JPH11262715A - Curtain coating method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curtain coating method and an apparatus therefor capable of carrying out stable coating by preventing roll contamination and coating defect occurrence, and preventing air flow attendance from occurring on the web surface at the time high speed coating. SOLUTION: In a curtain coating apparatus for forming a coating layer by bringing a curtain film 4 vertically dropping from a coater head 1 into contact with a continuously running web 5, the coater head 1 is an extrusion type and the curtain apparatus comprises a liquid receiving pan 12 to receive a coating liquid of a curtain film 4 before starting the coating and before stopping the coating and a movable type air cut apparatus 8 interlockingly moved with the liquid receiving pan 12. In this case, coating is carried out while keeping the distance between the air cut apparatus 2 and the liquid receiving pan 12 at a specified value. Moreover, the supply amount of the coating liquid before starting the coating and after stopping the coating is lowered to a regulated amount or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curtain coating apparatus widely used for coating, for example, a pigment coated paper for printing in the papermaking industry, and more particularly to a curtain coating apparatus provided with an air cutting apparatus suitable for high-speed coating. The present invention relates to an apparatus and a coating method using the curtain coating apparatus.

[0002]

2. Description of the Related Art A curtain coating apparatus is a so-called pre-metering type coating apparatus which performs measurement before performing a coating operation, and is a post-metering type in which an excess coating solution is supplied to a web and then measured to a specified amount. Unlike the coating method, the liquid composition of the coating liquid does not change with time, and a coated object of stable quality can be obtained for a long time. In addition, multi-layer coating is possible, and a step of scraping to a specified amount after supplying an excess coating liquid to the web is unnecessary, so that the upper limit of the coating speed is essentially higher than that of a post-metering type coating apparatus. Since it is high, it is possible to obtain a coating object efficiently.

As described above, since the curtain coating apparatus has many advantages, it can be used for photographic printing paper, magnetic recording paper, heat-sensitive recording paper, pressure-sensitive recording paper, ink-jet recording paper, thermal transfer recording paper, pigment-coated paper, and the like. This is a coating method used in various coating fields.

[0004] The problem with coating at a relatively high speed using a curtain coating apparatus is that as the coating speed increases, the amount of air entrained on the web surface and the speed of the entrained air increase, and the substrate-air Is not partially replaced with the solid-liquid interface of the base material-coating liquid, and a coating failure called an air entrainment phenomenon is observed.
For the purpose of reducing such a coating failure, a device (hereinafter, referred to as an air cut device) for shutting off air accompanying the substrate has been devised.

[0005] Incidentally, the installation position of the air cut device is restricted for the following reasons. That is, it is preferable to install the air cut device in the vicinity of the curtain film as is apparent from the purpose. However, a liquid receiving pan is indispensable for the curtain coating apparatus, and the liquid receiving pan becomes inevitably larger with an increase in the coating speed, and occurs with the start and stop of coating as described below. Since the excessive amount of application in the over-applied portion also increases, various measures have been taken to reduce this as much as possible, resulting in a considerable installation space. Therefore, the distance between the air cut device and the curtain film tends to increase as the coating speed increases.

At the start of coating in a curtain coating apparatus, a liquid receiving pan is provided between a curtain film and a web formed in advance, and all the coating liquid is supplemented by the liquid receiving pan. Is performed by bringing the curtain film into contact with the web.

On the other hand, the application is stopped by returning the liquid receiving pan to the position before the application and again shielding the curtain film from the web. In such a coating start and coating stop operation, as described in detail below, a portion where the coating liquid is excessively supplied to the web as compared with a specified amount (hereinafter, referred to as an excessive coating portion) occurs, and drying is not completed. Excessive coating after passing through the drying zone contaminates the rolls, complicating the coating operation and causing serious defects in quality, as well as significantly increasing production efficiency, such as the need to stop and clean the rolls. descend.

That is, the coating is started by moving and retreating a liquid receiving pan installed between a portion (hereinafter referred to as a lip) where the coating liquid is separated from the coater head and the web. At this time, the curtain film is cut by the end of the liquid receiving pan, and the cut end of the curtain film forms a liquid film thicker than the curtain film thickness due to the surface tension of the coating liquid. When this thick tip falls and contacts the web,
An excess coating portion is formed at the coating start portion where the coating amount becomes excessive.

[0009] The excessively coated portion formed on the web is in an insufficiently dry state in contact with the roll used for transporting the web, where the coated surface comes into contact after drying in a portion of a normal coating amount. Transfer to the surface of the roll. A part of the coating liquid transferred to the roll retransfers to the coating layer on the web surface, or disturbs and peels off the normal coating layer, thereby causing coating defects. Therefore, the formation of the over-applied portion adversely affects the quality of the coated object. Further, in order to remove the coating solution that has contaminated the rolls, the apparatus must be stopped, and the production efficiency must be significantly reduced.

