JPS62132566A - Coating method - Google Patents

Abstract

PURPOSE:To obtain stable and good quality without the generation of a line trouble by setting the thickness of a back blade and the entrance angle of a web to a coating head to specific values. CONSTITUTION:This invention relates to a coating method of a magnetic coating liquid for production of a magnetic recording material, etc., in which the thickness of the blade 2 corresponding to the surface of the coating head 1 nearest the web 6 of the back blade 2 is selected at 0.3-10mm and the entrance angle of the coating head 1 to the web 6 is specified in a +7--10 deg. range of the surface nearest the web 6 of the blade 2 in the case of pressing the extrusion type coating head to the unsupported part of the rear surface of the traveling web and coating the liquid to the web. The possibility of line trouble is thereby eliminated and the stable and good coating quality is obtd. The coating of a thin layer at a high speed is thus made easy and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of coating a flexible support with a coating liquid gold, and particularly to a method of coating a magnetic coating liquid in the production of magnetic recording materials and the like.

In the present invention, the flexible support refers to a flexible sheet or web such as a plastic film, paper, polyolefin coated paper, aluminum or tin metal sheet, and is provided with an undercoat layer or the like. Good too. For such a support,
Magnetic coating liquids, photosensitive coating liquids, and other various coating liquids are applied to produce magnetic recording media, various photographic films, photographic paper, etc.

[Conventional technology]

Conventionally, various methods have been used to apply a coating liquid to a long flexible support, such as roll coating, gravure coating, roll coating brass doctor method, extrusion coating, and slide bead coating. Among these, the extrusion coating method has been widely used in recent years (see Japanese Patent Laid-Open Nos. 57-84771, 58-104666, 58-109162, etc.). The feature of this coating method is that the coating liquid, which is a dispersion of magnetic material, is sent to the slot of the coating head using a metering liquid pump that can feed the liquid continuously at a constant flow rate. This is a method of applying it to the body (hereinafter referred to as the web).

Further, the coating head is pressed against an unsupported part of the back surface of the running web to perform the entire coating.

Therefore, during coating, the blade portion of the coating head and the web are separated by a very narrow gap consisting of only a liquid film.

[Problem that the invention seeks to solve]

Therefore, there is an inherent risk that protrusions of the web or dirt attached to the web may get caught in the coating head, resulting in streak failure.

Sea urchin protrusions, debris, etc. were often caught in pack blades.

Therefore, the object of the present invention is to solve the problems of the prior art,
An object of the present invention is to provide a coating method that does not cause streaks.

[Means to solve all problems]

As a result of extensive research, the inventors of the present invention found that the adhesion of dust and the like can be suppressed to the utmost by changing the thickness of the pack blade and the angle of approach of the web to the pack blade.

That is, the present invention provides a method for coating by pressing an extrusion-type coating head against an unsupported part of the back surface of a running web, in which the thickness of the blade corresponding to the surface of the coating head closest to the pack-grade web is
e Select from 0.3 to 101m.

and the approach angle of the web to the coating head is between +7° and - with respect to the plane closest to the pack grade web.
This is a coating method characterized by coating within a 10° range.

The present invention will be explained in more detail below with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of a coating head according to the present invention. 1 is an extrusion type coating head, 2 is a pack blade, and 3RI doctor blade. t and t2 are the thicknesses of the back blade and doctor blade, respectively, at the portions corresponding to the surfaces closest to the web.

The coating liquid 4 fed by the metering pump passes through the slot 5 and is applied to the web 6.

Figure 2, similar to Figure 1, shows the inclination angle of the pack blade surface, the thickness of the pack grade, and the web entry angle for a coating head in which the surface of the pack blade closest to the web is machined in one plane. FIG. The angle and thickness of the part (CA surface) close to the nib of the pack grade shown in the present invention are indicated by r and tl.

Incidentally, the inclination angle r of the pack blade surface is according to JP-A-58-109.
As shown in Japanese Patent No. 162, an angle of about 0.5 to 30 degrees is appropriate. The extension line of the grade surface inclination angle r is shown by a broken line,
As shown in Fig. 2, the approach angle of the Kuep is expressed as α degrees with the upper side of the extension line as plus (+), and β degrees with the lower side as minus (-).

