JP3419417B2 - Coating method and coating device - Google Patents

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 their tip (hereinafter referred to as a die head), and a slot portion capable of extruding a coating liquid (for example, a magnetic dispersion liquid) is formed between these lips. The coating liquid is applied to a support (for example, a web) that runs in opposition to the upstream lip and the downstream lip.

The slot portion of these coating devices is
In combination with a liquid buffer portion that distributes the coating liquid supplied from the coating liquid supply pump in the width direction, the coating liquid is uniformly extruded in the coating width direction of the coating device. In order to carry out this uniform extrusion, the slot length of the slot portion, the slot opening width (slot gap), the pressure distribution in the liquid buffer portion, etc. are determined by the coating operation conditions (coating speed, coating liquid physical properties (viscosity), etc.). Is set to an appropriate value.

[0004]

However, even when the slot portion of the coating device is set to a size capable of uniformly extruding the coating liquid in the coating width direction, when the coating operation is continuously performed for a long time, the coating film is Frequently uneven streaks occur on the surface, and there is a possibility that stable application cannot be performed.

The present invention has been made in consideration of the above circumstances, and a coating method capable of preventing streaking on the surface of a coating film even in a coating operation for a long time and realizing stable coating for a long time. And to provide a coating device.

The coating method according to the first aspect of the invention is
For a die head equipped with an upstream lip and a downstream lip
On the support made of a flexible web that runs toward
Slot formed between the flow-side lip and the downstream lip.
Apply the coating liquid extruded from the container directly by pressing
In the extrusion type coating device, a coating work surface facing the support and in contact with the coating liquid is formed on the downstream lip, and the minimum size of the gap between the coating work surface and the support is Gc. Then, the opening width Gs of the slot portion is set in the range of Gs / Gc≤4.

The coating apparatus according to the second aspect of the invention is
For a die head equipped with an upstream lip and a downstream lip
On the support made of a flexible web that runs toward
Slot formed between the flow-side lip and the downstream lip.
Apply the coating liquid extruded from the container directly by pressing
In the extrusion type coating device, a coating work surface facing the support and in contact with the coating liquid is formed on the downstream lip, and the minimum size of the gap between the coating work surface and the support is Gc. Then, the opening width Gs of the slot portion is set in the range of Gs / Gc≤4.

[0008]

According to the coating method of the first aspect and the coating device of the second aspect, the slot opening width G _{s of the} coating device is
And the minimum dimension G _c of the gap between the coating work surface of the downstream lip and the support body is set to G _s / G _c ≦ 4, the coating liquid extruded from the slot portion is the open end of the slot portion. Not staying in
During long-term application work, deterioration of paint characteristics due to stagnation does not occur easily. Further, the foreign matter attached to the support body is not trapped at the opening end of the slot portion. As a result of these, in the coating operation for a long time, the surface of the coating film coated on the support does not have stripe unevenness, and stable coating for a long time can be realized.

[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 a first embodiment of a coating apparatus according to the present invention. FIG. 2 is a cross-sectional view showing, together with the die head, a laser displacement meter that measures the gap between the coating work surface and the support. FIG. 3 is a cross-sectional view showing the microscope for observing the flow state of the coating liquid together with the die head.

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 configured to be convexly curved toward the web 21 side, and the 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.

Here, when the minimum size of the gap between the coating work surface 30 filled with the coating film 29 in a wet state immediately after coating and the web 21 is G _c , the slot opening width G _s (of the slot portion 26) G _s ( (Slot gap) is set to G _s / G _c ≦ 4 (1), preferably 1 ≦ G _s / G _c ≦ 3.

The slot opening width G _s is determined by the upstream lip 24.
The thickness is set to a predetermined value by changing the thickness of a spacer (not shown) provided between the downstream lip 25 and the downstream lip 25. This slot opening width G _s is defined as the minimum dimension G _{c of the} above gap.
4 times or more, a stagnant portion is generated in the magnetic dispersion liquid 22 at the downstream opening end O of the downstream lip 25 or at the position P corresponding to the minimum gap G _c on the coating work surface 30,
In the case of the pseudo-plastic dispersion liquid, agglomerates are generated in this retention part, and streak unevenness occurs on the surface of the coating film 29. In particular, in a coating liquid containing a fast-acting curing agent, aggregates are likely to be formed in a short time. In addition, if a stagnant portion occurs in the liquid flow path sandwiched between the application work surface and the web 21, the web 2
The foreign matter attached to No. 1 is likely to be trapped in the staying portion, and in this case as well, streaking occurs on the surface of the coating film 29. On the other hand, if the slot opening width G _s is set to a value equal to or smaller than the minimum dimension G _{c of the} gap, the generation of the retention portion can be prevented, but the flow of the magnetic dispersion liquid 22 becomes unstable in the opening portion of the slot portion 26 and becomes uniform. It is impossible to form a proper coating film 29. For these reasons, the slot opening width Gs is set within the range of Expression (1).

The gap between the coating work surface 30 of the downstream lip 25 and the web 21 is a laser displacement meter 31 shown in FIG.
Measured by That is, when the magnetic dispersion liquid 22 is not coated, the web 21 slides on the coating work surface 30 of the coating device 20, so that the measurement of the gap between the coating work surface 30 and the web 21 by the laser displacement meter 31 is not possible. , The web 21 and the laser displacement meter 31 during and without coating
The distance is measured and the difference is calculated.

