JP2003071353A - Coating method and coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method and a coating apparatus in which the occurrence of coating defects is avoided by preventing the swelling of a curtain film without making the curtain film rock so as to stabilize the curtain film. SOLUTION: In the slide curtain coating method for coating a continuously traveling supporting body by making a coating liquid free-fall as the curtain film, the pressure of a space in the upstream side in the traveling direction of the supporting body intercepted by the curtain film is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of silver halide photographic light-sensitive materials, magnetic recording materials, pressure- and heat-sensitive recording papers, art papers, coated papers, and ink jet recording sheets. , Called the web)
The present invention relates to a method and an apparatus for applying a curtain film by collision-crosslinking with a curtain film.

[0002]

2. Description of the Related Art A slide bead method or an extrusion method is generally known as a multi-layer simultaneous coating method, but in recent years, a curtain coating method has been widely used in accordance with a demand for high speed coating. The curtain coating method is a method in which a curtain film is freely dropped on a continuously running web to be coated, and is disclosed as a basic technique in Japanese Patent Publication Nos. 49-24133 and 49-35447.

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 solid-gas interface of the web-air is not sufficiently replaced with the solid-liquid interface of the web-coating liquid, so-called air entrainment. The phenomenon called is beginning to be seen. The entrainment of air causes the curtain film to sway and swells in a curved shape on the downstream side in the web traveling direction, causing application unevenness such as vertical streaks and unevenness of the horizontal step, and also the amount of entrained air increased. In this case, the coating liquid may eventually fly to the web without being crosslinked.

A method and an apparatus for removing air entrained in a web have been disclosed for the purpose of suppressing such a phenomenon and performing coating at a high speed without coating failure. For example, Japanese Patent Publication Sho 49
JP-A-35447 discloses that a shield plate is provided close to the web on the upstream side of the curtain film, and an air cut device having a slit-shaped suction nozzle is provided. However, removal of entrained air is insufficient with the shield plate, and in order to improve the removal capability of entrained air, the shield plate must be brought as close as possible to the web. In this case, the shield plate contacts the web. Therefore, there is a risk that the web may be scratched and the web may be cut by coming into contact with the joint between the webs.

Further, in the air cut device having the slit-shaped suction nozzle, the dynamic contact line (curtain film) of the curtain film (curtain film) is increased when the suction force is increased in order to suppress an increase in the amount of entrained air and a swelling of the curtain film due to the speedup. However, there is an inherent problem that the curtain film starts to oscillate due to the fact that the cross-linking point to the web) is attracted to the air cut device.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to prevent the curtain film from bulging without swinging the curtain film. Accordingly, it is an object of the present invention to provide a coating method and a coating device that stabilize the curtain film and prevent the occurrence of coating defects.

[0007]

The above objects can be achieved by the following coating apparatus and coating method. (1) In a slide curtain coating method in which a coating liquid is freely dropped as a curtain film and is applied onto a continuously running support, the pressure in the space upstream of the support transport direction, which is blocked by the curtain film, is reduced. Curtain coating method. (2) In a slide curtain coating device that applies a coating liquid as a curtain film to a free fall to apply it on a continuously running support, a decompression device is provided in a space surrounded by the curtain film, the slide curtain head, the backup roll, and the air cut device. A curtain coating device characterized by having. (3) The curtain coating apparatus according to the coating apparatus of (2), characterized in that a pressure adjusting chamber including at least two chambers is provided in the space, and a pressure reducing device is installed in the upstream chamber. (4) The curtain coating apparatus according to (2) or (3) above, wherein the decompression opening of the decompression device has a slit shape. (5) A curtain coating apparatus according to the coating apparatus of (4), wherein a porous member is loaded in the decompression opening. (6) In a slide curtain coating method in which a coating liquid is freely dropped as a curtain film and is applied onto a continuously running support, non-contact distance sensors are provided opposite to each other within a curtain film formation range, and the distance is obtained from the distance sensor. It is characterized in that the position of the curtain film is automatically adjusted by adjusting the depressurized state of the space upstream of the support film conveying direction, which is blocked by the curtain film, based on the comparison calculation result of the curtain film position signal and the target value. Curtain coating method.

Conventionally, the simplest device for removing entrained air is the shield plate described in Japanese Patent Publication No. 49-35447. The amount or velocity of entrained air generated as the web travels is greatest near the web and diminishes with distance from the web. Since the entrained air has a large flow velocity within 500 μm from the web, it was not possible to sufficiently remove the entrained air generated near the web even when the conventional shield plate was brought close to the web.

If these shield plates are brought as close as possible to the web, the risk of contact with the web increases.
Therefore, a method of sucking and blowing air that accompanies the web has been proposed, but it has the problems described above.

As a result of diligent experiments by the present inventors, in order to completely prevent the curtain film from bulging without rocking the curtain film for high-speed coating exceeding 300 m / min,
It has become clear that it is extremely effective to remove the air layer entrained in the web and reduce the pressure in the upstream side space (back side space) of the curtain film.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration side view showing an example of the curtain coating apparatus of the present invention. A thin layer of the coating solution is formed on the slide surface 8 and is allowed to fall freely as a curtain film 5 along a pair of edge guides (not shown) to collide with the web 4 supported by the backup roll 3 and continuously running. Application is performed.

