JP4010291B2 - Coating apparatus and coating method - Google Patents

Description

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

  As coaters, roll coaters, gravure coaters, extrusion coaters, slide bead coaters, curtain coaters, etc. are known, but roll coaters, gravure coaters, extrusion coaters are often used as coaters for magnetic recording media. ing.

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

  These coating methods are disclosed in JP-A-57-84771, JP-A-58-104666, JP-A-60-238179, JP-A-1-84072, JP-A1-2210072, JP-A1-288364 and JP-A-2-35959. No. 3-162. In these techniques, the cross-sectional shape of the back bar is 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, and the back bar has a single radius of curvature. In the figure, 1 is a front bar, 2 is a back bar, 3 is a slit, and when the shape of the back bar 2 is a single radius of curvature r1, r2, r3, r4 as shown in the figure, the support w It is difficult to control the distance between the back bar 2 and the coating liquid layer thickness.

  In the figure, d1, d2, and d3 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 varies depending on the position as d1, d2, and d3.

  When the radius of curvature is r1, the gap on the upstream side (slit side end) of the back bar is narrow, so that the liquid pool at the exit of the slit is small, and the change in velocity gradient is too large, so that the slit is between the support and the back bar. The coating liquid cannot be smoothly stretched, causing air entrainment, scraping, and non-uniform liquid flow, and uniform coating cannot be performed.

  In addition, when the radius of curvature is r4, d1 is large and d2 and d3 gradually decrease, so the change in velocity gradient is slow, but all the force from the support to the backbar is concentrated near d3 and downstream of the backbar. The hit becomes too strong, and the coating liquid is scraped off and the flow is disturbed, so that uniform coating cannot be performed.

  When the radius of curvature is r2 or the radius of curvature is r3, the change in the intermediate velocity gradient in the above case is moderately moderate, and the force from the support is also distributed over d2 and d3, facilitating uniform coating. However, this also has a limit if the coating speed is as high as 200 m / min or more, or the flow rate is as small as 10 μm or less in the wet film thickness, and stable coating cannot be achieved.

  FIG. 2 is a sectional view showing an example of a conventional coating apparatus, which is disclosed in JP-A-2-35959. In this example, a straight portion is provided on the slit side of the back bar (doctor edge in this specification), but the downstream end angle E of the straight portion is sharp to some extent, 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 (making a small interval), the force from the support concentrates on the corner E, and the liquid is scraped off or the flow is disturbed. And uniform application is difficult.

  In recent years, as the recording density of magnetic recording media has improved, the number of multi-layer magnetic recording media has increased. In order to achieve this multi-layering, for example, as disclosed in JP-A-51-119204, JP-A-52-51908, JP-A-53-16604, etc. There is a method of forming a multilayer magnetic recording medium by drying, and after the extrusion coating method corresponding to these multilayers has been devised, the multilayer magnetic recording medium is more expensive than the metal thin film magnetic recording medium. The ones that are excellent in the process and the electromagnetic conversion characteristics are very close.

  However, this method has problems such as poor productivity because it repeats coating and drying processes, and it is difficult to reduce the thickness of the uppermost layer. Japanese Patent Application Laid-Open Nos. 48-99803 and 61-111168 show a wet method. A method of manufacturing a magnetic recording medium by simultaneous on-wet multilayer coating is disclosed. Both methods apply a multilayer coating solution in advance to a continuously running support held on a back roll. Thus, the rotation blur accuracy of the back roll is insufficient, and coating unevenness tends to occur in the longitudinal direction of the coating, and it has not been possible to produce an optimum magnetic recording medium.

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

  On the other hand, in order to cover the above disadvantages, a coater head having a slit through which two coating liquids are led out as disclosed in JP-A-63-88080 and JP-A-2-251265 is devised. Has been.

  Such a coater head from which two coating liquids are derived 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 for determining the coating property of the thin film simultaneous multilayer coating is the cross-sectional shape of the liquid contact portion of each bar or the surface in contact with the continuously running support.

