JPH0780383A - Coating method and coating device - Google Patents

Abstract

(57) [Summary] [Object] The present invention is capable of forming a high-quality coating film having excellent surface properties. According to the present invention, an upstream lip 24 and a downstream lip 25 are provided, and a slot portion 26 for extruding the coating liquid 22 is formed between these lips, and the lip portion runs opposite the upstream lip and the downstream lip. In the coating device 20 for coating the coating liquid on the web 21, the coating work surface 30 facing the web and in contact with the coating liquid is formed on the downstream lip, and the downstream end O of this coating work surface and the corresponding one. If the gap between the web 21 and the position P of the web 21 is G _c, and the coating film thickness in a wet state immediately after coating the web is G _h , the gap G _c is set to a range of 0.3 <G _h / G _c ≦ 0.6. It was done.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and a coating device for coating a running support with a coating liquid, and more particularly to a coating method and a coating device for coating a flexible web with a magnetic dispersion liquid.

[0002]

2. Description of the Related Art In recent years, due to demands for high speed thin film coating,
Extrusion type coating devices have been adopted in various fields (JP-A-58-104666, JP-A-60-238179, JP-A-60-238179).
Inventions described in JP-A-62-117666 and JP-A-2-265672). These extrusion type coating devices are provided with an upstream lip and a downstream lip at the tip of the die head,
A slot portion capable of extruding a coating liquid (for example, a magnetic dispersion liquid) is formed between these lips, and the above coating liquid is applied to a support (for example, a web) that runs to face the upstream lip and the downstream lip. Is.

One of the largest coating failures in coating by this type of coating apparatus is streaking that occurs as a result of foreign matter such as agglomerates being trapped on the coating work surface including the slot portion. For this reason, the development of the conventional coating device has been spent on finding a shape in which foreign substances and agglomerates are not trapped as much as possible on the coating work surface.

[0004]

In the conventional coating apparatus,
As described above, measures have been taken to prevent streaking due to foreign matter and aggregates, but in particular, in recent years, magnetic recording media, high-quality products with excellent surface properties are required,
There is a problem of minute irregularities and irregularities on the surface of the coating film, which are caused by causes other than the above-mentioned foreign matters and agglomerates.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a coating method and a coating apparatus capable of forming a high-quality coating film having excellent surface properties.

[0006]

According to a first aspect of the present invention, there is provided a coating method including an upstream lip and a downstream lip, and a slot portion capable of extruding a coating liquid is formed between these lips. In a coating method of coating the coating liquid on a support that runs opposite an upstream lip and a downstream lip, a downstream end of a coating work surface that faces the support and is in contact with the coating liquid in the downstream lip. Correspondingly, when the gap between the support and the support is G _c , the traveling speed of the support is V, and the coating width on the support is W, the extrusion rate Q of the coating liquid is 0.3 G _c WV < The coating is carried out by adjusting to a range of Q ≦ 0.6 G _c WV.

Further, the coating apparatus according to the second aspect of the present invention comprises an upstream lip and a downstream lip, and a slot portion for extruding the coating liquid is formed between these lips, and the upstream lip and In a coating device for coating the above-mentioned coating liquid on a support that runs facing the downstream lip,
A coating work surface facing the support and in contact with the coating liquid is formed on the downstream lip, and the distance between the downstream end of the coating work surface and the corresponding support is G _c. The gap G _c is set in the range of 0.3 <G _h / G _c ≦ 0.6, where G _h is the coating thickness in a wet state immediately after being applied to the body.

[0008]

According to the coating method of claim 1, the extrusion amount of the coating liquid from the slot portion of the coating device is adjusted within the range of 0.3 G _c WV <Q ≦ 0.6 G _c WV for coating, and the coating method according to claim 2 According to the coating device described in (1), since the gap G _c between the downstream end of the coating work surface and the support in the coating device is set to G _h / G _c ≦ 0.6, the coating film in a wet state is not Meniscus (free interface) formed when leaving the downstream end
Is stabilized, and the surface of the coating film is not disturbed.
Further, by setting 0.3 <G _h <G _c , the meniscus does not develop three-dimensionally, and it is possible to prevent the generation of vertical stripe unevenness due to the three-dimensional meniscus. For these reasons, a high-quality coating film having excellent surface properties can be formed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a die head showing an embodiment of a coating apparatus according to the present invention. FIG. 2 is an operation diagram showing a situation in which the gap between the downstream end of the coating work surface and the support is set. FIG. 3 is a cross-sectional view showing, together with the die head, a laser displacement meter that measures the gap between the downstream end of the coating work surface and the support. 4A is a sectional view showing the coating film when the value of G _h / G _c is 0.6 or more, and FIG.
The value of _h / G _c is a perspective view showing a coating film when it is 0.3 or less.

