JP2003181367A - Coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method which can apply a coating liquid to the whole area of a support including both edges of the support, eliminate thick coating on both edges, and prevent a process from becoming dirty, wherein the coating liquid is applied to the surface of the support by the free-fall of the coating liquid in a curtain-like form onto the traveling support. <P>SOLUTION: Both edges, parallel to the travel direction, of the support are bent toward the back surface of the support, and the support is coated over the overall width including both edges in the bending state. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for coating a coating liquid on the surface of a support by free-falling the coating liquid in a curtain shape on a moving support.

[0002]

2. Description of the Related Art The curtain coating method as described above has been widely adopted in a process that requires uniform coating of a coating solution on a support.

FIG. 3 is a diagram showing an example of a conventional curtain coating method.

In this curtain coating method, the coating liquid 10 is free-falling in a curtain shape while being guided by the two edge guides 20 on both edges, and on the backup roll 40 arranged under the curtain-shaped coating liquid. Is applied to the entire surface of the support 30 that travels. FIG. 3B shows the support 30.
FIG. 4 is a diagram showing that it is applied to the entire surface of, and is shown for comparison with the diagrams (FIGS. 4 and 2) described later.

In the case of the curtain coating method shown in FIG. 3, formation of a thick coating portion on both edges of the coating layer is recognized as compared with the coating layers of other portions.

[0006] Therefore, various adverse effects occur in industrial implementation. That is, the thick coating portions formed on both edges of the coating layer require more drying time than other normally coated coating layers.

If the drying step does not have sufficient capacity to dry the thick coating portion, the thick coating portion remains undried and the undried coating liquid is transferred to the conveying roller after the drying step. However, there are problems such as the transfer to the sheet and the process being soiled, the edges being adhered when wound on a roll in the winding process, and the support being cut when unwinding in the cutting process.

Therefore, in order to dry the thick coating portion, an excessive drying ability must be added. Further, the thick coating portions on both edges of the coating layer have a width of at most a few mm, which requires a great amount of drying cost and is extremely uneconomical.

[0009] Further, aside from the problem of the cost of drying, even if the drying process is performed so that it is sufficiently dried, in the above method, sometimes the side of the support is coated, or the coating solution wraps around to the back of the support. Therefore, the rolls, belts, etc. that convey the support may be contaminated.
Furthermore, especially when pressure-sensitive copying recording paper, heat-sensitive recording paper, etc. using paper as a support, both edges of the coated paper are considerably curled in the direction opposite to the coated surface by being coated with the coating liquid. Due to curling in the opposite direction to the coating surface, both edges of the coating layer contact the transport roll until the coating layer enters the drying zone, the coating liquid is transferred to the roll, and roll contamination is extremely difficult. More likely to occur.

Further, in the drying process, in the case of the canvas conveying and drying process, both edges of the application surface are brought into contact with each other by the curl, so that the application liquid causes stains on the canvas before it is sufficiently dried. In the case of roll transfer drying process, stains on the coating liquid on the roll may occur,
Alternatively, in the case of a so-called floater dryer that performs non-contact conveyance and drying as disclosed in Japanese Patent Laid-Open No. 54-25066, curling of both edges of the coated paper causes flapping of both edges of the coated paper, and Nozzle contamination is likely to occur.

When the process contamination due to the adhesion of the coating liquid is continuously performed, the coating liquid is fixed and accumulated to cause cutting of the coated paper, or the deposit is peeled off and scattered and adhered to the coated surface. May cause product failure.

Also in the winding step after the thick coating portion has been sufficiently dried, both edge portions corresponding to the thick coating portion of the roll in which the thick coating portions of both edge portions are accumulated and wound are wound. In the case of a support that is convex and contains a thin plastic sheet, if the above convex is severe, the support may deform after winding, or in the case of a paper support, cracks from this protrusion Therefore, there is a problem that production efficiency is significantly reduced, such as long winding becomes difficult.

[0013]

In order to improve the above-mentioned problems, Japanese Patent Publication No. 2-1550 discloses a curtain in which both edges of a support are bent so that the edges are not coated. A coating method has been proposed.

FIG. 4 is a diagram showing a curtain coating method in which coating is not performed on both edges of the support.

As shown in FIG. 4, both edges 31 of the support 30 are provided between the folding member 50 and the folding assisting member 51 on the upstream side of the coating unit for performing curtain coating in the traveling direction of the support. It is sandwiched and bent about 7 to 8 mm at each edge.

The coating section for performing curtain coating is shown in FIG.
As shown in (B), both edges 31 of the support, which have been once bent, are returning to the original flat state to some extent, but they are still sufficiently bent. As shown in C), both edges of the support are left uncoated in a width of 5 to 6 mm for each edge. The folded edges return to their original flat state during traveling.