  In the prior art described above, 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, if the distances between the center bar and the support are d1, d2, and d3, it is ideal that d1> d2> d3. As described above, this is nothing but to make the velocity gradient of the support and the coating liquid in the direction of travel of the support gentle.

  However, in the technique of the above publication, a coating apparatus for a coating type magnetic recording medium having a thin film multi-layer structure in which a reversal phenomenon occurs at a part of these distances as shown in FIG. The present condition is that the coating method is not disclosed.

  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 positional relationship between the shape of the portion in contact with the support on which the front bar travels or the closest portion and the shape of the portion in which the back bar contacts the coating liquid. For example, when a coating liquid in which very fine magnetic powder is dispersed is applied, the viscosity characteristic deviates considerably from Newtonian fluid, and a considerable plastic flow characteristic is exhibited. That is, the viscosity is high when the coating solution is subjected to a very weak force (shearing speed 10 sec-1 or less) from the outside, and the viscosity is low when receiving a strong force (shearing speed 104 sec-1 or more). Cause the phenomenon. Therefore, in order to obtain good coating properties and coating surface uniformity, it is necessary that the coating solution is gradually and very smoothly accelerated on the back bar, particularly when the coating speed is high (300 m / min or more). Is even more important.

  Further, the positional relationship between the front bar and the back bar is extremely important, and is closely related to the shape of the back bar.

  Therefore, the present invention solves the conventional problems as described above by clarifying the positional relationship between the new shape of the back bar and the front bar, and enables uniform and stable thin film coating of multiple layers or single layers. The object of the present invention is to provide a coating apparatus and a coating method suitable for a magnetic recording medium that can be coated and particularly excellent in electromagnetic conversion properties. I have found that I can achieve this goal.

The object according to the present invention relates to a single-layer coating,
(1) A front bar having a front edge surface and located upstream with respect to the running direction of the support, a back bar having a back edge surface and located downstream with respect to the running direction of the support, and the front In a coating apparatus that has a slit positioned between the bar and the back bar and applies the coating to the support, on the cross-section of the coating apparatus in the running direction of the support, at the downstream end of the front edge surface A part of the back bar protrudes from the tangent to 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 upstream end of the back edge surface as an origin, X-Y when the X direction is the forward direction of the support, the straight line perpendicular to the X axis at the origin is the Y axis with the direction from the back bar toward the support being the positive direction In the plane, in the plane The shape of the back edge surface is expressed by the following relational expression y = a (x / Lb) n
(However, 0.1 ≦ a ≦ 1.0, 0.1 ≦ n ≦ 0.7, x is a distance from the origin on the cross section, y is a value in the Y-axis direction on the cross section, and Lb is the cross section. The length of projection of the back edge surface onto the X-axis, 0.2 ≦ Lb ≦ 5.0 (mm)) is satisfied. At this time, the angle θ formed between the tangent line 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 The coating is preferably performed while being in contact with the coating liquid surface.
(2) A front bar having a front edge surface and located upstream with respect to the travel direction of the support, a back bar having a back edge surface and located downstream with respect to the travel direction of the support, and the front A coating device having a slit positioned between the bar and the back bar, and applying the coating to the support, on the cross-section of the coating device in the traveling direction of the support, at the downstream end of the front edge surface A part of the back bar protrudes from the 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 device characterized in that the first arc, the second arc, and the third arc having different curvature radii are continuous.
(3) A front bar having a front edge surface and located upstream with respect to the running direction of the support, a back bar having a back edge surface and located downstream with respect to the running direction of the support, and the front In the coating apparatus having a slit positioned between the bar and the back bar and applying the coating to the support, the downstream end of the front edge surface on the cross section of the coating apparatus in the traveling direction of the support A part of the back bar protrudes from the tangent line of the front bar at the center, 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 curvature radii having the following are achieved by a coating apparatus characterized by:

  In (2) and (3), the angle θ formed between the tangent line 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 back The coating is preferably performed while the downstream end of the edge surface is in contact with the coating liquid surface.

