JPH02277579A - Coating method - Google Patents

Abstract

PURPOSE:To eliminate the discontinuity of a coating soln. in high-speed coating and to reduce the consumption of the soln. by forming a part of the lip surface into a specified shape, reducing the clearance between the remainder and a backup roller gradually in the traveling direction of a web and supplying the soln. under such conditions. CONSTITUTION:The coating soln. is discharged by a extrusion-type liq. injector and applied on a substrate traveling around the backup roller 3. A part of the front lip surface 9 of the discharge port of the injector close to the discharge rear end is directed vertically or at an angle of <5 deg. to the radius connecting the center of the roller 3 and the liq. discharge port 7. Furthermore, the clearance between the remaining lip surface extending from the straight part having the width l3 and the roller 3 is gradually decreased in the web traveling direction. Since the angle alpha is sufficiently enlarged, the soln. from the discharge port is firstly compressed by the web 1, allowed to collide with the web, turned in parallel with the web traveling direction, compressed and then pushed out. Consequently, the soln. can also be pressed in parallel with the traveling direction of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of photosensitive materials such as photographic film and photographic paper, photolithographic materials, magnetic recording materials such as magnetic recording tape, pressure-sensitive recording paper, heat-sensitive recording paper, etc. Regarding the improvement of the process of applying a liquid coating composition (hereinafter referred to as "coating liquid") to a continuously running long flexible support (hereinafter referred to as "web"), more specifically, an improved extrusion coating method. Or it relates to a bead coating method.

[Conventional technology]

Conventionally, various methods have been proposed as methods for applying a coating liquid to a continuously running web.

Generally, the coating process is divided into a part that transfers the coating liquid to the web (hereinafter referred to as the "application system") and a part that measures the coating liquid transferred to the web to the desired coating amount (hereinafter referred to as the "measuring system"). Therefore, coating methods were classified based on the differences in application type and measurement type.

Based on differences in application systems, roller coating methods, dip coating methods, fountain coating methods, etc., and based on differences in metering systems, air knife coating methods, blade coating methods, bar coating methods, etc. have been known. Also, assuming that the same part is responsible for application and measurement,
Extrusion coating methods, bead coating methods, and curtain coating methods were known. Among these methods, the extrusion coating method and bead coating method, in which liquid is discharged from a slot and coated onto a traveling support by winding it around a backup roller, have been used as precision coating methods that do not come into direct contact with the support. .

The above coating method is disclosed in, for example, Japanese Patent Publication No. 45-12390,
Regarding a multilayer coating device as disclosed in Japanese Patent Publication No. 46-26236, Japanese Patent Publication No. 50-142643
The coating method for a single layer disclosed in Japanese Patent Application Laid-open No. 56-95363, Japanese Patent Application Laid-open No. 62-41
Many patent applications have been filed, including a coating method and apparatus in which the ejection slot is located upward, as disclosed in Japanese Patent No. 0776.

[Problem to be solved by the invention]

However, one problem with the coating method using the extrusion coater is that the amount of coating that can be coated increases as the speed increases.

As a countermeasure against this, it is generally known to narrow the clearance between the tip of the coater's lip and the web, but on the other hand, narrowing the clearance between the tip of the coater's lip and the web can cause problems such as streaks due to deposits on the web. Due to defects in the web process, wrinkles, etc. may cause the web to get caught on the tip end of the lip. Therefore, there is a limit to how narrow the clearance between the web and the tip end surface of the lip can be to prevent this. On the other hand, for high-speed coating, Japanese Patent Publication No. 48-22985, Japanese Patent Publication No. 50-
As disclosed in Japanese Patent No. 28451, etc., it is known to reduce the pressure behind the liquid pool (hereinafter referred to as "bead") between the slit and the support to prevent the bead from being completely removed. As the degree of vacuum increases as the pressure increases, there are problems such as the degree of vacuum exceeding a certain level may cause the bead to become unstable, or the coating liquid may be drawn backwards, causing problems such as running out of liquid. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating method that solves the problems of the prior art described above, eliminates liquid shortage during high-speed coating, and enables coating with a low coating amount.

[Means and effects for solving the problems] The above-mentioned object of the present invention is to provide a method in which a coating liquid is discharged from an extrusion type liquid injection device, and applied onto a support that is wound around a backup roller and travels. A part of the lip surface on the front side of the liquid discharge port of the container toward the support, from the discharge port end,
The support is perpendicular to the radius connecting the center of the backup roller and the liquid discharge port, or at an angle within 15', and the clearance between the remaining lip surface and the backup roller gradually decreases as the web progresses. This is achieved by a coating method characterized by supplying a coating liquid to the body. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a coating device that is an embodiment of the coating method of the present invention.

′! In Figure J1, the width l of the front lip surface 90 is not particularly limited, but is generally about 0.2 to 5 mm, and the width 12 of the rear lip surface 8 is also not limited, but is generally about 0.2 to 5 mm. 2 mm to 5 g (however, the width of the lip surface refers to the projected width with respect to the tangent at the position of the slot with respect to the backup roller).