By doing so, the above-mentioned problems of thick coating of both edges and contamination of the process can be eliminated.

However, if an uncoated portion remains on both edges of the support, it cannot be shipped as a product including that portion, and both edges are completely wasted. is there.

In view of the above circumstances, the present invention provides a coating method which adopts a curtain coating method to coat the entire surface including both edge portions of a support and eliminate thick coating on both edge portions to prevent process stains. The purpose is to do.

[0020]

The coating method of the present invention which achieves the above-mentioned object is a coating method in which the coating solution is applied to the surface of a support by allowing the coating solution to freely fall in a curtain shape on a running support. In the method, both edges of the support, which are parallel to the running direction, are bent in the direction of the back surface of the support, and the coating liquid that freely falls in a curtain shape is applied to both edges of the support in the bent state. It is characterized by coating over the entire width including.

Like the method proposed in the above-mentioned publication, the coating method of the present invention bends both edges of the running support to the back side thereof, but by adjusting the bending angle and the like,
The coating is applied to the entire width of the support including both edges thereof. By doing so, thick coating of both edges can be avoided and contamination of the process after application can be prevented.

Here, in the coating method of the present invention,
The angle of both edges of the support at the coating position on the back surface side of the support is preferably 135 ° to 170 °.

By bending so that the angle at the coating position falls within this range, it is possible to stably coat the entire width of the support including both edges, and avoid thick coating of both edges. . Further, since the thick coating on both edges is eliminated, the curl on both edges of the coating is also suppressed, and the above-mentioned contamination of the process is prevented.

Further, in the above coating method of the present invention, the bending angle θ of both edges of the support, the dynamic surface tension σd of the coating liquid that freely falls in a curtain shape, the curtain film flow rate Q, and the curtain film flow velocity U are: It is preferable that sin θ> √ (2σd / QU) is satisfied.

By satisfying this condition, it is possible to eliminate the possibility that the coating liquid is not coated on both ends of the support and uncoated portions are generated.

Further, in the above coating method of the present invention,
The curtain film flow rate of the coating liquid that falls freely in a curtain is
It is preferably 0.5 ml / (cm · s) or more.

The curtain film flow rate is 0.5 ml / (cm ·
s) With the above values, coating failure such as liquid splashing can be prevented.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing an example of a coating apparatus for carrying out the coating method of the present invention.

The support 30 runs in the direction of arrow A,
The folding member 50 and the folding assisting member 5 before reaching the coating portion.
1, the traveling direction of the support 30 (direction of arrow A)
Both edges 31 (only one edge is shown in FIG. 1) parallel to are folded. The bending angle is adjusted so that the bending angle θ in the coating section is in the range of 135 ° to 170 °.

The coating liquid 10 is free-falling in the direction of arrow B in a curtain shape while both edges are being guided by the edge guides 20,
It is applied on the support 30 that runs on the backup roll 40 that rotates in the direction of arrow C. Here, the position of the bending member 50 is adjusted, and as a result, the bending angle θ of the both edge portions 31 of the support body 30 is adjusted. The coating layer 11 is formed on the entire surface of 30. Here, the coating layer 11 extends to both edge portions 31 of the support 30, but the both edge portions 31 are applied in a bent state, so that thick coating is generated and the coating liquid is spread on the back surface. Therefore, the back surface of the support is not soiled. At both ends 31 of the support 30, the coating amount is co
It becomes sθ times, which is smaller than the central portion other than both end portions 31 of the support 30. As a result, the edge of the support dries faster than the central part, and process contamination is less likely to occur. Depending on the product, a small amount of coating may cause performance problems,
This portion is the end of the product and is a portion that is not actually used for copying in the case of carbonless copy paper, for example, and there is no problem if the appearance as recording paper is the same.

After passing through the coating portion, the both edges 31 of the support are restored to their original flat state by canceling the bending due to their own restoring force. The coating liquid 31 is dried on the support 30 through a predetermined drying process and then wound up.

The bending angle θ is usually in the range of 135 to 170 °, preferably in the range of 150 to 160 °, but an optimum value is selected depending on the curtain film flow rate, the dynamic surface tension in the coating section and the curtain film flow velocity. , Sin θ> √ (2
σd / QU), σd: dynamic surface tension Q: curtain film flow rate U: curtain film flow rate. If this is not satisfied, the coating liquid may not be applied to both ends 31 of the support 30 and uncoated portions may occur.

