EP0841588B1 - Process and apparatus for curtain-coating a moving substrate - Google Patents

Description

The present invention relates to a method and a device for curtain coating a moving Carrier with a liquid coating material according to Preamble of claims 1 and 3. In this Coating, especially when the machine is wide and high speed, there are a large number of problems to stabilize the curtain and if possible to bring evenly on the surface.

In EP-B-281 520 the rinsing liquid film is put together with the curtain edge cut off by a knife diverted. The front edge of the knife stands with an angle α inwards. However, this causes the Edge zone of the curtain compressed and on the coating an edge bead is generated. This bead is one unwanted disruption that leads to material loss and Drying problems.

From EP-A-606 038 is also a device for Removal of the curtain edges with working as a knife Known plates, the plates approximately perpendicular to Curtain are arranged and the curtain edge over one arranged parallel to the length of the curtain Slot is sucked off. The height of these knives is very high small and there is a risk that part of the Coating solution gets under the whole device, what leads to contamination. In addition, there is the problem of the thickened edge and does not exist Danger that if the curtain moves, the Suction device touched.

In EP-A-139 211 two suction nozzles are used on both sides of the curtain, but no combination of Cutting knives with suction device.

In contrast, it is an object of the present invention to provide a method and an apparatus with which a uniform coating with clean edges without material loss can be achieved. This The task is accomplished with the method and the device according to the independent claims 1 and 3 solved. Further Advantages are defined in the dependent claims.

Figur 1

zeigt in perspektivischer Sicht und schematisch einen Teil einer Vorhangbeschichtungsanlage,

Figur 2

zeigt in einem Längsschnitt die wesentlichen Teile der erfindungsgemässen Vorrichtung,

Figur 3

ist ein Schnitt gemäss der Linie III-III in Figur 2,

Figur 4

zeigt in perspektivischer Sicht ein Detail der Vorrichtung von Figur 1, und

Figur 5

zeigt einen Schnitt gemäss der Linie V-V in Figur 4.

The invention is explained below with reference to a drawing of an embodiment.

Figure 1

shows a perspective view and schematically a part of a curtain coating system,

Figure 2

shows in a longitudinal section the essential parts of the device according to the invention,

Figure 3

is a section along the line III-III in Figure 2,

Figure 4

shows a perspective view of a detail of the device of Figure 1, and

Figure 5

shows a section along the line VV in Figure 4.

FIG. 1 schematically shows part of a coating device shown as part of a system. One recognises the foundry plates 1, see also Figure 4, with the side attached side boundary plates 2, which the Casting solution 3 is limited for the respective casting width.

The free begins at the lip 4 of the foundry front plate 5 Fall of the curtain. From this point on, the curtain 6 be stabilized by the side guides 7. Without these The curtains would be under the effect of the side guides Pull the surface tension towards the middle.

The coating device also assigns one coating carrier 8 on the casting roll 9 and is guided under the coating device. In Figure 1 the direction of rotation of the casting roll is also shown.

In the present device, the page-limiting Liquid film no longer parallel to the casting solution, or to the curtain, but across it, that is, see in particular Figure 3, the liquid film 10 parallel to the flow-limiting front wall 7 ' Lateral guide 7 initiated, the liquid film 10 flows in a groove 14 in the side guide and part forms the front wall of the side guide. As from Figure 2 emerges, the liquid, for example water or a water / gelatin solution through a metering slot 11 inserted, the slot end 12 being shaped such that the liquid film 10 regularly and with uniform thickness, the groove 14 in the side guide flows down.

This ensures that the liquid film and thus also the line of contact 13 between curtain 6 and Liquid film 10 is stable, which means uncontrolled wavy movements in the curtain can be avoided. To the Liquid film can be additives such as wetting agents and / or Substances to increase electrical conductivity be added.

At the bottom of the side guides is a knife 15 attached, the outer geometry is known per se. In particular, this knife also points to flow separations to avoid a leading edge 16 on that a sharp one with respect to the inside of the side guide Angle α of 0 - 30 °, for example 10 ° forms and parallel to the front wall of the side guide, i.e. perpendicular to the longitudinal extension the curtain is arranged.

