JPS6057387B2 - Application method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method, and more particularly to a continuously running strip support (hereinafter referred to as a "web").

) relates to a coating method capable of providing a coating film having a smooth surface on the surface of the coating material. Magnetic recording materials, pressure-sensitive copying paper, etc. are usually produced by coating a continuously running web using various coating methods, then drying, calendering, etc., and then cutting. However, since the surface of the coating film is not sufficiently smooth after application, it is necessary to use the air knife method, doctor bar method, smoothing blanking method, etc. while the coating film is not dry or solidified. It was common to perform a smoothing process.

Among these methods, the air knife method is a method in which an air jet is sprayed onto the coating film, and the excess coating liquid is scraped off using the gas pressure and the coating surface is smoothed. The problem is that it not only tends to become a mist and pollute the atmosphere, but also requires a large amount of power.
In addition, the doctor bar method uses a roll that is stationary or rotating in the opposite direction to the web running direction to scrape off the coating liquid on the web in order to measure and smooth the coating film.
Since it scrapes off the coating liquid, that is, it has a doctoring effect, the amount of scraped off of the coating liquid varies depending on fluctuations in the tension of the web, and it is difficult to achieve sufficient smoothing.

In addition, the smoothing blanket method is a method in which a flexible sheet is brought into surface contact with the surface of an undried, unsolidified paint film in order to smooth the paint film surface, and although a sufficient smoothing effect can be achieved, Since the target is a flexible material, there are problems in that it is troublesome to handle and stable operation is difficult. It is an object of the present invention to overcome the deficiencies of the prior art and to provide a coating method capable of obtaining a coating film with a smooth surface with a simple and stable operation. Such an object of the present invention is to prepare the coating film, while the coating film is still in an undried and unsolidified state, so that the downstream side of the coating film in the cross section in the running direction of the web is
A solid smoother with an edge shape of 50 mm or less and a radius of curvature of 10 R to 100 R at the part that first contacts the coating film, and a solid smoother with a contact length of 5 mm to 100 mm as measured in the web running direction.
300f1R, and the running direction of the web when the coating film leaves the solid smoother is made to coincide with the tangential plane direction of the surface of the solid smoother, and the tension of the web is set to 2k9/m to 50k9/Tr.
This is achieved by keeping it within the range of L.

In the present invention, the coating liquid is not scraped off,
Only the surface of the coating film is smoothed.

Generally, when a solid is responsible for the doctoring action, it is often difficult to maintain a constant coating thickness because changes in web tension are directly reflected in changes in coating thickness. However, in the present invention, Since the agent is not responsible for the doctoring action but merely for smoothing the surface of the coating film, there is no possibility of such inconvenience occurring. The purpose of scraping off excess coating liquid after coating is to measure the coating amount to the desired value, but it is not necessarily necessary to measure the coating liquid after coating. The present invention not only does not necessarily have to have a doctor effect, but also provides a smooth coating film with a uniform coating thickness. This is far preferable to the method of In this way, in order for the solid smoother to be responsible for only the smoothing effect, the shape of the solid smoother, the solid smoother and the coating must be adjusted not only to prevent the doctor effect from occurring, but also to prevent air entrainment. It is necessary to set the contact length with the membrane, web tension, etc. within specific ranges.

As for the shape of the solid smoother, in its longitudinal cross-sectional shape in the web running direction, the radius of curvature of the part that first contacts the coating film is 10R to 100R1, preferably 15R to 60R1.
More preferably, it is 20R to 40R, and the four downstream ends are required to have an edge shape of 150 or less, preferably 1350 or less, and even more preferably 1200 or less, and a solid smoother to be in contact with the coating film. It is necessary that the surface is smooth and its radius of curvature is larger than the above-mentioned value of the radius of curvature defined for the part that comes into contact with the coating film for the first time. Further, the contact length between the solid smoother and the coating film is required to be 5 to 300 w, preferably 20 to 15 l, more preferably 30 to 10 l. Also, the tension of the web should be 2 to 50k9/WLl, preferably 4 to 4.
It is necessary that it is within the range of 0 kg/Tn, more preferably 6 to 30 k9/m.

