JP2012076063A - Coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating apparatus and method for forming a multilayer with which the multilayer having three layers or more can be formed stably on a support.SOLUTION: The coating apparatus performs the coating of a multilayer having three layers or more, by using an extrusion type coater head for performing the coating by applying a coating liquid on a support through a slit communicating with a plurality of manifolds for supplying the coating liquid. The coater head includes: a main slit discharging the coating liquid from the tip thereof to a support; a plurality of manifolds for supplying the coating liquid; and a plurality of branched slits joining the main slit through the plurality of the manifolds. A plurality of junctures, in which the plurality of the branched slits join the main slit, are present respectively in different positions on the axis in a coating liquid discharge direction of the main slit.

Description

  The present invention relates to a coating apparatus and method for coating and forming three or more coating layers on a traveling support such as plastic, paper, and metal foil.

2. Description of the Related Art Conventionally, it has been widely practiced to produce functional sheets and the like by forming functional layers having various functions on a support by coating. Examples include production examples of packaging materials, photographic light-sensitive materials, optical films, magnetic recording media, steel plate surface treatments, and the like.
In the production of these products, various functional materials are mixed with a binder, and if necessary, other additives are added and diluted in a solvent, and then a coating solution obtained by coating on the support is applied to the functional layer. Is formed.

Examples of a method for applying such a coating solution to the support include various coating methods such as a roll coater, a gravure coater, a knife coater, an extrusion coater, and various reverse coaters. Among these, the extrusion type coater is not exposed to air until immediately before coating, so there is no change in the coating liquid, and excellent thickness uniformity in the width direction of the coating film, In recent years, its use has increased due to the excellent smoothness of the coated surface.
Furthermore, in recent years, there has been an increasing demand for higher functionality and thinner layers of products in, for example, the magnetic recording medium and display fields, and the coating film applied on the support is required to be thinner and from a single layer to multiple layers. There are many more.

The coating solution can be applied in multiple layers by using different coater heads for each layer, or one coater head has multiple coating solution discharge sections and is supported by the tip of the coater head. A method (for example, Patent Document 1) in which coating solutions that have joined together just before application to the body are applied in a multilayer state at a time is generally performed.
Also proposed is a method (for example, Patent Document 2) in which a plurality of coating liquids are merged in a slit inside the coater to perform multilayer coating.

JP 2002-18347 A Japanese Patent Laid-Open No. 2004-2502

However, in Patent Document 1, in order to form a multilayer on the support by joining three or more coating liquids just before application to the support at the tip of the coater head, a high shear rate is applied simultaneously with the merge. Therefore, when the viscosities of the coating liquids forming the respective layers are greatly different, or when forming a very thin layer, it is difficult to obtain a desired performance or it is difficult to apply a uniform thickness. There was a case.

  In Patent Document 2, since a plurality of coating liquids are merged in a slit inside the coater and then the coating liquid is extruded from the tip of the coater head to form a multilayer on the support, the above-described problems are considerably improved. However, when three-layer coating is performed, the coating solution is merged so that the upper layer and the lower layer merge with the intermediate layer at positions facing each other across the slit, so that collision may occur and the laminar flow may be easily disturbed. It was.

  The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a coating apparatus and method for forming a multilayer capable of stably forming a multilayer of three or more layers on a support.

As a result of intensive studies on the configuration of a coating apparatus for forming a multilayer, the present inventors have found that the above-described object can be achieved by setting the coating apparatus to the following configuration, and have made the present invention.

That is, a coating apparatus that performs multi-layer coating of three or more layers using an extrusion type coater head that coats and coats the coating liquid on a support via slits connected from a plurality of manifolds that supply the coating liquid And this coater head has a main slit for discharging the coating liquid from its tip to the support,
A plurality of manifolds for supplying the coating liquid;
A plurality of branch slits that merge from the plurality of manifolds into the main slit, and
A plurality of merge points where the plurality of branch slits merge with the main slit are at different positions on an axis of the main slit in the coating liquid discharge direction.
The slit thickness of the main slit is the same or smaller on the axis of the main slit in the coating liquid discharge direction from the tip to the direction away from the tip.
The thickness of the smallest portion of the main slit is equal to or larger than the thickness of the plurality of branch slits.

  When the coating apparatus of the present invention is used, a plurality of coating liquids are merged at a relatively low shear rate inside the slit, so that the layers are stably formed, and the merging is not performed at the same time but is performed sequentially. There is little disturbance of the layer. Further, since the slit thickness is appropriately controlled in each part, each layer with less disturbance is formed.

