JPH0757338B2 - Application method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to photographic light-sensitive materials such as photographic film and photographic paper, photoengraving materials, magnetic recording materials such as magnetic recording tape, pressure-sensitive recording paper, and heat-sensitive recording paper. In the production of a recording material such as a recording material, the invention relates to the improvement of the step of applying a liquid coating composition to a continuously running long flexible support (hereinafter referred to as "web"), and more specifically to an improved bar coating method and roller. It relates to a coating method.

[Conventional technology]

Conventionally, various methods have been proposed as a method for applying a coating liquid to a web that is continuously running. Generally, in the coating process, a portion that transfers the coating liquid to the web (hereinafter,
It is called "application system". ) And a portion for measuring the coating liquid transferred to the web to a desired coating amount (hereinafter referred to as “measuring system”), the coating method is classified according to the difference between the application system and the measuring system. It was

Based on the difference of application system, roller coating method,
An air knife coating method, a blade coating method, a bar coating method and the like have been known based on the difference in the measuring system such as the dip coating method and the counten coating method. In addition, the extrusion coating method, the bead coating method, and the curtain coating method have been known as those in charge of application and measurement in the same portion.

Of these coating methods, the bar coating method or the roller coating method transfers excess coating liquid to the web, and then the excess coating liquid is applied by a bar or roller that is stationary or is rotating at a lower peripheral speed in the opposite direction to the web. It has been widely used because it has a characteristic that a coating liquid is scraped off to obtain a desired coating amount, and a thin device can be coated at high speed with a simple device and operation.

For example, FIG. 7 is a schematic view showing an example of a bar coating device using a conventional coating rod for a coating device according to the present invention, in which coating is performed in the same direction as the web 1 which is continuously run or in the opposite direction. The rod 2 is rotated. A bar supporting member 3 is provided over the entire length of the bar 2, and has a function as a liquid feeder that prevents the bar 2 from being bent and supplies the coating liquid 4 to the bar 2. That is, the coating liquid 4 is supplied from the liquid supply port 5 provided in the bar support member 3 to the dam member 6, and the liquid supply guide groove 7 is formed.
It is supplied into the inside and is picked up by the rotating bar 2 and applied to the web 1. At this time, the web 1 and the bar 2
The coating liquid 4 is weighed at the contact portion with the coating liquid, only a desired coating amount is coated on the web 1, and the rest flows down to form a liquid pool 8 together with the newly supplied coating liquid 4. Therefore, in a steady state, the coating liquid 4 is applied to the web 1 via the liquid pool 8.

In the case of this coating method, since the edge portion of the web 1 is thickly coated, the following method is disclosed as a measure for preventing thick coating.

That is, a method of scraping off the coating liquid with a blade so that the thick coating portion of the web does not become thick coating (JP-A-60-225669) or a method of scraping off the thick coating portion with air of the coating liquid (JP-A-54-54). No. 142248) is disclosed.

[Problems to be solved by the invention]

However, when the coating speed is increased or the flow rate is increased, as shown in FIG. 8, the coating liquid 4 has a swelling shape on the end face 11 of the web 1 at the upper part of the liquid pool 8 and is remarkably formed. In this case, as shown in FIG. 9, the coating liquid 4 also adheres to the edge 9 of the anti-coating surface 12 of the web 1 (referred to as backside). Therefore, a large amount of the coating liquid 4 adheres to the end surface 11 of the coated web 10 as shown in FIG. 10, and further the coating liquid 4 adheres to the edge 9 of the non-coating surface 12 as shown in FIG. Becomes

In the latter case, the downstream pass rolls are naturally polluted, and in the former case, the coating liquid rises up the end surface 11 due to the surface tension effect, etc.
Of the liquid on the side of the coating, or the liquid swells on the side opposite to the coating surface 12 to contaminate the following pass rolls and the back surface of the support, and the excess coating liquid adheres to the edge of the web to cause edge of the web. Will result in a thick coating.

As a measure for preventing the back surface of the support from being soiled, the present inventors have formed a coating rod as shown in FIG. 3 and a weir member provided in a coater for supplying a coating liquid to the coating rod. A method in which air is blown to the cross-linking portion of the coating liquid from the inside on the side opposite to the coating surface of the support toward the edge of the support (application by the present applicant, Japanese Patent Application No. 62-2481).
No. 33). Immediately after the coating amount is formed by the coating roller or the coating rod, a method of blowing air from the outside of the non-coated surface of the edge of the support to the end surface of the edge of the support (application by the present applicant, Japanese Patent Application No. 62-248132). issue). Alternatively, a method has been proposed in which the coating liquid on the coating rod or coating roller outside the edge of the support, which is in contact with the coating rod or coating roller and the support, is sucked by a suction nozzle.