If it is less than 2k9/7n, there is no risk of doctoring, but c) problems with web handling will occur, which is not preferable.

Furthermore, it is possible to align the direction of the web when the coating leaves the solid smoother with the tangential plane at the edge of the solid smoother, as described by Dr. This is required to prevent the occurrence of scratches, streaks, etc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a coating apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a coating device showing an embodiment of the present invention.

After a coating film 2 is provided on the surface of the continuously running web 1 by various methods, it is transported to a smoothing zone, where a solid smoother 3 and the coating film 2 on the web 1 are brought into surface contact. At this time, the telesion of the web 1 is adjusted to a desired value by the rolls 4 and C. The web 1 carrying the coating film 2 whose surface has been smoothed in this way is sent to a drying zone and subjected to the necessary treatments for each product. FIG. 2 shows an example of the shape of the solid smoother used in the present invention.

The material of the solid smoother in the present invention may be any material that can be easily processed with high precision and is inert to the coating liquid, such as metals such as stainless steel and carbon steel, and alloys such as cemented carbide. Plastics such as , glass, polytetrafluoroethylene, polyacetal resin (trade name: 1 Delrin J, DuPont, USA), and polypropylene are examples that can be suitably used.

In the present invention, the coating method is not particularly limited, and includes bead coating method, extrusion coating method, curtain coating method,
Known coating methods such as gravure coating and reverse roll coating can be widely used, but it is necessary that the measurement of the coating liquid be completed before smoothing with a solid smoother.

The present invention can be suitably applied not only to coating in the manufacturing process of magnetic recording materials and pressure-sensitive copying paper, but also to a wide range of other fields where a smooth coating surface is required.

Example 1 A magnetic coating liquid having the composition shown in Table 1 was applied at a rate of 707 TL/min for 5 times.
A polyethylene terephthalate film having a thickness of 12 .mu.m and a width of 50 .mu.m was coated by gravure coating so that the coating width was 48 h and the wet thickness was 5 .mu.m.

While the coating film thus applied is still in a wet and unhardened state, a solid smoother made of stainless steel with a radius of curvature of 50R1 and a lower edge angle of 900 is applied to a solid smoother with a contact length of 50fn.
The paint film was smoothed by making contact with the paint so that the paint film was smoothed.
Before smoothing, the thickness variation in the web width direction is 10%.
Despite the heat, we were able to obtain a glossy coating over the entire width.

In addition, DC noise caused by minute irregularities was reduced to almost nothing, and a good product was obtained over the entire width.
Example 2 A magnetic coating liquid having the composition shown in Table 2 was applied to 100 m//
Thickness 16μ, width 100T1r running continuously in minutes! n
A coating width of 980 mm and a wet thickness of 50 μm were applied to a polyethylene terephthalate film using the reverse roll coating method.
It was applied so that

While the coating film thus applied was still in a non-dry and unsolidified state, it was brought into surface contact with a solid smoother having a shape as shown in FIG. 3 to smooth the coating film. Even though the thickness variation in the web width direction before the smoothing treatment was as much as 5%, a glossy coating film could be obtained over the entire width. In addition, cross noise caused by minute irregularities became negligible, and a good product could be obtained over the entire width. Table 2 Rice Condensation product of bisphenol A and epichlorohydrin.

Molecular weight about 900, epoxy equivalent weight 450-50, hydroxyl group content 0.29%.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of main parts of a coating device showing an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a solid smoother that can be used in the present invention, and FIG. 3 is a schematic diagram showing an example of a solid smoother used in Example 2. 1...Web, 2...Coating film, 3...Solid smoother.

Claims (1)

[Claims] 1. While the coating film provided on the continuously running web is in an undry and unsolidified state, the cross-sectional shape in the running direction of the web has a radius of curvature of 10R to 100R at the part where it contacts the coating film for the first time. , contact with a solid smoother whose downstream end has an edge shape of 150° or less so that the contact length is 5 to 300 mm in the web running direction, and the web running direction when the coating film leaves the solid smoother. coincide with the tangential plane of the solid smoother surface,
A coating method characterized in that the tension of the web is maintained within a range of 2 kg/m to 50 kg/m.