides used in curtain coating methods and apparatus are fixed, one-piece members that are attached to the hopper lip and stabilize the free-fall curtain as it leaves the lip. For example, US Patent No. 4, to Naruse et al.
No. 933,215 discloses a curtain coating hopper with an integral guide rod. However, supporting the free-falling curtain at its edges creates frictional drag on the curtain edges and destabilizes them, resulting in a loss of the curtain's ability to cover in a fairly stable manner.

Various solutions have been proposed for increasing the curtain stability while at the same time maintaining a high coating speed. One solution is to supply a low viscosity liquid (eg water) to the edge guide so that it can act as a liquid bridge means between the edge guide and the free-falling curtain edge. No. 1 US patent to Koepke etc.
No. 4,479,987 discloses a device for stabilizing a free-fall curtain by utilizing a liquid bridge means between an edge guide and a free-fall curtain. Ishizu
U.S. Pat. No. 4,974,533 to Ka) et al. discloses a coating device that uses a jet to spray auxiliary liquid onto the edge guides and to prevent the curtain from becoming thin near the edge guides of the device. Has been done. Reiter (Reite
U.S. Pat. No. 4,830,887 to r) discloses a method and apparatus for coating an area of the support which is narrower than its full width. This rater method and apparatus utilizes an edge guide, a cleaning means provided on the edge guide, and a suction device for adjusting the thickness of the coated edge.

In addition to using a cleaning liquid to mitigate the effects of frictional drag, a solution to this frictional drag problem is to use thin straight edge guides that are straight and vertically oriented. For example, US Pat.
See 632,374, U.S. Pat. No. 4,479,987 to Koepke et al., And U.S. Pat. No. 4,830,887 to Reiter. However, while edge rods that are about the same width as the curtain edge reduce frictional drag, they are not generally effective in avoiding the problems associated with another phenomenon associated with curtain coating, commonly referred to as "bendback." This bendback is characterized by bending the coating solution as it leaves the tip of the hopper lip. When the solution leaves the hopper lip, a moment is generated around the tip of the hopper lip,
There is also a horizontal velocity component that results in the coating solution curving inward toward the body of the hopper. This bendback phenomenon becomes remarkable as the curtain speed decreases, that is, as the flow rate per unit width of the curtain increases. Further, the bendback phenomenon becomes more remarkable as the surface tension decreases.

Bendback does not prevent the formation of a uniform coating layer on the support, but it cannot accommodate the bendback of the coating solution (ie the full width of the curtain follows its naturally curved path). If not), a "standing wave" occurs in the curtain. This standing wave generally occurs, for example, when a narrow edge guide is attached to the hopper lip and guides the coating liquid downwards along a vertical path different from its natural curvature path. As a result, perturbations occur where the edge guides act on the coating liquid. Standing waves arise from this perturbation source. This standing wave may cause streaks in the longitudinal direction in the dried coating.

US Patent No. 4,13 to Ridley
No. 5,477 addresses the problem of bendback. The U.S. patent discloses a curtain coating apparatus with a wide edge guide plate extending from the hopper lip to the support to be coated. This edge guide plate
It is wide enough to allow the curtain edges to follow their natural curved path to the support. In short, the edge guide plate is significantly wider than the curtain edge over the length of the curtain. However, this type of edge guide plate introduces another problem.

First, since the width of the edge guide plate is wider than the edge of the curtain, the curtain edge speed becomes slow. This decrease in speed results in a decrease in curtain stability. Second, a wide meniscus is formed between the curtain edge and the wide edge guide plate. As a result, the curtain adjacent to the meniscus is relatively thin. This allows
It will not be possible to coat it uniformly over the entire width of the outer edge of the curtain.

Third, the large surface area of the edge guide plates creates a pressure gradient between the front and rear sides of the curtain, resulting in the deposition of coating liquid when the free-falling curtain moves horizontally back and forth. Objects are more likely to adhere to the edge guide plate. These deposits eventually solidify or crosslink to form solid deposits that cause perturbations that cause standing waves in the curtain.