However, in the system shown in Japanese Patent Application No. 62-248132, the coating liquid is immediately transferred to the coating liquid bridging portion formed by the coating rod or the like and the support against the phenomenon of the coating liquid.
At the time of blowing the air, the liquid also circulates on the back surface, which is insufficient as a countermeasure.

Further, according to the method disclosed in Japanese Patent Application No. 62-248133, it is possible to prevent the occurrence of the backing phenomenon which occurs at the coating solution cross-linking part, but when the coating solution is composed of a quick-drying solvent. When the coating liquid dries, a surface defect occurs due to the dry matter or the weir member 6 shown in FIG. 3 dries.

Furthermore, according to the method disclosed in Japanese Patent Application No. 62-248134,
62-248132 and Japanese Patent Application No. 62-248133 can solve the above-mentioned problems, but there is a problem that the suction nozzle is used when it is used for a long time and the cost is increased due to the use of a cleaning liquid, especially when an expensive solvent is used. is there.

An object of the present invention is to solve the above problems and provide a coating method that prevents the coating liquid from drying and does not wrap around the back side of the support or stain the support by adhering to a downstream pass roller. To do.

[Means for solving problems]

Such an object of the present invention is a method of applying a coating liquid to a support that continuously travels using a coating rod,
It is contained in the coating solution from the inside on the side opposite to the coating surface of the support, in the bridge portion of the coating solution formed by the coating rod and the dam member provided in the coater for supplying the coating solution to the coating rod. This is achieved by a coating method characterized in that air containing a large amount of the vapor of the solvent is blown toward the edge of the support.

The coating liquid in the present invention is not particularly limited, and water or an organic solvent liquid of a polymer compound, a pigment water dispersion liquid, a colloidal solution or the like can be used. The physical properties of the coating liquid are also not particularly limited, but it is suitable that the viscosity of the coating liquid when spraying a gas toward the edge of the support is low, and a coating liquid of 100 cp or less, particularly 50 cp or less is suitable. ing.
The surface tension is not particularly limited, but particularly preferable results are obtained at 50 dyne / cm or less.

The web in the present invention includes paper, plastic film, resin coated paper, aluminum web, synthetic paper and the like. The material of the plastic film is
For example, polyolefins such as polyethylene and polypropylene, vinyl polymers such as polyvinyl acetate, polyvinyl chloride and polystyrene, polyamides such as 6,6-nylon and 6-nylon, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate. , Cellulose, cellulose triacetate, cellulose diacetate, etc. are used. As a resin used for resin coated paper, polyolefin such as polyethylene is typical,
It is not necessarily limited to this.

Although the thickness of the web is not particularly limited, a web having a thickness of about 0.01 mm to 1.0 mm is advantageous from the viewpoint of handling and versatility.

The air blown in the present invention has an air jet-like pressure or wind speed. 1 to 15 at the edge of the support
Determine the air volume, air pressure, and nozzle position so that a wind speed of approximately m / sec can be obtained.

[Action]

In the method of applying a coating liquid to a continuously traveling support using the coating rod of the present invention, the coating rod is formed by a dam member provided in a coater for supplying the coating liquid to the coating rod. By blowing air containing a large amount of the vapor of the solvent contained in the coating solution toward the edge of the support from the inside of the side opposite to the coating surface of the support, the coating solution is cross-linked. The coating liquid can be made to have a low viscosity without being dried, and can be surely extruded or blown out to the outside of the cross-linking portion to reduce the amount of the coating liquid adhering to the back side and the end surface of the support.

[Embodiment]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partial side sectional view showing the relationship between a solvent vapor generator and a jet nozzle around a coating device according to an embodiment of the present invention.

The bar coating apparatus itself is exactly the same as that shown in FIG. 3, except that the solvent vapor jet nozzle 13 is provided above the rod 2 and the liquid pool 8 in the bar coating apparatus.
An opening 14 such as a slit is provided at the tip of the ejection nozzle 13.

The gas supplied to the jet nozzle 13 is such that an air 20 is supplied to the upper portion of the solvent liquid level in the solvent evaporator 18 as shown in FIG. 1 by a compressor or the like so that a large amount of solvent is contained in the air.

In order to contain a large amount of solvent vapor in the air in the present invention, the solvent evaporator 18 is heated by a jacket 22 or the like as shown in FIG. 2, or the passage passage of air as shown in FIGS. Is bent using a jammer plate 23 or the like to increase the passage time at the generators 18 and 19, and the like. Alternatively, various methods such as positively contacting gas-liquid with a packed tower may be used.

