JP2004136282A - Coating apparatus and coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating apparatus which realize high speed, stable and uniform coating of thin film in an extrusion type coating apparatus continuously extruding a coating liquid from a slit between a first edge surface and a back edge surface to perform coating, and a coating method. <P>SOLUTION: The coating apparatus has a back edge having: a shape (1) of a curve satisfied by expression of y = a(x/Lb)n, wherein x is distance from an original point on the section, Lb is distance from an original point to a projected point of the section of the back edge face onto the X-axis; or a shape (2) with two or more curvature; or a shape (3) composed of combination of a face having curvature with a plane. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an extrusion coating apparatus and a coating method, and more particularly, to a coating apparatus suitable for coating a coating-type magnetic recording medium, and more specifically, to a high-speed, thin-film coating, which enables uniform and stable coating. It relates to a coating method.

As a coating apparatus, a roll coater, a gravure coater, an extrusion coater, a slide bead coater, a curtain coater, and the like are known, and as a coating apparatus for a magnetic recording medium, a roll coater, a gravure coater, and an extrusion coater are often used. ing.

The extrusion coater can easily obtain a uniform coating thickness, but has a problem that the range of good coating conditions is narrow. In particular, in the case of a high-speed coating such as a coating speed of 200 m / min or more, or a high-viscosity magnetic coating liquid of 4000 cps or more, the above problem is remarkable.

These coating methods are described in JP-A-57-84771, JP-A-58-104666, JP-A-60-238179, JP-A-1-84072, JP-A-1-210072, JP-A-1-88364, JP-A-2-35959. And No. 3-162 and the like. In these techniques, the cross-sectional shape of the back bar is configured as a curve having a single radius of curvature or a shape having a notch at the end of the curve.

FIG. 1 is a cross-sectional view of a back bar showing an example of a conventional coating apparatus, wherein the back bar has a single radius of curvature. In the figure, 1 is a front bar, 2 is a back bar, and 3 is a slit. When the shape of the back bar 2 is a single radius of curvature r1, r2, r3, r4 as shown in FIG. It is difficult to control the distance between the substrate and the back bar 2, that is, the thickness of the coating liquid layer.

に お い て In the figure, d1, d2, and d3 each represent the distance between the back bar surface and the support when the position is changed from the upstream side to the downstream side. For example, when the radius of curvature is r2, the distance changes as d1, d2, d3 depending on the position.

When the radius of curvature is r1, the gap at the upstream side of the back bar (the end on the slit side) is small, so that the liquid pool at the slit outlet is small, and the change in the velocity gradient is too large to allow the gap from the slit to the gap between the support and the back bar. The coating liquid cannot be smoothly stretched, causing air to be entrained or scraped off, causing a non-uniform liquid flow, making uniform coating impossible.

When the radius of curvature is r4, d1 is large and d2 and d3 gradually decrease, so that the speed gradient changes slowly, but the force from the support to the back bar is concentrated near d3, so that the downstream of the back bar is concentrated. The contact force becomes so strong that the coating solution is scraped off and the flow is disturbed, and uniform coating cannot be performed.

(4) When the radius of curvature is r2 or r3, the change in the speed gradient in the middle of the above case is moderately moderate, and the force from the support is dispersed over d2 and d3, so that uniform coating is facilitated. However, this also has a limit when the coating speed is as high as 200 m / min or more, or when the flow rate is as small as 10 μm or less in wet film thickness.

FIG. 2 is a sectional view showing an example of a conventional coating apparatus, which is disclosed in Japanese Patent Application Laid-Open No. 2-35959. In this example, a straight portion is provided on the slit side of the back bar (doctor edge in the specification), but the downstream end angle E of the straight portion is somewhat sharp, and the front bar is on the opposite side of the support. In addition, since the front bar is applied without making contact with the support (with a small gap), the force from the support concentrates on the corner E and the liquid is scraped off and the flow is disturbed. And uniform coating is difficult.

近年 In recent years, with the increase in the recording density of magnetic recording media, the number of multilayer magnetic recording media has also increased. In order to achieve the layering, for example, as disclosed in JP-A-51-119204, JP-A-52-51908 and JP-A-53-16604, a coating solution is applied one by one onto a support. There is a method of forming a multilayer magnetic recording medium by drying, and after the extrusion coating method corresponding to the multilayer is devised, the multilayer magnetic recording medium is more cost-effective than the metal thin film magnetic recording medium. The ones with excellent step and very good electromagnetic conversion characteristics have been produced.

However, in this method, there are problems such as poor productivity and difficulty in thinning the uppermost layer due to repetition of steps such as coating and drying, and the wet-wetting method disclosed in JP-A-48-99803 and JP-A-61-111168. A method for producing a magnetic recording medium by simultaneous on-wet multi-layer coating is disclosed. In both methods, a method of applying a coating liquid in a multi-layer state in advance on a continuously running support held on a back roll is used. In addition, the rotational deviation accuracy of the back roll is insufficient and coating unevenness is likely to occur in the coating longitudinal direction, so that it has not been possible to manufacture an optimal magnetic recording medium.

Therefore, there is a method of applying the upper layer while keeping the lower layer in a wet state on a support without holding a back roll with a single-layer extrusion coater as disclosed in JP-A-62-124631. However, under coating conditions such that the thickness after drying becomes 0.3 μm or less, for example, the upper layer thickness distribution in the width direction and the longitudinal direction is not good.

On the other hand, in order to cover the above-mentioned drawbacks, a coater head having a slit through which two coating liquids are led out has been devised as disclosed in JP-A-63-88080 and JP-A-2-25265. Have been.

Such a coater head of a type from which two coating liquids are led out is naturally composed of three parts, a front bar 1 ', a center bar 2' and a back bar 3 ', as shown in FIG. ing. When this coater head is used, an important factor that determines the applicability of the thin-film simultaneous multi-layer coating is the cross-sectional shape of the surface in contact with the liquid contact portion of each bar or the continuously running support.