Furthermore, the object according to the present invention is as follows:
(4) A front bar having a front edge surface and located upstream with respect to the running direction of the support, a back bar having a back edge surface and located downstream with respect to the running direction of the support, and the front A center bar located between the bar and the back bar and having a center edge surface, 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 the coating to the support, and the shape of the center edge surface is an upstream end of the center edge surface on the cross section of the coating device in the traveling direction of the support. The first arc, the second arc, and the third arc having different radii of curvature each having a center on the center bar side from the downstream end 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. Achieved.

  At this time, the angle θ formed between the tangent line 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 The coating is preferably performed while being in contact with 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 an embodiment of a 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 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 configuration (1) of the present invention. The figure 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 defined on the back edge surface. An X axis with the upstream end (A) as the origin and the running direction (R) of the support (w) as the positive direction, and a straight line perpendicular to the X axis at the origin from the back bar (2) to the support The shape of the back edge surface in the XY plane when the Y direction is the positive direction is the following relational expression y = a (x / Lb) n
(Where 0.1 ≦ a ≦ 1.0, 0.1 ≦ n ≦ 0.7, x is a distance from the origin on the cross section, and y is a value in the Y-axis direction on the cross section), and Lb Represents the projected length of the back edge surface on the X-axis on the cross section, and 0.2 ≦ Lb ≦ 5.0 (mm).

  Here, the reason why 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 is that the present inventors have made extensive studies and as a result, This is for the purpose of clarifying the shape of the back edge surface in consideration of this point and the positional relationship between the back bar (2) and the front bar (1). As a result, in the past, when a new coating apparatus was created, a new back bar was manufactured and the test was performed while adjusting the position with the front bar, which greatly improved efficiency.

  Then, by clarifying the positional relationship and making the shape of the back edge surface a very smooth curve, very good results were obtained in high-speed thin film coating, which was conventionally difficult to apply. For example, a magnetic recording medium with an undried film thickness of 10 μm or less and a coating speed of 500 m / min or more is achieved for the first time, and there is very little coating unevenness (yield 99% or more) 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 degrees to +30 degrees. However, it is preferably −10 ° to + 20 ° in consideration of maintaining the processing accuracy of the apparatus and a wide range of application conditions for obtaining good applicability.

  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 on the X-axis of the back edge surface is 1) FIG. 9 is an example of a coating apparatus according to the configuration (2) of the present invention. A part of the back bar (2) protrudes from the tangent to the front bar (1) in C), and the shape of the back edge surface on the cross section is downstream from the upstream end (A) of the back edge surface. From the end (B), arcs of curvature radii r1, r2, r3 each having a center on the back bar (2) side are continuous.

More specifically, in the coating apparatus according to the present invention, 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 defined as an upstream end (A) of the back edge surface. Is the origin, the running direction (R) of the support (w) is the positive direction, a straight line perpendicular to the X axis at the origin, and the direction from the backbar (2) toward the support is the positive direction In the XY plane when the Y-axis is assumed, the shape of the back edge surface in the plane 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 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. X1 is the length of projection on the X axis of the connection point between the first arc and the second arc on the cross section, and x2 is the second arc on the cross section. The length of the projection on the X axis of the connection point with the third arc, and Lb is the distance from the origin of the projection point on the X axis of the back edge surface 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 located on the negative side of the Y-axis)). In FIG. 10, the angle (θ1) between the tangent line of the first arc and the tangent line of the second arc at the connection point (b1) of the first arc and the second arc is 5 Less than and The angle (θ2) formed by the tangent line between the second arc and the third arc at the connection point (b2) between the second arc and the third arc is within 5 degrees. .

  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 curved line having a plurality of radii of curvature, the high-speed coating performance was dramatically improved.

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

  This is presumably because the shape of the back edge surface having a plurality of radii of curvature forms an optimum speed gradient of the coating liquid between the edge surface and the support (w). In particular, when the particle size is small (the major axis is 0.15 μm or less) as in the case of metal magnetic powder, the flow characteristics of the coating solution become considerably complicated, and such a back edge surface shape is particularly effective.