Fourth, when coating a continuous web,
It has been found that even better results are obtained by setting the coating position forward of top dead center on the coating roll conventionally used to convey the web below the coating hopper. The method of setting the covering position in front of this is that the wide edge guide plate must be centered at the top dead center of the roll, and at other positions,
It is impractical to use the lidley patented wide edge guide plate because the coating solution tends to leach out between the bottom of the wide edge guide plate and the top of the support.

Fifth, in the Lidley patent, the curtain is allowed to follow its own path along the length of the edge guide plate, thus maintaining a constant separation point from the edge guide plate. Is impossible. Therefore, it is not possible to accurately place the suction device required where the curtain separates from the edge guide plate, so that the coating method described in U.S. Pat. It is not possible to carry out a method of covering an area narrower than the full width of the so-called support.

Finally, the current edging devices used in the art are not adjustable to achieve different curtain widths. For example, the rimming device of the Lidley patent must be placed at the edge of the slide hopper with a predetermined width, which limits the coverage area of the hopper to that width.

[0014]

The present invention is also to solve the above-mentioned conventional drawbacks in the curtain coating method and apparatus.

[0015]

One aspect of the present invention is an apparatus for curtain-coating a moving support with one or more coating liquid layers, wherein (a) an inclined surface terminating in a lip. A hopper means for forming a free-fall coating liquid curtain, (b) transport means for moving the support along a path below the hopper means, and (c) edging means. The deciding means is
(1) Two edge walls each having a flat plane that is disposed at the other end of the lip and extends downward and rearward under the lip, the flat surface being the inclined surface of the hopper means. Two edge walls that are at right angles to and that are substantially above the edge thickness of the free-fall curtain, allowing the curtain edge to follow a natural path above the edge wall; ) Two edge guides extending downwardly from the edge wall towards the moving support, the edge guide having a width substantially smaller than the width of the edge wall, A free-fall curtain is precisely guided from the edge wall to the moving support and the free-fall curtain abuts the moving support laterally. Another aspect of the invention is a method of curtain coating a support with one or more layers of coating liquid, wherein (a) the liquid is continuously flowed on a downwardly sloping flat surface ending with a lip. That
(B) moving the support along a path through the coating area below the lip, and (c) falling from the lip and extending laterally across the path, within the coating area. Forming a free-fall coating liquid curtain that abuts the moving support, and (d) guiding the edge of the curtain immediately after falling from the lip by contacting a large area flat surface, This allows the curtain to be freely curved backward without being significantly restricted, and immediately after that, for the majority of the distance that the curtain falls, a long narrow strip having a width significantly narrower than the width of the flat surface of a large area. By contacting a linear guide means, the edge of the curtain is guided, whereby the support that moves the free-fall curtain from the lip. Guiding the body, the free-falling curtain is formed and a to ensure that impinge perpendicular to the moving support.

[0016]

In accordance with the present invention, maximum bendback of the curtain has been found to occur at the initial stage of free fall of the curtain (ie, immediately after the curtain leaves the hopper lip). As the curtain leaves the hopper lip, a moment is generated around the tip of the hopper lip and a horizontal velocity component is created, which results in the solution curving inward toward the body of the hopper. After this initial maximum angular displacement, the trajectory of the curtain is approximated to a substantially straight line until gravity dictates horizontal movement and strikes the support. The coating apparatus and method of the present invention is perturbed into the curtain where the curtain edge leaves the hopper lip,
Or prevent the standing wave from being formed,
Or reduce. The present invention provides a solution to this serious problem while providing rapid coating, minimal frictional drag, sufficient curtain stability, sufficient edge uniformity, the possibility of coating by the front application point, and It enables the coating method disclosed in U.S. Pat. No. 4,830,887 for a rater utilizing inner edge technology. In addition, the edging means in the device of the present invention can be adjusted on the hopper by repositioning the edge pad, edge wall and edge guide to coat the selected coating width.

The coating hopper of the present invention is significantly wider than the curtain edge and is provided with edging means comprising flat edged walls located at opposite ends of the hopper lip which extend downwardly and rearwardly beneath the hopper lip. Is adopted. The flat surface of the edge wall is perpendicular to the inclined surface of the hopper and is significantly wider than the width of the edge of the free-fall curtain, allowing the curtain edge to follow its natural path above the edge wall.