When the coating is stopped, the liquid receiving pan is inserted between the curtain film and the web, and the curtain film is cut again by the end of the liquid receiving pan. However, the end of the liquid receiving pan cuts the curtain film. Later, the curtain film contracts due to its surface tension, resulting in a liquid dripping thicker than the normal curtain film thickness, and falls on the web to form an over-coated portion. Further, when the curtain film is cut, the coating liquid adheres to the end of the liquid receiving pan, falls as droplets on the web, and forms an excess coating portion. Therefore, the roll is contaminated by the coating liquid in the excess coating portion, as in the case of starting the coating. In this case, too, the cleaning work of the roll is forced,
This results in a decrease in production efficiency.

As a means for suppressing the formation of an excessively coated portion immediately after the start of coating and the stop of coating, the position of the liquid receiving pan used in the operation of starting and stopping coating is brought as close as possible to the web, and the excess amount of the overcoated portion is reduced. There are ways to minimize it. Although this method is effective, on the other hand, the liquid receiving pan has a minimum required height at the end of the liquid receiving pan because the liquid receiving pan also needs a function of a liquid receiving tank for receiving a certain amount of coating liquid. You need a wall. Therefore, even when the liquid receiving pan is brought close to the web, a point (hereinafter, referred to as a curtain film cutting point) at which the curtain film is cut at the end of the liquid receiving pan in order to start and stop the application (hereinafter, referred to as a curtain film cutting point), Hereinafter, the height of the curtain film cutting point) will be somewhat high.

In particular, in the case of high-speed coating in which the coating speed exceeds 1000 m / min, an extrusion-type coater head is usually used, in which the initial speed of the curtain film falling is high. This tendency is inevitably increased in order to collect a large amount of the coating solution. In JP-A-5-168999, as shown in the schematic view of the color pan of the curtain coating apparatus in FIG.
The cutting point of the curtain film is reduced by providing a coating liquid collecting section having a low wall for collecting a limited amount of coating liquid immediately before the start of coating and immediately after the stop of coating, outside of 2).

However, two problems remain in the method disclosed in this publication. One of them is to collect the leading end of the curtain film cut by the wall of the main liquid receiving pan, and to start coating after the curtain film is stabilized again. It is necessary to provide a sufficient minimum length. This length increases as the coating speed increases. As a result, the distance between the curtain film and the air cut device must also be increased, and the effect of the air cut device is reduced. The other is that even if a coating liquid recovery section with a low wall height is provided, the excess coating area is dried by the wall height in response to the supply amount of coating liquid that increases with high-speed coating. Sometimes it has to be higher than the permissible limit for not passing the drying zone incompletely and fouling the rolls.

[0014]

SUMMARY OF THE INVENTION One object of the present invention is to provide a curtain coating apparatus which uses a curtain film and an air-cutting apparatus in spite of using a liquid receiving pan which increases as the coating speed increases. Is reduced to the distance required for high-speed coating, and the coating speed is 1000 m /
The purpose is to stably perform high-speed coating exceeding min. Another object of the present invention is to reduce the excessively applied amount of the over-applied portion generated at the start and stop of the application to an allowable limit or less, so that the over-applied portion that is insufficiently dried is rolled. To prevent the occurrence of coating defects due to contamination of the rolls, and to prevent a decrease in production efficiency due to the cleaning of the rolls.

[0015]

Means for Solving the Problems As a result of intensive studies, the present inventors have invented the curtain coating method and the apparatus of the present invention. That is, the curtain coating apparatus of the present invention is a curtain coating apparatus that forms a coating layer by bringing a curtain film that falls vertically from a coater head into contact with a continuously running web to form a coating layer when coating is started and stopped. A curtain coating device, comprising a movable air cut device interlocked with a liquid receiving pan for receiving a liquid.

In the present invention, the air cut device is provided with an air cut material at its end portion which comes into contact with the web over the entire width of the web, and the air cut material is made of a flexible film, a steel blade, or an elastic material. It is one kind selected from a hollow tube and a roll whose surface is made of an elastic body or metal.

The air cut device is a device in which a counter air nozzle is provided at the end portion over the entire width of the web.

The air cut device is an air suction type device that contacts the web over the entire width of the web.

The coater head of the curtain coating apparatus of the present invention is an extrusion type coater head.

In the curtain coating method of the present invention, the curtain coating method using the curtain coating apparatus is characterized in that the coating is performed while maintaining the distance between the air cutting apparatus and the curtain film at 5 to 80 mm. It is.

Further, in the curtain coating method according to the present invention, in the curtain coating method using the curtain coating apparatus, the supply amount of the coating liquid is reduced to 50 to 80% of a specified amount before the coating is started and before the coating is stopped. A curtain coating method characterized by the following.

