JP2000176344A - Method and apparatus for application - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform coated surface by forming stably a curtain film by a method wherein blowing and suction of air to and from a substrate are executed in a space wherein a space to the substrate is isolated by specific dimensions over in a width direction of the substrate on an upstream side of a free drop landing part of a coating liquid. SOLUTION: When a coating liquid of a laminated state is freely dropped vertically downward from a lip 8, a coating liquid film 9 is formed, and the coating liquid film 9 is allowed to collide onto a web 11 and coated. Then, a space forming member 21 is provided on an upstream side of a free drop landing part 14 of the coating liquid film 9, and a narrow space is formed between the member 21 and the web 11 over in a width direction of the web 11. The air forming member 21 installs its opposed face 21b at a space of <=5 mm to the web 11. Then, in order to execute simultaneously blowing and suction of air on and from the web in the space, an air blowing means, an air suction means, and the space forming member 21 are integrally provided. Thereby, an accompanied air being adjacent to the web in high speed application can be efficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and a coating apparatus used for producing recording materials such as silver halide photographic materials, magnetic recording materials, pressure- and heat-sensitive recording papers, and ink jet recording sheets. The present invention relates to a curtain coating method and a coating apparatus for coating a thin film of a coating liquid (hereinafter, referred to as a “coating liquid film”) on a continuously running belt-like support (hereinafter, referred to as a “web”). is there.

[0002]

2. Description of the Related Art As a multi-layer simultaneous coating method, a slide bead method or an extrusion method is generally known, but in recent years, a curtain coating method has been frequently used in accordance with a demand for high-speed coating. The curtain coating method is a method in which a coating liquid film is applied by freely falling onto a continuously running web and is applied as a basic technology.
Nos. 9-24133 and 49-35447.

[0003] In recent years, there has been a demand for higher speed coating in order to improve productivity. However,
As the coating speed increases, the amount and speed of air entrained on the web surface increases, and the web-air solid-gas interface is not sufficiently replaced with the web-coating liquid-solid interface, so-called air entrainment. A so-called phenomenon has come to be seen. Air entrainment is free falling coating liquid film (curtain film)
Oscillating or bulging in a curved shape on the downstream side in the web running direction, causing application unevenness such as vertical streak or horizontal unevenness, and when the amount of entrained air increases,
In some cases, the coating liquid film eventually scatters without being crosslinked on the web.

A method and an apparatus for removing air entrained in a web for the purpose of suppressing such a phenomenon and performing coating at a high speed without coating failure have been disclosed. For example,
JP-A-35447 discloses that a shield plate is provided near a web upstream of a coating liquid film, and that an entrained air suction device having a slit-shaped suction nose is provided. However, the shield plate does not sufficiently remove the entrained air.In order to improve the ability to remove the entrained air, the shield plate must be brought as close as possible to the web, and in this case, the shield plate contacts the web. There is a risk that the web may be scratched and that the web may be cut by contacting the seam between the webs. Also, the entrained air suction device having a slit-shaped suction nose, the coating liquid film is drawn to the entrained air suction device when the suction force is increased to suppress an increase in the amount of entrained air due to high speed,
There is a problem that the coating liquid film starts to swing.

A device for connecting a suction pump to the hollow portion of the air cut roll to remove the entrained air is disclosed in Japanese Utility Model Publication 8-10.
17 publication. According to the experiments of the present inventors, it was confirmed that the entrained air was effectively removed.However, since the air cut roll was in contact with the web, an accurate difference between the web running speed and the air cut roll peripheral speed was obtained. Need to synchronize. If there is a speed difference between the two due to slight speed fluctuation, the web surface will be scratched. In particular, it is a fatal defect in a field requiring a thin layer precision coating such as a photographic material.

[0006] Japanese Patent Application Laid-Open No. Hei 3-123657 and Hei 6
No. 39331, No. 10-277458,
It is disclosed to provide a decompression chamber facing the backup roller. These devices are difficult to adjust the degree of decompression of the decompression chamber with high accuracy when the amount of entrained air changes due to application conditions such as coating speed and web surface roughness. There is a problem that it becomes.