で は In the above-mentioned conventional technology, the cross-sectional shapes of the center bar and the back bar are configured with a single radius of curvature. Therefore, as shown in FIG. 3, for example, when the distances between the center bar and the support are d1, d2, and d3, it is important that the relation of d1> d2> d3 is ideal. As described above, this is nothing but reducing the velocity gradient between the support and the coating solution in the direction of travel of the support.

However, in the techniques disclosed in the above publications, a reversal phenomenon occurs at a part of these distances as shown in FIG. 3, and a coating apparatus for a coating type magnetic recording medium having a thin film multilayer structure with good electromagnetic conversion characteristics and few coating failures. At present, no application method is disclosed.

一番 The most important factor that affects the applicability of the extrusion applicator and the surface properties after application is the shape of each bar. The shape is the shape of the portion where the front bar contacts or is closest to the running support, the shape of the portion where the back bar contacts the coating solution, and the positional relationship between the two bars. For example, when applying a coating solution in which very fine magnetic powder is dispersed, the viscosity characteristics deviate considerably from the Newtonian fluid, and exhibit considerable plastic flow characteristics. That is, the viscosity is high when the coating liquid is subjected to a very weak force (shear speed 10 sec-1 or less) from the outside, and the viscosity is low when the coating liquid is subjected to a strong force (shear speed 104 sec-1 or more). Cause the phenomenon. Therefore, in order to obtain good coating properties and uniformity of the coating surface, the coating liquid needs to be gradually and very smoothly accelerated on the back bar, particularly when the coating speed is high (300 m / min or more). Becomes even more important.

位置 Also, the positional relationship between the front bar and the back bar is extremely important, and has a close relationship with the shape of the back bar.

Therefore, the present invention solves the above-described conventional problems by clarifying the new shape of the back bar and the positional relationship between the front bar, and achieves high-speed and uniform application of a multilayer or single-layer thin film. The purpose of the present invention is to provide a coating apparatus and a coating method suitable for a magnetic recording medium that is capable of being coated and has excellent electromagnetic conversion properties. We have found that we can achieve this goal.

The object according to the present invention, when it relates to single-layer coating
(1) A front bar having a front edge surface and located upstream with respect to the traveling direction of the support, a back bar having a back edge surface and located downstream with respect to the traveling direction of the support, and the front A coating device that has a slit positioned between the bar and the back bar, and that applies the coating to the support, on a cross section of the coating device in a running direction of the support, at a downstream end of the front edge surface; A part of the back bar protrudes from a tangent line of the front bar, and a straight line passing through the downstream end of the front edge surface and the upstream end of the back edge surface, the origin at the upstream end of the back edge surface, XY when the traveling direction of the support is a positive direction, and a straight line orthogonal to the X axis at the origin is a Y-axis where the direction from the back bar to the support is a positive direction. In a plane, in the plane The shape of the back edge surface is represented by the following relational expression y = a (x / Lb) n
(Where 0.1 ≦ a ≦ 1.0, 0.1 ≦ n ≦ 0.7, x is the distance from the origin on the cross section, y is the value in the Y-axis direction on the cross section, and Lb is the cross section. In the above, the projection length of the back edge surface onto the X-axis is 0.2 ≦ Lb ≦ 5.0 (mm). At this time, the angle θ between the tangent of the back bar at the downstream end of the back edge surface and the support located downstream from the downstream end is −10 ≦ θ ≦ 30 (degrees), and the downstream end of the back edge surface is It is preferable to apply while contacting the coating liquid surface.
(2) A front bar having a front edge surface and located upstream with respect to the traveling direction of the support, a back bar having a back edge surface and located downstream with respect to the traveling direction of the support, and the front bar A coating device that has a slit positioned between the bar and the back bar, and that applies the coating to the support, on a cross section of the coating device in the running direction of the support, at a downstream end of the front edge surface. A part of the back bar projects from a tangent line of the front bar, and the shape of the back edge surface on the cross section is centered on the back bar side from the upstream end to the downstream end of the back edge surface. This is achieved by a coating apparatus characterized in that the first, second and third arcs having different radii of curvature are continuous.
(3) A front bar having a front edge surface and located upstream with respect to the traveling direction of the support, a back bar having a back edge surface and located downstream with respect to the traveling direction of the support, and the front bar A coating device that has a slit positioned between the bar and the back bar and that applies the coating to the support; and a downstream end of the front edge surface on a cross section of the coating device in a running direction of the support. A part of the back bar protrudes from a tangent line of the front bar in the above, and the shape of the back edge surface on the cross section is centered on the back bar side from the upstream end to the downstream end of the back edge surface. The first arc, the second arc, and the straight line having different radii of curvature having the following are continuous.

In (2) and (3), the angle θ between the tangent to the back bar at the downstream end of the back edge surface and the support located downstream from the downstream end is −10 ≦ θ ≦ 30 (degrees), It is preferable that the coating is performed while the downstream end of the edge surface is in contact with the coating liquid surface.

Further, the object of the present invention is, in the case of multilayer coating,
(4) a front bar having a front edge surface and located upstream with respect to the traveling direction of the support; a back bar having a back edge surface and located downstream with respect to the traveling direction of the support; A center bar having a center edge surface located between the bar and the back bar, a first slit located between the front bar and the center bar, and located between the center bar and the back bar; An apparatus for applying a coating to the support, wherein the shape of the center edge surface on the cross section of the coating device in the running direction of the support is an upstream end of the center edge surface. A first arc, a second arc and a third arc each having a center on the side of the center bar and having different radii of curvature from the center to the downstream end, and the shape of the back edge surface is the bar. A fourth arc, a fifth arc and a sixth arc having different radii of curvature, each having a center on the back bar side from the upstream end to the downstream end of the back edge surface, and are continuous. Achieved.