ADVANTAGE OF THE INVENTION According to this invention, when forming the multilayer of 3 layers or more, the coating device and the coating method which can form the stable multilayer without disorder of each layer can be provided.

It is a principal part block diagram of the coating device of this invention. It is a principal part block diagram of the conventional coating device. FIG. 4 is a schematic diagram of a perpendicular magnetic recording medium having a three-layer structure on a nonmagnetic support, and an image diagram showing a method for determining the thickness of a mixed portion (mixed layer) at the interface of each layer.

  Hereinafter, embodiments of a coating apparatus and a coating method according to the present invention will be described with reference to the drawings, taking a coating apparatus for forming three layers as an example.

FIG. 1 shows a configuration diagram of a main part of a coating apparatus as an example of the present invention. In the coating apparatus 100 of the present embodiment, the tip of the coater head (die block) C is disposed on the backup roll 1 that guides the support B forming the coating layer with a slight gap from the support B. In order to form three coating layers on the support, the coater head C is composed of a number of blocks and parts.

The coater head C is largely composed of a downstream block 10, upstream block groups 20 to 23, and a main spacer 30 disposed between them to form a main slit MS. The upstream block groups 20 to 23 include the upstream tip block 20, the upstream first manifold block 21, the upstream second manifold block 22, and the upstream third manifold block 23, and branch slits S1 to S3 between these blocks. The slit spacers 31 to 33 are formed. In addition, the first to third manifolds M1 to M3 are formed by the upstream block groups 20 to 23. In the case of forming four or more multilayer coating layers, fourth and fifth manifold blocks and slit spacers can be added.

Although the main spacer 30 determines the slit thickness of the main slit MS, the thicknesses of the main slit portions, d1, d2, and d3 can be controlled by changing the shapes of the upstream block groups 22, 23, and 20. it can. These preferably satisfy the relationship of d1 ≦ d2 ≦ d3. Moreover, it is preferable to appropriately control the slit thicknesses da to dc of the branch slits S1 to S3 according to the thickness of each layer to be formed.

Next, operation | movement of this embodiment coating device 100 is demonstrated. The support B unwound from the unillustrated unwinding shaft is guided by a not-illustrated guide roll and wound around the backup roll 1. A coater head C is disposed on the side opposite to the backup roll 1 across the support B so that the support B and the tip thereof maintain a predetermined gap. Each coating material for forming each coating layer is supplied to each manifold M1 to M3 of the coater head C via a pump (not shown).
First, the uppermost layer-forming coating material that fills the first manifold M1 reaches the main slit MS via the first slit S1, and is pushed out from the tip of the coater head C via the main slit MS and onto the support B. The upper layer Ms is formed.

Next, in a state where the uppermost layer forming paint is continuously supplied from the first manifold M1, the first adjacent layer (intermediate layer) forming paint adjacent to the uppermost layer is supplied from the second manifold M2, and the second slit is formed. Via S2, it merges with the paint for forming the uppermost layer flowing through the main slit MS at the exit. After merging, the uppermost layer forming paint and the first adjacent layer forming paint are extruded from the tip of the coater head C while forming a laminar flow in the main slit MS, and the uppermost layer Ms and the first upper layer Ms are formed on the support B. The adjacent layer Mw is formed.

Thereafter, in a state in which the coating material for forming the uppermost layer is continuously supplied from the first manifold M1 and the coating material for forming the first adjacent layer adjacent to the uppermost layer is continuously supplied from the second manifold M2, the third manifold M3 is supplied to the first adjacent layer. The paint for forming the adjacent second adjacent layer (lowermost layer) is supplied, and merges with the paint for forming the first adjacent layer flowing through the main slit MS at the exit via the third slit S3. After merging, the uppermost layer forming paint, the first adjacent layer forming paint, and the second adjacent layer forming paint are extruded from the tip of the coater head C while forming three laminar flows in the main slit MS. Three layers of the uppermost layer Ms, the first adjacent layer Mw, and the second adjacent layer N are formed on B.

As described above, in the coating apparatus of the present invention, the first slit S1, the second slit S2, and the third slit S3 sequentially join the main slit MS from a position far from the tip of the main slit MS, so that each layer is disturbed. A three-layer laminar flow is formed without any problems.