As a result of experiments, the inventors found that in this case α=7°, β=10°
It has been found that good coating conditions are such that the web enters within a range within 100 m and the pack blade thickness t is within 10 m.

If the web enters at an angle that increases the value of α, air will easily enter between the Taezo and the grade surface.
Cannot be applied. Therefore, in order to perform high-speed coating and thin layer coating, it is preferable that α be as small as possible.

It has been found that in order to achieve very high speed and thin layer coating, it is desirable for the web entry angle to be more negative (-) than the extension of the blade surface.

If the web were a completely rigid body, the web would bend at point A of the trailing edge of the pack blade, and therefore the web would definitely get caught at point A of the trailing edge of the pack blade.

However, in actual tests, as shown in Figure 3, when coating is performed by entering the web at an angle within β = 100 (indicated by the dotted line) with respect to the extension line of the blade surface, the liquid on the doctor blade It was found that due to the pressure of the film and coating liquid, the web did not catch on the trailing edge point A of the floating pack blade, as shown by the solid line in FIG.

However, the thicker the pack blade (the larger tl), the closer the trailing edge point A of the pack blade is to the web and the easier it is to contact the web, so t11dlOm
It was found that it was necessary to be within

This can be understood from FIG. 3, where the gap between point B, which is t1 and t1', and the web is wider than the gap between point A and the web. In fact, the thinner the tl is than 10 mm, the less the protrusions of the web or dirt will get caught. However, the thinner it is, the more difficult it is to process the PACKZO V-dope, and the more difficult it is to achieve machining accuracy, so it is desirable to have a thickness of 0.3 rnx or more.

The above description has been made regarding the case where the pack blade is composed of one plane.

Next, in the case where the back blade is composed of two or more planes, the inclination angle r of the plane closest to the web of the pack blade (CA plane), the thickness tl of the grade, etc. in the present invention will be explained. Figure 4 shows three types of pack blades with different shapes: ta+, (b), t
Indicates c+.

Also for these back blades, α=7°, β=10
If the range of ° and tl are within 10W.

Good coating was achieved without getting caught by dirt, web protrusions, etc., and thin layer coating was possible at high speed.

In addition, dl shown in Fig. 4 is 0.03 to 3 dew, and d2 is 0.5.
~5w or less is appropriate. Also, the gap of the slot for pushing out the coating liquid (see 5 in Fig. 1 is 0.05 to 3iII!
, the thickness tl of the pack blade corresponding to the surface closest to the queso is 0.1 to 10 Ixo, and the shape of the pack grade is ta+, (b), (e) Any of the shapes is fine to 1°. There are no particular limitations on the physical properties of the liquid.

That is, water, an organic solvent alone, or a mixture of these solvents,
Furthermore, a liquid obtained by dispersing or dissolving a polymer material, a magnetic substance, a casene, etc. in these solvents may be used, and the viscosity is 0.01.
~50 P (share sort 5ec-').

The application head may be installed in any direction, such as upward, downward, or horizontal.

〔Example〕

After thoroughly mixing and dispersing each component of the composition shown in Table 1 in a Dahl mill, epoxy resin (epoxy equivalent: SOO
) was added thereto and uniformly mixed and dispersed to prepare a magnetic coating liquid.

Table 1 The equilibrium viscosity of the magnetic coating liquid thus obtained was measured using a Takasugi V-Ometer RM-t manufactured by Takasugi Seisakusho, and it showed 8 poise at a shear rate of 10 sec, and 1 poise at a shear rate of 500 sec.

Next, the coating liquid was coated using the coating apparatus according to the present invention under the following conditions.