At this time, the angle θ formed between the tangent of the back bar at the downstream end of the back edge surface and the support located downstream from the downstream end is -10 ≦ θ ≦ 30 (degrees), and the downstream end of the back edge surface is It is preferable to apply while contacting the coating liquid surface.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

4A is a perspective view of one embodiment of the coater head according to the present invention, FIG. 4B is a side view of FIG. 4A, and FIG. 4C is a cross-sectional view taken along line PP of FIG. (D) is an enlarged view of the Q portion of (c), and other drawings in this specification correspond to the enlarged view of the Q portion of (c) unless otherwise specified. It is.

FIG. 5 shows an example of the coating apparatus according to the present invention, that is, the coating apparatus according to the above configuration (1) of the present invention. FIG. 5 shows the front bar (1) at the downstream end (C) of the front edge surface. A part of the back bar (2) protrudes from the tangent line, and a straight line passing through the downstream end (C) of the front edge surface and the upstream end (A) of the back edge surface is drawn to the back edge surface. An X axis having the upstream end (A) as the origin, the traveling direction (R) of the support (w) as a positive direction, and a straight line orthogonal to the X axis at the origin is formed from the back bar (2) to the support. In the XY plane where the direction toward the front is the Y axis, the shape of the back edge surface in the plane is expressed by the following relational expression y = a (x / Lb) n
(Where 0.1 ≦ a ≦ 1.0, 0.1 ≦ n ≦ 0.7, x is the distance from the origin on the cross section, and y is the value in the Y-axis direction on the cross section), and Lb is satisfied. Indicates the projection length of the back edge surface on the X axis on the cross section, where 0.2 ≦ Lb ≦ 5.0 (mm).

Here, the X axis is a straight line connecting the downstream end (C) of the front edge surface and the upstream end (A) of the back edge surface. It is found that there is an optimum shape in terms of the shape of the back bar (2) and the positional relationship between the back bar (2) and the front bar (1), and the shape of the back edge surface is clarified in consideration of this point. As a result, when a new coating apparatus is conventionally made, a new back bar is manufactured, and the test is performed while adjusting the position with the front bar.

(4) By clarifying the positional relationship and making the shape of the back edge surface a very smooth curve, a very good result was obtained in high-speed thin film coating, which was difficult to apply conventionally. For example, it is possible to produce a magnetic recording medium with a coating thickness of 10 μm or less and a coating speed of 500 m / min or more for the first time, and with very little coating unevenness (99% or more yield) under the above conditions. Became.

When increasing the coating speed, the angle formed by the X-axis of the back edge surface and the slit (3) located between the front bar (1) and the back bar (2) is actually -10 to +30 degrees. Although it is possible to the extent, it is preferably −10 ° to + 20 ° in consideration of maintenance of the processing accuracy of the apparatus and a wide range of application conditions that can obtain good applicability.

FIGS. 6, 7, and 8 are examples of graphs showing the shape of the back edge surface according to the configuration (1) of the present invention. (However, when the projection length Lb of the back edge surface on the X axis is 1) FIG. 9 is an example of the coating apparatus according to the configuration (2) of the present invention, and the downstream end of the front edge surface ( Part of the back bar (2) protrudes from the tangent line of the front bar (1) in C), and the shape of the back edge surface in cross section is downstream from the upstream end (A) of the back edge surface. An arc having a radius of curvature of r1, r2, and r3 having a center on the side of the back bar (2) toward the end (B) is continuous.

More specifically, the coating apparatus according to the present invention is configured such that a straight line passing through the downstream end (C) of the front edge surface and the upstream end (A) of the back edge surface is drawn to the upstream end (A) of the back edge surface. Is the origin, the X axis with the traveling direction (R) of the support (w) as the positive direction, a straight line orthogonal to the X axis at the origin, and the direction from the back bar (2) toward the support is the positive direction. In the XY plane when the Y-axis is set, the shape of the back edge surface in the plane is expressed by the following relational expression:
0.2 ≤ Lb ≤ 5.0 (mm)
0 ≦ x1 / Lb ≦ 0.5
0.2 ≤ x2 / Lb ≤ 0.8
−0.5 ≦ Hb / Lb ≦ 0.5
0.05 ≦ r1 ≦ 2.0 (mm)
0.5 ≤ r2 ≤ 5.0 (mm)
6.0 ≤ r3 ≤ 30.0 (mm)
(Where x1 <r1, x2-x1 <r2, Lb-x2 <r3, r1 is the radius of curvature of the first arc, r2 is the radius of curvature of the second arc, and r3 is the radius of curvature of the third arc. Where x1 is a projection length on the X axis of a connection point of the first arc and the second arc on the cross section, and x2 is a length of the projection of the second arc on the cross section. Lb is the distance from the origin of the point of projection of the back-edge surface on the X-axis on the cross-section from the origin of the projection of the point of connection with the third arc on the X-axis; Hb is the distance from the origin of the point of projection of the back edge surface on the Y axis on the cross section (provided that Hb has a negative sign when located on the negative side of the Y axis). In FIG. 10, the angle (θ1) between the tangent to the first arc and the tangent to the second arc at the connection point (b1) between the first arc and the second arc is 5 Within degrees and The angle (θ2) between the tangent to the second arc and the tangent to the third arc at the connection point (b2) between the second arc and the third arc is within 5 degrees. .

(4) By clarifying the positional relationship between the front bar (1) and the back bar (2) and making the shape of the back edge surface a curve having a plurality of radii of curvature, high-speed coating performance has been dramatically improved.

For example, when the film thickness before drying was 10 μm or more, the coating speed of 800 m / min or more was achieved for the first time.

This is considered to be because the shape of the back edge surface having a plurality of radii of curvature causes an optimum velocity gradient of the coating liquid to be formed between the edge portion surface and the support (w). In particular, when the particle size is small (0.15 μm or less on the long axis) as in the case of metal magnetic powder, the flow characteristics of the coating liquid become considerably complicated, and such a back edge surface shape is particularly effective.

This enabled production of a magnetic recording medium with very little coating unevenness (99% or more yield) under the above conditions.