The edge wall extends downwardly from the hopper lip a sufficient distance for the curtain edge to return to the generally straight path. Thus, the curtain edge path will be substantially straight as it leaves the edge wall. After leaving the edge wall, the curtain edge is guided exactly to the moving support by means of a narrow edge guide with a width dimension equal to the thickness of the curtain edge. The novel combination of wide edge walls and narrow edge guides solves the problem of perturbation at the connection where the curtain edge leaves the edge wall and contacts the edge guide. In a preferred embodiment, the curtain coating apparatus has hopper edge pads that extend down the edges of the hopper ramps down to the edge walls. The hopper edge pad serves to guide the coating liquid downwardly from the inclined surface of the hopper to the edge wall.

The coating method of the present invention comprises continuously flowing a coating liquid onto a downwardly inclined flat surface terminating at a lip, whereby a free-falling coating liquid falling from the lip to a coating region. Forming a curtain. The support moves along a path through the coating area and below the lip, so that the coating liquid curtain strikes the moving support laterally. The curtain edge just below the lip is in contact with and guided by a large area of the flat surface, allowing the curtain to curve backwards without substantial restriction. Immediately below the surface of a large area and for the majority of the distance that the curtain falls, each edge of the curtain is contacted by a substantially linear guide means of a width significantly narrower than the width of the flat surface of the wide area. And it is guided by the guide means.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a slide hopper type curtain coater (coating apparatus) generally used in the photographic industry will be described in detail regarding the method and apparatus of the present invention. 1 and 2 are perspective views of an embodiment of a slide hopper type curtain coater of the present invention. FIG. 1 shows an embodiment of the device according to the invention for coating a moving support with a free-fall coating liquid curtain. FIG. 2 is a partial perspective view of the film curtain leaving the hopper lip. Referring to FIG. 1, there is shown a slide hopper 1 having an inclined surface terminating at a lip 7. The coating liquid is fed laterally into the slide hopper 1, rises to the outlet slot 3 and is extruded as individual layers onto the downwardly inclined surface 5. Under the action of gravity, the individual layers flow one after the other along the inclined surface 5, forming a set of separate liquid layers, flowing to the tip of the hopper lip 7,
Here, the free-fall curtain 9 is formed. The free-fall curtain 9 consists of a composite of separate coating liquid layers emerging from the slot 3. A composite free-fall curtain 9 perpendicular to the path of the moving support 11 or extending laterally across the path, has a height "h" and continuously advancing supports. It strikes the body 11 and forms a composite of a liquid layer on the support 11. The curtain 9 is the support 11
It is desirable that the support 11 is guided to and along the coating roll 13 at a position where it hits. The width of the coating roll 13 can be narrower or wider than the width of the support 11 guided along it, depending on the edge guiding technique. The coating roll 13 is driven by a motor (not shown).

The free-fall curtain 9 has a hopper edge pad 1
5, 15 ', edge wall 1 having a relatively large area of flat surface
7, 17 'and a long and relatively narrow edge guide 1
It is laterally guided by edging means comprising 9, 19 '. Hopper edge pad 15, 15 ', edge wall 1
7, 17 'and edge guides 19, 19' are arranged vertically and guide and stabilize the free-fall curtain 9 before it strikes the support 11. Figure 2
FIG. 4 is a partial perspective view of the film curtain leaving the hopper lip, showing the path of the free-fall curtain 9 formed upon leaving the lip 7 and following the edge wall 17 and the edge guide 19.

FIG. 1 shows a preferred embodiment of the curtain coater of the present invention. The edge pads 15, 15 ', the edge walls 17, 17' and the edge guides 19, 19 'are
It is positioned so that it can cover an area narrower than the full width of 1. The hopper 1 is positioned so as to cover the support 11 at a position on the coating roll 13 in front of the top dead center. In addition, the apparatus and method of the present invention includes the support 1
It is also possible to coat an area having the same width as or wider than that of No. 1 and operate at the top dead center of the coating roll 13 or at the coating position behind it.