The curtain film flow rate is 0.5 ml / (c
m · s) or more, preferably 1 to 4
More preferably, it is ml / (cm · s). Both ends 31 of the support 30 are unstable because they are not supported from the back side by the backup roll 40, and the web entrainment flow from the upstream side is insufficiently blocked from the central part, so that the membrane flow rate is 0.5 ml / If it is less than (cm · s), coating failure such as liquid splashing is likely to occur. The membrane flow rate is 1 ml / (cm ・
s) or more is more preferable. The membrane flow rate is 4 ml /
If it is more than (cm · s), process contamination due to the backside of the liquid is likely to occur.

The height of the curtain film is preferably 20 to 300 mm, more preferably 50 to 200 mm.

Optimum conditions for the bending angle and the curtain film height are actually selected according to the coating speed, the viscosity of the coating liquid, the surface tension, and the curtain film flow rate. Coating speed is 50
~ 200m / min, viscosity of coating liquid is 30 ~ 300mP
It is preferable that the a · s and the surface tension satisfy 20 to 50 mN / m.

The width of the edge of the support to be bent is selected so that a uniform thickness can be applied at least within the width where a product to be applied must be uniform, but if it is too narrow, uniform bending can be achieved. On the other hand, if it is too wide, the edge 31 of the support becomes unstable, so about 5 to 12 mm is selected.

FIG. 2 is an explanatory view of the curtain coating method of FIG.

Here, as shown in FIG. 2A, the bending support member 51 and the bending member 50 are adjusted to have a certain gap (for example, 5 mm in the example shown here). In the section, as shown in FIG. 2B, the angle θ on the back surface side of the support is within the range of 135 ° to 170 °. In this case, as shown in FIG. 2C, the entire area of the support including the support edge portions 31 is applied, and thick coating on both edge portions and wraparound to the back surface are also avoided. Here, the bending angle θ is defined by the bending member 50 and the bending auxiliary member 5
The distance can be adjusted by setting an appropriate distance to 1 or by setting an appropriate angle on the surface of one or both of the bending member 50 and the bending assisting member 51 that is in contact with the support.

[0040]

EXAMPLES Examples of the present invention will be described below.

Both sides of the support were bent using a bending member so that the bending angle at the coating position was 160 degrees, and coating was performed under the conditions shown in Table 1, and then a non-contact type floater dryer. After drying, a carbonless under paper was obtained.

[0042]

[Table 1]

In this example, good coating was performed over the entire width of the support, and no process stain was generated.

Further, as a result of performing similar coating while changing the bending angle at the coating position, good coating was performed over the entire width of the support in the range of 135 ° to 170 °, and there was no process stain. Moreover, no crease was left after the application. (Comparative Example 1) Coating and drying were carried out under the same conditions as in Example except that the ears were not bent to obtain a carbonless under paper.

In Comparative Example 1, dirt is attached to the nozzles of the pass roll and the float dryer before the dryer at the position corresponding to the end of the coated paper, and the coated paper is bonded at the end of the wound product. Sometimes I did. (Comparative Example 2) The same coating as that of the example was performed with the bending angle at the coating point set to 130 degrees.

In Comparative Example 2, the coating was not completely applied to the end of the support, and an uncoated portion was formed.

[0047]

As described above, according to the present invention,
Good coating is performed over the entire width of the support, and process contamination is prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a coating apparatus that carries out a coating method of the present invention.

FIG. 2 is an explanatory diagram of the curtain coating method of FIG.

FIG. 3 is a diagram showing an example of a conventional curtain coating method.

FIG. 4 is a diagram showing a curtain coating method in which coating is not performed on both edges of the support.

[Explanation of symbols]

10 coating liquid 11 coating layer 20 Edge guide 30 support 40 backup roll 50 folding members 51 Bending auxiliary member

Claims (4)

[Claims] 1. A coating method in which a coating solution is applied to the surface of the support by free-falling the coating solution in a curtain shape on a support that is traveling, and both edges of the support parallel to the traveling direction are provided. The coating method is characterized in that the part is bent in the direction of the back surface of the support, and the coating liquid that freely falls in a curtain shape is applied over the entire width of the support, including both edges in the bent state. 2. The coating method according to claim 1, wherein an angle of both edges of the support on the back surface side of the support at a coating position is 135 ° to 170 °. 3. A bending angle θ of both edges of the support,
The dynamic surface tension σd of the coating liquid that freely falls in the shape of a curtain,
The coating method according to claim 1, wherein the curtain film flow rate Q and the curtain film flow rate U satisfy sin θ> √ (2σd / QU). 4. The coating method according to claim 1, wherein the curtain film flow rate of the coating liquid that freely falls in a curtain shape is 0.5 ml / (cm · s) or more.