According to the present invention, the space on the upstream side in the conveying direction of the support, which is blocked by the curtain film, that is, the curtain film 5 is used.
And a pressure reducing means for reducing the pressure in the space surrounded by the slide curtain head 1, the backup roll 3 and the air cut device 2 (hereinafter referred to as the curtain film rear side space). For example, the decompression device 41 is installed in the space. The decompression pump 7 is connected to the decompression device 41 by piping, and the pressure control valve 6 is provided in the middle of the pipe connecting the decompression device 41 and the decompression pump 7.
To provide. The valve opening of the pressure control valve 6 is adjusted so that the curtain film bulge amount L becomes zero.

In the present invention, reducing the pressure in the space behind the curtain film means that when the curtain film 5 bulges convexly in the running direction of the web 4, the gauge pressure in the space behind the curtain film shifts to the plus side. This means that the pressure shifted to the plus side is reduced, but does not mean that the pressure in the space behind the curtain film is made negative. The preferred pressure range of the space behind the curtain film is ± 0.1 mmAq, more preferably ± 0.05 mm
It is Aq.

FIG. 2 is a schematic side view showing another embodiment of the present invention (a pressure adjusting chamber 21 having a two-chamber structure is installed in the space behind the curtain film). There are two pressure adjusting chambers 21 (the upstream chamber is 21a and the downstream chamber is 21b), and the upstream chamber 2
A decompression device 41 is installed at 1a. By installing the depressurizing device 41 in the chamber 21a on the upstream side of the pressure adjusting chamber 21, the air flow in the pressure adjusting chamber 21 becomes uniform, so that the swing of the curtain film 5 due to the depressurizing operation can be suppressed. .

When three or more pressure adjusting chambers 21 are provided,
A single or a plurality of decompression devices 41 can be installed in a chamber other than the most downstream chamber closest to the curtain film 5. It is preferable that the pressure adjusting chamber 21 is 2 or more and 4 or less, and the depressurizing device 41 is installed in the most upstream chamber.

FIG. 4 is an enlarged side sectional view of the decompression device 41 according to the present invention. The decompression pump 7 is connected to the decompression manifold 43 of the decompression device 41 via a pipe. The pressure head is lowered by the rapid reduction of the cross section from the decompression manifold 43 to the slit 42, so that the air flow in the width direction of the decompression device 41 is made uniform.

The slit 4 of the pressure reducing device 41 in the present invention
The clearance No. 2 needs to be set narrow from the viewpoint of making the air flow in the width direction of the decompression device 41 uniform, and is preferably set to 500 μm or less when the porous member is not loaded in the slit 42. When the porous member is loaded, there is no limitation on the clearance of the slit 42, as long as a space for loading the porous member can be secured.

As the material of the porous member, for example, a synthetic resin foam such as glass wool, urethane, felt, sponge, a filter material made of non-woven fabric or paper or a filler of glass fiber, an organic / inorganic substance composite material, etc., the slit 42. There is no particular limitation as long as it lowers the internal pressure head and makes the air flow uniform in the width direction of the slit 42.

FIG. 3 is a schematic side view showing another embodiment of the present invention (with a device for automatically adjusting the amount of bulging of the curtain film). The bulging amount L of the curtain film is detected by the non-contact distance sensor 31 installed on the front surface of the curtain film 5. The curtain film bulge amount L is transmitted to the calculator 32, and a comparison calculation with a preset target value is performed inside the calculator 32. The comparison calculation result is converted into a valve opening signal and transmitted to the pressure control valve 6.

The operation of the pressure control valve 6 is performed until the deviation inside the calculator 32 becomes zero, that is, the curtain film bulge amount L becomes zero. In practice, from the viewpoint of preventing hunting, it is preferable that the deviation has a certain width, for example, a width of about ± 2 mm.

Since the swelling state of the curtain film 5 is continuously monitored without manual intervention and the curtain film swelling amount L is automatically adjusted, not only the adjustment work time at the start of coating can be shortened but also the process conditions can be changed. For example, it is effective when the coating speed is changed or when disturbance occurs, for example, when the curtain film 5 swings due to passage of a joint or when the ambient air flow is disturbed. Since it is not necessary to manually adjust the curtain film bulge amount L in the related art, it is suitable for a dark room coating operation in manufacturing a photographic photosensitive material.

As the non-contact distance sensor 31 in the present invention, any sensor, such as an ultrasonic type, a laser type, an eddy current type, can be used as long as it can be placed in non-contact with the curtain film 5. When the coating liquid is a photosensitive material, it is preferable to use an ultrasonic displacement sensor.