[0022]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic view of a curtain coating apparatus showing one embodiment of the present invention. FIG.
, The web 5 is transferred from the transport roll 7 to the transport roll 1
5, the curtain film 4 formed by dropping vertically from the coater head 1 is in contact with the web 5 between the transport rolls 7 and 15. A liquid receiving pan 12 having a width exceeding the width of the curtain film 4 is attached to an upper portion of the web 5 where the curtain film 4 falls.
An air cut device 8 provided with an air cut material 9 is provided on the upstream side, and is a movable type in which the liquid receiving pan 12 and the air cut device 8 are interlocked.

The curtain head 1 according to the present invention may be of any type as long as it can form a curtain film 4 and form a coating layer on the web 5. Any type of hopper type, slot type, or extrusion type may be used, but as a high-speed coater head, an extrusion type coater head that has a manifold in the head and obtains a stable flow with a slit is available. preferable.

That is, in the present invention, the coating liquid prepared in advance is supplied from the storage tank 13 to the extrusion type coater head 1 by the liquid supply pump 14. The fed coating liquid fills the manifold 6, and in a narrow gap passing while being sent to the slit 2, the influence of the dynamic pressure by the liquid supply pump 14 is reduced, and the pressure distribution in the width direction is made uniform. Then, a curtain film 4 that falls vertically from the lip 3 is formed.

The vertical curtain film 4 having a uniform profile in the width direction comes into contact with the continuously running web 5 by a coating start operation described later, and is coated on the web 5. Here, the edge guide 16 is provided not to exceed the width of the coater head 1 and to exceed the width of the web 5, and the curtain film 4 is formed to exceed the width of the web 5. The coating liquid that falls beyond the width of the web 5 is collected in the liquid receiving tank 11,
After being returned to the coating liquid storage tank 13, the coating liquid is applied again. Also, when the application is interrupted due to cutting of the web 5 or the like, the application liquid is collected in the liquid receiving tank 11.

In the present invention, when the coating is started by moving the liquid receiving pan 12 separating the curtain film 4 from the web 5 and bringing the curtain film 4 into contact with the web 5, the liquid receiving pan 12 is again placed before coating. In any case where the application is stopped after returning to the position
The movable air cut device 8 installed on the upstream side of
A curtain coating apparatus having a mechanism for moving in the moving direction in conjunction with the liquid receiving pan 12 is used. This allows
Even in the case of using the liquid receiving pan 12 which increases as the coating speed increases, the distance between the curtain film 4 during coating and the air cutting device 8 is reduced and set to an optimum distance required for high-speed coating. Can be applied, and the coating speed can be reduced to 1
It is possible to stably perform high-speed coating such as exceeding 000 m / min.

In the present invention, the distance between the curtain film 4 and the air cutting device 8 is defined by the fact that the vertical line 17 that is lowered from the part where the curtain film 4 falls from the coater head 1 is the web 5.
And the distance a between the portion where the air cut material 9 contacts the web 5 (FIGS. 2 to 4). When the counter air nozzle 10 is used as the air cut material, the portion where the blown air contacts the web 5 and the vertical line 1
7 is the distance a between the portions contacting the web 5 (FIG. 5).

The distance between the curtain film 4 and the air cutting device 8 is 5 to 80 m according to the application speed and other conditions.
By selecting from the range of m, generation of a new air flow on the web surface due to running of the web 5 is prevented, and high-speed coating can be performed stably. The distance between the curtain film 4 and the air cut device 8 is more preferably 1
It is in the range of 0 to 30 mm.

If the length is less than 5 mm, the curtain film 4 may come into contact with the air cut device 8 due to the unsteady swing of the curtain film 4. In such a case, the curtain film 4 is cracked, an uncoated portion, an excessively applied portion, and the like occur, so that stable coating cannot be performed.

If it exceeds 80 mm, the effect of the air cutting device 8 is reduced, and the air flow newly generated on the web surface prevents the air from being replaced by the coating liquid on the web surface, and small air bubbles are generated. Crater-like unpainted failures (hereinafter referred to as craters) may occur on the web, and the stability of the curtain film may decrease, causing the curtain film to oscillate or crack. is there. In this case, a non-applied portion and an excessively applied portion occur, so that stable application cannot be performed.

In the meantime, when the air cut device is of a fixed type, the liquid receiving pan of the curtain coating device for performing high-speed coating with a coating speed exceeding 1000 m / min becomes large, so that the curtain film and the air cut device are used. It is extremely difficult to make the distance between them less than 80 mm.