In the present invention, the fact that a part of the front lip surface from the liquid discharge port end is perpendicular to the radius connecting the center of the backup roll and the liquid discharge port or has an angle within 15 degrees means that the width l is 0.2M. ~2 trm < leprosy is preferred, and more preferably 0.3 to 1 m.

In addition, the clearance between the remaining lip surface and the backup roll following the linear portion of radius β gradually decreases as the web progresses, and the angle α of the lip portion is t3.
°~145°, more preferably about tlo''~13
It is 0°.

In the present invention, by setting the front lip surface as described above and making the angle α sufficiently large, the coating liquid from the discharge port is first compressed and hits the web surface, and is oriented parallel to the web traveling direction. By changing, then compressing and extruding, it is possible to avoid increasing the clearance between the web and the discharge part at the liquid discharge part more than necessary, and reduce the pressure in the whole liquid discharge part and the coating liquid bridging part. As a result of being able to pressurize the liquid in parallel to the direction of movement of the support while avoiding liquid drop, it is possible to apply a low coating amount without running out of liquid even when the degree of vacuum in the vacuum chamber is low (described later) during high-speed coating. Become.

At this time, the lip surface 8 on the rear side can prevent air from being drawn in during coating by keeping the clearance parallel to the web as in the conventional case, and the decompression chamber 11 is provided to ensure that the liquid does not run out. You can wait.

Furthermore, the present invention is not limited to the coating method in which the coater is positioned on the left side of the backup roller as shown in FIG.
The coating may be applied by applying a coater to the web from various directions as shown in Figures (a) to (Company), or the coating may be applied by floating the web with an air floating drum as shown in Figure 2(e). The coating can be similarly applied by other methods.

That is, in FIGS. 2(a) to 2(e), a web 1 is supported by a backup roller 3 or an air floating drum 10, and an extrusion coater 4 discharges a coating liquid onto the web 1, increasing the amount of coating on the web 2. I can do it.

At this time, there is a pressure reduction chamber 11 and a pressure reduction pipe 12 for reducing the back pressure in order to stabilize the bead.

To further explain the present invention, the coating solution according to the present invention is not particularly limited, and includes a water or organic solvent solution of a polymer compound, an aqueous pigment dispersion, a colloidal solution, and the like. In addition, the physical properties of the coating liquid are not particularly limited, but - as conditions for the liquid coated on the support (web), it is suitable that the viscosity is low, and 10 Q
A state of less than cps, especially less than 5Qcps is suitable. The surface tension is also not limited, but preferable results can be obtained with a surface tension of 5 Qdyne/cps or less.

The support (web) in the present invention includes paper, plastic film, resin coated paper, aluminum web, synthetic paper and the like. Materials for the plastic film include, for example, polyolefins such as polyethylene and polypropylene, polyvinyl acetate, and polyvinyl chloride; beer polymers such as polystyrene; polyamides such as 6.6-nylon and 6-nylon; polyethylene terephthalate; polyethylene-2; Polyesters such as 6-naphthalate,
Polycarbonate, cellulose acetate such as cellulose triacetate, cellulose diacetate, etc. are used. Further, the resin used for resin coated paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto.

〔Example〕

Examples will be given to make the effects of the present invention more clear.

Coating liquid: Acrylic acid copolymer 9 parts by weight Ethyl glycol 60.0 Methanol
20.0 Dye
0.1 and a viscosity of 15 cps, coating was carried out on a support 1 having a thickness of 200 μm using an Extru-Silon hopper 4 as shown in FIG.

Front side lip surface 90 dimension II of coating device = 4n.

is=0. 5 fins, angle α=t30°, rear lip surface 80 dimensions1. = 4m, and the clearance between the web and the lip surface was 0.3H.
Minimum coating amount 8 at conventional coating speed of 100 m/ll 1 inch
What used to be 0cc/rn' can now be coated with a minimum coating amount of 40cc/rn' at a coating speed of 100m/win.

〔Effect of the invention〕

As is clear from the above, the coating method of the present invention eliminates bead drop during high-speed coating, enables coating with a low coating amount, and improves quality.

This greatly contributes to improving productivity.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the tip of a coater according to an embodiment of the coating method of the present invention, and FIG. 2 is a side view showing the position of the coater in relation to the backup roller in which the coating method of the present invention can be applied. ), bottom (b), bottom right (C), elegant (6
), and (e) when the backup roller is an air floating drum. 1... Web 2... Web after coating 3... Backup roller 4, 1j extrusion core 9- 5... Rear coater block 6... Front coater block 7... Liquid discharge port (Slot) 8... Rear lip surface 9... Front lip surface 10... Air floating drum 11... Decompression chamber 12... Decompression pipe

Claims (1)

[Claims] In a method in which a coating liquid is discharged from an extrusion type liquid injection device and coated onto a traveling support by being wound around a backup roller, the liquid discharge port of the liquid injection device is directed toward the forward side of the lip surface of the support. A part from the discharge port end is perpendicular to the radius connecting the center of the backup roller and the liquid discharge port, or forms an angle within ∠5°, and the clearance between the remaining lip surface and the backup roller is in the web traveling direction. A coating method characterized in that a coating liquid is supplied to the support in a state that gradually decreases as the coating progresses.