Particularly, it is preferable that the three radii of curvature gradually increase from the upstream end to the downstream end of the back bar (2). That is, it satisfies the relationship of 2 × r1 ≦ r2 ≦ 1/2 × r3.

Further, it is preferable that the length Lb of the back bar projected on the X axis decreases as the coating speed increases. Specifically, it is preferably 3 mm or less. Further, if the processing accuracy of the back bar is 0.3 mm or less, the film thickness distribution in the width direction becomes non-uniform, which is not preferable.

Hb / Lb, which is the ratio of the distance Lb from the origin of the point where the downstream end (B) of the back bar is projected on the X axis to the distance Hb from the origin of the point projected on the Y axis, is -0.5. From 0.5 to 0.5, and more preferably from about 0 to 0.4 when the coating speed is extremely high.

角度 Furthermore, the angle formed by the joint having a plurality of radii of curvature is preferably 1 degree or less in consideration of the occurrence of coating failure.

FIG. 11A shows an example of a coating apparatus according to the configuration (3) of the present invention. By forming the downstream end (B) of the back edge surface with a straight line part, the processing accuracy of the back bar is improved. If the film thickness before drying is 10 μm or more, the coating speed is up to 600 m / min. As a result, it became possible to manufacture a magnetic recording medium having considerably good electromagnetic conversion characteristics. This is because the surface properties after application depend most on the surface properties of the downstream end (B) of the back edge surface. If the shape of the back edge surface is constituted by a curve from the upstream end (A) to the downstream end (B), the limit of thin film and high-speed coating suitability is certainly improved. Providing a straight portion at the downstream end of the back edge surface makes it possible to obtain the advantages of both surfaces, which is the only thing.

Also, in the coating apparatus having the linear portion at the downstream end as described above, it is preferable that the length Lb of the back bar projected on the X axis is reduced as the coating speed is increased. Specifically, it is preferably 3 mm or less. Further, if the processing accuracy of the back bar is 0.3 mm or less, the film thickness distribution in the width direction becomes non-uniform, which is not preferable.

Hb / Lb, which is the ratio of the distance Lb from the origin of the point where the downstream end (B) of the back bar is projected on the X axis to the distance Hb from the origin of the point projected on the Y axis, is -0.5. From 0.5 to 0.5, and more preferably from about 0 to 0.4 when the coating speed is extremely high.

Furthermore, the angle formed by the joints having different radii of curvature is preferably 1 degree or less in consideration of the occurrence of coating failure.

Although the apparatus for single layer coating according to the present invention has been specifically described above, what is important as the conditions for performing the actual coating is that the downstream edge of the back edge surface in FIGS. It is preferable to apply under conditions that the angle θ between the tangent (l) of (B) and the support (w) is from -10 degrees to +30 degrees, and more preferably in the range of -5 degrees to +10 degrees. It is to apply with.

Various shapes of the front edge surface can be used in addition to the shape of the back edge surface described above, but those having a straight portion of 1 mm or less at the downstream end of the front edge surface, or having a radius of curvature of 1 mm or more at the downstream end Those having a part of an arc of 20 mm or less are preferable.

(4) Even if the support has a relatively strong film thickness of 50 μm or more, the applicability is not impaired.

In addition, the viscosity of the coating liquid can be sufficiently adjusted from 0.1 cps to 10,000 cps with a B-type viscometer, but it is 50 cps to 4,000 cps with a B-type viscometer, and other high-shear speed compatible viscometers The speed is preferably about 10 cps to 200 cps at a speed of 3,000 sec-1.

(4) The coating apparatus according to the present invention exhibits excellent coating properties even when a coating layer is already coated on a support and further coating is performed on a wet state. In particular, in that case, it is preferable that the viscosity of the coating solution to be applied thereon is low. Specifically, it is preferable that a B-type viscometer shows a value of about half or less of the above value.

Further, the slits in the single-layer coating device are formed of a plurality of slits in the middle, and even when a plurality of types of coating liquids are completely coated on the support in a laminar flow state, very good coating can be performed. .

Next, a multilayer coating apparatus having a front bar 1 ', a center bar 2', a back bar 3 'and two slits 4' and 5 'will be specifically described.

FIG. 12 shows an example of a coating apparatus according to the configuration (4) of the present invention.

On the cross section of the coating device in the running direction (R) of the support (w), the shape of the center edge surface is the center bar (2 ′) side from the upstream end (CA) to the downstream end (B) of the center edge surface. A first arc, a second arc and a third arc each having a center and having a different radius of curvature are continuous, and the shape of the back edge surface is downstream from the upstream end (BA) of the back edge surface. A fourth arc, a fifth arc and a sixth arc having different radii of curvature, each having a center on the side of the back bar (3 ') toward the end (D), are continuous.