Further, Japanese Patent Application Laid-Open Nos. 62-186966 and 3-65266 disclose a method of blowing air onto a web in a direction opposite to the running direction of the web. However, simply spraying air does not provide a sufficient effect, especially at a high speed of 200 m / min or more, and the air flow is easily disturbed by the rebound or leakage of the blown air, which adversely affects the curtain film. There was a case.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an entrained air which causes the swing and swelling of a coating liquid curtain film. It is an object of the present invention to provide a curtain coating method and a coating apparatus which form a curtain film stably and thereby obtain a uniform coating surface. Another object of the present invention is to
An object of the present invention is to provide a curtain coating method and a coating apparatus applicable to high-speed coating.

[0009]

The object of the present invention has been attained by a coating method and a coating apparatus having the following constitutions. (1) In a curtain coating method in which a coating liquid is freely dropped in a thin film form and coated on a continuously running support, the distance between the coating liquid and the support is 5 mm or less on the upstream side of the free fall landing portion of the coating liquid. A curtain coating method, comprising blowing and sucking air onto a support in a space that is blocked in the width direction of the body. (2) In a curtain coating apparatus for applying a coating liquid onto a continuously running support by freely falling in the form of a thin film, the distance between the coating and the support is 5 mm upstream of the free fall landing section of the coating liquid.
A space forming means for forming a space closed within the width direction of the support within, an air blowing means for blowing air to the support in the space, and air for sucking air A curtain coating apparatus, comprising: a suction unit.

The amount or speed of the entrained air generated as the support (web) travels is greatest near the web,
It gets smaller as you get away from the web,
Air entrainment occurs even at a distance of 0 cm. The entrained air has a large flow velocity within 500 μm from the web, and it is important to remove entrained air close to the web. It has been found that the above-described method and apparatus of the present invention can efficiently remove entrained air close to the web in high-speed coating.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The entrained air removal method of the present invention is not to simply blow air to the web as in the related art, but to create a narrow space close to the web and perform blowing and suction of air in the space. The space is 5mm from the web
It is formed by covering with a blocking member so as to block from the upper space in the width direction of the web at an interval within. The space is narrow with respect to the coating surface of the web, and there is no problem even if both ends of the web are open.

The narrow space provided on the web has a clearance (clearance) with the web of 5 mm or less, preferably in the range of 0.3 to 3 mm, more preferably 0.3 mm.
１1 mm.

Hereinafter, a coating apparatus for performing the coating method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration side view showing an example of a curtain coating device of the present invention. Slide head 1 by measuring pumps 7a, 7b
The application liquid sent to the internal supply paths 4a and 4b is discharged to the slide surface 2 through the slots 3a and 3b. The discharged coating liquid flows toward the lip 8 along the slide surface 2 by the action of gravity while maintaining the laminated state. A coating liquid film 9 is formed by allowing the coating liquid in a laminated state to fall vertically downward from the lip 8. The coating liquid film 9 that has been freely dropped is applied by colliding with a continuous running web 11 supported by a backup roller 10.

The curtain coating apparatus of the present invention comprises a coating liquid film 9
A space forming member 21, which is a means for removing entrained air, is provided upstream of the free-fall landing section 14 of FIG. The space forming member 21 extends over the web 11 in the width direction of the web 11.
And a member that forms a narrow space 22 between them. The space forming member 21 is a member that blocks entrained air in the width direction of the web 11, and includes a surface (hereinafter, referred to as an interrupted surface) 21 a that faces the web 11 (hereinafter, referred to as an interrupted surface). 21b). The space forming member 21 has its opposing surface 21b
1 is set at an interval of 5 mm or less, preferably 0.3 to 3 mm, more preferably 0.3 to 1 mm, and a narrow space 22 is formed between the space forming member 21 and the support 11.