  As a result, a magnetic recording medium with very little coating unevenness (99% or more yield) can be produced under the above conditions.

  In particular, 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, the relationship of 2 × r1 ≦ r2 ≦ 1/2 × r3 is satisfied.

  Further, it is preferable that the length Lb of the back bar projected on the X axis becomes shorter as the coating speed increases. Specifically, 3 mm or less is preferable. On the other hand, when the back bar processing accuracy is 0.3 mm or less, the film thickness distribution in the width direction is not uniform, which is not preferable.

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

  Further, the angle formed by the joint portions having a plurality of radii of curvature is preferably 1 degree or less in consideration of 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 edge (B) of the back edge surface as a straight section, the processing accuracy of the back bar is improved, and the coating speed is up to 600 m / min if the film thickness before drying is 10 μm or more. Thus, it is possible to manufacture a magnetic recording medium having considerably good electromagnetic conversion characteristics. This is because the surface property after coating is most dependent on the surface property of the downstream end (B) of the back edge surface. If the shape of the back edge surface is composed of a curved line from the upstream end (A) to the downstream end (B), the limit of the thin film and high-speed coating suitability is surely improved. This is because the advantage of both sides can be obtained by providing a straight portion at the downstream end of the back edge surface.

  Further, also in the coating apparatus in which the linear portion is provided at the downstream end as described above, it is preferable that the length Lb of the back bar projected on the X-axis decreases as the coating speed increases. Specifically, 3 mm or less is preferable. On the other hand, when the back bar processing accuracy is 0.3 mm or less, the film thickness distribution in the width direction is not uniform, which is not preferable.

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

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

  Although the description of the single-layer coating apparatus according to the present invention has been specifically described above, what is important as a condition for the actual coating is that the downstream edge of the back edge surface in FIGS. 11 (b) and 11 (c). It is preferable to apply under the condition that the angle θ formed between the tangent (l) of (B) and the support (w) is −10 degrees to +30 degrees, and more preferably in the range of −5 degrees to +10 degrees. It is to apply with.

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

  In addition, even if the support has a relatively strong film thickness of 50 μm or more, the coating property is not impaired.

  In addition, the viscosity of the coating solution can be adequate from 0.1 cps to 10,000 cps with a B-type viscometer, but from the viewpoint of applicability, the B-type viscometer has a viscosity of 50 cps to 4,000 cps. About 10 cps to 200 cps is preferable at a speed of 3,000 sec-1.

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

  Furthermore, the slit in the single-layer coating apparatus is composed of a plurality of slits on the way, 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 described in detail.

  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. The first arc, the second arc, and the third arc having different radii of curvature each having a center are continuously formed, 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 back bar (3 ′) side are continuous from the end (D).

More specifically, the coating apparatus according to the present invention has 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 with the upstream end (CA) as the origin, the traveling direction of the support (w) as the forward direction, and a straight line perpendicular to the X1 axis at the origin from the center bar (2 ′) to the support (w ) In the X1-Y1 plane with the Y1 axis having the positive direction as the direction toward), the shape of the center edge surface on the cross section 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 represents the radius of curvature of the first arc, r2 represents the radius of curvature of the second arc, and r3 represents the third radius of curvature. , X1 represents the projected length on the X1 axis of the connection point between the first arc and the second arc on the cross section, and x2 represents the second arc and the second arc on the cross section. The projection length of the connection point with the third arc on the X1 axis is indicated, LC indicates the distance from the origin of the projection point on the X1 axis of the center edge surface on the cross section, and Hc Represents the distance from the origin of the projection point on the Y1 axis of the downstream edge of the center edge surface on the cross section), and the downstream edge (B) of the center edge surface and the back edge surface A straight line passing through the upstream end (BA) is an X2 axis with the upstream end (BA) of the back edge surface as the origin and the traveling direction of the support (w) as the positive direction, and the X2 axis The back edge on the cross section in the X2-Y2 plane when a straight line perpendicular 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 surface shape is
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. X3 represents the projected length of the connection point between the fourth arc and the fifth arc on the X2 axis on the cross section, and x4 represents the fifth arc on the cross section. Indicates the projection length on the X2 axis of the connection point between the first arc and the sixth arc, and Lb indicates the distance from the origin of the projection point on the X2 axis of the back edge surface on the cross section. , Hb satisfy the distance from the origin of the projection point on the Y2 axis of the downstream end of the back edge surface on the cross section), and at the connection point of the first arc and the second arc The angle formed between the tangent to the first arc and the tangent to the second arc is within 5 degrees, and the second arc at the connection point between the second arc and the third arc. And the tangent The angle formed by the tangent to the arc of 3 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 formed between the tangent to the fifth arc and the tangent to the sixth arc at the connection point of the fifth arc and the sixth arc is 5 degrees or less. Is within degrees.