As a method of moving the liquid receiving pan 12 at the start of coating and at the time of stopping coating, in the case of starting coating, the end of the pan 12 moves to a position beyond the position of the curtain film 4 in the traveling direction (downstream side) of the web 5. In the case of stopping the application, any method such as driving by a gear or moving by a hydraulic cylinder may be used as long as it can be moved to a position before the start of the application. Further, even if the moving speed is constant, the liquid receiving pan 12 is moved to prevent the application liquid from overflowing the side wall of the liquid receiving pan 12 due to the shock at the start and stop of the movement of the liquid receiving pan 12. At the start, the moving speed may be increased with time, and when the moving is stopped, the moving speed may be decreased with time. The moving speed is preferably 10
It is appropriately selected from the range of ~ 1000 cm / min.

In the method of moving the air cut device 8 used in the present invention, when the coating is started, the air cut device 8 is moved so that the distance a between the air cut device 8 and the curtain film 4 is 5 to 80 mm.
In a specific position within the range, it is possible to stop with an accuracy of ± 0.5 mm, in the case of application stop, if it can be moved to the position before the start of application, drive by a gear, Any method such as movement by a hydraulic cylinder may be used. Further, the moving speeds of the liquid receiving pan 12 and the air cutting device 8 may be the same or different.

In the method of interlocking the liquid receiving pan 12 and the air cutting device 8 at the time of starting the application, the two may be started to move at the same time, and the movement of the liquid receiving pan 12 is started by a mechanical signal or an electric signal. The movement of the air cut device 8 may be automatically started based on the detected signal. Also,
After visually checking the start of movement of the liquid receiving pan 12, the start may be started manually. In order to avoid mistakes such as contact between the two, it is preferable to start the movement at the same time or automatically.

When the application is stopped, the operations are linked in accordance with the method described above. However, the liquid pan 12 and the air cut device 8
In order to avoid contact, the start of movement of the air cut device 8 needs to be detected or visually recognized, and the movement of the liquid receiving pan 12 needs to be started automatically or manually.

The moving speed of the air cutting device 8 may be constant. In addition, when approaching the curtain film 4, in order to prevent oscillation of the curtain film 4, the speed is reduced particularly in a region where the distance from the curtain film 4 is about 80 mm or less. It may be lowered over time.

One embodiment of the air cut device 8 provided on the upstream side of the curtain film 4 in the present invention is provided with an air cut material 9 which is always in contact with the web 5 in the entire width direction of the web 5 at its end. It is a form. As a result, web 5
Is shut off except for the part very close to the surface of the web. This effect does not depend on the coating speed, and the same effect is maintained even in the high-speed coating region.

The shape of the air cut material 9 used in the present invention is as follows.
Any shape may be used as long as the shape uniformly contacts the web 5 in the width direction of the web. For example, a blade, a shape in which a gentle curved surface facing upward is provided at a web contact portion of the blade (FIG. 2), a hollow tube, a shape in which the hollow tube is pressed and deformed from above and below (FIG. 3), or a roll ( 4) can be used. In particular, in the case of a roll, damage to the web can be avoided by rotating its surface in the same direction as the running direction of the web 5.

The material of the air cut material used in the present invention is preferably a soft and flexible material in consideration of the risk of damage to the web and cutting. Specifically, synthetic rubber,
Polymers such as natural rubber, silicone rubber, nylon, polyethylene, polypropylene, polyethylene terephthalate, polyurethane, polyvinyl chloride, and tetrafluoroethylene, and copolymers thereof are preferred. When a blade is used as the air cut material 9, a material in which the surface of a metal blade is coated with the above substance can be used. Similarly, when a roll is used as the air cut material, a material in which the surface of a metal roll is coated with the above substance can be used.

In the air cut device used in the present invention,
By depressurizing the enclosed space between the web and
It is possible to more completely shut off air entrained on the web surface.

Another embodiment of the air cut device 8 installed on the upstream side of the curtain film 4 in the present invention is a device in which a counter air nozzle 10 is provided at the end portion over the entire width of the web 5 in the width direction (FIG. 5). As a result, the air entrained on the web surface is removed by the air cut device 8 and the web 5.
Is pushed back into the closed space between them, and the entrained air can be cut off. Also in this case, it is preferable to reduce the pressure in the closed space between the air cut device 8 and the web 4.

The counter air nozzle 10 of the present invention
Any type of device can be used as long as air entrained on the web surface over the entire width of the web 5 can be pushed back to the closed space between the air cutting device 8 and the web 5. For example, a pipe having a diameter of 2 to 5 mm provided at an end of the air cut device 8 at intervals of 3 cm or less over the entire width in a pipe installed over the entire width in the width direction can be used. If the distance between the centers of the holes exceeds 3 cm, the air cut function is insufficient. Also, when the diameter is less than 2 mm, the air cut function is insufficient. If the diameter exceeds 5 mm, the amount of air blown out increases, and as a result, the amount of entrained air from the closed space between the air cutting device and the web increases, so that the effect of the air cutting device decreases. In order to avoid this, the amount of exhaust air from the closed space between the air cutting device and the web must be increased, which is disadvantageous in terms of the equipment cost of the air suction pump 18 and the power cost. The air pressure under the above conditions is appropriately selected from the range of 500 to 5000 mmAq depending on the application speed and other conditions.
Here, when it is less than 500 mmAq, the force for pushing back the air entrained on the web surface is insufficient, and the entrained airflow remains. If it exceeds 5000 mmAq, on the other hand, the force for pushing back the air becomes excessive, and an airflow is generated in the direction opposite to the running direction of the web, making it difficult to stably perform high-speed coating. Further, a pipe provided with a slit over the entire width of the pipe instead of the hole may be used. In addition, an air knife type can also be used. However, it is not limited to the illustrated device.