More specifically, the coating apparatus according to the present invention draws a straight line passing through the downstream end (C) of the front edge surface and the upstream end (CA) of the center edge surface on the cross section. An X1 axis whose origin is the upstream end (CA), the traveling direction of the support (w) is a positive direction, and a straight line orthogonal to the X1 axis at the origin is drawn from the center bar (2 ′) to the support (w). ), The shape of the center edge surface on the cross section in the X1-Y1 plane when the Y1 axis is defined as the positive direction is the following relational expression.
0.1 ≤ LC ≤ 5.0 (mm)
1 ≤ x1 / LC ≤ 0.5
0.2 ≤ x2 / LC ≤ 0.8
0 ≦ HC / LC ≦ 0.5
0.05 ≦ r1 ≦ 1.0 (mm)
0.5 ≤ r2 ≤ 5.0 (mm)
6.0 ≤ r3 ≤ 30.0 (mm)
(Where x1 <r1, x2-x1 <r2, LC-x2 <r3, r1 is the radius of curvature of the first arc, r2 is the radius of curvature of the second arc, and r3 is the third radius of curvature. , X1 indicates a projection length on the X1 axis of a connection point of the first arc and the second arc on the cross section, and x2 indicates the projection length of the second arc and the second arc on the cross section. Lc indicates the projection length of the connection point with the third arc on the X1 axis, LC indicates the distance from the origin of the projection point of the center edge surface on the X1 axis on the cross section, and HC Indicates the distance from the origin of the projection point on the Y1 axis of the downstream end of the center edge surface on the cross section, and the downstream end (B) of the center edge surface and the back edge surface A straight line passing through the upstream end (BA) is defined as an X2 axis having the origin at the upstream end (BA) of the back edge surface, a positive direction in the running direction of the support (w), and an X2 axis. The back edge on the cross section in the X2-Y2 plane when a straight line orthogonal to the point is defined as a Y2 axis having a direction from the back bar (3 ') toward the support (w) as a positive direction. The following relational expression
0.2 ≤ Lb ≤ 5.0 (mm)
0 ≦ x3 / Lb ≦ 0.5
0.2 ≤ x4 / Lb ≤ 0.8
0 ≦ Hb / Lb ≦ 0.5
0.05 ≦ r4 ≦ 5.0 (mm)
6.0 ≤ r5 ≤ 15.0 (mm)
10.0 ≤ r6 ≤ 30.0 (mm)
(Where x3 <r4, x4-x3 <r5, Lb-x4 <r6, r4 is the radius of curvature of the fourth arc, r5 is the radius of curvature of the fifth arc, and r6 is the radius of curvature of the sixth arc. And x3 indicates a projection length on the X2 axis of a connection point between the fourth arc and the fifth arc on the cross section, and x4 indicates the fifth arc on the cross section. Lb indicates the distance from the origin of the point of projection of the back edge surface on the X2 axis on the cross-section, and Lb indicates the projection length of the connection point between the point and the sixth arc on the X2 axis. , Hb on the cross section indicate the distance from the origin of the point of projection of the downstream edge of the back edge surface onto the Y2 axis) at the connection point of the first arc and the second arc. An angle between a tangent to the first arc and a tangent to the second arc is within 5 degrees, and the angle between the second arc and the third arc is equal to the second arc. Tangent and The angle between the tangent to the third arc and the tangent to the fifth arc is within 5 degrees, and the tangent to the fourth arc and the tangent to the fifth arc at the connection point of the fourth arc and the fifth arc And the angle between the tangent to the fifth arc and the tangent to the sixth arc at the connection point between the fifth arc and the sixth arc is 5 degrees. Within degrees.

The positional relationship between the three bars is very close, and it is clarified that as the position of each bar changes, the shapes of the center edge surface and the back edge surface also change in the same manner as in the aforementioned single-layer coating device. Was done.

By using a virtual coordinate system for the bars as described above, it is possible to use a virtual coordinate system for defining the shape by the angle formed by the tangents of the edges as shown in Japanese Patent Application Laid-Open No. 63-88080. The fact that the accuracy of the above measurement cannot be obtained can be considerably avoided.

In addition, since the actual coating properties of the center bar and the back bar are both composed of a part of an arc having a plurality of radii of curvature of two or more and three or less, both the center bar and the back bar are optimally coated with a coating liquid support. A velocity gradient parallel to the supporting direction can be obtained, especially when the shear speed is extremely high (for example, a shear speed of 106 sec-1 or more), and simultaneously apply a high-viscosity coating solution of 50 cps or more with a thin film at high speed (for example, after drying When the film thickness of the upper layer is 3 μm or less and the lower layer is 10 μm or less and the coating speed is 500 m / min or more), the effect becomes clear. Preferred results are also obtained when the difference in viscosity between the upper layer and the lower layer differs by 50 cps or more at a shear rate of 106 sec-1.

セ ン タ ー By using the shapes of the center edge surface and the back edge surface as described above, the high uniformity of the film thickness distribution of the upper layer can be maintained while improving the applicability of the high-speed thin film.

This is a valuable characteristic in recent years, in which the distribution of the upper layer thickness of the multilayer recording medium is very important due to the shortening of the recording wavelength with the rapid increase in the recording density of the magnetic recording medium. That is, when a video tape is taken as an example immediately, the change in the film thickness becomes a change in the RF output, which is the most important of the electromagnetic conversion characteristics, and can be clearly visually confirmed on a monitor. .

(4) When the coating speed increases, both LC and Lb are preferably shortened. Specifically, both are preferably 3 mm or less, but are preferably 0.3 mm or more in terms of bar processing accuracy.

What is important as a condition for performing the actual coating is that the coating is performed under such a condition that the angle formed between the tangent at the downstream end of the back edge surface and the support located downstream from the downstream end is from -10 degrees to +30 degrees. More preferably, the coating is performed within a range of -5 degrees to +10 degrees.

Various shapes can be used for the shapes of the center edge surface and the back edge surface, and also for the shape of the front edge surface, but those having a straight portion of 1 mm or less at the downstream end of the front edge surface, and those having the downstream end Preferably has a part of an arc having a curvature radius of 1 mm or more and 20 mm or less. Even if the support has a relatively strong film thickness of 50 μm or more, the applicability is not impaired.

Examples of the magnetic powder used in the magnetic paint for constituting the magnetic recording medium that can be used in the coating apparatus of the present invention include JP-A-3-12818, page 4, upper left column, lines 6 to 11 Those described before can be used.

The binder used in the magnetic paint for constituting the magnetic recording medium of the present invention is described in JP-A-3-12818, page 3, lower left column, line 7 to page 4, upper left column, line 1 Are available.

These binder resin components are used in an amount of about 5 to 100 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the magnetic powder.

Dispersants, lubricants, abrasives, antistatic agents, rust inhibitors, antifungal agents, etc. may be added as other parts to be added to the magnetic paint for constituting the magnetic recording medium of the present invention. JP-A-3-12818, page 4, upper left column, line 18, to lower left column, line 19, may be used.

