Patent Application
20110070377
1. Field of the Invention
The present invention relates to a slide curtain coating apparatus and slide curtain coating method for applying coating liquid on a running web.
2. Description of the Related Art
Curtain coating apparatuses are commonly used in manufacturing processes of photosensitive materials such as photographic films.
The curtain coating method according to the present invention is directed to a method of forming a multilayer coating which involves the use of the aforementioned curtain coating apparatus, wherein coating liquids with different functions are discharged from different slits such that the coating liquids are stacked on top of each other on the slide surface to form a curtain, which then falls freely down on the running web to form a coating thereon.
A key issue in such conventional curtain coating apparatuses/methods is that, as shown in
For this reason, this approach cannot be used for curtain coating in many cases. Japanese Patent Application Laid-Open (JP-A) Nos. 2000-513, 2000-218209, 2001-104856 and 2005-512768 propose techniques for preventing the edge regions from becoming thicker. In the proposed techniques, an auxiliary liquid is allowed to flow essentially parallel to the flow direction of the curtain along edge guides of the slide, so that the flow rates at the opposing edges of the slide are made close to the flow rate at the center. The proposed techniques are disadvantageous in that, since a large amount of the auxiliary liquid needs to be supplied along the edges of the slide, the auxiliary liquid may be easily mixed with the curtain. And further, these technique have met with difficulties in stably and uniformly supplying the auxiliary liquid along the edge regions, resulting in non-uniform in thickness along its width. An additional disadvantage is that a complicated coating apparatus is required for this.
The present invention is to solve the aforementioned problems and to achieve the following object. That is, the present invention is to provide a slide curtain coating apparatus and slide curtain coating method wherein coating liquids are applied in the form of a curtain on a running web to form a coating on the surface thereof, the apparatus and method being capable of preventing the curtain from converging to the center of the slide and of preventing the resultant coating from having greater thickness at its edge regions.
The means to solve the aforementioned problems are as follows:
The slide curtain coating apparatus of the present invention includes: a slit configured to discharge a coating liquid; a slide having an inclined surface on which the coating liquid flows down in the form of curtain; a slide edge guide provided at each of both edges of the slide; and auxiliary liquid supply means configured to discharge an auxiliary liquid from all over the surface thereof which touches the curtain at the edge guide.
In the slide curtain coating apparatus of the present invention, the curtain freely falls from the slide and contacts a running web to form a coating thereon. Since the auxiliary liquid supply means discharges an auxiliary liquid from all over the surface thereof which touches the curtain at the slide edge guide, it is possible to prevent deposition of a large amount of coating liquid onto edge regions of the web (i.e., to prevent the resulting coating on the web from having a greater thickness at its edge regions). In this way the coating can be prevented from adhering to any other surface of the web, and the web can be prevented from being torn up when it is rolled, thereby increasing the efficiency of curtain coating. And further, the auxiliary liquid supply means enable to reduce the required amount of the auxiliary liquid to be discharged, and thus the curtain can be almost completely prevented from being mixed with the auxiliary liquid. Thereby the coating can be prevented from having, or being mixed with, the auxiliary liquid at the edge regions.
The surface of each edge guide that makes contact with the auxiliary liquid is preferably made of porous material. With this configuration, it is possible to reduce the flow depth of the auxiliary liquid and to minimize the flow unevenness of the auxiliary liquid on the slide, thereby providing a coating having uniform thickness across its width.
The porous material preferably has an average pore size of 50 μm or smaller. With such a configuration, the auxiliary liquid supply means is able to stabilize and equalize the flow rate of the auxiliary liquid and, thus, the curtain, preventing the coating thickness at edge regions from being thicker than the center region. Thereby the coating can be prevented from adhering to the other surface of the web, and the web can be prevented from being torn up when the web is rolled, increasing the efficiency of curtain coating.
The porous material preferably has a porosity of 30% or higher. In such a configuration, the auxiliary liquid supply means enables to uniformly supply the auxiliary liquid on the slide, stabilize and equalize the flow rate of the curtain, prevent the coating thickness at edge regions from being thicker than the center region, and thereby the coating can be prevented from adhering to any other surface of the web, and the web can be prevented from being torn up when it is rolled, increasing the efficiency of curtain coating.
The height of the auxiliary liquid supply means is preferably equal to the thickness, or depth, of the flowing curtain. With this configuration, the curtain can be prevented from being mixed with the auxiliary liquid, and thereby the edge regions of the resulting coating can be prevented from being mixed with the auxiliary liquid.