FIG. 2 is a partially enlarged sectional view of the curtain coating apparatus shown in FIG. As described above, the distance L between the facing surface 21b of the space forming member 21 and the web 11 is set within 5 mm, and the space 22 is formed between the space forming member 21 and the web 11. The facing surface 21b may be a flat surface or a curved surface parallel to the facing web surface (when the web 11 is supported by the backup roller 10 as shown in FIG. 1). The space 22 has substantially the same size in the width direction and the running direction of the web 11. The method of the present invention is characterized in that air is simultaneously blown and sucked into the web 11 in the space 22. For that purpose, an air blowing means 23 and an air suction means 24 are provided integrally with the space forming member 21. Air blowing means 23
Is composed of a blowing slit 23a, a cavity 23b and a blower (not shown) which are substantially uniform in the width direction of the web 11. The air suction means 24 includes a suction slit 24a, a cavity 24b, and a suction pump (not shown) which are substantially uniform in the width direction of the web 11.
The blower and the suction pump are connected to the respective cavities 23b and 24b by piping from the side surface of the space forming member 21.

The blowing direction of the air in the space 22 is perpendicular or opposite to the conveying direction of the web 11. Preferably, the direction is opposite, and the angle θ between the blowing slit 23a and the web 11 is set in the range of 20 to 90 degrees, preferably 30 to 70 degrees. The slit width (clearance) of the blowing slit 23a is 0.3 to 1 m.
About m is appropriate. The blowing speed is adjusted according to the coating speed, but it is preferable to blow at a wind speed of 5 m / sec or more.

The suction of air in the space 22 is preferably performed on the upstream side with respect to the running direction of the web 11 from the position where the air is blown, and also on the downstream side as described later (shown in FIG. 4). More preferred. Air suction power is
It is preferably set to 50% or more of the air blowing amount, more preferably the same amount or more. The angle α of the suction slit 24a is perpendicular to the web 11 or opposite to the blowing slit 23a.
The preferred direction is the same as the transport direction. Suction slit 24a
Is suitably about 0.3 to 2 mm. The distance between the blowing slit 23a and the suction slit 24a on the facing surface 21b is set so that the air blown from the blowing slit hits the web 11 and then is sucked. That is, the distance between the blowing slit 23a and the suction slit 24a and the distance between the facing surface 21b and the web 11 vary depending on the angle between the two, but usually about 3 to 20 mm is appropriate.

According to the present invention, the space above the web surface (coated surface) is 5
mm, to create a narrow space close to the web surface, and to simultaneously spray and suction in the space, in that sense, the embodiment described below is also one of the present invention, and It has a great effect. FIG. 3 is a partial sectional view showing another embodiment of the space forming member. An air blowing means 23 is provided at the downstream end of the space forming member 21, and an air suction means 24 is provided at the upstream end. The angle of the blowing slit 23a of the air blowing means 23 is directed in the opposite direction to the transport direction of the web 11, and the space 2
It is sprayed in 2. The suction slit 24 a of the air suction unit 24 faces in the same direction as the transport direction of the web 11, and is sucked in the space 22.

As described above, in a preferred embodiment of the present invention, suction is performed on the upstream side of the blowing position in the space 22 as shown in FIG. 2, but also on the downstream side of the blowing position as shown in FIG. More preferably, In FIG. 4, air suction means 24 and 25 are provided upstream and downstream of the air blowing means 23, respectively. The downstream air suction means 25 includes a suction slit 25a, a cavity 25b, and a suction pump (not shown) which are substantially uniform in the width direction of the web 11. The angle β of the suction slit 25 a is preferably perpendicular to the web 11 or opposite to the transport direction of the web 11. The clearance of the suction slit 25a is suitably about 0.3 to 2 mm. Suction slit 25a in facing surface 21b
And the distance between the blowing slit 23a and 3 to 20
mm is appropriate. The suction force of the downstream air suction means 25 is set to be equal to or weaker than that of the upstream air suction means 24.