溶 剤 As the solvent used in the production of the magnetic paint, those described in JP-A-3-12818, page 4, lower left column, line 20 to lower right column, line 10 can be used.

の 中 Particularly preferred are those in the item of (solvent according to the present invention) in Table 1 on the upper right of page 3 of JP-A-3-119518.

Magnetic powder, binder, etc. are kneaded to form a magnetic paint. In kneading, the magnetic powder and each of the above-mentioned components are all charged into the kneader simultaneously or individually. In kneading and dispersing the magnetic paint, various kneading machines, such as a two-roll mill, a three-roll mill, a ball mill, a sand glider, a high-speed impeller disperser, a high-speed stone mill, a high-speed impact mill, a disper, a kneader, a high-speed mixer, a homogenizer, The dispersing is performed by an ultrasonic disperser or the like, and as a kneader, it is preferable to disperse by a pressure kneader, a continuous kneader, a Henschel mixer, or the like in order to maintain the degree of dispersion.

Then, a magnetic paint obtained by kneading and dispersing the magnetic powder, the binder, and various additives as described above in a solvent is coated on a non-magnetic support, oriented, and dried to obtain a coating type magnetic recording medium.

(4) According to such a method, the magnetic layer coated on the support is subjected to an orientation treatment of the magnetic powder in the magnetic layer if necessary, and then the magnetic layer is dried. Also, a magnetic recording medium can be obtained by subjecting the surface to a smoothing treatment as necessary, or by cutting into a desired shape.

As the material of the nonmagnetic support used in the magnetic recording medium of the present invention, those described in JP-A-3-17607, page 2, lower right column, lines 7 to 17 can be used. Is not limited to these.

According to the present invention, it was possible to provide a coating apparatus and a coating method capable of performing high-speed and thin-film coating uniformly and stably.

Hereinafter, the effects of the present invention will be illustrated by examples.
Example 1
The preparation of the magnetic paint uses the composition shown below.
<Magnetic paint>
Ferromagnetic powder (listed in Table 1) 100 parts Vinyl chloride resin (manufactured by Zeon Corporation, MR110) 8 parts Polyurethane resin containing sulfonic acid metal salt (UR8700, manufactured by Toyobo Co., Ltd.) 5 parts α-alumina 5 parts carbon black ( 0.5 parts Myristic acid 1 part Stearic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 40 parts Toluene 40 parts Cyclohexanone 40 parts

　上記組成で溶剤を固形分濃度で約80％になるように一部添加し、磁性粉１kg当たり実負荷電力として0.2kw以上かけ10分間以上混練を行い、高速ディスパー等の混合機を使用して、上記処方値になるように希釈を行い、平均粒径1.0mmのジルコニヤビーズを使用してサンドミルにて分散を行い、最後にポリイソシアネート化合物（コロネートＬ５部）を添加して調整した。

With the above composition, a part of the solvent is added so as to have a solid concentration of about 80%, and kneading is carried out for at least 0.2 kw as an actual load power per 1 kg of magnetic powder for at least 10 minutes, and using a mixer such as a high-speed disper. The mixture was diluted to the above prescribed value, dispersed in a sand mill using zirconia beads having an average particle size of 1.0 mm, and finally adjusted by adding a polyisocyanate compound (5 parts of coronate L).

Next, the preparation of non-magnetic paint
<Non-magnetic paint>
Non-magnetic powder (described in Table 2) 100 parts Vinyl chloride resin (manufactured by Zeon Corporation, MR110) 1 part Polyurethane resin containing sulfonic acid metal salt (UR8700, manufactured by Toyobo Co., Ltd.) 5 parts Myristinic acid 1 part Stearic acid 1 part Butyl stearate 1 part Methyl ethyl ketone 35 parts Toluene 35 parts Cyclohexanone 35 parts

　上記組成で溶剤を非磁性粉末１kg当たり実負荷電力として0.2kw以上かかるように一部添加し、10分間以上混練を行い、高速ディスパー等の混合機を使用して上記処方値になるように希釈を行い、平均粒径1.0mmのジルコニヤビースを使用してサンドミルにて分散を行い、最後にポリイソシアネート化合物（コロネートＬ５部）を添加して調整した。

A solvent having the above composition is partially added so as to take 0.2 kW or more as an actual load power per 1 kg of non-magnetic powder, kneaded for 10 minutes or more, and diluted using a mixer such as a high-speed disper to the above-mentioned prescribed value. Was dispersed in a sand mill using zirconia beads having an average particle size of 1.0 mm, and finally, a polyisocyanate compound (5 parts of coronate L) was added to adjust the dispersion.

液 The liquid having the composition described above was used as a basic liquid, and was adjusted to a predetermined viscosity at a shear rate shown in Table 4 with a diluent of methyl ethyl ketone / toluene / cyclohexanone = 1/1/1 (weight ratio). It is effective to add a certain amount of the diluent in advance, measure the viscosity under each shear rate, determine a calibration curve from the results, and estimate the approximate value of the addition amount to determine the amount. . The viscosity was measured using a Rotovisco viscometer (manufactured by Haake).

(4) The prepared coating dispersion was applied to an 8 μm pet base using the coater described in the constitution (1) of the present invention, using a coater described in JP-A-2-35959 as a comparative example. At this time, set the tip of the head almost at the middle position between two support rolls with a span of 500 mm, set the position where the head contacts the base supported by the roll to 0, and push the head into the base side to apply good coating. Extrusion coating was performed at a position where the property was obtained.

(4) As the conditions for coating, the angle between the tangent at the downstream end of the back edge and the continuously running support was kept at about -5 to +5 degrees, and the conditions for good coatability were applied.

At that time, the width of the coater was 660 mm, and the tension during transportation was 20 kg. The applicability is evaluated by measuring the film thickness distribution in the coating direction using X-rays continuously online during the coating, and a 1/2 inch width slit where the film thickness distribution fluctuates ± 10% in the coating direction. Was regarded as NG, and evaluation was performed by a non-defective rate (coating yield) (%) after 10,000 m coating. Since the coater is 660mm wide, 50 slits can be cut after coating and drying as a whole except for unnecessary parts on both sides.