In the slide curtain coating apparatus of the present invention, the height of the auxiliary liquid supply means is preferably made equal to the thickness of the curtain, and also, a thickness regulator is preferably provided on the auxiliary liquid supply means in such a manner that the contact angle between the thickness regulator and the auxiliary liquid is 90° or wider. By supplying the auxiliary liquid on the slide and providing the auxiliary liquid supply means and thickness regulator in such manner, it is possible to make the thicknesses of the edge regions of the curtain equal to the thickness of its center region. And thus, the resulting coating can be formed with uniform thickness, preventing it from adhering to any other surface of the web. In addition the web is prevented from being torn up when it is rolled, thereby increasing the efficiency of curtain coating.
In the slide curtain coating apparatus, the height of flowing auxiliary liquid being discharged from and adjacent to the auxiliary liquid supply means is preferably controlled at the level equal to the thickness of the curtain. In such a configuration, the curtain of coating liquid can be prevented from being mixed with the auxiliary liquid, and thereby the edge regions of the resulting coating can be prevented from mixed with the auxiliary liquid.
In the slide curtain coating method of the present invention, a plurality of coating liquids is discharged from the corresponding number of slits, and flows down the inclined surface of a slide while being laminated as a curtain, and the curtain falls freely from the slide and contacts a running web, forming a coating thereon, wherein the method is characterized in that an auxiliary liquid is supplied from auxiliary liquid supply means at a pair of slide edge guides provided at opposing edges on the slide, the auxiliary liquid supply means discharges the auxiliary liquid from all over the surface thereof which touches the curtain. The height of flowing auxiliary liquid discharged from the auxiliary liquid supply means is preferably equal to the thickness of the curtain.
In such a slide curtain coating method, it is possible to prevent the edge regions of the coating from having greater a thickness than its center region, preventing the coating from adhering to any other surface of the web. In addition, the web is prevented from being torn up when it is rolled, increasing the efficiency of curtain coating. And further, the auxiliary liquid supply means expanding all over the surface of each slide edge guide that touches the curtain achieves a reduction in the amount of auxiliary liquid needed to be discharged, and thus the curtain can be almost completely prevented from being mixed with the auxiliary liquid. Thereby the coating can be prevented from being mixed with the auxiliary liquid.
The slide curtain coating apparatus preferably includes a recovery blade at the downstream of each slide edge guide as means for collecting the auxiliary liquid that has been discharged from the auxiliary liquid supply means.
With this configuration, as the flowing auxiliary liquid is collected by the recovery blade, it is possible to prevent the curtain from being mixed with the auxiliary liquid and the resulting coating from having greater thickness at its edge regions, thereby the coating can be prevented from adhering to the other surface of the web, and the web will not be easily torn up when it is rolled, increasing the efficiency of curtain coating.
In the slide curtain coating apparatus of the present invention, it is preferable to provide recovery means at each edge for collecting the flowing auxiliary liquid at the downstream of the slide edge guide by means of recovery blade, while moving the position of each slide edge guide facing the auxiliary liquid and curtain from the edge of the flow of the curtain by a distance corresponding to the flow width of the auxiliary liquid.
With this configuration, it is possible to prevent the curtain from being mixed with the auxiliary liquid and the coating from having greater thickness at its edge regions, thereby the coating can be prevented from adhering to the other surface of the web. In addition the web will not be easily torn up when it is rolled, increasing the efficiency of curtain coating.
In the curtain coating apparatus with the recovery blade, the length of the blade is preferably equal to the flow width of the auxiliary liquid flowing between the auxiliary liquid supply means and the edge of the flowing curtain.
In the slide coating apparatus with the recovery blade provided in such a manner, it is possible to prevent the curtain from being mixed with the auxiliary liquid and the coating from having greater thickness at its edge regions, thereby the coating can be prevented from adhering to any other surface of the web. In addition, the web will not be easily torn up when it is rolled, increasing the efficiency of curtain coating.
In the slide curtain coating apparatus of the present invention, suction means is preferably provided for suctioning a flowing auxiliary liquid, which has been discharged from the auxiliary supply means, through a path formed at the downstream of each slide edge guide.
With the curtain coating apparatus with such suction means, it is possible to prevent the curtain from being mixed with the auxiliary liquid and the coating from having greater thickness at its edge regions, thereby the coating can be prevented from adhering to any other surface of the web, and the web will not be easily torn up when it is rolled, increasing the efficiency of curtain coating.
In the slide curtain coating apparatus of the present invention, it is preferable to provide suction means at each edge to collect flowing auxiliary liquid at the downstream of each slide edge guide, while moving the position of each of the slide edge guide facing the auxiliary liquid and curtain from the edge of the flow of the curtain by a distance corresponding to the flow width of the auxiliary liquid.