Air knife type counter air nozzle 1
When using the air cut device 8 provided with 0, the slit width of the air knife is usually selected from the range of 0.2 to 1.0 mm. The air pressure under these conditions is appropriately selected from the range of 500 to 5000 mmAq depending on the application speed and other conditions. Here, when less than 500 mmAq,
Lack of force to push back entrained air to the web surface leaves entrained airflow. If it exceeds 5000 mmAq, on the other hand, the force for pushing back the air becomes excessive, and an airflow is generated in the direction opposite to the running direction of the web, making it difficult to stably perform high-speed coating.

Another embodiment of the air cut device 8 installed on the upstream side of the curtain film 4 in the present invention is a web 5
This is an air suction type device that contacts the web over the entire width of the web (FIGS. 6 and 7). The contact surface of the air cut device 8 with the web is formed so that the contact start end and the contact end end with the web have smooth corners and a tetrafluoroethylene for the purpose of reducing the dynamic friction coefficient with the web. It is preferable to coat with such as. 6 and 7
The length of the portion not in contact with the web 5 shown as b in FIG.
It is selected from the range of 0 to 50 mm. If it is less than 10 mm, it is necessary to increase the negative pressure of the air suction, and the kinetic friction with the web 5 increases, so that the possibility of the web 5 pulsating increases. If it exceeds 50 mm, the deformation of the web 5 to the inside of the air cut device 8 increases, and the web 5
And the possibility of the web 5 pulsating increases.

As the liquid receiving pan 12 used in the present invention,
Any material may be used as long as it has a function of collecting the curtain film 4 over the entire width. For example, it may be composed of one application liquid recovery section (FIG. 8). However, as described above, a structure having a low-height coating liquid collecting section capable of collecting a limited volume of coating liquid immediately before the start of coating and immediately after stopping coating is provided upstream of the main liquid receiving pan. (FIG. 9) is preferred. Further, the coating liquid recovery section having a low wall height has an inclined structure (FIG. 10), so that it is possible to prevent the curtain film from being cut on the wall of the main liquid receiving pan. Further, it is also possible to adopt a structure in which the application liquid dropped in this portion is recovered by rotating and raising the rotating portion provided at the upper portion of the inclined portion as a fulcrum (FIG. 11). However, the invention is not limited to the illustrated device.

According to the present invention, when the coating is started, the application amount is reduced to 50 to 80% of the specified amount before the coating is started, and then the application amount is set to the specified amount. Raise to In the case of stopping the application, the application is stopped after the supply amount of the application liquid is reduced to 50 to 80% of the specified amount before the stop. By performing this operation, the following effects can be obtained, in addition to essentially reducing the amount of application of the over-applied portion that occurs when the application is started and stopped.

That is, the allowable limit of the height of the curtain film cutting point for preventing roll contamination due to the excessive amount of application of the excessively applied portion is about 9 mm. Therefore, the allowable limit of the height of the wall in the coating liquid collecting unit having a low wall is about 6 mm. In the case of high-speed coating in which the coating speed exceeds 1000 m / min, the supply amount of the coating liquid increases, so that the coating liquid may overflow from the coating liquid collecting section having a low wall height at this height. However, by employing the coating method shown in the present invention in which the supply amount of the coating liquid immediately before the start of application and the stop of application is reduced to 50 to 80% of the specified amount, the start of application and the end of application The coating liquid can be prevented from overflowing from the coating liquid collecting section having a low wall height. On the other hand, if the amount is less than 50% of the specified amount, the curtain film becomes too thin and the stability of the curtain film is impaired, such as tearing.

That is, by the above operation of the present invention, even when the coating liquid supply amount corresponding to the high-speed coating such that the coating speed exceeds 1000 m / min for the first time, the coating liquid is continuously provided upstream of the main liquid receiving pan. In addition, the height of the wall of the coating liquid collecting section where the wall height is low, which collects a limited volume of coating liquid immediately before the start of application and immediately after the stop, and the drying zone where the excess coating is not completely dried It is possible to keep it below the allowable limit for not passing and contaminating the roll.