Table 3 shows the parameter values of the used coater and Table 4 shows the experimental results.

　表より本発明の塗布装置により飛躍的な塗布の安定性が得られた事が解る。

From the table, it can be seen that a remarkable coating stability was obtained by the coating apparatus of the present invention.

Next, the coating apparatus and the method described in the configuration (2) of the present invention will be described.

The same coating distribution liquid as described above was applied to an 8 μm pet base using the coater described in the constitution (2) of the present invention, using the coater described in JP-A-2-35959 as a main comparative example. . At that time, set the tip of the head almost at the intermediate position between two support rolls with a span of 500 mm, set the position where the head comes in contact with the base supported by the roll to 0, and push the head into the base side for good coating properties. Extrusion coating was performed at the position where was obtained.

(4) As the conditions for coating, the angle between the tangent at the downstream end of the back edge and the continuously running support was kept at about -5 to +5 degrees, and the conditions for good coatability were applied.

The width of the coater was 660 mm and the tension during transportation was 20 kg, as in the above-described embodiment. The applicability is evaluated by measuring the film thickness distribution in the coating direction using X-rays continuously online during the coating, and a 1/2 inch width slit where the film thickness distribution fluctuates ± 10% in the coating direction. Was regarded as NG, and evaluation was performed by a non-defective rate (coating yield) (%) after 10,000 m coating.

Table 5 shows the parameter values of the used coater and Table 6 shows the experimental results.

　複数バックエッジの曲率の効果より非常に速い塗布速度でも優れた塗布収率が得られる事が解る。

It can be seen that excellent coating yield can be obtained even at a very high coating speed due to the effect of the curvature of the multiple back edges.

From the experimental results, it is understood that the coating apparatus of the present invention can obtain excellent coating properties not only with magnetic powders but also with coating liquids in which non-magnetic powders are dispersed.

{Circle around (2)} The results of experiments using the coating apparatus described in the configuration (3) of the present invention using the coating apparatus in which the cross-sectional shape of the back edge is constituted by a curve having one or two curvatures and a straight line are shown. Table 7 shows the parameter values of the used coater, and Table 8 shows the experimental results.

　尚、実験条件、塗布液等の表中に記載されていない条件は前述の実施例と全く同様であるから、電磁変換特性の値を比較するため、針状粉を使用した場合は長手方向に、板状粉を使用した場合には垂直に、電磁石を使用して6000ガウスの磁場配向を約２秒間行い、乾燥、カレンダー処理後スリット、ローディング８mmのカセットに行った。そして市販の８mmビデオレコーダー（Sony EVO9500）を用いて７MHzの単一波を記録し、この信号を再生し、７MHzの再生出力を、出力レベル測定機を使用し測定を行った。

In addition, since the experimental conditions and the conditions that are not described in the table such as the coating liquid are exactly the same as those in the above-described example, in order to compare the values of the electromagnetic conversion characteristics, when using acicular powder, the When a plate-like powder was used, a magnetic field of 6000 gauss was vertically oriented using an electromagnet for about 2 seconds, dried, calendered, and then slit and loaded into a 8 mm cassette. Using a commercially available 8 mm video recorder (Sony EVO9500), a single wave of 7 MHz was recorded, this signal was reproduced, and the reproduced output of 7 MHz was measured using an output level measuring device.

出力 The output as the electronic conversion characteristic was 0 db for the sample of Comparative Example-24. As a result, although there is an overall difference due to the difference in the magnetic powder, it can be seen that the output of the sample manufactured using the coating apparatus of the present invention has an excellent value as compared with the comparative example.

It can also be seen that the coating yield is considerably better than the comparative example. This effect is nothing less than the improvement in surface properties due to the straightness of the final portion at the downstream end of the back edge. However, the high-speed coating property of this coating apparatus was not a high-speed type as compared with the coating apparatus shown in Table 6, and coating was impossible at a coating speed of 800 m / min this time. Therefore, the back edge has a cross-sectional shape having a plurality of curvatures, so that the high-speed coating property is improved. If the back edge is composed of all the curvatures, it becomes a higher-speed type coating apparatus. It is understood that the surface properties after coating and drying are improved although the properties are impaired.
Example 2
Using the magnetic powder dispersion and the fine magnetic powder dispersion used in Example 1, simultaneous wet-on-wet consisting of two slits and a front bar, a center bar, and a back bar shown in the configuration (3) of the present invention Using a coater described in JP-A-2-25265 as a comparative example, a coater described in the constitution (3) of the present invention was used to coat a pet base of 8 μm using a multilayer coater. At that time, set the tip of the coater head almost at the intermediate position between two support rolls with a span of 500 mm, set the position where the head comes in contact with the base supported by the roll to 0, and push the head into the base side. Extrusion coating was performed at a position where good coatability was obtained.

(4) As the conditions for coating, the angle between the tangent at the downstream end of the back edge and the continuously running support was kept at about -5 to +5 degrees, and the conditions for good coatability were applied.

At that time, the width of the coater was 660 mm, and the tension during transportation was 20 kg. The applicability is evaluated by measuring the film thickness distribution in the coating direction using X-rays continuously online during the coating, and a 1/2 inch width slit where the film thickness distribution fluctuates ± 10% in the coating direction. Was regarded as NG, and evaluation was performed by a non-defective rate (coating yield) (%) after 10,000 m coating.

In addition, in order to compare the fluctuation values of the electromagnetic conversion characteristics, the film thickness after drying was 0.3 μm in the upper layer and 2.0 μm in the lower layer, The film thickness was set so as to give a magnetic field of 6000 gauss using an electromagnet for about 2 seconds. After drying and calendering, slitting and loading were performed on an 8 mm cassette.