The coating device 20 shown in FIG. 1 is an extrusion type coating device, and is for coating the coating liquid on a continuously running support. Here, the support is a flexible sheet or web of plastic, paper, cloth or metal. Further, the coating liquid is a magnetic dispersion liquid, a photosensitive liquid, a heat-sensitive dispersion liquid or an adhesive liquid, which is used to produce a magnetic recording medium, a photographic film, a thermal paper or an adhesive tape, respectively. In this example, the web 21 was used as the support, and the magnetic dispersion liquid 22 was used as the coating liquid.
The case where a magnetic recording medium is manufactured is shown.

The coating device 20 has a die head 23, and an upstream lip 24 and a downstream lip 25 are formed on the die head 23. A slot portion 26 is formed between the upstream lip 24 and the downstream lip 25, and the slot portion 26 communicates with the liquid buffer portion 27. The upstream lip 24 and the downstream lip 25 are set to have substantially the same width as the width of the web 21. Further, the slot portion 26 and the liquid buffer portion 27 are composed of the upstream lip 24 and the downstream lip 25.
Is formed so as to extend in substantially the entire width direction.

The liquid buffer unit 27 is connected to a coating liquid supply pump 28 of a liquid supply system, and the magnetic dispersion liquid 22 from the coating liquid supply pump 28 is distributed so that the coating amount becomes uniform in the coating width direction. Supply to the slot portion 26. Here, the web 21 is guided by a guide roller or the like (not shown), faces the upstream lip 24 and the downstream lip 25, and runs without supporting the back surface. The slot portion 26 of the coating device 20 is attached to the running web 21.
The magnetic dispersion liquid 22 is uniformly extruded and applied in the entire width direction of the slot portion 26 to form a uniform coating film 29 in the width direction of the web 21.

A surface of the tip end of the downstream lip 25 facing the web 21 and in contact with the magnetic dispersion liquid 22 is a coating work surface 30 that contributes to coating. The coating work surface 30 is formed so as to be convexly curved toward the web 21 side, and the wet magnetic dispersion liquid 22 extruded from the slot portion 26 is pressed against the web 21 to be coated to form a coating film 29.

Assuming that the thickness of the coating film 29 in a wet state immediately after coating is G _h , the downstream end O of the coating work surface 30 is O.
And the gap G _c between the downstream end O and the position P on the web 21 corresponding to the downstream end O is set to 0.3 <G _h / G _c ≦ 0.6 (1). As shown in FIG. 2, this gap G _c is set to a desired dimension by changing the relative position between the web 21 and the die head 23 on the downstream side of the die head 23. If the value of G _h / G _c is larger than 0.6, then FIG.
As shown in (A), since the meniscus (free interface) formed when the magnetic dispersion liquid 22 in a wet state separates from the downstream end O of the coating work surface 30 on the downstream lip 25 becomes unstable, the coating film The surface of 29 is disturbed. On the other hand, G
_When the value of _h / G _c becomes 0.3 or less, the curvature of the meniscus becomes large as shown in FIG. 4 (B), and the meniscus enters between the coating work surface 30 and the web 21 and becomes 3 Dimensionally develops, and as a result, vertical stripe unevenness matching the three-dimensional pitch occurs along the running direction of the web 21. For these reasons, the value of G _h / G _c is set within the range of equation (1).

The gap G _c between the coating work surface 30 of the downstream lip 25 and the web 21 is measured and confirmed by a laser displacement meter 31 shown in FIG. That is, when the magnetic dispersion liquid 22 is not coated, the web 21 slides on the coating work surface 30 of the downstream lip 25 of the coating device 20, so that the downstream end O of the coating work surface 30 by the laser displacement meter 31 and the web 21. The gap G _c at the time of coating with the upper position P can be obtained by measuring the distance between the web 21 and the laser displacement meter 31 at the time of coating and at the time of non-coating, and calculating from the difference between these distances.

The coating film thickness G _{h in the} wet state is the theoretical film of the coating film 29 when the magnetic dispersion liquid 22 extruded from the slot portion 26 is formed into a uniform sheet shape without being reduced due to drying or the like. It is thick. Therefore, the coating film thickness G _{h in the} wet state is such that the coating film coated on the web 21 separates from the downstream lip 25 and there is still a velocity gradient in the coating film, or the coating liquid containing the volatile component In some cases, the actual coating film thickness is slightly different from the measured value. The value of the coating film thickness G _{h in} this wet state is Q where the flow rate of the coating liquid supply pump 28 (that is, the extrusion flow rate from the slot portion 26) is V, the traveling speed of the web 21 is V, and the coating width of the web 21 is W. Then, G _h = Q / W · V (2) is calculated and set.