  The positional relationship of the three bars is very close, and it is clarified that the shape of the center edge surface and the back edge surface changes in the same way as the single-layer coating device described above by changing the position of each bar. It was done.

  By using a virtual coordinate system for the bar as described above, the shape is defined by the angle formed by the tangent lines of each edge as shown in Japanese Patent Laid-Open No. 63-88080, which is a conventional technique. The inaccuracy of the above measurement could be avoided considerably.

  In addition, since the actual coating property is composed of a part of an arc having a plurality of curvature radii of not less than 2 and not more than 3 for both the center bar and the back bar, both the center bar and the back bar are the optimum coating liquid support. A speed gradient parallel to the support direction can be obtained, especially when the shear rate is quite high (eg, shear rate of 106 sec-1 or more), and high-viscosity coating liquids of 50 cps or more are simultaneously applied in a thin film at a high speed (eg after undried When the upper layer is 3 μm or less in the upper layer, the lower layer is 10 μm or less and the coating speed is 500 m / min or more, the effect becomes a calendar. A preferable result can also be obtained when the viscosity difference between the upper layer and the lower layer differs by 50 cps or more at a shear rate of 106 sec-1.

  By using the shapes of the center edge surface and the back edge surface as described above, it is possible to maintain a high degree of uniformity in the film thickness distribution of the upper layer while improving the applicability of the high-speed thin film.

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

  Further, when the coating speed is increased, it is preferable that both LC and Lb are shortened. Specifically, both are preferably 3 mm or less, but are preferably 0.3 mm or more in view of the bar processing accuracy.

  What is important as a condition for actual application is that the angle between the tangent line at the downstream end of the back edge surface and the support located downstream from the downstream end is set to −10 degrees to +30 degrees. It is preferable to apply the coating within a range of -5 degrees to +10 degrees.

  Various shapes can be used for the shape of the center edge surface and the back edge surface, and the shape of the front edge surface can be used. Preferably has a part of an arc having a radius of curvature of 1 mm or more and 20 mm or less. Even if the thickness of the support is not less than 50 μm, the coatability is not impaired.

  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 is disclosed in JP-A-3-12818, page 4, upper left column, lines 6 to 11. Those described up to 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. Can be used.

  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, anticorrosives, antifungal agents, etc. may be added as other parts added to the magnetic paint for constituting the magnetic recording medium of the present invention. You may use what is described in Kaihei 3-12818 publication 4th page upper left column 18th line to lower left column 19th line.

  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.

  Particularly preferred are those in the item (solvent according to the present invention) in the upper right table-1 of JP-A-3-19518, page 3.

  Magnetic powder, a binder, and the like are kneaded to form a magnetic paint. In kneading, all of the magnetic powder and the above-described components are simultaneously or individually put into a kneader. In kneading and dispersing the magnetic paint, various kneaders 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, Although it is performed with an ultrasonic disperser or the like, it is preferable that the kneader is dispersed with a pressure kneader, a continuous kneader, a Henschel mixer or the like in order to maintain the degree of dispersion.

  A magnetic coating medium in which a magnetic powder, a binder, and various additives as described above are kneaded and dispersed in a solvent is applied, oriented and dried on a nonmagnetic support to obtain a coating type magnetic recording medium.