With the curtain coating apparatus having the suction means provided in such a manner, it is possible to prevent the curtain from being mixed with the auxiliary liquid and the coating from having greater thickness at their edge regions, thereby the coating can be prevented from adhering to the other surface of the web, and the web will not be easily torn up when the web is rolled, increasing the efficiency of curtain coating.
The curtain coating apparatus with the recovery blade preferably contains a suction means at the downstream of the slide edge guides for suctioning the auxiliary liquid collected by means of the recovery blade. With such a curtain coating apparatus having the recovery blades and suction means, it is possible to more effectively prevent the curtain from being mixed with the auxiliary liquid and the coating from having greater thickness at its edge regions, thereby the coating can be highly effectively prevented from adhering to the other surface of the web, and the web will not be easily torn up when the web is rolled, increasing the efficiency of curtain coating.
In the curtain coating method of the present invention, coating liquids are discharged through respective slits, flow as a curtain down the inclined surface of the slide, and freely fall from the slide and contact the running web, forming the coating thereon, wherein the method is characterized in that the auxiliary liquid is provided from the auxiliary liquid supply means at the slide edge guides provided at opposing edges of the slide, the auxiliary liquid supply means discharges the auxiliary liquid from all over the surface thereof which touches the curtain, and the flowing auxiliary liquid is then suctioned with the suction means through the path formed at the end of the slide edge guides at the downstream.
In the curtain coating method of the present invention, coating liquids are discharged through respective slits, flow as a curtain down the inclined surface of the slide, and freely fall from the slide and contact the running web, forming the coating thereon, wherein the method is characterized in that the slide curtain coating apparatus of the present invention which has the suction means is used to discharge the auxiliary liquid from all over a surface which touches the curtain at a slide edge guide, and to suction the auxiliary liquid at the downstream of the slide edge guide, with the position of the slide edge guide being moved in the direction opposite to the discharge direction of the auxiliary liquid from the slide edge guide by a distance corresponding to the flow width of the auxiliary liquid.
The slide curtain coating method of the present invention is further characterized in that the flowing auxiliary liquid is collected using the above-stated curtain coating apparatus provided with the recovery blade at the downstream of each slide edge guide.
The slide curtain coating method of the present invention is further characterized in that the flowing auxiliary liquid is collected at the downstream of the slide edge guide by means of recovery blade, while moving the position of each slide edge guide facing the auxiliary liquid and curtain from the edge of the flow of the curtain by a distance corresponding to the flow width of the auxiliary liquid.
In the slide curtain coating apparatus with such recovery blades, it is preferred that the auxiliary liquid collected through the recovery blades be suctioned with the suction means through the path formed at the end of the slide edge guides at the downstream.
The height of the auxiliary liquid being discharged from the auxiliary liquid supply means is preferably equal to the thickness of the curtain.
According to the slide curtain coating method of the present invention, as described above, it is possible to prevent the edge regions of the resulting coating from having greater thickness than its center region, preventing the coating from adhering to any other surface of the web. In addition the web is prevented from being torn up when it is rolled, increasing the efficiency of curtain coating. And further, the auxiliary liquid supply means expanded to the entire contact area at the surface of the slide edge guides enable to reduce the required amount of the auxiliary liquid to be discharged, and thus the auxiliary liquid can be almost completely prevented from being mixed with the curtain. Thereby the coating can be prevented from having non-uniform thickness in a direction lateral to web motion, the non-uniformity being caused when the curtain is mixed with the auxiliary liquid. In addition, by moving the position of each of the slide edge guides from the edge of the flow of the curtain by a distance corresponding to of the flow width of the auxiliary liquid, by providing a recovery blade for collecting a flowing auxiliary liquid, or by adopting these means in combination, it is possible to further effectively achieve improvements corresponding to the selected means. It is also desirable that the height of flowing auxiliary liquid be controlled at a level equal to the height of the curtain for more improvement.
In the slide curtain coating apparatus, it is preferred that the static surface tension of the auxiliary liquid be in the range of from 10 mN/m lower to 30 mN/m higher than that of the coating liquid. By this, the static surface tensions of the coating liquid and auxiliary liquid are balanced, and the resulting coating can be prevented from having greater thickness at its edge regions, and thereby the coating can be prevented from adhering to any other surface of the web, and the web can be prevented from being torn up when it is rolled, increasing the efficiency of curtain coating.