The coating solution in the present invention includes a photographic emulsion solution in which silver halide is dispersed in an aqueous gelatin solution, and a coating solution for forming a magnetic recording material in which magnetic particles are dispersed in water or an organic solvent. As a coating liquid for forming a heat-sensitive recording material, one in which a color former and a developer are dispersed, as a coating liquid for forming a pressure-sensitive recording material, one in which microcapsules containing a color former or a developer are dispersed,
As a coating liquid for forming an inkjet recording material, one in which porous silica is dispersed, as a coating liquid for forming a pigment coated paper, such as one in which an inorganic or organic pigment is dispersed, regardless of the viscosity of the liquid, the solid content concentration, etc. Any coating liquid capable of performing curtain coating can be used without limitation.

Examples of the web used in the present invention include generally used high-quality paper, medium-quality paper, paper-change, coated paper, art paper, cast-coated paper, synthetic paper, resin-coated paper, plastic film, metal plate, and the like. A rubber plate, a cloth woven of natural or synthetic fibers, or the like can be arbitrarily selected and used.

With respect to the coating speed, the effect of the present invention is not particularly reduced as long as it is within a condition range in which ordinary curtain coating can be performed.
A range of 00 m / min is preferred. On the other hand, the liquid amount per unit time and unit width applied to the web, that is, the flow rate is not particularly limited as long as it is within the range of ordinary curtain coating conditions, but a range of about 4 to 20 liters / min / m is preferable. . More preferably, 5 to 15 liters /
min / m.

[0052]

The following examples are provided to further clarify the effects of the present invention, but the present invention is not limited to these examples. In the examples, all the numbers of parts indicate parts by weight, and unless otherwise specified, the concentration indicates the weight% of the solid concentration, and the coating amount indicates the coating amount after drying.

Example 1 A coating solution for forming an undercoat layer having a solid content of 61% was prepared with the following composition, and a basis weight of 60 g /
a fine paper of m ^2, as absolute dry coating amount of the 10 g / m ^2, was coated at a coating speed of 1000 m / min, to produce a primed base paper.

<Undercoating liquid formulation> Commercially available heavy calcium carbonate (Carbital 90) 70 parts Commercially available secondary kaolin (caobrite) 30 parts Commercially available polyacrylic acid-based dispersant 0.2 parts Commercially available phosphorylated starch 7 parts Commercially available styrene Butadiene latex 10 parts Sodium hydroxide 0.1 part

A coating liquid for forming an overcoat layer having a solid content of 55% with the following composition was prepared, and as shown in FIG.
The upstream side of the liquid receiving pan 12 of the type
With the use of a movable curtain coating apparatus having a tie air cut device 8 of FIG. 2 in conjunction with the above, the coating liquid supply amount was reduced to 80% of the specified amount immediately before the start of coating, and then coating was started.
Immediately thereafter, the supply amount of the coating liquid was increased to a specified amount. Further, immediately before the application was stopped, the application liquid supply amount was reduced to 80% of the specified amount, and then the application was stopped. The undercoated base paper thus obtained was coated at a coating speed of 1000 m / min at a coating rate of 15 g / m ² and dried to produce a pigment coated paper for printing. The distance between the air cut device 8 and the curtain film 4 was 80 mm, and the height of the curtain film cutting point was 9 mm. Further, the coating length was set to 10,000 m after the application was stopped after 5 minutes had elapsed from the start of the application, and after 20 seconds had elapsed, the application was restarted and the application was performed for 5 minutes.

<Composition of overcoat liquid> Commercially available heavy calcium carbonate (Carbital 90) 10 parts Commercially available primary kaolin (Ultra White 90) 45 parts Commercially available secondary kaolin (caobrite) 25 parts Commercially available cubic light calcium carbonate (Brilliant 15) 10 parts Commercial Satin White 10 parts Commercially available polyacrylic acid-based dispersant 0.2 parts Commercially phosphorylated ester starch 2 parts Commercially available styrene / butadiene latex 16 parts

Example 2 Using the curtain coating apparatus shown in FIG. 1, a pigment-coated paper for printing was carried out in exactly the same manner as in Example 1 except that the distance between the air cutting apparatus 8 and the curtain film 4 was 30 mm. To 10,0
00m.

Example 3 A pigment coated paper for printing was used in exactly the same manner as in Example 1 except that the distance between the air cut device 8 and the curtain film 4 was changed to 5 mm using the curtain coating device shown in FIG. To 10,00
0 m was manufactured.

Example 4 Using the curtain coating apparatus shown in FIG.
A pigment-coated paper for printing was prepared in the same manner as in Example 2 except that the supply amount of the coating liquid was reduced to 50% of the specified amount immediately before the stop of the coating, and the coating was started and stopped.
0 m was manufactured.