  By 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. Further, the magnetic recording medium can be obtained by performing a surface smoothing treatment if necessary, or by cutting into a desired shape.

  As materials for the non-magnetic support used in the magnetic recording medium of the present invention, those described in JP-A-3-76807, page 2, lower right column, lines 7 to 17 can be used. However, it is not limited to these.

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

Hereinafter, the effect of the present invention is illustrated by examples.
Example 1
For production of the magnetic paint, one having the composition shown below is used.
<Magnetic paint>
Ferromagnetic powder (described in Table 1) 100 parts Vinyl chloride resin (manufactured by Nippon Zeon Co., Ltd., MR110) 8 parts Polyurethane resin containing sulfonic acid metal salt (manufactured by Toyobo Co., Ltd., UR8700) 5 parts α-alumina 5 parts Carbon black ( (Particle size 40μm) 0.5 part 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。

Add a part of the solvent with the above composition to a solid content concentration of about 80%, knead for 10 minutes or more over 0.2kw as the actual load power per kg of magnetic powder, and use a mixer such as a high-speed disper. Then, dilution was performed so as to achieve the above-mentioned prescription value, dispersion was performed with a sand mill using zirconia beads having an average particle diameter of 1.0 mm, and finally a polyisocyanate compound (5 parts of coronate L) was added for adjustment.

Next, the production of non-magnetic paints
<Non-magnetic paint>
Nonmagnetic powder (described in Table 2) 100 parts Vinyl chloride resin (manufactured by Nippon Zeon Co., Ltd., MR110) 1 part Polyurethane resin containing sulfonic acid metal salt (manufactured by Toyobo Co., Ltd., UR8700) 5 parts Myristic 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。

Add a part of the solvent with the above composition so that the actual load power per kg of non-magnetic powder is 0.2 kw or more, knead for 10 minutes or more, and use a mixer such as a high-speed disper to dilute to the prescribed value. And using a zirconia beads having an average particle diameter of 1.0 mm, dispersion was performed with a sand mill, and finally a polyisocyanate compound (5 parts of coronate L) was added for adjustment.

  A liquid having the composition described above was used as a base liquid, and a diluted solution of methyl ethyl ketone / toluene / cyclohexanone = 1/1/1 (weight ratio) was adjusted so as to have a predetermined viscosity at a shear rate shown in Table 4. It is effective to add a fixed amount of the diluent in advance, measure the viscosity at each shear rate, create a calibration curve based on the results, and determine a rough value for the amount added. . In addition, a Rotovisco viscometer (manufactured by Harke) was used for viscosity measurement.

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

  As an application condition, the angle between the tangent line at the downstream end of the back edge and the continuously running support was maintained at about -5 degrees to +5 degrees, and conditions with good application characteristics were applied.

  At that time, the coater width was 660 mm, and the tension during conveyance was 20 kg width. The coating property evaluation method uses X-rays continuously online during coating, measures the film thickness distribution in the coating direction, and slits the 1/2 inch width where the film thickness distribution fluctuates ± 10% in the coating direction. Was evaluated as a non-defective product rate (coating yield) (%) after coating 10,000 m. Since the coater is 660mm wide, 50 slits can be cut after coating and drying, excluding unnecessary parts on both sides.

  Table 3 shows the parameter values of the coater used, 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 dramatic coating stability was obtained by the coating apparatus of the present invention.

  Next, the coating apparatus and 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 JP-A-2-35959 as a main comparative example and using the coater shown in the configuration (2) of the present invention. . At that time, set the tip of the head at approximately the middle position between two support rolls with a span of 500 mm, and set the head to the base supported by the roll as 0, and push it toward the base side for good coating properties. Extrusion coating was performed at a position where

  As an application condition, the angle between the tangent line at the downstream end of the back edge and the continuously running support was maintained at about -5 degrees to +5 degrees, and conditions with good application characteristics were applied.