In the present invention, the air containing the evaporation of the solvent is supplied from a compressor, a blower or the like (not shown) as an air supply source to a solvent vapor generator 18 having a solvent 19 therein via a tube 17a or the like. The air that has passed through the solvent vapor generator 18 is supplied to the ejection nozzle 13 via the tube 17b. Use a method such as overflow 24 for the solvent vapor generator 18 so that a certain amount of liquid is always stocked, or make enough solvent for each production to store it in the container at the start. To do.

As the solvent 19 used in the present invention, it is safe to use a solvent contained in the coating liquid against coating failure and the like, and a solvent having a high content rate is usually used for the coating liquid.

Further, it is preferable to use a rubber-based material having good heat insulating properties for the tubes 17a and 17b.

The air jetted from the opening 14 at the tip of the jet nozzle 13 causes the liquid rise shown in FIGS. 8 and 9 formed by the rise of the liquid pool 8 to be evaporated by the air jet containing the solvent as shown in FIG. It is possible to reduce the amount of the coating liquid applied to the end face 11 by coating, and the end face after coating is also scraped off as shown in FIG.

As shown in FIG. 3, the jet nozzle 13 used in the embodiment is preferably applied to the edge of the web 1 at an angle θ with respect to the anti-application surface 12 of the web 1, and the angle is more preferably 20 to
It is 70 °. If the angle is too small, it will be insufficient to remove the swell of liquid, and if the angle is too large,
Similarly, it becomes insufficient to remove the swell of the liquid, and further the liquid pool 8 is disturbed.

It is usually preferable to use a narrow slit as the opening 14 of the nozzle 13, and the clearance C of the opening is 0.2 to 5 mm.
Is desirable. The width 1 of the slit depends on the structure of the coater, the diameter of the rod, etc., but the diameter of the rod 2 is 15 mm.
In this case, it is preferable that the width is 10 to 20 mm. The wind velocity at the tip is preferably 5 to 30 m / sec.

〔The invention's effect〕

The present invention relates to a method of applying a coating liquid to a continuously traveling support using a coating rod, which is formed by the coating rod and a dam member provided in a coater for supplying the coating liquid to the coating rod. By a coating method characterized in that the cross-linked portion of the coating liquid is sprayed with air containing solvent vapor contained in the coating liquid from the inner side of the non-coated surface side of the support toward the edge of the support, Prevents the backing of the edge of the web without causing the liquid near the rod and the dam plate to dry, and also prevents thick coating of the edge,
Furthermore, high-speed coating and drying became possible, and the quality could be improved.

[Brief description of drawings]

FIG. 1 is a system diagram from a solvent vapor generator to an ejection nozzle of one embodiment relating to the coating method of the present invention, FIG. 2 is another example of the solvent vapor generator, and FIG. 3 is solvent air according to the present invention. 4 is a partial front view of the air-jetting nozzle and the coating device, FIG. 4 is a partial front view of the air-jetting nozzle, FIG. 5 is a cross-sectional view of the edge of the web immediately below the air-jetting nozzle of the present invention, and FIG. 6 is FIG. FIG. 7 is a side sectional view of a coating device according to a conventional coating method, and FIGS. 8 and 9 are sectional views of a coating state of the coating liquid on the edge of the web in the liquid pool. FIGS. 10 and 11 are sectional views of the edges of the webs of FIGS. 8 and 9 after coating. 1 ... Web 2 ... Coating rod (bar) 3 ... Bar support member 4 ... Coating liquid, 5 ... Supply port 6 ... Dam member, 7 ... Liquid supply guide groove 8 ... Liquid pool, 9 ... … Edge 10 …… Coated web 11 …… End surface, 12 …… Uncoated surface 13 …… Spout nozzle, 14 …… Opening 15 …… Connecting pipe, 16 …… Supporting metal fitting 17a, 17b …… Tube 18 …… Solvent vapor generator 19 …… Solvent, 20 …… Air 21 …… Hot water, 22 …… Jacket 23 …… Weir 24 …… Overflow port

Claims (1)

[Claims] 1. A method of applying a coating liquid to a continuously traveling support using a coating rod, comprising: a coating member; and a dam member provided in a coater for supplying the coating liquid to the coating rod. A coating method, characterized in that air containing a vapor of a solvent contained in the coating liquid is blown onto the cross-linked portion of the coating liquid to be formed from the inside of the support on the side opposite to the coating surface.