Example 5 [Production method of coating liquid] <Capsule dispersion liquid> 5 parts of 200 parts of high boiling oil (KMC-113; KMC-113) in which 5 parts of crystal violet lactone (CVL) were dissolved. The mixture was added to 250 parts of a styrene-maleic anhydride copolymer aqueous solution (pH 5.0) and emulsified using a high-speed stirring type emulsifier so as to have an average particle diameter of 6 μm.

Next, a 40% melamine-formalin precondensate aqueous solution (Sumitetsu Chemical Co., Ltd. Sumiretz Resin) 20%
Was added to the above emulsion, and the mixture was reacted for 2 hours while maintaining the temperature at 75 ° C. with stirring, then cooled to room temperature with 20% aqueous sodium hydroxide to pH = 9.0, and dispersed in 40% microcapsules. A liquid was obtained.

<Coating liquid> The microcapsule dispersion thus obtained was mixed with the following composition, and water was further added to adjust the solid content to 33%. The coating solution was prepared. 40% microcapsule dispersion 100 parts Wheat starch (average particle diameter 20 μm) 50 parts 48% carboxy-modified styrene butadiene copolymer latex 20 parts

In the same manner as in Example 2, the amount of the coating liquid supplied was reduced to 80% of the specified amount immediately before the start of coating and immediately before the stop of coating, using the curtain coating apparatus shown in FIG. the high-quality paper having a basis weight 40g / m ^2, 1000m / min
Was applied at a coating speed of 3.5 g / m ² to obtain a coating amount of 3.5 g / m ² , and 10,000 m of pressure-sensitive recording paper was manufactured.

Example 6 A mixture having the following composition was pulverized and dispersed by a sand mill until the average particle size became about 1 μm, and [Solution A] and [B
Liquid] was prepared. [Solution A] 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran 40 parts 25% aqueous polyvinyl alcohol solution 20 parts Water 20 parts [Solution B] bisphenol A 50 parts 2-benzyl Oxynaphthalene 50 parts 25% polyvinyl alcohol aqueous solution 50 parts Water 60 parts

Next, using the prepared [Solution A] and [Solution B], a coating solution for forming a thermosensitive recording material having the following composition and a concentration of 40% was prepared. [Solution A] 50 parts [Solution B] 250 parts Zinc stearate (40% dispersion) 25 parts 25% aqueous polyvinyl alcohol solution 205 parts Calcium carbonate 50 parts

A coating solution for forming an intermediate layer having the following composition was prepared. [Intermediate layer coating solution] Calcined kaolin (Engelhard; Ansilex) 100 parts Commercial styrene / butadiene copolymer latex (50% aqueous dispersion) 24 parts Phosphated starch (Nippon Shokuhin Kako; MS-4600, (10% aqueous solution) 60 parts Water 52 parts

Using a blade coating device, a basis weight of 40 g / m ²
The coating liquid for forming an intermediate layer was applied to a high-quality paper at a coating speed of 800 m / min so as to have a coating amount of 5 g / m ² , and then dried. In the same manner as described above, the coating liquid supply amount was reduced to 80% of the specified amount immediately before the start of coating and immediately before the stop of coating, and the coating amount was increased at a coating speed of 1000 m / min using the curtain coating apparatus shown in FIG. Coating and drying were carried out at 4 g / m ² to produce a thermosensitive recording paper of 10,000 m.

Comparative Example 1 A pigment coated paper for printing was used in exactly the same manner as in Example 2 except that the distance between the air cut device 8 and the curtain film 4 was changed to 100 mm using the curtain coating device shown in FIG. To 10,
000 m. The coating defect of Comparative Example 1 shown in Table 1 is a crater.

Comparative Example 2 Using the curtain coating apparatus shown in FIG. 1, coating was performed in exactly the same manner as in Example 2 except that the distance between the air cut device 8 and the curtain film 4 was 3 mm. When the distance between the cutting device 8 and the curtain film 4 is insufficient, the curtain film comes into contact with the air cutting device due to the steady steady swinging of the curtain film, and an uncoated portion is generated and normal coating can be performed. The application was abandoned.

Comparative Example 3 Using the curtain coating apparatus shown in FIG.
In the same manner as in Example 2 except that the application liquid supply amount was not reduced to 80% of the specified amount immediately before the stop of the application, the application was started with the application liquid supply amount being the specified amount, and the application was stopped,
10,000 m printing pigment coated paper was produced.

Comparative Example 4 Using the curtain coating apparatus shown in FIG.
The application was performed in exactly the same manner as in Example 2, except that the application liquid supply amount was reduced to 40% of the specified amount immediately before the application was stopped, and the application was stopped. As a result, the uncoated portion was generated and normal coating could not be performed, and the coating was abandoned.

Comparative Example 5 Using the curtain coating apparatus shown in FIG.
In the same manner as in Example 5 except that the application liquid supply amount was not reduced to 80% of the specified amount immediately before the stop of the application, the application was started with the application liquid supply amount being the specified amount, and the application was stopped,
10,000 m of pressure-sensitive recording paper was manufactured.