  Similarly to the above-described embodiment, the coater width was 660 mm, and the tension during conveyance was 20 kg width. The coating property evaluation method uses X-rays continuously online during coating, measures the film thickness distribution in the coating direction, and slits the 1/2 inch width where the film thickness distribution fluctuates ± 10% in the coating direction. Was evaluated as a non-defective product rate (coating yield) (%) after coating 10,000 m.

  Table 5 shows the parameter values of the coater used, 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 an excellent coating yield can be obtained even at a coating speed much faster than the effect of the curvature of multiple back edges.

  From the experimental results, it can be seen that the coating apparatus of the present invention can provide excellent coating properties not only with magnetic powder but also with a coating liquid in which non-magnetic powder is dispersed.

  Furthermore, the experimental result using the coating device described in the configuration (3) of the present invention using the coating device in which the cross-sectional shape of the back edge is composed of a curve and a straight line having one or two curvatures is shown. Table 7 shows the parameter values of the coater used, 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 conditions that are not described in the table of the experimental conditions, the coating solution, etc. are exactly the same as the above-mentioned examples, in order to compare the electromagnetic conversion characteristics, when using acicular powder in the longitudinal direction When a plate-like powder was used, a magnetic field orientation of 6000 gauss was performed for about 2 seconds vertically using an electromagnet, and after drying and calendering, it was applied to a slit, loading 8 mm cassette. Then, a 7 MHz single wave was recorded using a commercially available 8 mm video recorder (Sony EVO9500), this signal was reproduced, and a 7 MHz reproduction output was measured using an output level measuring machine.

  The output as the electronic conversion characteristic was set to 0 db for the sample of Comparative Example-24. As a result, although there is an overall difference due to the difference in magnetic powder, it can be understood that the output of the sample produced using the coating apparatus of the present invention is superior to that of the comparative example.

It can also be seen that the yield of coating is considerably better than that of the comparative example. This effect is nothing but an improvement in surface quality due to the fact that the final part of the downstream end of the back edge is straight. However, the high-speed coating property of this coating device is not a high-speed type compared to the coating device shown in Table 6, and this time, the coating speed of 800 m / min was impossible. Therefore, the cross-sectional shape having a plurality of curvatures on the back edge improves the high-speed coating property, and when all are configured with a curvature, it becomes a higher-speed type coating device, and the downstream end portion is linearized to achieve a somewhat higher coating speed. It is understood that the surface property after coating and drying is improved although the property is inhibited.
Example 2
Using the magnetic powder dispersion and the fine magnetic powder dispersion used in Example 1, wet-on-wet consisting of two slits, front bar, center bar and back bar shown in the configuration (3) of the present invention. Using a multilayer coater, the coater described in JP-A-2-251265 was used as a comparative example, and coating was performed on an 8 μm pet base using the coater shown in the configuration (3) of the present invention. At that time, the tip of the coater head is set at an approximately middle position between two support rolls with a span of 500 mm, and the position where the head comes into contact with the base supported by the roll is set to 0 and the base is pushed in well. Extrusion coating was performed at a position where good coating properties were obtained.

  As an application condition, the angle between the tangent line at the downstream end of the back edge and the continuously running support was maintained at about -5 degrees to +5 degrees, and conditions with good application characteristics were applied.

  At that time, the coater width was 660 mm, and the tension during conveyance was 20 kg width. The coating property evaluation method uses X-rays continuously online during coating, measures the film thickness distribution in the coating direction, and slits the 1/2 inch width where the film thickness distribution fluctuates ± 10% in the coating direction. Was evaluated as a non-defective product rate (coating yield) (%) after coating 10,000 m.

  Also, in order to compare fluctuation values of electromagnetic conversion characteristics, the thickness after drying is 0.3 μm for the upper layer and 2.0 μm for the lower layer in the longitudinal direction when using acicular powder, and vertically when using plate-like powder. The film thickness was set so as to be, and a magnetic field orientation of 6000 Gauss was performed for about 2 seconds using an electromagnet, and after drying and calendering, slitting and loading were performed on an 8 mm cassette.