In the present invention, the blocking surface 21a of the space forming member 21 shown in FIGS. 1, 2, 3 and 4 functions to block the entrained air in the width direction of the web. As described above, air entrainment also occurs at a position 10 cm away from the web, and the blocking surface 21a needs to have a sufficient height dimension. Preferably, as shown in FIG. 1, a space forming member 21 is attached to the slide head 1 to shut off the entrained air integrally with the slide head 1.

[0021]

EXAMPLE 1 A coating test was carried out using the curtain coating apparatus shown in FIG. However, the following devices were used for removing the entrained air.

A: The entrained air removing device shown in FIG.
6 mm, the angle θ of the blowing slit 23a is 50 degrees, the clearance of the slit is 0.5 mm, the blowing speed (wind speed) is 10 m / sec, the clearance of the suction slit 24a is 1.0 mm, and the angle α is 60 degrees. The suction amount of the air suction means 24 was set to be substantially the same as the blowing amount of the air blowing means 23.

B: Entrained air removal apparatus shown in FIG. 5 The angle θ of the slit is 50 degrees, the clearance of the slit is 0.5 mm, the blowing speed (wind speed) is 10 m / sec,
The distance between the slit tip and the web is 0.6 mm.

Using the above-mentioned respective coating apparatuses, coating was performed under the following conditions. Web: polyethylene resin-coated paper having a thickness of 160 μm Web width: 1500 mm Application width: 1490 mm Coating liquid: Upper layer: protective layer Viscosity: 25 cP, surface tension: 30 dyne / cm (37
° C) Coating amount: 10 g / m ² Lower layer: silver halide emulsion layer Viscosity: 40 cP, surface tension: 33 dyne / cm (37
° C) Coating amount: 40 g / m ²

The results of the coating test are shown below. Entrained air removing device A (invention): The curtain film was formed stably even at a coating speed of 300 m / min, and a uniform coated surface was obtained. Entrained air removal device B (comparative): At a coating speed of 300 m / min, the curtain film oscillated, and vertical stripes were partially generated.

Example 2 Next, a coating test was performed using the entrained air removing device shown in FIG. In FIG. 4, the clearance of the downstream suction slit 25a is 1.0 mm, the angle β is 60 degrees, the suction amount is 20% of the upstream air suction means 23, and other components are the same as those of FIG. It is. The application test conditions were the same as in Example 1. As a result of the coating test, a stable curtain film was formed even at a high speed of 400 m / min, and a uniform coated surface was obtained.

[0027]

As described above, the curtain coating apparatus using the entrained air removing apparatus of the present invention can sufficiently remove the entrained air even at high-speed coating, and can obtain a uniform coated surface.

[Brief description of the drawings]

FIG. 1 is a schematic configuration side view of a curtain coating apparatus according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the curtain coating device of the present invention.

FIG. 3 is a partially enlarged sectional view showing another embodiment of the curtain coating device of the present invention.

FIG. 4 is a partially enlarged sectional view showing another embodiment of the curtain coating device of the present invention.

FIG. 5 is a partially enlarged sectional view of a conventional curtain coating apparatus.

[Description of Signs] 1 Slide head 9 Free-fall coating liquid film 11 Web (support) 21 Space forming member 22 Space 23 Air blowing means 24 Air suction means 25 Air suction means

Claims (2)

[Claims] 1. A curtain coating method in which a coating liquid is freely dropped in the form of a thin film and coated on a continuously running support,
The method is characterized in that air is blown and sucked to the support in a space closed across the width direction of the support within a distance of 5 mm from the support on the upstream side of the free fall landing portion of the coating liquid. Curtain coating method. 2. A curtain coating apparatus for free-falling a coating liquid in the form of a thin film and coating the coating liquid on a continuously running support,
A space forming means for forming a space closed in the width direction of the support within a distance of 5 mm from the support on the upstream side of the free fall landing portion of the coating liquid; and a support within the space. A curtain coating apparatus, comprising: air blowing means for blowing air to the air; and air suction means for sucking air.