Comparative Example 6 Using the curtain coating apparatus shown in FIG.
In the same manner as in Example 6 except that the application liquid supply amount was not reduced to 80% of the specified amount immediately before the stop of the application, the application was started with the application liquid supply amount being the specified amount, and the application was stopped,
Thermal recording paper of 10,000 m was manufactured.

The coated papers obtained in the above Examples 1 to 6 and Comparative Examples 1 to 6 were evaluated by the following evaluation methods, and the results are shown in Table 1. The item of the supply amount suppression rate in the table is a ratio (%) when the supply amount of the application liquid is reduced before the application is started and before the application is stopped.

[Coating Defects] The coating defects were detected from the start to the end of coating by a defect detection device installed in a curtain coating device, and evaluated by the length of the defects relative to the coating length. The coating defects that can be detected by the defect detection device are defects having uncoated portions such as streaks and scratches and over-coated portions such as dirt, and can be detected if the width of the defective portion is 0.3 mm or more. The length of the defect is 1 m before and after the defect, taking into account the margin before and after removing the defect.
Was added to the length. For example, if the actual length of the defect is
In the case of 0.1 m, the length of the defect was 2.1 m. (unit:%)

[Roll Soil] After the coating was completed, all the coating liquid adhering to the surface of the paper roll with which the coating surface first contacted was peeled off and collected, and dried with a hot air drier to determine the solid content. This was divided by the coating width of the web to determine the amount of solids adhered to the roll per unit coating width. (Unit: mg / mm)

[0077]

[Table 1]

[0078]

According to the evaluation results shown in Table 1 above, by using the curtain coating apparatus of the present invention and coating by the curtain coating method of the present invention, the coating can be performed stably even when the coating speed is extremely high. It can be carried out. Further, contamination of the mechanical roll for transporting the web with the coating liquid caused by the start and stop of the coating does not occur, and various coated papers free from coating defects can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a distance a between a curtain film and an air cut material.

FIG. 3 is a schematic side view of the vicinity of an air cut material of the curtain coating apparatus according to the embodiment of the present invention.

FIG. 4 is a schematic side view of the vicinity of an air cut material of the curtain coating apparatus according to the embodiment of the present invention.

FIG. 5 is a schematic side view of the vicinity of an air cut material of the curtain coating apparatus according to the embodiment of the present invention.

FIG. 6 is a schematic side view of an air suction type air cut device of a curtain coating device according to an embodiment of the present invention.

FIG. 7 is a schematic side view of an air suction type air cut device of a curtain coating device according to an embodiment of the present invention.

FIG. 8 is a schematic side view of a liquid receiving pan of the curtain coating device.

FIG. 9 is a schematic side view of a liquid receiving pan of the curtain coating device.

FIG. 10 is a schematic side view of a liquid receiving pan of the curtain coating device.

FIG. 11 is a schematic side view of a liquid receiving pan of the curtain coating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coater head 2 Slit 3 Lip 4 Curtain film 5 Web 6 Manifold 7, 15 Conveyance roll 8 Air cut device 9 Air cut material 10 Counter air nozzle 11 Liquid receiving tank 12 Liquid receiving pan 13 Storage tank 14 Supply pump 16 Edge guide 17 Vertical Line 18 Air suction pump 19 Air suction control valve

Claims (7)

[Claims] 1. A curtain coating apparatus for forming a coating layer by bringing a curtain film, which falls vertically from a coater head, into contact with a continuously running web, a liquid for receiving a coating liquid for the curtain film at the start and end of coating. A curtain coating device comprising a receiving pan and a movable air cut device interlocked with the liquid receiving pan. 2. An air-cut device, wherein an air-cut material is provided at the end of the air-cut device so as to contact the web over the entire width of the web, and the air-cut material is a flexible film, a steel blade, or an elastic hollow tube. And a member whose surface is selected from a roll made of an elastic material or a metal.
The curtain coating apparatus according to the above. 3. The curtain coating device according to claim 1, wherein the air cut device is a device provided with a counter air nozzle at the end thereof over the entire width of the web. 4. The curtain coating device according to claim 1, wherein the air cut device is an air suction type device that contacts the web over the entire width of the web. 5. The curtain coating apparatus according to claim 1, wherein the coater head is an extrusion coater head. 6. A curtain coating method using a curtain coating apparatus according to claim 1, wherein the coating is performed while maintaining a distance between the air cutting apparatus and the curtain film at 5 to 80 mm. Method. 7. A curtain coating method using a curtain coating apparatus according to claim 1, wherein a supply amount of the coating liquid is set to a specified amount of 50 to 80 before starting coating and before stopping coating.
%. A curtain coating method characterized in that the amount is reduced to 0.1%.