The layer of photographic coating composition can be coated on a variety of supports. Typically, photographic supports include adhesiveness, antistatic properties, size, wear, hardness,
A polymeric film, paper, sheet metal, metal foil, glass, or ceramic support element provided with one or more subbing layers to improve function, antihalation properties and / or other support properties. included. The support may be coated in the form of a separate sheet, plate or, preferably, continuous web.

The method according to the invention uses the wide edge walls 17, 1
It is possible to implement with edging means consisting only of 7'and elongated edge guides 19, 19 '. However, it is desirable that the hopper edge pads 15, 15 'extend along both ends of the sloped surface of the hopper 1. Hopper edge pad 15, 15 '
Is designed to be able to guide the coating liquid layer downwards along the inclined surface of the hopper 1, and thus extends along both ends of the inclined surface of the hopper 1 to the lip 7. The hopper edge pads 15, 15 'should be at least as high as the composite layer of coating liquid going down along the ramp of the hopper 1. The thickness of the hopper edge pads 15, 15 'is preferably equal to the thickness of the coating liquid downwards along the inclined surface of the hopper 1.

The edge walls 17, 17 'correspond to the hopper edge pad 1
Directly underneath 5, 15 ', respectively, are arranged at both ends of a lip 7 which extends downwards and rearwards. Edge wall 17, 17 '
Has a flat plane parallel to the edge of the free-fall curtain 9. The flat planes of the edge walls 17, 17 'are
When the edge of the curtain 9 leaves the lip 7, it needs to be wide enough to allow it to follow its natural path. “Natural path” means that the curtain is not restricted in flow direction and can curve backwards along the edge wall. In this way, the edge walls 17, 17 'must be of a large enough area to allow a backward curve without being significantly restricted on leaving the lip 7 when the coating liquid forms the free-falling curtain 9. I won't.

The area of the edge walls 17, 17 'can be varied somewhat depending on the viscosity of the coating liquid, the flow rate of the coating liquid and the surface tension. For example, the angle of separation of the coating liquid and the hopper lip is 50 ° from vertical for typical photographic materials. This requires that the edge walls 17, 17 'extend sufficiently rearwardly from the top of the walls to accommodate a 50 ° separation angle from vertical.

After the curtain 9 has undergone the initial maximum angular displacement, the trajectory of the curtain 9 returns to a substantially linear path. Thus, the edge walls 17, 17 'extend downwardly enough to allow the trajectory of the free-fall curtain 9 to be a substantially linear path. For example, if the coating liquid is a photographic material, the edge walls 17, 17 'may range from about 0.5 to about 1.0 cm,
Desirably, a downward extension of about 0.6 cm is required.

The edge walls 17, 17 'can be provided with a uniform rearward extension from the top to the bottom. Instead, the edge walls 17, 17 'are provided with a maximum rearward extension at the top (ie the part closest to the hopper lip 7) and at the connection between the edge walls 17, 17' and the edge guides 19, 19 '. Edge guide 1
It is possible to taper to a rear extension equal to the width of 9, 19 '. However, the rearward extension of the edge walls 17, 17 'allows the curtain edge to follow its natural path from the lip 7 and reach a position where the trajectory of the curtain 9 returns to a substantially vertical straight path. Must be enough to do.

Similarly, edge guides 19, 19 'are arranged on both edges of the free-fall curtain 9 and extend downwardly from the edge walls 17, 17' towards the support 11, respectively.
The edge walls 17, 17 'comprise a flat surface area which is much wider than the width of the edge of the curtain 9, but the edge guides 19, 1'
9'has a relatively narrow width. Its width is edge walls 17, 1
Remarkably narrower than the width of the flat surface of 7 '. Edge guides 19, 1
9'accurately guides the free-fall curtain 9 to the support 11. Due to the narrow edge guide, the meniscus, ie,
The contact width at each edge of the curtain is much narrower than the meniscus along the relatively wide back curve region along the edge walls 17, 17 'and the contact width. As a result, the problems associated with wide edge guides and similar problems in limiting back curve can be effectively avoided. Edge guide 19,
19 'is preferably a slotted rod, as disclosed in U.S. Pat. No. 4,830,887 to Reiter, but any shape sufficient to accurately guide free-fall curtain 9 to support 11. Good.

