JPH06142589A - Coating device - Google Patents

Abstract

PURPOSE:To reduce the coating troubles of a slide bead coating device adapted to coat the material running around a coating roll with a plurality of kinds of coating liquids by subjecting the vertical surface of the coating device to a hydrophilic treatment. CONSTITUTION:The vertical surface 19 of a coating device is coated with an inorganic acid, e.g. hydrochloric acid, to form an oxidized film to improve its hydrophilic property. This reduces the contact angle of the vertical surface 19 formed against coating liquid 13 and therefore the coating troubles including that in the transition to the subsequent coating of a web, particularly with lessened occurrence of streaks. In the coating device, a plurality of coating liquids 13 are sent through horizontal pockets 14 and vertical slots 15 and flow down a slide surface 16 reaching the end of the coating device 17 where the web 12 is coated with the coating liquid by a packing roll 10 via a bead 18. By the provision of the hydrophilic vertical surface 19 as mentioned above, the paintability of this coating device is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slide bead coating device, and more particularly to improvement of coating properties.

[0002]

BACKGROUND OF THE INVENTION A slide bead coating device is capable of high speed, thin film and multi-layer simultaneous coating, and is widely used as a coating device for photographic light-sensitive materials and magnetic recording materials due to its characteristics. In this type of coating device, the coating liquid flows down the slide surface through a slit that extends in the width direction called a slot in the coating machine, and the coating machine tip (also simply referred to as an edge or lip) and the coating machine vertical section below the tip are applied. On the surface, a coating solution reservoir called a bead is formed between the traveling flexible support (also referred to as a web), and coating is performed through the bead.

In such a so-called bead coater, the stability of the beads greatly affects the stability of the coating. The stability of the bead depends on the setting of the gap between the lip and the web, the environmental conditions, the physical properties of the coating liquid, that is, the viscosity, and the surface tension. As the film thickness decreases, it becomes difficult to stabilize the beads. If the bead is unstable, a failure such as a muscle failure, a tailing failure, or a liquid shortage may occur.

In order to improve the stability of the beads, for example, a method is known in which a pressure difference is provided above and below the beads. Specifically, measures are taken such as providing a decompression chamber below the bead and pulling the bead downward to improve the stability of the bead.

Further, in order to stabilize the beads, wetting of the coating liquid and the coating device is also an important problem. Beads are formed between the web and the vertical plane below the applicator edge as described above. Therefore, the wetting of the vertical surface has a great influence on the stability of the bead.

Regarding the wettability of such a vertical surface, for example, if conventionally wettability is rather good, the coating solution seeps out of the lip portion other than the bead and falls on the coating film or the support to cause tailing failure. There was an idea that the coating properties would deteriorate due to the occurrence of dripping or dripping.

For such a problem, for example,
1-57629 is a method of applying a water-repellent resin to the lip portion at the tip of the coating device, and Japanese Patent Application No. 4-9357 is a method of forming a composite plating film with a fluorine-containing resin, and Japanese Patent Application No. 4-1783.
No. 80 proposes a method for defining the surface roughness of the vertical surface. However, when continuously coating a long web, it is necessary to connect the webs. As a method of this connection, there are methods such as ultrasonic bonding or tape connection, but in any case, it is an unavoidable problem that the bead is disturbed when the connection portion passes the end of the coating machine. .

As measures against such a case, various measures have heretofore been disclosed, for example, Japanese Patent Laid-Open No. 57-14912.
58-88074, 60-28851, 60-28854, 60-28855
No. 60-28857, JP-A-2-307574, etc., increased pressure reduction at the bead portion, expanded bead gap, increased coating liquid flow rate, bead vibration, improved wettability at the rear end of the joint, and shape of the joint portion. Various methods have been proposed, such as sawing, roughening of joints and electric discharge treatment, but none of them are sufficient measures at present.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a slide bead coating of a long web having a connecting portion by stabilizing the bead to reduce coating failures and enable stable coating. The present invention is to provide a coating device.

[0010]

The above object of the present invention is to provide a method of applying a coating solution to at least one layer on a continuously running support by using a slide bead coating apparatus, and the vertical surface of the coating apparatus is made hydrophilic. It is achieved by a coating device characterized by a chemical treatment.

The present invention will be specifically described below.

FIG. 1 is a sectional view showing an example of a slide bead coating apparatus, which is a coating apparatus capable of simultaneously coating two layers. In the figure, a plurality of coating liquids 13 pass through a pocket 14 and a slot 15 extending in the width direction to reach a slide surface 16, and the coating liquid flows down the slide surface to reach a tip (also referred to as an edge or lip) 17 of a coating machine. Here, it is applied onto the running web 12 which is held by the backing roll 10 via a liquid pool called a bead 18.

The present invention enhances the stability of the coating property by changing the surface property of the vertical surface 19 from the edge in such a slide bead coating device.

As described above, the prior art discloses a method of lowering the wettability on the vertical surface, but the present inventors have little effect when applying the joint portion under reduced pressure, and rather wet it. It was found that the bead part can be stabilized by improving the property. The means for improving the wettability is not particularly limited, and it is desirable that the contact angle with the coating liquid be 30 ° or less, preferably 10 ° or less.

As a means therefor, in the present invention, formation of an oxide film by oxidation treatment can be mentioned. Incidentally, stainless steel is generally used for the coating device.

In the oxidation treatment method, an oxide film can be formed by applying an inorganic acid such as hydrochloric acid to the vertical surface of the end of the coating apparatus.

[0017]

EXAMPLES Hereinafter, the effects of the present invention will be specifically illustrated by examples.

Example 1 An oxide film was formed by applying hydrochloric acid to the vertical surface of the stainless steel slide hopper type shown in FIG. 1, and the contact angle with the coating solution A described below was measured depending on the presence or absence of the oxide film.

Coating solution A: A coating solution containing a silver chloride emulsion and 5% gelatin as a binder.

Viscosity including the specified additives and surfactants 10cp (35 ° C) Contact angle No oxide film 68 °, oxide film 7 ° From these results, the wettability is obviously improved by the formation of oxide film. I understand.

Further, this coating solution A is used as a lower layer, and the following coating solution B is used.
Was simultaneously applied as an upper layer.

Coating speed: 100 m / min Wet thickness:
Upper layer: about 20 μm Lower layer: about 50 μm Coating solution B: 5% gelatin solution Contains predetermined additives and surfactants.

Viscosity 12 cp (35 ° C.) In the meantime, put several tape joints in the middle of the web,
The coating test was conducted under the condition that failure is likely to occur.

As a result, in the case where the oxide film is formed on the vertical surface and the hydrophilicity is improved, the coating failure, especially the streak failure is reduced more than in the case where the oxide film is not formed, including the time of passing the joint, which is excellent. Results showing coatability were obtained.

[0025]

As described above, according to the present invention, it is possible to provide a coating apparatus capable of reducing coating failures and stabilizing coating in slide bead coating by stabilizing the beads.

[Brief description of drawings]

FIG. 1 is a sectional view of a slide bead coating device.

[Explanation of symbols]

 12 Web 16 Slide surface 18 Bead 19 Vertical surface

Claims (1)

[Claims] 1. A method of applying a coating solution to at least one layer on a continuously traveling support by using a slide bead coating apparatus, wherein a vertical surface of the coating apparatus is hydrophilized. Coating device.