At the top 17 of the knife is in the front wall Side guide arranged a suction slot 18, the height 0.05 - 0.5 mm, see Fig. 2. This slot 18 is via a suction duct 19 with a fan or other vacuum system connected to the cut Aspirate the edge of the curtain and the liquid film 10. there with the knife 15 a few mm of the curtain cut off. The suction of the liquid film and the Curtain edge brings about a substantial stabilization of the Curtain. By sucking off most of the time Water existing liquid film with the gelatin containing curtain liquid is a dilution of the Gelatin is achieved and thus a crusting of the suction paths prevented.

To the by the compressed curtain edge on the edge of the Avoiding suction knife formed bead is at the bottom edge of the knife arranged a suction slot 20, the connected to a vacuum system via a channel 21 which can be the same as for the suction slot 18. This channel preferably also contains a water rinse. As shown in Figure 2, this creates an edge of Coating 22 that can be used without loss.

The knife height at the cutting edge S of the knife can be 1 - 15 mm amount and it is appropriate to use the suction slot from one Knife height of 3 mm to be used, while at a Knife height of 1 - 3 mm dispenses with a suction slot can be.

Other disorders can be caused by the front of the lip arranged side boundary plates arise, so for example, layer thickness defects in the edge area that the casting solution under the effect of surface tension on the sides of the side boundary plates in the Height rises because of the previously known side boundary plates have a right-angled face. The side boundary plates 2 are sealed onto the foundry plates 1 assembled, see Figures 4 and 5, so that they all Giesserplatten and also the sheet 23 of the Giesserfrontplatte Cover 5 to the pouring lip 4.

It can be seen from FIG. 5 that the delimiting edge 25 of the Side boundary plates is not vertical, but one Has cutting edge 24, which cutting edge has an angle of for example includes 60 °, which means that the two Edge of the cutting edge with the 22 perpendicular to the coating an angle β and Γ of 10 - 80 °, preferably 60 °, exhibit. The distance H between the cutting edge is 24 and the surface of the foundry plates 0.3 - 2.5 mm, preferably 0.8 mm. This will make the effect of Surface tension is reduced to a minimum, and there will be lateral displacements of the casting solution largely avoided.

It goes without saying that the inventive Device can be varied with respect to the specified mass can and the most diverse coating conditions and Casting solution combinations can be adjusted. While every single measure already extensive improvements with regard to the quality of the coating results in a Combination of all improvements, such as Vacuuming the cut edges, vacuuming the at Knife jammed pouring solution as well as avoiding the by the Differences in layer thickness due to surface tension and guiding a thin film of liquid along the Side boundary plates a particularly stable Coating, the edges of which do not lose material or Cause more drying problems.

Claims (6)

1. Process for curtain coating a moving substrate with a liquid coating material, more particularly with photographic emulsions, a lateral flow (10) being supplied on both sides of the curtain (6) which is guided by lateral guides (7), and the width of the curtain being greater than the width of the coating on the substrate, and both sides of the curtain being cut by means of cutters (15) whose front edge (16) includes an acute angle (α) with respect to the inner side of the lateral guide, characterised in that in order to prevent the formation of a marginal bead, the portions of the coating solution which are stemmed by the front edge of the cutter are extracted perpendicularly to the longitudinal extension of the curtain through openings (20) of the cutter.
2. Process according to claim 1, characterised in that the cut side portions of the curtain (6) and of the lateral flow (10) are extracted by means of an extracting slit (18) of the cutter (15) and an extracting channel (19).
3. Apparatus for carrying out the process according to claim 1, comprising two lateral guides (7) for the curtain (6) and a respective cutter (15) disposed at the lower end of the lateral guides (7) and whose front edge (16) includes an acute angle (α) with respect to the inner side of the lateral guide, characterised in that an extracting slit (20) extending perpendicularly to the longitudinal extension of the curtain and connected to an extracting channel (21) is disposed at the lower edge of the cutter (15).
4. Apparatus according to claim 3, characterised in that an extracting slit (18) is disposed at the junction between the upper side (17) of each cutter (15) and the lateral guide (7), the extracting slit being connected to an extracting channel (19) in order to extract the cut side portions of the curtain (6) and of the lateral flow (10).
5. Apparatus according to claim 4, characterised in that the height of the extracting slit (18) on the upper side of each cutter is comprised between 0.05 and 0.5 mm.
6. Apparatus according to one of claims 3 to 5, characterised in that the extracting slit (18) on the upper side (17) of each cutter (15) and/or the extracting slit (20) at the lower edge (21) of the cutter is provided with a water flushing system.

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