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
The coating liquids 6 discharged through the slits S on the inclined surface of the slide 1 are laminated in the form of curtain 6, and move down the slide 1 by the force of gravity. At this point, the curtain 6 contacts the auxiliary liquid 7 at its ends, whereby the generation of converged flows as seen in the prior art is prevented and thus thickening of the edges of the curtain 6 can be prevented. The curtain 6 then falls from the slide 1 and contacts the running web 5, forming a coating thereon.
In this slide curtain apparatus 4, the auxiliary liquid 7 is discharged from the entire surface 2c of each of the opposing edge guides 2A on the slide 1, which surface 2c is in contact with the curtain 6. With this configuration, the flow rates of portions of the curtain 6 near the edges of the slide 1 increase, and thereby the difference in flow rate between the center and edges of the curtain 6 becomes small, preventing edge flows from converging to the center and preventing the resulting coating from having greater thickness at its edge regions.
In addition, with the configuration described above, the slide curtain coating apparatus 4 can reduce the amount of the auxiliary liquid 7 needed to be discharged and thus prevent the curtain 6 and the resulting coating from being mixed with the auxiliary liquid 7 at their edge regions by discharging an adequate amount of auxiliary liquid 7 from the entire contact area 2c.
The auxiliary liquid 7 is not particularly limited as long as it is liquid, i.e., has fluidity. Examples thereof include aqueous liquids, among which preferred are water and aqueous preparations obtained by mixing water with resin, surfactant or the like; and solvent-based liquids, among which preferred are solvents suitably contained in the curtain 6 and solvent preparations obtained by mixing the solvents with resin, surfactant or the like.
It is preferred that the static surface tension of the auxiliary liquid 7 be in the range of from 10 mN/m lower to 30 mN/m higher and further preferably in the range of from 5 mN/m lower to 20 mN/m higher than that of the coating liquids. When the static surface tension of the auxiliary liquid 7 is 10 mN/m lower than that of the coating liquids, the auxiliary liquid 7 may be drawn toward the curtain 6 flowing down the slide 1, causing the resulting coating to be mixed with a significant amount of the coating liquids at the edge regions. On the other hand, when the static surface tension of the auxiliary liquid 7 is 30 mN/m higher than that of the coating liquids, the curtain 6 may be drawn toward the auxiliary liquid 7 while flowing down the slide 1 and thus the coating liquid may be reduced at the edge regions, resulting in significantly insufficient amount of the coating thickness at the edge regions of the resulting coating.
The slide curtain coating method of the present invention may be performed with the above-stated slide curtain coating apparatus 4 which basically discharges the auxiliary liquid 7 from the contact area 2c at the slide edge guides 2A provided at both edges of the slide 1 to supply a small amount of the auxiliary liquid 7 at the edge regions of the curtain 6. Thereby, the flow rates at the edge regions of the curtain 6 are increased to minimize the difference in flow rate between the center region and the edge regions of the curtain 6, preventing the flow of the curtain 6 from being converged to the center, and preventing the resulting coating from having greater thickness at its edge regions.
By discharging the auxiliary liquid 7 from the entire surface 2c of each of the opposing edge guides 2A on the slide 1, the surface 2c being in contact with the curtain 6, it is possible to reduce the amount of auxiliary liquid needed to be discharged and to prevent the curtain 6 and the resulting coat on the running web 5 from being mixed with the auxiliary liquid 7 at the edge regions.
By adjusting the height of the auxiliary liquid 7 discharged between the slide edge guide 2A and the curtain 6 to a level equal to the height (thickness) of the curtain 6 as shown in
The wall member 8 shown in
When the height of the porous material member 8 is adjusted at a level equal to the thickness of the curtain 6 as shown in
In the above-described configuration where the height of the porous material member 8 is made equal to the height of the coating liquid, it is further preferable, as shown in
In addition to the above described configuration, a suction means is preferably provided in fourth embodiment. In fourth embodiment shown in
In fifth embodiment shown in
In sixth embodiment shown in
In addition, the recovery blade 10 in the above-stated configuration may be provided in such a manner that the horizontal length of the recovery blade 10 is equal to the flow width of the auxiliary liquid 7 between the porous material member 8 and curtain 6, thereby more effectively preventing the curtain 6 from being mixed with the auxiliary liquid 7.
Still another embodiment will be explained hereinafter. In the embodiment shown in
Also in such a configuration, the curtain 7 can be prevented from being mixed with the auxiliary liquid 6, and thereby the edge regions of the resulting coating on the web can be prevented from being mixed with the auxiliary liquid 7 and from having greater thickness at its edge regions. The slide curtain coating apparatus in this embodiment further includes a suction means configured to suction the auxiliary liquid 7 collected by the recovery blade 10. By providing such a suction means in the above-stated configuration, the curtain 7 can be more effectively prevented from being mixed with the auxiliary liquid 6, and thereby the edge regions of the resulting coating on a web can be further effectively prevented from being mixed with the auxiliary liquid 7 and from having greater thickness at its edge regions.