As an air-cutting device in the present invention, for example, a device having a shield plate installed in the vicinity of the web on the upstream side of the curtain film and a slit-shaped suction nozzle described in JP-B-49-35447, JP-A-3-12365.
No. 7, Dohei 6-39331, Dodaira 10-277458
Any of the entrained air removal devices provided by the decompression chamber installed close to and facing the backup roll described in Japanese Patent Laid-Open Publication No. JP-A-2003-13853 can be used, but is not limited to these as long as the air layer entrained in the web can be separated and removed.

[0024]

[Example] Example 1 Coating was performed according to the following conditions. Web: 160 μm thick polyethylene resin coated paper Web width: 1500 mm Curtain film width: 1490 mm Curtain height: 80mm

Top protective layer of coating liquid (viscosity 40 cP, surface tension 30 dyne / cm (37
℃)) Coating amount: 10g / m ² Coating solution Lower layer Silver halide emulsion layer (viscosity 45cP, surface tension 33dyne / c
m (37 ℃)) Coating weight: 50g / m ²

As shown in FIG. 1, when decompressing the space on the back side of the curtain film, a decompression device 41 was installed at the center of the space. As shown in FIG. 2, when the pressure regulating chamber 21 having a two-chamber structure was provided in the space behind the curtain film, the decompression device 41 was installed in the upstream chamber. A porous member made of polyester fiber was loaded in the slit 42 of the decompression device 41.

When the upstream air-curving plate shown in FIG. 5 is used, the distance from the web is 300 μm at the minimum portion.
It was adjusted to be m. When the air cut plate having the slit shown in FIG. 6 was used, the gap between the web and the tip of the slit was adjusted to 300 μm, and a suction pump (not shown) was connected to the slit to perform the suction operation.

The installation position of the air-cutting device shown in FIGS. 5 and 6 was set at a position 3 cm upstream from the top of the backup roll 3 along the web 4.

Evaluation criteria for the swing of the curtain film and the swelling of the curtain film are as follows. ○: There is no problem in operation. Δ: Minor substance that does not cause uneven coating. X: Level at which coating unevenness occurs.

The results of the coating test are shown in Table 1.

[0031]

[Table 1]

Example 2 As shown in FIG. 3, a coating test was conducted under the same conditions as in Example 1 except that a control system including a non-contact distance sensor 31 and a calculator 32 was added. Non-contact distance sensor 3
1 is an ultrasonic displacement sensor (U
D310) was used. The sensor was placed facing the curtain film 5 at a position of 30 cm downstream from the center of the curtain film 5 in the width direction. As a result of being able to automate the adjustment work of the curtain film bulge amount L, which was conventionally required by human, the curtain film bulge amount L of the photographic light-sensitive material at the start of coating in the dark room and at the time of changing the coating speed and flow rate can be improved. We were able to halve the product loss that was constantly occurring due to the adjustment work.

[0033]

According to the present invention, by suppressing the bulging of the curtain film without swaying the curtain film, the curtain film is stabilized and the swelling of the curtain film and the occurrence of coating defects caused by the swaying of the curtain film are prevented. I was able to prevent it. In particular, a remarkable effect was observed at the time of high-speed coating such that the coating speed exceeded 300 m / min.

[Brief description of drawings]

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

FIG. 2 is a schematic side view showing another embodiment of the curtain coating device according to the present invention.

FIG. 3 is a schematic side view showing another embodiment of the curtain coating device according to the present invention.

FIG. 4 is an enlarged side cross-sectional view of a pressure reducing device according to the present invention.

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

FIG. 6 is a partially enlarged sectional view of a conventional curtain coating device.

[Explanation of symbols]

1 Slide curtain head 2 Air cut device 3 backup roll 5 curtain film 7 Decompression pump 21 Pressure adjustment chamber 31 Non-contact distance sensor 32 arithmetic unit 41 Pressure reducer 42 slits 43 Decompression manifold L Curtain film bulge

Claims (6)

[Claims] 1. A slide curtain coating method in which a coating liquid is applied as a curtain film onto a support that continuously travels by free fall, and the pressure in a space on the upstream side in the transfer direction of the support that is blocked by the curtain film is reduced. Curtain coating method characterized by the following. 2. A slide curtain coating apparatus which coats a coating solution as a curtain film on a support which is free-falling and continuously running, wherein the pressure is reduced in a space surrounded by the curtain film, the slide curtain head, a backup roll and an air cut device. A curtain coating apparatus having a device. 3. The curtain coating apparatus according to claim 2, wherein a pressure adjusting chamber including at least two chambers is provided in the space, and a pressure reducing device is installed in the upstream chamber. 4. The curtain coating apparatus according to claim 2, wherein the decompression opening of the decompression device has a slit shape. 5. The curtain coating apparatus according to claim 4, wherein a porous member is loaded in the pressure reducing opening. 6. A slide curtain coating method in which a coating liquid is applied as a curtain film onto a support that continuously travels by free fall, and a non-contact distance sensor is disposed oppositely within the curtain film formation range, and the distance sensor is The position of the curtain film is automatically adjusted by adjusting the depressurized state of the space upstream of the support film conveyance direction, which is blocked by the curtain film, based on the comparison calculation result of the obtained curtain film position signal and the target value. Curtain coating method.