Next, an experimental example will be shown. In Example 1, a coating liquid binder dilute solution A (viscosity 20 _c P; transparency) and binder dilution B; and (viscosity 100 _c P transparent body), the coating thickness in the wet state and 16 [mu] m, the web 21 A polyethylene terephthalate (PET) film is used, the running speed (coating speed) V of the web 21 is V = 100 m / min, and the minimum gap G _c between the coating work surface 30 and the web 21 is G.
_c = 30 μm, and the slot opening width G _s is G _s = 15 μ
An experiment is carried out using each coating device 20 of m, 30 μm, 60 μm, 90 μm, 120 μm, and 150 μm.

In this experiment, as shown in FIG. 3, tracer particles are mixed in the coating liquid (22), and the behavior of the tracer particles is observed with the microscope 32. The microscope 32 has a bead portion 3 for the coating liquid (22).
The section from 3 to the downstream end position of the downstream lip 25 is scanned to photograph the behavior of the bubbles. Thereby, the coating liquid (22) flowing from the slot portion 26 to the space between the coating work surface 30 of the downstream lip 25 and the web 21 is observed to confirm the presence or absence of retention.

In Experimental Example 1, as shown in Table 1, G
_When the value of _s / G _c is within the range of formula (1), the coating liquid (2
The state of 2) becomes good.

[0020]

[Table 1]

In Experimental Example 2, the coating liquid was 1 ×
A magnetic dispersion liquid showing pseudoplasticity at 1 poise at 10 ² _sec ^-1 was used, the wet coating thickness was 16 μm, the web 21 was a PET film, and the running speed (coating speed) V of this web 21 was V = 10m / min, further coating work surface 30
And the minimum gap G _c between the web 21 and the web 21 is G _c = 30 μm, and the slot opening width G _s is G _s = 15 μm, 30 μm, 60 μm, 90
For each coating device 20 of μm, 120 μm, and 150 μm,
The coating is continuously performed for a coating time of 10 hours.

Also in this case, when the state of the magnetic dispersion liquid 22 is observed using the microscope 32, as shown in Table 2, the value of G _s / G _c of the magnetic dispersion liquid 22 is within the range of the formula (1). The condition is good.

[0023]

[Table 2]

As is apparent from the above-described experimental example, according to the above-described embodiment, the slot opening width G _s in the slot portion 26 of the coating apparatus 20 is set to G _s / G _c ≦ 4. The coating liquid such as the magnetic dispersion liquid 22 extruded from the slot portion 26 during the coating operation does not stay at the downstream open end O of the slot portion 26, and the formation of aggregates due to this stay can be prevented. Further, since there is no retention portion, foreign matter attached to the web 21 will not be tripped to the open end of the slot portion 26. As a result, the web
No streaks are generated on the surface of the coating film 29 applied to No. 1. Of course, this coating film 29 is a uniform coating film. Therefore, it is possible to form a uniform coating film 29 which does not cause stripe unevenness even in a coating operation for a long time.

FIG. 4 is a sectional view of a die head showing a second embodiment of the coating apparatus according to the present invention. In the second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The coating device 40 in the second embodiment is
A backup roll 41 is arranged at a position facing the die head 23, and the back surface of the web 21 is supported by the backup roll 41 while the magnetic dispersion liquid 22 is being coated by the die head 23. Also in this embodiment, the slot portion 2
6 has a slot opening width G _s of the coating work surface 30 and the web 2
Since G _s / G _c ≦ 4, where G _c is the minimum size of the gap between the two, the occurrence of streaking on the surface of the coating film during long-time coating operation is the same as in the first embodiment. It can prevent and realize stable coating for a long time.

[0027]

As described above, according to the coating method and the coating apparatus of the present invention, it is possible to prevent streaking from occurring on the surface of the coating film even during the coating operation for a long time and realize stable coating for a long time. it can.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a laser displacement meter for measuring a gap between a coating work surface and a support together with a die head.

FIG. 3 is a sectional view showing a microscope for observing a flow state of a coating liquid together with a die head.

FIG. 4 is a sectional view of a die head showing a second embodiment of the coating apparatus according to the present invention.

[Explanation of symbols]

20 Coating Device 21 Web 22 Magnetic Dispersion Liquid 24 Upstream Lip 25 Downstream Lip 26 Slot 28 Coating Liquid Supply Pump 29 Coating Film 30 Coating Work Surface G _c Minimum Dimension of Gap between Coating Work Surface and Web G _s Slot Opening Width

Continued front page    (72) Inventor Yutaka Nakama               2-1-3 Bunka, Sumida-ku, Tokyo Kao Corporation               In the company (72) Inventor Chen Ei               2606 Akabane, Kai Town, Haga-gun, Tochigi Kao Corporation               In the company                (56) Reference JP-A-6-285410 (JP, A)

Claims (2)

(57) [Claims] 1. An upstream lip and a downstream lip are provided.
A support consisting of a flexible web that runs opposite the die head.
In the holding body, between the upstream lip and the downstream lip
Directly press the coating solution extruded from the formed slot
Extrusion type applying method
Te, the support and the facing portion in contact with the coating solution of the downstream lip and the coating work surface, the minimum dimension of the gap between the coating work surface and the support and Gc, the opening width of the slot portion Where Gs is Gs, Gs / Gc is adjusted to a range of 4 to carry out the coating. 2. An upstream lip and a downstream lip are provided.
A support consisting of a flexible web that runs opposite the die head.
In the holding body, between the upstream lip and the downstream lip
Directly press the coating solution extruded from the formed slot
Extrusion type coating device for applying and applying
On the downstream lip, a coating work surface facing the support and in contact with the coating liquid is formed. When the minimum size of the gap between the coating work surface and the support is Gc, the slot portion is formed. The opening width Gs is set to a range of Gs / Gc≤4.