Also in the above configuration, the recovery blade 10 may be provided in such a manner that the horizontal length of the recovery blade 10 is equal to the flow width of the auxiliary liquid 7 between the porous material member 8 and curtain 6, to thereby enhance the capability of the recovery blade 10 to prevent the curtain 6 from being mixed with the auxiliary liquid 7.
The slide curtain coating method of the present invention is a method including the step of discharging coating liquids through the slits on the slide such that they flow as layers or curtain down the inclined surface of the slide and freely fall from the slide and contacts the running web to form a coating thereon, wherein the method is characterized in that the auxiliary liquid is discharged from all over the surfaces of the opposing edge guides on the slide, which surfaces being in contact with the curtain. It is thus possible to prevent the flow of the curtain from converging to the center region and to prevent the resulting coating from having greater thickness at the edge regions. The present invention will be understood more readily with reference to the following Examples and Comparative Examples; however, these are intended to illustrate the invention and should not be construed as limiting the scope of the present invention.
As shown in
A coating liquid (having a viscosity of 300 mPa·s and static surface tension of 35 mN/m) having the below mentioned ingredients was applied on a web (paper) by slide curtain coating under the following conditions: coating speed=400 mm/min; coating width=250 mm; and flow rate of coating liquid discharged through slits=3,000 g per minute. The variation of the average thickness across the width of the resulting coating was measured with X-Rite 938 (a color differential meter manufactured by X-Rite, UK; aperture=5 mm) by assaying the amounts of deposit on the web over the half width (from center to one edge). The measurements are shown in
—Ingredients of Coating Liquid—
85 parts by mass of polyvinyl alcohol
5 parts by mass of a green pigment
915 parts by mass of water
The coating liquid of Example 1 was applied to paper and the resulting coating was investigated in the same manner as in Example 1, except that the height of the ceramic pieces was made equal to the height of the thickness of the curtain (2.5 mm). The obtained results are shown in Table 1 and
The coating liquid of Example 1 was applied to paper and the resulting coating was investigated in the same manner as in Example 1, except that the height of the ceramic pieces was made equal to the height of the thickness of the curtain (2.5 mm), and that a 5 mm thick TEFLON®-coated piece was provided on the ceramic piece as the thickness regulator 9 in
The coating liquid of Example 1 was applied to paper and the resulting coating was investigated in the same manner as in Example 1, except that upon coating the auxiliary liquid was suctioned at the downstream of the slide edge guides 2A. The thus obtained results are shown in Table 1 and
The coating liquid of Example 1 was applied to paper and the resulting coating was investigated in the same manner as in Example 4, except that, as shown in
The coating liquid of Example 1 was deposited onto paper and the resulting coating was investigated in the same manner as in Example 2, except that a 0.5 mm long recovery blade and suction means were provided at the downstream of each slide edge guide 2A for collecting and suctioning the flowing auxiliary liquid. The obtained results are shown in Table 1 and
The coating liquid of Example 1 was deposited onto paper and the resulting coating was investigated in the same manner as in Example 6 except that, as shown in
The coating liquid of Example 1 was deposited onto paper and the resulting coating was investigated in the same manner as in Example 4, except that as an auxiliary liquid a solution prepared by adding a surfactant to water such that the solution has a static surface tension of 54 mN/m was used. The obtained results are shown in Table 1 and
The coating liquid of Example 1 was deposited onto paper and the resulting coating was investigated in the same manner as in Example 4, except that as an auxiliary liquid a solution prepared by adding a surfactant to water such that the solution has a static surface tension of 28 mN/m was used. The obtained results are shown in Table 1 and
The coating liquid of Example 1 was deposited onto paper and the resulting coating was investigated in the same manner as in Example 1, except that no auxiliary liquid was supplied. The obtained results are shown in Table 1 and
The coating liquid of Example 1 was deposited onto paper and the resulting coating was investigated in the same manner as in Example 1, except that water as an auxiliary liquid was supplied from the upstream of the slide along the slide edge guides. The obtained results are shown in Table 1 and
(Evaluation and Result)
As
As
In accordance with the present invention, the present invention can solve conventional problems and provide a slide curtain coating apparatus and slide curtain coating method that can prevent the resulting coating from having greater thickness at the edge regions than at the center region.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-251633 | Sep 2006 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11901045 | Sep 2007 | US |
| Child | 12958835 | US |