Using a commercially available 8mm video recorder (Sony EVO9500), a single wave of 7MHz was recorded, this signal was reproduced and measured for 30 seconds, and the reproduced output of 7MHz was output for 30 seconds using an output level measuring device. Was measured.

In addition, coating conditions not described in the table were performed in exactly the same manner as in Example 1.

Table 9 shows the values of the parameters of the coater used, and Table 10 shows the experimental results.

　結果の表より明らかなように、本発明の塗布装置を使用することによって、従来では非常に均一で且つ高速重層塗布が出来なかったものが、非常に優れた塗布が可能となった。

As is clear from the table of results, the use of the coating apparatus of the present invention has made it possible to perform very excellent coating, which was conventionally not possible to perform a uniform and high-speed multilayer coating.

(4) Along with that, it became possible to manufacture a multilayer recording medium with extremely excellent output fluctuation. Particularly, in the present invention, more preferable results are obtained when the lower layer is a non-magnetic coating solution. Further, in this case, a preferable result is obtained when the magnetic powder contained in the upper layer has a plate shape and has a magnetic anisotropy axis perpendicular to the plate surface.

Sectional drawing of the conventional single layer coating device. Sectional drawing of the conventional single layer coating device. Sectional drawing of the conventional multilayer coating device. (A) The perspective view which cut and showed a part of embodiment of the extruder concerning this invention, (b) Side view, (c) Sectional view, (d) Sectional enlarged view. FIG. 2 is a cross-sectional view of the coating apparatus according to the present invention. 4 is a graph showing a shape of a back edge surface according to the present invention. 4 is a graph showing a shape of a back edge surface according to the present invention. 4 is a graph showing a shape of a back edge surface according to the present invention. FIG. 2 is a cross-sectional view of the single-layer coating device according to the present invention. FIG. 2 is a cross-sectional view of the single-layer coating device according to the present invention. FIG. 2 is a cross-sectional view of the single-layer coating device according to the present invention. FIG. 2 is a cross-sectional view of the multilayer coating device according to the present invention.

Explanation of reference numerals

1, 1 'Front bar 2, 3' Back bar 2 'Center bar 3, 4', 5 'Slit d1, d2, d3 Represents the shape of bar r1, r2, r3, r4 between back bar surface and support Curvature radius W Position of support A, B, C, D Bar surface

Claims (4)

A front bar having a front edge surface and located upstream with respect to the traveling direction of the support, a back bar having a back edge surface and located downstream with respect to the traveling direction of the support, and the front bar; A coating device having a slit positioned between the back bar and the back bar, wherein the front bar at a downstream end of the front edge surface on a cross section of the coating device in a running direction of the support; A part of the back bar protrudes from the tangent line of the back edge surface, and a straight line passing through the downstream end of the front edge surface and the upstream end of the back edge surface. In the XY plane, a straight line perpendicular to the X-axis at the origin is defined as a Y-axis in which a direction from the back bar toward the support is defined as a positive direction. In the plane Relationship shape following the back edge surface y = a (x / Lb) n
(However, 0.1 ≦ a ≦ 1.0, 0.1 ≦ n ≦ 0.7,
x is the distance from the origin on the cross section, y is the value in the Y axis direction on the cross section,
Lb is a distance from the origin of a projection point of the back edge surface on the X axis on the cross section,
0.2 ≦ Lb ≦ 5.0 (mm). ). A front bar having a front edge surface and located upstream with respect to the traveling direction of the support; a back bar having a back edge surface located downstream with respect to the traveling direction of the support; and the front bar and the back A coating device for applying the coating to the support, wherein the front bar is provided at a downstream end of the front edge surface on a cross section of the coating device in a running direction of the support. A part of the back bar protrudes from a tangent line of the back edge surface, and a shape of the back edge surface on the cross section has a radius of curvature having a center on the back bar side from an upstream end to a downstream end of the back edge surface. Wherein the first arc, the second arc and the third arc which are different from each other are continuous. On the cross section, a straight line passing through the downstream end of the front edge surface and the upstream end of the back edge surface, the origin is the upstream end of the back edge surface, and the X axis has the traveling direction of the support as a positive direction, The shape of the back edge surface in the XY plane in a case where a straight line orthogonal to the X axis at the origin is defined as a Y axis having a direction from the back bar toward the support as a positive direction, Is the following relational expression
0.2 ≤ Lb ≤ 5.0 (mm)
0 ≦ x1 / Lb ≦ 0.5
0.2 ≤ x2 / Lb ≤ 0.8
−0.5 ≦ Hb / Lb ≦ 0.5
0.05 ≦ r1 ≦ 2.0 (mm)
0.5 ≤ r2 ≤ 5.0 (mm)
6.0 ≤ r3 ≤ 30.0 (mm)
(Where x1 <r1, x2-x1 <r2, Lb-x2 <r3,
r1 indicates the radius of curvature of the first arc, r2 indicates the radius of curvature of the second arc, and r3 indicates the radius of curvature of the third arc.
x1 is a projection length on the X axis of a connection point between the first arc and the second arc on the cross section, and x2 is a length of the second arc and the third arc on the cross section. Is the length of the projection of the connection point with the arc on the X axis,
Lb is the distance from the origin of the projection point of the back edge surface on the X axis on the cross section,
Hb is the distance from the origin of the projection point of the back edge surface on the Y axis on the cross section. (However, Hb has a negative sign when it is located on the negative side of the Y-axis.)), And the tangent line between the first arc and the first arc at the connection point of the first arc and the second arc. The angle between the tangent to the second arc and the tangent to the second arc is within 5 degrees, and the tangent between the second arc and the third arc at the connection point of the second arc and the third arc. 3. The coating device according to claim 2, wherein the angle between the coating device and the coating film is within 5 degrees. The angle θ formed between the tangent of the back bar at the downstream end of the back edge surface and the support located downstream from the downstream end is −10 by using the coating apparatus according to claim 1. A coating method, wherein the coating is performed at ≦ θ ≦ 30 (degrees).

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