Therefore, from the equations (1) and (2), the pump flow rate Q of the coating liquid supply pump 28 is set in the range of 0.3 G _c · W · V <Q ≦ 0.6 G _c · W · V, The magnetic dispersion liquid 22 is applied to the web 21.

Next, an experimental example will be shown. In the experimental example, a magnetic dispersion liquid that exhibits pseudoplasticity at 1 poise at a share rate of 1 × 10 ² sec ⁻¹ is used, and the wet coating film thickness G _h is G
_h = 15 μm, the web 21 is a polyethylene terephthalate (PET) film, the traveling speed (coating speed) V of this web 21 is V = 100 m / min, and the downstream end O of the coating work surface 30 and the position P of the web 21 are The gap G _c of
_c = 75 μm, 60 μm, 50 μm, 45 μm, 30 μm, 25 μm
, 20 μm in each case.

In this experimental example, as shown in Table 1, G _h
When the value of / G _c is within the range of the formula (1), there is no unevenness or unevenness on the surface of the coating film 29, and the high-quality coating film 29 having excellent surface properties is obtained.

[0020]

[Table 1]

As is apparent from the above-mentioned experimental example, according to the above-described embodiment, the downstream lip 25 of the coating device 20 is provided.
The gap G _c between the downstream end O of the coating work surface 30 and the position P of the web 21 is set to 0.3 <G _h / G _c ≦ 0.6, that is, the coating liquid supply pump 2 of the coating apparatus 20.
Since the pump flow rate Q in No. 8 is set to 0.3 G _c WV <Q ≦ 0.6 G _c WV, the wet coating film 29 is formed when the downstream lip 25 is separated from the downstream end O of the coating work surface 30. The meniscus is stabilized and the surface of the coating film 29 is not disturbed. Further, since this meniscus does not become larger than necessary, the meniscus does not enter between the coating work surface 30 of the downstream lip 25 and the web 21 and does not develop in the coating width direction of the coating film 29.
It is also possible to prevent the occurrence of vertical streak unevenness due to the meniscus. For these reasons, it is possible to form a high-quality coating film 29 having excellent surface properties.

[0022]

As described above, according to the coating method and coating apparatus of the present invention, a high-quality coating film having excellent surface properties can be formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a die head showing an embodiment of a coating apparatus according to the present invention.

FIG. 2 is an operation diagram showing a situation in which a gap between a downstream end of a coating work surface and a support is set.

FIG. 3 is a sectional view showing, together with a die head, a laser displacement meter that measures a gap between a downstream end of a coating work surface and a support.

FIG. 4 (A) is a cross-sectional view showing a coating film when the value of G _h / G _c is 0.6 or more, and FIG. 4 (B) shows G
The value of _h / G _c is a perspective view showing a coating film when it is 0.3 or less.

[Explanation of symbols]

10 Coating Device 21 Web 22 Magnetic Dispersion Liquid 23 Upstream Lip 25 Downstream Lip 26 Slot Section 28 Coating Liquid Supply Pump 29 Coating Film 30 Coating Work Surface G _h Wet Coating Thickness G _c Downstream End of Coating Work Surface and Web Gap with P position Q Pump flow rate V Coating speed W Coating width

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ei Chen Chen 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Kao Stock Association In-house

Claims (2)

[Claims] 1. An upstream lip and a downstream lip are provided,
In the coating method in which a slot portion capable of extruding the coating liquid is formed between these lips, and the coating liquid is applied to a support that runs facing the upstream lip and the downstream lip, The gap between the downstream end of the coating work surface facing the support and in contact with the coating solution and the corresponding support is G _c , the traveling speed of the support is V, and the coating width on the support Where W is W, the extrusion amount Q of the coating solution is adjusted to a range of 0.3 G _c WV <Q ≦ 0.6 G _c WV, and the coating is performed. 2. An upstream lip and a downstream lip are provided,
In a coating device in which a slot portion capable of extruding a coating liquid is formed between these lips, and the coating liquid is coated on a support body that faces the upstream lip and the downstream lip, the downstream lip is A coating work surface facing the support and in contact with the coating liquid is formed, and the gap between the downstream end of the coating work surface and the corresponding support is G _c, and immediately after coating on the support. The coating apparatus is characterized in that the gap G _c is set in a range of 0.3 <G _h / G _c ≦ 0.6, where G _h is a coating thickness in a wet state.