Hopper edge pads 15, 15 ', edge wall 17,
17 'and the edge guides 19, 19' can be made of the same material or different materials. The components of the edging means are preferably made of an easily wettable material such as polycarbonate, metal or powdered glass.

The device of the present invention is by adjusting the edge walls 17, 17 ', edge guides 19, 19' and hopper edge pads 15, 15 '(if present) to the desired width on the hopper 1. , Adjustable to cover multiple coating widths.

FIGS. 3, 4 and 5 are sectional views showing different forms of the edging means of the present invention in which the coating method and apparatus of the present invention are embodied. FIG. 3 is a cross-sectional view of one embodiment of the edging means of the present invention showing the edge wall 27 with the hopper edge pad 25 as a unitary body. The edge guide 29 is pivotally connected to the bottom of the edge wall 27 at a pivot point 33. With this configuration, the edge guide 29
Can be adjusted so that at the point where the curtain abuts the support, the guide can be precisely adapted to the position of the free-fall coating liquid curtain.

FIG. 4 illustrates the edging means of the present invention, showing the hopper edge pad 35 as a separate component and the edge wall 37 with the edge guide 39 as a unitary body.
FIG. 6 is a cross-sectional view of another example of FIG. FIG. 5 shows the edging mea of the present invention, showing the hopper edge pad 43, the edge wall 45, and the edge guide 39, all constructed as a single piece.
ns) is a sectional view of another embodiment. 5 shows the path of the free-fall curtain 9 on the edge wall 45 and the edge guide 47. The configurations of FIGS. 4 and 5 do not adversely affect the functioning of the present invention, and
Or, it brings a great advantage in terms of function.

The method and apparatus of the present invention is described in US Pat. No. 4, rater, incorporated herein by reference, the disclosure of which is incorporated herein by reference.
It can be used with the curtain coating method and apparatus disclosed in the specification of 830,887.

The following experimental examples demonstrate the advantages of the method and apparatus of the present invention in making photographic materials. In each experimental example, the slide coater is provided with the edging means of the present invention for a three-layer coating as shown in FIG. 3, FIG. 4 or FIG.

The height "h" of the curtain that falls freely is 25
cm, and the position where the curtain abuts the support (“application position”) is set 45 ° forward from the midpoint (top dead center) of the coating roll that conveys the support (“+45”).
° ''). The coating speed was set to 400 cm / sec.

A three-layer photographic coating composition consisting of a water-soluble gelatin pack having a bottom layer of 15 centipoise viscosity, an intermediate layer of 50 centipoise viscosity, and a top layer of 70 centipoise viscosity was used.

Experimental Example 1 An edge wall having a 0.475 cm rear extension on its top (just below the edge pad) is utilized. The front of the edge wall is 15
° It is displaced backward. The rear extension of the edge wall is tapered so that the connection between the edge wall and the edge guide connection is 0.150 cm. The edge wall extends 0.635 cm below the tip of the hopper lip.

The slotted edge guides are arranged such that the coating width is less than the total width of the support. Thickness 0.
A continuous web of cellulose triacetate film of 13 cm is used as a support. Aqueous solution is fed to the top of the slotted edge guide where the edge guide contacts the fluid curtain. A vacuum source is applied to the air vent hole provided at the end of the edge guide to remove the cleaning liquid. The flow rate of the three-layer composite photographic coating composition is 3 cm ³ / sec per cm coating width.

The solution thickness on the sloped surface of the hopper is calculated and the height of the hopper edge pad is adapted to this thickness so that it can provide a fixing point for the solution and prevent meniscus formation. The solution is about 30 ° from vertical as a result of the curtain bending.
Leave the hopper lip at an angle of. The edge wall is large enough that the solution is not fixed at the corners of the wall,
The curtain edge follows the same trajectory as the curtain center. Both lateral uniformity near the edge and curtain stability are not significantly affected by the edge wall. After a free fall of about 0.6 cm, the curtain trajectory begins to approximate a straight line at a constant angle from vertical. At this point, the curtain is transferred from the edge wall to a relatively narrow straight edge guide that pivots at the edge of the edge wall, with the bottom of the edge guide orthogonal to the trajectory of the curtain. To do so. At the bottom of the edge guide, the cleaning liquid is drained from the vacuum system and the curtain separates from the edge guide close to the support, +45
Hit the support at the application position of °. The bottom of the edge guide is positioned 2.0 cm behind the vertical plane of the hopper lip to accommodate the vertical displacement of the curtain due to curtain bending. The wetting line is linear along the full width of the curtain and there are no streaks in the dried coating.