1. Support: Material: Polyethylene terephthane film Thickness: 20 ttm Width: 300 Tension: 4 instant/ Full width movement speed - 100m/min, 200m/m1n2
, an extrusion type coating head as shown in FIG. Pack blade thickness t15++na 3, coating liquid thickness 10μ, 20μ, 50μ4, web entry angle in 7 stages in the range of +12 to -15° and the results are shown in the table below. (The marks marked with ○ could be applied well. The marks marked with Δ could give good results, but the reproducibility was poor. The marks marked with X could not be applied uniformly.

Furthermore, - cannot be evaluated. ) The results are shown in Table-2.

Table 2 Summary of results ■ When the web approach angle is +12°, coating is not possible at all coating amounts (Comparative Examples Nα1 to 3) Although it is possible to apply the product locally, it is not possible to apply it stably at high speeds. (Comparative example Nα4
~9)■ When the web approach angle is in the range of +7° to -10°, stable coating can be performed regardless of the coating amount and coating speed. (Example points 1 to 12) ■ Comparative examples 10 to 15 when the web entry angle is 112°
As shown in the figure, it is not possible to apply at a low coating amount without adjusting the coating speed. Furthermore, even if a high coating amount can be applied, the scratches and smudges are extremely poor. This is because the web gets caught at point A shown in FIGS. 2 and 3.

■ Comparative examples 16 to 18 when the web entry angle is 115°
As shown in , it cannot be applied for the same reason as ①.

In the above results, the influence of the web entry angle on the angle of the pack blade surface was explained in detail.

Next, we changed the thickness of the pack blade and tested it.

Example-2 Same as Example-1, but the thickness of the pack blade was reduced to 0.
．． The test was carried out by changing 5 levels in the range of 5 to 15zz. The results are shown in Table-3.

The coating speed was 200 m/min, the web entry angle was constant at -10', and the coating liquid thickness was 10 and 20.50 μm.

Table 3 Summary of Results ■ When the thickness of the pack blade was in the range of 0.5 to 11011I, coating was possible under any conditions and good samples were obtained. (Examples k13 to 20) ■ When the thickness of the pack V-do was 121 m, the occurrence of streaks and scratches was noticeable in the low coating amount region, and good coating could not be achieved.

This is the second. This is because the web gets caught at point A shown in FIG. (Comparative Examples Nα19 to 21) ■ When the thickness of the pack blade was 15 mm, good coating could not be achieved at all for the same reason as in ■ above. ,,(Comparative example Nα22,
23) Example-3 A test was conducted with the thickness of the Kueppu being 75μ.

Except for the thickness of the paste, it is the same as Example-2.Table-4 The results are shown in Table-4.It is almost the same as Example-2, but
The thicker the Kuep, the better the results.

〔Effect of the invention〕

According to the present invention, when coating is applied by pressing the extrusion type coating head against the unsupported part of the back surface of the running web, by setting the thickness of the back Zod and the angle of approach of the web to the coating head to specific values. , there is no risk of streak failure.

Stable and good coating quality can now be obtained.

This also facilitates high-speed thin layer coating, which greatly contributes to productivity and cost.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the coating head according to the present invention. Figures 2 and 3 are explanatory diagrams of the thickness of the pack grade portion of the coating head of Figure 1, the entrance angle of the web, etc., and Figure 4 is an explanatory diagram of the complex-shaped back blade in the present invention. 1... Application head, 2... Pack V-do, 3...
・Doctor grade, 4... Coating liquid, 5... Slot, 6... Web, r... Blade surface inclination angle,
α, β...Entry angle of Kuep, t,...Thickness of Pu-V-do corresponding to the Zo-V-do surface closest to the web.Director of the Japan Patent Office Ugaman 1031E1 1.1 Display of 1985 Patent Application No. 272393 2, Method of applying the name of the invention 3, Name to correct 7IIi 4, Agent

Claims (1)

[Claims] In a method of applying by pressing an extrusion-type coating head against an unsupported part of the back side of a running web, the thickness of the back blade of the coating head corresponding to the surface closest to the web is 0.3 to 10 mm. and the angle of entry of the web into the coating head is selected to be +7 with respect to the surface of the back blade closest to the web.
A coating method characterized in that coating is carried out at an angle of 10° to -10°.