Hereinafter, based on an Example, this invention is demonstrated more concretely.
Ferromagnetic paint in which metal magnetic powder (ferromagnetic powder) is dispersed in a binder, soft magnetic paint in which Fe-Co based soft magnetic powder is dispersed in a binder, non-magnetic paint in which α-Fe ₂ O ₃ and carbon black are dispersed in a binder Using the coating apparatus of the present invention shown in FIG. 1, three layers of a nonmagnetic layer N, a soft magnetic layer Mw, and a ferromagnetic layer Ms are formed on a nonmagnetic support made of PET (polyethylene terephthalate) film having a thickness of 6 μm. A magnetic recording medium for perpendicular recording having A ferromagnetic paint is supplied from the first manifold, a soft magnetic paint is supplied from the second manifold, and a nonmagnetic paint is supplied from the third manifold. The magnetic sheet was prepared by coating so that the thickness after drying of the soft magnetic layer was 0.6 μm and the thickness of the nonmagnetic layer after drying was 1.0 μm.

At this time, the thickness intervals (d1 to d3) of the respective parts of the main slit are changed as shown in the table below, and the thickness intervals of the first to third slits are set to 0.2 mm. A sheet was produced. The first to third slits are arranged on one side with respect to the main slit as shown in FIG.

On the other hand, as shown in FIG. 2, the first slit is located on the opposite side of the second slit and the third slit across the main slit, and the junction where the first slit and the third slit merge with the main slit is the main. A magnetic sheet for evaluation of Comparative Example 1 was produced in the same manner as in Example 1 except that the coating apparatus at the same position on the axis of the slit in the direction of coating liquid discharge was used.

Next, except that the confluence of the first slit and the main slit is located between the confluence of the second slit and the third slit on the axis of the coating liquid discharge direction of the main slit, as in Comparative Example 1, The magnetic sheet for evaluation of Example 4 was produced.
The formation state of each layer of the obtained magnetic sheet for evaluation was evaluated by the following method.

<Evaluation of mixed state of each layer>
A cross section including a ferromagnetic layer, a soft magnetic layer, and a nonmagnetic layer having a carbon layer and a Pt—Pd layer deposited on the surface of the ferromagnetic layer was prepared by a focused ion beam (FIB) apparatus, and the obtained cross section was scanned. Observation with an electron microscope (SEM) using a YAG (Yttrium Aluminum Garnet) detector gives a backscattered electron (BSE) image. The image data is digitized to obtain brightness data in the thickness direction.

FIG. 3 shows a cross-sectional configuration (a) and a luminance curve (b) of the perpendicular recording magnetic recording medium manufactured in the example. The brightness a, b, and c at the center of each layer in FIG. 3A is defined as the brightness of each layer, and the range between 70 and 30 when the distance between a and b of the brightness axis is 100 is a ferromagnetic layer-soft magnetic layer. The mixed portion of 70 and 30 to 30 when the bc between luminance axes is defined as 100 is defined as the mixed portion of the soft magnetic layer and the nonmagnetic layer. Based on this definition, the thickness ma of the mixed portion of the ferromagnetic layer and the soft magnetic layer and the thickness mb of the mixed portion of the soft magnetic layer and the nonmagnetic layer are obtained. The smaller the thickness, the paint at the boundary portion of each layer. It was judged that there was little mixing.

By using the coating apparatus and the coating method of the present invention, a high-quality functional film having three or more layers can be provided.

1 backup roll 10 downstream block 20 upstream tip block 21 upstream first manifold block 22 upstream second manifold block 23 upstream third manifold block 30 main spacer 31 first slit spacer 32 second slit spacer 33 third slit spacer 100 coating device B Support C Coater head (die block)
M1 1st manifold M2 2nd manifold M3 3rd manifold MS Main slit S1 1st slit S2 2nd slit S3 3rd slit Ms Ferromagnetic layer Mw Soft magnetic layer N Nonmagnetic layer

Claims (2)

A coating apparatus that performs multi-layer coating of three or more layers using an extrusion type coater head that coats the coating liquid by coating the coating liquid on a support through slits communicating from a plurality of manifolds that supply the coating liquid. The coater head has a main slit for discharging the coating liquid from its tip to the support,
A plurality of manifolds for supplying the coating liquid;
A plurality of branch slits that merge from the plurality of manifolds into the main slit, and
A coating apparatus, wherein a plurality of junctions where the plurality of branch slits merge with the main slit are located at different positions on the axis of the coating liquid discharge direction of the main slit.
  2. The coating apparatus according to claim 1, wherein the slit thickness of the main slit is the same or smaller on the axis in the coating liquid discharge direction of the main slit in a direction away from the tip.

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