  A commercially available 8mm video recorder (Sony EVO9500) is used to record a 7MHz single wave, and this signal is played back and measured for 30 seconds. The 7MHz playback output is output to the output level measuring machine for 30 seconds. Measurements of fluctuations were made.

  The coating conditions not described in the table were the same as those shown in Example 1.

  The parameter values of the coater used are shown in Table 9, and the experimental results are shown in Table 10.

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 apparent from the table of results, by using the coating apparatus of the present invention, it was possible to perform very excellent coating which was very uniform and could not be applied in a high-speed multilayer coating.

  Along with this, it has become possible to produce a multi-layer recording medium with extremely excellent output fluctuations. Particularly, in the present invention, more preferable results can be obtained when the lower layer is a nonmagnetic coating solution. Further, in that case, a preferable result is obtained when the magnetic powder contained in the upper layer is plate-shaped 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 apparatus. (A) The perspective view which cut and showed a part of one embodiment of the extruder concerning this invention, (b) Side view, (c) Sectional drawing, (d) Sectional enlarged view. Sectional drawing of the coating device concerning this invention. The graph showing the shape of the back edge surface concerning this invention. The graph showing the shape of the back edge surface concerning this invention. The graph showing the shape of the back edge surface concerning this invention. Sectional drawing of the single layer coating device concerning this invention. Sectional drawing of the single layer coating device concerning this invention. Sectional drawing of the single layer coating device concerning this invention. Sectional drawing of the multilayer coating apparatus concerning this invention.

Explanation of symbols

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

Claims (4)

A front bar having a front edge surface and located upstream of the running direction of the support, a back bar having a back edge surface and located downstream of the running direction of the support, and the front bar and In the coating apparatus which has a slit located between the back bar and coats the support, the front bar at the downstream end of the front edge surface on the cross section of the coating apparatus in the running direction of the support A part of the back bar protrudes from the tangent line, and a straight line passing through the downstream end of the front edge surface and the upstream end of the back edge surface, the upstream end of the back edge surface as the origin, and the support In the XY plane when the X axis is the positive direction of the traveling direction, the straight line orthogonal to the X axis at the origin is the Y axis with the direction from the back bar toward the support being the 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 a distance from the origin on the cross section, y is a value in the Y-axis direction on the cross section,
Lb is the distance from the origin of the projection point on the X axis of the back edge surface on the cross section,
It is 0.2 <= Lb <= 5.0 (mm). The coating apparatus characterized by satisfy | filling.
A front bar having a front edge surface and located upstream with respect to the running direction of the support, a back bar having a back edge surface and located downstream with respect to the running direction of the support, and the front bar and the back And a slit disposed between the bar and the front bar at the downstream end of the front edge surface on the cross-section of the coating apparatus in the running direction of the support. A part of the back bar protrudes from the tangent line, and the shape of the back edge surface on the cross section has a radius of curvature having a center on the back bar side from the upstream end to the downstream end of the back edge surface. A coating apparatus, wherein the first arc, the second arc, and the third arc having different diameters 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 X axis with the upstream end of the back edge surface as the origin and the traveling direction of the support as the positive direction, The shape of the back edge surface in the XY plane when the straight line perpendicular to the X axis at the origin is the Y axis with the direction from the back bar toward the support as the 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)
(However, 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,
x1 is the length of projection on the X axis of the connection point between the first arc and the second arc on the cross section, and x2 is the second arc and the third on the cross section. The length of the projection on the X axis of the connection point with the arc of
Lb is the distance from the origin of the projection point on the X axis of the back edge surface on the cross section,
Hb is the distance from the origin of the projection point on the Y axis of the back edge surface 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 at the connection point of the first arc and the second arc and the first arc The angle formed by 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 The coating apparatus according to claim 2, wherein an angle formed by the above is within 5 degrees. Using the coating apparatus according to claim 1, an angle θ formed by a tangent of the back bar at the downstream end of the back edge surface and the support positioned downstream from the downstream end is −10. ≦ θ ≦ 30 (degrees) for coating

Images