Experimental Example 2 An edge wall having a 0.475 cm rear extension at the top (just below the edge pad) is utilized. The front of the edge wall is displaced 25 ° rearward from vertical. The rear extension of the rim wall is tapered so that the connection between the rim wall and the rim guide is 0.150 cm. The edge wall is 0 downward from the tip of the hopper lip.
It is extended by 635 cm.

The slotted edge guide with the edge wall integrated at the top of the edge guide is arranged to cover less than the width of the support to be coated. The support has a thickness of 0.02
3 cm polyethylene coated paper web. In Experimental Example 2, an aqueous solution is supplied to clean the surface of the edge guide by the method disclosed in US Pat. No. 4,830,887 to Rater.

The total flow rate of the three-layer composite coating is 5 cm ³ / sec per cm of coating width. The bottom of the edge guide is positioned 3.0 cm rearward from the vertical plane of the hopper lip to accommodate the curtain displacement due to curtain bending.

Calculate the thickness of the solution on the inclined surface of the hopper so that the height of the vertical edge pad can be adapted to this thickness so as to provide a fixing point for the solution and prevent the formation of meniscus .. The solution leaves the hopper lip at an angle of about 45 ° from vertical as a result of the curtain curving backwards.
The edge wall is large enough so that the solution is not fixed at the corners of the wall, so the curtain edge follows the same trajectory as the curtain center. Neither the widthwise uniformity near the edges nor the stability of the curtain are significantly affected by the edge walls. After about 0.6 cm of free fall, the curtain trajectory begins to approximate a straight line at a constant angle from vertical. At this point, the curtain is transferred from the edge wall to a narrow linear edge guide which, when pivoting at the edge of the edge wall, has the bottom of the edge guide orthogonal to the trajectory of the curtain. At the bottom of the edge guide, the cleaning liquid is sucked by the vacuum pressure and the curtain is separated from the edge guide in the vicinity of the support. The curtain strikes the support at a + 55 ° application position. The wetting line is straight across the width of the curtain and there is no streaking in the coating after drying.

Example 3 An edge wall with a 0.475 cm rear extension at the top (just below the edge pad) is utilized. The angle of displacement of the front of the edge wall from the vertical to the rear is 0 °. The rear extension of the edge wall is tapered so that the connection between the edge wall and the edge guide is 0.150 cm. The edge wall extends 0.635 cm below the tip of the hopper lip.

The integral edge guides are arranged such that they can form a coating thinner than the width of the support to be coated.
A 0.018 cm thick polyethylene terephthalate film web is used as a support. At the top of the edge guide,
An aqueous solution is provided and vacuum pressure is applied to the end of the lower edge guide to expel the end guide cleaning solution. The total flow rate of the three-layer composite coating is 1 per cm coating width.
cm ³ / sec. The bottom of the edge guide is located directly below the hopper lip to accommodate the relatively minor back curve that occurs.

The solution thickness on the sloped surface of the hopper lip is calculated and the height of the vertical edge pad is adapted to this thickness so that it can provide a fixing point for the solution and prevent meniscus formation. The solution leaves the hopper lip approximately vertically and no significant curvature occurs. The edge wall is large enough so that the solution does not stick to the corners of the wall and therefore the curtain edge follows the same trajectory as the curtain center. Neither widthwise uniformity near the edge nor curtain stability is significantly affected by the edge wall. At this point, the curtain is transferred from the end wall to a narrow linear edge guide which pivots at the edge of the edge wall with the bottom of the edge guide orthogonal to the curtain trajectory. At the bottom of the edge guide, the cleaning liquid is sucked by the vacuum device and the curtain separates from the edge guide in the vicinity of the support and strikes the support at a + 20 ° application position. The wetting line is straight across the full width of the curtain and there is no streaking in the coating after drying.

Although the present invention has been described in detail for purposes of explanation, those skilled in the art will be able to devise variations thereof without departing from the spirit and scope of the invention as claimed. Conceivable.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a slide hopper curtain coating apparatus including a coating liquid and a free-falling curtain according to the present invention.

FIG. 2 is a partial three-dimensional view of the film curtain when leaving the hopper lip.

FIG. 3 is a cross-sectional view of one embodiment of the edging means of the present invention showing the edge wall integrated with the hopper edge as a unitary body.

FIG. 4 is a cross-sectional view of another embodiment showing the edge wall integrated with the edge guide as a unitary body.

FIG. 5: another implementation of the edging means of the invention, showing the hopper edge pad, the edge wall, the edge guide, all integrated as a single body, and also the path of the free-fall curtain on the edge wall and the edge guide It is sectional drawing of an example.

[Explanation of symbols]

1 Slide Hopper 3 Exit Slot 5 Inclined Surface 7 Hopper Lip 9 Curtain 11 Support 13 Coating Roll 15 Hopper Edge Pad 15 'Hopper Edge Pad 17 Edge Wall 17' Edge Wall 19 Edge Guide 19 Edge Guide h Curtain Height

Claims (10)

[Claims] 1. An apparatus for curtain coating a moving support with one or more layers of coating liquid to form a free-fall coating liquid curtain having (a) an inclined surface terminating in a lip. Hopper means for performing, (b) conveying means for moving the support along a path below the hopper means, and (c) edging means, wherein the edging means includes (1) each of the lips. Two edge walls located at the other end of the lips and having flat flat surfaces extending downwardly and rearwardly beneath the lip, the flat surfaces being perpendicular to the inclined surface of the hopper means and Two edge walls having a width substantially above the thickness of the edge of the free-fall curtain, allowing the curtain edge to follow a natural path above the edge wall; The edge towards the body Two edge guides extending downwardly from the edge guide having a width substantially less than a width of the edge wall to support the free-fall curtain moving from the edge wall. A device for accurately guiding the body and laterally abutting the free-falling curtain on the moving support. 2. The curtain coating apparatus according to claim 1, wherein the edging means extends along both ends of the inclined surface to regulate an edge of the coating liquid and the coating liquid to the inclined surface. The device further comprising two hopper edge pads that guide downwardly from the to the lip. 3. A curtain coating apparatus according to claim 1, wherein each of said edge guides is pivotally connected to one of each of said edge walls. 4. A curtain coating apparatus according to claim 1, wherein the coating liquid is a photographic material. 5. The curtain coating apparatus according to claim 4, wherein the edge wall extends downward by about 0.6 cm. 6. A method of curtain coating a support with one or more coating liquid layers, comprising: (a) continuously flowing the liquid on a downwardly sloping flat surface ending with a lip. (B) moving the support along a path through the coating area below the lip, and (c) falling from the lip and extending laterally across the path in the coating area. Forming a free-falling coating liquid curtain that abuts the support moving at, and (d) guiding the curtain edge immediately after falling from the lip by contacting a large area flat surface,
This allows the curtain to bend freely backwards without being significantly restricted, and immediately thereafter, for the majority of the distance that the curtain falls, an elongated strip with a width significantly narrower than the width of the flat surface of a large area. By contacting the substantially linear guide means, the edge of the curtain is guided, whereby the free-fall curtain is guided from the lip to the support moving, and the free-fall curtain moves. Abutting the support at right angles. 7. The curtain coating method according to claim 6, wherein the edge determining means regulates both edges of the coating liquid on the inclined surface.
Thereby, further comprising guiding the coating liquid downwardly from the inclined surface to the lip. 8. The method of curtain coating according to claim 6, wherein the support is a continuous web moving below the hopper means on a coating roll and the free-fall curtain of the coating roll. A method of hitting the moving web at a coating position in front of top dead center. 9. The method of curtain coating according to claim 6, wherein the edging means are spaced so as to cover a portion of the support that is narrower than its full width. 10. The method of curtain coating according to claim 6, wherein the coating liquid is a photographic material.